# Tallow Expert > Auto-triggers on tallow internals, architecture, extensions, configuration, or the pi framework API. Spawns the tallow-expert agent for codebase discovery. Use when this capability is needed. - Skill: `tomevault-io/tallow-expert` (Agent Skill, multi-file: 2 files) - Install (CLI): `npx skillmds@latest add tomevault-io/tallow-expert` - Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/tallow-expert/raw - Safety review: pending (external: skill-scanner PASS, skillspector PASS) - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Product & Planning - Author: tomevault-io (https://skillmd.com/u/tomevault-io) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/tomevault-io/tallow-expert --- # Tallow Expert Skill ## When This Triggers - User asks about tallow architecture, internals, or source code - How extensions work, their API, or how to create them - The pi framework (ExtensionAPI, tools, commands, events, types) - Configuration (settings.json, themes, keybindings, packages) - How skills, agents, or prompts are loaded and discovered - Debugging or troubleshooting tallow itself - How the TUI, session management, or model registry works ## Procedure Invoke the `tallow-expert` agent via the subagent tool: ```json { "agent": "tallow-expert", "task": "" } ``` The agent explores the tallow source code and returns an answer. Relay that answer to the user. ## Quick Reference | Component | Location | |-----------|----------| | Core source | `src/` (agent-runner.ts, atomic-write.ts, auth-hardening.ts, cli-auto-rebuild.ts, cli.ts, compaction-cancel-patch.ts, config.ts, extensions-global.d.ts, fatal-errors.ts, index.ts, install.ts, interactive-mode-patch.ts, interactive-reset.ts, model-metadata-overrides.ts, otel.ts, pi-tui-editor-patch.ts, pi-tui-patch.ts, pi-tui-settings-list-patch.ts, pid-manager.ts, pid-schema.ts, plugins.ts, process-cleanup.ts, project-trust-banner.ts, project-trust-interop.ts, project-trust.ts, reset-diagnostics.ts, runtime-path-provider.ts, runtime-provenance.ts, sdk.ts, session-migration.ts, session-utils.ts, startup-profile.ts, startup-timing.ts, streaming-yield-patch.ts, workspace-transition-interactive.ts, workspace-transition-relay.ts, workspace-transition.ts, yield-to-io.ts) | | Extensions | `extensions/` — extension.json + index.ts each (52 bundled) | | Skills | `skills/` — subdirs with SKILL.md | | Agents | `agents/` — markdown with YAML frontmatter | | Themes | `themes/` — JSON files (34 dark-only themes) | | Forked TUI | `packages/tallow-tui/` — forked `@mariozechner/pi-tui` | | Pi framework types | `node_modules/@mariozechner/pi-coding-agent/dist/core/extensions/types.d.ts` | | User config | `~/.tallow/` (settings.json, auth.json, keybindings.json) | | User extensions | `~/.tallow/extensions/` | | User agents | `~/.tallow/agents/`, `~/.claude/agents/` | | User skills | `~/.tallow/skills/`, `~/.claude/skills/` | | User commands | `~/.tallow/commands/`, `~/.claude/commands/` | | Project agents | `.tallow/agents/`, `.claude/agents/` | | Project skills | `.tallow/skills/`, `.claude/skills/` | | Project commands | `.tallow/commands/`, `.claude/commands/` | | Sessions | `~/.tallow/sessions/` — per-cwd subdirs | | Docs site | `docs/` — Astro Starlight site | **Agent frontmatter fields**: `tools`, `disallowedTools`, `maxTurns`, `mcpServers`, `context: fork`, `agent`, `model` ### Extension API Surface Extensions export a default function receiving `ExtensionAPI` (conventionally named `pi`): #### Registration - `registerTool(tool: ToolDefinition)` — Register a tool that the LLM can call. - `registerCommand(name: string, options: Omit)` — Register a custom command. - `registerFlag(name: string, options: object)` — Register a CLI flag. - `registerMessageRenderer(customType: string, renderer: MessageRenderer)` — Register a custom renderer for CustomMessageEntry. - `registerProvider(name: string, config: ProviderConfig)` — Register or override a model provider. #### Messaging - `sendMessage(message: Pick, "customType" | "content" | "display" | "details">, options?: object)` — Send a custom message to the session. - `appendEntry(customType: string, data?: T)` — Append a custom entry to the session for state persistence (not sent to LLM). #### Session - `setSessionName(name: string)` — Set the session display name (shown in session selector). - `getSessionName()` — Get the current session name, if set. - `setLabel(entryId: string, label: string)` — Set or clear a label on an entry. #### Tools & Model - `getFlag(name: string)` — Get the value of a registered CLI flag. - `exec(command: string, args: string[], options?: ExecOptions)` — Execute a shell command. - `getActiveTools()` — Get the list of currently active tool names. - `getAllTools()` — Get all configured tools with parameter schema and source metadata. - `setActiveTools(toolNames: string[])` — Set the active tools by name. - `getCommands()` — Get available slash commands in the current session. - `setModel(model: Model)` — Set the current model. - `getThinkingLevel()` — Get current thinking level. - `setThinkingLevel(level: ThinkingLevel)` — Set thinking level (clamped to model capabilities). - `unregisterProvider(name: string)` — Unregister a previously registered provider. - `events` — Shared event bus for extension communication. ### Events (`pi.on(event, handler)`) #### Session lifecycle | Event | Payload | Can return | |-------|---------|------------| | `resources_discover` | `ResourcesDiscoverEvent` | `ResourcesDiscoverResult` | | `session_start` | `SessionStartEvent` | — | | `session_before_switch` | `SessionBeforeSwitchEvent` | `SessionBeforeSwitchResult` | | `session_before_fork` | `SessionBeforeForkEvent` | `SessionBeforeForkResult` | | `session_before_compact` | `SessionBeforeCompactEvent` | `SessionBeforeCompactResult` | | `session_compact` | `SessionCompactEvent` | — | | `session_shutdown` | `SessionShutdownEvent` | — | | `session_before_tree` | `SessionBeforeTreeEvent` | `SessionBeforeTreeResult` | | `session_tree` | `SessionTreeEvent` | — | #### Agent lifecycle | Event | Payload | Can return | |-------|---------|------------| | `before_agent_start` | `BeforeAgentStartEvent` | `BeforeAgentStartEventResult` | | `agent_start` | `AgentStartEvent` | — | | `agent_end` | `AgentEndEvent` | — | | `turn_start` | `TurnStartEvent` | — | | `turn_end` | `TurnEndEvent` | — | | `model_select` | `ModelSelectEvent` | — | #### Tool events | Event | Payload | Can return | |-------|---------|------------| | `tool_execution_start` | `ToolExecutionStartEvent` | — | | `tool_execution_update` | `ToolExecutionUpdateEvent` | — | | `tool_execution_end` | `ToolExecutionEndEvent` | — | | `tool_call` | `ToolCallEvent` | `ToolCallEventResult` | | `tool_result` | `ToolResultEvent` | `ToolResultEventResult` | #### Input & resources | Event | Payload | Can return | |-------|---------|------------| | `context` | `ContextEvent` | `ContextEventResult` | | `user_bash` | `UserBashEvent` | `UserBashEventResult` | | `input` | `InputEvent` | `InputEventResult` | #### Message streaming | Event | Payload | Can return | |-------|---------|------------| | `message_start` | `MessageStartEvent` | — | | `message_update` | `MessageUpdateEvent` | — | | `message_end` | `MessageEndEvent` | `MessageEndEventResult` | ### ExtensionContext (`ctx` in event handlers) - `ui` — UI methods for user interaction - `hasUI` — Whether UI is available (false in print/RPC mode) - `cwd` — Current working directory - `sessionManager` — Session manager (read-only) - `modelRegistry` — Model registry for API key resolution - `model` — Current model (may be undefined) - `isIdle()` — Whether the agent is idle (not streaming) - `signal` — The current abort signal, or undefined when the agent is not streaming. - `abort()` — Abort the current agent operation - `hasPendingMessages()` — Whether there are queued messages waiting - `shutdown()` — Gracefully shutdown pi and exit. - `getContextUsage()` — Get current context usage for the active model. - `compact(options?: CompactOptions)` — Trigger compaction without awaiting completion. - `getSystemPrompt()` — Get the current effective system prompt. ### ExtensionCommandContext (`ctx` in command handlers, extends ExtensionContext) - `waitForIdle()` — Wait for the agent to finish streaming - `navigateTree(targetId: string, options?: object)` — Navigate to a different point in the session tree. - `reload()` — Reload extensions, skills, prompts, and themes. ### ExtensionUIContext (`ctx.ui`) - `select(title: string, options: string[], opts?: ExtensionUIDialogOptions)` — Show a selector and return the user's choice. - `confirm(title: string, message: string, opts?: ExtensionUIDialogOptions)` — Show a confirmation dialog. - `input(title: string, placeholder?: string, opts?: ExtensionUIDialogOptions)` — Show a text input dialog. - `notify(message: string, type?: "info" | "warning" | "error")` — Show a notification to the user. - `onTerminalInput(handler: TerminalInputHandler)` — Listen to raw terminal input (interactive mode only). - `setStatus(key: string, text: string)` — Set status text in the footer/status bar. - `setWorkingMessage(message?: string)` — Set the working/loading message shown during streaming. - `setWorkingVisible(visible: boolean)` — Show or hide the built-in interactive working loader row during streaming. - `setWorkingIndicator(options?: WorkingIndicatorOptions)` — Configure the interactive working indicator shown during streaming. - `setHiddenThinkingLabel(label?: string)` — Set the label shown for hidden thinking blocks. - `setWidget(key: string, content: string[], options?: ExtensionWidgetOptions)` — Set a widget to display above or below the editor. - `setTitle(title: string)` — Set the terminal window/tab title. - `pasteToEditor(text: string)` — Paste text into the editor, triggering paste handling (collapse for large content). - `setEditorText(text: string)` — Set the text in the core input editor. - `getEditorText()` — Get the current text from the core input editor. - `editor(title: string, prefill?: string)` — Show a multi-line editor for text editing. - `addAutocompleteProvider(factory: AutocompleteProviderFactory)` — Stack additional autocomplete behavior on top of the built-in provider. - `setEditorComponent(factory: EditorFactory)` — Set a custom editor component via factory function. - `getEditorComponent()` — Get the currently configured custom editor factory, or undefined when using the default editor. - `readonly theme` — Get the current theme for styling. - `getAllThemes()` — Get all available themes with their names and file paths. - `getTheme(name: string)` — Load a theme by name without switching to it. - `setTheme(theme: string | Theme)` — Set the current theme by name or Theme object. - `getToolsExpanded()` — Get current tool output expansion state. - `setToolsExpanded(expanded: boolean)` — Set tool output expansion state. --- > Source: [dungle-scrubs/tallow](https://github.com/dungle-scrubs/tallow) — distributed by [TomeVault](https://tomevault.io).