Reverse-engineer a month of your own local Claude Code logs (~/.claude/projects/*/*.jsonl) into where the tokens, time, and cost actually go — and run it on yours. Reads only local logs; nothing is sent anywhere.

What it found (one month of my own logs — 181 sessions, 25,564 model calls):

• You don't pay to generate, you pay to re-read. ~29M unique tokens → 4.35B billed (~150×), because every turn re-sends the whole ~173K-token context.
• The bill is 84% input / 16% output — and re-reading the same context is 64% of it.
• The biggest line is the one you never see: hidden reasoning is 84% of output and ~60% of everything re-read.
• ~$3,371 for the month at Opus 4.7 list rates. Caching already serves 98% of input — and re-reading is still 64% of the bill.

Full write-up (all the tables, the why, the main-thread-vs-subagent split) → coralbricks.ai/blog/claude-code-token-xray

Quickstart

pip install -r requirements.txt   # just tiktoken
python3 token_time_breakdown.py
python3 cost.py
python3 main_vs_sidecar.py
python3 reread_breakdown.py

tiktoken is OpenAI's tokenizer, not Claude's, so token proportions are reliable to ~±15%, not Claude-exact. The billed-token counts in cost.py come straight from the API usage blocks and are exact.

What a month cost

From cost.py on my logs, priced at Opus 4.7 list rates:

Caching is the only thing keeping it sane — without it the same work lists at ~$22,630 (~7×). Your numbers will differ; that's the point. Run it on yours.

Scripts

• token_time_breakdown.py — the headline table: tokens (marked input/output) and wall-clock time per activity (reasoning, running commands, writing tool calls, subagents, summaries, reading/searching, editing) plus the passive-context rows (system prompt + tools, attachments, the typed prompt, injected reminders). One pass, so tokens and time stay consistent. Reasoning isn't stored in plaintext (only an encrypted signature), so it's recovered by subtraction: output − tool_calls − summaries. Time is reconstructed from event timestamps.
• cost.py — billed token totals (cache reads / cache writes by TTL / fresh input / output) priced at Opus 4.7 list rates, plus the no-caching counterfactual.
• main_vs_sidecar.py — splits the human-driven main thread from spawned subagents (logged under nested */subagents/*.jsonl); reports billed tokens, per-model mix, cache-hit rate, turns per agent (per session for the main thread, per subagent for the sidecar), and cost for each, plus the combined total.
• reread_breakdown.py — per-activity cumulative input: replays each session's context growth to show what each kind of context costs once it's re-read every turn. Reports unique vs re-read tokens per activity (reasoning is the biggest re-read line). The replay is scaled to the measured billed input (exact); the per-activity split is a model.

Caveats

• One person's month on one machine — directional, not a benchmark. Claude Code is dynamic, so your split will differ. That's the point: run it on yours.
• A generation-time gap also includes the model reading its context before it writes; Bash time is real execution (commands auto-approved), but code run in the background or a separate terminal isn't counted.
• The system-prompt row is estimated from each session's first cache write.

Found this useful?

If this helped you see where your Claude Code tokens, time, and cost actually go, please ⭐ the repo — it helps others find it. Curious what your re-read share comes out to.

License

Apache 2.0 — see the repository LICENSE.