diff --git a/automerge-js/src/constants.ts b/automerge-js/src/constants.ts
index aa414c8b..e37835d1 100644
--- a/automerge-js/src/constants.ts
+++ b/automerge-js/src/constants.ts
@@ -3,6 +3,7 @@
 //const CACHE     = Symbol('_cache')     // map from objectId to immutable object
 export const STATE      = Symbol.for('_am_state')     // object containing metadata about current state (e.g. sequence numbers)
 export const HEADS      = Symbol.for('_am_heads')     // object containing metadata about current state (e.g. sequence numbers)
+export const TRACE      = Symbol.for('_am_trace')     // object containing metadata about current state (e.g. sequence numbers)
 export const OBJECT_ID  = Symbol.for('_am_objectId')     // object containing metadata about current state (e.g. sequence numbers)
 export const READ_ONLY  = Symbol.for('_am_readOnly')     // object containing metadata about current state (e.g. sequence numbers)
 export const FROZEN     = Symbol.for('_am_frozen')     // object containing metadata about current state (e.g. sequence numbers)
diff --git a/automerge-js/src/index.ts b/automerge-js/src/index.ts
index ef231727..a8e3e2be 100644
--- a/automerge-js/src/index.ts
+++ b/automerge-js/src/index.ts
@@ -2,7 +2,7 @@
 export { uuid } from './uuid'
 
 import { rootProxy, listProxy, textProxy, mapProxy } from "./proxies"
-import { STATE, HEADS, OBJECT_ID, READ_ONLY, FROZEN  } from "./constants"
+import { STATE, HEADS, TRACE, OBJECT_ID, READ_ONLY, FROZEN  } from "./constants"
 
 import { AutomergeValue, Counter } from "./types"
 export { AutomergeValue, Text, Counter, Int, Uint, Float64 } from "./types"
@@ -48,6 +48,20 @@ function _heads<T>(doc: Doc<T>) : Heads | undefined {
   return Reflect.get(doc,HEADS)
 }
 
+function _trace<T>(doc: Doc<T>) : string | undefined {
+  return Reflect.get(doc,TRACE)
+}
+
+function _set_heads<T>(doc: Doc<T>, heads: Heads) {
+  Reflect.set(doc,HEADS,heads)
+  Reflect.set(doc,TRACE,(new Error()).stack)
+}
+
+function _clear_heads<T>(doc: Doc<T>) {
+  Reflect.set(doc,HEADS,undefined)
+  Reflect.set(doc,TRACE,undefined)
+}
+
 function _obj<T>(doc: Doc<T>) : ObjID {
   return Reflect.get(doc,OBJECT_ID)
 }
@@ -104,7 +118,7 @@ function _change<T>(doc: Doc<T>, options: ChangeOptions, callback: ChangeFn<T>):
     throw new RangeError("Attempting to use an outdated Automerge document")
   }
   if (!!_heads(doc) === true) {
-    throw new RangeError("Attempting to change an out of date document");
+    throw new RangeError("Attempting to change an out of date document - set at: " + _trace(doc));
   }
   if (_readonly(doc) === false) {
     throw new RangeError("Calls to Automerge.change cannot be nested")
@@ -112,13 +126,13 @@ function _change<T>(doc: Doc<T>, options: ChangeOptions, callback: ChangeFn<T>):
   const state = _state(doc)
   const heads = state.getHeads()
   try {
-    Reflect.set(doc,HEADS,heads)
+    _set_heads(doc,heads)
     Reflect.set(doc,FROZEN,true)
     const root : T = rootProxy(state);
     callback(root)
     if (state.pendingOps() === 0) {
       Reflect.set(doc,FROZEN,false)
-      Reflect.set(doc,HEADS,undefined)
+      _clear_heads(doc)
       return doc
     } else {
       state.commit(options.message, options.time)
@@ -127,7 +141,7 @@ function _change<T>(doc: Doc<T>, options: ChangeOptions, callback: ChangeFn<T>):
   } catch (e) {
     //console.log("ERROR: ",e)
     Reflect.set(doc,FROZEN,false)
-    Reflect.set(doc,HEADS,undefined)
+    _clear_heads(doc)
     state.rollback()
     throw e
   }
@@ -168,14 +182,14 @@ export function save<T>(doc: Doc<T>) : Uint8Array  {
 
 export function merge<T>(local: Doc<T>, remote: Doc<T>) : Doc<T> {
   if (!!_heads(local) === true) {
-    throw new RangeError("Attempting to change an out of date document");
+    throw new RangeError("Attempting to change an out of date document - set at: " + _trace(doc));
   }
   const localState = _state(local)
   const heads = localState.getHeads()
   const remoteState = _state(remote)
   const changes = localState.getChangesAdded(remoteState)
   localState.applyChanges(changes)
-  Reflect.set(local,HEADS,heads)
+  _set_heads(local,heads)
   return rootProxy(localState, true)
 }
 
@@ -267,7 +281,7 @@ export function applyChanges<T>(doc: Doc<T>, changes: Change[]) : [Doc<T>] {
   const state = _state(doc)
   const heads = state.getHeads()
   state.applyChanges(changes)
-  Reflect.set(doc,HEADS,heads)
+  _set_heads(doc,heads)
   return [rootProxy(state, true)];
 }
 
@@ -322,7 +336,7 @@ export function receiveSyncMessage<T>(doc: Doc<T>, inState: SyncState, message:
     throw new RangeError("Attempting to use an outdated Automerge document")
   }
   if (!!_heads(doc) === true) {
-    throw new RangeError("Attempting to change an out of date document");
+    throw new RangeError("Attempting to change an out of date document - set at: " + _trace(doc));
   }
   if (_readonly(doc) === false) {
     throw new RangeError("Calls to Automerge.change cannot be nested")
@@ -330,7 +344,7 @@ export function receiveSyncMessage<T>(doc: Doc<T>, inState: SyncState, message:
   const state = _state(doc)
   const heads = state.getHeads()
   state.receiveSyncMessage(syncState, message)
-  Reflect.set(doc,HEADS,heads)
+  _set_heads(doc,heads)
   const outState = ApiHandler.exportSyncState(syncState)
   return [rootProxy(state, true), outState, null];
 }
diff --git a/automerge-js/src/proxies.ts b/automerge-js/src/proxies.ts
index a19a1b9f..8de6c954 100644
--- a/automerge-js/src/proxies.ts
+++ b/automerge-js/src/proxies.ts
@@ -5,7 +5,7 @@ import { AutomergeValue, ScalarValue, MapValue, ListValue, TextValue } from "./t
 import { Int, Uint, Float64 } from "./numbers"
 import { Counter, getWriteableCounter } from "./counter"
 import { Text } from "./text"
-import { STATE, HEADS, FROZEN, OBJECT_ID, READ_ONLY, COUNTER, INT, UINT, F64, TEXT } from "./constants"
+import { STATE, HEADS, TRACE, FROZEN, OBJECT_ID, READ_ONLY, COUNTER, INT, UINT, F64, TEXT } from "./constants"
 
 function parseListIndex(key) {
   if (typeof key === 'string' && /^[0-9]+$/.test(key)) key = parseInt(key, 10)
@@ -108,6 +108,7 @@ const MapHandler = {
     if (key === READ_ONLY) return readonly
     if (key === FROZEN) return frozen
     if (key === HEADS) return heads
+    if (key === TRACE) return target.trace
     if (key === STATE) return context;
     if (!cache[key]) {
       cache[key] = valueAt(target, key)
@@ -129,6 +130,10 @@ const MapHandler = {
       target.heads = val
       return true
     }
+    if (key === TRACE) {
+      target.trace = val
+      return true
+    }
     const [ value, datatype ] = import_value(val)
     if (frozen) {
       throw new RangeError("Attempting to use an outdated Automerge document")
@@ -211,6 +216,7 @@ const ListHandler = {
     if (index === READ_ONLY) return readonly
     if (index === FROZEN) return frozen
     if (index === HEADS) return heads
+    if (index === TRACE) return target.trace
     if (index === STATE) return context;
     if (index === 'length') return context.length(objectId, heads);
     if (index === Symbol.iterator) {
@@ -246,6 +252,10 @@ const ListHandler = {
       target.heads = val
       return true
     }
+    if (index === TRACE) {
+      target.trace = val
+      return true
+    }
     if (typeof index == "string") {
       throw new RangeError('list index must be a number')
     }
@@ -356,6 +366,7 @@ const TextHandler = Object.assign({}, ListHandler, {
     if (index === READ_ONLY) return readonly
     if (index === FROZEN) return frozen
     if (index === HEADS) return heads
+    if (index === TRACE) return target.trace
     if (index === STATE) return context;
     if (index === 'length') return context.length(objectId, heads);
     if (index === Symbol.iterator) {
diff --git a/automerge-wasm/.gitignore b/automerge-wasm/.gitignore
index a5ef445c..90f5b649 100644
--- a/automerge-wasm/.gitignore
+++ b/automerge-wasm/.gitignore
@@ -1,5 +1,7 @@
 /node_modules
 /dev
+/node
+/web
 /target
 Cargo.lock
 yarn.lock
diff --git a/automerge-wasm/Cargo.toml b/automerge-wasm/Cargo.toml
index f7668bfa..e80e8798 100644
--- a/automerge-wasm/Cargo.toml
+++ b/automerge-wasm/Cargo.toml
@@ -40,10 +40,10 @@ version = "^0.2"
 features = ["serde-serialize", "std"]
 
 [package.metadata.wasm-pack.profile.release]
-# wasm-opt = false
+wasm-opt = true
 
 [package.metadata.wasm-pack.profile.profiling]
-wasm-opt = false
+wasm-opt = true
 
