Spawn child processes directly and drop the Deno.Command shim

.agents/memory/bot-agents-child-processes.md

@@ -0,0 +1,39 @@
+---
+description: Child processes use plain node:child_process spawn (explicit stdio, uid/gid, whole env); src/child.ts has exitCode (128+signo) and echo; no execFile maxBuffer
+---
+
+Every call site calls `spawn` from `node:child_process` itself, with
+everything explicit:
+
+- **`uid`/`gid`** of the profile for anything an agent profile runs (each
+  profile is its own UID, 20000+). Never drop them.
+- **`env`** is the whole environment the child gets (a sanitized one for
+  agents); nothing from the coordinator is merged in.
+- **`stdio`**: stdin is `"ignore"` so an agent CLI never waits on input
+  (only `codex login --with-api-key` pipes the token in). Output that is not
+  read is `"ignore"`; output that is read is `"pipe"` and streamed.
+- No `execFile`/`exec`: their `maxBuffer` (1 MiB) kills a chatty child. Read
+  piped streams incrementally instead.
+
+`src/child.ts` holds what the call sites share:
+
+- **`exitCode(child)`**: call it right after `spawn`. It settles on `exit`
+  (not `close`, which a daemonized grandchild can hold open), maps a signal to
+  `128 + signo` as a shell does, and rejects on a failed start. The rejection
+  is pre-caught so it is not reported as unhandled before the caller awaits it.
+- **`echo(stream, chunk)`**: writes and waits for `drain` when the buffer is
+  full, so echoing never outruns a slow reader.
+
+Tests use `spawnSync` for short commands.
+
+Other port details:
+
+- **`src/errors.ts`** `isNotFound` checks `ENOENT` (file) or `ESRCH` (process).
+- Temporary files are an exclusive `wx` create with mode `0600`.
+- `src/json.ts` holds type guards used instead of `as` casts on parsed JSON.
+- `process` and `Buffer` must come from `node:` imports:
+  `no-restricted-globals` in `scripts/project-lint.ts` enforces it
+  ([[lint-parity-never-shrinks]]).
+
+Related: how each agent CLI reports bad credentials is in
+[[agent-cli-auth-failures]].

.agents/memory/bot-agents-node-command-shim.md

@@ -1,25 +0,0 @@
----
-description: src/command.ts reproduces Deno.Command on child_process.spawn (stdio defaults, clearEnv, uid/gid, 128+signo); src/errors.ts maps NotFound to ENOENT/ESRCH
----
-
-The Deno code was ported one for one; two small modules keep the old shapes
-so callers barely changed:
-
-- **`src/command.ts`** wraps `child_process.spawn` with `Deno.Command`'s API:
-  `output()` and `spawn()`, `clearEnv`, `uid`/`gid` (the agent isolation runs
-  each profile as its own UID, 20000+), and Deno's stdio defaults: stdin
-  inherited; stdout/stderr piped for `output()`, inherited for `spawn()`. A
-  signal exit maps to status `128 + signo`. Status settles on process exit,
-  not on stream close. Use it instead of calling `node:child_process`
-  directly so isolation and status handling stay uniform.
-- **`src/errors.ts`** replaces `Deno.errors.NotFound` checks with an
-  `ENOENT`/`ESRCH` code check.
-- `makeTempFile` became an exclusive `wx` create with mode `0600`.
-- `src/json.ts` holds type guards used instead of `as` casts on parsed JSON.
-- `process` and `Buffer` must come from `node:` imports:
-  `no-restricted-globals` in `scripts/project-lint.ts` maps Deno's
-  `no-window`/`no-process-global`/`no-node-globals` there
-  ([[lint-parity-never-shrinks]]).
-
-Related: how each agent CLI reports bad credentials is in
-[[agent-cli-auth-failures]].

.agents/memory/bot-agents-tests-root-only.md

@@ -7,10 +7,10 @@ credential cleanup. They need root and are written as
 `test.skipIf(!IS_ROOT)(...)` (`IS_ROOT` from `#testing`), so they show
 as skipped instead of silently passing.
 
