# Load an extension with --extension flag
pi --extension examples/extensions/permission-gate.ts

# Or copy to extensions directory for auto-discovery
cp permission-gate.ts ~/.pi/agent/extensions/

import type { ExtensionAPI } from "@mariozechner/pi-coding-agent";
import { Type } from "typebox";

export default function (pi: ExtensionAPI) {
  // Subscribe to lifecycle events
  pi.on("tool_call", async (event, ctx) => {
    if (event.toolName === "bash" && event.input.command?.includes("rm -rf")) {
      const ok = await ctx.ui.confirm("Dangerous!", "Allow rm -rf?");
      if (!ok) return { block: true, reason: "Blocked by user" };
    }
  });

  // Register custom tools
  pi.registerTool({
    name: "greet",
    label: "Greeting",
    description: "Generate a greeting",
    parameters: Type.Object({
      name: Type.String({ description: "Name to greet" }),
    }),
    async execute(toolCallId, params, onUpdate, ctx, signal) {
      return {
        content: [{ type: "text", text: `Hello, ${params.name}!` }],
        details: {},
      };
    },
  });

  // Register commands
  pi.registerCommand("hello", {
    description: "Say hello",
    handler: async (args, ctx) => {
      ctx.ui.notify("Hello!", "info");
    },
  });
}

import { StringEnum } from "@mariozechner/pi-ai";

// Good
action: StringEnum(["list", "add"] as const)

// Bad - doesn't work with Google
action: Type.Union([Type.Literal("list"), Type.Literal("add")])

// Store state in tool result details for proper forking support
return {
  content: [{ type: "text", text: "Done" }],
  details: { todos: [...todos], nextId },  // Persisted in session
};

// Reconstruct on session events
pi.on("session_start", async (_event, ctx) => {
  for (const entry of ctx.sessionManager.getBranch()) {
    if (entry.type === "message" && entry.message.toolName === "my_tool") {
      const details = entry.message.details;
      // Reconstruct state from details
    }
  }
});