The best Stagehand alternative
is 40× cheaper.
Sentinel and Stagehand have nearly identical APIs — but Sentinel defaults to Gemini Flash instead of GPT-4o. That single difference saves ~$78 per 1,000 runs. On top of that: self-healing locators, parallel execution, MCP server, CLI, and Playwright Test integration — none of which Stagehand has.
Full comparison
| Metric | Sentinel | Stagehand |
|---|---|---|
| Default LLM | Gemini 3 Flash | GPT-4o |
| Cost / run | ~$0.002 | ~$0.08 |
| Cost / 10k runs | ~$20 | ~$800 |
| Avg. latency | ~2.8s | ~4.2s |
| Self-healing locators | ✓ | ✗ |
| Prompt caching | ✓ | ✗ |
| Parallel sessions | ✓ built-in | manual |
| Autonomous agent loop | ✓ run(goal) | partial |
| Selector export | ✓ result.selectors | ✗ |
| MCP server | ✓ | ✗ |
| CLI | ✓ | ✗ |
| Playwright Test fixture | ✓ | ✗ |
| Custom LLM provider | ✓ any | OpenAI only |
| OpenTelemetry | ✓ | ✗ |
| Shadow DOM | ✓ full | partial |
| Open source | ✓ MIT | ✓ MIT |
What Sentinel adds that Stagehand doesn't have
Self-healing locators
The first successful act() caches the CSS selector. Every subsequent call uses Playwright directly — zero tokens. If the element changes, the cache invalidates and the LLM re-discovers it. Stagehand has no equivalent.
// Stagehand: no locator caching — every call hits the LLM
await stagehand.act({ action: 'Click the login button' }); // LLM call
await stagehand.act({ action: 'Click the login button' }); // LLM call again
// Sentinel: cache successful selectors — LLM only called once
const sentinel = new Sentinel({
apiKey: process.env.GEMINI_API_KEY,
locatorCache: '.sentinel-cache.json', // persists across process restarts
});
await sentinel.act('Click the login button'); // LLM call → caches selector
await sentinel.act('Click the login button'); // direct Playwright → zero tokensParallel execution
Sentinel.parallel() runs N tasks in separate browser sessions with a concurrency-limited worker pool. One failure never affects others. Stagehand requires you to manage multiple instances and error handling yourself.
// Stagehand: no built-in parallel — you manage sessions manually
// Sentinel: built-in worker pool, error isolation, progress callbacks
const results = await Sentinel.parallel(
sites.map((url) => ({ url, goal: 'Extract top product name and price' })),
{ apiKey: process.env.GEMINI_API_KEY, concurrency: 5 }
);Autonomous agent loop
Stagehand exposes act/extract/observe primitives — you write the loop. Sentinel's run(goal) runs a full Plan → Execute → Verify → Reflect cycle autonomously. It also exports stable CSS selectors you can paste directly into Playwright tests.
// Stagehand: you write the loop yourself
await stagehand.act({ action: 'Search for laptop' });
await stagehand.act({ action: 'Click first result' });
const data = await stagehand.extract({ instruction: 'Get price', schema });
// Sentinel: autonomous — give it a goal, let it figure out the steps
const result = await sentinel.run(
'Go to amazon.de, search for laptop, extract the top 5 results with prices'
);
console.log(result.data); // structured products
console.log(result.selectors); // stable CSS selectors for Playwright testsMigration is a find-and-replace
The APIs are intentionally similar. For most projects, migration is renaming the import and removing the object wrapper from act() and extract().
// Before — Stagehand
import { Stagehand } from '@browserbasehq/stagehand';
const stagehand = new Stagehand({ env: 'LOCAL' });
await stagehand.init();
await stagehand.act({ action: 'Search for laptop' });
const data = await stagehand.extract({ instruction: '...', schema });
// After — Sentinel (find & replace, done)
import { Sentinel } from '@isoldex/sentinel';
const sentinel = new Sentinel({ apiKey: process.env.GEMINI_API_KEY });
await sentinel.init();
await sentinel.act('Search for laptop');
const data = await sentinel.extract('...', schema);Try it in 30 seconds
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