diff --git a/scripts/dev/tui-pty-test-watch.ts b/scripts/dev/tui-pty-test-watch.ts
index a604897b85e7..0b2863c74083 100644
--- a/scripts/dev/tui-pty-test-watch.ts
+++ b/scripts/dev/tui-pty-test-watch.ts
@@ -7,6 +7,7 @@ import { pathToFileURL } from "node:url";
 
 type Options = {
   altScreen: boolean;
+  help: boolean;
   mirrorPath: string;
   mode: "fake" | "local" | "all";
   vitestArgs: string[];
@@ -26,6 +27,12 @@ const CHILD_SIGTERM_GRACE_MS = 500;
 const CHILD_SIGKILL_GRACE_MS = 5_000;
 const MIRROR_READ_CHUNK_BYTES = 1024 * 1024;
 const CHILD_OUTPUT_TAIL_BYTES = 128 * 1024;
+const BOOLEAN_OPTIONS = new Set(["--help", "-h", "--no-alt-screen"]);
+const VALUE_OPTIONS = new Set(["--mode", "--mirror-path"]);
+
+class CliArgumentError extends Error {
+  override name = "CliArgumentError";
+}
 
 type KillableChild = {
   pid?: number;
@@ -48,7 +55,11 @@ function readOption(args: string[], name: string): string | undefined {
   if (idx < 0) {
     return undefined;
   }
-  return args[idx + 1]?.trim() || undefined;
+  const value = args[idx + 1];
+  if (!value || value.startsWith("--")) {
+    throw new CliArgumentError(`${name} requires a value`);
+  }
+  return value.trim();
 }
 
 function readMode(args: string[]): Options["mode"] {
@@ -56,20 +67,46 @@ function readMode(args: string[]): Options["mode"] {
   if (mode === "fake" || mode === "local" || mode === "all") {
     return mode;
   }
-  throw new Error(`--mode must be fake, local, or all; got ${JSON.stringify(mode)}`);
+  throw new CliArgumentError(`--mode must be fake, local, or all; got ${JSON.stringify(mode)}`);
+}
+
+function usage(): string {
+  return [
+    "Usage: node --import tsx scripts/dev/tui-pty-test-watch.ts [options] [-- vitest args...]",
+    "",
+    "Options:",
+    "  --mode <fake|local|all>   Select TUI PTY test group (default: fake)",
+    "  --mirror-path <path>       Write/read mirrored ANSI output at this path",
+    "  --no-alt-screen            Print without switching to the terminal alt screen",
+    "  -h, --help                 Show this help",
+  ].join("\n");
+}
+
+function validateOwnArgs(args: string[]): void {
+  for (let idx = 0; idx < args.length; idx += 1) {
+    const arg = args[idx] ?? "";
+    if (BOOLEAN_OPTIONS.has(arg)) {
+      continue;
+    }
+    if (VALUE_OPTIONS.has(arg)) {
+      idx += 1;
+      continue;
+    }
+    throw new CliArgumentError(`Unknown argument: ${arg}`);
+  }
 }
 
 function parseOptions(args = process.argv.slice(2)): Options {
   const separator = args.indexOf("--");
   const ownArgs = separator >= 0 ? args.slice(0, separator) : args;
   const vitestArgs = separator >= 0 ? args.slice(separator + 1) : [];
-  const mirrorPath =
-    readOption(ownArgs, "--mirror-path") !== undefined
-      ? path.resolve(readOption(ownArgs, "--mirror-path") ?? "")
-      : DEFAULT_MIRROR_PATH;
+  validateOwnArgs(ownArgs);
+  const mirrorPathOption = readOption(ownArgs, "--mirror-path");
   return {
     altScreen: !ownArgs.includes("--no-alt-screen"),
-    mirrorPath,
+    help: ownArgs.includes("--help") || ownArgs.includes("-h"),
+    mirrorPath:
+      mirrorPathOption !== undefined ? path.resolve(mirrorPathOption) : DEFAULT_MIRROR_PATH,
     mode: readMode(ownArgs),
     vitestArgs,
   };
@@ -209,6 +246,10 @@ async function drainNewMirrorData(
 
 async function main(): Promise<void> {
   const options = parseOptions();
+  if (options.help) {
+    process.stdout.write(`${usage()}\n`);
+    return;
+  }
   const useAltScreen = shouldUseAltScreen(options);
   await createMirrorFile(options.mirrorPath);
 
@@ -422,6 +463,10 @@ async function main(): Promise<void> {
 
 if (import.meta.url === pathToFileURL(process.argv[1] ?? "").href) {
   main().catch((error: unknown) => {
+    if (error instanceof CliArgumentError) {
+      process.stderr.write(`${error.message}\n`);
+      process.exit(1);
+    }
     process.stderr.write(
       `${error instanceof Error ? error.stack || error.message : String(error)}\n`,
     );
@@ -433,6 +478,8 @@ export const testing = {
   appendBufferTail,
   createChildStopper,
   drainNewMirrorData,
+  parseOptions,
   readNewMirrorData,
   signalChildProcessTree,
+  usage,
 };
diff --git a/test/scripts/dev-tooling-safety.test.ts b/test/scripts/dev-tooling-safety.test.ts
index a53590be1e6e..51191d41a21a 100644
--- a/test/scripts/dev-tooling-safety.test.ts
+++ b/test/scripts/dev-tooling-safety.test.ts
@@ -1,4 +1,5 @@
 // Dev Tooling Safety tests cover dev tooling safety script behavior.
+import { spawnSync } from "node:child_process";
 import { EventEmitter } from "node:events";
 import fs from "node:fs/promises";
 import os from "node:os";
@@ -205,6 +206,45 @@ describe("script-specific dev tooling hardening", () => {
     expect(calls).toBe(1);
   });
 
+  it("prints TUI PTY watch usage without launching the watcher", () => {
+    const result = spawnSync(
+      process.execPath,
+      ["--import", "tsx", "scripts/dev/tui-pty-test-watch.ts", "--help"],
+      {
+        cwd: process.cwd(),
+        encoding: "utf8",
+      },
+    );
+
+    expect(result.status).toBe(0);
+    expect(result.stdout).toContain("Usage: node --import tsx scripts/dev/tui-pty-test-watch.ts");
+    expect(result.stderr).toBe("");
+  });
+
+  it("rejects unknown TUI PTY watch args before launching the watcher", () => {
+    expect(() => tuiPtyWatchTesting.parseOptions(["--wat"])).toThrow("Unknown argument: --wat");
+
+    const result = spawnSync(
+      process.execPath,
+      ["--import", "tsx", "scripts/dev/tui-pty-test-watch.ts", "--wat"],
+      {
+        cwd: process.cwd(),
+        encoding: "utf8",
+      },
+    );
+
+    expect(result.status).toBe(1);
+    expect(result.stderr.trim()).toBe("Unknown argument: --wat");
+    expect(result.stdout).toBe("");
+  });
+
+  it("keeps TUI PTY watch vitest args behind the separator", () => {
+    expect(tuiPtyWatchTesting.parseOptions(["--mode", "all", "--", "--help"])).toMatchObject({
+      mode: "all",
+      vitestArgs: ["--help"],
+    });
+  });
+
   it("escalates stalled TUI PTY watch children after interrupt cleanup", async () => {
     vi.useFakeTimers();
     const signals: NodeJS.Signals[] = [];