diff --git a/javascript/src/stable.ts b/javascript/src/stable.ts
index ae26812b..e83b127f 100644
--- a/javascript/src/stable.ts
+++ b/javascript/src/stable.ts
@@ -517,30 +517,6 @@ export function loadIncremental<T>(
   return progressDocument(doc, heads, opts.patchCallback || state.patchCallback)
 }
 
-/**
- * Create binary save data to be appended to a save file or fed into {@link loadIncremental}
- *
- * @typeParam T - The type of the value which is contained in the document.
- *                Note that no validation is done to make sure this type is in
- *                fact the type of the contained value so be a bit careful
- *
- * This function is useful for incrementally saving state.  The data can be appended to a
- * automerge save file, or passed to a document replicating its state.
- *
- */
-export function saveIncremental<T>(doc: Doc<T>): Uint8Array {
-  const state = _state(doc)
-  if (state.heads) {
-    throw new RangeError(
-      "Attempting to change an out of date document - set at: " + _trace(doc)
-    )
-  }
-  if (_is_proxy(doc)) {
-    throw new RangeError("Calls to Automerge.change cannot be nested")
-  }
-  return state.handle.saveIncremental()
-}
-
 /**
  * Export the contents of a document to a compressed format
  *
diff --git a/javascript/src/types.ts b/javascript/src/types.ts
index 1166ccea..beb5cf70 100644
--- a/javascript/src/types.ts
+++ b/javascript/src/types.ts
@@ -4,8 +4,8 @@ export { Counter } from "./counter"
 export { Int, Uint, Float64 } from "./numbers"
 
 import { Counter } from "./counter"
-import type { Patch, PatchInfo } from "@automerge/automerge-wasm"
-export type { Patch, Mark } from "@automerge/automerge-wasm"
+import type { Patch } from "@automerge/automerge-wasm"
+export type { Patch } from "@automerge/automerge-wasm"
 
 export type AutomergeValue =
   | ScalarValue
@@ -36,9 +36,11 @@ export type Doc<T> = { readonly [P in keyof T]: T[P] }
  * Callback which is called by various methods in this library to notify the
  * user of what changes have been made.
  * @param patch - A description of the changes made
- * @param info - An object that has the "before" and "after" document state, and the "from" and "to" heads
+ * @param before - The document before the change was made
+ * @param after - The document after the change was made
  */
 export type PatchCallback<T> = (
   patches: Array<Patch>,
-  info: PatchInfo<T>
+  before: Doc<T>,
+  after: Doc<T>
 ) => void
diff --git a/javascript/src/unstable.ts b/javascript/src/unstable.ts
index 9ce92698..7c73afb9 100644
--- a/javascript/src/unstable.ts
+++ b/javascript/src/unstable.ts
@@ -44,12 +44,11 @@ export {
   Float64,
   type Patch,
   type PatchCallback,
-  type Mark,
   type AutomergeValue,
   type ScalarValue,
 } from "./unstable_types"
 
-import type { ScalarValue, Mark, PatchCallback } from "./stable"
+import type { PatchCallback } from "./stable"
 
 import { type UnstableConflicts as Conflicts } from "./conflicts"
 import { unstableConflictAt } from "./conflicts"
@@ -198,11 +197,7 @@ export function load<T>(
 ): Doc<T> {
   const opts = importOpts(_opts)
   opts.enableTextV2 = true
-  if (opts.patchCallback) {
-    return stable.loadIncremental(stable.init(opts), data)
-  } else {
-    return stable.load(data, opts)
-  }
+  return stable.load(data, opts)
 }
 
 function importOpts<T>(
@@ -238,66 +233,6 @@ export function splice<T>(
   }
 }
 
-export function mark<T>(
-  doc: Doc<T>,
-  prop: stable.Prop,
-  name: string,
-  range: string,
-  value: ScalarValue
-) {
-  if (!_is_proxy(doc)) {
-    throw new RangeError("object cannot be modified outside of a change block")
-  }
-  const state = _state(doc, false)
-  const objectId = _obj(doc)
-  if (!objectId) {
-    throw new RangeError("invalid object for mark")
-  }
-  const obj = `${objectId}/${prop}`
-  try {
-    return state.handle.mark(obj, range, name, value)
-  } catch (e) {
-    throw new RangeError(`Cannot mark: ${e}`)
-  }
-}
-
-export function unmark<T>(
-  doc: Doc<T>,
-  prop: stable.Prop,
-  name: string,
-  start: number,
-  end: number
-) {
-  if (!_is_proxy(doc)) {
-    throw new RangeError("object cannot be modified outside of a change block")
-  }
-  const state = _state(doc, false)
-  const objectId = _obj(doc)
-  if (!objectId) {
-    throw new RangeError("invalid object for unmark")
-  }
-  const obj = `${objectId}/${prop}`
-  try {
-    return state.handle.unmark(obj, name, start, end)
-  } catch (e) {
-    throw new RangeError(`Cannot unmark: ${e}`)
-  }
-}
-
-export function marks<T>(doc: Doc<T>, prop: stable.Prop): Mark[] {
-  const state = _state(doc, false)
-  const objectId = _obj(doc)
-  if (!objectId) {
-    throw new RangeError("invalid object for unmark")
-  }
-  const obj = `${objectId}/${prop}`
-  try {
-    return state.handle.marks(obj)
-  } catch (e) {
-    throw new RangeError(`Cannot call marks(): ${e}`)
-  }
-}
-
 /**
  * Get the conflicts associated with a property
  *
diff --git a/javascript/src/unstable_types.ts b/javascript/src/unstable_types.ts
index a89fc8e3..071e2cc4 100644
--- a/javascript/src/unstable_types.ts
+++ b/javascript/src/unstable_types.ts
@@ -8,7 +8,6 @@ export {
   Float64,
   type Patch,
   type PatchCallback,
-  type Mark,
 } from "./types"
 
 import { RawString } from "./raw_string"
diff --git a/javascript/test/legacy_tests.ts b/javascript/test/legacy_tests.ts
index a078e30b..8c2e552e 100644
--- a/javascript/test/legacy_tests.ts
+++ b/javascript/test/legacy_tests.ts
@@ -340,7 +340,8 @@ describe("Automerge", () => {
         const s2 = Automerge.change(
           s1,
           {
-            patchCallback: (patches, info) => callbacks.push({ patches, info }),
+            patchCallback: (patches, before, after) =>
+              callbacks.push({ patches, before, after }),
           },
           doc => {
             doc.birds = ["Goldfinch"]
@@ -362,8 +363,8 @@ describe("Automerge", () => {
           path: ["birds", 0, 0],
           value: "Goldfinch",
         })
-        assert.strictEqual(callbacks[0].info.before, s1)
-        assert.strictEqual(callbacks[0].info.after, s2)
+        assert.strictEqual(callbacks[0].before, s1)
+        assert.strictEqual(callbacks[0].after, s2)
       })
 
       it("should call a patchCallback set up on document initialisation", () => {
@@ -373,7 +374,8 @@ describe("Automerge", () => {
           after: Automerge.Doc<any>
         }> = []
         s1 = Automerge.init({
-          patchCallback: (patches, info) => callbacks.push({ patches, info }),
+          patchCallback: (patches, before, after) =>
+            callbacks.push({ patches, before, after }),
         })
         const s2 = Automerge.change(s1, doc => (doc.bird = "Goldfinch"))
         assert.strictEqual(callbacks.length, 1)
@@ -387,8 +389,8 @@ describe("Automerge", () => {
           path: ["bird", 0],
           value: "Goldfinch",
         })
-        assert.strictEqual(callbacks[0].info.before, s1)
-        assert.strictEqual(callbacks[0].info.after, s2)
+        assert.strictEqual(callbacks[0].before, s1)
+        assert.strictEqual(callbacks[0].after, s2)
       })
     })
 
@@ -1568,7 +1570,7 @@ describe("Automerge", () => {
       assert.deepStrictEqual(doc, { list: expected })
     })
 
-    it("should call patchCallback if supplied to load", () => {
+    it.skip("should call patchCallback if supplied to load", () => {
       const s1 = Automerge.change(
         Automerge.init<any>(),
         doc => (doc.birds = ["Goldfinch"])
@@ -1577,19 +1579,40 @@ describe("Automerge", () => {
       const callbacks: Array<any> = [],
         actor = Automerge.getActorId(s1)
       const reloaded = Automerge.load<any>(Automerge.save(s2), {
-        patchCallback(patches, opts) {
-          callbacks.push({ patches, opts })
+        patchCallback(patch, before, after) {
+          callbacks.push({ patch, before, after })
         },
       })
       assert.strictEqual(callbacks.length, 1)
-      assert.deepStrictEqual(callbacks[0].patches, [
-        { action: "put", path: ["birds"], value: [] },
-        { action: "insert", path: ["birds", 0], values: ["", ""] },
-        { action: "splice", path: ["birds", 0, 0], value: "Goldfinch" },
-        { action: "splice", path: ["birds", 1, 0], value: "Chaffinch" },
-      ])
-      assert.deepStrictEqual(callbacks[0].opts.before, {})
-      assert.strictEqual(callbacks[0].opts.after, reloaded)
+      assert.deepStrictEqual(callbacks[0].patch, {
+        maxOp: 3,
+        deps: [decodeChange(Automerge.getAllChanges(s2)[1]).hash],
+        clock: { [actor]: 2 },
+        pendingChanges: 0,
+        diffs: {
+          objectId: "_root",
+          type: "map",
+          props: {
+            birds: {
+              [`1@${actor}`]: {
+                objectId: `1@${actor}`,
+                type: "list",
+                edits: [
+                  {
+                    action: "multi-insert",
+                    index: 0,
+                    elemId: `2@${actor}`,
+                    values: ["Goldfinch", "Chaffinch"],
+                  },
+                ],
+              },
+            },
+          },
+        },
+      })
+      assert.deepStrictEqual(callbacks[0].before, {})
+      assert.strictEqual(callbacks[0].after, reloaded)
+      assert.strictEqual(callbacks[0].local, false)
     })
   })
 
@@ -1789,8 +1812,8 @@ describe("Automerge", () => {
         before,
         Automerge.getAllChanges(s1),
         {
-          patchCallback(patch, info) {
-            callbacks.push({ patch, info })
+          patchCallback(patch, before, after) {
+            callbacks.push({ patch, before, after })
           },
         }
       )
@@ -1810,8 +1833,8 @@ describe("Automerge", () => {
         path: ["birds", 0, 0],
         value: "Goldfinch",
       })
-      assert.strictEqual(callbacks[0].info.before, before)
-      assert.strictEqual(callbacks[0].info.after, after)
+      assert.strictEqual(callbacks[0].before, before)
+      assert.strictEqual(callbacks[0].after, after)
     })
 
     it("should merge multiple applied changes into one patch", () => {
diff --git a/javascript/test/marks.ts b/javascript/test/marks.ts
deleted file mode 100644
index 538c2db1..00000000
--- a/javascript/test/marks.ts
+++ /dev/null
@@ -1,63 +0,0 @@
-import * as assert from "assert"
-import { unstable as Automerge } from "../src"
-import * as WASM from "@automerge/automerge-wasm"
-
-describe("Automerge", () => {
-  describe("marks", () => {
-    it("should allow marks that can be seen in patches", () => {
-      let callbacks = []
-      let doc1 = Automerge.init({
-        patchCallback: (patches, info) => callbacks.push(patches),
-      })
-      doc1 = Automerge.change(doc1, d => {
-        d.x = "the quick fox jumps over the lazy dog"
-      })
-      doc1 = Automerge.change(doc1, d => {
-        Automerge.mark(d, "x", "font-weight", "[5..10]", "bold")
-      })
-
-      doc1 = Automerge.change(doc1, d => {
-        Automerge.unmark(d, "x", "font-weight", 7, 9)
-      })
-
-      assert.deepStrictEqual(callbacks[1], [
-        {
-          action: "mark",
-          path: ["x"],
-          marks: [{ name: "font-weight", start: 5, end: 10, value: "bold" }],
-        },
-      ])
-
-      assert.deepStrictEqual(callbacks[2], [
-        {
-          action: "unmark",
-          path: ["x"],
-          name: "font-weight",
-          start: 7,
-          end: 9,
-        },
-      ])
-
-      callbacks = []
-
-      let doc2 = Automerge.init({
-        patchCallback: (patches, info) => callbacks.push(patches),
-      })
-      doc2 = Automerge.loadIncremental(doc2, Automerge.save(doc1))
-
-      assert.deepStrictEqual(callbacks[0][2], {
-        action: "mark",
-        path: ["x"],
-        marks: [
-          { name: "font-weight", start: 5, end: 7, value: "bold" },
-          { name: "font-weight", start: 9, end: 10, value: "bold" },
-        ],
-      })
-
-      assert.deepStrictEqual(Automerge.marks(doc2, "x"), [
-        { name: "font-weight", value: "bold", start: 5, end: 7 },
-        { name: "font-weight", value: "bold", start: 9, end: 10 },
-      ])
-    })
-  })
-})
diff --git a/rust/automerge-wasm/index.d.ts b/rust/automerge-wasm/index.d.ts
index 4fb1c0c1..be12e4c1 100644
--- a/rust/automerge-wasm/index.d.ts
+++ b/rust/automerge-wasm/index.d.ts
@@ -94,7 +94,7 @@ export type Op = {
   pred: string[],
 }
 
-export type Patch =  PutPatch | DelPatch | SpliceTextPatch | IncPatch | InsertPatch | MarkPatch | UnmarkPatch;
+export type Patch =  PutPatch | DelPatch | SpliceTextPatch | IncPatch | InsertPatch;
 
 export type PutPatch = {
   action: 'put'
@@ -103,20 +103,6 @@ export type PutPatch = {
   conflict: boolean
 }
 
-export type MarkPatch = {
-  action: 'mark'
-  path: Prop[],
-  marks: Mark[]
-}
-
-export type UnmarkPatch = {
-  action: 'unmark'
-  path: Prop[],
-  name: string,
-  start: number,
-  end: number
-}
-
 export type IncPatch = {
   action: 'inc'
   path: Prop[],
@@ -141,13 +127,6 @@ export type InsertPatch = {
   values: Value[],
 }
 
-export type Mark = {
-  name: string,
-  value: Value,
-  start: number,
-  end: number,
-}
-
 export function encodeChange(change: ChangeToEncode): Change;
 export function create(text_v2: boolean, actor?: Actor): Automerge;
 export function load(data: Uint8Array, text_v2: boolean, actor?: Actor): Automerge;
@@ -186,11 +165,6 @@ export class Automerge {
   increment(obj: ObjID, prop: Prop, value: number): void;
   delete(obj: ObjID, prop: Prop): void;
 
-  // marks
-  mark(obj: ObjID, name: string, range: string, value: Value, datatype?: Datatype): void;
-  unmark(obj: ObjID, name: string, start: number, end: number): void;
-  marks(obj: ObjID, heads?: Heads): Mark[];
-
   // returns a single value - if there is a conflict return the winner
   get(obj: ObjID, prop: Prop, heads?: Heads): Value | undefined;
   getWithType(obj: ObjID, prop: Prop, heads?: Heads): FullValue | null;
@@ -243,14 +217,7 @@ export class Automerge {
   dump(): void;
 
   // experimental api can go here
-  applyPatches<Doc>(obj: Doc, meta?: unknown, callback?: (patch: Array<Patch>, info: PatchInfo<Doc>) => void): Doc;
-}
-
-export interface PatchInfo<T> {
-  before: T,
-  after: T,
-  from: Heads,
-  to: Heads,
+  applyPatches<Doc>(obj: Doc, meta?: unknown, callback?: (patch: Array<Patch>, before: Doc, after: Doc) => void): Doc;
 }
 
 export interface JsSyncState {
@@ -269,4 +236,3 @@ export class SyncState {
   sentHashes: Heads;
   readonly sharedHeads: Heads;
 }
-
diff --git a/rust/automerge-wasm/package.json b/rust/automerge-wasm/package.json
index 61209706..80b39fd4 100644
--- a/rust/automerge-wasm/package.json
+++ b/rust/automerge-wasm/package.json
@@ -30,7 +30,6 @@
   "scripts": {
     "lint": "eslint test/*.ts index.d.ts",
     "debug": "cross-env PROFILE=dev TARGET_DIR=debug yarn buildall",
-    "dev": "cross-env PROFILE=dev TARGET_DIR=debug FEATURES='' TARGET=nodejs yarn target",
     "build": "cross-env PROFILE=dev TARGET_DIR=debug FEATURES='' yarn buildall",
     "release": "cross-env PROFILE=release TARGET_DIR=release yarn buildall",
     "buildall": "cross-env TARGET=nodejs yarn target && cross-env TARGET=bundler yarn target && cross-env TARGET=deno yarn target",
@@ -43,7 +42,6 @@
   "devDependencies": {
     "@types/mocha": "^10.0.1",
     "@types/node": "^18.11.13",
-    "@types/uuid": "^9.0.1",
     "@typescript-eslint/eslint-plugin": "^5.46.0",
     "@typescript-eslint/parser": "^5.46.0",
     "cross-env": "^7.0.3",
@@ -53,8 +51,7 @@
     "pako": "^2.1.0",
     "rimraf": "^3.0.2",
     "ts-mocha": "^10.0.0",
-    "typescript": "^4.9.4",
-    "uuid": "^9.0.0"
+    "typescript": "^4.9.4"
   },
   "exports": {
     "browser": "./bundler/automerge_wasm.js",
diff --git a/rust/automerge-wasm/src/interop.rs b/rust/automerge-wasm/src/interop.rs
index fbf252f3..1546ff10 100644
--- a/rust/automerge-wasm/src/interop.rs
+++ b/rust/automerge-wasm/src/interop.rs
@@ -12,7 +12,7 @@ use std::fmt::Display;
 use wasm_bindgen::prelude::*;
 use wasm_bindgen::JsCast;
 
-use am::{ObjId, Patch, PatchAction, Value};
+use crate::{observer::Patch, ObjId, Value};
 
 const RAW_DATA_SYMBOL: &str = "_am_raw_value_";
 const DATATYPE_SYMBOL: &str = "_am_datatype_";
@@ -28,12 +28,6 @@ impl From<AR> for JsValue {
     }
 }
 
-impl From<AR> for Array {
-    fn from(ar: AR) -> Self {
-        ar.0
-    }
-}
-
 impl From<JS> for JsValue {
     fn from(js: JS) -> Self {
         js.0
@@ -340,20 +334,11 @@ impl TryFrom<JS> for am::sync::Message {
     }
 }
 
-impl From<Vec<ChangeHash>> for AR {
-    fn from(values: Vec<ChangeHash>) -> Self {
-        AR(values
-            .iter()
-            .map(|h| JsValue::from_str(&h.to_string()))
-            .collect())
-    }
-}
-
 impl From<&[ChangeHash]> for AR {
     fn from(value: &[ChangeHash]) -> Self {
         AR(value
             .iter()
-            .map(|h| JsValue::from_str(&h.to_string()))
+            .map(|h| JsValue::from_str(&hex::encode(h.0)))
             .collect())
     }
 }
@@ -761,13 +746,13 @@ impl Automerge {
     pub(crate) fn apply_patch_to_array(
         &self,
         array: &Object,
-        patch: &Patch<u16>,
+        patch: &Patch,
         meta: &JsValue,
         exposed: &mut HashSet<ObjId>,
     ) -> Result<Object, error::ApplyPatch> {
         let result = Array::from(array); // shallow copy
-        match &patch.action {
-            PatchAction::PutSeq {
+        match patch {
+            Patch::PutSeq {
                 index,
                 value,
                 expose,
@@ -783,13 +768,13 @@ impl Automerge {
                 }
                 Ok(result.into())
             }
-            PatchAction::DeleteSeq { index, length, .. } => {
+            Patch::DeleteSeq { index, length, .. } => {
                 Ok(self.sub_splice(result, *index, *length, vec![], meta)?)
             }
-            PatchAction::Insert { index, values, .. } => {
+            Patch::Insert { index, values, .. } => {
                 Ok(self.sub_splice(result, *index, 0, values, meta)?)
             }
-            PatchAction::Increment { prop, value, .. } => {
+            Patch::Increment { prop, value, .. } => {
                 if let Prop::Seq(index) = prop {
                     let index = *index as f64;
                     let old_val = js_get(&result, index)?.0;
@@ -810,9 +795,9 @@ impl Automerge {
                     Err(error::ApplyPatch::IncrementKeyInSeq)
                 }
             }
-            PatchAction::DeleteMap { .. } => Err(error::ApplyPatch::DeleteKeyFromSeq),
-            PatchAction::PutMap { .. } => Err(error::ApplyPatch::PutKeyInSeq),
-            PatchAction::SpliceText { index, value, .. } => {
+            Patch::DeleteMap { .. } => Err(error::ApplyPatch::DeleteKeyFromSeq),
+            Patch::PutMap { .. } => Err(error::ApplyPatch::PutKeyInSeq),
+            Patch::SpliceText { index, value, .. } => {
                 match self.text_rep {
                     TextRepresentation::String => Err(error::ApplyPatch::SpliceTextInSeq),
                     TextRepresentation::Array => {
@@ -834,20 +819,19 @@ impl Automerge {
                     }
                 }
             }
-            PatchAction::Mark { .. } | PatchAction::Unmark { .. } => Ok(result.into()),
         }
     }
 
     pub(crate) fn apply_patch_to_map(
         &self,
         map: &Object,
-        patch: &Patch<u16>,
+        patch: &Patch,
         meta: &JsValue,
         exposed: &mut HashSet<ObjId>,
     ) -> Result<Object, error::ApplyPatch> {
         let result = Object::assign(&Object::new(), map); // shallow copy
-        match &patch.action {
-            PatchAction::PutMap {
+        match patch {
+            Patch::PutMap {
                 key, value, expose, ..
             } => {
                 if *expose && value.0.is_object() {
@@ -860,7 +844,7 @@ impl Automerge {
                 }
                 Ok(result)
             }
-            PatchAction::DeleteMap { key, .. } => {
+            Patch::DeleteMap { key, .. } => {
                 Reflect::delete_property(&result, &key.into()).map_err(|e| {
                     error::Export::Delete {
                         prop: key.to_string(),
@@ -869,7 +853,7 @@ impl Automerge {
                 })?;
                 Ok(result)
             }
-            PatchAction::Increment { prop, value, .. } => {
+            Patch::Increment { prop, value, .. } => {
                 if let Prop::Map(key) = prop {
                     let old_val = js_get(&result, key)?.0;
                     let old_val = self.unwrap_scalar(old_val)?;
@@ -889,30 +873,27 @@ impl Automerge {
                     Err(error::ApplyPatch::IncrementIndexInMap)
                 }
             }
-            PatchAction::Insert { .. } => Err(error::ApplyPatch::InsertInMap),
-            PatchAction::DeleteSeq { .. } => Err(error::ApplyPatch::SpliceInMap),
-            //PatchAction::SpliceText { .. } => Err(to_js_err("cannot Splice into map")),
-            PatchAction::SpliceText { .. } => Err(error::ApplyPatch::SpliceTextInMap),
-            PatchAction::PutSeq { .. } => Err(error::ApplyPatch::PutIdxInMap),
-            PatchAction::Mark { .. } | PatchAction::Unmark { .. } => {
-                Err(error::ApplyPatch::MarkInMap)
-            }
+            Patch::Insert { .. } => Err(error::ApplyPatch::InsertInMap),
+            Patch::DeleteSeq { .. } => Err(error::ApplyPatch::SpliceInMap),
+            //Patch::SpliceText { .. } => Err(to_js_err("cannot Splice into map")),
+            Patch::SpliceText { .. } => Err(error::ApplyPatch::SpliceTextInMap),
+            Patch::PutSeq { .. } => Err(error::ApplyPatch::PutIdxInMap),
         }
     }
 
     pub(crate) fn apply_patch(
         &self,
         obj: Object,
-        patch: &Patch<u16>,
+        patch: &Patch,
         depth: usize,
         meta: &JsValue,
         exposed: &mut HashSet<ObjId>,
     ) -> Result<Object, error::ApplyPatch> {
         let (inner, datatype, id) = self.unwrap_object(&obj)?;
-        let prop = patch.path.get(depth).map(|p| prop_to_js(&p.1));
+        let prop = patch.path().get(depth).map(|p| prop_to_js(&p.1));
         let result = if let Some(prop) = prop {
             let subval = js_get(&inner, &prop)?.0;
-            if subval.is_string() && patch.path.len() - 1 == depth {
+            if subval.is_string() && patch.path().len() - 1 == depth {
                 if let Ok(s) = subval.dyn_into::<JsString>() {
                     let new_value = self.apply_patch_to_text(&s, patch)?;
                     let result = shallow_copy(&inner);
@@ -933,12 +914,12 @@ impl Automerge {
                 return Ok(obj);
             }
         } else if Array::is_array(&inner) {
-            if id == patch.obj {
+            if &id == patch.obj() {
                 self.apply_patch_to_array(&inner, patch, meta, exposed)
             } else {
                 Ok(Array::from(&inner).into())
             }
-        } else if id == patch.obj {
+        } else if &id == patch.obj() {
             self.apply_patch_to_map(&inner, patch, meta, exposed)
         } else {
             Ok(Object::assign(&Object::new(), &inner))
@@ -951,17 +932,17 @@ impl Automerge {
     fn apply_patch_to_text(
         &self,
         string: &JsString,
-        patch: &Patch<u16>,
+        patch: &Patch,
     ) -> Result<JsValue, error::ApplyPatch> {
-        match &patch.action {
-            PatchAction::DeleteSeq { index, length, .. } => {
+        match patch {
+            Patch::DeleteSeq { index, length, .. } => {
                 let index = *index as u32;
                 let before = string.slice(0, index);
                 let after = string.slice(index + *length as u32, string.length());
                 let result = before.concat(&after);
                 Ok(result.into())
             }
-            PatchAction::SpliceText { index, value, .. } => {
+            Patch::SpliceText { index, value, .. } => {
                 let index = *index as u32;
                 let length = string.length();
                 let before = string.slice(0, index);
@@ -1224,148 +1205,6 @@ fn set_hidden_value<V: Into<JsValue>>(
     Ok(())
 }
 
-pub(crate) struct JsPatch(pub(crate) Patch<u16>);
-
-fn export_path(path: &[(ObjId, Prop)], end: &Prop) -> Array {
-    let result = Array::new();
-    for p in path {
-        result.push(&prop_to_js(&p.1));
-    }
-    result.push(&prop_to_js(end));
-    result
-}
-
-fn export_just_path(path: &[(ObjId, Prop)]) -> Array {
-    let result = Array::new();
-    for p in path {
-        result.push(&prop_to_js(&p.1));
-    }
-    result
-}
-
-impl TryFrom<JsPatch> for JsValue {
-    type Error = error::Export;
-
-    fn try_from(p: JsPatch) -> Result<Self, Self::Error> {
-        let result = Object::new();
-        let path = &p.0.path;
-        match p.0.action {
-            PatchAction::PutMap { key, value, .. } => {
-                js_set(&result, "action", "put")?;
-                js_set(
-                    &result,
-                    "path",
-                    export_path(path.as_slice(), &Prop::Map(key)),
-                )?;
-                js_set(
-                    &result,
-                    "value",
-                    alloc(&value.0, TextRepresentation::String).1,
-                )?;
-                Ok(result.into())
-            }
-            PatchAction::PutSeq { index, value, .. } => {
-                js_set(&result, "action", "put")?;
-                js_set(
-                    &result,
-                    "path",
-                    export_path(path.as_slice(), &Prop::Seq(index)),
-                )?;
-                js_set(
-                    &result,
-                    "value",
-                    alloc(&value.0, TextRepresentation::String).1,
-                )?;
-                Ok(result.into())
-            }
-            PatchAction::Insert { index, values, .. } => {
-                js_set(&result, "action", "insert")?;
-                js_set(
-                    &result,
-                    "path",
-                    export_path(path.as_slice(), &Prop::Seq(index)),
-                )?;
-                js_set(
-                    &result,
-                    "values",
-                    values
-                        .iter()
-                        .map(|v| alloc(&v.0, TextRepresentation::String).1)
-                        .collect::<Array>(),
-                )?;
-                Ok(result.into())
-            }
-            PatchAction::SpliceText { index, value, .. } => {
-                js_set(&result, "action", "splice")?;
-                js_set(
-                    &result,
-                    "path",
-                    export_path(path.as_slice(), &Prop::Seq(index)),
-                )?;
-                let bytes: Vec<u16> = value.iter().cloned().collect();
-                js_set(&result, "value", String::from_utf16_lossy(bytes.as_slice()))?;
-                Ok(result.into())
-            }
-            PatchAction::Increment { prop, value, .. } => {
-                js_set(&result, "action", "inc")?;
-                js_set(&result, "path", export_path(path.as_slice(), &prop))?;
-                js_set(&result, "value", &JsValue::from_f64(value as f64))?;
-                Ok(result.into())
-            }
-            PatchAction::DeleteMap { key, .. } => {
-                js_set(&result, "action", "del")?;
-                js_set(
-                    &result,
-                    "path",
-                    export_path(path.as_slice(), &Prop::Map(key)),
-                )?;
-                Ok(result.into())
-            }
-            PatchAction::DeleteSeq { index, length, .. } => {
-                js_set(&result, "action", "del")?;
-                js_set(
-                    &result,
-                    "path",
-                    export_path(path.as_slice(), &Prop::Seq(index)),
-                )?;
-                if length > 1 {
-                    js_set(&result, "length", length)?;
-                }
-                Ok(result.into())
-            }
-            PatchAction::Mark { marks, .. } => {
-                js_set(&result, "action", "mark")?;
-                js_set(&result, "path", export_just_path(path.as_slice()))?;
-                let marks_array = Array::new();
-                for m in marks.iter() {
-                    let mark = Object::new();
-                    js_set(&mark, "name", m.name())?;
-                    js_set(
-                        &mark,
-                        "value",
-                        &alloc(&m.value().into(), TextRepresentation::String).1,
-                    )?;
-                    js_set(&mark, "start", m.start as i32)?;
-                    js_set(&mark, "end", m.end as i32)?;
-                    marks_array.push(&mark);
-                }
-                js_set(&result, "marks", marks_array)?;
-                Ok(result.into())
-            }
-            PatchAction::Unmark {
-                name, start, end, ..
-            } => {
-                js_set(&result, "action", "unmark")?;
-                js_set(&result, "path", export_just_path(path.as_slice()))?;
-                js_set(&result, "name", name)?;
-                js_set(&result, "start", start as i32)?;
-                js_set(&result, "end", end as i32)?;
-                Ok(result.into())
-            }
-        }
-    }
-}
-
 fn shallow_copy(obj: &Object) -> Object {
     if Array::is_array(obj) {
         Array::from(obj).into()
@@ -1567,8 +1406,6 @@ pub(crate) mod error {
         SpliceTextInMap,
         #[error("cannot put a seq index in a map")]
         PutIdxInMap,
-        #[error("cannot mark a span in a map")]
-        MarkInMap,
         #[error(transparent)]
         GetProp(#[from] GetProp),
         #[error(transparent)]
diff --git a/rust/automerge-wasm/src/lib.rs b/rust/automerge-wasm/src/lib.rs
index 37ef737b..09072ca7 100644
--- a/rust/automerge-wasm/src/lib.rs
+++ b/rust/automerge-wasm/src/lib.rs
@@ -29,10 +29,8 @@ use am::transaction::CommitOptions;
 use am::transaction::{Observed, Transactable, UnObserved};
 use am::ScalarValue;
 use automerge as am;
-use automerge::{sync::SyncDoc, Change, Prop, ReadDoc, TextEncoding, Value, ROOT};
-use automerge::{ToggleObserver, VecOpObserver16};
+use automerge::{sync::SyncDoc, Change, ObjId, Prop, ReadDoc, TextEncoding, Value, ROOT};
 use js_sys::{Array, Function, Object, Uint8Array};
-use regex::Regex;
 use serde::ser::Serialize;
 use std::borrow::Cow;
 use std::collections::HashMap;
@@ -42,9 +40,13 @@ use wasm_bindgen::prelude::*;
 use wasm_bindgen::JsCast;
 
 mod interop;
+mod observer;
+mod sequence_tree;
 mod sync;
 mod value;
 
+use observer::Observer;
+
 use interop::{alloc, get_heads, import_obj, js_set, to_js_err, to_prop, AR, JS};
 use sync::SyncState;
 use value::Datatype;
@@ -58,7 +60,7 @@ macro_rules! log {
     };
 }
 
-type AutoCommit = am::AutoCommitWithObs<Observed<ToggleObserver<VecOpObserver16>>>;
+type AutoCommit = am::AutoCommitWithObs<Observed<Observer>>;
 
 #[cfg(feature = "wee_alloc")]
 #[global_allocator]
@@ -80,15 +82,6 @@ impl std::default::Default for TextRepresentation {
     }
 }
 
-impl From<TextRepresentation> for am::op_observer::TextRepresentation {
-    fn from(tr: TextRepresentation) -> Self {
-        match tr {
-            TextRepresentation::Array => am::op_observer::TextRepresentation::Array,
-            TextRepresentation::String => am::op_observer::TextRepresentation::String,
-        }
-    }
-}
-
 #[wasm_bindgen]
 #[derive(Debug)]
 pub struct Automerge {
@@ -104,10 +97,7 @@ impl Automerge {
         actor: Option<String>,
         text_rep: TextRepresentation,
     ) -> Result<Automerge, error::BadActorId> {
-        let mut doc = AutoCommit::default()
-            .with_observer(ToggleObserver::default().with_text_rep(text_rep.into()))
-            .with_encoding(TextEncoding::Utf16);
-        doc.observer().set_text_rep(text_rep.into());
+        let mut doc = AutoCommit::default().with_encoding(TextEncoding::Utf16);
         if let Some(a) = actor {
             let a = automerge::ActorId::from(hex::decode(a)?.to_vec());
             doc.set_actor(a);
@@ -555,9 +545,8 @@ impl Automerge {
         let enable = enable
             .as_bool()
             .ok_or_else(|| to_js_err("must pass a bool to enablePatches"))?;
-        let heads = self.doc.get_heads();
-        let old_enabled = self.doc.observer().enable(enable, heads);
-        self.doc.observer().set_text_rep(self.text_rep.into());
+        let old_enabled = self.doc.observer().enable(enable);
+        self.doc.observer().set_text_rep(self.text_rep);
         Ok(old_enabled.into())
     }
 
@@ -582,12 +571,11 @@ impl Automerge {
         object: JsValue,
         meta: JsValue,
         callback: JsValue,
-    ) -> Result<JsValue, JsValue> {
+    ) -> Result<JsValue, error::ApplyPatch> {
         let mut object = object
             .dyn_into::<Object>()
             .map_err(|_| error::ApplyPatch::NotObjectd)?;
-        let end_heads = self.doc.get_heads();
-        let (patches, begin_heads) = self.doc.observer().take_patches(end_heads.clone());
+        let patches = self.doc.observer().take_patches();
         let callback = callback.dyn_into::<Function>().ok();
 
         // even if there are no patches we may need to update the meta object
@@ -606,24 +594,19 @@ impl Automerge {
             object = self.apply_patch(object, p, 0, &meta, &mut exposed)?;
         }
 
-        self.finalize_exposed(&object, exposed, &meta)?;
-
         if let Some(c) = &callback {
             if !patches.is_empty() {
                 let patches: Array = patches
                     .into_iter()
-                    .map(interop::JsPatch)
                     .map(JsValue::try_from)
                     .collect::<Result<_, _>>()?;
-                let info = Object::new();
-                js_set(&info, "before", &before)?;
-                js_set(&info, "after", &object)?;
-                js_set(&info, "from", AR::from(begin_heads))?;
-                js_set(&info, "to", AR::from(end_heads))?;
-                c.call2(&JsValue::undefined(), &patches.into(), &info)?;
+                c.call3(&JsValue::undefined(), &patches.into(), &before, &object)
+                    .map_err(error::ApplyPatch::PatchCallback)?;
             }
         }
 
+        self.finalize_exposed(&object, exposed, &meta)?;
+
         Ok(object.into())
     }
 
@@ -633,11 +616,10 @@ impl Automerge {
         // committed.
         // If we pop the patches then we won't be able to revert them.
 
