JSONL Format

Every batch is driven by three JSONL files:

File	Direction	Purpose
Input	You upload it	One request per line; describes what the batch should do
Output	Service writes it	One result per successful line
Error	Service writes it	One record per failed line

This page is the canonical specification for all three line schemas.

Input JSONL

The input is a JSONL file (one JSON object per line, separated by \n). You upload it via POST /v1/files with purpose=batch, then reference its ID when you call POST /v1/batches.

Line schema

{
  "custom_id": "request-1",
  "method":    "POST",
  "url":       "/v1/chat/completions",
  "body":      { /* endpoint-specific payload */ }
}

Field	Type	Required	Description
`custom_id`	string	Yes	Your identifier for this request. Must be non-empty and unique within the batch. Returned verbatim in the corresponding output or error line so you can match results to inputs.
`method`	string	Yes	HTTP method, case-insensitive. Only `POST` (any case) is accepted today.
`url`	string	Yes	Must be `/v1/chat/completions`, the only batchable endpoint. All lines in a single batch must share the same `url`, and it must match the `endpoint` field on the create call.
`body`	object	Yes	The request body that would be sent to the synchronous endpoint. See Supported endpoints for the shape. The field `stream: true` is rejected.

Validation rules

The service performs all of the following checks at POST /v1/batches time (not at upload time). Failure returns 400 with the offending line:

Each line must be valid JSON (not arrays, not primitives, must be an object).
custom_id non-empty string, unique across the whole batch.
method is case-insensitive; the upper-cased value must equal "POST".
url must be exactly /v1/chat/completions on every line in the file. Other ZeroGPU sync routes are rejected here.
body must be a non-empty object.
body.stream === true is rejected (streaming is not supported in batch mode).
Per-line size ≤ 1 MB.
Total file size ≤ 200 MB.
Total line count ≤ 50,000.
The file must contain at least one line.

Format details

Lines are separated by \n (LF). A trailing newline is allowed.
Blank lines are skipped.
UTF-8 encoding is required.
The url value matches the endpoint field on the create request exactly, no trailing slash, no query string, no protocol/host prefix.

Example, chat completions

{"custom_id":"req-1","method":"POST","url":"/v1/chat/completions","body":{"model":"<model-id>","messages":[{"role":"user","content":"What is the capital of France?"}]}}
{"custom_id":"req-2","method":"POST","url":"/v1/chat/completions","body":{"model":"<model-id>","messages":[{"role":"user","content":"What is the capital of Germany?"}]}}
{"custom_id":"req-3","method":"POST","url":"/v1/chat/completions","body":{"model":"<model-id>","messages":[{"role":"user","content":"What is the capital of Italy?"}]}}

See Supported endpoints for the /v1/chat/completions body schema.

Output JSONL

When a batch reaches status: "completed", the service writes the successful results to a file referenced by output_file_id on the Batch object. You download it via GET /v1/files/{file_id}/content. Only lines that received a 2xx response from the underlying endpoint appear in the output file. Failed lines go to the error file (see below). The order of lines in the output file is not guaranteed to match the order of lines in the input file, match results to inputs by custom_id.

Line schema

{
  "id":        "batch_req_abc123...",
  "custom_id": "request-1",
  "response": {
    "status_code": 200,
    "request_id":  "req_xyz789...",
    "body":        { /* the endpoint's normal response body */ }
  }
}

Field	Type	Description
`id`	string	Line-level identifier (prefix `batch_req_`). Stable across retries.
`custom_id`	string	Echo of the `custom_id` you supplied on the input line.
`response.status_code`	integer	HTTP status from the underlying endpoint (will always be 2xx in this file).
`response.request_id`	string \| null	The synchronous request id (`req_…`) of the underlying call to the orchestration API. Useful for cross-referencing logs. `null` if the upstream service didn’t surface a request id.
`response.body`	object	The same JSON body the synchronous endpoint would have returned for this request.

See Supported endpoints for the exact response.body shape (OpenAI chat.completion).

Example, chat completions output

{"id":"batch_req_a","custom_id":"req-1","response":{"status_code":200,"request_id":"req_xyz","body":{"id":"chatcmpl-abc","object":"chat.completion","created":1736295000,"model":"<model-id>","choices":[{"index":0,"message":{"role":"assistant","content":"Paris."},"finish_reason":"stop"}],"usage":{"prompt_tokens":12,"completion_tokens":2,"total_tokens":14},"system_fingerprint":null}}}
{"id":"batch_req_b","custom_id":"req-2","response":{"status_code":200,"request_id":"req_uvw","body":{"id":"chatcmpl-def","object":"chat.completion","created":1736295001,"model":"<model-id>","choices":[{"index":0,"message":{"role":"assistant","content":"Berlin."},"finish_reason":"stop"}],"usage":{"prompt_tokens":12,"completion_tokens":2,"total_tokens":14},"system_fingerprint":null}}}

Reading the output

import json

with open("output.jsonl") as f:
    for line in f:
        record = json.loads(line)
        custom_id = record["custom_id"]
        body      = record["response"]["body"]
        answer    = body["choices"][0]["message"]["content"]
        print(f"{custom_id}: {answer}")

Error JSONL

When a batch reaches status: "completed" (or expired) and at least one line failed, the service writes the failures to a file referenced by error_file_id. Successful lines go to the output file; the two are disjoint.

