Restore inline task checklists and historical update diffs

src/renderer/src/components/native-chat/NativeChatMessageList.tsx

@@ -8,6 +8,7 @@ import { stripNoiseMessages } from './native-chat-noise'
 import { foldToolMessages } from './native-chat-tool-fold'
 import { isNearBottom, shouldShowJumpToLatest, type ScrollGeometry } from './native-chat-autoscroll'
 import { nativeChatTaskListState } from './native-chat-task-list-state'
+import { nativeChatTaskListPredecessors } from './native-chat-task-list-history'
 import { NativeChatTaskList } from './NativeChatTaskList'
 import { projectNativeChatTaskListFrames } from './native-chat-task-list-frames'
 import { MessageRow } from './NativeChatMessageRow'
@@ -90,6 +91,7 @@ export function NativeChatMessageList({
       ),
     [session.messages]
   )
+  const taskListPredecessors = useMemo(() => nativeChatTaskListPredecessors(messages), [messages])
   const taskListState = useMemo(() => nativeChatTaskListState(messages), [messages])
   const showTypingIndicator = showTurnStatus
     ? isWorking
@@ -239,6 +241,8 @@ export function NativeChatMessageList({
                 <Fragment key={message.id}>
                   <MessageRow
                     message={message}
+                    previousTodoWrite={taskListPredecessors.get(message.id)?.todowrite}
+                    previousUpdatePlan={taskListPredecessors.get(message.id)?.update_plan}
                     expandSignal={expandSignal}
                     // A missing transcript lifecycle is not evidence that the turn
                     // ended. Structured sessions and legacy live hooks still expose

src/renderer/src/components/native-chat/NativeChatMessageRow.tsx

@@ -8,7 +8,7 @@ import {
   isSubagentGroupFallbackText,
   subagentGroupBlocks
 } from '../../../../shared/native-chat-subagent-summary'
-import { isSubagentGroupBlock, type NativeChatMessage } from '../../../../shared/native-chat-types'
+import { isSubagentGroupBlock, type NativeChatMessage, type NativeChatToolCallBlock } from '../../../../shared/native-chat-types'
 import { splitNativeChatBlocks } from './native-chat-tool-fold'
 import { NativeChatToolRun } from './NativeChatToolRun'
 import { NativeChatMessageTimestamp } from './NativeChatMessageTimestamp'
@@ -27,6 +27,8 @@ import type { RuntimeFileOperationArgs } from '@/runtime/runtime-file-client'
  *  keep their block identity, so only the changed row re-renders. */
 export const MessageRow = memo(function MessageRow({
   message,
+  previousTodoWrite,
+  previousUpdatePlan,
   expandSignal,
   activeTurnIsWorking,
   onScrollMessageToTop,
@@ -38,6 +40,8 @@ export const MessageRow = memo(function MessageRow({
   runtimeContext
 }: {
   message: NativeChatMessage
+  previousTodoWrite?: NativeChatToolCallBlock
+  previousUpdatePlan?: NativeChatToolCallBlock
   expandSignal: boolean
   activeTurnIsWorking?: boolean
   /** Align this message's top to the top of the scroll viewport. */
@@ -180,6 +184,8 @@ export const MessageRow = memo(function MessageRow({
       {tools.length > 0 || subagentGroups.length > 0 ? (
         <NativeChatToolRun
           blocks={tools}
+          previousTodoWrite={previousTodoWrite}
+          previousUpdatePlan={previousUpdatePlan}
           onLinkClick={onLinkClick}
           subagentGroups={subagentGroups}
           expandSignal={expandSignal}

