diff --git a/config/scripts/rebuild-native-deps-node-pty.test.mjs b/config/scripts/rebuild-native-deps-node-pty.test.mjs
index 871732dd53d..c3a8f9bbd83 100644
--- a/config/scripts/rebuild-native-deps-node-pty.test.mjs
+++ b/config/scripts/rebuild-native-deps-node-pty.test.mjs
@@ -173,6 +173,28 @@ describe('rebuild-native-deps patched node-pty rebuild', () => {
     }
   })
 
+  it('refuses a Windows rebuild when the process creation-time patch is missing', () => {
+    const projectDir = mkTempProject()
+
+    try {
+      writeFakeUsableElectronPackage(projectDir, { platform: 'win32' })
+      writeFakeElectronRebuild(projectDir)
+      writeFakeNodePtyConptyPayload(projectDir, 'x64')
+      writeFakeWindowsProcessTreeWithNodeAddonApi(projectDir, { creationTimePatchApplied: false })
+
+      const result = runRebuildScript(
+        projectDir,
+        { npm_config_platform: 'win32', npm_config_arch: 'x64' },
+        ['--platform=win32', '--arch=x64', '--force']
+      )
+
+      expect(result.status).not.toBe(0)
+      expect(result.stderr).toContain('process creation-time patch')
+    } finally {
+      removeTreeSync(projectDir)
+    }
+  })
+
   it('restores the ConPTY runtime payload after a Windows Electron rebuild', () => {
     const projectDir = mkTempProject()
 
diff --git a/config/scripts/rebuild-native-deps-test-fixtures.mjs b/config/scripts/rebuild-native-deps-test-fixtures.mjs
index 2cb7d8ba8b4..db5af45a454 100644
--- a/config/scripts/rebuild-native-deps-test-fixtures.mjs
+++ b/config/scripts/rebuild-native-deps-test-fixtures.mjs
@@ -374,13 +374,18 @@ export function writeFakeWindowsProcessTree(projectDir) {
 
 export function writeFakeWindowsProcessTreeWithNodeAddonApi(
   projectDir,
-  { commandLinePatchApplied = true } = {}
+  { commandLinePatchApplied = true, creationTimePatchApplied = true } = {}
 ) {
   const processTreeDir = join(projectDir, 'node_modules', '@vscode', 'windows-process-tree')
   const nodeAddonApiDir = join(processTreeDir, 'node_modules', 'node-addon-api')
   mkdirSync(nodeAddonApiDir, { recursive: true })
   writeFileSync(join(processTreeDir, 'package.json'), '{"dependencies":{"node-addon-api":"*"}}\n')
-  writeFileSync(join(processTreeDir, 'index.js'), 'module.exports = {}\n')
+  writeFileSync(
+    join(processTreeDir, 'index.js'),
+    creationTimePatchApplied
+      ? 'exports.ProcessDataFlag = { None: 0, Memory: 1, CommandLine: 2, CreationTime: 4 }\n'
+      : 'exports.ProcessDataFlag = { None: 0, Memory: 1, CommandLine: 2 }\n'
+  )
   mkdirSync(join(processTreeDir, 'src'), { recursive: true })
   writeFileSync(
     join(processTreeDir, 'src', 'process_commandline.cc'),
@@ -388,6 +393,36 @@ export function writeFakeWindowsProcessTreeWithNodeAddonApi(
       ? '// kProcessCommandLineInformation = 60\n'
       : unpatchedWindowsProcessTreeCommandLineSource()
   )
+  writeFileSync(
+    join(processTreeDir, 'src', 'process.h'),
+    creationTimePatchApplied
+      ? 'enum ProcessDataFlags { NONE = 0, MEMORY = 1, COMMANDLINE = 2, CREATIONTIME = 4 };\nULONGLONG creationTimeMs;\n'
+      : 'enum ProcessDataFlags { NONE = 0, MEMORY = 1, COMMANDLINE = 2 };\n'
+  )
+  writeFileSync(
+    join(processTreeDir, 'src', 'process.cc'),
+    creationTimePatchApplied
+      ? 'GetProcessCreationTime(pinfo);\nGetProcessTimes(hProcess, &creationTime, &exitTime, &kernelTime, &userTime);\n'
+      : 'GetProcessMemoryUsage(pinfo);\n'
+  )
+  writeFileSync(
+    join(processTreeDir, 'src', 'process_worker.cc'),
+    creationTimePatchApplied ? 'object.Set("creationTimeMs", process.creationTimeMs);\n' : '\n'
+  )
+  mkdirSync(join(processTreeDir, 'lib'), { recursive: true })
+  writeFileSync(
+    join(processTreeDir, 'lib', 'index.js'),
+    creationTimePatchApplied ? 'exports.ProcessDataFlag["CreationTime"] = 4;\n' : '\n'
+  )
+  writeFileSync(
+    join(processTreeDir, 'lib', 'index.ts'),
+    creationTimePatchApplied ? 'export enum ProcessDataFlag { CreationTime = 4 }\n' : '\n'
+  )
+  mkdirSync(join(processTreeDir, 'typings'), { recursive: true })
+  writeFileSync(
+    join(processTreeDir, 'typings', 'windows-process-tree.d.ts'),
+    creationTimePatchApplied ? 'creationTimeMs?: number\n' : '\n'
+  )
   writeFileSync(join(nodeAddonApiDir, 'package.json'), '{"name":"node-addon-api"}\n')
   writeFileSync(join(nodeAddonApiDir, 'napi.h'), '// napi.h\n')
   writeFileSync(join(nodeAddonApiDir, 'napi-inl.h'), '// napi-inl.h\n')
diff --git a/config/scripts/windows-process-tree-gyp-rebuild.mjs b/config/scripts/windows-process-tree-gyp-rebuild.mjs
index 20d91e55497..6f21fb2a153 100644
--- a/config/scripts/windows-process-tree-gyp-rebuild.mjs
+++ b/config/scripts/windows-process-tree-gyp-rebuild.mjs
@@ -33,6 +33,17 @@ export const WINDOWS_PROCESS_TREE_PATCH_PATH = join(
 /** Only the patched reader defines this; the upstream one walks the PEB. */
 const COMMAND_LINE_PATCH_MARKER = 'kProcessCommandLineInformation'
 
+const CREATION_TIME_PATCH_MARKERS = [
+  ['src/process.h', 'CREATIONTIME = 4'],
+  ['src/process.h', 'ULONGLONG creationTimeMs'],
+  ['src/process.cc', 'GetProcessCreationTime(pinfo)'],
+  ['src/process.cc', 'GetProcessTimes(hProcess, &creationTime'],
+  ['src/process_worker.cc', 'object.Set("creationTimeMs"'],
+  ['lib/index.js', '["CreationTime"] = 4'],
+  ['lib/index.ts', 'CreationTime = 4'],
+  ['typings/windows-process-tree.d.ts', 'creationTimeMs?: number']
+]
+
 export const WINDOWS_PROCESS_TREE_NODE_ADDON_API_HEADERS = [
   'napi.h',
   'napi-inl.h',
@@ -83,6 +94,36 @@ export function inspectWindowsProcessTreeAddon(addonPath) {
   return readFileSync(addonPath).includes(FLAGGED_IMPORT) ? 'unpatched' : 'clean'
 }
 
+export function assertWindowsProcessTreeCreationTimePatch(
+  packageDir = WINDOWS_PROCESS_TREE_PACKAGE_DIR
+) {
+  for (const [relativePath, expected] of CREATION_TIME_PATCH_MARKERS) {
+    const filePath = join(packageDir, relativePath)
+    if (!existsSync(filePath)) {
+      throw new Error(
+        `${filePath} is missing, so the process creation-time patch cannot be verified. ` +
+          'Run pnpm install.'
+      )
+    }
+    if (!readFileSync(filePath, 'utf8').includes(expected)) {
+      throw new Error(
+        `${relativePath} does not contain the process creation-time patch (${expected}). ` +
+          'Run pnpm install.'
+      )
+    }
+  }
+}
+
+export function assertWindowsProcessTreeRuntimeCreationTime(windowsProcessTree) {
+  if (windowsProcessTree?.ProcessDataFlag?.CreationTime !== 4) {
+    throw new Error(
+      '@vscode/windows-process-tree does not expose ProcessDataFlag.CreationTime, so native ' +
+        'Windows structured agent-session process ownership cannot be PID-reuse safe. Rebuild it ' +
+        '(pnpm run rebuild:electron) rather than using the published prebuild.'
+    )
+  }
+}
+
 /**
  * Refuse to compile or load the upstream command-line reader.
  *
@@ -159,6 +200,7 @@ export function ensureWindowsProcessTreeCommandLinePatch(
     rmSync(windowsProcessTreeAddonPath(packageDir), { force: true })
     repaired = true
   }
+  assertWindowsProcessTreeCreationTimePatch(packageDir)
 
   return repaired
 }
diff --git a/config/scripts/windows-process-tree-gyp-rebuild.test.mjs b/config/scripts/windows-process-tree-gyp-rebuild.test.mjs
index f2939b71179..56bd9a385c7 100644
--- a/config/scripts/windows-process-tree-gyp-rebuild.test.mjs
+++ b/config/scripts/windows-process-tree-gyp-rebuild.test.mjs
@@ -12,12 +12,15 @@ import { tmpdir } from 'node:os'
 import { join, resolve } from 'node:path'
 import { afterEach, beforeEach, describe, expect, it } from 'vitest'
 import {
+  assertWindowsProcessTreeCreationTimePatch,
+  assertWindowsProcessTreeRuntimeCreationTime,
   inspectWindowsProcessTreeAddon,
   nodeGypRebuildInvocation,
   stageWindowsProcessTreeNodeAddonApiHeaders,
   WINDOWS_PROCESS_TREE_NODE_ADDON_API_HEADERS,
   WINDOWS_PROCESS_TREE_PACKAGE_DIR
 } from './windows-process-tree-gyp-rebuild.mjs'
+import { writeFakeWindowsProcessTreeWithNodeAddonApi } from './rebuild-native-deps-test-fixtures.mjs'
 
 describe('windows-process-tree node-gyp rebuild', () => {
   it("resolves node-addon-api's gyp target from the rebuild cwd", () => {
@@ -97,3 +100,47 @@ describe('inspecting a compiled windows-process-tree addon', () => {
     expect(inspectWindowsProcessTreeAddon(staged)).toBe('unpatched')
   })
 })
+
+describe('windows-process-tree CreationTime patch assertion', () => {
+  let dir
+
+  beforeEach(() => {
+    dir = mkdtempSync(join(tmpdir(), 'orca-windows-process-tree-creation-time-'))
+  })
+  afterEach(() => {
+    rmSync(dir, { recursive: true, force: true })
+  })
+
+  it('accepts a package whose source and JS surfaces expose process creation time', () => {
+    writeFakeWindowsProcessTreeWithNodeAddonApi(dir)
+
+    expect(() =>
+      assertWindowsProcessTreeCreationTimePatch(
+        join(dir, 'node_modules', '@vscode', 'windows-process-tree')
+      )
+    ).not.toThrow()
+  })
+
+  it('rejects a package missing the process creation-time patch', () => {
+    writeFakeWindowsProcessTreeWithNodeAddonApi(dir, { creationTimePatchApplied: false })
+
+    expect(() =>
+      assertWindowsProcessTreeCreationTimePatch(
+        join(dir, 'node_modules', '@vscode', 'windows-process-tree')
+      )
+    ).toThrow('process creation-time patch')
+  })
+
+  it('requires the runtime ProcessDataFlag.CreationTime enum', () => {
+    expect(() =>
+      assertWindowsProcessTreeRuntimeCreationTime({
+        ProcessDataFlag: { None: 0, Memory: 1, CommandLine: 2, CreationTime: 4 }
+      })
+    ).not.toThrow()
+    expect(() =>
+      assertWindowsProcessTreeRuntimeCreationTime({
+        ProcessDataFlag: { None: 0, Memory: 1, CommandLine: 2 }
+      })
+    ).toThrow('ProcessDataFlag.CreationTime')
+  })
+})
diff --git a/config/tsconfig.cli.json b/config/tsconfig.cli.json
index 80cf4a511f2..a23d90e6a1e 100644
--- a/config/tsconfig.cli.json
+++ b/config/tsconfig.cli.json
@@ -32,6 +32,7 @@
     "../src/main/codex/codex-app-server-capability-cache.ts",
     "../src/main/codex/codex-app-server-capability-signal.ts",
     "../src/main/codex/codex-app-server-client.ts",
+    "../src/main/codex/codex-app-server-process-tree-kill.ts",
     "../src/main/codex/codex-app-server-record-reader.ts",
     "../src/main/codex/codex-app-server-session.ts",
     "../src/main/codex/codex-config-mirror.ts",
diff --git a/src/main/codex/codex-app-server-client.test.ts b/src/main/codex/codex-app-server-client.test.ts
index b845d3a9694..ce98288bdf0 100644
--- a/src/main/codex/codex-app-server-client.test.ts
+++ b/src/main/codex/codex-app-server-client.test.ts
@@ -11,7 +11,8 @@ import {
   runCodexHookTrustGrantSession,
   type CodexHookTrustGrantRequest
 } from './codex-app-server-client'
-import { killCodexAppServerProcessTree, runCodexAppServerSession } from './codex-app-server-session'
+import { killCodexAppServerProcessTree } from './codex-app-server-process-tree-kill'
+import { runCodexAppServerSession } from './codex-app-server-session'
 
 // Stub codex app-server speaking the same JSONL protocol: initialize →
 // initialized → hooks/list → config/batchWrite → hooks/list. Scenario-driven
diff --git a/src/main/codex/codex-app-server-client.ts b/src/main/codex/codex-app-server-client.ts
index 8c95562e66c..efdee5de8bf 100644
--- a/src/main/codex/codex-app-server-client.ts
+++ b/src/main/codex/codex-app-server-client.ts
@@ -1,4 +1,5 @@
-import { spawn } from 'node:child_process'
+import type { ChildProcessHandle, ProcessSpec } from '../../shared/child-process/process-spec'
+import { spawnProcess } from '../../shared/child-process/run-process'
 import { normalizeHookTrustKeyForLookup } from './config-toml-trust'
 import { runCodexAppServerSession, type CodexAppServerInvocation } from './codex-app-server-session'
 
