# Fen extension contributions

Discovered `(api.register :kind {...})` sites across the
first-party extensions and core. Names extracted from
literal `:name` fields; dynamic registrations show the
source path with the name omitted.

## Table of contents

- [:auth-backend](#extension-kind-auth-backend)
- [:command](#extension-kind-command)
- [:control](#extension-kind-control)
- [:extension](#extension-kind-extension)
- [:introspect](#extension-kind-introspect)
- [:panel](#extension-kind-panel)
- [:presenter](#extension-kind-presenter)
- [:provider](#extension-kind-provider)
- [:session-backend](#extension-kind-session-backend)
- [:status](#extension-kind-status)
- [:tool](#extension-kind-tool)

## <a id="extension-kind-auth-backend"></a>:auth-backend

- <a id="register-site-auth-backend-openai-codex-extensions-adapters-providers-openai-init-fnl-54"></a>`openai-codex` — ChatGPT subscription PKCE OAuth credentials stored in fen's auth.json. — _extensions/adapters/providers/openai/init.fnl:54_

## <a id="extension-kind-command"></a>:command

- <a id="register-site-command-expand-extensions-adapters-presenters-tui-init-fnl-665"></a>`expand` — Toggle full vs collapsed tool-result bodies — _extensions/adapters/presenters/tui/init.fnl:665_
- <a id="register-site-command-markdown-extensions-adapters-presenters-tui-init-fnl-681"></a>`markdown` — Toggle Markdown rendering of assistant text — _extensions/adapters/presenters/tui/init.fnl:681_
- <a id="register-site-command-animations-extensions-adapters-presenters-tui-init-fnl-697"></a>`animations` — Toggle TUI busy animations — _extensions/adapters/presenters/tui/init.fnl:697_
- <a id="register-site-command-thinking-blocks-extensions-adapters-presenters-tui-init-fnl-714"></a>`thinking-blocks` — Show or hide assistant thinking blocks — _extensions/adapters/presenters/tui/init.fnl:714_
- <a id="register-site-command-errors-extensions-adapters-presenters-tui-init-fnl-733"></a>`errors` — Toggle recent error details / tracebacks — _extensions/adapters/presenters/tui/init.fnl:733_
- <a id="register-site-command-redraw-extensions-adapters-presenters-tui-init-fnl-753"></a>`redraw` — Force a full terminal repaint to recover from corruption — _extensions/adapters/presenters/tui/init.fnl:753_
- <a id="register-site-command-new-extensions-behaviors-actions-sessions-commands-session-fnl-159"></a>`new` — Reset the current conversation and start a fresh session — _extensions/behaviors/actions/sessions/commands/session.fnl:159_
- <a id="register-site-command-reload-extensions-behaviors-actions-sessions-commands-session-fnl-265"></a>`reload` — Hot-reload core modules and source overlays — _extensions/behaviors/actions/sessions/commands/session.fnl:265_
- <a id="register-site-command-n-extensions-behaviors-actions-sessions-commands-session-fnl-319"></a>`n` — Alias for /new — _extensions/behaviors/actions/sessions/commands/session.fnl:319_
- <a id="register-site-command-sessions-extensions-behaviors-actions-sessions-commands-session-fnl-326"></a>`sessions` — Pick a recent session to resume (overlay) — _extensions/behaviors/actions/sessions/commands/session.fnl:326_
- <a id="register-site-command-resume-extensions-behaviors-actions-sessions-commands-session-fnl-332"></a>`resume` — Resume a session (overlay if no arg; id/prefix/path/index if given) — _extensions/behaviors/actions/sessions/commands/session.fnl:332_
- <a id="register-site-command-r-extensions-behaviors-actions-sessions-commands-session-fnl-343"></a>`r` — Alias for /reload — _extensions/behaviors/actions/sessions/commands/session.fnl:343_
