diff --git a/CLAUDE.md b/CLAUDE.md
index 0fbfa60..434cd60 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -26,6 +26,7 @@ Use the `/add-agent` skill — see `.claude/skills/add-agent/skill.md` for the f
 | opencode | `opencode` | `upgrade` |
 | cursor-agent | `cursor-agent` | `update` |
 | copilot | `copilot` | `update` |
+| pi | `pi` | `update pi` |
 
 ## Key files
 
@@ -34,4 +35,4 @@ Use the `/add-agent` skill — see `.claude/skills/add-agent/skill.md` for the f
 
 ## Versioning
 
-`getVersion` extracts the first `/\d+\.\d+\.\d+/` match from `<tool> --version` stdout. If the output format doesn't match, set `versioned: false`.
+`getVersion` extracts the first `/\d+\.\d+\.\d+/` match from `<tool> --version` stdout or stderr. If the output format doesn't match, set `versioned: false`.
diff --git a/README.md b/README.md
index 8a98f6a..ec9efa5 100644
--- a/README.md
+++ b/README.md
@@ -31,6 +31,7 @@ Each tool runs concurrently. After updating, aiupdate shows the version change (
 | [OpenCode](https://opencode.ai) | `opencode upgrade` |
 | [Cursor Agent](https://cursor.com) | `cursor-agent update` |
 | [GitHub Copilot CLI](https://githubnext.com/projects/copilot-cli) | `copilot update` |
+| [pi](https://pi.dev/) | `pi update pi` |
 | [skills](https://github.com/anthropics/skills) | `npx skills update -g -p -y` |
 
 Tools not installed on your machine are silently skipped.
diff --git a/src/cli.test.ts b/src/cli.test.ts
index 22852d9..0f878f0 100644
--- a/src/cli.test.ts
+++ b/src/cli.test.ts
@@ -1,5 +1,8 @@
+import { mkdtemp, writeFile, chmod, rm } from 'fs/promises';
+import { tmpdir } from 'os';
+import { join } from 'path';
 import { describe, it, expect } from 'vitest';
-import { selectTools, run, formatTitle, AI_TOOLS, SKILLS_TASK } from './cli.js';
+import { selectTools, run, formatTitle, getVersion, AI_TOOLS, SKILLS_TASK } from './cli.js';
 
 const allInstalled: (cmd: string) => Promise<boolean> = async () => true;
 const noneInstalled: (cmd: string) => Promise<boolean> = async () => false;
@@ -26,6 +29,22 @@ describe('formatTitle', () => {
   });
 });
 
+describe('getVersion', () => {
+  it('extracts versions from stderr', async () => {
+    const dir = await mkdtemp(join(tmpdir(), 'aiupdate-'));
+    const command = join(dir, 'version-stderr');
+
+    try {
+      await writeFile(command, "#!/usr/bin/env node\nprocess.stderr.write('fake 9.8.7\\n');\n");
+      await chmod(command, 0o755);
+
+      await expect(getVersion(command)).resolves.toBe('9.8.7');
+    } finally {
+      await rm(dir, { recursive: true, force: true });
+    }
+  });
+});
+
 describe('selectTools', () => {
   it('returns all AI tools + skills when no args', () => {
     const { selectedAITools, includeSkills } = selectTools([]);
diff --git a/src/cli.ts b/src/cli.ts
index 238fbec..ab07893 100644
--- a/src/cli.ts
+++ b/src/cli.ts
@@ -21,6 +21,7 @@ export const AI_TOOLS: Tool[] = [
   { name: 'opencode', command: 'opencode', args: ['upgrade'], versioned: true },
   { name: 'cursor-agent', command: 'cursor-agent', args: ['update'], versioned: true },
   { name: 'copilot', command: 'copilot', args: ['update'], versioned: true },
+  { name: 'pi', command: 'pi', args: ['update', 'pi'], versioned: true },
 ];
 
 export const SKILLS_TASK: Tool = {
@@ -38,10 +39,10 @@ async function defaultChecker(command: string): Promise<boolean> {
   }
 }
 
-async function getVersion(command: string): Promise<string | null> {
+export async function getVersion(command: string): Promise<string | null> {
   try {
-    const { stdout } = await execa(command, ['--version']);
-    const match = stdout.match(/\d+\.\d+\.\d+/);
+    const { stdout, stderr } = await execa(command, ['--version']);
+    const match = `${stdout}\n${stderr}`.match(/\d+\.\d+\.\d+/);
     return match ? match[0] : null;
   } catch {
     return null;