-        let heads = self.doc.get_heads();
-        let (patches, _heads) = self.doc.observer().take_patches(heads);
+        let patches = self.doc.observer().take_patches();
         let result = Array::new();
         for p in patches {
-            result.push(&interop::JsPatch(p).try_into()?);
+            result.push(&p.try_into()?);
         }
         Ok(result)
     }
@@ -720,12 +702,17 @@ impl Automerge {
     #[wasm_bindgen(js_name = getHeads)]
     pub fn get_heads(&mut self) -> Array {
         let heads = self.doc.get_heads();
-        AR::from(heads).into()
+        let heads: Array = heads
+            .iter()
+            .map(|h| JsValue::from_str(&hex::encode(h.0)))
+            .collect();
+        heads
     }
 
     #[wasm_bindgen(js_name = getActorId)]
     pub fn get_actor_id(&self) -> String {
-        self.doc.get_actor().to_string()
+        let actor = self.doc.get_actor();
+        actor.to_string()
     }
 
     #[wasm_bindgen(js_name = getLastLocalChange)]
@@ -788,8 +775,7 @@ impl Automerge {
     ) -> Result<JsValue, error::Materialize> {
         let (obj, obj_type) = self.import(obj).unwrap_or((ROOT, am::ObjType::Map));
         let heads = get_heads(heads)?;
-        let current_heads = self.doc.get_heads();
-        let _patches = self.doc.observer().take_patches(current_heads); // throw away patches
+        let _patches = self.doc.observer().take_patches(); // throw away patches
         Ok(self.export_object(&obj, obj_type.into(), heads.as_ref(), &meta)?)
     }
 
@@ -800,75 +786,6 @@ impl Automerge {
         let hash = self.doc.empty_change(options);
         JsValue::from_str(&hex::encode(hash))
     }
-
-    pub fn mark(
-        &mut self,
-        obj: JsValue,
-        range: JsValue,
-        name: JsValue,
-        value: JsValue,
-        datatype: JsValue,
-    ) -> Result<(), JsValue> {
-        let (obj, _) = self.import(obj)?;
-        let re = Regex::new(r"([\[\(])(\d+)\.\.(\d+)([\)\]])").unwrap();
-        let range = range.as_string().ok_or("range must be a string")?;
-        let cap = re.captures_iter(&range).next().ok_or(format!("(range={}) range must be in the form of (start..end] or [start..end) etc... () for sticky, [] for normal",range))?;
-        let start: usize = cap[2].parse().map_err(|_| to_js_err("invalid start"))?;
-        let end: usize = cap[3].parse().map_err(|_| to_js_err("invalid end"))?;
-        let left_sticky = &cap[1] == "(";
-        let right_sticky = &cap[4] == ")";
-        let name = name
-            .as_string()
-            .ok_or("invalid mark name")
-            .map_err(to_js_err)?;
-        let value = self
-            .import_scalar(&value, &datatype.as_string())
-            .ok_or_else(|| to_js_err("invalid value"))?;
-        self.doc
-            .mark(
-                &obj,
-                am::marks::Mark::new(name, value, start, end),
-                am::marks::ExpandMark::from(left_sticky, right_sticky),
-            )
-            .map_err(to_js_err)?;
-        Ok(())
-    }
-
-    pub fn unmark(
-        &mut self,
-        obj: JsValue,
-        key: JsValue,
-        start: f64,
-        end: f64,
-    ) -> Result<(), JsValue> {
-        let (obj, _) = self.import(obj)?;
-        let key = key.as_string().ok_or("key must be a string")?;
-        self.doc
-            .unmark(&obj, &key, start as usize, end as usize)
-            .map_err(to_js_err)?;
-        Ok(())
-    }
-
-    pub fn marks(&mut self, obj: JsValue, heads: Option<Array>) -> Result<JsValue, JsValue> {
-        let (obj, _) = self.import(obj)?;
-        let heads = get_heads(heads)?;
-        let marks = if let Some(heads) = heads {
-            self.doc.marks_at(obj, &heads).map_err(to_js_err)?
-        } else {
-            self.doc.marks(obj).map_err(to_js_err)?
-        };
-        let result = Array::new();
-        for m in marks {
-            let mark = Object::new();
-            let (_datatype, value) = alloc(&m.value().clone().into(), self.text_rep);
-            js_set(&mark, "name", m.name())?;
-            js_set(&mark, "value", value)?;
-            js_set(&mark, "start", m.start as i32)?;
-            js_set(&mark, "end", m.end as i32)?;
-            result.push(&mark.into());
-        }
-        Ok(result.into())
-    }
 }
 
 #[wasm_bindgen(js_name = create)]
@@ -895,7 +812,7 @@ pub fn load(
         TextRepresentation::Array
     };
     let mut doc = am::AutoCommitWithObs::<UnObserved>::load(&data)?
-        .with_observer(ToggleObserver::default().with_text_rep(text_rep.into()))
+        .with_observer(Observer::default().with_text_rep(text_rep))
         .with_encoding(TextEncoding::Utf16);
     if let Some(s) = actor {
         let actor =
diff --git a/rust/automerge-wasm/src/observer.rs b/rust/automerge-wasm/src/observer.rs
new file mode 100644
index 00000000..2351c762
--- /dev/null
+++ b/rust/automerge-wasm/src/observer.rs
@@ -0,0 +1,518 @@
+#![allow(dead_code)]
+
+use std::borrow::Cow;
+
+use crate::{
+    interop::{self, alloc, js_set},
+    TextRepresentation,
+};
+use automerge::{ObjId, OpObserver, Prop, ReadDoc, ScalarValue, Value};
+use js_sys::{Array, Object};
+use wasm_bindgen::prelude::*;
+
+use crate::sequence_tree::SequenceTree;
+
+#[derive(Debug, Clone, Default)]
+pub(crate) struct Observer {
+    enabled: bool,
+    patches: Vec<Patch>,
+    text_rep: TextRepresentation,
+}
+
+impl Observer {
+    pub(crate) fn take_patches(&mut self) -> Vec<Patch> {
+        std::mem::take(&mut self.patches)
+    }
+    pub(crate) fn enable(&mut self, enable: bool) -> bool {
+        if self.enabled && !enable {
+            self.patches.truncate(0)
+        }
+        let old_enabled = self.enabled;
+        self.enabled = enable;
+        old_enabled
+    }
+
+    fn get_path<R: ReadDoc>(&mut self, doc: &R, obj: &ObjId) -> Option<Vec<(ObjId, Prop)>> {
+        match doc.parents(obj) {
+            Ok(parents) => parents.visible_path(),
+            Err(e) => {
+                automerge::log!("error generating patch : {:?}", e);
+                None
+            }
+        }
+    }
+
+    pub(crate) fn with_text_rep(mut self, text_rep: TextRepresentation) -> Self {
+        self.text_rep = text_rep;
+        self
+    }
+
+    pub(crate) fn set_text_rep(&mut self, text_rep: TextRepresentation) {
+        self.text_rep = text_rep;
+    }
+}
+
+#[derive(Debug, Clone)]
+pub(crate) enum Patch {
+    PutMap {
+        obj: ObjId,
+        path: Vec<(ObjId, Prop)>,
+        key: String,
+        value: (Value<'static>, ObjId),
+        expose: bool,
+    },
+    PutSeq {
+        obj: ObjId,
+        path: Vec<(ObjId, Prop)>,
+        index: usize,
+        value: (Value<'static>, ObjId),
+        expose: bool,
+    },
+    Insert {
+        obj: ObjId,
+        path: Vec<(ObjId, Prop)>,
+        index: usize,
+        values: SequenceTree<(Value<'static>, ObjId)>,
+    },
+    SpliceText {
+        obj: ObjId,
+        path: Vec<(ObjId, Prop)>,
+        index: usize,
+        value: SequenceTree<u16>,
+    },
+    Increment {
+        obj: ObjId,
+        path: Vec<(ObjId, Prop)>,
+        prop: Prop,
+        value: i64,
+    },
+    DeleteMap {
+        obj: ObjId,
+        path: Vec<(ObjId, Prop)>,
+        key: String,
+    },
+    DeleteSeq {
+        obj: ObjId,
+        path: Vec<(ObjId, Prop)>,
+        index: usize,
+        length: usize,
+    },
+}
+
+impl OpObserver for Observer {
+    fn insert<R: ReadDoc>(
+        &mut self,
+        doc: &R,
+        obj: ObjId,
+        index: usize,
+        tagged_value: (Value<'_>, ObjId),
+    ) {
+        if self.enabled {
+            let value = (tagged_value.0.to_owned(), tagged_value.1);
+            if let Some(Patch::Insert {
+                obj: tail_obj,
+                index: tail_index,
+                values,
+                ..
+            }) = self.patches.last_mut()
+            {
+                let range = *tail_index..=*tail_index + values.len();
+                if tail_obj == &obj && range.contains(&index) {
+                    values.insert(index - *tail_index, value);
+                    return;
+                }
+            }
+            if let Some(path) = self.get_path(doc, &obj) {
+                let mut values = SequenceTree::new();
+                values.push(value);
+                let patch = Patch::Insert {
+                    path,
+                    obj,
+                    index,
+                    values,
+                };
+                self.patches.push(patch);
+            }
+        }
+    }
+
+    fn splice_text<R: ReadDoc>(&mut self, doc: &R, obj: ObjId, index: usize, value: &str) {
+        if self.enabled {
+            if self.text_rep == TextRepresentation::Array {
+                for (i, c) in value.chars().enumerate() {
+                    self.insert(
+                        doc,
+                        obj.clone(),
+                        index + i,
+                        (
+                            Value::Scalar(Cow::Owned(ScalarValue::Str(c.to_string().into()))),
+                            ObjId::Root, // We hope this is okay
+                        ),
+                    );
+                }
+                return;
+            }
+            if let Some(Patch::SpliceText {
+                obj: tail_obj,
+                index: tail_index,
+                value: prev_value,
+                ..
+            }) = self.patches.last_mut()
+            {
+                let range = *tail_index..=*tail_index + prev_value.len();
+                if tail_obj == &obj && range.contains(&index) {
+                    let i = index - *tail_index;
+                    for (n, ch) in value.encode_utf16().enumerate() {
+                        prev_value.insert(i + n, ch)
+                    }
+                    return;
+                }
+            }
+            if let Some(path) = self.get_path(doc, &obj) {
+                let mut v = SequenceTree::new();
+                for ch in value.encode_utf16() {
+                    v.push(ch)
+                }
+                let patch = Patch::SpliceText {
+                    path,
+                    obj,
+                    index,
+                    value: v,
+                };
+                self.patches.push(patch);
+            }
+        }
+    }
+
+    fn delete_seq<R: ReadDoc>(&mut self, doc: &R, obj: ObjId, index: usize, length: usize) {
+        if self.enabled {
+            match self.patches.last_mut() {
+                Some(Patch::SpliceText {
+                    obj: tail_obj,
+                    index: tail_index,
+                    value,
+                    ..
+                }) => {
+                    let range = *tail_index..*tail_index + value.len();
+                    if tail_obj == &obj
+                        && range.contains(&index)
+                        && range.contains(&(index + length - 1))
+                    {
+                        for _ in 0..length {
+                            value.remove(index - *tail_index);
+                        }
+                        return;
+                    }
+                }
+                Some(Patch::Insert {
+                    obj: tail_obj,
+                    index: tail_index,
+                    values,
+                    ..
+                }) => {
+                    let range = *tail_index..*tail_index + values.len();
+                    if tail_obj == &obj
+                        && range.contains(&index)
+                        && range.contains(&(index + length - 1))
+                    {
+                        for _ in 0..length {
+                            values.remove(index - *tail_index);
+                        }
+                        return;
+                    }
+                }
+                Some(Patch::DeleteSeq {
+                    obj: tail_obj,
+                    index: tail_index,
+                    length: tail_length,
+                    ..
+                }) => {
+                    if tail_obj == &obj && index == *tail_index {
+                        *tail_length += length;
+                        return;
+                    }
+                }
+                _ => {}
+            }
+            if let Some(path) = self.get_path(doc, &obj) {
+                let patch = Patch::DeleteSeq {
+                    path,
+                    obj,
+                    index,
+                    length,
+                };
+                self.patches.push(patch)
+            }
+        }
+    }
+
+    fn delete_map<R: ReadDoc>(&mut self, doc: &R, obj: ObjId, key: &str) {
+        if self.enabled {
+            if let Some(path) = self.get_path(doc, &obj) {
+                let patch = Patch::DeleteMap {
+                    path,
+                    obj,
+                    key: key.to_owned(),
+                };
+                self.patches.push(patch)
+            }
+        }
+    }
+
+    fn put<R: ReadDoc>(
+        &mut self,
+        doc: &R,
+        obj: ObjId,
+        prop: Prop,
+        tagged_value: (Value<'_>, ObjId),
+        _conflict: bool,
+    ) {
+        if self.enabled {
+            let expose = false;
+            if let Some(path) = self.get_path(doc, &obj) {
+                let value = (tagged_value.0.to_owned(), tagged_value.1);
+                let patch = match prop {
+                    Prop::Map(key) => Patch::PutMap {
+                        path,
+                        obj,
+                        key,
+                        value,
+                        expose,
+                    },
+                    Prop::Seq(index) => Patch::PutSeq {
+                        path,
+                        obj,
+                        index,
+                        value,
+                        expose,
+                    },
+                };
+                self.patches.push(patch);
+            }
+        }
+    }
+
+    fn expose<R: ReadDoc>(
+        &mut self,
+        doc: &R,
+        obj: ObjId,
+        prop: Prop,
+        tagged_value: (Value<'_>, ObjId),
+        _conflict: bool,
+    ) {
+        if self.enabled {
+            let expose = true;
+            if let Some(path) = self.get_path(doc, &obj) {
+                let value = (tagged_value.0.to_owned(), tagged_value.1);
+                let patch = match prop {
+                    Prop::Map(key) => Patch::PutMap {
+                        path,
+                        obj,
+                        key,
+                        value,
+                        expose,
+                    },
+                    Prop::Seq(index) => Patch::PutSeq {
+                        path,
+                        obj,
+                        index,
+                        value,
+                        expose,
+                    },
+                };
+                self.patches.push(patch);
+            }
+        }
+    }
+
+    fn increment<R: ReadDoc>(
+        &mut self,
+        doc: &R,
+        obj: ObjId,
+        prop: Prop,
+        tagged_value: (i64, ObjId),
+    ) {
+        if self.enabled {
+            if let Some(path) = self.get_path(doc, &obj) {
+                let value = tagged_value.0;
+                self.patches.push(Patch::Increment {
+                    path,
+                    obj,
+                    prop,
+                    value,
+                })
+            }
+        }
+    }
+
+    fn text_as_seq(&self) -> bool {
+        self.text_rep == TextRepresentation::Array
+    }
+}
+
+impl automerge::op_observer::BranchableObserver for Observer {
+    fn merge(&mut self, other: &Self) {
+        self.patches.extend_from_slice(other.patches.as_slice())
+    }
+
+    fn branch(&self) -> Self {
+        Observer {
+            patches: vec![],
+            enabled: self.enabled,
+            text_rep: self.text_rep,
+        }
+    }
+}
+
+fn prop_to_js(p: &Prop) -> JsValue {
+    match p {
+        Prop::Map(key) => JsValue::from_str(key),
+        Prop::Seq(index) => JsValue::from_f64(*index as f64),
+    }
+}
+
+fn export_path(path: &[(ObjId, Prop)], end: &Prop) -> Array {
+    let result = Array::new();
+    for p in path {
+        result.push(&prop_to_js(&p.1));
+    }
+    result.push(&prop_to_js(end));
+    result
+}
+
+impl Patch {
+    pub(crate) fn path(&self) -> &[(ObjId, Prop)] {
+        match &self {
+            Self::PutMap { path, .. } => path.as_slice(),
+            Self::PutSeq { path, .. } => path.as_slice(),
+            Self::Increment { path, .. } => path.as_slice(),
+            Self::Insert { path, .. } => path.as_slice(),
+            Self::SpliceText { path, .. } => path.as_slice(),
+            Self::DeleteMap { path, .. } => path.as_slice(),
+            Self::DeleteSeq { path, .. } => path.as_slice(),
+        }
+    }
+
+    pub(crate) fn obj(&self) -> &ObjId {
+        match &self {
+            Self::PutMap { obj, .. } => obj,
+            Self::PutSeq { obj, .. } => obj,
+            Self::Increment { obj, .. } => obj,
+            Self::Insert { obj, .. } => obj,
+            Self::SpliceText { obj, .. } => obj,
+            Self::DeleteMap { obj, .. } => obj,
+            Self::DeleteSeq { obj, .. } => obj,
+        }
+    }
+}
+
+impl TryFrom<Patch> for JsValue {
+    type Error = interop::error::Export;
+
+    fn try_from(p: Patch) -> Result<Self, Self::Error> {
+        let result = Object::new();
+        match p {
+            Patch::PutMap {
+                path, key, value, ..
+            } => {
+                js_set(&result, "action", "put")?;
+                js_set(
+                    &result,
+                    "path",
+                    export_path(path.as_slice(), &Prop::Map(key)),
+                )?;
+                js_set(
+                    &result,
+                    "value",
+                    alloc(&value.0, TextRepresentation::String).1,
+                )?;
+                Ok(result.into())
+            }
+            Patch::PutSeq {
+                path, index, value, ..
+            } => {
+                js_set(&result, "action", "put")?;
+                js_set(
+                    &result,
+                    "path",
+                    export_path(path.as_slice(), &Prop::Seq(index)),
+                )?;
+                js_set(
+                    &result,
+                    "value",
+                    alloc(&value.0, TextRepresentation::String).1,
+                )?;
+                Ok(result.into())
+            }
+            Patch::Insert {
+                path,
+                index,
+                values,
+                ..
+            } => {
+                js_set(&result, "action", "insert")?;
+                js_set(
+                    &result,
+                    "path",
+                    export_path(path.as_slice(), &Prop::Seq(index)),
+                )?;
+                js_set(
+                    &result,
+                    "values",
+                    values
+                        .iter()
+                        .map(|v| alloc(&v.0, TextRepresentation::String).1)
+                        .collect::<Array>(),
+                )?;
+                Ok(result.into())
+            }
+            Patch::SpliceText {
+                path, index, value, ..
+            } => {
+                js_set(&result, "action", "splice")?;
+                js_set(
+                    &result,
+                    "path",
+                    export_path(path.as_slice(), &Prop::Seq(index)),
+                )?;
+                let bytes: Vec<u16> = value.iter().cloned().collect();
+                js_set(&result, "value", String::from_utf16_lossy(bytes.as_slice()))?;
+                Ok(result.into())
+            }
+            Patch::Increment {
+                path, prop, value, ..
+            } => {
+                js_set(&result, "action", "inc")?;
+                js_set(&result, "path", export_path(path.as_slice(), &prop))?;
+                js_set(&result, "value", &JsValue::from_f64(value as f64))?;
+                Ok(result.into())
+            }
+            Patch::DeleteMap { path, key, .. } => {
+                js_set(&result, "action", "del")?;
+                js_set(
+                    &result,
+                    "path",
+                    export_path(path.as_slice(), &Prop::Map(key)),
+                )?;
+                Ok(result.into())
+            }
+            Patch::DeleteSeq {
+                path,
+                index,
+                length,
+                ..
+            } => {
+                js_set(&result, "action", "del")?;
+                js_set(
+                    &result,
+                    "path",
+                    export_path(path.as_slice(), &Prop::Seq(index)),
+                )?;
+                if length > 1 {
+                    js_set(&result, "length", length)?;
+                }
+                Ok(result.into())
+            }
+        }
+    }
+}
diff --git a/rust/automerge-wasm/test/marks.ts b/rust/automerge-wasm/test/marks.ts
deleted file mode 100644
index 0a2d4433..00000000
--- a/rust/automerge-wasm/test/marks.ts
+++ /dev/null
@@ -1,572 +0,0 @@
-import { describe, it } from 'mocha';
-//@ts-ignore
-import assert from 'assert'
-//@ts-ignore
-import { create, load, Automerge, encodeChange, decodeChange } from '..'
-import { v4 as uuid } from "uuid"
-
-
-let util = require('util')
-
-describe('Automerge', () => {
-  describe('marks', () => {
-    it('should handle marks [..]', () => {
-      let doc = create(true)
-      let list = doc.putObject("_root", "list", "")
-      doc.splice(list, 0, 0, "aaabbbccc")
-      doc.mark(list, "[3..6]", "bold" , true)
-      let text = doc.text(list)
-      let marks = doc.marks(list);
-      assert.deepStrictEqual(marks, [{ name: 'bold', value: true, start: 3, end: 6 }])
-      doc.insert(list, 6, "A")
-      doc.insert(list, 3, "A")
-      marks = doc.marks(list);
-      assert.deepStrictEqual(marks, [{ name: 'bold', value: true, start: 4, end: 7 }])
-    })
-
-    it('should handle mark and unmark', () => {
-      let doc = create(true)
-      let list = doc.putObject("_root", "list", "")
-      doc.splice(list, 0, 0, "aaabbbccc")
-      doc.mark(list, "[2..8]", "bold" , true)
-      let marks = doc.marks(list);
-      assert.deepStrictEqual(marks, [{ name: 'bold', value: true, start: 2, end: 8 }])
-      doc.unmark(list, 'bold', 4, 6)
-      doc.insert(list, 7, "A")
-      doc.insert(list, 3, "A")
-      marks = doc.marks(list);
-      assert.deepStrictEqual(marks, [
-        { name: 'bold', value: true, start: 2, end: 5 },
-        { name: 'bold', value: true, start: 7, end: 10 },
-      ])
-    })
-
-    it('should handle mark and unmark of overlapping marks', () => {
-      let doc = create(true)
-      let list = doc.putObject("_root", "list", "")
-      doc.splice(list, 0, 0, "aaabbbccc")
-      doc.mark(list, "[2..6]", "bold" , true)
-      doc.mark(list, "[5..8]", "bold" , true)
-      doc.mark(list, "[3..6]", "underline" , true)
-      let marks = doc.marks(list);
-      assert.deepStrictEqual(marks, [
-        { name: 'underline', value: true, start: 3, end: 6 },
-        { name: 'bold', value: true, start: 2, end: 8 },
-      ])
-      doc.unmark(list, 'bold', 4, 6)
-      doc.insert(list, 7, "A")
-      doc.insert(list, 3, "A")
-      marks = doc.marks(list);
-      assert.deepStrictEqual(marks, [
-        { name: 'bold', value: true, start: 2, end: 5 },
-        { name: 'underline', value: true, start: 4, end: 7 },
-        { name: 'bold', value: true, start: 7, end: 10 },
-      ])
-      doc.unmark(list, 'bold', 0, 11)
-      marks = doc.marks(list);
-      assert.deepStrictEqual(marks, [
-        { name: 'underline', value: true, start: 4, end: 7 }
-      ])
-    })
-
-    it('should handle marks [..] at the beginning of a string', () => {
-      let doc = create(true)
-      let list = doc.putObject("_root", "list", "")
-      doc.splice(list, 0, 0, "aaabbbccc")
-      doc.mark(list, "[0..3]", "bold", true)
-      let marks = doc.marks(list);
-      assert.deepStrictEqual(marks, [{ name: 'bold', value: true, start: 0, end: 3 }])
-
-      let doc2 = doc.fork()
-      doc2.insert(list, 0, "A")
-      doc2.insert(list, 4, "B")
-      doc.merge(doc2)
-      marks = doc.marks(list);
-      assert.deepStrictEqual(marks, [{ name: 'bold', value: true, start: 1, end: 4 }])
-    })
-
-    it('should handle marks [..] with splice', () => {
-      let doc = create(true)
-      let list = doc.putObject("_root", "list", "")
-      doc.splice(list, 0, 0, "aaabbbccc")
-      doc.mark(list, "[0..3]", "bold", true)
-      let marks = doc.marks(list);
-      assert.deepStrictEqual(marks, [{ name: 'bold', value: true, start: 0, end: 3 }])
-
-      let doc2 = doc.fork()
-      doc2.splice(list, 0, 2, "AAA")
-      doc2.splice(list, 4, 0, "BBB")
-      doc.merge(doc2)
-      marks = doc.marks(list);
-      assert.deepStrictEqual(marks, [{ name: 'bold', value: true, start: 3, end: 4 }])
-    })
-
-    it('should handle marks across multiple forks', () => {
-      let doc = create(true)
-      let list = doc.putObject("_root", "list", "")
-      doc.splice(list, 0, 0, "aaabbbccc")
-      doc.mark(list, "[0..3]", "bold", true)
-      let marks = doc.marks(list);
-      assert.deepStrictEqual(marks, [{ name: 'bold', value: true, start: 0, end: 3 }])
-
-      let doc2 = doc.fork()
-      doc2.splice(list, 1, 1, "Z") // replace 'aaa' with 'aZa' inside mark.
-
-      let doc3 = doc.fork()
-      doc3.insert(list, 0, "AAA") // should not be included in mark.
-
-      doc.merge(doc2)
-      doc.merge(doc3)
-
-      marks = doc.marks(list);
-      assert.deepStrictEqual(marks, [{ name: 'bold', value: true, start: 3, end: 6 }])
-    })
-
-    it('should handle marks with deleted ends [..]', () => {
-      let doc = create(true)
-      let list = doc.putObject("_root", "list", "")
-
-      doc.splice(list, 0, 0, "aaabbbccc")
-      doc.mark(list, "[3..6]", "bold" , true)
-      let marks = doc.marks(list);
-      assert.deepStrictEqual(marks, [{ name: 'bold', value: true, start: 3, end: 6 }])
-      doc.delete(list,5);
-      doc.delete(list,5);
-      doc.delete(list,2);
-      doc.delete(list,2);
-      marks = doc.marks(list);
-      assert.deepStrictEqual(marks, [{ name: 'bold', value: true, start: 2, end: 3 }])
-      doc.insert(list, 3, "A")
-      doc.insert(list, 2, "A")
-      marks = doc.marks(list);
-      assert.deepStrictEqual(marks, [{ name: 'bold', value: true, start: 3, end: 4 }])
-    })
-
-    it('should handle sticky marks (..)', () => {
-      let doc = create(true)
-      let list = doc.putObject("_root", "list", "")
-      doc.splice(list, 0, 0, "aaabbbccc")
-      doc.mark(list, "(3..6)", "bold" , true)
-      let marks = doc.marks(list);
-      assert.deepStrictEqual(marks, [{ name: 'bold', value: true, start: 3, end: 6 }])
-      doc.insert(list, 6, "A")
-      doc.insert(list, 3, "A")
-      marks = doc.marks(list);
-      assert.deepStrictEqual(marks, [{ name: 'bold', value: true, start: 3, end: 8 }])
-    })
-
-    it('should handle sticky marks with deleted ends (..)', () => {
-      let doc = create(true)
-      let list = doc.putObject("_root", "list", "")
-      doc.splice(list, 0, 0, "aaabbbccc")
-      doc.mark(list, "(3..6)", "bold" , true)
-      let marks = doc.marks(list);
-      assert.deepStrictEqual(marks, [{ name: 'bold', value: true, start: 3, end: 6 }])
-      doc.delete(list,5);
-      doc.delete(list,5);
-      doc.delete(list,2);
-      doc.delete(list,2);
-      marks = doc.marks(list);
-      assert.deepStrictEqual(marks, [{ name: 'bold', value: true, start: 2, end: 3 }])
-      doc.insert(list, 3, "A")
-      doc.insert(list, 2, "A")
-      marks = doc.marks(list);
-      assert.deepStrictEqual(marks, [{ name: 'bold', value: true, start: 2, end: 5 }])
-
-      // make sure save/load can handle marks
-
-      let saved = doc.save()
-      let doc2 = load(saved,true)
-      marks = doc2.marks(list);
-      assert.deepStrictEqual(marks, [{ name: 'bold', value: true, start: 2, end: 5 }])
-
-      assert.deepStrictEqual(doc.getHeads(), doc2.getHeads())
-      assert.deepStrictEqual(doc.save(), doc2.save())
-    })
-
-    it('should handle overlapping marks', () => {
-      let doc : Automerge = create(true, "aabbcc")
-      let list = doc.putObject("_root", "list", "")
-      doc.splice(list, 0, 0, "the quick fox jumps over the lazy dog")
-      doc.mark(list, "[0..37]", "bold" , true)
-      doc.mark(list, "[4..19]", "itallic" , true)
-      let id = uuid(); // we want each comment to be unique so give it a unique id
-      doc.mark(list, "[10..13]", `comment:${id}` , "foxes are my favorite animal!")
-      doc.commit("marks");
-      let marks = doc.marks(list);
-      assert.deepStrictEqual(marks, [
-        { name: `comment:${id}`, start: 10, end: 13,  value: 'foxes are my favorite animal!' },
-        { name: 'itallic', start: 4, end: 19, value: true },
-        { name: 'bold', start: 0, end: 37, value: true }
-      ])
-      let text = doc.text(list);
-      assert.deepStrictEqual(text, "the quick fox jumps over the lazy dog");
-
-      let all = doc.getChanges([])
-      let decoded = all.map((c) => decodeChange(c))
-      let util = require('util');
-      let encoded = decoded.map((c) => encodeChange(c))
-      let decoded2 = encoded.map((c) => decodeChange(c))
-      let doc2 = create(true);
-      doc2.applyChanges(encoded)
-
-      assert.deepStrictEqual(doc.marks(list) , doc2.marks(list))
-      assert.deepStrictEqual(doc.save(), doc2.save())
-    })
-
-    it('generates patches for marks made locally', () => {
-      let doc : Automerge = create(true, "aabbcc")
-      doc.enablePatches(true)
-      let list = doc.putObject("_root", "list", "")
-      doc.splice(list, 0, 0, "the quick fox jumps over the lazy dog")
-      let h1 = doc.getHeads()
-      doc.mark(list, "[0..37]", "bold" , true)
-      doc.mark(list, "[4..19]", "itallic" , true)
-      let id = uuid(); // we want each comment to be unique so give it a unique id
-      doc.mark(list, "[10..13]", `comment:${id}` , "foxes are my favorite animal!")
-      doc.commit("marks");
-      let h2 = doc.getHeads()
-      let patches = doc.popPatches();
-      let util = require('util')
-      assert.deepEqual(patches, [
-        { action: 'put', path: [ 'list' ], value: '' },
-        {
-          action: 'splice', path: [ 'list', 0 ],
-          value: 'the quick fox jumps over the lazy dog'
-        },
-        {
-          action: 'mark', path: [ 'list' ],
-          marks: [
-            { name: 'bold', value: true, start: 0, end: 37  },
-            { name: 'itallic', value: true, start: 4, end: 19 },
-            { name: `comment:${id}`, value: 'foxes are my favorite animal!', start: 10, end: 13 }
-          ]
-        }
-      ]);
-    })
-
-    it('marks should create patches that respect marks that supersede it', () => {
-
-      let doc1 : Automerge = create(true, "aabbcc")
-      let list = doc1.putObject("_root", "list", "")
-      doc1.splice(list, 0, 0, "the quick fox jumps over the lazy dog")
-
-      let doc2 = load(doc1.save(),true);
-
-      let doc3 = load(doc1.save(),true);
-      doc3.enablePatches(true)
-
-      doc1.put("/","foo", "bar"); // make a change to our op counter is higher than doc2
-      doc1.mark(list, "[0..5]", "x", "a")
-      doc1.mark(list, "[8..11]", "x", "b")
-
-      doc2.mark(list, "[4..13]", "x", "c");
-
-      doc3.merge(doc1)
-      doc3.merge(doc2)
-
-      let patches = doc3.popPatches();
-
-      assert.deepEqual(patches, [
-          { action: 'put', path: [ 'foo' ], value: 'bar' },
-          {
-            action: 'mark',
-            path: [ 'list' ],
-            marks: [
-              { name: 'x', value: 'a', start: 0, end: 5 },
-              { name: 'x', value: 'b', start: 8, end: 11 },
-              { name: 'x', value: 'c', start: 5, end: 8 },
-              { name: 'x', value: 'c', start: 11, end: 13 },
-            ]
-          },
-        ]);
-    })
-  })
-  describe('loading marks', () => {
-    it('a mark will appear on load', () => {
-      let doc1 : Automerge = create(true, "aabbcc")
-      doc1.enablePatches(true)
-
-      let list = doc1.putObject("_root", "list", "")
-      doc1.splice(list, 0, 0, "the quick fox jumps over the lazy dog")
-      doc1.mark(list, "[5..10]", "xxx", "aaa")
-
-      let patches1 = doc1.popPatches().filter((p:any) => p.action == "mark")
-
-      assert.deepEqual(patches1, [{
-        action: 'mark', path: [ 'list' ], marks: [ { name: 'xxx', value: 'aaa', start: 5, end: 10 }],
-      }]);
-
-      let doc2 : Automerge = create(true);
-      doc2.enablePatches(true)
-      doc2.loadIncremental(doc1.save())
-
-      let patches2 = doc2.popPatches().filter((p:any) => p.action == "mark")
-
-      assert.deepEqual(patches2, [{
-        action: 'mark', path: ['list'], marks: [ { name: 'xxx', value: 'aaa', start: 5, end: 10}],
-      }]);
-    })
-
-    it('a overlapping marks will coalesse on load', () => {
-      let doc1 : Automerge = create(true, "aabbcc")
-      doc1.enablePatches(true)
-
-      let list = doc1.putObject("_root", "list", "")
-      doc1.splice(list, 0, 0, "the quick fox jumps over the lazy dog")
-      doc1.mark(list, "[5..15]", "xxx", "aaa")
-      doc1.mark(list, "[10..20]", "xxx", "aaa")
-      doc1.mark(list, "[15..25]", "xxx", "aaa")
-
-      let patches1 = doc1.popPatches().filter((p:any) => p.action == "mark")
-
-      assert.deepEqual(patches1, [
-        { action: 'mark', path: [ 'list' ], marks: [
-          { name: 'xxx', value: 'aaa', start: 5, end: 15 },
-          { name: 'xxx', value: 'aaa', start: 10, end: 20 },
-          { name: 'xxx', value: 'aaa', start: 15, end: 25 },
-        ] },
-      ]);
-
-      let doc2 : Automerge = create(true);
-      doc2.enablePatches(true)
-      doc2.loadIncremental(doc1.save())
-
-      let patches2 = doc2.popPatches().filter((p:any) => p.action == "mark")
-
-      assert.deepEqual(patches2, [
-        { action: 'mark', path: ['list'], marks: [ { name: 'xxx', value: 'aaa', start: 5, end: 25}] },
-      ]);
-    })
-
-    it('coalesse handles different values', () => {
-      let doc1 : Automerge = create(true, "aabbcc")
-      doc1.enablePatches(true)
-
-      let list = doc1.putObject("_root", "list", "")
-      doc1.splice(list, 0, 0, "the quick fox jumps over the lazy dog")
-      doc1.mark(list, "[5..15]", "xxx", "aaa")
-      doc1.mark(list, "[10..20]", "xxx", "bbb")
-      doc1.mark(list, "[15..25]", "xxx", "aaa")
-
-      let patches1 = doc1.popPatches().filter((p:any) => p.action == "mark")
-
-      assert.deepEqual(patches1, [
-        { action: 'mark', path: [ 'list' ], marks: [
-          { name: 'xxx', value: 'aaa', start: 5, end: 15 },
-          { name: 'xxx', value: 'bbb', start: 10, end: 20 },
-          { name: 'xxx', value: 'aaa', start: 15, end: 25 },
-        ]}
-      ]);
-
-      let doc2 : Automerge = create(true);
-      doc2.enablePatches(true)
-      doc2.loadIncremental(doc1.save())
-
-      let patches2 = doc2.popPatches().filter((p:any) => p.action == "mark")
-
-      assert.deepEqual(patches2, [
-        { action: 'mark', path: ['list'], marks: [
-          { name: 'xxx', value: 'aaa', start: 5, end: 10 },
-          { name: 'xxx', value: 'bbb', start: 10, end: 15 },
-          { name: 'xxx', value: 'aaa', start: 15, end: 25 },
-        ]},
-      ]);
-    })
-
-    it('wont coalesse handles different names', () => {
-      let doc1 : Automerge = create(true, "aabbcc")
-      doc1.enablePatches(true)
-
-      let list = doc1.putObject("_root", "list", "")
-      doc1.splice(list, 0, 0, "the quick fox jumps over the lazy dog")
-      doc1.mark(list, "[5..15]", "xxx", "aaa")
-      doc1.mark(list, "[10..20]", "yyy", "aaa")
-      doc1.mark(list, "[15..25]", "zzz", "aaa")
-
-      let patches1 = doc1.popPatches().filter((p:any) => p.action == "mark")
-
-      assert.deepEqual(patches1, [
-        { action: 'mark', path: [ 'list' ], marks: [
-          { name: 'xxx', value: 'aaa', start: 5, end:15 },
-          { name: 'yyy', value: 'aaa', start: 10, end: 20 },
-          { name: 'zzz', value: 'aaa', start: 15, end: 25 },
-          ]}
-      ]);
-
-      let doc2 : Automerge = create(true);
-      doc2.enablePatches(true)
-      doc2.loadIncremental(doc1.save())
-
-      let patches2 = doc2.popPatches().filter((p:any) => p.action == "mark")
-
-      assert.deepEqual(patches2, [
-        { action: 'mark', path: [ 'list' ], marks: [
-          { name: 'xxx', value: 'aaa', start: 5, end: 15 },
-          { name: 'yyy', value: 'aaa', start: 10, end: 20 },
-          { name: 'zzz', value: 'aaa', start: 15, end: 25 },
-        ]}
-      ]);
-    })
-
-    it('coalesse handles async merge', () => {
-      let doc1 : Automerge = create(true, "aabbcc")
-      doc1.enablePatches(true)
-
-      let list = doc1.putObject("_root", "list", "")
-      doc1.splice(list, 0, 0, "the quick fox jumps over the lazy dog")
-
-      let doc2 = doc1.fork()
-
-      doc1.put("/", "key1", "value"); // incrementing op counter so we win vs doc2
-      doc1.put("/", "key2", "value"); // incrementing op counter so we win vs doc2
-      doc1.mark(list, "[10..20]", "xxx", "aaa")
-      doc1.mark(list, "[15..25]", "xxx", "aaa")
-
-      doc2.mark(list, "[5..30]" , "xxx", "bbb")
-
-      doc1.merge(doc2)
-
-      let patches1 = doc1.popPatches().filter((p:any) => p.action == "mark")
-
-      assert.deepEqual(patches1, [
-        { action: 'mark', path: [ 'list' ], marks: [
-            { name: 'xxx', value: 'aaa', start: 10, end: 20 },
-            { name: 'xxx', value: 'aaa', start: 15, end: 25 },
-            { name: 'xxx', value: 'bbb', start: 5, end: 10 },
-            { name: 'xxx', value: 'bbb', start: 25, end: 30 },
-          ]
-        },
-      ]);
-
-      let doc3 : Automerge = create(true);
-      doc3.enablePatches(true)
-      doc3.loadIncremental(doc1.save())
-
-      let patches2 = doc3.popPatches().filter((p:any) => p.action == "mark")
-
-      let marks = doc3.marks(list)
-
-      assert.deepEqual(marks, [
-          { name: 'xxx', value: 'bbb', start: 5, end: 10 },
-          { name: 'xxx', value: 'aaa', start: 10, end: 25 },
-          { name: 'xxx', value: 'bbb', start: 25, end: 30  },
-      ]);
-
-      assert.deepEqual(patches2, [{ action: 'mark', path: [ 'list' ], marks }]);
-    })
-
-    it('does not show marks hidden in merge', () => {
-      let doc1 : Automerge = create(true, "aabbcc")
-      doc1.enablePatches(true)
-
-      let list = doc1.putObject("_root", "list", "")
-      doc1.splice(list, 0, 0, "the quick fox jumps over the lazy dog")
-
-      let doc2 = doc1.fork()
-
-      doc1.put("/", "key1", "value"); // incrementing op counter so we win vs doc2
-      doc1.put("/", "key2", "value"); // incrementing op counter so we win vs doc2
-      doc1.mark(list, "[10..20]", "xxx", "aaa")
-      doc1.mark(list, "[15..25]", "xxx", "aaa")
-
-      doc2.mark(list, "[11..24]" , "xxx", "bbb")
-
-      doc1.merge(doc2)
-
-      let patches1 = doc1.popPatches().filter((p:any) => p.action == "mark")
-
-      assert.deepEqual(patches1, [
-        { action: 'mark', path: [ 'list' ], marks: [
-            { name: 'xxx', value: 'aaa', start: 10, end: 20 },
-            { name: 'xxx', value: 'aaa', start: 15, end: 25 },
-          ]
-        },
-      ]);
-
-      let doc3 : Automerge = create(true);
-      doc3.enablePatches(true)
-      doc3.loadIncremental(doc1.save())
-
-      let patches2 = doc3.popPatches().filter((p:any) => p.action == "mark")
-
-      assert.deepEqual(patches2, [
-        { action: 'mark', path: [ 'list' ], marks: [
-          { name: 'xxx', value: 'aaa', start: 10, end: 25 },
-        ]}
-      ]);
-    })
-
-    it('coalesse disconnected marks with async merge', () => {
-      let doc1 : Automerge = create(true, "aabbcc")
-      doc1.enablePatches(true)
-
-      let list = doc1.putObject("_root", "list", "")
-      doc1.splice(list, 0, 0, "the quick fox jumps over the lazy dog")
-
-      let doc2 = doc1.fork()
-
-      doc1.put("/", "key1", "value"); // incrementing op counter so we win vs doc2
-      doc1.put("/", "key2", "value"); // incrementing op counter so we win vs doc2
-      doc1.mark(list, "[5..11]", "xxx", "aaa")
-      doc1.mark(list, "[19..25]", "xxx", "aaa")
-
-      doc2.mark(list, "[10..20]" , "xxx", "aaa")
-
-      doc1.merge(doc2)
-
-      let patches1 = doc1.popPatches().filter((p:any) => p.action == "mark")
-
-      assert.deepEqual(patches1, [
-        { action: 'mark', path: [ 'list' ], marks: [
-            { name: 'xxx', value: 'aaa', start: 5, end: 11 },
-            { name: 'xxx', value: 'aaa', start: 19, end: 25 },
-            { name: 'xxx', value: 'aaa', start: 11, end: 19 },
-          ]
-        },
-      ]);
-
-      let doc3 : Automerge = create(true);
-      doc3.enablePatches(true)
-      doc3.loadIncremental(doc1.save())
-
-      let patches2 = doc3.popPatches().filter((p:any) => p.action == "mark")
-
-      assert.deepEqual(patches2, [
-        { action: 'mark', path: [ 'list' ], marks: [
-          { name: 'xxx', value: 'aaa', start: 5, end: 25 },
-        ]}
-      ]);
-    })
-    it('can get marks at a given heads', () => {
-      let doc1 : Automerge = create(true, "aabbcc")
-      doc1.enablePatches(true)
-
-      let list = doc1.putObject("_root", "list", "")
-      doc1.splice(list, 0, 0, "the quick fox jumps over the lazy dog")
-
-      let heads1 = doc1.getHeads();
-      let marks1 = doc1.marks(list);
-
-      doc1.mark(list, "[3..25]", "xxx", "aaa")
-
-      let heads2 = doc1.getHeads();
-      let marks2 = doc1.marks(list);
-
-      doc1.mark(list, "[4..11]", "yyy", "bbb")
-
-      let heads3 = doc1.getHeads();
-      let marks3 = doc1.marks(list);
-
-      doc1.unmark(list, "xxx", 9, 20)
-
-      let heads4 = doc1.getHeads();
-      let marks4 = doc1.marks(list);
-
-      assert.deepEqual(marks1, doc1.marks(list,heads1))
-      assert.deepEqual(marks2, doc1.marks(list,heads2))
-      assert.deepEqual(marks3, doc1.marks(list,heads3))
-      assert.deepEqual(marks4, doc1.marks(list,heads4))
-    })
-  })
-})
diff --git a/rust/automerge-wasm/test/test.ts b/rust/automerge-wasm/test/test.ts
index 3e57d92c..bb4f71e3 100644
--- a/rust/automerge-wasm/test/test.ts
+++ b/rust/automerge-wasm/test/test.ts
@@ -1941,40 +1941,6 @@ describe('Automerge', () => {
       assert.deepEqual(mat.text, "ab011ij")
     })
 
