diff --git a/apps/desktop/src/components/assistant-ui/tool/fallback-model/index.ts b/apps/desktop/src/components/assistant-ui/tool/fallback-model/index.ts
index 9e569a6d41..3bd3141e41 100644
--- a/apps/desktop/src/components/assistant-ui/tool/fallback-model/index.ts
+++ b/apps/desktop/src/components/assistant-ui/tool/fallback-model/index.ts
@@ -5,6 +5,7 @@ import { normalizeExternalUrl } from '@/lib/external-link'
 import { summarizeShellCommand } from '@/lib/summarize-command'
 import { capitalize, firstStringField, normalize } from '@/lib/text'
 import { isCardTool, isFileEditTool, isSilentTool } from '@/lib/tool-render-class'
+import { toolResultRecord } from '@/lib/tool-result-metadata'
 import { extractToolErrorMessage, formatToolResultSummary } from '@/lib/tool-result-summary'
 
 import {
@@ -694,7 +695,7 @@ function toolErrorText(part: ToolPart, result: Record<string, unknown>): string
 
 function toolStatus(part: ToolPart, resultRecord: Record<string, unknown>): ToolStatus {
   if (part.result === undefined) {
-    return 'running'
+    return part.completedAt === undefined ? 'running' : part.isError ? 'error' : 'warning'
   }
 
   // Explicit success wins over isError / nested-error heuristics. Memory writes
@@ -1418,7 +1419,7 @@ function dynamicTitle(
 
 export function buildToolView(part: ToolPart, inlineDiff: string): ToolView {
   const argsRecord = parseMaybeObject(part.args)
-  const resultRecord = parseMaybeObject(part.result)
+  const resultRecord = toolResultRecord(part)
   const meta = toolMeta(part.toolName)
   const status = toolStatus(part, resultRecord)
   // Skip residual error-heuristic text once status is success (stale isError
@@ -1441,7 +1442,8 @@ export function buildToolView(part: ToolPart, inlineDiff: string): ToolView {
     titlePartsFromAction(baseTitle, part.result === undefined ? meta.pendingAction : undefined)
   )
 
-  const title = titleParts.title
+  const unavailable = part.result === undefined && part.completedAt !== undefined
+  const title = unavailable ? translateNow('assistant.tool.resultUnavailable') : titleParts.title
   const titleEnriched = title !== baseTitle
   const baseSubtitle = error || toolSubtitle(part, argsRecord, resultRecord)
 
@@ -1503,7 +1505,7 @@ export function buildToolView(part: ToolPart, inlineDiff: string): ToolView {
     status,
     subtitle,
     title,
-    titleAction: titleParts.action,
+    titleAction: unavailable ? undefined : titleParts.action,
     tone: meta.tone
   }
 }
diff --git a/apps/desktop/src/components/assistant-ui/tool/fallback-model/types.ts b/apps/desktop/src/components/assistant-ui/tool/fallback-model/types.ts
index 9aa5b8dca7..3fde8136d5 100644
--- a/apps/desktop/src/components/assistant-ui/tool/fallback-model/types.ts
+++ b/apps/desktop/src/components/assistant-ui/tool/fallback-model/types.ts
@@ -1,7 +1,10 @@
+import type { ToolResultMetadata } from '@/lib/tool-result-metadata'
+
 export type ToolTone = 'agent' | 'browser' | 'default' | 'file' | 'image' | 'terminal' | 'web'
 export type ToolStatus = 'error' | 'notice' | 'running' | 'success' | 'warning'
 
