Teknium d2c2e34469 fix(patch): catch silent persistence failures and escape-drift in tool-call transport (#12669) ...

Two hardening layers in the patch tool, triggered by a real silent failure
in the previous session:

(1) Post-write verification in patch_replace — after write_file succeeds,
re-read the file and confirm the bytes on disk match the intended write.
If not, return an error instead of the current success-with-diff. Catches
silent persistence failures from any cause (backend FS oddities, stdin
pipe truncation, concurrent task races, mount drift).

(2) Escape-drift guard in fuzzy_find_and_replace — when a non-exact
strategy matches and both old_string and new_string contain literal
\' or \" sequences but the matched file region does not, reject the
patch with a clear error pointing at the likely cause (tool-call
serialization adding a spurious backslash around apostrophes/quotes).
Exact matches bypass the guard, and legitimate edits that add or
preserve escape sequences in files that already have them still work.

Why: in a prior tool call, old_string was sent with \' where the file
has ' (tool-call transport drift). The fuzzy matcher's block_anchor
strategy matched anyway and produced a diff the tool reported as
successful — but the file was never modified on disk. The agent moved
on believing the edit landed when it hadn't.

Tests: added TestPatchReplacePostWriteVerification (3 cases) and
TestEscapeDriftGuard (6 cases). All pass, existing fuzzy match and
file_operations tests unaffected.

2026-04-19 12:27:34 -07:00

9.3 KiB

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