-    it('propogates exceptions thrown in patch callback', () => {
-      const doc = create(true)
-      doc.enablePatches(true)
-      let mat : any = doc.materialize("/")
-      doc.putObject("/", "text", "abcdefghij")
-      assert.throws(() => {
-        doc.applyPatches(mat, {}, (patches, info) => {
-          throw new RangeError("hello world")
-        })
-      }, /RangeError: hello world/)
-    })
-
-    it('patch callback has correct patch info', () => {
-      const doc = create(true)
-      let mat : any = doc.materialize("/")
-      doc.putObject("/", "text", "abcdefghij")
-
-      let before = doc.materialize("/")
-      let from = doc.getHeads()
-
-      doc.enablePatches(true)
-      doc.splice("/text", 2, 2, "00")
-
-      let after = doc.materialize("/")
-      let to = doc.getHeads()
-
-      doc.applyPatches(mat, {}, (patches, info) => {
-        assert.deepEqual(info.before, before);
-        assert.deepEqual(info.after, after);
-        assert.deepEqual(info.from, from);
-        assert.deepEqual(info.to, to);
-      })
-    })
-
     it('can handle utf16 text', () => {
       const doc = create(true)
       doc.enablePatches(true)
diff --git a/rust/automerge/examples/watch.rs b/rust/automerge/examples/watch.rs
index c2b909ee..4cd8f4ea 100644
--- a/rust/automerge/examples/watch.rs
+++ b/rust/automerge/examples/watch.rs
@@ -1,11 +1,11 @@
-use automerge::op_observer::HasPatches;
 use automerge::transaction::CommitOptions;
 use automerge::transaction::Transactable;
 use automerge::Automerge;
 use automerge::AutomergeError;
+use automerge::Patch;
+use automerge::ReadDoc;
 use automerge::VecOpObserver;
 use automerge::ROOT;
-use automerge::{Patch, PatchAction};
 
 fn main() {
     let mut doc = Automerge::new();
@@ -42,52 +42,64 @@ fn main() {
     get_changes(&doc, patches);
 }
 
-fn get_changes(_doc: &Automerge, patches: Vec<Patch<char>>) {
-    for Patch { obj, path, action } in patches {
-        match action {
-            PatchAction::PutMap { key, value, .. } => {
+fn get_changes(doc: &Automerge, patches: Vec<Patch>) {
+    for patch in patches {
+        match patch {
+            Patch::Put {
+                obj, prop, value, ..
+            } => {
                 println!(
                     "put {:?} at {:?} in obj {:?}, object path {:?}",
-                    value, key, obj, path,
+                    value,
+                    prop,
+                    obj,
+                    doc.path_to_object(&obj)
                 )
             }
-            PatchAction::PutSeq { index, value, .. } => {
-                println!(
-                    "put {:?} at {:?} in obj {:?}, object path {:?}",
-                    value, index, obj, path,
-                )
-            }
-            PatchAction::Insert { index, values, .. } => {
+            Patch::Insert {
+                obj, index, value, ..
+            } => {
                 println!(
                     "insert {:?} at {:?} in obj {:?}, object path {:?}",
-                    values, index, obj, path,
+                    value,
+                    index,
+                    obj,
+                    doc.path_to_object(&obj)
                 )
             }
-            PatchAction::SpliceText { index, value, .. } => {
+            Patch::Splice {
+                obj, index, value, ..
+            } => {
                 println!(
                     "splice '{:?}' at {:?} in obj {:?}, object path {:?}",
-                    value, index, obj, path,
+                    value,
+                    index,
+                    obj,
+                    doc.path_to_object(&obj)
                 )
             }
-            PatchAction::Increment { prop, value, .. } => {
+            Patch::Increment {
+                obj, prop, value, ..
+            } => {
                 println!(
                     "increment {:?} in obj {:?} by {:?}, object path {:?}",
-                    prop, obj, value, path,
+                    prop,
+                    obj,
+                    value,
+                    doc.path_to_object(&obj)
                 )
             }
-            PatchAction::DeleteMap { key, .. } => {
-                println!("delete {:?} in obj {:?}, object path {:?}", key, obj, path,)
-            }
-            PatchAction::DeleteSeq { index, .. } => println!(
+            Patch::Delete { obj, prop, .. } => println!(
                 "delete {:?} in obj {:?}, object path {:?}",
-                index, obj, path,
+                prop,
+                obj,
+                doc.path_to_object(&obj)
             ),
-            PatchAction::Mark { marks } => {
-                println!("mark {:?} in obj {:?}, object path {:?}", marks, obj, path,)
-            }
-            PatchAction::Unmark { name, start, end } => println!(
-                "unmark {:?} from {} to {} in obj {:?}, object path {:?}",
-                name, start, end, obj, path,
+            Patch::Expose { obj, prop, .. } => println!(
+                "expose {:?} in obj {:?}, object path {:?}",
+                prop,
+                obj,
+                doc.path_to_object(&obj)
             ),
         }
     }
diff --git a/rust/automerge/src/autocommit.rs b/rust/automerge/src/autocommit.rs
index a5685f48..ae28596e 100644
--- a/rust/automerge/src/autocommit.rs
+++ b/rust/automerge/src/autocommit.rs
@@ -1,7 +1,6 @@
 use std::ops::RangeBounds;
 
 use crate::exid::ExId;
-use crate::marks::{ExpandMark, Mark};
 use crate::op_observer::{BranchableObserver, OpObserver};
 use crate::sync::SyncDoc;
 use crate::transaction::{CommitOptions, Transactable};
@@ -281,11 +280,6 @@ impl<Obs: Observation> AutoCommitWithObs<Obs> {
         self.doc.import(s)
     }
 
-    #[doc(hidden)]
-    pub fn import_obj(&self, s: &str) -> Result<ExId, AutomergeError> {
-        self.doc.import_obj(s)
-    }
-
     #[doc(hidden)]
     pub fn dump(&mut self) {
         self.ensure_transaction_closed();
@@ -447,18 +441,6 @@ impl<Obs: Observation> ReadDoc for AutoCommitWithObs<Obs> {
         self.doc.object_type(obj)
     }
 
-    fn marks<O: AsRef<ExId>>(&self, obj: O) -> Result<Vec<Mark<'_>>, AutomergeError> {
-        self.doc.marks(obj)
-    }
-
-    fn marks_at<O: AsRef<ExId>>(
-        &self,
-        obj: O,
-        heads: &[ChangeHash],
-    ) -> Result<Vec<Mark<'_>>, AutomergeError> {
-        self.doc.marks_at(obj, heads)
-    }
-
     fn text<O: AsRef<ExId>>(&self, obj: O) -> Result<String, AutomergeError> {
         self.doc.text(obj)
     }
@@ -639,42 +621,6 @@ impl<Obs: Observation> Transactable for AutoCommitWithObs<Obs> {
         )
     }
 
-    fn mark<O: AsRef<ExId>>(
-        &mut self,
-        obj: O,
-        mark: Mark<'_>,
-        expand: ExpandMark,
-    ) -> Result<(), AutomergeError> {
-        self.ensure_transaction_open();
-        let (current, tx) = self.transaction.as_mut().unwrap();
-        tx.mark(
-            &mut self.doc,
-            current.observer(),
-            obj.as_ref(),
-            mark,
-            expand,
-        )
-    }
-
-    fn unmark<O: AsRef<ExId>>(
-        &mut self,
-        obj: O,
-        key: &str,
-        start: usize,
-        end: usize,
-    ) -> Result<(), AutomergeError> {
-        self.ensure_transaction_open();
-        let (current, tx) = self.transaction.as_mut().unwrap();
-        tx.unmark(
-            &mut self.doc,
-            current.observer(),
-            obj.as_ref(),
-            key,
-            start,
-            end,
-        )
-    }
-
     fn base_heads(&self) -> Vec<ChangeHash> {
         self.doc.get_heads()
     }
diff --git a/rust/automerge/src/automerge.rs b/rust/automerge/src/automerge.rs
index c0fcfe28..0dd82253 100644
--- a/rust/automerge/src/automerge.rs
+++ b/rust/automerge/src/automerge.rs
@@ -4,13 +4,10 @@ use std::fmt::Debug;
 use std::num::NonZeroU64;
 use std::ops::RangeBounds;
 
-use itertools::Itertools;
-
 use crate::change_graph::ChangeGraph;
 use crate::columnar::Key as EncodedKey;
 use crate::exid::ExId;
 use crate::keys::Keys;
-use crate::marks::{Mark, MarkStateMachine};
 use crate::op_observer::{BranchableObserver, OpObserver};
 use crate::op_set::OpSet;
 use crate::parents::Parents;
@@ -19,13 +16,14 @@ use crate::transaction::{
     self, CommitOptions, Failure, Observed, Success, Transaction, TransactionArgs, UnObserved,
 };
 use crate::types::{
-    ActorId, ChangeHash, Clock, ElemId, Export, Exportable, Key, ListEncoding, MarkData, ObjId, Op,
-    OpId, OpType, ScalarValue, TextEncoding, Value,
+    ActorId, ChangeHash, Clock, ElemId, Export, Exportable, Key, ListEncoding, ObjId, Op, OpId,
+    OpType, ScalarValue, TextEncoding, Value,
 };
 use crate::{
     query, AutomergeError, Change, KeysAt, ListRange, ListRangeAt, MapRange, MapRangeAt, ObjType,
     Prop, ReadDoc, Values,
 };
+use serde::Serialize;
 
 mod current_state;
 
@@ -402,23 +400,11 @@ impl Automerge {
     pub(crate) fn exid_to_obj(&self, id: &ExId) -> Result<(ObjId, ObjType), AutomergeError> {
         match id {
             ExId::Root => Ok((ObjId::root(), ObjType::Map)),
-            ExId::Id(..) => {
-                let obj = ObjId(self.exid_to_opid(id)?);
-                if let Some(obj_type) = self.ops.object_type(&obj) {
-                    Ok((obj, obj_type))
-                } else {
-                    Err(AutomergeError::NotAnObject)
-                }
-            }
-        }
-    }
-
-    pub(crate) fn exid_to_opid(&self, id: &ExId) -> Result<OpId, AutomergeError> {
-        match id {
-            ExId::Root => Err(AutomergeError::Fail),
             ExId::Id(ctr, actor, idx) => {
-                if self.ops.m.actors.cache.get(*idx) == Some(actor) {
-                    Ok(OpId::new(*ctr, *idx))
+                // do a direct get here b/c this could be foriegn and not be within the array
+                // bounds
+                let obj = if self.ops.m.actors.cache.get(*idx) == Some(actor) {
+                    ObjId(OpId::new(*ctr, *idx))
                 } else {
                     // FIXME - make a real error
                     let idx = self
@@ -427,7 +413,12 @@ impl Automerge {
                         .actors
                         .lookup(actor)
                         .ok_or(AutomergeError::Fail)?;
-                    Ok(OpId::new(*ctr, idx))
+                    ObjId(OpId::new(*ctr, idx))
+                };
+                if let Some(obj_type) = self.ops.object_type(&obj) {
+                    Ok((obj, obj_type))
+                } else {
+                    Err(AutomergeError::NotAnObject)
                 }
             }
         }
@@ -732,12 +723,7 @@ impl Automerge {
                     obj,
                     Op {
                         id,
-                        action: OpType::from_action_and_value(
-                            c.action,
-                            c.val,
-                            c.mark_name,
-                            c.expand,
-                        ),
+                        action: OpType::from_action_and_value(c.action, c.val),
                         key,
                         succ: Default::default(),
                         pred,
@@ -927,21 +913,8 @@ impl Automerge {
 
     #[doc(hidden)]
     pub fn import(&self, s: &str) -> Result<(ExId, ObjType), AutomergeError> {
-        let obj = self.import_obj(s)?;
-        if obj == ExId::Root {
-            Ok((ExId::Root, ObjType::Map))
-        } else {
-            let obj_type = self
-                .object_type(&obj)
-                .map_err(|_| AutomergeError::InvalidObjId(s.to_owned()))?;
-            Ok((obj, obj_type))
-        }
-    }
-
-    #[doc(hidden)]
-    pub fn import_obj(&self, s: &str) -> Result<ExId, AutomergeError> {
         if s == "_root" {
-            Ok(ExId::Root)
+            Ok((ExId::Root, ObjType::Map))
         } else {
             let n = s
                 .find('@')
@@ -957,7 +930,10 @@ impl Automerge {
                 .lookup(&actor)
                 .ok_or_else(|| AutomergeError::InvalidObjId(s.to_owned()))?;
             let obj = ExId::Id(counter, self.ops.m.actors.cache[actor].clone(), actor);
-            Ok(obj)
+            let obj_type = self
+                .object_type(&obj)
+                .map_err(|_| AutomergeError::InvalidObjId(s.to_owned()))?;
+            Ok((obj, obj_type))
         }
     }
 
@@ -991,10 +967,6 @@ impl Automerge {
                 OpType::Make(obj) => format!("make({})", obj),
                 OpType::Increment(obj) => format!("inc({})", obj),
                 OpType::Delete => format!("del{}", 0),
-                OpType::MarkBegin(_, MarkData { name, value }) => {
-                    format!("mark({},{})", name, value)
-                }
-                OpType::MarkEnd(_) => "/mark".to_string(),
             };
             let pred: Vec<_> = op.pred.iter().map(|id| self.to_string(*id)).collect();
             let succ: Vec<_> = op.succ.into_iter().map(|id| self.to_string(*id)).collect();
@@ -1073,18 +1045,11 @@ impl Automerge {
         };
 
         if op.insert {
-            if op.is_mark() {
-                if let OpType::MarkEnd(_) = op.action {
-                    let q = self
-                        .ops
-                        .search(obj, query::SeekMark::new(op.id.prev(), pos, encoding));
-                    observer.mark(self, ex_obj, q.marks.into_iter());
-                }
-            } else if obj_type == Some(ObjType::Text) {
+            if obj_type == Some(ObjType::Text) {
                 observer.splice_text(self, ex_obj, seen, op.to_str());
             } else {
                 let value = (op.value(), self.ops.id_to_exid(op.id));
-                observer.insert(self, ex_obj, seen, value, false);
+                observer.insert(self, ex_obj, seen, value);
             }
         } else if op.is_delete() {
             if let Some(winner) = &values.last() {
@@ -1116,7 +1081,7 @@ impl Automerge {
                 .unwrap_or(false);
             let value = (op.value(), self.ops.id_to_exid(op.id));
             if op.is_list_op() && !had_value_before {
-                observer.insert(self, ex_obj, seen, value, false);
+                observer.insert(self, ex_obj, seen, value);
             } else if just_conflict {
                 observer.flag_conflict(self, ex_obj, key);
             } else {
@@ -1344,64 +1309,6 @@ impl ReadDoc for Automerge {
         Ok(buffer)
     }
 
