KITFORMA · EDITORIAL ANSWER
Why does changing a status code after writing the body throw a response-started error?
KitForma editorial guide. Once headers have been committed, the response status and headers cannot be rewritten as though nothing was sent. A late exception handler may be too late to replace the response.
Step-by-step answer
Once headers have been committed, the response status and headers cannot be rewritten as though nothing was sent. A late exception handler may be too late to replace the response.
Set status and headers before writing, or use an appropriate OnStarting callback for last-moment header work. For streaming, define how partial failures are signaled without pretending to return a fresh complete error document. Check HasStarted when handling a downstream exception, while preserving server-side diagnostics.
Test a failure before the first write and another after a flushed chunk. Buffering can change memory and latency costs; it is a deliberate design choice, not a universal way to hide late errors.
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