refactor(ui): update menu, selector for TTY detection; thin dispatcher

- Update menu.ts and selector.ts to use isStdinTTY() and function-based
  terminal colors
- Refactor index.ts from 995-line monolith to ~270-line dispatcher that
  registers all commands via the CLI parser and delegates to modules
- Add initTTY() call at startup for correct pipe/TTY detection
- Interactive menu expanded to include new commands (explain, review,
  changelog, suggest, amend)

src/ai.ts

@@ -1,29 +1,20 @@
-import type { Config } from "./types";
+import type { Config, StreamCallbacks } from "./types";
 
 interface ChatMessage {
   role: "system" | "user" | "assistant";
   content: string;
 }
 
-interface ChatCompletionResponse {
-  choices?: Array<{
-    message?: {
-      content?: string | null;
-    };
-    finish_reason?: string;
-  }>;
-  error?: {
-    message?: string;
-    type?: string;
-    code?: string;
-  };
-}
-
 const MAX_RETRIES = 3;
-const RETRY_DELAY = 1000;
+const RETRY_DELAY_MS = 1000;
+
+async function sleep(ms: number) {
+  return new Promise((resolve) => setTimeout(resolve, ms));
+}
 
 function cleanMessage(raw: string): string {
   let msg = raw.trim();
+  // Strip code fences if the whole response is wrapped
   if (msg.startsWith("```") && msg.endsWith("```")) {
     const lines = msg.split("\n");
     if (lines.length > 2) {
@@ -35,16 +26,14 @@ function cleanMessage(raw: string): string {
   return msg;
 }
 
-async function sleep(ms: number) {
-  return new Promise((resolve) => setTimeout(resolve, ms));
-}
-
 export async function callAI(
   config: Config,
   systemPrompt: string,
   userPrompt: string,
+  callbacks?: StreamCallbacks,
 ): Promise<string> {
   const url = `${config.apiBase.replace(/\/$/, "")}/chat/completions`;
+  const stream = callbacks != null;
 
   const messages: ChatMessage[] = [
     { role: "system", content: systemPrompt },
@@ -64,45 +53,45 @@ export async function callAI(
           max_tokens: config.maxTokens,
           temperature: config.temperature,
           messages,
+          stream,
         }),
       });
 
       if (!response.ok) {
         const text = await response.text();
         if (response.status === 429 && attempt < MAX_RETRIES) {
-          await sleep(RETRY_DELAY * attempt);
+          await sleep(RETRY_DELAY_MS * attempt);
           continue;
         }
         throw new Error(`API request failed (${response.status}): ${text}`);
       }
 
-      const data = (await response.json()) as ChatCompletionResponse;
+      if (stream && response.body) {
+        return await readStream(response.body, callbacks!);
+      }
+
+      const data = (await response.json()) as {
+        choices?: Array<{ message?: { content?: string | null }; finish_reason?: string }>;
+        error?: { message?: string; type?: string; code?: string };
+      };
 
       if (data.error) {
-        throw new Error(
-          `API error: ${data.error.message ?? JSON.stringify(data.error)}`,
-        );
+        throw new Error(`API error: ${data.error.message ?? JSON.stringify(data.error)}`);
       }
 
       const raw = data.choices?.[0]?.message?.content;
       const finishReason = data.choices?.[0]?.finish_reason;
 
-      if (raw && raw.trim()) {
-        return raw;
-      }
+      if (raw && raw.trim()) return raw;
 
       if (finishReason === "length") {
-        throw new Error(
-          "Response truncated (max_tokens too low). Try increasing GAI_MAX_TOKENS.",
-        );
+        throw new Error("Response truncated (max_tokens too low). Try increasing GAI_MAX_TOKENS.");
       }
-
       if (finishReason === "content_filter") {
         throw new Error("Response blocked by content filter.");
       }
-
       if (attempt < MAX_RETRIES) {
-        await sleep(RETRY_DELAY * attempt);
+        await sleep(RETRY_DELAY_MS * attempt);
         continue;
       }
 
@@ -113,21 +102,70 @@ export async function callAI(
       if (attempt >= MAX_RETRIES) throw err;
       if (err instanceof Error && err.message.startsWith("API error")) throw err;
       if (err instanceof Error && err.message.includes("max_tokens")) throw err;
-      if (err instanceof Error && err.message.includes("content filter"))
-        throw err;
-      await sleep(RETRY_DELAY * attempt);
+      if (err instanceof Error && err.message.includes("content filter")) throw err;
+      await sleep(RETRY_DELAY_MS * attempt);
     }
   }
 
   throw new Error("Failed to generate response");
 }
 
+async function readStream(body: ReadableStream<Uint8Array>, callbacks: StreamCallbacks): Promise<string> {
+  const reader = body.getReader();
+  const decoder = new TextDecoder();
+  let fullText = "";
+  let buffer = "";
+
+  try {
+    while (true) {
+      const { done, value } = await reader.read();
+      if (done) break;
+
+      buffer += decoder.decode(value, { stream: true });
+      const lines = buffer.split("\n");
+      // Keep the last potentially incomplete line
+      buffer = lines.pop() ?? "";
+
+      for (const line of lines) {
+        const trimmed = line.trim();
+        if (!trimmed || !trimmed.startsWith("data:")) continue;
+
+        const data = trimmed.slice(5).trim();
+        if (data === "[DONE]") continue;
+
+        try {
+          const parsed = JSON.parse(data) as {
+            choices?: Array<{ delta?: { content?: string }; finish_reason?: string }>;
+          };
+          const token = parsed.choices?.[0]?.delta?.content;
+          if (token) {
+            fullText += token;
+            callbacks.onToken?.(token);
+          }
+          const finishReason = parsed.choices?.[0]?.finish_reason;
+          if (finishReason === "length") {
+            callbacks.onError?.(new Error("Response truncated (max_tokens too low)."));
+          }
+        } catch {
+          // Skip unparseable SSE lines
+        }
+      }
+    }
+  } finally {
+    reader.releaseLock();
+  }
+
+  callbacks.onDone?.(fullText);
+  return fullText;
+}
+
 export async function generateCommitMessage(
   config: Config,
   systemPrompt: string,
   userPrompt: string,
+  callbacks?: StreamCallbacks,
 ): Promise<string> {
-  const raw = await callAI(config, systemPrompt, userPrompt);
+  const raw = await callAI(config, systemPrompt, userPrompt, callbacks);
   return cleanMessage(raw);
 }
 
@@ -135,8 +173,9 @@ export async function generatePRMessage(
   config: Config,
   systemPrompt: string,
   userPrompt: string,
+  callbacks?: StreamCallbacks,
 ): Promise<{ title: string; body: string }> {
-  const raw = await callAI(config, systemPrompt, userPrompt);
+  const raw = await callAI(config, systemPrompt, userPrompt, callbacks);
   const cleaned = cleanMessage(raw);
 
   const lines = cleaned.split("\n");
@@ -148,6 +187,5 @@ export async function generatePRMessage(
   }
 
   const body = lines.slice(bodyStart).join("\n").trim();
-
   return { title, body };
 }