src/renderer/src/components/native-chat/NativeChatTaskList.test.tsx

@@ -22,14 +22,11 @@ const current: TaskList = {
 }
 
 describe('NativeChatTaskList', () => {
-  it('starts as quiet chrome and reveals tri-state tasks on demand', () => {
+  it('shows tri-state glyphs, progress, and activeForm in the first checklist', () => {
     const { container } = render(<NativeChatTaskList list={current} />)
-    const toggle = screen.getByRole('button', { name: 'Tasks 1 of 3 tasks completed' })
-    expect(toggle).toHaveAttribute('aria-expanded', 'false')
-    expect(screen.queryByText('Test')).toBeNull()
-    fireEvent.click(toggle)
     expect(screen.getByText('Read')).toHaveClass('line-through')
     expect(screen.getByText('Writing').closest('li')).toHaveClass('text-foreground')
+    expect(screen.getByText('Test')).toBeInTheDocument()
     expect(screen.getByLabelText('1 of 3 tasks completed')).toHaveTextContent('1/3')
     for (const glyph of ['circle', 'circle-dot', 'circle-check']) {
       expect(container.querySelector(`.lucide-${glyph}`)).not.toBeNull()
@@ -37,18 +34,42 @@ describe('NativeChatTaskList', () => {
     expect(screen.getByText('In progress:')).toHaveClass('sr-only')
   })
 
-  it('updates the same expanded list without appending a change feed', () => {
-    const { rerender } = render(<NativeChatTaskList list={previous} />)
-    const toggle = screen.getByRole('button', { name: 'Tasks 0 of 3 tasks completed' })
-    fireEvent.click(toggle)
-    rerender(<NativeChatTaskList list={{ ...current, explanation: 'Continuing verification' }} />)
-    expect(screen.getByRole('button', { name: 'Tasks 1 of 3 tasks completed' })).toBe(toggle)
-    expect(toggle).toHaveAttribute('aria-expanded', 'true')
-    expect(screen.getAllByRole('list')).toHaveLength(1)
-    expect(screen.getByText('Read')).toHaveClass('line-through')
+  it('leads with the diff and expands the complete checklist on demand', () => {
+    render(<NativeChatTaskList list={current} previous={previous} />)
+    expect(screen.getByText('Completed Read')).toBeInTheDocument()
+    expect(screen.getByText('Started Write')).toBeInTheDocument()
+    expect(screen.queryByText('Test')).toBeNull()
+    const disclosure = screen.getByRole('button', { name: 'Full task list' })
+    expect(disclosure).toHaveAttribute('aria-expanded', 'false')
+    fireEvent.click(disclosure)
+    expect(disclosure).toHaveAttribute('aria-expanded', 'true')
     expect(screen.getByText('Writing')).toBeInTheDocument()
-    expect(screen.queryByText('Completed Read')).toBeNull()
-    expect(screen.queryByText('Started Write')).toBeNull()
+    expect(screen.getByText('Test')).toBeInTheDocument()
+  })
+
+  it('shows unchanged feedback and the current explanation', () => {
+    render(
+      <NativeChatTaskList
+        list={{ ...current, explanation: 'Continuing verification' }}
+        previous={current}
+      />
+    )
+    expect(screen.getByText('Tasks unchanged')).toBeInTheDocument()
     expect(screen.getByText('Continuing verification')).toBeInTheDocument()
+    expect(screen.queryByText('Test')).toBeNull()
+  })
+
+  it('renders empty lists without claiming any task completed', () => {
+    render(<NativeChatTaskList list={{ tasks: [] }} />)
+    expect(screen.getByText('No tasks')).toBeInTheDocument()
+    expect(screen.getByLabelText('0 of 0 tasks completed')).toHaveTextContent('0/0')
+  })
+
+  it('switches from full list to diff when earlier history supplies a predecessor', () => {
+    const { rerender } = render(<NativeChatTaskList list={current} />)
+    expect(screen.getByText('Test')).toBeInTheDocument()
+    rerender(<NativeChatTaskList list={current} previous={previous} />)
+    expect(screen.queryByText('Test')).toBeNull()
+    expect(screen.getByText('Started Write')).toBeInTheDocument()
   })
 })

src/renderer/src/components/native-chat/NativeChatTaskList.tsx

@@ -3,8 +3,10 @@ import { Collapsible, CollapsibleContent, CollapsibleTrigger } from '@/component
 import { cn } from '@/lib/utils'
 import { translate } from '@/i18n/i18n'
 import {
+  diffNativeChatTaskLists,
   nativeChatTaskLabel,
   type NativeChatTask,
+  type NativeChatTaskChange,
   type NativeChatTaskList as TaskList
 } from '../../../../shared/native-chat-task-list'
 
