> ## Documentation Index > Fetch the complete documentation index at: https://docs.lerian.studio/llms.txt > Use this file to discover all available pages before exploring further. # Submit a message to a lane > Submits a message into a specific lane — the side conversation, or a subagent lane. Same 202 contract as the session-level message: a turn is accepted and its results stream over events, never on this response. One case answers 204 instead: a lane STOPPED on a question takes the message as the answer to that question, which unblocks the agent already running on it and opens no turn of its own. ## OpenAPI ````yaml /en/openapi/v3-current/narya.yaml post /v1/sessions/{sessionId}/lanes/{laneId}/messages openapi: 3.1.0 info: title: Narya Host API version: 1.0.0 description: >- The contract between the Narya host and every client. One long-lived host runs on your machine and serves this API over a Unix socket in your Narya home. Narya creates the socket owner-only, and file permissions are the whole authorization. There is no password, no token and no TLS. The terminal client and the one-shot command that Lerian ships drive this API, and a client you write drives the same one. Results never arrive on the response of the request that caused them. Submitting a message returns 202 with a turn id. Everything the turn produces streams over GET /v1/events as server-sent events with a typed envelope, and a stream resumes from a Last-Event-ID header. One error envelope: code, title, message, and fields on 422. Codes are NRY- followed by four digits. A paged list answers items, limit and a nextCursor when more remains. Cursors are opaque. servers: [] security: [] tags: - name: host description: The host process itself — version, uptime, mode, store. - name: sessions description: Durable conversation containers. Archive, never destroy. - name: messages description: Submitting work into a session and interrupting it. - name: events description: The server-sent event stream every client consumes. - name: lanes description: Parallel tracks inside a session — main, subagent, side. - name: agents description: Named recipes — instructions, tools, model, policy. Read-only in v1. - name: ladder description: >- What a person can type: the skills and command files in force for one repository, and expanding one into text. Five origins merged, nearest winning a name, the repository's own rungs gated on trust. - name: permissions description: Pending permission asks, decisions, and the decision audit. - name: intercom description: Sessions on one machine finding and messaging each other. - name: packages description: The one thing a user installs — resources, Go code, or both. - name: workflows description: Deterministic multi-agent orchestration runs. - name: providers description: Model suppliers, their auth state, and the model catalogue. - name: monitors description: >- Long-running watchers a session keeps beside its conversation — a test runner in watch mode, a build, a log being followed. Started by the model or by the person, always listed, always killable. - name: records description: The queryable local record of everything that happened. - name: schedules description: >- Work the host's own clock starts with nobody present — a repository, a prompt, a rule and what one fire may spend. Cancel, never destroy. paths: /v1/sessions/{sessionId}/lanes/{laneId}/messages: parameters: - $ref: '#/components/parameters/SessionIdParam' - $ref: '#/components/parameters/LaneIdParam' post: tags: - lanes summary: Submit a message to a lane description: >- Submits a message into a specific lane — the side conversation, or a subagent lane. Same 202 contract as the session-level message: a turn is accepted and its results stream over events, never on this response. One case answers 204 instead: a lane STOPPED on a question takes the message as the answer to that question, which unblocks the agent already running on it and opens no turn of its own. operationId: createLaneMessage requestBody: required: true content: application/json: schema: $ref: '#/components/schemas/MessageCreate' responses: '202': description: Accepted; results stream over the event stream. content: application/json: schema: $ref: '#/components/schemas/TurnAccepted' '204': description: >- The message answered the question this lane was stopped on. The agent carries on inside the turn it was already running, so there is no new turn to correlate and no body to return. '400': $ref: '#/components/responses/BadRequest' '404': $ref: '#/components/responses/NotFound' '409': $ref: '#/components/responses/Conflict' '413': description: >- The message's attachments together weigh more than one supplier request can carry (NRY-0027). Nothing was admitted; the bytes stored for the files earlier in the list were removed with the refusal. content: application/json: schema: $ref: '#/components/schemas/Error' '422': $ref: '#/components/responses/UnprocessableEntity' '500': $ref: '#/components/responses/InternalServerError' components: parameters: SessionIdParam: name: sessionId in: path required: true description: The session's id. schema: type: string format: uuid LaneIdParam: name: laneId in: path required: true description: The lane's id. schema: type: string format: uuid schemas: MessageCreate: type: object description: >- A user message submitted into a session or lane. Posted while work is running it is a steering message, queued and delivered between tool batches without discarding work already done. required: - content properties: content: type: string minLength: 1 description: The message text. attachments: type: array maxItems: 32 description: Absolute paths of files to attach. items: type: string maxLength: 4096 queueKind: type: string enum: - steer - follow-up default: steer description: >- While a turn is running, steer delivers after a complete tool batch and follow-up starts a fresh turn after turn-finished. Defaults to steer. During a final stream with no subsequent tool batch, steer is durably converted to follow-up with the same admitted entry and turn id. agent: type: string pattern: ^[^\s/\\]+$ maxLength: 128 description: >- Named agent recipe this message runs under: its prompt replaces the system prompt for the turn, its model overrides the session's, and its tool allowlist is the only catalogue the turn can see. The session's own behaviour when absent. Recorded on the admitted message, so the transcript says which agent each turn ran under — there is no session-wide current agent. Ignored on a side lane, exactly as LaneCreate ignores it there: a side conversation always runs the host's read-only explorer, and that is not the caller's to change on any road. examples: - content: Run the ledger test suite and fix the flaky test. attachments: - /Users/dev/repos/midaz/components/ledger/test.log TurnAccepted: type: object description: >- Acknowledgement of a submitted message. Everything the turn produces streams over GET /v1/events, correlated by this turn id — never over the submitting response. required: - turnId properties: turnId: type: string format: uuid description: Correlates this turn's events on the stream. examples: - turnId: 4d8e2f6a-0b1c-4d3e-9f5a-7b9c1d3e5f0a Error: type: object description: >- The single error envelope every operation returns. Codes are NRY- followed by four digits and are catalogued in the top-level x-error-catalog extension. fields appears only on 422 validation errors, mapping each offending property to its problem. required: - code - title - message properties: code: type: string pattern: ^NRY-[0-9]{4}$ description: Machine-readable error code from the NRY catalogue. title: type: string maxLength: 256 description: Short human-readable summary of the error class. message: type: string maxLength: 4096 description: Specific, actionable description of what went wrong. fields: type: object description: Per-field validation problems. Present on 422 only. additionalProperties: type: string examples: - code: NRY-0002 title: Session not found message: >- No session with id 6b9f6d2e-1c3a-4f5b-9d7e-2a8c4e6f0b1d exists on this host. responses: BadRequest: description: Malformed request — invalid parameter, cursor, or JSON body. content: application/json: schema: $ref: '#/components/schemas/Error' NotFound: description: The addressed resource does not exist on this host. content: application/json: schema: $ref: '#/components/schemas/Error' Conflict: description: >- The resource's current state rejects the request — archived session, busy lane, slot conflict, failed build, already-final state. content: application/json: schema: $ref: '#/components/schemas/Error' UnprocessableEntity: description: >- The request was well-formed but failed validation. The error's fields map names each offending property. content: application/json: schema: $ref: '#/components/schemas/Error' InternalServerError: description: The host failed — including a store that refuses writes (NRY-0012). content: application/json: schema: $ref: '#/components/schemas/Error' ````