src/cli.ts

@@ -0,0 +1,295 @@
+// Lightweight CLI argument parser aligned with mainstream CLI conventions.
+// Supports: subcommands, short/long flags, flag values, positional args, --help, --version.
+
+export interface FlagDef {
+  long: string; // e.g. "dry-run"
+  short?: string; // e.g. "d"
+  type: "boolean" | "string";
+  description: string;
+  default?: unknown; // boolean flags default to false
+}
+
+export interface CommandDef {
+  name: string;
+  aliases?: string[];
+  description: string;
+  usage?: string; // one-line usage, e.g. "gai commit [-a|--all] [-d|--dry-run]"
+  flags?: FlagDef[];
+  examples?: string[];
+  handler: (args: ParsedArgs) => Promise<number>; // returns exit code
+}
+
+export interface ParsedArgs {
+  command: string; // matched command name
+  flags: Record<string, unknown>; // resolved flags by long name
+  positional: string[]; // remaining positional args
+  raw: string[]; // original argv
+  subcommand: CommandDef;
+}
+
+// Global flags available to all commands
+const GLOBAL_FLAGS: FlagDef[] = [
+  { long: "help", short: "h", type: "boolean", description: "Show help for this command" },
+  { long: "version", short: "V", type: "boolean", description: "Show version" },
+  { long: "verbose", short: "v", type: "boolean", description: "Enable verbose output" },
+  { long: "no-color", type: "boolean", description: "Disable colored output" },
+];
+
+function buildFlagIndex(flags: FlagDef[]): Map<string, FlagDef> {
+  const index = new Map<string, FlagDef>();
+  for (const f of flags) {
+    index.set("--" + f.long, f);
+    if (f.short) index.set("-" + f.short, f);
+  }
+  return index;
+}
+
+function resolveFlagName(raw: string): { flag: FlagDef; value?: string } | null {
+  // "--key=value"
+  const eqIndex = raw.indexOf("=");
+  if (eqIndex !== -1) {
+    const name = raw.slice(0, eqIndex);
+    const value = raw.slice(eqIndex + 1);
+    const allFlags = buildFlagIndex([...GLOBAL_FLAGS]); // we'll rebuild in context
+    // We'll handle = syntax in the main parse loop with proper index
+    return null; // handled inline
+  }
+  return null; // handled inline
+}
+
+function parseArgs(
+  rawArgs: string[],
+  commands: Map<string, CommandDef>,
+): ParsedArgs | { error: string } {
+  const args = [...rawArgs];
+  let cmdName = "";
+
+  // Find subcommand
+  for (let i = 0; i < args.length; i++) {
+    const arg = args[i]!;
+    if (arg.startsWith("-")) continue; // skip flags before subcommand
+    cmdName = arg;
+    args.splice(i, 1);
+    break;
+  }
+
+  // Resolve subcommand (including aliases)
+  let subcommand: CommandDef | undefined;
+  if (cmdName) {
+    subcommand = commands.get(cmdName);
+    if (!subcommand) {
+      // Try aliases
+      for (const [, cmd] of commands) {
+        if (cmd.aliases?.includes(cmdName)) {
+          subcommand = cmd;
+          cmdName = cmd.name;
+          break;
+        }
+      }
+    }
+    if (!subcommand) {
+      return { error: `Unknown command: ${cmdName}\nRun 'gai --help' for usage.` };
+    }
+  } else {
+    // Default: interactive menu
+    subcommand = commands.get("")!;
+  }
+
+  const flags = subcommand.flags ?? [];
+  const allFlags = [...GLOBAL_FLAGS, ...flags];
+  const flagIndex = buildFlagIndex(allFlags);
+
+  const resolved: Record<string, unknown> = {};
+  // Set defaults
+  for (const f of allFlags) {
+    if (f.type === "boolean") {
+      resolved[f.long] = f.default ?? false;
+    } else if (f.default !== undefined) {
+      resolved[f.long] = f.default;
+    }
+  }
+
+  const positional: string[] = [];
+
+  // Parse remaining args
+  for (let i = 0; i < args.length; i++) {
+    const arg = args[i]!;
+
+    // Handle --flag=value
+    if (arg.startsWith("--") && arg.includes("=")) {
+      const eqIdx = arg.indexOf("=");
+      const name = arg.slice(0, eqIdx);
+      const value = arg.slice(eqIdx + 1);
+      const flag = flagIndex.get(name);
+      if (!flag) return { error: `Unknown flag: ${name}` };
+      if (flag.type === "boolean") {
+        resolved[flag.long] = value === "true" || value === "1" || value === "";
+      } else {
+        resolved[flag.long] = value;
+      }
+      continue;
+    }
+
+    // Handle --flag or -f
+    if (arg.startsWith("-")) {
+      const flag = flagIndex.get(arg);
+      if (!flag) return { error: `Unknown flag: ${arg}` };
+      if (flag.type === "boolean") {
+        resolved[flag.long] = true;
+      } else {
+        // Consume next arg as value
+        i++;
+        if (i >= args.length || args[i]!.startsWith("-")) {
+          return { error: `Flag ${arg} requires a value.` };
+        }
+        resolved[flag.long] = args[i]!;
+      }
+      continue;
+    }
+
+    // Positional
+    positional.push(arg);
+  }
+
+  return {
+    command: cmdName || "",
+    flags: resolved,
+    positional,
+    raw: rawArgs,
+    subcommand,
+  };
+}
+
+export function registerCommands(...cmds: CommandDef[]): Map<string, CommandDef> {
+  const map = new Map<string, CommandDef>();
+  for (const cmd of cmds) {
+    map.set(cmd.name, cmd);
+    if (cmd.aliases) {
+      for (const alias of cmd.aliases) {
+        if (!map.has(alias)) {
+          map.set(alias, cmd);
+        }
+      }
+    }
+  }
+  return map;
+}
+
+export function formatHelp(commands: Map<string, CommandDef>, cmdName?: string): string {
+  if (cmdName) {
+    const cmd = commands.get(cmdName);
+    if (!cmd) return `Unknown command: ${cmdName}`;
+
+    const lines: string[] = [];
+    lines.push("");
+    lines.push(`  gai ${cmdName} — ${cmd.description}`);
+    lines.push("");
+
+    if (cmd.usage) {
+      lines.push(`  Usage: ${cmd.usage}`);
+      lines.push("");
+    }
+
+    const flags = cmd.flags ?? [];
+    if (flags.length > 0) {
+      lines.push("  Flags:");
+      for (const f of flags) {
+        const shorts = f.short ? `-${f.short}, ` : "      ";
+        const typeHint = f.type === "string" ? " <value>" : "";
+        lines.push(`    ${shorts}--${f.long}${typeHint}`);
+        lines.push(`          ${f.description}`);
+      }
+      lines.push("");
+    }
+
+    lines.push("  Global flags:");
+    for (const f of GLOBAL_FLAGS) {
+      const shorts = f.short ? `-${f.short}, ` : "      ";
+      const typeHint = f.type === "string" ? " <value>" : "";
+      lines.push(`    ${shorts}--${f.long}${typeHint}`);
+      lines.push(`          ${f.description}`);
+    }
+    lines.push("");
+
+    if (cmd.examples && cmd.examples.length > 0) {
+      lines.push("  Examples:");
+      for (const ex of cmd.examples) {
+        lines.push(`    $ ${ex}`);
+      }
+      lines.push("");
+    }
+
+    return lines.join("\n");
+  }
+
+  // General help — deduplicate: show only canonical command names
+  const lines: string[] = [];
+  lines.push("");
+  lines.push("  gai — AI-powered git commit and PR helper");
+  lines.push("");
+  lines.push("  Usage: gai <command> [flags]");
+  lines.push("");
+  lines.push("  Commands:");
+
+  // Deduplicate: only show canonical names (not aliases)
+  const seen = new Set<string>();
+  let maxLen = 0;
+  const entries: { name: string; desc: string }[] = [];
+  for (const [name, cmd] of commands) {
+    if (!name) continue; // skip default
+    // Skip if this name is an alias of another command (i.e., not the canonical name)
+    if (cmd.name !== name) continue;
+    if (seen.has(name)) continue;
+    seen.add(name);
+    const aliases = cmd.aliases && cmd.aliases.length > 0 ? ` (${cmd.aliases.join(", ")})` : "";
+    const label = `  ${name}${aliases}`;
+    entries.push({ name: label, desc: cmd.description });
+    if (label.length > maxLen) maxLen = label.length;
+  }
+  maxLen += 4;
+
+  for (const entry of entries) {
+    const padding = " ".repeat(Math.max(2, maxLen - entry.name.length));
+    lines.push(`${entry.name}${padding}${entry.desc}`);
+  }
+
+  lines.push("");
+  lines.push("  Global flags:");
+  for (const f of GLOBAL_FLAGS) {
+    const shorts = f.short ? `-${f.short}, ` : "      ";
+    lines.push(`    ${shorts}--${f.long}  ${f.description}`);
+  }
+  lines.push("");
+  lines.push(`  Run 'gai help <command>' for command-specific help.`);
+  lines.push("");
+
+  return lines.join("\n");
+}
+
+export async function runCLI(rawArgs: string[], commands: Map<string, CommandDef>): Promise<number> {
+  const result = parseArgs(rawArgs, commands);
+
+  if ("error" in result) {
+    console.error(`\n  Error: ${result.error}\n`);
+    return 1;
+  }
+
+  // Handle --help globally
+  if (result.flags["help"]) {
+    console.log(formatHelp(commands, result.command || undefined));
+    return 0;
+  }
+
+  // Handle --version globally
+  if (result.flags["version"]) {
+    console.log("gai v0.2.0");
+    return 0;
+  }
+
+  try {
+    return await result.subcommand.handler(result);
+  } catch (err) {
+    console.error(`\n  Error: ${err instanceof Error ? err.message : err}\n`);
+    return 1;
+  }
+}

src/commands/changelog.ts

@@ -0,0 +1,81 @@
+import { loadConfig } from "../config";
+import { isGitRepo, getRecentCommits } from "../git";
+import { CHANGELOG_SYSTEM_PROMPT, buildChangelogPrompt } from "../prompt";
+import { callAI } from "../ai";
+import { BOLD, RED, DIM, RESET, CYAN } from "../terminal";
+import { isStdinTTY } from "../tty";
+import type { StreamCallbacks } from "../types";
+import type { ParsedArgs } from "../cli";
+
+export async function handleChangelog(args: ParsedArgs): Promise<number> {
+  const config = await loadConfig();
+
+  if (!config.apiKey) {
+    console.error(`\n  ${RED()}Error: API key not set. Run ${BOLD()}gai config${RESET()}${RED()} to configure.${RESET()}\n`);
+    return 1;
+  }
+
+  if (!(await isGitRepo())) {
+    console.error(`\n  ${RED()}Error: Not a git repository.${RESET()}\n`);
+    return 1;
+  }
+
+  const from = args.flags["from"] as string | undefined;
+  const to = args.flags["to"] as string | undefined;
+  const countFlag = args.flags["count"] as number | undefined;
+  const verbose = args.flags["verbose"] as boolean;
+
+  // Collect commits
+  let commits: string[];
+
+  if (from) {
+    // Range-based: get commits between from..to
+    const range = to ? `${from}..${to}` : `${from}..HEAD`;
+    try {
+      const result = await Bun.$`git log --oneline ${range}`.quiet().text();
+      commits = result.trim().split("\n").filter(Boolean);
+    } catch {
+      console.error(`\n  ${RED()}Error: Invalid range: ${range}${RESET()}\n`);
+      return 1;
+    }
+  } else {
+    // Count-based
+    const count = typeof countFlag === "number" ? countFlag : 20;
+    commits = await getRecentCommits(count);
+  }
+
+  if (commits.length === 0) {
+    console.log(`  ${DIM()}No commits found for the specified range.${RESET()}`);
+    return 0;
+  }
+
+  if (verbose) {
+    console.log(`  ${DIM()}Processing ${commits.length} commits${RESET()}`);
+    console.log(`  ${DIM()}Model: ${config.model} | API: ${config.apiBase}${RESET()}`);
+  }
+
+  const userPrompt = buildChangelogPrompt(commits, from, to);
+
+  const tty = isStdinTTY();
+  if (tty) {
+    console.log(`\n  ${BOLD()}${CYAN()}Generating changelog from ${commits.length} commits...${RESET()}\n`);
+  }
+
+  try {
+    const callbacks: StreamCallbacks = tty ? {
+      onToken: (token) => process.stdout.write(token),
+    } : undefined;
+
+    const result = await callAI(config, CHANGELOG_SYSTEM_PROMPT, userPrompt, callbacks);
+    if (callbacks) {
+      process.stdout.write("\n");
+    } else {
+      process.stdout.write(result + "\n");
+    }
+  } catch (err) {
+    console.error(`\n  ${RED()}AI request failed: ${err instanceof Error ? err.message : err}${RESET()}\n`);
+    return 1;
+  }
+
+  return 0;
+}