 # The `web-sys` crate allows you to interact with the various browser APIs,
 # like the DOM.
diff --git a/automerge-wasm/attr_bug.js b/automerge-wasm/attr_bug.js
new file mode 100644
index 00000000..324fba33
--- /dev/null
+++ b/automerge-wasm/attr_bug.js
@@ -0,0 +1,15 @@
+let Automerge = require(".")
+let util = require('util')
+
+let heads = ['d138235e8123c407852968a976bb3d05bb30b9f7639854e64cb4adee98a407a6']
+let newHeads = ['d2a0500dad1b4ef1ca0f66015ae24f5cd7bec8316aa8e1115640a665e188147e']
+let text = '10@e1761c3ec92a87d3620d1bc007bdf83a000015ca0b60684edfd007672a0f00113ba1'
+let data = '133,111,74,131,126,182,225,217,0,130,22,22,34,0,174,8,20,12,38,118,140,95,76,123,139,6,212,187,22,0,0,45,11,84,68,75,148,168,76,245,27,147,189,91,99,157,102,34,0,174,8,20,12,38,118,140,95,76,123,139,6,212,187,22,0,0,60,72,31,34,255,16,190,226,176,124,232,19,117,181,152,202,34,0,174,8,20,12,38,118,140,95,76,123,139,6,212,187,22,0,0,173,17,57,82,13,196,120,217,253,4,117,222,120,203,127,31,34,0,174,8,20,12,38,118,140,95,76,123,139,6,212,187,22,0,0,195,238,208,1,215,183,150,181,230,202,10,131,10,53,212,98,16,118,64,44,216,205,38,70,50,172,104,141,96,213,70,225,153,34,225,118,28,62,201,42,135,211,98,13,27,192,7,189,248,58,0,0,7,90,18,166,242,242,169,181,172,173,95,218,197,230,53,171,34,225,118,28,62,201,42,135,211,98,13,27,192,7,189,248,58,0,0,20,123,52,22,113,155,106,167,61,96,211,220,13,176,202,18,34,225,118,28,62,201,42,135,211,98,13,27,192,7,189,248,58,0,0,21,202,11,96,104,78,223,208,7,103,42,15,0,17,59,161,34,225,118,28,62,201,42,135,211,98,13,27,192,7,189,248,58,0,0,49,157,99,144,176,89,107,142,238,50,16,33,198,172,12,98,34,225,118,28,62,201,42,135,211,98,13,27,192,7,189,248,58,0,0,49,160,189,244,223,205,155,34,245,110,74,38,170,63,47,165,34,225,118,28,62,201,42,135,211,98,13,27,192,7,189,248,58,0,0,101,43,36,88,127,139,248,176,98,81,75,151,178,155,65,235,34,225,118,28,62,201,42,135,211,98,13,27,192,7,189,248,58,0,0,104,72,125,26,22,39,88,236,174,2,180,0,186,44,23,100,34,225,118,28,62,201,42,135,211,98,13,27,192,7,189,248,58,0,0,106,192,146,37,220,38,124,176,133,96,99,183,52,146,51,32,34,225,118,28,62,201,42,135,211,98,13,27,192,7,189,248,58,0,0,137,185,129,79,171,192,93,254,162,191,198,11,166,169,184,231,34,225,118,28,62,201,42,135,211,98,13,27,192,7,189,248,58,0,0,183,221,99,120,31,214,103,85,152,145,225,205,226,10,71,148,34,225,118,28,62,201,42,135,211,98,13,27,192,7,189,248,58,0,0,204,247,249,8,135,23,98,57,29,144,111,93,62,1,176,68,34,225,118,28,62,201,42,135,211,98,13,27,192,7,189,248,58,0,0,243,90,241,176,57,235,58,247,98,38,71,96,245,193,178,119,34,229,150,245,136,76,151,59,113,93,112,149,234,7,68,20,213,0,0,23,61,123,236,184,3,106,194,171,46,241,84,223,211,110,241,34,229,150,245,136,76,151,59,113,93,112,149,234,7,68,20,213,0,0,32,181,113,40,11,161,118,67,217,36,93,201,189,221,55,174,34,229,150,245,136,76,151,59,113,93,112,149,234,7,68,20,213,0,0,97,188,15,173,96,163,123,87,228,32,227,245,56,237,53,228,34,229,150,245,136,76,151,59,113,93,112,149,234,7,68,20,213,0,0,97,221,248,228,210,133,45,170,105,131,177,2,9,124,254,61,16,255,46,217,125,15,181,79,74,181,101,95,13,121,190,236,160,1,210,160,80,13,173,27,78,241,202,15,102,1,90,226,79,92,215,190,200,49,106,168,225,17,86,64,166,101,225,136,20,126,8,1,48,3,78,19,38,35,3,53,77,64,17,67,20,86,3,14,1,11,2,17,17,165,1,27,242,1,21,202,1,33,238,1,43,187,2,52,4,66,51,86,78,95,177,2,128,1,45,129,1,15,131,1,23,127,7,21,4,24,8,12,15,3,14,15,6,193,0,12,8,13,3,10,127,9,6,11,127,16,3,2,20,3,10,5,33,3,126,5,17,17,1,11,17,24,21,12,0,125,18,20,19,126,1,0,20,1,127,108,23,1,127,105,11,1,127,117,2,1,127,126,14,1,127,114,192,0,1,127,64,7,1,127,121,2,1,126,126,0,5,1,126,123,0,2,1,127,126,19,1,127,109,9,1,127,11,32,1,125,86,118,0,16,1,127,113,10,1,127,117,23,1,127,105,11,1,127,117,2,0,127,14,2,3,16,1,127,3,2,1,127,2,9,1,2,2,14,1,121,2,1,2,1,2,1,2,171,1,1,127,2,28,1,126,0,4,38,1,167,2,0,255,1,0,127,70,123,34,97,117,116,104,111,114,73,100,34,58,34,101,49,55,54,49,99,51,101,99,57,50,97,56,55,100,51,54,50,48,100,49,98,99,48,48,55,98,100,102,56,51,97,34,44,34,109,101,115,115,97,103,101,34,58,34,74,97,102,102,97,32,67,97,107,101,34,125,39,0,127,0,192,1,1,127,2,32,1,127,2,18,1,127,2,49,1,127,0,191,1,1,126,119,10,33,1,126,95,34,17,1,126,112,17,49,1,167,2,7,0,17,161,2,7,127,4,3,8,4,15,0,17,3,9,157,2,10,119,12,19,42,53,55,71,74,77,80,0,21,5,7,124,6,7,15,7,3,4,127,3,4,4,127,6,7,4,124,6,12,3,4,2,15,127,3,2,15,127,6,15,3,127,6,14,3,11,21,2,3,127,6,11,4,126,6,12,15,1,5,4,126,12,3,13,4,127,14,3,4,2,14,124,6,12,3,4,3,8,127,10,9,17,126,8,12,10,21,126,8,6,5,8,127,3,3,8,127,12,8,13,3,8,127,6,6,8,2,14,124,6,12,3,8,4,15,127,6,2,8,123,15,12,3,15,6,2,8,127,12,2,2,123,8,6,12,3,8,4,15,127,6,6,8,125,12,10,3,5,8,127,6,2,8,11,0,16,8,127,6,2,12,127,9,6,11,126,16,3,2,4,0,10,69,142,189,75,66,97,28,133,207,121,223,50,149,140,140,43,213,32,45,125,64,208,93,226,6,81,75,83,67,4,145,91,91,67,91,229,216,7,250,187,16,33,53,93,250,35,154,171,185,177,32,130,162,156,36,18,84,156,28,85,80,55,125,95,21,228,89,14,156,7,206,129,35,152,28,195,113,30,79,254,230,110,8,250,133,63,2,226,23,207,62,97,121,67,162,128,188,184,184,103,91,48,27,112,138,82,149,46,98,244,189,40,211,59,108,202,235,80,181,124,192,185,179,74,32,84,56,225,63,62,81,148,65,165,161,76,114,15,21,214,48,190,250,142,178,85,36,199,10,194,204,62,72,17,143,140,48,211,202,122,123,74,243,58,96,221,28,249,195,66,136,87,184,49,11,235,251,70,191,32,22,161,189,173,154,36,53,206,166,83,42,254,5,55,231,39,15,88,198,10,59,178,180,189,81,147,121,83,57,41,104,5,150,48,23,239,244,247,151,143,194,13,70,121,122,43,151,163,183,150,196,55,24,155,96,102,166,32,233,115,68,122,127,8,97,114,99,104,105,118,101,100,2,6,97,117,116,104,111,114,126,8,99,111,109,109,101,110,116,115,12,99,111,110,116,114,105,98,117,116,111,114,115,3,7,109,101,115,115,97,103,101,2,9,112,97,114,101,110,116,95,105,100,125,6,112,105,110,110,101,100,6,115,104,97,114,101,100,4,116,101,120,116,3,4,116,105,109,101,124,5,116,105,116,108,101,32,48,48,97,101,48,56,49,52,48,99,50,54,55,54,56,99,53,102,52,99,55,98,56,98,48,54,100,52,98,98,49,54,32,101,49,55,54,49,99,51,101,99,57,50,97,56,55,100,51,54,50,48,100,49,98,99,48,48,55,98,100,102,56,51,97,32,101,53,57,54,102,53,56,56,52,99,57,55,51,98,55,49,53,100,55,48,57,53,101,97,48,55,52,52,49,52,100,53,0,157,2,9,4,116,121,112,101,2,7,127,21,3,7,124,4,21,4,21,4,7,119,4,21,7,1,7,17,7,5,3,2,12,121,6,12,15,12,4,12,4,2,3,111,12,4,12,6,12,4,12,4,12,4,12,6,12,3,5,15,5,2,3,126,12,6,30,3,12,21,2,3,115,12,4,12,4,12,4,12,4,12,4,12,6,12,16,1,123,4,10,12,4,12,2,3,102,4,12,4,12,4,12,4,12,4,12,4,12,14,12,4,12,14,12,6,12,3,5,8,5,3,10,10,17,127,12,11,21,126,6,12,4,8,2,3,125,12,8,12,7,13,102,5,13,8,12,6,12,8,5,12,8,12,14,12,6,12,3,5,15,5,3,12,6,12,8,15,12,2,3,124,6,12,8,12,3,2,117,6,12,3,5,15,5,3,12,6,12,15,2,8,124,12,8,12,10,2,3,121,8,12,8,12,6,12,8,12,0,112,12,8,12,8,12,8,12,8,12,8,12,8,12,8,12,6,2,12,127,9,6,11,125,16,3,5,2,4,2,7,127,4,3,8,4,15,117,143,207,43,131,113,28,199,63,239,103,101,241,236,49,19,113,115,81,147,178,56,108,10,7,92,108,56,40,162,20,218,193,109,139,210,52,179,231,251,41,23,148,103,59,40,7,57,176,54,155,205,197,143,63,65,106,53,57,49,108,53,187,56,104,23,66,118,179,135,92,148,195,235,211,235,240,254,244,249,188,157,85,193,93,169,164,194,95,187,37,125,168,154,244,164,178,113,85,214,164,103,181,140,144,120,129,38,46,193,147,253,203,242,76,235,17,223,81,138,79,128,40,167,248,150,2,198,36,103,233,23,79,99,150,228,55,161,33,104,218,97,79,24,102,176,91,1,219,101,44,14,96,157,227,252,64,127,241,54,108,84,98,179,97,177,13,231,33,231,40,77,200,139,28,233,170,147,224,123,210,79,234,209,137,14,125,142,219,166,218,47,200,116,35,142,177,226,46,82,53,68,73,196,80,3,53,41,218,98,108,64,32,12,184,244,181,150,42,204,93,211,41,175,85,124,218,26,231,12,66,223,31,12,119,143,218,123,149,178,216,132,111,112,172,43,202,150,12,217,16,225,206,3,126,36,171,132,249,61,238,115,40,239,149,18,75,174,17,199,25,123,165,2,69,184,64,205,22,124,138,31,29,234,73,240,43,100,120,243,98,159,139,244,31,231,124,69,80,140,240,213,155,211,98,193,47,25,155,100,169,206,96,248,2,20,157,2,9,3,1,2,0,7,1,127,4,7,1,127,0,28,1,127,0,235,0,1,127,0,43,1,127,7,6,1,127,9,9,1,127,0,5,1,127,0,15,1,127,0,5,1,2,0,55,1,127,0,10,1,127,1,2,134,4,2,0,125,230,1,166,1,182,1,2,214,2,2,1,126,0,105,2,100,127,6,3,2,127,0,28,22,127,0,30,22,127,38,204,0,22,127,0,43,22,125,102,2,6,6,22,127,2,9,22,127,0,5,22,127,0,15,22,127,0,5,22,2,0,54,22,125,38,0,22,9,150,1,173,80,75,78,195,48,16,189,74,110,208,184,78,234,100,87,17,85,21,16,169,5,129,248,108,208,56,246,164,85,211,16,98,47,210,172,145,216,245,2,108,122,150,46,144,224,74,116,193,36,161,233,5,106,217,158,55,243,230,243,108,205,196,136,37,92,39,225,16,2,161,248,104,232,42,38,19,215,21,82,97,192,65,251,225,8,253,32,240,146,80,112,41,152,175,132,27,250,26,92,225,121,204,83,254,253,252,97,18,199,47,183,179,217,221,120,60,190,2,68,112,34,88,233,233,50,79,117,41,75,13,10,163,236,102,184,201,46,39,69,52,227,79,38,136,179,231,183,245,133,143,108,90,101,139,98,190,102,122,163,217,99,140,215,209,251,215,246,251,119,240,209,222,135,159,207,237,97,32,107,107,43,203,44,88,131,96,149,229,22,27,76,177,90,202,26,201,46,150,198,161,13,14,161,60,117,122,127,191,107,2,70,33,28,15,145,170,45,111,110,110,13,41,51,10,254,121,84,176,34,138,16,145,202,58,132,129,186,55,147,186,89,85,223,135,90,244,80,85,173,131,77,54,118,203,216,242,53,79,201,240,118,208,177,158,140,75,237,121,151,216,199,154,199,164,8,157,164,147,86,210,211,82,39,193,21,125,4,45,206,121,85,203,253,206,41,160,132,180,132,98,113,46,240,7,126,0,1,3,0,2,1,126,0,1,4,0,2,1,51,0,127,1,10,0,127,1,219,0,0,127,1,15,0,3,1,36,0,127,1,21,0,2,1,54,0,127,1,11,0,126,21,4,2,21,123,4,21,18,19,20,6,15,127,4,118,156,2,243,125,140,2,3,242,125,141,2,37,2,127,145,126,2,127,3,125,127,92'
+
+let doc = Automerge.loadDoc(new Uint8Array(data.toString().split(",").map((n) => parseInt(n))))
+
+console.log(doc.text(text,heads))
+console.log(doc.text(text,newHeads))
+console.log(doc.text(text))
+console.log(util.inspect(doc.attribute(text,heads,[newHeads]), false, null, false))
+
diff --git a/automerge-wasm/index.d.ts b/automerge-wasm/index.d.ts
index d515b3c7..eb48c402 100644
--- a/automerge-wasm/index.d.ts
+++ b/automerge-wasm/index.d.ts
@@ -1,2 +1,38 @@
+import { Automerge as VanillaAutomerge } from "automerge-types"
+
 export * from "automerge-types"
 export { default } from "automerge-types"
+
+export class Automerge extends VanillaAutomerge {
+  // experimental spans api - unstable!
+  mark(obj: ObjID, name: string, range: string, value: Value, datatype?: Datatype): void;
+  unmark(obj: ObjID, mark: ObjID): void;
+  spans(obj: ObjID): any;
+  raw_spans(obj: ObjID): any;
+  blame(obj: ObjID, baseline: Heads, changeset: Heads[]): ChangeSet[];
+  attribute(obj: ObjID, baseline: Heads, changeset: Heads[]): ChangeSet[];
+  attribute2(obj: ObjID, baseline: Heads, changeset: Heads[]): ChangeSet[];
+
+  // override old methods that return automerge
+  clone(actor?: string): Automerge;
+  fork(actor?: string): Automerge;
+  forkAt(heads: Heads, actor?: string): Automerge;
+}
+
+export type ChangeSetDeletion = {
+  pos: number;
+  val: string;
+}
+
+export type ChangeSetAddition = {
+  start: number;
+  end: number;
+};
+
+export type ChangeSet = {
+  add: ChangeSetAddition[];
+  del: ChangeSetDeletion[];
+};
+
+export function create(actor?: Actor): Automerge;
+export function load(data: Uint8Array, actor?: Actor): Automerge;
diff --git a/automerge-wasm/nodejs-index.js b/automerge-wasm/nodejs-index.js
index 07087e59..4a42f201 100644
--- a/automerge-wasm/nodejs-index.js
+++ b/automerge-wasm/nodejs-index.js
@@ -2,6 +2,4 @@ let wasm = require("./bindgen")
 module.exports = wasm
 module.exports.load = module.exports.loadDoc
 delete module.exports.loadDoc
-Object.defineProperty(module.exports, "__esModule", { value: true })
 module.exports.init = () => (new Promise((resolve,reject) => { resolve(module.exports) }))
-module.exports.default = module.exports.init
diff --git a/automerge-wasm/package.json b/automerge-wasm/package.json
index 50744364..9f7a2a30 100644
--- a/automerge-wasm/package.json
+++ b/automerge-wasm/package.json
@@ -4,11 +4,11 @@
     "Alex Good <alex@memoryandthought.me>",
     "Martin Kleppmann"
   ],
-  "name": "automerge-wasm",
+  "name": "automerge-wasm-pack",
   "description": "wasm-bindgen bindings to the automerge rust implementation",
   "homepage": "https://github.com/automerge/automerge-rs/tree/main/automerge-wasm",
   "repository": "github:automerge/automerge-rs",
-  "version": "0.1.6",
+  "version": "0.1.8",
   "license": "MIT",
   "files": [
     "README.md",
diff --git a/automerge-wasm/src/interop.rs b/automerge-wasm/src/interop.rs
index bc17c018..a8ced00b 100644
--- a/automerge-wasm/src/interop.rs
+++ b/automerge-wasm/src/interop.rs
@@ -352,6 +352,15 @@ pub(crate) fn get_heads(heads: Option<Array>) -> Option<Vec<ChangeHash>> {
     heads.ok()
 }
 
