diff --git a/scripts/fixtures/browser-network-site.mjs b/scripts/fixtures/browser-network-site.mjs
index 6973ce4055..7e8cc64b50 100644
--- a/scripts/fixtures/browser-network-site.mjs
+++ b/scripts/fixtures/browser-network-site.mjs
@@ -1,5 +1,5 @@
+import { createVerifierHttpServer } from "../lib/verifier-http-server.mjs";
 import { once } from "node:events";
-import { createServer } from "node:http";
 import { gzipSync } from "node:zlib";
 
 export const networkFixtureSecret = "私密-network-fixture";
@@ -23,7 +23,7 @@ const html = `<!doctype html><meta charset="utf-8"><body><button id="start">Run<
 export async function startBrowserNetworkSite() {
   const counts = new Map();
   const timers = new Set();
-  const server = createServer(async (request, response) => {
+  const handleRequest = async (request, response) => {
     const path = new URL(request.url, "http://fixture.test").pathname;
     counts.set(path, (counts.get(path) ?? 0) + 1);
     if (path === "/same") {
@@ -89,7 +89,8 @@ export async function startBrowserNetworkSite() {
       response.writeHead(200, { "Content-Type": "text/html; charset=utf-8" });
       response.end(html);
     }
-  });
+  };
+  const { server, close } = createVerifierHttpServer(handleRequest);
   server.listen(0, "127.0.0.1");
   await once(server, "listening");
   const address = server.address();
@@ -100,10 +101,7 @@ export async function startBrowserNetworkSite() {
     counts,
     async close() {
       for (const timer of timers) clearTimeout(timer);
-      server.closeAllConnections();
-      await new Promise((resolve, reject) =>
-        server.close((error) => (error ? reject(error) : resolve())),
-      );
+      await close();
     },
   };
 }
diff --git a/scripts/fixtures/browser-request-site.mjs b/scripts/fixtures/browser-request-site.mjs
index 6695e5d2bd..a8b4343849 100644
--- a/scripts/fixtures/browser-request-site.mjs
+++ b/scripts/fixtures/browser-request-site.mjs
@@ -1,5 +1,5 @@
+import { createVerifierHttpServer } from "../lib/verifier-http-server.mjs";
 import { once } from "node:events";
-import { createServer } from "node:http";
 
 /** The CSRF cookie and the stored bearer token the page holds; request steps must send both and the capture must not keep them. */
 export const requestFixtureCsrf = "csrf-fixture-7c1d2e";
@@ -52,7 +52,7 @@ export async function startBrowserRequestSite() {
   };
   const writes = [];
   const hosts = [];
-  const server = createServer(async (request, response) => {
+  const handleRequest = async (request, response) => {
     const url = new URL(request.url, "http://fixture.test");
     hosts.push(`${request.headers.host} ${url.pathname}`);
     const chunks = [];
@@ -108,7 +108,8 @@ export async function startBrowserRequestSite() {
     }
     const [status, value] = answerItems(store, request.method, id, body);
     json(response, status, value);
-  });
+  };
+  const { server, close } = createVerifierHttpServer(handleRequest);
   server.listen(0, "127.0.0.1");
   await once(server, "listening");
   const address = server.address();
@@ -120,11 +121,6 @@ export async function startBrowserRequestSite() {
     /** Host header and path of every request the server received. */
     hosts,
     items: store.items,
-    async close() {
-      server.closeAllConnections();
-      await new Promise((resolve, reject) =>
-        server.close((error) => (error ? reject(error) : resolve())),
-      );
-    },
+    close,
   };
 }
diff --git a/scripts/lib/verifier-http-server.d.mts b/scripts/lib/verifier-http-server.d.mts
new file mode 100644
index 0000000000..7d03a4876d
--- /dev/null
+++ b/scripts/lib/verifier-http-server.d.mts
@@ -0,0 +1,12 @@
+import type { IncomingMessage, Server, ServerResponse } from "node:http";
+
+/** Own admitted fixture requests through transport closure and report unexpected failures. */
+export function createVerifierHttpServer(
+  handleRequest: (
+    request: IncomingMessage,
+    response: ServerResponse,
+  ) => Promise<void>,
+): {
+  readonly server: Server;
+  close(): Promise<void>;
+};
diff --git a/scripts/lib/verifier-http-server.mjs b/scripts/lib/verifier-http-server.mjs
new file mode 100644
index 0000000000..7087e54290
--- /dev/null
+++ b/scripts/lib/verifier-http-server.mjs
@@ -0,0 +1,39 @@
+import { createServer } from "node:http";
+import { withVerifierCleanup } from "./verifier-cleanup.mjs";
+
+/** Own admitted fixture requests through transport closure and report unexpected failures. */
+export function createVerifierHttpServer(handleRequest) {
+  const pending = new Set();
+  let failure;
+  const server = createServer((request, response) => {
+    const work = handleRequest(request, response)
+      .catch((cause) => {
+        failure ??= { cause };
+        response.destroy();
+      })
+      .finally(() => {
+        pending.delete(work);
+      });
+    pending.add(work);
+  });
+  return {
+    server,
+    close() {
+      return withVerifierCleanup(
+        () =>
+          new Promise((resolve, reject) => {
+            server.close((cause) =>
+              cause === undefined ? resolve() : reject(cause),
+            );
+            server.closeAllConnections();
+          }),
+        [
+          async () => {
+            await Promise.all(pending);
+            if (failure !== undefined) throw failure.cause;
+          },
+        ],
+      );
+    },
+  };
+}
diff --git a/src/application/AppBundleExecutable.ts b/src/application/AppBundleExecutable.ts
index c4aba66d81..6f907730cb 100644
--- a/src/application/AppBundleExecutable.ts
+++ b/src/application/AppBundleExecutable.ts
@@ -78,12 +78,16 @@ export const resolveAppBundleExecutable = async (
   try {
     const layout = await presentLayout(path);
     if (layout !== undefined)
-      return resolveLayoutExecutable(path, layout, fileSystem);
+      return await resolveLayoutExecutable(path, layout, fileSystem);
     const wrapped = await wrappedBundle(path);
     if (wrapped !== undefined) {
       const wrappedLayout = await presentLayout(wrapped);
       if (wrappedLayout !== undefined)
-        return resolveLayoutExecutable(wrapped, wrappedLayout, fileSystem);
+        return await resolveLayoutExecutable(
+          wrapped,
+          wrappedLayout,
+          fileSystem,
+        );
     }
   } catch (cause: unknown) {
     if (cause instanceof BinaryTargetError) return err(cause);
diff --git a/src/application/LinuxHopperPublisher.ts b/src/application/LinuxHopperPublisher.ts
index 5fb01f5679..d4525ee273 100644
--- a/src/application/LinuxHopperPublisher.ts
+++ b/src/application/LinuxHopperPublisher.ts
@@ -772,7 +772,7 @@ export class LinuxHopperPublisher {
           { cause },
         );
       }
-      return this.#verifyArchive(
+      return await this.#verifyArchive(
         parsed.data.family,
         release.value,
         join(root, "archive"),
diff --git a/src/application/SetupClientConfiguration.ts b/src/application/SetupClientConfiguration.ts
index 4b5be1a502..ca0e1b3d05 100644
--- a/src/application/SetupClientConfiguration.ts
+++ b/src/application/SetupClientConfiguration.ts
@@ -6,6 +6,7 @@ import {
   effectiveClientConfiguration,
   readConfigurationText,
   type ClientConfigurationSource,
+  type ClientConfigurationFileError,
 } from "./ClientConfigurationFiles.js";
 import { err, ok, type Result } from "../domain/result.js";
 import { ConfigurationError } from "../domain/configurationErrors.js";
@@ -55,7 +56,6 @@ import {
   preserveCurrentRecoveryBackup,
   selectCurrentRecoveryBackup,
 } from "./SetupRecoveryBackup.js";
-import type { ClientConfigurationFileError } from "./ClientConfigurationFiles.js";
 import type {
   ClientConfigurationInspection,
   ClientConfigurationResult,
@@ -376,7 +376,7 @@ const persistClientConfiguration = async ({
             !clientConfigurationValuesEqual(readback.servers[name], entry),
         )
       ) {
-        return rollbackOrReadbackFailure(
+        return await rollbackOrReadbackFailure(
           publication,
           original,
           recoveryBackupPath,
diff --git a/src/application/environment/environmentExport.ts b/src/application/environment/environmentExport.ts
index 738b50a6a0..2c224433b3 100644
--- a/src/application/environment/environmentExport.ts
+++ b/src/application/environment/environmentExport.ts
@@ -243,7 +243,7 @@ export const environmentExportEvidenceFile = async (
       const refused = headroomRefusal(operation, path, size);
       if (refused !== undefined) throw refused;
     });
-    return environmentExportFile(role, path, bytes, operation);
+    return await environmentExportFile(role, path, bytes, operation);
   } catch (cause: unknown) {
     if (cause instanceof AnalysisResourceConstraintError) return err(cause);
     throw cause;
diff --git a/src/artifacts/pyinstaller/PyInstallerBoundaries.test.ts b/src/artifacts/pyinstaller/PyInstallerBoundaries.test.ts
index 8c46ce1593..93fc2c32f5 100644
--- a/src/artifacts/pyinstaller/PyInstallerBoundaries.test.ts
+++ b/src/artifacts/pyinstaller/PyInstallerBoundaries.test.ts
@@ -746,18 +746,20 @@ it.each([false, true])(
           release = deferred();
         const handles = new Set<FileHandle>();
         const stat = borrowed.stat;
+        const prototype: Pick<FileHandle, "stat"> =
+          Object.getPrototypeOf(borrowed);
         const spy = vi
-          .spyOn(Object.getPrototypeOf(borrowed), "stat")
+          .spyOn(prototype, "stat")
           .mockImplementation(async function (
             this: FileHandle,
-            ...args: unknown[]
+            ...args: Parameters<FileHandle["stat"]>
           ) {
             if (this !== borrowed) {
               handles.add(this);
               entered.resolve();
               await release.promise;
             }
-            return Reflect.apply(stat, this, args);
+            return stat.call(this, ...args);
           });
         const caller = new AbortController(),
           reason = new Error("one admission waiter leaves");
diff --git a/src/browser/PlaywrightScenarioSession.test.ts b/src/browser/PlaywrightScenarioSession.test.ts
index 9e5b0c3df0..eba287f60e 100644
--- a/src/browser/PlaywrightScenarioSession.test.ts
+++ b/src/browser/PlaywrightScenarioSession.test.ts
@@ -1,20 +1,23 @@
-import { AnalysisCleanupLeaseGroup } from "../artifacts/AnalysisCleanupLease.js";
+import {
+  AnalysisCleanupLeaseGroup,
+  AnalysisCleanupLease,
+} from "../artifacts/AnalysisCleanupLease.js";
 import { projectAnalysisError } from "../domain/analysisErrorProjection.js";
 import { ProviderCleanupError } from "../domain/providerCleanupError.js";
 import { PlaywrightBrowserScenarioProvider } from "./PlaywrightBrowserScenarioProvider.js";
-import { AnalysisCleanupLease } from "../artifacts/AnalysisCleanupLease.js";
 import { EventEmitter } from "node:events";
 