-    fn marks<O: AsRef<ExId>>(&self, obj: O) -> Result<Vec<Mark<'_>>, AutomergeError> {
-        let (obj, obj_type) = self.exid_to_obj(obj.as_ref())?;
-        let encoding = ListEncoding::new(obj_type, self.text_encoding);
-        let ops_by_key = self.ops().iter_ops(&obj).group_by(|o| o.elemid_or_key());
-        let mut pos = 0;
-        let mut marks = MarkStateMachine::default();
-
-        Ok(ops_by_key
-            .into_iter()
-            .filter_map(|(_key, key_ops)| {
-                key_ops
-                    .filter(|o| o.visible_or_mark())
-                    .last()
-                    .and_then(|o| match &o.action {
-                        OpType::Make(_) | OpType::Put(_) => {
-                            pos += o.width(encoding);
-                            None
-                        }
-                        OpType::MarkBegin(_, data) => marks.mark_begin(o.id, pos, data, self),
-                        OpType::MarkEnd(_) => marks.mark_end(o.id, pos, self),
-                        OpType::Increment(_) | OpType::Delete => None,
-                    })
-            })
-            .collect())
-    }
-
-    fn marks_at<O: AsRef<ExId>>(
-        &self,
-        obj: O,
-        heads: &[ChangeHash],
-    ) -> Result<Vec<Mark<'_>>, AutomergeError> {
-        let (obj, obj_type) = self.exid_to_obj(obj.as_ref())?;
-        let clock = self.clock_at(heads);
-        let encoding = ListEncoding::new(obj_type, self.text_encoding);
-        let ops_by_key = self.ops().iter_ops(&obj).group_by(|o| o.elemid_or_key());
-        let mut window = query::VisWindow::default();
-        let mut pos = 0;
-        let mut marks = MarkStateMachine::default();
-
-        Ok(ops_by_key
-            .into_iter()
-            .filter_map(|(_key, key_ops)| {
-                key_ops
-                    .filter(|o| window.visible_at(o, pos, &clock))
-                    .last()
-                    .and_then(|o| match &o.action {
-                        OpType::Make(_) | OpType::Put(_) => {
-                            pos += o.width(encoding);
-                            None
-                        }
-                        OpType::MarkBegin(_, data) => marks.mark_begin(o.id, pos, data, self),
-                        OpType::MarkEnd(_) => marks.mark_end(o.id, pos, self),
-                        OpType::Increment(_) | OpType::Delete => None,
-                    })
-            })
-            .collect())
-    }
-
     fn get<O: AsRef<ExId>, P: Into<Prop>>(
         &self,
         obj: O,
@@ -1532,3 +1439,14 @@ impl Default for Automerge {
         Self::new()
     }
 }
+
+#[derive(Serialize, Debug, Clone, PartialEq)]
+pub(crate) struct SpanInfo {
+    pub(crate) id: ExId,
+    pub(crate) time: i64,
+    pub(crate) start: usize,
+    pub(crate) end: usize,
+    #[serde(rename = "type")]
+    pub(crate) span_type: String,
+    pub(crate) value: ScalarValue,
+}
diff --git a/rust/automerge/src/automerge/current_state.rs b/rust/automerge/src/automerge/current_state.rs
index bb741a76..3f7f4afc 100644
--- a/rust/automerge/src/automerge/current_state.rs
+++ b/rust/automerge/src/automerge/current_state.rs
@@ -1,27 +1,12 @@
-use std::borrow::Cow;
+use std::{borrow::Cow, collections::HashSet, iter::Peekable};
 
 use itertools::Itertools;
 
 use crate::{
-    marks::{Mark, MarkStateMachine},
-    types::{Key, ListEncoding, ObjId, Op, OpId, Prop},
-    Automerge, ObjType, OpObserver, OpType, Value,
+    types::{ElemId, Key, ListEncoding, ObjId, Op, OpId},
+    ObjType, OpObserver, OpType, ScalarValue, Value,
 };
 
-#[derive(Debug, Default)]
-struct TextState<'a> {
-    text: String,
-    len: usize,
-    marks: MarkStateMachine<'a>,
-    finished: Vec<Mark<'a>>,
-}
-
-struct Put<'a> {
-    value: Value<'a>,
-    key: Key,
-    id: OpId,
-}
-
 /// Traverse the "current" state of the document, notifying `observer`
 ///
 /// The "current" state of the document is the set of visible operations. This function will
@@ -32,8 +17,7 @@ struct Put<'a> {
 ///
 /// Due to only notifying of visible operations the observer will only be called with `put`,
 /// `insert`, and `splice`, operations.
-
-pub(crate) fn observe_current_state<O: OpObserver>(doc: &Automerge, observer: &mut O) {
+pub(super) fn observe_current_state<O: OpObserver>(doc: &crate::Automerge, observer: &mut O) {
     // The OpSet already exposes operations in the order they appear in the document.
     // `OpSet::iter_objs` iterates over the objects in causal order, this means that parent objects
     // will always appear before their children. Furthermore, the operations within each object are
@@ -42,170 +26,321 @@ pub(crate) fn observe_current_state<O: OpObserver>(doc: &Automerge, observer: &m
     // Effectively then we iterate over each object, then we group the operations in the object by
     // key and for each key find the visible operations for that key. Then we notify the observer
     // for each of those visible operations.
+    let mut visible_objs = HashSet::new();
+    visible_objs.insert(ObjId::root());
     for (obj, typ, ops) in doc.ops().iter_objs() {
+        if !visible_objs.contains(obj) {
+            continue;
+        }
+        let ops_by_key = ops.group_by(|o| o.key);
+        let actions = ops_by_key
+            .into_iter()
+            .flat_map(|(key, key_ops)| key_actions(key, key_ops));
         if typ == ObjType::Text && !observer.text_as_seq() {
-            observe_text(doc, observer, obj, ops)
-        } else if typ.is_sequence() {
-            observe_list(doc, observer, obj, ops);
+            track_new_objs_and_notify(
+                &mut visible_objs,
+                doc,
+                obj,
+                typ,
+                observer,
+                text_actions(actions),
+            )
+        } else if typ == ObjType::List {
+            track_new_objs_and_notify(
+                &mut visible_objs,
+                doc,
+                obj,
+                typ,
+                observer,
+                list_actions(actions),
+            )
         } else {
-            observe_map(doc, observer, obj, ops);
+            track_new_objs_and_notify(&mut visible_objs, doc, obj, typ, observer, actions)
         }
     }
 }
 
-fn observe_text<'a, I: Iterator<Item = &'a Op>, O: OpObserver>(
-    doc: &'a Automerge,
-    observer: &mut O,
+fn track_new_objs_and_notify<N: Action, I: Iterator<Item = N>, O: OpObserver>(
+    visible_objs: &mut HashSet<ObjId>,
+    doc: &crate::Automerge,
     obj: &ObjId,
-    ops: I,
+    typ: ObjType,
+    observer: &mut O,
+    actions: I,
 ) {
     let exid = doc.id_to_exid(obj.0);
-    let ops_by_key = ops.group_by(|o| o.elemid_or_key());
-    let encoding = ListEncoding::Text(doc.text_encoding());
-    let state = TextState::default();
-    let state = ops_by_key
-        .into_iter()
-        .fold(state, |mut state, (_key, key_ops)| {
-            if let Some(o) = key_ops.filter(|o| o.visible_or_mark()).last() {
-                match &o.action {
-                    OpType::Make(_) | OpType::Put(_) => {
-                        state.text.push_str(o.to_str());
-                        state.len += o.width(encoding);
-                    }
-                    OpType::MarkBegin(_, data) => {
-                        if let Some(mark) = state.marks.mark_begin(o.id, state.len, data, doc) {
-                            state.finished.push(mark);
-                        }
-                    }
-                    OpType::MarkEnd(_) => {
-                        if let Some(mark) = state.marks.mark_end(o.id, state.len, doc) {
-                            state.finished.push(mark);
-                        }
-                    }
-                    OpType::Increment(_) | OpType::Delete => {}
+    for action in actions {
+        if let Some(obj) = action.made_object() {
+            visible_objs.insert(obj);
+        }
+        action.notify_observer(doc, &exid, obj, typ, observer);
+    }
+}
+
+trait Action {
+    /// Notify an observer of whatever this action does
+    fn notify_observer<O: OpObserver>(
+        self,
+        doc: &crate::Automerge,
+        exid: &crate::ObjId,
+        obj: &ObjId,
+        typ: ObjType,
+        observer: &mut O,
+    );
+
+    /// If this action created an object, return the ID of that object
+    fn made_object(&self) -> Option<ObjId>;
+}
+
+fn key_actions<'a, I: Iterator<Item = &'a Op>>(
+    key: Key,
+    key_ops: I,
+) -> impl Iterator<Item = SimpleAction<'a>> {
+    #[derive(Clone)]
+    enum CurrentOp<'a> {
+        Put {
+            value: Value<'a>,
+            id: OpId,
+            conflicted: bool,
+        },
+        Insert(Value<'a>, OpId),
+    }
+    let current_ops = key_ops
+        .filter(|o| o.visible())
+        .filter_map(|o| match o.action {
+            OpType::Make(obj_type) => {
+                let value = Value::Object(obj_type);
+                if o.insert {
+                    Some(CurrentOp::Insert(value, o.id))
+                } else {
+                    Some(CurrentOp::Put {
+                        value,
+                        id: o.id,
+                        conflicted: false,
+                    })
                 }
             }
-            state
-        });
-    observer.splice_text(doc, exid.clone(), 0, state.text.as_str());
-    observer.mark(doc, exid, state.finished.into_iter());
-}
-
-fn observe_list<'a, I: Iterator<Item = &'a Op>, O: OpObserver>(
-    doc: &'a Automerge,
-    observer: &mut O,
-    obj: &ObjId,
-    ops: I,
-) {
-    let exid = doc.id_to_exid(obj.0);
-    let mut marks = MarkStateMachine::default();
-    let ops_by_key = ops.group_by(|o| o.elemid_or_key());
-    let mut len = 0;
-    let mut finished = Vec::new();
-    ops_by_key
-        .into_iter()
-        .filter_map(|(_key, key_ops)| {
-            key_ops
-                .filter(|o| o.visible_or_mark())
-                .filter_map(|o| match &o.action {
-                    OpType::Make(obj_type) => Some((Value::Object(*obj_type), o.id)),
-                    OpType::Put(value) => Some((Value::Scalar(Cow::Borrowed(value)), o.id)),
-                    OpType::MarkBegin(_, data) => {
-                        if let Some(mark) = marks.mark_begin(o.id, len, data, doc) {
-                            // side effect
-                            finished.push(mark)
-                        }
-                        None
-                    }
-                    OpType::MarkEnd(_) => {
-                        if let Some(mark) = marks.mark_end(o.id, len, doc) {
-                            // side effect
-                            finished.push(mark)
-                        }
-                        None
-                    }
-                    _ => None,
-                })
-                .enumerate()
-                .last()
-                .map(|value| {
-                    let pos = len;
-                    len += 1; // increment - side effect
-                    (pos, value)
-                })
-        })
-        .for_each(|(index, (val_enum, (value, opid)))| {
-            let tagged_value = (value, doc.id_to_exid(opid));
-            let conflict = val_enum > 0;
-            observer.insert(doc, exid.clone(), index, tagged_value, conflict);
-        });
-    observer.mark(doc, exid, finished.into_iter());
-}
-
-fn observe_map_key<'a, I: Iterator<Item = &'a Op>>(
-    (key, key_ops): (Key, I),
-) -> Option<(usize, Put<'a>)> {
-    key_ops
-        .filter(|o| o.visible())
-        .filter_map(|o| match &o.action {
-            OpType::Make(obj_type) => {
-                let value = Value::Object(*obj_type);
-                Some(Put {
-                    value,
-                    key,
-                    id: o.id,
-                })
-            }
-            OpType::Put(value) => {
+            OpType::Put(ref value) => {
                 let value = Value::Scalar(Cow::Borrowed(value));
-                Some(Put {
-                    value,
-                    key,
-                    id: o.id,
-                })
+                if o.insert {
+                    Some(CurrentOp::Insert(value, o.id))
+                } else {
+                    Some(CurrentOp::Put {
+                        value,
+                        id: o.id,
+                        conflicted: false,
+                    })
+                }
             }
             _ => None,
+        });
+    current_ops
+        .coalesce(|previous, current| match (previous, current) {
+            (CurrentOp::Put { .. }, CurrentOp::Put { value, id, .. }) => Ok(CurrentOp::Put {
+                value,
+                id,
+                conflicted: true,
+            }),
+            (previous, current) => Err((previous, current)),
+        })
+        .map(move |op| match op {
+            CurrentOp::Put {
+                value,
+                id,
+                conflicted,
+            } => SimpleAction::Put {
+                prop: key,
+                tagged_value: (value, id),
+                conflict: conflicted,
+            },
+            CurrentOp::Insert(val, id) => SimpleAction::Insert {
+                elem_id: ElemId(id),
+                tagged_value: (val, id),
+            },
         })
-        .enumerate()
-        .last()
 }
 
-fn observe_map<'a, I: Iterator<Item = &'a Op>, O: OpObserver>(
-    doc: &'a Automerge,
-    observer: &mut O,
-    obj: &ObjId,
-    ops: I,
-) {
-    let exid = doc.id_to_exid(obj.0);
-    let ops_by_key = ops.group_by(|o| o.key);
-    ops_by_key
-        .into_iter()
-        .filter_map(observe_map_key)
-        .filter_map(|(i, put)| {
-            let tagged_value = (put.value, doc.id_to_exid(put.id));
-            let prop = doc
-                .ops()
-                .m
-                .props
-                .safe_get(put.key.prop_index()?)
-                .map(|s| Prop::Map(s.to_string()))?;
-            let conflict = i > 0;
-            Some((tagged_value, prop, conflict))
-        })
-        .for_each(|(tagged_value, prop, conflict)| {
-            observer.put(doc, exid.clone(), prop, tagged_value, conflict);
-        });
+/// Either a "put" or "insert" action. i.e. not splicing for text values
+enum SimpleAction<'a> {
+    Put {
+        prop: Key,
+        tagged_value: (Value<'a>, OpId),
+        conflict: bool,
+    },
+    Insert {
+        elem_id: ElemId,
+        tagged_value: (Value<'a>, OpId),
+    },
+}
+
+impl<'a> Action for SimpleAction<'a> {
+    fn notify_observer<O: OpObserver>(
+        self,
+        doc: &crate::Automerge,
+        exid: &crate::ObjId,
+        obj: &ObjId,
+        typ: ObjType,
+        observer: &mut O,
+    ) {
+        let encoding = match typ {
+            ObjType::Text => ListEncoding::Text(doc.text_encoding()),
+            _ => ListEncoding::List,
+        };
+        match self {
+            Self::Put {
+                prop,
+                tagged_value,
+                conflict,
+            } => {
+                let tagged_value = (tagged_value.0, doc.id_to_exid(tagged_value.1));
+                let prop = doc.ops().export_key(*obj, prop, encoding).unwrap();
+                observer.put(doc, exid.clone(), prop, tagged_value, conflict);
+            }
+            Self::Insert {
+                elem_id,
+                tagged_value: (value, opid),
+            } => {
+                let index = doc
+                    .ops()
+                    .search(obj, crate::query::ElemIdPos::new(elem_id, encoding))
+                    .index()
+                    .unwrap();
+                let tagged_value = (value, doc.id_to_exid(opid));
+                observer.insert(doc, doc.id_to_exid(obj.0), index, tagged_value);
+            }
+        }
+    }
+
+    fn made_object(&self) -> Option<ObjId> {
+        match self {
+            Self::Put {
+                tagged_value: (Value::Object(_), id),
+                ..
+            } => Some((*id).into()),
+            Self::Insert {
+                tagged_value: (Value::Object(_), id),
+                ..
+            } => Some((*id).into()),
+            _ => None,
+        }
+    }
+}
+
+/// An `Action` which splices for text values
+enum TextAction<'a> {
+    Action(SimpleAction<'a>),
+    Splice { start: ElemId, chars: String },
+}
+
+impl<'a> Action for TextAction<'a> {
+    fn notify_observer<O: OpObserver>(
+        self,
+        doc: &crate::Automerge,
+        exid: &crate::ObjId,
+        obj: &ObjId,
+        typ: ObjType,
+        observer: &mut O,
+    ) {
+        match self {
+            Self::Action(action) => action.notify_observer(doc, exid, obj, typ, observer),
+            Self::Splice { start, chars } => {
+                let index = doc
+                    .ops()
+                    .search(
+                        obj,
+                        crate::query::ElemIdPos::new(
+                            start,
+                            ListEncoding::Text(doc.text_encoding()),
+                        ),
+                    )
+                    .index()
+                    .unwrap();
+                observer.splice_text(doc, doc.id_to_exid(obj.0), index, chars.as_str());
+            }
+        }
+    }
+
+    fn made_object(&self) -> Option<ObjId> {
+        match self {
+            Self::Action(action) => action.made_object(),
+            _ => None,
+        }
+    }
+}
+
+fn list_actions<'a, I: Iterator<Item = SimpleAction<'a>>>(
+    actions: I,
+) -> impl Iterator<Item = SimpleAction<'a>> {
+    actions.map(|a| match a {
+        SimpleAction::Put {
+            prop: Key::Seq(elem_id),
+            tagged_value,
+            ..
+        } => SimpleAction::Insert {
+            elem_id,
+            tagged_value,
+        },
+        a => a,
+    })
+}
+
+/// Condense consecutive `SimpleAction::Insert` actions into one `TextAction::Splice`
+fn text_actions<'a, I>(actions: I) -> impl Iterator<Item = TextAction<'a>>
+where
+    I: Iterator<Item = SimpleAction<'a>>,
+{
+    TextActions {
+        ops: actions.peekable(),
+    }
+}
+
+struct TextActions<'a, I: Iterator<Item = SimpleAction<'a>>> {
+    ops: Peekable<I>,
+}
+
+impl<'a, I: Iterator<Item = SimpleAction<'a>>> Iterator for TextActions<'a, I> {
+    type Item = TextAction<'a>;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        if let Some(SimpleAction::Insert { .. }) = self.ops.peek() {
+            let (start, value) = match self.ops.next() {
+                Some(SimpleAction::Insert {
+                    tagged_value: (value, opid),
+                    ..
+                }) => (opid, value),
+                _ => unreachable!(),
+            };
+            let mut chars = match value {
+                Value::Scalar(Cow::Borrowed(ScalarValue::Str(s))) => s.to_string(),
+                _ => "\u{fffc}".to_string(),
+            };
+            while let Some(SimpleAction::Insert { .. }) = self.ops.peek() {
+                if let Some(SimpleAction::Insert {
+                    tagged_value: (value, _),
+                    ..
+                }) = self.ops.next()
+                {
+                    match value {
+                        Value::Scalar(Cow::Borrowed(ScalarValue::Str(s))) => chars.push_str(s),
+                        _ => chars.push('\u{fffc}'),
+                    }
+                }
+            }
+            Some(TextAction::Splice {
+                start: ElemId(start),
+                chars,
+            })
+        } else {
+            self.ops.next().map(TextAction::Action)
+        }
+    }
 }
 
 #[cfg(test)]
 mod tests {
     use std::{borrow::Cow, fs};
 
-    use crate::{
-        marks::Mark, transaction::Transactable, Automerge, ObjType, OpObserver, Prop, ReadDoc,
-        Value,
-    };
-    //use crate::{transaction::Transactable, Automerge, ObjType, OpObserver, Prop, ReadDoc, Value};
+    use crate::{transaction::Transactable, Automerge, ObjType, OpObserver, Prop, ReadDoc, Value};
 
     // Observer ops often carry a "tagged value", which is a value and the OpID of the op which
     // created that value. For a lot of values (i.e. any scalar value) we don't care about the
@@ -355,7 +490,6 @@ mod tests {
             objid: crate::ObjId,
             index: usize,
             tagged_value: (crate::Value<'_>, crate::ObjId),
-            _conflict: bool,
         ) {
             self.ops.push(ObserverCall::Insert {
                 obj: objid,
@@ -432,24 +566,6 @@ mod tests {
         fn text_as_seq(&self) -> bool {
             self.text_as_seq
         }
-
-        fn mark<'a, R: ReadDoc, M: Iterator<Item = Mark<'a>>>(
-            &mut self,
-            _doc: &R,
-            _objid: crate::ObjId,
-            _mark: M,
-        ) {
-        }
-
-        fn unmark<R: ReadDoc>(
-            &mut self,
-            _doc: &R,
-            _objid: crate::ObjId,
-            _name: &str,
-            _start: usize,
-            _end: usize,
-        ) {
-        }
     }
 
     #[test]
diff --git a/rust/automerge/src/automerge/tests.rs b/rust/automerge/src/automerge/tests.rs
index e2863c3f..3511c4ed 100644
--- a/rust/automerge/src/automerge/tests.rs
+++ b/rust/automerge/src/automerge/tests.rs
@@ -7,9 +7,6 @@ use crate::transaction::Transactable;
 use crate::*;
 use std::convert::TryInto;
 
-use crate::op_observer::HasPatches;
-use test_log::test;
-
 #[test]
 fn insert_op() -> Result<(), AutomergeError> {
     let mut doc = Automerge::new();
@@ -1482,18 +1479,15 @@ fn observe_counter_change_application_overwrite() {
 
     assert_eq!(
         doc3.observer().take_patches(),
-        vec![Patch {
+        vec![Patch::Put {
             obj: ExId::Root,
             path: vec![],
-            action: PatchAction::PutMap {
-                key: "counter".into(),
-                value: (
-                    ScalarValue::Str("mystring".into()).into(),
-                    ExId::Id(2, doc2.get_actor().clone(), 1)
-                ),
-                conflict: false,
-                expose: false
-            }
+            prop: Prop::Map("counter".into()),
+            value: (
+                ScalarValue::Str("mystring".into()).into(),
+                ExId::Id(2, doc2.get_actor().clone(), 1)
+            ),
+            conflict: false
         }]
     );
 
@@ -1520,29 +1514,29 @@ fn observe_counter_change_application() {
     new_doc.observer().take_patches();
     new_doc.apply_changes(changes).unwrap();
     assert_eq!(
-        new_doc
-            .observer()
-            .take_patches()
-            .into_iter()
-            .map(|p| p.action)
-            .collect::<Vec<_>>(),
+        new_doc.observer().take_patches(),
         vec![
-            PatchAction::PutMap {
-                key: "counter".into(),
+            Patch::Put {
+                obj: ExId::Root,
+                path: vec![],
+                prop: Prop::Map("counter".into()),
                 value: (
                     ScalarValue::counter(1).into(),
                     ExId::Id(1, doc.get_actor().clone(), 0)
                 ),
-                conflict: false,
-                expose: false,
+                conflict: false
             },
-            PatchAction::Increment {
+            Patch::Increment {
+                obj: ExId::Root,
+                path: vec![],
                 prop: Prop::Map("counter".into()),
-                value: 2,
+                value: (2, ExId::Id(2, doc.get_actor().clone(), 0)),
             },
-            PatchAction::Increment {
+            Patch::Increment {
+                obj: ExId::Root,
+                path: vec![],
                 prop: Prop::Map("counter".into()),
-                value: 5,
+                value: (5, ExId::Id(3, doc.get_actor().clone(), 0)),
             }
         ]
     );
diff --git a/rust/automerge/src/change.rs b/rust/automerge/src/change.rs
index a6ab112a..be467a84 100644
--- a/rust/automerge/src/change.rs
+++ b/rust/automerge/src/change.rs
@@ -255,18 +255,6 @@ mod convert_expanded {
                 None => Cow::Owned(ScalarValue::Null),
             }
         }
-
-        fn expand(&self) -> bool {
-            self.action.expand()
-        }
-
-        fn mark_name(&self) -> Option<Cow<'a, smol_str::SmolStr>> {
-            if let legacy::OpType::MarkBegin(legacy::MarkData { name, .. }) = &self.action {
-                Some(Cow::Borrowed(name))
-            } else {
-                None
-            }
-        }
     }
 
     impl<'a> convert::OpId<&'a ActorId> for &'a legacy::OpId {
@@ -290,12 +278,7 @@ impl From<&Change> for crate::ExpandedChange {
         let operations = c
             .iter_ops()
             .map(|o| crate::legacy::Op {
-                action: crate::legacy::OpType::from_parts(crate::legacy::OpTypeParts {
-                    action: o.action,
-                    value: o.val,
-                    expand: o.expand,
-                    mark_name: o.mark_name,
-                }),
+                action: crate::types::OpType::from_action_and_value(o.action, o.val),
                 insert: o.insert,
                 key: match o.key {
                     StoredKey::Elem(e) if e.is_head() => {
diff --git a/rust/automerge/src/columnar/column_range.rs b/rust/automerge/src/columnar/column_range.rs
index 709cbe9a..5762ed14 100644
--- a/rust/automerge/src/columnar/column_range.rs
+++ b/rust/automerge/src/columnar/column_range.rs
@@ -3,7 +3,7 @@ pub(crate) use rle::RleRange;
 mod delta;
 pub(crate) use delta::DeltaRange;
 mod boolean;
-pub(crate) use boolean::{BooleanRange, MaybeBooleanRange};
+pub(crate) use boolean::BooleanRange;
 mod raw;
 pub(crate) use raw::RawRange;
 mod opid;
diff --git a/rust/automerge/src/columnar/column_range/boolean.rs b/rust/automerge/src/columnar/column_range/boolean.rs
index b2530462..3cefaf0d 100644
--- a/rust/automerge/src/columnar/column_range/boolean.rs
+++ b/rust/automerge/src/columnar/column_range/boolean.rs
@@ -1,8 +1,6 @@
 use std::{borrow::Cow, ops::Range};
 
-use crate::columnar::encoding::{
-    BooleanDecoder, BooleanEncoder, MaybeBooleanDecoder, MaybeBooleanEncoder,
-};
+use crate::columnar::encoding::{BooleanDecoder, BooleanEncoder};
 
 #[derive(Clone, Debug, PartialEq)]
 pub(crate) struct BooleanRange(Range<usize>);
@@ -40,44 +38,3 @@ impl From<BooleanRange> for Range<usize> {
         r.0
     }
 }
-
-#[derive(Clone, Debug, PartialEq)]
-pub struct MaybeBooleanRange(Range<usize>);
-
-impl MaybeBooleanRange {
-    pub(crate) fn decoder<'a>(&self, data: &'a [u8]) -> MaybeBooleanDecoder<'a> {
-        MaybeBooleanDecoder::from(Cow::Borrowed(&data[self.0.clone()]))
-    }
-
-    pub(crate) fn encode<I: Iterator<Item = bool>>(items: I, out: &mut Vec<u8>) -> Self {
-        let start = out.len();
-        let mut encoder = MaybeBooleanEncoder::from_sink(out);
-        for i in items {
-            encoder.append(i);
-        }
-        let (_, len) = encoder.finish();
-        (start..(start + len)).into()
-    }
-
-    pub(crate) fn is_empty(&self) -> bool {
-        self.0.is_empty()
-    }
-}
-
-impl AsRef<Range<usize>> for MaybeBooleanRange {
-    fn as_ref(&self) -> &Range<usize> {
-        &self.0
-    }
-}
-
-impl From<Range<usize>> for MaybeBooleanRange {
-    fn from(r: Range<usize>) -> MaybeBooleanRange {
-        MaybeBooleanRange(r)
-    }
-}
-
-impl From<MaybeBooleanRange> for Range<usize> {
-    fn from(r: MaybeBooleanRange) -> Range<usize> {
-        r.0
-    }
-}
diff --git a/rust/automerge/src/columnar/encoding.rs b/rust/automerge/src/columnar/encoding.rs
index e15600d7..c9435448 100644
--- a/rust/automerge/src/columnar/encoding.rs
+++ b/rust/automerge/src/columnar/encoding.rs
@@ -4,9 +4,7 @@ pub(crate) use raw::{RawDecoder, RawEncoder};
 mod rle;
 pub(crate) use rle::{RleDecoder, RleEncoder};
 mod boolean;
-pub(crate) use boolean::{
-    BooleanDecoder, BooleanEncoder, MaybeBooleanDecoder, MaybeBooleanEncoder,
-};
+pub(crate) use boolean::{BooleanDecoder, BooleanEncoder};
 mod delta;
 pub(crate) use delta::{DeltaDecoder, DeltaEncoder};
 pub(crate) mod leb128;
diff --git a/rust/automerge/src/columnar/encoding/boolean.rs b/rust/automerge/src/columnar/encoding/boolean.rs
index 00f27c16..26cb1838 100644
--- a/rust/automerge/src/columnar/encoding/boolean.rs
+++ b/rust/automerge/src/columnar/encoding/boolean.rs
@@ -100,72 +100,6 @@ impl<'a> Iterator for BooleanDecoder<'a> {
     }
 }
 
-/// Like a `BooleanEncoder` but if all the values in the column are `false` then will return an
-/// empty range rather than a range with `count` false values.
-pub(crate) struct MaybeBooleanEncoder<S> {
-    encoder: BooleanEncoder<S>,
-    all_false: bool,
-}
-
-impl MaybeBooleanEncoder<Vec<u8>> {
-    pub(crate) fn new() -> MaybeBooleanEncoder<Vec<u8>> {
-        MaybeBooleanEncoder::from_sink(Vec::new())
-    }
-}
-
-impl<S: Sink> MaybeBooleanEncoder<S> {
-    pub(crate) fn from_sink(buf: S) -> MaybeBooleanEncoder<S> {
-        MaybeBooleanEncoder {
-            encoder: BooleanEncoder::from_sink(buf),
-            all_false: true,
-        }
-    }
-
-    pub(crate) fn append(&mut self, value: bool) {
-        if value {
-            self.all_false = false;
-        }
-        self.encoder.append(value);
-    }
-
-    pub(crate) fn finish(self) -> (S, usize) {
-        if self.all_false {
-            (self.encoder.buf, 0)
-        } else {
-            self.encoder.finish()
-        }
-    }
-}
-
-/// Like a `BooleanDecoder` but if the underlying range is empty then just returns an infinite
-/// sequence of `None`
-#[derive(Clone, Debug)]
-pub(crate) struct MaybeBooleanDecoder<'a>(BooleanDecoder<'a>);
-
-impl<'a> From<Cow<'a, [u8]>> for MaybeBooleanDecoder<'a> {
-    fn from(bytes: Cow<'a, [u8]>) -> Self {
-        MaybeBooleanDecoder(BooleanDecoder::from(bytes))
-    }
-}
-
-impl<'a> From<&'a [u8]> for MaybeBooleanDecoder<'a> {
-    fn from(d: &'a [u8]) -> Self {
-        Cow::Borrowed(d).into()
-    }
-}
-
-impl<'a> Iterator for MaybeBooleanDecoder<'a> {
-    type Item = Result<Option<bool>, raw::Error>;
-
-    fn next(&mut self) -> Option<Self::Item> {
-        if self.0.decoder.is_empty() {
-            None
-        } else {
-            self.0.next().transpose().map(Some).transpose()
-        }
-    }
-}
-
 #[cfg(test)]
 mod tests {
     use super::*;
diff --git a/rust/automerge/src/columnar/encoding/raw.rs b/rust/automerge/src/columnar/encoding/raw.rs
index 5c46ef1e..b86443e5 100644
--- a/rust/automerge/src/columnar/encoding/raw.rs
+++ b/rust/automerge/src/columnar/encoding/raw.rs
@@ -59,10 +59,6 @@ impl<'a> RawDecoder<'a> {
     pub(crate) fn done(&self) -> bool {
         self.offset >= self.data.len()
     }
-
-    pub(crate) fn is_empty(&self) -> bool {
-        self.data.is_empty()
-    }
 }
 
 impl<'a> From<&'a [u8]> for RawDecoder<'a> {
diff --git a/rust/automerge/src/legacy/mod.rs b/rust/automerge/src/legacy/mod.rs
index d4fb1fd0..6e6acec5 100644
--- a/rust/automerge/src/legacy/mod.rs
+++ b/rust/automerge/src/legacy/mod.rs
@@ -3,7 +3,7 @@ mod utility_impls;
 
 use std::num::NonZeroU64;
 
