diff --git a/src/renderer/src/hooks/composer-state/composer-submit-orchestration.ts b/src/renderer/src/hooks/composer-state/composer-submit-orchestration.ts
index 09f9e8f8b94..023a7263b86 100644
--- a/src/renderer/src/hooks/composer-state/composer-submit-orchestration.ts
+++ b/src/renderer/src/hooks/composer-state/composer-submit-orchestration.ts
@@ -77,7 +77,6 @@ export function useComposerSubmitOrchestration(
     repoId: target.initialTargetState.repoId,
     resolvedSetupDecision: target.derivedComposerState.resolvedSetupDecision,
     selectedRepo: target.runtimeTargetSelection.selectedRepo,
-    selectedRepoAgentLaunchPlatform: target.runtimeTargetSelection.selectedRepoAgentLaunchPlatform,
     selectedRepoExecutionHostId: target.runtimeTargetSelection.selectedRepoExecutionHostId,
     selectedRepoIsGit: target.runtimeTargetSelection.selectedRepoIsGit,
     selectedRepoIsRemote: target.runtimeTargetSelection.selectedRepoIsRemote,
diff --git a/src/renderer/src/hooks/composer-state/full-creation-execution.test.ts b/src/renderer/src/hooks/composer-state/full-creation-execution.test.ts
index 71a81019e03..0ec9cf9baef 100644
--- a/src/renderer/src/hooks/composer-state/full-creation-execution.test.ts
+++ b/src/renderer/src/hooks/composer-state/full-creation-execution.test.ts
@@ -79,7 +79,6 @@ describe('useFullCreationExecution cancellation', () => {
         .fn<FullCreationExecutionInput['prepareFullSubmit']>()
         .mockResolvedValue(prepared),
       resolvedInitialWorkspaceStatus: undefined,
-      selectedRepoAgentLaunchPlatform: 'darwin',
       selectedRepoExecutionHostId: 'local',
       selectedRepoIsGit: true,
       selectedRepoIsRemote: false,
diff --git a/src/renderer/src/hooks/composer-state/full-creation-execution.ts b/src/renderer/src/hooks/composer-state/full-creation-execution.ts
index 3787b18b31c..80844c86331 100644
--- a/src/renderer/src/hooks/composer-state/full-creation-execution.ts
+++ b/src/renderer/src/hooks/composer-state/full-creation-execution.ts
@@ -17,7 +17,6 @@ export type FullCreationExecutionInput = Pick<
   | 'persistSetupAgentStartupPolicy'
   | 'prepareFullSubmit'
   | 'resolvedInitialWorkspaceStatus'
-  | 'selectedRepoAgentLaunchPlatform'
   | 'selectedRepoExecutionHostId'
   | 'selectedRepoIsGit'
   | 'selectedRepoIsRemote'
@@ -34,7 +33,7 @@ import type { PendingSmartGitHubSubmitResolution } from './source-selection-deci
 import { translate } from '@/i18n/i18n'
 import { settleComposerSubmit } from '@/lib/composer-submit-cancellation'
 import { toFolderWorkspaceLinkedTask } from '@/components/sidebar/folder-workspace-composer-helpers'
-import { ensureAgentStartupInTerminal } from '@/lib/new-workspace'
+import { CLIENT_PLATFORM, ensureAgentStartupInTerminal } from '@/lib/new-workspace'
 import { createBrowserUuid } from '@/lib/browser-uuid'
 import { activateAndRevealWorktree } from '@/lib/worktree-activation'
 import { seedNativeChatAppliedSessionOptions } from '@/components/native-chat/native-chat-session-option-cache'
@@ -66,7 +65,6 @@ export function useFullCreationExecution(input: FullCreationExecutionInput) {
     persistSetupAgentStartupPolicy,
     prepareFullSubmit,
     resolvedInitialWorkspaceStatus,
-    selectedRepoAgentLaunchPlatform,
     selectedRepoExecutionHostId,
     selectedRepoIsGit,
     selectedRepoIsRemote,
@@ -142,7 +140,7 @@ export function useFullCreationExecution(input: FullCreationExecutionInput) {
         agent: tuiAgent,
         settings,
         executionHostId: selectedRepoExecutionHostId ?? 'local',
-        platform: selectedRepoAgentLaunchPlatform,
+        platform: CLIENT_PLATFORM,
         hostCapabilities: readLocalRuntimeCapabilities(),
         workspaceKind: selectedRepoIsGit ? 'git-worktree' : 'folder',
         promptDelivery: startupPlan?.draftPrompt ? 'draft' : 'auto-submit',
@@ -301,7 +299,6 @@ export function useFullCreationExecution(input: FullCreationExecutionInput) {
       persistSetupAgentStartupPolicy,
       prepareFullSubmit,
       resolvedInitialWorkspaceStatus,
-      selectedRepoAgentLaunchPlatform,
       selectedRepoExecutionHostId,
       selectedRepoIsGit,
       selectedRepoIsRemote,
diff --git a/src/renderer/src/hooks/composer-state/quick-creation-execution.ts b/src/renderer/src/hooks/composer-state/quick-creation-execution.ts
index 7ecc0915562..7160cb48b4c 100644
--- a/src/renderer/src/hooks/composer-state/quick-creation-execution.ts
+++ b/src/renderer/src/hooks/composer-state/quick-creation-execution.ts
@@ -51,6 +51,7 @@ import {
   resolveAgentLaunchRoute
 } from '@/lib/agent-launch-routing'
 import { readLocalRuntimeCapabilities } from '@/runtime/local-runtime-capabilities'
+import { CLIENT_PLATFORM } from '@/lib/new-workspace'
 