@@ -18,7 +20,27 @@ function statusLabel(task: NativeChatTask): string {
   return translate('components.native-chat.taskList.pending', 'Pending')
 }
 
-function TaskRow({ task }: { task: NativeChatTask }): React.JSX.Element {
+function changeLabel(change: NativeChatTaskChange): string {
+  const values = { task: change.task.content }
+  switch (change.kind) {
+    case 'added':
+      return translate('components.native-chat.taskList.added', 'Added {{task}}', values)
+    case 'removed':
+      return translate('components.native-chat.taskList.removed', 'Removed {{task}}', values)
+    case 'started':
+      return translate('components.native-chat.taskList.started', 'Started {{task}}', values)
+    case 'completed':
+      return translate('components.native-chat.taskList.finished', 'Completed {{task}}', values)
+    case 'pending':
+      return translate('components.native-chat.taskList.reset', 'Marked pending: {{task}}', values)
+    case 'updated':
+      return translate('components.native-chat.taskList.updated', 'Updated {{task}}', {
+        task: nativeChatTaskLabel(change.task)
+      })
+  }
+}
+
+function TaskRow({ task, label }: { task: NativeChatTask; label?: string }): React.JSX.Element {
   const Icon =
     task.status === 'completed' ? CircleCheck : task.status === 'in_progress' ? CircleDot : Circle
   return (
@@ -33,10 +55,10 @@ function TaskRow({ task }: { task: NativeChatTask }): React.JSX.Element {
       <span
         className={cn(
           'min-w-0 whitespace-pre-wrap break-words',
-          task.status === 'completed' && 'line-through'
+          !label && task.status === 'completed' && 'line-through'
         )}
       >
-        {nativeChatTaskLabel(task)}
+        {label ?? nativeChatTaskLabel(task)}
       </span>
     </li>
   )
@@ -59,13 +81,20 @@ function Checklist({ list }: { list: TaskList }): React.JSX.Element {
   )
 }
 
-export function NativeChatTaskList({ list }: { list: TaskList }): React.JSX.Element {
+export function NativeChatTaskList({
+  list,
+  previous
+}: {
+  list: TaskList
+  previous?: TaskList
+}): React.JSX.Element {
   const completed = list.tasks.filter((task) => task.status === 'completed').length
+  const changes = previous ? diffNativeChatTaskLists(previous, list) : null
   return (
-    <Collapsible className="rounded-md border border-border bg-muted/30">
-      <CollapsibleTrigger className="group flex w-full items-center gap-1.5 rounded-md px-3 py-2 text-left text-xs text-muted-foreground hover:bg-accent hover:text-accent-foreground focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring">
+    <div className="space-y-1 py-1">
+      <div className="flex items-center gap-1.5 text-xs text-muted-foreground">
         <ListChecks aria-hidden className="size-4 shrink-0" />
-        <span className="flex-1 font-medium">
+        <span className="font-medium">
           {translate('components.native-chat.taskList.title', 'Tasks')}
         </span>
         <span
@@ -78,18 +107,42 @@ export function NativeChatTaskList({ list }: { list: TaskList }): React.JSX.Elem
         >
           {completed}/{list.tasks.length}
         </span>
-        <ChevronRight aria-hidden className="size-3.5 group-data-[state=open]:rotate-90" />
-      </CollapsibleTrigger>
-      <CollapsibleContent>
-        <div className="max-h-40 overflow-y-auto px-3 pb-2 scrollbar-sleek">
-          <Checklist list={list} />
-          {list.explanation ? (
-            <p className="whitespace-pre-wrap break-words text-xs text-muted-foreground">
-              {list.explanation}
+      </div>
+      {changes ? (
+        <>
+          {changes.length > 0 ? (
+            <ul className="space-y-1 py-1">
+              {changes.map((change, index) => (
+                <TaskRow
+                  key={`${change.kind}:${index}`}
+                  task={change.task}
+                  label={changeLabel(change)}
+                />
+              ))}
+            </ul>
+          ) : (
+            <p className="text-xs text-muted-foreground">
+              {translate('components.native-chat.taskList.unchanged', 'Tasks unchanged')}
             </p>
-          ) : null}
-        </div>
-      </CollapsibleContent>
-    </Collapsible>
+          )}
+          <Collapsible>
+            <CollapsibleTrigger className="group flex items-center gap-1 rounded py-0.5 text-xs text-muted-foreground hover:text-foreground focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring">
+              <ChevronRight aria-hidden className="size-3.5 group-data-[state=open]:rotate-90" />
+              {translate('components.native-chat.taskList.showAll', 'Full task list')}
+            </CollapsibleTrigger>
+            <CollapsibleContent>
+              <Checklist list={list} />
+            </CollapsibleContent>
+          </Collapsible>
+        </>
+      ) : (
+        <Checklist list={list} />
+      )}
+      {list.explanation ? (
+        <p className="whitespace-pre-wrap break-words text-xs text-muted-foreground">
+          {list.explanation}
+        </p>
+      ) : null}
+    </div>
   )
 }

