diff --git a/src/main/text-generation/commit-message-text-generation.test.ts b/src/main/text-generation/commit-message-text-generation.test.ts
index 77665b899..e9e5b5f42 100644
--- a/src/main/text-generation/commit-message-text-generation.test.ts
+++ b/src/main/text-generation/commit-message-text-generation.test.ts
@@ -6,9 +6,9 @@ import type * as ChildProcess from 'child_process'
 import { beforeEach, describe, expect, it, vi } from 'vitest'
 import { getDefaultSettings } from '../../shared/constants'
 import {
-  applyOrcaAttribution,
   generateCommitMessageFromContext,
-  resolveCommitMessageSettings
+  resolveCommitMessageSettings,
+  trimGeneratedCommitMessage
 } from './commit-message-text-generation'
 
 vi.mock('child_process', async (importOriginal) => {
@@ -54,10 +54,25 @@ describe('resolveCommitMessageSettings', () => {
       ok: true,
       params: {
         agentId: 'codex',
-        model: 'gpt-5.4-mini',
+        model: 'gpt-5.5',
         thinkingLevel: 'low',
-        customPrompt: 'Use Conventional Commits.',
-        attributionEnabled: true
+        customPrompt: 'Use Conventional Commits.'
+      }
+    })
+  })
+
+  it("uses the user's default agent when the AI setting has no explicit agent", () => {
+    const settings = getDefaultSettings('/tmp')
+    settings.defaultTuiAgent = 'codex'
+
+    const result = resolveCommitMessageSettings(settings)
+
+    expect(result).toMatchObject({
+      ok: true,
+      params: {
+        agentId: 'codex',
+        model: 'gpt-5.5',
+        thinkingLevel: 'low'
       }
     })
   })
@@ -67,8 +82,8 @@ describe('resolveCommitMessageSettings', () => {
     settings.commitMessageAi = {
       enabled: true,
       agentId: 'codex',
-      selectedModelByAgent: { codex: 'gpt-5.5' },
-      selectedThinkingByModel: { 'gpt-5.5': 'turbo' },
+      selectedModelByAgent: { codex: 'gpt-5.4-mini' },
+      selectedThinkingByModel: { 'gpt-5.4-mini': 'turbo' },
       customPrompt: '',
       customAgentCommand: ''
     }
@@ -79,7 +94,7 @@ describe('resolveCommitMessageSettings', () => {
       ok: true,
       params: {
         agentId: 'codex',
-        model: 'gpt-5.5',
+        model: 'gpt-5.4-mini',
         thinkingLevel: 'low'
       }
     })
@@ -239,8 +254,7 @@ describe('generateCommitMessageFromContext', () => {
       {
         agentId: 'custom',
         model: '',
-        customAgentCommand: 'agent',
-        attributionEnabled: true
+        customAgentCommand: 'agent'
       },
       {
         kind: 'remote',
@@ -257,8 +271,7 @@ describe('generateCommitMessageFromContext', () => {
 
     expect(result).toEqual({
       success: true,
-      message:
-        'Update README\n\n- Explain the generated commit-message flow\n\nCo-authored-by: Orca <help@stably.ai>',
+      message: 'Update README\n\n- Explain the generated commit-message flow',
       agentLabel: 'agent'
     })
   })
@@ -464,10 +477,10 @@ describe('generateCommitMessageFromContext', () => {
   })
 })
 
-describe('applyOrcaAttribution', () => {
-  it('does not duplicate the Orca trailer', () => {
-    const message = applyOrcaAttribution('Update docs', true)
+describe('trimGeneratedCommitMessage', () => {
+  it('removes trailing whitespace from generated messages', () => {
+    const message = trimGeneratedCommitMessage('Update docs\n\n')
 