@@ -105,7 +106,12 @@ function collectHookListings(result: unknown): CodexHookListing[] {
  */
 export async function runCodexHookTrustGrantSession(
   request: CodexHookTrustGrantRequest,
-  spawnImpl: typeof spawn = spawn
+  spawnImpl: (
+    program: string,
+    args: string[],
+    options: Record<string, unknown>
+  ) => ChildProcessHandle = (program, args, options) =>
+    spawnProcess({ program, args, ...options } as ProcessSpec)
 ): Promise<CodexHookTrustGrantSessionResult> {
   return runCodexAppServerSession(
     request.invocation,
diff --git a/src/main/codex/codex-app-server-process-tree-kill.ts b/src/main/codex/codex-app-server-process-tree-kill.ts
new file mode 100644
index 00000000000..315246aaa9f
--- /dev/null
+++ b/src/main/codex/codex-app-server-process-tree-kill.ts
@@ -0,0 +1,76 @@
+import { spawnProcess } from '../../shared/child-process/run-process'
+import type { ChildProcessHandle, ProcessSpec } from '../../shared/child-process/process-spec'
+import { admitProcessTreeKill } from '../../shared/child-process/process-tree-kill-gate'
+
+/** Spawn seam for tests; production always goes through the hardened spawnProcess wrapper. */
+export type CodexAppServerSpawn = (
+  program: string,
+  args: string[],
+  options: Record<string, unknown>
+) => ChildProcessHandle
+
+export const spawnCodexAppServerProcess: CodexAppServerSpawn = (program, args, options) =>
+  spawnProcess({ program, args, ...options } as ProcessSpec)
+
+export function killCodexAppServerProcessTree(
+  child: Pick<ChildProcessHandle, 'pid' | 'kill'>,
+  options: { platform?: NodeJS.Platform; spawnImpl?: CodexAppServerSpawn } = {}
+): void {
+  const platform = options.platform ?? process.platform
+  const spawnImpl = options.spawnImpl ?? spawnCodexAppServerProcess
+  if (platform === 'win32' && child.pid) {
+    if (
+      !admitProcessTreeKill({
+        pid: child.pid,
+        site: 'codex-app-server-session-deadline',
+        scope: 'win-taskkill-tree'
+      })
+    ) {
+      // Refusal blocks the tree walk, not the termination: the root kill is
+      // handle-addressed, so it cannot reach the recycled pid we refused.
+      child.kill('SIGKILL')
+      return
+    }
+    try {
+      // Why: npm-installed Codex runs behind cmd.exe; killing only that wrapper
+      // leaves the app-server child alive after a timeout or failed shutdown.
+      const killer = spawnImpl('taskkill', ['/pid', String(child.pid), '/t', '/f'], {
+        stdio: 'ignore',
+        windowsHide: true
+      })
+      let fellBack = false
+      const killDirectChild = (): void => {
+        if (!fellBack) {
+          fellBack = true
+          child.kill('SIGKILL')
+        }
+      }
+      killer.on('error', killDirectChild)
+      killer.on('exit', (code) => {
+        if (code !== 0) {
+          killDirectChild()
+        }
+      })
+      killer.unref()
+      return
+    } catch {
+      // Fall through to the direct-child best effort when taskkill cannot start.
+    }
+  }
+  if (child.pid) {
+    try {
+      // npm/package-manager launchers insert a shim child on POSIX. Reap its
+      // direct descendants before signalling the wrapper itself.
+      const descendants = spawnImpl('pkill', ['-KILL', '-P', String(child.pid)], {
+        stdio: 'ignore'
+      })
+      // A missing pkill surfaces as an async 'error' event, and an unhandled one
+      // takes down the main process.
+      descendants.on('error', () => undefined)
+      descendants.unref()
+    } catch {
+      // The direct kill below remains the fallback when pkill is unavailable.
+    }
+  }
+  child.kill('SIGKILL')
+}
diff --git a/src/main/codex/codex-app-server-session.ts b/src/main/codex/codex-app-server-session.ts
index cef7f40c66b..6db33b4c85d 100644
--- a/src/main/codex/codex-app-server-session.ts
+++ b/src/main/codex/codex-app-server-session.ts
@@ -1,9 +1,13 @@
-import { spawn, type ChildProcess, type ChildProcessWithoutNullStreams } from 'node:child_process'
+import type { ChildProcessWithoutNullStreams } from 'node:child_process'
 import { waitForProcessExitUntil } from './codex-process-exit-deadline'
 import { stderrIndicatesMissingAppServer } from './codex-app-server-capability-signal'
 import { withCliRuntimeOnPath } from '../../shared/node-cli-command-resolution'
+import {
+  killCodexAppServerProcessTree,
+  spawnCodexAppServerProcess,
+  type CodexAppServerSpawn
+} from './codex-app-server-process-tree-kill'
 import { createCodexAppServerRecordReader } from './codex-app-server-record-reader'
-import { admitProcessTreeKill } from '../../shared/child-process/process-tree-kill-gate'
 
 // Why: `codex app-server` is Orca's sanctioned RPC surface into Codex-owned
 // state (hook trust hashes, the sqlite thread index). This module owns the
@@ -68,69 +72,6 @@ export type CodexAppServerRpc = {
 const JSON_RPC_METHOD_NOT_FOUND = -32601
 const STDERR_TAIL_MAX_BYTES = 8192
 
-export function killCodexAppServerProcessTree(
-  child: Pick<ChildProcess, 'pid' | 'kill'>,
-  options: { platform?: NodeJS.Platform; spawnImpl?: typeof spawn } = {}
-): void {
-  const platform = options.platform ?? process.platform
-  const spawnImpl = options.spawnImpl ?? spawn
-  if (platform === 'win32' && child.pid) {
-    if (
-      !admitProcessTreeKill({
-        pid: child.pid,
-        site: 'codex-app-server-session-deadline',
-        scope: 'win-taskkill-tree'
-      })
-    ) {
-      // Refusal blocks the tree walk, not the termination: the root kill is
-      // handle-addressed, so it cannot reach the recycled pid we refused.
-      child.kill('SIGKILL')
-      return
-    }
-    try {
-      // Why: npm-installed Codex runs behind cmd.exe; killing only that wrapper
-      // leaves the app-server child alive after a timeout or failed shutdown.
-      const killer = spawnImpl('taskkill', ['/pid', String(child.pid), '/t', '/f'], {
-        stdio: 'ignore',
-        windowsHide: true
-      })
-      let fellBack = false
-      const killDirectChild = (): void => {
-        if (!fellBack) {
-          fellBack = true
-          child.kill('SIGKILL')
-        }
-      }
-      killer.on('error', killDirectChild)
-      killer.on('exit', (code) => {
-        if (code !== 0) {
-          killDirectChild()
-        }
-      })
-      killer.unref()
-      return
-    } catch {
-      // Fall through to the direct-child best effort when taskkill cannot start.
-    }
-  }
-  if (child.pid) {
-    try {
-      // npm/package-manager launchers insert a shim child on POSIX. Reap its
-      // direct descendants before signalling the wrapper itself.
-      const descendants = spawnImpl('pkill', ['-KILL', '-P', String(child.pid)], {
-        stdio: 'ignore'
-      })
-      // A missing pkill surfaces as an async 'error' event, and an unhandled one
-      // takes down the main process.
-      descendants.on('error', () => undefined)
-      descendants.unref()
-    } catch {
-      // The direct kill below remains the fallback when pkill is unavailable.
-    }
-  }
-  child.kill('SIGKILL')
-}
-
 /** Codex answering "no such method" is the only response that proves the RPC
  *  surface is absent rather than temporarily failing. */
 export function isCodexMethodNotFoundError(error: unknown): boolean {
@@ -152,7 +93,7 @@ export function isCodexMethodNotFoundError(error: unknown): boolean {
 export async function runCodexAppServerSession<T>(
   invocation: CodexAppServerInvocation,
   body: (rpc: CodexAppServerRpc) => Promise<T>,
-  spawnImpl: typeof spawn = spawn
+  spawnImpl: CodexAppServerSpawn = spawnCodexAppServerProcess
 ): Promise<T> {
   // Why: a default-home grant must run against the real ~/.codex, so strip an
   // inherited CODEX_HOME (envToDelete) after applying the overlay, not before.
diff --git a/src/main/codex/codex-structured-launch-resolution.test.ts b/src/main/codex/codex-structured-launch-resolution.test.ts
index 484f7c1ee80..de83e74c6c8 100644
--- a/src/main/codex/codex-structured-launch-resolution.test.ts
+++ b/src/main/codex/codex-structured-launch-resolution.test.ts
@@ -44,7 +44,8 @@ function resolverFor(
     store: { getRecord: () => value } as unknown as AgentSessionRecordStore,
     resolveWorkspacePath,
     resolveCommand: () => '/usr/local/bin/codex',
-    resolveRollout
+    resolveRollout,
+    isWindowsProcessStartTimeAvailable: () => true
   })
 }
 
@@ -68,7 +69,8 @@ describe('codex structured launch resolution', () => {
       const resolveLaunch = createCodexStructuredLaunchResolver({
         store: { getRecord: () => record() } as unknown as AgentSessionRecordStore,
         resolveWorkspacePath: async () => String.raw`C:\workspaces\orca`,
-        resolveCommand: () => command
+        resolveCommand: () => command,
+        isWindowsProcessStartTimeAvailable: () => true
       })
 
       await expect(resolveLaunch({ identity: IDENTITY })).resolves.toMatchObject({
@@ -78,6 +80,22 @@ describe('codex structured launch resolution', () => {
     })
   })
 
+  it('fails closed before resolving a Windows launch without creation-time proof', async () => {
+    await withPlatform('win32', async () => {
+      const resolveWorkspacePath = vi.fn(async () => String.raw`C:\workspaces\orca`)
+      const resolveLaunch = createCodexStructuredLaunchResolver({
+        store: { getRecord: () => record() } as unknown as AgentSessionRecordStore,
+        resolveWorkspacePath,
+        isWindowsProcessStartTimeAvailable: () => false
+      })
+
+      await expect(resolveLaunch({ identity: IDENTITY })).rejects.toThrow(
+        'Windows process creation-time proof'
+      )
+      expect(resolveWorkspacePath).not.toHaveBeenCalled()
+    })
+  })
+
   it('resumes the last thread this session actually proved, not one a caller names', async () => {
     const launch = await resolverFor(
       record({
diff --git a/src/main/codex/codex-structured-launch-resolution.ts b/src/main/codex/codex-structured-launch-resolution.ts
index b1cc7854808..d395ee87c12 100644
--- a/src/main/codex/codex-structured-launch-resolution.ts
+++ b/src/main/codex/codex-structured-launch-resolution.ts
@@ -13,6 +13,7 @@ import { resolveCodexCommand } from '../codex-cli/command'
 import type { AgentSessionRecordStore } from '../runtime/agent-session-record-store'
 import type { CodexStructuredLaunch } from './codex-structured-session-adapter'
 import { resolvePinnedCodexRolloutProof } from './codex-tui-rollout-proof'
+import { isWindowsProcessStartTimeAvailable } from '../windows/windows-process-table'
 
 export type CodexStructuredLaunchResolverDeps = {
   store: AgentSessionRecordStore
@@ -24,6 +25,8 @@ export type CodexStructuredLaunchResolverDeps = {
   /** Fresh shell/configured environment for this spawn; never written to the session record. */
   resolveEnvironment?: () => Promise<NodeJS.ProcessEnv>
   resolveRollout?: typeof resolvePinnedCodexRolloutProof
+  /** Test seam for the host capability; production uses the native process table. */
+  isWindowsProcessStartTimeAvailable?: () => boolean
 }
 
 export function createCodexStructuredLaunchResolver(
@@ -46,6 +49,13 @@ export function createCodexStructuredLaunchResolver(
         `codex structured sessions run on the local host, not ${location.executionHostId}`
       )
     }
+    // Refuse before resolving launch data; a PID alone cannot prove Windows ownership.
+    if (
+      process.platform === 'win32' &&
+      !(deps.isWindowsProcessStartTimeAvailable ?? isWindowsProcessStartTimeAvailable)()
+    ) {
+      throw new Error('codex structured sessions require Windows process creation-time proof')
+    }
     if (accountHome.variable !== 'CODEX_HOME') {
       throw new Error(`codex sessions pin CODEX_HOME, not ${accountHome.variable}`)
     }
diff --git a/src/main/codex/codex-structured-location-support.test.ts b/src/main/codex/codex-structured-location-support.test.ts
new file mode 100644
index 00000000000..324568956d8
--- /dev/null
+++ b/src/main/codex/codex-structured-location-support.test.ts
@@ -0,0 +1,47 @@
+import { describe, expect, it } from 'vitest'
+import type { AgentSessionExecutionLocation } from '../../shared/agent-session-record'
+import { supportsCodexStructuredLocation } from './codex-structured-location-support'
+
+const LOCAL_WINDOWS_LOCATION: AgentSessionExecutionLocation = {
+  executionHostId: 'local',
+  wslDistro: null,
+  workspaceId: 'workspace-1',
+  workspaceKind: 'folder'
+}
+
+const WSL_WINDOWS_LOCATION: AgentSessionExecutionLocation = {
+  ...LOCAL_WINDOWS_LOCATION,
+  wslDistro: 'Ubuntu'
+}
+
+function withPlatform<T>(platform: NodeJS.Platform, run: () => T): T {
+  const original = process.platform
+  Object.defineProperty(process, 'platform', { configurable: true, value: platform })
+  try {
+    return run()
+  } finally {
+    Object.defineProperty(process, 'platform', { configurable: true, value: original })
+  }
+}
+
+describe('Codex structured location support', () => {
+  it('uses the injected Windows identity capability for location admission', () => {
+    let proofAvailable = false
+    withPlatform('win32', () => {
+      expect(supportsCodexStructuredLocation(LOCAL_WINDOWS_LOCATION, () => proofAvailable)).toBe(
+        false
+      )
+      proofAvailable = true
+      expect(supportsCodexStructuredLocation(LOCAL_WINDOWS_LOCATION, () => proofAvailable)).toBe(
+        true
+      )
+    })
+  })
+
+  it('rejects WSL locations while retaining native folder support on Windows', () => {
+    withPlatform('win32', () => {
+      expect(supportsCodexStructuredLocation(WSL_WINDOWS_LOCATION, () => true)).toBe(false)
+      expect(supportsCodexStructuredLocation(LOCAL_WINDOWS_LOCATION, () => true)).toBe(true)
+    })
+  })
+})
diff --git a/src/main/codex/codex-structured-location-support.ts b/src/main/codex/codex-structured-location-support.ts
index 915d9edaa83..ad0bbefa4d3 100644
--- a/src/main/codex/codex-structured-location-support.ts
+++ b/src/main/codex/codex-structured-location-support.ts
@@ -2,10 +2,14 @@ import { LOCAL_EXECUTION_HOST_ID } from '../../shared/execution-host'
 import type { AgentSessionExecutionLocation } from '../../shared/agent-session-record'
 import { isWindowsProcessStartTimeAvailable } from '../windows/windows-process-table'
 
-export function supportsCodexStructuredLocation(location: AgentSessionExecutionLocation): boolean {
+export function supportsCodexStructuredLocation(
+  location: AgentSessionExecutionLocation,
+  // Injected by the adapter, which owns this dep for every other Codex gate too.
+  hasWindowsProcessStartTimeProof: () => boolean = isWindowsProcessStartTimeAvailable
+): boolean {
   return (
     location.executionHostId === LOCAL_EXECUTION_HOST_ID &&
     location.wslDistro === null &&
-    (process.platform !== 'win32' || isWindowsProcessStartTimeAvailable())
+    (process.platform !== 'win32' || hasWindowsProcessStartTimeProof())
   )
 }
diff --git a/src/main/codex/codex-structured-session-adapter.ts b/src/main/codex/codex-structured-session-adapter.ts
index afa881f8254..5b551c8b01e 100644
--- a/src/main/codex/codex-structured-session-adapter.ts
+++ b/src/main/codex/codex-structured-session-adapter.ts
@@ -74,7 +74,8 @@ export class CodexStructuredSessionAdapter implements StructuredAgentSessionAdap
     })
   }
 
-  supportsLocation = supportsCodexStructuredLocation
+  supportsLocation = (location: Parameters<typeof supportsCodexStructuredLocation>[0]): boolean =>
+    supportsCodexStructuredLocation(location, this.deps.isWindowsProcessStartTimeAvailable)
 
   acquire = (input: StructuredAgentSessionAcquireInput): Promise<AgentSessionAcquisition> =>
     acquireCodexStructuredSession({
diff --git a/src/main/codex/codex-structured-session-state.ts b/src/main/codex/codex-structured-session-state.ts
index 2f805e8570f..5fd82f22ff9 100644
--- a/src/main/codex/codex-structured-session-state.ts
+++ b/src/main/codex/codex-structured-session-state.ts
@@ -41,6 +41,8 @@ export type CodexStructuredSessionAdapterDeps = {
   resolveLaunch: (input: {
     identity: AgentSessionJournalIdentity
   }) => Promise<CodexStructuredLaunch>
+  /** Host capability seam; production uses the native Windows process table. */
+  isWindowsProcessStartTimeAvailable?: () => boolean
   onEvent?: (event: CodexStructuredSessionEvent) => void
   openConnection?: typeof openCodexAppServerConnection
   readProcessStartTime?: (pid: number) => Promise<number | null>
diff --git a/src/main/native-chat/agent-session-wire/structured-agent-session-acquisition.ts b/src/main/native-chat/agent-session-wire/structured-agent-session-acquisition.ts
new file mode 100644
index 00000000000..cbaafa5ff32
--- /dev/null
+++ b/src/main/native-chat/agent-session-wire/structured-agent-session-acquisition.ts
@@ -0,0 +1,78 @@
+import { isDeepStrictEqual } from 'node:util'
+import type { AgentSessionRecord } from '../../../shared/agent-session-record'
+import {
+  AgentSessionPreSpawnError,
+  isAgentSessionPreSpawnError,
+  rethrowAfterAgentSessionAcquisitionCleanup
+} from './structured-agent-session-adapter'
+import { journalIdentityFor } from './structured-agent-session-attach'
+import type { AttachFlowInput } from './structured-agent-session-attach-flow'
+import { readNativeSessionOptions } from './structured-agent-session-option-restoration'
+
+/** A reservation with no process behind it is only a promise to spawn; the
+ * adapter makes it real and the store then grants the writer. */
+export async function acquireOwner(
+  input: AttachFlowInput,
+  record: AgentSessionRecord
+): Promise<{ record: AgentSessionRecord; acquisitionGeneration: string | null }> {
+  const fence = record.lease.runtimeFence
+  const spawnToken = record.lease.reservedSpawnToken
+  if (!spawnToken) {
+    throw new Error('agent_session_ownership_unknown')
+  }
+  // Pre-spawn proof is single-use: this retry may create a child after the durable clear.
+  try {
+    try {
+      record = await input.store.setReservationProcesslessProof({
+        sessionId: record.sessionId,
+        fence,
+        spawnToken,
+        processlessAt: null,
+        now: input.now()
+      })
+      await input.onAcquiring?.()
+    } catch (error) {
+      throw new AgentSessionPreSpawnError(error)
+    }
+    const acquired = await input.adapter.acquire({
+      identity: journalIdentityFor(record, input.params),
+      fence,
+      // Retries must recover the original reservation, not mint a second child.
+      spawnToken,
+      ...(record.options ? { options: record.options } : {}),
+      ...(input.eventSink ? { events: input.eventSink } : {})
+    })
+    const options = await readNativeSessionOptions({
+      adapter: input.adapter,
+      sessionId: record.sessionId,
+      fence,
+      ...(record.options ? { priorOptions: record.options } : {})
+    })
+    if (record.lease.ownerProcess === null) {
+      await input.store.commitProcessIdentity({
+        sessionId: record.sessionId,
+        fence,
+        process: acquired.process,
+        now: input.now()
+      })
+    } else if (!isDeepStrictEqual(record.lease.ownerProcess, acquired.process)) {
+      throw new Error('agent_session_ownership_unknown')
+    }
+    const proved = await input.store.proveOwner({
+      sessionId: record.sessionId,
+      fence,
+      link: acquired.link,
+      now: input.now(),
+      ...(options ? { options } : {})
+    })
+    return {
+      record: proved,
+      acquisitionGeneration: acquired.acquisitionGeneration ?? null
+    }
+  } catch (error) {
+    if (isAgentSessionPreSpawnError(error)) {
+      throw error
+    }
+    return rethrowAfterAgentSessionAcquisitionCleanup(input.adapter, record.sessionId, error)
+  }
+}
diff --git a/src/main/native-chat/agent-session-wire/structured-agent-session-attach-flow.ts b/src/main/native-chat/agent-session-wire/structured-agent-session-attach-flow.ts
index 8697e76ba3b..4bbdd51cdf9 100644
--- a/src/main/native-chat/agent-session-wire/structured-agent-session-attach-flow.ts
+++ b/src/main/native-chat/agent-session-wire/structured-agent-session-attach-flow.ts
@@ -5,7 +5,6 @@
 // the decisions that must not be client-supplied — the spawn token, the claim
 // key, the owner probe — and passes them in.
 
