You pay for the same context on every turn.
A system prompt, a tool catalog and your instruction files load before you type a word, then get re-read on every turn after the first. contextbill prices the transcripts already on your disk.
Where the money actually goes.
19.6%of the bill on the machine this was built for, measured across 2,424 transcripts.
That share is overhead. It is written to cache once and re-read on every turn after it, so a 500-turn session pays for it 500 times. You shrink it by deleting connectors you never call, not by prompting differently.
contextbill breaks the same total down by model, by session and by what each session actually produced, so you can tell an expensive session from a wasted one.
A model with no published rate in the table is counted and named rather than quietly folded in at zero, so a total that does not cover everything says which part it missed.
Every figure is API-equivalent: what that usage would cost metered at Anthropic's published API rates. On a subscription you paid a flat fee instead, so the dollars value the usage rather than restate your invoice. This app reads Claude Code transcripts. The command line also reads OpenAI Codex CLI rollouts on request, priced at OpenAI's own published rates.
Four steps, and your transcripts stay on your machine.
Point it at a folder
Usually ~/.claude/projects. Nothing is uploaded to choose it.
Parsing runs in your browser
Token counts, model ids and timestamps. Never message content.
Only totals are saved
Aggregates reach the server. Raw transcripts never leave the tab.
Compare over time
Reports are kept, so you can watch a number move after you change something.
What actually leaves your computer.
- Aggregates only
- Totals, per-model spend and session-level counts. No prompts, no completions, no file contents.
- Paths redacted
- Project folder names encode your OS username. contextbill strips that before anything is stored.
- Or no account
- The CLI runs the same analysis with no network access at all. Same engine, same numbers.
See your number in about a minute.
Runs offline and uploads nothing.