-    expect(applyOrcaAttribution(message, true)).toBe(message)
+    expect(message).toBe('Update docs')
   })
 })
diff --git a/src/main/text-generation/commit-message-text-generation.ts b/src/main/text-generation/commit-message-text-generation.ts
index e056270f8..cb6aa1c31 100644
--- a/src/main/text-generation/commit-message-text-generation.ts
+++ b/src/main/text-generation/commit-message-text-generation.ts
@@ -15,16 +15,15 @@ import {
 } from '../../shared/commit-message-prompt'
 import {
   CUSTOM_AGENT_ID,
-  DEFAULT_COMMIT_MESSAGE_AGENT_ID,
   getCommitMessageAgentSpec,
   getCommitMessageModel,
-  isCustomAgentId
+  isCustomAgentId,
+  resolveCommitMessageAgentChoice
 } from '../../shared/commit-message-agent-spec'
 import {
   planCommitMessageGeneration,
   type CommitMessagePlan
 } from '../../shared/commit-message-plan'
-import { ORCA_GIT_COMMIT_TRAILER } from '../../shared/orca-attribution'
 import { resolveCliCommand } from '../codex-cli/command'
 import {
   getSpawnArgsForWindows,
@@ -42,8 +41,6 @@ export type GenerateCommitMessageParams = {
   customPrompt?: string
   customAgentCommand?: string
   agentCommandOverride?: string
-  /** When true, append `Co-authored-by: Orca ...` after the cleaned message. */
-  attributionEnabled?: boolean
 }
 
 export type GenerateCommitMessageResult =
@@ -80,33 +77,29 @@ type InternalCommitMessageGenerationResult =
   | { success: true; commitMessage: GeneratedCommitMessage; agentLabel?: string }
   | { success: false; error: string; canceled?: boolean }
 
-/** Appends the Orca trailer if the message does not already include it. */
-export function applyOrcaAttribution(message: string, enabled: boolean): string {
-  if (!enabled) {
-    // Why: trim trailing whitespace even on the no-attribution path so a
-    // stray "\n" from the agent's output never reaches the textarea as a
-    // visible blank line.
-    return message.replace(/\s+$/, '')
-  }
-  const stripped = message.replace(/\s+$/, '')
-  if (stripped.includes(ORCA_GIT_COMMIT_TRAILER)) {
-    return stripped
-  }
-  // Why: a blank line separates the trailer block from the body so `git
-  // interpret-trailers` and most parsers treat it as a real trailer instead
-  // of a paragraph continuation.
-  return `${stripped}\n\n${ORCA_GIT_COMMIT_TRAILER}`
+export function trimGeneratedCommitMessage(message: string): string {
+  return message.replace(/\s+$/, '')
 }
 
 export function resolveCommitMessageSettings(
   settings: GlobalSettings
 ): ResolveCommitMessageSettingsResult {
   const config = settings.commitMessageAi
-  if (!config?.enabled || !config.agentId) {
-    return { ok: false, error: 'Enable AI commit messages and choose an agent in Settings -> Git.' }
+  if (!config?.enabled) {
+    return { ok: false, error: 'Enable AI commit messages in Settings -> Git.' }
   }
 
-  if (isCustomAgentId(config.agentId)) {
+  const agentChoice = resolveCommitMessageAgentChoice(config.agentId, settings.defaultTuiAgent)
+  if (!agentChoice) {
+    return {
+      ok: false,
+      error:
+        `Default agent "${settings.defaultTuiAgent}" does not support AI commit messages. ` +
+        'Choose Claude or Codex in Settings -> Git -> AI Commit Messages.'
+    }
+  }
+
+  if (isCustomAgentId(agentChoice)) {
     const customAgentCommand = config.customAgentCommand.trim()
     if (!customAgentCommand) {
       return {
@@ -120,13 +113,12 @@ export function resolveCommitMessageSettings(
         agentId: CUSTOM_AGENT_ID,
         model: '',
         customPrompt: config.customPrompt,
-        customAgentCommand,
-        attributionEnabled: settings.enableGitHubAttribution === true
+        customAgentCommand
       }
     }
   }
 