-import { isDeepStrictEqual } from 'node:util'
 import type {
   AgentSessionAttachResult,
   AgentSessionMutationResult
@@ -16,7 +15,6 @@ import {
   admitAttachOrRefuse,
   attachJournal,
   classifyStoreFailure,
-  journalIdentityFor,
   reserveRequestFor,
   type AgentSessionAttachAuthority,
   type AgentSessionAttachParams,
@@ -24,18 +22,18 @@ import {
 } from './structured-agent-session-attach'
 import type { AgentSessionRecordStore } from '../../runtime/agent-session-record-store'
 import type { StructuredAgentSessionAdapter } from './structured-agent-session-adapter'
+import { adapterSupportsCreateIfDeclared } from './structured-agent-session-provider-support'
 import {
   AgentSessionAcquisitionExitUnprovenError,
   AgentSessionAcquisitionRootExitObservedError,
   AgentSessionAcquisitionRefusal,
-  AgentSessionPreSpawnError,
   isAgentSessionPreSpawnError,
   rethrowAfterAgentSessionAcquisitionCleanup
 } from './structured-agent-session-adapter'
 import type { StructuredAgentSessionEventSink } from './structured-agent-session-event-sink'
-import { readNativeSessionOptions } from './structured-agent-session-option-restoration'
 import { resolveAgentSessionReplayOutcome } from './structured-agent-session-replay-outcome'
 import { readAgentSessionHydrationPage } from './agent-session-history-page'
+import { acquireOwner } from './structured-agent-session-acquisition'
 import {
   importAdoptedTranscript,
   prepareAdoptedTranscript
@@ -72,15 +70,27 @@ export async function performAttach(
   input: AttachFlowInput
 ): Promise<AgentSessionMutationResult<AgentSessionAttachResult>> {
   const { params, store } = input
+  const unsupported = (): AgentSessionMutationResult<AgentSessionAttachResult> => ({
+    ok: false,
+    refusal: {
+      code: 'structured_agent_session_unsupported',
+      message: 'This execution host cannot create the requested structured agent session.'
+    }
+  })
   const sessionId = params.envelope.sessionId
   const admitted = admitAttachOrRefuse(params)
   if (!admitted.ok) {
     return admitted
   }
+  // Ensure/recovery bypass create-intent, so recheck before reserving or spawning.
+  if (!adapterSupportsCreateIfDeclared(input.adapter, params.location, params.agent)) {
+    return unsupported()
+  }
 
   let record: AgentSessionRecord
   let acquisitionGeneration: string | null = null
   let reservedRecord: AgentSessionRecord | null = null
+  let unsupportedReservationSettlementAttempted = false
   let replayed = false
   const preparedTranscript = store.getRecord(sessionId)
     ? { ok: true as const, items: null }
@@ -101,6 +111,21 @@ export async function performAttach(
     )
     record = reserved.record
     replayed = reserved.disposition === 'replayed'
+    // Capability can change while the durable reservation is in flight. Recheck
+    // every reservation at its effect boundary so it cannot bypass the support
+    // gate, and release a pending reservation that support drift invalidated.
+    reservedRecord = record
+    if (!adapterSupportsCreateIfDeclared(input.adapter, params.location, params.agent)) {
+      if (
+        record.lease.claimStatus === 'reserved' &&
+        record.lease.handoffStage === 'new-owner-proving' &&
+        record.lease.reservedSpawnToken
+      ) {
+        unsupportedReservationSettlementAttempted = true
+        await settleUnsupportedReservation(input, record)
+      }
+      return unsupported()
+    }
     if (
       replayed &&
       reserved.operationRow.outcome.status !== 'pending' &&
@@ -115,7 +140,6 @@ export async function performAttach(
         return { ok: false, refusal: replay.refusal }
       }
     }
-    reservedRecord = record
     if (!agentSessionLeaseAdmitsWriter(record.lease)) {
       const acquired = await acquireOwner(input, record)
       record = acquired.record
@@ -123,7 +147,7 @@ export async function performAttach(
     }
   } catch (error) {
     const spawnToken = reservedRecord?.lease.reservedSpawnToken
-    if (reservedRecord && spawnToken) {
+    if (reservedRecord && spawnToken && !unsupportedReservationSettlementAttempted) {
       // A pre-spawn failure is its own processless proof; the settlement records the
       // evidence and the failed operation in one durable transaction.
       const exitProof = isAgentSessionPreSpawnError(error)
@@ -217,6 +241,34 @@ export async function performAttach(
   }
 }
 
+async function settleUnsupportedReservation(
+  input: AttachFlowInput,
+  record: AgentSessionRecord
+): Promise<void> {
+  const spawnToken = record.lease.reservedSpawnToken
+  if (!spawnToken) {
+    return
+  }
+  try {
+    await input.store.settleFailedAcquisition({
+      sessionId: record.sessionId,
+      fence: record.lease.runtimeFence,
+      spawnToken,
+      callerKey: input.callerKey,
+      operationId: input.params.envelope.clientOperationId,
+      outcome: {
+        status: 'failed',
+        code: 'structured_agent_session_unsupported',
+        message: 'Structured session support changed before the provider could start.'
+      },
+      exitProof: 'processless',
+      now: input.now()
+    })
+  } catch (error) {
+    throw new AggregateError([error], 'agent session unsupported reservation settlement failed')
+  }
+}
+
 async function settlePostAcquisitionAttachFailure(
   input: AttachFlowInput,
   record: AgentSessionRecord,
@@ -261,71 +313,3 @@ async function settlePostAcquisitionAttachFailure(
   }
   throw cleanupError
 }
-
-/** A reservation with no process behind it is only a promise to spawn; the
- *  adapter makes it real and the store then grants the writer. */
-async function acquireOwner(
-  input: AttachFlowInput,
-  record: AgentSessionRecord
-): Promise<{ record: AgentSessionRecord; acquisitionGeneration: string | null }> {
-  const fence = record.lease.runtimeFence
-  const spawnToken = record.lease.reservedSpawnToken
-  if (!spawnToken) {
-    throw new Error('agent_session_ownership_unknown')
-  }
-  // Pre-spawn proof is single-use: this retry may create a child after the durable clear.
-  try {
-    try {
-      record = await input.store.setReservationProcesslessProof({
-        sessionId: record.sessionId,
-        fence,
-        spawnToken,
-        processlessAt: null,
-        now: input.now()
-      })
-      await input.onAcquiring?.()
-    } catch (error) {
-      throw new AgentSessionPreSpawnError(error)
-    }
-    const acquired = await input.adapter.acquire({
-      identity: journalIdentityFor(record, input.params),
-      fence,
-      // Retries must recover the original reservation, not mint a second child.
-      spawnToken,
-      ...(record.options ? { options: record.options } : {}),
-      ...(input.eventSink ? { events: input.eventSink } : {})
-    })
-    const options = await readNativeSessionOptions({
-      adapter: input.adapter,
-      sessionId: record.sessionId,
-      fence,
-      ...(record.options ? { priorOptions: record.options } : {})
-    })
-    if (record.lease.ownerProcess === null) {
-      await input.store.commitProcessIdentity({
-        sessionId: record.sessionId,
-        fence,
-        process: acquired.process,
-        now: input.now()
-      })
-    } else if (!isDeepStrictEqual(record.lease.ownerProcess, acquired.process)) {
-      throw new Error('agent_session_ownership_unknown')
-    }
-    const proved = await input.store.proveOwner({
-      sessionId: record.sessionId,
-      fence,
-      link: acquired.link,
-      now: input.now(),
-      ...(options ? { options } : {})
-    })
-    return {
-      record: proved,
-      acquisitionGeneration: acquired.acquisitionGeneration ?? null
-    }
-  } catch (error) {
-    if (isAgentSessionPreSpawnError(error)) {
-      throw error
-    }
-    return rethrowAfterAgentSessionAcquisitionCleanup(input.adapter, record.sessionId, error)
-  }
-}
diff --git a/src/main/native-chat/agent-session-wire/structured-agent-session-host-handoff.test.ts b/src/main/native-chat/agent-session-wire/structured-agent-session-host-handoff.test.ts
index 9bf27a11106..bf2a1381b3b 100644
--- a/src/main/native-chat/agent-session-wire/structured-agent-session-host-handoff.test.ts
+++ b/src/main/native-chat/agent-session-wire/structured-agent-session-host-handoff.test.ts
@@ -11,6 +11,7 @@ import { LOCAL_EXECUTION_HOST_ID } from '../../../shared/execution-host'
 import { AgentSessionRecordStore } from '../../runtime/agent-session-record-store'
 import { createTrackedJournalOpener } from '../agent-session-journal/journal-store-test-open'
 import { createDeferredStructuredAgentSessionEventSink } from './structured-agent-session-event-sink'
+import type { StructuredAgentSessionHostDeps } from './structured-agent-session-host-types'
 import {
   acquireNativeHandoffOwner,
   createStructuredAgentSessionHostHandoff,
@@ -202,6 +203,191 @@ describe('native handoff acquisition', () => {
 
     expect(order).toEqual(['append-entered', 'append-complete', 'unbind', 'acquire'])
   })
+
+  it('refuses an unsupported adapter before unbinding the TUI owner', async () => {
+    const location: AgentSessionExecutionLocation = {
+      executionHostId: LOCAL_EXECUTION_HOST_ID,
+      wslDistro: null,
+      workspaceId: 'workspace-unsupported',
+      workspaceKind: 'folder'
+    }
+    const operationId = `${now}-00000000000000000000000000000011`
+    const reserved = await store.reserveOwner({
+      sessionId: 'session-handoff-unsupported',
+      location,
+      provider: 'codex',
+      accountHome: { variable: 'CODEX_HOME', path: join(root, 'codex-home') },
+      runtimeKind: 'native',
+      expectedFence: null,
+      spawnToken: 'unsupported-spawn',
+      claimKeyId: 'key-1',
+      handoffOperationId: operationId,
+      probe: { outcome: 'reservation-unused' },
+      operation: { callerKey: 'test', operationId, fingerprint: 'unsupported' },
+      now
+    })
+    const journal = await journals.open({
+      identity: {
+        sessionId: 'session-handoff-unsupported',
+        workspaceId: location.workspaceId,
+        hostId: location.executionHostId,
+        agent: 'codex',
+        providerHandle: { kind: 'codex', threadId: 'unsupported-thread' }
+      },
+      journalDir: join(root, 'unsupported-journal')
+    })
+    const eventSink = createDeferredStructuredAgentSessionEventSink()
+    eventSink.bind({ journal, fence: reserved.record.lease.runtimeFence, publish: () => undefined })
+    const unbind = vi.spyOn(eventSink, 'unbind')
+    const acquire = vi.fn<NonNullable<StructuredAgentSessionHostDeps['adapter']['acquire']>>()
+    const adapter = {
+      supportsLocation: vi.fn(() => false),
+      acquire
+    }
+    const session = {
+      journal,
+      params: {
+        envelope: {
+          sessionId: 'session-handoff-unsupported',
+          clientOperationId: `${now}-00000000000000000000000000000012`,
+          expectedRuntimeFence: reserved.record.lease.runtimeFence,
+          payloadFingerprint: 'unsupported'
+        },
+        location,
+        provider: 'codex' as const,
+        agent: 'codex' as const,
+        accountHome: { variable: 'CODEX_HOME' as const, path: join(root, 'codex-home') },
+        runtimeKind: 'native' as const,
+        providerHandle: { kind: 'codex' as const, threadId: 'unsupported-thread' }
+      },
+      fence: reserved.record.lease.runtimeFence,
+      hasProviderChild: false,
+      acquisitionGeneration: null
+    }
+
+    await expect(
+      acquireNativeHandoffOwner(
+        {
+          store,
+          adapter: adapter as never,
+          journalRoot: root,
+          claimKeyId: 'key-1'
+        },
+        {
+          session: () => session,
+          findSession: () => session,
+          eventSink: () => eventSink,
+          flush: async () => undefined,
+          serialize: async (_sessionId, task) => task(),
+          subscribers: {
+            publish: vi.fn(),
+            reset: vi.fn(),
+            handoff: vi.fn(),
+            snapshot: vi.fn()
+          } as never,
+          now: () => now
+        },
+        {
+          sessionId: 'session-handoff-unsupported',
+          fence: reserved.record.lease.runtimeFence,
+          spawnToken: 'unsupported-spawn'
+        }
+      )
+    ).rejects.toThrow('structured_agent_session_unsupported')
+    expect(unbind).not.toHaveBeenCalled()
+    expect(acquire).not.toHaveBeenCalled()
+  })
+
+  it('rechecks adapter support immediately before handoff acquisition', async () => {
+    const sessionId = 'session-handoff-drift'
+    const location: AgentSessionExecutionLocation = {
+      executionHostId: LOCAL_EXECUTION_HOST_ID,
+      wslDistro: null,
+      workspaceId: 'workspace-drift',
+      workspaceKind: 'folder'
+    }
+    const operationId = `${now}-00000000000000000000000000000021`
+    const reserved = await store.reserveOwner({
+      sessionId,
+      location,
+      provider: 'codex',
+      accountHome: { variable: 'CODEX_HOME', path: join(root, 'codex-home') },
+      runtimeKind: 'native',
+      expectedFence: null,
+      spawnToken: 'drift-spawn',
+      claimKeyId: 'key-1',
+      handoffOperationId: operationId,
+      probe: { outcome: 'reservation-unused' },
+      operation: { callerKey: 'test', operationId, fingerprint: 'drift' },
+      now
+    })
+    const journal = await journals.open({
+      identity: {
+        sessionId,
+        workspaceId: location.workspaceId,
+        hostId: location.executionHostId,
+        agent: 'codex',
+        providerHandle: { kind: 'codex', threadId: 'drift-thread' }
+      },
+      journalDir: join(root, 'drift-journal')
+    })
+    const eventSink = createDeferredStructuredAgentSessionEventSink()
+    eventSink.bind({ journal, fence: reserved.record.lease.runtimeFence, publish: () => undefined })
+    const unbind = vi.spyOn(eventSink, 'unbind')
+    const supportsLocation = vi.fn(() => true)
+    supportsLocation.mockReturnValueOnce(true).mockReturnValueOnce(false)
+    const acquire = vi.fn<NonNullable<StructuredAgentSessionHostDeps['adapter']['acquire']>>()
+    const adapter = { supportsLocation, acquire }
+    const session = {
+      journal,
+      params: {
+        envelope: {
+          sessionId,
+          clientOperationId: `${now}-00000000000000000000000000000022`,
+          expectedRuntimeFence: reserved.record.lease.runtimeFence,
+          payloadFingerprint: 'drift'
+        },
+        location,
+        provider: 'codex' as const,
+        agent: 'codex' as const,
+        accountHome: { variable: 'CODEX_HOME' as const, path: join(root, 'codex-home') },
+        runtimeKind: 'native' as const,
+        providerHandle: { kind: 'codex' as const, threadId: 'drift-thread' }
+      },
+      fence: reserved.record.lease.runtimeFence,
+      hasProviderChild: false,
+      acquisitionGeneration: null
+    }
+
+    await expect(
+      acquireNativeHandoffOwner(
+        {
+          store,
+          adapter: adapter as never,
+          journalRoot: root,
+          claimKeyId: 'key-1'
+        },
+        {
+          session: () => session,
+          findSession: () => session,
+          eventSink: () => eventSink,
+          flush: async () => undefined,
+          serialize: async (_sessionId, task) => task(),
+          subscribers: {
+            publish: vi.fn(),
+            reset: vi.fn(),
+            handoff: vi.fn(),
+            snapshot: vi.fn()
+          } as never,
+          now: () => now
+        },
+        { sessionId, fence: reserved.record.lease.runtimeFence, spawnToken: 'drift-spawn' }
+      )
+    ).rejects.toThrow('structured_agent_session_unsupported')
+    expect(supportsLocation).toHaveBeenCalledTimes(2)
+    expect(unbind).toHaveBeenCalledOnce()
+    expect(acquire).not.toHaveBeenCalled()
+  })
 })
 