-- As a normal user `vp test` passes 56 and skips 5. In CI (self-hosted
+- As a normal user `vp test` passes 61 and skips 5. In CI (self-hosted
-  runner, root) all 61 run.
+  runner, root) all 66 run.
 - When changing `isolation.ts`, `runtime.ts`, `credentials.ts`, `prepare.ts`,
-  or `command.ts`, run the suite as root in `node:24-bookworm` (e.g. a
+  or `child.ts`, run the suite as root in `node:24-bookworm` (e.g. a
   container with the repo mounted) before pushing; a green non-root run
   proves nothing about those paths.
 - The migration also ran an end-to-end smoke as root with fake

src/auth.test.ts

@@ -17,7 +17,7 @@ test("retries once after an invalid refresh token", async () => {
   const result = await retryInvalidToken(
     () =>
       Promise.resolve({
-        status: { success: false },
+        code: 1,
         error: attempts++ === 0 ? "ERROR: invalid_refresh_token" : "still failed",
       }),
     () => {
@@ -40,7 +40,7 @@ test("does not retry an unrelated failure", async () => {
     () => {
       attempts++;
       return Promise.resolve({
-        status: { success: false },
+        code: 1,
         error: "rate limited",
       });
     },
@@ -86,7 +86,7 @@ test("re-logs in after the job 9837 revoked-session stderr", async () => {
   const result = await retryInvalidToken(
     () =>
       Promise.resolve({
-        status: { success: attempts++ > 0 },
+        code: attempts++ > 0 ? 0 : 1,
         error: attempts === 1 ? REVOKED_CODEX.join("\n") : "",
       }),
     () => {
@@ -95,9 +95,9 @@ test("re-logs in after the job 9837 revoked-session stderr", async () => {
     },
   );
 
-  expect({ relogins, success: result.status.success }).toStrictEqual({
+  expect({ relogins, code: result.code }).toStrictEqual({
     relogins: 1,
-    success: true,
+    code: 0,
   });
 });
 

src/auth.ts

@@ -48,12 +48,12 @@ export function isClaudeAuthFailure(result: ClaudeFailureFields): boolean {
   );
 }
 
-export async function retryInvalidToken<T extends { status: { success: boolean }; error: string }>(
+export async function retryInvalidToken<T extends { code: number; error: string }>(
   attempt: () => Promise<T>,
   relogin: () => Promise<void>,
 ): Promise<T> {
   let result = await attempt();
-  if (!result.status.success && isCodexAuthFailure(result.error)) {
+  if (result.code !== 0 && isCodexAuthFailure(result.error)) {
     await relogin();
     result = await attempt();
   }
@@ -111,7 +111,7 @@ export async function stageCodexAuth(
   return stagedPath;
 }
 
-// Creates an empty private file under a fresh name, as Deno.makeTempFile did.
+// Creates an empty private file under a fresh name.
 async function makeTempFile(directory: string): Promise<string> {
   const path = join(directory, `.tmp-${randomUUID()}`);
   const handle = await open(path, "wx", 0o600);

src/child.test.ts

@@ -0,0 +1,35 @@
+import { spawn } from "node:child_process";
+
+import { expect, test } from "vite-plus/test";
+
+import { isNotFound } from "./errors.ts";
+import { exitCode } from "./child.ts";
+
+test("reports the exit code", async () => {
+  expect(await exitCode(spawn("/bin/sh", ["-c", "exit 0"], { stdio: "ignore" }))).toBe(0);
+  expect(await exitCode(spawn("/bin/sh", ["-c", "exit 3"], { stdio: "ignore" }))).toBe(3);
+});
+
+test("reports a signal as 128 plus its number", async () => {
+  const child = spawn("/bin/sh", ["-c", "kill -KILL $$"], { stdio: "ignore" });
+  expect(await exitCode(child)).toBe(137);
+});
+
+test("resolves on exit while a grandchild still holds the output open", async () => {
+  const child = spawn("/bin/sh", ["-c", "sleep 2 & exit 5"], { stdio: ["ignore", "pipe", "pipe"] });
+  const started = Date.now();
+  expect(await exitCode(child)).toBe(5);
+  expect(Date.now() - started).toBeLessThan(1500);
+  child.stdout.destroy();
+  child.stderr.destroy();
+});
+
+test("rejects when the command does not exist", async () => {
+  const child = spawn("/nonexistent/command", [], { stdio: "ignore" });
+  const code = exitCode(child);
+  // The rejection must stay unhandled-safe until it is awaited.
+  await new Promise((resolve) => {
+    setTimeout(resolve, 50);
+  });
+  await expect(code).rejects.toSatisfy(isNotFound);
+});

src/child.ts

@@ -0,0 +1,30 @@
+// What the child process call sites share: the exit status, read right after
+// `spawn` so the exit event cannot pass unseen while the caller reads the
+// streams, and echoing output without outrunning a slow reader.
+import type { ChildProcess } from "node:child_process";
+import { once } from "node:events";
+import { constants } from "node:os";
+import type { Writable } from "node:stream";
+
+// Resolves once the process exits, before its streams close, with its exit
+// code, or with 128 plus the signal number if a signal killed it, as a shell
+// reports. A process that fails to start rejects with the spawn error.
+export function exitCode(child: ChildProcess): Promise<number> {
+  const code = new Promise<number>((resolve, reject) => {
+    child.once("error", reject);
+    child.once("exit", (exit, signal) => {
+      resolve(exit ?? (signal === null ? 1 : 128 + constants.signals[signal]));
+    });
+  });
+  // Callers await it after draining the streams; a failed start must not be
+  // reported as an unhandled rejection before then.
+  code.catch(() => {});
+  return code;
+}
+
+// Writes a chunk, waiting for the stream to drain when its buffer is full.
+export async function echo(stream: Writable, chunk: string | Uint8Array): Promise<void> {
+  if (!stream.write(chunk)) {
+    await once(stream, "drain");
+  }
+}

