[Bug] Anthropic API Error: Intermittent false-positive safeguard errors with large MCP tool results

Bug Description
Repeated false-positive safeguard errors with detail [reasoning_extraction] in a normal software release-management session (git verification, Shortcut MCP task updates, Slack message drafting - nothing sensitive). The error fired 3+ times in a row on consecutive turns; retrying the same message eventually worked each time, so the content itself seems fine. It appears correlated with turns that process large MCP tool results (Shortcut story JSON).

Request IDs: req_011CeEKufJrBDi9PpANTfrry, req_011CeELecA3Y4jE1VVef7UKA, req_011CeELgcpHTW7P8vyz1XPss

Environment Info

• Platform: win32
• Terminal: windows-terminal
• Version: 2.1.237
• Feedback ID: 0ed31157-4075-4ae5-8f88-21c062b79791

Errors

[{"error":"TelemetrySafeError: VirtualMessageList: itemKeys/messages length desync (keys=141 messages=140 range=[81,141))\n    at lGE (B:/~BUN/root/cli:23198:33898)\n    at i8h (B:/~BUN/root/cli:23198:26870)\n    at vi (B:/~BUN/root/cli:2140:21439)\n    at Lm (B:/~BUN/root/cli:2140:40550)\n    at Iy (B:/~BUN/root/cli:2140:51489)\n    at ii (B:/~BUN/root/cli:2140:89194)\n    at co (B:/~BUN/root/cli:2140:88149)\n    at $t (B:/~BUN/root/cli:2140:87970)\n    at kUe (B:/~BUN/root/cli:2140:84225)\n    at gt (B:/~BUN/root/cli:2140:6694)","timestamp":"2026-08-20T13:11:13.311Z"}]