 describe('handoff status published for a session the host no longer holds', () => {
diff --git a/src/main/native-chat/agent-session-wire/structured-agent-session-host-handoff.ts b/src/main/native-chat/agent-session-wire/structured-agent-session-host-handoff.ts
index cb316850e5b..7c8c65a5292 100644
--- a/src/main/native-chat/agent-session-wire/structured-agent-session-host-handoff.ts
+++ b/src/main/native-chat/agent-session-wire/structured-agent-session-host-handoff.ts
@@ -14,6 +14,7 @@ import { recoverDeadTuiHandoffStatus } from './structured-agent-session-dead-tui
 import { readNativeSessionOptions } from './structured-agent-session-option-restoration'
 import type { AgentSessionSubscribers } from './structured-agent-session-subscribers'
 import { StructuredTuiTranscriptCatchup } from './structured-tui-transcript-catchup'
+import { adapterSupportsCreateIfDeclared } from './structured-agent-session-provider-support'
 import { retryLoadedStructuredAgentSessionSettlement } from './structured-agent-session-settlement-retry'
 
 type HostHandoffAccess = {
@@ -195,12 +196,21 @@ export async function acquireNativeHandoffOwner(
   if (!record) {
     throw new Error('agent_session_identity_required')
   }
+  // Native handoff bypasses attach admission; reject before unbinding TUI ownership.
+  if (!adapterSupportsCreateIfDeclared(deps.adapter, record.location, record.provider)) {
+    throw new Error('structured_agent_session_unsupported')
+  }
   const eventSink = host.eventSink(input.sessionId)
   const priorBarrier = await eventSink.drained()
   if (!priorBarrier.ok) {
     throw priorBarrier.error
   }
   eventSink.unbind()
+  // Recheck immediately before acquisition; capability probes may drift while
+  // the old TUI event sink is draining.
+  if (!adapterSupportsCreateIfDeclared(deps.adapter, record.location, record.provider)) {
+    throw new Error('structured_agent_session_unsupported')
+  }
   const acquired = await deps.adapter.acquire({
     identity: journalIdentityFor(record, session.params),
     fence: input.fence,
diff --git a/src/main/native-chat/agent-session-wire/structured-agent-session-processless-reservation.test.ts b/src/main/native-chat/agent-session-wire/structured-agent-session-processless-reservation.test.ts
index a1b6b39f5e0..0f115da5ebd 100644
--- a/src/main/native-chat/agent-session-wire/structured-agent-session-processless-reservation.test.ts
+++ b/src/main/native-chat/agent-session-wire/structured-agent-session-processless-reservation.test.ts
@@ -64,6 +64,151 @@ function attachParams(
 }
 
 describe('processless structured session reservation', () => {
+  it('refuses an adapter that declares no create support before reserving a lease', async () => {
+    root = await mkdtemp(join(tmpdir(), 'orca-unsupported-attach-'))
+    const store = await AgentSessionRecordStore.open({
+      directory: join(root, 'store'),
+      hostId: 'local'
+    })
+    const reserveOwner = vi.spyOn(store, 'reserveOwner')
+    const acquire = vi.fn<StructuredAgentSessionAdapter['acquire']>()
+    const adapter = {
+      supportsCreate: vi.fn(() => false),
+      acquire,
+      dispatch: vi.fn(),
+      cancelTurn: vi.fn(),
+      answerPrompt: vi.fn(),
+      setOption: vi.fn()
+    } as unknown as StructuredAgentSessionAdapter
+
+    await expect(
+      performAttach({
+        store,
+        adapter,
+        journalRoot: root,
+        authority: {
+          spawnToken: 'spawn-a',
+          claimKeyId: 'key-1',
+          handoffOperationId: OPERATION,
+          probe: { outcome: 'reservation-unused' }
+        },
+        callerKey: 'client-1',
+        params: attachParams(),
+        now: () => NOW,
+        onAttached: () => {}
+      })
+    ).resolves.toMatchObject({
+      ok: false,
+      refusal: { code: 'structured_agent_session_unsupported' }
+    })
+    expect(reserveOwner).not.toHaveBeenCalled()
+    expect(acquire).not.toHaveBeenCalled()
+  })
+
+  it('refuses a replay when adapter support drifts after durable reservation', async () => {
+    root = await mkdtemp(join(tmpdir(), 'orca-replay-support-drift-'))
+    const store = await AgentSessionRecordStore.open({
+      directory: join(root, 'store'),
+      hostId: 'local'
+    })
+    const supportsCreate = vi
+      .fn<NonNullable<StructuredAgentSessionAdapter['supportsCreate']>>()
+      .mockReturnValueOnce(true)
+      .mockReturnValueOnce(true)
+      .mockReturnValueOnce(false)
+    const adapter = {
+      supportsCreate,
+      acquire: vi.fn(async ({ fence, spawnToken }) => ({
+        process: { hostId: 'local', pid: 4242, processStartTimeMs: NOW, spawnToken },
+        link: {
+          linkId: 'link-1',
+          handle: { provider: 'codex' as const, threadId: 'thread-1' },
+          origin: 'created' as const,
+          mintedAtFence: fence,
+          observedAt: NOW
+        }
+      }))
+    } as unknown as StructuredAgentSessionAdapter
+    const input = {
+      store,
+      adapter,
+      journalRoot: root,
+      authority: {
+        spawnToken: 'spawn-a',
+        claimKeyId: 'key-1',
+        handoffOperationId: OPERATION,
+        probe: { outcome: 'reservation-unused' as const }
+      },
+      callerKey: 'client-1',
+      params: attachParams(),
+      now: () => NOW,
+      onAttached: () => {}
+    }
+
+    await expect(performAttach(input)).resolves.toMatchObject({ ok: true })
+    await expect(performAttach(input)).resolves.toMatchObject({
+      ok: false,
+      refusal: { code: 'structured_agent_session_unsupported' }
+    })
+    expect(supportsCreate).toHaveBeenCalledTimes(3)
+    expect(adapter.acquire).toHaveBeenCalledOnce()
+  })
+
+  it('releases a new reservation when support drifts before acquisition', async () => {
+    root = await mkdtemp(join(tmpdir(), 'orca-support-drift-reservation-'))
+    const store = await AgentSessionRecordStore.open({
+      directory: join(root, 'store'),
+      hostId: 'local'
+    })
+    const supportsCreate = vi
+      .fn<NonNullable<StructuredAgentSessionAdapter['supportsCreate']>>()
+      .mockReturnValueOnce(true)
+      .mockReturnValueOnce(false)
+      .mockReturnValueOnce(true)
+      .mockReturnValueOnce(true)
+    const acquire = vi.fn<StructuredAgentSessionAdapter['acquire']>()
+    const adapter = { supportsCreate, acquire } as unknown as StructuredAgentSessionAdapter
+    const input = {
+      store,
+      adapter,
+      journalRoot: root,
+      authority: {
+        spawnToken: 'spawn-drift',
+        claimKeyId: 'key-1',
+        handoffOperationId: OPERATION,
+        probe: { outcome: 'reservation-unused' as const }
+      },
+      callerKey: 'client-1',
+      params: attachParams(),
+      now: () => NOW,
+      onAttached: () => {}
+    }
+
+    await expect(performAttach(input)).resolves.toMatchObject({
+      ok: false,
+      refusal: { code: 'structured_agent_session_unsupported' }
+    })
+
+    expect(acquire).not.toHaveBeenCalled()
+    expect(store.getRecord(SESSION)?.lease).toMatchObject({
+      claimStatus: 'released',
+      handoffStage: null,
+      reservedSpawnToken: null,
+      processlessAt: null,
+      runtimeFence: 2,
+      deathEvidence: { kind: 'pid-absent', detail: 'reservation failed before spawn' }
+    })
+    expect(store.listOperationRows()[0]?.outcome).toMatchObject({
+      status: 'failed',
+      code: 'structured_agent_session_unsupported'
+    })
+    await expect(performAttach(input)).resolves.toMatchObject({
+      ok: false,
+      refusal: { code: 'structured_agent_session_unsupported' }
+    })
+    expect(acquire).not.toHaveBeenCalled()
+  })
+
   it('settles a pre-spawn failure and its processless evidence in one durable transaction', async () => {
     root = await mkdtemp(join(tmpdir(), 'orca-processless-reservation-'))
     const storeDir = join(root, 'store')
diff --git a/src/main/native-chat/agent-session-wire/structured-agent-session-provider-support.ts b/src/main/native-chat/agent-session-wire/structured-agent-session-provider-support.ts
index 99958a2bcb0..15af150c12f 100644
--- a/src/main/native-chat/agent-session-wire/structured-agent-session-provider-support.ts
+++ b/src/main/native-chat/agent-session-wire/structured-agent-session-provider-support.ts
@@ -9,17 +9,35 @@ export function adapterSupportsCreate(
   location: AgentSessionExecutionLocation,
   agent: string
 ): boolean {
-  return (
-    adapter.supportsCreate?.(location, agent) ??
-    (agent === 'codex' && (adapter.supportsLocation?.(location) ?? false))
-  )
+  if (adapter.supportsCreate) {
+    return adapter.supportsCreate(location, agent)
+  }
+  if (agent !== 'codex') {
+    return false
+  }
+  // Older Codex adapters exposed only location support; absence still fails closed here.
+  return adapter.supportsLocation?.(location) ?? false
+}
+
+/** Honors declared gates while retaining legacy adapters whose acquire path is authoritative. */
+export function adapterSupportsCreateIfDeclared(
+  adapter: StructuredAgentSessionAdapter,
+  location: AgentSessionExecutionLocation,
+  agent: string
+): boolean {
+  if (!adapter.supportsCreate && !adapter.supportsLocation) {
+    return true
+  }
+  return adapterSupportsCreate(adapter, location, agent)
 }
 
 export function adapterSupportsRecord(
   adapter: StructuredAgentSessionAdapter,
   record: AgentSessionRecord
 ): boolean {
-  return adapter.supportsCreate
-    ? adapter.supportsCreate(record.location, record.provider)
-    : record.provider === 'codex'
+  if (adapter.supportsCreate) {
+    return adapter.supportsCreate(record.location, record.provider)
+  }
+  // Old Codex records stay readable unless the adapter explicitly rejects their location.
+  return record.provider === 'codex' && (adapter.supportsLocation?.(record.location) ?? true)
 }
diff --git a/src/main/own-chromium-tree-kill-guard.test.ts b/src/main/own-chromium-tree-kill-guard.test.ts
index 7b9c30687bc..5bfad815631 100644
--- a/src/main/own-chromium-tree-kill-guard.test.ts
+++ b/src/main/own-chromium-tree-kill-guard.test.ts
@@ -17,7 +17,7 @@ import {
   admitSelfInitiatedTreeKill,
   installMainProcessTreeKillGate
 } from './own-chromium-tree-kill-guard'
-import { killCodexAppServerProcessTree } from './codex/codex-app-server-session'
+import { killCodexAppServerProcessTree } from './codex/codex-app-server-process-tree-kill'
 import { setProcessTreeKillGate } from '../shared/child-process/process-tree-kill-gate'
 import { resetSelfInitiatedTreeKillLogForTest } from './crash-reporting/self-initiated-tree-kill-log'
 import {
diff --git a/src/main/refused-tree-kill-root-termination.test.ts b/src/main/refused-tree-kill-root-termination.test.ts
index ada4b5942a9..3912d6e946e 100644
--- a/src/main/refused-tree-kill-root-termination.test.ts
+++ b/src/main/refused-tree-kill-root-termination.test.ts
@@ -34,7 +34,7 @@ import { terminateNotebookProcessTree } from './ipc/notebook'
 import { killLocalPrecheckProcessTree } from './automations/precheck-runner'
 import { killRecipeProcess } from '../shared/ephemeral-vm-recipe-process'
 import { killSpawnedCommandTree } from './git/command-runner/spawned-command-tree-kill'
-import { killCodexAppServerProcessTree } from './codex/codex-app-server-session'
+import { killCodexAppServerProcessTree } from './codex/codex-app-server-process-tree-kill'
 import { signalProcessTree } from '../shared/child-process/process-tree-termination'
 import { killSourceControlAgentProcess } from './text-generation/source-control-local-process'
 import { terminateCodexTurnProcesses } from './codex/codex-structured-turn-processes'
diff --git a/src/main/runtime/agent-session-process-identity-probe-windows-batch.test.ts b/src/main/runtime/agent-session-process-identity-probe-windows-batch.test.ts
new file mode 100644
index 00000000000..5e8ef48ad62
--- /dev/null
+++ b/src/main/runtime/agent-session-process-identity-probe-windows-batch.test.ts
@@ -0,0 +1,42 @@
+import { afterEach, describe, expect, it, vi } from 'vitest'
+
+const { isWindowsProcessStartTimeAvailable, readWindowsProcessIdentityTableFresh } = vi.hoisted(
+  () => ({
+    isWindowsProcessStartTimeAvailable: vi.fn(() => true),
+    readWindowsProcessIdentityTableFresh: vi.fn()
+  })
+)
+
+vi.mock('../windows/windows-process-table', async (importOriginal) => ({
+  ...(await importOriginal<object>()),
+  isWindowsProcessStartTimeAvailable,
+  readWindowsProcessIdentityTableFresh
+}))
+
+const { readProcessStartTimesMs } = await import('./agent-session-process-identity-probe')
+
+const START_TIME = 1_700_000_000_000
+
+afterEach(() => {
+  isWindowsProcessStartTimeAvailable.mockReset()
+  isWindowsProcessStartTimeAvailable.mockReturnValue(true)
+  readWindowsProcessIdentityTableFresh.mockReset()
+})
+
+describe('Windows owner identity batch probe', () => {
+  it('reads Windows start times for a batch from one process-table snapshot', async () => {
+    readWindowsProcessIdentityTableFresh.mockResolvedValue([
+      { pid: 4242, ppid: 1, name: 'codex.exe', creationTimeMs: START_TIME },
+      { pid: 4243, ppid: 1, name: 'codex.exe', creationTimeMs: START_TIME + 10 }
+    ])
+
+    await expect(readProcessStartTimesMs([4242, 4243, 4242], 'win32')).resolves.toEqual(
+      new Map([
+        [4242, START_TIME],
+        [4243, START_TIME + 10]
+      ])
+    )
+
+    expect(readWindowsProcessIdentityTableFresh).toHaveBeenCalledOnce()
+  })
+})
diff --git a/src/main/runtime/agent-session-process-identity-probe.ts b/src/main/runtime/agent-session-process-identity-probe.ts
index 5d441782ca8..3fa1971b830 100644
--- a/src/main/runtime/agent-session-process-identity-probe.ts
+++ b/src/main/runtime/agent-session-process-identity-probe.ts
@@ -131,6 +131,25 @@ async function readWindowsProcessStartTimeMs(pid: number): Promise<number | null
   }
 }
 
