"status": "incomplete", "incomplete_details": {"reason": "max_output_tokens"}
This is not an error message, and that is the problem with it. The Responses API does not raise when a response runs out of output budget; it hands you a response object whose status is incomplete and whose incomplete_details names the reason. Code that only reads the text gets whatever was written before the budget ran out, and carries on as if it were the whole answer.
The value is one of four in a single type, in OpenAI’s own Python SDK:
class IncompleteDetails(BaseModel): """Details about why the response is incomplete.""" reason: Optional[Literal["max_output_tokens", "max_messages", "content_filter", "steered"]] = None
From src/openai/types/responses/response.py at commit 09c5b6f1. The same file declares the field on Response as incomplete_details: Optional[IncompleteDetails] = None, and documents status as “One of completed, failed, in_progress, cancelled, queued, or incomplete.”
Two details in that file are worth more than the value itself.
It is a field on a model, not an exception. IncompleteDetails is a BaseModel, carried on the Response you get back. Nothing in that type raises; the response is delivered and the status is a value you have to read.
The convenience text does not look at the status. The same file defines output_text as a “Convenience property that aggregates all output_text items from the output list,” and says: “If no output_text content blocks exist, then an empty string is returned.” So a response that ran out of budget gives output_text whatever text exists, or an empty string — the same type you get from a finished answer.
If you stream, the ending is an event rather than a field:
class ResponseIncompleteEvent(BaseModel): """An event that is emitted when a response finishes as incomplete.
From src/openai/types/responses/response_incomplete_event.py at commit 09f446f5, where the event’s type is Literal["response.incomplete"] and it carries the full response, with the same incomplete_details on it.
Print two fields from the response you already have.
The check that should sit in front of every read of output_text:
if response.status == "incomplete": reason = response.incomplete_details.reason if response.incomplete_details else None raise RuntimeError(f"response incomplete: {reason}")
The budget is not only for the text you read. The SDK documents max_output_tokens as “An upper bound for the number of tokens that can be generated for a response, including visible output tokens and reasoning tokens.” On a reasoning model, the thinking and the answer draw on the same number, so a budget that looks generous for the answer you expected can be spent before the answer is written.
Raising it is the right fix once, when you can say how long the answer actually needs to be. What a bigger number does not change is what an incomplete response leaves behind: still a response, still no exception, still text that reads like an answer. If the job is to write everything about a whole list in one response, a larger budget lets the list get longer before the same cut-off arrives. Raising it twice is a signal to change the shape of the work.
Treat incomplete as a failure in code, not in review. The three lines above turn a silent truncation into an exception at the place it happened, which is the only place anyone can still do something about it.
Ask for one piece per response. Most responses that run out of budget are being asked for a whole list or a whole document at once. One item per call, or one section per call, keeps each response inside a budget you can predict, and a cut-off on item seven is a cut-off on item seven.
Write each finished piece out before asking for the next. The responses that completed are the work. Persist them as they arrive, so a run that stops leaves the finished pieces on disk rather than in a variable that is about to be discarded.
There is a written guide: the iteration arithmetic as a formula you can run against a job before you launch it, the reasons raising a cap does not finish the job, and batch.py, one standard-library file that collapses a per-item loop into a single pass. It is $19. One working way to pay today is 19 USDC on Base, and delivery is manual: you email the transaction hash and the files come back as a reply. This page is free, ungated, and sells nothing on its own.
The short version: incomplete_details.reason: "max_output_tokens" is a value on a response whose status is incomplete, not an exception, and output_text returns whatever was written without looking at the status. The budget includes reasoning tokens. Check status before you read the text, raise the budget once when you can say what the answer needs, and ask for the work in pieces that can each finish.
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