> ## 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. # Open a lane > Opens a parallel track inside the session. kind side opens a side conversation that runs without pausing or contaminating the main work; kind subagent delegates to the named agent recipe, running concurrently with other delegated work. The initial message starts the lane's first turn; its results stream over the event stream. A session holds at most one OPEN side conversation. A side conversation is a conversation, so a follow-up question belongs in the lane that already has one rather than in a new lane that never saw the exchange: list the session's lanes, find the side lane whose status is not closed, and submit the question to it (createLaneMessage). Asking for a second one answers 409 and names the lane that holds it. Closing the open one and opening another is how a fresh side conversation is started. ## OpenAPI ````yaml /en/openapi/v3-current/narya.yaml post /v1/sessions/{sessionId}/lanes 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: parameters: - $ref: '#/components/parameters/SessionIdParam' post: tags: - lanes summary: Open a lane description: >- Opens a parallel track inside the session. kind side opens a side conversation that runs without pausing or contaminating the main work; kind subagent delegates to the named agent recipe, running concurrently with other delegated work. The initial message starts the lane's first turn; its results stream over the event stream. A session holds at most one OPEN side conversation. A side conversation is a conversation, so a follow-up question belongs in the lane that already has one rather than in a new lane that never saw the exchange: list the session's lanes, find the side lane whose status is not closed, and submit the question to it (createLaneMessage). Asking for a second one answers 409 and names the lane that holds it. Closing the open one and opening another is how a fresh side conversation is started. operationId: createLane requestBody: required: true content: application/json: schema: $ref: '#/components/schemas/LaneCreate' responses: '201': description: The opened lane. content: application/json: schema: $ref: '#/components/schemas/Lane' '400': $ref: '#/components/responses/BadRequest' '404': $ref: '#/components/responses/NotFound' '409': $ref: '#/components/responses/Conflict' '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 schemas: LaneCreate: type: object description: >- Request to open a lane. kind side opens a side conversation; kind subagent delegates to a named agent recipe — agent is required in that case, and ignored for kind side. required: - kind - message properties: kind: type: string enum: - side - subagent agent: type: string maxLength: 128 description: >- The agent recipe to delegate to. Required when kind is subagent. Ignored when kind is side: a side conversation always runs the host's read-only explorer, and the lane comes back naming it — an unknown name here is neither honoured nor refused. message: type: string minLength: 1 description: The initial message that starts the lane's first turn. examples: - kind: subagent agent: reviewer message: Review the diff of components/ledger for correctness. Lane: type: object description: >- A parallel track of execution inside a session. The main lane carries the primary conversation; subagent lanes carry delegated work; side lanes carry conversations opened mid-run without interrupting the work. Workflow lanes carry one step of a workflow run: they have no parent lane and sit at depth 0, because a run starts from a request rather than from anybody's turn. required: - id - sessionId - kind - status - createdAt properties: id: type: string format: uuid sessionId: type: string format: uuid kind: type: string enum: - main - side - subagent - workflow status: type: string enum: - idle - running - waiting - closed agent: type: string description: >- The agent recipe running in the lane, for subagent and workflow lanes. activity: type: string maxLength: 1024 description: What the lane is currently doing, in one line. createdAt: type: string format: date-time examples: - id: 1a2b3c4d-5e6f-4a7b-8c9d-0e1f2a3b4c5d sessionId: 6b9f6d2e-1c3a-4f5b-9d7e-2a8c4e6f0b1d kind: subagent status: running agent: reviewer activity: Reviewing the diff of components/ledger createdAt: '2026-08-08T12:10:00.000Z' 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' ````