SlimAtlas

- Browser Automation: Navigate, click, type, fill forms, and evaluate JavaScript
- Lightweight by Default: ~5x less memory than Chromium, ~25x smaller snapshots than raw HTML
- Page Snapshots: Get compact YAML accessibility tree snapshots with unique node IDs for precise element targeting
- LLM-Optimized Context: Snapshots are stripped to semantic essentials, keeping context usage tiny so you can fit more pages and longer sessions into the same window
- Configurable Fallback Browser: Two-level model — lightweight browser first, then escalate toheadful Chrome,BrowserlessorBrowserbasecloud browsers only when the default is bot-detected, crashes, or times out.
- Rate Limiting: Stay under the radar. Enforce a configurable minimum delay between requests to specific domains with wildcard patterns (,.reddit.com) plus optional jitter, so your agent paces itself instead of hammering a site and tripping its bot defenses.
- Proxy Support: Route every request through an HTTP proxy with a singlePROXY_SERVERsetting — applied automatically tobothbrowser layers, so your real IP never touches the target. Supports inline basic auth (http://user:pass@host:port).
- Robust Session Management: Per-session serialization, optional session cap (MAX_SESSIONS), mid-session crash recovery with history replay, and graceful shutdown.
- Session Management: Reuse sessions across multiple operations with unique session IDs
- Cross-Platform: Works on Linux and macOS, with a configurable real-browser fallback when needed

Setup: Each service runs as an MCP server in its own Docker container. The benchmark harness measures per-tool-call latency (navigate + snapshot) vialangchain-mcp-adapters, and captures container RAM via the Docker stats API. Snapshots are token-estimated at ~4 chars/token (same methodology as the raw HTML baseline).

SlimAtlas trades navigation speed for dramatically lower resource usage. Chromium is faster on page load, but uses5–6x more RAMand produces2–4x more tokensper snapshot — the two costs that dominate at scale in agent workflows.

Browser binary is downloaded automatically on first run.

Fallback browser: Level 1 is always the lightweight browser. Level 2 isFALLBACK_BROWSER— one ofheadful(headful Chrome),browserbase(cloud),browserless(cloud), ornone(default, no fallback). When the default crashes, times out, or is bot-detected, the session switches once to the configured fallback. Chrome is bundled by Puppeteer; Browserbase/Browserless require API credentials (see below).

# Standalone HTTP server (default) bun run src/index.ts --port=8080 # Remote, authenticated MCP_AUTH_TOKEN=s3cret bun run src/index.ts --host=0.0.0.0 --port=8080

SlimAtlas exposes a singleStreamable HTTP/mcpendpoint. Each client gets its own session via themcp-session-idheader;MAX_SESSIONSbounds concurrency. Point your MCP client at it:

{ "mcpServers": { "slimatlas": { "url": "http://localhost:8080/mcp", "transport": "http" } } }

{ "mcpServers": { "slimatlas": { "url": "http://your-host:8080/mcp", "transport": "http", "headers": { "Authorization": "Bearer s3cret" } } } }

Tip: Use--host=0.0.0.0to expose remotely, but always setMCP_AUTH_TOKENwhen doing so. The server speaks plain HTTP only — terminate TLS in front (Caddy/nginx) or the Bearer token travels the network in cleartext.

The image bundles the Lightpanda binary at build time, so the container starts self-contained and never re-downloads:

docker build -t slimatlas . docker run -p 8080:8080 -e MCP_AUTH_TOKEN=s3cret slimatlas # -> http://localhost:8080/mcp

Pin a Lightpanda release for reproducible builds (anylightpanda-io/browsertag — defaultnightly):

docker build --build-arg LIGHTPANDA_VERSION=0.3.3 -t slimatlas:0.3.3 .

Multi-arch is handled automatically — the build detects the container's arch viauname -m(x86_64→lightpanda-x86_64-linux,aarch64→lightpanda-aarch64-linux), so the binary always matches the platform being built.

Apple Silicon (M-series Macs):pass--platform linux/arm64to build/run natively. Without it, Docker Desktop may default toamd64and run the container under Rosetta, which fails to launch the Lightpanda binary (rosetta error: failed to open elf …).

docker build --platform linux/arm64 --build-arg FALLBACK_BROWSER=headful -t slimatlas . docker run --platform linux/arm64 --name slimatlas -p 8080:8080 -e MCP_AUTH_TOKEN=s3cret -e LIGHTPANDA_POOL_SIZE=10 -e CHROME_POOL_SIZE=10 slimatlas

Headful fallback variant.The default image runs Lightpanda only (FALLBACK_BROWSER=none). To enable the headful Chrome fallback (needed only if you setFALLBACK_BROWSER=headfulat runtime), build the headful variant — it adds the Chrome runtime libraries + Xvfb (~150MB) and presetsFALLBACK_BROWSER=headful:

docker build --build-arg LIGHTPANDA_VERSION=0.3.3 FALLBACK_BROWSER=headful -t slimatlas:headful . docker run -p 8080:8080 -e MCP_AUTH_TOKEN=s3cret slimatlas:headful

Xvfb is started lazily inside the container on the first session that escalates to headful Chrome — no entrypoint or manualxvfb-runneeded.

For MCP clients that spawn the server as a subprocess (local, single-client), use stdio transport:

Skip the default browser for known-hard domainswithSKIP_LIGHTPANDA_DOMAINS(comma-separated, subdomain-aware). Matched hosts start directly on the fallback browser. RequiresFALLBACK_BROWSER != none(otherwise the list is ignored with a warning).

Polite, anti-detection pacing for your agent.RateLimiterenforces a server-wide minimum delay betweenbrowser_navigatecalls to the domains you list, with optional random jitter so the cadence isn't a fixed, fingerprintable interval. Buckets are keyed per host acrossallsessions (because the target site sees your IP, not your sessions), and patterns support wildcards:

Disabled by default. Enable with a non-empty domain listanda non-zero delay:

# Via CLI flags bun run src/index.ts --rate-limit-domains=.reddit.com,g2.com --rate-limit-min-delay-ms=2000 --rate-limit-jitter-ms=1500 # Or via environment / .env RATE_LIMIT_DOMAINS=.reddit.com,g2.com RATE_LIMIT_MIN_DELAY_MS=2000 RATE_LIMIT_JITTER_MS=1500

Keep your real IP off the target. Set a singlePROXY_SERVERand SlimAtlas routesallHTTP traffic frombothbrowser layers through it — no per-browser wiring needed:

- Lightweight browser (level 1)— forwarded via its native--http-proxyflag.
- Chrome fallback (level 2)— applied via--proxy-serverat launch.

# Via CLI flag bun run src/index.ts --proxy-server=http://host:8080 # Or via environment / .env PROXY_SERVER=http://user:pass@host:8080

Inline basic auth (http://user:pass@host:port) is supported on the lightweight browser layer. For IP-allowlisted proxies (no credentials) it just works on both layers.(Per-page Chrome authentication viapage.authenticateis on the roadmap.)

bun run src/index.ts --fallback-browser=headful --lightpanda-pool-size=3 --skip-lightpanda-domains=g2.com --navigate-timeout=60000

To use flags from an MCP client, append them to theargsarray:

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