src/renderer/src/components/native-chat/NativeChatToolRun.test.tsx

@@ -616,3 +616,58 @@ describe('NativeChatToolRun', () => {
     expect(screen.getByTitle('ls')).toHaveTextContent('ls')
   })
 })
+
+describe('NativeChatToolRun task lists', () => {
+  it('renders task updates instead of JSON and consumes successful results', () => {
+    const blocks: NativeChatBlock[] = [
+      {
+        type: 'tool-call',
+        name: 'update_plan',
+        input: {
+          plan: [
+            { step: 'Read', status: 'in_progress' },
+            { step: 'Test', status: 'pending' }
+          ]
+        }
+      },
+      { type: 'tool-result', output: 'Plan updated' },
+      {
+        type: 'tool-call',
+        name: 'update_plan',
+        input: {
+          plan: [
+            { step: 'Read', status: 'completed' },
+            { step: 'Test', status: 'in_progress' }
+          ]
+        }
+      }
+    ]
+    const { container } = render(<NativeChatToolRun blocks={blocks} expandSignal />)
+    expect(screen.getByText('Completed Read')).toBeInTheDocument()
+    expect(screen.getByText('Started Test')).toBeInTheDocument()
+    expect(screen.getByText('1/2')).toBeInTheDocument()
+    expect(screen.queryByText('Plan updated')).toBeNull()
+    expect(container.querySelector('pre')).toBeNull()
+  })
+
+  it('keeps malformed calls and failed results visible in the generic view', () => {
+    render(
+      <NativeChatToolRun
+        blocks={[
+          { type: 'tool-call', name: 'TodoWrite', input: '{' },
+          { type: 'tool-result', output: 'Invalid arguments', isError: true },
+          {
+            type: 'tool-call',
+            name: 'TodoWrite',
+            input: { todos: [{ content: 'Test', status: 'completed' }] }
+          },
+          { type: 'tool-result', output: 'Update rejected', isError: true }
+        ]}
+        expandSignal
+      />
+    )
+    expect(screen.getByText('Invalid arguments', { selector: 'pre' })).toBeInTheDocument()
+    expect(screen.getByText('Update rejected', { selector: 'pre' })).toBeInTheDocument()
+    expect(screen.queryByText('1/1')).toBeNull()
+  })
+})