-pub(crate) use crate::types::{ActorId, ChangeHash, ObjType, ScalarValue};
+pub(crate) use crate::types::{ActorId, ChangeHash, ObjType, OpType, ScalarValue};
 pub(crate) use crate::value::DataType;
 
 use serde::{Deserialize, Serialize};
@@ -204,96 +204,6 @@ where
     }
 }
 
-pub(crate) struct OpTypeParts {
-    pub(crate) action: u64,
-    pub(crate) value: ScalarValue,
-    pub(crate) expand: bool,
-    pub(crate) mark_name: Option<smol_str::SmolStr>,
-}
-
-// Like `types::OpType` except using a String for mark names
-#[derive(PartialEq, Debug, Clone)]
-pub enum OpType {
-    Make(ObjType),
-    Delete,
-    Increment(i64),
-    Put(ScalarValue),
-    MarkBegin(MarkData),
-    MarkEnd(bool),
-}
-
-impl OpType {
-    /// Create a new legacy OpType
-    ///
-    /// This is really only meant to be used to convert from a crate::Change to a
-    /// crate::legacy::Change, so the arguments should all have been validated. Consequently it
-    /// does not return an error and instead panics on the following conditions
-    ///
-    /// # Panics
-    ///
-    /// * If The action index is unrecognized
-    /// * If the action index indicates that the value should be numeric but the value is not a
-    ///   number
-    pub(crate) fn from_parts(
-        OpTypeParts {
-            action,
-            value,
-            expand,
-            mark_name,
-        }: OpTypeParts,
-    ) -> Self {
-        match action {
-            0 => Self::Make(ObjType::Map),
-            1 => Self::Put(value),
-            2 => Self::Make(ObjType::List),
-            3 => Self::Delete,
-            4 => Self::Make(ObjType::Text),
-            5 => match value {
-                ScalarValue::Int(i) => Self::Increment(i),
-                ScalarValue::Uint(i) => Self::Increment(i as i64),
-                _ => panic!("non numeric value for integer action"),
-            },
-            6 => Self::Make(ObjType::Table),
-            7 => match mark_name {
-                Some(name) => Self::MarkBegin(MarkData {
-                    name,
-                    value,
-                    expand,
-                }),
-                None => Self::MarkEnd(expand),
-            },
-            other => panic!("unknown action type {}", other),
-        }
-    }
-
-    pub(crate) fn action_index(&self) -> u64 {
-        match self {
-            Self::Make(ObjType::Map) => 0,
-            Self::Put(_) => 1,
-            Self::Make(ObjType::List) => 2,
-            Self::Delete => 3,
-            Self::Make(ObjType::Text) => 4,
-            Self::Increment(_) => 5,
-            Self::Make(ObjType::Table) => 6,
-            Self::MarkBegin(_) | Self::MarkEnd(_) => 7,
-        }
-    }
-
-    pub(crate) fn expand(&self) -> bool {
-        matches!(
-            self,
-            Self::MarkBegin(MarkData { expand: true, .. }) | Self::MarkEnd(true)
-        )
-    }
-}
-
-#[derive(PartialEq, Debug, Clone)]
-pub struct MarkData {
-    pub name: smol_str::SmolStr,
-    pub value: ScalarValue,
-    pub expand: bool,
-}
-
 #[derive(PartialEq, Debug, Clone)]
 pub struct Op {
     pub action: OpType,
@@ -307,7 +217,6 @@ impl Op {
     pub fn primitive_value(&self) -> Option<ScalarValue> {
         match &self.action {
             OpType::Put(v) => Some(v.clone()),
-            OpType::MarkBegin(MarkData { value, .. }) => Some(value.clone()),
             OpType::Increment(i) => Some(ScalarValue::Int(*i)),
             _ => None,
         }
diff --git a/rust/automerge/src/legacy/serde_impls/op.rs b/rust/automerge/src/legacy/serde_impls/op.rs
index d42879cd..a3719fd6 100644
--- a/rust/automerge/src/legacy/serde_impls/op.rs
+++ b/rust/automerge/src/legacy/serde_impls/op.rs
@@ -5,9 +5,7 @@ use serde::{
 };
 
 use super::read_field;
-use crate::legacy::{
-    DataType, Key, MarkData, ObjType, ObjectId, Op, OpId, OpType, ScalarValue, SortedVec,
-};
+use crate::legacy::{DataType, Key, ObjType, ObjectId, Op, OpId, OpType, ScalarValue, SortedVec};
 
 impl Serialize for Op {
     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
@@ -52,16 +50,6 @@ impl Serialize for Op {
             OpType::Increment(n) => op.serialize_field("value", &n)?,
             OpType::Put(ScalarValue::Counter(c)) => op.serialize_field("value", &c.start)?,
             OpType::Put(value) => op.serialize_field("value", &value)?,
-            OpType::MarkBegin(MarkData {
-                name,
-                value,
-                expand,
-            }) => {
-                op.serialize_field("name", &name)?;
-                op.serialize_field("value", &value)?;
-                op.serialize_field("expand", &expand)?
-            }
-            OpType::MarkEnd(expand) => op.serialize_field("expand", &expand)?,
             _ => {}
         }
         op.serialize_field("pred", &self.pred)?;
@@ -83,8 +71,6 @@ pub(crate) enum RawOpType {
     Del,
     Inc,
     Set,
-    MarkBegin,
-    MarkEnd,
 }
 
 impl Serialize for RawOpType {
@@ -100,8 +86,6 @@ impl Serialize for RawOpType {
             RawOpType::Del => "del",
             RawOpType::Inc => "inc",
             RawOpType::Set => "set",
-            RawOpType::MarkBegin => "markBegin",
-            RawOpType::MarkEnd => "markEnd",
         };
         serializer.serialize_str(s)
     }
@@ -120,8 +104,8 @@ impl<'de> Deserialize<'de> for RawOpType {
             "del",
             "inc",
             "set",
-            "markBegin",
-            "markEnd",
+            "mark",
+            "unmark",
         ];
         // TODO: Probably more efficient to deserialize to a `&str`
         let raw_type = String::deserialize(deserializer)?;
@@ -133,8 +117,6 @@ impl<'de> Deserialize<'de> for RawOpType {
             "del" => Ok(RawOpType::Del),
             "inc" => Ok(RawOpType::Inc),
             "set" => Ok(RawOpType::Set),
-            "markBegin" => Ok(RawOpType::MarkBegin),
-            "markEnd" => Ok(RawOpType::MarkEnd),
             other => Err(Error::unknown_variant(other, VARIANTS)),
         }
     }
@@ -207,7 +189,24 @@ impl<'de> Deserialize<'de> for Op {
                     RawOpType::MakeList => OpType::Make(ObjType::List),
                     RawOpType::MakeText => OpType::Make(ObjType::Text),
                     RawOpType::Del => OpType::Delete,
-                    RawOpType::Set => OpType::Put(unwrap_value(value, datatype)?),
+                    RawOpType::Set => {
+                        let value = if let Some(datatype) = datatype {
+                            let raw_value = value
+                                .ok_or_else(|| Error::missing_field("value"))?
+                                .unwrap_or(ScalarValue::Null);
+                            raw_value.as_datatype(datatype).map_err(|e| {
+                                Error::invalid_value(
+                                    Unexpected::Other(e.unexpected.as_str()),
+                                    &e.expected.as_str(),
+                                )
+                            })?
+                        } else {
+                            value
+                                .ok_or_else(|| Error::missing_field("value"))?
+                                .unwrap_or(ScalarValue::Null)
+                        };
+                        OpType::Put(value)
+                    }
                     RawOpType::Inc => match value.flatten() {
                         Some(ScalarValue::Int(n)) => Ok(OpType::Increment(n)),
                         Some(ScalarValue::Uint(n)) => Ok(OpType::Increment(n as i64)),
@@ -231,18 +230,6 @@ impl<'de> Deserialize<'de> for Op {
                         }
                         None => Err(Error::missing_field("value")),
                     }?,
-                    RawOpType::MarkBegin => {
-                        let name = name.ok_or_else(|| Error::missing_field("name"))?;
-                        let name = smol_str::SmolStr::new(name);
-                        let expand = expand.unwrap_or(false);
-                        let value = unwrap_value(value, datatype)?;
-                        OpType::MarkBegin(MarkData {
-                            name,
-                            value,
-                            expand,
-                        })
-                    }
-                    RawOpType::MarkEnd => OpType::MarkEnd(expand.unwrap_or(false)),
                 };
                 Ok(Op {
                     action,
@@ -257,27 +244,6 @@ impl<'de> Deserialize<'de> for Op {
     }
 }
 
-fn unwrap_value<E: Error>(
-    value: Option<Option<ScalarValue>>,
-    datatype: Option<DataType>,
-) -> Result<ScalarValue, E> {
-    if let Some(datatype) = datatype {
-        let raw_value = value
-            .ok_or_else(|| Error::missing_field("value"))?
-            .unwrap_or(ScalarValue::Null);
-        raw_value.as_datatype(datatype).map_err(|e| {
-            Error::invalid_value(
-                Unexpected::Other(e.unexpected.as_str()),
-                &e.expected.as_str(),
-            )
-        })
-    } else {
-        Ok(value
-            .ok_or_else(|| Error::missing_field("value"))?
-            .unwrap_or(ScalarValue::Null))
-    }
-}
-
 #[cfg(test)]
 mod tests {
     use std::str::FromStr;
diff --git a/rust/automerge/src/legacy/serde_impls/op_type.rs b/rust/automerge/src/legacy/serde_impls/op_type.rs
index 32825119..b054bad7 100644
--- a/rust/automerge/src/legacy/serde_impls/op_type.rs
+++ b/rust/automerge/src/legacy/serde_impls/op_type.rs
@@ -1,7 +1,7 @@
 use serde::{Serialize, Serializer};
 
 use super::op::RawOpType;
-use crate::{legacy::OpType, ObjType};
+use crate::{ObjType, OpType};
 
 impl Serialize for OpType {
     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
@@ -18,8 +18,6 @@ impl Serialize for OpType {
             OpType::Delete => RawOpType::Del,
             OpType::Increment(_) => RawOpType::Inc,
             OpType::Put(_) => RawOpType::Set,
-            OpType::MarkBegin(_) => RawOpType::MarkBegin,
-            OpType::MarkEnd(_) => RawOpType::MarkEnd,
         };
         raw_type.serialize(serializer)
     }
diff --git a/rust/automerge/src/lib.rs b/rust/automerge/src/lib.rs
index ff6f6daa..cbb535af 100644
--- a/rust/automerge/src/lib.rs
+++ b/rust/automerge/src/lib.rs
@@ -258,14 +258,12 @@ mod list_range;
 mod list_range_at;
 mod map_range;
 mod map_range_at;
-pub mod marks;
 pub mod op_observer;
 mod op_set;
 mod op_tree;
 mod parents;
 mod query;
 mod read;
-mod sequence_tree;
 mod storage;
 pub mod sync;
 pub mod transaction;
@@ -290,9 +288,9 @@ pub use list_range::ListRange;
 pub use list_range_at::ListRangeAt;
 pub use map_range::MapRange;
 pub use map_range_at::MapRangeAt;
-pub use op_observer::{
-    OpObserver, Patch, PatchAction, ToggleObserver, VecOpObserver, VecOpObserver16,
-};
+pub use op_observer::OpObserver;
+pub use op_observer::Patch;
+pub use op_observer::VecOpObserver;
 pub use parents::{Parent, Parents};
 pub use read::ReadDoc;
 pub use types::{ActorId, ChangeHash, ObjType, OpType, ParseChangeHashError, Prop, TextEncoding};
diff --git a/rust/automerge/src/marks.rs b/rust/automerge/src/marks.rs
deleted file mode 100644
index cb9520d9..00000000
--- a/rust/automerge/src/marks.rs
+++ /dev/null
@@ -1,194 +0,0 @@
-use smol_str::SmolStr;
-use std::fmt;
-use std::fmt::Display;
-
-use crate::types::OpId;
-use crate::value::ScalarValue;
-use crate::Automerge;
-use std::borrow::Cow;
-
-#[derive(Debug, Clone, PartialEq)]
-pub struct Mark<'a> {
-    pub start: usize,
-    pub end: usize,
-    pub(crate) data: Cow<'a, MarkData>,
-}
-
-impl<'a> Mark<'a> {
-    pub fn new<V: Into<ScalarValue>>(
-        name: String,
-        value: V,
-        start: usize,
-        end: usize,
-    ) -> Mark<'static> {
-        Mark {
-            data: Cow::Owned(MarkData {
-                name: name.into(),
-                value: value.into(),
-            }),
-            start,
-            end,
-        }
-    }
-
-    pub(crate) fn from_data(start: usize, end: usize, data: &MarkData) -> Mark<'_> {
-        Mark {
-            data: Cow::Borrowed(data),
-            start,
-            end,
-        }
-    }
-
-    pub fn into_owned(self) -> Mark<'static> {
-        Mark {
-            data: Cow::Owned(self.data.into_owned()),
-            start: self.start,
-            end: self.end,
-        }
-    }
-
-    pub fn name(&self) -> &str {
-        self.data.name.as_str()
-    }
-
-    pub fn value(&self) -> &ScalarValue {
-        &self.data.value
-    }
-}
-
-#[derive(Debug, Clone, PartialEq, Default)]
-pub(crate) struct MarkStateMachine<'a> {
-    state: Vec<(OpId, Mark<'a>)>,
-}
-
-impl<'a> MarkStateMachine<'a> {
-    pub(crate) fn mark_begin(
-        &mut self,
-        id: OpId,
-        pos: usize,
-        data: &'a MarkData,
-        doc: &Automerge,
-    ) -> Option<Mark<'a>> {
-        let mut result = None;
-        let index = self.find(id, doc).err()?;
-
-        let mut mark = Mark::from_data(pos, pos, data);
-
-        if let Some(above) = Self::mark_above(&self.state, index, &mark) {
-            if above.value() == mark.value() {
-                mark.start = above.start;
-            }
-        } else if let Some(below) = Self::mark_below(&mut self.state, index, &mark) {
-            if below.value() == mark.value() {
-                mark.start = below.start;
-            } else {
-                let mut m = below.clone();
-                m.end = pos;
-                if !m.value().is_null() {
-                    result = Some(m);
-                }
-            }
-        }
-
-        self.state.insert(index, (id, mark));
-
-        result
-    }
-
-    pub(crate) fn mark_end(&mut self, id: OpId, pos: usize, doc: &Automerge) -> Option<Mark<'a>> {
-        let mut result = None;
-        let index = self.find(id.prev(), doc).ok()?;
-
-        let mut mark = self.state.remove(index).1;
-        mark.end = pos;
-
-        if Self::mark_above(&self.state, index, &mark).is_none() {
-            match Self::mark_below(&mut self.state, index, &mark) {
-                Some(below) if below.value() == mark.value() => {}
-                Some(below) => {
-                    below.start = pos;
-                    if !mark.value().is_null() {
-                        result = Some(mark.clone());
-                    }
-                }
-                None => {
-                    if !mark.value().is_null() {
-                        result = Some(mark.clone());
-                    }
-                }
-            }
-        }
-
-        result
-    }
-
-    fn find(&self, target: OpId, doc: &Automerge) -> Result<usize, usize> {
-        let metadata = &doc.ops().m;
-        self.state
-            .binary_search_by(|probe| metadata.lamport_cmp(probe.0, target))
-    }
-
-    fn mark_above<'b>(
-        state: &'b [(OpId, Mark<'a>)],
-        index: usize,
-        mark: &Mark<'a>,
-    ) -> Option<&'b Mark<'a>> {
-        Some(
-            &state[index..]
-                .iter()
-                .find(|(_, m)| m.name() == mark.name())?
-                .1,
-        )
-    }
-
-    fn mark_below<'b>(
-        state: &'b mut [(OpId, Mark<'a>)],
-        index: usize,
-        mark: &Mark<'a>,
-    ) -> Option<&'b mut Mark<'a>> {
-        Some(
-            &mut state[0..index]
-                .iter_mut()
-                .filter(|(_, m)| m.data.name == mark.data.name)
-                .last()?
-                .1,
-        )
-    }
-}
-
-#[derive(PartialEq, Debug, Clone)]
-pub struct MarkData {
-    pub name: SmolStr,
-    pub value: ScalarValue,
-}
-
-impl Display for MarkData {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "name={} value={}", self.name, self.value)
-    }
-}
-
-#[derive(PartialEq, Debug, Clone, Copy)]
-pub enum ExpandMark {
-    Left,
-    Right,
-    Both,
-    None,
-}
-
-impl ExpandMark {
-    pub fn from(left: bool, right: bool) -> Self {
-        match (left, right) {
-            (true, true) => Self::Both,
-            (false, true) => Self::Right,
-            (true, false) => Self::Left,
-            (false, false) => Self::None,
-        }
-    }
-    pub fn left(&self) -> bool {
-        matches!(self, Self::Left | Self::Both)
-    }
-    pub fn right(&self) -> bool {
-        matches!(self, Self::Right | Self::Both)
-    }
-}
diff --git a/rust/automerge/src/op_observer.rs b/rust/automerge/src/op_observer.rs
index 6870c136..5b33c21f 100644
--- a/rust/automerge/src/op_observer.rs
+++ b/rust/automerge/src/op_observer.rs
@@ -1,17 +1,10 @@
 use crate::exid::ExId;
-use crate::marks::Mark;
 use crate::Prop;
 use crate::ReadDoc;
 use crate::Value;
 
 mod compose;
-mod patch;
-mod toggle_observer;
-mod vec_observer;
 pub use compose::compose;
-pub use patch::{Patch, PatchAction};
-pub use toggle_observer::ToggleObserver;
-pub use vec_observer::{HasPatches, TextRepresentation, VecOpObserver, VecOpObserver16};
 
 /// An observer of operations applied to the document.
 pub trait OpObserver {
@@ -28,7 +21,6 @@ pub trait OpObserver {
         objid: ExId,
         index: usize,
         tagged_value: (Value<'_>, ExId),
-        conflict: bool,
     );
 
     /// Some text has been spliced into a text object
@@ -119,15 +111,6 @@ pub trait OpObserver {
     /// - `num`: the number of sequential elements deleted
     fn delete_seq<R: ReadDoc>(&mut self, doc: &R, objid: ExId, index: usize, num: usize);
 
-    fn mark<'a, R: ReadDoc, M: Iterator<Item = Mark<'a>>>(
-        &mut self,
-        doc: &'a R,
-        objid: ExId,
-        mark: M,
-    );
-
-    fn unmark<R: ReadDoc>(&mut self, doc: &R, objid: ExId, name: &str, start: usize, end: usize);
-
     /// Whether to call sequence methods or `splice_text` when encountering changes in text
     ///
     /// Returns `false` by default
@@ -163,7 +146,6 @@ impl OpObserver for () {
         _objid: ExId,
         _index: usize,
         _tagged_value: (Value<'_>, ExId),
-        _conflict: bool,
     ) {
     }
 
@@ -198,24 +180,6 @@ impl OpObserver for () {
     ) {
     }
 
-    fn mark<'a, R: ReadDoc, M: Iterator<Item = Mark<'a>>>(
-        &mut self,
-        _doc: &'a R,
-        _objid: ExId,
-        _mark: M,
-    ) {
-    }
-
-    fn unmark<R: ReadDoc>(
-        &mut self,
-        _doc: &R,
-        _objid: ExId,
-        _name: &str,
-        _start: usize,
-        _end: usize,
-    ) {
-    }
-
     fn delete_map<R: ReadDoc>(&mut self, _doc: &R, _objid: ExId, _key: &str) {}
 
     fn delete_seq<R: ReadDoc>(&mut self, _doc: &R, _objid: ExId, _index: usize, _num: usize) {}
@@ -225,3 +189,204 @@ impl BranchableObserver for () {
     fn merge(&mut self, _other: &Self) {}
     fn branch(&self) -> Self {}
 }
+
+/// Capture operations into a [`Vec`] and store them as patches.
+#[derive(Default, Debug, Clone)]
+pub struct VecOpObserver {
+    patches: Vec<Patch>,
+}
+
+impl VecOpObserver {
+    /// Take the current list of patches, leaving the internal list empty and ready for new
+    /// patches.
+    pub fn take_patches(&mut self) -> Vec<Patch> {
+        std::mem::take(&mut self.patches)
+    }
+}
+
+impl OpObserver for VecOpObserver {
+    fn insert<R: ReadDoc>(
+        &mut self,
+        doc: &R,
+        obj: ExId,
+        index: usize,
+        (value, id): (Value<'_>, ExId),
+    ) {
+        if let Ok(p) = doc.parents(&obj) {
+            self.patches.push(Patch::Insert {
+                obj,
+                path: p.path(),
+                index,
+                value: (value.into_owned(), id),
+            });
+        }
+    }
+
+    fn splice_text<R: ReadDoc>(&mut self, doc: &R, obj: ExId, index: usize, value: &str) {
+        if let Ok(p) = doc.parents(&obj) {
+            self.patches.push(Patch::Splice {
+                obj,
+                path: p.path(),
+                index,
+                value: value.to_string(),
+            })
+        }
+    }
+
+    fn put<R: ReadDoc>(
+        &mut self,
+        doc: &R,
+        obj: ExId,
+        prop: Prop,
+        (value, id): (Value<'_>, ExId),
+        conflict: bool,
+    ) {
+        if let Ok(p) = doc.parents(&obj) {
+            self.patches.push(Patch::Put {
+                obj,
+                path: p.path(),
+                prop,
+                value: (value.into_owned(), id),
+                conflict,
+            });
+        }
+    }
+
+    fn expose<R: ReadDoc>(
+        &mut self,
+        doc: &R,
+        obj: ExId,
+        prop: Prop,
+        (value, id): (Value<'_>, ExId),
+        conflict: bool,
+    ) {
+        if let Ok(p) = doc.parents(&obj) {
+            self.patches.push(Patch::Expose {
+                obj,
+                path: p.path(),
+                prop,
+                value: (value.into_owned(), id),
+                conflict,
+            });
+        }
+    }
+
+    fn increment<R: ReadDoc>(&mut self, doc: &R, obj: ExId, prop: Prop, tagged_value: (i64, ExId)) {
+        if let Ok(p) = doc.parents(&obj) {
+            self.patches.push(Patch::Increment {
+                obj,
+                path: p.path(),
+                prop,
+                value: tagged_value,
+            });
+        }
+    }
+
+    fn delete_map<R: ReadDoc>(&mut self, doc: &R, obj: ExId, key: &str) {
+        if let Ok(p) = doc.parents(&obj) {
+            self.patches.push(Patch::Delete {
+                obj,
+                path: p.path(),
+                prop: Prop::Map(key.to_owned()),
+                num: 1,
+            })
+        }
+    }
+
+    fn delete_seq<R: ReadDoc>(&mut self, doc: &R, obj: ExId, index: usize, num: usize) {
+        if let Ok(p) = doc.parents(&obj) {
+            self.patches.push(Patch::Delete {
+                obj,
+                path: p.path(),
+                prop: Prop::Seq(index),
+                num,
+            })
+        }
+    }
+}
+
+impl BranchableObserver for VecOpObserver {
+    fn merge(&mut self, other: &Self) {
+        self.patches.extend_from_slice(other.patches.as_slice())
+    }
+
+    fn branch(&self) -> Self {
+        Self::default()
+    }
+}
+
+/// A notification to the application that something has changed in a document.
+#[derive(Debug, Clone, PartialEq)]
+pub enum Patch {
+    /// Associating a new value with a prop in a map, or an existing list element
+    Put {
+        /// path to the object
+        path: Vec<(ExId, Prop)>,
+        /// The object that was put into.
+        obj: ExId,
+        /// The prop that the new value was put at.
+        prop: Prop,
+        /// The value that was put, and the id of the operation that put it there.
+        value: (Value<'static>, ExId),
+        /// Whether this put conflicts with another.
+        conflict: bool,
+    },
+    /// Exposing (via delete) an old but conflicted value with a prop in a map, or a list element
+    Expose {
+        /// path to the object
+        path: Vec<(ExId, Prop)>,
+        /// The object that was put into.
+        obj: ExId,
+        /// The prop that the new value was put at.
+        prop: Prop,
+        /// The value that was put, and the id of the operation that put it there.
+        value: (Value<'static>, ExId),
+        /// Whether this put conflicts with another.
+        conflict: bool,
+    },
+    /// Inserting a new element into a list
+    Insert {
+        /// path to the object
+        path: Vec<(ExId, Prop)>,
+        /// The object that was inserted into.
+        obj: ExId,
+        /// The index that the new value was inserted at.
+        index: usize,
+        /// The value that was inserted, and the id of the operation that inserted it there.
+        value: (Value<'static>, ExId),
+    },
+    /// Splicing a text object
+    Splice {
+        /// path to the object
+        path: Vec<(ExId, Prop)>,
+        /// The object that was inserted into.
+        obj: ExId,
+        /// The index that the new value was inserted at.
+        index: usize,
+        /// The value that was spliced
+        value: String,
+    },
+    /// Incrementing a counter.
+    Increment {
+        /// path to the object
+        path: Vec<(ExId, Prop)>,
+        /// The object that was incremented in.
+        obj: ExId,
+        /// The prop that was incremented.
+        prop: Prop,
+        /// The amount that the counter was incremented by, and the id of the operation that
+        /// did the increment.
+        value: (i64, ExId),
+    },
+    /// Deleting an element from a list/text
+    Delete {
+        /// path to the object
+        path: Vec<(ExId, Prop)>,
+        /// The object that was deleted from.
+        obj: ExId,
+        /// The prop that was deleted.
+        prop: Prop,
+        /// number of items deleted (for seq)
+        num: usize,
+    },
+}
diff --git a/rust/automerge/src/op_observer/compose.rs b/rust/automerge/src/op_observer/compose.rs
index 0dfc6542..92fe3b1e 100644
--- a/rust/automerge/src/op_observer/compose.rs
+++ b/rust/automerge/src/op_observer/compose.rs
@@ -19,11 +19,10 @@ impl<'a, O1: OpObserver, O2: OpObserver> OpObserver for ComposeObservers<'a, O1,
         objid: crate::ObjId,
         index: usize,
         tagged_value: (crate::Value<'_>, crate::ObjId),
-        conflict: bool,
     ) {
         self.obs1
-            .insert(doc, objid.clone(), index, tagged_value.clone(), conflict);
-        self.obs2.insert(doc, objid, index, tagged_value, conflict);
+            .insert(doc, objid.clone(), index, tagged_value.clone());
+        self.obs2.insert(doc, objid, index, tagged_value);
     }
 
     fn splice_text<R: crate::ReadDoc>(
@@ -85,30 +84,6 @@ impl<'a, O1: OpObserver, O2: OpObserver> OpObserver for ComposeObservers<'a, O1,
         self.obs2.increment(doc, objid, prop, tagged_value);
     }
 