 export interface ToolPart {
+  toolResultMetadata?: ToolResultMetadata
   args?: unknown
   completedAt?: number
   isError?: boolean
diff --git a/apps/desktop/src/components/assistant-ui/tool/fallback.tsx b/apps/desktop/src/components/assistant-ui/tool/fallback.tsx
index 527d97206e..6c9112e9ba 100644
--- a/apps/desktop/src/components/assistant-ui/tool/fallback.tsx
+++ b/apps/desktop/src/components/assistant-ui/tool/fallback.tsx
@@ -45,6 +45,7 @@ import { connectorCalls } from '@/lib/connector-tools'
 import { PrettyLink, LinkifiedText as SharedLinkifiedText, urlSlugTitleLabel } from '@/lib/external-link'
 import { AlertCircle, CheckCircle2 } from '@/lib/icons'
 import { isOnboardingEnabled } from '@/lib/onboarding-enabled'
+import { toolResultRecord } from '@/lib/tool-result-metadata'
 import { useEnterAnimation } from '@/lib/use-enter-animation'
 import { cn } from '@/lib/utils'
 import { recordPreviewArtifact } from '@/store/preview-status'
@@ -360,20 +361,30 @@ function ToolEntry({ part }: ToolEntryProps) {
   // below and re-running buildToolView (full JSON.stringify of result) on every
   // stream delta — the freeze on big `/learn` runs. Re-derive a stable part from
   // the referentially-stable args/result so the memos hold across deltas.
-  const { args, completedAt, isError, result, timestamp, toolCallId, toolName } = part
+  const { args, completedAt, isError, result, toolResultMetadata, timestamp, toolCallId, toolName } = part
 
   const stablePart = useMemo<ToolPart>(
-    () => ({ args, completedAt, isError, result, timestamp, toolCallId, toolName, type: 'tool-call' }),
-    [args, completedAt, isError, result, timestamp, toolCallId, toolName]
+    () => ({
+      args,
+      completedAt,
+      isError,
+      result,
+      toolResultMetadata,
+      timestamp,
+      toolCallId,
+      toolName,
+      type: 'tool-call'
+    }),
+    [args, completedAt, isError, result, toolResultMetadata, timestamp, toolCallId, toolName]
   )
 
   const disclosureId = toolEntryDisclosureId(messageId, stablePart)
   const dismissed = useStore($toolRowDismissed(disclosureId))
-  const isPending = messageRunning && result === undefined
+  const isPending = messageRunning && result === undefined && completedAt === undefined
   // Subscribe to this tool's diff only, so a live patch for one tool doesn't
   // re-render every mounted tool row (the factory caches a per-id atom).
   const sideDiff = useStore($toolInlineDiff(toolCallId ?? ''))
-  const inlineDiff = stripInlineDiffChrome(sideDiff) || inlineDiffFromResult(result)
+  const inlineDiff = stripInlineDiffChrome(sideDiff) || inlineDiffFromResult(toolResultRecord(stablePart))
   const isFileEdit = isFileEditTool(toolName)
   const defaultOpen = Boolean(inlineDiff)
   const open = useDisclosureOpen(disclosureId, defaultOpen)
@@ -385,11 +396,11 @@ function ToolEntry({ part }: ToolEntryProps) {
   const enterRef = useEnterAnimation(messageRunning && !embedded, `tool-entry:${disclosureId}`)
   const elapsed = useElapsedSeconds(isPending, `tool:${disclosureId}`)
 
-  // Stale parts (no result, but message stopped running) get a synthetic empty
-  // result so buildToolView treats them as completed-no-output. Keyed on
-  // stablePart so it recomputes only when this tool's data changes.
+  // A stopped turn is not evidence that an unobserved tool succeeded. Use a
+  // presentation-only completion marker, never manufacture a result.
   const view = useMemo(() => {
-    const p = !isPending && result === undefined ? { ...stablePart, result: {} } : stablePart
+    const p =
+      !isPending && result === undefined ? { ...stablePart, completedAt: stablePart.completedAt ?? 0 } : stablePart
 
