Fix -n flag ignored by adding --file prompt input and stdin support (#90)

The -n flag was consumed by shell expansion when prompts contained
special characters. Fix: make prompt optional, add --file flag to read
from file, and support stdin piping. resolvePrompt() utility handles
all three input methods with clear error messages.

Generated by thinktank Opus (5 agents, all pass, Agent #1 recommended).

Closes #87

Co-authored-by: unknown <that-github-user@github.com>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: 3 people

src/cli.ts

@@ -6,6 +6,7 @@ import { compare } from "./commands/compare.js";
 import { list } from "./commands/list.js";
 import { run } from "./commands/run.js";
 import { stats } from "./commands/stats.js";
+import { resolvePrompt } from "./utils/prompt.js";
 
 const program = new Command();
 
@@ -19,14 +20,17 @@ program
 program
   .command("run")
   .description("Run a task with N parallel AI coding agents")
-  .argument("<prompt>", "The coding task to perform")
+  .argument("[prompt]", "The coding task to perform")
   .option("-n, --attempts <number>", "Number of parallel attempts", "3")
+  .option("-f, --file <path>", "Read prompt from a file (avoids shell expansion issues)")
   .option("-t, --test-cmd <command>", "Test command to verify results (e.g., 'npm test')")
   .option("--timeout <seconds>", "Timeout per agent in seconds", "300")
   .option("--model <model>", "Claude model to use", "sonnet")
   .option("-r, --runner <name>", "AI coding tool to use (default: claude-code)")
   .option("--verbose", "Show detailed output from each agent")
-  .action(async (prompt: string, opts) => {
+  .action(async (promptArg: string | undefined, opts) => {
+    const prompt = resolvePrompt(promptArg, opts.file);
+
     const attempts = parseInt(opts.attempts, 10);
     if (Number.isNaN(attempts) || attempts < 1 || attempts > 20) {
       console.error("Error: --attempts must be a number between 1 and 20");

src/utils/prompt.test.ts

@@ -0,0 +1,58 @@
+import assert from "node:assert/strict";
+import { unlinkSync, writeFileSync } from "node:fs";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+import { describe, it } from "node:test";
+import { resolvePrompt } from "./prompt.js";
+
+describe("resolvePrompt", () => {
+  it("returns positional argument when provided", () => {
+    const result = resolvePrompt("fix the bug", undefined);
+    assert.equal(result, "fix the bug");
+  });
+
+  it("reads prompt from file via --file", () => {
+    const tmpFile = join(tmpdir(), `thinktank-test-prompt-${Date.now()}.txt`);
+    writeFileSync(tmpFile, "prompt from file\nwith newlines\n");
+    try {
+      const result = resolvePrompt(undefined, tmpFile);
+      assert.equal(result, "prompt from file\nwith newlines");
+    } finally {
+      unlinkSync(tmpFile);
+    }
+  });
+
+  it("--file takes priority over positional argument", () => {
+    const tmpFile = join(tmpdir(), `thinktank-test-prompt-${Date.now()}.txt`);
+    writeFileSync(tmpFile, "file wins\n");
+    try {
+      const result = resolvePrompt("positional", tmpFile);
+      assert.equal(result, "file wins");
+    } finally {
+      unlinkSync(tmpFile);
+    }
+  });
+
+  it("handles prompt containing flag-like strings via --file", () => {
+    const tmpFile = join(tmpdir(), `thinktank-test-prompt-${Date.now()}.txt`);
+    writeFileSync(tmpFile, "Fix the -n parsing bug and --timeout handling\n");
+    try {
+      const result = resolvePrompt(undefined, tmpFile);
+      assert.equal(result, "Fix the -n parsing bug and --timeout handling");
+    } finally {
+      unlinkSync(tmpFile);
+    }
+  });
+
+  it("handles prompt with special characters via --file", () => {
+    const tmpFile = join(tmpdir(), `thinktank-test-prompt-${Date.now()}.txt`);
+    const specialPrompt = "Line 1\nLine 2\n---\n- bullet with -n 5\n$VAR `backticks`";
+    writeFileSync(tmpFile, specialPrompt);
+    try {
+      const result = resolvePrompt(undefined, tmpFile);
+      assert.equal(result, specialPrompt);
+    } finally {
+      unlinkSync(tmpFile);
+    }
+  });
+});

src/utils/prompt.ts

@@ -0,0 +1,47 @@
+import { readFileSync } from "node:fs";
+
+/**
+ * Resolve the prompt from positional arg, --file, or stdin (piped).
+ * Exits with a helpful error when no prompt source is found.
+ */
+export function resolvePrompt(
+  positionalArg: string | undefined,
+  filePath: string | undefined,
+): string {
+  if (filePath) {
+    try {
+      const content = readFileSync(filePath, "utf-8").trim();
+      if (!content) {
+        console.error(`Error: prompt file is empty: ${filePath}`);
+        process.exit(1);
+      }
+      return content;
+    } catch (err) {
+      console.error(`Error: could not read prompt file: ${filePath}`);
+      console.error((err as Error).message);
+      process.exit(1);
+    }
+  }
+
+  if (positionalArg) {
+    return positionalArg;
+  }
+
+  // Try reading from stdin if it's piped (not a TTY)
+  if (!process.stdin.isTTY) {
+    try {
+      const stdinContent = readFileSync(0, "utf-8").trim();
+      if (stdinContent) {
+        return stdinContent;
+      }
+    } catch {
+      // stdin not readable, fall through to error
+    }
+  }
+
+  console.error("Error: no prompt provided.");
+  console.error("Usage: thinktank run <prompt>");
+  console.error("       thinktank run -f <file>");
+  console.error("       echo 'prompt' | thinktank run");
+  process.exit(1);
+}