src/renderer/src/components/native-chat/NativeChatToolRun.tsx

@@ -34,6 +34,9 @@ import {
   selectActiveToolCall
 } from '../../../../shared/native-chat-tool-activity'
 import { nativeChatToolRunIconName } from '../../../../shared/native-chat-tool-icon'
+import type { NativeChatToolCallBlock } from '../../../../shared/native-chat-types'
+import { NativeChatTaskList } from './NativeChatTaskList'
+import { buildNativeChatTaskListRows } from './native-chat-task-list-history'
 import { NativeChatDiffView } from './NativeChatDiffView'
 import { NativeChatSubagentRun } from './NativeChatSubagentRun'
 import { NativeChatToolIcon, NativeChatToolRunIcon } from './NativeChatToolIcon'
@@ -205,6 +208,8 @@ function buildEditCards(blocks: NativeChatBlock[]): EditCardModel {
  *  toolbar toggle drive every run at once while still allowing per-run override. */
 export function NativeChatToolRun({
   blocks,
+  previousTodoWrite,
+  previousUpdatePlan,
   subagentGroups = NO_SUBAGENT_GROUPS,
   expandSignal,
   activeTurnIsWorking,
@@ -213,6 +218,8 @@ export function NativeChatToolRun({
   onLinkClick
 }: {
   blocks: NativeChatBlock[]
+  previousTodoWrite?: NativeChatToolCallBlock
+  previousUpdatePlan?: NativeChatToolCallBlock
   /** Spawn-group rosters that belong with this run's activity, one row each. */
   subagentGroups?: NativeChatSubagentGroupBlock[]
   /** Toolbar-driven desired open state. Each change re-syncs this run's state. */
@@ -247,6 +254,7 @@ export function NativeChatToolRun({
   const expandToolLines = expandOverride === undefined ? open : false
   // Diffing every edit is the run's most expensive work, so a collapsed run —
   // which renders none of it — never pays for it.
+  const taskLists = useMemo(() => open ? buildNativeChatTaskListRows(blocks, {todowrite: previousTodoWrite, update_plan: previousUpdatePlan}) : null, [open, blocks, previousTodoWrite, previousUpdatePlan])
   const { editCards, consumedResults } = useMemo(
     () => (open ? buildEditCards(blocks) : NO_EDIT_CARDS),
     [open, blocks]
@@ -349,7 +357,10 @@ export function NativeChatToolRun({
         <div className="mt-1">
           {(() => {
             const seen = new Map<string, number>()
-            return blocks.map((block) => {
+            return blocks.map((block, blockIndex) => {
+              const taskList = taskLists?.rows.get(block)
+              if (taskList) return <NativeChatTaskList key={`tasks:${blockIndex}`} {...taskList} />
+              if (taskLists?.consumedResults.has(block)) return null
               const edit = editCards.get(block)
               if (edit) {
                 return (

