fix(automations): stop offering Blank Terminal where it cannot be chosen (#26961)

Blank Terminal is now opt-in on AgentCombobox. Only the new-workspace
composer opts in; automations, source-control agent actions, and chat
continuation offer agents only. The props are a discriminated union so
agent-only callers' onValueChange never receives null.

Fixes STA-9868

src/renderer/src/components/agent-session-continuation/AgentSessionContinuationDialog.test.tsx

@@ -23,8 +23,17 @@ vi.mock('@/lib/agent-catalog', () => ({
   getAgentLabel: () => 'Codex'
 }))
 vi.mock('@/components/agent/AgentCombobox', () => ({
-  default: ({ value }: { value: string | null }) =>
-    React.createElement('div', { 'data-agent': value ?? '' })
+  default: ({
+    value,
+    allowBlankTerminal
+  }: {
+    value: string | null
+    allowBlankTerminal?: boolean
+  }) =>
+    React.createElement('div', {
+      'data-agent': value ?? '',
+      'data-allow-blank': String(allowBlankTerminal === true)
+    })
 }))
 vi.mock('@/components/ui/dialog', () => ({
   Dialog: ({ open, children }: { open: boolean; children?: ReactNode }) =>
@@ -105,5 +114,7 @@ describe('AgentSessionContinuationDialog', () => {
 
     await act(async () => resolveSecond(['codex']))
     await vi.waitFor(() => expect(container.querySelector('[data-agent="codex"]')).not.toBeNull())
+    // Why: continuing a chat needs an agent to resume it into.
+    expect(container.querySelector('[data-allow-blank="false"]')).not.toBeNull()
   })
 })

src/renderer/src/components/agent-session-continuation/AgentSessionContinuationDialog.tsx

@@ -200,12 +200,7 @@ export function AgentSessionContinuationDialog({
               agents={agents}
               value={selectedAgent}
               onValueChange={setSelectedAgent}
-              allowBlankTerminal={false}
               allowNarrowTrigger
-              emptyLabel={translate(
-                'components.agentSessionContinuation.selectAgent',
-                'Select an Agent'
-              )}
               triggerClassName="min-w-0 w-full"
             />
             {detecting ? (

src/renderer/src/components/agent/AgentCombobox.test.tsx

@@ -38,6 +38,7 @@ describe('AgentCombobox', () => {
         agents={AGENT_CATALOG}
         value={null}
         onValueChange={vi.fn()}
+        allowBlankTerminal
         defaultAgent="codex"
         onSetDefault={onSetDefault}
       />
@@ -52,14 +53,7 @@ describe('AgentCombobox', () => {
   it('does not offer a default action for an Agent-only empty state', () => {
     const onSetDefault = vi.fn()
     render(
-      <AgentCombobox
-        agents={[]}
-        value={null}
-        onValueChange={vi.fn()}
-        allowBlankTerminal={false}
-        emptyLabel="Select an Agent"
-        onSetDefault={onSetDefault}
-      />
+      <AgentCombobox agents={[]} value={null} onValueChange={vi.fn()} onSetDefault={onSetDefault} />
     )
 
     fireEvent.contextMenu(screen.getByRole('combobox'))
@@ -162,21 +156,41 @@ describe('AgentCombobox', () => {
     }
   })
 
-  it('supports an Agent-only empty state without presenting a blank terminal', () => {
+  it('defaults to an Agent-only empty state without presenting a blank terminal', () => {
     const markup = renderToStaticMarkup(
-      <AgentCombobox
-        agents={[]}
-        value={null}
-        onValueChange={vi.fn()}
-        allowBlankTerminal={false}
-        emptyLabel="Select an Agent"
-      />
+      <AgentCombobox agents={[]} value={null} onValueChange={vi.fn()} />
     )
 
     expect(markup).toContain('Select an Agent')
     expect(markup).not.toContain('Blank Terminal')
   })
 