+pub(crate) fn get_js_heads(heads: JsValue) -> Result<Vec<ChangeHash>, JsValue> {
+    let heads = heads.dyn_into::<Array>()?;
+    heads
+        .iter()
+        .map(|j| j.into_serde())
+        .collect::<Result<Vec<_>, _>>()
+        .map_err(to_js_err)
+}
+
 pub(crate) fn map_to_js(doc: &am::AutoCommit, obj: &ObjId) -> JsValue {
     let keys = doc.keys(obj);
     let map = Object::new();
diff --git a/automerge-wasm/src/lib.rs b/automerge-wasm/src/lib.rs
index 9111a4de..49c321a9 100644
--- a/automerge-wasm/src/lib.rs
+++ b/automerge-wasm/src/lib.rs
@@ -34,6 +34,7 @@ use automerge::Patch;
 use automerge::VecOpObserver;
 use automerge::{Change, ObjId, Prop, Value, ROOT};
 use js_sys::{Array, Object, Uint8Array};
+use regex::Regex;
 use std::convert::TryInto;
 use wasm_bindgen::prelude::*;
 use wasm_bindgen::JsCast;
@@ -43,8 +44,8 @@ mod sync;
 mod value;
 
 use interop::{
-    get_heads, js_get, js_set, list_to_js, list_to_js_at, map_to_js, map_to_js_at, to_js_err,
-    to_objtype, to_prop, AR, JS,
+    get_heads, get_js_heads, js_get, js_set, list_to_js, list_to_js_at, map_to_js, map_to_js_at,
+    to_js_err, to_objtype, to_prop, AR, JS,
 };
 use sync::SyncState;
 use value::{datatype, ScalarValue};
@@ -161,12 +162,9 @@ impl Automerge {
         } else {
             ApplyOptions::default()
         };
-        let heads = self.doc.merge_with(&mut other.doc, options)?;
-        let heads: Array = heads
-            .iter()
-            .map(|h| JsValue::from_str(&hex::encode(&h.0)))
-            .collect();
-        Ok(heads)
+        let objs = self.doc.merge_with(&mut other.doc, options)?;
+        let objs: Array = objs.iter().map(|o| JsValue::from(o.to_string())).collect();
+        Ok(objs)
     }
 
     pub fn rollback(&mut self) -> f64 {
@@ -292,6 +290,18 @@ impl Automerge {
         Ok(())
     }
 
+    pub fn make(
+        &mut self,
+        obj: JsValue,
+        prop: JsValue,
+        value: JsValue,
+        _datatype: JsValue,
+    ) -> Result<JsValue, JsValue> {
+        // remove this
+        am::log!("doc.make() is depricated - please use doc.set_object() or doc.insert_object()");
+        self.put_object(obj, prop, value)
+    }
+
     #[wasm_bindgen(js_name = putObject)]
     pub fn put_object(
         &mut self,
@@ -311,7 +321,7 @@ impl Automerge {
     fn subset(&mut self, obj: &am::ObjId, vals: Vec<(am::Prop, JsValue)>) -> Result<(), JsValue> {
         for (p, v) in vals {
             let (value, subvals) = self.import_value(&v, None)?;
-            //let opid = self.0.set(id, p, value)?;
+            //let opid = self.doc.set(id, p, value)?;
             let opid = match (p, value) {
                 (Prop::Map(s), Value::Object(objtype)) => {
                     Some(self.doc.put_object(obj, s, objtype)?)
@@ -551,6 +561,209 @@ impl Automerge {
         Ok(())
     }
 