+async function readWindowsProcessStartTimesMs(
+  pids: readonly number[]
+): Promise<Map<number, number | null>> {
+  const observed = new Map<number, number | null>(pids.map((pid) => [pid, null]))
+  if (pids.length === 0 || !isWindowsProcessStartTimeAvailable()) {
+    return observed
+  }
+  try {
+    const table = await readWindowsProcessIdentityTableFresh()
+    const startTimesByPid = new Map(table.map((row) => [row.pid, row.creationTimeMs ?? null]))
+    for (const pid of pids) {
+      observed.set(pid, startTimesByPid.get(pid) ?? null)
+    }
+  } catch {
+    // A missing process table is unknown, never evidence that every owner exited.
+  }
+  return observed
+}
+
 /**
  * Process start time is the cross-platform PID-reuse guard when no provider hook can echo the
  * spawn token back to the owner probe.
@@ -160,6 +179,9 @@ export async function readProcessStartTimesMs(
     const table = await readDarwinProcessStartTimesMs(uniquePids)
     return new Map(uniquePids.map((pid) => [pid, table.get(pid) ?? null]))
   }
+  if (platform === 'win32') {
+    return readWindowsProcessStartTimesMs(uniquePids)
+  }
   return new Map(
     await Promise.all(
       uniquePids.map(async (pid) => [pid, await readProcessStartTimeMs(pid, platform)] as const)
diff --git a/src/main/runtime/orca-runtime-get-status.ts b/src/main/runtime/orca-runtime-get-status.ts
index bd378ea2bf7..d177c8fe64d 100644
--- a/src/main/runtime/orca-runtime-get-status.ts
+++ b/src/main/runtime/orca-runtime-get-status.ts
@@ -20,6 +20,7 @@ import {
   browserUnavailableMessage
 } from '../../shared/runtime-types'
 import { runtimeTerminalDegradation } from './native-terminal-availability'
+import { isWindowsProcessStartTimeAvailable } from '../windows/windows-process-table'
 import type { RuntimeWorktreeLifecycleEvent } from './orca-runtime-core'
 import { WORKTREE_CREATE_RESULT_TTL_MS } from './orca-runtime-core'
 import type { RuntimePtyController } from './runtime-pty-controller-contract'
@@ -56,6 +57,10 @@ export class OrcaRuntimeWithGetStatus extends OrcaRuntimeWithGetRuntimeId {
     const hasOffscreen = !hasRenderer && Boolean(this.offscreenBrowserBackend)
     const hasHeadlessCommands = runtimeBrowserCommandsFactoryIsHeadless()
     const canBrowse = hasRenderer || hasOffscreen
+    // This field reports current Windows process-identity proof. Structured RPC
+    // support itself stays advertised; agentSession.createSupport owns current eligibility.
+    const windowsProcessStartTimeAvailable =
+      process.platform === 'win32' && isWindowsProcessStartTimeAvailable()
     const capabilities: RuntimeCapability[] = RUNTIME_CAPABILITIES.filter(
       (capability) =>
         (capability !== 'browser.screencast.v1' || canBrowse) &&
@@ -110,6 +115,7 @@ export class OrcaRuntimeWithGetStatus extends OrcaRuntimeWithGetRuntimeId {
       capabilities,
       ...(degradations.length > 0 ? { degradations } : {}),
       worktreeCreateIdempotency: { dedupeTtlMs: WORKTREE_CREATE_RESULT_TTL_MS },
+      ...(windowsProcessStartTimeAvailable ? { windowsProcessStartTimeAvailable } : {}),
       hostPlatform: process.platform,
       terminalWindowsShell: this.store?.getSettings?.().terminalWindowsShell ?? null,
       floatingWorkspaceEnabled: this.store?.getSettings?.().floatingTerminalEnabled !== false,
diff --git a/src/main/runtime/orca-runtime-resolve-recovered-structured-tui-transcript.ts b/src/main/runtime/orca-runtime-resolve-recovered-structured-tui-transcript.ts
index 37752d207e6..6448cc3911d 100644
--- a/src/main/runtime/orca-runtime-resolve-recovered-structured-tui-transcript.ts
+++ b/src/main/runtime/orca-runtime-resolve-recovered-structured-tui-transcript.ts
@@ -22,6 +22,8 @@ import { hasPersistedStructuredAgentSessionStore as hasPersistedStructuredAgentS
 import { getProfileUserDataPath } from '../orca-profiles/profile-storage-paths'
 import { homedir } from 'node:os'
 import { join } from 'node:path'
+import { parseWslUncPath } from '../../shared/wsl-paths'
+import { parseWorkspaceKey } from '../../shared/workspace-scope'
 
 export class OrcaRuntimeWithResolveRecoveredStructuredTuiTranscript extends OrcaRuntimeWithStopStructuredSessionProcess {
   protected async resolveRecoveredStructuredTuiTranscript(input: {
@@ -95,14 +97,23 @@ export class OrcaRuntimeWithResolveRecoveredStructuredTuiTranscript extends Orca
   protected async resolveStructuredAgentSessionLocation(worktreeSelector: string) {
     const target = await this.resolveRuntimeFileTarget(worktreeSelector)
     const repo = this.store?.getRepo(target.worktree.repoId)
-    // WSL routing describes *this* machine; no remote or runtime host may inherit it.
-    const wslDistro =
-      repo && target.executionHostId === LOCAL_EXECUTION_HOST_ID
+    const folderScope = parseWorkspaceKey(target.worktree.id)
+    const folderWorkspace = folderScope?.type === 'folder'
+    // WSL routing describes *this* machine; no remote or runtime host may inherit
+    // it. Both branches key on executionHostId: the target no longer carries a
+    // connectionId, which used to spell remote, unresolved and local alike.
+    const isLocalHost = target.executionHostId === LOCAL_EXECUTION_HOST_ID
+    const configuredWslDistro =
+      repo && isLocalHost
         ? (getLocalProjectWorktreeGitOptions(this.requireStore(), repo).wslDistro ?? null)
         : null
-    const folderWorkspace = this.store
-      ?.getFolderWorkspaces?.()
-      .some((workspace) => workspace.id === target.worktree.id)
+    // Folder workspaces have no repo Git options, so a WSL UNC path is the only
+    // durable signal that native Windows structured Codex cannot safely use it.
+    const wslDistro =
+      configuredWslDistro ??
+      (folderWorkspace && isLocalHost
+        ? (parseWslUncPath(target.worktree.path)?.distro ?? null)
+        : null)
     return {
       executionHostId: target.executionHostId,
       wslDistro,
diff --git a/src/main/runtime/rpc/methods/orchestration-worker-start-mode.test.ts b/src/main/runtime/rpc/methods/orchestration-worker-start-mode.test.ts
index 7eafe9c86d4..23ed5b5a549 100644
--- a/src/main/runtime/rpc/methods/orchestration-worker-start-mode.test.ts
+++ b/src/main/runtime/rpc/methods/orchestration-worker-start-mode.test.ts
@@ -23,13 +23,11 @@ function decide(
   overrides: {
     params?: Parameters<typeof decideWorkerStartMode>[0]['params']
     settings?: Parameters<typeof decideWorkerStartMode>[0]['settings']
-    platform?: NodeJS.Platform
   } = {}
 ): WorkerStartModeReceipt {
   return decideWorkerStartMode({
     params: { agent: 'claude', ...overrides.params },
-    settings: overrides.settings === undefined ? STRUCTURED_DEFAULT : overrides.settings,
-    platform: overrides.platform ?? 'darwin'
+    settings: overrides.settings === undefined ? STRUCTURED_DEFAULT : overrides.settings
   })
 }
 
@@ -90,12 +88,10 @@ describe('a structured default this dispatch cannot honour', () => {
     ).toMatchObject({ mode: 'terminal', reason: 'tui_launch_customization' })
   })
 
-  it('keeps Codex terminal-backed on Windows and leaves Claude to the host', () => {
-    expect(decide({ params: { agent: 'codex' }, platform: 'win32' })).toMatchObject({
-      mode: 'terminal',
-      reason: 'codex_on_windows'
-    })
-    expect(decide({ params: { agent: 'claude' }, platform: 'win32' }).mode).toBe('structured')
+  // Neither provider is refused here on the client's platform: only the executing host knows
+  // whether it can read a provider child's start time, and it answers at create time.
+  it.each(['claude', 'codex'] as const)('leaves a Windows %s worker to the host', (agent) => {
+    expect(decide({ params: { agent } }).mode).toBe('structured')
   })
 })
 
diff --git a/src/main/runtime/rpc/methods/orchestration-worker-start-mode.ts b/src/main/runtime/rpc/methods/orchestration-worker-start-mode.ts
index 7c02c2a688f..c1f22a2c3f4 100644
--- a/src/main/runtime/rpc/methods/orchestration-worker-start-mode.ts
+++ b/src/main/runtime/rpc/methods/orchestration-worker-start-mode.ts
@@ -87,7 +87,6 @@ const BLOCKER_REASON: Record<
   'floating-workspace': 'structured_unsupported_on_host',
   'tui-launch-customization': 'tui_launch_customization',
   'remote-execution-host': 'remote_execution_host',
-  'codex-on-windows': 'codex_on_windows',
   'project-runtime': 'wsl_execution_runtime',
   'runtime-capability': 'structured_sessions_unavailable'
 }
@@ -105,7 +104,6 @@ const HOST_SUPPORT_REASON: Record<
 export function decideWorkerStartMode(args: {
   params: WorkerStartModePlacement
   settings: WorkerStartModeSettings | null | undefined
-  platform: NodeJS.Platform
 }): WorkerStartModeReceipt {
   const { params, settings } = args
   if (!prefersStructuredNativeChatByDefault(settings)) {
@@ -125,7 +123,6 @@ export function decideWorkerStartMode(args: {
     agent,
     // Set only by --on, which the placement check above already turned into a fallback.
     executionHostId: 'local',
-    platform: args.platform,
     hostCapabilities: RUNTIME_CAPABILITIES,
     // Orchestration resolves a managed worktree or folder workspace; a floating terminal is never
     // a worker placement. WSL is left to the executing host's own create-support probe, which
diff --git a/src/main/runtime/rpc/methods/orchestration/worker/workers.ts b/src/main/runtime/rpc/methods/orchestration/worker/workers.ts
index 6ccac1dea9e..8b14ec044cf 100644
--- a/src/main/runtime/rpc/methods/orchestration/worker/workers.ts
+++ b/src/main/runtime/rpc/methods/orchestration/worker/workers.ts
@@ -51,8 +51,7 @@ export const ORCHESTRATION_WORKER_START_METHODS: RpcMethod[] = [
       await assertWorkerStartTaskSpecWithinPromptBudget(params.spec ?? existingTask!.spec)
       const mode = decideWorkerStartMode({
         params,
-        settings: readWorkerStartModeSettings(runtime),
-        platform: process.platform
+        settings: readWorkerStartModeSettings(runtime)
       })
       if (params.on) {
         // A remote worker is always a terminal agent; the mode receipt rides along so the
diff --git a/src/main/runtime/rpc/methods/structured-agent-session-gate.ts b/src/main/runtime/rpc/methods/structured-agent-session-gate.ts
index de83820e9c3..60b28425057 100644
--- a/src/main/runtime/rpc/methods/structured-agent-session-gate.ts
+++ b/src/main/runtime/rpc/methods/structured-agent-session-gate.ts
@@ -80,7 +80,10 @@ export function requireStructuredCleanupHost(ctx: RpcContext): StructuredAgentSe
 export async function ensureStructuredHostInstalled(ctx: RpcContext): Promise<void> {
   // Gated first: a client that cannot read structured sessions must not be able
   // to make the host exist, which is an observable side effect of the surface.
-  if (!supportsStructuredSessions(ctx) || getStructuredAgentSessionHost()) {
+  if (!supportsStructuredSessions(ctx)) {
+    return
+  }
+  if (getStructuredAgentSessionHost()) {
     return
   }
   await ctx.runtime.ensureStructuredAgentSessionHost()
diff --git a/src/main/runtime/structured-agent-session-runtime.test.ts b/src/main/runtime/structured-agent-session-runtime.test.ts
index 3b69a0a4be3..2ce51b1c29b 100644
--- a/src/main/runtime/structured-agent-session-runtime.test.ts
+++ b/src/main/runtime/structured-agent-session-runtime.test.ts
@@ -8,9 +8,11 @@ import { createTrackedJournalOpener } from '../native-chat/agent-session-journal
 import type { AgentSessionJournal } from '../native-chat/agent-session-journal/journal-store'
 import type {
   AgentSessionClaimStatus,
+  AgentSessionExecutionLocation,
   AgentSessionProcessIdentity,
   AgentSessionRecord
 } from '../../shared/agent-session-record'
+import { __setWindowsProcessTreeLoaderForTests } from '../windows/windows-process-table'
 import {
   createStructuredAgentSessionOwnerProbe,
   createStructuredAgentSessionOwnerProbes
@@ -270,6 +272,35 @@ describe('structured agent-session runtime install', () => {
       )
     )
   })
+
+  it('does not infer Windows process identity support from an injected reader', async () => {
+    stateDirectory = await mkdtemp(join(tmpdir(), 'orca-structured-runtime-'))
+    const originalPlatform = process.platform
+    const location: AgentSessionExecutionLocation = {
+      executionHostId: 'local',
+      wslDistro: null,
+      workspaceId: 'workspace-1',
+      workspaceKind: 'folder'
+    }
+    Object.defineProperty(process, 'platform', { configurable: true, value: 'win32' })
+    __setWindowsProcessTreeLoaderForTests(() => null)
+    try {
+      const host = await ensureStructuredAgentSessionHost({
+        stateDirectory,
+        hostId: HOST_ID,
+        claimKeyId: 'key-1',
+        resolveWorkspacePath: async () => stateDirectory!,
+        resolveEnvironment: async () => ({}),
+        resolveClaudeAuthPolicy: () => ({ stripAuthEnv: true }),
+        readProcessStartTime: async () => 1_700_000_000_000
+      })
+
+      expect(host.supportsCreate(location, 'codex')).toBe(false)
+    } finally {
+      __setWindowsProcessTreeLoaderForTests()
+      Object.defineProperty(process, 'platform', { configurable: true, value: originalPlatform })
+    }
+  })
 })
 
 // A stop whose teardown fails must not forget the runtime it was tearing down.
diff --git a/src/main/runtime/structured-agent-session-support-probe.test.ts b/src/main/runtime/structured-agent-session-support-probe.test.ts
index e393e41f3a4..f55a802e979 100644
--- a/src/main/runtime/structured-agent-session-support-probe.test.ts
+++ b/src/main/runtime/structured-agent-session-support-probe.test.ts
@@ -6,6 +6,21 @@ import {
 } from '../native-chat/agent-session-wire/structured-agent-session-registry'
 import { agentSessionPtyWriteGate } from './agent-session-pty-write-gate'
 
+const { isWindowsProcessStartTimeAvailable } = vi.hoisted(() => ({
+  isWindowsProcessStartTimeAvailable: vi.fn(() => true)
+}))
+
+vi.mock('../windows/windows-process-table', async (importOriginal) => ({
+  ...(await importOriginal<object>()),
+  isWindowsProcessStartTimeAvailable
+}))
+
+const originalPlatform = process.platform
+
+function setPlatform(platform: NodeJS.Platform): void {
+  Object.defineProperty(process, 'platform', { configurable: true, value: platform })
+}
+
 type InstallEffects = {
   storeOpened: boolean
   writeGateAttached: boolean
@@ -94,6 +109,9 @@ async function expectSupportWithoutInstall(input: {
 
 describe('structured agent-session create-support probe', () => {
   afterEach(() => {
+    setPlatform(originalPlatform)
+    isWindowsProcessStartTimeAvailable.mockReset()
+    isWindowsProcessStartTimeAvailable.mockReturnValue(true)
     setStructuredAgentSessionHost(null)
     agentSessionPtyWriteGate.detachRecordLookup()
     vi.restoreAllMocks()
@@ -111,6 +129,27 @@ describe('structured agent-session create-support probe', () => {
     }
   )
 
