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

# Update trace metadata

> Update metadata on a trace after creation. Inserts a synthetic span carrying the new attributes through the standard ingestion pipeline. New keys are added, existing keys are updated, missing keys are preserved. Labels replace entirely.



## OpenAPI

````yaml PATCH /api/traces/{traceId}/metadata
openapi: 3.1.0
info:
  title: LangWatch API
  version: 1.0.0
  description: LangWatch openapi spec
servers:
  - url: https://app.langwatch.ai
security:
  - project_api_key: []
paths:
  /api/traces/{traceId}/metadata:
    patch:
      tags:
        - Traces
      summary: Update trace metadata
      description: >-
        Update metadata on a trace after creation. Inserts a synthetic span
        carrying the new attributes through the standard ingestion pipeline. New
        keys are added, existing keys are updated, missing keys are preserved.
        Labels replace entirely.
      operationId: patchApiTracesByTraceIdMetadata
      parameters:
        - schema:
            type: string
          in: path
          name: traceId
          required: true
      requestBody:
        content:
          application/json:
            schema:
              type: object
              properties:
                metadata:
                  type: object
                  additionalProperties:
                    anyOf:
                      - type: string
                        maxLength: 4096
                      - type: number
                      - type: boolean
                      - type: array
                        items:
                          type: string
                      - type: object
                        additionalProperties: {}
              required:
                - metadata
      responses:
        '200':
          description: Metadata updated successfully
          content:
            application/json:
              schema:
                type: object
                properties:
                  traceId:
                    type: string
                required:
                  - traceId
        '400':
          description: Bad Request
          content:
            application/json:
              schema:
                type: object
                properties:
                  error:
                    type: string
                  message:
                    type: string
                required:
                  - error
        '401':
          description: Unauthorized
          content:
            application/json:
              schema:
                type: object
                properties:
                  error:
                    type: string
                  message:
                    type: string
                required:
                  - error
        '422':
          description: Unprocessable Entity
          content:
            application/json:
              schema:
                type: object
                properties:
                  error:
                    type: string
                  message:
                    type: string
                required:
                  - error
        '500':
          description: Internal Server Error
          content:
            application/json:
              schema:
                type: object
                properties:
                  error:
                    type: string
                  message:
                    type: string
                required:
                  - error
components:
  securitySchemes:
    project_api_key:
      type: apiKey
      in: header
      name: X-Auth-Token
      description: >-
        Project API key for sending traces and accessing project-scoped
        resources. Format: sk-lw-... (no underscore). Obtain one by creating a
        project via the Admin API or the LangWatch UI.

````