The first version of the config.yaml round-trip gate (PR #2773)
captured curl output with `-w '\n%{http_code}\n'` and parsed via
`tail -n 2 | head -n 1`. That broke because bash's $(...) strips the
trailing newline, leaving only 2 lines in the captured value:
line 1: <response body>
line 2: <status code>
`tail -n 2 | head -n 1` then returned line 1 (the body), not the
status code. The gate misreported 200-with-JSON-body responses as
"PUT returned <body>" and failed the canary post-merge at 22:06 UTC.
Fix: write body to a tempfile via `-o "$PUT_TMP"` and use
`-w '%{http_code}'` as the sole stdout. Status code is now
unambiguously the captured value, body is read separately from the
tempfile. No newline-counting heuristic needed.
Verification:
- bash -n clean
- shellcheck clean on the modified block
- Will be exercised by the next continuous-synth-e2e firing
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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