     return buildToolView(p, inlineDiff)
   }, [inlineDiff, isPending, result, stablePart])
@@ -895,7 +906,9 @@ function useToolRun(startIndex: number, endIndex: number): ToolRunState {
                   : Math.min(earliest, tool.timestamp),
             undefined
           ),
-          pendingApprovalTool: tools.some(tool => tool.result === undefined && APPROVAL_TOOLS.has(tool.toolName)),
+          pendingApprovalTool: timelineTools.some(
+            tool => tool.result === undefined && tool.completedAt === undefined && APPROVAL_TOOLS.has(tool.toolName)
+          ),
           summary: summarizeToolRun(tools, live)
         }
       }
@@ -1030,7 +1043,8 @@ export const ToolGroupSlot: FC<PropsWithChildren<{ endIndex: number; startIndex:
  * its return type and the underlying ToolEntry stays mounted across
  * group-shape changes.
  */
-type TimelineToolCallProps = ToolCallMessagePartProps & { completedAt?: number; timestamp?: number }
+type TimelineToolCallProps = ToolCallMessagePartProps &
+  Pick<ToolPart, 'completedAt' | 'timestamp' | 'toolResultMetadata'>
 
 export const ToolFallback = ({
   toolCallId,
@@ -1039,9 +1053,20 @@ export const ToolFallback = ({
   completedAt,
   isError,
   result,
+  toolResultMetadata,
   timestamp
 }: TimelineToolCallProps) => {
-  const part: ToolPart = { args, completedAt, isError, result, timestamp, toolCallId, toolName, type: 'tool-call' }
+  const part: ToolPart = {
+    args,
+    completedAt,
+    isError,
+    result,
+    toolResultMetadata,
+    timestamp,
+    toolCallId,
+    toolName,
+    type: 'tool-call'
+  }
 
   return <ToolEntry part={part} />
 }
diff --git a/apps/desktop/src/i18n/ar.ts b/apps/desktop/src/i18n/ar.ts
index de746c054a..c8702f0a00 100644
--- a/apps/desktop/src/i18n/ar.ts
+++ b/apps/desktop/src/i18n/ar.ts
@@ -2912,6 +2912,7 @@ export const ar = defineLocale({
       statusError: 'خطأ',
       statusRecovered: 'تم الاسترداد',
       statusDone: 'تم',
+      resultUnavailable: 'النتيجة غير متاحة',
       memoryWriteNoted: 'تم تسجيل كتابة الذاكرة',
       actions: {
         read: 'قراءة',
diff --git a/apps/desktop/src/i18n/en.ts b/apps/desktop/src/i18n/en.ts
index 1081677745..48323d57f3 100644
--- a/apps/desktop/src/i18n/en.ts
+++ b/apps/desktop/src/i18n/en.ts
@@ -3975,6 +3975,7 @@ export const en: Translations = {
       statusError: 'Error',
       statusRecovered: 'Recovered',
       statusDone: 'Done',
+      resultUnavailable: 'Result unavailable',
       memoryWriteNoted: 'Memory write noted',
       actions: {
         read: 'Read',
diff --git a/apps/desktop/src/i18n/ja.ts b/apps/desktop/src/i18n/ja.ts
index 0d9c63d7d0..f725cb9b98 100644
--- a/apps/desktop/src/i18n/ja.ts
+++ b/apps/desktop/src/i18n/ja.ts
@@ -3370,6 +3370,7 @@ export const ja = defineLocale({
       statusError: 'エラー',
       statusRecovered: '回復しました',
       statusDone: '完了',
+      resultUnavailable: '結果を取得できません',
       memoryWriteNoted: 'メモリへの書き込みを記録',
       actions: {
         read: '読み取り完了',
diff --git a/apps/desktop/src/i18n/ru.ts b/apps/desktop/src/i18n/ru.ts
index 8a1918268c..663e4dd7ab 100644
--- a/apps/desktop/src/i18n/ru.ts
+++ b/apps/desktop/src/i18n/ru.ts
@@ -3673,6 +3673,7 @@ export const ru = defineLocale({
       statusError: 'Ошибка',
       statusRecovered: 'Восстановлено',
       statusDone: 'Готово',
+      resultUnavailable: 'Результат недоступен',
       memoryWriteNoted: 'Запись в память отмечена',
       actions: {
         read: 'Чтение',
diff --git a/apps/desktop/src/i18n/types.ts b/apps/desktop/src/i18n/types.ts
index b8be7faeae..38bf01eb15 100644
--- a/apps/desktop/src/i18n/types.ts
+++ b/apps/desktop/src/i18n/types.ts
@@ -3502,6 +3502,7 @@ export interface Translations {
       statusRecovered: string
       statusDone: string
       /** Over-budget / rejected memory write title — not "Saved to memory". */
+      resultUnavailable: string
       memoryWriteNoted: string
       actions: {
         read: string
diff --git a/apps/desktop/src/i18n/zh-hant.ts b/apps/desktop/src/i18n/zh-hant.ts
index 33652efd81..5311161ed8 100644
--- a/apps/desktop/src/i18n/zh-hant.ts
+++ b/apps/desktop/src/i18n/zh-hant.ts
@@ -3323,6 +3323,7 @@ export const zhHant = defineLocale({
       statusError: '錯誤',
       statusRecovered: '已復原',
       statusDone: '完成',
+      resultUnavailable: '結果無法使用',
       memoryWriteNoted: '已記下記憶寫入',
       actions: {
         read: '已讀取',
diff --git a/apps/desktop/src/i18n/zh.ts b/apps/desktop/src/i18n/zh.ts
index 7646bacee6..f5d17844cc 100644
--- a/apps/desktop/src/i18n/zh.ts
+++ b/apps/desktop/src/i18n/zh.ts
@@ -4129,6 +4129,7 @@ export const zh = defineLocale({
       statusError: '错误',
       statusRecovered: '已恢复',
       statusDone: '完成',
+      resultUnavailable: '结果不可用',
       memoryWriteNoted: '已记下记忆写入',
       actions: {
         read: '已读取',
diff --git a/apps/desktop/src/lib/chat-messages.test.ts b/apps/desktop/src/lib/chat-messages.test.ts
index 0874c2a6c6..5d67d31517 100644
--- a/apps/desktop/src/lib/chat-messages.test.ts
+++ b/apps/desktop/src/lib/chat-messages.test.ts
@@ -1,5 +1,6 @@
 import { describe, expect, it } from 'vitest'
 
