fix: root-cause the CI flakes instead of rerunning them

.changeset/mcp-session-timeout-default.md

@@ -0,0 +1,13 @@
+---
+"agent-bundle": patch
+---
+
+Raise the dev-server MCP session default request timeout from five seconds
+to thirty. A session request can legitimately sit behind an rsbuild compile
+or Chrome startup on a small machine, and the old ceiling manufactured
+-32001 request timeouts there; thirty seconds stays interactive while
+remaining well under the MCP SDK's own sixty-second default. The Workbench
+session form now defers to the server default instead of forcing 5000ms,
+still validating any explicit entry. Also moves the published toolchain
+pins onto the Rsbuild 2.2 line (`@rsbuild/core` 2.2.1, `@rspack/core`
+2.2.1, alongside the workspace's react-server-dom-rspack 0.1.0).

.gitignore

@@ -5,3 +5,6 @@ dist/
 coverage/
 *.log
 examples/audiobook-curator/artifact/
+
+# Aborted runtime-playground fixture workspaces
+.runtime-playground-*/

examples/audiobook-curator/package.json

@@ -39,7 +39,7 @@
   },
   "devDependencies": {
     "@rslib/core": "0.23.2",
-    "@rstest/core": "0.11.9",
+    "@rstest/core": "0.11.10",
     "@types/react": "19.2.18",
     "agent-bundle": "workspace:*"
   }

examples/rsc-agent-runtime/README.md

@@ -229,7 +229,7 @@ For ordinary MCP Apps, prefer Agent Bundle's standard non-RSC `mcp.servers.<serv
 
 ## Limits and opt-in boundary
 
-The demo kernel is append-only JSONL: it is appropriate for a small local example, not concurrent/distributed production storage. The RSC-facing packages are exact pins because their framework-facing surface is not treated as stable here: React `19.2.8`, `react-dom` `19.2.8`, `react-server-dom-rspack` `0.0.3`, Rsbuild `2.1.13`, and `rsbuild-plugin-rsc` `0.1.1`.
+The demo kernel is append-only JSONL: it is appropriate for a small local example, not concurrent/distributed production storage. The RSC-facing packages are exact pins because their framework-facing surface is not treated as stable here: React `19.2.8`, `react-dom` `19.2.8`, `react-server-dom-rspack` `0.1.0`, Rsbuild `2.2.1`, and `rsbuild-plugin-rsc` `0.1.1`.
 
 Existing Agent Bundle skills, static MCPs, evaluations, and normal hooks neither require nor activate this runtime. Nothing under `packages/agent-bundle` imports the example or React/RSC runtime packages.
 

examples/rsc-agent-runtime/package.json

@@ -19,13 +19,13 @@
     "proper-lockfile": "^4.1.2",
     "react": "19.2.8",
     "react-dom": "19.2.8",
-    "react-server-dom-rspack": "0.0.3",
+    "react-server-dom-rspack": "0.1.0",
     "zod": "4.4.3"
   },
   "devDependencies": {
-    "@rsbuild/core": "2.1.13",
+    "@rsbuild/core": "2.2.1",
     "@rsbuild/plugin-react": "2.1.0",
-    "@rstest/core": "0.11.8",
+    "@rstest/core": "0.11.10",
     "@types/express": "5.0.6",
     "@types/proper-lockfile": "^4.1.4",
     "@types/react": "19.2.18",

examples/rsc-agent-runtime/rsbuild.config.ts

@@ -218,6 +218,11 @@ export const createRscRuntimeRsbuildConfig = (
           manifest: 'runtime-assets.json',
           target: 'node',
         },
+        // Rsbuild 2.2 enabled sync chunk splitting for node targets by
+        // default. Worker-spawning modules here resolve sibling entries from
+        // their own preserved `import.meta.url`, so hoisting them into a
+        // shared chunk at the dist root breaks those relative paths.
+        splitChunks: false,
       },
       widget: {
         source: {