Line schema

{
  "id":        "batch_req_def456...",
  "custom_id": "request-5",
  "response":  null,
  "error": {
    "code":    "invalid_request_error",
    "message": "[legacy:http_400] request body is invalid",
    "param":   "model"
  }
}

Field	Type	Description
`id`	string	Line-level identifier (prefix `batch_req_`).
`custom_id`	string	Echo of the `custom_id` you supplied on the input line.
`response`	null	Always `null` on error lines. Mirrors OpenAI’s `{id, custom_id, response, error}` discriminator so SDK type-guards work unchanged.
`error.code`	string	OpenAI semantic error code. See the table below.
`error.message`	string	Human-readable description. The original ZeroGPU internal code is preserved as a `[legacy:<old>]` prefix on this string for forensics.
`error.param`	string \| null	Name of the offending parameter when known.

Each error line carries an error.code (invalid_request_error, internal_error, batch_cancelled, and so on). The full list, what triggers each, and how to recover is in the Errors reference.

Example, error file

{"id":"batch_req_e1","custom_id":"req-5","response":null,"error":{"code":"invalid_request_error","message":"[legacy:http_400] {\"message\":\"messages: missing required field\",\"type\":\"invalid_request_error\"}","param":null}}
{"id":"batch_req_e2","custom_id":"req-9","response":null,"error":{"code":"internal_error","message":"[legacy:retries_exhausted] Line failed after 4 attempts: orchestration-api returned 503: upstream timeout","param":null}}
{"id":"batch_req_e3","custom_id":"req-12","response":null,"error":{"code":"internal_error","message":"[legacy:dlq_exhausted] Message exhausted main-queue retries and was routed to the DLQ","param":null}}

Reading the error file

import json

with open("errors.jsonl") as f:
    for line in f:
        record = json.loads(line)
        line_id   = record["id"]            # batch_req_…
        custom_id = record["custom_id"]
        code      = record["error"]["code"]  # OpenAI semantic code
        msg       = record["error"]["message"]
        print(f"FAIL {custom_id} ({line_id}) [{code}]: {msg}")

Matching outputs and errors back to inputs

The output and error files together account for all lines in your input file, but their order is not preserved and they may be split across the two files. To reconstruct results for your dataset:

import json

results = {}                                # custom_id -> result-or-error
with open("output.jsonl") as f:
    for line in f:
        rec = json.loads(line)
        results[rec["custom_id"]] = ("ok", rec["response"]["body"])
with open("errors.jsonl") as f:
    for line in f:
        rec = json.loads(line)
        results[rec["custom_id"]] = ("err", rec["error"])

# now iterate your original inputs and look up by custom_id

If a custom_id you submitted is missing from both files, the batch is not complete yet, re-check status and download again.

Always match by custom_idOutput and error lines are not guaranteed to appear in input order. Index your inputs by custom_id in your code and look results up by that key.

Next steps

Supported endpoints →

Body and response shape for /v1/chat/completions.

Quickstart →

Full end-to-end walkthrough in curl and Python.

Errors reference →

Every JSONL validation message and error code, with recovery guidance.

Get Started

Models

Guides

Platform

Input JSONL

Line schema

Validation rules

Format details

Example, chat completions

Output JSONL

Line schema

Example, chat completions output

Reading the output

Error JSONL

Line schema

Example, error file

Reading the error file

Matching outputs and errors back to inputs

Next steps

Supported endpoints →

Quickstart →

Errors reference →

​Input JSONL

​Line schema

​Validation rules

​Format details

​Example, chat completions

​Output JSONL

​Line schema

​Example, chat completions output

​Reading the output

​Error JSONL

​Line schema

​Example, error file

​Reading the error file

​Matching outputs and errors back to inputs

​Next steps

Supported endpoints →

Quickstart →

Errors reference →

Input JSONL

Line schema

Validation rules

Format details

Example, chat completions

Output JSONL

Line schema

Example, chat completions output

Reading the output

Error JSONL

Line schema

Example, error file

Reading the error file

Matching outputs and errors back to inputs

Next steps