src/commands/commit.ts

@@ -0,0 +1,418 @@
+import * as readline from "node:readline";
+import {
+  isGitRepo,
+  getRepoRoot,
+  getStagedFiles,
+  getUnstagedFiles,
+  getStagedDiff,
+  getRecentCommits,
+  stageFiles,
+  commit,
+} from "../git";
+import { selectFiles } from "../selector";
+import { BACK } from "../menu";
+import { collectProjectContext } from "../context";
+import { buildPrompt, SYSTEM_PROMPT } from "../prompt";
+import { generateCommitMessage } from "../ai";
+import { copyToClipboard } from "../clipboard";
+import { BOLD, GREEN, YELLOW, CYAN, RED, DIM, RESET } from "../terminal";
+import { isStdinTTY } from "../tty";
+import type { Config, CommitResult, StreamCallbacks } from "../types";
+import { loadConfig } from "../config";
+import type { ParsedArgs } from "../cli";
+
+function ask(question: string): Promise<string> {
+  const rl = readline.createInterface({ input: process.stdin, output: process.stdout });
+  return new Promise((resolve) => {
+    rl.question(question, (answer) => {
+      rl.close();
+      resolve(answer.trim());
+    });
+  });
+}
+
+function printCommitResult(result: CommitResult, msg: string) {
+  console.log(`\n  ${GREEN()}${BOLD()}✔ Committed successfully!${RESET()}`);
+  const id = result.branch && result.hash
+    ? `${YELLOW()}[${result.branch} ${result.hash}]${RESET()}`
+    : result.hash
+      ? `${YELLOW()}${result.hash}${RESET()}`
+      : "";
+  console.log(`    ${id}  ${msg}`);
+
+  const parts: string[] = [];
+  if (result.files > 0)
+    parts.push(`${YELLOW()}${result.files} file${result.files > 1 ? "s" : ""} changed${RESET()}`);
+  if (result.insertions > 0)
+    parts.push(`${GREEN()}${result.insertions} insertion${result.insertions > 1 ? "s" : ""}(+)${RESET()}`);
+  if (result.deletions > 0)
+    parts.push(`${RED()}${result.deletions} deletion${result.deletions > 1 ? "s" : ""}(-)${RESET()}`);
+  if (parts.length > 0) console.log(`    ${parts.join(", ")}`);
+}
+
+async function confirmCommit(message: string): Promise<"y" | "n" | "e"> {
+  console.log(`\n  ${BOLD()}Generated commit message:${RESET()}`);
+  console.log(`    ${GREEN()}${message}${RESET()}\n`);
+  const answer = await ask(`  Use this message? [${GREEN()}Y${RESET()}/n/e] `);
+  const lower = answer.toLowerCase();
+  if (lower === "n") return "n";
+  if (lower === "e") return "e";
+  return "y";
+}
+
+async function editMessage(current: string): Promise<string | null> {
+  if (!isStdinTTY()) return null;
+  process.stdout.write(`  ${DIM()}Edit message (Enter to confirm, Esc to abort):${RESET()}\n`);
+
+  const savedRaw = process.stdin.isRaw;
+  process.stdin.setRawMode(true);
+  process.stdin.resume();
+
+  let buffer = current;
+  let cursor = current.length;
+
+  function render() {
+    process.stdout.write("\x1b[2K\r  > " + buffer);
+    if (cursor < buffer.length) {
+      process.stdout.write(`\x1b[${buffer.length - cursor}D`);
+    }
+  }
+
+  process.stdout.write("  > ");
+  process.stdout.write(buffer);
+
+  return new Promise((resolve) => {
+    let escapeBuf = "";
+
+    process.stdin.on("data", (data: Buffer) => {
+      const key = data.toString();
+
+      if (key === "\x03") {
+        process.stdin.setRawMode(savedRaw === true);
+        process.stdin.pause();
+        process.stdin.removeAllListeners("data");
+        process.stdout.write("\n");
+        resolve(null);
+        return;
+      }
+
+      if (key === "\x1b" || key.startsWith("\x1b[")) {
+        escapeBuf = key;
+        if (key.length >= 3) { handleSeq(key); escapeBuf = ""; }
+        return;
+      }
+
+      if (escapeBuf) {
+        escapeBuf += key;
+        if (/^[A-Za-z~]$/.test(key)) { handleSeq(escapeBuf); escapeBuf = ""; }
+        else if (escapeBuf.length > 8) escapeBuf = "";
+        return;
+      }
+
+      if (key === "\r") {
+        process.stdin.setRawMode(savedRaw === true);
+        process.stdin.pause();
+        process.stdin.removeAllListeners("data");
+        process.stdout.write("\n");
+        const result = buffer.trim();
+        resolve(result || null);
+        return;
+      }
+
+      if (key === "\x7f") {
+        if (cursor > 0) {
+          buffer = buffer.slice(0, cursor - 1) + buffer.slice(cursor);
+          cursor--;
+          render();
+        }
+        return;
+      }
+
+      if (key === "\x01") { if (cursor > 0) { process.stdout.write(`\x1b[${cursor}D`); cursor = 0; } return; }
+      if (key === "\x05") { if (cursor < buffer.length) { process.stdout.write(`\x1b[${buffer.length - cursor}C`); cursor = buffer.length; } return; }
+      if (key === "\x0b") { buffer = buffer.slice(0, cursor); render(); return; }
+      if (key === "\x15") { buffer = buffer.slice(cursor); cursor = 0; render(); return; }
+
+      if (key.charCodeAt(0) >= 32 && key.charCodeAt(0) < 127) {
+        buffer = buffer.slice(0, cursor) + key + buffer.slice(cursor);
+        cursor++;
+        render();
+      }
+    });
+
+    function handleSeq(seq: string) {
+      if (seq === "\x1b[D" || seq === "\x1bOD") {
+        if (cursor > 0) { cursor--; process.stdout.write("\x1b[D"); }
+      } else if (seq === "\x1b[C" || seq === "\x1bOC") {
+        if (cursor < buffer.length) { cursor++; process.stdout.write("\x1b[C"); }
+      } else if (seq === "\x1b[H" || seq === "\x1b[1~" || seq === "\x1bOH") {
+        if (cursor > 0) { process.stdout.write(`\x1b[${cursor}D`); cursor = 0; }
+      } else if (seq === "\x1b[F" || seq === "\x1b[4~" || seq === "\x1bOF") {
+        if (cursor < buffer.length) { process.stdout.write(`\x1b[${buffer.length - cursor}C`); cursor = buffer.length; }
+      } else if (seq === "\x1b[3~") {
+        if (cursor < buffer.length) { buffer = buffer.slice(0, cursor) + buffer.slice(cursor + 1); render(); }
+      }
+    }
+  });
+}
+
+export async function handleCommit(args: ParsedArgs): Promise<number> {
+  const autoMode = args.flags["all"] as boolean || args.flags["auto"] as boolean;
+  const dryRun = args.flags["dry-run"] as boolean;
+  const amend = args.flags["amend"] as boolean;
+  const customMessage = args.flags["message"] as string | undefined;
+  const verbose = args.flags["verbose"] as boolean;
+
+  if (!(await isGitRepo())) {
+    console.error(`\n  ${RED()}Error: Not a git repository.${RESET()}\n`);
+    return 1;
+  }
+
+  // If a custom message is provided, skip AI and commit directly
+  if (customMessage) {
+    const stagedFiles = await getStagedFiles();
+    const unstagedFiles = await getUnstagedFiles();
+
+    if (stagedFiles.length === 0 && !amend) {
+      if (autoMode && unstagedFiles.length > 0) {
+        await stageFiles(unstagedFiles.map((f) => f.path));
+        console.log(`  ${GREEN()}Auto-staged ${unstagedFiles.length} file(s).${RESET()}`);
+      } else if (unstagedFiles.length > 0) {
+        console.error(`\n  ${RED()}Error: No staged changes. Use -a to auto-stage, or stage files manually.${RESET()}\n`);
+        return 1;
+      } else {
+        console.error(`\n  ${RED()}Error: Nothing to commit.${RESET()}\n`);
+        return 1;
+      }
+    }
+
+    const diff = await getStagedDiff();
+    if (!diff && !amend) {
+      console.log(`  ${DIM()}Nothing to commit.${RESET()}`);
+      return 0;
+    }
+
+    try {
+      const result = await commit(customMessage);
+      printCommitResult(result, customMessage);
+      return 0;
+    } catch (err) {
+      console.error(`\n  ${RED()}Commit failed: ${err instanceof Error ? err.message : err}${RESET()}\n`);
+      return 1;
+    }
+  }
+
+  // Handle amend
+  if (amend) {
+    return handleAmendCommit(args);
+  }
+
+  const stagedFiles = await getStagedFiles();
+  const unstagedFiles = await getUnstagedFiles();
+
+  if (stagedFiles.length === 0 && unstagedFiles.length === 0) {
+    console.log(`  ${DIM()}Nothing to commit. No staged or unstaged changes.${RESET()}`);
+    return 0;
+  }
+
+  if (unstagedFiles.length > 0) {
+    if (autoMode) {
+      await stageFiles(unstagedFiles.map((f) => f.path));
+      console.log(`  ${GREEN()}Auto-staged ${unstagedFiles.length} file(s).${RESET()}`);
+    } else {
+      const selected = await selectFiles(stagedFiles, unstagedFiles);
+      if (selected === BACK) return 0;
+      if (selected.length > 0) {
+        await stageFiles(selected);
+        console.log(`  ${GREEN()}Staged ${selected.length} file(s).${RESET()}`);
+      }
+    }
+  }
+
+  const diff = await getStagedDiff();
+  if (!diff) {
+    console.log(`  ${DIM()}Nothing to commit. No staged changes to commit.${RESET()}`);
+    return 0;
+  }
+
+  const config = await loadConfig();
+
+  if (!config.apiKey) {
+    console.error(`\n  ${RED()}Error: API key not set. Run ${BOLD()}gai config${RESET()}${RED()} to configure.${RESET()}\n`);
+    return 1;
+  }
+
+  const MAX_DIFF_SIZE = 15000;
+  const truncatedDiff = diff.length > MAX_DIFF_SIZE
+    ? diff.substring(0, MAX_DIFF_SIZE) + "\n... (truncated)"
+    : diff;
+
+  const repoRoot = await getRepoRoot();
+  const projectCtx = await collectProjectContext(repoRoot);
+  const recentCommits = await getRecentCommits(10);
+
+  const userPrompt = buildPrompt({
+    readme: projectCtx.readme,
+    packageDescription: projectCtx.packageDescription,
+    structure: projectCtx.structure,
+    recentCommits,
+    diff: truncatedDiff,
+  });
+
+  if (verbose) {
+    console.log(`  ${DIM()}Model: ${config.model} | API: ${config.apiBase}${RESET()}`);
+  }
+
+  const tty = isStdinTTY();
+  if (tty) {
+    console.log("\n  Generating commit message...");
+  }
+
+  let message: string;
+  try {
+    const callbacks: StreamCallbacks | undefined = tty ? {
+      onToken: (token) => process.stdout.write(token),
+    } : undefined;
+
+    if (callbacks) process.stdout.write("  ");
+
+    message = await generateCommitMessage(config, SYSTEM_PROMPT, userPrompt, callbacks);
+
+    if (callbacks) process.stdout.write("\n");
+  } catch (err) {
+    console.error(`\n  ${RED()}AI request failed: ${err instanceof Error ? err.message : err}${RESET()}\n`);
+    return 1;
+  }
+
+  if (dryRun) {
+    console.log(`\n  ${BOLD()}Generated commit message:${RESET()}`);
+    console.log(`    ${GREEN()}${message}${RESET()}`);
+    await copyToClipboard(message);
+    console.log(`\n  ${DIM()}(dry-run, message copied to clipboard)${RESET()}`);
+    return 0;
+  }
+
+  const action = await confirmCommit(message);
+
+  if (action === "y") {
+    try {
+      const result = await commit(message);
+      printCommitResult(result, message);
+    } catch (err) {
+      console.error(`\n  ${RED()}Commit failed: ${err instanceof Error ? err.message : err}${RESET()}\n`);
+      return 1;
+    }
+  } else if (action === "e") {
+    const edited = await editMessage(message);
+    if (edited) {
+      try {
+        const result = await commit(edited);
+        printCommitResult(result, edited);
+      } catch (err) {
+        console.error(`\n  ${RED()}Commit failed: ${err instanceof Error ? err.message : err}${RESET()}\n`);
+        return 1;
+      }
+    } else {
+      console.log("  Aborted.");
+    }
+  } else {
+    const copied = await copyToClipboard(message);
+    console.log(copied ? `  Aborted. Message copied to clipboard.` : `  Aborted. Message: ${message}`);
+  }
+
+  return 0;
+}
+
+async function handleAmendCommit(args: ParsedArgs): Promise<number> {
+  const config = await loadConfig();
+  if (!config.apiKey) {
+    console.error(`\n  ${RED()}Error: API key not set.${RESET()}\n`);
+    return 1;
+  }
+
+  // Get the diff of the last commit (what would be amended)
+  let diff: string;
+  try {
+    diff = await Bun.$`git diff HEAD~1..HEAD`.quiet().text();
+    diff = diff.trim();
+  } catch {
+    // If there's no previous commit (first commit), get staged diff
+    diff = await getStagedDiff();
+  }
+
+  if (!diff) {
+    // Try getting the commit message from HEAD
+    try {
+      const lastMsg = await Bun.$`git log -1 --format=%B`.quiet().text();
+      if (lastMsg.trim()) {
+        console.log(`  Last commit message: ${DIM()}${lastMsg.trim()}${RESET()}`);
+        const newMsg = await editMessage(lastMsg.trim());
+        if (newMsg) {
+          await Bun.spawn(["git", "commit", "--amend", "-m", newMsg], { stdio: ["inherit", "inherit", "inherit"] });
+        }
+        return 0;
+      }
+    } catch {}
+    console.log(`  ${DIM()}No changes to amend.${RESET()}`);
+    return 0;
+  }
+
+  const repoRoot = await getRepoRoot();
+  const projectCtx = await collectProjectContext(repoRoot);
+  const recentCommits = await getRecentCommits(10);
+
+  const MAX_DIFF_SIZE = 15000;
+  const truncatedDiff = diff.length > MAX_DIFF_SIZE
+    ? diff.substring(0, MAX_DIFF_SIZE) + "\n... (truncated)"
+    : diff;
+
+  const userPrompt = buildPrompt({
+    readme: projectCtx.readme,
+    packageDescription: projectCtx.packageDescription,
+    structure: projectCtx.structure,
+    recentCommits,
+    diff: truncatedDiff,
+  });
+
+  console.log("\n  Generating amended commit message...");
+
+  let message: string;
+  try {
+    message = await generateCommitMessage(config, SYSTEM_PROMPT, userPrompt);
+  } catch (err) {
+    console.error(`\n  ${RED()}AI request failed: ${err instanceof Error ? err.message : err}${RESET()}\n`);
+    return 1;
+  }
+
+  console.log(`\n  ${BOLD()}Generated amended message:${RESET()}`);
+  console.log(`    ${GREEN()}${message}${RESET()}\n`);
+
+  const answer = await ask(`  Amend commit with this message? [${GREEN()}Y${RESET()}/n/e] `);
+  const lower = answer.toLowerCase();
+
+  if (lower === "n") {
+    console.log("  Aborted.");
+    return 0;
+  }
+
+  if (lower === "e") {
+    const edited = await editMessage(message);
+    if (!edited) { console.log("  Aborted."); return 0; }
+    message = edited;
+  }
+
+  try {
+    const proc = Bun.spawn(["git", "commit", "--amend", "-m", message], {
+      stdio: ["inherit", "inherit", "inherit"],
+    });
+    const exitCode = await proc.exited;
+    if (exitCode !== 0) {
+      throw new Error(`git commit --amend failed (exit code ${exitCode})`);
+    }
+  } catch (err) {
+    console.error(`\n  ${RED()}Amend failed: ${err instanceof Error ? err.message : err}${RESET()}\n`);
+    return 1;
+  }
+
+  return 0;
+}