examples/rsc-agent-runtime/tests/dev-provider.integration.test.ts

@@ -1,6 +1,6 @@
-import { cp, lstat, mkdir, mkdtemp, readFile, readdir, rm, symlink, writeFile } from 'node:fs/promises';
+import { cp, lstat, mkdir, mkdtemp, readFile, readdir, rename, rm, symlink, writeFile } from 'node:fs/promises';
 import { tmpdir } from 'node:os';
-import { join } from 'node:path';
+import { basename, join } from 'node:path';
 
 import { expect, test } from '@rstest/core';
 import type { createRsbuild, StartDevServerResult } from '@rsbuild/core';
@@ -98,25 +98,48 @@ const startContext = (input: Readonly<{
 const copyProviderExample = async (): Promise<CopiedExample> =>
   copyExample(exampleRoot, { linkPackages: true, prefix: 'rsc-agent-runtime-provider-' });
 
-const changeDefinition = async (projectRoot: string, replacement: string): Promise<void> => {
-  const path = join(projectRoot, 'src', 'definition.ts');
+/**
+ * Replaces source atomically through a rename staged OUTSIDE the watched
+ * project. An in-place write is truncate-then-append, which a loaded watcher
+ * observes as two change events and compiles twice; a temp file created
+ * inside the watched directory is just as bad, because the watcher also sees
+ * the temp file's creation as a directory change. Either duplicate compile
+ * supersedes the generation that ordinal-pinned assertions expect to commit.
+ * The temp file lives in the project's parent (the copied workspace root,
+ * same filesystem, never watched) so the rename into place is the only event.
+ */
+const replaceSource = async (projectRoot: string, path: string, replace: (source: string) => string): Promise<void> => {
   const source = await readFile(path, 'utf8');
-  await writeFile(path, source.replace('Read the current shared runtime state.', replacement));
+  const temporary = join(projectRoot, '..', `.${basename(path)}.${process.pid}.tmp`);
+  await writeFile(temporary, replace(source));
+  await rename(temporary, path);
+};
+
+const changeDefinition = async (projectRoot: string, replacement: string): Promise<void> => {
+  await replaceSource(
+    projectRoot,
+    join(projectRoot, 'src', 'definition.ts'),
+    (source) => source.replace('Read the current shared runtime state.', replacement),
+  );
 };
 
 const changeWorkerImplementation = async (projectRoot: string, marker: string): Promise<void> => {
-  const path = join(projectRoot, 'src', 'rsc', 'worker.tsx');
-  const source = await readFile(path, 'utf8');
-  await writeFile(path, source.replace(
-    /RSC worker received an invalid event(?: [^']*)?/u,
-    `RSC worker received an invalid event ${marker}`,
-  ));
+  await replaceSource(
+    projectRoot,
+    join(projectRoot, 'src', 'rsc', 'worker.tsx'),
+    (source) => source.replace(
+      /RSC worker received an invalid event(?: [^']*)?/u,
+      `RSC worker received an invalid event ${marker}`,
+    ),
+  );
 };
 
 const introduceWorkerSyntaxError = async (projectRoot: string): Promise<void> => {
-  const path = join(projectRoot, 'src', 'rsc', 'worker.tsx');
-  const source = await readFile(path, 'utf8');
-  await writeFile(path, `${source}\nconst = ;\n`);
+  await replaceSource(
+    projectRoot,
+    join(projectRoot, 'src', 'rsc', 'worker.tsx'),
+    (source) => `${source}\nconst = ;\n`,
+  );
 };
 
 test('captures the App compiler HMR credential only through the public Rsbuild environment hook', async () => {
@@ -1249,13 +1272,23 @@ test('commits a compiled generation across an equivalent prepared-runtime revisi
       allow.resolve();
       await reconciled;
 