-import { beforeEach, expect, it, vi } from "vitest";
+import { beforeEach, expect, it, vi, type Mock } from "vitest";
+import type { PlaywrightScenarioStorage } from "./PlaywrightScenarioStorage.js";
 
 const mocks = vi.hoisted(() => ({
   openBrowser: vi.fn(),
   storage: undefined as
     | {
-        initialize: ReturnType<typeof vi.fn>;
-        settle: ReturnType<typeof vi.fn>;
-        limitations: ReturnType<typeof vi.fn>;
-        close: ReturnType<typeof vi.fn>;
+        initialize: Mock<PlaywrightScenarioStorage["initialize"]>;
+        settle: Mock<PlaywrightScenarioStorage["settle"]>;
+        limitations: Mock<PlaywrightScenarioStorage["limitations"]>;
+        close: Mock<PlaywrightScenarioStorage["close"]>;
       }
     | undefined,
   finishEvents: vi.fn(),
@@ -216,12 +219,16 @@ const fixture = () => {
     profilePath: "/tmp/profile",
   });
   mocks.storage = {
-    initialize: vi.fn(async () => undefined),
-    settle: vi.fn(async () => undefined),
-    limitations: vi.fn(() => []),
-    close: vi.fn(async (stopLoading = false) => ({
-      loadingStopped: stopLoading,
-    })),
+    initialize: vi.fn<PlaywrightScenarioStorage["initialize"]>(
+      async () => undefined,
+    ),
+    settle: vi.fn<PlaywrightScenarioStorage["settle"]>(async () => undefined),
+    limitations: vi.fn<PlaywrightScenarioStorage["limitations"]>(() => []),
+    close: vi.fn<PlaywrightScenarioStorage["close"]>(
+      async (stopLoading = false) => ({
+        loadingStopped: stopLoading,
+      }),
+    ),
   };
   return { cleanup, page, storage: mocks.storage };
 };
@@ -1328,9 +1335,7 @@ it("preserves both cleanup failures and retries retained owners", async () => {
   const { cleanup, storage } = fixture();
   const detachFailure = new Error("CDP detach rejected");
   const transportFailure = new Error("Playwright transport close failed");
-  storage.close
-    .mockRejectedValueOnce(detachFailure)
-    .mockResolvedValueOnce(undefined);
+  storage.close.mockRejectedValueOnce(detachFailure);
   cleanup.close
     .mockRejectedValueOnce(transportFailure)
     .mockImplementationOnce(async (finishEvents?: () => Promise<void>) => {
diff --git a/src/gdb/GdbSessionManager.ts b/src/gdb/GdbSessionManager.ts
index 9f5e72143e..734bee97ef 100644
--- a/src/gdb/GdbSessionManager.ts
+++ b/src/gdb/GdbSessionManager.ts
@@ -1,3 +1,4 @@
+import { ABORTED, waitForAbortable } from "../process/AbortablePromise.js";
 import { snapshotGdbCommandRecords } from "./GdbCommandRecords.js";
 import { randomUUID } from "node:crypto";
 import { constants as fsConstants } from "node:fs";
@@ -2430,25 +2431,8 @@ export const waitForGdbCommandTurn = (
   signal?: AbortSignal,
 ): Promise<void> => {
   if (signal === undefined) return previous;
-  if (signal.aborted)
-    return Promise.reject(
-      new AnalysisCancelledError("gdb_console", { cause: signal.reason }),
-    );
-  return new Promise<void>((resolve, reject) => {
-    const onAbort = (): void =>
-      reject(
-        new AnalysisCancelledError("gdb_console", { cause: signal.reason }),
-      );
-    signal.addEventListener("abort", onAbort, { once: true });
-    previous.then(
-      () => {
-        signal.removeEventListener("abort", onAbort);
-        resolve();
-      },
-      (cause: unknown) => {
-        signal.removeEventListener("abort", onAbort);
-        reject(cause);
-      },
-    );
+  return waitForAbortable(previous, signal).then((outcome) => {
+    if (outcome === ABORTED)
+      throw new AnalysisCancelledError("gdb_console", { cause: signal.reason });
   });
 };
diff --git a/src/ghidra/GhidraClient.ts b/src/ghidra/GhidraClient.ts
index 1b13410dd7..5aebe394b4 100644
--- a/src/ghidra/GhidraClient.ts
+++ b/src/ghidra/GhidraClient.ts
@@ -858,7 +858,7 @@ export class GhidraClient {
     try {
       const result = await this.#startWithin(deadline);
       return result.ok && deadline.signal.aborted
-        ? this.#startupInterrupted(deadline)
+        ? await this.#startupInterrupted(deadline)
         : result;
     } catch (cause: unknown) {
       if (cause instanceof GhidraSessionError) return err(cause);
diff --git a/src/hopper/HopperClient.ts b/src/hopper/HopperClient.ts
index d6e3a1a187..789d109216 100644
--- a/src/hopper/HopperClient.ts
+++ b/src/hopper/HopperClient.ts
@@ -453,7 +453,7 @@ export class HopperClient {
     try {
       const result = await this.#startWithin(deadline);
       return result.ok && deadline.signal.aborted
-        ? this.#startupFailure(await this.#interruptionFailure(deadline))
+        ? await this.#startupFailure(await this.#interruptionFailure(deadline))
         : result;
     } finally {
       deadline.signal.removeEventListener("abort", onStartupAbort);
diff --git a/src/kuna/KunaTargetCommands.ts b/src/kuna/KunaTargetCommands.ts
index aecf6126cb..1d55701080 100644
--- a/src/kuna/KunaTargetCommands.ts
+++ b/src/kuna/KunaTargetCommands.ts
@@ -291,7 +291,7 @@ export class KunaTargetCommands {
         this.lifetime.signal,
       );
       if (digest !== this.target.sha256)
-        return this.#workspaceFailure(
+        return await this.#workspaceFailure(
           new AnalysisArtifactChangedError(
             "kuna:workspace",
             this.target.path,
diff --git a/src/rizin/RizinDebugSessionManager.ts b/src/rizin/RizinDebugSessionManager.ts
index 5bb4592cdd..cdcbe9b8ea 100644
--- a/src/rizin/RizinDebugSessionManager.ts
+++ b/src/rizin/RizinDebugSessionManager.ts
@@ -32,6 +32,7 @@ import {
   type OwnedDebuggerDetachResult,
 } from "../process/ownedDebuggerSession.js";
 import { absoluteCallerPath } from "../filesystem/callerPath.js";
+import { ABORTED, waitForAbortable } from "../process/AbortablePromise.js";
 