src/commands/config.ts

@@ -0,0 +1,332 @@
+import { loadConfig, saveConfig } from "../config";
+import { BOLD, GREEN, YELLOW, CYAN, RED, DIM, RESET } from "../terminal";
+import { isStdinTTY } from "../tty";
+import type { Config } from "../types";
+import type { ParsedArgs } from "../cli";
+
+type ConfigKey = keyof Config;
+
+interface ConfigField {
+  key: ConfigKey;
+  label: string;
+  format: (config: Config) => string;
+  initialEditValue: (config: Config) => string;
+  parse: (value: string) => { value: Config[ConfigKey] } | { error: string };
+}
+
+const CONFIG_FIELDS: ConfigField[] = [
+  {
+    key: "apiKey",
+    label: "API Key",
+    format: (config) =>
+      config.apiKey ? `****${config.apiKey.slice(-4)}` : `${YELLOW()}(not set)${RESET()}`,
+    initialEditValue: () => "",
+    parse: (value) => ({ value }),
+  },
+  {
+    key: "apiBase",
+    label: "API Base",
+    format: (config) => config.apiBase,
+    initialEditValue: (config) => config.apiBase,
+    parse: (value) => ({ value }),
+  },
+  {
+    key: "model",
+    label: "Model",
+    format: (config) => config.model,
+    initialEditValue: (config) => config.model,
+    parse: (value) => ({ value }),
+  },
+  {
+    key: "maxTokens",
+    label: "Max Tokens",
+    format: (config) => String(config.maxTokens),
+    initialEditValue: (config) => String(config.maxTokens),
+    parse: (value) => {
+      const parsed = Number(value);
+      if (!Number.isInteger(parsed) || parsed <= 0) {
+        return { error: "Max Tokens must be a positive integer." };
+      }
+      return { value: parsed };
+    },
+  },
+  {
+    key: "temperature",
+    label: "Temperature",
+    format: (config) => String(config.temperature),
+    initialEditValue: (config) => String(config.temperature),
+    parse: (value) => {
+      const parsed = Number(value);
+      if (!Number.isFinite(parsed)) {
+        return { error: "Temperature must be a finite number." };
+      }
+      return { value: parsed };
+    },
+  },
+];
+
+function visibleLength(value: string) {
+  return value.replace(/\x1b\[[0-9;]*m/g, "").length;
+}
+
+function clearLine() {
+  process.stdout.write("\r\x1b[2K");
+}
+
+function moveUp(lines: number) {
+  if (lines > 0) process.stdout.write(`\x1b[${lines}A`);
+}
+
+function renderConfigPage(
+  config: Config,
+  cursor: number,
+  previousLines: number,
+  status: string | null,
+  editState: { buffer: string; cursor: number } | null,
+) {
+  if (previousLines > 0) {
+    for (let i = 0; i < previousLines; i++) {
+      clearLine();
+      process.stdout.write("\n");
+    }
+    moveUp(previousLines);
+  }
+
+  const labelWidth = Math.max(...CONFIG_FIELDS.map((field) => field.label.length)) + 2;
+  const lines = [
+    "",
+    `  ${BOLD()}Configuration${RESET()}`,
+    editState
+      ? `  ${DIM()}editing · enter save · esc cancel · ctrl+c cancel${RESET()}`
+      : `  ${DIM()}↑/↓ navigate · space edit · ←/backspace back · ctrl+c cancel${RESET()}`,
+    "",
+  ];
+
+  let activeValueOffset = 0;
+  for (let i = 0; i < CONFIG_FIELDS.length; i++) {
+    const field = CONFIG_FIELDS[i]!;
+    const active = i === cursor;
+    const pointer = active ? `${CYAN()}❯${RESET()}` : " ";
+    const marker = active ? `${GREEN()}●${RESET()}` : `${DIM()}○${RESET()}`;
+    const label = active ? `${BOLD()}${field.label}${RESET()}` : field.label;
+    const padding = " ".repeat(Math.max(1, labelWidth - visibleLength(field.label)));
+    const value = active && editState ? editState.buffer : field.format(config);
+    if (active && editState) {
+      activeValueOffset = visibleLength(`  ${pointer} ${marker} ${label}${padding}`);
+    }
+    lines.push(`  ${pointer} ${marker} ${label}${padding}${value}`);
+  }
+
+  if (status) {
+    lines.push("", `  ${status}`);
+  }
+
+  for (const line of lines) {
+    process.stdout.write(`${line}\n`);
+  }
+  if (editState) {
+    moveUp(lines.length - (4 + cursor));
+    const column = activeValueOffset + editState.cursor;
+    process.stdout.write(`\r${column > 0 ? `\x1b[${column}C` : ""}`);
+  } else {
+    moveUp(lines.length);
+  }
+  return lines.length;
+}
+
+async function interactiveConfig(): Promise<"done" | "back"> {
+  if (!isStdinTTY()) {
+    console.error(`\n  ${RED()}Error: Interactive config requires a TTY.${RESET()}\n`);
+    process.exit(1);
+  }
+
+  let config = await loadConfig();
+  let cursor = 0;
+  let renderedLines = 0;
+  let status: string | null = null;
+  let editState: { buffer: string; cursor: number } | null = null;
+  let renderedCursorRow = 0;
+  const wasRaw = process.stdin.isRaw;
+
+  if (wasRaw !== true) process.stdin.setRawMode(true);
+  process.stdin.resume();
+  process.stdout.write("\x1b[?25l");
+
+  const render = () => {
+    moveUp(renderedCursorRow);
+    renderedLines = renderConfigPage(config, cursor, renderedLines, status, editState);
+    renderedCursorRow = editState ? 4 + cursor : 0;
+    process.stdout.write(editState ? "\x1b[?25h" : "\x1b[?25l");
+  };
+
+  render();
+
+  return new Promise((resolve) => {
+    const finish = (value: "done" | "back") => {
+      process.stdin.setRawMode(wasRaw === true);
+      process.stdin.pause();
+      process.stdin.removeListener("data", onData);
+      moveUp(renderedCursorRow);
+      for (let i = 0; i < renderedLines; i++) {
+        clearLine();
+        process.stdout.write("\n");
+      }
+      moveUp(renderedLines);
+      process.stdout.write("\x1b[?25h");
+      resolve(value);
+    };
+
+    const saveEdit = async () => {
+      if (!editState) return;
+      const field = CONFIG_FIELDS[cursor]!;
+      const value = editState.buffer.trim();
+      editState = null;
+
+      if (value === "") {
+        status = `${DIM()}No changes.${RESET()}`;
+      } else {
+        const parsed = field.parse(value);
+        if ("error" in parsed) {
+          status = `${RED()}${parsed.error}${RESET()}`;
+        } else {
+          await saveConfig({ [field.key]: parsed.value } as Partial<Config>);
+          config = await loadConfig();
+          status = `${GREEN()}${field.label} saved.${RESET()}`;
+        }
+      }
+      render();
+    };
+
+    const onData = (data: Buffer) => {
+      const key = data.toString();
+
+      if (editState) {
+        if (key === "\x03" || key === "\x1b") {
+          editState = null;
+          status = `${DIM()}No changes.${RESET()}`;
+          render();
+          return;
+        }
+        if (key === "\r") { void saveEdit(); return; }
+        if (key === "\x01") { editState.cursor = 0; render(); return; }
+        if (key === "\x05") { editState.cursor = editState.buffer.length; render(); return; }
+        if (key === "\x0b") { editState.buffer = editState.buffer.slice(0, editState.cursor); render(); return; }
+        if (key === "\x15") { editState.buffer = editState.buffer.slice(editState.cursor); editState.cursor = 0; render(); return; }
+        if (key === "\x7f") {
+          if (editState.cursor > 0) {
+            editState.buffer = editState.buffer.slice(0, editState.cursor - 1) + editState.buffer.slice(editState.cursor);
+            editState.cursor--;
+            render();
+          }
+          return;
+        }
+        if (key === "\x1b[D" || key === "\x1bOD") { if (editState.cursor > 0) editState.cursor--; render(); return; }
+        if (key === "\x1b[C" || key === "\x1bOC") { if (editState.cursor < editState.buffer.length) editState.cursor++; render(); return; }
+        if (key === "\x1b[H" || key === "\x1b[1~") { editState.cursor = 0; render(); return; }
+        if (key === "\x1b[F" || key === "\x1b[4~") { editState.cursor = editState.buffer.length; render(); return; }
+        if (key === "\x1b[3~" && editState.cursor < editState.buffer.length) {
+          editState.buffer = editState.buffer.slice(0, editState.cursor) + editState.buffer.slice(editState.cursor + 1);
+          render();
+          return;
+        }
+        if (key >= " " && key !== "\x7f") {
+          editState.buffer = editState.buffer.slice(0, editState.cursor) + key + editState.buffer.slice(editState.cursor);
+          editState.cursor += key.length;
+          render();
+        }
+        return;
+      }
+
+      // Not editing
+      if (key === "\x03") return finish("done");
+      if (key === "\x1b[A" || key === "\x1bOA") {
+        if (cursor > 0) { cursor--; status = null; render(); }
+      } else if (key === "\x1b[B" || key === "\x1bOB") {
+        if (cursor < CONFIG_FIELDS.length - 1) { cursor++; status = null; render(); }
+      } else if (key === "\x1b[D" || key === "\x1bOD" || key === "\x7f") {
+        return finish("back");
+      } else if (key === " ") {
+        const value = CONFIG_FIELDS[cursor]!.initialEditValue(config);
+        editState = { buffer: value, cursor: value.length };
+        status = null;
+        render();
+      }
+    };
+
+    process.stdin.on("data", onData);
+  });
+}
+
+export async function handleConfig(args: ParsedArgs): Promise<number> {
+  const positional = args.positional;
+
+  // gai config get <key>
+  if (positional[0] === "get") {
+    const key = positional[1];
+    if (!key) {
+      console.error(`\n  ${RED()}Error: Usage: gai config get <key>${RESET()}\n`);
+      return 1;
+    }
+    const config = await loadConfig();
+    const field = CONFIG_FIELDS.find((f) => f.key === key);
+    if (!field) {
+      console.error(`\n  ${RED()}Error: Unknown config key: ${key}${RESET()}`);
+      console.error(`  Valid keys: ${CONFIG_FIELDS.map((f) => f.key).join(", ")}\n`);
+      return 1;
+    }
+    // For apiKey, show masked value
+    if (key === "apiKey") {
+      console.log(config.apiKey || "");
+    } else {
+      console.log(String(config[key as keyof Config]));
+    }
+    return 0;
+  }
+
+  // gai config set <key> <value>
+  if (positional[0] === "set") {
+    const key = positional[1];
+    const value = positional.slice(2).join(" ");
+    if (!key || value === undefined) {
+      console.error(`\n  ${RED()}Error: Usage: gai config set <key> <value>${RESET()}\n`);
+      return 1;
+    }
+    const field = CONFIG_FIELDS.find((f) => f.key === key);
+    if (!field) {
+      console.error(`\n  ${RED()}Error: Unknown config key: ${key}${RESET()}`);
+      console.error(`  Valid keys: ${CONFIG_FIELDS.map((f) => f.key).join(", ")}\n`);
+      return 1;
+    }
+    const parsed = field.parse(value);
+    if ("error" in parsed) {
+      console.error(`\n  ${RED()}Error: ${parsed.error}${RESET()}\n`);
+      return 1;
+    }
+    await saveConfig({ [field.key]: parsed.value } as Partial<Config>);
+    console.log(`  ${GREEN()}${field.label} set.${RESET()}`);
+    return 0;
+  }
+
+  // gai config list
+  if (positional[0] === "list" || positional[0] === "ls") {
+    const config = await loadConfig();
+    const labelWidth = Math.max(...CONFIG_FIELDS.map((f) => f.label.length)) + 2;
+    console.log("");
+    for (const field of CONFIG_FIELDS) {
+      const padding = " ".repeat(Math.max(1, labelWidth - field.label.length));
+      console.log(`  ${BOLD()}${field.label}${RESET()}${padding}${field.format(config)}`);
+    }
+    console.log("");
+    return 0;
+  }
+
+  // gai config (no args) → interactive
+  if (positional.length === 0) {
+    const result = await interactiveConfig();
+    return result === "back" ? 0 : 0;
+  }
+
+  console.error(`\n  ${RED()}Error: Unknown config subcommand: ${positional[0]}${RESET()}`);
+  console.error(`  Try: gai config [get|set|list]\n`);
+  return 1;
+}