- <a id="register-site-command-compact-extensions-behaviors-companions-compact-init-fnl-233"></a>`compact` — Summarize older context and keep recent messages in this session — _extensions/behaviors/companions/compact/init.fnl:233_
- <a id="register-site-command-handoff-extensions-behaviors-companions-handoff-init-fnl-141"></a>`handoff` — Summarize this session, seed a fresh session with the summary — _extensions/behaviors/companions/handoff/init.fnl:141_
- <a id="register-site-command-mem-extensions-behaviors-companions-mem-init-fnl-246"></a>`mem` — Toggle the memory diagnostics panel; /mem gc forces a GC pass — _extensions/behaviors/companions/mem/init.fnl:246_
- <a id="register-site-command-skills-extensions-behaviors-companions-skills-init-fnl-711"></a>`skills` — Pick a skill, show details, or list discovered Agent Skills — _extensions/behaviors/companions/skills/init.fnl:711_
- <a id="register-site-command-todos-extensions-behaviors-companions-todo-init-fnl-305"></a>`todos` — Toggle the todo panel; /todos show prints the current list — _extensions/behaviors/companions/todo/init.fnl:305_
- <a id="register-site-command-reload-extension-extensions-behaviors-inspectors-extensions-commands-extension-fnl-464"></a>`reload-extension` — Reload one external extension by name — _extensions/behaviors/inspectors/extensions/commands/extension.fnl:464_
- <a id="register-site-command-extensions-extensions-behaviors-inspectors-extensions-commands-extension-fnl-494"></a>`extensions` — Pick an extension, show details, or inspect live registry — _extensions/behaviors/inspectors/extensions/commands/extension.fnl:494_
- <a id="register-site-command-prompt-extensions-behaviors-inspectors-prompt-commands-prompt-fnl-105"></a>`prompt` — Toggle the prompt-fragments panel; /prompt rendered emits the rendered prompt — _extensions/behaviors/inspectors/prompt/commands/prompt.fnl:105_
- <a id="register-site-command-queue-extensions-behaviors-inspectors-queue-commands-queue-fnl-148"></a>`queue` — Toggle the queue panel; /queue clear|mode preserve their actions — _extensions/behaviors/inspectors/queue/commands/queue.fnl:148_
- <a id="register-site-command-cancel-all-extensions-behaviors-inspectors-queue-commands-queue-fnl-163"></a>`cancel-all` — Cancel current turn and clear queues — _extensions/behaviors/inspectors/queue/commands/queue.fnl:163_
- <a id="register-site-command-status-extensions-behaviors-inspectors-status-commands-status-fnl-157"></a>`status` — Toggle the status panel (model, provider, tokens, session) — _extensions/behaviors/inspectors/status/commands/status.fnl:157_
- <a id="register-site-command-docs-extensions-behaviors-kernel-docs-init-fnl-484"></a>`docs` — Browse runtime docs: /docs [topic] [name] — _extensions/behaviors/kernel/docs/init.fnl:484_
- <a id="register-site-command-help-extensions-behaviors-kernel-essentials-commands-help-fnl-94"></a>`help` — Show available commands and controls — _extensions/behaviors/kernel/essentials/commands/help.fnl:94_
- <a id="register-site-command-model-extensions-behaviors-kernel-essentials-commands-model-fnl-121"></a>`model` — Switch model (overlay if no arg; index/name/substring if given) — _extensions/behaviors/kernel/essentials/commands/model.fnl:121_
- <a id="register-site-command-thinking-extensions-behaviors-kernel-essentials-commands-thinking-fnl-115"></a>`thinking` — Show/set thinking effort; /thinking blocks on|off toggles display — _extensions/behaviors/kernel/essentials/commands/thinking.fnl:115_