 const MAX_SESSIONS = 8;
 const MAX_PENDING_COMMANDS = 16;
@@ -1839,19 +1840,11 @@ const waitForTurn = (
   signal?: AbortSignal,
 ): Promise<void> => {
   if (signal === undefined) return previous;
-  if (signal.aborted)
-    return Promise.reject(rizinCancellation("rizin_debug_command", signal));
-  return new Promise<void>((resolve, reject) => {
-    const onAbort = (): void =>
-      reject(rizinCancellation("rizin_debug_command", signal));
-    signal.addEventListener("abort", onAbort, { once: true });
-    previous.then(() => {
-      signal.removeEventListener("abort", onAbort);
-      resolve();
-    });
+  return waitForAbortable(previous, signal).then((outcome) => {
+    if (outcome === ABORTED)
+      throw rizinCancellation("rizin_debug_command", signal);
   });
 };
-
 /** Translate only this transport's typed cancellation, preserving opaque/null caller reasons. */
 const rizinCancellation = (
   operation: string,
diff --git a/tests/boundary/cli/cliWorkerCompletion.test.ts b/tests/boundary/cli/cliWorkerCompletion.test.ts
new file mode 100644
index 0000000000..f0ed533307
--- /dev/null
+++ b/tests/boundary/cli/cliWorkerCompletion.test.ts
@@ -0,0 +1,160 @@
+import { readFile, writeFile } from "node:fs/promises";
+import { join } from "node:path";
+import { fileURLToPath } from "node:url";
+import { expect } from "vitest";
+import { z } from "zod";
+
+import { createTestTempDirectory } from "../../fixtures/temporaryDirectory.js";
+import {
+  createCliSessionFrameReader,
+  encodeCliSessionFrame,
+} from "../../support/cli/cliCommandSessionFrames.mjs";
+import {
+  processTest,
+  waitForExit,
+} from "../../support/process/processFixture.js";
+
+const worker = fileURLToPath(
+  new URL("../../support/cli/cliCommandSessionWorker.mjs", import.meta.url),
+);
+
+processTest(
+  "keeps a real CLI worker frame failure nonzero when EOF joins command completion",
+  async ({ processes }) => {
+    const root = await createTestTempDirectory("rea-cli-worker-completion-");
+    const preload = join(root, "deny-response-frame.mjs");
+    await writeFile(
+      preload,
+      `
+const write = process.stdout.write.bind(process.stdout);
+const failure = new Error("selected CLI response frame write failed");
+process.stdout.write = (chunk, ...arguments_) => {
+  const frame = Buffer.isBuffer(chunk)
+    ? JSON.parse(chunk.subarray(4).toString("utf8"))
+    : undefined;
+  if (frame?.ready === true) return write(chunk, ...arguments_);
+  const callback = arguments_.find((value) => typeof value === "function");
+  const deny = () => callback(failure);
+  if (process.stdin.readableEnded) setImmediate(deny);
+  else process.stdin.once("end", () => setImmediate(deny));
+  return true;
+};
+`,
+    );
+    const result = await processes.run(
+      process.execPath,
+      ["--import", preload, worker],
+      {
+        input: encodeCliSessionFrame({
+          id: 1,
+          arguments: ["--help"],
+          cwd: root,
+          env: { PATH: process.env.PATH ?? "", REA_LOG_LEVEL: "silent" },
+        }),
+        timeoutMs: 15_000,
+      },
+    );
+    expect(result.signal, result.stderr).toBeNull();
+    expect(result.exitCode, result.stderr).toBe(1);
+    expect(result.stderr).toContain("selected CLI response frame write failed");
+  },
+);
+
+processTest(
+  "settles an active CLI response and skips queued work after malformed input",
+  async ({ processes }) => {
+    const root = await createTestTempDirectory("rea-cli-worker-malformed-");
+    const marker = join(root, "response-completed");
+    const preload = join(root, "hold-response-frame.mjs");
+    await writeFile(
+      preload,
+      `
+import { writeFileSync } from "node:fs";
+const write = process.stdout.write.bind(process.stdout);
+process.stdout.write = (chunk, ...arguments_) => {
+  const frame = Buffer.isBuffer(chunk)
+    ? JSON.parse(chunk.subarray(4).toString("utf8"))
+    : undefined;
+  if (frame?.id !== 1 || frame.fatal === true) return write(chunk, ...arguments_);
+  const callback = arguments_.find((value) => typeof value === "function");
+  const continued = new Promise((resolve) => process.stdin.once("data", resolve));
+  return write(chunk, (error) => {
+    if (error) callback(error);
+    else continued.then(() => {
+      writeFileSync(${JSON.stringify(marker)}, "response completed");
+      callback();
+    });
+  });
+};
+`,
+    );
+    const child = processes.spawn(process.execPath, [
+      "--import",
+      preload,
+      worker,
+    ]);
+    const closed = new Promise<void>((resolve) => {
+      child.once("close", () => resolve());
+    });
+    let stderr = "";
+    child.stderr.on("data", (chunk: Buffer) => {
+      stderr += chunk.toString("utf8");
+    });
+    const ids: number[] = [];
+    const request = (id: number) =>
+      encodeCliSessionFrame({
+        id,
+        arguments: ["--help"],
+        cwd: root,
+        env: { PATH: process.env.PATH ?? "", REA_LOG_LEVEL: "silent" },
+      });
+    const reader = createCliSessionFrameReader((value: unknown) => {
+      const frame = z
+        .object({ ready: z.boolean().optional(), id: z.number().optional() })
+        .parse(value);
+      if (frame.ready === true) child.stdin.write(request(1));
+      if (frame.id === undefined) return;
+      ids.push(frame.id);
+      if (frame.id === 1) {
+        const malformed = Buffer.from([0, 0, 0, 1, 123]);
+        child.stdin.write(Buffer.concat([request(2), malformed]));
+      }
+    });
+    child.stdout.on("data", reader);
+
+    expect(await waitForExit(child, 15_000), stderr).toBe(true);
+    await closed;
+    expect(child.signalCode, stderr).toBeNull();
+    expect(child.exitCode, stderr).toBe(1);
+    expect(stderr).toMatch(/JSON/u);
+    expect(ids).toEqual([1]);
+    expect(await readFile(marker, "utf8")).toBe("response completed");
+  },
+);
+
+processTest(
+  "publishes one fatal CLI response and does not dispatch commands queued behind it",
+  async ({ processes }) => {
+    const root = await createTestTempDirectory("rea-cli-worker-fatal-");
+    const result = await processes.run(process.execPath, [worker], {
+      input: Buffer.concat([
+        encodeCliSessionFrame({ id: 1, arguments: null, cwd: root, env: {} }),
+        encodeCliSessionFrame({
+          id: 2,
+          arguments: ["--help"],
+          cwd: root,
+          env: { PATH: process.env.PATH ?? "", REA_LOG_LEVEL: "silent" },
+        }),
+      ]),
+      timeoutMs: 15_000,
+    });
+    expect(result.signal, result.stderr).toBeNull();
+    expect(result.exitCode, result.stderr).toBe(1);
+    expect(result.stderr).toContain(
+      "CLI session command is missing its arguments, cwd, or environment",
+    );
+    expect(result.stdout).toContain('"id":1');
+    expect(result.stdout).toContain('"fatal":true');
+    expect(result.stdout).not.toContain('"id":2');
+  },
+);
diff --git a/tests/boundary/cli/idaStartupAttributionCli.test.ts b/tests/boundary/cli/idaStartupAttributionCli.test.ts
index 2eac95b715..0668ddbf71 100644
--- a/tests/boundary/cli/idaStartupAttributionCli.test.ts
+++ b/tests/boundary/cli/idaStartupAttributionCli.test.ts
@@ -1,4 +1,5 @@
-import { createServer } from "node:http";
+import { createVerifierHttpServer } from "../../../scripts/lib/verifier-http-server.mjs";
+import type { IncomingMessage, ServerResponse } from "node:http";
 import { expect } from "vitest";
 import { z } from "zod";
 import { workspaceCliTest } from "../../support/cli/workspaceCliFixture.js";
@@ -38,132 +39,156 @@ type StartupMode =
   | "unexpected-worker"
   | "success";
 
+type StartupSupervisorState = {
+  readonly mode: StartupMode;
+  readonly calls: string[];
+  database: string | undefined;
+  input: string | undefined;
+};
+const handleStartupRequest = async (
+  state: StartupSupervisorState,
+  request: IncomingMessage,
+  response: ServerResponse,
+) => {
+  if (request.method !== "POST") {
+    response.writeHead(405).end();
+    return;
+  }
+  let body = "";
+  for await (const chunk of request) body += String(chunk);
+  const rpc = requestSchema.parse(JSON.parse(body));
+  if (rpc.id === undefined) {
+    response.writeHead(202).end();
+    return;
+  }
+  const send = (result: unknown) =>
+    response
+      .writeHead(200, { "Content-Type": "application/json" })
+      .end(JSON.stringify({ jsonrpc: "2.0", id: rpc.id, result }));
+  if (rpc.method === "initialize") {
+    if (state.mode === "connect-timeout") return;
+    send({
+      protocolVersion: rpc.params?.protocolVersion,
+      capabilities: { tools: {} },
+      serverInfo: { name: "ida-startup-fixture", version: "1" },
+    });
+    return;
+  }
+  if (rpc.method === "tools/list") {
+    if (state.mode === "catalog-timeout") return;
+    if (state.mode === "catalog-refused") {
+      response.writeHead(200, { "Content-Type": "application/json" }).end(
+        JSON.stringify({
+          jsonrpc: "2.0",
+          id: rpc.id,
+          error: { code: -32603, message: "fixture catalog refused" },
+        }),
+      );
+      return;
+    }
+    send({
+      tools: tools
+        .filter(
+          (name) => state.mode !== "missing-profile" || name !== "list_funcs",
+        )
+        .map((name) => ({
+          name,
+          inputSchema: { type: "object", properties: {} },
+        })),
+    });
+    return;
+  }
+  const name = rpc.params?.name;
+  const args = rpc.params?.arguments;
+  if (name === undefined || args === undefined)
+    throw new Error("Unexpected RPC");
+  state.calls.push(name);
+  let result: unknown;
+  if (name === "idb_open") {
+    state.database = z.string().parse(args.preferred_session_id);
+    state.input = z.string().parse(args.input_path);
+    result = {
+      success: true,
+      session: {
+        session_id:
+          state.mode === "unexpected-worker"
+            ? "unexpected-worker"
+            : state.database,
+        input_path: state.input,
+      },
+    };
+  } else if (name === "idb_list")
+    result = {
+      sessions:
+        state.database === undefined
+          ? []
+          : [
+              {
+                session_id: state.database,
+                input_path: state.input,
+                owned: true,
+                backend: "worker",
+                is_active: true,
+              },
+            ],
+    };
+  else if (name === "idb_close") {
+    result = {
+      success: true,
+      session_id: state.database,
+      saved: null,
+      owned: true,
+      backend: "worker",
+    };
+    state.database = undefined;
+  } else if (name === "server_health")
+    result = {
+      status: "ok",
+      input_path:
+        state.mode === "headless-input-mismatch"
+          ? state.input + ".other"
+          : state.input,
+      idb_path: state.input + ".i64",
+      module: "target.elf",
+      imagebase: "0x1000",
+      auto_analysis_ready: true,
+    };
+  else if (name === "lookup_funcs")
+    result = z
+      .array(z.string())
+      .parse(args.queries)
+      .map((query) => ({
+        query,
+        fn: { addr: "0x1000", name: "main", size: "0x20" },
+        error: null,
+      }));
+  else if (name === "decompile")
+    result = {
+      code: "int main(void) { return 42; }",
+      cursor: { done: true },
+    };
+  else throw new Error("Unexpected tool: " + name);
+  send({ content: [{ type: "text", text: JSON.stringify(result) }] });
+};
+
 const createStartupSupervisor = async (mode: StartupMode) => {
-  const calls: string[] = [];
-  let database: string | undefined;
-  let input: string | undefined;
-  const server = createServer(async (request, response) => {
-    if (request.method !== "POST") {
-      response.writeHead(405).end();
-      return;
-    }
-    let body = "";
-    for await (const chunk of request) body += String(chunk);
-    const rpc = requestSchema.parse(JSON.parse(body));
-    if (rpc.id === undefined) {
-      response.writeHead(202).end();
-      return;
-    }
-    const send = (result: unknown) =>
-      response
-        .writeHead(200, { "Content-Type": "application/json" })
-        .end(JSON.stringify({ jsonrpc: "2.0", id: rpc.id, result }));
-    if (rpc.method === "initialize") {
-      if (mode === "connect-timeout") return;
-      send({
-        protocolVersion: rpc.params?.protocolVersion,
-        capabilities: { tools: {} },
-        serverInfo: { name: "ida-startup-fixture", version: "1" },
-      });
-      return;
-    }
-    if (rpc.method === "tools/list") {
-      if (mode === "catalog-timeout") return;
-      if (mode === "catalog-refused") {
-        response.writeHead(200, { "Content-Type": "application/json" }).end(
-          JSON.stringify({
-            jsonrpc: "2.0",
-            id: rpc.id,
-            error: { code: -32603, message: "fixture catalog refused" },
-          }),
-        );
-        return;
-      }
-      send({
-        tools: tools
-          .filter((name) => mode !== "missing-profile" || name !== "list_funcs")
-          .map((name) => ({
-            name,
-            inputSchema: { type: "object", properties: {} },
-          })),
-      });
-      return;
-    }
-    const name = rpc.params?.name;
-    const args = rpc.params?.arguments;
-    if (name === undefined || args === undefined)
-      throw new Error("Unexpected RPC");
-    calls.push(name);
-    let result: unknown;
-    if (name === "idb_open") {
-      database = z.string().parse(args.preferred_session_id);
-      input = z.string().parse(args.input_path);
-      result = {
-        success: true,
-        session: {
-          session_id:
-            mode === "unexpected-worker" ? "unexpected-worker" : database,
-          input_path: input,
-        },
-      };
-    } else if (name === "idb_list")
-      result = {
-        sessions:
-          database === undefined
-            ? []
-            : [
-                {
-                  session_id: database,
-                  input_path: input,
-                  owned: true,
-                  backend: "worker",
-                  is_active: true,
-                },
-              ],
-      };
-    else if (name === "idb_close") {
-      result = {
-        success: true,
-        session_id: database,
-        saved: null,
-        owned: true,
-        backend: "worker",
-      };
-      database = undefined;
-    } else if (name === "server_health")
-      result = {
-        status: "ok",
-        input_path:
-          mode === "headless-input-mismatch" ? input + ".other" : input,
-        idb_path: input + ".i64",
-        module: "target.elf",
-        imagebase: "0x1000",
-        auto_analysis_ready: true,
-      };
-    else if (name === "lookup_funcs")
-      result = z
-        .array(z.string())
-        .parse(args.queries)
-        .map((query) => ({
-          query,
-          fn: { addr: "0x1000", name: "main", size: "0x20" },
-          error: null,
-        }));
-    else if (name === "decompile")
-      result = {
-        code: "int main(void) { return 42; }",
-        cursor: { done: true },
-      };
-    else throw new Error("Unexpected tool: " + name);
-    send({ content: [{ type: "text", text: JSON.stringify(result) }] });
-  });
+  const state: StartupSupervisorState = {
+    mode,
+    calls: [],
+    database: undefined,
+    input: undefined,
+  };
+  const { server, close } = createVerifierHttpServer((request, response) =>
+    handleStartupRequest(state, request, response),
+  );
   await new Promise<void>((resolve) => server.listen(0, "127.0.0.1", resolve));
   return {
     server,
-    calls,
+    calls: state.calls,
     get database() {
-      return database;
+      return state.database;
     },
+    close,
   };
 };
 