src/commands/explain.ts

@@ -0,0 +1,129 @@
+import { loadConfig } from "../config";
+import { isGitRepo, getStagedDiff, getUnstagedFiles, getRepoRoot, stageFiles } from "../git";
+import { selectFiles } from "../selector";
+import { BACK } from "../menu";
+import { collectProjectContext } from "../context";
+import { EXPLAIN_SYSTEM_PROMPT, buildExplainPrompt } from "../prompt";
+import { callAI } from "../ai";
+import { BOLD, GREEN, RED, DIM, RESET, CYAN } from "../terminal";
+import { isStdinTTY } from "../tty";
+import type { StreamCallbacks } from "../types";
+import type { ParsedArgs } from "../cli";
+
+export async function handleExplain(args: ParsedArgs): Promise<number> {
+  const config = await loadConfig();
+
+  if (!config.apiKey) {
+    console.error(`\n  ${RED()}Error: API key not set. Run ${BOLD()}gai config${RESET()}${RED()} to configure.${RESET()}\n`);
+    return 1;
+  }
+
+  const unstaged = args.flags["unstaged"] as boolean;
+  const staged = args.flags["staged"] as boolean;
+  const verbose = args.flags["verbose"] as boolean;
+
+  // Determine which diff to explain
+  let diff: string;
+  let sourceLabel: string;
+
+  if (unstaged) {
+    if (!(await isGitRepo())) {
+      console.error(`\n  ${RED()}Error: Not a git repository.${RESET()}\n`);
+      return 1;
+    }
+    try {
+      diff = (await Bun.$`git diff`.quiet().text()).trim();
+    } catch {
+      diff = "";
+    }
+    sourceLabel = "unstaged changes";
+  } else {
+    // Default: staged changes (or piped)
+    if (isStdinTTY()) {
+      if (!(await isGitRepo())) {
+        console.error(`\n  ${RED()}Error: Not a git repository.${RESET()}\n`);
+        return 1;
+      }
+      diff = await getStagedDiff();
+      sourceLabel = "staged changes";
+
+      // If no staged changes, offer to stage unstaged files
+      if (!diff) {
+        const unstagedFiles = await getUnstagedFiles();
+        if (unstagedFiles.length > 0) {
+          const selected = await selectFiles([], unstagedFiles);
+          if (selected === BACK) return 0;
+          if (selected.length > 0) {
+            await stageFiles(selected);
+            console.log(`  ${GREEN()}Staged ${selected.length} file(s).${RESET()}`);
+            diff = await getStagedDiff();
+          }
+        }
+      }
+    } else {
+      // Read from pipe
+      const chunks: Buffer[] = [];
+      for await (const chunk of process.stdin) {
+        chunks.push(typeof chunk === "string" ? Buffer.from(chunk) : chunk);
+      }
+      diff = Buffer.concat(chunks).toString("utf-8").trim();
+      sourceLabel = "piped input";
+    }
+  }
+
+  if (!diff) {
+    console.log(`  ${DIM()}No ${sourceLabel} to explain.${RESET()}`);
+    return 0;
+  }
+
+  if (args.flags["verbose"]) {
+    console.log(`  ${DIM()}Explaining ${sourceLabel} (${diff.length} bytes)${RESET()}`);
+  }
+
+  const MAX_DIFF_SIZE = 15000;
+  const truncatedDiff = diff.length > MAX_DIFF_SIZE
+    ? diff.substring(0, MAX_DIFF_SIZE) + "\n... (truncated)"
+    : diff;
+
+  // Collect project context for better explanations
+  let contextPrefix = "";
+  try {
+    if (await isGitRepo()) {
+      const repoRoot = await getRepoRoot();
+      const ctx = await collectProjectContext(repoRoot);
+      if (ctx.packageDescription) {
+        contextPrefix = `Project: ${ctx.packageDescription}\n\n`;
+      }
+    }
+  } catch {}
+
+  const userPrompt = contextPrefix + buildExplainPrompt(truncatedDiff);
+
+  if (verbose) {
+    console.log(`  ${DIM()}Model: ${config.model} | API: ${config.apiBase}${RESET()}`);
+  }
+
+  const tty = isStdinTTY();
+  if (tty) {
+    console.log(`\n  ${BOLD()}${CYAN()}Analyzing ${sourceLabel}...${RESET()}\n`);
+  }
+
+  try {
+    const callbacks: StreamCallbacks = tty ? {
+      onToken: (token) => process.stdout.write(token),
+    } : undefined;
+
+    const explanation = await callAI(config, EXPLAIN_SYSTEM_PROMPT, userPrompt, callbacks);
+    if (callbacks) {
+      process.stdout.write("\n");
+    } else {
+      // Non-TTY: print the result directly
+      process.stdout.write(explanation + "\n");
+    }
+  } catch (err) {
+    console.error(`\n  ${RED()}AI request failed: ${err instanceof Error ? err.message : err}${RESET()}\n`);
+    return 1;
+  }
+
+  return 0;
+}

src/commands/pr.ts

@@ -0,0 +1,209 @@
+import * as readline from "node:readline";
+import { loadConfig } from "../config";
+import { isGitRepo, getRepoRoot } from "../git";
+import { collectProjectContext } from "../context";
+import { PR_SYSTEM_PROMPT, buildPRPrompt } from "../prompt";
+import { generatePRMessage } from "../ai";
+import { BACK, selectOne } from "../menu";
+import {
+  getDefaultBranch,
+  getBranchName,
+  getBranchPushStatus,
+  pushCurrentBranch,
+  getBranchCommits,
+  getBranchDiff,
+  detectPlatform,
+  getRemoteHostname,
+  createPR,
+} from "../pr";
+import type { Platform } from "../pr";
+import { BOLD, GREEN, YELLOW, CYAN, RED, DIM, RESET } from "../terminal";
+import { isStdinTTY } from "../tty";
+import { copyToClipboard } from "../clipboard";
+import type { ParsedArgs } from "../cli";
+
+function ask(question: string): Promise<string> {
+  const rl = readline.createInterface({ input: process.stdin, output: process.stdout });
+  return new Promise((resolve) => {
+    rl.question(question, (answer) => {
+      rl.close();
+      resolve(answer.trim());
+    });
+  });
+}
+
+async function selectPlatform(hostname: string): Promise<Platform | null | typeof BACK> {
+  if (!isStdinTTY()) {
+    console.error(`\n  ${RED()}Error: Platform selection requires a TTY.${RESET()}\n`);
+    process.exit(1);
+  }
+  return selectOne({
+    title: "Select remote platform",
+    subtitle: `Remote ${hostname} could not be auto-detected`,
+    items: [
+      { label: "GitHub", value: "github" as Platform, description: "Use gh CLI" },
+      { label: "Gitea", value: "gitea" as Platform, description: "Use tea CLI" },
+      { label: "GitLab", value: "gitlab" as Platform, description: "Use glab CLI" },
+    ],
+  });
+}
+
+export async function handlePR(args: ParsedArgs): Promise<number> {
+  const config = await loadConfig();
+
+  if (!config.apiKey) {
+    console.error(`\n  ${RED()}Error: API key not set. Run ${BOLD()}gai config${RESET()}${RED()} to configure.${RESET()}\n`);
+    return 1;
+  }
+
+  if (!(await isGitRepo())) {
+    console.error(`\n  ${RED()}Error: Not a git repository.${RESET()}\n`);
+    return 1;
+  }
+
+  const draft = args.flags["draft"] as boolean;
+  const verbose = args.flags["verbose"] as boolean;
+
+  let platform = await detectPlatform();
+  if (!platform) {
+    const hostname = (await getRemoteHostname()) || "unknown";
+    const chosen = await selectPlatform(hostname);
+    if (chosen === BACK) return 0;
+    if (!chosen) {
+      console.log("  Aborted.");
+      return 0;
+    }
+    platform = chosen;
+  }
+
+  const platformLabel = platform === "github" ? "GitHub" : platform === "gitlab" ? "GitLab" : "Gitea";
+  console.log(`  Using: ${CYAN()}${platformLabel}${RESET()}`);
+
+  const baseBranch = await getDefaultBranch();
+  const branchName = await getBranchName();
+
+  if (branchName === baseBranch) {
+    console.error(`\n  ${RED()}Error: You are on the default branch (${baseBranch}). Switch to a feature branch first.${RESET()}\n`);
+    return 1;
+  }
+
+  console.log(`  Branch: ${CYAN()}${branchName}${RESET()} → base: ${CYAN()}${baseBranch}${RESET()}`);
+
+  const commits = await getBranchCommits(baseBranch);
+
+  if (commits.length === 0) {
+    const choice = await selectOne({
+      title: "No commits to compare",
+      subtitle: `No commits on ${branchName} compared to ${baseBranch}. Commit something first.`,
+      items: [{ label: "Back", value: "back" as const }],
+    });
+    if (choice === null) process.exit(0);
+    return 0;
+  }
+
+  console.log(`  ${commits.length} commit${commits.length > 1 ? "s" : ""} on this branch`);
+
+  if (verbose) {
+    console.log(`  ${DIM()}Model: ${config.model} | API: ${config.apiBase}${RESET()}`);
+  }
+
+  const pushStatus = await getBranchPushStatus();
+  if (!pushStatus.pushed) {
+    const target = pushStatus.upstream ?? `origin/${branchName}`;
+    const answer = await ask(
+      `  Branch is not pushed to ${CYAN()}${target}${RESET()}. Push now? [${GREEN()}Y${RESET()}/n] `,
+    );
+
+    if (answer.toLowerCase() === "n") {
+      console.log("  Aborted.");
+      return 0;
+    }
+
+    console.log(`  Pushing ${CYAN()}${branchName}${RESET()}...`);
+    try {
+      await pushCurrentBranch(branchName, pushStatus.upstream);
+      console.log(`  ${GREEN()}Pushed ${branchName}.${RESET()}`);
+    } catch (err) {
+      console.error(`\n  ${RED()}Push failed: ${err instanceof Error ? err.message : err}${RESET()}\n`);
+      return 1;
+    }
+  }
+
+  const diff = await getBranchDiff(baseBranch);
+  if (!diff) {
+    console.error(`\n  ${RED()}Error: No diff from base branch.${RESET()}\n`);
+    return 1;
+  }
+
+  const MAX_DIFF_SIZE = 15000;
+  const truncatedDiff = diff.length > MAX_DIFF_SIZE
+    ? diff.substring(0, MAX_DIFF_SIZE) + "\n... (truncated)"
+    : diff;
+
+  const repoRoot = await getRepoRoot();
+  const projectCtx = await collectProjectContext(repoRoot);
+
+  const userPrompt = buildPRPrompt({
+    readme: projectCtx.readme,
+    packageDescription: projectCtx.packageDescription,
+    structure: projectCtx.structure,
+    branchName,
+    baseBranch,
+    branchCommits: commits,
+    diff: truncatedDiff,
+  });
+
+  console.log("\n  Generating PR title and description...");
+
+  let title: string;
+  let body: string;
+  try {
+    const result = await generatePRMessage(config, PR_SYSTEM_PROMPT, userPrompt);
+    title = result.title;
+    body = result.body;
+  } catch (err) {
+    console.error(`\n  ${RED()}AI request failed: ${err instanceof Error ? err.message : err}${RESET()}\n`);
+    return 1;
+  }
+
+  console.log(`\n  ${BOLD()}Generated PR:${RESET()}`);
+  console.log(`    Title: ${GREEN()}${title}${RESET()}`);
+  if (body) {
+    console.log(`    Body:  ${DIM()}${body.replace(/\n/g, "\n           ")}${RESET()}`);
+  }
+  console.log("");
+
+  const answer = await ask(`  Create this PR? [${GREEN()}Y${RESET()}/n/e] `);
+  const lower = answer.toLowerCase();
+
+  if (lower === "n") {
+    console.log("  Aborted.");
+    await copyToClipboard(`${title}\n\n${body}`);
+    console.log(`  ${DIM()}PR title copied to clipboard.${RESET()}`);
+    return 0;
+  }
+
+  if (lower === "e") {
+    const newTitle = await ask("  Title: ");
+    const newBody = await ask("  Body (optional): ");
+    if (!newTitle.trim()) {
+      console.log("  Aborted.");
+      return 0;
+    }
+    title = newTitle;
+    body = newBody;
+  }
+
+  console.log(`\n  Creating PR...`);
+
+  try {
+    const url = await createPR(platform, title, body, baseBranch, draft);
+    console.log(`\n  ${GREEN()}${BOLD()}✔ PR created!${RESET()}`);
+    console.log(`    ${CYAN()}${url}${RESET()}`);
+  } catch (err) {
+    console.error(`\n  ${RED()}PR creation failed: ${err instanceof Error ? err.message : err}${RESET()}\n`);
+    return 1;
+  }
+
+  return 0;
+}

