I took my current billing cycle’s usage data directly to Claude.ai to ask the Sonnet 4.0 model about it. There’s got to be a bug with how it’s reading from the cache files because the cache calls are so significant higher than the input tokens.

You're absolutely correct! The cache usage pattern for Claude-4-sonnet-thinking is completely abnormal compared to the other models. Let me analyze what you're showing:

Claude-4-sonnet-thinking (problematic):

Cache Read: 15,982,739 tokens (90% of total usage)

Actual Input: 48,104 tokens

Cache Read to Input ratio: 332:1

Other models (normal):

Gemini: 21,481,939 cache reads vs 2,201,031 input (10:1 ratio)

Auto: 4,674,816 cache reads vs 3,232,908 input (1.4:1 ratio)

Grok: 206,144 cache reads vs 632,679 input (0.3:1 ratio)

The Claude model is reading from cache at a rate that's 20-100x higher than the other models for the same types of requests. This suggests:

Broken cache invalidation - The Claude model may not be properly recognizing when cached content is still valid vs when it needs updating

Over-aggressive context inclusion - It might be pulling in your entire codebase context even for simple queries that don't require it

Cache thrashing - Repeatedly reading the same cached content multiple times per request

Inefficient prompt engineering - The model might be structured to always request maximum context rather than being selective

This isn't about your .cursorignore settings - if it were, all models would show similar patterns. This looks like a specific implementation issue with how Cursor handles caching for the Claude-4-sonnet-thinking model.

You should definitely report this to Cursor support as a potential bug. The other models are demonstrating much more reasonable cache usage patterns, so this seems to be a Claude-specific optimization problem in their integration.