src/command.ts

@@ -1,160 +0,0 @@
-// A child process with the call shapes the runner was reviewed with: `output()`
-// collects both streams, `spawn()` hands them out, and `clearEnv` passes only
-// the given environment. Streams default as Deno's did: stdin is inherited,
-// stdout and stderr are piped for `output()` and inherited for `spawn()`.
-import { spawn as spawnProcess } from "node:child_process";
-import type { ChildProcess, StdioOptions } from "node:child_process";
-import { Buffer } from "node:buffer";
-import { constants } from "node:os";
-import process from "node:process";
-import type { Readable, Writable } from "node:stream";
-import { buffer } from "node:stream/consumers";
-import { finished } from "node:stream/promises";
-
-export type StdioMode = "inherit" | "piped" | "null";
-
-export interface CommandOptions {
-  args?: string[];
-  cwd?: string;
-  env?: Record<string, string>;
-  clearEnv?: boolean;
-  uid?: number;
-  gid?: number;
-  stdin?: StdioMode;
-  stdout?: StdioMode;
-  stderr?: StdioMode;
-}
-
-export interface CommandStatus {
-  success: boolean;
-  code: number;
-}
-
-export interface CommandOutput extends CommandStatus {
-  stdout: Uint8Array;
-  stderr: Uint8Array;
-}
-
-export interface CommandChild {
-  status: Promise<CommandStatus>;
-  stdin: Writable;
-  stdout: Readable;
-  stderr: Readable;
-}
-
-const STDIO: Record<StdioMode, "inherit" | "pipe" | "ignore"> = {
-  inherit: "inherit",
-  piped: "pipe",
-  null: "ignore",
-};
-
-function signalNumber(signal: NodeJS.Signals): number {
-  return constants.signals[signal];
-}
-
-function startProcess(
-  command: string,
-  options: CommandOptions,
-  outputDefault: StdioMode,
-): ChildProcess {
-  const stdio: StdioOptions = [
-    STDIO[options.stdin ?? "inherit"],
-    STDIO[options.stdout ?? outputDefault],
-    STDIO[options.stderr ?? outputDefault],
-  ];
-  const environment = options.clearEnv === true ? options.env : { ...process.env, ...options.env };
-  return spawnProcess(command, options.args ?? [], {
-    stdio,
-    ...(options.cwd !== undefined && { cwd: options.cwd }),
-    ...(environment !== undefined && { env: environment }),
-    ...(options.uid !== undefined && { uid: options.uid }),
-    ...(options.gid !== undefined && { gid: options.gid }),
-  });
-}
-
-// Settles when the process exits, before its streams close, as Deno's did. A
-// signal-killed process reports 128 plus the signal number, as a shell does.
-function waitForStatus(child: ChildProcess): Promise<CommandStatus> {
-  return new Promise((resolve, reject) => {
-    child.once("error", reject);
-    child.once("exit", (code, signal) => {
-      const exitCode = code ?? (signal === null ? 1 : 128 + signalNumber(signal));
-      resolve({ success: exitCode === 0, code: exitCode });
-    });
-  });
-}
-
-function piped<T>(stream: T | null, name: string): T {
-  if (stream === null) {
-    throw new TypeError(`${name} is not piped`);
-  }
-  return stream;
-}
-
-function collect(stream: Readable | null): Promise<Uint8Array> {
-  return stream === null ? Promise.resolve(new Uint8Array()) : buffer(stream);
-}
-
-// A stream's chunks as bytes, whether or not it has an encoding set.
-export async function* chunks(stream: Readable): AsyncGenerator<Uint8Array> {
-  for await (const chunk of stream) {
-    const value: unknown = chunk;
-    if (value instanceof Uint8Array) {
-      yield value;
-    } else if (typeof value === "string") {
-      yield Buffer.from(value);
-    }
-  }
-}
-
-export function spawn(command: string, options: CommandOptions = {}): CommandChild {
-  const child = startProcess(command, options, "inherit");
-  const status = waitForStatus(child);
-  // A failed start rejects `status`; the caller sees it once it awaits that.
-  status.catch(() => {});
-  return {
-    status,
-    get stdin(): Writable {
-      return piped(child.stdin, "stdin");
-    },
-    get stdout(): Readable {
-      return piped(child.stdout, "stdout");
-    },
-    get stderr(): Readable {
-      return piped(child.stderr, "stderr");
-    },
-  };
-}
-
-export async function output(
-  command: string,
-  options: CommandOptions = {},
-): Promise<CommandOutput> {
-  const child = startProcess(command, options, "piped");
-  const [status, stdout, stderr] = await Promise.all([
-    waitForStatus(child),
-    collect(child.stdout),
-    collect(child.stderr),
-  ]);
-  return { ...status, stdout, stderr };
-}
-
-// Writes one chunk and settles once the stream has taken it, as Deno's
-// `Deno.stdout.write` did.
-export async function writeChunk(stream: Writable, chunk: Uint8Array): Promise<void> {
-  await new Promise<void>((resolve, reject) => {
-    stream.write(chunk, (error) => {
-      if (error) {
-        reject(error);
-      } else {
-        resolve();
-      }
-    });
-  });
-}
-
-// Writes the last chunk and settles once the stream has flushed and closed.
-export async function endWith(stream: Writable, chunk: string): Promise<void> {
-  stream.end(chunk);
-  await finished(stream);
-}