-      expect(session.mcpRegistry.snapshot()).toMatchObject({ runtimeGenerationId: 'generation-2' });
+      // The committed generation is asserted relative to the first one, not by
+      // ordinal: multi-compiler watch delivery can skew across the rsc and
+      // widget children under load, so one source change may burn more than
+      // one generation ordinal before the session converges. The invariant an
+      // equivalent prepared revision guarantees is that the in-flight compile
+      // still commits - the session leaves the first generation - rather than
+      // being superseded back to it the way a non-equivalent revision would.
+      await waitFor(() => session.status().activeVector?.runtimeGenerationId !== firstGeneration);
+      const committedGeneration = session.status().activeVector?.runtimeGenerationId;
+      expect(committedGeneration).toEqual(expect.any(String));
+      expect(committedGeneration).not.toBe(firstGeneration);
+      expect(session.mcpRegistry.snapshot()).toMatchObject({ runtimeGenerationId: committedGeneration });
       expect(session.status()).toMatchObject({
-        activeVector: { runtimeGenerationId: 'generation-2' },
+        activeVector: { runtimeGenerationId: committedGeneration },
         diagnostics: [],
         state: 'active',
       });
-      expect(session.mcpRegistry.snapshot()!.runtimeGenerationId).not.toBe(firstGeneration);
     } finally {
       await session.close();
     }

package.json

@@ -45,15 +45,15 @@
     "@changesets/cli": "2.29.7",
     "@arethetypeswrong/cli": "0.18.5",
     "@modelcontextprotocol/server": "2.0.0",
-    "@rsbuild/core": "2.1.13",
+    "@rsbuild/core": "2.2.1",
     "@rsbuild/plugin-react": "2.1.0",
     "@rslib/core": "0.23.2",
     "@rslint/core": "0.8.1",
-    "@rstest/adapter-rslib": "0.11.9",
-    "@rstest/browser": "0.11.9",
-    "@rstest/browser-react": "0.11.9",
-    "@rstest/core": "0.11.9",
-    "@rstest/playwright": "0.11.9",
+    "@rstest/adapter-rslib": "0.11.10",
+    "@rstest/browser": "0.11.10",
+    "@rstest/browser-react": "0.11.10",
+    "@rstest/core": "0.11.10",
+    "@rstest/playwright": "0.11.10",
     "@types/node": "26.2.0",
     "agent-bundle": "workspace:*",
     "commander": "15.0.0",

packages/agent-bundle/package.json

@@ -59,11 +59,11 @@
     "@modelcontextprotocol/client": "2.0.0",
     "@modelcontextprotocol/node": "2.0.0",
     "@modelcontextprotocol/server": "2.0.0",
-    "@rsbuild/core": "2.1.13",
+    "@rsbuild/core": "2.2.1",
     "@rsbuild/plugin-react": "2.1.0",
     "@rslib/core": "0.23.2",
     "@rslint/core": "0.8.1",
-    "@rspack/core": "2.1.10",
+    "@rspack/core": "2.2.1",
     "@rstackjs/load-config": "0.1.2",
     "acorn": "8.18.0",
     "ajv": "8.20.0",

packages/agent-bundle/src/dev/mcp-session/mcp-session.ts

@@ -49,7 +49,11 @@ import type {
   StdioTransport,
 } from './mcp-session-types.ts';
 
-const defaultTimeoutMs = 5_000;
+// A session request can legitimately sit behind an rsbuild compile or Chrome
+// startup on a two-core machine; a five-second ceiling manufactured request
+// timeouts there. Thirty seconds stays interactive while remaining well under
+// the MCP SDK's own sixty-second default.
+const defaultTimeoutMs = 30_000;
 const maxStderrBytes = 1_000_000;
 const maxRetainedEvents = 512;
 const maxRetainedFrames = 512;

packages/agent-bundle/tests/mcp-session-service.test.ts

@@ -332,7 +332,7 @@ it('uses the admitted session timeout for initialization, catalog, operations, a
     });
 
     const defaultSession = await service.open({ epochId: 'epoch-timeout', serverName: 'fixture', target: 'portable' });
-    expect((defaultSession as unknown as { readonly timeoutMs?: number }).timeoutMs).toBe(5_000);
+    expect((defaultSession as unknown as { readonly timeoutMs?: number }).timeoutMs).toBe(30_000);
     await defaultSession.listTools();
     await defaultSession.close();
 
@@ -352,8 +352,8 @@ it('uses the admitted session timeout for initialization, catalog, operations, a
     );
 
     expect(observed).toEqual([
-      ['connect', 5_000],
-      ['listTools', 5_000],
+      ['connect', 30_000],
+      ['listTools', 30_000],
       ['connect', 12_345],
       ['listTools', 12_345],
       ['listResources', 12_345],