 export function useQuickCreationExecution(input: QuickCreationExecutionInput) {
   const {
@@ -205,7 +206,7 @@ export function useQuickCreationExecution(input: QuickCreationExecutionInput) {
             executionHostId: ephemeralVmRecipe
               ? 'runtime:pending-ephemeral-vm'
               : (workspaceRunContext?.hostId ?? selectedRepoExecutionHostId ?? 'local'),
-            platform: selectedRepoAgentLaunchPlatform,
+            platform: CLIENT_PLATFORM,
             hostCapabilities: readLocalRuntimeCapabilities(),
             workspaceKind: selectedRepoIsGit ? 'git-worktree' : 'folder',
             promptDelivery: quickDraftPrompt ? 'draft' : 'auto-submit',
diff --git a/src/renderer/src/hooks/useComposerState-host-context-boundaries.test.ts b/src/renderer/src/hooks/useComposerState-host-context-boundaries.test.ts
index 24704283f64..764a033275f 100644
--- a/src/renderer/src/hooks/useComposerState-host-context-boundaries.test.ts
+++ b/src/renderer/src/hooks/useComposerState-host-context-boundaries.test.ts
@@ -660,14 +660,22 @@ describe('useComposerState host-context boundaries', () => {
       'getAgentLaunchPlatformForRepo(selectedRepo, projectRuntime)'
     )
 
-    const fullSubmit = COMPOSER_SOURCE.fullSubmitPreparation + COMPOSER_SOURCE.fullCreation
-    expect(fullSubmit).toContain('platform: selectedRepoAgentLaunchPlatform')
-    expect(fullSubmit).toContain('startupDraft: startupPlan.draftPrompt')
-    expect(fullSubmit).not.toContain('platform: CLIENT_PLATFORM')
+    const fullStartupPlan = sourceBetween(
+      COMPOSER_SOURCE.fullSubmitPreparation,
+      'const startupPlan = buildAgentStartupPlan({',
+      'const shouldSeedInitialAgentStatus ='
+    )
+    expect(fullStartupPlan).toContain('platform: selectedRepoAgentLaunchPlatform')
+    expect(fullStartupPlan).not.toContain('platform: CLIENT_PLATFORM')
+    expect(COMPOSER_SOURCE.fullCreation).toContain('startupDraft: startupPlan.draftPrompt')
 
-    const quickSubmit = COMPOSER_SOURCE.quickCreation
-    expect(quickSubmit).toContain('platform: selectedRepoAgentLaunchPlatform')
-    expect(quickSubmit).not.toContain('platform: CLIENT_PLATFORM')
+    const quickStartupPlan = sourceBetween(
+      COMPOSER_SOURCE.quickCreation,
+      'buildQuickComposerStartup({',
+      'const startupPolicySettlement ='
+    )
+    expect(quickStartupPlan).toContain('platform: selectedRepoAgentLaunchPlatform')
+    expect(quickStartupPlan).not.toContain('platform: CLIENT_PLATFORM')
   })
 
   // Why: activation no longer rebuilds a startup from `createdWithAgent`, so this