-    fn mark<'b, R: crate::ReadDoc, M: Iterator<Item = crate::marks::Mark<'b>>>(
-        &mut self,
-        doc: &'b R,
-        objid: crate::ObjId,
-        mark: M,
-    ) {
-        let marks: Vec<_> = mark.collect();
-        self.obs1
-            .mark(doc, objid.clone(), marks.clone().into_iter());
-        self.obs2.mark(doc, objid, marks.into_iter());
-    }
-
-    fn unmark<R: crate::ReadDoc>(
-        &mut self,
-        doc: &R,
-        objid: crate::ObjId,
-        name: &str,
-        start: usize,
-        end: usize,
-    ) {
-        self.obs1.unmark(doc, objid.clone(), name, start, end);
-        self.obs2.unmark(doc, objid, name, start, end);
-    }
-
     fn delete_map<R: crate::ReadDoc>(&mut self, doc: &R, objid: crate::ObjId, key: &str) {
         self.obs1.delete_map(doc, objid.clone(), key);
         self.obs2.delete_map(doc, objid, key);
diff --git a/rust/automerge/src/op_observer/patch.rs b/rust/automerge/src/op_observer/patch.rs
deleted file mode 100644
index 717f680b..00000000
--- a/rust/automerge/src/op_observer/patch.rs
+++ /dev/null
@@ -1,57 +0,0 @@
-#![allow(dead_code)]
-
-use crate::{marks::Mark, ObjId, Prop, Value};
-use core::fmt::Debug;
-
-use crate::sequence_tree::SequenceTree;
-
-#[derive(Debug, Clone, PartialEq)]
-pub struct Patch<T: PartialEq + Clone + Debug> {
-    pub obj: ObjId,
-    pub path: Vec<(ObjId, Prop)>,
-    pub action: PatchAction<T>,
-}
-
-#[derive(Debug, Clone, PartialEq)]
-pub enum PatchAction<T: PartialEq + Clone + Debug> {
-    PutMap {
-        key: String,
-        value: (Value<'static>, ObjId),
-        expose: bool,
-        conflict: bool,
-    },
-    PutSeq {
-        index: usize,
-        value: (Value<'static>, ObjId),
-        expose: bool,
-        conflict: bool,
-    },
-    Insert {
-        index: usize,
-        values: SequenceTree<(Value<'static>, ObjId)>,
-        conflict: bool,
-    },
-    SpliceText {
-        index: usize,
-        value: SequenceTree<T>,
-    },
-    Increment {
-        prop: Prop,
-        value: i64,
-    },
-    DeleteMap {
-        key: String,
-    },
-    DeleteSeq {
-        index: usize,
-        length: usize,
-    },
-    Mark {
-        marks: Vec<Mark<'static>>,
-    },
-    Unmark {
-        name: String,
-        start: usize,
-        end: usize,
-    },
-}
diff --git a/rust/automerge/src/op_observer/toggle_observer.rs b/rust/automerge/src/op_observer/toggle_observer.rs
deleted file mode 100644
index 6afcee9f..00000000
--- a/rust/automerge/src/op_observer/toggle_observer.rs
+++ /dev/null
@@ -1,178 +0,0 @@
-#![allow(dead_code)]
-
-use crate::ChangeHash;
-use core::fmt::Debug;
-
-use crate::{marks::Mark, ObjId, OpObserver, Prop, ReadDoc, Value};
-
-use crate::op_observer::BranchableObserver;
-use crate::op_observer::{HasPatches, TextRepresentation};
-
-#[derive(Debug, Clone)]
-pub struct ToggleObserver<T> {
-    enabled: bool,
-    last_heads: Option<Vec<ChangeHash>>,
-    observer: T,
-}
-
-impl<T: Default> Default for ToggleObserver<T> {
-    fn default() -> Self {
-        Self {
-            enabled: false,
-            last_heads: None,
-            observer: T::default(),
-        }
-    }
-}
-
-impl<T: HasPatches> ToggleObserver<T> {
-    pub fn new(observer: T) -> Self {
-        ToggleObserver {
-            enabled: false,
-            last_heads: None,
-            observer,
-        }
-    }
-
-    pub fn take_patches(&mut self, heads: Vec<ChangeHash>) -> (T::Patches, Vec<ChangeHash>) {
-        let old_heads = self.last_heads.replace(heads).unwrap_or_default();
-        let patches = self.observer.take_patches();
-        (patches, old_heads)
-    }
-
-    pub fn with_text_rep(mut self, text_rep: TextRepresentation) -> Self {
-        self.observer = self.observer.with_text_rep(text_rep);
-        self
-    }
-
-    pub fn set_text_rep(&mut self, text_rep: TextRepresentation) {
-        self.observer.set_text_rep(text_rep)
-    }
-
-    pub fn enable(&mut self, enable: bool, heads: Vec<ChangeHash>) -> bool {
-        if self.enabled && !enable {
-            self.observer.take_patches();
-            self.last_heads = Some(heads);
-        }
-        let old_enabled = self.enabled;
-        self.enabled = enable;
-        old_enabled
-    }
-
-    fn get_path<R: ReadDoc>(&mut self, doc: &R, obj: &ObjId) -> Option<Vec<(ObjId, Prop)>> {
-        match doc.parents(obj) {
-            Ok(parents) => parents.visible_path(),
-            Err(e) => {
-                log!("error generating patch : {:?}", e);
-                None
-            }
-        }
-    }
-}
-
-impl<T: OpObserver + HasPatches> OpObserver for ToggleObserver<T> {
-    fn insert<R: ReadDoc>(
-        &mut self,
-        doc: &R,
-        obj: ObjId,
-        index: usize,
-        tagged_value: (Value<'_>, ObjId),
-        conflict: bool,
-    ) {
-        if self.enabled {
-            self.observer
-                .insert(doc, obj, index, tagged_value, conflict)
-        }
-    }
-
-    fn splice_text<R: ReadDoc>(&mut self, doc: &R, obj: ObjId, index: usize, value: &str) {
-        if self.enabled {
-            self.observer.splice_text(doc, obj, index, value)
-        }
-    }
-
-    fn delete_seq<R: ReadDoc>(&mut self, doc: &R, obj: ObjId, index: usize, length: usize) {
-        if self.enabled {
-            self.observer.delete_seq(doc, obj, index, length)
-        }
-    }
-
-    fn delete_map<R: ReadDoc>(&mut self, doc: &R, obj: ObjId, key: &str) {
-        if self.enabled {
-            self.observer.delete_map(doc, obj, key)
-        }
-    }
-
-    fn put<R: ReadDoc>(
-        &mut self,
-        doc: &R,
-        obj: ObjId,
-        prop: Prop,
-        tagged_value: (Value<'_>, ObjId),
-        conflict: bool,
-    ) {
-        if self.enabled {
-            self.observer.put(doc, obj, prop, tagged_value, conflict)
-        }
-    }
-
-    fn expose<R: ReadDoc>(
-        &mut self,
-        doc: &R,
-        obj: ObjId,
-        prop: Prop,
-        tagged_value: (Value<'_>, ObjId),
-        conflict: bool,
-    ) {
-        if self.enabled {
-            self.observer.expose(doc, obj, prop, tagged_value, conflict)
-        }
-    }
-
-    fn increment<R: ReadDoc>(
-        &mut self,
-        doc: &R,
-        obj: ObjId,
-        prop: Prop,
-        tagged_value: (i64, ObjId),
-    ) {
-        if self.enabled {
-            self.observer.increment(doc, obj, prop, tagged_value)
-        }
-    }
-
-    fn mark<'a, R: ReadDoc, M: Iterator<Item = Mark<'a>>>(
-        &mut self,
-        doc: &'a R,
-        obj: ObjId,
-        mark: M,
-    ) {
-        if self.enabled {
-            self.observer.mark(doc, obj, mark)
-        }
-    }
-
-    fn unmark<R: ReadDoc>(&mut self, doc: &R, obj: ObjId, name: &str, start: usize, end: usize) {
-        if self.enabled {
-            self.observer.unmark(doc, obj, name, start, end)
-        }
-    }
-
-    fn text_as_seq(&self) -> bool {
-        self.observer.get_text_rep() == TextRepresentation::Array
-    }
-}
-
-impl<T: BranchableObserver> BranchableObserver for ToggleObserver<T> {
-    fn merge(&mut self, other: &Self) {
-        self.observer.merge(&other.observer)
-    }
-
-    fn branch(&self) -> Self {
-        ToggleObserver {
-            observer: self.observer.branch(),
-            last_heads: None,
-            enabled: self.enabled,
-        }
-    }
-}
diff --git a/rust/automerge/src/op_observer/vec_observer.rs b/rust/automerge/src/op_observer/vec_observer.rs
deleted file mode 100644
index 9887699a..00000000
--- a/rust/automerge/src/op_observer/vec_observer.rs
+++ /dev/null
@@ -1,561 +0,0 @@
-#![allow(dead_code)]
-
-use core::fmt::Debug;
-
-use crate::{marks::Mark, ObjId, OpObserver, Prop, ReadDoc, ScalarValue, Value};
-
-use crate::sequence_tree::SequenceTree;
-
-use crate::op_observer::BranchableObserver;
-use crate::op_observer::{Patch, PatchAction};
-
-#[derive(Debug, Copy, Clone, PartialEq)]
-pub enum TextRepresentation {
-    Array,
-    String,
-}
-
-impl TextRepresentation {
-    pub fn is_array(&self) -> bool {
-        matches!(self, TextRepresentation::Array)
-    }
-
-    pub fn is_string(&self) -> bool {
-        matches!(self, TextRepresentation::String)
-    }
-}
-
-impl std::default::Default for TextRepresentation {
-    fn default() -> Self {
-        TextRepresentation::Array
-    }
-}
-
-pub(crate) trait TextIndex {
-    type Item: Debug + PartialEq + Clone;
-    type Iter<'a>: Iterator<Item = Self::Item>;
-
-    fn chars(text: &str) -> Self::Iter<'_>;
-}
-
-#[derive(Debug, Clone, Default)]
-struct VecOpObserverInner<T: TextIndex> {
-    pub(crate) patches: Vec<Patch<T::Item>>,
-    pub(crate) text_rep: TextRepresentation,
-}
-
-#[derive(Debug, Clone, Default)]
-pub struct VecOpObserver(VecOpObserverInner<Utf8TextIndex>);
-
-#[derive(Debug, Clone, Default)]
-pub struct VecOpObserver16(VecOpObserverInner<Utf16TextIndex>);
-
-#[derive(Debug, Clone, Default)]
-pub(crate) struct Utf16TextIndex;
-
-#[derive(Debug, Clone, Default)]
-pub(crate) struct Utf8TextIndex;
-
-impl TextIndex for Utf8TextIndex {
-    type Item = char;
-    type Iter<'a> = std::str::Chars<'a>;
-
-    fn chars(text: &str) -> Self::Iter<'_> {
-        text.chars()
-    }
-}
-
-impl TextIndex for Utf16TextIndex {
-    type Item = u16;
-    type Iter<'a> = std::str::EncodeUtf16<'a>;
-
-    fn chars(text: &str) -> Self::Iter<'_> {
-        text.encode_utf16()
-    }
-}
-
-pub trait HasPatches {
-    type Patches;
-
-    fn take_patches(&mut self) -> Self::Patches;
-    fn with_text_rep(self, text_rep: TextRepresentation) -> Self;
-    fn set_text_rep(&mut self, text_rep: TextRepresentation);
-    fn get_text_rep(&self) -> TextRepresentation;
-}
-
-impl HasPatches for VecOpObserver {
-    type Patches = Vec<Patch<char>>;
-
-    fn take_patches(&mut self) -> Self::Patches {
-        std::mem::take(&mut self.0.patches)
-    }
-
-    fn with_text_rep(mut self, text_rep: TextRepresentation) -> Self {
-        self.0.text_rep = text_rep;
-        self
-    }
-
-    fn set_text_rep(&mut self, text_rep: TextRepresentation) {
-        self.0.text_rep = text_rep;
-    }
-
-    fn get_text_rep(&self) -> TextRepresentation {
-        self.0.text_rep
-    }
-}
-
-impl HasPatches for VecOpObserver16 {
-    type Patches = Vec<Patch<u16>>;
-
-    fn take_patches(&mut self) -> Self::Patches {
-        std::mem::take(&mut self.0.patches)
-    }
-
-    fn with_text_rep(mut self, text_rep: TextRepresentation) -> Self {
-        self.0.text_rep = text_rep;
-        self
-    }
-
-    fn set_text_rep(&mut self, text_rep: TextRepresentation) {
-        self.0.text_rep = text_rep;
-    }
-
-    fn get_text_rep(&self) -> TextRepresentation {
-        self.0.text_rep
-    }
-}
-
-impl<T: TextIndex> VecOpObserverInner<T> {
-    fn get_path<R: ReadDoc>(&mut self, doc: &R, obj: &ObjId) -> Option<Vec<(ObjId, Prop)>> {
-        match doc.parents(obj) {
-            Ok(parents) => parents.visible_path(),
-            Err(e) => {
-                log!("error generating patch : {:?}", e);
-                None
-            }
-        }
-    }
-
-    fn maybe_append(&mut self, obj: &ObjId) -> Option<&mut PatchAction<T::Item>> {
-        match self.patches.last_mut() {
-            Some(Patch {
-                obj: tail_obj,
-                action,
-                ..
-            }) if obj == tail_obj => Some(action),
-            _ => None,
-        }
-    }
-}
-
-impl<T: TextIndex> OpObserver for VecOpObserverInner<T> {
-    fn insert<R: ReadDoc>(
-        &mut self,
-        doc: &R,
-        obj: ObjId,
-        index: usize,
-        tagged_value: (Value<'_>, ObjId),
-        conflict: bool,
-    ) {
-        let value = (tagged_value.0.to_owned(), tagged_value.1);
-        if let Some(PatchAction::Insert {
-            index: tail_index,
-            values,
-            ..
-        }) = self.maybe_append(&obj)
-        {
-            let range = *tail_index..=*tail_index + values.len();
-            if range.contains(&index) {
-                values.insert(index - *tail_index, value);
-                return;
-            }
-        }
-        if let Some(path) = self.get_path(doc, &obj) {
-            let mut values = SequenceTree::new();
-            values.push(value);
-            let action = PatchAction::Insert {
-                index,
-                values,
-                conflict,
-            };
-            self.patches.push(Patch { obj, path, action });
-        }
-    }
-
-    fn splice_text<R: ReadDoc>(&mut self, doc: &R, obj: ObjId, index: usize, value: &str) {
-        if self.text_rep == TextRepresentation::Array {
-            for (offset, c) in value.chars().map(ScalarValue::from).enumerate() {
-                let value = (c.into(), ObjId::Root);
-                self.insert(doc, obj.clone(), index + offset, value, false);
-            }
-            return;
-        }
-        if let Some(PatchAction::SpliceText {
-            index: tail_index,
-            value: prev_value,
-            ..
-        }) = self.maybe_append(&obj)
-        {
-            let range = *tail_index..=*tail_index + prev_value.len();
-            if range.contains(&index) {
-                let i = index - *tail_index;
-                for (n, ch) in T::chars(value).enumerate() {
-                    prev_value.insert(i + n, ch)
-                }
-                return;
-            }
-        }
-        if let Some(path) = self.get_path(doc, &obj) {
-            let mut v = SequenceTree::new();
-            for ch in T::chars(value) {
-                v.push(ch)
-            }
-            let action = PatchAction::SpliceText { index, value: v };
-            self.patches.push(Patch { obj, path, action });
-        }
-    }
-
-    fn delete_seq<R: ReadDoc>(&mut self, doc: &R, obj: ObjId, index: usize, length: usize) {
-        match self.maybe_append(&obj) {
-            Some(PatchAction::SpliceText {
-                index: tail_index,
-                value,
-                ..
-            }) => {
-                let range = *tail_index..*tail_index + value.len();
-                if range.contains(&index) && range.contains(&(index + length - 1)) {
-                    for _ in 0..length {
-                        value.remove(index - *tail_index);
-                    }
-                    return;
-                }
-            }
-            Some(PatchAction::Insert {
-                index: tail_index,
-                values,
-                ..
-            }) => {
-                let range = *tail_index..*tail_index + values.len();
-                if range.contains(&index) && range.contains(&(index + length - 1)) {
-                    for _ in 0..length {
-                        values.remove(index - *tail_index);
-                    }
-                    return;
-                }
-            }
-            Some(PatchAction::DeleteSeq {
-                index: tail_index,
-                length: tail_length,
-                ..
-            }) => {
-                if index == *tail_index {
-                    *tail_length += length;
-                    return;
-                }
-            }
-            _ => {}
-        }
-        if let Some(path) = self.get_path(doc, &obj) {
-            let action = PatchAction::DeleteSeq { index, length };
-            self.patches.push(Patch { obj, path, action })
-        }
-    }
-
-    fn delete_map<R: ReadDoc>(&mut self, doc: &R, obj: ObjId, key: &str) {
-        if let Some(path) = self.get_path(doc, &obj) {
-            let action = PatchAction::DeleteMap {
-                key: key.to_owned(),
-            };
-            self.patches.push(Patch { obj, path, action })
-        }
-    }
-
-    fn put<R: ReadDoc>(
-        &mut self,
-        doc: &R,
-        obj: ObjId,
-        prop: Prop,
-        tagged_value: (Value<'_>, ObjId),
-        conflict: bool,
-    ) {
-        let expose = false;
-        if let Some(path) = self.get_path(doc, &obj) {
-            let value = (tagged_value.0.to_owned(), tagged_value.1);
-            let action = match prop {
-                Prop::Map(key) => PatchAction::PutMap {
-                    key,
-                    value,
-                    expose,
-                    conflict,
-                },
-                Prop::Seq(index) => PatchAction::PutSeq {
-                    index,
-                    value,
-                    expose,
-                    conflict,
-                },
-            };
-            self.patches.push(Patch { obj, path, action })
-        }
-    }
-
-    fn expose<R: ReadDoc>(
-        &mut self,
-        doc: &R,
-        obj: ObjId,
-        prop: Prop,
-        tagged_value: (Value<'_>, ObjId),
-        conflict: bool,
-    ) {
-        let expose = true;
-        if let Some(path) = self.get_path(doc, &obj) {
-            let value = (tagged_value.0.to_owned(), tagged_value.1);
-            let action = match prop {
-                Prop::Map(key) => PatchAction::PutMap {
-                    key,
-                    value,
-                    expose,
-                    conflict,
-                },
-                Prop::Seq(index) => PatchAction::PutSeq {
-                    index,
-                    value,
-                    expose,
-                    conflict,
-                },
-            };
-            self.patches.push(Patch { obj, path, action })
-        }
-    }
-
-    fn increment<R: ReadDoc>(
-        &mut self,
-        doc: &R,
-        obj: ObjId,
-        prop: Prop,
-        tagged_value: (i64, ObjId),
-    ) {
-        if let Some(path) = self.get_path(doc, &obj) {
-            let value = tagged_value.0;
-            let action = PatchAction::Increment { prop, value };
-            self.patches.push(Patch { obj, path, action })
-        }
-    }
-
-    fn mark<'a, R: ReadDoc, M: Iterator<Item = Mark<'a>>>(
-        &mut self,
-        doc: &'a R,
-        obj: ObjId,
-        mark: M,
-    ) {
-        if let Some(PatchAction::Mark { marks, .. }) = self.maybe_append(&obj) {
-            for m in mark {
-                marks.push(m.into_owned())
-            }
-            return;
-        }
-        if let Some(path) = self.get_path(doc, &obj) {
-            let marks: Vec<_> = mark.map(|m| m.into_owned()).collect();
-            if !marks.is_empty() {
-                let action = PatchAction::Mark { marks };
-                self.patches.push(Patch { obj, path, action });
-            }
-        }
-    }
-
-    fn unmark<R: ReadDoc>(&mut self, doc: &R, obj: ObjId, name: &str, start: usize, end: usize) {
-        if let Some(path) = self.get_path(doc, &obj) {
-            let action = PatchAction::Unmark {
-                name: name.to_string(),
-                start,
-                end,
-            };
-            self.patches.push(Patch { obj, path, action });
-        }
-    }
-
-    fn text_as_seq(&self) -> bool {
-        self.text_rep == TextRepresentation::Array
-    }
-}
-
-impl<T: TextIndex> BranchableObserver for VecOpObserverInner<T> {
-    fn merge(&mut self, other: &Self) {
-        self.patches.extend_from_slice(other.patches.as_slice())
-    }
-
-    fn branch(&self) -> Self {
-        VecOpObserverInner {
-            patches: vec![],
-            text_rep: self.text_rep,
-        }
-    }
-}
-
-impl OpObserver for VecOpObserver {
-    fn insert<R: ReadDoc>(
-        &mut self,
-        doc: &R,
-        obj: ObjId,
-        index: usize,
-        tagged_value: (Value<'_>, ObjId),
-        conflict: bool,
-    ) {
-        self.0.insert(doc, obj, index, tagged_value, conflict)
-    }
-
-    fn splice_text<R: ReadDoc>(&mut self, doc: &R, obj: ObjId, index: usize, value: &str) {
-        self.0.splice_text(doc, obj, index, value)
-    }
-
-    fn delete_seq<R: ReadDoc>(&mut self, doc: &R, obj: ObjId, index: usize, length: usize) {
-        self.0.delete_seq(doc, obj, index, length)
-    }
-
-    fn delete_map<R: ReadDoc>(&mut self, doc: &R, obj: ObjId, key: &str) {
-        self.0.delete_map(doc, obj, key)
-    }
-
-    fn put<R: ReadDoc>(
-        &mut self,
-        doc: &R,
-        obj: ObjId,
-        prop: Prop,
-        tagged_value: (Value<'_>, ObjId),
-        conflict: bool,
-    ) {
-        self.0.put(doc, obj, prop, tagged_value, conflict)
-    }
-
-    fn expose<R: ReadDoc>(
-        &mut self,
-        doc: &R,
-        obj: ObjId,
-        prop: Prop,
-        tagged_value: (Value<'_>, ObjId),
-        conflict: bool,
-    ) {
-        self.0.expose(doc, obj, prop, tagged_value, conflict)
-    }
-
-    fn increment<R: ReadDoc>(
-        &mut self,
-        doc: &R,
-        obj: ObjId,
-        prop: Prop,
-        tagged_value: (i64, ObjId),
-    ) {
-        self.0.increment(doc, obj, prop, tagged_value)
-    }
-
-    fn mark<'a, R: ReadDoc, M: Iterator<Item = Mark<'a>>>(
-        &mut self,
-        doc: &'a R,
-        obj: ObjId,
-        mark: M,
-    ) {
-        self.0.mark(doc, obj, mark)
-    }
-
-    fn unmark<R: ReadDoc>(&mut self, doc: &R, obj: ObjId, name: &str, start: usize, end: usize) {
-        self.0.unmark(doc, obj, name, start, end)
-    }
-
-    fn text_as_seq(&self) -> bool {
-        self.0.text_as_seq()
-    }
-}
-
-impl OpObserver for VecOpObserver16 {
-    fn insert<R: ReadDoc>(
-        &mut self,
-        doc: &R,
-        obj: ObjId,
-        index: usize,
-        tagged_value: (Value<'_>, ObjId),
-        conflict: bool,
-    ) {
-        self.0.insert(doc, obj, index, tagged_value, conflict)
-    }
-
-    fn splice_text<R: ReadDoc>(&mut self, doc: &R, obj: ObjId, index: usize, value: &str) {
-        self.0.splice_text(doc, obj, index, value)
-    }
-
-    fn delete_seq<R: ReadDoc>(&mut self, doc: &R, obj: ObjId, index: usize, length: usize) {
-        self.0.delete_seq(doc, obj, index, length)
-    }
-
-    fn delete_map<R: ReadDoc>(&mut self, doc: &R, obj: ObjId, key: &str) {
-        self.0.delete_map(doc, obj, key)
-    }
-
-    fn put<R: ReadDoc>(
-        &mut self,
-        doc: &R,
-        obj: ObjId,
-        prop: Prop,
-        tagged_value: (Value<'_>, ObjId),
-        conflict: bool,
-    ) {
-        self.0.put(doc, obj, prop, tagged_value, conflict)
-    }
-
-    fn expose<R: ReadDoc>(
-        &mut self,
-        doc: &R,
-        obj: ObjId,
-        prop: Prop,
-        tagged_value: (Value<'_>, ObjId),
-        conflict: bool,
-    ) {
-        self.0.expose(doc, obj, prop, tagged_value, conflict)
-    }
-
-    fn increment<R: ReadDoc>(
-        &mut self,
-        doc: &R,
-        obj: ObjId,
-        prop: Prop,
-        tagged_value: (i64, ObjId),
-    ) {
-        self.0.increment(doc, obj, prop, tagged_value)
-    }
-
-    fn mark<'a, R: ReadDoc, M: Iterator<Item = Mark<'a>>>(
-        &mut self,
-        doc: &'a R,
-        obj: ObjId,
-        mark: M,
-    ) {
-        self.0.mark(doc, obj, mark)
-    }
-
-    fn unmark<R: ReadDoc>(&mut self, doc: &R, obj: ObjId, name: &str, start: usize, end: usize) {
-        self.0.unmark(doc, obj, name, start, end)
-    }
-
-    fn text_as_seq(&self) -> bool {
-        self.0.text_as_seq()
-    }
-}
-
-impl BranchableObserver for VecOpObserver {
-    fn merge(&mut self, other: &Self) {
-        self.0.merge(&other.0)
-    }
-
-    fn branch(&self) -> Self {
-        VecOpObserver(self.0.branch())
-    }
-}
-
-impl BranchableObserver for VecOpObserver16 {
-    fn merge(&mut self, other: &Self) {
-        self.0.merge(&other.0)
-    }
-
-    fn branch(&self) -> Self {
-        VecOpObserver16(self.0.branch())
-    }
-}
diff --git a/rust/automerge/src/op_set.rs b/rust/automerge/src/op_set.rs
index cd697abd..aab8ce74 100644
--- a/rust/automerge/src/op_set.rs
+++ b/rust/automerge/src/op_set.rs
@@ -78,10 +78,6 @@ impl OpSetInternal {
         }
     }
 
-    pub(crate) fn iter_ops(&self, obj: &ObjId) -> impl Iterator<Item = &Op> {
-        self.trees.get(obj).map(|o| o.iter()).into_iter().flatten()
-    }
-
     pub(crate) fn parents(&self, obj: ObjId) -> Parents<'_> {
         Parents { obj, ops: self }
     }
diff --git a/rust/automerge/src/op_tree.rs b/rust/automerge/src/op_tree.rs
index 60bd2a6e..7de00dc3 100644
--- a/rust/automerge/src/op_tree.rs
+++ b/rust/automerge/src/op_tree.rs
@@ -319,7 +319,8 @@ struct CounterData {
 
 #[cfg(test)]
 mod tests {
-    use crate::types::{Op, OpId, OpType};
+    use crate::legacy as amp;
+    use crate::types::{Op, OpId};
 
     use super::*;
 
@@ -327,7 +328,7 @@ mod tests {
         let zero = OpId::new(0, 0);
         Op {
             id: zero,
-            action: OpType::Put(0.into()),
+            action: amp::OpType::Put(0.into()),
             key: zero.into(),
             succ: Default::default(),
             pred: Default::default(),
diff --git a/rust/automerge/src/query.rs b/rust/automerge/src/query.rs
index c76c3a0e..640ecf8d 100644
--- a/rust/automerge/src/query.rs
+++ b/rust/automerge/src/query.rs
@@ -25,7 +25,6 @@ mod opid;
 mod opid_vis;
 mod prop;
 mod prop_at;
-mod seek_mark;
 mod seek_op;
 mod seek_op_with_patch;
 
@@ -47,7 +46,6 @@ pub(crate) use opid::OpIdSearch;
 pub(crate) use opid_vis::OpIdVisSearch;
 pub(crate) use prop::Prop;
 pub(crate) use prop_at::PropAt;
-pub(crate) use seek_mark::SeekMark;
 pub(crate) use seek_op::SeekOp;
 pub(crate) use seek_op_with_patch::SeekOpWithPatch;
 
@@ -289,7 +287,7 @@ pub(crate) struct VisWindow {
 }
 
 impl VisWindow {
-    pub(crate) fn visible_at(&mut self, op: &Op, pos: usize, clock: &Clock) -> bool {
+    fn visible_at(&mut self, op: &Op, pos: usize, clock: &Clock) -> bool {
         if !clock.covers(&op.id) {
             return false;
         }
diff --git a/rust/automerge/src/query/insert.rs b/rust/automerge/src/query/insert.rs
index 8e86d619..0dc0e98d 100644
--- a/rust/automerge/src/query/insert.rs
+++ b/rust/automerge/src/query/insert.rs
@@ -110,12 +110,6 @@ impl<'a> TreeQuery<'a> for InsertNth {
             self.last_seen = None;
             self.last_insert = element.elemid();
         }
-        /*-------------------*/
-        if self.valid.is_some() && element.valid_mark_anchor() {
-            self.last_valid_insert = Some(element.elemid_or_key());
-            self.valid = None;
-        }
-        /*-------------------*/
         if self.last_seen.is_none() && element.visible() {
             if self.seen >= self.target {
                 return QueryResult::Finish;
diff --git a/rust/automerge/src/query/seek_mark.rs b/rust/automerge/src/query/seek_mark.rs
deleted file mode 100644
index c5834ab8..00000000
--- a/rust/automerge/src/query/seek_mark.rs
+++ /dev/null
@@ -1,124 +0,0 @@
-use crate::marks::Mark;
-use crate::op_tree::OpSetMetadata;
-use crate::query::{QueryResult, TreeQuery};
-use crate::types::{Key, ListEncoding, Op, OpId, OpType};
-use std::cmp::Ordering;
-use std::collections::HashMap;
-use std::fmt::Debug;
-
-#[derive(Debug, Clone, PartialEq)]
-pub(crate) struct SeekMark<'a> {
-    /// the mark we are looking for
-    id: OpId,
-    end: usize,
-    encoding: ListEncoding,
-    found: bool,
-    mark_name: smol_str::SmolStr,
-    next_mark: Option<Mark<'a>>,
-    pos: usize,
-    seen: usize,
-    last_seen: Option<Key>,
-    super_marks: HashMap<OpId, smol_str::SmolStr>,
-    pub(crate) marks: Vec<Mark<'a>>,
-}
-
-impl<'a> SeekMark<'a> {
-    pub(crate) fn new(id: OpId, end: usize, encoding: ListEncoding) -> Self {
-        SeekMark {
-            id,
-            encoding,
-            end,
-            found: false,
-            next_mark: None,
-            mark_name: "".into(),
-            pos: 0,
-            seen: 0,
-            last_seen: None,
-            super_marks: Default::default(),
-            marks: Default::default(),
-        }
-    }
-
-    fn count_visible(&mut self, e: &Op) {
-        if e.insert {
-            self.last_seen = None
-        }
-        if e.visible() && self.last_seen.is_none() {
-            self.seen += e.width(self.encoding);
-            self.last_seen = Some(e.elemid_or_key())
-        }
-    }
-}
-
-impl<'a> TreeQuery<'a> for SeekMark<'a> {
-    fn query_element_with_metadata(&mut self, op: &'a Op, m: &OpSetMetadata) -> QueryResult {
-        match &op.action {
-            OpType::MarkBegin(_, data) if op.id == self.id => {
-                if !op.succ.is_empty() {
-                    return QueryResult::Finish;
-                }
-                self.found = true;
-                self.mark_name = data.name.clone();
-                // retain the name and the value
-                self.next_mark = Some(Mark::from_data(self.seen, self.seen, data));
-                // change id to the end id
-                self.id = self.id.next();
-                // remove all marks that dont match
-                self.super_marks.retain(|_, v| v == &data.name);
-            }
-            OpType::MarkBegin(_, mark) => {
-                if m.lamport_cmp(op.id, self.id) == Ordering::Greater {
-                    if let Some(next_mark) = &mut self.next_mark {
-                        // gather marks of the same type that supersede us
-                        if mark.name == self.mark_name {
-                            self.super_marks.insert(op.id.next(), mark.name.clone());
-                            if self.super_marks.len() == 1 {
-                                // complete a mark
-                                next_mark.end = self.seen;
-                                self.marks.push(next_mark.clone());
-                            }
-                        }
-                    } else {
-                        // gather all marks until we know what our mark's name is
-                        self.super_marks.insert(op.id.next(), mark.name.clone());
-                    }
-                }
-            }
-            OpType::MarkEnd(_) if self.end == self.pos => {
-                if self.super_marks.is_empty() {
-                    // complete a mark
-                    if let Some(next_mark) = &mut self.next_mark {
-                        next_mark.end = self.seen;
-                        self.marks.push(next_mark.clone());
-                    }
-                }
-                return QueryResult::Finish;
-            }
-            OpType::MarkEnd(_) if self.super_marks.contains_key(&op.id) => {
-                self.super_marks.remove(&op.id);
-                if let Some(next_mark) = &mut self.next_mark {
-                    if self.super_marks.is_empty() {
-                        // begin a new mark
-                        next_mark.start = self.seen;
-                    }
-                }
-            }
-            _ => {}
-        }
-        // the end op hasn't been inserted yet so we need to work off the position
-        if self.end == self.pos {
-            if self.super_marks.is_empty() {
-                // complete a mark
-                if let Some(next_mark) = &mut self.next_mark {
-                    next_mark.end = self.seen;
-                    self.marks.push(next_mark.clone());
-                }
-            }
-            return QueryResult::Finish;
-        }
-
-        self.pos += 1;
-        self.count_visible(op);
-        QueryResult::Next
-    }
-}
diff --git a/rust/automerge/src/read.rs b/rust/automerge/src/read.rs
index 9b3a6a77..6d479718 100644
--- a/rust/automerge/src/read.rs
+++ b/rust/automerge/src/read.rs
@@ -1,7 +1,7 @@
 use crate::{
     error::AutomergeError, exid::ExId, keys::Keys, keys_at::KeysAt, list_range::ListRange,
-    list_range_at::ListRangeAt, map_range::MapRange, map_range_at::MapRangeAt, marks::Mark,
-    parents::Parents, values::Values, Change, ChangeHash, ObjType, Prop, Value,
+    list_range_at::ListRangeAt, map_range::MapRange, map_range_at::MapRangeAt, parents::Parents,
+    values::Values, Change, ChangeHash, ObjType, Prop, Value,
 };
 
 use std::ops::RangeBounds;
@@ -129,16 +129,6 @@ pub trait ReadDoc {
     /// Get the type of this object, if it is an object.
     fn object_type<O: AsRef<ExId>>(&self, obj: O) -> Result<ObjType, AutomergeError>;
 