+  it('hides Blank Terminal from the list unless the caller opts in', () => {
+    render(<AgentCombobox agents={AGENT_CATALOG} value="codex" onValueChange={vi.fn()} />)
+
+    fireEvent.click(screen.getByRole('combobox'))
+
+    expect(screen.getByRole('option', { name: 'Claude' })).toBeTruthy()
+    expect(screen.queryByRole('option', { name: 'Blank Terminal' })).toBeNull()
+  })
+
+  it('offers Blank Terminal and reports null when the caller opts in', () => {
+    const onValueChange = vi.fn()
+    render(
+      <AgentCombobox
+        agents={AGENT_CATALOG}
+        value="codex"
+        onValueChange={onValueChange}
+        allowBlankTerminal
+      />
+    )
+
+    fireEvent.click(screen.getByRole('combobox'))
+    fireEvent.click(screen.getByRole('option', { name: 'Blank Terminal' }))
+
+    expect(onValueChange).toHaveBeenCalledWith(null)
+  })
+
   it('uses the bundled OpenClaude favicon crop instead of Claude or GitHub artwork', () => {
     const markup = renderToStaticMarkup(<AgentIcon agent="openclaude" />)
 

src/renderer/src/components/agent/AgentCombobox.tsx

@@ -32,11 +32,15 @@ import { translate } from '@/i18n/i18n'
 
 type DefaultAgentPreference = TuiAgent | 'blank' | null
 
-type AgentComboboxProps = {
+// Why: Blank Terminal is opt-in so agent-only flows (automations, source-control
+// actions) never offer a choice they cannot run, and never receive null for it.
+type AgentComboboxSelectionProps =
+  | { allowBlankTerminal: true; onValueChange: (agent: TuiAgent | null) => void }
+  | { allowBlankTerminal?: false; onValueChange: (agent: TuiAgent) => void }
+
+type AgentComboboxProps = AgentComboboxSelectionProps & {
   agents: AgentCatalogEntry[]
   value: TuiAgent | null
-  onValueChange: (agent: TuiAgent | null) => void
-  onValueSelected?: (agent: TuiAgent | null) => void
   onOpenManageAgents?: () => void
   /** Current saved default agent preference. Used to render a subtle "default"
    *  indicator in the list and to tell which right-click menu item is the
@@ -51,8 +55,6 @@ type AgentComboboxProps = {
    *  field as the last keyboard-submit step. */
   onTriggerEnter?: () => void
   allowNarrowTrigger?: boolean
-  allowBlankTerminal?: boolean
-  emptyLabel?: string
 }
 
 const BLANK_VALUE = '__none__'
@@ -150,17 +152,15 @@ function renderItem({
 export default function AgentCombobox({
   agents,
   value,
-  onValueChange,
-  onValueSelected,
   onOpenManageAgents,
   defaultAgent,
   onSetDefault,
   triggerClassName,
   onTriggerEnter,
   allowNarrowTrigger = false,
-  allowBlankTerminal = true,
-  emptyLabel
+  ...selection
 }: AgentComboboxProps): React.JSX.Element {
+  const allowBlankTerminal = selection.allowBlankTerminal === true
   const [open, setOpen] = useState(false)
   const [query, setQuery] = useState('')
   // Why: controlled cmdk selection so hovering the footer (which lives outside
@@ -251,15 +251,22 @@ export default function AgentCombobox({
     [cancelFocusFrame, value]
   )
 
-  const handleSelect = useCallback(
-    (nextValue: TuiAgent | null) => {
-      onValueChange(nextValue)
-      setOpen(false)
-      setQuery('')
-      onValueSelected?.(nextValue)
-    },
-    [onValueChange, onValueSelected]
-  )
+  const closePicker = useCallback(() => {
+    setOpen(false)
+    setQuery('')
+  }, [])
+
+  const handleSelectAgent = (nextValue: TuiAgent): void => {
+    selection.onValueChange(nextValue)
+    closePicker()
+  }
+
+  const handleSelectBlank = (): void => {
+    if (selection.allowBlankTerminal) {
+      selection.onValueChange(null)
+    }
+    closePicker()
+  }
 
