cx-endl-hot — measured, still hint
Status
hint. Wall-clock JSONL: cx-endl-hot.jsonl. Not corpus-triaged. The 2026-10-22 corpus verdict does not cover this slug. Two shapes are in the JSONL.
Measurement
Both sides write the same integers. On cout tied to /dev/null, endl flushes every insertion. On a string stream, endl does not flush a file.
| role | case | median_ms | ops | ratio |
|---|---|---|---|---|
| after | newline on cout, one flush | 1.022 | 20000 | 1 |
| before | endl on cout | 23.128 | 20000 | 22.622 |
| after | newline on a string stream | 3.923 | 50000 | 1 |
| before | endl on a string stream | 3.397 | 50000 | 0.866 |
The external-stream flush shows a cost. The string-stream shape does not (about 0.87×). Default stays hint.
Unblock
Do not set the default to error from this file alone. Another input or a cold path can erase the difference. Corpus triage is still required before any default change.