5e3e5cc5a0
`LC_CTYPE=C tr -dc '[:alnum:]' </dev/urandom` in the upstream runner's certs.sh trips "tr: Illegal byte sequence" on macOS — LC_CTYPE alone doesn't override the runtime locale chain. Only the amplificationlimit testcase exercises this loop (chain length > 1 → fakedns SAN inflation), but if it aborts the runner stops the whole matrix BEFORE any later test in TESTCASES_QUIC runs: handshakeloss, transferloss, handshakecorruption, transfercorruption, ipv6, v2, rebind-port, rebind-addr, connectionmigration, and the goodput/crosstraffic measurements all silently never execute. The post-mortem summary shows the 12 testcases that ran before the abort and looks deceptively complete. Add an idempotent `sed` step to run-matrix.sh that rewrites the line to `LC_ALL=C tr` on every invocation, plus a plan-file note so the next person hitting the deceptive summary doesn't repeat the diagnosis. The patch is a working-tree edit to ../quic-interop-runner/, not a fork; re-applied on every clone. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>