[Bug] Edit tool corrupts Unicode (Armenian) text in multi-line replacements

Bug Description
Edit tool corrupts Armenian (Unicode) text in multi-line replacements

When using the Edit tool to insert/replace large blocks of text containing Armenian script (Unicode range U+0530–U+058F) mixed with
code syntax (Dart string literals with single quotes), the Armenian characters get silently replaced with garbage English text (e.g.
"delays", "Delays"). The corruption is not random — the same wrong substitutions appear consistently.

Reproduces with: Edit tool new_string parameter containing Armenian characters like Հայերdelays inside Dart code like nativeLabel:
'Ուdelays'. The model's output is correct (verified by inspecting plain text output and Write tool), but what lands in the file is
corrupted.

Does NOT reproduce with:

• Plain text output (Armenian renders correctly)
• Write tool (Armenian writes correctly to files)
• Small/single-line Edit operations (untested but suspected OK)

Workaround: Use a Python script with \uXXXX escape sequences and pathlib.write_text(), or use the Write tool instead of Edit for
affected sections.

Session context: Occurred while adding Armenian language support to a Flutter app — writing ~60 lines of Dart containing Armenian
grammar terms (Ուղغakan, Սeéakan, etc.) as string literals. Model is Claude Opus 4.6. Multiple Edit attempts all produced the same
corruption pattern.

Environment Info

• Platform: darwin
• Terminal: Apple_Terminal
• Version: 2.1.39
• Feedback ID: d66bb898-73ba-40d7-aba7-37ed211f44e3

Errors

[{"error":"Error: NON-FATAL: Lock acquisition failed for /Users/me/.local/share/claude/versions/2.1.39 (expected in multi-process scenarios)\n    at wVR (/$bunfs/root/claude:3626:2098)\n    at DjA (/$bunfs/root/claude:3626:1209)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-02-13T22:06:16.990Z"}]