+    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("range must be in the form of (start..end] or [start..end) etc... () for sticky, [] for normal")?;
+        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 start_sticky = &cap[1] == "(";
+        let end_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, start, start_sticky, end, end_sticky, &name, value)
+            .map_err(to_js_err)?;
+        Ok(())
+    }
+
+    pub fn unmark(&mut self, obj: JsValue, mark: JsValue) -> Result<(), JsValue> {
+        let obj = self.import(obj)?;
+        let mark = self.import(mark)?;
+        self.doc.unmark(&obj, &mark).map_err(to_js_err)?;
+        Ok(())
+    }
+
+    pub fn spans(&mut self, obj: JsValue) -> Result<JsValue, JsValue> {
+        let obj = self.import(obj)?;
+        let text: Vec<_> = self.doc.list_range(&obj, ..).collect();
+        let spans = self.doc.spans(&obj).map_err(to_js_err)?;
+        let mut last_pos = 0;
+        let result = Array::new();
+        for s in spans {
+            let marks = Array::new();
+            for m in s.marks {
+                let mark = Array::new();
+                mark.push(&m.0.into());
+                mark.push(&datatype(&m.1).into());
+                mark.push(&ScalarValue(m.1).into());
+                marks.push(&mark.into());
+            }
+            let text_span = &text[last_pos..s.pos]; //.slice(last_pos, s.pos);
+            if !text_span.is_empty() {
+                let t: String = text_span
+                    .iter()
+                    .filter_map(|(_, v, _)| v.as_string())
+                    .collect();
+                result.push(&t.into());
+            }
+            result.push(&marks);
+            last_pos = s.pos;
+            //let obj = Object::new().into();
+            //js_set(&obj, "pos", s.pos as i32)?;
+            //js_set(&obj, "marks", marks)?;
+            //result.push(&obj.into());
+        }
+        let text_span = &text[last_pos..];
+        if !text_span.is_empty() {
+            let t: String = text_span
+                .iter()
+                .filter_map(|(_, v, _)| v.as_string())
+                .collect();
+            result.push(&t.into());
+        }
+        Ok(result.into())
+    }
+
+    pub fn raw_spans(&mut self, obj: JsValue) -> Result<Array, JsValue> {
+        let obj = self.import(obj)?;
+        let spans = self.doc.raw_spans(&obj).map_err(to_js_err)?;
+        let result = Array::new();
+        for s in spans {
+            result.push(&JsValue::from_serde(&s).map_err(to_js_err)?);
+        }
+        Ok(result)
+    }
+
+    pub fn blame(
+        &mut self,
+        obj: JsValue,
+        baseline: JsValue,
+        change_sets: JsValue,
+    ) -> Result<Array, JsValue> {
+        am::log!("doc.blame() is depricated - please use doc.attribute()");
+        self.attribute(obj, baseline, change_sets)
+    }
+
+    pub fn attribute(
+        &mut self,
+        obj: JsValue,
+        baseline: JsValue,
+        change_sets: JsValue,
+    ) -> Result<Array, JsValue> {
+        let obj = self.import(obj)?;
+        let baseline = get_js_heads(baseline)?;
+        let change_sets = change_sets.dyn_into::<Array>()?;
+        let change_sets = change_sets
+            .iter()
+            .map(get_js_heads)
+            .collect::<Result<Vec<_>, _>>()?;
+        let result = self.doc.attribute(&obj, &baseline, &change_sets)?;
+        let result = result
+            .into_iter()
+            .map(|cs| {
+                let add = cs
+                    .add
+                    .iter()
+                    .map::<Result<JsValue, JsValue>, _>(|range| {
+                        let r = Object::new();
+                        js_set(&r, "start", range.start as f64)?;
+                        js_set(&r, "end", range.end as f64)?;
+                        Ok(JsValue::from(&r))
+                    })
+                    .collect::<Result<Vec<JsValue>, JsValue>>()?
+                    .iter()
+                    .collect::<Array>();
+                let del = cs
+                    .del
+                    .iter()
+                    .map::<Result<JsValue, JsValue>, _>(|d| {
+                        let r = Object::new();
+                        js_set(&r, "pos", d.0 as f64)?;
+                        js_set(&r, "val", &d.1)?;
+                        Ok(JsValue::from(&r))
+                    })
+                    .collect::<Result<Vec<JsValue>, JsValue>>()?
+                    .iter()
+                    .collect::<Array>();
+                let obj = Object::new();
+                js_set(&obj, "add", add)?;
+                js_set(&obj, "del", del)?;
+                Ok(obj.into())
+            })
+            .collect::<Result<Vec<JsValue>, JsValue>>()?
+            .iter()
+            .collect::<Array>();
+        Ok(result)
+    }
+
+    pub fn attribute2(
+        &mut self,
+        obj: JsValue,
+        baseline: JsValue,
+        change_sets: JsValue,
+    ) -> Result<Array, JsValue> {
+        let obj = self.import(obj)?;
+        let baseline = get_js_heads(baseline)?;
+        let change_sets = change_sets.dyn_into::<Array>()?;
+        let change_sets = change_sets
+            .iter()
+            .map(get_js_heads)
+            .collect::<Result<Vec<_>, _>>()?;
+        let result = self.doc.attribute2(&obj, &baseline, &change_sets)?;
+        let result = result
+            .into_iter()
+            .map(|cs| {
+                let add = cs
+                    .add
+                    .iter()
+                    .map::<Result<JsValue, JsValue>, _>(|a| {
+                        let r = Object::new();
+                        js_set(&r, "actor", &self.doc.actor_to_str(a.actor))?;
+                        js_set(&r, "start", a.range.start as f64)?;
+                        js_set(&r, "end", a.range.end as f64)?;
+                        Ok(JsValue::from(&r))
+                    })
+                    .collect::<Result<Vec<JsValue>, JsValue>>()?
+                    .iter()
+                    .collect::<Array>();
+                let del = cs
+                    .del
+                    .iter()
+                    .map::<Result<JsValue, JsValue>, _>(|d| {
+                        let r = Object::new();
+                        js_set(&r, "actor", &self.doc.actor_to_str(d.actor))?;
+                        js_set(&r, "pos", d.pos as f64)?;
+                        js_set(&r, "val", &d.span)?;
+                        Ok(JsValue::from(&r))
+                    })
+                    .collect::<Result<Vec<JsValue>, JsValue>>()?
+                    .iter()
+                    .collect::<Array>();
+                let obj = Object::new();
+                js_set(&obj, "add", add)?;
+                js_set(&obj, "del", del)?;
+                Ok(obj.into())
+            })
+            .collect::<Result<Vec<JsValue>, JsValue>>()?
+            .iter()
+            .collect::<Array>();
+        Ok(result)
+    }
+
     pub fn save(&mut self) -> Uint8Array {
         self.ensure_transaction_closed();
         Uint8Array::from(self.doc.save().as_slice())
diff --git a/automerge-wasm/test/attribute.ts b/automerge-wasm/test/attribute.ts
new file mode 100644
index 00000000..3369acae
--- /dev/null
+++ b/automerge-wasm/test/attribute.ts
@@ -0,0 +1,188 @@
+import { describe, it } from 'mocha';
+//@ts-ignore
+import assert from 'assert'
+//@ts-ignore
+import { BloomFilter } from './helpers/sync'
+import { create, load, SyncState, Automerge, encodeChange, decodeChange, initSyncState, decodeSyncMessage, decodeSyncState, encodeSyncState, encodeSyncMessage } from '..'
+import { DecodedSyncMessage, Hash } from '..'
+
+describe('Automerge', () => {
+  describe('attribute', () => {
+    it('should be able to attribute text segments on change sets', () => {
+      let doc1 = create()
+      let text = doc1.putObject("_root", "notes","hello little world")
+      let h1 = doc1.getHeads();
+
+      let doc2 = doc1.fork();
+      doc2.splice(text, 5, 7, " big");
+      doc2.text(text)
+      let h2 = doc2.getHeads();
+      assert.deepEqual(doc2.text(text), "hello big world")
+
+      let doc3 = doc1.fork();
+      doc3.splice(text, 0, 0, "Well, ");
+      let h3 = doc3.getHeads();
+      assert.deepEqual(doc3.text(text), "Well, hello little world")
+
+      doc1.merge(doc2)
+      doc1.merge(doc3)
+      assert.deepEqual(doc1.text(text), "Well, hello big world")
+      let attribute = doc1.attribute(text, h1, [h2, h3])
+
+      assert.deepEqual(attribute, [
+        { add: [ { start: 11, end: 15 } ], del: [ { pos: 15, val: ' little' } ] },
+        { add: [ { start: 0,  end: 6  } ], del: [] }
+      ])
+    })
+
+    it('should be able to hand complex attribute change sets', () => {
+      let doc1 = create("aaaa")
+      let text = doc1.putObject("_root", "notes","AAAAAA")
+      let h1 = doc1.getHeads();
+
+      let doc2 = doc1.fork("bbbb");
+      doc2.splice(text, 0, 2, "BB");
+      doc2.commit()
+      doc2.splice(text, 2, 2, "BB");
+      doc2.commit()
+      doc2.splice(text, 6, 0, "BB");
+      doc2.commit()
+      let h2 = doc2.getHeads();
+      assert.deepEqual(doc2.text(text), "BBBBAABB")
+
+      let doc3 = doc1.fork("cccc");
+      doc3.splice(text, 1, 1, "C");
+      doc3.commit()
+      doc3.splice(text, 3, 1, "C");
+      doc3.commit()
+      doc3.splice(text, 5, 1, "C");
+      doc3.commit()
+      let h3 = doc3.getHeads();
+      // with tombstones its 
+      // AC.AC.AC.
+      assert.deepEqual(doc3.text(text), "ACACAC")
+
+      doc1.merge(doc2)
+
+      assert.deepEqual(doc1.attribute(text, h1, [h2]), [
+        { add: [ {start:0, end: 4}, { start: 6, end: 8 } ], del: [ { pos: 4, val: 'AAAA' } ] },
+      ])
+
+      doc1.merge(doc3)
+
+      assert.deepEqual(doc1.text(text), "BBBBCCACBB")
+
+      // with tombstones its 
+      // BBBB.C..C.AC.BB
+      assert.deepEqual(doc1.attribute(text, h1, [h2,h3]), [  
+        { add: [ {start:0, end: 4}, { start: 8, end: 10 } ], del: [ { pos: 4, val: 'A' }, { pos: 5, val: 'AA' }, { pos: 6, val: 'A' } ] },
+        { add: [ {start:4, end: 6}, { start: 7, end: 8 } ], del: [ { pos: 5, val: 'A' }, { pos: 6, val: 'A' }, { pos: 8, val: 'A' } ] }
+      ])
+    })
+
+    it('should not include attribution of text that is inserted and deleted only within change sets', () => {
+      let doc1 = create()
+      let text = doc1.putObject("_root", "notes","hello little world")
+      let h1 = doc1.getHeads();
+
+      let doc2 = doc1.fork();
+      doc2.splice(text, 5, 7, " big");
+      doc2.splice(text, 9, 0, " bad");
+      doc2.splice(text, 9, 4)
+      doc2.text(text)
+      let h2 = doc2.getHeads();
+      assert.deepEqual(doc2.text(text), "hello big world")
+
+      let doc3 = doc1.fork();
+      doc3.splice(text, 0, 0, "Well, HI THERE");
+      doc3.splice(text, 6, 8, "")
+      let h3 = doc3.getHeads();
+      assert.deepEqual(doc3.text(text), "Well, hello little world")
+
+      doc1.merge(doc2)
+      doc1.merge(doc3)
+      assert.deepEqual(doc1.text(text), "Well, hello big world")
+      let attribute = doc1.attribute(text, h1, [h2, h3])
+
+      assert.deepEqual(attribute, [
+        { add: [ { start: 11, end: 15 } ], del: [ { pos: 15, val: ' little' } ] },
+        { add: [ { start: 0,  end: 6  } ], del: [] }
+      ])
+    })
+
+  })
+  describe('attribute2', () => {
+    it('should be able to attribute text segments on change sets', () => {
+      let doc1 = create("aaaa")
+      let text = doc1.putObject("_root", "notes","hello little world")
+      let h1 = doc1.getHeads();
+
+      let doc2 = doc1.fork("bbbb");
+      doc2.splice(text, 5, 7, " big");
+      doc2.text(text)
+      let h2 = doc2.getHeads();
+      assert.deepEqual(doc2.text(text), "hello big world")
+
+      let doc3 = doc1.fork("cccc");
+      doc3.splice(text, 0, 0, "Well, ");
+      let doc4 = doc3.fork("dddd")
+      doc4.splice(text, 0, 0, "Gee, ");
+      let h3 = doc4.getHeads();
+      assert.deepEqual(doc4.text(text), "Gee, Well, hello little world")
+
+      doc1.merge(doc2)
+      doc1.merge(doc4)
+      assert.deepEqual(doc1.text(text), "Gee, Well, hello big world")
+      let attribute = doc1.attribute2(text, h1, [h2, h3])
+
+      assert.deepEqual(attribute, [
+        { add: [ { actor: "bbbb", start: 16, end: 20 } ], del: [ { actor: "bbbb", pos: 20, val: ' little' } ] },
+        { add: [ { actor: "dddd", start:0, end: 5 }, { actor: "cccc", start: 5,  end: 11  } ], del: [] }
+      ])
+    })
+
+    it('should not include attribution of text that is inserted and deleted only within change sets', () => {
+      let doc1 = create("aaaa")
+      let text = doc1.putObject("_root", "notes","hello little world")
+      let h1 = doc1.getHeads();
+
+      let doc2 = doc1.fork("bbbb");
+      doc2.splice(text, 5, 7, " big");
+      doc2.splice(text, 9, 0, " bad");
+      doc2.splice(text, 9, 4)
+      doc2.text(text)
+      let h2 = doc2.getHeads();
+      assert.deepEqual(doc2.text(text), "hello big world")
+
+      let doc3 = doc1.fork("cccc");
+      doc3.splice(text, 0, 0, "Well, HI THERE");
+      doc3.splice(text, 6, 8, "")
+      let h3 = doc3.getHeads();
+      assert.deepEqual(doc3.text(text), "Well, hello little world")
+
+      doc1.merge(doc2)
+      doc1.merge(doc3)
+      assert.deepEqual(doc1.text(text), "Well, hello big world")
+      let attribute = doc1.attribute2(text, h1, [h2, h3])
+
+      assert.deepEqual(attribute, [
+        { add: [ { start: 11, end: 15, actor: "bbbb" } ], del: [ { pos: 15, val: ' little', actor: "bbbb" } ] },
+        { add: [ { start: 0,  end: 6,  actor: "cccc" } ], del: [] }
+      ])
+
+      let h4 = doc1.getHeads()
+
+      doc3.splice(text, 24, 0, "!!!")
+      doc1.merge(doc3)
+
+      let h5 = doc1.getHeads()
+
+      assert.deepEqual(doc1.text(text), "Well, hello big world!!!")
+      attribute = doc1.attribute2(text, h4, [h5])
+
+      assert.deepEqual(attribute, [
+        { add: [ { start: 21, end: 24, actor: "cccc" } ], del: [] },
+      ])
+    })
+  })
+})
diff --git a/automerge-wasm/test/marks.ts b/automerge-wasm/test/marks.ts
new file mode 100644
index 00000000..a525a2cf
--- /dev/null
+++ b/automerge-wasm/test/marks.ts
@@ -0,0 +1,201 @@
+import { describe, it } from 'mocha';
+//@ts-ignore
+import assert from 'assert'
+//@ts-ignore
+import { create, load, Automerge, encodeChange, decodeChange } from '..'
+
+describe('Automerge', () => {
+  describe('marks', () => {
+    it('should handle marks [..]', () => {
+      let doc = create()
+      let list = doc.putObject("_root", "list", "")
+      doc.splice(list, 0, 0, "aaabbbccc")
+      doc.mark(list, "[3..6]", "bold" , true)
+      let spans = doc.spans(list);
+      assert.deepStrictEqual(spans, [ 'aaa', [ [ 'bold', 'boolean', true ] ], 'bbb', [], 'ccc' ]);
+      doc.insert(list, 6, "A")
+      doc.insert(list, 3, "A")
+      spans = doc.spans(list);
+      assert.deepStrictEqual(spans, [ 'aaaA', [ [ 'bold', 'boolean', true ] ], 'bbb', [], 'Accc' ]);
+    })
+
+    it('should handle marks [..] at the beginning of a string', () => {
+      let doc = create()
+      let list = doc.putObject("_root", "list", "")
+      doc.splice(list, 0, 0, "aaabbbccc")
+      doc.mark(list, "[0..3]", "bold", true)
+      let spans = doc.spans(list);
+      assert.deepStrictEqual(spans, [ [ [ 'bold', 'boolean', true ] ], 'aaa', [], 'bbbccc' ]);
+
+      let doc2 = doc.fork()
+      doc2.insert(list, 0, "A")
+      doc2.insert(list, 4, "B")
+      doc.merge(doc2)
+      spans = doc.spans(list);
+      assert.deepStrictEqual(spans, [ 'A', [ [ 'bold', 'boolean', true ] ], 'aaa', [], 'Bbbbccc' ]);
+    })
+
+    it('should handle marks [..] with splice', () => {
+      let doc = create()
+      let list = doc.putObject("_root", "list", "")
+      doc.splice(list, 0, 0, "aaabbbccc")
+      doc.mark(list, "[0..3]", "bold", true)
+      let spans = doc.spans(list);
+      assert.deepStrictEqual(spans, [ [ [ 'bold', 'boolean', true ] ], 'aaa', [], 'bbbccc' ]);
+
+      let doc2 = doc.fork()
+      doc2.splice(list, 0, 2, "AAA")
+      doc2.splice(list, 4, 0, "BBB")
+      doc.merge(doc2)
+      spans = doc.spans(list);
+      assert.deepStrictEqual(spans, [ 'AAA', [ [ 'bold', 'boolean', true ] ], 'a', [], 'BBBbbbccc' ]);
+    })
+
+    it('should handle marks across multiple forks', () => {
+      let doc = create()
+      let list = doc.putObject("_root", "list", "")
+      doc.splice(list, 0, 0, "aaabbbccc")
+      doc.mark(list, "[0..3]", "bold", true)
+      let spans = doc.spans(list);
+      assert.deepStrictEqual(spans, [ [ [ 'bold', 'boolean', true ] ], 'aaa', [], 'bbbccc' ]);
+
+      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)
+
+      spans = doc.spans(list);
+      assert.deepStrictEqual(spans, [ 'AAA', [ [ 'bold', 'boolean', true ] ], 'aZa', [], 'bbbccc' ]);
+    })
+
+
+    it('should handle marks with deleted ends [..]', () => {
+      let doc = create()
+      let list = doc.putObject("_root", "list", "")
+
+      doc.splice(list, 0, 0, "aaabbbccc")
+      doc.mark(list, "[3..6]", "bold" , true)
+      let spans = doc.spans(list);
+      assert.deepStrictEqual(spans, [ 'aaa', [ [ 'bold', 'boolean', true ] ], 'bbb', [], 'ccc' ]);
+      doc.delete(list,5);
+      doc.delete(list,5);
+      doc.delete(list,2);
+      doc.delete(list,2);
+      spans = doc.spans(list);
+      assert.deepStrictEqual(spans, [ 'aa', [ [ 'bold', 'boolean', true ] ], 'b', [], 'cc' ])
+      doc.insert(list, 3, "A")
+      doc.insert(list, 2, "A")
+      spans = doc.spans(list);
+      assert.deepStrictEqual(spans, [ 'aaA', [ [ 'bold', 'boolean', true ] ], 'b', [], 'Acc' ])
+    })
+
+    it('should handle sticky marks (..)', () => {
+      let doc = create()
+      let list = doc.putObject("_root", "list", "")
+      doc.splice(list, 0, 0, "aaabbbccc")
+      doc.mark(list, "(3..6)", "bold" , true)
+      let spans = doc.spans(list);
+      assert.deepStrictEqual(spans, [ 'aaa', [ [ 'bold', 'boolean', true ] ], 'bbb', [], 'ccc' ]);
+      doc.insert(list, 6, "A")
+      doc.insert(list, 3, "A")
+      spans = doc.spans(list);
+      assert.deepStrictEqual(spans, [ 'aaa', [ [ 'bold', 'boolean', true ] ], 'AbbbA', [], 'ccc' ]);
+    })
+
+    it('should handle sticky marks with deleted ends (..)', () => {
+      let doc = create()
+      let list = doc.putObject("_root", "list", "")
+      doc.splice(list, 0, 0, "aaabbbccc")
+      doc.mark(list, "(3..6)", "bold" , true)
+      let spans = doc.spans(list);
+      assert.deepStrictEqual(spans, [ 'aaa', [ [ 'bold', 'boolean', true ] ], 'bbb', [], 'ccc' ]);
+      doc.delete(list,5);
+      doc.delete(list,5);
+      doc.delete(list,2);
+      doc.delete(list,2);
+      spans = doc.spans(list);
+      assert.deepStrictEqual(spans, [ 'aa', [ [ 'bold', 'boolean', true ] ], 'b', [], 'cc' ])
+      doc.insert(list, 3, "A")
+      doc.insert(list, 2, "A")
+      spans = doc.spans(list);
+      assert.deepStrictEqual(spans, [ 'aa', [ [ 'bold', 'boolean', true ] ], 'AbA', [], 'cc' ])
+
+      // make sure save/load can handle marks
+
+      let doc2 = load(doc.save())
+      spans = doc2.spans(list);
+      assert.deepStrictEqual(spans, [ 'aa', [ [ 'bold', 'boolean', true ] ], 'AbA', [], 'cc' ])
+
+      assert.deepStrictEqual(doc.getHeads(), doc2.getHeads())
+      assert.deepStrictEqual(doc.save(), doc2.save())
+    })
+
+    it('should handle overlapping marks', () => {
+      let doc : Automerge = create("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)
+      doc.mark(list, "[10..13]", "comment" , "foxes are my favorite animal!")
+      doc.commit("marks");
+      let spans = doc.spans(list);
+      assert.deepStrictEqual(spans,
+        [
+          [ [ 'bold', 'boolean', true ] ],
+          'the ',
+          [ [ 'bold', 'boolean', true ], [ 'itallic', 'boolean', true ] ],
+          'quick ',
+          [
+            [ 'bold', 'boolean', true ],
+            [ 'comment', 'str', 'foxes are my favorite animal!' ],
+            [ 'itallic', 'boolean', true ]
+          ],
+          'fox',
+          [ [ 'bold', 'boolean', true ], [ 'itallic', 'boolean', true ] ],
+          ' jumps',
+          [ [ 'bold', 'boolean', true ] ],
+          ' over the lazy dog',
+          [],
+        ]
+      )
+      let text = doc.text(list);
+      assert.deepStrictEqual(text, "the quick fox jumps over the lazy dog");
+      let raw_spans = doc.raw_spans(list);
+      assert.deepStrictEqual(raw_spans,
+        [
+          { id: "39@aabbcc", start: 0, end: 37, type: 'bold', value: true },
+          { id: "41@aabbcc", start: 4, end: 19, type: 'itallic', value: true },
+          { id: "43@aabbcc", start: 10, end: 13, type: 'comment', value: 'foxes are my favorite animal!' }
+        ]);
+
+      doc.unmark(list, "41@aabbcc")
+      raw_spans = doc.raw_spans(list);
+      assert.deepStrictEqual(raw_spans,
+        [
+          { id: "39@aabbcc", start: 0, end: 37, type: 'bold', value: true },
+          { id: "43@aabbcc", start: 10, end: 13, type: 'comment', value: 'foxes are my favorite animal!' }
+        ]);
+      // mark sure encode decode can handle marks
+
+      doc.unmark(list, "39@aabbcc")
+      raw_spans = doc.raw_spans(list);
+      assert.deepStrictEqual(raw_spans,
+        [
+          { id: "43@aabbcc", start: 10, end: 13, type: 'comment', value: 'foxes are my favorite animal!' }
+        ]);
+
+      let all = doc.getChanges([])
+      let decoded = all.map((c) => decodeChange(c))
+      let encoded = decoded.map((c) => encodeChange(c))
+      let doc2 = create();
+      doc2.applyChanges(encoded)
+
+      assert.deepStrictEqual(doc.spans(list) , doc2.spans(list))
+      assert.deepStrictEqual(doc.save(), doc2.save())
+    })
+  })
+})
diff --git a/automerge-wasm/test/test.ts b/automerge-wasm/test/test.ts
index 7c573061..bb906e70 100644
--- a/automerge-wasm/test/test.ts
+++ b/automerge-wasm/test/test.ts
@@ -396,6 +396,8 @@ describe('Automerge', () => {
       assert.deepEqual(change2, null)
       if (change1 === null) { throw new RangeError("change1 should not be null") }
       assert.deepEqual(decodeChange(change1).hash, head1[0])
+      assert.deepEqual(head1.some((hash) => doc1.getChangeByHash(hash) === null), false)
+      assert.deepEqual(head2.some((hash) => doc1.getChangeByHash(hash) === null), true)
     })
 
