Fen contracts

events #

Event-bus shapes.

agent-shutdown #

Emitted once per run during teardown. :error is present for crashed paths.

Fields for agent-shutdown event contract

Field	Type	Required	Summary
:agent #	Agent	yes	Agent instance associated with the event.
:error #	string		Crash details when shutdown follows an error path.
:reason #	keyword	yes	:normal | :crashed
:type #	:agent-shutdown	yes	Event discriminator for :agent-shutdown events.

agent-started #

Emitted once per run after setup and before the first new step.

Fields for agent-started event contract

Field	Type	Required	Summary
:agent #	Agent	yes	Agent instance associated with the event.
:cwd #	string	yes	Working directory for the active agent run.
:model #	string	yes	Model identifier selected for the active run.
:provider #	keyword|string	yes	Provider name selected for the active run.
:type #	:agent-started	yes	Event discriminator for :agent-started events.

agent-turn-complete #

Emitted once per submitted user turn after the agent coroutine finishes and the presenter busy flag has been cleared.

Fields for agent-turn-complete event contract

Field	Type	Required	Summary
:agent #	Agent	yes	Agent instance associated with the completed turn.
:error #	string		Error summary when the turn ended with :status :error.
:message-count #	number	yes	Conversation message count after the turn finished.
:result #	string		Final visible assistant text for successful or cancelled turns, when available.
:status #	keyword	yes	:ok | :cancelled | :error
:type #	:agent-turn-complete	yes	Event discriminator for :agent-turn-complete events.

assistant-stream-end #

Stream finished. Emitted once after all per-block end events for a single AssistantMessage.

Fields for assistant-stream-end event contract

Field	Type	Required	Summary
:type #	:assistant-stream-end	yes	Event discriminator for :assistant-stream-end events.

assistant-text #

Final visible text emitted by the assistant. One per AssistantMessage with text blocks.

Fields for assistant-text event contract

Field	Type	Required	Summary
:final? #	boolean		True when this is the final aggregate payload for the current block.
:text #	string	yes	Complete assistant text payload for this event.
:type #	:assistant-text	yes	Event discriminator for :assistant-text events.

assistant-text-delta #

Streaming text token. Aggregated by presenters during a stream.

Fields for assistant-text-delta event contract

Field	Type	Required	Summary
:delta #	string	yes	Incremental streamed text fragment for the open content block.
:type #	:assistant-text-delta	yes	Event discriminator for :assistant-text-delta events.

assistant-thinking #

Final reasoning text from the assistant (for providers that surface reasoning content).

Fields for assistant-thinking event contract

Field	Type	Required	Summary
:final? #	boolean		True when this is the final aggregate payload for the current block.
:text #	string	yes	Complete assistant text payload for this event.
:type #	:assistant-thinking	yes	Event discriminator for :assistant-thinking events.

assistant-thinking-delta #

Streaming reasoning token.

Fields for assistant-thinking-delta event contract

Field	Type	Required	Summary
:delta #	string	yes	Incremental streamed text fragment for the open content block.
:type #	:assistant-thinking-delta	yes	Event discriminator for :assistant-thinking-delta events.

cancelled #

Cooperative cancel observed; the current step appended an aborted assistant message.

Fields for cancelled event contract

Field	Type	Required	Summary
:type #	:cancelled	yes	Event discriminator for :cancelled events.

compaction-summary #

Context compaction completed and produced a summary for older messages.

Fields for compaction-summary event contract

Field	Type	Required	Summary
:guidance #	string		Optional user guidance supplied to /compact.
:messages-kept #	number		Number of recent messages kept verbatim.
:messages-summarized #	number		Number of older messages summarized.
:summary #	string	yes	Summary text installed into the compacted model context.
:tokens-after #	number		Approximate context tokens after compaction.
:tokens-before #	number		Approximate context tokens before compaction.
:trigger #	keyword		Why compaction ran, such as :manual.
:type #	:compaction-summary	yes	Event discriminator for :compaction-summary events.

dismiss #

Presenter signal that an open overlay/picker should close.

