create-gsd-extension

name

create-gsd-extension

description

Create, debug, and iterate on GSD extensions (TypeScript modules that add tools, commands, event hooks, custom UI, and providers to GSD). Use when asked to build an extension, add a tool the LLM can call, register a slash command, hook into GSD events, create custom TUI components, or modify GSD behavior. Triggers on "create extension", "build extension", "add a tool", "register command", "hook into gsd", "custom tool", "gsd plugin", "gsd extension".

<essential_principles>

Extensions are TypeScript modules that hook into GSD's runtime (built on pi). They export a default function receiving ExtensionAPI and use it to subscribe to events, register tools/commands/shortcuts, and interact with the session.

GSD extension paths (community/user-installed extensions):

• Global: ~/.pi/agent/extensions/*.ts or ~/.pi/agent/extensions/*/index.ts
• Project-local: .gsd/extensions/*.ts or .gsd/extensions/*/index.ts

Note: ~/.gsd/agent/extensions/ is reserved for bundled extensions synced from the gsd-pi package. Community extensions placed there are silently ignored by the loader.

The three primitives:

1. Events — Listen and react (pi.on("event", handler)). Can block tool calls, modify messages, inject context.
2. Tools — Give the LLM new abilities (pi.registerTool()). LLM calls them autonomously.
3. Commands — Give users slash commands (pi.registerCommand()). Users type /mycommand.

Non-negotiable rules:

• Use StringEnum from @gsd/pi-ai for string enum params (NOT Type.Union/Type.Literal — breaks Google's API)
• Truncate tool output to 50KB / 2000 lines max (use truncateHead/truncateTail from @gsd/pi-coding-agent)
• Store stateful tool state in details for branching support
• Check signal?.aborted in long-running tool executions
• Use pi.exec() not child_process for shell commands
• Check ctx.hasUI before dialog methods (non-interactive modes exist)
• Session control methods (waitForIdle, newSession, fork, navigateTree, reload) are ONLY available in command handlers — they deadlock in event handlers
• Lines from render() must not exceed width — use truncateToWidth()
• Use theme from callback params, never import directly
• Strip leading @ from path params in custom tools (some models add it)

Available imports:

Package	Purpose
@gsd/pi-coding-agent	ExtensionAPI, ExtensionContext, Theme, event types, tool utilities, DynamicBorder, BorderedLoader, CustomEditor, highlightCode
@sinclair/typebox	Type.Object, Type.String, Type.Number, Type.Optional, Type.Boolean, Type.Array
@gsd/pi-ai	StringEnum (required for string enums), Type re-export
@gsd/pi-tui	Text, Box, Container, Spacer, Markdown, SelectList, Input, matchesKey, Key, truncateToWidth, visibleWidth
Node.js built-ins	node:fs, node:path, node:child_process, etc.

</essential_principles>

Based on user intent, route to the appropriate workflow:

Building a new extension:

• "Create an extension", "build a tool", "I want to add a command" → workflows/create-extension.md

Adding capabilities to an existing extension:

• "Add a tool to my extension", "add event hook", "add custom rendering" → workflows/add-capability.md

Debugging an extension:

• "My extension doesn't work", "tool not showing up", "event not firing" → workflows/debug-extension.md

If user intent is clear from context, skip the question and go directly to the workflow.

<reference_index> All domain knowledge in references/:

Core architecture: extension-lifecycle.md, events-reference.md API surface: extensionapi-reference.md, extensioncontext-reference.md Capabilities: custom-tools.md, custom-commands.md, custom-ui.md, custom-rendering.md Patterns: state-management.md, system-prompt-modification.md, compaction-session-control.md Infrastructure: model-provider-management.md, remote-execution-overrides.md, packaging-distribution.md, mode-behavior.md Spec: docs/extension-sdk/manifest-spec.md — manifest format, tiers, validation Testing: docs/extension-sdk/testing.md — mock patterns, test conventions SDK: docs/extension-sdk/ — the authoritative GSD-2 extension guide Gotchas: key-rules-gotchas.md </reference_index>

<workflows_index>

Workflow	Purpose
create-extension.md	Build a new extension from scratch
add-capability.md	Add tools, commands, hooks, UI to an existing extension
debug-extension.md	Diagnose and fix extension issues
</workflows_index>

<success_criteria> Extension is complete when:

• extension-manifest.json exists with accurate provides listing all registered tools/commands/hooks/shortcuts
• TypeScript compiles without errors (jiti handles this at runtime)
• Extension loads on GSD startup or /reload without errors
• Tools appear in the LLM's system prompt and are callable
• Commands respond to /command input
• Event hooks fire at the expected lifecycle points
• Custom UI renders correctly within terminal width
• State persists correctly across session restarts (if stateful)
• Output is truncated to safe limits (if tools produce variable output) </success_criteria>