@@ -278,12 +303,7 @@ workspaceCliTest.for([
           },
         });
     } finally {
-      server.closeAllConnections();
-      await new Promise<void>((resolve, reject) =>
-        server.close((error) =>
-          error === undefined ? resolve() : reject(error),
-        ),
-      );
+      await supervisor.close();
     }
   },
 );
diff --git a/tests/boundary/filesystem/browserFixtureRequestFailures.test.ts b/tests/boundary/filesystem/browserFixtureRequestFailures.test.ts
new file mode 100644
index 0000000000..bfe54017ce
--- /dev/null
+++ b/tests/boundary/filesystem/browserFixtureRequestFailures.test.ts
@@ -0,0 +1,67 @@
+import { fileURLToPath } from "node:url";
+import { expect } from "vitest";
+
+import { processTest } from "../../support/process/processFixture.js";
+
+for (const [fixture, factory, ordinaryPath, malformedPath] of [
+  ["browser-network-site", "startBrowserNetworkSite", "/binary", "/same"],
+  [
+    "browser-request-site",
+    "startBrowserRequestSite",
+    "/api/items",
+    "/api/items",
+  ],
+] as const) {
+  processTest(
+    `${fixture} retains malformed request failure through physical close`,
+    async ({ processes }) => {
+      const module = new URL(
+        `../../../scripts/fixtures/${fixture}.mjs`,
+        import.meta.url,
+      ).href;
+      const cleanup = new URL(
+        "../../../scripts/lib/verifier-cleanup.mjs",
+        import.meta.url,
+      ).href;
+      const program = `
+      import assert from "node:assert/strict";
+      import { withVerifierCleanup } from ${JSON.stringify(cleanup)};
+      const { ${factory}: start } = await import(${JSON.stringify(module)});
+      const site = await start();
+      let closed = false;
+      await withVerifierCleanup(async () => {
+        const ordinary = await fetch(site.origin + ${JSON.stringify(ordinaryPath)}, { signal: AbortSignal.timeout(2000) });
+        assert.equal(ordinary.status, 200);
+        await ordinary.arrayBuffer();
+        await assert.rejects(fetch(site.origin + ${JSON.stringify(malformedPath)}, {
+          method: "POST", body: "{", signal: AbortSignal.timeout(2000),
+        }));
+        const outcome = await site.close().then(
+          () => ({ ok: true }), cause => ({ ok: false, cause }),
+        );
+        closed = true;
+        assert.equal(outcome.ok, false);
+        assert(outcome.cause instanceof AggregateError);
+        assert.equal(outcome.cause.errors.length, 1);
+        assert(outcome.cause.errors[0] instanceof SyntaxError);
+        await assert.rejects(fetch(site.origin, { signal: AbortSignal.timeout(2000) }));
+        console.log("ordinary response preserved; malformed request retained; endpoint closed");
+      }, [async () => { if (!closed) await site.close(); }]);
+    `;
+      const result = await processes.run(
+        process.execPath,
+        ["--input-type=module", "-e", program],
+        {
+          cwd: fileURLToPath(new URL("../../../", import.meta.url)),
+          timeoutMs: 10_000,
+        },
+      );
+      expect(result.signal, result.stderr).toBeNull();
+      expect(result.exitCode, result.stderr).toBe(0);
+      expect(result.stderr).toBe("");
+      expect(result.stdout).toBe(
+        "ordinary response preserved; malformed request retained; endpoint closed\n",
+      );
+    },
+  );
+}
diff --git a/tests/boundary/filesystem/ghidraPspExtension.test.ts b/tests/boundary/filesystem/ghidraPspExtension.test.ts
index 572269b119..97668eb08b 100644
--- a/tests/boundary/filesystem/ghidraPspExtension.test.ts
+++ b/tests/boundary/filesystem/ghidraPspExtension.test.ts
@@ -744,8 +744,9 @@ describe.skipIf(process.platform === "win32")(
       controls.directory = (handle) => {
         controls.directory = undefined;
         vi.spyOn(handle, "read").mockRejectedValue(readFailure);
-        const close = handle.close.bind(handle);
-        vi.spyOn(handle, "close").mockImplementation(async () => {
+        const directory: { close(): Promise<void> } = handle;
+        const close = directory.close.bind(handle);
+        vi.spyOn(directory, "close").mockImplementation(async () => {
           closes++;
           await close();
           controller.abort({ caller: "directory finalization" });
diff --git a/tests/boundary/filesystem/referenceSourceCleanupOwnership.test.ts b/tests/boundary/filesystem/referenceSourceCleanupOwnership.test.ts
index e4c3079969..788c216b47 100644
--- a/tests/boundary/filesystem/referenceSourceCleanupOwnership.test.ts
+++ b/tests/boundary/filesystem/referenceSourceCleanupOwnership.test.ts
@@ -6,6 +6,7 @@ import {
   type FileHandle,
 } from "node:fs/promises";
 import { join } from "node:path";
+import type { Dirent } from "node:fs";
 
 import { afterEach, beforeEach, expect, it, onTestFinished, vi } from "vitest";
 
@@ -28,6 +29,11 @@ const openMock = vi.mocked(fsOpen);
 const opendirMock = vi.mocked(fsOpendir);
 let actual: typeof import("node:fs/promises");
 
+interface DirectoryOperations {
+  read(): Promise<Dirent | null>;
+  close(): Promise<void>;
+}
+
 beforeEach(async () => {
   actual =
     await vi.importActual<typeof import("node:fs/promises")>(
@@ -63,13 +69,14 @@ it.each([
     let readCalls = 0;
     opendirMock.mockImplementation(async (...args) => {
       const directory = await actual.opendir(...args);
-      const read = directory.read.bind(directory);
-      vi.spyOn(directory, "read").mockImplementation(async () => {
+      const operations: DirectoryOperations = directory;
+      const read = operations.read.bind(directory);
+      vi.spyOn(operations, "read").mockImplementation(async () => {
         readCalls += 1;
         return read();
       });
-      const close = directory.close.bind(directory);
-      vi.spyOn(directory, "close").mockImplementation(async () => {
+      const close = operations.close.bind(directory);
+      vi.spyOn(operations, "close").mockImplementation(async () => {
         closeCalls += 1;
         if (outcome === "refusal-late-cancel") controller.abort(reason);
         await close();
@@ -296,13 +303,14 @@ it("preserves a directory read failure when closing that directory also fails",
 
   opendirMock.mockImplementation(async (...args) => {
     const directory = await actual.opendir(...args);
-    const read = directory.read.bind(directory);
-    vi.spyOn(directory, "read").mockImplementation(async () => {
+    const operations: DirectoryOperations = directory;
+    const read = operations.read.bind(directory);
+    vi.spyOn(operations, "read").mockImplementation(async () => {
       if (readCalls++ > 0) throw readFailure;
       return read();
     });
-    const close = directory.close.bind(directory);
-    vi.spyOn(directory, "close").mockImplementation(async () => {
+    const close = operations.close.bind(directory);
+    vi.spyOn(operations, "close").mockImplementation(async () => {
       closeCalls += 1;
       await close();
       throw closeFailure;
@@ -361,15 +369,16 @@ it("keeps cancelled traversal typed when native directory close rejects after in
 
