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.
- Bug 1: replace read_file(limit=10000) with read_file_raw in _apply_update,
preventing silent truncation of files >2000 lines and corruption of lines
>2000 chars; add read_file_raw to FileOperations abstract interface and
ShellFileOperations
- Bug 2: split apply_v4a_operations into validate-then-apply phases; if any
hunk fails validation, zero writes occur (was: continue after failure,
leaving filesystem partially modified)
- Bug 3: parse_v4a_patch now returns an error for begin-marker-with-no-ops,
empty file paths, and moves missing a destination (was: always returned
error=None)
- Bug 4: raise strategy 7 (block anchor) single-candidate similarity threshold
from 0.10 to 0.50, eliminating false-positive matches in repetitive code
- Bug 5: add _strategy_unicode_normalized (new strategy 7) with position
mapping via _build_orig_to_norm_map; smart quotes and em-dashes in
LLM-generated patches now match via strategies 1-6 before falling through
to fuzzy strategies
- Bug 6: extend fuzzy_find_and_replace to return 4-tuple (content, count,
error, strategy); update all 5 call sites across patch_parser.py,
file_operations.py, and skill_manager_tool.py
- Bug 7: guard in _apply_update returns error when addition-only context hint
is ambiguous (>1 occurrences); validation phase errors on both 0 and >1
- Bug 8: _apply_delete returns error (not silent success) on missing file
- Bug 9: _validate_operations checks source existence and destination absence
for MOVE operations before any write occurs
