diff --git a/.project-docs/30-worklog/tasks/20260818-video-duration-client-a7c42f.md b/.project-docs/30-worklog/tasks/20260818-video-duration-client-a7c42f.md
new file mode 100644
index 0000000..5a01280
--- /dev/null
+++ b/.project-docs/30-worklog/tasks/20260818-video-duration-client-a7c42f.md
@@ -0,0 +1,55 @@
+# Task: Fix AI design video duration selector
+
+## Identity
+
+- Task ID: 20260818-video-duration-client-a7c42f
+- Mode: Feature
+- Branch: main
+- Worktree: D:\Datas\OthersProjects\makelore
+- Base commit: 9e1e03f58312dcdff53f520be7247c9921ec288b
+- Owner: codex-video-duration-client
+- Status: Ready for integration
+
+## Scope
+
+- Audit and fix the AI Design video confirmation duration selector in `src/pages/ImageCanvas/index.tsx`.
+- Defensively expose only enabled server-provided duration options from 2 through 6 seconds, including when an older server Quote still selects or advertises 7-15 seconds.
+- Verify that selecting 6 seconds survives Quote repricing and is sent by both the Quote PATCH and final confirmation request.
+- Add focused Renderer regression coverage in `tests/unit/image-canvas-page.test.tsx` and verify the existing Main-to-Works snake-case request mapping in `tests/unit/works-square-design-workspace.test.ts`.
+
+## Intent And Constraints
+
+- Own only `src/pages/ImageCanvas/index.tsx`, `tests/unit/image-canvas-page.test.tsx`, `tests/unit/works-square-design-workspace.test.ts`, and this task record.
+- Preserve Conversation-owned Quote state, server-authoritative repricing, and existing request field naming across Renderer and Main.
+- Do not modify the Works Square server, Electron Main routes/adapters, unrelated AI Design interactions, or files owned by peer tasks.
+- Keep invalid legacy selected durations visibly unselected until the user chooses an allowed value; do not silently submit a replacement duration without a fresh server Quote.
+
+## Outcome
+
+- The confirmation card now filters enabled server-provided video durations to the inclusive 2-6 second client boundary.
+- A legacy Quote whose selected duration is outside that boundary renders an explicit disabled `请选择时长` placeholder instead of visually selecting one allowed value while retaining a different hidden draft value.
+- Selecting 6 seconds updates the controlled draft, survives the debounced server re-quote, and is used by final confirmation.
+- Existing request seams were verified: Renderer sends `durationSeconds: 6`, and the Main cloud adapter sends `duration_seconds: 6` to Works Square.
+
+## Verification
+
+- Red test: the new legacy-duration regression initially failed because the native select visually resolved the unmatched controlled value `10` to option `2`.
+- `corepack pnpm exec vitest run tests/unit/image-canvas-page.test.tsx -t "limits legacy video durations"` — passed after the fix (1 passed, 46 skipped).
+- `corepack pnpm exec vitest run tests/unit/image-canvas-page.test.tsx tests/unit/image-workspace-api.test.ts tests/unit/works-square-design-workspace.test.ts` — passed (3 files, 92 tests).
+- `corepack pnpm run typecheck` — passed.
+- `corepack pnpm exec eslint src/pages/ImageCanvas/index.tsx tests/unit/image-canvas-page.test.tsx tests/unit/works-square-design-workspace.test.ts` — passed with no output.
+- `corepack pnpm run build:vite` — passed for Renderer, Electron Main, and Preload; only the existing dynamic-import and chunk-size warnings were reported.
+- `git diff --check` — passed; Git reported only the repository's LF-to-CRLF checkout warning.
+
+## Follow-ups
+
+- Production acceptance still requires a real server Quote containing the supported duration options; the client intentionally does not synthesize missing 2-6 second choices.
+
+## Promotion Candidates
+
+- Target: `.project-docs/40-domain/business-rules.md` during Integration Gate.
+  - Proposal: record that the AI Design client displays only enabled server-provided video duration options in the inclusive 2-6 second range; legacy selected values outside the range require an explicit allowed selection and fresh server Quote before confirmation.
+  - Evidence: focused controlled-select regression, Quote PATCH assertion, confirmation assertion, and Main-to-Works `duration_seconds: 6` contract test.
+  - Future impact: prevents older server configuration from re-exposing unsupported long video durations or silently submitting a hidden value different from the visible selection.
+  - Semantic conflicts: none; server pricing and option authority remain unchanged.
+  - Human confirmation required: no.