   opendirMock.mockImplementation(async (...args) => {
     const directory = await actual.opendir(...args);
+    const operations: DirectoryOperations = directory;
     openedPath = String(args[0]);
-    const read = directory.read.bind(directory);
-    vi.spyOn(directory, "read").mockImplementation(async () => {
+    const read = operations.read.bind(directory);
+    vi.spyOn(operations, "read").mockImplementation(async () => {
       const child = await read();
       if (child !== null) controller.abort();
       return child;
     });
-    const close = directory.close.bind(directory);
-    vi.spyOn(directory, "close").mockImplementation(async () => {
+    const close = operations.close.bind(directory);
+    vi.spyOn(operations, "close").mockImplementation(async () => {
       closeCalls += 1;
       await close();
       throw closeFailure;
diff --git a/tests/boundary/mcp/idaTransport.test.ts b/tests/boundary/mcp/idaTransport.test.ts
index 1bb8db727d..b53d2e422f 100644
--- a/tests/boundary/mcp/idaTransport.test.ts
+++ b/tests/boundary/mcp/idaTransport.test.ts
@@ -1,4 +1,5 @@
-import { createServer } from "node:http";
+import { createVerifierHttpServer } from "../../../scripts/lib/verifier-http-server.mjs";
+import type { IncomingMessage, ServerResponse } from "node:http";
 import { inspect } from "node:util";
 import { ProtocolError } from "@modelcontextprotocol/client";
 import { afterEach, expect, it } from "vitest";
@@ -49,23 +50,90 @@ type IdaTransportFixtureOptions = {
   readonly configurationHeaders?: Readonly<Record<string, string>>;
   readonly connectionDependencies?: IdaMcpConnectionDependencies;
 };
-const fixture = async ({
-  redirectUrl,
-  cycle = false,
-  native = false,
-  toolResult,
-  resourceResponseText,
-  toolRpcError,
-  toolStatus = 200,
-  toolStatusText,
-  toolContentType = "application/json",
-  toolResponseBody,
-  configurationHeaders = { Authorization: "Bearer transport-fixture-secret" },
-  connectionDependencies,
-}: IdaTransportFixtureOptions = {}) => {
+const fixtureResponse = (
+  input: z.infer<typeof requestSchema>,
+  options: IdaTransportFixtureOptions,
+): unknown =>
+  input.method === "initialize"
+    ? {
+        protocolVersion: input.params?.protocolVersion,
+        capabilities: {
+          tools: {},
+          ...(options.native ? { resources: {} } : {}),
+        },
+        serverInfo: {
+          name: "ida-transport-fixture",
+          version: "observed-server-version",
+        },
+      }
+    : input.method === "tools/list"
+      ? {
+          tools: [
+            {
+              name: input.params?.cursor === undefined ? "first" : "second",
+              inputSchema: { type: "object", properties: {} },
+            },
+          ],
+          ...(input.params?.cursor === undefined
+            ? { nextCursor: "next-page" }
+            : options.cycle
+              ? {
+                  nextCursor:
+                    input.params.cursor === "next-page"
+                      ? "other-page"
+                      : "next-page",
+                }
+              : {}),
+        }
+      : input.method === "resources/read"
+        ? {
+            contents: [
+              {
+                uri: "ida://idb/metadata",
+                mimeType: "application/json",
+                text:
+                  options.resourceResponseText ??
+                  JSON.stringify({
+                    path: "/fixture/input.i64",
+                    sha256: "a".repeat(64),
+                    base: "0x1000",
+                    module: "input",
+                  }),
+              },
+            ],
+          }
+        : options.toolResult !== undefined
+          ? options.toolResult
+          : options.native
+            ? {
+                content: [
+                  {
+                    type: "text",
+                    text: JSON.stringify([{ observed: true }]),
+                  },
+                ],
+                structuredContent: { result: [], _output_truncated: true },
+              }
+            : { content: [], structuredContent: { observed: true } };
+
+const fixture = async (options: IdaTransportFixtureOptions = {}) => {
+  const {
+    redirectUrl,
+    native = false,
+    toolRpcError,
+    toolStatus = 200,
+    toolStatusText,
+    toolContentType = "application/json",
+    toolResponseBody,
+    configurationHeaders = { Authorization: "Bearer transport-fixture-secret" },
+    connectionDependencies,
+  } = options;
   const methods: string[] = [];
   const headers: (string | undefined)[] = [];
-  const server = createServer(async (request, response) => {
+  const handleRequest = async (
+    request: IncomingMessage,
+    response: ServerResponse,
+  ) => {
     if (redirectUrl !== undefined) {
       response.writeHead(307, { Location: redirectUrl });
       response.end();
@@ -86,65 +154,7 @@ const fixture = async ({
       response.end();
       return;
     }
-    const result =
-      input.method === "initialize"
-        ? {
-            protocolVersion: input.params?.protocolVersion,
-            capabilities: { tools: {}, ...(native ? { resources: {} } : {}) },
-            serverInfo: {
-              name: "ida-transport-fixture",
-              version: "observed-server-version",
-            },
-          }
-        : input.method === "tools/list"
-          ? {
-              tools: [
-                {
-                  name: input.params?.cursor === undefined ? "first" : "second",
-                  inputSchema: { type: "object", properties: {} },
-                },
-              ],
-              ...(input.params?.cursor === undefined
-                ? { nextCursor: "next-page" }
-                : cycle
-                  ? {
-                      nextCursor:
-                        input.params.cursor === "next-page"
-                          ? "other-page"
-                          : "next-page",
-                    }
-                  : {}),
-            }
-          : input.method === "resources/read"
-            ? {
-                contents: [
-                  {
-                    uri: "ida://idb/metadata",
-                    mimeType: "application/json",
-                    text:
-                      resourceResponseText ??
-                      JSON.stringify({
-                        path: "/fixture/input.i64",
-                        sha256: "a".repeat(64),
-                        base: "0x1000",
-                        module: "input",
-                      }),
-                  },
-                ],
-              }
-            : toolResult !== undefined
-              ? toolResult
-              : native
-                ? {
-                    content: [
-                      {
-                        type: "text",
-                        text: JSON.stringify([{ observed: true }]),
-                      },
-                    ],
-                    structuredContent: { result: [], _output_truncated: true },
-                  }
-                : { content: [], structuredContent: { observed: true } };
+    const result = fixtureResponse(input, options);
     if (input.method === "tools/call" && toolStatusText !== undefined)
       response.statusMessage = toolStatusText;
     response.writeHead(input.method === "tools/call" ? toolStatus : 200, {
@@ -162,17 +172,10 @@ const fixture = async ({
               : { result }),
           }),
     );
-  });
+  };
+  const { server, close } = createVerifierHttpServer(handleRequest);
   await new Promise<void>((resolve) => server.listen(0, "127.0.0.1", resolve));
-  cleanups.push(
-    () =>
-      new Promise<void>((resolve, reject) => {
-        server.close((error) =>
-          error === undefined ? resolve() : reject(error),
-        );
-        server.closeAllConnections();
-      }),
-  );
+  cleanups.push(close);
   const address = server.address();
   if (address === null || typeof address === "string")
     throw new Error("Missing HTTP fixture address");
diff --git a/tests/boundary/process/domCallbackFailures.test.ts b/tests/boundary/process/domCallbackFailures.test.ts
new file mode 100644
index 0000000000..b069057287
--- /dev/null
+++ b/tests/boundary/process/domCallbackFailures.test.ts
@@ -0,0 +1,210 @@
+import { copyFile, writeFile } from "node:fs/promises";
+import { join } from "node:path";
+import { fileURLToPath } from "node:url";
+import { expect } from "vitest";
+
+import { createTestTempDirectory } from "../../fixtures/temporaryDirectory.js";
+import { processTest } from "../../support/process/processFixture.js";
+
+processTest(
+  "renderer DOM callbacks report rejected bridge actions and preserve successful actions",
+  async ({ processes }) => {
+    const cases = [
+      {
+        path: fileURLToPath(
+          new URL(
+            "../../../website/public/examples/notes-electron/renderer.js",
+            import.meta.url,
+          ),
+        ),
+        button: "#export",
+        output: "#status",
+        failure: "Export failed",
+        diagnostic: "Notes export failed",
+        successfulReply: "/selected/notes.csv",
+        success: "Saved to /selected/notes.csv",
+        api: "notes",
+      },
+      {
+        path: fileURLToPath(
+          new URL(
+            "../../conformance/readiness/electron/renderer.js",
+            import.meta.url,
+          ),
+        ),
+        button: "#run",
+        output: "#result",
+        failure: "Echo failed",
+        diagnostic: "Renderer echo failed",
+        successfulReply: "renderer reply",
+        success: "renderer reply",
+        api: "readiness",
+      },
+    ];
+    // Execute the real classic scripts with controlled DOM/bridge seams. This
+    // covers discarded event returns, not a live Electron or browser runtime.
+    const source = `
+import assert from "node:assert/strict";
+import { readFileSync } from "node:fs";
+import { runInNewContext } from "node:vm";
+for (const scenario of ${JSON.stringify(cases)}) {
+  const failure = new Error("selected bridge rejected");
+  const errors = [];
+  let action, deepLink, finish, text = "";
+  let reply = () => Promise.reject(failure);
+  const output = {
+    get textContent() { return text; },
+    set textContent(value) { text = value; finish(); },
+  };
+  const button = { addEventListener(type, callback) {
+    assert.equal(type, "click"); action = callback;
+  }};
+  const api = scenario.api === "notes"
+    ? { exportCsv: () => reply() }
+    : { echo: (value) => { assert.equal(value, "renderer"); return reply(); },
+        onDeepLink: (callback) => { deepLink = callback; } };
+  runInNewContext(readFileSync(scenario.path, "utf8"), {
+    document: { querySelector(selector) {
+      if (selector === scenario.button) return button;
+      assert.equal(selector, scenario.output); return output;
+    }},
+    window: { [scenario.api]: api },
+    console: { error: (...arguments_) => errors.push(arguments_) },
+  }, { filename: scenario.path });
