revert(native-chat): drop the speculative Fable model-switch detections (#18215)

Both changes shipped in #18055 were written against strings never observed
in a real session, and neither fixed a reported problem. Guessing at agent
output we have not seen is how the picker got a row that silently no-ops.

Fable consent detection is removed outright. It watched the session for
"Fable N uses usage credits and needs a one-time consent" and answered
`interaction-required`. No consent prompt appeared in any validation run —
the test account had already consented — so the matched wording was never
confirmed. With the detector gone nothing produces `interaction-required`,
so the outcome leaves the union and its unreachable handler goes with it.
A real consent prompt now reports the switch as unverified, which is the
honest failure mode for output we cannot recognize.

The weekly usage scope goes back to exact `display_name === 'fable'`. It
had been widened to `/^fable\b/` against a hypothetical rename of
Anthropic's own usage window; the API still reports "Fable", so the match
was insurance against a scenario with no evidence behind it.

Tests covering the removed behavior are deleted rather than rewritten,
including the two pre-existing `interaction-required` cases that asserted
the terminal is revealed.

The disabled-row filter from #18055 is deliberately untouched.

Claude-Session: https://claude.ai/code/session_01SJy4XGrdre6YaU1wYNKak4

Co-authored-by: Merge Sim <sim@local>

src/main/rate-limits/claude-fetcher-fable-usage.test.ts

@@ -144,51 +144,6 @@ describe('fetchClaudeRateLimits', () => {
     expect(fetchViaPty).not.toHaveBeenCalled()
   })
 
-  it('maps a scoped Fable window whose display name carries a point release', async () => {
-    const configDir = '/Users/test/.claude'
-    const authPreparation: ClaudeRuntimeAuthPreparation = {
-      configDir,
-      envPatch: { CLAUDE_CONFIG_DIR: configDir },
-      stripAuthEnv: false,
-      provenance: 'managed:account-1'
-    }
-    vi.mocked(readActiveClaudeKeychainCredentialsStrict).mockResolvedValueOnce(
-      JSON.stringify({ claudeAiOauth: { accessToken: 'oauth-token' } })
-    )
-    netFetchMock.mockResolvedValueOnce(
-      new Response(
-        JSON.stringify({
-          five_hour: { utilization: 36 },
-          seven_day: { utilization: 73 },
-          // Discriminating: a passing scope match must beat this fallback.
-          fable_weekly: { utilization: 12 },
-          limits: [
-            {
-              kind: 'weekly_scoped',
-              percent: 64,
-              resets_at: '2026-07-17T20:00:00.099908+00:00',
-              is_active: true,
-              scope: { model: { display_name: 'Fable 5.1' } }
-            }
-          ]
-        }),
-        { status: 200 }
-      )
-    )
-
-    await expect(
-      fetchClaudeRateLimits({ authPreparation, allowUsagePanelSupplement: true })
-    ).resolves.toMatchObject({
-      provider: 'claude',
-      status: 'ok',
-      fableWeekly: {
-        usedPercent: 64,
-        resetsAt: Date.parse('2026-07-17T20:00:00.099908+00:00')
-      }
-    })
-    expect(fetchViaPty).not.toHaveBeenCalled()
-  })
-
   it('surfaces inactive scoped Fable usage over the legacy OAuth fallback', async () => {
     const configDir = '/Users/test/.claude'
     const authPreparation: ClaudeRuntimeAuthPreparation = {

src/main/rate-limits/claude-oauth-usage-request.ts

@@ -32,17 +32,13 @@ async function ensureProxyFromEnvironment(): Promise<void> {
   }).catch(() => {})
 }
 
-// Why: the scope name carries the shipped version once a point release exists
-// ("Fable 5.1"), so exact equality would drop the window.
-const FABLE_SCOPE_RE = /^fable\b/
-
 function mapFableWeeklyWindow(data: OAuthUsageResponse): RateLimitWindow | null {
   const scoped = Array.isArray(data.limits)
     ? data.limits.find(
         (limit) =>
           limit?.kind === 'weekly_scoped' &&
           Number.isFinite(limit.percent) &&
-          FABLE_SCOPE_RE.test(limit.scope?.model?.display_name?.trim().toLowerCase() ?? '')
+          limit.scope?.model?.display_name?.trim().toLowerCase() === 'fable'
       )
     : undefined
   return (