## <a id="extension-kind-control"></a>:control

- <a id="register-site-control-jump-to-user-message-extensions-adapters-presenters-tui-init-fnl-623"></a>`jump-to-user-message` — Jump to the latest user message; repeat for previous messages — _extensions/adapters/presenters/tui/init.fnl:623_
- <a id="register-site-control-jump-to-live-bottom-extensions-adapters-presenters-tui-init-fnl-629"></a>`jump-to-live-bottom` — Jump to the live bottom and resume following transcript output — _extensions/adapters/presenters/tui/init.fnl:629_
- <a id="register-site-control-toggle-tool-results-extensions-adapters-presenters-tui-init-fnl-635"></a>`toggle-tool-results` — Toggle tool-result bodies — _extensions/adapters/presenters/tui/init.fnl:635_
- <a id="register-site-control-toggle-thinking-blocks-extensions-adapters-presenters-tui-init-fnl-641"></a>`toggle-thinking-blocks` — Toggle thinking blocks — _extensions/adapters/presenters/tui/init.fnl:641_
- <a id="register-site-control-quit-extensions-adapters-presenters-tui-init-fnl-647"></a>`quit` — Quit; ctrl-c also clears input or cancels a busy turn — _extensions/adapters/presenters/tui/init.fnl:647_
- <a id="register-site-control-hard-refresh-extensions-adapters-presenters-tui-init-fnl-653"></a>`hard-refresh` — Redraw the screen / recover from terminal corruption — _extensions/adapters/presenters/tui/init.fnl:653_
- <a id="register-site-control-suspend-extensions-adapters-presenters-tui-init-fnl-659"></a>`suspend` — Suspend to the shell (resume with fg) — _extensions/adapters/presenters/tui/init.fnl:659_

## <a id="extension-kind-extension"></a>:extension

- <a id="register-site-extension-print-extensions-adapters-presenters-print-manifest-fnl-1"></a>`print` — One-shot stdout presenter for --print — _extensions/adapters/presenters/print/manifest.fnl:1_
- <a id="register-site-extension-stdio-extensions-adapters-presenters-stdio-manifest-fnl-1"></a>`stdio` — Line-mode stdin/stdout presenter — _extensions/adapters/presenters/stdio/manifest.fnl:1_
- <a id="register-site-extension-tui-extensions-adapters-presenters-tui-manifest-fnl-1"></a>`tui` — First-party termbox2 presenter — _extensions/adapters/presenters/tui/manifest.fnl:1_
- <a id="register-site-extension-web-extensions-adapters-presenters-web-manifest-fnl-1"></a>`web` — First-party LuaSocket/SSE browser presenter — _extensions/adapters/presenters/web/manifest.fnl:1_
- <a id="register-site-extension-provider-anthropic-extensions-adapters-providers-anthropic-manifest-fnl-1"></a>`provider_anthropic` — First-party Anthropic Messages provider. — _extensions/adapters/providers/anthropic/manifest.fnl:1_
- <a id="register-site-extension-provider-openai-extensions-adapters-providers-openai-manifest-fnl-1"></a>`provider_openai` — First-party OpenAI provider family (Chat Completions, Responses, Codex subscription, and Codex OAuth auth). — _extensions/adapters/providers/openai/manifest.fnl:1_
- <a id="register-site-extension-session-jsonl-extensions-adapters-session-backends-jsonl-manifest-fnl-1"></a>`session_jsonl` — JSONL session backend — _extensions/adapters/session-backends/jsonl/manifest.fnl:1_
- <a id="register-site-extension-sessions-extensions-behaviors-actions-sessions-manifest-fnl-1"></a>`sessions` — Conversation and session lifecycle commands: new, reload, sessions, resume, and aliases. — _extensions/behaviors/actions/sessions/manifest.fnl:1_