src/errors.ts

@@ -1,5 +1,4 @@
-// Node reports a missing file as ENOENT and a missing process as ESRCH, where
+// A missing file or a missing process: Node reports them as ENOENT and ESRCH.
-// Deno threw `Deno.errors.NotFound` for both.
 export function isNotFound(error: unknown): boolean {
   if (!(error instanceof Error) || !("code" in error)) {
     return false;

src/isolation.test.ts

@@ -1,14 +1,11 @@
+import { spawnSync } from "node:child_process";
+import type { SpawnSyncReturns } from "node:child_process";
 import { expect, test } from "vite-plus/test";
 import { chmod, chown, mkdir, readFile, rm, symlink, writeFile } from "node:fs/promises";
 import process from "node:process";
 
 import { isNotFound } from "./errors.ts";
-import {
+import { isRunnableProfileProcess, killProfileProcesses, readProfileFile } from "./isolation.ts";
-  agentCommand,
-  isRunnableProfileProcess,
-  killProfileProcesses,
-  readProfileFile,
-} from "./isolation.ts";
 import type { RuntimeProfile } from "./runtime.ts";
 import { currentUid, IS_ROOT, IS_WINDOWS, makeTempDir } from "#testing";
 
@@ -22,6 +19,23 @@ const profile = (uid: number, home: string): RuntimeProfile => ({
   tokenFile: null,
 });
 
+// Runs a command as the profile's user from the root directory. Without `env`
+// it inherits this process's environment.
+function runAs(
+  selected: RuntimeProfile,
+  command: string,
+  args: string[],
+  env?: Record<string, string>,
+): SpawnSyncReturns<string> {
+  return spawnSync(command, args, {
+    cwd: "/",
+    uid: selected.uid,
+    gid: selected.gid,
+    encoding: "utf8",
+    ...(env !== undefined && { env }),
+  });
+}
+
 test("zombie process entries are already quiescent", () => {
   const status = "State:\tZ (zombie)\nUid:\t20010\t20010\t20010\t20010\n";
   expect(isRunnableProfileProcess(status, 20_010)).toBe(false);
@@ -60,20 +74,14 @@ test.skipIf(!IS_ROOT)("a profile process can read only its own private files", a
     await writeFile(`${root}/reviewer`, "root", { mode: 0o600 });
 
     const selected = profile(20_000, homeA);
-    const own = await agentCommand(selected, "/bin/cat", [`${homeA}/token`], {
+    const own = runAs(selected, "/bin/cat", [`${homeA}/token`]);
-      cwd: "/",
+    const sibling = runAs(selected, "/bin/cat", [`${homeB}/token`]);
-    }).output();
+    const reviewer = runAs(selected, "/bin/cat", [`${root}/reviewer`]);
-    const sibling = await agentCommand(selected, "/bin/cat", [`${homeB}/token`], {
-      cwd: "/",
-    }).output();
-    const reviewer = await agentCommand(selected, "/bin/cat", [`${root}/reviewer`], {
-      cwd: "/",
-    }).output();
 