Fields for dismiss event contract

Field	Type	Required	Summary
:type #	:dismiss	yes	Event discriminator for :dismiss events.

done #

Provider stream: terminal event for a successful AssistantMessage.

Fields for done event contract

Field	Type	Required	Summary
:message #	AssistantMessage	yes	Canonical assistant message produced by the provider stream.
:type #	:done	yes	Event discriminator for :done events.

error #

Generic surface error — typically command-dispatch or user-input failures.

Fields for error event contract

Field	Type	Required	Summary
:error #	string	yes	Human-readable error message for presenters and logs.
:type #	:error	yes	Event discriminator for :error events.

extension-error #

Emitted when an extension event handler raises. Suppressed for recursive extension-error events to prevent loops.

Fields for extension-error event contract

Field	Type	Required	Summary
:error #	string	yes	Human-readable error message for presenters and logs.
:event #	keyword|string		Original event being handled when the extension error occurred.
:owner #	keyword|string		Extension owner whose handler raised, when known.
:type #	:extension-error	yes	Event discriminator for :extension-error events.

extension-loaded #

Emitted by the loader for each successfully loaded extension manifest.

Fields for extension-loaded event contract

Field	Type	Required	Summary
:first-party? #	boolean		True when the loaded extension came from fen's bundled extension set.
:name #	string	yes	Extension manifest name that was loaded.
:type #	:extension-loaded	yes	Event discriminator for :extension-loaded events.

info #

Transient informational message intended for the presenter status row or panel.

Fields for info event contract

Field	Type	Required	Summary
:info #	string		Human-readable informational message payload.
:text #	string		Alternative human-readable informational text.
:type #	:info	yes	Event discriminator for :info events.

llm-end #

Provider call completed (success or error). The :message field carries the canonical AssistantMessage.

Fields for llm-end event contract

Field	Type	Required	Summary
:message #	AssistantMessage	yes	Canonical assistant message produced by the provider stream.
:type #	:llm-end	yes	Event discriminator for :llm-end events.

llm-start #

Provider call beginning.

Fields for llm-start event contract

Field	Type	Required	Summary
:model #	string		Model identifier used for the provider request, when known.
:provider #	keyword		Provider name for the outbound LLM call, when known.
:type #	:llm-start	yes	Event discriminator for :llm-start events.

message-appended #

Emitted by fen.core.agent immediately after agent.messages grows.

Fields for message-appended event contract

Field	Type	Required	Summary
:agent #	Agent	yes	Agent instance associated with the event.
:index #	number	yes	1-based index of the appended message.
:message #	Message	yes	Canonical message that was appended to the conversation.
:type #	:message-appended	yes	Event discriminator for :message-appended events.

queued #

User-line queued while the agent is busy. Consumed by the agent on natural-stop.

Fields for queued event contract

Field	Type	Required	Summary
:line #	string	yes	Raw user input line associated with the event.
:type #	:queued	yes	Event discriminator for :queued events.

redraw #

Presenter hint that a registered panel needs to be repainted.

Fields for redraw event contract

Field	Type	Required	Summary
:type #	:redraw	yes	Event discriminator for :redraw events.

reinit-presenter #

Presenter signal that the UI should be torn down and re-initialized (used by /reload).

Fields for reinit-presenter event contract

Field	Type	Required	Summary
:type #	:reinit-presenter	yes	Event discriminator for :reinit-presenter events.

reset-conversation #

Presenter signal that the active conversation should be cleared (used by /new).

Fields for reset-conversation event contract

Field	Type	Required	Summary
:type #	:reset-conversation	yes	Event discriminator for :reset-conversation events.

set-status-info #

Presenter-level status hint. Owners post a transient status line; nil clears.

