> ## Documentation Index
> Fetch the complete documentation index at: https://docs.acornops.dev/llms.txt
> Use this file to discover all available pages before exploring further.

# Append user message and trigger run dispatch



## OpenAPI

````yaml /openapi/control-plane-public.json post /api/v1/sessions/{sessionId}/messages
openapi: 3.1.0
info:
  title: AcornOps Control Plane API
  version: 0.0.1-experimental.1
  description: >-
    Control plane API for workspaces, targets, Kubernetes clusters, virtual
    machines, sessions, runs, auth, and internal execution wiring.
servers:
  - url: https://api.acornops.dev
security: []
tags:
  - name: health
    description: Health and readiness endpoints.
  - name: auth
    description: >-
      OIDC, password, browser session, and external integration account link
      endpoints.
  - name: workspaces
    description: Workspace, target, Kubernetes cluster, and VM management endpoints.
  - name: webhooks
    description: Best-effort webhook subscription and delivery history endpoints.
  - name: sessions
    description: Session and message endpoints.
  - name: runs
    description: Run query, cancel, and stream endpoints.
  - name: workflows
    description: >-
      Workspace workflow definitions, schedules, sessions, and approval inbox
      endpoints.
  - name: agents
    description: >-
      Workspace-scoped custom agent definitions, triggers, versions, tests, and
      activity.
  - name: admin
    description: Operator-only admin API protected exclusively by admin bearer tokens.
  - name: internal
    description: Internal execution endpoints for execution-engine.
paths:
  /api/v1/sessions/{sessionId}/messages:
    post:
      tags:
        - sessions
      summary: Append user message and trigger run dispatch
      parameters:
        - in: path
          name: sessionId
          required: true
          schema:
            type: string
            format: uuid
            example: 6e30d188-7e4f-4cce-a368-40b34004d725
      requestBody:
        required: true
        content:
          application/json:
            schema:
              type: object
              required:
                - content
              properties:
                content:
                  type: string
                  example: >-
                    Pods restarted after rollout, but p95 latency is still
                    elevated. Check likely causes.
                toolAccessMode:
                  type: string
                  enum:
                    - read_only
                    - read_write
                  example: read_only
                clientMessageId:
                  type: string
                  example: 4f004ae2-4288-4baf-9be4-124d61180f0c-msg-1
                llm:
                  type: object
                  properties:
                    provider:
                      type: string
                      enum:
                        - openai
                        - anthropic
                        - gemini
                      example: openai
                      description: Must be supplied together with model.
                    model:
                      type: string
                      example: gpt-5-nano
                      description: Required when provider is supplied.
                    reasoningEffort:
                      type: string
                      enum:
                        - 'off'
                        - low
                        - medium
                        - high
                      example: high
                  description: >-
                    Optional per-message runtime override. Omit to use workspace
                    defaults.
              example:
                content: >-
                  Pods restarted after rollout, but p95 latency is still
                  elevated. Check likely causes.
                toolAccessMode: read_only
                clientMessageId: 4f004ae2-4288-4baf-9be4-124d61180f0c-msg-1
                llm:
                  provider: openai
                  model: gpt-5-nano
                  reasoningEffort: high
      responses:
        '202':
          description: Run accepted for processing.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/MessageAccepted'
        '400':
          description: >-
            Invalid AI runtime selection, disallowed model/provider, missing
            provider credential, or unsupported target type.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorResponse'
        '401':
          description: Error response.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorResponse'
        '403':
          description: >-
            CONVERSATION_OWNER_REQUIRED when the authenticated user did not
            create the conversation, or FORBIDDEN when the owner lacks run
            creation permission.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorResponse'
        '404':
          description: Error response.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorResponse'
        '409':
          description: Error response.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorResponse'
        '429':
          description: Error response.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorResponse'
        '500':
          description: Error response.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorResponse'
      security:
        - userSession: []
components:
  schemas:
    MessageAccepted:
      type: object
      required:
        - message_id
        - run_id
      properties:
        message_id:
          type: string
          format: uuid
        run_id:
          type: string
          format: uuid
    ErrorResponse:
      type: object
      required:
        - error
      properties:
        error:
          type: object
          required:
            - code
            - message
          properties:
            code:
              type: string
            message:
              type: string
            retryable:
              type: boolean
            details:
              type: object
              additionalProperties: true
              description: Optional structured error details.
  securitySchemes:
    userSession:
      type: apiKey
      in: cookie
      name: acornops_cp_session

````