-    expect(new TextDecoder().decode(own.stdout)).toBe("own");
+    expect(own.stdout).toBe("own");
-    expect(own.success).toBe(true);
+    expect(own.status).toBe(0);
-    expect(sibling.success).toBe(false);
+    expect(sibling.status).not.toBe(0);
-    expect(reviewer.success).toBe(false);
+    expect(reviewer.status).not.toBe(0);
   } finally {
     await rm(root, { recursive: true });
   }
@@ -81,13 +89,8 @@ test.skipIf(!IS_ROOT)("a profile process can read only its own private files", a
 
 test.skipIf(!IS_ROOT)("cleanup leaves no runnable daemonized process", async () => {
   const selected = profile(20_010, "/tmp");
-  const launched = await agentCommand(
+  const launched = runAs(selected, "/bin/sh", ["-c", "sleep 60 >/dev/null 2>&1 & echo $!"]);
-    selected,
+  const pid = Number(launched.stdout.trim());
-    "/bin/sh",
-    ["-c", "sleep 60 >/dev/null 2>&1 & echo $!"],
-    { cwd: "/" },
-  ).output();
-  const pid = Number(new TextDecoder().decode(launched.stdout).trim());
   expect(Number.isInteger(pid)).toBe(true);
 
   await killProfileProcesses(selected.uid);
@@ -99,14 +102,11 @@ test.skipIf(!IS_ROOT)("cleanup leaves no runnable daemonized process", async ()
   expect(status === null || !isRunnableProfileProcess(status, selected.uid)).toBe(true);
 });
 
-test.skipIf(!IS_ROOT)("the agent process cannot read its coordinator environment", async () => {
+test.skipIf(!IS_ROOT)("the agent process cannot read its coordinator environment", () => {
   const selected = profile(20_020, "/tmp");
-  const result = await agentCommand(selected, "/usr/bin/cat", [`/proc/${process.pid}/environ`], {
+  const result = runAs(selected, "/usr/bin/cat", [`/proc/${process.pid}/environ`], {
-    cwd: "/",
+    PARENT_SECRET: "must-not-cross-boundary",
-    env: { PARENT_SECRET: "must-not-cross-boundary" },
+  });
-    clearEnv: true,
+
-    stderr: "piped",
+  expect(result.status).not.toBe(0);
-  }).output();
-
-  expect(result.success).toBe(false);
 });

src/isolation.ts

@@ -2,31 +2,9 @@ import { lstat, readdir, readFile } from "node:fs/promises";
 import process from "node:process";
 import { setTimeout as sleep } from "node:timers/promises";
 
-import { output, spawn } from "./command.ts";
-import type { CommandChild, CommandOptions, CommandOutput } from "./command.ts";
 import { isNotFound } from "./errors.ts";
 import type { RuntimeProfile } from "./runtime.ts";
 
-export type AgentCommandOptions = Omit<CommandOptions, "args" | "uid" | "gid">;
-
-export interface AgentCommand {
-  output(): Promise<CommandOutput>;
-  spawn(): CommandChild;
-}
-
-export function agentCommand(
-  profile: RuntimeProfile,
-  command: string,
-  args: string[],
-  options: AgentCommandOptions = {},
-): AgentCommand {
-  const full: CommandOptions = { ...options, args, uid: profile.uid, gid: profile.gid };
-  return {
-    output: () => output(command, full),
-    spawn: () => spawn(command, full),
-  };
-}
-
 export function isRunnableProfileProcess(status: string, uid: number): boolean {
   const owner = /^Uid:\s+(\d+)/mu.exec(status)?.[1];
   const state = /^State:\s+(\w)/mu.exec(status)?.[1];

src/run.ts

@@ -1,10 +1,12 @@
 // Runs one ordered agent profile. Credential decryption and reviewer posting
 // live in separate processes so neither privileged secret reaches this runner.
+import { spawn } from "node:child_process";
 import { chmod, chown, readFile, writeFile } from "node:fs/promises";
 import process from "node:process";
 import { createInterface } from "node:readline";
 import type { Readable } from "node:stream";
 import { text as readText } from "node:stream/consumers";
+import { finished } from "node:stream/promises";
 import { setTimeout as sleep } from "node:timers/promises";
 
 import {
@@ -16,9 +18,8 @@ import {
   stageCodexAuth,
 } from "./auth.ts";
 import type { ClaudeFailureFields, CodexAuthentication } from "./auth.ts";
-import { chunks, endWith, output, writeChunk } from "./command.ts";
+import { echo, exitCode } from "./child.ts";
-import type { CommandStatus } from "./command.ts";
+import { killProfileProcesses, readProfileFile } from "./isolation.ts";
-import { agentCommand, killProfileProcesses, readProfileFile } from "./isolation.ts";
 import { isObject } from "./json.ts";
 import {
   collectOpenCodeOutput,
@@ -98,8 +99,8 @@ async function postAuthorComment(body: string): Promise<void> {
 }
 
 async function runRoot(command: string, args: string[]): Promise<void> {
-  const { success, code } = await output(command, { args, env: PROCESS_ENV, clearEnv: true });
+  const code = await exitCode(spawn(command, args, { env: PROCESS_ENV, stdio: "ignore" }));
-  if (!success) throw new Error(`${command} ${args[0]} exited with ${code}`);
+  if (code !== 0) throw new Error(`${command} ${args[0]} exited with ${code}`);
 }
 