   // Why: mirror RepoCombobox's trigger-keydown handling — the button-style
   // trigger treats the current value as a confirmed selection. Plain focus does
@@ -344,8 +351,15 @@ export default function AgentCombobox({
                 <AgentIconLabel
                   icon={<Terminal className="size-3.5" />}
                   label={
-                    emptyLabel ??
-                    translate('auto.components.agent.AgentCombobox.986f946354', 'Blank Terminal')
+                    allowBlankTerminal
+                      ? translate(
+                          'auto.components.agent.AgentCombobox.986f946354',
+                          'Blank Terminal'
+                        )
+                      : translate(
+                          'components.agentSessionContinuation.selectAgent',
+                          'Select an Agent'
+                        )
                   }
                 />
               )}
@@ -388,7 +402,7 @@ export default function AgentCombobox({
                     itemValue: BLANK_VALUE,
                     isChecked: value === null,
                     isDefault: defaultAgent === 'blank',
-                    onSelect: () => handleSelect(null),
+                    onSelect: handleSelectBlank,
                     onSetDefault: onSetDefault ? () => onSetDefault('blank') : undefined,
                     icon: <Terminal className="size-3.5" />,
                     label: translate(
@@ -403,7 +417,7 @@ export default function AgentCombobox({
                   itemValue: agent.id,
                   isChecked: value === agent.id,
                   isDefault: defaultAgent === agent.id,
-                  onSelect: () => handleSelect(agent.id),
+                  onSelect: () => handleSelectAgent(agent.id),
                   onSetDefault: onSetDefault ? () => onSetDefault(agent.id) : undefined,
                   icon: <AgentIcon agent={agent.id} />,
                   label: agent.label

src/renderer/src/components/automations/AutomationEditorSettingsSidebar.test.tsx

@@ -0,0 +1,80 @@
+// @vitest-environment happy-dom
+
+import { cleanup, fireEvent, render, screen } from '@testing-library/react'
+import { afterEach, describe, expect, it, vi } from 'vitest'
+import { AGENT_CATALOG } from '@/lib/agent-catalog'
+import type { AutomationDraft } from './AutomationEditorDialog'
+import { AutomationEditorSettingsSidebar } from './AutomationEditorSettingsSidebar'
+
+// Why: only the Agent field is under test; the sibling fields own their own coverage.
+vi.mock('./AutomationProjectCombobox', () => ({ default: () => null }))
+vi.mock('./AutomationWorkspaceField', () => ({ AutomationWorkspaceField: () => null }))
+vi.mock('./AutomationSessionField', () => ({ AutomationSessionField: () => null }))
+vi.mock('./AutomationSchedulePicker', () => ({ AutomationSchedulePicker: () => null }))
+vi.mock('./AutomationMissedRunGraceField', () => ({ AutomationMissedRunGraceField: () => null }))
+vi.mock('./AutomationPrecheckFields', () => ({ AutomationPrecheckFields: () => null }))
+vi.mock('./AutomationSetupDecisionField', () => ({ AutomationSetupDecisionField: () => null }))
+vi.mock('./AutomationDestinationField', () => ({ AutomationDestinationField: () => null }))
+vi.mock('./AutomationExtraAgentArgsField', () => ({ AutomationExtraAgentArgsField: () => null }))
+
+const DRAFT: AutomationDraft = {
+  name: '',
+  prompt: '',
+  agentId: 'codex',
+  extraAgentArgs: '',
+  projectId: '',
+  workspaceMode: 'existing',
+  workspaceId: '',
+  baseBranch: '',
+  reuseSession: false,
+  precheckCommand: '',
+  precheckTimeoutSeconds: '30',
+  preset: 'weekly',
+  time: '09:15',
+  dayOfWeek: '5',
+  customSchedule: '',
+  missedRunGraceMinutes: '720',
+  savedSchedule: null,
+  scheduleWarning: null
+}
+
+function renderSidebar(onDraftChange: (updater: (d: AutomationDraft) => AutomationDraft) => void) {
+  return render(
+    <AutomationEditorSettingsSidebar
+      isHermesTarget={false}
+      isHermesCreate={false}
+      repos={[]}
+      projectHostSetups={[]}
+      automationYamlHooksByRepoKey={{}}
+      getAutomationHooksCacheKey={(repoId) => repoId}
+      repoMap={new Map()}
+      worktrees={[]}
+      settings={null}
+      draft={DRAFT}
+      visibleAgents={AGENT_CATALOG}
+      pickerTriggerClassName=""
+      segmentedGroupClassName=""
+      segmentedItemClassName=""
+      onProjectChange={vi.fn()}
+      onDraftChange={onDraftChange}
+      onSetupDecisionTouched={vi.fn()}
+    />
+  )
+}
+
+afterEach(cleanup)
+
+describe('AutomationEditorSettingsSidebar agent picker', () => {
+  it('offers agents only, never Blank Terminal', () => {
+    const onDraftChange = vi.fn()
+    renderSidebar(onDraftChange)
+
+    fireEvent.click(screen.getByRole('combobox'))
+
+    expect(screen.queryByRole('option', { name: 'Blank Terminal' })).toBeNull()
+    fireEvent.click(screen.getByRole('option', { name: 'Claude' }))
+    expect(onDraftChange).toHaveBeenCalledTimes(1)
+    const updater = onDraftChange.mock.calls[0][0]
+    expect(updater(DRAFT).agentId).toBe('claude')
+  })
+})