-  const agentId = config.agentId ?? DEFAULT_COMMIT_MESSAGE_AGENT_ID
+  const agentId = agentChoice
   const spec = getCommitMessageAgentSpec(agentId)
   if (!spec) {
     return { ok: false, error: `Agent "${agentId}" does not support AI commit messages.` }
@@ -153,8 +145,7 @@ export function resolveCommitMessageSettings(
       model: model.id,
       thinkingLevel,
       customPrompt: config.customPrompt,
-      ...(agentCommandOverride ? { agentCommandOverride } : {}),
-      attributionEnabled: settings.enableGitHubAttribution === true
+      ...(agentCommandOverride ? { agentCommandOverride } : {})
     }
   }
 }
@@ -418,15 +409,14 @@ async function runRemotePlan(
 }
 
 function formatCommitMessageGenerationResult(
-  result: InternalCommitMessageGenerationResult,
-  attributionEnabled: boolean
+  result: InternalCommitMessageGenerationResult
 ): GenerateCommitMessageResult {
   if (!result.success) {
     return result
   }
   return {
     success: true,
-    message: applyOrcaAttribution(result.commitMessage.message, attributionEnabled),
+    message: trimGeneratedCommitMessage(result.commitMessage.message),
     agentLabel: result.agentLabel
   }
 }
@@ -446,5 +436,5 @@ export async function generateCommitMessageFromContext(
     target.kind === 'remote'
       ? await runRemotePlan(planned.plan, target)
       : await runLocalPlan(planned.plan, target.cwd, target.env)
-  return formatCommitMessageGenerationResult(internalResult, params.attributionEnabled === true)
+  return formatCommitMessageGenerationResult(internalResult)
 }
diff --git a/src/renderer/src/components/right-sidebar/CommitArea.generate.test.tsx b/src/renderer/src/components/right-sidebar/CommitArea.generate.test.tsx
index cce1ecae3..83c9c0872 100644
--- a/src/renderer/src/components/right-sidebar/CommitArea.generate.test.tsx
+++ b/src/renderer/src/components/right-sidebar/CommitArea.generate.test.tsx
@@ -184,6 +184,7 @@ describe('CommitArea AI generation', () => {
 
     const button = findNativeButtonByAriaLabel(element, 'Stop generating commit message')
     expect(button.props.title).toBe('Stop generating')
+    expect(hasText(element, 'Generating commit message. Click to stop.')).toBe(true)
     ;(button.props.onClick as () => void)()
     expect(onCancelGenerate).toHaveBeenCalledTimes(1)
   })
diff --git a/src/renderer/src/components/right-sidebar/SourceControl.tsx b/src/renderer/src/components/right-sidebar/SourceControl.tsx
index 35536944b..13b490239 100644
--- a/src/renderer/src/components/right-sidebar/SourceControl.tsx
+++ b/src/renderer/src/components/right-sidebar/SourceControl.tsx
@@ -132,6 +132,10 @@ import type {
   HostedReviewInfo
 } from '../../../../shared/hosted-review'
 import { STATUS_COLORS, STATUS_LABELS } from './status-display'
+import {
+  isCustomAgentId,
+  resolveCommitMessageAgentChoice
+} from '../../../../shared/commit-message-agent-spec'
 
 type SourceControlScope = 'all' | 'uncommitted'
 type SourceControlViewMode = 'list' | 'tree'
@@ -485,6 +489,10 @@ function SourceControlInner(): React.JSX.Element {
   const [createPrDialogOpen, setCreatePrDialogOpen] = useState(false)
   const [createPrPushFirst, setCreatePrPushFirst] = useState(false)
   const commitMessageAi = useAppStore((s) => s.settings?.commitMessageAi)
+  const effectiveCommitMessageAgentId = useMemo(
+    () => resolveCommitMessageAgentChoice(commitMessageAi?.agentId, settings?.defaultTuiAgent),
+    [commitMessageAi?.agentId, settings?.defaultTuiAgent]
+  )
   const filterInputRef = useRef<HTMLInputElement>(null)
   const commitMessage = readCommitDraftForWorktree(commitDrafts, activeWorktreeId)
   const commitError = commitErrors[activeWorktreeId ?? ''] ?? null
@@ -982,11 +990,11 @@ function SourceControlInner(): React.JSX.Element {
     if (generateInFlightRef.current[activeWorktreeId]) {
       return
     }
-    if (!commitMessageAi?.enabled || !commitMessageAi.agentId) {
+    if (!commitMessageAi?.enabled || !effectiveCommitMessageAgentId) {
       return
     }
 