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

@@ -27,10 +27,10 @@ const mocks = vi.hoisted(() => ({
     sessionOptionsSnapshot?: SessionOptionDescriptor[]
     attachDisabled?: boolean
   } | null,
-  modelSwitchOutcome: 'applied' as 'applied' | 'rejected' | 'interaction-required' | 'unknown',
+  modelSwitchOutcome: 'applied' as 'applied' | 'rejected' | 'unknown',
   confirmationObserver: null as {
     ready: Promise<void>
-    result: Promise<'applied' | 'rejected' | 'interaction-required' | 'unknown'>
+    result: Promise<'applied' | 'rejected' | 'unknown'>
     arm: ReturnType<typeof vi.fn>
     startDetection: ReturnType<typeof vi.fn>
     dispose: ReturnType<typeof vi.fn>
@@ -731,33 +731,6 @@ describe('NativeChatComposer', () => {
     expect(onSwitchToTerminal).not.toHaveBeenCalled()
   })
 
-  it('reveals Claude interaction only when the model switch needs user input', async () => {
-    mocks.sendHandle.settleAfterMs = 0
-    mocks.modelSwitchOutcome = 'interaction-required'
-    const onSwitchToTerminal = vi.fn()
-    render(
-      <NativeChatComposer
-        terminalTabId="tab-1"
-        paneKey="tab-1:leaf-1"
-        targetPtyId="pty-1"
-        agent="claude"
-        onSwitchToTerminal={onSwitchToTerminal}
-      />
-    )
-
-    await act(async () => {
-      await mocks.fieldProps?.sessionOptionsSurface?.setOption('model', 'fable')
-    })
-
-    expect(mocks.sendNativeChatMessageVerified).toHaveBeenCalledWith(
-      {},
-      'pty-1',
-      '/model fable',
-      expect.any(AbortSignal)
-    )
-    expect(onSwitchToTerminal).toHaveBeenCalledOnce()
-  })
-
   it('types the Codex picker command and switches to the terminal', async () => {
     mocks.sendHandle.settleAfterMs = 0
     const onSwitchToTerminal = vi.fn()

src/renderer/src/components/native-chat/claude-model-switch-confirmation.test.ts

@@ -138,69 +138,6 @@ describe('Claude model switch confirmation detection', () => {
     await expect(observer.result).resolves.toBe('rejected')
   })
 
-  it('requests interaction for Fable one-time usage-credit consent', async () => {
-    const dataObserver = { current: (_data: string): void => {} }
-    const observer = createClaudeModelSwitchConfirmationObserver({
-      ptyId: 'pty-1',
-      settings: {},
-      expectedModelLabel: 'Fable 5',
-      subscribeToData: (watcher) => {
-        dataObserver.current = watcher
-        return vi.fn(() => {})
-      },
-      timeoutMs: 100
-    })
-
-    await observer.ready
-    observer.arm()
-    dataObserver.current('Fable 5 uses usage credits and needs a one-time consent — ')
-    dataObserver.current('pick Fable from /model in an interactive session to set it up')
-
-    await expect(observer.result).resolves.toBe('interaction-required')
-  })
-
-  it('requests interaction for a Fable point-release consent prompt', async () => {
-    const dataObserver = { current: (_data: string): void => {} }
-    const observer = createClaudeModelSwitchConfirmationObserver({
-      ptyId: 'pty-1',
-      settings: {},
-      expectedModelLabel: 'Fable 5.1',
-      subscribeToData: (watcher) => {
-        dataObserver.current = watcher
-        return vi.fn(() => {})
-      },
-      timeoutMs: 100
-    })
-
-    await observer.ready
-    observer.arm()
-    // Only the versioned consent line: the generic "pick Fable from /model"
-    // sentence must not be what carries this case.
-    dataObserver.current('Fable 5.1 uses usage credits and needs a one-time consent')
-
-    await expect(observer.result).resolves.toBe('interaction-required')
-  })
-
-  it('requests interaction for a versioned Fable switch prompt', async () => {
-    const dataObserver = { current: (_data: string): void => {} }
-    const observer = createClaudeModelSwitchConfirmationObserver({
-      ptyId: 'pty-1',
-      settings: {},
-      expectedModelLabel: 'Fable 5.1',
-      subscribeToData: (watcher) => {
-        dataObserver.current = watcher
-        return vi.fn(() => {})
-      },
-      timeoutMs: 100
-    })
-
-    await observer.ready
-    observer.arm()
-    dataObserver.current('Switch to \u001b[1mFable 5.1\u001b[0m? This model uses usage credits.')
-
-    await expect(observer.result).resolves.toBe('interaction-required')
-  })
-
   it('reports unknown when the PTY observer cannot be established', async () => {
     const observer = createClaudeModelSwitchConfirmationObserver({
       ptyId: 'pty-1',

src/renderer/src/components/native-chat/claude-model-switch-confirmation.ts

@@ -10,7 +10,7 @@ const MAX_OBSERVED_BYTES = 64 * 1024
 
 type SubscribeToData = (watcher: (data: string) => void) => Promise<() => void> | (() => void)
 
