Make --typecheck a true compile-only mode in launcher

README.md

@@ -280,7 +280,7 @@ Pass `--server` to start the Copilot server automatically as part of the run:
 cat ./program.ts | node skills/rig/rig.ts --server
 ```
 
-Pass `--typecheck` to typecheck the rig program before execution:
+Pass `--typecheck` to typecheck the rig program and exit without executing it:
 
 ```bash
 cat ./program.ts | node skills/rig/rig.ts --typecheck

skills/rig/SKILL.md

@@ -312,7 +312,7 @@ Pass `--server` to have the harness start the Copilot server automatically befor
 echo "Review this diff" | node skills/rig/rig.ts src/program.ts --server
 ```
 
-Pass `--typecheck` to typecheck the rig program before execution:
+Pass `--typecheck` to typecheck the rig program and exit without executing it:
 
 ```bash
 cat <<'RIG' | node skills/rig/rig.ts --typecheck

skills/rig/rig.ts

@@ -863,7 +863,20 @@ function withInjectedRigImport(programCode: string): string {
   if (/\bfrom\s*["']rig["']/.test(programCode)) {
     return programCode;
   }
-  return `import { agent, p, s } from "rig";\n\n${programCode}`;
+  const names: string[] = [];
+  if (/\bagent\s*\(/u.test(programCode)) {
+    names.push("agent");
+  }
+  if (/\bp(?:\s*`|\s*\.)/u.test(programCode)) {
+    names.push("p");
+  }
+  if (/\bs\s*\./u.test(programCode)) {
+    names.push("s");
+  }
+  if (names.length === 0) {
+    return programCode;
+  }
+  return `import { ${names.join(", ")} } from "rig";\n\n${programCode}`;
 }
 
 function withInjectedDefaultRootAgent(programCode: string): string {
@@ -909,7 +922,7 @@ function renderStdout(value: unknown): string {
   return JSON.stringify(value);
 }
 
-async function typecheckProgram(programPath: string, cwd: string): Promise<void> {
+async function typecheckProgram(programPath: string, cwd: string, displayPath = programPath): Promise<void> {
   const execFileAsync = promisify(execFile);
   const skillTsconfigPath = resolve(dirname(fileURLToPath(import.meta.url)), "tsconfig.json");
   const candidateTsconfigPaths = [resolve(cwd, "tsconfig.json"), skillTsconfigPath];
@@ -955,7 +968,7 @@ async function typecheckProgram(programPath: string, cwd: string): Promise<void>
       .join("\n")
       .trim();
     const detail = diagnostics ? `\n${diagnostics}` : "";
-    throw new Error(`Typecheck failed for ${programPath}.${detail}`);
+    throw new Error(`Typecheck failed for ${displayPath}.${detail}`);
   } finally {
     await rm(tempDir, { recursive: true, force: true });
   }
@@ -967,15 +980,16 @@ async function runRootAgentFromStdin(
   io: LauncherIo,
   scriptName: string,
 ): Promise<void> {
-  const prompt = await readStdin(io.stdin);
-  if (!prompt.trim()) {
-    throw new Error(`Usage: ${scriptName} <program-file>`);
-  }
-
   const cwd = options.cwd ?? process.cwd();
   const resolvedPath = isAbsolute(programPath) ? programPath : resolve(cwd, programPath);
   if (options.typecheck) {
     await typecheckProgram(resolvedPath, cwd);
+    return;
+  }
+
+  const prompt = await readStdin(io.stdin);
+  if (!prompt.trim()) {
+    throw new Error(`Usage: ${scriptName} <program-file>`);
   }
 
   configureAgent(copilotEngine(resolveCopilotOptions(cwd, options)));
@@ -1008,7 +1022,8 @@ async function runProgramCodeFromStdin(
   await writeFile(tempProgramPath, transformedProgramCode, "utf8");
   try {
     if (options.typecheck) {
-      await typecheckProgram(tempProgramPath, cwd);
+      await typecheckProgram(tempProgramPath, cwd, "<stdin>");
+      return;
     }
     configureAgent(copilotEngine(resolveCopilotOptions(cwd, options)));
     const mod = await import(pathToFileURL(tempProgramPath).href);

src/launcher.test.ts

@@ -240,7 +240,7 @@ it("accepts --server flag without rejecting", async () => {
   expect(mocks.forStdio).toHaveBeenCalled();
 });
 
-it("accepts --typecheck flag without rejecting", async () => {
+it("typechecks a program file without executing it", async () => {
   const fixturePath = resolve(dirname(fileURLToPath(import.meta.url)), "./launcher.stdin.fixture.ts");
   const stdin = Readable.from(["Review this patch"]);
   const output: string[] = [];
@@ -253,7 +253,8 @@ it("accepts --typecheck flag without rejecting", async () => {
 
   await runLauncherCli([fixturePath, "--typecheck"], {}, { stdin, stdout });
 
-  expect(output.join("")).toBe("done");
+  expect(output.join("")).toBe("");
+  expect(mocks.createSession).not.toHaveBeenCalled();
 });
 
 it("falls back to the skill tsconfig when cwd tsconfig is missing", async () => {
@@ -270,7 +271,8 @@ it("falls back to the skill tsconfig when cwd tsconfig is missing", async () =>
 
   await runLauncherCli([fixturePath, "--typecheck"], { cwd: skillDirCwd }, { stdin, stdout });
 
-  expect(output.join("")).toBe("done");
+  expect(output.join("")).toBe("");
+  expect(mocks.createSession).not.toHaveBeenCalled();
 });
 
 it("rejects --typecheck when inline program fails typecheck", async () => {
@@ -292,6 +294,28 @@ export default root;
   );
 });
 
+it("typechecks an inline program from stdin without executing it", async () => {
+  const stdin = Readable.from([`
+const root = agent({
+  name: "launcher-stdin-program",
+  instructions: "Write a short note.",
+});
+export default root;
+`]);
+  const output: string[] = [];
+  const stdout = new Writable({
+    write(chunk, _encoding, callback) {
+      output.push(chunk.toString());
+      callback();
+    },
+  });
+
+  await runLauncherCli(["--typecheck"], {}, { stdin, stdout });
+
+  expect(output.join("")).toBe("");
+  expect(mocks.createSession).not.toHaveBeenCalled();
+});
+
 it("rejects --typecheck when program file fails typecheck before execution", async () => {
   const tempDir = await mkdtemp(resolve(tmpdir(), "rig-launcher-test-"));
   const fixturePath = resolve(tempDir, "typecheck-fail.ts");