-    if (commitMessageAi.agentId === 'custom') {
+    if (isCustomAgentId(effectiveCommitMessageAgentId)) {
       const command = commitMessageAi.customAgentCommand?.trim() ?? ''
       if (!command) {
         setGenerateErrors((prev) => ({
@@ -1045,7 +1053,7 @@ function SourceControlInner(): React.JSX.Element {
       setGenerateInFlightByWorktree((prev) => ({ ...prev, [activeWorktreeId]: false }))
       generateInFlightRef.current[activeWorktreeId] = false
     }
-  }, [activeWorktreeId, commitMessageAi, worktreePath])
+  }, [activeWorktreeId, commitMessageAi, effectiveCommitMessageAgentId, worktreePath])
 
   const handleCancelGenerate = useCallback((): void => {
     if (!activeWorktreeId || !worktreePath) {
@@ -2488,11 +2496,11 @@ function SourceControlInner(): React.JSX.Element {
               aiEnabled={commitMessageAi?.enabled === true}
               aiAgentConfigured={
                 commitMessageAi?.enabled === true &&
-                commitMessageAi.agentId !== null &&
+                effectiveCommitMessageAgentId !== null &&
                 // Why: 'custom' is configured only once the user types a command.
                 // Without this guard, Generate would spawn an empty command and
                 // fail with a confusing error.
-                (commitMessageAi.agentId !== 'custom' ||
+                (!isCustomAgentId(effectiveCommitMessageAgentId) ||
                   (commitMessageAi.customAgentCommand ?? '').trim().length > 0)
               }
               isGenerating={isGenerating}
@@ -3048,16 +3056,23 @@ export function CommitArea({
             // swap to a Square ("stop") with a destructive tint so the user
             // sees that clicking will abort the run. Group/group-hover toggles
             // keep this stateless on the React side.
-            <button
-              type="button"
-              onClick={() => onCancelGenerate()}
-              title="Stop generating"
-              aria-label="Stop generating commit message"
-              className="group absolute right-1.5 top-1.5 inline-flex size-5 items-center justify-center rounded text-muted-foreground transition-colors hover:bg-destructive/10 hover:text-destructive focus-visible:bg-destructive/10 focus-visible:text-destructive focus-visible:outline-none focus-visible:ring-1 focus-visible:ring-destructive/40"
-            >
-              <RefreshCw className="size-3.5 animate-spin group-hover:hidden group-focus-visible:hidden" />
-              <Square className="hidden size-3.5 fill-current group-hover:block group-focus-visible:block" />
-            </button>
+            <Tooltip>
+              <TooltipTrigger asChild>
+                <button
+                  type="button"
+                  onClick={() => onCancelGenerate()}
+                  title="Stop generating"
+                  aria-label="Stop generating commit message"
+                  className="group absolute right-1.5 top-1.5 inline-flex size-5 items-center justify-center rounded text-muted-foreground transition-colors hover:bg-destructive/10 hover:text-destructive focus-visible:bg-destructive/10 focus-visible:text-destructive focus-visible:outline-none focus-visible:ring-1 focus-visible:ring-destructive/40"
+                >
+                  <RefreshCw className="size-3.5 animate-spin group-hover:hidden group-focus-visible:hidden" />
+                  <Square className="hidden size-3.5 fill-current group-hover:block group-focus-visible:block" />
+                </button>
+              </TooltipTrigger>
+              <TooltipContent side="left" sideOffset={6}>
+                Generating commit message. Click to stop.
+              </TooltipContent>
+            </Tooltip>
           ) : (
             <button
               type="button"
diff --git a/src/renderer/src/components/settings/CommitMessageAiPane.test.tsx b/src/renderer/src/components/settings/CommitMessageAiPane.test.tsx
index 464bf60c9..dd1c16b22 100644
--- a/src/renderer/src/components/settings/CommitMessageAiPane.test.tsx
+++ b/src/renderer/src/components/settings/CommitMessageAiPane.test.tsx
@@ -87,6 +87,28 @@ describe('CommitMessageAiPane', () => {
     expect(markup).toContain('ollama run llama3.1 {prompt}')
   })
 
