GitHub - AlistairClark7/context-autopsy: Find out what's actually filling your coding agent's context window. Local analysis of Claude Code & Codex sessions.

Find out what's actually filling your coding agent's context window.

Your agent has a 200k–1M token window. You'd think most of it is spent on your code. Run this and see what it's really spent on.

It reads the coding-agent transcripts already on your machine (Claude Code, Codex, Cursor, OpenCode, Pi, Gemini CLI, Qwen Code, Cline, Roo Code, Kilo Code, Factory Droid, Amp and Goose) and breaks every token down by what it was for: reading code, writing code, build and test logs, wrangling Docker, cloud CLIs and env vars, failed commands, fixed overhead, and more.

Everything runs locally. Nothing is uploaded. No dependencies.

What you get

First, a card sized for one post (example output):

🩻 I autopsied my Claude Code context window.

Only 27% of it was my actual code.

🔑 It saw 23 secret keys & passwords
💥 1,204 failed commands
🔧 21% was build logs & env wrangling
🧠 Hit its context limit 87 times

1.9B tokens in 60 days
npx context-autopsy

The headline and stats are picked from whatever is most striking in your data. The card always fits in 280 characters and contains no paths, project names or commands. --share --copy puts it on your clipboard and prints a link to post it.

Below the card is the full breakdown:

WHERE YOUR CONTEXT WENT
                                  processed*   share  in context
Reading code                          512.3M   27.0%        9.1M  ██████████████████████████████
Fixed overhead                        398.4M   21.0%        5.2M  ███████████████████▍··········
Build, test & run output              246.6M   13.0%        4.4M  █████████████▏················
Reasoning                             227.6M   12.0%        4.6M  ████████▍·····················
Environment & infrastructure          151.8M    8.0%        2.7M  ████████▏·····················
Git & version control                 132.8M    7.0%        2.4M  ███████▍······················
...

THE HEADLINES
▸ 21% of everything your agents processed was build output and environment wrangling.
▸ 1,204 failed commands and tool calls (7% of all tool calls), 64.0M tokens of error output processed.
▸ 23 credentials passed through the model's context (9 Database URL with password, 6 AWS access key, …).
▸ Most expensive single output: a 14k-token `pnpm install` result, re-sent 212 times = 3.0M tokens.
▸ 41 sessions filled the window and compacted (87 times).

Also shown:

• At peak: what your fullest context was made of at the moment it was fullest.
• Most expensive tool outputs: the single results that cost you the most.
• Sessions most buried in plumbing: the ones where the agent spent its time on setup instead of your feature.

Why "processed" and not just "size"?

An LLM is stateless. On every turn the whole context is sent again, so a 15k-token npm install log that lands early in a 200-turn session isn't 15k tokens. It's 15k tokens × every remaining turn, until the session compacts.

context-autopsy follows each piece of content from the turn it entered the context to the turn it left. It reports two numbers:

• in context: the tokens added.
• processed: tokens × the number of model calls they rode along for. This is what drives cost, latency and context rot.

Estimates are calibrated against the real token counts the API reported in each transcript, so the totals add up to what was actually processed. The hidden system prompt and tool schemas are inferred from the size of the first request.

The groups

It also flags cross-cutting waste: failed commands, exact duplicates (the same file read twice, the same command re-run), lockfiles and build artefacts read into context, compactions, and credentials (AWS, GitHub, Stripe, OpenAI and Anthropic keys, private keys, JWTs, database URLs with passwords, *_SECRET= assignments).

Credentials are fingerprinted with a one-way hash so they can be counted. The values are never stored or printed.

Options

npx context-autopsy [options] [transcript.jsonl | directory ...]

  --agent <ids>                Only these agents, comma-separated (default: all)
                               claude, codex, cursor, opencode, pi, gemini, qwen,
                               cline, roo, kilo, droid, amp, goose
  --since <7d|2026-09-01>      Only sessions active since this date or age
  --project <text>             Only sessions whose working directory contains <text>
  --last <n>                   Only the n most recent sessions
  --no-subagents               Skip subagent / child-thread transcripts
  --detail                     Show sub-categories (which tools, which commands)
  --top <n>                    Rows in the "most expensive" table
  --share                      Just the post-ready card, plus a link to post it
  --copy                       Copy the card to the clipboard
  --json                       Machine-readable output

Supported agents

Every agent found on your machine is read automatically.

¹ Cursor doesn't store per-request usage. Sizes are calibrated from the context-window snapshot Cursor saves with each message you send. ² Droid and Amp are closed source. Their formats come from open-source parsers, not vendor code. ³ "The extension's storage" means VS Code's global storage for the extension, in VS Code, Insiders, VSCodium, Cursor, Windsurf, Trae or Kiro, including remote (~/.vscode-server) installs.

SQLite-backed agents (Cursor, OpenCode, Kilo Code 7.x, Goose) need Node 22.5 or later. On older versions of Node they're skipped. Not supported yet: Cursor's CLI (cursor-agent), which uses undocumented protobuf storage, and GitHub Copilot Chat and Aider, which don't keep tool output in a usable form.

Is your agent missing? Open an issue with where it stores sessions.

Share yours

npx context-autopsy --share --copy

This prints just the card, copies it to your clipboard, and gives you a link that opens a pre-filled post.

Use it from inside Claude Code

Install it as a plugin, then ask "where is my context going?" or run /context-autopsy:

/plugin marketplace add AlistairClark7/context-autopsy
/plugin install context-autopsy@context-autopsy

Or copy skills/context-autopsy into ~/.claude/skills/. The skill runs the analysis, explains the numbers, and suggests fixes specific to what it found.

Caveats

• Token counts per item are estimated from text length (about 3.8 characters per token), then scaled per session to match the API's reported totals. Category shares are good. Individual items are approximate.
• Category rules are heuristics over tool names, commands and file paths. --detail shows exactly what went where. PRs that improve the rules are welcome.
• Transcript formats change between agent versions. Claude Code, Codex and Roo Code have been tested against real sessions. The other agents' parsers were built from their source code and are tested with synthetic sessions. If something looks off, run with DEBUG=1 and open an issue.

Licence

MIT