- <a id="register-site-extension-agent-state-extensions-behaviors-companions-agent-state-manifest-fnl-1"></a>`agent_state` — Read-only introspection tool for the running agent — _extensions/behaviors/companions/agent-state/manifest.fnl:1_
- <a id="register-site-extension-compact-extensions-behaviors-companions-compact-manifest-fnl-1"></a>`compact` — Context compaction command: summarize older messages and keep recent context. — _extensions/behaviors/companions/compact/manifest.fnl:1_
- <a id="register-site-extension-handoff-extensions-behaviors-companions-handoff-manifest-fnl-1"></a>`handoff` — Session handoff command: summarize current context and seed a fresh session. — _extensions/behaviors/companions/handoff/manifest.fnl:1_
- <a id="register-site-extension-mem-extensions-behaviors-companions-mem-manifest-fnl-1"></a>`mem` — Runtime memory diagnostics command — _extensions/behaviors/companions/mem/manifest.fnl:1_
- <a id="register-site-extension-skills-extensions-behaviors-companions-skills-manifest-fnl-1"></a>`skills` — Agent Skills discovery and prompt fragment — _extensions/behaviors/companions/skills/manifest.fnl:1_
- <a id="register-site-extension-todo-extensions-behaviors-companions-todo-manifest-fnl-1"></a>`todo` — Structured todo list companion tool, panel, and status item — _extensions/behaviors/companions/todo/manifest.fnl:1_
- <a id="register-site-extension-extensions-inspector-extensions-behaviors-inspectors-extensions-manifest-fnl-1"></a>`extensions_inspector` — Extension inspector: /extensions, /reload-extension, and extension detail panel. — _extensions/behaviors/inspectors/extensions/manifest.fnl:1_
- <a id="register-site-extension-prompt-extensions-behaviors-inspectors-prompt-manifest-fnl-1"></a>`prompt` — Prompt inspector: /prompt command and prompt-fragment panel. — _extensions/behaviors/inspectors/prompt/manifest.fnl:1_
- <a id="register-site-extension-queue-extensions-behaviors-inspectors-queue-manifest-fnl-1"></a>`queue` — Queue inspector: /queue, /cancel-all, and queue panel. — _extensions/behaviors/inspectors/queue/manifest.fnl:1_
- <a id="register-site-extension-status-extensions-behaviors-inspectors-status-manifest-fnl-1"></a>`status` — Runtime status inspector: /status command and status panel. — _extensions/behaviors/inspectors/status/manifest.fnl:1_
- <a id="register-site-extension-builtin-tools-extensions-behaviors-kernel-builtin-tools-manifest-fnl-1"></a>`builtin_tools` — Built-in fen tools: bash, read, write, ls, edit, grep, find. — _extensions/behaviors/kernel/builtin-tools/manifest.fnl:1_
- <a id="register-site-extension-default-prompt-extensions-behaviors-kernel-default-prompt-manifest-fnl-1"></a>`default_prompt` — First-party default system prompt policy — _extensions/behaviors/kernel/default-prompt/manifest.fnl:1_
- <a id="register-site-extension-docs-extensions-behaviors-kernel-docs-manifest-fnl-1"></a>`docs` — In-agent runtime documentation browser — _extensions/behaviors/kernel/docs/manifest.fnl:1_
- <a id="register-site-extension-essentials-extensions-behaviors-kernel-essentials-manifest-fnl-1"></a>`essentials` — Essential fen slash commands: help and model selection. — _extensions/behaviors/kernel/essentials/manifest.fnl:1_

