---
title: reeval studio
description: Serve the web studio locally, or build it as a static site.
---
> ## Documentation Index
> Fetch the complete documentation index at: https://docs.reeval.ai/llms.txt
> Use this file to discover all available pages before exploring further.

`reeval studio` serves a web viewer for the history folder on `127.0.0.1`. `reeval studio build` writes the same app as a static site.

```bash
npx reeval studio --open
npx reeval studio build --out site
```

## reeval studio

[//]: # (generated:cli-help:studio)

```text
reeval studio                 Browse runs, evals and transcripts in the web studio (127.0.0.1)
  --port <n>                  First port to try (default 4984); --host <addr> (default 127.0.0.1)
  --open                      Open the browser; --no-scratch hides unrecorded runs from .reeval/runs
  --no-token                  Skip the session token (for scripts; anyone local can then read it)
```

[//]: # (/generated:cli-help:studio)

```text
reeval studio · capproj · evals/.history/
  http://127.0.0.1:4992/?token=rM5MMmCSd-Imd-n8w3TdNbkoBJ8gpuL1QGLl9c7qwgY
Ctrl-C to stop.
```

- **Port:** 4984, or the next free port. It runs until Ctrl-C.
- **Live:** it watches the history folder and `.reeval/runs/`. New runs appear within about a second. Unrecorded runs show a `scratch` badge unless you pass `--no-scratch`.
- **Runs in progress:** a running `reeval run` keeps `.reeval/staging/<runId>/live.json` (its planned attempts, each one's status and duration, and a heartbeat), replaced whole on every change. The studio shows the run at the top of the list until its record lands. A run whose process has exited, or whose heartbeat is over 15 seconds old, shows as `Stopped`. A finished attempt's transcript is served from the staged attempt record, redacted as records are. `--no-scratch` hides runs in progress too.
- **Debug tab:** attempts with local debug data in `.reeval/debug` get a Debug tab (phase timeline, gateway requests, `trace.ndjson` when kept).
- **Security:** the printed URL carries a random per-session token. Opening it sets an httpOnly, SameSite=Strict cookie and strips the token. Without it every route answers 401. The server checks `Host` and `Origin`, sends no CORS headers, answers GET and HEAD only, maps URLs to files through an allowlist and a realpath check, and serves artifacts as `text/plain` with `nosniff` and a sandboxing CSP.

<Warning>
  `--no-token` and a non-local `--host` let any process (or host) that can reach the port read your history. reeval prints a warning for each.
</Warning>

## reeval studio build

[//]: # (generated:cli-help:studio-build)

```text
reeval studio build           Write the studio as a static site for Pages, Netlify or any host
  --out <dir>                 Output folder (default studio-dist beside the config); --scratch
                              adds unrecorded runs
  --no-artifacts              Records and index only: no transcripts, diffs, logs or judge inputs
```

[//]: # (/generated:cli-help:studio-build)

```text
built ../capsite/: 2 runs, 83 files, 913 KB (records, transcripts, diffs, logs and judge inputs)
Serve it from any static host. Anyone who can open it can read every included file.
```

- **Layout:** `index.html`, `assets/`, `studio.json` and `data/`, with relative paths and hash routing, so it works at `/`, a subpath or a GitHub Pages project path with no rewrites.
- **Contents:** records plus transcripts, diffs, check logs, judge inputs and `worktree.patch` by default. `--no-artifacts` keeps records only. `--scratch` adds unrecorded runs. Debug data and symlinks are never included.
- **Refuses** an `--out` folder that isn't empty and isn't a previous build.

## File layout

The server and the static build serve the same paths:

```text
studio.json                               { mode: live|static, reeval, project, generatedAt, features }
data/index/manifest.json                  { shards: [{ id: "2026-09", runs }], latest, evals }
data/index/<YYYY-MM>.json                 run headers started that UTC month, newest first
data/runs/<runId>.json                    the record, byte for byte
data/runs/<runId>/<artifact path>         summary.md, worktree.patch, <eval>/<cell>/<n>/…
api/events                                live mode only: SSE history.changed and run.progress
api/live                                  live mode only: { runs: [...] }, the runs in progress
api/live/<runId>/transcript?attempt=<key> live mode only: a finished attempt's transcript
```

## Related

- [The studio](/guide/studio)
- [Nightly matrix and Pages](/recipes/nightly-pages)