src/renderer/src/components/native-chat/native-chat-task-list-history.test.ts

@@ -0,0 +1,114 @@
+import { describe, expect, it } from 'vitest'
+import type {
+  NativeChatBlock,
+  NativeChatMessage,
+  NativeChatToolCallBlock
+} from '../../../../shared/native-chat-types'
+import {
+  buildNativeChatTaskListRows,
+  nativeChatTaskListPredecessors
+} from './native-chat-task-list-history'
+
+function call(name = 'TodoWrite', status = 'pending'): NativeChatToolCallBlock {
+  return {
+    type: 'tool-call',
+    name,
+    input:
+      name === 'TodoWrite'
+        ? { todos: [{ content: 'Test', status }] }
+        : { plan: [{ step: 'Test', status }] }
+  }
+}
+function message(
+  id: string,
+  blocks: NativeChatBlock[],
+  role: NativeChatMessage['role'] = 'assistant'
+): NativeChatMessage {
+  return { id, blocks, role, timestamp: 1, source: 'transcript' }
+}
+
+describe('native chat task list history', () => {
+  it('carries predecessors across prose, ordinary tools, and user turns', () => {
+    const first = call()
+    const next = call('TodoWrite', 'completed')
+    const history = nativeChatTaskListPredecessors([
+      message('a', [first]),
+      message('b', [{ type: 'text', text: 'Continue' }], 'user'),
+      message('c', [{ type: 'tool-call', name: 'Read', input: {} }]),
+      message('d', [next])
+    ])
+    expect(history.get('d')?.todowrite).toBe(first)
+    expect(
+      buildNativeChatTaskListRows([next], history.get('d')).rows.get(next)?.previous?.tasks[0]
+        .status
+    ).toBe('pending')
+  })
+
+  it('keeps interleaved tool families separate and ignores MCP lookalikes', () => {
+    const claude = call()
+    const codex = call('update_plan')
+    const next = call('TodoWrite', 'completed')
+    const model = buildNativeChatTaskListRows([claude, codex, call('mcp__x__TodoWrite'), next])
+    expect(model.rows.get(codex)?.previous).toBeUndefined()
+    expect(model.rows.get(next)?.previous).toEqual(model.rows.get(claude)?.list)
+    const history = nativeChatTaskListPredecessors([
+      message('a', [claude]),
+      message('b', [codex]),
+      message('c', [next])
+    ])
+    expect(history.get('c')).toEqual({ todowrite: claude, update_plan: codex })
+  })
+
+  it('skips failed and malformed calls and keeps errors unconsumed', () => {
+    const first = call()
+    const failed = { ...call(), state: 'failed' as const }
+    const rejected = call('TodoWrite', 'completed')
+    const error: NativeChatBlock = { type: 'tool-result', output: 'Rejected', isError: true }
+    const next = call('TodoWrite', 'in_progress')
+    const blocks: NativeChatBlock[] = [
+      first,
+      { type: 'tool-result', output: 'ok' },
+      failed,
+      { type: 'tool-result', output: 'failed' },
+      rejected,
+      error,
+      { ...call(), input: '{' },
+      next
+    ]
+    const model = buildNativeChatTaskListRows(blocks)
+    expect(model.rows.has(failed)).toBe(false)
+    expect(model.rows.has(rejected)).toBe(false)
+    expect(model.consumedResults.has(error)).toBe(false)
+    expect(model.rows.get(next)?.previous).toEqual(model.rows.get(first)?.list)
+    const history = nativeChatTaskListPredecessors([
+      message('a', blocks.slice(0, -1)),
+      message('b', [next])
+    ])
+    expect(history.get('b')?.todowrite).toBe(first)
+  })
+
+  it('updates predecessor identity after pagination and remains stable on rerender', () => {
+    const first = call()
+    const second = call('TodoWrite', 'in_progress')
+    const tail = message('b', [second])
+    expect(nativeChatTaskListPredecessors([tail]).get('b')?.todowrite).toBeUndefined()
+    const history = nativeChatTaskListPredecessors([message('a', [first]), tail])
+    expect(history.get('b')?.todowrite).toBe(first)
+    expect(nativeChatTaskListPredecessors([message('a', [first]), tail]).get('b')?.todowrite).toBe(
+      history.get('b')?.todowrite
+    )
+    expect(nativeChatTaskListPredecessors([tail]).get('b')?.todowrite).toBeUndefined()
+  })
+
+  it('diffs a running call before its result arrives and consumes a successful result', () => {
+    const first = call()
+    const running = { ...call('TodoWrite', 'in_progress'), state: 'running' as const }
+    const result: NativeChatBlock = { type: 'tool-result', output: 'ok' }
+    const model = buildNativeChatTaskListRows([running, result], {
+      todowrite: first,
+      update_plan: undefined
+    })
+    expect(model.rows.get(running)?.previous).toBeDefined()
+    expect(model.consumedResults.has(result)).toBe(true)
+  })
+})

