> ## Documentation Index > Fetch the complete documentation index at: https://docs.labelbox.com/llms.txt > Use this file to discover all available pages before exploring further. # Attach files to a running session > Attaches files to the session. Each attaches the file's content as it is now, is placed in the sandbox on the session's next tool call, and is visible to the agent from its next turn under the session's files directory. All-or-nothing: one unknown file_id answers 404 and one path colliding with, or nesting inside, another's answers 409, and nothing is attached either way. A member session of a multi-agent tree answers 409: files are attached to its root. A completed, failed, or cancelled root session is accepted, and its next message resumes it with the file already staged. ## OpenAPI ````yaml /managed-agents/openapi.yaml post /managed-agents/v1/sessions/{session_id}/resources openapi: 3.1.0 info: title: Managed Agents API version: 0.13.0 description: >- The Recursion Managed Agents REST API. Authenticate with a Recursion API key as a bearer token. An organization-scoped key acts in its own organization and needs nothing else; a tenant-scoped key must also send `x-organization-id` with an organization id or `default`. Field names follow each operation's published schema. servers: - url: https://api.recursion.labelbox.com security: - bearerAuth: [] paths: /managed-agents/v1/sessions/{session_id}/resources: post: tags: - Sessions summary: Attach files to a running session description: >- Attaches files to the session. Each attaches the file's content as it is now, is placed in the sandbox on the session's next tool call, and is visible to the agent from its next turn under the session's files directory. All-or-nothing: one unknown file_id answers 404 and one path colliding with, or nesting inside, another's answers 409, and nothing is attached either way. A member session of a multi-agent tree answers 409: files are attached to its root. A completed, failed, or cancelled root session is accepted, and its next message resumes it with the file already staged. operationId: managedAgentsAddSessionResources parameters: - description: Session id (UUID) as returned by startSession or listSessions. in: path name: session_id required: true schema: description: Session id (UUID) as returned by startSession or listSessions. format: uuid type: string requestBody: content: application/json: schema: $ref: '#/components/schemas/ManagedAgentsAddSessionResourcesRequest' required: true responses: '201': content: application/json: schema: $ref: '#/components/schemas/ManagedAgentsSessionResourceListResponse' description: >- Response body of GET and POST /v1/sessions/{session_id}/resources. A POST returns only the resources it attached. '400': description: The request was rejected by schema or semantic validation. content: application/json: schema: $ref: '#/components/schemas/ManagedAgentsApiError' '401': description: The caller is unauthenticated. content: application/json: schema: $ref: '#/components/schemas/ManagedAgentsApiError' '403': description: The caller lacks a required permission or capability. content: application/json: schema: $ref: '#/components/schemas/ManagedAgentsApiErrorForbidden' '404': description: No such resource is reachable for this caller. content: application/json: schema: $ref: '#/components/schemas/ManagedAgentsApiError' '409': description: >- The request conflicts with the resource state, or with an in-flight idempotent replay. content: application/json: schema: $ref: '#/components/schemas/ManagedAgentsApiError' '413': description: The request exceeds a size or transaction budget. content: application/json: schema: $ref: '#/components/schemas/ManagedAgentsApiError' '415': description: The request body uses a media type this operation does not accept. content: application/json: schema: $ref: '#/components/schemas/ManagedAgentsApiErrorUnsupportedMediaType' '429': headers: Retry-After: description: Seconds the caller should wait before retrying. schema: type: string style: simple description: A rate limit is exhausted. Honor `Retry-After`. content: application/json: schema: $ref: '#/components/schemas/ManagedAgentsApiError' '500': description: An unexpected server-side failure. content: application/json: schema: $ref: '#/components/schemas/ManagedAgentsApiError' '502': description: The service returned an invalid response. content: application/json: schema: $ref: '#/components/schemas/ManagedAgentsApiErrorBadGateway' '503': headers: Retry-After: description: Seconds the caller should wait before retrying. schema: type: string style: simple description: A dependency is unavailable. Retryable. content: application/json: schema: $ref: '#/components/schemas/ManagedAgentsApiError' '504': headers: Retry-After: description: When to retry, as delay seconds or an HTTP date. schema: type: string description: The service did not respond before the timeout. Retryable. content: application/json: schema: $ref: '#/components/schemas/ManagedAgentsApiErrorGatewayTimeout' components: schemas: ManagedAgentsAddSessionResourcesRequest: description: >- Request body for attaching files to a running session. The files are staged into the sandbox on the session's next tool call and are visible to the agent from its next turn. properties: resources: description: >- Files to attach. All-or-nothing: one unknown file_id or one path collision refuses the whole batch and attaches nothing. items: $ref: '#/components/schemas/ManagedAgentsSessionResourceRequest' maxItems: 500 minItems: 1 type: - array - 'null' type: object example: resources: - file_id: 9f8b1c2d-3e4f-5a6b-7c8d-9e0f1a2b3c4d mount_path: example relative_path: example type: file ManagedAgentsSessionResourceListResponse: description: >- Response body of GET and POST /v1/sessions/{session_id}/resources. A POST returns only the resources it attached. properties: resources: description: >- Every file attached to the session, in attachment order, each with its sandbox path once staged. items: $ref: '#/components/schemas/ManagedAgentsSessionResource' type: - array - 'null' required: - resources type: object example: resources: - byte_size: 1 created_at: '2026-02-18T09:30:00.000Z' file_id: 9f8b1c2d-3e4f-5a6b-7c8d-9e0f1a2b3c4d filename: example media_type: example mount_path: example relative_path: example resource_id: 9f8b1c2d-3e4f-5a6b-7c8d-9e0f1a2b3c4d sha256: example type: file ManagedAgentsApiError: type: object properties: code: type: string minLength: 1 description: Stable machine-readable error code. enum: - analytics - analytics_not_ready - artifact_fetch_unavailable - artifact_generation_mismatch - artifact_hash_mismatch - artifact_invalid_events - artifact_invalid_json - artifact_not_allowlisted - artifact_size_mismatch - atomic_ingest_timeout - auth_unavailable - automation_event_source_invalid - automation_memory_unavailable - automation_reference_invalid - automation_runs_unconfigured - automations_unconfigured - bad_gateway - built_in_catalog_unavailable - built_in_integrations_unconfigured - compute_offerings_unavailable - conflict - content_store_request_canceled - content_store_unavailable - content_store_upload_timeout - credential_encryption_unconfigured - delegate_preparation_failed - entity_family_not_permitted - environment_not_verified - evaluation_cancellation_pending - evaluation_deletion_pending - event_admission_unavailable - event_ingress_unavailable - event_source_verification_credential_invalid - event_sources_unconfigured - execution_unconfigured - file_quota_exceeded - file_storage_unconfigured - forbidden - gateway_timeout - gestalt_unconfigured - github_rate_limited - github_unavailable - handoff_access_invalid - handoff_access_unavailable - handoff_access_unsupported - handoff_capture_unavailable - handoff_requires_retest - handoff_revoke_unavailable - handoff_signal_unavailable - idempotency_conflict - idempotency_in_progress - idempotency_unavailable - ingest_policy_changed - ingest_policy_not_found - ingest_policy_revoked - integrations_unconfigured - internal_error - invalid_json - invalid_pull_request_review_result - invalid_request - invalid_scope - invariant_violation - live_fleet_unconfigured - managed_agents_unavailable - missing_dependency - model_gateway_metadata_missing - model_gateway_unconfigured - model_gateway_unreachable - mutation_transaction_budget_exceeded - not_found - page_token_expired - payload_too_large - persistence_busy - precondition_failed - precondition_required - provider_registration_unsupported - provider_selection_unsupported - rate_limit_exceeded - rate_limited - repository_automation_unconfigured - request_too_large - reserved_source_type - revision_conflict - run_log_store_unavailable - runner_image_resolution_failed - sandbox_provider_disabled - service_unavailable - session_analyst_busy - session_analyst_model_unavailable - session_analyst_unconfigured - session_start_admission_unavailable - session_start_not_admitted - setup_fallback_environment_unsafe - setup_run_finished - setup_run_in_progress - setup_run_limit - setup_run_not_started - setup_runs_unavailable - skill_storage_unconfigured - slack_channels_rejected - slack_channels_unavailable - slack_channels_unconfigured - slack_connection_malformed - slack_event_intake_unavailable - slack_installation_mismatch - slack_missing_scope - slack_rate_limited - slack_reapproval_required - source_ownership_mismatch - source_revision_conflict - spanner_unavailable - streaming_unsupported - submission_transaction_budget_exceeded - task_version_number_conflict - team_board_unconfigured - too_many_streams - unauthorized - unsupported_media_type - vault_creation_retired - version_content_conflict - webhook_delivery_too_large - workspace_boundary_denied message: type: string minLength: 1 description: Human-readable error message. details: description: Optional structured error details. type: object propertyNames: type: string additionalProperties: {} required: - code - message additionalProperties: false description: Standard flat error