+  it.each([
+    ['codex', true, { supported: true }],
+    ['codex', false, { supported: false, reason: 'agent' }],
+    ['claude', true, { supported: true }],
+    ['claude', false, { supported: false, reason: 'agent' }]
+  ] as const)(
+    'requires native Windows process identity proof before answering %s support (%s)',
+    async (agent, proofAvailable, expected) => {
+      setPlatform('win32')
+      isWindowsProcessStartTimeAvailable.mockReturnValue(proofAvailable)
+
+      await expectSupportWithoutInstall({
+        agent,
+        location: { executionHostId: 'local', wslDistro: null },
+        expected
+      })
+
+      expect(isWindowsProcessStartTimeAvailable).toHaveBeenCalled()
+    }
+  )
+
   it.each(['codex', 'claude'] as const)(
     'still reports an unsupported remote %s location without installing the host',
     async (agent) => {
diff --git a/src/renderer/src/components/right-sidebar/ai-vault-session-resume-in-chat-workspace.ts b/src/renderer/src/components/right-sidebar/ai-vault-session-resume-in-chat-workspace.ts
index adedc94b22a..a1f2a296748 100644
--- a/src/renderer/src/components/right-sidebar/ai-vault-session-resume-in-chat-workspace.ts
+++ b/src/renderer/src/components/right-sidebar/ai-vault-session-resume-in-chat-workspace.ts
@@ -3,7 +3,6 @@ import {
   type AgentLaunchRoutingInput
 } from '@/lib/agent-launch-routing'
 import { getLocalProjectExecutionRuntimeContext } from '@/lib/local-preflight-context'
-import { CLIENT_PLATFORM } from '@/lib/new-workspace'
 import { getExecutionHostIdForWorktree } from '@/lib/worktree-runtime-owner'
 import { readLocalRuntimeCapabilities } from '@/runtime/local-runtime-capabilities'
 import { useAppStore } from '@/store'
@@ -47,7 +46,6 @@ export function resolveAiVaultSessionResumeInChatForWorkspace(args: {
           useAppStore.getState(),
           targetWorkspaceId as string
         ),
-        platform: CLIENT_PLATFORM,
         hostCapabilities: readLocalRuntimeCapabilities(),
         workspaceKind: (targetWorkspaceId as string).startsWith('folder:')
           ? 'folder'
diff --git a/src/renderer/src/components/sidebar/folder-workspace-composer-submit.ts b/src/renderer/src/components/sidebar/folder-workspace-composer-submit.ts
index ca685dded64..c016538cac9 100644
--- a/src/renderer/src/components/sidebar/folder-workspace-composer-submit.ts
+++ b/src/renderer/src/components/sidebar/folder-workspace-composer-submit.ts
@@ -1,8 +1,4 @@
-import {
-  CLIENT_PLATFORM,
-  ensureAgentStartupInTerminal,
-  type LinkedWorkItemSummary
-} from '@/lib/new-workspace'
+import { ensureAgentStartupInTerminal, type LinkedWorkItemSummary } from '@/lib/new-workspace'
 import { seedNativeChatLaunchDraftForAgentTab } from '@/lib/agent-launch-prompt-delivery'
 import { createBrowserUuid } from '@/lib/browser-uuid'
 import { buildAgentStartupPlan } from '@/lib/tui-agent-startup'
@@ -151,7 +147,6 @@ export async function submitFolderWorkspaceCreate({
         executionHostId: runtimeEnvironmentId
           ? `runtime:${encodeURIComponent(runtimeEnvironmentId)}`
           : (projectGroup.connectionId ?? 'local'),
-        platform: CLIENT_PLATFORM,
         hostCapabilities: readLocalRuntimeCapabilities(),
         workspaceKind: 'folder',
         promptDelivery: launchDraftPrompt ? 'draft' : 'auto-submit',
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 f199ca66f0c..0118f6c2236 100644
--- a/src/renderer/src/hooks/composer-state/full-creation-execution.ts
+++ b/src/renderer/src/hooks/composer-state/full-creation-execution.ts
@@ -33,7 +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 { CLIENT_PLATFORM, ensureAgentStartupInTerminal } from '@/lib/new-workspace'
+import { 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'
@@ -140,7 +140,6 @@ export function useFullCreationExecution(input: FullCreationExecutionInput) {
         agent: tuiAgent,
         settings,
         executionHostId: selectedRepoExecutionHostId ?? 'local',
-        platform: CLIENT_PLATFORM,
         hostCapabilities: readLocalRuntimeCapabilities(),
         workspaceKind: selectedRepoIsGit ? 'git-worktree' : 'folder',
         promptDelivery: startupPlan?.draftPrompt ? 'draft' : 'auto-submit',
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 7160cb48b4c..a25afd9106c 100644
--- a/src/renderer/src/hooks/composer-state/quick-creation-execution.ts
+++ b/src/renderer/src/hooks/composer-state/quick-creation-execution.ts
@@ -51,7 +51,6 @@ 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 {
@@ -206,7 +205,6 @@ export function useQuickCreationExecution(input: QuickCreationExecutionInput) {
             executionHostId: ephemeralVmRecipe
               ? 'runtime:pending-ephemeral-vm'
               : (workspaceRunContext?.hostId ?? selectedRepoExecutionHostId ?? 'local'),
-            platform: CLIENT_PLATFORM,
             hostCapabilities: readLocalRuntimeCapabilities(),
             workspaceKind: selectedRepoIsGit ? 'git-worktree' : 'folder',
             promptDelivery: quickDraftPrompt ? 'draft' : 'auto-submit',
diff --git a/src/renderer/src/lib/agent-launch-routing.test.ts b/src/renderer/src/lib/agent-launch-routing.test.ts
index af219bab633..cb3a2b70b00 100644
--- a/src/renderer/src/lib/agent-launch-routing.test.ts
+++ b/src/renderer/src/lib/agent-launch-routing.test.ts
@@ -19,7 +19,6 @@ function route(overrides: Partial<Parameters<typeof resolveAgentLaunchRoute>[0]>
     agent: 'codex',
     settings,
     executionHostId: 'local',
-    platform: 'darwin',
     hostCapabilities: [STRUCTURED_AGENT_SESSION_RUNTIME_CAPABILITY],
     workspaceKind: 'git-worktree',
     nativeChatTranscriptIsLocalReadable: true,
@@ -41,57 +40,16 @@ describe('resolveAgentLaunchRoute', () => {
     }
   )
 
-  /** Boundary guard between this lane and the one that owns Windows Codex. Codex's win32 refusal is
-   *  deliberate, so it is asserted against whatever currently lets Claude through rather than
-   *  against one host answer — a future gate swap must not be able to flip Codex on quietly. */
-  describe("Codex's Windows refusal", () => {
-    it('holds in the exact situation that routes Claude to structured', () => {
-      const onWindows = { platform: 'win32' } as const
-      expect(route({ ...onWindows, agent: 'claude' })).toBe('structured-native-chat')
-      expect(route({ ...onWindows, agent: 'codex' })).toBe('legacy-native-chat')
-    })
-
-    it('holds for every host capability set, including ones that carry extra gates', () => {
-      for (const hostCapabilities of [
-        [STRUCTURED_AGENT_SESSION_RUNTIME_CAPABILITY],
-        [STRUCTURED_AGENT_SESSION_RUNTIME_CAPABILITY, 'agent-session.structured.claude.v1'],
-        [STRUCTURED_AGENT_SESSION_RUNTIME_CAPABILITY, 'agent-session.structured.hold.v1']
-      ]) {
-        expect(route({ agent: 'codex', platform: 'win32', hostCapabilities })).toBe(
-          'legacy-native-chat'
-        )
-      }
-    })
-
-    it('holds for prompted and folder-workspace launches too', () => {
-      expect(
-        route({
-          agent: 'codex',
-          platform: 'win32',
-          launchText: 'go',
-          promptDelivery: 'auto-submit'
-        })
-      ).toBe('legacy-native-chat')
-      expect(route({ agent: 'codex', platform: 'win32', workspaceKind: 'folder' })).toBe(
-        'legacy-native-chat'
-      )
-    })
-  })
-
-  /** Pins Codex's whole platform answer, not just win32, so no platform silently changes here. */
-  it.each([
-    ['darwin', 'structured-native-chat'],
-    ['linux', 'structured-native-chat'],
-    ['win32', 'legacy-native-chat']
-  ] as const)('leaves Codex routing on %s unchanged', (platform, expected) => {
-    expect(route({ agent: 'codex', platform })).toBe(expected)
-  })
-
-  /** Claude's Windows answer is not a client-side platform guess: the route lets it through and the
-   *  executing host settles it with agentSession.createSupport at create time. */
-  it('lets a Windows Claude launch reach the host-measured create support check', () => {
-    expect(route({ agent: 'claude', platform: 'win32' })).toBe('structured-native-chat')
-  })
+  /** Windows eligibility is no client-side platform guess for either provider: the route lets the
+   *  launch through and the executing host settles it with agentSession.createSupport at create
+   *  time. A stale caller still passing the removed `platform` input must not flip Codex off the
+   *  structured route — the field is gone, not reinterpreted. */
+  it.each(['claude', 'codex'] as const)(
+    'routes %s to structured even when the caller claims a win32 client platform',
+    (agent) => {
+      expect(route({ agent, ...({ platform: 'win32' } as object) })).toBe('structured-native-chat')
+    }
+  )
 
   it('routes a supported local Codex launch to structured native chat', () => {
     expect(route()).toBe('structured-native-chat')
@@ -134,15 +92,13 @@ describe('resolveAgentLaunchRoute', () => {
   it.each(['git-worktree', 'folder'] as const)(
     'supports a local %s without widening floating-terminal scope',
     (workspaceKind) => {
-      expect(route({ workspaceKind, platform: 'linux' })).toBe('structured-native-chat')
+      expect(route({ workspaceKind })).toBe('structured-native-chat')
     }
   )
 
   it('keeps floating, WSL, and repair-required launches terminal-backed', () => {
     expect(route({ workspaceKind: 'floating' })).toBe('legacy-native-chat')
-    expect(route({ agent: 'claude', workspaceKind: 'floating', platform: 'win32' })).toBe(
-      'legacy-native-chat'
-    )
+    expect(route({ agent: 'claude', workspaceKind: 'floating' })).toBe('legacy-native-chat')
     expect(
       route({
         projectRuntime: {
diff --git a/src/renderer/src/lib/agent-launch-routing.ts b/src/renderer/src/lib/agent-launch-routing.ts
index 2bca72ba3ae..090ef3c9108 100644
--- a/src/renderer/src/lib/agent-launch-routing.ts
+++ b/src/renderer/src/lib/agent-launch-routing.ts
@@ -30,7 +30,6 @@ export type AgentLaunchRoutingInput = {
     | null
     | undefined
   executionHostId: string
-  platform: NodeJS.Platform
   hostCapabilities: readonly string[]
   workspaceKind?: 'git-worktree' | 'folder' | 'floating'
   projectRuntime?: ProjectExecutionRuntimeResolution | null
@@ -68,7 +67,6 @@ export function structuredAgentLaunchSupported(
     resolveStructuredNativeChatSupport({
       agent: input.agent,
       executionHostId: input.executionHostId,
-      platform: input.platform,
       hostCapabilities: input.hostCapabilities,
       workspaceKind: input.workspaceKind,
       projectRuntime: input.projectRuntime,
diff --git a/src/renderer/src/lib/launch-agent-in-new-tab.ts b/src/renderer/src/lib/launch-agent-in-new-tab.ts
index 118fcdbeda8..cb3187878ef 100644
--- a/src/renderer/src/lib/launch-agent-in-new-tab.ts
+++ b/src/renderer/src/lib/launch-agent-in-new-tab.ts
@@ -213,7 +213,6 @@ function launchAgentInNewTabInternal(
         agent,
         settings: store.settings,
         executionHostId: getExecutionHostIdForWorktree(store, worktreeId),
-        platform: CLIENT_PLATFORM,
         hostCapabilities: readLocalRuntimeCapabilities(),
         workspaceKind,
         projectRuntime: getLocalProjectExecutionRuntimeContext(store, worktreeId),
diff --git a/src/renderer/src/lib/launch-structured-agent-session.test.ts b/src/renderer/src/lib/launch-structured-agent-session.test.ts
index d9a75ee2827..1d7dec2cdf3 100644
--- a/src/renderer/src/lib/launch-structured-agent-session.test.ts
+++ b/src/renderer/src/lib/launch-structured-agent-session.test.ts
@@ -19,37 +19,43 @@ describe('structured agent session launch', () => {
   })
 
   it('creates a native session with a host-verifiable launch intent', async () => {
-    vi.mocked(callStructuredAgentSession).mockImplementation(async (_target, _method, params) => ({
-      ok: true,
-      replayed: false,
-      fence: 1,
-      cursor: { epoch: 'epoch-1', sequence: 0 },
-      value: {
-        sessionId: (params as { envelope: { sessionId: string } }).envelope.sessionId,
-        fence: 1,
-        page: {
-          sessionId: 'session-1',
-          epoch: 'epoch-1',
-          direction: 'tail',
-          items: [],
-          removedItemIds: [],
-          submissions: [],
-          window: {
-            oldest: null,
-            newest: null,
-            nextCursor: { epoch: 'epoch-1', sequence: 0 }
-          },
-          liveCursor: { epoch: 'epoch-1', sequence: 0 },
-          hasOlder: false,
-          hasNewer: false
-        },
-        unconfirmedClientMessageIds: []
-      }
-    }))
+    vi.mocked(callStructuredAgentSession).mockImplementation(async (_target, method, params) =>
+      method === 'agentSession.createSupport'
+        ? { supported: true }
+        : {
+            ok: true,
+            replayed: false,
+            fence: 1,
+            cursor: { epoch: 'epoch-1', sequence: 0 },
+            value: {
+              sessionId: (params as { envelope: { sessionId: string } }).envelope.sessionId,
+              fence: 1,
+              page: {
+                sessionId: 'session-1',
+                epoch: 'epoch-1',
+                direction: 'tail',
+                items: [],
+                removedItemIds: [],
+                submissions: [],
+                window: {
+                  oldest: null,
+                  newest: null,
+                  nextCursor: { epoch: 'epoch-1', sequence: 0 }
+                },
+                liveCursor: { epoch: 'epoch-1', sequence: 0 },
+                hasOlder: false,
+                hasNewer: false
+              },
+              unconfirmedClientMessageIds: []
+            }
+          }
+    )
 
     const intent = createStructuredAgentSessionLaunchIntent('workspace-1', 'codex')
     const receipt = await launchStructuredAgentSession(intent)
-    const params = vi.mocked(callStructuredAgentSession).mock.calls[0]?.[2] as {
+    const params = vi
+      .mocked(callStructuredAgentSession)
+      .mock.calls.find(([, method]) => method === 'agentSession.create')?.[2] as {
       envelope: { sessionId: string; payloadFingerprint: string }
       worktree: string
       agent: 'codex'
@@ -87,40 +93,46 @@ describe('structured agent session launch', () => {
     )
   })
 
-  it('asks the executing host for create support before creating a Claude session', async () => {
-    vi.mocked(callStructuredAgentSession).mockImplementation(async (_target, method) =>
-      method === 'agentSession.createSupport'
-        ? { supported: true }
-        : { ok: true, replayed: false, value: { sessionId: 'claude_1', fence: 1 } }
-    )
+  it.each(['claude', 'codex'] as const)(
+    'asks the executing host for create support before creating a %s session',
+    async (agent) => {
+      vi.mocked(callStructuredAgentSession).mockImplementation(async (_target, method) =>
+        method === 'agentSession.createSupport'
+          ? { supported: true }
+          : { ok: true, replayed: false, value: { sessionId: `${agent}_1`, fence: 1 } }
+      )
 
-    const intent = createStructuredAgentSessionLaunchIntent('workspace-1', 'claude')
-    await launchStructuredAgentSession(intent)
+      const intent = createStructuredAgentSessionLaunchIntent('workspace-1', agent)
+      await launchStructuredAgentSession(intent)
 
-    expect(vi.mocked(callStructuredAgentSession).mock.calls.map(([, method]) => method)).toEqual([
-      'agentSession.createSupport',
-      'agentSession.create'
-    ])
-    expect(callStructuredAgentSession).toHaveBeenNthCalledWith(
-      1,
-      { kind: 'local' },
-      'agentSession.createSupport',
-      { worktree: 'id:workspace-1', agent: 'claude' }
-    )
-  })
+      expect(vi.mocked(callStructuredAgentSession).mock.calls.map(([, method]) => method)).toEqual([
+        'agentSession.createSupport',
+        'agentSession.create'
+      ])
+      expect(callStructuredAgentSession).toHaveBeenNthCalledWith(
+        1,
+        { kind: 'local' },
+        'agentSession.createSupport',
+        { worktree: 'id:workspace-1', agent }
+      )
+    }
+  )
 
-  it('refuses a Claude launch the host says it cannot support, without creating', async () => {
-    vi.mocked(callStructuredAgentSession).mockResolvedValue({ supported: false, reason: 'agent' })
+  it.each(['claude', 'codex'] as const)(
+    'refuses a %s launch the host says it cannot support, without creating',
+    async (agent) => {
+      vi.mocked(callStructuredAgentSession).mockResolvedValue({ supported: false, reason: 'agent' })
 
-    const intent = createStructuredAgentSessionLaunchIntent('workspace-1', 'claude')
+      const intent = createStructuredAgentSessionLaunchIntent('workspace-1', agent)
 