+  it('shows an unconfigured state when the default agent is unsupported', () => {
+    const markup = renderPane(
+      buildSettings({
+        defaultTuiAgent: 'gemini',
+        commitMessageAi: {
+          enabled: true,
+          agentId: null,
+          selectedModelByAgent: {},
+          selectedThinkingByModel: {},
+          customPrompt: '',
+          customAgentCommand: ''
+        }
+      })
+    )
+
+    expect(markup).toContain('Not configured')
+    expect(markup).toContain('Your default agent is Gemini')
+    expect(markup).toContain('Choose Claude, Codex, or Custom')
+    expect(markup).not.toContain('Which model the selected agent uses')
+    expect(markup).not.toContain('Thinking effort')
+  })
+
   it('keeps custom command discoverable in settings search metadata', () => {
     const customCommandEntry = COMMIT_MESSAGE_AI_PANE_SEARCH_ENTRIES.find(
       (entry) => entry.title === 'Custom command'
diff --git a/src/renderer/src/components/settings/CommitMessageAiPane.tsx b/src/renderer/src/components/settings/CommitMessageAiPane.tsx
index 19685413b..58887223b 100644
--- a/src/renderer/src/components/settings/CommitMessageAiPane.tsx
+++ b/src/renderer/src/components/settings/CommitMessageAiPane.tsx
@@ -7,11 +7,10 @@ import { Terminal } from 'lucide-react'
 import type { CommitMessageAiSettings, GlobalSettings, TuiAgent } from '../../../../shared/types'
 import {
   CUSTOM_AGENT_ID,
-  DEFAULT_COMMIT_MESSAGE_AGENT_ID,
   getCommitMessageAgentCapability,
   isCustomAgentId,
   listCommitMessageAgentCapabilities,
-  type CommitMessageAgentChoice,
+  resolveCommitMessageAgentChoice,
   type CommitMessageAgentCapability,
   type CommitMessageModelCapability
 } from '../../../../shared/commit-message-agent-spec'
@@ -40,6 +39,8 @@ const EMPTY_SETTINGS: CommitMessageAiSettings = {
   customAgentCommand: ''
 }
 
+const UNCONFIGURED_AGENT_SELECT_VALUE = ''
+
 function readSettings(settings: GlobalSettings): CommitMessageAiSettings {
   return settings.commitMessageAi ?? EMPTY_SETTINGS
 }
@@ -119,9 +120,24 @@ export function CommitMessageAiPane({
   )
 
   const agentCapabilities = useMemo(listCommitMessageAgentCapabilities, [])
-  const activeAgentId: CommitMessageAgentChoice = config.agentId ?? DEFAULT_COMMIT_MESSAGE_AGENT_ID
-  const isCustom = isCustomAgentId(activeAgentId)
-  const activeCapability = isCustom ? undefined : getCommitMessageAgentCapability(activeAgentId)
+  const resolvedAgentId = resolveCommitMessageAgentChoice(config.agentId, settings.defaultTuiAgent)
+  const activeAgentSelectValue = resolvedAgentId ?? UNCONFIGURED_AGENT_SELECT_VALUE
+  const unsupportedDefaultAgent =
+    resolvedAgentId === null &&
+    !config.agentId &&
+    settings.defaultTuiAgent &&
+    settings.defaultTuiAgent !== 'blank'
+      ? settings.defaultTuiAgent
+      : null
+  const unsupportedDefaultAgentLabel = unsupportedDefaultAgent
+    ? (AGENT_CATALOG.find((a) => a.id === unsupportedDefaultAgent)?.label ??
+      unsupportedDefaultAgent)
+    : null
+  const isCustom = isCustomAgentId(resolvedAgentId)
+  const activeCapability =
+    resolvedAgentId && !isCustomAgentId(resolvedAgentId)
+      ? getCommitMessageAgentCapability(resolvedAgentId)
+      : undefined
   const activeModel = activeCapability ? resolveSelectedModel(config, activeCapability) : null
   const activeThinking = activeModel ? resolveSelectedThinking(config, activeModel) : undefined
 