     it('recursive sets are possible', () => {
@@ -1654,7 +1656,7 @@ describe('Automerge', () => {
         if (m2 === null) { throw new RangeError("message should not be null") }
         n1.receiveSyncMessage(s1, m2)
         n2.receiveSyncMessage(s2, m1)
-
+        
         // Then n1 and n2 send each other their changes, except for the false positive
         m1 = n1.generateSyncMessage(s1)
         m2 = n2.generateSyncMessage(s2)
diff --git a/automerge-wasm/types/index.d.ts b/automerge-wasm/types/index.d.ts
index 68277203..ea57f9c2 100644
--- a/automerge-wasm/types/index.d.ts
+++ b/automerge-wasm/types/index.d.ts
@@ -205,5 +205,5 @@ export class SyncState {
   readonly sharedHeads: Heads;
 }
 
-export default function init (): Promise<API>;
 export function init (): Promise<API>;
+
diff --git a/automerge-wasm/web-index.js b/automerge-wasm/web-index.js
index 6510fe05..9bbe47df 100644
--- a/automerge-wasm/web-index.js
+++ b/automerge-wasm/web-index.js
@@ -47,7 +47,3 @@ export function init() {
   }))
 }
 
-// depricating default export
-export default function() {
-  return init()
-}
diff --git a/automerge/src/autocommit.rs b/automerge/src/autocommit.rs
index 1233c1e0..ac72c60c 100644
--- a/automerge/src/autocommit.rs
+++ b/automerge/src/autocommit.rs
@@ -3,13 +3,14 @@ use std::ops::RangeBounds;
 use crate::exid::ExId;
 use crate::op_observer::OpObserver;
 use crate::transaction::{CommitOptions, Transactable};
+use crate::Parents;
 use crate::{
-    sync, ApplyOptions, Keys, KeysAt, ListRange, ListRangeAt, MapRange, MapRangeAt, ObjType,
-    Parents, ScalarValue,
+    query, transaction::TransactionInner, ActorId, Automerge, AutomergeError, Change, ChangeHash,
+    Prop, Value, Values,
 };
 use crate::{
-    transaction::TransactionInner, ActorId, Automerge, AutomergeError, Change, ChangeHash, Prop,
-    Value, Values,
+    sync, ApplyOptions, Keys, KeysAt, ListRange, ListRangeAt, MapRange, MapRangeAt, ObjType,
+    ScalarValue,
 };
 
 /// An automerge document that automatically manages transactions.
@@ -33,6 +34,11 @@ impl AutoCommit {
         }
     }
 
+    // FIXME : temp
+    pub fn actor_to_str(&self, actor: usize) -> String {
+        self.doc.ops.m.actors.cache[actor].to_hex_string()
+    }
+
     /// Get the inner document.
     #[doc(hidden)]
     pub fn document(&mut self) -> &Automerge {
@@ -404,6 +410,37 @@ impl Transactable for AutoCommit {
         tx.insert(&mut self.doc, obj.as_ref(), index, value)
     }
 
+    #[allow(clippy::too_many_arguments)]
+    fn mark<O: AsRef<ExId>>(
+        &mut self,
+        obj: O,
+        start: usize,
+        expand_start: bool,
+        end: usize,
+        expand_end: bool,
+        mark: &str,
+        value: ScalarValue,
+    ) -> Result<(), AutomergeError> {
+        self.ensure_transaction_open();
+        let tx = self.transaction.as_mut().unwrap();
+        tx.mark(
+            &mut self.doc,
+            obj,
+            start,
+            expand_start,
+            end,
+            expand_end,
+            mark,
+            value,
+        )
+    }
+
+    fn unmark<O: AsRef<ExId>>(&mut self, obj: O, mark: O) -> Result<(), AutomergeError> {
+        self.ensure_transaction_open();
+        let tx = self.transaction.as_mut().unwrap();
+        tx.unmark(&mut self.doc, obj, mark)
+    }
+
     fn insert_object<O: AsRef<ExId>>(
         &mut self,
         obj: O,
@@ -462,6 +499,32 @@ impl Transactable for AutoCommit {
         self.doc.text_at(obj, heads)
     }
 
+    fn spans<O: AsRef<ExId>>(&self, obj: O) -> Result<Vec<query::Span<'_>>, AutomergeError> {
+        self.doc.spans(obj)
+    }
+
+    fn raw_spans<O: AsRef<ExId>>(&self, obj: O) -> Result<Vec<query::SpanInfo>, AutomergeError> {
+        self.doc.raw_spans(obj)
+    }
+
+    fn attribute<O: AsRef<ExId>>(
+        &self,
+        obj: O,
+        baseline: &[ChangeHash],
+        change_sets: &[Vec<ChangeHash>],
+    ) -> Result<Vec<query::ChangeSet>, AutomergeError> {
+        self.doc.attribute(obj, baseline, change_sets)
+    }
+
+    fn attribute2<O: AsRef<ExId>>(
+        &self,
+        obj: O,
+        baseline: &[ChangeHash],
+        change_sets: &[Vec<ChangeHash>],
+    ) -> Result<Vec<query::ChangeSet2>, AutomergeError> {
+        self.doc.attribute2(obj, baseline, change_sets)
+    }
+
     // TODO - I need to return these OpId's here **only** to get
     // the legacy conflicts format of { [opid]: value }
     // Something better?
diff --git a/automerge/src/automerge.rs b/automerge/src/automerge.rs
index c167178b..0c08f6d2 100644
--- a/automerge/src/automerge.rs
+++ b/automerge/src/automerge.rs
@@ -452,6 +452,28 @@ impl Automerge {
         }
     }
 
+    pub(crate) fn exid_to_obj_tmp_unchecked(&self, id: &ExId) -> Result<ObjId, AutomergeError> {
+        match id {
+            ExId::Root => Ok(ObjId::root()),
+            ExId::Id(ctr, actor, idx) => {
+                // do a direct get here b/c this could be foriegn and not be within the array
+                // bounds
+                if self.ops.m.actors.cache.get(*idx) == Some(actor) {
+                    Ok(ObjId(OpId(*ctr, *idx)))
+                } else {
+                    // FIXME - make a real error
+                    let idx = self
+                        .ops
+                        .m
+                        .actors
+                        .lookup(actor)
+                        .ok_or(AutomergeError::Fail)?;
+                    Ok(ObjId(OpId(*ctr, idx)))
+                }
+            }
+        }
+    }
+
     pub(crate) fn id_to_exid(&self, id: OpId) -> ExId {
         self.ops.id_to_exid(id)
     }
@@ -491,6 +513,71 @@ impl Automerge {
         Ok(buffer)
     }
 
+    pub fn spans<O: AsRef<ExId>>(&self, obj: O) -> Result<Vec<query::Span<'_>>, AutomergeError> {
+        let obj = self.exid_to_obj(obj.as_ref())?;
+        let mut query = self.ops.search(&obj, query::Spans::new());
+        query.check_marks();
+        Ok(query.spans)
+    }
+
+    pub fn attribute<O: AsRef<ExId>>(
+        &self,
+        obj: O,
+        baseline: &[ChangeHash],
+        change_sets: &[Vec<ChangeHash>],
+    ) -> Result<Vec<query::ChangeSet>, AutomergeError> {
+        let obj = self.exid_to_obj(obj.as_ref())?;
+        let baseline = self.clock_at(baseline);
+        let change_sets: Vec<Clock> = change_sets
+            .iter()
+            .map(|p| self.clock_at(p).unwrap())
+            .collect();
+        let mut query = self
+            .ops
+            .search(&obj, query::Attribute::new(baseline.unwrap(), change_sets));
+        query.finish();
+        Ok(query.change_sets)
+    }
+
+    pub fn attribute2<O: AsRef<ExId>>(
+        &self,
+        obj: O,
+        baseline: &[ChangeHash],
+        change_sets: &[Vec<ChangeHash>],
+    ) -> Result<Vec<query::ChangeSet2>, AutomergeError> {
+        let obj = self.exid_to_obj(obj.as_ref())?;
+        let baseline = self.clock_at(baseline);
+        let change_sets: Vec<Clock> = change_sets
+            .iter()
+            .map(|p| self.clock_at(p).unwrap())
+            .collect();
+        let mut query = self
+            .ops
+            .search(&obj, query::Attribute2::new(baseline.unwrap(), change_sets));
+        query.finish();
+        Ok(query.change_sets)
+    }
+
+    pub fn raw_spans<O: AsRef<ExId>>(
+        &self,
+        obj: O,
+    ) -> Result<Vec<query::SpanInfo>, AutomergeError> {
+        let obj = self.exid_to_obj(obj.as_ref())?;
+        let query = self.ops.search(&obj, query::RawSpans::new());
+        let result = query
+            .spans
+            .into_iter()
+            .map(|s| query::SpanInfo {
+                id: self.id_to_exid(s.id),
+                start: s.start,
+                end: s.end,
+                span_type: s.name,
+                value: s.value,
+            })
+            .collect();
+        Ok(result)
+    }
+
     // TODO - I need to return these OpId's here **only** to get
     // the legacy conflicts format of { [opid]: value }
     // Something better?
@@ -1041,6 +1128,8 @@ impl Automerge {
                 OpType::Put(value) => format!("{}", value),
                 OpType::Make(obj) => format!("make({})", obj),
                 OpType::Increment(obj) => format!("inc({})", obj),
+                OpType::MarkBegin(m) => format!("mark({}={})", m.name, m.value),
+                OpType::MarkEnd(_) => "/mark".into(),
                 OpType::Delete => format!("del{}", 0),
             };
             let pred: Vec<_> = op.pred.iter().map(|id| self.to_string(*id)).collect();
diff --git a/automerge/src/columnar.rs b/automerge/src/columnar.rs
index 25748a25..6cd3b2fb 100644
--- a/automerge/src/columnar.rs
+++ b/automerge/src/columnar.rs
@@ -137,6 +137,15 @@ impl<'a> Iterator for OperationIterator<'a> {
             Action::MakeTable => OpType::Make(ObjType::Table),
             Action::Del => OpType::Delete,
             Action::Inc => OpType::Increment(value.to_i64()?),
+            Action::MarkBegin => {
+                // mark has 3 things in the val column
+                let name = value.as_string()?;
+                let expand = self.value.next()?.to_bool()?;
+                let value = self.value.next()?;
+                OpType::mark(name, expand, value)
+            }
+            Action::MarkEnd => OpType::MarkEnd(value.to_bool()?),
+            Action::Unused => panic!("invalid action"),
         };
         Some(amp::Op {
             action,
@@ -178,6 +187,15 @@ impl<'a> Iterator for DocOpIterator<'a> {
             Action::MakeTable => OpType::Make(ObjType::Table),
             Action::Del => OpType::Delete,
             Action::Inc => OpType::Increment(value.to_i64()?),
+            Action::MarkBegin => {
+                // mark has 3 things in the val column
+                let name = value.as_string()?;
+                let expand = self.value.next()?.to_bool()?;
+                let value = self.value.next()?;
+                OpType::mark(name, expand, value)
+            }
+            Action::MarkEnd => OpType::MarkEnd(value.to_bool()?),
+            Action::Unused => panic!("invalid action"),
         };
         Some(DocOp {
             actor,
@@ -1082,6 +1100,16 @@ impl DocOpEncoder {
                     self.val.append_null();
                     Action::Del
                 }
+                amp::OpType::MarkBegin(m) => {
+                    self.val.append_value(&m.name.clone().into(), actors);
+                    self.val.append_value(&m.expand.into(), actors);
+                    self.val.append_value(&m.value.clone(), actors);
+                    Action::MarkBegin
+                }
+                amp::OpType::MarkEnd(s) => {
+                    self.val.append_value(&(*s).into(), actors);
+                    Action::MarkEnd
+                }
                 amp::OpType::Make(kind) => {
                     self.val.append_null();
                     match kind {
@@ -1191,6 +1219,16 @@ impl ColumnEncoder {
                 self.val.append_null();
                 Action::Del
             }
+            OpType::MarkBegin(m) => {
+                self.val.append_value2(&m.name.clone().into(), actors);
+                self.val.append_value2(&m.expand.into(), actors);
+                self.val.append_value2(&m.value.clone(), actors);
+                Action::MarkBegin
+            }
+            OpType::MarkEnd(s) => {
+                self.val.append_value2(&(*s).into(), actors);
+                Action::MarkEnd
+            }
             OpType::Make(kind) => {
                 self.val.append_null();
                 match kind {
@@ -1296,8 +1334,11 @@ pub(crate) enum Action {
     MakeText,
     Inc,
     MakeTable,
+    MarkBegin,
+    Unused, // final bit is used to mask `Make` actions
+    MarkEnd,
 }
-const ACTIONS: [Action; 7] = [
+const ACTIONS: [Action; 10] = [
     Action::MakeMap,
     Action::Set,
     Action::MakeList,
@@ -1305,6 +1346,9 @@ const ACTIONS: [Action; 7] = [
     Action::MakeText,
     Action::Inc,
     Action::MakeTable,
+    Action::MarkBegin,
+    Action::Unused,
+    Action::MarkEnd,
 ];
 