src/renderer/src/components/native-chat/native-chat-task-list-history.ts

@@ -0,0 +1,83 @@
+import {
+  nativeChatTaskListTool,
+  normalizeNativeChatTaskList,
+  type NativeChatTaskList,
+  type NativeChatTaskListTool
+} from '../../../../shared/native-chat-task-list'
+import type {
+  NativeChatBlock,
+  NativeChatMessage,
+  NativeChatToolCallBlock
+} from '../../../../shared/native-chat-types'
+import { pairToolBlocks } from './native-chat-tool-fold'
+
+export type NativeChatTaskListPredecessors = Partial<
+  Record<NativeChatTaskListTool, NativeChatToolCallBlock>
+>
+export type NativeChatTaskListRow = { list: NativeChatTaskList; previous?: NativeChatTaskList }
+
+function taskListFromCall(call: NativeChatToolCallBlock): NativeChatTaskList | null {
+  return call.state === 'failed' ? null : normalizeNativeChatTaskList(call.name, call.input)
+}
+
+/** Store call identities so unchanged rows stay memoized, while prepends replace their context. */
+export function nativeChatTaskListPredecessors(
+  messages: readonly NativeChatMessage[]
+): Map<string, NativeChatTaskListPredecessors> {
+  const history = new Map<string, NativeChatTaskListPredecessors>()
+  const previous: NativeChatTaskListPredecessors = {}
+  for (const message of messages) {
+    history.set(message.id, { ...previous })
+    if (message.role === 'user') {
+      continue
+    }
+    for (const { call, result } of pairToolBlocks(message.blocks)) {
+      if (!call || result?.isError) {
+        continue
+      }
+      const tool = nativeChatTaskListTool(call.name)
+      if (tool && taskListFromCall(call)) {
+        previous[tool] = call
+      }
+    }
+  }
+  return history
+}
+
+export function buildNativeChatTaskListRows(
+  blocks: readonly NativeChatBlock[],
+  predecessors: NativeChatTaskListPredecessors = {}
+): {
+  rows: Map<NativeChatBlock, NativeChatTaskListRow>
+  consumedResults: Set<NativeChatBlock>
+} {
+  const rows = new Map<NativeChatBlock, NativeChatTaskListRow>()
+  const consumedResults = new Set<NativeChatBlock>()
+  const previous = new Map<NativeChatTaskListTool, NativeChatTaskList>()
+  for (const call of Object.values(predecessors)) {
+    if (!call) {
+      continue
+    }
+    const tool = nativeChatTaskListTool(call.name)
+    const list = taskListFromCall(call)
+    if (tool && list) {
+      previous.set(tool, list)
+    }
+  }
+  for (const { call, result } of pairToolBlocks(blocks)) {
+    if (!call || result?.isError) {
+      continue
+    }
+    const tool = nativeChatTaskListTool(call.name)
+    const list = taskListFromCall(call)
+    if (!tool || !list) {
+      continue
+    }
+    rows.set(call, { list, previous: previous.get(tool) })
+    previous.set(tool, list)
+    if (result) {
+      consumedResults.add(result)
+    }
+  }
+  return { rows, consumedResults }
+}

src/renderer/src/components/native-chat/native-chat-task-list-state.ts

@@ -52,13 +52,9 @@ export function nativeChatTaskListState(messages: readonly NativeChatMessage[]):
   list: NativeChatTaskList | null
 } {
   let list: NativeChatTaskList | null = null
-  const transcript: NativeChatMessage[] = []
   for (const message of messages) {
     const projection = projectMessage(message)
-    if (projection.list) {
-      list = projection.list
-    }
-    transcript.push(projection.message)
+    if (projection.list) list = projection.list
   }
-  return { messages: transcript, list }
+  return { messages: [...messages], list }
 }