 async function configureGitAuthor(): Promise<void> {
@@ -122,12 +123,15 @@ async function runAgentCommand(
   args: string[],
   token?: string,
 ): Promise<void> {
-  const { success, code } = await agentCommand(profile, command, args, {
+  const child = spawn(command, args, {
     cwd: WORKSPACE,
     env: agentEnvironment(PROCESS_ENV, profile, token),
-    clearEnv: true,
+    uid: profile.uid,
-  }).output();
+    gid: profile.gid,
-  if (!success) throw new Error(`${command} ${args[0]} exited with ${code}`);
+    stdio: "ignore",
+  });
+  const code = await exitCode(child);
+  if (code !== 0) throw new Error(`${command} ${args[0]} exited with ${code}`);
 }
 
 async function prepareProfile(profile: RuntimeProfile): Promise<void> {
@@ -189,8 +193,7 @@ async function renderPrompt(
 }
 
 async function runClaude(profile: RuntimeProfile, token: string, prompt: string): Promise<string> {
-  const claude = agentCommand(
+  const claude = spawn(
-    profile,
     "claude",
     [
       "--print",
@@ -208,21 +211,21 @@ async function runClaude(profile: RuntimeProfile, token: string, prompt: string)
         ...agentEnvironment(PROCESS_ENV, profile, token),
         IS_SANDBOX: "1",
       },
-      clearEnv: true,
+      uid: profile.uid,
-      stdout: "piped",
+      gid: profile.gid,
-      stderr: "piped",
+      stdio: ["ignore", "pipe", "pipe"],
     },
-  ).spawn();
+  );
+  const status = exitCode(claude);
   let result: ClaudeResult | undefined;
   let error = "";
   const copyError = (async (): Promise<void> => {
-    const decoder = new TextDecoder();
+    claude.stderr.setEncoding("utf8");
-    for await (const chunk of chunks(claude.stderr)) {
+    for await (const chunk of claude.stderr) {
-      const part = decoder.decode(chunk, { stream: true });
+      const part = String(chunk);
       error += part;
       console.error(part);
     }
-    error += decoder.decode();
   })();
   for await (const line of createInterface({ input: claude.stdout, crlfDelay: Infinity })) {
     if (line !== "") {
@@ -250,7 +253,7 @@ async function runClaude(profile: RuntimeProfile, token: string, prompt: string)
       }
     }
   }
-  const [status] = await Promise.all([claude.status, copyError]);
+  const [code] = await Promise.all([status, copyError]);
   if (result?.is_error === true) {
     const failure = new Error(result.result ?? `claude ended with ${result.subtype}`);
     if (isClaudeAuthFailure(result)) {
@@ -261,8 +264,8 @@ async function runClaude(profile: RuntimeProfile, token: string, prompt: string)
   if (result?.result === undefined) {
     throw new Error(error.trim() || `claude ended with ${result?.subtype ?? "no result"}`);
   }
-  if (!status.success) {
+  if (code !== 0) {
-    throw new Error(error.trim() || `claude exited with ${status.code}`);
+    throw new Error(error.trim() || `claude exited with ${code}`);
   }
   return result.result;
 }
@@ -270,7 +273,7 @@ async function runClaude(profile: RuntimeProfile, token: string, prompt: string)
 // Polls every 100 ms until the login prints something, failing if it exits first.
 async function pollForInstructions(
   shownText: () => string,
-  status: Promise<CommandStatus>,
+  status: Promise<number>,
 ): Promise<void> {
   if (shownText().trim() !== "") {
     return;
@@ -286,29 +289,28 @@ async function codexDeviceLogin(
   profile: RuntimeProfile,
   environment: Record<string, string>,
 ): Promise<void> {
-  const login = agentCommand(profile, "codex", ["login", "--device-auth"], {
+  const login = spawn("codex", ["login", "--device-auth"], {
     cwd: WORKSPACE,
     env: environment,
-    clearEnv: true,
+    uid: profile.uid,
-    stdout: "piped",
+    gid: profile.gid,
-    stderr: "piped",
+    stdio: ["ignore", "pipe", "pipe"],
-  }).spawn();
+  });
+  const status = exitCode(login);
   let shown = "";
   const collect = async (stream: Readable): Promise<void> => {
-    const decoder = new TextDecoder();
+    stream.setEncoding("utf8");
-    for await (const chunk of chunks(stream)) {
+    for await (const chunk of stream) {
-      shown += decoder.decode(chunk, { stream: true });
+      shown += String(chunk);
     }
-    shown += decoder.decode();
   };
   const drained = Promise.all([collect(login.stdout), collect(login.stderr)]);
-  const status = login.status;
   await sleep(3000);
   await pollForInstructions(() => shown, status);
   await postAuthorComment(withProfile(shown, profile));
-  const [result] = await Promise.all([status, drained]);
+  const [code] = await Promise.all([status, drained]);
-  if (!result.success) {
+  if (code !== 0) {
-    throw new AgentAuthError(`codex login exited with ${result.code}`);
+    throw new AgentAuthError(`codex login exited with ${code}`);
   }
 }
 
