CRLF Line-Ending Normalization in File-Editing Tools

Summary

Codex CLI rust-v0.162.0 (2026-10-08, PR #51203) changed apply_patch to preserve an existing file's CRLF line endings by default. A live probe of the yoyo/yoagent 0.25.2 edit stack found the complementary failure mode on the other side: the same class of tool can succeed on single-line edits of CRLF files but fail on multi-line edits, because the model-supplied old_text uses bare LF while the file stores CRLF and no normalization is applied before matching.

Key Points

• Codex 0.162.0: apply_patch no longer rewrites CRLF files with LF; existing CRLF endings are preserved by default (PR #51203).
• Live probe target: yoyo b57d5831 — yoagent 0.25.2 EditFileTool, wrapped by yoyo's src/smart_edit.rs SmartEditTool.
• Single-line edit on a CRLF file succeeds and keeps CRLF intact — no data loss, correct endings out.
• Multi-line old_text fails with old_text not found, because the model joins lines with LF while the file contains CRLF.
• The error message is actively misleading: it reports "Nearest match at line 1 with text identical to old_text". The match looks identical because str::lines() strips the \r, so the displayed text and the supplied text are visually the same.
• The recovery hint is unusable: it tells the model to read_file and copy the exact text. The model cannot see the \r characters, so copying can never reproduce them.
• Downstream failure: given a plausible-but-then-refuted error, the model invented a wrong diagnosis rather than converging on the line-ending cause.
• Root cause: yoagent edit.rs calls content.matches(old_text) with .