diff --git a/src/pages/ImageCanvas/index.tsx b/src/pages/ImageCanvas/index.tsx
index 67ba57a..721b641 100644
--- a/src/pages/ImageCanvas/index.tsx
+++ b/src/pages/ImageCanvas/index.tsx
@@ -265,6 +265,9 @@ type EditableGenerationParameters = Partial<Pick<
   'resolution' | 'aspectRatio' | 'durationSeconds'
 >>;
 
+const MIN_VIDEO_DURATION_SECONDS = 2;
+const MAX_VIDEO_DURATION_SECONDS = 6;
+
 function quoteDraftFromQuote(quote: DesignGenerationQuote): GenerationQuoteDraft {
   return {
     quoteId: quote.quoteId,
@@ -728,8 +731,15 @@ function QuoteCard({
   onConfirm: () => void;
 }) {
   const availableResolutions = quote.generationOptions.resolutions.filter((option) => !option.disabled);
-  const availableDurations = quote.generationOptions.durations.filter((option) => !option.disabled);
+  const availableDurations = quote.generationOptions.durations.filter((option) => (
+    !option.disabled
+    && option.value >= MIN_VIDEO_DURATION_SECONDS
+    && option.value <= MAX_VIDEO_DURATION_SECONDS
+  ));
   const availableAspectRatios = quote.generationOptions.aspectRatios.filter((option) => !option.disabled);
+  const selectedDuration = availableDurations.some(
+    (option) => option.value === draft.generationParameters.durationSeconds,
+  ) ? String(draft.generationParameters.durationSeconds) : '';
   const updateParameters = (next: EditableGenerationParameters) => {
     onDraftChange({
       ...draft,
@@ -819,9 +829,7 @@ function QuoteCard({
                 aria-label="视频时长"
                 data-testid="design-quote-duration"
                 className="mt-1.5 h-9 bg-background text-xs"
-                value={draft.generationParameters.durationSeconds === null
-                  ? ''
-                  : String(draft.generationParameters.durationSeconds)}
+                value={selectedDuration}
                 disabled={busy}
                 onChange={(event) => {
                   const option = availableDurations.find(
@@ -830,6 +838,9 @@ function QuoteCard({
                   if (option) updateParameters({ durationSeconds: option.value });
                 }}
               >
+                {selectedDuration === '' ? (
+                  <option value="" disabled>请选择时长</option>
+                ) : null}
                 {availableDurations.map((option) => (
                   <option key={option.value} value={option.value}>
                     {option.label}
diff --git a/tests/unit/image-canvas-page.test.tsx b/tests/unit/image-canvas-page.test.tsx
index b2714ed..3428ab7 100644
--- a/tests/unit/image-canvas-page.test.tsx
+++ b/tests/unit/image-canvas-page.test.tsx
@@ -510,6 +510,69 @@ describe('ImageCanvas Workspace-first design experience', () => {
     expect(screen.getByRole('button', { name: '确认并开始生成' })).toBeEnabled();
   });
 
+  it('limits legacy video durations to 2-6 seconds and preserves 6 seconds through confirmation', async () => {
+    const videoConversation = conversationFixture();
+    const videoQuote = videoConversation.messages[1].generationQuote!;
+    videoConversation.brief.medium = 'video';
+    videoQuote.medium = 'video';
+    videoQuote.generationParameters = {
+      ...videoQuote.generationParameters,
+      durationSeconds: 10,
+    };
+    videoQuote.generationOptions.durations = [2, 6, 7, 15].map((value) => ({
+      value,
+      label: `${value} 秒`,
+      default: value === 10,
+      disabled: false,
+      multiplier: 1,
+    }));
+    fetchImageWorkspaceConversationMock.mockResolvedValueOnce(videoConversation);
+    updateImageWorkspaceGenerationQuoteMock.mockImplementationOnce(async (
+      _workspaceId: string,
+      _quoteId: string,
+      finalPrompt: string,
+      generationParameters: DesignGenerationQuote['generationParameters'],
+    ) => ({
+      ...videoQuote,
+      finalPrompt,
+      generationParameters,
+    }));
+
+    render(<MemoryRouter><ImageCanvas /></MemoryRouter>);
+
+    const durationSelect = await screen.findByTestId('design-quote-duration');
+    expect(durationSelect).toHaveValue('');
+    expect(within(durationSelect).getAllByRole('option').map((option) => option.getAttribute('value')))
+      .toEqual(['', '2', '6']);
+
+    fireEvent.change(durationSelect, { target: { value: '6' } });
+
+    await waitFor(() => expect(updateImageWorkspaceGenerationQuoteMock).toHaveBeenCalledWith(
+      'workspace-cloud',
+      'quote-one',
+      videoQuote.finalPrompt,
+      {
+        ...videoQuote.generationParameters,
+        durationSeconds: 6,
+      },
+    ));
+    await waitFor(() => expect(screen.getByTestId('design-quote-duration')).toHaveValue('6'));
+    fireEvent.click(screen.getByRole('button', { name: '确认并开始生成' }));
+
+    await waitFor(() => expect(confirmImageWorkspaceGenerationMock).toHaveBeenCalledWith(
+      'workspace-cloud',
+      'conversation-cloud',
+      1,
+      'quote-one',
+      expect.stringMatching(/^turn-/),
+      videoQuote.finalPrompt,
+      {
+        ...videoQuote.generationParameters,
+        durationSeconds: 6,
+      },
+    ));
+  });
+
   it('offers an actionable retry when re-quoting fails', async () => {
     updateImageWorkspaceGenerationQuoteMock.mockRejectedValueOnce(
       new ImageWorkspaceApiError(409, 'generation_quote_invalid', '当前生成方案已失效'),
diff --git a/tests/unit/works-square-design-workspace.test.ts b/tests/unit/works-square-design-workspace.test.ts
index 143f3df..b0de8aa 100644
--- a/tests/unit/works-square-design-workspace.test.ts
+++ b/tests/unit/works-square-design-workspace.test.ts
@@ -567,7 +567,7 @@ describe('Works Square AI design adapter', () => {
         model: 'image-model-one',
         resolution: '1024x1024',
         aspectRatio: '16:9',
-        durationSeconds: null,
+        durationSeconds: 6,
       },
     })).resolves.toMatchObject({
       quoteId: 'quote-one',
@@ -586,7 +586,7 @@ describe('Works Square AI design adapter', () => {
           model: 'image-model-one',
           resolution: '1024x1024',
           aspect_ratio: '16:9',
-          duration_seconds: null,
+          duration_seconds: 6,
         }),
       }),
     );