src/shared/native-chat-task-list.test.ts

@@ -1,5 +1,6 @@
 import { describe, expect, it } from 'vitest'
 import {
+  diffNativeChatTaskLists,
   nativeChatTaskLabel,
   normalizeNativeChatTaskList,
   type NativeChatTask,
@@ -73,3 +74,65 @@ describe('normalizeNativeChatTaskList', () => {
     expect(normalizeNativeChatTaskList('update_plan', { todos: [] })).toBeNull()
   })
 })
+
+describe('diffNativeChatTaskLists', () => {
+  it('reports completions and starts, omitting unchanged tasks', () => {
+    expect(
+      diffNativeChatTaskLists(
+        list(task('Read', 'in_progress'), task('Write'), task('Test')),
+        list(task('Read', 'completed'), task('Write', 'in_progress'), task('Test'))
+      )
+    ).toEqual([
+      { kind: 'completed', task: task('Read', 'completed') },
+      { kind: 'started', task: task('Write', 'in_progress') }
+    ])
+  })
+
+  it('ignores reorder-only updates and explanation changes', () => {
+    expect(
+      diffNativeChatTaskLists(list(task('A'), task('B')), {
+        tasks: [task('B'), task('A')],
+        explanation: 'Reordered'
+      })
+    ).toEqual([])
+  })
+
+  it('matches duplicate contents by occurrence', () => {
+    expect(
+      diffNativeChatTaskLists(
+        list(task('A'), task('A', 'in_progress')),
+        list(task('A', 'completed'), task('A', 'in_progress'))
+      )
+    ).toEqual([{ kind: 'completed', task: task('A', 'completed') }])
+  })
+
+  it('reports renamed content as an addition and removal', () => {
+    expect(diffNativeChatTaskLists(list(task('Old')), list(task('New')))).toEqual([
+      { kind: 'added', task: task('New') },
+      { kind: 'removed', task: task('Old') }
+    ])
+  })
+
+  it('reports resets, reopening, and activeForm-only edits', () => {
+    const changed = { ...task('C', 'in_progress'), activeForm: 'Checking C' }
+    expect(
+      diffNativeChatTaskLists(
+        list(task('A', 'completed'), task('B', 'completed'), task('C', 'in_progress')),
+        list(task('A'), task('B', 'in_progress'), changed)
+      )
+    ).toEqual([
+      { kind: 'pending', task: task('A') },
+      { kind: 'started', task: task('B', 'in_progress') },
+      { kind: 'updated', task: changed }
+    ])
+  })
+
+  it('reports clearing a list and removing a duplicate', () => {
+    expect(diffNativeChatTaskLists(list(task('A')), list())).toEqual([
+      { kind: 'removed', task: task('A') }
+    ])
+    expect(diffNativeChatTaskLists(list(task('A'), task('A')), list(task('A')))).toEqual([
+      { kind: 'removed', task: task('A') }
+    ])
+  })
+})

src/shared/native-chat-task-list.ts

@@ -5,6 +5,10 @@ export type NativeChatTask = {
   activeForm?: string
 }
 export type NativeChatTaskList = { tasks: NativeChatTask[]; explanation?: string }
+export type NativeChatTaskChange = {
+  kind: 'added' | 'removed' | 'started' | 'completed' | 'pending' | 'updated'
+  task: NativeChatTask
+}
 export type NativeChatTaskListTool = 'todowrite' | 'update_plan'
 
 export function nativeChatTaskListTool(name: string): NativeChatTaskListTool | null {
@@ -68,3 +72,51 @@ export function normalizeNativeChatTaskList(
 export function nativeChatTaskLabel(task: NativeChatTask): string {
   return task.status === 'in_progress' && task.activeForm ? task.activeForm : task.content
 }
+
+/** Content plus occurrence is the only identity the providers give these entries. */
+export function diffNativeChatTaskLists(
+  previous: NativeChatTaskList,
+  current: NativeChatTaskList
+): NativeChatTaskChange[] {
+  const byContent = new Map<string, NativeChatTask[]>()
+  for (const task of previous.tasks) {
+    const matches = byContent.get(task.content)
+    if (matches) {
+      matches.push(task)
+    } else {
+      byContent.set(task.content, [task])
+    }
+  }
+  const occurrences = new Map<string, number>()
+  const consumed = new Set<NativeChatTask>()
+  const changes: NativeChatTaskChange[] = []
+  for (const task of current.tasks) {
+    const occurrence = occurrences.get(task.content) ?? 0
+    occurrences.set(task.content, occurrence + 1)
+    const before = byContent.get(task.content)?.[occurrence]
+    if (!before) {
+      changes.push({ kind: 'added', task })
+      continue
+    }
+    consumed.add(before)
+    if (before.status !== task.status) {
+      changes.push({
+        kind:
+          task.status === 'completed'
+            ? 'completed'
+            : task.status === 'in_progress'
+              ? 'started'
+              : 'pending',
+        task
+      })
+    } else if (before.activeForm !== task.activeForm) {
+      changes.push({ kind: 'updated', task })
+    }
+  }
+  for (const task of previous.tasks) {
+    if (!consumed.has(task)) {
+      changes.push({ kind: 'removed', task })
+    }
+  }
+  return changes
+}