diff --git a/plugins/codex/scripts/codex-companion.mjs b/plugins/codex/scripts/codex-companion.mjs
index 83df468ad..e06b12e52 100644
--- a/plugins/codex/scripts/codex-companion.mjs
+++ b/plugins/codex/scripts/codex-companion.mjs
@@ -140,14 +140,25 @@ function normalizeArgv(argv) {
 
 function parseCommandInput(argv, config = {}) {
   return parseArgs(normalizeArgv(argv), {
+    rejectUnknownOptions: true,
     ...config,
+    booleanOptions: ["help", ...(config.booleanOptions ?? [])],
     aliasMap: {
       C: "cwd",
+      h: "help",
       ...(config.aliasMap ?? {})
     }
   });
 }
 
+function maybePrintCommandHelp(options) {
+  if (!options.help) {
+    return false;
+  }
+  printUsage();
+  return true;
+}
+
 function resolveCommandCwd(options = {}) {
   return options.cwd ? path.resolve(process.cwd(), options.cwd) : process.cwd();
 }
@@ -217,6 +228,9 @@ async function handleSetup(argv) {
     valueOptions: ["cwd"],
     booleanOptions: ["json", "enable-review-gate", "disable-review-gate"]
   });
+  if (maybePrintCommandHelp(options)) {
+    return;
+  }
 
   if (options["enable-review-gate"] && options["disable-review-gate"]) {
     throw new Error("Choose either --enable-review-gate or --disable-review-gate.");
@@ -717,6 +731,9 @@ async function handleReviewCommand(argv, config) {
       m: "model"
     }
   });
+  if (maybePrintCommandHelp(options)) {
+    return;
+  }
 
   const cwd = resolveCommandCwd(options);
   const workspaceRoot = resolveCommandWorkspace(options);
@@ -767,6 +784,9 @@ async function handleTask(argv) {
       m: "model"
     }
   });
+  if (maybePrintCommandHelp(options)) {
+    return;
+  }
 
   const cwd = resolveCommandCwd(options);
   const workspaceRoot = resolveCommandWorkspace(options);
@@ -827,6 +847,9 @@ async function handleTransfer(argv) {
     valueOptions: ["cwd", "source"],
     booleanOptions: ["json"]
   });
+  if (maybePrintCommandHelp(options)) {
+    return;
+  }
 
   const cwd = resolveCommandCwd(options);
   const { payload, rendered } = await executeTransfer(cwd, {
@@ -885,6 +908,9 @@ async function handleStatus(argv) {
     valueOptions: ["cwd", "timeout-ms", "poll-interval-ms"],
     booleanOptions: ["json", "all", "wait"]
   });
+  if (maybePrintCommandHelp(options)) {
+    return;
+  }
 
   const cwd = resolveCommandCwd(options);
   const reference = positionals[0] ?? "";
@@ -912,6 +938,9 @@ function handleResult(argv) {
     valueOptions: ["cwd"],
     booleanOptions: ["json"]
   });
+  if (maybePrintCommandHelp(options)) {
+    return;
+  }
 
   const cwd = resolveCommandCwd(options);
   const reference = positionals[0] ?? "";
@@ -930,6 +959,9 @@ function handleTaskResumeCandidate(argv) {
     valueOptions: ["cwd"],
     booleanOptions: ["json"]
   });
+  if (maybePrintCommandHelp(options)) {
+    return;
+  }
 
   const cwd = resolveCommandCwd(options);
   const workspaceRoot = resolveCommandWorkspace(options);
@@ -965,6 +997,9 @@ async function handleCancel(argv) {
     valueOptions: ["cwd"],
     booleanOptions: ["json"]
   });
+  if (maybePrintCommandHelp(options)) {
+    return;
+  }
 
   const cwd = resolveCommandCwd(options);
   const reference = positionals[0] ?? "";
diff --git a/plugins/codex/scripts/lib/args.mjs b/plugins/codex/scripts/lib/args.mjs
index 6b1518502..463a94216 100644
--- a/plugins/codex/scripts/lib/args.mjs
+++ b/plugins/codex/scripts/lib/args.mjs
@@ -2,6 +2,7 @@ export function parseArgs(argv, config = {}) {
   const valueOptions = new Set(config.valueOptions ?? []);
   const booleanOptions = new Set(config.booleanOptions ?? []);
   const aliasMap = config.aliasMap ?? {};
+  const rejectUnknownOptions = Boolean(config.rejectUnknownOptions);
   const options = {};
   const positionals = [];
   let passthrough = false;
@@ -45,6 +46,10 @@ export function parseArgs(argv, config = {}) {
         continue;
       }
 
