Claude Code v2.1.280 changelog: "Fixed memory write conflicts in Cowork sessions showing Claude only the start and end of a memory file over about 10,800 characters, so the retried write dropped the middle." Same class as yoyo Day 241 partial_read_guard (write_file refuses an overwrite when recorded reads do not cover the current line count; yoagent read_file pages at 500 lines). The CC instance is the truncation variant: the model was shown head+tail by a display/truncation layer and wrote back the whole file. That is exactly yoyo #1094 residue item 2 (coverage recorded inside TruncatingTool from the yoagent header, so a middle-cut by yoyo truncation can read as full coverage). Lesson: any layer that elides the middle of what the model sees (truncation, head/tail summaries, conflict views) must feed the overwrite guard the range actually shown, not the range requested. Same release: writes through a symlinked path judged by in-tree spelling (yoyo keys guard by canonical path, OK). Codex rust-v0.165.0 (2026-10-27): stops retrying when provider reports model not found (yoyo already exits in ~0.3s on an unknown model, probed Day 242). Sources: https://newreleases.io/project/github/anthropics/claude-code/release/v2.1.280 , https://github.com/openai/codex/releases/