Fields for set-status-info event contract

Field	Type	Required	Summary
:info #	string|nil		Transient status text to show, or nil to clear it.
:type #	:set-status-info	yes	Event discriminator for :set-status-info events.

start #

Provider stream opened. Marker event emitted before any block events.

Fields for start event contract

Field	Type	Required	Summary
:type #	:start	yes	Event discriminator for :start events.

text-delta #

Provider stream: incremental text token within the open block.

Fields for text-delta event contract

Field	Type	Required	Summary
:content-index #	number	yes	Position within the assistant's content array.
:delta #	string	yes	Incremental streamed text fragment for the open content block.
:type #	:text-delta	yes	Event discriminator for :text-delta events.

text-end #

Provider stream: TextContent block closed; full text supplied.

Fields for text-end event contract

Field	Type	Required	Summary
:content #	string	yes	Complete text or thinking content for the closed stream block.
:content-index #	number	yes	Position within the assistant's content array.
:type #	:text-end	yes	Event discriminator for :text-end events.

text-start #

Provider stream: a TextContent block is starting.

Fields for text-start event contract

Field	Type	Required	Summary
:content-index #	number	yes	Position within the assistant's content array.
:type #	:text-start	yes	Event discriminator for :text-start events.

thinking-delta #

Provider stream: incremental reasoning token within the open block.

Fields for thinking-delta event contract

Field	Type	Required	Summary
:content-index #	number	yes	Position within the assistant's content array.
:delta #	string	yes	Incremental streamed text fragment for the open content block.
:type #	:thinking-delta	yes	Event discriminator for :thinking-delta events.

thinking-end #

Provider stream: ThinkingContent block closed; full text supplied.

Fields for thinking-end event contract

Field	Type	Required	Summary
:content #	string	yes	Complete text or thinking content for the closed stream block.
:content-index #	number	yes	Position within the assistant's content array.
:type #	:thinking-end	yes	Event discriminator for :thinking-end events.

thinking-start #

Provider stream: a ThinkingContent block is starting.

Fields for thinking-start event contract

Field	Type	Required	Summary
:content-index #	number	yes	Position within the assistant's content array.
:type #	:thinking-start	yes	Event discriminator for :thinking-start events.

tool-call #

Tool call about to execute. Carries the canonical ToolCall block.

Fields for tool-call event contract

Field	Type	Required	Summary
:tool-call #	ToolCall	yes	Canonical tool-call block associated with this event.
:type #	:tool-call	yes	Event discriminator for :tool-call events.

tool-call-delta #

Provider stream: incremental JSON-text fragment for the open ToolCall arguments. Some providers stream arguments token-by-token; consumers may concatenate.

Fields for tool-call-delta event contract

Field	Type	Required	Summary
:content-index #	number	yes	Position within the assistant's content array.
:delta #	string	yes	Incremental streamed text fragment for the open content block.
:type #	:tool-call-delta	yes	Event discriminator for :tool-call-delta events.

tool-call-end #

Provider stream: ToolCall block closed; complete canonical ToolCall block supplied.

Fields for tool-call-end event contract

Field	Type	Required	Summary
:content-index #	number	yes	Position within the assistant's content array.
:tool-call #	ToolCall	yes	Canonical tool-call block associated with this event.
:type #	:tool-call-end	yes	Event discriminator for :tool-call-end events.

tool-call-start #

Provider stream: a ToolCall block is starting; arguments not yet known.

Fields for tool-call-start event contract

Field	Type	Required	Summary
:content-index #	number	yes	Position within the assistant's content array.
:type #	:tool-call-start	yes	Event discriminator for :tool-call-start events.

tool-result #

Tool execution finished. Carries the canonical ToolResultMessage.

Fields for tool-result event contract

Field	Type	Required	Summary
:result #	ToolResultMessage	yes	Canonical tool-result message produced by the tool executor.
:type #	:tool-result	yes	Event discriminator for :tool-result events.

user #

User-submitted line accepted by the presenter input layer. Distinct from :queued (which fires when the line is queued during a busy turn).