+      if (rejectUnknownOptions) {
+        throw new Error(`Unknown option: --${rawKey}`);
+      }
+
       positionals.push(token);
       continue;
     }
@@ -67,6 +72,10 @@ export function parseArgs(argv, config = {}) {
       continue;
     }
 
+    if (rejectUnknownOptions) {
+      throw new Error(`Unknown option: -${shortKey}`);
+    }
+
     positionals.push(token);
   }
 
diff --git a/tests/args.test.mjs b/tests/args.test.mjs
new file mode 100644
index 000000000..e977a80bc
--- /dev/null
+++ b/tests/args.test.mjs
@@ -0,0 +1,86 @@
+import test from "node:test";
+import assert from "node:assert/strict";
+import { fileURLToPath } from "node:url";
+import path from "node:path";
+
+import { parseArgs } from "../plugins/codex/scripts/lib/args.mjs";
+import { makeTempDir, run, initGitRepo } from "./helpers.mjs";
+import { buildEnv, installFakeCodex } from "./fake-codex-fixture.mjs";
+import fs from "node:fs";
+
+const ROOT = path.resolve(path.dirname(fileURLToPath(import.meta.url)), "..");
+const SCRIPT = path.join(ROOT, "plugins", "codex", "scripts", "codex-companion.mjs");
+
+test("parseArgs rejects unknown long options when configured", () => {
+  const helped = parseArgs(["--help", "--cwd", "/tmp"], {
+    booleanOptions: ["help"],
+    valueOptions: ["cwd"],
+    rejectUnknownOptions: true
+  });
+  assert.equal(helped.options.help, true);
+  assert.equal(helped.options.cwd, "/tmp");
+  assert.deepEqual(helped.positionals, []);
+
+  assert.throws(
+    () =>
+      parseArgs(["--not-a-flag"], {
+        booleanOptions: ["json"],
+        rejectUnknownOptions: true
+      }),
+    /Unknown option: --not-a-flag/
+  );
+});
+
+test("parseArgs keeps unknown options as positionals by default", () => {
+  const { options, positionals } = parseArgs(["--not-a-flag", "hello"], {
+    booleanOptions: ["json"]
+  });
+  assert.deepEqual(options, {});
+  assert.deepEqual(positionals, ["--not-a-flag", "hello"]);
+});
+
+test("task --help prints usage and does not dispatch a Codex thread", () => {
+  const repo = makeTempDir();
+  const binDir = makeTempDir();
+  installFakeCodex(binDir);
+  initGitRepo(repo);
+  fs.writeFileSync(path.join(repo, "README.md"), "hello\n");
+
+  const result = run("node", [SCRIPT, "task", "--help", "--cwd", repo, "--json"], {
+    cwd: repo,
+    env: buildEnv(binDir)
+  });
+
+  assert.equal(result.status, 0, result.stderr);
+  assert.match(result.stdout, /Usage:/);
+  assert.match(result.stdout, /codex-companion\.mjs task/);
+  assert.equal(result.stderr.trim(), "");
+
+  const fakeStatePath = path.join(binDir, "fake-codex-state.json");
+  if (fs.existsSync(fakeStatePath)) {
+    const state = JSON.parse(fs.readFileSync(fakeStatePath, "utf8"));
+    assert.equal((state.threads ?? []).length, 0);
+  }
+});
+
+test("task unknown --flag errors without dispatching a Codex thread", () => {
+  const repo = makeTempDir();
+  const binDir = makeTempDir();
+  installFakeCodex(binDir);
+  initGitRepo(repo);
+  fs.writeFileSync(path.join(repo, "README.md"), "hello\n");
+
+  const result = run("node", [SCRIPT, "task", "--not-a-real-flag", "--cwd", repo], {
+    cwd: repo,
+    env: buildEnv(binDir)
+  });
+
+  assert.notEqual(result.status, 0);
+  assert.match(result.stderr, /Unknown option: --not-a-real-flag/);
+
+  const fakeStatePath = path.join(binDir, "fake-codex-state.json");
+  if (fs.existsSync(fakeStatePath)) {
+    const state = JSON.parse(fs.readFileSync(fakeStatePath, "utf8"));
+    assert.equal((state.threads ?? []).length, 0);
+  }
+});