src/commands/review.ts

@@ -0,0 +1,129 @@
+import { loadConfig } from "../config";
+import { isGitRepo, getStagedDiff, getUnstagedFiles, getRepoRoot, stageFiles } from "../git";
+import { selectFiles } from "../selector";
+import { BACK } from "../menu";
+import { collectProjectContext } from "../context";
+import { REVIEW_SYSTEM_PROMPT, buildReviewPrompt } from "../prompt";
+import { callAI } from "../ai";
+import { BOLD, GREEN, YELLOW, RED, DIM, RESET, CYAN } from "../terminal";
+import { isStdinTTY } from "../tty";
+import type { StreamCallbacks } from "../types";
+import type { ParsedArgs } from "../cli";
+
+export async function handleReview(args: ParsedArgs): Promise<number> {
+  const config = await loadConfig();
+
+  if (!config.apiKey) {
+    console.error(`\n  ${RED()}Error: API key not set. Run ${BOLD()}gai config${RESET()}${RED()} to configure.${RESET()}\n`);
+    return 1;
+  }
+
+  const strictnessFlag = args.flags["strict"] as boolean
+    ? "strict"
+    : args.flags["lenient"] as boolean
+      ? "lenient"
+      : "normal";
+
+  const unstaged = args.flags["unstaged"] as boolean;
+  const verbose = args.flags["verbose"] as boolean;
+
+  let diff: string;
+  let sourceLabel: string;
+
+  if (unstaged) {
+    if (!(await isGitRepo())) {
+      console.error(`\n  ${RED()}Error: Not a git repository.${RESET()}\n`);
+      return 1;
+    }
+    try {
+      diff = (await Bun.$`git diff`.quiet().text()).trim();
+    } catch {
+      diff = "";
+    }
+    sourceLabel = "unstaged changes";
+  } else if (!isStdinTTY()) {
+    const chunks: Buffer[] = [];
+    for await (const chunk of process.stdin) {
+      chunks.push(typeof chunk === "string" ? Buffer.from(chunk) : chunk);
+    }
+    diff = Buffer.concat(chunks).toString("utf-8").trim();
+    sourceLabel = "piped input";
+  } else {
+    if (!(await isGitRepo())) {
+      console.error(`\n  ${RED()}Error: Not a git repository.${RESET()}\n`);
+      return 1;
+    }
+    diff = await getStagedDiff();
+    sourceLabel = "staged changes";
+
+    // If no staged changes, offer to stage unstaged files
+    if (!diff) {
+      const unstagedFiles = await getUnstagedFiles();
+      if (unstagedFiles.length > 0) {
+        const selected = await selectFiles([], unstagedFiles);
+        if (selected === BACK) return 0;
+        if (selected.length > 0) {
+          await stageFiles(selected);
+          console.log(`  ${GREEN()}Staged ${selected.length} file(s).${RESET()}`);
+          diff = await getStagedDiff();
+        }
+      }
+    }
+  }
+
+  if (!diff) {
+    console.log(`  ${DIM()}No ${sourceLabel} to review.${RESET()}`);
+    return 0;
+  }
+
+  const MAX_DIFF_SIZE = 15000;
+  const truncatedDiff = diff.length > MAX_DIFF_SIZE
+    ? diff.substring(0, MAX_DIFF_SIZE) + "\n... (truncated)"
+    : diff;
+
+  let contextPrefix = "";
+  try {
+    if (await isGitRepo()) {
+      const repoRoot = await getRepoRoot();
+      const ctx = await collectProjectContext(repoRoot);
+      if (ctx.packageDescription) {
+        contextPrefix = `Project: ${ctx.packageDescription}\n\n`;
+      }
+    }
+  } catch {}
+
+  const userPrompt = contextPrefix + buildReviewPrompt(truncatedDiff, strictnessFlag);
+
+  const strictnessLabel = strictnessFlag === "strict"
+    ? `${RED()}strict${RESET()}`
+    : strictnessFlag === "lenient"
+      ? `${GREEN()}lenient${RESET()}`
+      : `${YELLOW()}normal${RESET()}`;
+
+  if (verbose) {
+    console.log(`  ${DIM()}Model: ${config.model} | API: ${config.apiBase} | Strictness: ${strictnessFlag}${RESET()}`);
+  }
+
+  const tty = isStdinTTY();
+  if (tty) {
+    console.log(`\n  ${BOLD()}${CYAN()}Reviewing ${sourceLabel} (${strictnessLabel})...${RESET()}\n`);
+  }
+
+  try {
+    const callbacks: StreamCallbacks = tty ? {
+      onToken: (token) => process.stdout.write(token),
+    } : undefined;
+
+    const result = await callAI(config, REVIEW_SYSTEM_PROMPT, userPrompt, callbacks);
+    if (callbacks) {
+      process.stdout.write("\n");
+    } else {
+      process.stdout.write(result + "\n");
+    }
+  } catch (err) {
+    console.error(`\n  ${RED()}AI request failed: ${err instanceof Error ? err.message : err}${RESET()}\n`);
+    return 1;
+  }
+
+  return 0;
+}

src/commands/suggest.ts

@@ -0,0 +1,146 @@
+import { loadConfig } from "../config";
+import { isGitRepo, getStagedDiff, getUnstagedFiles, stageFiles } from "../git";
+import { selectFiles } from "../selector";
+import { BACK } from "../menu";
+import {
+  SUGGEST_SYSTEM_PROMPT,
+  buildSuggestBranchPrompt,
+  buildSuggestTypePrompt,
+} from "../prompt";
+import { callAI } from "../ai";
+import { BOLD, GREEN, YELLOW, RED, DIM, RESET, CYAN } from "../terminal";
+import { isStdinTTY } from "../tty";
+import type { Config } from "../types";
+import type { ParsedArgs } from "../cli";
+
+export async function handleSuggest(args: ParsedArgs): Promise<number> {
+  const config = await loadConfig();
+
+  if (!config.apiKey) {
+    console.error(`\n  ${RED()}Error: API key not set. Run ${BOLD()}gai config${RESET()}${RED()} to configure.${RESET()}\n`);
+    return 1;
+  }
+
+  const mode = args.positional[0] || "branch";
+  const verbose = args.flags["verbose"] as boolean;
+
+  if (mode !== "branch" && mode !== "type") {
+    console.error(`\n  ${RED()}Error: Unknown suggest mode: ${mode}${RESET()}`);
+    console.error(`  Try: gai suggest branch | gai suggest type\n`);
+    return 1;
+  }
+
+  // Get diff (staged, or unstaged if --unstaged, or piped)
+  let diff: string;
+  if (!isStdinTTY()) {
+    const chunks: Buffer[] = [];
+    for await (const chunk of process.stdin) {
+      chunks.push(typeof chunk === "string" ? Buffer.from(chunk) : chunk);
+    }
+    diff = Buffer.concat(chunks).toString("utf-8").trim();
+  } else {
+    if (!(await isGitRepo())) {
+      console.error(`\n  ${RED()}Error: Not a git repository.${RESET()}\n`);
+      return 1;
+    }
+
+    if (args.flags["unstaged"] as boolean) {
+      try {
+        diff = (await Bun.$`git diff`.quiet().text()).trim();
+      } catch {
+        diff = "";
+      }
+    } else {
+      diff = await getStagedDiff();
+
+      // If no staged changes, offer to stage unstaged files
+      if (!diff) {
+        const unstagedFiles = await getUnstagedFiles();
+        if (unstagedFiles.length > 0) {
+          const selected = await selectFiles([], unstagedFiles);
+          if (selected === BACK) return 0;
+          if (selected.length > 0) {
+            await stageFiles(selected);
+            console.log(`  ${GREEN()}Staged ${selected.length} file(s).${RESET()}`);
+            diff = await getStagedDiff();
+          }
+        }
+      }
+    }
+  }
+
+  if (!diff) {
+    console.log(`  ${DIM()}No changes to suggest from.${RESET()}`);
+    return 0;
+  }
+
+  const MAX_DIFF_SIZE = 15000;
+  const truncatedDiff = diff.length > MAX_DIFF_SIZE
+    ? diff.substring(0, MAX_DIFF_SIZE) + "\n... (truncated)"
+    : diff;
+
+  if (verbose) {
+    console.log(`  ${DIM()}Model: ${config.model} | API: ${config.apiBase}${RESET()}`);
+  }
+
+  if (mode === "branch") {
+    return handleSuggestBranch(config, truncatedDiff);
+  } else {
+    return handleSuggestType(config, truncatedDiff);
+  }
+}
+
+async function handleSuggestBranch(config: Config, diff: string): Promise<number> {
+  const tty = isStdinTTY();
+  if (tty) {
+    console.log(`\n  ${BOLD()}${CYAN()}Suggesting branch names...${RESET()}\n`);
+  }
+
+  try {
+    const raw = await callAI(config, SUGGEST_SYSTEM_PROMPT, buildSuggestBranchPrompt(diff));
+    const suggestions = raw
+      .split("\n")
+      .map((line) => line.replace(/^[\d.\s\-*]+/, "").trim())
+      .filter(Boolean);
+
+    if (suggestions.length === 0) {
+      console.log(`  ${DIM()}No suggestions generated.${RESET()}`);
+      return 0;
+    }
+
+    for (const s of suggestions) {
+      console.log(`    ${GREEN()}${s}${RESET()}`);
+    }
+    console.log("");
+  } catch (err) {
+    console.error(`\n  ${RED()}AI request failed: ${err instanceof Error ? err.message : err}${RESET()}\n`);
+    return 1;
+  }
+
+  return 0;
+}
+
+async function handleSuggestType(config: Config, diff: string): Promise<number> {
+  const tty = isStdinTTY();
+  if (tty) {
+    console.log(`\n  ${BOLD()}${CYAN()}Suggesting commit type...${RESET()}\n`);
+  }
+
+  try {
+    const raw = await callAI(config, SUGGEST_SYSTEM_PROMPT, buildSuggestTypePrompt(diff));
+    const type = raw.trim().toLowerCase();
+    const validTypes = ["feat", "fix", "docs", "style", "refactor", "perf", "test", "build", "ci", "chore", "revert"];
+
+    if (validTypes.includes(type)) {
+      console.log(`    Suggested type: ${GREEN()}${BOLD()}${type}${RESET()}\n`);
+    } else {
+      console.log(`    Suggested type: ${YELLOW()}${raw.trim()}${RESET()}`);
+      console.log(`    ${DIM()}(Not a standard Conventional Commit type)${RESET()}\n`);
+    }
+  } catch (err) {
+    console.error(`\n  ${RED()}AI request failed: ${err instanceof Error ? err.message : err}${RESET()}\n`);
+    return 1;
+  }
+
+  return 0;
+}

src/menu.ts

@@ -1,4 +1,5 @@
 import { BOLD, GREEN, CYAN, DIM, RESET } from "./terminal";
+import { isStdinTTY } from "./tty";
 
 const UP = "\x1b[A";
 const DOWN = "\x1b[B";
@@ -38,13 +39,8 @@ interface MultiPromptOptions<T> extends BasePromptOptions {
   doneLabel?: string;
 }
 
