fix(test): cap Rstest worker socket paths

.changeset/short-rstest-socket-roots.md

@@ -0,0 +1,5 @@
+---
+"agent-bundle": patch
+---
+
+Keep Doctor socket fixtures reliable under long local-CI temporary directory names by deriving short, isolated Rstest worker roots.

docs/local-ci.md

@@ -42,9 +42,13 @@ each other's temp traffic: suites that assert temp-root hygiene (for example
 `cli.test.ts` scans `os.tmpdir()` for leaked `agent-bundle-artifact-*`
 directories) only ever see their own leg's directories, so a sibling leg's
 in-flight work cannot fail them — while a directory the leg itself leaks
-still fails its own scan. Legs live under `.worktrees/local-ci/`
-(gitignored), are reused across runs for warm caches, and can be recreated
-with `--fresh`.
+still fails its own scan. Rstest re-hashes that leg directory, worker ID, and
+invocation identity to `/tmp/ab-rstest-<hash16>` before exposing its worker
+`TMPDIR`; this leaves headroom below Linux's 108-byte `sun_path` cap for nested
+socket fixtures without sacrificing per-leg, per-worker, or concurrent-run
+isolation. Legs live under
+`.worktrees/local-ci/` (gitignored), are reused across runs for warm caches,
+and can be recreated with `--fresh`.
 
 The three Verify legs below mirror the hosted `main`-push matrix. On PRs,
 only `verify (24)` runs hosted.

packages/agent-bundle/tests/rstest-worker-isolation.test.ts

@@ -0,0 +1,29 @@
+import { join } from 'node:path';
+
+import { expect, it } from '@rstest/core';
+
+import { rstestWorkerRootPath } from '../../../rstest.worker-isolation.ts';
+
+it('keeps Doctor socket fixtures below the Linux AF_UNIX pathname cap', () => {
+  const longLocalCiRoot = join(
+    '/tmp',
+    `abci-repository-hash-${'verify-current-pathological-node-version-'.repeat(3)}`,
+  );
+  const workerRoot = rstestWorkerRootPath(longLocalCiRoot, '123', 'linux');
+  const longestDoctorEndpoint = join(
+    workerRoot,
+    'agent-bundle-doctor-XXXXXX',
+    'endpoints',
+    'event-identity.sock',
+  );
+
+  // Linux sun_path is 108 bytes including NUL; 96 leaves 12 bytes of headroom.
+  expect(Buffer.byteLength(longestDoctorEndpoint, 'utf8') + 1).toBeLessThanOrEqual(96);
+});
+
+it('isolates concurrent Rstest invocations that share a host temporary root', () => {
+  const firstRoot = rstestWorkerRootPath('/tmp', '1', 'linux', '/workspace/first\0' + '101');
+  const secondRoot = rstestWorkerRootPath('/tmp', '1', 'linux', '/workspace/second\0' + '202');
+
+  expect(firstRoot).not.toBe(secondRoot);
+});

rstest.worker-isolation.ts

@@ -1,3 +1,4 @@
+import { createHash } from 'node:crypto';
 import { mkdirSync } from 'node:fs';
 import { tmpdir } from 'node:os';
 import { join } from 'node:path';
@@ -6,8 +7,26 @@ export const rstestWorkerId = (): string => process.env['RSTEST_WORKER_ID'] ?? '
 
 const hostTemporaryRoot = tmpdir();
 
+export const rstestWorkerRootPath = (
+  temporaryRoot: string,
+  workerId: string,
+  platform: NodeJS.Platform = process.platform,
+  invocationId: string = process.cwd() + '\0' + String(process.pid),
+): string => {
+  if (platform === 'win32') return join(temporaryRoot, 'agent-bundle-rstest-w' + workerId);
+  const hash = createHash('sha256')
+    .update(temporaryRoot, 'utf8')
+    .update('\0', 'utf8')
+    .update(workerId, 'utf8')
+    .update('\0', 'utf8')
+    .update(invocationId, 'utf8')
+    .digest('hex')
+    .slice(0, 16);
+  return join('/tmp', `ab-rstest-${hash}`);
+};
+
 export const rstestWorkerRoot = (): string => {
-  const root = join(hostTemporaryRoot, 'agent-bundle-rstest-w' + rstestWorkerId());
+  const root = rstestWorkerRootPath(hostTemporaryRoot, rstestWorkerId());
   mkdirSync(root, { recursive: true });
   return root;
 };