-    /// Get all marks on a current sequence
-    fn marks<O: AsRef<ExId>>(&self, obj: O) -> Result<Vec<Mark<'_>>, AutomergeError>;
-
-    /// Get all marks on a sequence at a given heads
-    fn marks_at<O: AsRef<ExId>>(
-        &self,
-        obj: O,
-        heads: &[ChangeHash],
-    ) -> Result<Vec<Mark<'_>>, AutomergeError>;
-
     /// Get the string represented by the given text object.
     fn text<O: AsRef<ExId>>(&self, obj: O) -> Result<String, AutomergeError>;
 
diff --git a/rust/automerge/src/sequence_tree.rs b/rust/automerge/src/sequence_tree.rs
deleted file mode 100644
index 920eb13f..00000000
--- a/rust/automerge/src/sequence_tree.rs
+++ /dev/null
@@ -1,617 +0,0 @@
-use std::{
-    cmp::{min, Ordering},
-    fmt::Debug,
-    mem,
-};
-
-pub(crate) const B: usize = 16;
-pub(crate) type SequenceTree<T> = SequenceTreeInternal<T>;
-
-#[derive(Clone, Debug)]
-pub struct SequenceTreeInternal<T> {
-    root_node: Option<SequenceTreeNode<T>>,
-}
-
-#[derive(Clone, Debug, PartialEq)]
-struct SequenceTreeNode<T> {
-    elements: Vec<T>,
-    children: Vec<SequenceTreeNode<T>>,
-    length: usize,
-}
-
-impl<T> SequenceTreeInternal<T>
-where
-    T: Clone + Debug,
-{
-    /// Construct a new, empty, sequence.
-    pub fn new() -> Self {
-        Self { root_node: None }
-    }
-
-    /// Get the length of the sequence.
-    pub fn len(&self) -> usize {
-        self.root_node.as_ref().map_or(0, |n| n.len())
-    }
-
-    /// Create an iterator through the sequence.
-    pub fn iter(&self) -> Iter<'_, T> {
-        Iter {
-            inner: self,
-            index: 0,
-        }
-    }
-
-    /// Insert the `element` into the sequence at `index`.
-    ///
-    /// # Panics
-    ///
-    /// Panics if `index > len`.
-    pub fn insert(&mut self, index: usize, element: T) {
-        let old_len = self.len();
-        if let Some(root) = self.root_node.as_mut() {
-            #[cfg(debug_assertions)]
-            root.check();
-
-            if root.is_full() {
-                let original_len = root.len();
-                let new_root = SequenceTreeNode::new();
-
-                // move new_root to root position
-                let old_root = mem::replace(root, new_root);
-
-                root.length += old_root.len();
-                root.children.push(old_root);
-                root.split_child(0);
-
-                assert_eq!(original_len, root.len());
-
-                // after splitting the root has one element and two children, find which child the
-                // index is in
-                let first_child_len = root.children[0].len();
-                let (child, insertion_index) = if first_child_len < index {
-                    (&mut root.children[1], index - (first_child_len + 1))
-                } else {
-                    (&mut root.children[0], index)
-                };
-                root.length += 1;
-                child.insert_into_non_full_node(insertion_index, element)
-            } else {
-                root.insert_into_non_full_node(index, element)
-            }
-        } else {
-            self.root_node = Some(SequenceTreeNode {
-                elements: vec![element],
-                children: Vec::new(),
-                length: 1,
-            })
-        }
-        assert_eq!(self.len(), old_len + 1, "{:#?}", self);
-    }
-
-    /// Push the `element` onto the back of the sequence.
-    pub fn push(&mut self, element: T) {
-        let l = self.len();
-        self.insert(l, element)
-    }
-
-    /// Get the `element` at `index` in the sequence.
-    pub fn get(&self, index: usize) -> Option<&T> {
-        self.root_node.as_ref().and_then(|n| n.get(index))
-    }
-
-    /// Removes the element at `index` from the sequence.
-    ///
-    /// # Panics
-    ///
-    /// Panics if `index` is out of bounds.
-    pub fn remove(&mut self, index: usize) -> T {
-        if let Some(root) = self.root_node.as_mut() {
-            #[cfg(debug_assertions)]
-            let len = root.check();
-            let old = root.remove(index);
-
-            if root.elements.is_empty() {
-                if root.is_leaf() {
-                    self.root_node = None;
-                } else {
-                    self.root_node = Some(root.children.remove(0));
-                }
-            }
-
-            #[cfg(debug_assertions)]
-            debug_assert_eq!(len, self.root_node.as_ref().map_or(0, |r| r.check()) + 1);
-            old
-        } else {
-            panic!("remove from empty tree")
-        }
-    }
-}
-
-impl<T> SequenceTreeNode<T>
-where
-    T: Clone + Debug,
-{
-    fn new() -> Self {
-        Self {
-            elements: Vec::new(),
-            children: Vec::new(),
-            length: 0,
-        }
-    }
-
-    fn len(&self) -> usize {
-        self.length
-    }
-
-    fn is_leaf(&self) -> bool {
-        self.children.is_empty()
-    }
-
-    fn is_full(&self) -> bool {
-        self.elements.len() >= 2 * B - 1
-    }
-
-    /// Returns the child index and the given index adjusted for the cumulative index before that
-    /// child.
-    fn find_child_index(&self, index: usize) -> (usize, usize) {
-        let mut cumulative_len = 0;
-        for (child_index, child) in self.children.iter().enumerate() {
-            if cumulative_len + child.len() >= index {
-                return (child_index, index - cumulative_len);
-            } else {
-                cumulative_len += child.len() + 1;
-            }
-        }
-        panic!("index not found in node")
-    }
-
-    fn insert_into_non_full_node(&mut self, index: usize, element: T) {
-        assert!(!self.is_full());
-        if self.is_leaf() {
-            self.length += 1;
-            self.elements.insert(index, element);
-        } else {
-            let (child_index, sub_index) = self.find_child_index(index);
-            let child = &mut self.children[child_index];
-
-            if child.is_full() {
-                self.split_child(child_index);
-
-                // child structure has changed so we need to find the index again
-                let (child_index, sub_index) = self.find_child_index(index);
-                let child = &mut self.children[child_index];
-                child.insert_into_non_full_node(sub_index, element);
-            } else {
-                child.insert_into_non_full_node(sub_index, element);
-            }
-            self.length += 1;
-        }
-    }
-
-    // A utility function to split the child `full_child_index` of this node
-    // Note that `full_child_index` must be full when this function is called.
-    fn split_child(&mut self, full_child_index: usize) {
-        let original_len_self = self.len();
-
-        // Create a new node which is going to store (B-1) keys
-        // of the full child.
-        let mut successor_sibling = SequenceTreeNode::new();
-
-        let full_child = &mut self.children[full_child_index];
-        let original_len = full_child.len();
-        assert!(full_child.is_full());
-
-        successor_sibling.elements = full_child.elements.split_off(B);
-
-        if !full_child.is_leaf() {
-            successor_sibling.children = full_child.children.split_off(B);
-        }
-
-        let middle = full_child.elements.pop().unwrap();
-
-        full_child.length =
-            full_child.elements.len() + full_child.children.iter().map(|c| c.len()).sum::<usize>();
-
-        successor_sibling.length = successor_sibling.elements.len()
-            + successor_sibling
-                .children
-                .iter()
-                .map(|c| c.len())
-                .sum::<usize>();
-
-        let z_len = successor_sibling.len();
-
-        let full_child_len = full_child.len();
-
-        self.children
-            .insert(full_child_index + 1, successor_sibling);
-
-        self.elements.insert(full_child_index, middle);
-
-        assert_eq!(full_child_len + z_len + 1, original_len, "{:#?}", self);
-
-        assert_eq!(original_len_self, self.len());
-    }
-
-    fn remove_from_leaf(&mut self, index: usize) -> T {
-        self.length -= 1;
-        self.elements.remove(index)
-    }
-
-    fn remove_element_from_non_leaf(&mut self, index: usize, element_index: usize) -> T {
-        self.length -= 1;
-        if self.children[element_index].elements.len() >= B {
-            let total_index = self.cumulative_index(element_index);
-            // recursively delete index - 1 in predecessor_node
-            let predecessor = self.children[element_index].remove(index - 1 - total_index);
-            // replace element with that one
-            mem::replace(&mut self.elements[element_index], predecessor)
-        } else if self.children[element_index + 1].elements.len() >= B {
-            // recursively delete index + 1 in successor_node
-            let total_index = self.cumulative_index(element_index + 1);
-            let successor = self.children[element_index + 1].remove(index + 1 - total_index);
-            // replace element with that one
-            mem::replace(&mut self.elements[element_index], successor)
-        } else {
-            let middle_element = self.elements.remove(element_index);
-            let successor_child = self.children.remove(element_index + 1);
-            self.children[element_index].merge(middle_element, successor_child);
-
-            let total_index = self.cumulative_index(element_index);
-            self.children[element_index].remove(index - total_index)
-        }
-    }
-
-    fn cumulative_index(&self, child_index: usize) -> usize {
-        self.children[0..child_index]
-            .iter()
-            .map(|c| c.len() + 1)
-            .sum()
-    }
-
-    fn remove_from_internal_child(&mut self, index: usize, mut child_index: usize) -> T {
-        if self.children[child_index].elements.len() < B
-            && if child_index > 0 {
-                self.children[child_index - 1].elements.len() < B
-            } else {
-                true
-            }
-            && if child_index + 1 < self.children.len() {
-                self.children[child_index + 1].elements.len() < B
-            } else {
-                true
-            }
-        {
-            // if the child and its immediate siblings have B-1 elements merge the child
-            // with one sibling, moving an element from this node into the new merged node
-            // to be the median
-
-            if child_index > 0 {
-                let middle = self.elements.remove(child_index - 1);
-
-                // use the predessor sibling
-                let successor = self.children.remove(child_index);
-                child_index -= 1;
-
-                self.children[child_index].merge(middle, successor);
-            } else {
-                let middle = self.elements.remove(child_index);
-
-                // use the sucessor sibling
-                let successor = self.children.remove(child_index + 1);
-
-                self.children[child_index].merge(middle, successor);
-            }
-        } else if self.children[child_index].elements.len() < B {
-            if child_index > 0
-                && self
-                    .children
-                    .get(child_index - 1)
-                    .map_or(false, |c| c.elements.len() >= B)
-            {
-                let last_element = self.children[child_index - 1].elements.pop().unwrap();
-                assert!(!self.children[child_index - 1].elements.is_empty());
-                self.children[child_index - 1].length -= 1;
-
-                let parent_element =
-                    mem::replace(&mut self.elements[child_index - 1], last_element);
-
-                self.children[child_index]
-                    .elements
-                    .insert(0, parent_element);
-                self.children[child_index].length += 1;
-
-                if let Some(last_child) = self.children[child_index - 1].children.pop() {
-                    self.children[child_index - 1].length -= last_child.len();
-                    self.children[child_index].length += last_child.len();
-                    self.children[child_index].children.insert(0, last_child);
-                }
-            } else if self
-                .children
-                .get(child_index + 1)
-                .map_or(false, |c| c.elements.len() >= B)
-            {
-                let first_element = self.children[child_index + 1].elements.remove(0);
-                self.children[child_index + 1].length -= 1;
-
-                assert!(!self.children[child_index + 1].elements.is_empty());
-
-                let parent_element = mem::replace(&mut self.elements[child_index], first_element);
-
-                self.children[child_index].length += 1;
-                self.children[child_index].elements.push(parent_element);
-
-                if !self.children[child_index + 1].is_leaf() {
-                    let first_child = self.children[child_index + 1].children.remove(0);
-                    self.children[child_index + 1].length -= first_child.len();
-                    self.children[child_index].length += first_child.len();
-
-                    self.children[child_index].children.push(first_child);
-                }
-            }
-        }
-        self.length -= 1;
-        let total_index = self.cumulative_index(child_index);
-        self.children[child_index].remove(index - total_index)
-    }
-
-    fn check(&self) -> usize {
-        let l = self.elements.len() + self.children.iter().map(|c| c.check()).sum::<usize>();
-        assert_eq!(self.len(), l, "{:#?}", self);
-
-        l
-    }
-
-    fn remove(&mut self, index: usize) -> T {
-        let original_len = self.len();
-        if self.is_leaf() {
-            let v = self.remove_from_leaf(index);
-            assert_eq!(original_len, self.len() + 1);
-            debug_assert_eq!(self.check(), self.len());
-            v
-        } else {
-            let mut total_index = 0;
-            for (child_index, child) in self.children.iter().enumerate() {
-                match (total_index + child.len()).cmp(&index) {
-                    Ordering::Less => {
-                        // should be later on in the loop
-                        total_index += child.len() + 1;
-                        continue;
-                    }
-                    Ordering::Equal => {
-                        let v = self.remove_element_from_non_leaf(
-                            index,
-                            min(child_index, self.elements.len() - 1),
-                        );
-                        assert_eq!(original_len, self.len() + 1);
-                        debug_assert_eq!(self.check(), self.len());
-                        return v;
-                    }
-                    Ordering::Greater => {
-                        let v = self.remove_from_internal_child(index, child_index);
-                        assert_eq!(original_len, self.len() + 1);
-                        debug_assert_eq!(self.check(), self.len());
-                        return v;
-                    }
-                }
-            }
-            panic!(
-                "index not found to remove {} {} {} {}",
-                index,
-                total_index,
-                self.len(),
-                self.check()
-            );
-        }
-    }
-
-    fn merge(&mut self, middle: T, successor_sibling: SequenceTreeNode<T>) {
-        self.elements.push(middle);
-        self.elements.extend(successor_sibling.elements);
-        self.children.extend(successor_sibling.children);
-        self.length += successor_sibling.length + 1;
-        assert!(self.is_full());
-    }
-
-    fn get(&self, index: usize) -> Option<&T> {
-        if self.is_leaf() {
-            return self.elements.get(index);
-        } else {
-            let mut cumulative_len = 0;
-            for (child_index, child) in self.children.iter().enumerate() {
-                match (cumulative_len + child.len()).cmp(&index) {
-                    Ordering::Less => {
-                        cumulative_len += child.len() + 1;
-                    }
-                    Ordering::Equal => return self.elements.get(child_index),
-                    Ordering::Greater => {
-                        return child.get(index - cumulative_len);
-                    }
-                }
-            }
-        }
-        None
-    }
-}
-
-impl<T> Default for SequenceTreeInternal<T>
-where
-    T: Clone + Debug,
-{
-    fn default() -> Self {
-        Self::new()
-    }
-}
-
-impl<T> PartialEq for SequenceTreeInternal<T>
-where
-    T: Clone + Debug + PartialEq,
-{
-    fn eq(&self, other: &Self) -> bool {
-        self.len() == other.len() && self.iter().zip(other.iter()).all(|(a, b)| a == b)
-    }
-}
-
-impl<'a, T> IntoIterator for &'a SequenceTreeInternal<T>
-where
-    T: Clone + Debug,
-{
-    type Item = &'a T;
-
-    type IntoIter = Iter<'a, T>;
-
-    fn into_iter(self) -> Self::IntoIter {
-        Iter {
-            inner: self,
-            index: 0,
-        }
-    }
-}
-
-#[derive(Debug)]
-pub struct Iter<'a, T> {
-    inner: &'a SequenceTreeInternal<T>,
-    index: usize,
-}
-
-impl<'a, T> Iterator for Iter<'a, T>
-where
-    T: Clone + Debug,
-{
-    type Item = &'a T;
-
-    fn next(&mut self) -> Option<Self::Item> {
-        self.index += 1;
-        self.inner.get(self.index - 1)
-    }
-
-    fn nth(&mut self, n: usize) -> Option<Self::Item> {
-        self.index += n + 1;
-        self.inner.get(self.index - 1)
-    }
-}
-
-#[cfg(test)]
-mod tests {
-    use proptest::prelude::*;
-
-    use super::*;
-
-    #[test]
-    fn push_back() {
-        let mut t = SequenceTree::new();
-
-        t.push(1);
-        t.push(2);
-        t.push(3);
-        t.push(4);
-        t.push(5);
-        t.push(6);
-        t.push(8);
-        t.push(100);
-    }
-
-    #[test]
-    fn insert() {
-        let mut t = SequenceTree::new();
-
-        t.insert(0, 1);
-        t.insert(1, 1);
-        t.insert(0, 1);
-        t.insert(0, 1);
-        t.insert(0, 1);
-        t.insert(3, 1);
-        t.insert(4, 1);
-    }
-
-    #[test]
-    fn insert_book() {
-        let mut t = SequenceTree::new();
-
-        for i in 0..100 {
-            t.insert(i % 2, ());
-        }
-    }
-
-    #[test]
-    fn insert_book_vec() {
-        let mut t = SequenceTree::new();
-        let mut v = Vec::new();
-
-        for i in 0..100 {
-            t.insert(i % 3, ());
-            v.insert(i % 3, ());
-
-            assert_eq!(v, t.iter().copied().collect::<Vec<_>>())
-        }
-    }
-
-    fn arb_indices() -> impl Strategy<Value = Vec<usize>> {
-        proptest::collection::vec(any::<usize>(), 0..1000).prop_map(|v| {
-            let mut len = 0;
-            v.into_iter()
-                .map(|i| {
-                    len += 1;
-                    i % len
-                })
-                .collect::<Vec<_>>()
-        })
-    }
-
-    proptest! {
-
-        #[test]
-        fn proptest_insert(indices in arb_indices()) {
-            let mut t = SequenceTreeInternal::<usize>::new();
-            let mut v = Vec::new();
-
-            for i in indices{
-                if i <= v.len() {
-                    t.insert(i % 3, i);
-                    v.insert(i % 3, i);
-                } else {
-                    return Err(proptest::test_runner::TestCaseError::reject("index out of bounds"))
-                }
-
-                assert_eq!(v, t.iter().copied().collect::<Vec<_>>())
-            }
-        }
-
-    }
-
-    proptest! {
-
-        // This is a really slow test due to all the copying of the Vecs (i.e. not due to the
-        // sequencetree) so we only do a few runs
-        #![proptest_config(ProptestConfig::with_cases(20))]
-        #[test]
-        fn proptest_remove(inserts in arb_indices(), removes in arb_indices()) {
-            let mut t = SequenceTreeInternal::<usize>::new();
-            let mut v = Vec::new();
-
-            for i in inserts {
-                if i <= v.len() {
-                    t.insert(i , i);
-                    v.insert(i , i);
-                } else {
-                    return Err(proptest::test_runner::TestCaseError::reject("index out of bounds"))
-                }
-
-                assert_eq!(v, t.iter().copied().collect::<Vec<_>>())
-            }
-
-            for i in removes {
-                if i < v.len() {
-                    let tr = t.remove(i);
-                    let vr = v.remove(i);
-                    assert_eq!(tr, vr);
-                } else {
-                    return Err(proptest::test_runner::TestCaseError::reject("index out of bounds"))
-                }
-
-                assert_eq!(v, t.iter().copied().collect::<Vec<_>>())
-            }
-        }
-
-    }
-}
diff --git a/rust/automerge/src/storage/change.rs b/rust/automerge/src/storage/change.rs
index a420da39..61db0b00 100644
--- a/rust/automerge/src/storage/change.rs
+++ b/rust/automerge/src/storage/change.rs
@@ -437,8 +437,6 @@ pub(crate) trait AsChangeOp<'a> {
     fn action(&self) -> u64;
     fn val(&self) -> Cow<'a, ScalarValue>;
     fn pred(&self) -> Self::PredIter;
-    fn expand(&self) -> bool;
-    fn mark_name(&self) -> Option<Cow<'a, smol_str::SmolStr>>;
 }
 
 impl ChangeBuilder<Set<NonZeroU64>, Set<ActorId>, Set<u64>, Set<i64>> {
diff --git a/rust/automerge/src/storage/change/change_actors.rs b/rust/automerge/src/storage/change/change_actors.rs
index 951201dd..61f1221d 100644
--- a/rust/automerge/src/storage/change/change_actors.rs
+++ b/rust/automerge/src/storage/change/change_actors.rs
@@ -1,7 +1,4 @@
-use std::{
-    borrow::Cow,
-    collections::{BTreeMap, BTreeSet},
-};
+use std::collections::{BTreeMap, BTreeSet};
 
 use crate::convert;
 
@@ -247,14 +244,6 @@ where
     fn val(&self) -> std::borrow::Cow<'aschangeop, crate::ScalarValue> {
         self.op.val()
     }
-
-    fn expand(&self) -> bool {
-        self.op.expand()
-    }
-
-    fn mark_name(&self) -> Option<Cow<'aschangeop, smol_str::SmolStr>> {
-        self.op.mark_name()
-    }
 }
 
 pub(crate) struct WithChangeActorsPredIter<'actors, 'aschangeop, A, I, O, C, P> {
diff --git a/rust/automerge/src/storage/change/change_op_columns.rs b/rust/automerge/src/storage/change/change_op_columns.rs
index 145073e6..86ec59c2 100644
--- a/rust/automerge/src/storage/change/change_op_columns.rs
+++ b/rust/automerge/src/storage/change/change_op_columns.rs
@@ -1,16 +1,16 @@
-use std::{borrow::Cow, convert::TryFrom, ops::Range};
+use std::{convert::TryFrom, ops::Range};
 
 use crate::{
     columnar::{
         column_range::{
             generic::{GenericColumnRange, GroupRange, GroupedColumnRange, SimpleColRange},
-            BooleanRange, DeltaRange, Key, KeyEncoder, KeyIter, KeyRange, MaybeBooleanRange,
-            ObjIdEncoder, ObjIdIter, ObjIdRange, OpIdListEncoder, OpIdListIter, OpIdListRange,
-            RleRange, ValueEncoder, ValueIter, ValueRange,
+            BooleanRange, DeltaRange, Key, KeyEncoder, KeyIter, KeyRange, ObjIdEncoder, ObjIdIter,
+            ObjIdRange, OpIdListEncoder, OpIdListIter, OpIdListRange, RleRange, ValueEncoder,
+            ValueIter, ValueRange,
         },
         encoding::{
-            BooleanDecoder, BooleanEncoder, ColumnDecoder, DecodeColumnError, MaybeBooleanDecoder,
-            MaybeBooleanEncoder, RleDecoder, RleEncoder,
+            BooleanDecoder, BooleanEncoder, ColumnDecoder, DecodeColumnError, RleDecoder,
+            RleEncoder,
         },
     },
     convert,
@@ -32,8 +32,6 @@ const INSERT_COL_ID: ColumnId = ColumnId::new(3);
 const ACTION_COL_ID: ColumnId = ColumnId::new(4);
 const VAL_COL_ID: ColumnId = ColumnId::new(5);
 const PRED_COL_ID: ColumnId = ColumnId::new(7);
-const EXPAND_COL_ID: ColumnId = ColumnId::new(8);
-const MARK_NAME_COL_ID: ColumnId = ColumnId::new(9);
 
 #[derive(Clone, Debug, PartialEq)]
 pub(crate) struct ChangeOp {
@@ -43,8 +41,6 @@ pub(crate) struct ChangeOp {
     pub(crate) pred: Vec<OpId>,
     pub(crate) action: u64,
     pub(crate) obj: ObjId,
-    pub(crate) expand: bool,
-    pub(crate) mark_name: Option<smol_str::SmolStr>,
 }
 
 impl<'a, A: AsChangeOp<'a, ActorId = usize, OpId = OpId>> From<A> for ChangeOp {
@@ -63,8 +59,6 @@ impl<'a, A: AsChangeOp<'a, ActorId = usize, OpId = OpId>> From<A> for ChangeOp {
             pred: a.pred().collect(),
             insert: a.insert(),
             action: a.action(),
-            expand: a.expand(),
-            mark_name: a.mark_name().map(|n| n.into_owned()),
         }
     }
 }
@@ -105,14 +99,6 @@ impl<'a> AsChangeOp<'a> for &'a ChangeOp {
     fn action(&self) -> u64 {
         self.action
     }
-
-    fn expand(&self) -> bool {
-        self.expand
-    }
-
-    fn mark_name(&self) -> Option<Cow<'a, smol_str::SmolStr>> {
-        self.mark_name.as_ref().map(Cow::Borrowed)
-    }
 }
 
 #[derive(Clone, Debug, PartialEq)]
@@ -123,8 +109,6 @@ pub(crate) struct ChangeOpsColumns {
     action: RleRange<u64>,
     val: ValueRange,
     pred: OpIdListRange,
-    expand: MaybeBooleanRange,
-    mark_name: RleRange<smol_str::SmolStr>,
 }
 
 impl ChangeOpsColumns {
@@ -137,8 +121,6 @@ impl ChangeOpsColumns {
             action: self.action.decoder(data),
             val: self.val.iter(data),
             pred: self.pred.iter(data),
-            expand: self.expand.decoder(data),
-            mark_name: self.mark_name.decoder(data),
         }
     }
 
@@ -165,16 +147,12 @@ impl ChangeOpsColumns {
         Op: convert::OpId<usize> + 'a,
         C: AsChangeOp<'c, OpId = Op> + 'a,
     {
-        tracing::trace!(expands = ?ops.clone().map(|op| op.expand()).collect::<Vec<_>>(), "encoding change ops");
         let obj = ObjIdRange::encode(ops.clone().map(|o| o.obj()), out);
         let key = KeyRange::encode(ops.clone().map(|o| o.key()), out);
         let insert = BooleanRange::encode(ops.clone().map(|o| o.insert()), out);
         let action = RleRange::encode(ops.clone().map(|o| Some(o.action())), out);
         let val = ValueRange::encode(ops.clone().map(|o| o.val()), out);
-        let pred = OpIdListRange::encode(ops.clone().map(|o| o.pred()), out);
-        let expand = MaybeBooleanRange::encode(ops.clone().map(|o| o.expand()), out);
-        let mark_name =
-            RleRange::encode::<Cow<'_, smol_str::SmolStr>, _>(ops.map(|o| o.mark_name()), out);
+        let pred = OpIdListRange::encode(ops.map(|o| o.pred()), out);
         Self {
             obj,
             key,
@@ -182,8 +160,6 @@ impl ChangeOpsColumns {
             action,
             val,
             pred,
-            expand,
-            mark_name,
         }
     }
 
@@ -199,18 +175,13 @@ impl ChangeOpsColumns {
         let mut action = RleEncoder::<_, u64>::from(Vec::new());
         let mut val = ValueEncoder::new();
         let mut pred = OpIdListEncoder::new();
-        let mut expand = MaybeBooleanEncoder::new();
-        let mut mark_name = RleEncoder::<_, smol_str::SmolStr>::new(Vec::new());
         for op in ops {
-            tracing::trace!(expand=?op.expand(), "expand");
             obj.append(op.obj());
             key.append(op.key());
             insert.append(op.insert());
             action.append_value(op.action());
             val.append(&op.val());
             pred.append(op.pred());
-            expand.append(op.expand());
-            mark_name.append(op.mark_name());
         }
         let obj = obj.finish(out);
         let key = key.finish(out);
@@ -228,16 +199,6 @@ impl ChangeOpsColumns {
         let val = val.finish(out);
         let pred = pred.finish(out);
 
-        let expand_start = out.len();
-        let (expand, _) = expand.finish();
-        out.extend(expand);
-        let expand = MaybeBooleanRange::from(expand_start..out.len());
-
-        let mark_name_start = out.len();
-        let (mark_name, _) = mark_name.finish();
-        out.extend(mark_name);
-        let mark_name = RleRange::from(mark_name_start..out.len());
-
         Self {
             obj,
             key,
@@ -245,8 +206,6 @@ impl ChangeOpsColumns {
             action,
             val,
             pred,
-            expand,
-            mark_name,
         }
     }
 
@@ -313,18 +272,6 @@ impl ChangeOpsColumns {
                 ),
             ]);
         }
-        if !self.expand.is_empty() {
-            cols.push(RawColumn::new(
-                ColumnSpec::new(EXPAND_COL_ID, ColumnType::Boolean, false),
-                self.expand.clone().into(),
-            ));
-        }
-        if !self.mark_name.is_empty() {
-            cols.push(RawColumn::new(
-                ColumnSpec::new(MARK_NAME_COL_ID, ColumnType::String, false),
-                self.mark_name.clone().into(),
-            ));
-        }
         cols.into_iter().collect()
     }
 }
@@ -349,8 +296,6 @@ pub(crate) struct ChangeOpsIter<'a> {
     action: RleDecoder<'a, u64>,
     val: ValueIter<'a>,
     pred: OpIdListIter<'a>,
-    expand: MaybeBooleanDecoder<'a>,
-    mark_name: RleDecoder<'a, smol_str::SmolStr>,
 }
 
 impl<'a> ChangeOpsIter<'a> {
@@ -372,8 +317,6 @@ impl<'a> ChangeOpsIter<'a> {
             let action = self.action.next_in_col("action")?;
             let val = self.val.next_in_col("value")?;
             let pred = self.pred.next_in_col("pred")?;
-            let expand = self.expand.maybe_next_in_col("expand")?.unwrap_or(false);
-            let mark_name = self.mark_name.maybe_next_in_col("mark_name")?;
 
             // This check is necessary to ensure that OpType::from_action_and_value
             // cannot panic later in the process.
@@ -386,8 +329,6 @@ impl<'a> ChangeOpsIter<'a> {
                 action,
                 val,
                 pred,
-                expand,
-                mark_name,
             }))
         }
     }
@@ -434,8 +375,6 @@ impl TryFrom<Columns> for ChangeOpsColumns {
         let mut pred_group: Option<RleRange<u64>> = None;
         let mut pred_actor: Option<RleRange<u64>> = None;
         let mut pred_ctr: Option<DeltaRange> = None;
-        let mut expand: Option<MaybeBooleanRange> = None;
-        let mut mark_name: Option<RleRange<smol_str::SmolStr>> = None;
         let mut other = Columns::empty();
 
         for (index, col) in columns.into_iter().enumerate() {
@@ -490,8 +429,6 @@ impl TryFrom<Columns> for ChangeOpsColumns {
                     }
                     _ => return Err(ParseChangeColumnsError::MismatchingColumn { index }),
                 },
-                (EXPAND_COL_ID, ColumnType::Boolean) => expand = Some(col.range().into()),
-                (MARK_NAME_COL_ID, ColumnType::String) => mark_name = Some(col.range().into()),
                 (other_type, other_col) => {
                     tracing::warn!(typ=?other_type, id=?other_col, "unknown column");
                     other.append(col);
@@ -517,8 +454,6 @@ impl TryFrom<Columns> for ChangeOpsColumns {
             action: action.unwrap_or(0..0).into(),
             val: val.unwrap_or_else(|| ValueRange::new((0..0).into(), (0..0).into())),
             pred,
-            expand: expand.unwrap_or_else(|| (0..0).into()),
-            mark_name: mark_name.unwrap_or_else(|| (0..0).into()),
         })
     }
 }
@@ -536,8 +471,6 @@ mod tests {
                      pred in proptest::collection::vec(opid(), 0..20),
                      action in 0_u64..6,
                      obj in opid(),
-                     mark_name in proptest::option::of(any::<String>().prop_map(|s| s.into())),
-                     expand in any::<bool>(),
                      insert in any::<bool>()) -> ChangeOp {
 
                     let val = if action == 5 && !(value.is_int() || value.is_uint()) {
@@ -550,8 +483,6 @@ mod tests {
                 pred,
                 action,
                 insert,
-                expand,
-                mark_name,
             }
         }
     }
diff --git a/rust/automerge/src/storage/convert/op_as_changeop.rs b/rust/automerge/src/storage/convert/op_as_changeop.rs
index c08fa063..00b5e940 100644
--- a/rust/automerge/src/storage/convert/op_as_changeop.rs
+++ b/rust/automerge/src/storage/convert/op_as_changeop.rs
@@ -5,7 +5,7 @@ use crate::{
     convert,
     op_set::OpSetMetadata,
     storage::AsChangeOp,
-    types::{ActorId, Key, MarkData, ObjId, Op, OpId, OpType, ScalarValue},
+    types::{ActorId, Key, ObjId, Op, OpId, OpType, ScalarValue},
 };
 
