register-kinds

Extension API register kinds.

auth-backend #

Auth credential backend. Resolves an api-key or rotates an OAuth token for one or more providers.

Fields for auth-backend register-kind contract

Field	Type	Required	Summary
:api-key #	() -> string|nil	yes	Return the current bearer/API key, refreshing or loading secrets as needed.
:login! #	(opts) -> any		Optional. Drives fen --login <name>.
:logout! #	() -> any		Optional. Drives fen --logout <name>.
:name #	keyword|string	yes	Auth backend name selected by provider configuration or CLI login/logout flags.

command #

Slash command contribution. Looked up by name when the user submits /<name> <args> from a presenter.

Fields for command register-kind contract

Field	Type	Required	Summary
:description #	string		Human-readable command help shown in command listings and docs.
:handler #	(args caller-state) -> any	yes	Callback invoked with raw command arguments and the caller's runtime state.
:idle-only? #	boolean		Refuse the command while the agent is busy.
:name #	keyword|string	yes	Command name without the leading slash.
:order #	number		Sort hint for /help.

control #

Keyboard/UI control surface for presenters that support typed input bindings.

Fields for control register-kind contract

Field	Type	Required	Summary
:description #	string		Human-readable explanation of the control's UI effect.
:handler #	(ctx) -> any	yes	Callback invoked by the presenter when the control is activated.
:name #	keyword|string	yes	Stable control name exposed to presenter help and docs.

hook #

Lifecycle hook (currently before-tool). Inspects a tool call before it executes.

Fields for hook register-kind contract

Field	Type	Required	Summary
:before-tool #	(tool-name args ctx) -> any	yes	Return {:block true :reason string} to veto.

introspect #

Read-only extension state snapshot provider. Collected on demand for agent_state, /extensions, and runtime diagnostics.

Fields for introspect register-kind contract

Field	Type	Required	Summary
:description #	string		Human-readable description shown by diagnostics and docs.
:name #	keyword|string	yes	Owner-scoped snapshot name. Multiple extensions may reuse the same name.
:snapshot #	(ctx) -> table	yes	Cheap, side-effect-free thunk returning JSON-friendly data. It is pcall-isolated and should not expose secrets.

panel #

Non-modal side panel contribution rendered by presenters that support panels.

Fields for panel register-kind contract

Field	Type	Required	Summary
:enabled? #	(ctx) -> boolean		Optional predicate that hides the panel without unregistering it.
:name #	keyword|string	yes	Stable panel name used for toggles, docs, and diagnostics.
:render #	(ctx) -> any	yes	Callback returning rows or presenter-specific content for the panel body.
:title #	string		Optional display title when the presenter renders panel chrome.

presenter #

UI driver. Owns the input/output loop. Exactly one is active per run; the loader picks based on flags and manifest hints.

Fields for presenter register-kind contract

Field	Type	Required	Summary
:init #	(ctx) -> nil		Optional lifecycle callback run before the presenter loop starts.
:name #	keyword|string	yes	Presenter name selected by CLI flags or extension activation rules.
:run #	(ctx) -> nil	yes	Main input/output loop for the selected presenter.
:shutdown #	(ctx) -> nil		Optional lifecycle callback used to release terminal, socket, or other UI resources.

provider #

LLM provider contribution. See the :provider-interface contract for the required record.

Fields for provider register-kind contract

Field	Type	Required	Summary
:api #	keyword	yes	Protocol family (:openai-completions, :anthropic-messages, ...). Many providers may share an :api.
:build-body #	(model ctx options) -> table	yes	Build the provider request body from a model id, AgentContext, and call options.
:complete #	(model ctx options ?on-event ?yield-fn) -> AssistantMessage	yes	High-level provider entry point that runs one model turn and returns a canonical assistant message.
:convert-messages #	([Message]) -> [WireMessage]	yes	Translate canonical conversation messages into this provider's wire message format.
:convert-tools #	([Tool]) -> [WireTool]	yes	Translate canonical tool specs into this provider's wire tool schema.
:map-stop-reason #	(string) -> StopReason	yes	Normalize provider stop reasons into fen's canonical StopReason enum.
:name #	keyword|string	yes	Provider name selected by settings or CLI options.
:parse-response #	(WireResponse) -> AssistantMessage	yes	Convert a non-streaming provider response payload into an AssistantMessage.

session-backend #

Persistence backend for canonical JSONL-style sessions. The --session flag selects one and fen.core.extensions.register.session_backend.set-active! activates it.

Fields for session-backend register-kind contract

Field	Type	Required	Summary
:append #	(session message) -> nil	yes	Persist one canonical Message to the active session.
:close #	(session) -> nil	yes	Flush and release backend resources for an open session.
:find #	(opts) -> [SessionInfo]	yes	Search sessions using backend-specific filters.
:latest #	(opts) -> SessionInfo|nil	yes	Return the newest matching session, if any.
:list #	(opts) -> [SessionInfo]	yes	List sessions visible to this backend in a stable display order.
:load #	(path opts) -> [Message]	yes	Read canonical messages from a stored session path.
:name #	keyword|string	yes	Session backend name selected by CLI flags or extension configuration.
:open #	(opts) -> session	yes	Create or open the active session for a new run.
:open-existing #	(path opts) -> session	yes	Open an existing session file or directory for appending.

status #

Status-line contributor — produces a short string for the presenter's status row.

Fields for status register-kind contract

Field	Type	Required	Summary
:name #	keyword|string	yes	Stable status item name used for sorting, diagnostics, and docs.
:order #	number		Sort hint within the status side; lower values render earlier.
:render #	(ctx) -> string|nil	yes	Callback returning the current status text, or nil/empty text to hide it.

tool #

Agent tool contribution. Merged into the per-step AgentContext.tools and dispatched by name when the assistant emits a ToolCall.

Fields for tool register-kind contract

Field	Type	Required	Summary
:description #	string	yes	Provider-facing guidance explaining when the model should call this tool.
:execute #	(args ?yield-fn) -> AgentToolResult	yes	Runtime callback that executes decoded arguments and returns canonical tool content.
:label #	string		Optional short UI label shown by presenters while the tool runs.
:name #	string	yes	Unique tool name exposed to providers and matched against ToolCall.name.
:parameters #	JSONSchema	yes	JSON object schema describing the tool arguments providers may emit.