 impl Decodable for Action {
diff --git a/automerge/src/legacy/serde_impls/op.rs b/automerge/src/legacy/serde_impls/op.rs
index 0f7ef8c2..c540097f 100644
--- a/automerge/src/legacy/serde_impls/op.rs
+++ b/automerge/src/legacy/serde_impls/op.rs
@@ -50,6 +50,12 @@ 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(m) => {
+                op.serialize_field("name", &m.name)?;
+                op.serialize_field("expand", &m.expand)?;
+                op.serialize_field("value", &m.value)?;
+            }
+            OpType::MarkEnd(s) => op.serialize_field("expand", &s)?,
             _ => {}
         }
         op.serialize_field("pred", &self.pred)?;
@@ -71,6 +77,8 @@ pub(crate) enum RawOpType {
     Del,
     Inc,
     Set,
+    MarkBegin,
+    MarkEnd,
 }
 
 impl Serialize for RawOpType {
@@ -86,6 +94,8 @@ impl Serialize for RawOpType {
             RawOpType::Del => "del",
             RawOpType::Inc => "inc",
             RawOpType::Set => "set",
+            RawOpType::MarkBegin => "mark_begin",
+            RawOpType::MarkEnd => "mark_end",
         };
         serializer.serialize_str(s)
     }
@@ -117,6 +127,8 @@ impl<'de> Deserialize<'de> for RawOpType {
             "del" => Ok(RawOpType::Del),
             "inc" => Ok(RawOpType::Inc),
             "set" => Ok(RawOpType::Set),
+            "mark_begin" => Ok(RawOpType::MarkBegin),
+            "mark_end" => Ok(RawOpType::MarkEnd),
             other => Err(Error::unknown_variant(other, VARIANTS)),
         }
     }
@@ -189,6 +201,30 @@ impl<'de> Deserialize<'de> for Op {
                     RawOpType::MakeList => OpType::Make(ObjType::List),
                     RawOpType::MakeText => OpType::Make(ObjType::Text),
                     RawOpType::Del => OpType::Delete,
+                    RawOpType::MarkBegin => {
+                        let name = name.ok_or_else(|| Error::missing_field("mark(name)"))?;
+                        let expand = expand.unwrap_or(false);
+                        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::mark(name, expand, value)
+                    }
+                    RawOpType::MarkEnd => {
+                        let expand = expand.unwrap_or(true);
+                        OpType::MarkEnd(expand)
+                    }
                     RawOpType::Set => {
                         let value = if let Some(datatype) = datatype {
                             let raw_value = value
diff --git a/automerge/src/legacy/serde_impls/op_type.rs b/automerge/src/legacy/serde_impls/op_type.rs
index b054bad7..c2711d0c 100644
--- a/automerge/src/legacy/serde_impls/op_type.rs
+++ b/automerge/src/legacy/serde_impls/op_type.rs
@@ -15,6 +15,8 @@ impl Serialize for OpType {
             OpType::Make(ObjType::Table) => RawOpType::MakeTable,
             OpType::Make(ObjType::List) => RawOpType::MakeList,
             OpType::Make(ObjType::Text) => RawOpType::MakeText,
+            OpType::MarkBegin(_) => RawOpType::MarkBegin,
+            OpType::MarkEnd(_) => RawOpType::MarkEnd,
             OpType::Delete => RawOpType::Del,
             OpType::Increment(_) => RawOpType::Inc,
             OpType::Put(_) => RawOpType::Set,
diff --git a/automerge/src/query.rs b/automerge/src/query.rs
index f09ed0c1..f92c4f3c 100644
--- a/automerge/src/query.rs
+++ b/automerge/src/query.rs
@@ -1,10 +1,14 @@
+use crate::exid::ExId;
 use crate::op_tree::{OpSetMetadata, OpTreeNode};
 use crate::types::{Clock, Counter, Key, Op, OpId, OpType, ScalarValue};
 use fxhash::FxBuildHasher;
+use serde::Serialize;
 use std::cmp::Ordering;
 use std::collections::{HashMap, HashSet};
 use std::fmt::Debug;
 
+mod attribute;
+mod attribute2;
 mod elem_id_pos;
 mod insert;
 mod keys;
@@ -22,9 +26,13 @@ mod nth_at;
 mod opid;
 mod prop;
 mod prop_at;
+mod raw_spans;
 mod seek_op;
 mod seek_op_with_patch;
+mod spans;
 
+pub(crate) use attribute::{Attribute, ChangeSet};
+pub(crate) use attribute2::{Attribute2, ChangeSet2};
 pub(crate) use elem_id_pos::ElemIdPos;
 pub(crate) use insert::InsertNth;
 pub(crate) use keys::Keys;
@@ -42,8 +50,20 @@ pub(crate) use nth_at::NthAt;
 pub(crate) use opid::OpIdSearch;
 pub(crate) use prop::Prop;
 pub(crate) use prop_at::PropAt;
+pub(crate) use raw_spans::RawSpans;
 pub(crate) use seek_op::SeekOp;
 pub(crate) use seek_op_with_patch::SeekOpWithPatch;
+pub(crate) use spans::{Span, Spans};
+
+#[derive(Serialize, Debug, Clone, PartialEq)]
+pub struct SpanInfo {
+    pub id: ExId,
+    pub start: usize,
+    pub end: usize,
+    #[serde(rename = "type")]
+    pub span_type: String,
+    pub value: ScalarValue,
+}
 
 // use a struct for the args for clarity as they are passed up the update chain in the optree
 #[derive(Debug, Clone)]
diff --git a/automerge/src/query/attribute.rs b/automerge/src/query/attribute.rs
new file mode 100644
index 00000000..ca0b28f7
--- /dev/null
+++ b/automerge/src/query/attribute.rs
@@ -0,0 +1,129 @@
+use crate::clock::Clock;
+use crate::query::{OpSetMetadata, QueryResult, TreeQuery};
+use crate::types::{ElemId, Op};
+use std::fmt::Debug;
+use std::ops::Range;
+
+#[derive(Debug, Clone, PartialEq)]
+pub(crate) struct Attribute {
+    pos: usize,
+    seen: usize,
+    last_seen: Option<ElemId>,
+    baseline: Clock,
+    pub(crate) change_sets: Vec<ChangeSet>,
+}
+
+#[derive(Debug, Clone, PartialEq)]
+pub struct ChangeSet {
+    clock: Clock,
+    next_add: Option<Range<usize>>,
+    next_del: Option<(usize, String)>,
+    pub add: Vec<Range<usize>>,
+    pub del: Vec<(usize, String)>,
+}
+
+impl From<Clock> for ChangeSet {
+    fn from(clock: Clock) -> Self {
+        ChangeSet {
+            clock,
+            next_add: None,
+            next_del: None,
+            add: Vec::new(),
+            del: Vec::new(),
+        }
+    }
+}
+
+impl ChangeSet {
+    fn cut_add(&mut self) {
+        if let Some(add) = self.next_add.take() {
+            self.add.push(add)
+        }
+    }
+
+    fn cut_del(&mut self) {
+        if let Some(del) = self.next_del.take() {
+            self.del.push(del)
+        }
+    }
+}
+
+impl Attribute {
+    pub(crate) fn new(baseline: Clock, change_sets: Vec<Clock>) -> Self {
+        Attribute {
+            pos: 0,
+            seen: 0,
+            last_seen: None,
+            baseline,
+            change_sets: change_sets.into_iter().map(|c| c.into()).collect(),
+        }
+    }
+
+    fn update_add(&mut self, element: &Op) {
+        let baseline = self.baseline.covers(&element.id);
+        for cs in &mut self.change_sets {
+            if !baseline && cs.clock.covers(&element.id) {
+                // is part of the change_set
+                if let Some(range) = &mut cs.next_add {
+                    range.end += 1;
+                } else {
+                    cs.next_add = Some(Range {
+                        start: self.seen,
+                        end: self.seen + 1,
+                    });
+                }
+            } else {
+                cs.cut_add();
+            }
+            cs.cut_del();
+        }
+    }
+
+    // id is in baseline
+    // succ is not in baseline but is in cs
+
+    fn update_del(&mut self, element: &Op) {
+        if !self.baseline.covers(&element.id)
+            || element.succ.iter().any(|id| self.baseline.covers(id))
+        {
+            return;
+        }
+        for cs in &mut self.change_sets {
+            if element.succ.iter().any(|id| cs.clock.covers(id)) {
+                // was deleted by change set
+                if let Some(s) = element.as_string() {
+                    if let Some((_, span)) = &mut cs.next_del {
+                        span.push_str(&s);
+                    } else {
+                        cs.next_del = Some((self.seen, s))
+                    }
+                }
+            }
+        }
+    }
+
+    pub(crate) fn finish(&mut self) {
+        for cs in &mut self.change_sets {
+            cs.cut_add();
+            cs.cut_del();
+        }
+    }
+}
+
+impl<'a> TreeQuery<'a> for Attribute {
+    fn query_element_with_metadata(&mut self, element: &Op, _m: &OpSetMetadata) -> QueryResult {
+        if element.insert {
+            self.last_seen = None;
+        }
+        if self.last_seen.is_none() && element.visible() {
+            self.update_add(element);
+            self.seen += 1;
+            self.last_seen = element.elemid();
+        }
+        if !element.succ.is_empty() {
+            self.update_del(element);
+        }
+        self.pos += 1;
+        QueryResult::Next
+    }
+}
diff --git a/automerge/src/query/attribute2.rs b/automerge/src/query/attribute2.rs
new file mode 100644
index 00000000..48ab9040
--- /dev/null
+++ b/automerge/src/query/attribute2.rs
@@ -0,0 +1,174 @@
+use crate::clock::Clock;
+use crate::query::{OpSetMetadata, QueryResult, TreeQuery};
+use crate::types::{ElemId, Op};
+use std::fmt::Debug;
+use std::ops::Range;
+
+#[derive(Debug, Clone, PartialEq)]
+pub(crate) struct Attribute2 {
+    pos: usize,
+    seen: usize,
+    last_seen: Option<ElemId>,
+    baseline: Clock,
+    pub(crate) change_sets: Vec<ChangeSet2>,
+}
+
+#[derive(Debug, Clone, PartialEq)]
+pub struct ChangeSet2 {
+    clock: Clock,
+    next_add: Option<CS2Add>,
+    next_del: Option<CS2Del>,
+    pub add: Vec<CS2Add>,
+    pub del: Vec<CS2Del>,
+}
+
+#[derive(Debug, Clone, PartialEq)]
+pub struct CS2Add {
+    pub actor: usize,
+    pub range: Range<usize>,
+}
+
+#[derive(Debug, Clone, PartialEq)]
+pub struct CS2Del {
+    pub pos: usize,
+    pub actor: usize,
+    pub span: String,
+}
+
+impl From<Clock> for ChangeSet2 {
+    fn from(clock: Clock) -> Self {
+        ChangeSet2 {
+            clock,
+            next_add: None,
+            next_del: None,
+            add: Vec::new(),
+            del: Vec::new(),
+        }
+    }
+}
+
+impl ChangeSet2 {
+    fn cut_add(&mut self) {
+        if let Some(add) = self.next_add.take() {
+            self.add.push(add)
+        }
+    }
+
+    fn cut_del(&mut self) {
+        if let Some(del) = self.next_del.take() {
+            self.del.push(del)
+        }
+    }
+}
+
+impl Attribute2 {
+    pub(crate) fn new(baseline: Clock, change_sets: Vec<Clock>) -> Self {
+        Attribute2 {
+            pos: 0,
+            seen: 0,
+            last_seen: None,
+            baseline,
+            change_sets: change_sets.into_iter().map(|c| c.into()).collect(),
+        }
+    }
+
+    fn update_add(&mut self, element: &Op) {
+        let baseline = self.baseline.covers(&element.id);
+        for cs in &mut self.change_sets {
+            if !baseline && cs.clock.covers(&element.id) {
+                // is part of the change_set
+                if let Some(CS2Add { range, actor }) = &mut cs.next_add {
+                    if *actor == element.id.actor() {
+                        range.end += 1;
+                    } else {
+                        cs.cut_add();
+                        cs.next_add = Some(CS2Add {
+                            actor: element.id.actor(),
+                            range: Range {
+                                start: self.seen,
+                                end: self.seen + 1,
+                            },
+                        });
+                    }
+                } else {
+                    cs.next_add = Some(CS2Add {
+                        actor: element.id.actor(),
+                        range: Range {
+                            start: self.seen,
+                            end: self.seen + 1,
+                        },
+                    });
+                }
+            } else {
+                cs.cut_add();
+            }
+            cs.cut_del();
+        }
+    }
+
+    // id is in baseline
+    // succ is not in baseline but is in cs
+
+    fn update_del(&mut self, element: &Op) {
+        if !self.baseline.covers(&element.id)
+            || element.succ.iter().any(|id| self.baseline.covers(id))
+        {
+            return;
+        }
+        for cs in &mut self.change_sets {
+            let succ: Vec<_> = element
+                .succ
+                .iter()
+                .filter(|id| cs.clock.covers(id))
+                .collect();
+            // was deleted by change set
+            if let Some(suc) = succ.get(0) {
+                if let Some(s) = element.as_string() {
+                    if let Some(CS2Del { actor, span, .. }) = &mut cs.next_del {
+                        if suc.actor() == *actor {
+                            span.push_str(&s);
+                        } else {
+                            cs.cut_del();
+                            cs.next_del = Some(CS2Del {
+                                pos: self.seen,
+                                actor: suc.actor(),
+                                span: s,
+                            })
+                        }
+                    } else {
+                        cs.next_del = Some(CS2Del {
+                            pos: self.seen,
+                            actor: suc.actor(),
+                            span: s,
+                        })
+                    }
+                }
+            }
+        }
+    }
+
+    pub(crate) fn finish(&mut self) {
+        for cs in &mut self.change_sets {
+            cs.cut_add();
+            cs.cut_del();
+        }
+    }
+}
+
+impl<'a> TreeQuery<'a> for Attribute2 {
+    fn query_element_with_metadata(&mut self, element: &Op, _m: &OpSetMetadata) -> QueryResult {
+        if element.insert {
+            self.last_seen = None;
+        }
+        if self.last_seen.is_none() && element.visible() {
+            self.update_add(element);
+            self.seen += 1;
+            self.last_seen = element.elemid();
+        }
+        if !element.succ.is_empty() {
+            self.update_del(element);
+        }
+        self.pos += 1;
+        QueryResult::Next
+    }
+}
diff --git a/automerge/src/query/insert.rs b/automerge/src/query/insert.rs
index 9e495c49..ed59cf76 100644
--- a/automerge/src/query/insert.rs
+++ b/automerge/src/query/insert.rs
@@ -99,6 +99,10 @@ 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/automerge/src/query/list_vals.rs b/automerge/src/query/list_vals.rs
index 4ad2f47b..aee172e2 100644
--- a/automerge/src/query/list_vals.rs
+++ b/automerge/src/query/list_vals.rs
@@ -19,7 +19,7 @@ impl ListVals {
 }
 