@@ -136,11 +152,15 @@ export function CommitMessageAiPane({
       return
     }
     // Why: when the user enables the feature for the first time, hydrate the
-    // agent / model / thinking choices from provider capabilities so the
-    // Generate button works immediately without forcing them to pick first.
-    // If the user previously persisted 'custom', we keep that and let them
-    // re-edit the command — no implicit reset to a preset.
-    const seedAgentId: TuiAgent | 'custom' = config.agentId ?? DEFAULT_COMMIT_MESSAGE_AGENT_ID
+    // agent / model / thinking choices from their default agent when possible
+    // so Generate works without maintaining a second agent preference. If the
+    // user previously persisted 'custom', keep it and let them re-edit the
+    // command — no implicit reset to a preset.
+    const seedAgentId = resolveCommitMessageAgentChoice(config.agentId, settings.defaultTuiAgent)
+    if (!seedAgentId) {
+      writeConfig({ enabled: true, agentId: null })
+      return
+    }
     const seedCapability = isCustomAgentId(seedAgentId)
       ? undefined
       : getCommitMessageAgentCapability(seedAgentId)
@@ -164,6 +184,9 @@ export function CommitMessageAiPane({
   }
 
   const onAgentChange = (newAgentId: string): void => {
+    if (newAgentId === UNCONFIGURED_AGENT_SELECT_VALUE) {
+      return
+    }
     if (isCustomAgentId(newAgentId)) {
       writeConfig({ agentId: CUSTOM_AGENT_ID })
       return
@@ -317,30 +340,38 @@ export function CommitMessageAiPane({
             worktrees, or the SSH host for remote ones.
           </p>
         </div>
-        <Select value={activeAgentId} onValueChange={onAgentChange}>
-          <SelectTrigger size="sm" className="h-8 text-xs w-[180px]">
-            <SelectValue />
-          </SelectTrigger>
-          <SelectContent>
-            {agentCapabilities.map((capability) => {
-              const id = capability.id
-              return (
-                <SelectItem key={id} value={id} className="cursor-pointer">
-                  <span className="flex items-center gap-2">
-                    <AgentIcon agent={id} size={14} />
-                    <span>{agentLabel(id, capability)}</span>
-                  </span>
-                </SelectItem>
-              )
-            })}
-            <SelectItem value={CUSTOM_AGENT_ID} className="cursor-pointer">
-              <span className="flex items-center gap-2">
-                <Terminal className="size-3.5" />
-                <span>Custom</span>
-              </span>
-            </SelectItem>
-          </SelectContent>
-        </Select>
+        <div className="flex flex-col items-end gap-1">
+          <Select value={activeAgentSelectValue} onValueChange={onAgentChange}>
+            <SelectTrigger size="sm" className="h-8 text-xs w-[180px]">
+              <SelectValue placeholder="Not configured" />
+            </SelectTrigger>
+            <SelectContent>
+              {agentCapabilities.map((capability) => {
+                const id = capability.id
+                return (
+                  <SelectItem key={id} value={id} className="cursor-pointer">
+                    <span className="flex items-center gap-2">
+                      <AgentIcon agent={id} size={14} />
+                      <span>{agentLabel(id, capability)}</span>
+                    </span>
+                  </SelectItem>
+                )
+              })}
+              <SelectItem value={CUSTOM_AGENT_ID} className="cursor-pointer">
+                <span className="flex items-center gap-2">
+                  <Terminal className="size-3.5" />
+                  <span>Custom</span>
+                </span>
+              </SelectItem>
+            </SelectContent>
+          </Select>
+          {unsupportedDefaultAgentLabel ? (
+            <p className="max-w-[260px] text-right text-[11px] text-muted-foreground">
+              Your default agent is {unsupportedDefaultAgentLabel}, which does not support commit
+              message generation yet. Choose Claude, Codex, or Custom.
+            </p>
+          ) : null}
+        </div>
       </SearchableSetting>
     )
   }
@@ -413,8 +444,8 @@ export function CommitMessageAiPane({
         <div className="space-y-0.5">
           <Label>Model</Label>
           <p className="text-xs text-muted-foreground">
-            Smaller models default to lower latency and cost. Pick a larger one if the diffs you
-            review tend to need more reasoning.
+            Defaults to the strongest available model for the selected agent. Pick a smaller one if
+            you prefer lower latency or cost.
           </p>
         </div>
         <Select value={activeModel.id} onValueChange={onModelChange}>
diff --git a/src/shared/commit-message-agent-spec.test.ts b/src/shared/commit-message-agent-spec.test.ts
index d6f6ed158..e08f591fe 100644
--- a/src/shared/commit-message-agent-spec.test.ts
+++ b/src/shared/commit-message-agent-spec.test.ts
@@ -18,9 +18,9 @@ describe('COMMIT_MESSAGE_AGENT_SPECS', () => {
     expect(ids).toEqual(['claude', 'codex'])
   })
 
