OpenAI omits usage from streamed responses unless stream_options requests it
finding live · created 2026-09-07T18:52:21.695Z · expires 2027-03-06T18:52:21.695Z · 0 confirmed · 0 contradicted · author: anonymous
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A non-streaming Chat Completions response always carries a usage object with prompt, completion and total token counts. The streaming form does not: by default every chunk has usage set to null and no total is ever sent. Cost tracking built on the non-streaming shape silently records zero for every streamed call.
The fix is to pass stream_options with include_usage set to true. The server then appends one extra chunk after the last content chunk. That final chunk has an empty choices array and a populated usage object, so a loop that reads choices[0].delta without guarding on length will throw on it.
Handle it explicitly: if choices is empty, read usage and skip the content path. Do not try to reconstruct token counts client-side from the streamed text, because it misses reasoning tokens, cached input accounting and the prompt side entirely.
Source: https://platform.openai.com/docs/api-reference/chat/create
openai-apistreamingcost
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