@@ -317,17 +319,19 @@ async function codexApiLogin(
   environment: Record<string, string>,
   token: string,
 ): Promise<void> {
-  const login = agentCommand(profile, "codex", ["login", "--with-api-key"], {
+  const login = spawn("codex", ["login", "--with-api-key"], {
     cwd: WORKSPACE,
     env: environment,
-    clearEnv: true,
+    uid: profile.uid,
-    stdin: "piped",
+    gid: profile.gid,
-    stderr: "piped",
+    stdio: ["pipe", "inherit", "pipe"],
-  }).spawn();
+  });
-  await endWith(login.stdin, `${token}\n`);
+  const status = exitCode(login);
-  const [status, error] = await Promise.all([login.status, readText(login.stderr)]);
+  login.stdin.end(`${token}\n`);
-  if (!status.success) {
+  await finished(login.stdin);
-    throw new Error(error.trim() || `codex login exited with ${status.code}`);
+  const [code, error] = await Promise.all([status, readText(login.stderr)]);
+  if (code !== 0) {
+    throw new Error(error.trim() || `codex login exited with ${code}`);
   }
 }
 
@@ -349,17 +353,18 @@ async function runCodex(
   if (authentication.kind === "api-key") {
     await codexApiLogin(profile, environment, authentication.token);
   } else {
-    const loggedIn = await agentCommand(profile, "codex", ["login", "status"], {
+    const check = spawn("codex", ["login", "status"], {
       cwd: WORKSPACE,
       env: environment,
-      clearEnv: true,
+      uid: profile.uid,
-    }).output();
+      gid: profile.gid,
-    if (!loggedIn.success) await codexDeviceLogin(profile, environment);
+      stdio: "ignore",
+    });
+    if ((await exitCode(check)) !== 0) await codexDeviceLogin(profile, environment);
   }
   const outputPath = await makeProfileFile(profile, "result.md");
-  const attempt = async (): Promise<{ status: CommandStatus; error: string }> => {
+  const attempt = async (): Promise<{ code: number; error: string }> => {
-    const codex = agentCommand(
+    const codex = spawn(
-      profile,
       "codex",
       [
         "exec",
@@ -373,20 +378,21 @@ async function runCodex(
       {
         cwd: WORKSPACE,
         env: environment,
-        clearEnv: true,
+        uid: profile.uid,
-        stdout: "inherit",
+        gid: profile.gid,
-        stderr: "piped",
+        stdio: ["ignore", "inherit", "pipe"],
       },
-    ).spawn();
+    );
-    const decoder = new TextDecoder();
+    const status = exitCode(codex);
+    codex.stderr.setEncoding("utf8");
     let error = "";
-    for await (const chunk of chunks(codex.stderr)) {
+    for await (const chunk of codex.stderr) {
-      await writeChunk(process.stderr, chunk);
+      const part = String(chunk);
-      error += decoder.decode(chunk, { stream: true });
+      await echo(process.stderr, part);
+      error += part;
     }
-    error += decoder.decode();
     // Codex echoes the prompt, whose comments may quote auth errors.
-    return { status: await codex.status, error: error.replaceAll(prompt, "") };
+    return { code: await status, error: error.replaceAll(prompt, "") };
   };
   const result =
     authentication.kind === "api-key"
@@ -395,8 +401,8 @@ async function runCodex(
           await runAgentCommand(profile, "codex", ["logout"]);
           await codexDeviceLogin(profile, environment);
         });
-  if (!result.status.success) {
+  if (result.code !== 0) {
-    const failure = new Error(result.error.trim() || `codex exited with ${result.status.code}`);
+    const failure = new Error(result.error.trim() || `codex exited with ${result.code}`);
     if (isCodexAuthFailure(result.error)) {
       throw new AgentAuthError("codex sign-in failed", { cause: failure });
     }
@@ -410,29 +416,24 @@ async function runOpenCode(
   token: string,
   prompt: string,
 ): Promise<string> {
-  const child = agentCommand(profile, "opencode", openCodeArgs(profile.model, prompt), {
+  const child = spawn("opencode", openCodeArgs(profile.model, prompt), {
     cwd: WORKSPACE,
     env: agentEnvironment(PROCESS_ENV, profile, token),
-    clearEnv: true,
+    uid: profile.uid,
-    stdout: "piped",
+    gid: profile.gid,
-    stderr: "piped",
+    stdio: ["ignore", "pipe", "pipe"],
-  }).spawn();
+  });
+  const status = exitCode(child);
   const collected = collectOpenCodeOutput(
-    chunks(child.stdout),
+    child.stdout,
-    chunks(child.stderr),
+    child.stderr,
-    async (chunk) => {
+    (chunk) => echo(process.stdout, chunk),
-      await writeChunk(process.stdout, chunk);
+    (chunk) => echo(process.stderr, chunk),
-    },
-    async (chunk) => {
-      await writeChunk(process.stderr, chunk);
-    },
   );
-  const [status, streams] = await Promise.all([child.status, collected]);
+  const [code, streams] = await Promise.all([status, collected]);
   const error = streams.stderr.trim();
-  if (!status.success) {
+  if (code !== 0) {
-    throw (
+    throw openCodeError(streams.stdout) ?? new Error(error || `opencode exited with ${code}`);
-      openCodeError(streams.stdout) ?? new Error(error || `opencode exited with ${status.code}`)
-    );
   }
   return parseOpenCodeEvents(streams.stdout);
 }

