[BUG} API Error: 400 'input length and `max_tokens` exceed context limit' occurs when close to compaction

Environment

• Platform (select one):
• [ ] Anthropic API
• [ ] AWS Bedrock
• [ ] Google Vertex AI
• [x ] Other: local
• Claude CLI version: 0.2.40 (Claude Code)
• Operating System: MacOS 15.3.1 arm64
• Terminal: iTerm2

Bug Description

When i'm within about 5% of needing to /compact , I consistently get:

API Error: 400 {"type":"error","error":{"type":"invalid_request_error","message":"input length and max_tokens exceed context limit: 186433 + 20000 > 200000, decrease input

Steps to Reproduce

1. do a long running activity
2. continue until context available <5%
3. ask something quite hard
4. error

Expected Behavior

Error not thrown and handled gracefully, either with meaningful error message with user next steps, or transparently.
I think i would also expect that claude code also prompts at suitable times to compact. Unfortunatly after a compact you then need to 'get it back up to speed' with what it was doing when the error occured

Actual Behavior

error thrown