> ## Documentation Index > Fetch the complete documentation index at: https://haico.gr/docs/llms.txt > Use this file to discover all available pages before exploring further. # Branch Conversation > Fork a conversation at a completed user turn. Creates a NEW thread whose message history is the parent's prefix up to ``from_turn`` and whose workspace (document / preferences / todos / artifacts) is copied as-of that turn. The service manages its own sessions because the LangGraph checkpointer seeding must happen between two committed transactions. Args: payload: ``from_turn`` (>= 0; 0 forks from the empty start) and an optional ``reason`` label. user: The authenticated user (must own the conversation). thread_id: The conversation to fork. Returns: ``BranchCreateResponse`` with the new thread id and branch metadata. Raises: HTTPException 400: ``from_turn`` at or before the thread's own branch point. HTTPException 403: The conversation belongs to another user. HTTPException 404: Unknown conversation, or ``from_turn`` beyond the latest turn. HTTPException 409: The snapshot needed to reconstruct the workspace is missing. HTTPException 502: Checkpointer seeding failed (branch fully rolled back). ## OpenAPI ````yaml /openapi.json post /api/conversations/{thread_id}/branch openapi: 3.1.0 info: title: HAI-Co² API description: Human-AI Co-Construction reference implementation. version: 0.1.0 servers: - url: https://haico.gr description: Production - url: https://dev.haico.gr description: Development - url: http://localhost:8000 description: Local development security: [] paths: /api/conversations/{thread_id}/branch: post: tags: - Conversations summary: Branch Conversation description: |- Fork a conversation at a completed user turn. Creates a NEW thread whose message history is the parent's prefix up to ``from_turn`` and whose workspace (document / preferences / todos / artifacts) is copied as-of that turn. The service manages its own sessions because the LangGraph checkpointer seeding must happen between two committed transactions. Args: payload: ``from_turn`` (>= 0; 0 forks from the empty start) and an optional ``reason`` label. user: The authenticated user (must own the conversation). thread_id: The conversation to fork. Returns: ``BranchCreateResponse`` with the new thread id and branch metadata. Raises: HTTPException 400: ``from_turn`` at or before the thread's own branch point. HTTPException 403: The conversation belongs to another user. HTTPException 404: Unknown conversation, or ``from_turn`` beyond the latest turn. HTTPException 409: The snapshot needed to reconstruct the workspace is missing. HTTPException 502: Checkpointer seeding failed (branch fully rolled back). operationId: branch_conversation_api_conversations__thread_id__branch_post parameters: - name: thread_id in: path required: true schema: type: string maxLength: 255 minLength: 1 title: Thread Id requestBody: required: true content: application/json: schema: $ref: '#/components/schemas/BranchCreateRequest' responses: '200': description: Successful Response content: application/json: schema: $ref: '#/components/schemas/BranchCreateResponse' '422': description: Validation Error content: application/json: schema: $ref: '#/components/schemas/HTTPValidationError' security: - HTTPBearer: [] components: schemas: BranchCreateRequest: properties: from_turn: type: integer minimum: 0 title: From Turn description: >- Parent turn index to branch from. 0 forks from the empty start (used to retry/edit the very first turn). reason: anyOf: - type: string maxLength: 500 - type: 'null' title: Reason description: Optional branch label workspace: anyOf: - $ref: '#/components/schemas/BranchWorkspaceOverride' - type: 'null' description: >- Displayed workspace to seed the branch with (restored-preview edits included). Omit to seed from the as-of-turn snapshot. type: object required: - from_turn title: BranchCreateRequest description: Payload for forking a conversation at a completed user turn. BranchCreateResponse: properties: thread_id: type: string title: Thread Id parent_thread_id: type: string title: Parent Thread Id branch_point_turn: type: integer title: Branch Point Turn title: type: string title: Title type: object required: - thread_id - parent_thread_id - branch_point_turn - title title: BranchCreateResponse description: Response returned after a branch thread has been fully created. HTTPValidationError: properties: detail: items: $ref: '#/components/schemas/ValidationError' type: array title: Detail type: object title: HTTPValidationError BranchWorkspaceOverride: properties: preferences: anyOf: - items: $ref: '#/components/schemas/BranchPreferenceSeed' type: array maxItems: 200 - type: 'null' title: Preferences todos: anyOf: - items: $ref: '#/components/schemas/BranchTodoSeed' type: array maxItems: 500 - type: 'null' title: Todos objective: anyOf: - type: string maxLength: 5000 - type: 'null' title: Objective document: anyOf: - $ref: '#/components/schemas/BranchDocumentSeed' - type: 'null' type: object title: BranchWorkspaceOverride description: >- The displayed workspace to seed a branch with, overriding the snapshot. Sent when forking from a restored preview the user has edited, so the branch starts from exactly what they see (their edits — including a lock — included) instead of the raw as-of-turn snapshot. Any field left unset falls back to the resolved snapshot; ``position`` is intentionally not accepted (the backend re-derives it from list order). ValidationError: properties: loc: items: anyOf: - type: string - type: integer type: array title: Location msg: type: string title: Message type: type: string title: Error Type input: title: Input ctx: type: object title: Context type: object required: - loc - msg - type title: ValidationError BranchPreferenceSeed: properties: title: type: string maxLength: 500 title: Title subtitle: anyOf: - type: string maxLength: 2000 - type: 'null' title: Subtitle kind: type: string enum: - hard - soft title: Kind default: soft locked: type: boolean title: Locked default: false type: object required: - title title: BranchPreferenceSeed description: One preference to seed into a branch (from the displayed preview). BranchTodoSeed: properties: text: type: string maxLength: 2000 title: Text done: type: boolean title: Done default: false depth: type: integer maximum: 20 minimum: 0 title: Depth default: 0 type: object required: - text title: BranchTodoSeed description: One todo to seed into a branch (from the displayed preview). BranchDocumentSeed: properties: title: anyOf: - type: string maxLength: 500 - type: 'null' title: Title content: anyOf: - type: string - type: 'null' title: Content type: object title: BranchDocumentSeed description: Document to seed into a branch; empty ``content`` creates no document. securitySchemes: HTTPBearer: type: http description: >- A personal access token (`haico_pat_...`), created under Profile → API keys. Send it as `Authorization: Bearer `. The browser session JWT is also accepted but is an internal mechanism and is not part of the public contract. scheme: bearer ````