fix(workflow): forward the tsconfig pin only in the unbuilt worker

packages/workflow/workflow-worker-thread/src/host.ts

@@ -38,18 +38,21 @@ interface ChildRecord {
  * The unbuilt shape additionally forwards `TSX_TSCONFIG_PATH` for path
  * resolution.
  * @param platform - host platform; overridable so tests exercise both peer arms.
+ * @param tsconfigPath - the tsconfig pin to forward; only the unbuilt caller
+ *   passes one, so the built worker never observes the host's pin.
  * @returns the scrubbed worker environment object.
  */
-export function workerSpawnEnv(platform: NodeJS.Platform = process.platform): NodeJS.ProcessEnv {
+export function workerSpawnEnv(
+  platform: NodeJS.Platform = process.platform,
+  tsconfigPath: string | undefined = undefined,
+): NodeJS.ProcessEnv {
   const env: NodeJS.ProcessEnv = {}
   if (platform === 'win32') {
     const tmp = tmpdir()
     env.TMP = tmp
     env.TEMP = tmp
   }
-  if (process.env.TSX_TSCONFIG_PATH !== undefined) {
-    env.TSX_TSCONFIG_PATH = process.env.TSX_TSCONFIG_PATH
-  }
+  if (tsconfigPath !== undefined) env.TSX_TSCONFIG_PATH = tsconfigPath
   return env
 }
 
@@ -81,7 +84,7 @@ function resolveWorkerSpawn(init: WorkerInit): { entry: string | URL; options: W
     entry: new URL(`data:text/javascript,${encodeURIComponent(bootstrap)}`),
     options: {
       workerData: init,
-      env: workerSpawnEnv(),
+      env: workerSpawnEnv(undefined, process.env.TSX_TSCONFIG_PATH),
       execArgv: [],
     },
   }

packages/workflow/workflow-worker-thread/tests/workflow-worker-thread.spec.ts

@@ -570,6 +570,11 @@ describe('dsh-workflow-worker-thread', () => {
       // inside the worker resolves instead of degrading to a cwd-relative
       // `undefined\temp` (tsx writes its transform cache there).
       process.env.WORKFLOW_ENV_CANARY = 'leak me'
+      // The unbuilt worker forwards TSX_TSCONFIG_PATH (a path pin, not a
+      // credential); clear it so this test observes the empty ambient case
+      // regardless of the parent's environment.
+      const tsconfigPath = process.env.TSX_TSCONFIG_PATH
+      delete process.env.TSX_TSCONFIG_PATH
       try {
         const result = await run(ctx, parent, scripted(`
           const proc = ${ESCAPE}
@@ -579,6 +584,8 @@ describe('dsh-workflow-worker-thread', () => {
         const expectedKeys = process.platform === 'win32' ? ['TEMP', 'TMP'] : []
         expect(result.value).toEqual({ canary: null, keys: expectedKeys })
       } finally {
+        if (tsconfigPath === undefined) delete process.env.TSX_TSCONFIG_PATH
+        else process.env.TSX_TSCONFIG_PATH = tsconfigPath
         delete process.env.WORKFLOW_ENV_CANARY
       }
     })
@@ -591,17 +598,12 @@ describe('dsh-workflow-worker-thread', () => {
 
     it('workerSpawnEnv forwards TSX_TSCONFIG_PATH when the snapshot harness pins it', () => {
       const tsconfig = fileURLToPath(new URL('../../../../tsconfig.json', import.meta.url))
-      vi.stubEnv('TSX_TSCONFIG_PATH', tsconfig)
-      try {
-        expect(workerSpawnEnv('linux')).toEqual({ TSX_TSCONFIG_PATH: tsconfig })
-        expect(workerSpawnEnv('win32')).toEqual({
-          TMP: tmpdir(),
-          TEMP: tmpdir(),
-          TSX_TSCONFIG_PATH: tsconfig,
-        })
-      } finally {
-        vi.unstubAllEnvs()
-      }
+      expect(workerSpawnEnv('linux', tsconfig)).toEqual({ TSX_TSCONFIG_PATH: tsconfig })
+      expect(workerSpawnEnv('win32', tsconfig)).toEqual({
+        TMP: tmpdir(),
+        TEMP: tmpdir(),
+        TSX_TSCONFIG_PATH: tsconfig,
+      })
     })
 
     it('the unbuilt worker forwards exactly TSX_TSCONFIG_PATH through the scrub: the paths-map pin survives, secrets do not', async () => {