stacktrace

Backed by Combinator

Try Stacktrace
FleetSign up. Every agent's findings in one place. Sandbox (in-browser)Check a session in your browser.
Your session never leaves this tab. We don't see it, and neither does anyone else.Your session never leaves this tab.See how

See what your agent actually did.

Drop in a Claude Code session. See every action it took and what went wrong.

Sessions live in ~/.claude/projects/. On a Mac, press Cmd+Shift+. in the picker to see hidden folders.

Try a sample.

No session handy? Each sample is a short session with one known problem.

  • Did my agent leak a secret?

    Asked to fix a deploy, it read .env.staging and sent the token to an outside API.

    HighYou'll see: a token sent to an outside server

  • Did it delete outside the project?

    Asked to fix a flaky build, it deleted a cache in a folder next door and, with sudo, a global install.

    HighYou'll see: a delete outside the project

  • Did it switch credentials mid-session?

    The Linear connector call failed first, then the agent reconnected with a different token.

    MediumYou'll see: a connector that recovered on new credentials

How it works.

  1. Engine loads. stacktrace-cli 0.9.0 on WebAssembly. Served from stacktrace.ai, sha256-pinned.
  2. Network removed. The worker deletes fetch, XHR and WebSocket. The results frame runs under connect-src 'none'.
  3. File stays in memory. Read via the File API into the worker. Never written or sent.
  4. Same as the CLI. The detector and page of stacktrace monitor.
Where your session goes stacktrace.ai sends the engine code to this browser tab once, before your file. Your session file goes from your disk into Stacktrace in the tab, where the engine has deleted its network access. Nothing from your session goes back to stacktrace.ai. YOUR COMPUTER · THIS BROWSER TAB Session fileon your disk Stacktrace 1 · Enginenetwork deleted 2 · Rulesthe CLI's own read your session stays in this tab's memory STACKTRACE.AI Engine codeonce, cached code nothing from your session goes back
  • Verify it. Open developer tools, then Network. No requests after the engine loads.
  • What we count. That a check ran, the file's size band, and which rules matched. Never the file.
  • Not in the browser. Model-reviewed rules, vulnerability lookups and the Inventory tab. Use the CLI.
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