-function hideCursor() {
-  process.stdout.write("\x1b[?25l");
-}
-
-function showCursor() {
-  process.stdout.write("\x1b[?25h");
-}
+function hideCursor() { process.stdout.write("\x1b[?25l"); }
+function showCursor() { process.stdout.write("\x1b[?25h"); }
 
 function moveUp(lines: number) {
   if (lines > 0) process.stdout.write(`\x1b[${lines}A`);
@@ -65,10 +61,10 @@ function padLabel(label: string, width: number) {
 function controls(mode: "single" | "multi", showBackHint = true) {
   if (mode === "single") {
     const backHint = showBackHint ? " · ←/backspace back" : "";
-    return `${DIM}↑/↓ navigate · enter/space select${backHint} · ctrl+c cancel${RESET}`;
+    return `${DIM()}↑/↓ navigate · enter/space select${backHint} · ctrl+c cancel${RESET()}`;
   }
   const backHint = showBackHint ? " · ←/backspace back" : "";
-  return `${DIM}↑/↓ navigate · space toggle · enter confirm${backHint} · ctrl+c cancel${RESET}`;
+  return `${DIM()}↑/↓ navigate · space toggle · enter confirm${backHint} · ctrl+c cancel${RESET()}`;
 }
 
 function renderPrompt(lines: string[], previousLines: number) {
@@ -79,10 +75,7 @@ function renderPrompt(lines: string[], previousLines: number) {
     }
     moveUp(previousLines);
   }
-
-  for (const line of lines) {
-    process.stdout.write(`${line}\n`);
-  }
+  for (const line of lines) process.stdout.write(`${line}\n`);
   moveUp(lines.length);
   return lines.length;
 }
@@ -98,28 +91,19 @@ function clearPrompt(lines: number) {
 function normalizeKey(key: string, escapeBuf: string) {
   if (key === UP || key === ALT_UP) return { action: "up", escapeBuf: "" };
   if (key === DOWN || key === ALT_DOWN) return { action: "down", escapeBuf: "" };
-  if (key === LEFT || key === ALT_LEFT || key === BACKSPACE) {
-    return { action: "back", escapeBuf: "" };
-  }
+  if (key === LEFT || key === ALT_LEFT || key === BACKSPACE) return { action: "back", escapeBuf: "" };
   if (key === SPACE) return { action: "space", escapeBuf: "" };
   if (key === ENTER) return { action: "enter", escapeBuf: "" };
   if (key === CTRL_C) return { action: "cancel", escapeBuf: "" };
 
-  if (key === "\x1b" || key.startsWith("\x1b[")) {
-    return { action: null, escapeBuf: key };
-  }
+  if (key === "\x1b" || key.startsWith("\x1b[")) return { action: null, escapeBuf: key };
 
   if (escapeBuf) {
     const next = escapeBuf + key;
     if (next === UP || next === ALT_UP) return { action: "up", escapeBuf: "" };
     if (next === DOWN || next === ALT_DOWN) return { action: "down", escapeBuf: "" };
-    if (next === LEFT || next === ALT_LEFT) {
-      return { action: "back", escapeBuf: "" };
-    }
-    return {
-      action: null,
-      escapeBuf: /^[A-Za-z~]$/.test(key) || next.length > 8 ? "" : next,
-    };
+    if (next === LEFT || next === ALT_LEFT) return { action: "back", escapeBuf: "" };
+    return { action: null, escapeBuf: /^[A-Za-z~]$/.test(key) || next.length > 8 ? "" : next };
   }
 
   return { action: null, escapeBuf: "" };
@@ -130,41 +114,35 @@ function createLines<T>(
   mode: "single" | "multi",
   cursor: number,
 ) {
-  const labelWidth = Math.max(
-    ...options.items.map((item) => visibleLength(item.label)),
-    0,
-  ) + 2;
-
+  const labelWidth = Math.max(...options.items.map((item) => visibleLength(item.label)), 0) + 2;
   const lines = [
     "",
-    `  ${BOLD}${options.title}${RESET}`,
+    `  ${BOLD()}${options.title}${RESET()}`,
   ];
 
-  if (options.subtitle) lines.push(`  ${DIM}${options.subtitle}${RESET}`);
+  if (options.subtitle) lines.push(`  ${DIM()}${options.subtitle}${RESET()}`);
   lines.push(`  ${controls(mode, options.allowBack !== false)}`, "");
 
   for (let i = 0; i < options.items.length; i++) {
     const item = options.items[i]!;
     const active = i === cursor;
-    const pointer = active ? `${CYAN}❯${RESET}` : " ";
+    const pointer = active ? `${CYAN()}❯${RESET()}` : " ";
     const marker = mode === "single"
-      ? active ? `${GREEN}●${RESET}` : `${DIM}○${RESET}`
-      : item.selected ? `${GREEN}◼${RESET}` : `${DIM}□${RESET}`;
-    const label = active ? `${BOLD}${item.label}${RESET}` : item.label;
+      ? active ? `${GREEN()}●${RESET()}` : `${DIM()}○${RESET()}`
+      : item.selected ? `${GREEN()}◼${RESET()}` : `${DIM()}□${RESET()}`;
+    const label = active ? `${BOLD()}${item.label}${RESET()}` : item.label;
     const description = item.description
-      ? active ? item.description : `${DIM}${item.description}${RESET}`
+      ? active ? item.description : `${DIM()}${item.description}${RESET()}`
       : "";
 
-    lines.push(
-      `  ${pointer} ${marker} ${padLabel(label, labelWidth)}${description}`,
-    );
+    lines.push(`  ${pointer} ${marker} ${padLabel(label, labelWidth)}${description}`);
   }
 
   return lines;
 }
 
 function ensureTTY(title: string) {
-  if (process.stdin.isTTY !== true) {
+  if (!isStdinTTY()) {
     throw new Error(`${title} requires a TTY.`);
   }
 }
@@ -184,12 +162,8 @@ export async function selectOne<T>(
   hideCursor();
 
   const render = () => {
-    renderedLines = renderPrompt(
-      createLines(options, "single", cursor),
-      renderedLines,
-    );
+    renderedLines = renderPrompt(createLines(options, "single", cursor), renderedLines);
   };
-
   render();
 
   return new Promise((resolve) => {
@@ -210,16 +184,10 @@ export async function selectOne<T>(
       escapeBuf = result.escapeBuf;
 
       if (result.action === "cancel") return finish(null);
-      if (result.action === "back" && options.allowBack !== false) {
-        return finish(BACK);
-      }
-      if (result.action === "up" && cursor > 0) {
-        cursor--;
-        render();
-      } else if (result.action === "down" && cursor < options.items.length - 1) {
-        cursor++;
-        render();
-      } else if (result.action === "space" || result.action === "enter") {
+      if (result.action === "back" && options.allowBack !== false) return finish(BACK);
+      if (result.action === "up" && cursor > 0) { cursor--; render(); }
+      else if (result.action === "down" && cursor < options.items.length - 1) { cursor++; render(); }
+      else if (result.action === "space" || result.action === "enter") {
         finish(options.items[cursor]!.value);
       }
     };
@@ -257,11 +225,8 @@ export async function selectMany<T>(
   const toggle = (index: number) => {
     const item = items[index]!;
     item.selected = !item.selected;
-
     if (options.selectAllLabel && index === 0) {
-      for (let i = 1; i < items.length; i++) {
-        items[i]!.selected = item.selected;
-      }
+      for (let i = 1; i < items.length; i++) items[i]!.selected = item.selected;
     } else {
       syncSelectAll();
     }
@@ -269,19 +234,10 @@ export async function selectMany<T>(
 
   const render = () => {
     renderedLines = renderPrompt(
-      createLines(
-        {
-          title: options.title,
-          subtitle: options.subtitle,
-          items,
-        },
-        "multi",
-        cursor,
-      ),
+      createLines({ title: options.title, subtitle: options.subtitle, items }, "multi", cursor),
       renderedLines,
     );
   };
-
   render();
 
   return new Promise((resolve) => {
@@ -302,24 +258,12 @@ export async function selectMany<T>(
       escapeBuf = result.escapeBuf;
 
       if (result.action === "cancel") return finish(null);
-      if (result.action === "back" && options.allowBack !== false) {
-        return finish(BACK);
-      }
-      if (result.action === "up" && cursor > 0) {
-        cursor--;
-        render();
-      } else if (result.action === "down" && cursor < items.length - 1) {
-        cursor++;
-        render();
-      } else if (result.action === "space") {
-        toggle(cursor);
-        render();
-      } else if (result.action === "enter") {
-        finish(
-          items
-            .filter((item) => item.selected && item.value !== null)
-            .map((item) => item.value as T),
-        );
+      if (result.action === "back" && options.allowBack !== false) return finish(BACK);
+      if (result.action === "up" && cursor > 0) { cursor--; render(); }
+      else if (result.action === "down" && cursor < items.length - 1) { cursor++; render(); }
+      else if (result.action === "space") { toggle(cursor); render(); }
+      else if (result.action === "enter") {
+        finish(items.filter((item) => item.selected && item.value !== null).map((item) => item.value as T));
       }
     };
 

src/prompt.ts

@@ -1,5 +1,7 @@
 import type { PRContext, ProjectContext } from "./types";
 
+// ── Commit System Prompt ──────────────────────────────────────────────
+
 export const SYSTEM_PROMPT = `You are an expert at writing concise, meaningful git commit messages following the Conventional Commits specification.
 
 Format: <type>(<scope>): <description>
@@ -19,29 +21,17 @@ Rules:
 export function buildPrompt(context: ProjectContext): string {
   const parts: string[] = [];
 
-  if (
-    context.packageDescription ||
-    context.readme ||
-    context.structure
-  ) {
+  if (context.packageDescription || context.readme || context.structure) {
     parts.push("## Project Context");
-    if (context.packageDescription) {
-      parts.push(`Description: ${context.packageDescription}`);
-    }
-    if (context.structure) {
-      parts.push(`Structure: ${context.structure}`);
-    }
-    if (context.readme) {
-      parts.push(`README:\n${context.readme}`);
-    }
+    if (context.packageDescription) parts.push(`Description: ${context.packageDescription}`);
+    if (context.structure) parts.push(`Structure: ${context.structure}`);
+    if (context.readme) parts.push(`README:\n${context.readme}`);
     parts.push("");
   }
 
   if (context.recentCommits.length > 0) {
     parts.push("## Recent Commits (for style reference)");
-    for (const c of context.recentCommits) {
-      parts.push(c);
-    }
+    for (const c of context.recentCommits) parts.push(c);
     parts.push("");
   }
 
@@ -55,6 +45,8 @@ export function buildPrompt(context: ProjectContext): string {
   return parts.join("\n");
 }
 
+// ── PR System Prompt ───────────────────────────────────────────────────
+
 export const PR_SYSTEM_PROMPT = `You are an expert at writing clear, concise pull request titles and descriptions.
 