-  it('uses the smallest model as the default for each agent', () => {
-    expect(COMMIT_MESSAGE_AGENT_SPECS.claude?.defaultModelId).toBe('claude-haiku-4-5')
-    expect(COMMIT_MESSAGE_AGENT_SPECS.codex?.defaultModelId).toBe('gpt-5.4-mini')
+  it('uses the smartest model as the default for each agent', () => {
+    expect(COMMIT_MESSAGE_AGENT_SPECS.claude?.defaultModelId).toBe('claude-opus-4-7')
+    expect(COMMIT_MESSAGE_AGENT_SPECS.codex?.defaultModelId).toBe('gpt-5.5')
   })
 
   it('defaults the agent picker to Claude', () => {
@@ -86,7 +86,7 @@ describe('COMMIT_MESSAGE_AGENT_SPECS', () => {
     expect(codex).toMatchObject({
       id: 'codex',
       label: 'Codex',
-      defaultModelId: 'gpt-5.4-mini'
+      defaultModelId: 'gpt-5.5'
     })
     expect(codex).not.toHaveProperty('binary')
     expect(codex).not.toHaveProperty('buildArgs')
diff --git a/src/shared/commit-message-agent-spec.ts b/src/shared/commit-message-agent-spec.ts
index af4f366cc..6556ae854 100644
--- a/src/shared/commit-message-agent-spec.ts
+++ b/src/shared/commit-message-agent-spec.ts
@@ -94,7 +94,7 @@ export const COMMIT_MESSAGE_AGENT_SPECS: Partial<Record<TuiAgent, CommitMessageA
         defaultThinkingLevel: 'low'
       }
     ],
-    defaultModelId: 'claude-haiku-4-5'
+    defaultModelId: 'claude-opus-4-7'
   },
   codex: {
     id: 'codex',
@@ -118,7 +118,6 @@ export const COMMIT_MESSAGE_AGENT_SPECS: Partial<Record<TuiAgent, CommitMessageA
     ],
     // Why: ordered to match the official `codex` model picker — descending
     // by version so the frontier model lands on top and legacy models trail.
-    // Default still resolves by id (`gpt-5.4-mini`), independent of order.
     models: [
       {
         id: 'gpt-5.5',
@@ -191,7 +190,7 @@ export const COMMIT_MESSAGE_AGENT_SPECS: Partial<Record<TuiAgent, CommitMessageA
         defaultThinkingLevel: 'low'
       }
     ],
-    defaultModelId: 'gpt-5.4-mini'
+    defaultModelId: 'gpt-5.5'
   }
 }
 