+  let completed = new Promise((resolve) => { finish = resolve; });
+  action(); // DOM event dispatch ignores any callback return value.
+  await completed;
+  assert.equal(text, scenario.failure);
+  assert.deepEqual(errors, [[scenario.diagnostic, failure]]);
+  reply = () => Promise.resolve(scenario.successfulReply);
+  completed = new Promise((resolve) => { finish = resolve; });
+  action();
+  await completed;
+  assert.equal(text, scenario.success);
+  assert.equal(errors.length, 1);
+  if (deepLink) {
+    deepLink({}, "rea://selected/link");
+    assert.equal(text, "rea://selected/link");
+  }
+}
+`;
+    const result = await processes.run(
+      process.execPath,
+      [
+        "--unhandled-rejections=strict",
+        "--input-type=module",
+        "--eval",
+        source,
+      ],
+      { timeoutMs: 10_000 },
+    );
+    expect(result.signal, result.stderr).toBeNull();
+    expect(result.exitCode, result.stderr).toBe(0);
+  },
+);
+
+processTest(
+  "theme translation failure preserves the applied base theme and hides the toggle",
+  async ({ processes }) => {
+    const failureRoot = await createTestTempDirectory("rea-theme-failure-");
+    const successRoot = await createTestTempDirectory("rea-theme-success-");
+    const theme = fileURLToPath(
+      new URL("../../../website/public/assets/theme.js", import.meta.url),
+    );
+    await Promise.all([
+      ...[failureRoot, successRoot].map((root) =>
+        copyFile(theme, join(root, "theme.js")),
+      ),
+      ...[failureRoot, successRoot].map((root) =>
+        writeFile(join(root, "package.json"), '{"type":"module"}\n'),
+      ),
+      writeFile(
+        join(failureRoot, "i18n.js"),
+        "throw globalThis.translationFailure;\n",
+      ),
+      writeFile(
+        join(successRoot, "i18n.js"),
+        'export const t = (value) => "translated:" + value;\n',
+      ),
+    ]);
+    const source = `
+import assert from "node:assert/strict";
+import { readFileSync } from "node:fs";
+import { join } from "node:path";
+import { pathToFileURL } from "node:url";
+import { Script } from "node:vm";
+globalThis.translationFailure = new Error("selected theme translation failed");
+for (const [directory, fails] of ${JSON.stringify([
+      [failureRoot, true],
+      [successRoot, false],
+    ])}) {
+  const errors = [], listeners = new Map(), clicks = new Map(), writes = [];
+  const root = { dataset: {} }, meta = { content: "" };
+  let ready, finish, hidden = true;
+  const settled = new Promise((resolve) => { finish = resolve; });
+  const button = {
+    get hidden() { return hidden; },
+    set hidden(value) { hidden = value; if (!value) finish(); },
+    setAttribute(key, value) { this[key] = value; },
+    addEventListener(type, callback) { clicks.set(type, callback); },
+  };
+  const path = join(directory, "theme.js");
+  new Script(readFileSync(path, "utf8"), {
+    filename: path,
+    importModuleDynamically: (specifier) => import(new URL(specifier, pathToFileURL(path)).href),
+  }).runInNewContext({
+    document: {
+      documentElement: root,
+      querySelector(selector) {
+        if (selector === 'meta[name="theme-color"]') return meta;
+        assert.equal(selector, "[data-theme-toggle]"); return button;
+      },
+      addEventListener(type, callback) { assert.equal(type, "DOMContentLoaded"); ready = callback; },
+    },
+    window: {
+      localStorage: { getItem: () => null, setItem: (...values) => writes.push(values) },
+      matchMedia: () => ({ matches: true, addEventListener() {} }),
+      addEventListener(type, callback) { listeners.set(type, callback); },
+      dispatchEvent(event) { listeners.get(event.type)?.(event); },
+    },
+    Event,
+    console: { error: (...arguments_) => { errors.push(arguments_); finish(); } },
+  });
+  assert.equal(root.dataset.theme, "dark");
+  assert.equal(meta.content, "#1e1e2e");
+  assert.equal(hidden, true);
+  ready(); // No event dispatcher awaits this return value.
+  await settled;
+  if (fails) {
+    assert.deepEqual(errors, [["Theme toggle initialization failed", globalThis.translationFailure]]);
+    assert.equal(hidden, true);
+    assert.equal(root.dataset.theme, "dark");
+    assert.equal(meta.content, "#1e1e2e");
+    assert.equal(clicks.size, 0);
+  } else {
+    assert.deepEqual(errors, []);
+    assert.equal(hidden, false);
+    assert.equal(button["aria-label"], "translated:Switch to light mode");
+    clicks.get("click")();
+    assert.equal(root.dataset.theme, "light");
+    assert.equal(meta.content, "#ffffff");
+    assert.equal(button["aria-label"], "translated:Switch to dark mode");
+    assert.deepEqual(writes, [["rea-theme", "light"]]);
+  }
+}
+`;
+    const result = await processes.run(
+      process.execPath,
+      [
+        "--experimental-vm-modules",
+        "--unhandled-rejections=strict",
+        "--input-type=module",
+        "--eval",
+        source,
+      ],
+      { timeoutMs: 10_000 },
+    );
+    expect(result.signal, result.stderr).toBeNull();
+    expect(result.exitCode, result.stderr).toBe(0);
+  },
+);
diff --git a/tests/boundary/process/fixtureAsyncFailures.test.ts b/tests/boundary/process/fixtureAsyncFailures.test.ts
new file mode 100644
index 0000000000..0ffff41141
--- /dev/null
+++ b/tests/boundary/process/fixtureAsyncFailures.test.ts
@@ -0,0 +1,78 @@
+import { mkdir, readFile, stat, writeFile } from "node:fs/promises";
+import { join } from "node:path";
+import { fileURLToPath } from "node:url";
+import { expect } from "vitest";
+
+import { createTestTempDirectory } from "../../fixtures/temporaryDirectory.js";
+import { processTest } from "../../support/process/processFixture.js";
+
+const hopper = fileURLToPath(
+  new URL("../../fixtures/hopperLaunchAdmission.mjs", import.meta.url),
+);
+const ghidra = fileURLToPath(
+  new URL("../../fixtures/fakeGhidra.mjs", import.meta.url),
+);
+
+for (const blocked of [false, true]) {
+  processTest(
+    `Hopper admission completes handoff publication before denial exit (blocked=${blocked})`,
+    async ({ processes }) => {
+      const root = await createTestTempDirectory(
+        "rea-hopper-fixture-publication-",
+      );
+      const mode = join(root, "mode");
+      const receipt = join(root, "receipt");
+      const handoff = `${receipt}.document-created`;
+      await writeFile(mode, "denied-after-handoff");
+      if (blocked) await mkdir(handoff);
+      const result = await processes.run(
+        process.execPath,
+        [hopper, mode, receipt, "-Y", "controlled-bootstrap"],
+        { timeoutMs: 5_000 },
+      );
+      expect(result.signal, result.stderr).toBeNull();
+      expect(result.exitCode, result.stderr).toBe(blocked ? 1 : 2);
+      expect(result.stderr).toContain("Not authorized to send Apple events");
+      expect(await readFile(receipt, "utf8")).toBe("controlled-bootstrap");
+      if (blocked) {
+        expect(result.stderr).toContain(handoff);
+        expect((await stat(handoff)).isDirectory()).toBe(true);
+      } else {
+        expect(await readFile(handoff, "utf8")).toBe("unconfirmed");
+      }
+    },
+  );
+}
+
+processTest(
+  "Ghidra endpoint publication reports exclusive-file refusal without declaring readiness",
+  async ({ processes }) => {
+    const root = await createTestTempDirectory(
+      "rea-ghidra-fixture-publication-",
+    );
+    const endpointPath = join(root, "endpoint.json");
+    const pending = `${endpointPath}.pending`;
+    await writeFile(pending, "previous selected evidence");
+    const result = await processes.run(process.execPath, [ghidra], {
+      timeoutMs: 5_000,
+      env: {
+        ...process.env,
+        REA_GHIDRA_FIXTURE_CONFIG: JSON.stringify({
+          endpointPath,
+          transport: "authenticated-loopback-tcp",
+          token: "fixture-token",
+          runId: "fixture-run",
+          providerVersion: "fixture-version",
+          profileDigest: "a".repeat(64),
+          targetSha256: "b".repeat(64),
+        }),
+      },
+    });
+    expect(result.signal, result.stderr).toBeNull();
+    expect(result.exitCode, result.stderr).toBe(1);
+    expect(result.stderr).toContain("EEXIST");
+    expect(result.stderr).toContain(pending);
+    expect(await readFile(pending, "utf8")).toBe("previous selected evidence");
+    await expect(stat(endpointPath)).rejects.toMatchObject({ code: "ENOENT" });
+  },
+);
diff --git a/tests/boundary/process/websiteInitialization.test.ts b/tests/boundary/process/websiteInitialization.test.ts
new file mode 100644
index 0000000000..73b5fa1bf4
--- /dev/null
+++ b/tests/boundary/process/websiteInitialization.test.ts
@@ -0,0 +1,47 @@
+import { copyFile, writeFile } from "node:fs/promises";
+import { join } from "node:path";
+import { fileURLToPath, pathToFileURL } from "node:url";
+import { expect } from "vitest";
+
+import { createTestTempDirectory } from "../../fixtures/temporaryDirectory.js";
+import { processTest } from "../../support/process/processFixture.js";
+
+processTest(
+  "reports the original website translation import failure at the startup boundary",
+  async ({ processes }) => {
+    const root = await createTestTempDirectory("rea-website-initialization-");
+    const main = join(root, "main.mjs");
+    await Promise.all([
+      copyFile(
+        fileURLToPath(
+          new URL("../../../website/public/assets/main.js", import.meta.url),
+        ),
+        main,
+      ),
+      writeFile(join(root, "package.json"), '{"type":"module"}\n'),
+      writeFile(
+        join(root, "i18n.js"),
+        "throw globalThis.translationFailure;\n",
+      ),
+    ]);
+    // Execute the public startup code; this does not exercise browser DOM behavior.
+    const source = `
+import assert from "node:assert/strict";
+globalThis.translationFailure = new Error("selected translation import failed");
+const reported = new Promise((resolve) => {
+  console.error = (...arguments_) => resolve(arguments_);
+});
+await import(${JSON.stringify(pathToFileURL(main).href)});
+const [message, cause] = await reported;
+assert.equal(message, "Website initialization failed");
+assert.equal(cause, globalThis.translationFailure);
+`;
+    const result = await processes.run(
+      process.execPath,
+      ["--input-type=module", "--eval", source],
+      { timeoutMs: 10_000 },
+    );
+    expect(result.signal, result.stderr).toBeNull();
+    expect(result.exitCode, result.stderr).toBe(0);
+  },
+);
diff --git a/tests/boundary/providers/jebMcpCatalog.test.ts b/tests/boundary/providers/jebMcpCatalog.test.ts
index 2ba02f2a11..3322cb67d9 100644
--- a/tests/boundary/providers/jebMcpCatalog.test.ts
+++ b/tests/boundary/providers/jebMcpCatalog.test.ts
@@ -1,4 +1,6 @@
-import { createServer } from "node:http";
+import { createVerifierHttpServer } from "../../../scripts/lib/verifier-http-server.mjs";
+import { withVerifierCleanup } from "../../../scripts/lib/verifier-cleanup.mjs";
+import type { IncomingMessage, ServerResponse } from "node:http";
 