## <a id="extension-kind-introspect"></a>:introspect

- <a id="register-site-introspect-runtime-extensions-adapters-presenters-tui-init-fnl-760"></a>`runtime` — Current TUI presenter state summary without transcript or input contents — _extensions/adapters/presenters/tui/init.fnl:760_
- <a id="register-site-introspect-runtime-extensions-adapters-presenters-web-init-fnl-181"></a>`runtime` — Current web presenter server/client state summary — _extensions/adapters/presenters/web/init.fnl:181_
- <a id="register-site-introspect-active-session-extensions-behaviors-actions-sessions-commands-session-fnl-351"></a>`active-session` — Current session selection and persistence backend summary — _extensions/behaviors/actions/sessions/commands/session.fnl:351_
- <a id="register-site-introspect-tool-extensions-behaviors-companions-agent-state-init-fnl-29"></a>`tool` — agent_state query language capabilities — _extensions/behaviors/companions/agent-state/init.fnl:29_
- <a id="register-site-introspect-diagnostics-extensions-behaviors-companions-mem-init-fnl-262"></a>`diagnostics` — Current memory diagnostics panel, heap, and sample history summary — _extensions/behaviors/companions/mem/init.fnl:262_
- <a id="register-site-introspect-discovered-skills-extensions-behaviors-companions-skills-init-fnl-734"></a>`discovered-skills` — Discovered Agent Skills, source scopes, paths, and model visibility — _extensions/behaviors/companions/skills/init.fnl:734_
- <a id="register-site-introspect-state-extensions-behaviors-companions-todo-init-fnl-317"></a>`state` — Current todo list counts and panel state — _extensions/behaviors/companions/todo/init.fnl:317_
- <a id="register-site-introspect-panel-extensions-behaviors-inspectors-extensions-commands-extension-fnl-512"></a>`panel` — Current /extensions panel state and cache metadata — _extensions/behaviors/inspectors/extensions/commands/extension.fnl:512_
- <a id="register-site-introspect-panel-extensions-behaviors-inspectors-prompt-commands-prompt-fnl-120"></a>`panel` — Current prompt-fragment panel state and fragment counts — _extensions/behaviors/inspectors/prompt/commands/prompt.fnl:120_
- <a id="register-site-introspect-panel-extensions-behaviors-inspectors-queue-commands-queue-fnl-182"></a>`panel` — Current queue panel and pending steering/follow-up counts — _extensions/behaviors/inspectors/queue/commands/queue.fnl:182_
- <a id="register-site-introspect-panel-extensions-behaviors-inspectors-status-commands-status-fnl-169"></a>`panel` — Current status panel cache and last captured run-state summary — _extensions/behaviors/inspectors/status/commands/status.fnl:169_
- <a id="register-site-introspect-panel-extensions-behaviors-kernel-docs-init-fnl-528"></a>`panel` — Current docs browser panel state and topic counts — _extensions/behaviors/kernel/docs/init.fnl:528_

## <a id="extension-kind-panel"></a>:panel

- <a id="register-site-panel-errors-extensions-adapters-presenters-tui-init-fnl-589"></a>`errors` — TUI error introspection panel showing recent error summaries and traceback details. — _extensions/adapters/presenters/tui/init.fnl:589_
- <a id="register-site-panel-busy-extensions-adapters-presenters-tui-init-fnl-593"></a>`busy` — TUI busy-state panel showing spinner, retry information, and current turn elapsed time. — _extensions/adapters/presenters/tui/init.fnl:593_
- <a id="register-site-panel-busy-extensions-adapters-presenters-web-init-fnl-162"></a>`busy` — Web presenter spinner row shown while the agent is busy. — _extensions/adapters/presenters/web/init.fnl:162_
- <a id="register-site-panel-mem-extensions-behaviors-companions-mem-init-fnl-260"></a>`mem` — Memory diagnostics panel backing the /mem command and heap history display. — _extensions/behaviors/companions/mem/init.fnl:260_
- <a id="register-site-panel-skills-extensions-behaviors-companions-skills-init-fnl-733"></a>`skills` — Skill picker/detail panel backing the /skills command. — _extensions/behaviors/companions/skills/init.fnl:733_
- <a id="register-site-panel-dynamic-extensions-behaviors-companions-todo-init-fnl-311"></a>_(dynamic)_ — Registered (dynamic) panel contribution. — _extensions/behaviors/companions/todo/init.fnl:311_
- <a id="register-site-panel-extensions-extensions-behaviors-inspectors-extensions-commands-extension-fnl-510"></a>`extensions` — Extension detail and picker panel backing the /extensions command. — _extensions/behaviors/inspectors/extensions/commands/extension.fnl:510_
- <a id="register-site-panel-prompt-extensions-behaviors-inspectors-prompt-commands-prompt-fnl-118"></a>`prompt` — Prompt-fragment inspection panel backing the /prompt command. — _extensions/behaviors/inspectors/prompt/commands/prompt.fnl:118_
- <a id="register-site-panel-queue-extensions-behaviors-inspectors-queue-commands-queue-fnl-180"></a>`queue` — Queued follow-up/cancel-all panel backing queue-management commands. — _extensions/behaviors/inspectors/queue/commands/queue.fnl:180_
- <a id="register-site-panel-status-extensions-behaviors-inspectors-status-commands-status-fnl-167"></a>`status` — Runtime status details panel backing the /status command. — _extensions/behaviors/inspectors/status/commands/status.fnl:167_
- <a id="register-site-panel-docs-extensions-behaviors-kernel-docs-init-fnl-526"></a>`docs` — Runtime documentation browser panel backing the /docs command and fen_docs tool. — _extensions/behaviors/kernel/docs/init.fnl:526_

