Fixed Windows start-dev EPERM by opening wrangler/ops-ui logs with write mode instead of append-plus-ftruncate.

Date: 2026-08-28 13:29 Summary: Fixed Windows start-dev EPERM by opening wrangler/ops-ui logs with write mode instead of append-plus-ftruncate.

[question] @c:\Users\matth.cursor\projects\c-Users-matth-onlinefreetools\terminals\1.txt:580-593 (npm run start:dev failed after upload:r2 with EPERM ftruncate in spawnWrangler)

[try to solve] build:site and local R2 seed succeeded. Failure was in spawnWrangler when clearing .run/wrangler-dev.log.

Root cause: the 2026-08-07 ENOENT fix opened the log with 'a' then called ftruncateSync(fd, 0). On Windows, an append handle does not have truncate rights, so Node throws EPERM: operation not permitted, ftruncate. Reproduced independently: append+ftruncate → EPERM; openSync(path, 'w') → OK.

Fix: openTruncatedLogFd() uses 'w' (create + truncate in one open). If the old process still locks the file (EPERM/EACCES/EBUSY), unlink then reopen 'w'. Same helper is used for Ops UI logs.

Verified: npm run start:dev -- --no-build --no-seed-r2 reached ready at http://127.0.0.1:8787/ and Ops UI at http://127.0.0.1:8791/.

[actions]

Updated ops/dev/start-dev.mjs (openTruncatedLogFd for wrangler and Ops UI logs)

Fixed Windows start-dev EPERM by opening wrangler/ops-ui logs with write mode instead of append-plus-ftruncate. | Dev Logs