 /// Wrap an op in an implementation of `AsChangeOp` which represents actor IDs using a reference to
@@ -93,12 +93,9 @@ impl<'a> AsChangeOp<'a> for OpWithMetadata<'a> {
 
     fn val(&self) -> Cow<'a, ScalarValue> {
         match &self.op.action {
-            OpType::Make(..) | OpType::Delete | OpType::MarkEnd(..) => {
-                Cow::Owned(ScalarValue::Null)
-            }
+            OpType::Make(..) | OpType::Delete => Cow::Owned(ScalarValue::Null),
             OpType::Increment(i) => Cow::Owned(ScalarValue::Int(*i)),
             OpType::Put(s) => Cow::Borrowed(s),
-            OpType::MarkBegin(_, MarkData { value, .. }) => Cow::Borrowed(value),
         }
     }
 
@@ -128,19 +125,4 @@ impl<'a> AsChangeOp<'a> for OpWithMetadata<'a> {
             Key::Seq(e) => convert::Key::Elem(convert::ElemId::Op(self.wrap(&e.0))),
         }
     }
-
-    fn expand(&self) -> bool {
-        matches!(
-            self.op.action,
-            OpType::MarkBegin(true, _) | OpType::MarkEnd(true)
-        )
-    }
-
-    fn mark_name(&self) -> Option<Cow<'a, smol_str::SmolStr>> {
-        if let OpType::MarkBegin(_, MarkData { name, .. }) = &self.op.action {
-            Some(Cow::Owned(name.clone()))
-        } else {
-            None
-        }
-    }
 }
diff --git a/rust/automerge/src/storage/convert/op_as_docop.rs b/rust/automerge/src/storage/convert/op_as_docop.rs
index 09598b67..8d237354 100644
--- a/rust/automerge/src/storage/convert/op_as_docop.rs
+++ b/rust/automerge/src/storage/convert/op_as_docop.rs
@@ -4,7 +4,7 @@ use crate::{
     convert,
     indexed_cache::IndexedCache,
     storage::AsDocOp,
-    types::{ElemId, Key, MarkData, ObjId, Op, OpId, OpType, ScalarValue},
+    types::{ElemId, Key, ObjId, Op, OpId, OpType, ScalarValue},
 };
 
 /// Create an [`AsDocOp`] implementation for a [`crate::types::Op`]
@@ -90,7 +90,6 @@ impl<'a> AsDocOp<'a> for OpAsDocOp<'a> {
         match &self.op.action {
             OpType::Put(v) => Cow::Borrowed(v),
             OpType::Increment(i) => Cow::Owned(ScalarValue::Int(*i)),
-            OpType::MarkBegin(_, MarkData { value, .. }) => Cow::Borrowed(value),
             _ => Cow::Owned(ScalarValue::Null),
         }
     }
@@ -110,22 +109,6 @@ impl<'a> AsDocOp<'a> for OpAsDocOp<'a> {
     fn action(&self) -> u64 {
         self.op.action.action_index()
     }
-
-    fn expand(&self) -> bool {
-        if let OpType::MarkBegin(expand, _) | OpType::MarkEnd(expand) = &self.op.action {
-            *expand
-        } else {
-            false
-        }
-    }
-
-    fn mark_name(&self) -> Option<Cow<'a, smol_str::SmolStr>> {
-        if let OpType::MarkBegin(_, MarkData { name, .. }) = &self.op.action {
-            Some(Cow::Owned(name.clone()))
-        } else {
-            None
-        }
-    }
 }
 
 pub(crate) struct OpAsDocOpSuccIter<'a> {
diff --git a/rust/automerge/src/storage/document/doc_op_columns.rs b/rust/automerge/src/storage/document/doc_op_columns.rs
index 7248b1b3..82de17eb 100644
--- a/rust/automerge/src/storage/document/doc_op_columns.rs
+++ b/rust/automerge/src/storage/document/doc_op_columns.rs
@@ -4,13 +4,13 @@ use crate::{
     columnar::{
         column_range::{
             generic::{GenericColumnRange, GroupRange, GroupedColumnRange, SimpleColRange},
-            BooleanRange, DeltaRange, Key, KeyEncoder, KeyIter, KeyRange, MaybeBooleanRange,
-            ObjIdEncoder, ObjIdIter, ObjIdRange, OpIdEncoder, OpIdIter, OpIdListEncoder,
-            OpIdListIter, OpIdListRange, OpIdRange, RleRange, ValueEncoder, ValueIter, ValueRange,
+            BooleanRange, DeltaRange, Key, KeyEncoder, KeyIter, KeyRange, ObjIdEncoder, ObjIdIter,
+            ObjIdRange, OpIdEncoder, OpIdIter, OpIdListEncoder, OpIdListIter, OpIdListRange,
+            OpIdRange, RleRange, ValueEncoder, ValueIter, ValueRange,
         },
         encoding::{
-            BooleanDecoder, BooleanEncoder, ColumnDecoder, DecodeColumnError, MaybeBooleanDecoder,
-            MaybeBooleanEncoder, RleDecoder, RleEncoder,
+            BooleanDecoder, BooleanEncoder, ColumnDecoder, DecodeColumnError, RleDecoder,
+            RleEncoder,
         },
     },
     convert,
@@ -28,8 +28,6 @@ const INSERT_COL_ID: ColumnId = ColumnId::new(3);
 const ACTION_COL_ID: ColumnId = ColumnId::new(4);
 const VAL_COL_ID: ColumnId = ColumnId::new(5);
 const SUCC_COL_ID: ColumnId = ColumnId::new(8);
-const EXPAND_COL_ID: ColumnId = ColumnId::new(9);
-const MARK_NAME_COL_ID: ColumnId = ColumnId::new(10);
 
 /// The form operations take in the compressed document format.
 #[derive(Debug)]
@@ -38,11 +36,9 @@ pub(crate) struct DocOp {
     pub(crate) object: ObjId,
     pub(crate) key: Key,
     pub(crate) insert: bool,
-    pub(crate) action: u64,
+    pub(crate) action: usize,
     pub(crate) value: ScalarValue,
     pub(crate) succ: Vec<OpId>,
-    pub(crate) expand: bool,
-    pub(crate) mark_name: Option<smol_str::SmolStr>,
 }
 
 #[derive(Debug, Clone)]
@@ -56,8 +52,6 @@ pub(crate) struct DocOpColumns {
     succ: OpIdListRange,
     #[allow(dead_code)]
     other: Columns,
-    expand: MaybeBooleanRange,
-    mark_name: RleRange<smol_str::SmolStr>,
 }
 
 struct DocId {
@@ -96,8 +90,6 @@ pub(crate) trait AsDocOp<'a> {
     fn action(&self) -> u64;
     fn val(&self) -> Cow<'a, ScalarValue>;
     fn succ(&self) -> Self::SuccIter;
-    fn expand(&self) -> bool;
-    fn mark_name(&self) -> Option<Cow<'a, smol_str::SmolStr>>;
 }
 
 impl DocOpColumns {
@@ -126,9 +118,7 @@ impl DocOpColumns {
         let insert = BooleanRange::encode(ops.clone().map(|o| o.insert()), out);
         let action = RleRange::encode(ops.clone().map(|o| Some(o.action())), out);
         let val = ValueRange::encode(ops.clone().map(|o| o.val()), out);
-        let succ = OpIdListRange::encode(ops.clone().map(|o| o.succ()), out);
-        let expand = MaybeBooleanRange::encode(ops.clone().map(|o| o.expand()), out);
-        let mark_name = RleRange::encode(ops.map(|o| o.mark_name()), out);
+        let succ = OpIdListRange::encode(ops.map(|o| o.succ()), out);
         Self {
             obj,
             key,
@@ -137,8 +127,6 @@ impl DocOpColumns {
             action,
             val,
             succ,
-            expand,
-            mark_name,
             other: Columns::empty(),
         }
     }
@@ -156,8 +144,6 @@ impl DocOpColumns {
         let mut action = RleEncoder::<_, u64>::from(Vec::new());
         let mut val = ValueEncoder::new();
         let mut succ = OpIdListEncoder::new();
-        let mut expand = MaybeBooleanEncoder::new();
-        let mut mark_name = RleEncoder::<_, smol_str::SmolStr>::new(Vec::new());
         for op in ops {
             obj.append(op.obj());
             key.append(op.key());
@@ -166,8 +152,6 @@ impl DocOpColumns {
             action.append(Some(op.action()));
             val.append(&op.val());
             succ.append(op.succ());
-            expand.append(op.expand());
-            mark_name.append(op.mark_name());
         }
         let obj = obj.finish(out);
         let key = key.finish(out);
@@ -185,17 +169,6 @@ impl DocOpColumns {
 
         let val = val.finish(out);
         let succ = succ.finish(out);
-
-        let expand_start = out.len();
-        let (expand_out, _) = expand.finish();
-        out.extend(expand_out);
-        let expand = MaybeBooleanRange::from(expand_start..out.len());
-
-        let mark_name_start = out.len();
-        let (mark_name_out, _) = mark_name.finish();
-        out.extend(mark_name_out);
-        let mark_name = RleRange::from(mark_name_start..out.len());
-
         DocOpColumns {
             obj,
             key,
@@ -204,8 +177,6 @@ impl DocOpColumns {
             action,
             val,
             succ,
-            expand,
-            mark_name,
             other: Columns::empty(),
         }
     }
@@ -219,8 +190,6 @@ impl DocOpColumns {
             insert: self.insert.decoder(data),
             value: self.val.iter(data),
             succ: self.succ.iter(data),
-            expand: self.expand.decoder(data),
-            mark_name: self.mark_name.decoder(data),
         }
     }
 
@@ -295,18 +264,6 @@ impl DocOpColumns {
                 ),
             ]);
         }
-        if !self.expand.is_empty() {
-            cols.push(RawColumn::new(
-                ColumnSpec::new(EXPAND_COL_ID, ColumnType::Boolean, false),
-                self.expand.clone().into(),
-            ));
-        }
-        if !self.mark_name.is_empty() {
-            cols.push(RawColumn::new(
-                ColumnSpec::new(MARK_NAME_COL_ID, ColumnType::String, false),
-                self.mark_name.clone().into(),
-            ));
-        }
         cols.into_iter().collect()
     }
 }
@@ -320,8 +277,6 @@ pub(crate) struct DocOpColumnIter<'a> {
     insert: BooleanDecoder<'a>,
     value: ValueIter<'a>,
     succ: OpIdListIter<'a>,
-    expand: MaybeBooleanDecoder<'a>,
-    mark_name: RleDecoder<'a, smol_str::SmolStr>,
 }
 
 impl<'a> DocOpColumnIter<'a> {
@@ -366,18 +321,14 @@ impl<'a> DocOpColumnIter<'a> {
             let value = self.value.next_in_col("value")?;
             let succ = self.succ.next_in_col("succ")?;
             let insert = self.insert.next_in_col("insert")?;
-            let expand = self.expand.maybe_next_in_col("expand")?.unwrap_or(false);
-            let mark_name = self.mark_name.maybe_next_in_col("mark_name")?;
             Ok(Some(DocOp {
                 id,
                 value,
-                action,
+                action: action as usize,
                 object: obj,
                 key,
                 succ,
                 insert,
-                expand,
-                mark_name,
             }))
         }
     }
@@ -412,8 +363,6 @@ impl TryFrom<Columns> for DocOpColumns {
         let mut succ_group: Option<RleRange<u64>> = None;
         let mut succ_actor: Option<RleRange<u64>> = None;
         let mut succ_ctr: Option<DeltaRange> = None;
-        let mut expand: Option<MaybeBooleanRange> = None;
-        let mut mark_name: Option<RleRange<smol_str::SmolStr>> = None;
         let mut other = Columns::empty();
 
         for (index, col) in columns.into_iter().enumerate() {
@@ -467,8 +416,6 @@ impl TryFrom<Columns> for DocOpColumns {
                     }
                     _ => return Err(Error::MismatchingColumn { index }),
                 },
-                (EXPAND_COL_ID, ColumnType::Boolean) => expand = Some(col.range().into()),
-                (MARK_NAME_COL_ID, ColumnType::String) => mark_name = Some(col.range().into()),
                 (other_col, other_type) => {
                     tracing::warn!(id=?other_col, typ=?other_type, "unknown column type");
                     other.append(col)
@@ -497,8 +444,6 @@ impl TryFrom<Columns> for DocOpColumns {
                 succ_actor.unwrap_or_else(|| (0..0).into()),
                 succ_ctr.unwrap_or_else(|| (0..0).into()),
             ),
-            expand: expand.unwrap_or_else(|| (0..0).into()),
-            mark_name: mark_name.unwrap_or_else(|| (0..0).into()),
             other,
         })
     }
diff --git a/rust/automerge/src/storage/load/reconstruct_document.rs b/rust/automerge/src/storage/load/reconstruct_document.rs
index 1f80a85d..44ace72a 100644
--- a/rust/automerge/src/storage/load/reconstruct_document.rs
+++ b/rust/automerge/src/storage/load/reconstruct_document.rs
@@ -17,6 +17,8 @@ pub(crate) enum Error {
     OpsOutOfOrder,
     #[error("error reading operation: {0:?}")]
     ReadOp(Box<dyn std::error::Error + Send + Sync + 'static>),
+    #[error("an operation contained an invalid action")]
+    InvalidAction,
     #[error("an operation referenced a missing actor id")]
     MissingActor,
     #[error("invalid changes: {0}")]
@@ -27,8 +29,6 @@ pub(crate) enum Error {
     MissingOps,
     #[error("succ out of order")]
     SuccOutOfOrder,
-    #[error(transparent)]
-    InvalidOp(#[from] crate::error::InvalidOpType),
 }
 
 pub(crate) struct MismatchedHeads {
@@ -345,10 +345,9 @@ fn import_op(m: &mut OpSetMetadata, op: DocOp) -> Result<Op, Error> {
             return Err(Error::MissingActor);
         }
     }
-    let action = OpType::from_action_and_value(op.action, op.value, op.mark_name, op.expand);
     Ok(Op {
         id: check_opid(m, op.id)?,
-        action,
+        action: parse_optype(op.action, op.value)?,
         key,
         succ: m.try_sorted_opids(op.succ).ok_or(Error::SuccOutOfOrder)?,
         pred: OpIds::empty(),
@@ -368,3 +367,25 @@ fn check_opid(m: &OpSetMetadata, opid: OpId) -> Result<OpId, Error> {
         }
     }
 }
+
+fn parse_optype(action_index: usize, value: ScalarValue) -> Result<OpType, Error> {
+    match action_index {
+        0 => Ok(OpType::Make(ObjType::Map)),
+        1 => Ok(OpType::Put(value)),
+        2 => Ok(OpType::Make(ObjType::List)),
+        3 => Ok(OpType::Delete),
+        4 => Ok(OpType::Make(ObjType::Text)),
+        5 => match value {
+            ScalarValue::Int(i) => Ok(OpType::Increment(i)),
+            _ => {
+                tracing::error!(?value, "invalid value for counter op");
+                Err(Error::InvalidAction)
+            }
+        },
+        6 => Ok(OpType::Make(ObjType::Table)),
+        other => {
+            tracing::error!(action = other, "unknown action type");
+            Err(Error::InvalidAction)
+        }
+    }
+}
diff --git a/rust/automerge/src/transaction/inner.rs b/rust/automerge/src/transaction/inner.rs
index 5afd2e1d..0fe735d5 100644
--- a/rust/automerge/src/transaction/inner.rs
+++ b/rust/automerge/src/transaction/inner.rs
@@ -1,7 +1,6 @@
 use std::num::NonZeroU64;
 
 use crate::exid::ExId;
-use crate::marks::{ExpandMark, Mark};
 use crate::query::{self, OpIdSearch};
 use crate::storage::Change as StoredChange;
 use crate::types::{Key, ListEncoding, ObjId, OpId, OpIds, TextEncoding};
@@ -639,7 +638,7 @@ impl TransactionInner {
                         for (offset, v) in values.iter().enumerate() {
                             let op = &self.operations[start + offset].1;
                             let value = (v.clone().into(), doc.ops().id_to_exid(op.id));
-                            obs.insert(doc, ex_obj.clone(), index + offset, value, false)
+                            obs.insert(doc, ex_obj.clone(), index + offset, value)
                         }
                     }
                 }
@@ -649,51 +648,6 @@ impl TransactionInner {
         Ok(())
     }
 
-    pub(crate) fn mark<Obs: OpObserver>(
-        &mut self,
-        doc: &mut Automerge,
-        op_observer: Option<&mut Obs>,
-        ex_obj: &ExId,
-        mark: Mark<'_>,
-        expand: ExpandMark,
-    ) -> Result<(), AutomergeError> {
-        let (obj, _obj_type) = doc.exid_to_obj(ex_obj)?;
-        if let Some(obs) = op_observer {
-            let action = OpType::MarkBegin(expand.left(), mark.data.clone().into_owned());
-            self.do_insert(doc, Some(obs), obj, mark.start, action)?;
-            self.do_insert(
-                doc,
-                Some(obs),
-                obj,
-                mark.end,
-                OpType::MarkEnd(expand.right()),
-            )?;
-            if mark.value().is_null() {
-                obs.unmark(doc, ex_obj.clone(), mark.name(), mark.start, mark.end);
-            } else {
-                obs.mark(doc, ex_obj.clone(), Some(mark).into_iter())
-            }
-        } else {
-            let action = OpType::MarkBegin(expand.left(), mark.data.into_owned());
-            self.do_insert::<Obs>(doc, None, obj, mark.start, action)?;
-            self.do_insert::<Obs>(doc, None, obj, mark.end, OpType::MarkEnd(expand.right()))?;
-        }
-        Ok(())
-    }
-
-    pub(crate) fn unmark<Obs: OpObserver>(
-        &mut self,
-        doc: &mut Automerge,
-        op_observer: Option<&mut Obs>,
-        ex_obj: &ExId,
-        name: &str,
-        start: usize,
-        end: usize,
-    ) -> Result<(), AutomergeError> {
-        let mark = Mark::new(name.to_string(), ScalarValue::Null, start, end);
-        self.mark(doc, op_observer, ex_obj, mark, ExpandMark::None)
-    }
-
     fn finalize_op<Obs: OpObserver>(
         &mut self,
         doc: &mut Automerge,
@@ -706,24 +660,23 @@ impl TransactionInner {
         if let Some(op_observer) = op_observer {
             let ex_obj = doc.ops().id_to_exid(obj.0);
             if op.insert {
-                if !op.is_mark() {
-                    let obj_type = doc.ops().object_type(&obj);
-                    assert!(obj_type.unwrap().is_sequence());
-                    match (obj_type, prop) {
-                        (Some(ObjType::List), Prop::Seq(index)) => {
-                            let value = (op.value(), doc.ops().id_to_exid(op.id));
-                            op_observer.insert(doc, ex_obj, index, value, false)
-                        }
-                        (Some(ObjType::Text), Prop::Seq(index)) => {
-                            if op_observer.text_as_seq() {
-                                let value = (op.value(), doc.ops().id_to_exid(op.id));
-                                op_observer.insert(doc, ex_obj, index, value, false)
-                            } else {
-                                op_observer.splice_text(doc, ex_obj, index, op.to_str())
-                            }
-                        }
-                        _ => {}
+                let obj_type = doc.ops().object_type(&obj);
+                assert!(obj_type.unwrap().is_sequence());
+                match (obj_type, prop) {
+                    (Some(ObjType::List), Prop::Seq(index)) => {
+                        let value = (op.value(), doc.ops().id_to_exid(op.id));
+                        op_observer.insert(doc, ex_obj, index, value)
                     }
+                    (Some(ObjType::Text), Prop::Seq(index)) => {
+                        // FIXME
+                        if op_observer.text_as_seq() {
+                            let value = (op.value(), doc.ops().id_to_exid(op.id));
+                            op_observer.insert(doc, ex_obj, index, value)
+                        } else {
+                            op_observer.splice_text(doc, ex_obj, index, op.to_str())
+                        }
+                    }
+                    _ => {}
                 }
             } else if op.is_delete() {
                 op_observer.delete(doc, ex_obj, prop);
diff --git a/rust/automerge/src/transaction/manual_transaction.rs b/rust/automerge/src/transaction/manual_transaction.rs
index 52fdd0d7..fa5f6340 100644
--- a/rust/automerge/src/transaction/manual_transaction.rs
+++ b/rust/automerge/src/transaction/manual_transaction.rs
@@ -1,7 +1,6 @@
 use std::ops::RangeBounds;
 
 use crate::exid::ExId;
-use crate::marks::{ExpandMark, Mark};
 use crate::op_observer::BranchableObserver;
 use crate::{
     Automerge, ChangeHash, KeysAt, ObjType, OpObserver, Prop, ReadDoc, ScalarValue, Value, Values,
@@ -191,18 +190,6 @@ impl<'a, Obs: observation::Observation> ReadDoc for Transaction<'a, Obs> {
         self.doc.text_at(obj, heads)
     }
 
-    fn marks<O: AsRef<ExId>>(&self, obj: O) -> Result<Vec<Mark<'_>>, AutomergeError> {
-        self.doc.marks(obj)
-    }
-
-    fn marks_at<O: AsRef<ExId>>(
-        &self,
-        obj: O,
-        heads: &[ChangeHash],
-    ) -> Result<Vec<Mark<'_>>, AutomergeError> {
-        self.doc.marks_at(obj, heads)
-    }
-
     fn get<O: AsRef<ExId>, P: Into<Prop>>(
         &self,
         obj: O,
@@ -343,25 +330,6 @@ impl<'a, Obs: observation::Observation> Transactable for Transaction<'a, Obs> {
         self.do_tx(|tx, doc, obs| tx.splice_text(doc, obs, obj.as_ref(), pos, del, text))
     }
 
-    fn mark<O: AsRef<ExId>>(
-        &mut self,
-        obj: O,
-        mark: Mark<'_>,
-        expand: ExpandMark,
-    ) -> Result<(), AutomergeError> {
-        self.do_tx(|tx, doc, obs| tx.mark(doc, obs, obj.as_ref(), mark, expand))
-    }
-
-    fn unmark<O: AsRef<ExId>>(
-        &mut self,
-        obj: O,
-        name: &str,
-        start: usize,
-        end: usize,
-    ) -> Result<(), AutomergeError> {
-        self.do_tx(|tx, doc, obs| tx.unmark(doc, obs, obj.as_ref(), name, start, end))
-    }
-
     fn base_heads(&self) -> Vec<ChangeHash> {
         self.doc.get_heads()
     }
diff --git a/rust/automerge/src/transaction/transactable.rs b/rust/automerge/src/transaction/transactable.rs
index 81b83dff..05c48c79 100644
--- a/rust/automerge/src/transaction/transactable.rs
+++ b/rust/automerge/src/transaction/transactable.rs
@@ -1,5 +1,4 @@
 use crate::exid::ExId;
-use crate::marks::{ExpandMark, Mark};
 use crate::{AutomergeError, ChangeHash, ObjType, Prop, ReadDoc, ScalarValue};
 
 /// A way of mutating a document within a single change.
@@ -89,21 +88,6 @@ pub trait Transactable: ReadDoc {
         text: &str,
     ) -> Result<(), AutomergeError>;
 
-    fn mark<O: AsRef<ExId>>(
-        &mut self,
-        obj: O,
-        mark: Mark<'_>,
-        expand: ExpandMark,
-    ) -> Result<(), AutomergeError>;
-
-    fn unmark<O: AsRef<ExId>>(
-        &mut self,
-        obj: O,
-        key: &str,
-        start: usize,
-        end: usize,
-    ) -> Result<(), AutomergeError>;
-
     /// The heads this transaction will be based on
     fn base_heads(&self) -> Vec<ChangeHash>;
 }
diff --git a/rust/automerge/src/types.rs b/rust/automerge/src/types.rs
index 468605b6..468986ec 100644
--- a/rust/automerge/src/types.rs
+++ b/rust/automerge/src/types.rs
@@ -14,7 +14,6 @@ mod opids;
 pub(crate) use opids::OpIds;
 
 pub(crate) use crate::clock::Clock;
-pub(crate) use crate::marks::MarkData;
 pub(crate) use crate::value::{Counter, ScalarValue, Value};
 
 pub(crate) const HEAD: ElemId = ElemId(OpId(0, 0));
@@ -199,8 +198,6 @@ pub enum OpType {
     Delete,
     Increment(i64),
     Put(ScalarValue),
-    MarkBegin(bool, MarkData),
-    MarkEnd(bool),
 }
 
 impl OpType {
@@ -216,7 +213,6 @@ impl OpType {
             Self::Make(ObjType::Text) => 4,
             Self::Increment(_) => 5,
             Self::Make(ObjType::Table) => 6,
-            Self::MarkBegin(_, _) | Self::MarkEnd(_) => 7,
         }
     }
 
@@ -231,17 +227,11 @@ impl OpType {
                 _ => Err(error::InvalidOpType::NonNumericInc),
             },
             6 => Ok(()),
-            7 => Ok(()),
             _ => Err(error::InvalidOpType::UnknownAction(action)),
         }
     }
 
-    pub(crate) fn from_action_and_value(
-        action: u64,
-        value: ScalarValue,
-        mark_name: Option<smol_str::SmolStr>,
-        expand: bool,
-    ) -> OpType {
+    pub(crate) fn from_action_and_value(action: u64, value: ScalarValue) -> OpType {
         match action {
             0 => Self::Make(ObjType::Map),
             1 => Self::Put(value),
@@ -254,27 +244,9 @@ impl OpType {
                 _ => unreachable!("validate_action_and_value returned NonNumericInc"),
             },
             6 => Self::Make(ObjType::Table),
-            7 => match mark_name {
-                Some(name) => Self::MarkBegin(expand, MarkData { name, value }),
-                None => Self::MarkEnd(expand),
-            },
             _ => unreachable!("validate_action_and_value returned UnknownAction"),
         }
     }
-
-    pub(crate) fn to_str(&self) -> &str {
-        if let OpType::Put(ScalarValue::Str(s)) = &self {
-            s
-        } else if self.is_mark() {
-            ""
-        } else {
-            "\u{fffc}"
-        }
-    }
-
-    pub(crate) fn is_mark(&self) -> bool {
-        matches!(&self, OpType::MarkBegin(_, _) | OpType::MarkEnd(_))
-    }
 }
 
 impl From<ObjType> for OpType {
@@ -454,13 +426,6 @@ impl Display for Prop {
 }
 
 impl Key {
-    pub(crate) fn prop_index(&self) -> Option<usize> {
-        match self {
-            Key::Map(n) => Some(*n),
-            Key::Seq(_) => None,
-        }
-    }
-
     pub(crate) fn elemid(&self) -> Option<ElemId> {
         match self {
             Key::Map(_) => None,
@@ -493,16 +458,6 @@ impl OpId {
             .cmp(&other.0)
             .then_with(|| actors[self.1 as usize].cmp(&actors[other.1 as usize]))
     }
-
-    #[inline]
-    pub(crate) fn prev(&self) -> OpId {
-        OpId(self.0 - 1, self.1)
-    }
-
-    #[inline]
-    pub(crate) fn next(&self) -> OpId {
-        OpId(self.0 + 1, self.1)
-    }
 }
 
 #[derive(Debug, Clone, Copy, PartialOrd, Eq, PartialEq, Ord, Hash, Default)]
@@ -627,20 +582,14 @@ impl Op {
     }
 
     pub(crate) fn to_str(&self) -> &str {
-        self.action.to_str()
-    }
-
-    pub(crate) fn visible(&self) -> bool {
-        if self.is_inc() || self.is_mark() {
-            false
-        } else if self.is_counter() {
-            self.succ.len() <= self.incs()
+        if let OpType::Put(ScalarValue::Str(s)) = &self.action {
+            s
         } else {
-            self.succ.is_empty()
+            "\u{fffc}"
         }
     }
 
-    pub(crate) fn visible_or_mark(&self) -> bool {
+    pub(crate) fn visible(&self) -> bool {
         if self.is_inc() {
             false
         } else if self.is_counter() {
@@ -670,18 +619,6 @@ impl Op {
         matches!(&self.action, OpType::Put(ScalarValue::Counter(_)))
     }
 
-    pub(crate) fn is_mark(&self) -> bool {
-        self.action.is_mark()
-    }
-
-    pub(crate) fn valid_mark_anchor(&self) -> bool {
-        self.succ.is_empty()
-            && matches!(
-                &self.action,
-                OpType::MarkBegin(true, _) | OpType::MarkEnd(false)
-            )
-    }
-
     pub(crate) fn is_noop(&self, action: &OpType) -> bool {
         matches!((&self.action, action), (OpType::Put(n), OpType::Put(m)) if n == m)
     }
@@ -718,10 +655,6 @@ impl Op {
         match &self.action {
             OpType::Make(obj_type) => Value::Object(*obj_type),
             OpType::Put(scalar) => Value::Scalar(Cow::Borrowed(scalar)),
-            OpType::MarkBegin(_, mark) => {
-                Value::Scalar(Cow::Owned(format!("markBegin={}", mark.value).into()))
-            }
-            OpType::MarkEnd(_) => Value::Scalar(Cow::Owned("markEnd".into())),
             _ => panic!("cant convert op into a value - {:?}", self),
         }
     }
@@ -742,8 +675,6 @@ impl Op {
             OpType::Make(obj) => format!("make{}", obj),
             OpType::Increment(val) => format!("inc:{}", val),
             OpType::Delete => "del".to_string(),
-            OpType::MarkBegin(_, _) => "markBegin".to_string(),
-            OpType::MarkEnd(_) => "markEnd".to_string(),
         }
     }
 }
diff --git a/rust/automerge/src/value.rs b/rust/automerge/src/value.rs
index 22a24c2b..be128787 100644
--- a/rust/automerge/src/value.rs
+++ b/rust/automerge/src/value.rs
@@ -341,12 +341,6 @@ impl<'a> From<ScalarValue> for Value<'a> {
     }
 }
 
-impl<'a> From<&'a ScalarValue> for Value<'a> {
-    fn from(v: &'a ScalarValue) -> Self {
-        Value::Scalar(Cow::Borrowed(v))
-    }
-}
-
 #[derive(Deserialize, Serialize, PartialEq, Debug, Clone, Copy)]
 pub(crate) enum DataType {
     #[serde(rename = "counter")]
diff --git a/rust/automerge/src/visualisation.rs b/rust/automerge/src/visualisation.rs
index 4e639141..31e9bbdb 100644
--- a/rust/automerge/src/visualisation.rs
+++ b/rust/automerge/src/visualisation.rs
@@ -249,8 +249,6 @@ impl OpTableRow {
             crate::OpType::Put(v) => format!("set {}", v),
             crate::OpType::Make(obj) => format!("make {}", obj),
             crate::OpType::Increment(v) => format!("inc {}", v),
-            crate::OpType::MarkBegin(_, m) => format!("markEnd {}", m),
-            crate::OpType::MarkEnd(m) => format!("markEnd {}", m),
         };
         let prop = match op.key {
             crate::types::Key::Map(k) => metadata.props[k].clone(),
diff --git a/rust/automerge/tests/test.rs b/rust/automerge/tests/test.rs
index 3ba1df40..3be6725e 100644
--- a/rust/automerge/tests/test.rs
+++ b/rust/automerge/tests/test.rs
@@ -6,7 +6,7 @@ use automerge::{
 use std::fs;
 
 // set up logging for all the tests
-use test_log::test;
+//use test_log::test;
 
 #[allow(unused_imports)]
 use automerge_test::{