@@ -205,6 +204,7 @@ export const DEFAULT_COMMIT_MESSAGE_AGENT_ID: TuiAgent = 'claude'
 export const CUSTOM_AGENT_ID = 'custom' as const
 export type CustomAgentId = typeof CUSTOM_AGENT_ID
 export type CommitMessageAgentChoice = TuiAgent | CustomAgentId
+export type DefaultTuiAgentPreference = TuiAgent | 'blank' | null | undefined
 
 export function isCustomAgentId(id: string | null | undefined): id is CustomAgentId {
   return id === CUSTOM_AGENT_ID
@@ -214,6 +214,19 @@ export function getCommitMessageAgentSpec(agentId: TuiAgent): CommitMessageAgent
   return COMMIT_MESSAGE_AGENT_SPECS[agentId]
 }
 
+export function resolveCommitMessageAgentChoice(
+  configuredAgentId: CommitMessageAgentChoice | null | undefined,
+  defaultTuiAgent: DefaultTuiAgentPreference
+): CommitMessageAgentChoice | null {
+  if (configuredAgentId) {
+    return configuredAgentId
+  }
+  if (defaultTuiAgent && defaultTuiAgent !== 'blank') {
+    return getCommitMessageAgentSpec(defaultTuiAgent) ? defaultTuiAgent : null
+  }
+  return DEFAULT_COMMIT_MESSAGE_AGENT_ID
+}
+
 export function getCommitMessageModel(
   agentId: TuiAgent,
   modelId: string
diff --git a/src/shared/commit-message-generation.ts b/src/shared/commit-message-generation.ts
index 2c3eee8c1..fb2d2c3cb 100644
--- a/src/shared/commit-message-generation.ts
+++ b/src/shared/commit-message-generation.ts
@@ -45,7 +45,7 @@ export function buildCommitMessagePrompt(
     '- Optional body: blank line, then short wrapped bullet points or prose explaining WHY.',
     '- Capture the primary user-visible or developer-visible change.',
     '- Use only the staged changes below as context.',
-    '- Do not include "Co-authored-by" trailers - Orca appends them after generation when configured.',
+    '- Do not include "Co-authored-by" or other git trailers.',
     '',
     `Branch: ${context.branch ?? '(detached)'}`,
     '',
diff --git a/src/shared/constants.test.ts b/src/shared/constants.test.ts
index e361daa9e..e5cf126fa 100644
--- a/src/shared/constants.test.ts
+++ b/src/shared/constants.test.ts
@@ -9,4 +9,12 @@ describe('getDefaultSettings', () => {
   it('enables separate light terminal theme by default', () => {
     expect(getDefaultSettings('/tmp').terminalUseSeparateLightTheme).toBe(true)
   })
+
+  it('enables AI commit messages by default without pinning a separate agent', () => {
+    expect(getDefaultSettings('/tmp').commitMessageAi).toMatchObject({
+      enabled: true,
+      agentId: null,
+      selectedModelByAgent: {}
+    })
+  })
 })
diff --git a/src/shared/constants.ts b/src/shared/constants.ts
index 4c11d089b..3e21a440a 100644
--- a/src/shared/constants.ts
+++ b/src/shared/constants.ts
@@ -274,12 +274,12 @@ export function getDefaultSettings(homedir: string): GlobalSettings {
       lastViewByProject: {},
       activeProject: null
     },
-    // Why: opt-in feature — `enabled: false` keeps the Generate button hidden
-    // for existing users until they discover and turn it on in Settings. The
-    // per-agent / per-model maps stay empty until the user activates the
-    // toggle, at which point the pane fills them with the spec defaults.
+    // Why: default-on uses the user's default agent when it supports
+    // non-interactive commit-message generation. Keep agent/model maps empty
+    // so first use follows the default agent's configured default model instead
+    // of freezing a stale choice into new profiles.
     commitMessageAi: {
-      enabled: false,
+      enabled: true,
       agentId: null,
       selectedModelByAgent: {},
       selectedThinkingByModel: {},