 import { expect, it } from "vitest";
 import { z } from "zod";
@@ -12,13 +14,18 @@ const requestSchema = z.object({
   params: z.object({ cursor: z.string().optional() }).passthrough().optional(),
 });
 
-it("reads every JEB catalog page and refreshes the connected engine catalog", async () => {
-  let includeOpen = true;
-  let repeatedCursor = false;
-  let infinitePages = false;
-  let pageCount = 0;
+const createCatalogServer = async () => {
+  const controls = {
+    includeOpen: true,
+    repeatedCursor: false,
+    infinitePages: false,
+    pageCount: 0,
+  };
   const cursors: (string | undefined)[] = [];
-  const server = createServer(async (request, response) => {
+  const handleRequest = async (
+    request: IncomingMessage,
+    response: ServerResponse,
+  ) => {
     if (request.method !== "POST") {
       request.resume();
       response.writeHead(request.method === "DELETE" ? 200 : 405).end();
@@ -45,12 +52,12 @@ it("reads every JEB catalog page and refreshes the connected engine catalog", as
       };
     } else if (message.method === "tools/list") {
       const cursor = message.params?.cursor;
-      pageCount += 1;
-      if (!infinitePages) cursors.push(cursor);
+      controls.pageCount += 1;
+      if (!controls.infinitePages) cursors.push(cursor);
       const names =
         cursor === undefined
           ? ["get_client_information"]
-          : includeOpen
+          : controls.includeOpen
             ? ["open_project"]
             : ["list_units"];
       result = {
@@ -58,9 +65,9 @@ it("reads every JEB catalog page and refreshes the connected engine catalog", as
           name,
           inputSchema: { type: "object" },
         })),
-        ...(infinitePages
-          ? { nextCursor: `fresh-page-${pageCount}` }
-          : cursor === undefined || repeatedCursor
+        ...(controls.infinitePages
+          ? { nextCursor: `fresh-page-${controls.pageCount}` }
+          : cursor === undefined || controls.repeatedCursor
             ? { nextCursor: "second-page" }
             : {}),
       };
@@ -69,21 +76,32 @@ it("reads every JEB catalog page and refreshes the connected engine catalog", as
     }
     response.writeHead(200, { "Content-Type": "application/json" });
     response.end(JSON.stringify({ jsonrpc: "2.0", id: message.id, result }));
-  });
+  };
+  const { server, close } = createVerifierHttpServer(handleRequest);
   await new Promise<void>((resolve) => server.listen(0, "127.0.0.1", resolve));
   const address = server.address();
   if (address === null || typeof address === "string")
     throw new Error("Expected an ephemeral TCP listener");
-  const connection = createStreamableHttpJebMcpConnection(
-    new URL(`http://127.0.0.1:${address.port}/mcp`),
-    { discoveryTimeoutMs: 1_000 },
-  );
+
+  return {
+    controls,
+    cursors,
+    endpoint: `http://127.0.0.1:${address.port}/mcp`,
+    close,
+  };
+};
+
+it("reads every JEB catalog page and refreshes the connected engine catalog", async () => {
+  const { controls, cursors, endpoint, close } = await createCatalogServer();
+  const connection = createStreamableHttpJebMcpConnection(new URL(endpoint), {
+    discoveryTimeoutMs: 1_000,
+  });
   try {
     expect(await connection.listTools()).toEqual([
       "get_client_information",
       "open_project",
     ]);
-    includeOpen = false;
+    controls.includeOpen = false;
     expect(await connection.listTools()).toEqual([
       "get_client_information",
       "list_units",
@@ -94,29 +112,28 @@ it("reads every JEB catalog page and refreshes the connected engine catalog", as
       undefined,
       "second-page",
     ]);
-    infinitePages = true;
-    const before = pageCount;
+    controls.infinitePages = true;
+    const before = controls.pageCount;
     await expect(connection.listTools()).rejects.toBeInstanceOf(
       AnalysisTimeoutError,
     );
-    expect(pageCount - before).toBeGreaterThan(2);
-    infinitePages = false;
+    expect(controls.pageCount - before).toBeGreaterThan(2);
+    controls.infinitePages = false;
     expect(await connection.listTools()).toEqual([
       "get_client_information",
       "list_units",
     ]);
 
     // Shared initial acquisition also owns a finite deadline and can recover.
-    const acquiring = createStreamableHttpJebMcpConnection(
-      new URL(`http://127.0.0.1:${address.port}/mcp`),
-      { discoveryTimeoutMs: 1_000 },
-    );
+    const acquiring = createStreamableHttpJebMcpConnection(new URL(endpoint), {
+      discoveryTimeoutMs: 1_000,
+    });
     try {
-      infinitePages = true;
+      controls.infinitePages = true;
       await expect(acquiring.listTools()).rejects.toBeInstanceOf(
         AnalysisTimeoutError,
       );
-      infinitePages = false;
+      controls.infinitePages = false;
       expect(await acquiring.listTools()).toEqual([
         "get_client_information",
         "list_units",
@@ -124,21 +141,16 @@ it("reads every JEB catalog page and refreshes the connected engine catalog", as
     } finally {
       await acquiring.close();
     }
-    repeatedCursor = true;
+    controls.repeatedCursor = true;
     await expect(connection.listTools()).rejects.toThrow(
       "repeated a tool catalog cursor",
     );
-    repeatedCursor = false;
+    controls.repeatedCursor = false;
     expect(await connection.listTools()).toEqual([
       "get_client_information",
       "list_units",
     ]);
   } finally {
-    await connection.close();
-    await new Promise<void>((resolve, reject) =>
-      server.close((cause) =>
-        cause === undefined ? resolve() : reject(cause),
-      ),
-    );
+    await withVerifierCleanup(() => connection.close(), [close]);
   }
 });
diff --git a/tests/conformance/readiness/electron/renderer.js b/tests/conformance/readiness/electron/renderer.js
index 9c18ac5654..cccfbfe0e3 100644
--- a/tests/conformance/readiness/electron/renderer.js
+++ b/tests/conformance/readiness/electron/renderer.js
@@ -1,6 +1,13 @@
-document.querySelector("#run").addEventListener("click", async () => {
+async function echoRenderer() {
   document.querySelector("#result").textContent =
     await window.readiness.echo("renderer");
+}
+
+document.querySelector("#run").addEventListener("click", () => {
+  echoRenderer().catch((cause) => {
+    document.querySelector("#result").textContent = "Echo failed";
+    console.error("Renderer echo failed", cause);
+  });
 });
 window.readiness.onDeepLink((_event, url) => {
   document.querySelector("#result").textContent = url;
diff --git a/tests/fixtures/evidencePublicationPreload.mjs b/tests/fixtures/evidencePublicationPreload.mjs
index b18fe14223..5ceeae1cb9 100644
--- a/tests/fixtures/evidencePublicationPreload.mjs
+++ b/tests/fixtures/evidencePublicationPreload.mjs
@@ -24,7 +24,7 @@ const require = createRequire(import.meta.url);
 const fs = require("node:fs/promises");
 const owned = (path) => String(path).startsWith(input.prefix);
 let signalled = input.signal === undefined;
-const deliver = (observe) => {
+const recordDelivery = () => {
   writeFileSync(
     input.marker,
     JSON.stringify({
@@ -34,24 +34,32 @@ const deliver = (observe) => {
       listeners: process.listenerCount(input.signal),
     }),
   );
+};
+const emitSignal = () => {
+  if (input.delivery === "os") process.kill(process.pid, input.signal);
+  else process.emit(input.signal);
+};
+const deliver = () => {
+  recordDelivery();
+  emitSignal();
+};
+const deliverAndObserve = async () => {
+  recordDelivery();
   // Registered after the marker so it never stands in for the CLI handler.
   // Signal watchers do not keep the event loop alive; the timer does, and
   // reports a signal that was never observed. It never selects the phase.
-  const observed = observe
-    ? new Promise((resolve, reject) => {
-        const timeout = setTimeout(
-          () => reject(new Error(`${input.signal} was not observed`)),
-          5_000,
-        );
-        process.once(input.signal, () => {
-          clearTimeout(timeout);
-          resolve();
-        });
-      })
-    : undefined;
-  if (input.delivery === "os") process.kill(process.pid, input.signal);
-  else process.emit(input.signal);
-  return observed;
+  const observed = new Promise((resolve, reject) => {
+    const timeout = setTimeout(
+      () => reject(new Error(`${input.signal} was not observed`)),
+      5_000,
+    );
+    process.once(input.signal, () => {
+      clearTimeout(timeout);
+      resolve();
+    });
+  });
+  emitSignal();
+  await observed;
 };
 
 const remove = fs.rmdir;
@@ -65,7 +73,7 @@ fs.rmdir = async (...arguments_) => {
   const result = await remove(...arguments_);
   if (phase === "cleanup" && !signalled && owned(arguments_[0])) {
     signalled = true;
-    setImmediate(() => deliver(false));
+    setImmediate(deliver);
   }
   return result;
 };
@@ -75,7 +83,7 @@ fs.mkdtemp = async (...arguments_) => {
   const directory = await stage(...arguments_);
   if (phase === "staging" && !signalled && owned(directory)) {
     signalled = true;
-    await deliver(true);
+    await deliverAndObserve();
   }
   return directory;
 };
diff --git a/tests/fixtures/fakeGhidra.mjs b/tests/fixtures/fakeGhidra.mjs
index 3a10184b44..5af2455a1e 100644
--- a/tests/fixtures/fakeGhidra.mjs
+++ b/tests/fixtures/fakeGhidra.mjs
@@ -62,6 +62,7 @@ const cutIdentifierAtBudget = async () => {
 const writeThen = (stream, text, then) =>
   stream.write(text, () => setTimeout(then, 10));
 
+let endpointPublication;
 if (mode === "exit") process.exit(73);
 if (mode === "flood_silent") {
   await floodStdout();
@@ -102,7 +103,14 @@ else {
   });
   if (transport === "unix-socket") server.listen(endpointPath);
   else {
-    server.listen(0, "127.0.0.1", async () => {
+    endpointPublication = (async () => {
+      await new Promise((resolve, reject) => {
+        server.once("error", reject);
+        server.listen(0, "127.0.0.1", () => {
+          server.off("error", reject);
+          resolve();
+        });
+      });
       const address = server.address();
       if (address === null || typeof address === "string") process.exit(65);
       const pending = `${endpointPath}.pending`;
@@ -115,7 +123,7 @@ else {
         { flag: "wx" },
       );
       await rename(pending, endpointPath);
-    });
+    })();
   }
 }
 
@@ -509,3 +517,5 @@ const stringSearchItem = () => ({
   address: "0x2000",
   value: "fixture value",
 });
+
+await endpointPublication;
diff --git a/tests/fixtures/hopperLaunchAdmission.mjs b/tests/fixtures/hopperLaunchAdmission.mjs
index 6a5033d6b9..cb311a3ce3 100644
--- a/tests/fixtures/hopperLaunchAdmission.mjs
+++ b/tests/fixtures/hopperLaunchAdmission.mjs
@@ -7,25 +7,27 @@ const bootstrapIndex = process.argv.indexOf("-Y") + 1;
 if (bootstrapIndex === 0) throw new Error("Missing Hopper bootstrap argument");
 const bootstrapPath = process.argv[bootstrapIndex];
 await writeFile(receiptPath, bootstrapPath);
+const writeDiagnostic = (text) =>
+  new Promise((resolve, reject) => {
+    process.stderr.write(text, (cause) => (cause ? reject(cause) : resolve()));
+  });
 if (mode === "denied" || mode === "denied-after-handoff") {
-  process.stderr.write(
+  await writeDiagnostic(
     "Cannot launch Hopper!\nNot authorized to send Apple events to Hopper Disassembler.\n",
-    async () => {
-      if (mode === "denied-after-handoff") {
-        // A real native helper can create a document before emitting this same
-        // diagnostic when caller literals alter its AppleScript construction.
-        await writeFile(`${receiptPath}.document-created`, "unconfirmed");
-      }
-      process.exit(2);
-    },
   );
+  if (mode === "denied-after-handoff") {
+    // A real native helper can create a document before emitting this same
+    // diagnostic when caller literals alter its AppleScript construction.
+    await writeFile(`${receiptPath}.document-created`, "unconfirmed");
+  }
+  process.exit(2);
 } else if (mode === "not-found") {
   // A custom wrapper can forward the native diagnostic after a handoff.
   await writeFile(`${receiptPath}.document-created`, "unconfirmed");
-  process.stderr.write(
+  await writeDiagnostic(
     "Hopper has not been found.\nPlease make sure that Spotlight is active in order for this tool to find Hopper's executable.\n",
-    () => process.exit(3),
   );
+  process.exit(3);
 } else if (mode === "handoff") {
   process.exit(0);
 } else if (mode === "bridge") {
diff --git a/tests/fixtures/processCaptureCancellation.mjs b/tests/fixtures/processCaptureCancellation.mjs
index 501588b205..93dca8dc53 100644
--- a/tests/fixtures/processCaptureCancellation.mjs
+++ b/tests/fixtures/processCaptureCancellation.mjs
@@ -1,6 +1,9 @@
 import { spawn } from "node:child_process";
+import { once } from "node:events";
 import { rename, writeFile } from "node:fs/promises";
 import { join } from "node:path";
+import { setTimeout as delay } from "node:timers/promises";
+import { withVerifierCleanup } from "../../scripts/lib/verifier-cleanup.mjs";
 
 const [mode, root] = process.argv.slice(2);
 
