What
The diagnostics file set with CLAUDE_CODE_DIAGNOSTICS_FILE can now capture stalls in streamed responses. A streamed response arrives as a series of pieces, called frames. When a frame arrives slowly, Claude Code writes a cli_sse_frame_stall record noting:
- the gap before the frame arrived
- how far Claude Code's own processing had fallen behind
- how much CPU time was used
The stall watcher is only created when CLAUDE_CODE_DIAGNOSTICS_FILE is set and the code reading the stream asks for it. Otherwise nothing is measured.
Separately, the waits between reconnect attempts and between retried requests are now worked out by one shared routine instead of separate calculations.
Why
This is for troubleshooting only. Nothing changes unless you set the diagnostics file, and if you do, it gives you a way to see where a slow response was held up.
Names in the bundleCLAUDE_CODE_DIAGNOSTICS_FILE
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It is not clear whether every streamed response is watched once the diagnostics file is set, or only some.