+import { toolResultRecord } from '@/lib/tool-result-metadata'
 import type { SessionMessage } from '@/types/hermes'
 
 import type { ChatMessage, ChatMessagePart } from './chat-messages'
@@ -766,7 +767,7 @@ describe('upsertToolPart', () => {
     const [part] = parts
 
     expect(part?.type).toBe('tool-call')
-    expect(part && 'result' in part ? part.result : undefined).toMatchObject({
+    expect(part && 'result' in part ? toolResultRecord(part) : undefined).toMatchObject({
       inline_diff: '--- a/foo.ts\n+++ b/foo.ts\n@@\n-old\n+new'
     })
   })
@@ -828,10 +829,9 @@ describe('upsertToolPart', () => {
       'complete'
     )
 
-    const completedResult =
-      completed[0] && 'result' in completed[0] ? (completed[0].result as Record<string, unknown>) : {}
+    const completedResult = completed[0] && 'result' in completed[0] ? toolResultRecord(completed[0]) : {}
 
-    const clearedResult = cleared[0] && 'result' in cleared[0] ? (cleared[0].result as Record<string, unknown>) : {}
+    const clearedResult = cleared[0] && 'result' in cleared[0] ? toolResultRecord(cleared[0]) : {}
 
     expect(completedResult.todos).toEqual([{ content: 'Boil water', id: 'boil', status: 'in_progress' }])
     expect(clearedResult.todos).toEqual([])
@@ -885,13 +885,7 @@ describe('upsertToolPart', () => {
 
     const contexts = webParts.map(part => String((part.args as Record<string, unknown>)?.context || ''))
 