response. ManagedAgentsApiErrorForbidden: type: object properties: code: type: string minLength: 1 description: Stable machine-readable error code. enum: - forbidden message: type: string minLength: 1 description: Human-readable error message. details: description: Optional structured error details. type: object propertyNames: type: string additionalProperties: {} required: - code - message additionalProperties: false description: Standard flat error response. ManagedAgentsApiErrorUnsupportedMediaType: type: object properties: code: type: string minLength: 1 description: Stable machine-readable error code. enum: - unsupported_media_type message: type: string minLength: 1 description: Human-readable error message. details: description: Optional structured error details. type: object propertyNames: type: string additionalProperties: {} required: - code - message additionalProperties: false description: Standard flat error response. ManagedAgentsApiErrorBadGateway: type: object properties: code: type: string minLength: 1 description: Stable machine-readable error code. enum: - bad_gateway message: type: string minLength: 1 description: Human-readable error message. details: description: Optional structured error details. type: object propertyNames: type: string additionalProperties: {} required: - code - message additionalProperties: false description: Standard flat error response. ManagedAgentsApiErrorGatewayTimeout: type: object properties: code: type: string minLength: 1 description: Stable machine-readable error code. enum: - gateway_timeout message: type: string minLength: 1 description: Human-readable error message. details: description: Optional structured error details. type: object propertyNames: type: string additionalProperties: {} required: - code - message additionalProperties: false description: Standard flat error response. ManagedAgentsSessionResourceRequest: description: One file to attach to a session. properties: file_id: description: >- The file to mount. Must belong to the caller's organization and not have expired. format: uuid type: string mount_path: description: >- The same place named absolutely, with the session's files directory as its root: /data/input.csv lands at data/input.csv, as does the directory's own absolute path copied from a session's resource list, and the /mnt/session/uploads/ prefix is accepted as an alias for the directory. Any other absolute root is likewise a path beneath the directory, never a mount elsewhere. Paths take the same shape rules as relative_path (no . or .. segments, no control characters, at most 255 characters); the filename's reserved-character rule does not apply to paths. Set this or relative_path; both are accepted only when they agree. type: string relative_path: description: >- Where the file lands relative to the session's files directory, e.g. data/input.csv. Defaults to the file's own name. Must be unique within the session and may not contain . or .. segments. type: string type: description: Always file. enum: - file type: string type: object example: file_id: 9f8b1c2d-3e4f-5a6b-7c8d-9e0f1a2b3c4d mount_path: example relative_path: example type: file ManagedAgentsSessionResource: description: >- A file attached to a session. The file is placed read-only in the session's sandbox under its files directory, and the agent knows it is there, so it can read it with read_file or from a shell without being told where to look. properties: byte_size: description: Size of the file in bytes. format: int64 type: integer created_at: description: When the resource was attached. format: date-time type: string file_id: description: The attached file. type: string filename: description: The file's name at upload. type: string media_type: description: The file's declared media type. type: string mount_path: description: >- The absolute path where the file is readable inside the sandbox. Absent until staging reaches the sandbox; a resource attached mid-session is staged on the next sandbox call. type: string relative_path: description: >- Where the file lands relative to the session's files directory. Defaults to the filename; set it on attach to rename the file or place it in a subdirectory. type: string resource_id: description: Server-assigned id of the attachment, used to detach it. type: string sha256: description: >- SHA-256 of the bytes the session mounts. Frozen at attach: a later change to the file does not change this session. type: string type: description: Always file. enum: - file type: string required: - resource_id - type - file_id - filename - media_type - byte_size - sha256 - relative_path - created_at type: object example: byte_size: 1 created_at: '2026-02-18T09:30:00.000Z' file_id: 9f8b1c2d-3e4f-5a6b-7c8d-9e0f1a2b3c4d filename: example media_type: example mount_path: example relative_path: example resource_id: 9f8b1c2d-3e4f-5a6b-7c8d-9e0f1a2b3c4d sha256: example type: file securitySchemes: bearerAuth: type: http scheme: bearer description: A Recursion API key, created in the console under API keys. ````