## <a id="extension-kind-presenter"></a>:presenter

- <a id="register-site-presenter-print-extensions-adapters-presenters-print-init-fnl-34"></a>`print` — Registered print presenter contribution. — _extensions/adapters/presenters/print/init.fnl:34_
- <a id="register-site-presenter-stdio-extensions-adapters-presenters-stdio-init-fnl-281"></a>`stdio` — Registered stdio presenter contribution. — _extensions/adapters/presenters/stdio/init.fnl:281_
- <a id="register-site-presenter-tui-extensions-adapters-presenters-tui-init-fnl-601"></a>`tui` — Registered tui presenter contribution. — _extensions/adapters/presenters/tui/init.fnl:601_
- <a id="register-site-presenter-web-extensions-adapters-presenters-web-init-fnl-170"></a>`web` — Registered web presenter contribution. — _extensions/adapters/presenters/web/init.fnl:170_

## <a id="extension-kind-provider"></a>:provider

- <a id="register-site-provider-anthropic-extensions-adapters-providers-anthropic-init-fnl-20"></a>`anthropic` — Anthropic Messages provider using ANTHROPIC_API_KEY and the default claude-haiku-4-5 model. — _extensions/adapters/providers/anthropic/init.fnl:20_
- <a id="register-site-provider-openai-extensions-adapters-providers-openai-init-fnl-44"></a>`openai` — OpenAI Chat Completions provider using OPENAI_API_KEY and the default gpt-5.4-nano model. — _extensions/adapters/providers/openai/init.fnl:44_
- <a id="register-site-provider-openai-responses-extensions-adapters-providers-openai-init-fnl-50"></a>`openai-responses` — OpenAI Responses API provider using OPENAI_API_KEY and the default gpt-5.4-nano model. — _extensions/adapters/providers/openai/init.fnl:50_
- <a id="register-site-provider-openai-codex-extensions-adapters-providers-openai-init-fnl-66"></a>`openai-codex` — ChatGPT subscription/Codex Responses provider using the openai-codex OAuth auth backend and default gpt-5.5 model. — _extensions/adapters/providers/openai/init.fnl:66_

## <a id="extension-kind-session-backend"></a>:session-backend

- <a id="register-site-session-backend-jsonl-extensions-adapters-session-backends-jsonl-init-fnl-9"></a>`jsonl` — Append-only JSONL session backend under XDG state. Records canonical messages, replayable via --continue / /resume. — _extensions/adapters/session-backends/jsonl/init.fnl:9_

