Claude

Limits and plans · 9 min read

What actually uses up your Claude usage limits

Anthropic publishes the plan tiers; it does not publish what a limit is spent on. The meter runs on tokens rather than messages, a long chat re-sends itself every turn, and attachments, project knowledge, tool results and thinking all land in the same budget. Mechanism first, numbers last.

How it works · 9 min read

Why the same prompt gives you a different answer

You changed nothing and the answer changed anyway. A mental model of what actually varies between two runs of an identical prompt: sampling that never fully stops, a context window that grows every turn, a system prompt the vendor rewrites, memory you cannot see, and infrastructure that moves under a pinned model.

Troubleshooting · 10 min read

Why ChatGPT and Claude didn't really read your file

The upload succeeded and the answer is about the wrong thing. Both vendors document the formats they accept; neither documents what happens between the upload and the model. Eight causes, each with a distinct fingerprint, and three probes that tell you what the model actually saw.