 impl<'a> TreeQuery<'a> for ListVals {
-    fn query_node(&mut self, child: &OpTreeNode) -> QueryResult {
+    fn query_node(&mut self, child: &'a OpTreeNode) -> QueryResult {
         let start = 0;
         for pos in start..child.len() {
             let op = child.get(pos).unwrap();
diff --git a/automerge/src/query/raw_spans.rs b/automerge/src/query/raw_spans.rs
new file mode 100644
index 00000000..e3b54f46
--- /dev/null
+++ b/automerge/src/query/raw_spans.rs
@@ -0,0 +1,78 @@
+use crate::query::{OpSetMetadata, QueryResult, TreeQuery};
+use crate::types::{ElemId, Op, OpId, OpType, ScalarValue};
+use std::fmt::Debug;
+
+#[derive(Debug, Clone, PartialEq)]
+pub(crate) struct RawSpans {
+    pos: usize,
+    seen: usize,
+    last_seen: Option<ElemId>,
+    last_insert: Option<ElemId>,
+    changed: bool,
+    pub(crate) spans: Vec<RawSpan>,
+}
+
+#[derive(Debug, Clone, PartialEq)]
+pub(crate) struct RawSpan {
+    pub(crate) id: OpId,
+    pub(crate) start: usize,
+    pub(crate) end: usize,
+    pub(crate) name: String,
+    pub(crate) value: ScalarValue,
+}
+
+impl RawSpans {
+    pub(crate) fn new() -> Self {
+        RawSpans {
+            pos: 0,
+            seen: 0,
+            last_seen: None,
+            last_insert: None,
+            changed: false,
+            spans: Vec::new(),
+        }
+    }
+}
+
+impl<'a> TreeQuery<'a> for RawSpans {
+    fn query_element_with_metadata(&mut self, element: &Op, m: &OpSetMetadata) -> QueryResult {
+        // find location to insert
+        // mark or set
+        if element.succ.is_empty() {
+            if let OpType::MarkBegin(md) = &element.action {
+                let pos = self
+                    .spans
+                    .binary_search_by(|probe| m.lamport_cmp(probe.id, element.id))
+                    .unwrap_err();
+                self.spans.insert(
+                    pos,
+                    RawSpan {
+                        id: element.id,
+                        start: self.seen,
+                        end: 0,
+                        name: md.name.clone(),
+                        value: md.value.clone(),
+                    },
+                );
+            }
+            if let OpType::MarkEnd(_) = &element.action {
+                for s in self.spans.iter_mut() {
+                    if s.id == element.id.prev() {
+                        s.end = self.seen;
+                        break;
+                    }
+                }
+            }
+        }
+        if element.insert {
+            self.last_seen = None;
+            self.last_insert = element.elemid();
+        }
+        if self.last_seen.is_none() && element.visible() {
+            self.seen += 1;
+            self.last_seen = element.elemid();
+        }
+        self.pos += 1;
+        QueryResult::Next
+    }
+}
diff --git a/automerge/src/query/spans.rs b/automerge/src/query/spans.rs
new file mode 100644
index 00000000..8459c0bc
--- /dev/null
+++ b/automerge/src/query/spans.rs
@@ -0,0 +1,109 @@
+use crate::query::{OpSetMetadata, QueryResult, TreeQuery};
+use crate::types::{ElemId, Op, OpType, ScalarValue};
+use std::borrow::Cow;
+use std::collections::HashMap;
+use std::fmt::Debug;
+
+#[derive(Debug, Clone, PartialEq)]
+pub(crate) struct Spans<'a> {
+    pos: usize,
+    seen: usize,
+    last_seen: Option<ElemId>,
+    last_insert: Option<ElemId>,
+    seen_at_this_mark: Option<ElemId>,
+    seen_at_last_mark: Option<ElemId>,
+    ops: Vec<&'a Op>,
+    marks: HashMap<String, &'a ScalarValue>,
+    changed: bool,
+    pub(crate) spans: Vec<Span<'a>>,
+}
+
+#[derive(Debug, Clone, PartialEq)]
+pub struct Span<'a> {
+    pub pos: usize,
+    pub marks: Vec<(String, Cow<'a, ScalarValue>)>,
+}
+
+impl<'a> Spans<'a> {
+    pub(crate) fn new() -> Self {
+        Spans {
+            pos: 0,
+            seen: 0,
+            last_seen: None,
+            last_insert: None,
+            seen_at_last_mark: None,
+            seen_at_this_mark: None,
+            changed: false,
+            ops: Vec::new(),
+            marks: HashMap::new(),
+            spans: Vec::new(),
+        }
+    }
+
+    pub(crate) fn check_marks(&mut self) {
+        let mut new_marks = HashMap::new();
+        for op in &self.ops {
+            if let OpType::MarkBegin(m) = &op.action {
+                new_marks.insert(m.name.clone(), &m.value);
+            }
+        }
+        if new_marks != self.marks {
+            self.changed = true;
+            self.marks = new_marks;
+        }
+        if self.changed
+            && (self.seen_at_last_mark != self.seen_at_this_mark
+                || self.seen_at_last_mark.is_none() && self.seen_at_this_mark.is_none())
+        {
+            self.changed = false;
+            self.seen_at_last_mark = self.seen_at_this_mark;
+            let mut marks: Vec<_> = self
+                .marks
+                .iter()
+                .map(|(key, val)| (key.clone(), Cow::Borrowed(*val)))
+                .collect();
+            marks.sort_by(|(k1, _), (k2, _)| k1.cmp(k2));
+            self.spans.push(Span {
+                pos: self.seen,
+                marks,
+            });
+        }
+    }
+}
+
+impl<'a> TreeQuery<'a> for Spans<'a> {
+    /*
+    fn query_node(&mut self, _child: &OpTreeNode) -> QueryResult {
+        unimplemented!()
+    }
+    */
+
+    fn query_element_with_metadata(&mut self, element: &'a Op, m: &OpSetMetadata) -> QueryResult {
+        // find location to insert
+        // mark or set
+        if element.succ.is_empty() {
+            if let OpType::MarkBegin(_) = &element.action {
+                let pos = self
+                    .ops
+                    .binary_search_by(|probe| m.lamport_cmp(probe.id, element.id))
+                    .unwrap_err();
+                self.ops.insert(pos, element);
+            }
+            if let OpType::MarkEnd(_) = &element.action {
+                self.ops.retain(|op| op.id != element.id.prev());
+            }
+        }
+        if element.insert {
+            self.last_seen = None;
+            self.last_insert = element.elemid();
+        }
+        if self.last_seen.is_none() && element.visible() {
+            self.check_marks();
+            self.seen += 1;
+            self.last_seen = element.elemid();
+            self.seen_at_this_mark = element.elemid();
+        }
+        self.pos += 1;
+        QueryResult::Next
+    }
+}
diff --git a/automerge/src/sync.rs b/automerge/src/sync.rs
index 2b4b454b..99e6fedd 100644
--- a/automerge/src/sync.rs
+++ b/automerge/src/sync.rs
@@ -1,3 +1,6 @@
+use crate::{
+    decoding, decoding::Decoder, encoding::Encodable, Automerge, AutomergeError, Change, ChangeHash,
+};
 use itertools::Itertools;
 use std::{
     borrow::Cow,
@@ -6,10 +9,7 @@ use std::{
     io::Write,
 };
 
-use crate::{
-    decoding, decoding::Decoder, encoding::Encodable, types::HASH_SIZE, ApplyOptions, Automerge,
-    AutomergeError, Change, ChangeHash, OpObserver,
-};
+use crate::{types::HASH_SIZE, ApplyOptions, OpObserver};
 
 mod bloom;
 mod state;
diff --git a/automerge/src/transaction/inner.rs b/automerge/src/transaction/inner.rs
index 86936492..dbd67342 100644
--- a/automerge/src/transaction/inner.rs
+++ b/automerge/src/transaction/inner.rs
@@ -171,6 +171,73 @@ impl TransactionInner {
         self.operations.push((obj, prop, op));
     }
 
+    #[allow(clippy::too_many_arguments)]
+    pub(crate) fn mark<O: AsRef<ExId>>(
+        &mut self,
+        doc: &mut Automerge,
+        obj: O,
+        start: usize,
+        expand_start: bool,
+        end: usize,
+        expand_end: bool,
+        mark: &str,
+        value: ScalarValue,
+    ) -> Result<(), AutomergeError> {
+        let obj = doc.exid_to_obj(obj.as_ref())?;
+
+        self.do_insert(
+            doc,
+            obj,
+            start,
+            OpType::mark(mark.into(), expand_start, value),
+        )?;
+        self.do_insert(doc, obj, end, OpType::MarkEnd(expand_end))?;
+
+        Ok(())
+    }
+
+    pub(crate) fn unmark<O: AsRef<ExId>>(
+        &mut self,
+        doc: &mut Automerge,
+        obj: O,
+        mark: O,
+    ) -> Result<(), AutomergeError> {
+        let obj = doc.exid_to_obj(obj.as_ref())?;
+        let markid = doc.exid_to_obj_tmp_unchecked(mark.as_ref())?.0;
+        let op1 = Op {
+            id: self.next_id(),
+            action: OpType::Delete,
+            key: markid.into(),
+            succ: Default::default(),
+            pred: doc.ops.m.sorted_opids(vec![markid].into_iter()),
+            insert: false,
+        };
+        let q1 = doc.ops.search(&obj, query::SeekOp::new(&op1));
+        doc.ops.add_succ(&obj, q1.succ.into_iter(), &op1);
+        //for i in q1.succ {
+        //    doc.ops.replace(&obj, i, |old_op| old_op.add_succ(&op1));
+        //}
+        self.operations.push((obj, Prop::Map("".into()), op1));
+
+        let markid = markid.next();
+        let op2 = Op {
+            id: self.next_id(),
+            action: OpType::Delete,
+            key: markid.into(),
+            succ: Default::default(),
+            pred: doc.ops.m.sorted_opids(vec![markid].into_iter()),
+            insert: false,
+        };
+        let q2 = doc.ops.search(&obj, query::SeekOp::new(&op2));
+
+        doc.ops.add_succ(&obj, q2.succ.into_iter(), &op2);
+        //for i in q2.succ {
+        //    doc.ops.replace(&obj, i, |old_op| old_op.add_succ(&op2));
+        //}
+        self.operations.push((obj, Prop::Map("".into()), op2));
+        Ok(())
+    }
+
     pub(crate) fn insert<V: Into<ScalarValue>>(
         &mut self,
         doc: &mut Automerge,
diff --git a/automerge/src/transaction/manual_transaction.rs b/automerge/src/transaction/manual_transaction.rs
index 58c5ca88..b7c3fc9b 100644
--- a/automerge/src/transaction/manual_transaction.rs
+++ b/automerge/src/transaction/manual_transaction.rs
@@ -1,12 +1,12 @@
 use std::ops::RangeBounds;
 
