[Bug] Opus 4.5 recurring errors causing "model_not_supported" failures in integrations

Bug Description
Community reaction (developer-facing)
On GitHub and Reddit, the dominant tone is frustration and lost productivity: people describe recurring errors making Opus 4.5 hard to rely on for day-to-day
coding work.

Some reports show abrupt “model_not_supported” behavior (e.g., Opus 4.5 disappearing from a tool’s model picker after errors), which users interpret as
instability or backend policy changes depending on the integration.

The reaction pattern is “try again / switch models / wait for incident to clear”, rather than “model quality feels worse,” which is a key difference vs. the
August 2025 narrative.

======

HAVE U EVER HEARD ABOUT CANARY TEST AND TESTING?
U R IN GOOD WAY TO REPEAT AUGUST 2025
HOW MANY TIMES WILL U ABLE TYO RELASE NEXT OPUS TO DRAW PEOPLE BACK?

YOUR OPUS BUTCHERED MY PROJECT A DAY BEFORE FINAL DEMO BEFORE STAKERHOLDERS

THANK YOU SO MUCH!!!!

Environment Info

• Platform: darwin
• Terminal: windsurf
• Version: 2.1.7
• Feedback ID: 61c87745-fc44-430d-bdc7-2b7192b2333a

Errors

[{"error":"Error: Error opening file /Users/bprzybyszi/.claude/projects/-Users-bprzybyszi-nc-src-ccm-chat/agent-a895e8d.jsonl: Error: ENOENT: no such file or directory, open '/Users/bprzybyszi/.claude/projects/-Users-bprzybyszi-nc-src-ccm-chat/agent-a895e8d.jsonl'\n    at Fg (file:///opt/homebrew/lib/node_modules/@anthropic-ai/claude-code/cli.js:74:170)\n    at async file:///opt/homebrew/lib/node_modules/@anthropic-ai/claude-code/cli.js:4065:3920\n    at async Promise.all (index 4)\n    at async W$A (file:///opt/homebrew/lib/node_modules/@anthropic-ai/claude-code/cli.js:4065:3756)\n    at async file:///opt/homebrew/lib/node_modules/@anthropic-ai/claude-code/cli.js:4065:11070\n    at async mT0 (file:///opt/homebrew/lib/node_modules/@anthropic-ai/claude-code/cli.js:4065:203)\n    at async HY9 (file:///opt/homebrew/lib/node_modules/@anthropic-ai/claude-code/cli.js:4065:10568)","timestamp":"2026-01-15T08:50:44.919Z"},{"error":"Error: Error opening file /Users/bprzybyszi/.claude/projects/-Users-bprzybyszi-nc-src-ccm-chat/agent-adb51e6.jsonl: Error: ENOENT: no such file or directory, open '/Users/bprzybyszi/.claude/projects/-Users-bprzybyszi-nc-src-ccm-chat/agent-adb51e6.jsonl'\n    at Fg (file:///opt/homebrew/lib/node_modules/@anthropic-ai/claude-code/cli.js:74:170)\n    at async file:///opt/homebrew/lib/node_modules/@anthropic-ai/claude-code/cli.js:4065:3920\n    at async Promise.all (index 9)\n    at async W$A (file:///opt/homebrew/lib/node_modules/@anthropic-ai/claude-code/cli.js:4065:3756)\n    at async file:///opt/homebrew/lib/node_modules/@anthropic-ai/claude-code/cli.js:4065:11070\n    at async mT0 (file:///opt/homebrew/lib/node_modules/@anthropic-ai/claude-code/cli.js:4065:203)\n    at async HY9 (file:///opt/homebrew/lib/node_modules/@anthropic-ai/claude-code/cli.js:4065:10568)","timestamp":"2026-01-15T08:50:44.919Z"},{"error":"Error: Error opening file /Users/bprzybyszi/.claude/projects/-Users-bprzybyszi-nc-src-ccm-chat/d2bd2868-1ab0-4670-999b-86cf5b931d66.jsonl: Error: ENOENT: no such file or directory, open '/Users/bprzybyszi/.claude/projects/-Users-bprzybyszi-nc-src-ccm-chat/d2bd2868-1ab0-4670-999b-86cf5b931d66.jsonl'\n    at Fg (file:///opt/homebrew/lib/node_modules/@anthropic-ai/claude-code/cli.js:74:170)\n    at async file:///opt/homebrew/lib/node_modules/@anthropic-ai/claude-code/cli.js:4065:3920\n    at async Promise.all (index 9)\n    at async W$A (file:///opt/homebrew/lib/node_modules/@anthropic-ai/claude-code/cli.js:4065:3756)\n    at async file:///opt/homebrew/lib/node_modules/@anthropic-ai/claude-code/cli.js:4065:11070\n    at async mT0 (file:///opt/homebrew/lib/node_modules/@anthropic-ai/claude-code/cli.js:4065:203)\n    at async HY9 (file:///opt/homebrew/lib/node_modules/@anthropic-ai/claude-code/cli.js:4065:10568)","timestamp":"2026-01-15T08:50:44.920Z"},{"error":"Error: Error opening file /Users/bprzybyszi/.claude/projects/-Users-bprzybyszi-nc-src-certinia/99569763-b0d7-4158-a3b6-4e3021a54f6c.jsonl: Error: ENOENT: no such file or directory, open '/Users/bprzybyszi/.claude/projects/-Users-bprzybyszi-nc-src-certinia/99569763-b0d7-4158-a3b6-4e3021a54f6c.jsonl'\n    at Fg (file:///opt/homebrew/lib/node_modules/@anthropic-ai/claude-code/cli.js:74:170)\n    at async file:///opt/homebrew/lib/node_modules/@anthropic-ai/claude-code/cli.js:4065:3920\n    at async Promise.all (index 14)\n    at async W$A (file:///opt/homebrew/lib/node_modules/@anthropic-ai/claude-code/cli.js:4065:3756)\n    at async file:///opt/homebrew/lib/node_modules/@anthropic-ai/claude-code/cli.js:4065:11070\n    at async mT0 (file:///opt/homebrew/lib/node_modules/@anthropic-ai/claude-code/cli.js:4065:203)\n    at async HY9 (file:///opt/homebrew/lib/node_modules/@anthropic-ai/claude-code/cli.js:4065:10568)","timestamp":"2026-01-15T08:50:44.937Z"},{"error":"Error: Error opening file /Users/bprzybyszi/.claude/projects/-Users-bprzybyszi-nc-src-certinia/agent-a6d1f22.jsonl: Error: ENOENT: no such file or directory, open '/U

Note: Error logs were truncated.