src/renderer/src/components/automations/AutomationEditorSettingsSidebar.tsx

@@ -102,9 +102,7 @@ export function AutomationEditorSettingsSidebar({
                 <AgentCombobox
                   agents={visibleAgents}
                   value={draft.agentId}
-                  onValueChange={(agentId) =>
-                    agentId && onDraftChange((current) => ({ ...current, agentId }))
-                  }
+                  onValueChange={(agentId) => onDraftChange((current) => ({ ...current, agentId }))}
                   defaultAgent={settings?.defaultTuiAgent ?? null}
                   triggerClassName={`h-9 w-full min-w-0 ${pickerTriggerClassName}`}
                   allowNarrowTrigger

src/renderer/src/components/new-workspace/NewWorkspaceComposerAgentSection.test.tsx

@@ -0,0 +1,36 @@
+// @vitest-environment happy-dom
+
+import { cleanup, fireEvent, render, screen } from '@testing-library/react'
+import { afterEach, describe, expect, it, vi } from 'vitest'
+import { TooltipProvider } from '@/components/ui/tooltip'
+import { AGENT_CATALOG } from '@/lib/agent-catalog'
+import { NewWorkspaceComposerAgentSection } from './NewWorkspaceComposerAgentSection'
+
+afterEach(cleanup)
+
+describe('NewWorkspaceComposerAgentSection agent picker', () => {
+  it('offers Blank Terminal because a workspace can start without an agent', () => {
+    const onQuickAgentChange = vi.fn()
+    render(
+      <TooltipProvider>
+        <NewWorkspaceComposerAgentSection
+          quickAgent="codex"
+          onQuickAgentChange={onQuickAgentChange}
+          onOpenAgentSettings={vi.fn()}
+          createDisabled={false}
+          onCreate={vi.fn()}
+          advancedOpen={false}
+          onToggleAdvanced={vi.fn()}
+          visibleQuickAgents={AGENT_CATALOG}
+          defaultTuiAgent="blank"
+          handleSetDefaultAgent={vi.fn()}
+        />
+      </TooltipProvider>
+    )
+
+    fireEvent.click(screen.getByRole('combobox'))
+    fireEvent.click(screen.getByRole('option', { name: 'Blank Terminal' }))
+
+    expect(onQuickAgentChange).toHaveBeenCalledWith(null)
+  })
+})

src/renderer/src/components/new-workspace/NewWorkspaceComposerAgentSection.tsx

@@ -71,6 +71,7 @@ export function NewWorkspaceComposerAgentSection({
           agents={visibleQuickAgents}
           value={quickAgent}
           onValueChange={onQuickAgentChange}
+          allowBlankTerminal
           onOpenManageAgents={onOpenAgentSettings}
           defaultAgent={defaultTuiAgent}
           onSetDefault={handleSetDefaultAgent}

src/renderer/src/components/right-sidebar/SourceControlAgentActionDialogForm.test.tsx

@@ -6,8 +6,17 @@ import type { GlobalSettings } from '../../../../shared/global-settings-types'
 import type { Repo } from '../../../../shared/repo-types'
 
 vi.mock('@/components/agent/AgentCombobox', () => ({
-  default: ({ value }: { value: string | null }) =>
-    React.createElement('div', { 'data-agent-value': value ?? '' })
+  default: ({
+    value,
+    allowBlankTerminal
+  }: {
+    value: string | null
+    allowBlankTerminal?: boolean
+  }) =>
+    React.createElement('div', {
+      'data-agent-value': value ?? '',
+      'data-allow-blank': String(allowBlankTerminal === true)
+    })
 }))
 
 vi.mock('@/components/ui/dialog', () => ({
@@ -110,6 +119,10 @@ describe('SourceControlAgentActionDialogForm', () => {
     expect(markup).toContain('Resolve the merge conflicts reported for this pull request.')
   })
 
+  it('offers agents only, since an action cannot start without one', () => {
+    expect(renderForm()).toContain('data-allow-blank="false"')
+  })
+
   it('checks already-saved copy against the selected save target', () => {
     const settings = settingsWithSavedGlobalRecipe()
     const saveTargets = [