write_file confirmed only SIZE (wc -c) after writing — never content.
Models compensated by re-reading files immediately after writing them
(154 verify-reads in a 400k-msg production window), and a corrupted
write (truncated pipe, backend FS oddity) could silently pass.
The write path now compares the on-disk sha256 against the intended
content (one shell call). Three outcomes:
- match -> result carries verified: true; the schema tells the model
an explicit contract: do NOT re-read to check the write landed.
- mismatch -> hard error ('The write did not persist correctly'),
mirroring patch_replace's existing post-write verification.
- backend can't hash (no sha256sum) -> flag omitted, write unaffected.
Hashes the shim-adjusted content (after CRLF/BOM preservation) so
Windows-line-ending and BOM round-trips verify correctly; surrogatepass
encoding matches the rest of the codebase's hashing of model text.
Teknium