[Bug] Anthropic API Error: 500 Internal Server Error on claude.md rule creation
Open 💬 0 comments Opened Jun 16, 2026 by ubandaru
Bug Description
API Error: 500 Internal Server error when trying to write a generic rule in claude.md
Environment Info
- Platform: darwin
- Terminal: Apple_Terminal
- Version: 2.1.173
- Feedback ID: 2efa709f-9a95-45cf-9b38-7e0c2c8027b4
Errors
[{"error":"Error: 404 {\"type\":\"error\",\"error\":{\"type\":\"not_found_error\",\"message\":\"Claude Fable 5 is not available. Please use Opus 4.8. Learn more: https://www.anthropic.com/news/fable-mythos-access\"},\"request_id\":\"req_011CbzSi2Ms89itarXstVkzN\"}\n at generate (/$bunfs/root/src/entrypoints/cli.js:12:66126)\n at makeRequest (/$bunfs/root/src/entrypoints/cli.js:52:7694)\n at processTicksAndRejections (native:7:39)","timestamp":"2026-06-13T02:08:33.976Z"},{"error":"Error: 404 {\"type\":\"error\",\"error\":{\"type\":\"not_found_error\",\"message\":\"Claude Fable 5 is not available. Please use Opus 4.8. Learn more: https://www.anthropic.com/news/fable-mythos-access\"},\"request_id\":\"req_011Cc5JxKHaS1nhjonasv73q\"}\n at generate (/$bunfs/root/src/entrypoints/cli.js:12:66126)\n at makeRequest (/$bunfs/root/src/entrypoints/cli.js:52:7694)\n at processTicksAndRejections (native:7:39)","timestamp":"2026-06-15T15:49:51.573Z"},{"error":"Error: 500 {\"type\":\"error\",\"error\":{\"type\":\"api_error\",\"message\":\"Internal server error\"},\"request_id\":\"req_011Cc7LCdfPJm1LmLW59rRzN\"}\n at generate (/$bunfs/root/src/entrypoints/cli.js:12:66273)\n at makeRequest (/$bunfs/root/src/entrypoints/cli.js:52:7694)\n at processTicksAndRejections (native:7:39)","timestamp":"2026-06-16T17:27:31.099Z"}]