## <a id="extension-kind-status"></a>:status

- <a id="register-site-status-model-extensions-adapters-presenters-tui-init-fnl-506"></a>`model` — Registered model status-line item contribution. — _extensions/adapters/presenters/tui/init.fnl:506_
- <a id="register-site-status-thinking-extensions-adapters-presenters-tui-init-fnl-515"></a>`thinking` — Registered thinking status-line item contribution. — _extensions/adapters/presenters/tui/init.fnl:515_
- <a id="register-site-status-context-extensions-adapters-presenters-tui-init-fnl-524"></a>`context` — Registered context status-line item contribution. — _extensions/adapters/presenters/tui/init.fnl:524_
- <a id="register-site-status-steering-queue-extensions-adapters-presenters-tui-init-fnl-533"></a>`steering-queue` — Registered steering-queue status-line item contribution. — _extensions/adapters/presenters/tui/init.fnl:533_
- <a id="register-site-status-follow-up-queue-extensions-adapters-presenters-tui-init-fnl-543"></a>`follow-up-queue` — Registered follow-up-queue status-line item contribution. — _extensions/adapters/presenters/tui/init.fnl:543_
- <a id="register-site-status-attention-extensions-adapters-presenters-tui-init-fnl-553"></a>`attention` — Registered attention status-line item contribution. — _extensions/adapters/presenters/tui/init.fnl:553_
- <a id="register-site-status-scroll-extensions-adapters-presenters-tui-init-fnl-564"></a>`scroll` — Registered scroll status-line item contribution. — _extensions/adapters/presenters/tui/init.fnl:564_
- <a id="register-site-status-version-extensions-adapters-presenters-tui-init-fnl-574"></a>`version` — Registered version status-line item contribution. — _extensions/adapters/presenters/tui/init.fnl:574_
- <a id="register-site-status-model-extensions-adapters-presenters-web-init-fnl-115"></a>`model` — Registered model status-line item contribution. — _extensions/adapters/presenters/web/init.fnl:115_
- <a id="register-site-status-context-extensions-adapters-presenters-web-init-fnl-124"></a>`context` — Registered context status-line item contribution. — _extensions/adapters/presenters/web/init.fnl:124_
- <a id="register-site-status-steering-queue-extensions-adapters-presenters-web-init-fnl-133"></a>`steering-queue` — Registered steering-queue status-line item contribution. — _extensions/adapters/presenters/web/init.fnl:133_
- <a id="register-site-status-follow-up-queue-extensions-adapters-presenters-web-init-fnl-143"></a>`follow-up-queue` — Registered follow-up-queue status-line item contribution. — _extensions/adapters/presenters/web/init.fnl:143_
- <a id="register-site-status-attention-extensions-adapters-presenters-web-init-fnl-153"></a>`attention` — Registered attention status-line item contribution. — _extensions/adapters/presenters/web/init.fnl:153_
- <a id="register-site-status-todo-extensions-behaviors-companions-todo-init-fnl-312"></a>`todo` — Registered todo status-line item contribution. — _extensions/behaviors/companions/todo/init.fnl:312_

## <a id="extension-kind-tool"></a>:tool

- <a id="register-site-tool-agent-state-extensions-behaviors-companions-agent-state-init-fnl-13"></a>`agent_state` — Read structured state of the running agent. Read-only; does not evaluate code. Query is a tiny Fennel-shaped data language. Examples: (:get :model), (:get :thinking), (:count (:get :messages)), (:get :messages -1), (:pluck (:get :tools) :name), (:get :extensions :panels), (:where (:get :messages) :role :assistant), (:last (:where (:get :messages) :role :assistant)), (:slice (:get :messages) -5 5), (:keys (:get)). Prefer narrow queries over dumping large roots. Output defaults to JSON; use format=fennel for Fennel rendering when available. — _extensions/behaviors/companions/agent-state/init.fnl:13_
- <a id="register-site-tool-todo-write-extensions-behaviors-companions-todo-init-fnl-289"></a>`todo_write` — Create or update the structured todo list for this session. Use for non-trivial multi-step work. This tool overwrites the full current list; provide every item that should remain. Status must be pending, in_progress, or completed, with at most one in_progress item. Use an empty items array to clear the list. — _extensions/behaviors/companions/todo/init.fnl:289_
- <a id="register-site-tool-builtin-tool-registry-extensions-behaviors-kernel-builtin-tools-init-fnl-17"></a>`builtin-tool-registry` — Dynamic loop registering every built-in tool spec from the builtin tools registry. — _extensions/behaviors/kernel/builtin-tools/init.fnl:17_
- <a id="register-site-tool-fen-docs-extensions-behaviors-kernel-docs-init-fnl-506"></a>`fen_docs` — Read or search fen runtime docs and extension contracts. Useful for implementing extensions: inspect register kinds, canonical types, event shapes, and live commands/tools/providers. Topics: topics, commands, tools, providers, auth-backends, session-backends, presenters, controls, status, panels, prompt-fragments, introspectors, events, types, register-kinds, interfaces, extensions. Use name for a specific entry, e.g. {topic:'register-kinds', name:'tool'} or {topic:'types', name:'ToolResultMessage'}. Use query to search docs, optionally scoped by topic. — _extensions/behaviors/kernel/docs/init.fnl:506_