src/runtime.test.ts

@@ -1,10 +1,10 @@
+import { spawnSync } from "node:child_process";
 import { chmod, readdir, readFile, rm, stat, writeFile } from "node:fs/promises";
 import process from "node:process";
 import { fileURLToPath } from "node:url";
 
 import { assert, expect, test } from "vite-plus/test";
 
-import { output } from "./command.ts";
 import { prepareRuntime } from "./runtime.ts";
 import type { RuntimeProfile } from "./runtime.ts";
 import { IS_ROOT, makeTempDir } from "#testing";
@@ -13,14 +13,9 @@ const MASTER_KEY = "AAECAwQFBgcICQoLDA0ODxAREhMUFRYXGBkaGxwdHh8";
 const ENCRYPTED = "v1:ICEiIyQlJicoKSor:oV_FAgnsN3p1FyegJxwGVdyjfyPio6qDeSUwbA";
 
 // Runs `command` as the profile's user, from the root directory.
-async function runAs(profile: RuntimeProfile, command: string, path: string): Promise<boolean> {
+function runAs(profile: RuntimeProfile, command: string, path: string): boolean {
-  const result = await output(command, {
+  const result = spawnSync(command, [path], { cwd: "/", uid: profile.uid, gid: profile.gid });
-    args: [path],
+  return result.status === 0;
-    cwd: "/",
-    uid: profile.uid,
-    gid: profile.gid,
-  });
-  return result.success;
 }
 
 async function expectPrivate(path: string, uid: number, mode: number): Promise<void> {
@@ -58,16 +53,16 @@ test.skipIf(!IS_ROOT)("prepares root-only reviewer and isolated profile credenti
     expect((await stat(codex.home)).uid).toStrictEqual(codex.uid);
     expect(codex.tokenFile).toBe(null);
 
-    const ownToken = await output("/bin/cat", {
+    const ownToken = spawnSync("/bin/cat", [claude.tokenFile], {
-      args: [claude.tokenFile],
       cwd: "/",
       uid: claude.uid,
       gid: claude.gid,
+      encoding: "utf8",
     });
-    expect(ownToken.success).toBe(true);
+    expect(ownToken.status).toBe(0);
-    expect(new TextDecoder().decode(ownToken.stdout)).toBe("secret-token");
+    expect(ownToken.stdout).toBe("secret-token");
-    expect(await runAs(claude, "/bin/cat", manifest.reviewerFile)).toBe(false);
+    expect(runAs(claude, "/bin/cat", manifest.reviewerFile)).toBe(false);
-    expect(await runAs(claude, "/bin/ls", codex.home)).toBe(false);
+    expect(runAs(claude, "/bin/ls", codex.home)).toBe(false);
   } finally {
     await rm(root, { recursive: true });
     await rm(action, { recursive: true });
@@ -85,18 +80,20 @@ test.skipIf(!IS_ROOT)("removes prepared credentials when output publication fail
         profiles: [{ type: "claude", token: ENCRYPTED }],
       }),
     );
-    const result = await output(process.execPath, {
+    const result = spawnSync(
-      args: [fileURLToPath(new URL("prepare.ts", import.meta.url))],
+      process.execPath,
+      [fileURLToPath(new URL("prepare.ts", import.meta.url))],
+      {
         env: {
           ACTION_PATH: action,
           RUNNER_TEMP: root,
           BOT_AGENTS_MASTER_KEY: MASTER_KEY,
           GITHUB_OUTPUT: action,
         },
-      clearEnv: true,
+      },
-    });
+    );
 
-    expect(result.success).toBe(false);
+    expect(result.status).not.toBe(0);
     expect(await readdir(root)).toStrictEqual([]);
   } finally {
     await rm(root, { recursive: true });