-    const summaries = webParts.map(part => {
-      if (!('result' in part) || !part.result || typeof part.result !== 'object') {
-        return ''
-      }
-
-      return String((part.result as Record<string, unknown>).summary || '')
-    })
+    const summaries = webParts.map(part => String(toolResultRecord(part).summary || ''))
 
     expect(webParts).toHaveLength(2)
     expect(contexts).toEqual(['tokyo weather', 'reykjavik weather'])
@@ -957,7 +951,7 @@ describe('upsertToolPart', () => {
     expect((part as Extract<ChatMessagePart, { type: 'tool-call' }>).args).toMatchObject({
       context: 'auckland weather today and tomorrow forecast'
     })
-    expect((part as Extract<ChatMessagePart, { type: 'tool-call' }>).result).toMatchObject({
+    expect(toolResultRecord(part as Extract<ChatMessagePart, { type: 'tool-call' }>)).toMatchObject({
       summary: 'Did 5 searches in 1.1s'
     })
   })
@@ -1026,7 +1020,7 @@ describe('upsertToolPart', () => {
 
     expect(webParts).toHaveLength(1)
     expect(webParts[0].toolCallId).toBe('search-asuncion')
-    expect(webParts[0].result).toMatchObject({ summary: 'Did 5 searches in 1.1s' })
+    expect(toolResultRecord(webParts[0])).toMatchObject({ summary: 'Did 5 searches in 1.1s' })
   })
 
   it('matches id-less live starts with later identified progress updates', () => {
@@ -1125,10 +1119,7 @@ describe('upsertToolPart', () => {
       .map(part => ({
         id: part.toolCallId,
         query: String((part.args as Record<string, unknown>)?.query || ''),
-        summary:
-          part.result && typeof part.result === 'object'
-            ? String((part.result as Record<string, unknown>).summary || '')
-            : ''
+        summary: String(toolResultRecord(part).summary || '')
       }))
 
     expect(webParts).toEqual([
@@ -1172,7 +1163,7 @@ describe('upsertToolPart', () => {
     const [part] = completed
 
     expect(part?.type).toBe('tool-call')
-    expect((part as Extract<ChatMessagePart, { type: 'tool-call' }>).result).toMatchObject({
+    expect(toolResultRecord(part as Extract<ChatMessagePart, { type: 'tool-call' }>)).toMatchObject({
       data: { web: [{ title: 'Suva forecast' }] },
       summary: 'Did 1 search in 0.5s'
     })
diff --git a/apps/desktop/src/lib/chat-messages/tool-parts.ts b/apps/desktop/src/lib/chat-messages/tool-parts.ts
index 392ec58b4f..366ccaeeea 100644
--- a/apps/desktop/src/lib/chat-messages/tool-parts.ts
+++ b/apps/desktop/src/lib/chat-messages/tool-parts.ts
@@ -1,5 +1,6 @@
 import { firstStringField, normalize } from '@/lib/text'
 import { isTodoToolName, parseTodos } from '@/lib/todos'
+import type { ToolResultMetadata } from '@/lib/tool-result-metadata'
 import type { SessionMessage } from '@/types/hermes'
 
 import type { ChatMessage, ChatMessagePart, GatewayEventPayload } from './types'
@@ -184,7 +185,18 @@ function findToolPartIndex(
   for (let index = 0; index < parts.length; index += 1) {
     const part = parts[index]
 
-    if (part.type === 'tool-call' && part.toolName === name && part.result === undefined) {
+    if (
+      part.type === 'tool-call' &&
+      part.toolName === name &&
+      part.result === undefined &&
+      part.completedAt === undefined
+    ) {
+      // A new identified start cannot replace a different identified call.
+      // Only id-less placeholders may acquire an ID on a later start event.
+      if (stableId && phase === 'running' && part.toolCallId && !part.toolCallId.startsWith('live-tool:')) {
+        continue
+      }
+
       pendingIndices.push(index)
     }
   }
@@ -264,22 +276,21 @@ function toolArgs(payload: GatewayEventPayload | undefined, prevArgs?: unknown):
   }
 }
 