@@ -15,8 +18,11 @@ if (mode === "settlement") {
   const child = spawn(process.execPath, [process.argv[1], "workload", root], {
     stdio: ["ignore", "ignore", "ignore", "ipc"],
   });
-  child.on("message", async (message) => {
-    if (message !== "ready" || child.pid === undefined) return;
+  let handedOff = false;
+  await withVerifierCleanup(async () => {
+    const [message] = await once(child, "message");
+    if (message !== "ready" || child.pid === undefined)
+      throw new Error("Owned capture workload did not report ready");
     await publishReadyMarker({
       rootPid: process.pid,
       childPid: child.pid,
@@ -24,17 +30,28 @@ if (mode === "settlement") {
     });
     child.disconnect();
     child.unref();
-    process.stdout.write("root exiting; owned workload remains\n");
-    process.exit(0);
-  });
+    handedOff = true;
+  }, [
+    async () => {
+      if (
+        !handedOff &&
+        child.pid !== undefined &&
+        child.exitCode === null &&
+        child.signalCode === null
+      ) {
+        const stopped = once(child, "exit");
+        child.kill("SIGTERM");
+        await stopped;
+      }
+    },
+  ]);
+  process.stdout.write("root exiting; owned workload remains\n");
+  process.exit(0);
 } else {
   // A closed PTY must not masquerade as capture cancellation in this fixture.
   process.on("SIGHUP", () => undefined);
-  setTimeout(
-    () => void writeFile(join(root, "late-write"), "still running"),
-    6_000,
-  );
-  setTimeout(() => process.exit(0), 12_000);
+  const lateWrite = delay(6_000);
+  const lifetime = delay(12_000);
   if (mode === "workload") process.send?.("ready");
   else {
     await publishReadyMarker({
@@ -43,4 +60,8 @@ if (mode === "settlement") {
     });
     process.stdout.write("owned workload ready\n");
   }
+  await lateWrite;
+  await writeFile(join(root, "late-write"), "still running");
+  await lifetime;
+  process.exit(0);
 }
diff --git a/tests/process-global/filesystemSnapshotRaces.test.ts b/tests/process-global/filesystemSnapshotRaces.test.ts
index 7a82870747..7095d7125a 100644
--- a/tests/process-global/filesystemSnapshotRaces.test.ts
+++ b/tests/process-global/filesystemSnapshotRaces.test.ts
@@ -89,8 +89,9 @@ vi.mock("node:fs/promises", async (importOriginal) => {
       if (args[0] === race.target && race.mode === "directory_missing")
         race.opened = true;
       if (args[0] === race.target && race.mode === "cancel_directory_close") {
-        const close = directory.close.bind(directory);
-        vi.spyOn(directory, "close").mockImplementation(async () => {
+        const closing: { close(): Promise<void> } = directory;
+        const close = closing.close.bind(directory);
+        vi.spyOn(closing, "close").mockImplementation(async () => {
           await close();
           race.closeCompleted = true;
           race.controller?.abort(race.reason);
diff --git a/tests/process-global/mcpDeliveryEnvironment.test.ts b/tests/process-global/mcpDeliveryEnvironment.test.ts
index 2fa60f878a..896c5e1993 100644
--- a/tests/process-global/mcpDeliveryEnvironment.test.ts
+++ b/tests/process-global/mcpDeliveryEnvironment.test.ts
@@ -182,8 +182,8 @@ it("snapshots the runtime-selected environment before optional loading and reuse
       return server;
     },
     serve: (factory) => {
-      factory({ era: "modern" });
-      factory({ era: "legacy" });
+      expect(factory({ era: "modern" })).toBe(observed[0]);
+      expect(factory({ era: "legacy" })).toBe(observed[1]);
       return {
         close: async () => {
           await Promise.all(observed.map((server) => server.close()));
diff --git a/tests/process-global/referenceSourceSymlinkRace.test.ts b/tests/process-global/referenceSourceSymlinkRace.test.ts
index 7dd1be27fd..1b3803ccec 100644
--- a/tests/process-global/referenceSourceSymlinkRace.test.ts
+++ b/tests/process-global/referenceSourceSymlinkRace.test.ts
@@ -16,8 +16,9 @@ vi.mock("node:fs/promises", async (importOriginal) => {
     opendir: async (...args: Parameters<typeof filesystem.opendir>) => {
       const directory = await filesystem.opendir(...args);
       if (String(args[0]) === race.directory) {
-        const close = directory.close.bind(directory);
-        vi.spyOn(directory, "close").mockImplementation(async () => {
+        const closing: { close(): Promise<void> } = directory;
+        const close = closing.close.bind(directory);
+        vi.spyOn(closing, "close").mockImplementation(async () => {
           await close();
           const hook = race.afterDirectoryClose;
           race.afterDirectoryClose = undefined;
diff --git a/tests/support/cli/cliCommandSessionWorker.mjs b/tests/support/cli/cliCommandSessionWorker.mjs
index c75e3a33da..42d11c8842 100644
--- a/tests/support/cli/cliCommandSessionWorker.mjs
+++ b/tests/support/cli/cliCommandSessionWorker.mjs
@@ -4,6 +4,7 @@ import { dirname, resolve } from "node:path";
 import { fileURLToPath } from "node:url";
 
 import { prepareCliProcessEnvironment } from "../../../scripts/lib/cli-process-environment.mjs";
+import { withVerifierCleanup } from "../../../scripts/lib/verifier-cleanup.mjs";
 import {
   createCliSessionFrameReader,
   encodeCliSessionFrame,
@@ -64,28 +65,51 @@ const writeFrame = (value) =>
 await writeFrame({ ready: true });
 
 let chain = Promise.resolve();
+// EOF drains admitted commands; failure seals input and skips commands not yet started.
+/** @type {{ kind: "open" } | { kind: "ended" } | { kind: "failed", cause: unknown }} */
+let completion = { kind: "open" };
+/** @type {(() => void) | undefined} */
+let resolveInput;
+/** @type {Promise<void>} */
+const inputStopped = new Promise((resolve) => {
+  resolveInput = resolve;
+});
+const failInput = (cause) => {
+  if (completion.kind !== "failed") completion = { kind: "failed", cause };
+  process.stdin.pause();
+  resolveInput?.();
+};
+process.stdin.once("end", () => {
+  if (completion.kind === "open") completion = { kind: "ended" };
+  resolveInput?.();
+});
 const reader = createCliSessionFrameReader((value) => {
-  chain = chain.then(
-    () => handle(value),
-    () => handle(value),
-  );
+  if (completion.kind !== "open") return;
+  chain = chain
+    .then(async () => {
+      if (completion.kind !== "failed") await handle(value);
+    })
+    .catch(failInput);
 });
 process.stdin.on("data", (chunk) => {
+  if (completion.kind !== "open") return;
   try {
     reader(chunk);
-  } catch (error) {
-    process.stderr.write(
-      `${error instanceof Error ? error.message : String(error)}\n`,
-    );
-    process.exit(1);
+  } catch (cause) {
+    failInput(cause);
   }
 });
-process.stdin.on("end", () => {
-  chain.finally(async () => {
-    await closeCliJavaScriptResources();
-    process.exit(0);
-  });
-});
+try {
+  await withVerifierCleanup(async () => {
+    await inputStopped;
+    await chain;
+    if (completion.kind === "failed") throw completion.cause;
+  }, [closeCliJavaScriptResources]);
+} catch (cause) {
+  console.error(cause);
+  process.exit(1);
+}
+process.exit(0);
 
 async function handle(value) {
   const request = value;
@@ -120,6 +144,7 @@ async function handle(value) {
       ...result,
     });
   } catch (error) {
+    failInput(error);
     const id =
       request !== null && typeof request === "object" ? request.id : undefined;
     await writeFrame({
@@ -131,7 +156,6 @@ async function handle(value) {
         error instanceof Error ? (error.stack ?? error.message) : String(error),
       fatal: true,
     });
-    process.exit(1);
   } finally {
     for (const key of Object.keys(process.env)) delete process.env[key];
     Object.assign(process.env, savedEnv);
diff --git a/website/public/assets/main.js b/website/public/assets/main.js
index 2c235ae4df..77fe859cf9 100644
--- a/website/public/assets/main.js
+++ b/website/public/assets/main.js
@@ -165,7 +165,9 @@ async function initializeWebsite() {
     }
   }
 
-  initializeGitHubStars();
+  return initializeGitHubStars();
 }
 
-initializeWebsite();
+initializeWebsite().catch((cause) => {
+  console.error("Website initialization failed", cause);
+});
diff --git a/website/public/assets/theme.js b/website/public/assets/theme.js
index 77f51417d0..87683fc7c6 100644
--- a/website/public/assets/theme.js
+++ b/website/public/assets/theme.js
@@ -42,7 +42,7 @@
     }
   });
 
-  document.addEventListener("DOMContentLoaded", async () => {
+  const initializeToggle = async () => {
     const button = document.querySelector("[data-theme-toggle]");
     if (button === null) return;
     const { t } = await import("./i18n.js");
@@ -66,5 +66,10 @@
     });
     updateLabel();
     button.hidden = false;
+  };
+  document.addEventListener("DOMContentLoaded", () => {
+    initializeToggle().catch((cause) => {
+      console.error("Theme toggle initialization failed", cause);
+    });
   });
 })();
diff --git a/website/public/examples/notes-electron/renderer.js b/website/public/examples/notes-electron/renderer.js
index 50feeb443c..e534a52aab 100644
--- a/website/public/examples/notes-electron/renderer.js
+++ b/website/public/examples/notes-electron/renderer.js
@@ -1,4 +1,11 @@
-document.querySelector("#export").addEventListener("click", async () => {
+async function exportNotes() {
   const destination = await window.notes.exportCsv();
   document.querySelector("#status").textContent = `Saved to ${destination}`;
+}
+
+document.querySelector("#export").addEventListener("click", () => {
+  exportNotes().catch((cause) => {
+    document.querySelector("#status").textContent = "Export failed";
+    console.error("Notes export failed", cause);
+  });
 });