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

# Existence check for a blob by blake3 hash

> `200` if the calling account can mint from this blob, `404` otherwise. Same account-scoping as `from-hash`; lets a client decide between the dedup fast-path and a full upload before sending bytes.



## OpenAPI

````yaml /openapi-v2.yaml head /api/v2/assets/by-hash/{hash}
openapi: 3.0.3
info:
  title: Comfy API v2
  version: 2.0.0
  description: |
    The official, versioned HTTP API for running ComfyUI workflows from
    external applications: upload inputs, submit a workflow, observe
    execution, retrieve results.

    Design principles:
    - **Poll-first.** Every capability is reachable via plain GET polling;
      the SSE stream is a live enhancement, never the source of truth.
    - **Everything is resumable.** Submission is idempotent; job state and
      outputs are retrievable by ID until `expires_at`.
    - **UUID identity, content-addressed dedup.** Assets are UUID-identified
      records over blobs keyed by a server-computed blake3 hash. The hash is
      nullable and may be computed lazily.
    - **Follow links, don't build URLs.** Responses embed follow-up URLs.

    Additive changes only within v2; breaking changes require v3.
servers:
  - url: http://127.0.0.1:8189
    description: Self-hosted (comfy-api-proxy)
  - url: https://cloud.comfy.org
    description: Comfy Cloud
  - url: https://{deployment}.comfy.org
    description: Serverless deployment (URL shape not final)
    variables:
      deployment:
        default: my-deployment
security:
  - bearerAuth: []
  - {}
tags:
  - name: assets
    description: UUID-identified records over content-addressed blobs.
  - name: jobs
    description: One execution of a workflow — durable, pollable, cancelable.
paths:
  /api/v2/assets/by-hash/{hash}:
    head:
      tags:
        - assets
      summary: Existence check for a blob by blake3 hash
      description: >-
        `200` if the calling account can mint from this blob, `404` otherwise.
        Same account-scoping as `from-hash`; lets a client decide between the
        dedup fast-path and a full upload before sending bytes.
      operationId: headAssetByHash
      parameters:
        - $ref: '#/components/parameters/BlakeHash'
      responses:
        '200':
          description: Blob present and mintable by the caller.
        '401':
          $ref: '#/components/responses/Unauthorized'
        '404':
          description: No blob the caller may mint from.
        '500':
          $ref: '#/components/responses/UpstreamError'
components:
  parameters:
    BlakeHash:
      name: hash
      in: path
      required: true
      schema:
        type: string
      description: Content hash, written `blake3:<hex>`.
      example: blake3:9f8a1c0d...
  responses:
    Unauthorized:
      description: '`unauthorized` — missing or invalid credentials.'
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/ErrorEnvelope'
    UpstreamError:
      description: >-
        `upstream_error` — an unexpected failure reaching or processing the
        request in this implementation's backing services. The message is always
        a generic, safe-to-display string; implementation detail (the specific
        upstream, its error text, transport failures) is never included here —
        see each implementation's own error-mapping notes. Every operation in
        this contract can fail this way.
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/ErrorEnvelope'
  schemas:
    ErrorEnvelope:
      type: object
      description: |
        Shared error envelope with machine-readable codes. Core codes (v1):
        `invalid_workflow` (422), `workflow_format_ui` (422),
        `missing_asset` (422), `hash_mismatch` (409), `blob_not_found`
        (404), `idempotency_key_reuse` (422),
        `queue_full` (429 + Retry-After), `insufficient_credits` (402),
        `not_found` (404), `unauthorized` (401), `forbidden` (403).
        Deployment-scoped surfaces add: `deployment_not_ready` (429 +
        Retry-After — the deployment can still reach ready; retry) and
        `deployment_stopped` (422 — terminal deployment state; a retry
        cannot succeed without operator action). A 429 is disambiguated
        by `error.code` alone; clients should treat any 429 + Retry-After
        as "back off and retry".
      required:
        - error
      properties:
        error:
          type: object
          required:
            - code
            - message
          properties:
            code:
              type: string
              example: invalid_workflow
            message:
              type: string
              example: 'Node 12 (KSampler): required input ''model'' is not connected'
            details:
              type: object
              nullable: true
              additionalProperties: true
              example:
                node_errors:
                  '12':
                    - field: model
                      reason: missing_input
  securitySchemes:
    bearerAuth:
      type: http
      scheme: bearer
      description: >-
        `Authorization: Bearer <api-key>` — account-scoped API keys on Cloud and
        serverless. Self-hosted accepts unauthenticated requests by default and
        can be configured with a static bearer token.

````