Fields for user event contract

Field	Type	Required	Summary
:line #	string	yes	Raw user input line associated with the event.
:type #	:user	yes	Event discriminator for :user events.

types #

Canonical message/tool types.

AgentContext #

Per-call payload handed to a provider's :complete.

Fields for AgentContext type contract

Field	Type	Required	Summary
:max-tokens #	number	yes	Maximum output token budget requested for the provider call.
:messages #	[Message]	yes	Canonical conversation history to convert into provider wire format.
:system-prompt #	string|nil		Fully rendered system prompt for the current step, or nil when omitted.
:tools #	[Tool]	yes	Provider-visible tool specs available for this step.

AgentTool #

Tool extended with execution metadata for the agent loop. Registered through (api.register :tool ...).

Fields for AgentTool type contract

Field	Type	Required	Summary
:description #	string	yes	Provider-facing description included in the tool schema.
:execute #	(args ?yield-fn) -> AgentToolResult	yes	Runtime callback that executes the tool with decoded arguments.
:label #	string		UI label.
:name #	string	yes	Registry name used to merge and dispatch the tool.
:parameters #	JSONSchema	yes	Provider-facing argument schema used for validation and prompting.

AgentToolResult #

Outcome of a tool execution.

Fields for AgentToolResult type contract

Field	Type	Required	Summary
:content #	[TextContent]	yes	Text content returned to the provider as the tool observation.
:details #	any		Opaque presenter payload (UI-only).
:is-error? #	boolean	yes	True when the tool observation represents a failed call.

AssistantMessage #

Single model response. Content is always an array, even when empty.

Fields for AssistantMessage type contract

Field	Type	Required	Summary
:api #	keyword		:openai-completions | :openai-responses | :anthropic-messages | :openai-codex
:content #	[TextContent|ThinkingContent|ToolCall]	yes	Ordered assistant output blocks, including visible text, reasoning, and tool calls.
:error-message #	string		Present only when stop-reason = :error.
:model #	string		Provider model identifier that produced this response.
:provider #	keyword		Registered provider :name (e.g. :openai, :anthropic).
:role #	:assistant	yes	Message role discriminator for model-authored turns.
:stop-reason #	StopReason		Normalized reason the provider stopped generation.
:timestamp #	number	yes	Milliseconds since epoch when the assistant message was recorded.
:usage #	Usage		Optional token accounting returned by the provider for this response.

Message #

Union of UserMessage, AssistantMessage, ToolResultMessage. Stored on agent.messages and passed to providers in AgentContext.messages.

Members for Message type contract

Member	Kind	Summary
UserMessage #	variant	UserMessage is a Message union variant.
AssistantMessage #	variant	AssistantMessage is a Message union variant.
ToolResultMessage #	variant	ToolResultMessage is a Message union variant.

StopReason #

Why the assistant stopped producing output.

Members for StopReason type contract

Member	Kind	Summary
:stop #	enum	:stop is a StopReason enum value.
:length #	enum	:length is a StopReason enum value.
:tool-use #	enum	:tool-use is a StopReason enum value.
:error #	enum	:error is a StopReason enum value.
:aborted #	enum	:aborted is a StopReason enum value.

TextContent #

Plain visible text block.

Fields for TextContent type contract

Field	Type	Required	Summary
:text #	string	yes	Visible UTF-8 text payload.
:type #	:text	yes	Content-block discriminator for visible text.

ThinkingContent #

Reasoning/extended-thinking block. Surfaces both Anthropic extended thinking and OpenAI reasoning items.

Fields for ThinkingContent type contract

Field	Type	Required	Summary
:redacted? #	boolean		True when the provider redacted visible text.
:thinking #	string	yes	Reasoning or extended-thinking text emitted by the provider.
:thinking-signature #	string		Opaque echo signature; required for multi-turn extended thinking.
:type #	:thinking	yes	Content-block discriminator for provider reasoning text.