 Format:
@@ -74,21 +66,11 @@ Rules:
 export function buildPRPrompt(context: PRContext): string {
   const parts: string[] = [];
 
-  if (
-    context.packageDescription ||
-    context.readme ||
-    context.structure
-  ) {
+  if (context.packageDescription || context.readme || context.structure) {
     parts.push("## Project Context");
-    if (context.packageDescription) {
-      parts.push(`Description: ${context.packageDescription}`);
-    }
-    if (context.structure) {
-      parts.push(`Structure: ${context.structure}`);
-    }
-    if (context.readme) {
-      parts.push(`README:\n${context.readme}`);
-    }
+    if (context.packageDescription) parts.push(`Description: ${context.packageDescription}`);
+    if (context.structure) parts.push(`Structure: ${context.structure}`);
+    if (context.readme) parts.push(`README:\n${context.readme}`);
     parts.push("");
   }
 
@@ -99,9 +81,7 @@ export function buildPRPrompt(context: PRContext): string {
 
   if (context.branchCommits.length > 0) {
     parts.push("## Commits on This Branch");
-    for (const c of context.branchCommits) {
-      parts.push(c);
-    }
+    for (const c of context.branchCommits) parts.push(c);
     parts.push("");
   }
 
@@ -110,9 +90,141 @@ export function buildPRPrompt(context: PRContext): string {
   parts.push(context.diff);
   parts.push("```");
   parts.push("");
-  parts.push(
-    "Generate a pull request title and brief body for the above changes.",
-  );
+  parts.push("Generate a pull request title and brief body for the above changes.");
 
   return parts.join("\n");
 }
+
+// ── Explain Prompt ─────────────────────────────────────────────────────
+
+export const EXPLAIN_SYSTEM_PROMPT = `You are an expert software engineer explaining code changes in plain, accessible language.
+
+Given a git diff, explain:
+1. WHAT changed at a high level (1 sentence summary)
+2. WHY these changes matter (what problem they solve or what they enable)
+3. A brief breakdown of the key changes (bullet points, one per file/module)
+
+Rules:
+- Be concise but thorough
+- Use plain language suitable for both junior and senior engineers
+- Focus on the intent and impact, not just restating the diff
+- Do NOT use markdown headings (no ##, ###). Use bold text markers like **Section:** instead.
+- Keep each bullet point to 1-2 lines
+- If the diff is trivial, say so and keep the explanation short`;
+
+export function buildExplainPrompt(diff: string): string {
+  const parts: string[] = [];
+  parts.push("## Changes to Explain");
+  parts.push("```diff");
+  parts.push(diff);
+  parts.push("```");
+  parts.push("");
+  parts.push("Explain these changes in plain language as described.");
+  return parts.join("\n");
+}
+
+// ── Review Prompt ──────────────────────────────────────────────────────
+
+export const REVIEW_SYSTEM_PROMPT = `You are a senior software engineer performing a thorough but friendly code review.
+
+Review the following code changes and provide feedback in these categories:
+1. **Bugs & Logic Errors** — actual bugs, off-by-one errors, null safety, edge cases
+2. **Code Quality** — readability, naming, duplication, complexity
+3. **Performance** — inefficient patterns, unnecessary allocations, N+1 queries
+4. **Security** — injection risks, exposed secrets, unsafe operations
+5. **Suggestions** — concrete improvements with code snippets where helpful
+
+Rules:
+- Be constructive, not harsh. Use "consider" and "suggest" instead of "you should".
+- Prioritize by severity. Mention critical issues first.
+- If the code looks great, say so! Don't fabricate issues.
+- Keep feedback actionable — every issue should have a clear suggestion.
+- Use **bold** for section headers and \`code\` for code references.
+- Do NOT output a concluding summary paragraph. End with the last suggestion.`;
+
+export function buildReviewPrompt(diff: string, strictness: "lenient" | "normal" | "strict"): string {
+  const strictnessHints: Record<string, string> = {
+    lenient: "Focus only on major issues. Skip minor style nits.",
+    normal: "Provide balanced feedback covering all categories.",
+    strict: "Be thorough. Flag even minor issues and style inconsistencies.",
+  };
+
+  const parts: string[] = [];
+  parts.push(`Review strictness: ${strictnessHints[strictness]}`);
+  parts.push("");
+  parts.push("## Code Changes to Review");
+  parts.push("```diff");
+  parts.push(diff);
+  parts.push("```");
+  parts.push("");
+  parts.push("Please review the above changes.");
+  return parts.join("\n");
+}
+
+// ── Changelog Prompt ───────────────────────────────────────────────────
+
+export const CHANGELOG_SYSTEM_PROMPT = `You are an expert at writing clear, user-facing changelogs from git commit history.
+
+Given a list of commits, generate a changelog organized by type:
+- **Features** (feat commits)
+- **Bug Fixes** (fix commits)
+- **Improvements** (refactor, perf, style commits)
+- **Documentation** (docs commits)
+- **Chores & Maintenance** (chore, build, ci, test commits)
+
+Rules:
+- Group by type, with the heading in **bold**
+- Each entry should be a single line describing the change in user-friendly language
+- Translate technical commit messages into language a user would understand
+- Skip merge commits and trivial chore commits if they don't add value
+- If a type has no entries, omit that section
+- Output ONLY the changelog text, no preamble or markdown code blocks`;
+
+export function buildChangelogPrompt(commits: string[], from?: string, to?: string): string {
+  const parts: string[] = [];
+  const range = from ? `from ${from}${to ? ` to ${to}` : " to HEAD"}` : "";
+  parts.push(range ? `Generate a changelog for commits ${range}.` : "Generate a changelog from the following commits.");
+  parts.push("");
+  parts.push("## Commits");
+  for (const c of commits) parts.push(c);
+  parts.push("");
+  parts.push("Generate a changelog from these commits.");
+  return parts.join("\n");
+}
+
+// ── Suggest Prompt ─────────────────────────────────────────────────────
+
+export const SUGGEST_SYSTEM_PROMPT = `You are an expert at suggesting git branch names and commit types based on code changes.
+
+For branch name suggestions:
+- Use format: <type>/<short-description>
+- Types: feat, fix, refactor, docs, chore, perf, test
+- Description should be 2-4 hyphenated words
+- Provide exactly 3 suggestions, one per line
+
+For commit type suggestions:
+- Return exactly one Conventional Commit type that best matches the changes
+- Valid types: feat, fix, docs, style, refactor, perf, test, build, ci, chore, revert
+- Output ONLY the type name`;
+
+export function buildSuggestBranchPrompt(diff: string): string {
+  const parts: string[] = [];
+  parts.push("## Changes");
+  parts.push("```diff");
+  parts.push(diff);
+  parts.push("```");
+  parts.push("");
+  parts.push("Suggest 3 branch names for these changes. Output one per line, no numbering.");
+  return parts.join("\n");
+}
+
+export function buildSuggestTypePrompt(diff: string): string {
+  const parts: string[] = [];
+  parts.push("## Changes");
+  parts.push("```diff");
+  parts.push(diff);
+  parts.push("```");
+  parts.push("");
+  parts.push("What Conventional Commit type best describes these changes? Output ONLY the type name.");
+  return parts.join("\n");
+}

src/selector.ts

@@ -1,5 +1,6 @@
 import type { FileEntry } from "./types";
 import { BOLD, GREEN, YELLOW, RESET } from "./terminal";
+import { isStdinTTY } from "./tty";
 import { BACK, selectMany } from "./menu";
 import type { PromptBack } from "./menu";
 
@@ -10,13 +11,13 @@ export async function selectFiles(
   if (unstagedFiles.length === 0) return [];
 
   if (stagedFiles.length > 0) {
-    process.stdout.write(`\n  ${BOLD}Staged files (will be included):${RESET}\n`);
+    process.stdout.write(`\n  ${BOLD()}Staged files (will be included):${RESET()}\n`);
     for (const f of stagedFiles) {
-      process.stdout.write(`    ${GREEN}✓${RESET} ${f.path} (${YELLOW}${f.label}${RESET})\n`);
+      process.stdout.write(`    ${GREEN()}✓${RESET()} ${f.path} (${YELLOW()}${f.label}${RESET()})\n`);
     }
   }
 
-  if (process.stdin.isTTY !== true) return [];
+  if (!isStdinTTY()) return [];
 
   const selected = await selectMany({
     title: "Select files to stage",
@@ -35,7 +36,7 @@ export async function selectFiles(
 
   if (selected.length > 0) {
     process.stdout.write(
-      `  ${GREEN}Staged ${selected.length} file(s):${RESET} ${selected.join(", ")}\n`,
+      `  ${GREEN()}Staged ${selected.length} file(s):${RESET()} ${selected.join(", ")}\n`,
     );
   }
 

src/terminal.ts

@@ -1,7 +1,35 @@
-export const BOLD = "\x1b[1m";
-export const GREEN = "\x1b[32m";
-export const YELLOW = "\x1b[33m";
-export const CYAN = "\x1b[36m";
-export const RED = "\x1b[31m";
-export const DIM = "\x1b[2m";
-export const RESET = "\x1b[0m";
+// Terminal styling utilities.
+// Respects NO_COLOR convention, --no-color flag, and TTY detection.
+
+import { isStdoutTTY } from "./tty";
+
+let _enabled: boolean | null = null;
+
+export function setColorEnabled(enabled: boolean): void {
+  _enabled = enabled;
+}
+
+export function isColorEnabled(): boolean {
+  if (_enabled !== null) return _enabled;
+
+  // Respect NO_COLOR: https://no-color.org/
+  if (process.env.NO_COLOR !== undefined && process.env.NO_COLOR !== "") {
+    return false;
+  }
+  if (!isStdoutTTY()) return false;
+  if (process.env.FORCE_COLOR && process.env.FORCE_COLOR !== "0") return true;
+
+  return true;
+}
+
+function s(code: string): string {
+  return isColorEnabled() ? code : "";
+}
+
+export const BOLD = () => s("\x1b[1m");
+export const DIM = () => s("\x1b[2m");
+export const GREEN = () => s("\x1b[32m");
+export const YELLOW = () => s("\x1b[33m");
+export const CYAN = () => s("\x1b[36m");
+export const RED = () => s("\x1b[31m");
+export const RESET = () => s("\x1b[0m");

src/tty.ts

@@ -0,0 +1,36 @@
+// TTY detection for Bun compatibility.
+// Bun does not set process.stdin.isTTY, so we use fs.fstatSync.
+
+import { fstatSync } from "node:fs";
+
+let _stdinTTY: boolean | null = null;
+
+export function initTTY(): void {
+  if (_stdinTTY !== null) return;
+
+  try {
+    // fd 0 = stdin. On Unix, a TTY is a character device.
+    const stat = fstatSync(0);
+    _stdinTTY = stat.isCharacterDevice();
+  } catch {
+    _stdinTTY = false;
+  }
+}
+
+export function isStdinTTY(): boolean {
+  if (_stdinTTY === null) initTTY();
+  return _stdinTTY!;
+}
+
+export function isStdoutTTY(): boolean {
+  // Use a heuristic for stdout — check if we're in a terminal
+  if (process.env.TERM || process.env.TERM_PROGRAM) return true;
+  if (process.env.NO_COLOR) return false;
+  // Try fstat on fd 1 (stdout)
+  try {
+    const stat = fstatSync(1);
+    return stat.isCharacterDevice();
+  } catch {
+    return false;
+  }
+}

src/types.ts

@@ -29,3 +29,17 @@ export interface PRContext {
   branchCommits: string[];
   diff: string;
 }
+
+export interface CommitResult {
+  branch: string;
+  hash: string;
+  files: number;
+  insertions: number;
+  deletions: number;
+}
+
+export interface StreamCallbacks {
+  onToken?: (token: string) => void;
+  onDone?: (fullText: string) => void;
+  onError?: (err: Error) => void;
+}