-    await expect(launchStructuredAgentSession(intent)).rejects.toBeInstanceOf(
-      StructuredAgentSessionCreateRefusalError
-    )
-    expect(vi.mocked(callStructuredAgentSession).mock.calls.map(([, method]) => method)).toEqual([
-      'agentSession.createSupport'
-    ])
-  })
+      await expect(launchStructuredAgentSession(intent)).rejects.toBeInstanceOf(
+        StructuredAgentSessionCreateRefusalError
+      )
+      expect(vi.mocked(callStructuredAgentSession).mock.calls.map(([, method]) => method)).toEqual([
+        'agentSession.createSupport'
+      ])
+    }
+  )
 
   it('fails closed when the create support probe cannot be answered', async () => {
     vi.mocked(callStructuredAgentSession).mockRejectedValue(new Error('runtime unreachable'))
@@ -212,46 +224,40 @@ describe('structured agent session launch', () => {
     expect(callStructuredAgentSession).toHaveBeenCalledOnce()
   })
 
-  /** Codex's support answer is settled by the launch route and owned elsewhere; this pins that the
-   *  Claude probe did not change Codex's wire traffic. */
-  it('does not probe create support for Codex', async () => {
-    vi.mocked(callStructuredAgentSession).mockResolvedValue({
-      ok: true,
-      replayed: false,
-      value: { sessionId: 'codex_1', fence: 1 }
-    })
-
-    await launchStructuredAgentSession(
-      createStructuredAgentSessionLaunchIntent('workspace-1', 'codex')
+  /** The probe now runs for Codex too, so create-outcome tests script it to say yes. */
+  function mockSupportedCreate(create: () => unknown): void {
+    vi.mocked(callStructuredAgentSession).mockImplementation(async (_target, method) =>
+      method === 'agentSession.createSupport' ? { supported: true } : create()
     )
-
-    expect(vi.mocked(callStructuredAgentSession).mock.calls.map(([, method]) => method)).toEqual([
-      'agentSession.create'
-    ])
-  })
+  }
 
   it('replays the exact create envelope when an unknown outcome is retried', async () => {
     const intent = createStructuredAgentSessionLaunchIntent('workspace-retry', 'codex')
-    vi.mocked(callStructuredAgentSession).mockRejectedValue(new Error('response lost'))
+    mockSupportedCreate(() => {
+      throw new Error('response lost')
+    })
 
     await expect(launchStructuredAgentSession(intent)).rejects.toThrow('response lost')
     await expect(launchStructuredAgentSession(intent)).rejects.toThrow('response lost')
 
-    const first = vi.mocked(callStructuredAgentSession).mock.calls[0]?.[2]
-    const second = vi.mocked(callStructuredAgentSession).mock.calls[1]?.[2]
+    const createCalls = vi
+      .mocked(callStructuredAgentSession)
+      .mock.calls.filter(([, method]) => method === 'agentSession.create')
+    const first = createCalls[0]?.[2]
+    const second = createCalls[1]?.[2]
     expect(first).toBe(intent.params)
     expect(second).toBe(first)
     expect(intent.params.envelope.clientOperationId).toMatch(/^\d{13}-[0-9a-f]{32}$/)
   })
 
   it('preserves an unknown refusal code without classifying it as fallback-safe', async () => {
-    vi.mocked(callStructuredAgentSession).mockResolvedValue({
+    mockSupportedCreate(() => ({
       ok: false,
       refusal: {
         code: 'agent_session_operation_unknown',
         message: 'The chat may already exist.'
       }
-    })
+    }))
 
     const error = await launchStructuredAgentSession(
       createStructuredAgentSessionLaunchIntent('workspace-unknown', 'codex')
@@ -266,13 +272,13 @@ describe('structured agent session launch', () => {
   /** The class is the verdict, so a refusal message that happens to end in a definitive token
    *  must not be re-read into one by the transport-error matcher. */
   it('keeps an unknown outcome unknown even when its message ends in a definitive token', async () => {
-    vi.mocked(callStructuredAgentSession).mockResolvedValue({
+    mockSupportedCreate(() => ({
       ok: false,
       refusal: {
         code: 'agent_session_ownership_unknown',
         message: 'Owner check failed: method_not_found'
       }
-    })
+    }))
 
     const error = await launchStructuredAgentSession(
       createStructuredAgentSessionLaunchIntent('workspace-unknown-token', 'codex')
@@ -283,13 +289,13 @@ describe('structured agent session launch', () => {
   })
 
   it('preserves a definitive refusal code for the fallback path', async () => {
-    vi.mocked(callStructuredAgentSession).mockResolvedValue({
+    mockSupportedCreate(() => ({
       ok: false,
       refusal: {
         code: 'structured_agent_session_unsupported',
         message: 'Structured chat is unavailable.'
       }
-    })
+    }))
 
     const error = await launchStructuredAgentSession(
       createStructuredAgentSessionLaunchIntent('workspace-unsupported', 'codex')
@@ -303,9 +309,9 @@ describe('structured agent session launch', () => {
   it.each(['method_not_found', 'structured_agent_session_unsupported'])(
     'turns an old-host %s error into a definitive transport refusal',
     async (code) => {
-      vi.mocked(callStructuredAgentSession).mockRejectedValueOnce(
-        Object.assign(new Error(code), { code })
-      )
+      mockSupportedCreate(() => {
+        throw Object.assign(new Error(code), { code })
+      })
       const oldHostError = await launchStructuredAgentSession(
         createStructuredAgentSessionLaunchIntent(`workspace-old-host-${code}`, 'codex')
       ).catch((caught: unknown) => caught)
@@ -316,9 +322,9 @@ describe('structured agent session launch', () => {
   )
 
   it('keeps an unclassified transport failure outcome unknown', async () => {
-    vi.mocked(callStructuredAgentSession).mockRejectedValueOnce(
-      Object.assign(new Error('Connection lost'), { code: 'runtime_error' })
-    )
+    mockSupportedCreate(() => {
+      throw Object.assign(new Error('Connection lost'), { code: 'runtime_error' })
+    })
     const transportError = await launchStructuredAgentSession(
       createStructuredAgentSessionLaunchIntent('workspace-offline', 'codex')
     ).catch((caught: unknown) => caught)
diff --git a/src/renderer/src/lib/launch-structured-agent-session.ts b/src/renderer/src/lib/launch-structured-agent-session.ts
index 503ae771419..0694090fc5c 100644
--- a/src/renderer/src/lib/launch-structured-agent-session.ts
+++ b/src/renderer/src/lib/launch-structured-agent-session.ts
@@ -174,17 +174,10 @@ async function hostSupportsCreate(intent: StructuredAgentSessionLaunchIntent): P
 /**
  * Only the host that will execute the session can answer whether it supports creating one there —
  * on Windows that means reading the provider child's process start time, which a client cannot
- * observe.
- *
- * Codex is absent on purpose: its answer is settled by the launch route and owned elsewhere, so
- * probing here would change Codex's wire traffic. Note that this early return is also why the
- * unresolvable-selector race above has never been able to refuse a Codex launch — the race is
- * identical for Codex, nothing asks. Whoever gives Codex a probe inherits it.
+ * observe. Both providers ask: the host classifies per agent, and Codex inherits the
+ * unresolvable-selector retry above along with the probe.
  */
 async function requireHostCreateSupport(intent: StructuredAgentSessionLaunchIntent): Promise<void> {
-  if (intent.agent !== 'claude') {
-    return
-  }
   if (!(await hostSupportsCreate(intent))) {
     abandonStructuredAgentSessionLaunchIntent(intent)
     throw new StructuredAgentSessionCreateRefusalError(
diff --git a/src/renderer/src/lib/launch-work-item-direct-route-preparation.ts b/src/renderer/src/lib/launch-work-item-direct-route-preparation.ts
index 55aa77bddbe..1fdc3b6fa69 100644
--- a/src/renderer/src/lib/launch-work-item-direct-route-preparation.ts
+++ b/src/renderer/src/lib/launch-work-item-direct-route-preparation.ts
@@ -97,7 +97,6 @@ export async function prepareDirectWorkItemAgentLaunch(args: {
       agent: effectiveAgent,
       settings: args.settings,
       executionHostId: getExecutionHostIdForWorktree(args.latestStore, args.worktreeId),
-      platform: CLIENT_PLATFORM,
       hostCapabilities: readLocalRuntimeCapabilities(),
       workspaceKind: 'git-worktree',
       projectRuntime: getLocalProjectExecutionRuntimeContext(
diff --git a/src/renderer/src/lib/onboarding-folder-agent-startup.ts b/src/renderer/src/lib/onboarding-folder-agent-startup.ts
index 958f43eda28..a4341a4dc87 100644
--- a/src/renderer/src/lib/onboarding-folder-agent-startup.ts
+++ b/src/renderer/src/lib/onboarding-folder-agent-startup.ts
@@ -135,7 +135,6 @@ export function resolveDismissedOnboardingFolderAgentLaunch(args: {
     agent,
     settings: args.settings,
     executionHostId: args.executionHostId,
-    platform: getClientPlatform(),
     hostCapabilities: readLocalRuntimeCapabilities(),
     workspaceKind: 'folder',
     nativeChatTranscriptIsLocalReadable: args.nativeChatTranscriptIsLocalReadable,
diff --git a/src/renderer/src/lib/structured-agent-session-launch-refusal-fallback.test.ts b/src/renderer/src/lib/structured-agent-session-launch-refusal-fallback.test.ts
index 45c41bd111e..9139b1c122a 100644
--- a/src/renderer/src/lib/structured-agent-session-launch-refusal-fallback.test.ts
+++ b/src/renderer/src/lib/structured-agent-session-launch-refusal-fallback.test.ts
@@ -58,6 +58,9 @@ type CreateReply = { ok: boolean; refusal?: { code: string; message: string } }
 function replyToCreates(...replies: CreateReply[]): void {
   let index = 0
   mocks.call.mockImplementation(async (_target: unknown, method: string, params: unknown) => {
+    if (method === 'agentSession.createSupport') {
+      return { supported: true }
+    }
     if (method !== 'agentSession.create') {
       return { ok: true, page: { fence: 1 } }
     }
diff --git a/src/renderer/src/lib/structured-agent-session-launch-resume-identity.test.ts b/src/renderer/src/lib/structured-agent-session-launch-resume-identity.test.ts
index 7e99ff73fe6..f93437bc088 100644
--- a/src/renderer/src/lib/structured-agent-session-launch-resume-identity.test.ts
+++ b/src/renderer/src/lib/structured-agent-session-launch-resume-identity.test.ts
@@ -63,11 +63,16 @@ describe('a launch that adopts a conversation is its own identity', () => {
     vi.clearAllMocks()
     localStorage.clear()
     mocks.refresh.mockResolvedValue([])
-    mocks.call.mockImplementation(async (_target: unknown, method: string) =>
-      method === 'agentSession.create'
-        ? new Promise(() => {})
-        : { ok: true, value: { submission: { dispatchState: 'accepted' } } }
-    )
+    mocks.call.mockImplementation(async (_target: unknown, method: string) => {
+      if (method === 'agentSession.create') {
+        return new Promise(() => {})
+      }
+      // Both providers now ask the executing host before creating.
+      if (method === 'agentSession.createSupport') {
+        return { supported: true }
+      }
+      return { ok: true, value: { submission: { dispatchState: 'accepted' } } }
+    })
   })
 
   it('does not hand a resume the blank launch already pending for the same worktree', async () => {
diff --git a/src/renderer/src/lib/web-client-location.test.ts b/src/renderer/src/lib/web-client-location.test.ts
new file mode 100644
index 00000000000..9ea2886e533
--- /dev/null
+++ b/src/renderer/src/lib/web-client-location.test.ts
@@ -0,0 +1,43 @@
+import { afterEach, describe, expect, it, vi } from 'vitest'
+import { isWebClientLocation } from './web-client-location'
+
+afterEach(() => {
+  vi.unstubAllGlobals()
+})
+
+describe('isWebClientLocation', () => {
+  it('reports false when there is no window at all', () => {
+    vi.stubGlobal('window', undefined)
+    expect(isWebClientLocation()).toBe(false)
+  })
+
+  // Why: this runs on the launch-routing path, where a throw is swallowed and
+  // silently becomes a failed launch. A window without a usable `location`
+  // must answer the question, not throw.
+  it('does not throw when window exists without a location', () => {
+    vi.stubGlobal('window', { api: {} })
+    expect(() => isWebClientLocation()).not.toThrow()
+    expect(isWebClientLocation()).toBe(false)
+  })
+
+  it('does not throw when location exists without a pathname', () => {
+    vi.stubGlobal('window', { location: {} })
+    expect(() => isWebClientLocation()).not.toThrow()
+    expect(isWebClientLocation()).toBe(false)
+  })
+
+  it('detects the web client by its entry path', () => {
+    vi.stubGlobal('window', { location: { pathname: '/web-index.html' } })
+    expect(isWebClientLocation()).toBe(true)
+  })
+
+  it('detects the web client by its global marker', () => {
+    vi.stubGlobal('window', { __ORCA_WEB_CLIENT__: true, location: { pathname: '/' } })
+    expect(isWebClientLocation()).toBe(true)
+  })
+
+  it('reports false for a normal desktop renderer path', () => {
+    vi.stubGlobal('window', { location: { pathname: '/index.html' } })
+    expect(isWebClientLocation()).toBe(false)
+  })
+})
diff --git a/src/renderer/src/lib/web-client-location.ts b/src/renderer/src/lib/web-client-location.ts
index 26c7e70bb21..94d751b8ab1 100644
--- a/src/renderer/src/lib/web-client-location.ts
+++ b/src/renderer/src/lib/web-client-location.ts
@@ -2,8 +2,13 @@ export function isWebClientLocation(): boolean {
   if (typeof window === 'undefined') {
     return false
   }
+  // Why the pathname guard: `window` can exist without a usable `location`
+  // (partial test doubles, and any embedder that stubs the global), and this
+  // runs on the launch-routing path where a throw is swallowed and silently
+  // turns into a failed launch rather than a visible error.
+  const pathname = (window as { location?: { pathname?: unknown } }).location?.pathname
   return (
     Boolean((window as unknown as { __ORCA_WEB_CLIENT__?: boolean }).__ORCA_WEB_CLIENT__) ||
-    window.location.pathname.endsWith('/web-index.html')
+    (typeof pathname === 'string' && pathname.endsWith('/web-index.html'))
   )
 }
diff --git a/src/renderer/src/lib/windows-terminal-capabilities-race.test.ts b/src/renderer/src/lib/windows-terminal-capabilities-race.test.ts
new file mode 100644
index 00000000000..0439e5c76bf
--- /dev/null
+++ b/src/renderer/src/lib/windows-terminal-capabilities-race.test.ts
@@ -0,0 +1,80 @@
+// @vitest-environment happy-dom
+
+import { afterEach, describe, expect, it, vi } from 'vitest'
+import {
+  getCachedWindowsTerminalCapabilities,
+  loadWindowsTerminalCapabilities,
+  resetWindowsTerminalCapabilitiesForTests
+} from './windows-terminal-capabilities'
+import { resetWindowsTerminalCapabilityReprobeForTests } from './windows-terminal-capability-reprobe'
+
+describe('Windows terminal capability probe ordering', () => {
+  afterEach(() => {
+    resetWindowsTerminalCapabilitiesForTests()
+    resetWindowsTerminalCapabilityReprobeForTests()
+    vi.unstubAllGlobals()
+  })
+
+  it('does not let an older forced probe overwrite a newer identity proof', async () => {
+    let resolveOlderStatus!: (status: { hostPlatform: NodeJS.Platform }) => void
+    let resolveNewerStatus!: (status: {
+      hostPlatform: NodeJS.Platform
+      windowsProcessStartTimeAvailable: boolean
+    }) => void
+    const olderStatus = new Promise<{ hostPlatform: NodeJS.Platform }>((resolve) => {
+      resolveOlderStatus = resolve
+    })
+    const newerStatus = new Promise<{
+      hostPlatform: NodeJS.Platform
+      windowsProcessStartTimeAvailable: boolean
+    }>((resolve) => {
+      resolveNewerStatus = resolve
+    })
+    const runtimeGetStatus = vi
+      .fn<() => Promise<unknown>>()
+      .mockReturnValueOnce(olderStatus)
+      .mockReturnValueOnce(newerStatus)
+    vi.stubGlobal('window', {
+      api: {
+        wsl: {
+          isAvailable: vi.fn().mockResolvedValue(false),
+          listDistros: vi.fn().mockResolvedValue([])
+        },
+        pwsh: { isAvailable: vi.fn().mockResolvedValue(false) },
+        gitBash: { isAvailable: vi.fn().mockResolvedValue(false) },
+        runtime: { getStatus: runtimeGetStatus }
+      }
+    })
+
+    const olderProbe = loadWindowsTerminalCapabilities({
+      ownerKey: 'local',
+      force: true,
+      now: 1_000
+    })
+    const newerProbe = loadWindowsTerminalCapabilities({
+      ownerKey: 'local',
+      force: true,
+      now: 2_000
+    })
+
+    resolveNewerStatus({ hostPlatform: 'win32', windowsProcessStartTimeAvailable: true })
+    await expect(newerProbe).resolves.toMatchObject({
+      hostPlatform: 'win32',
+      windowsProcessStartTimeAvailable: true
+    })
+    expect(getCachedWindowsTerminalCapabilities('local')).toMatchObject({
+      hostPlatform: 'win32',
+      windowsProcessStartTimeAvailable: true
+    })
+
+    resolveOlderStatus({ hostPlatform: 'win32' })
+    await expect(olderProbe).resolves.toMatchObject({
+      hostPlatform: 'win32',
+      windowsProcessStartTimeAvailable: true
+    })
+    expect(getCachedWindowsTerminalCapabilities('local')).toMatchObject({
+      hostPlatform: 'win32',
+      windowsProcessStartTimeAvailable: true
+    })
+  })
+})
diff --git a/src/renderer/src/lib/windows-terminal-capabilities.test.ts b/src/renderer/src/lib/windows-terminal-capabilities.test.ts
index 1f1a83dec9e..d1ad22b463d 100644
--- a/src/renderer/src/lib/windows-terminal-capabilities.test.ts
+++ b/src/renderer/src/lib/windows-terminal-capabilities.test.ts
@@ -70,6 +70,7 @@ function stubTerminalCapabilityApi(args: {
   wslDistros?: string[]
   gitBashAvailable?: boolean
   hostPlatform?: NodeJS.Platform | null
+  windowsProcessStartTimeAvailable?: boolean
 }): {
   wslIsAvailable: ReturnType<typeof vi.fn>
   wslListDistros: ReturnType<typeof vi.fn>
@@ -81,9 +82,12 @@ function stubTerminalCapabilityApi(args: {
   const wslListDistros = vi.fn().mockResolvedValue(args.wslDistros ?? [])
   const pwshIsAvailable = vi.fn().mockResolvedValue(args.pwshAvailable)
   const isGitBashAvailable = vi.fn().mockResolvedValue(args.gitBashAvailable ?? false)
-  const runtimeGetStatus = vi
-    .fn()
-    .mockResolvedValue({ hostPlatform: 'hostPlatform' in args ? args.hostPlatform : 'win32' })
+  const runtimeGetStatus = vi.fn().mockResolvedValue({
+    hostPlatform: 'hostPlatform' in args ? args.hostPlatform : 'win32',
+    ...(args.windowsProcessStartTimeAvailable !== undefined
+      ? { windowsProcessStartTimeAvailable: args.windowsProcessStartTimeAvailable }
+      : {})
+  })
 