-function toolResult(
+function toolResultMetadata(
   payload: GatewayEventPayload | undefined,
+  previous: ToolResultMetadata | undefined,
   prevResult?: unknown,
   prevArgs?: unknown
-): Record<string, unknown> {
-  const parsedResult = parseMaybeJsonObject(payload?.result)
-
+): ToolResultMetadata {
   return {
-    ...parsedResult,
-    ...(payload?.inline_diff ? { inline_diff: payload.inline_diff } : {}),
-    ...(payload?.summary ? { summary: payload.summary } : {}),
-    ...(payload?.message ? { message: payload.message } : {}),
-    ...(payload?.preview ? { preview: payload.preview } : {}),
+    ...previous,
+    ...(payload?.inline_diff !== undefined ? { inline_diff: payload.inline_diff } : {}),
+    ...(payload?.summary !== undefined ? { summary: payload.summary } : {}),
+    ...(payload?.message !== undefined ? { message: payload.message } : {}),
+    ...(payload?.preview !== undefined ? { preview: payload.preview } : {}),
     ...(payload?.duration_s !== undefined ? { duration_s: payload.duration_s } : {}),
     ...carryTodos(payload, prevResult, prevArgs),
-    ...(payload?.error ? { error: payload.error } : {})
+    ...(payload?.error !== undefined ? { error: payload.error } : {})
   }
 }
 
@@ -330,8 +341,10 @@ export function upsertToolPart(
     timestamp: prev?.timestamp ?? occurredAt,
     ...(phase === 'complete' && {
       completedAt: occurredAt,
-      result: toolResult(payload, prevResult, prevArgs),
-      isError: Boolean(payload?.error)
+      result: payload?.result !== undefined ? payload.result : prevResult,
+      toolResultMetadata: toolResultMetadata(payload, prev?.toolResultMetadata, prevResult, prevArgs),
+      isError:
+        payload?.error !== undefined ? Boolean(payload.error) : Boolean(prev && 'isError' in prev && prev.isError)
     })
   } satisfies ChatMessagePart
 