+use super::{CommitOptions, Transactable, TransactionInner};
 use crate::exid::ExId;
+use crate::query;
 use crate::{Automerge, ChangeHash, KeysAt, ObjType, OpObserver, Prop, ScalarValue, Value, Values};
 use crate::{AutomergeError, Keys};
 use crate::{ListRange, ListRangeAt, MapRange, MapRangeAt};
 
-use super::{CommitOptions, Transactable, TransactionInner};
-
 /// A transaction on a document.
 /// Transactions group operations into a single change so that no other operations can happen
 /// in-between.
@@ -129,6 +129,33 @@ impl<'a> Transactable for Transaction<'a> {
             .insert(self.doc, obj.as_ref(), index, value)
     }
 
+    #[allow(clippy::too_many_arguments)]
+    fn mark<O: AsRef<ExId>>(
+        &mut self,
+        obj: O,
+        start: usize,
+        expand_start: bool,
+        end: usize,
+        expand_end: bool,
+        mark: &str,
+        value: ScalarValue,
+    ) -> Result<(), AutomergeError> {
+        self.inner.as_mut().unwrap().mark(
+            self.doc,
+            obj,
+            start,
+            expand_start,
+            end,
+            expand_end,
+            mark,
+            value,
+        )
+    }
+
+    fn unmark<O: AsRef<ExId>>(&mut self, obj: O, mark: O) -> Result<(), AutomergeError> {
+        self.inner.as_mut().unwrap().unmark(self.doc, obj, mark)
+    }
+
     fn insert_object<O: AsRef<ExId>>(
         &mut self,
         obj: O,
@@ -253,6 +280,32 @@ impl<'a> Transactable for Transaction<'a> {
         self.doc.text_at(obj, heads)
     }
 
+    fn spans<O: AsRef<ExId>>(&self, obj: O) -> Result<Vec<query::Span<'_>>, AutomergeError> {
+        self.doc.spans(obj)
+    }
+
+    fn raw_spans<O: AsRef<ExId>>(&self, obj: O) -> Result<Vec<query::SpanInfo>, AutomergeError> {
+        self.doc.raw_spans(obj)
+    }
+
+    fn attribute<O: AsRef<ExId>>(
+        &self,
+        obj: O,
+        baseline: &[ChangeHash],
+        change_sets: &[Vec<ChangeHash>],
+    ) -> Result<Vec<query::ChangeSet>, AutomergeError> {
+        self.doc.attribute(obj, baseline, change_sets)
+    }
+
+    fn attribute2<O: AsRef<ExId>>(
+        &self,
+        obj: O,
+        baseline: &[ChangeHash],
+        change_sets: &[Vec<ChangeHash>],
+    ) -> Result<Vec<query::ChangeSet2>, AutomergeError> {
+        self.doc.attribute2(obj, baseline, change_sets)
+    }
+
     fn get<O: AsRef<ExId>, P: Into<Prop>>(
         &self,
         obj: O,
diff --git a/automerge/src/transaction/transactable.rs b/automerge/src/transaction/transactable.rs
index 0c7f6c45..c6546c38 100644
--- a/automerge/src/transaction/transactable.rs
+++ b/automerge/src/transaction/transactable.rs
@@ -1,6 +1,7 @@
 use std::ops::RangeBounds;
 
 use crate::exid::ExId;
+use crate::query;
 use crate::{
     AutomergeError, ChangeHash, Keys, KeysAt, ListRange, ListRangeAt, MapRange, MapRangeAt,
     ObjType, Parents, Prop, ScalarValue, Value, Values,
@@ -61,6 +62,21 @@ pub trait Transactable {
         object: ObjType,
     ) -> Result<ExId, AutomergeError>;
 
+    /// Set a mark within a range on a list
+    #[allow(clippy::too_many_arguments)]
+    fn mark<O: AsRef<ExId>>(
+        &mut self,
+        obj: O,
+        start: usize,
+        expand_start: bool,
+        end: usize,
+        expand_end: bool,
+        mark: &str,
+        value: ScalarValue,
+    ) -> Result<(), AutomergeError>;
+
+    fn unmark<O: AsRef<ExId>>(&mut self, obj: O, mark: O) -> Result<(), AutomergeError>;
+
     /// Increment the counter at the prop in the object by `value`.
     fn increment<O: AsRef<ExId>, P: Into<Prop>>(
         &mut self,
@@ -151,6 +167,28 @@ pub trait Transactable {
         heads: &[ChangeHash],
     ) -> Result<String, AutomergeError>;
 
+    /// test spans api for mark/span experiment
+    fn spans<O: AsRef<ExId>>(&self, obj: O) -> Result<Vec<query::Span<'_>>, AutomergeError>;
+
+    /// test raw_spans api for mark/span experiment
+    fn raw_spans<O: AsRef<ExId>>(&self, obj: O) -> Result<Vec<query::SpanInfo>, AutomergeError>;
+
+    /// test attribute api for mark/span experiment
+    fn attribute<O: AsRef<ExId>>(
+        &self,
+        obj: O,
+        baseline: &[ChangeHash],
+        change_sets: &[Vec<ChangeHash>],
+    ) -> Result<Vec<query::ChangeSet>, AutomergeError>;
+
+    /// test attribute api for mark/span experiment
+    fn attribute2<O: AsRef<ExId>>(
+        &self,
+        obj: O,
+        baseline: &[ChangeHash],
+        change_sets: &[Vec<ChangeHash>],
+    ) -> Result<Vec<query::ChangeSet2>, AutomergeError>;
+
     /// Get the value at this prop in the object.
     fn get<O: AsRef<ExId>, P: Into<Prop>>(
         &self,
diff --git a/automerge/src/types.rs b/automerge/src/types.rs
index 288c2846..397aa4c1 100644
--- a/automerge/src/types.rs
+++ b/automerge/src/types.rs
@@ -182,9 +182,29 @@ impl fmt::Display for ObjType {
 #[derive(PartialEq, Debug, Clone)]
 pub enum OpType {
     Make(ObjType),
+    /// Perform a deletion, expanding the operation to cover `n` deletions (multiOp).
     Delete,
     Increment(i64),
     Put(ScalarValue),
+    MarkBegin(MarkData),
+    MarkEnd(bool),
+}
+
+impl OpType {
+    pub(crate) fn mark(name: String, expand: bool, value: ScalarValue) -> Self {
+        OpType::MarkBegin(MarkData {
+            name,
+            expand,
+            value,
+        })
+    }
+}
+
+#[derive(PartialEq, Debug, Clone)]
+pub struct MarkData {
+    pub name: String,
+    pub value: ScalarValue,
+    pub expand: bool,
 }
 
 impl From<ObjType> for OpType {
@@ -219,6 +239,14 @@ impl OpId {
     pub(crate) fn actor(&self) -> usize {
         self.1
     }
+    #[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)
+    }
 }
 
 impl Exportable for ObjId {
@@ -419,7 +447,7 @@ impl Op {
     }
 
     pub(crate) fn visible(&self) -> bool {
-        if self.is_inc() {
+        if self.is_inc() || self.is_mark() {
             false
         } else if self.is_counter() {
             self.succ.len() <= self.incs()
@@ -444,6 +472,18 @@ impl Op {
         matches!(&self.action, OpType::Increment(_))
     }
 
+    pub(crate) fn valid_mark_anchor(&self) -> bool {
+        self.succ.is_empty()
+            && matches!(
+                &self.action,
+                OpType::MarkBegin(MarkData { expand: true, .. }) | OpType::MarkEnd(false)
+            )
+    }
+
+    pub(crate) fn is_mark(&self) -> bool {
+        matches!(&self.action, OpType::MarkBegin(_) | OpType::MarkEnd(_))
+    }
+
     pub(crate) fn is_counter(&self) -> bool {
         matches!(&self.action, OpType::Put(ScalarValue::Counter(_)))
     }
@@ -472,6 +512,13 @@ impl Op {
         }
     }
 
+    pub(crate) fn as_string(&self) -> Option<String> {
+        match &self.action {
+            OpType::Put(scalar) => scalar.as_string(),
+            _ => None,
+        }
+    }
+
     pub(crate) fn get_increment_value(&self) -> Option<i64> {
         if let OpType::Increment(i) = self.action {
             Some(i)
@@ -484,6 +531,8 @@ 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.name, mark.value).into())),
+            OpType::MarkEnd(_) => Value::Scalar(Cow::Owned("markEnd".into())),
             _ => panic!("cant convert op into a value - {:?}", self),
         }
     }
@@ -492,6 +541,8 @@ impl Op {
         match &self.action {
             OpType::Make(obj_type) => Value::Object(*obj_type),
             OpType::Put(scalar) => Value::Scalar(Cow::Owned(scalar.clone())),
+            OpType::MarkBegin(mark) => Value::Scalar(Cow::Owned(format!("markBegin[{}]={}",mark.name, mark.value).into())),
+            OpType::MarkEnd(_) => Value::Scalar(Cow::Owned("markEnd".into())),
             _ => panic!("cant convert op into a value - {:?}", self),
         }
     }
@@ -502,6 +553,8 @@ impl Op {
             OpType::Put(value) if self.insert => format!("i:{}", value),
             OpType::Put(value) => format!("s:{}", value),
             OpType::Make(obj) => format!("make{}", obj),
+            OpType::MarkBegin(m) => format!("mark{}={}", m.name, m.value),
+            OpType::MarkEnd(_) => "unmark".into(),
             OpType::Increment(val) => format!("inc:{}", val),
             OpType::Delete => "del".to_string(),
         }
diff --git a/automerge/src/value.rs b/automerge/src/value.rs
index 1df87ace..7464a92d 100644
--- a/automerge/src/value.rs
+++ b/automerge/src/value.rs
@@ -14,6 +14,13 @@ pub enum Value<'a> {
 }
 
 impl<'a> Value<'a> {
+    pub fn as_string(&self) -> Option<String> {
+        match self {
+            Value::Scalar(val) => val.as_string(),
+            _ => None,
+        }
+    }
+
     pub fn map() -> Value<'a> {
         Value::Object(ObjType::Map)
     }
@@ -629,6 +636,13 @@ impl ScalarValue {
         }
     }
 
+    pub fn as_string(&self) -> Option<String> {
+        match self {
+            ScalarValue::Str(s) => Some(s.to_string()),
+            _ => None,
+        }
+    }
+
     pub fn counter(n: i64) -> ScalarValue {
         ScalarValue::Counter(n.into())
     }
diff --git a/automerge/src/visualisation.rs b/automerge/src/visualisation.rs
index 5e6dae6f..b4410e4b 100644
--- a/automerge/src/visualisation.rs
+++ b/automerge/src/visualisation.rs
@@ -238,6 +238,8 @@ 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(v) => format!("mark {}={}", v.name, v.value),
+            crate::OpType::MarkEnd(v) => format!("/mark {}", v),
         };
         let prop = match op.key {
             crate::types::Key::Map(k) => metadata.props[k].clone(),
diff --git a/automerge/tests/attribute.rs b/automerge/tests/attribute.rs
new file mode 100644
index 00000000..9968b248
--- /dev/null
+++ b/automerge/tests/attribute.rs
@@ -0,0 +1,39 @@
+use automerge::transaction::Transactable;
+use automerge::{AutoCommit, AutomergeError, ROOT};
+
+/*
+mod helpers;
+use helpers::{
+    pretty_print, realize, realize_obj,
+    RealizedObject,
+};
+*/
+
+#[test]
+fn simple_attribute_text() -> Result<(), AutomergeError> {
+    let mut doc = AutoCommit::new();
+    let note = doc.put_object(&ROOT, "note", automerge::ObjType::Text)?;
+    doc.splice_text(&note, 0, 0, "hello little world")?;
+    let baseline = doc.get_heads();
+    assert!(doc.text(&note).unwrap() == "hello little world");
+    let mut doc2 = doc.fork();
+    doc2.splice_text(&note, 5, 7, " big")?;
+    let h2 = doc2.get_heads();
+    assert!(doc2.text(&note)? == "hello big world");
+    let mut doc3 = doc.fork();
+    doc3.splice_text(&note, 0, 0, "Well, ")?;
+    let h3 = doc3.get_heads();
+    assert!(doc3.text(&note)? == "Well, hello little world");
+    doc.merge(&mut doc2)?;
+    doc.merge(&mut doc3)?;
+    let text = doc.text(&note)?;
+    assert!(text == "Well, hello big world");
+    let cs = vec![h2, h3];
+    let attribute = doc.attribute(&note, &baseline, &cs)?;
+    assert!(&text[attribute[0].add[0].clone()] == " big");
+    assert!(attribute[0].del[0] == (15, " little".to_owned()));
+    //println!("{:?} == {:?}", attribute[0].del[0] , (15, " little".to_owned()));
+    assert!(&text[attribute[1].add[0].clone()] == "Well, ");
+    //println!("- ------- attribute = {:?}", attribute);
+    Ok(())
+}
diff --git a/scripts/ci/js_tests b/scripts/ci/js_tests
index 9b1d0e77..6c4a16d4 100755
--- a/scripts/ci/js_tests
+++ b/scripts/ci/js_tests
@@ -7,9 +7,9 @@ yarn --cwd $WASM_PROJECT install;
 yarn --cwd $WASM_PROJECT build;
 # If the dependencies are already installed we delete automerge-wasm. This makes
 # this script usable for iterative development.
-if [ -d $JS_PROJECT/node_modules/automerge-wasm ]; then
-    rm -rf $JS_PROJECT/node_modules/automerge-wasm
-fi
+#if [ -d $JS_PROJECT/node_modules/automerge-wasm ]; then
+#    rm -rf $JS_PROJECT/node_modules/automerge-wasm
+#fi
 # --check-files forces yarn to check if the local dep has changed
 yarn --cwd $JS_PROJECT install --check-files;
 yarn --cwd $JS_PROJECT test;