feat: add Pi coding agent support

src/agents/definitions/pi.ts

@@ -0,0 +1,30 @@
+import { join } from "node:path";
+import { homedir } from "node:os";
+import type { AgentDefinition } from "../types.js";
+import { UnsupportedFeature } from "../errors.js";
+import { envRecord, httpServer } from "./helpers.js";
+
+const pi: AgentDefinition = {
+  id: "pi",
+  displayName: "Pi",
+  configDir: ".pi",
+  skillsParentDir: ".pi",
+  userSkillsParentDirs: [join(homedir(), ".pi", "agent")],
+  mcp: {
+    filePath: ".pi/mcp.json",
+    rootKey: "mcpServers",
+    format: "json",
+    shared: false,
+  },
+  serializeServer(s) {
+    if (s.url) return httpServer(s);
+    const env = envRecord(s.env, (k) => `\${${k}}`);
+    return [s.name, { command: s.command, args: s.args ?? [], ...(env && { env }) }];
+  },
+  hooks: undefined,
+  serializeHooks() {
+    throw new UnsupportedFeature("pi", "hooks");
+  },
+};
+
+export default pi;

src/agents/paths.test.ts

@@ -38,6 +38,12 @@ describe("getUserMcpTarget", () => {
     expect(t.shared).toBe(true);
   });
 
+  it("pi targets ~/.pi/agent/mcp.json (not shared)", () => {
+    const t = getUserMcpTarget("pi");
+    expect(t.filePath).toBe(join(home, ".pi", "agent", "mcp.json"));
+    expect(t.shared).toBe(false);
+  });
+
   it("throws for unknown agent", () => {
     expect(() => getUserMcpTarget("emacs")).toThrow("Unknown agent");
   });
@@ -77,4 +83,10 @@ describe("skill discovery paths", () => {
     expect(agent.skillsParentDir).toBeUndefined();
     expect(agent.userSkillsParentDirs).toBeUndefined();
   });
+
+  it("pi needs project and user symlinks", () => {
+    const agent = getAgent("pi")!;
+    expect(agent.skillsParentDir).toBe(".pi");
+    expect(agent.userSkillsParentDirs).toEqual([join(home, ".pi", "agent")]);
+  });
 });

src/agents/paths.ts

@@ -25,6 +25,8 @@ export function getUserMcpTarget(agentId: string): UserMcpTarget {
       return { filePath: vscodeMcpPath(), shared: false };
     case "opencode":
       return { filePath: join(home, ".config", "opencode", "opencode.json"), shared: true };
+    case "pi":
+      return { filePath: join(home, ".pi", "agent", "mcp.json"), shared: false };
     default:
       throw new Error(`Unknown agent for user-scope MCP: ${agentId}`);
   }

src/agents/registry.test.ts

@@ -22,14 +22,15 @@ const STDIO_NO_ENV: McpDeclaration = {
 };
 
 describe("allAgentIds", () => {
-  it("returns all 5 agents", () => {
+  it("returns all 6 agents", () => {
     const ids = allAgentIds();
     expect(ids).toContain("claude");
     expect(ids).toContain("cursor");
     expect(ids).toContain("codex");
     expect(ids).toContain("vscode");
     expect(ids).toContain("opencode");
-    expect(ids).toHaveLength(5);
+    expect(ids).toContain("pi");
+    expect(ids).toHaveLength(6);
   });
 });
 
@@ -174,3 +175,43 @@ describe("opencode serializer", () => {
     expect(agent.skillsParentDir).toBeUndefined();
   });
 });
+
+describe("pi serializer", () => {
+  const agent = getAgent("pi")!;
+
+  it("serializes stdio server", () => {
+    const [name, config] = agent.serializeServer(STDIO_SERVER);
+    expect(name).toBe("github");
+    expect(config).toEqual({
+      command: "npx",
+      args: ["-y", "@modelcontextprotocol/server-github"],
+      env: { GITHUB_TOKEN: "${GITHUB_TOKEN}" },
+    });
+  });
+
+  it("serializes http server natively", () => {
+    const [name, config] = agent.serializeServer(HTTP_SERVER);
+    expect(name).toBe("remote-api");
+    expect(config).toEqual({
+      url: "https://mcp.example.com/sse",
+      headers: { Authorization: "Bearer tok" },
+    });
+  });
+
+  it("omits env when empty", () => {
+    const [, config] = agent.serializeServer(STDIO_NO_ENV);
+    expect(config).toEqual({ command: "mcp-server", args: [] });
+    expect(config).not.toHaveProperty("env");
+  });
+
+  it("needs project and user symlinks for skills", () => {
+    expect(agent.skillsParentDir).toBe(".pi");
+    expect(agent.userSkillsParentDirs).toHaveLength(1);
+    expect(agent.userSkillsParentDirs![0]).toMatch(/\.pi[/\\]agent$/);
+  });
+
+  it("does not support hooks", () => {
+    expect(agent.hooks).toBeUndefined();
+    expect(() => agent.serializeHooks([])).toThrow();
+  });
+});

src/agents/registry.ts

@@ -4,8 +4,9 @@ import cursor from "./definitions/cursor.js";
 import codex from "./definitions/codex.js";
 import vscode from "./definitions/vscode.js";
 import opencode from "./definitions/opencode.js";
+import pi from "./definitions/pi.js";
 
-const ALL_AGENTS: AgentDefinition[] = [claude, cursor, codex, vscode, opencode];
+const ALL_AGENTS: AgentDefinition[] = [claude, cursor, codex, vscode, opencode, pi];
 
 const AGENT_REGISTRY = new Map<string, AgentDefinition>(
   ALL_AGENTS.map((a) => [a.id, a]),