[Bug] Anthropic API Error: Overly aggressive AUP filtering blocks legitimate defensive security code

Bug Description
Model: Fable 5 · Claude Code v2.1.220 Request IDs: req_011CdRJ12gxDrDyHACNpSgvc, req_011CdRJ1xn5j3HUNnESx1HSJ Two consecutive responses were blocked by AUP safeguards during routine defensive-security engineering on a personal project — an end-to-end encrypted messaging transport running between machines I own, used by me and a handful of friends and family I onboarded personally. The specific work at the moment of the block: implementing a message-queue purge in a relay broker, so frames queued for a peer that has since re-keyed are discarded rather than delivered as undecryptable garbage — plus the acceptance test for it. Adjacent work in the same session included Ed25519 signature verification and Unicode control-character filtering for a user-set status field. All of it is defensive. It exists to close bugs that were silently destroying messages, and to stop a compromised relay from forging content attributed to a user. No third-party system is involved, and nothing is being attacked. Impact: the session became unusable mid-build, with uncommitted work recovered by a second thread on a different model. This is the second occurrence on this project. Observation that may help triage: defensive security work is lexically indistinguishable from the thing being screened for. The session was necessarily full of words like purge, forge, hostile, injection, attack surface, corpses, poison — used to describe threats being eliminated. A classifier keying on that vocabulary will fire hardest on exactly the engineering that most deserves to happen. Request: when a response is blocked, some way to continue the session would help more than the block costs. Right now the thread is simply dead, and the model's own in-progress work has to be reconstructed from the filesystem by someone else.

Environment Info

• Platform: win32
• Terminal: windows-terminal
• Version: 2.1.220
• Feedback ID: deebc085-f946-4ee1-b7ad-b289b369c64f

Errors

[{"error":"TelemetrySafeError: VirtualMessageList: itemKeys/messages length desync (keys=148 messages=147 range=[116,148))\n    at Gzb (B:/~BUN/root/src/entrypoints/cli.js:21739:8188)\n    at Hhf (B:/~BUN/root/src/entrypoints/cli.js:21739:1103)\n    at no (B:/~BUN/root/src/entrypoints/cli.js:2061:21369)\n    at DA (B:/~BUN/root/src/entrypoints/cli.js:2061:40466)\n    at q3 (B:/~BUN/root/src/entrypoints/cli.js:2061:51400)\n    at Mne (B:/~BUN/root/src/entrypoints/cli.js:2061:89060)\n    at ULe (B:/~BUN/root/src/entrypoints/cli.js:2061:88007)\n    at Wge (B:/~BUN/root/src/entrypoints/cli.js:2061:87827)\n    at nQ (B:/~BUN/root/src/entrypoints/cli.js:2061:84091)\n    at Rt (B:/~BUN/root/src/entrypoints/cli.js:2061:6668)","timestamp":"2026-07-26T19:37:32.657Z"}]