// Authoring Pi TypeScript extensions — ExtensionAPI, custom tools, commands, UI hooks, resources_discover, `registerProvider()`, and how extendResources merges skill paths after base reload. Use when the user builds or debugs pi extensions, registers tools, adds /commands, hooks events, integrates TUI components, or ships extension examples. Use for "how do I extend pi", "extension API", "registerTool", "registerProvider", even if pi-mono is not mentioned.
Authoring Pi TypeScript extensions — ExtensionAPI, custom tools, commands, UI hooks, resources_discover, `registerProvider()`, and how extendResources merges skill paths after base reload. Use when the user builds or debugs pi extensions, registers tools, adds /commands, hooks events, integrates TUI components, or ships extension examples. Use for "how do I extend pi", "extension API", "registerTool", "registerProvider", even if pi-mono is not mentioned.
compatibility
TypeScript/Node extension host; read pi-mono/packages/coding-agent for ExtensionAPI and loader behavior cited in this skill.
pi-mono/packages/coding-agent/src/core/resource-loader.ts — extendResources() appends paths via mergePaths after existing lastSkillPaths (late paths lose name collisions to earlier ones unless names differ).
pi-mono/packages/coding-agent/src/core/agent-session.ts — extension commands vs queued prompts; skill expansion hooks.
pi-mono/packages/coding-agent/docs/tui.md — extension TUI component integration with @mariozechner/pi-tui: Component rendering contract, overlay patterns, input handling in extension context.
pi-mono/packages/coding-agent/docs/custom-provider.md — registerProvider() for proxies, OAuth/SSO, custom APIs, and custom model definitions.
Invariants
Extensions can register tools, commands, themes, prompts, and extra skill paths; exact API surface is defined in docs and example modules — start from docs/extensions.md, not memory.
Dynamic resource discovery patterns live under pi-mono/packages/coding-agent/examples/extensions/ (e.g. dynamic-resources/ listing in examples README).
Workflows
New extension: Read docs/extensions.md, clone the closest examples/extensions/ template, then align with project AGENTS.md if working inside pi-mono.
Skills from extensions: Trace extendResources + mergePaths in resource-loader.ts to explain ordering with user/project/package skills.
Extension TUI: Read docs/tui.md for the Component rendering contract in extension context; combine with pi-tui skill for library-level APIs.
Custom providers via extension: See pi-mono/packages/coding-agent/docs/custom-provider.md for registerProvider() OAuth flows and proxy patterns (grounded in pi-cli-workspace).
Anti-patterns
Do not assert MCP support in core; optional via extension (see coding-agent README philosophy).