-export type ClaudeModelSwitchOutcome = 'applied' | 'rejected' | 'interaction-required' | 'unknown'
+export type ClaudeModelSwitchOutcome = 'applied' | 'rejected' | 'unknown'
 
 export type ClaudeModelSwitchConfirmationObserver = {
   ready: Promise<void>
@@ -62,22 +62,6 @@ function hasClaudeModelSwitchRejection(buffer: string): boolean {
   return compactTerminalText(buffer).includes('keptmodelas')
 }
 
-// Why: compactTerminalText only strips whitespace, so a point release keeps its
-// dot ("fable5.1uses..."). The version is optional because the CLI's own label
-// for the newest Fable carries no number at all.
-const FABLE_VERSION = String.raw`fable(?:\d+(?:\.\d+)*)?`
-const FABLE_CONSENT_RE = new RegExp(`${FABLE_VERSION}usesusagecreditsandneedsaone-timeconsent`)
-const FABLE_SWITCH_PROMPT_RE = new RegExp(`switchto${FABLE_VERSION}\\?`)
-
-function hasClaudeModelSwitchInteraction(buffer: string): boolean {
-  const text = compactTerminalText(buffer)
-  return (
-    FABLE_CONSENT_RE.test(text) ||
-    text.includes('pickfablefrom/modelinaninteractivesessiontosetitup') ||
-    (FABLE_SWITCH_PROMPT_RE.test(text) && text.includes('usagecredits'))
-  )
-}
-
 function subscribeToClaudeModelSwitchData(args: {
   ptyId: string
   settings: Pick<GlobalSettings, 'activeRuntimeEnvironmentId'> | null | undefined
@@ -156,10 +140,6 @@ export function createClaudeModelSwitchConfirmationObserver(args: {
       finish('rejected')
       return
     }
-    if (hasClaudeModelSwitchInteraction(observed)) {
-      finish('interaction-required')
-      return
-    }
     if (!confirmationSubmitted && hasClaudeModelSwitchConfirmation(observed)) {
       confirmationSubmitted = true
       try {

src/renderer/src/components/native-chat/native-chat-pty-session-options.test.ts

@@ -159,28 +159,6 @@ describe('native chat PTY session options', () => {
     })
   })
 
-  it('reveals the terminal only when Claude actually requires model-switch interaction', async () => {
-    seedNativeChatAppliedSessionOptions('pty-1', 'claude', { model: 'sonnet' })
-    const dispatch = vi.fn().mockResolvedValue({ outcome: 'interaction-required' })
-    const onAgentPicker = vi.fn()
-    const surface = createNativeChatPtySessionOptions({
-      agent: 'claude',
-      scopeKey: 'pty-1',
-      mode: 'live',
-      dispatchCommand: dispatch,
-      onAgentPicker
-    })!
-
-    const result = await surface.setOption('model', 'haiku')
-
-    expect(dispatch).toHaveBeenCalledWith('/model haiku', {
-      detectAgentInteraction: 'claude-model-switch-confirmation',
-      expectedChoiceLabel: 'Haiku'
-    })
-    expect(onAgentPicker).toHaveBeenCalledOnce()
-    expect(result.snapshot[0]).toMatchObject({ valueSource: 'unknown' })
-  })
-
   it('keeps the prior model and persistence when Claude rejects the switch', async () => {
     seedNativeChatAppliedSessionOptions('pty-1', 'claude', {
       model: 'fable',

src/renderer/src/components/native-chat/native-chat-session-option-apply.ts

@@ -171,12 +171,6 @@ function applyDispatchOutcome(
     ctx.publish()
     throw new Error('Could not verify the model change; open the terminal to check.')
   }
-  if (dispatchResult?.outcome === 'interaction-required') {
-    ctx.clearModelTruth()
-    const snapshot = ctx.publish()
-    ctx.onAgentPicker?.()
-    return { snapshot }
-  }
   return null
 }