From bcaed523cd4a6e37f1c80ff7323b00d078d00700 Mon Sep 17 00:00:00 2001
From: Neil <4138956+nwparker@users.noreply.github.com>
Date: Wed, 14 Oct 2026 20:22:13 -0700
Subject: [PATCH] ci: contain persistent transforms and trim model overhead
 (#28948)

---
 config/scripts/ci-shard-assignment.test.mjs     | 17 +++++++++++++++++
 config/vitest.config.ts                         |  3 ++-
 ...e-terminal-input-delivery-model.unit.test.ts | 11 +++++++----
 3 files changed, 26 insertions(+), 5 deletions(-)

diff --git a/config/scripts/ci-shard-assignment.test.mjs b/config/scripts/ci-shard-assignment.test.mjs
index 5c83bdc272a..44ccf5d4d4f 100644
--- a/config/scripts/ci-shard-assignment.test.mjs
+++ b/config/scripts/ci-shard-assignment.test.mjs
@@ -100,6 +100,23 @@ describe('timing-weighted shard selection', () => {
     }
   })
 
+  it.each([
+    { name: 'absent', path: undefined, enabled: false },
+    { name: 'empty', path: '', enabled: false },
+    { name: 'explicit', path: join(tmpdir(), 'orca-unit-cache-experiment'), enabled: true }
+  ])(
+    'uses persistent transforms only with an explicit cache path ($name)',
+    async ({ path, enabled }) => {
+      vi.stubEnv('ORCA_UNIT_MODULE_CACHE_PATH', path)
+      vi.resetModules()
+      const { default: config } = await import('../vitest.config')
+      for (const test of [config.test, ...config.test.projects.map((project) => project.test)]) {
+        expect(test.fsModuleCache).toBe(enabled)
+        expect(test.fsModuleCachePath).toBe(enabled ? path : undefined)
+      }
+    }
+  )
+
   it('keeps nested/serial E2E files atomic and fails closed on discovery errors', () => {
     const spec = (id, file) => ({ id, file, tests: [{ projectName: 'electron-headless' }] })
     const report = {
diff --git a/config/vitest.config.ts b/config/vitest.config.ts
index 1485f61565d..4ab7a3750ad 100644
--- a/config/vitest.config.ts
+++ b/config/vitest.config.ts
@@ -29,7 +29,8 @@ const transforms = {
 const testOptions = {
   environment: 'node',
   clearMocks: false,
-  fsModuleCache: true,
+  // Persistent transforms can miss source additions; only explicit cache experiments opt in.
+  fsModuleCache: Boolean(process.env.ORCA_UNIT_MODULE_CACHE_PATH),
   ...(process.env.ORCA_UNIT_MODULE_CACHE_PATH
     ? { fsModuleCachePath: process.env.ORCA_UNIT_MODULE_CACHE_PATH }
     : {}),
diff --git a/tests/e2e/remote-terminal-input-delivery-model.unit.test.ts b/tests/e2e/remote-terminal-input-delivery-model.unit.test.ts
index ffc7fe4a9a6..9bed931217a 100644
--- a/tests/e2e/remote-terminal-input-delivery-model.unit.test.ts
+++ b/tests/e2e/remote-terminal-input-delivery-model.unit.test.ts
@@ -372,7 +372,7 @@ async function runSchedule(seed: number, stats: Stats): Promise<void> {
   const arrived = checkPty(ptyWrites.join(''), ops, seed)
   for (const op of ops) {
     // A write the pane reported applied really reached the PTY, whole.
-    if (op.result === true) {
+    if (op.result === true && !arrived.has(op.id)) {
       expect(arrived.has(op.id), `seed ${seed} op ${op.id} reported applied`).toBe(true)
     }
   }
@@ -389,15 +389,18 @@ function checkPty(pty: string, ops: readonly Op[], seed: number): Set<number> {
   const arrived = new Set<number>()
   let position = 0
   for (const op of ops) {
-    const where = `seed ${seed} op ${op.id} (${op.status}) at ${position}: ${JSON.stringify(pty.slice(position, position + 40))}`
+    const where = (): string =>
+      `seed ${seed} op ${op.id} (${op.status}) at ${position}: ${JSON.stringify(pty.slice(position, position + 40))}`
     if (pty.startsWith(op.text, position)) {
-      expect(op.status, where).not.toBe('forbidden')
+      if (op.status === 'forbidden') {
+        expect(op.status, where()).not.toBe('forbidden')
+      }
       arrived.add(op.id)
       position += op.text.length
       continue
     }
     if (op.status === 'required') {
-      throw new Error(`missing or out of order: ${where}`)
+      throw new Error(`missing or out of order: ${where()}`)
     }
     if (op.status === 'optional') {
       // A withdrawn chunked paste or a restart can cut it after a whole chunk.