diff --git a/apps/desktop/src/lib/chat-messages/tool-result-preservation.test.ts b/apps/desktop/src/lib/chat-messages/tool-result-preservation.test.ts
new file mode 100644
index 0000000000..ce9f6a4a09
--- /dev/null
+++ b/apps/desktop/src/lib/chat-messages/tool-result-preservation.test.ts
@@ -0,0 +1,89 @@
+import { fromThreadMessageLike, getAutoStatus } from '@assistant-ui/core/internal'
+import { describe, expect, it } from 'vitest'
+
+import { buildToolView } from '@/components/assistant-ui/tool/fallback-model'
+import { toRuntimeMessage } from '@/lib/chat-runtime'
+
+import { upsertToolPart } from './tool-parts'
+import type { ChatMessagePart } from './types'
+
+describe('live tool result evidence', () => {
+  it('preserves every JSON value and display hints through the real runtime adapter and replay', () => {
+    const values = [
+      'plain text\n',
+      '',
+      '{"answer":1}',
+      '[1,false]',
+      0,
+      false,
+      null,
+      [],
+      [1, false],
+      { summary: 'original', output: 'ok' }
+    ]
+
+    for (const [index, result] of values.entries()) {
+      const tool_id = `call-${index}`
+
+      const parts = upsertToolPart(
+        [],
+        { name: 'terminal', tool_id, result, summary: 'abbreviated', duration_s: 0 },
+        'complete',
+        2
+      )
+
+      const [part] = parts
+      expect(part.type).toBe('tool-call')
+
+      if (part.type !== 'tool-call') {
+        throw new Error('Missing tool call')
+      }
+
+      expect(part.result).toBe(result)
+      expect(part.toolResultMetadata).toMatchObject({ summary: 'abbreviated', duration_s: 0 })
+
+      const replayed = upsertToolPart(parts, { name: 'terminal', tool_id, message: 'completed' }, 'complete', 3)
+      expect((replayed[0] as typeof part).result).toBe(result)
+
+      const runtime = fromThreadMessageLike(
+        toRuntimeMessage({ id: tool_id, role: 'assistant', parts: replayed }),
+        tool_id,
+        getAutoStatus(false, false, false, false, undefined)
+      )
+
+      const received = runtime.content[0] as typeof part
+      expect(received.result).toEqual(result)
+      expect(received.toolResultMetadata).toMatchObject({ summary: 'abbreviated', message: 'completed' })
+
+      if (typeof result === 'object' && result && 'summary' in result) {
+        expect((received.result as typeof result).summary).toBe(result.summary)
+      }
+    }
+  })
+
+  it('distinguishes a missing completion result from empty results and keeps parallel completions separate', () => {
+    let parts: ChatMessagePart[] = []
+
+    for (const [tool_id, command] of [
+      ['a', 'echo a'],
+      ['b', 'echo b']
+    ]) {
+      parts = upsertToolPart(parts, { name: 'terminal', tool_id, args: { command } }, 'running', 1)
+    }
+
+    parts = upsertToolPart(parts, { name: 'terminal', tool_id: 'b', result: '' }, 'complete', 2)
+    parts = upsertToolPart(parts, { name: 'terminal', tool_id: 'a', summary: 'done' }, 'complete', 3)
+    expect(parts).toHaveLength(2)
+    const [missing, empty] = parts
+
+    if (missing.type !== 'tool-call' || empty.type !== 'tool-call') {
+      throw new Error('Missing tool call')
+    }
+
+    expect(missing.result).toBeUndefined()
+    expect(missing.completedAt).toBe(3)
+    expect(buildToolView(missing, '').status).toBe('warning')
+    expect(empty.result).toBe('')
+    expect(buildToolView(empty, '').status).toBe('success')
+  })
+})
diff --git a/apps/desktop/src/lib/chat-messages/types.ts b/apps/desktop/src/lib/chat-messages/types.ts
index d29f7dab1c..1cf7d325dd 100644
--- a/apps/desktop/src/lib/chat-messages/types.ts
+++ b/apps/desktop/src/lib/chat-messages/types.ts
@@ -2,9 +2,11 @@ import type { ThreadMessageLike } from '@assistant-ui/react'
 import { type BillingBlock } from '@hermes/shared'
 
 import type { ErrorSurface } from '@/lib/error-surface'
+import type { ToolResultMetadata } from '@/lib/tool-result-metadata'
 import type { MessageReaction, SessionMessage, UsageStats } from '@/types/hermes'
 
 export interface TimelinePartMetadata {
+  toolResultMetadata?: ToolResultMetadata
   /** Unix seconds when this visible activity segment began. Fractional values
    * preserve the millisecond precision available on live gateway events. */
   timestamp?: number
diff --git a/apps/desktop/src/lib/tool-result-metadata.ts b/apps/desktop/src/lib/tool-result-metadata.ts
new file mode 100644
index 0000000000..bace491003
--- /dev/null
+++ b/apps/desktop/src/lib/tool-result-metadata.ts
@@ -0,0 +1,34 @@
+/** Gateway display hints are not the tool's result. Keep them off the raw
+ * payload so summaries cannot overwrite evidence, including false/null/"". */
+export interface ToolResultMetadata {
+  duration_s?: number
+  error?: string | boolean
+  inline_diff?: string
+  message?: string
+  preview?: string
+  summary?: string
+  todos?: unknown
+}
+
+export interface ToolResultSource {
+  result?: unknown
+  toolResultMetadata?: ToolResultMetadata
+}
+
+/** A derived record for existing presentation code; never stored as the result. */
+export function toolResultRecord(source: ToolResultSource): Record<string, unknown> {
+  let value = source.result
+
+  if (typeof value === 'string') {
+    try {
+      value = JSON.parse(value)
+    } catch {
+      value = undefined
+    }
+  }
+
+  const record = value && typeof value === 'object' && !Array.isArray(value) ? value : {}
+
+  // Authoritative result fields win over fallible/abbreviated display hints.
+  return { ...source.toolResultMetadata, ...record }
+}