Tool #

Provider-agnostic tool spec — what providers see in AgentContext.tools.

Fields for Tool type contract

Field	Type	Required	Summary
:description #	string	yes	Provider-visible explanation of when and how to call the tool.
:name #	string	yes	Provider-visible tool name used in tool-call blocks.
:parameters #	JSONSchema	yes	{:type :object :properties {...} :required [...]}

ToolCall #

Assistant request to invoke a tool. Arguments are a parsed Lua table — providers JSON-decode wire arguments before constructing this block.

Fields for ToolCall type contract

Field	Type	Required	Summary
:arguments #	table	yes	Decoded argument table validated by the target tool implementation.
:id #	string	yes	Provider- or agent-generated id used to match the eventual tool result.
:name #	string	yes	Registered tool name to execute.
:type #	:tool-call	yes	Content-block discriminator for tool invocation requests.

ToolResultMessage #

Result of a single tool call, carried back to the provider on the next turn.

Fields for ToolResultMessage type contract

Field	Type	Required	Summary
:content #	[TextContent]	yes	Tool output blocks returned to the provider on the next turn.
:details #	any		Opaque presenter payload (UI-only).
:is-error? #	boolean	yes	True when the tool result should be treated as an error observation.
:role #	:tool-result	yes	Message role discriminator for tool execution results.
:timestamp #	number	yes	Milliseconds since epoch when the tool result was recorded.
:tool-call-id #	string	yes	Matches the originating ToolCall.id.
:tool-name #	string	yes	Tool name that produced the result, copied from the originating call.

Usage #

Token usage counters returned by the provider (best-effort — providers fill what they can).

Fields for Usage type contract

Field	Type	Required	Summary
:cache-read #	number		Provider cache-read tokens credited for the response.
:cache-write #	number		Provider cache-write tokens billed or recorded for the response.
:input #	number		Input or prompt tokens counted for the response.
:output #	number		Generated output tokens counted for the response.
:total-tokens #	number		Provider-reported total tokens, or the best available aggregate.

UserMessage #

Single user turn. Content is either a plain string or an array of TextContent blocks.

Fields for UserMessage type contract

Field	Type	Required	Summary
:content #	string|[TextContent]	yes	Visible user input as plain text or canonical text content blocks.
:role #	:user	yes	Message role discriminator for user-authored turns.
:timestamp #	number	yes	Milliseconds since epoch.

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.

interfaces #

Provider/auth/session interface records.

auth-backend #

Required record shape for (api.register :auth-backend ...).

Members for auth-backend interface contract

Member	Kind	Summary
:api-key #	method	:api-key is a required auth-backend interface method.
:login! #	optional-method	:login! is an optional auth-backend interface method.
:logout! #	optional-method	:logout! is an optional auth-backend interface method.

provider #

Required record shape for (api.register :provider ...). See the :provider register-kind for field details.

Members for provider interface contract

Member	Kind	Summary
:complete #	method	:complete is a required provider interface method.
:convert-messages #	method	:convert-messages is a required provider interface method.
:convert-tools #	method	:convert-tools is a required provider interface method.
:map-stop-reason #	method	:map-stop-reason is a required provider interface method.
:parse-response #	method	:parse-response is a required provider interface method.
:build-body #	method	:build-body is a required provider interface method.

session-backend #

Required record shape for (api.register :session-backend ...).

Members for session-backend interface contract

Member	Kind	Summary
:open #	method	:open is a required session-backend interface method.
:open-existing #	method	:open-existing is a required session-backend interface method.
:append #	method	:append is a required session-backend interface method.
:close #	method	:close is a required session-backend interface method.
:load #	method	:load is a required session-backend interface method.
:find #	method	:find is a required session-backend interface method.
:list #	method	:list is a required session-backend interface method.
:latest #	method	:latest is a required session-backend interface method.