   vi.stubGlobal('window', {
     api: {
@@ -583,7 +587,8 @@ describe('windows terminal capabilities', () => {
     const { wslIsAvailable, wslListDistros } = stubTerminalCapabilityApi({
       wslAvailable: false,
       pwshAvailable: true,
-      wslDistros: []
+      wslDistros: [],
+      windowsProcessStartTimeAvailable: true
     })
     wslIsAvailable.mockResolvedValueOnce(false).mockResolvedValue(true)
     wslListDistros.mockResolvedValueOnce([]).mockResolvedValue(['Ubuntu'])
diff --git a/src/renderer/src/lib/windows-terminal-capabilities.ts b/src/renderer/src/lib/windows-terminal-capabilities.ts
index c759567df15..4bc5d6d7b6e 100644
--- a/src/renderer/src/lib/windows-terminal-capabilities.ts
+++ b/src/renderer/src/lib/windows-terminal-capabilities.ts
@@ -11,6 +11,8 @@ export type WindowsTerminalCapabilities = {
   pwshAvailable: boolean
   gitBashAvailable: boolean
   hostPlatform: NodeJS.Platform | null
+  /** Host-owned PID-reuse proof; absent means the host did not advertise it. */
+  windowsProcessStartTimeAvailable?: boolean
   isLoading: boolean
 }
 
diff --git a/src/renderer/src/lib/windows-terminal-capability-read.ts b/src/renderer/src/lib/windows-terminal-capability-read.ts
index 3c9a7edc6bc..9a77538cefc 100644
--- a/src/renderer/src/lib/windows-terminal-capability-read.ts
+++ b/src/renderer/src/lib/windows-terminal-capability-read.ts
@@ -49,16 +49,13 @@ export async function readWindowsTerminalCapabilities(
   }
 
   if (target.kind === 'local') {
-    const [wslAvailable, wslDistros, pwshAvailable, gitBashAvailable, hostPlatform] =
+    const [wslAvailable, wslDistros, pwshAvailable, gitBashAvailable, runtimeStatus] =
       await Promise.all([
         window.api.wsl.isAvailable().catch(() => false),
         window.api.wsl.listDistros().catch(() => []),
         window.api.pwsh.isAvailable().catch(() => false),
         window.api.gitBash.isAvailable().catch(() => false),
-        window.api.runtime
-          .getStatus()
-          .then((status) => status.hostPlatform ?? null)
-          .catch(() => null)
+        window.api.runtime.getStatus().catch(() => null)
       ])
     const reconciledWslAvailable = await reconcileWslAvailability(wslAvailable, wslDistros, () =>
       window.api.wsl.isAvailable()
@@ -68,7 +65,10 @@ export async function readWindowsTerminalCapabilities(
       wslDistros,
       pwshAvailable,
       gitBashAvailable,
-      hostPlatform,
+      hostPlatform: runtimeStatus?.hostPlatform ?? null,
+      ...(runtimeStatus?.windowsProcessStartTimeAvailable !== undefined
+        ? { windowsProcessStartTimeAvailable: runtimeStatus.windowsProcessStartTimeAvailable }
+        : {}),
       isLoading: false
     }
   }
diff --git a/src/renderer/src/lib/windows-terminal-capability-reprobe.test.ts b/src/renderer/src/lib/windows-terminal-capability-reprobe.test.ts
index ad35839ba3d..3d3d476753e 100644
--- a/src/renderer/src/lib/windows-terminal-capability-reprobe.test.ts
+++ b/src/renderer/src/lib/windows-terminal-capability-reprobe.test.ts
@@ -40,6 +40,36 @@ afterEach(() => {
 })
 
 describe('windows terminal capability re-probe', () => {
+  it('reprobes usable WSL until Windows process identity is proved', async () => {
+    vi.useFakeTimers()
+    let current: WindowsTerminalCapabilities = USABLE_WSL
+    const probe = vi.fn(async () => {
+      current = { ...current, windowsProcessStartTimeAvailable: true }
+      return current
+    })
+    const readCached = () => current
+    startWindowsTerminalCapabilityReprobe({ ownerKey: 'local', probe, readCached })
+
+    await vi.advanceTimersByTimeAsync(30_000)
+    expect(probe).toHaveBeenCalledTimes(1)
+    expect(readCached().windowsProcessStartTimeAvailable).toBe(true)
+
+    await vi.advanceTimersByTimeAsync(30 * 60_000)
+    expect(probe).toHaveBeenCalledTimes(1)
+  })
+
+  it('resets the backoff when only process identity capability changes', async () => {
+    vi.useFakeTimers()
+    const identityAvailable = { ...ABSENT_WSL, windowsProcessStartTimeAvailable: true }
+    const { probe, readCached } = createWatcher([identityAvailable, identityAvailable])
+    startWindowsTerminalCapabilityReprobe({ ownerKey: 'local', probe, readCached })
+
+    await vi.advanceTimersByTimeAsync(30_000)
+    expect(probe).toHaveBeenCalledTimes(1)
+    await vi.advanceTimersByTimeAsync(30_000)
+    expect(probe).toHaveBeenCalledTimes(2)
+  })
+
   it('backs off to a five-minute ceiling on a stable answer', async () => {
     vi.useFakeTimers()
     const { probe, readCached } = createWatcher()
@@ -55,7 +85,9 @@ describe('windows terminal capability re-probe', () => {
 
   it('still re-checks a transient absent answer, then stops once WSL answers', async () => {
     vi.useFakeTimers()
-    const { probe, readCached } = createWatcher([USABLE_WSL])
+    const { probe, readCached } = createWatcher([
+      { ...USABLE_WSL, windowsProcessStartTimeAvailable: true }
+    ])
     startWindowsTerminalCapabilityReprobe({ ownerKey: 'local', probe, readCached })
 
     await vi.advanceTimersByTimeAsync(30_000)
diff --git a/src/renderer/src/lib/windows-terminal-capability-reprobe.ts b/src/renderer/src/lib/windows-terminal-capability-reprobe.ts
index 674adc565d7..f9b9d44b025 100644
--- a/src/renderer/src/lib/windows-terminal-capability-reprobe.ts
+++ b/src/renderer/src/lib/windows-terminal-capability-reprobe.ts
@@ -31,13 +31,21 @@ function capabilitySignature(capabilities: WindowsTerminalCapabilities): string
     capabilities.wslDistros.join('\u0000'),
     capabilities.pwshAvailable,
     capabilities.gitBashAvailable,
-    capabilities.hostPlatform ?? ''
+    capabilities.hostPlatform ?? '',
+    capabilities.windowsProcessStartTimeAvailable
   ].join('|')
 }
 
-/** The answer #11295 waits for: a usable WSL. Nothing further to watch for. */
+/** A usable WSL is settled only after Windows hosts also prove PID identity. */
 function isSettled(capabilities: WindowsTerminalCapabilities): boolean {
-  return capabilities.wslAvailable && capabilities.wslDistros.length > 0
+  if (!capabilities.wslAvailable || capabilities.wslDistros.length === 0) {
+    return false
+  }
+  if (capabilities.hostPlatform === 'win32') {
+    return capabilities.windowsProcessStartTimeAvailable === true
+  }
+  // A missing platform means the status probe may have failed; keep checking until it recovers.
+  return capabilities.hostPlatform !== null
 }
 
 function clearRunnerTimer(runner: CapabilityReprobeRunner): void {
diff --git a/src/shared/child-process/__fixtures__/child-process-import-allowlist.txt b/src/shared/child-process/__fixtures__/child-process-import-allowlist.txt
index fd8502d8913..d7a503bbaf2 100644
--- a/src/shared/child-process/__fixtures__/child-process-import-allowlist.txt
+++ b/src/shared/child-process/__fixtures__/child-process-import-allowlist.txt
@@ -57,7 +57,6 @@ src/main/codex-accounts/legacy-wsl-runtime-auth-drain-recovery-script-harness.ts
 src/main/codex-accounts/legacy-wsl-runtime-auth-drain-script-harness.ts
 src/main/codex-accounts/legacy-wsl-runtime-auth-drain-script-interference-shims.ts
 src/main/codex-accounts/service.ts
-src/main/codex/codex-app-server-client.ts
 src/main/codex/codex-app-server-posix-supervisor.ts
 src/main/codex/codex-app-server-session.ts
 src/main/codex/codex-state-db-backfill-recovery.ts
diff --git a/src/shared/child-process/child-process-import-boundary.test.ts b/src/shared/child-process/child-process-import-boundary.test.ts
index 3abdf8023c4..ac4a02f6ee5 100644
--- a/src/shared/child-process/child-process-import-boundary.test.ts
+++ b/src/shared/child-process/child-process-import-boundary.test.ts
@@ -29,7 +29,7 @@ const CHILD_PROCESS_IMPORT_ALLOWLIST: readonly string[] = readFileSync(
  * May only ever be DECREASED, and only by migrating a file off
  * `node:child_process`. Raising it is never the fix.
  */
-const DIRECT_IMPORTER_PIN = 156
+const DIRECT_IMPORTER_PIN = 155
 
 const IMPORT_PATTERN =
   /(?:from\s+['"]node:child_process['"]|from\s+['"]child_process['"]|require\(\s*['"]node:child_process['"]|require\(\s*['"]child_process['"])/
diff --git a/src/shared/runtime-session-contracts.ts b/src/shared/runtime-session-contracts.ts
index 9b7bf2ee0cd..99b4fbe4d6f 100644
--- a/src/shared/runtime-session-contracts.ts
+++ b/src/shared/runtime-session-contracts.ts
@@ -78,6 +78,8 @@ export type RuntimeStatus = {
   worktreeCreateIdempotency?: {
     dedupeTtlMs: number
   }
+  /** True only when this Windows host can prove process creation times for PID ownership. */
+  windowsProcessStartTimeAvailable?: boolean
   /**
    * Optional for mixed-version peers. Absence means the host predates structured
    * degradation reporting, not that the host proved every optional feature available.
diff --git a/src/shared/structured-native-chat-launch-route.test.ts b/src/shared/structured-native-chat-launch-route.test.ts
index 48cb117fdf5..ee13a8fb590 100644
--- a/src/shared/structured-native-chat-launch-route.test.ts
+++ b/src/shared/structured-native-chat-launch-route.test.ts
@@ -22,7 +22,6 @@ function support(overrides: Partial<StructuredNativeChatSupportInput> = {}) {
   return resolveStructuredNativeChatSupport({
     agent: 'claude',
     executionHostId: 'local',
-    platform: 'darwin',
     hostCapabilities: [STRUCTURED_AGENT_SESSION_RUNTIME_CAPABILITY],
     workspaceKind: 'git-worktree',
     ...overrides
@@ -64,7 +63,6 @@ describe('per-launch structured feasibility', () => {
     ['a floating workspace', { workspaceKind: 'floating' }, 'floating-workspace'],
     ['a custom TUI launch', { requiresTuiLaunchCustomization: true }, 'tui-launch-customization'],
     ['an SSH host', { executionHostId: 'ssh:host-a' }, 'remote-execution-host'],
-    ['Codex on Windows', { agent: 'codex', platform: 'win32' }, 'codex-on-windows'],
     ['a missing capability', { hostCapabilities: [] }, 'runtime-capability']
   ] as [string, Partial<StructuredNativeChatSupportInput>, string][])(
     'names %s as the blocker',
@@ -73,9 +71,14 @@ describe('per-launch structured feasibility', () => {
     }
   )
 
-  it('leaves a Windows Claude launch to the executing host', () => {
-    expect(support({ agent: 'claude', platform: 'win32' })).toEqual({ supported: true })
-  })
+  // The client cannot see whether the host can read a provider child's start time, so neither
+  // provider is refused here on platform; agentSession.createSupport answers that at create time.
+  it.each(['claude', 'codex'] as const)(
+    'leaves a Windows %s launch to the executing host',
+    (agent) => {
+      expect(support({ agent })).toEqual({ supported: true })
+    }
+  )
 
   it('blocks a WSL or repair-required project runtime', () => {
     expect(
diff --git a/src/shared/structured-native-chat-launch-route.ts b/src/shared/structured-native-chat-launch-route.ts
index b97ffcc0dac..8498fe674ce 100644
--- a/src/shared/structured-native-chat-launch-route.ts
+++ b/src/shared/structured-native-chat-launch-route.ts
@@ -26,7 +26,6 @@ export type StructuredNativeChatBlocker =
   | 'floating-workspace'
   | 'tui-launch-customization'
   | 'remote-execution-host'
-  | 'codex-on-windows'
   | 'project-runtime'
   | 'runtime-capability'
 
@@ -37,7 +36,6 @@ export type StructuredNativeChatSupport =
 export type StructuredNativeChatSupportInput = {
   agent: TuiAgent
   executionHostId: string
-  platform: NodeJS.Platform
   hostCapabilities: readonly string[]
   workspaceKind?: 'git-worktree' | 'folder' | 'floating'
   projectRuntime?: ProjectExecutionRuntimeResolution | null
@@ -82,12 +80,6 @@ export function resolveStructuredNativeChatSupport(
   if (input.executionHostId !== 'local') {
     return { supported: false, blocker: 'remote-execution-host' }
   }
-  // Codex's Windows refusal is deliberate and settled elsewhere, so it stays a client-side answer.
-  // Claude's is measured by the executing host at create time (agentSession.createSupport) because
-  // only that host knows whether it can read a provider child's start time.
-  if (input.agent === 'codex' && input.platform === 'win32') {
-    return { supported: false, blocker: 'codex-on-windows' }
-  }
   const projectRuntime = input.projectRuntime
   if (projectRuntime?.status === 'repair-required' || projectRuntime?.runtime.kind === 'wsl') {
     return { supported: false, blocker: 'project-runtime' }