We built Stagehand 2 years ago (24k stars and 4M monthly npm downloads) and recently fixed its biggest flaw: round-trip latency.
Every action performed requires a round trip between your script and the browser (short when running locally but increased when running in the cloud). We also saw multiple posts complaining about the eager token appetite of Playwright MCP.
For this reason, we rebuilt Stagehand from the ground up and shipped v4, where Stagehand controls the browser from an extension automatically loaded upon your browser startup.
Stagehand v4 comes with batch command support, dedicated token-efficient methods `act()` and `extract()`, and a brand new architecture making it 2x faster than Playwright and 80% more token efficient.
You can see for yourself by looking at our benchmarks, comparing its performance across a dozen models (frontier and open weights) and tools (Codex, Claude Code, and more): https://www.stagehand.dev/evals
I'm using playwright to do diagnosis on customer sites, and I'm wondering some things:
1) Does it have full Chrome Devtools support? Like, able to diagnose where a fetch() came from, what script sets a cookie?
2) How hard would it be to set up in an AWS Lambda (I can run Playwright without needing to run a container, which saves a lot of startup time/cost)?
Always interesting to see forward work on these kinds of tools which get used so foundationally billions of times a day.
I've been using Playwright a lot, this looks very interesting!
How does stagehand deal with complex http/websocket request/response and or console message filtering? https://docs.stagehand.dev/v4/reference/page#on E.g. I would like a script that tracks all communication that matches a specific filter (implemented as an anonymous function/lambda). This filter may look at patterns in the url, but sometimes needs to do a deeper inspection of also the payload (if the url does not carry enough information in itself).
I've found playwright to be prohibitively slow at this, not only because of the round-trip latency, but just the simple fact that it needs to pump the complete response to my filter function, which then proceeds to read only a couple of bytes to make the filtering decision. There are a lot of cases where I am only interested in around 1% of the total requests processed by the filter, which makes this behaviour massively wasteful.
Ideally I would like to run this filter in the browser as well. From the documentation, I don't see this use-case is currently supported. Are there any plans along these lines? :)
It still uses CDP but communicates from an extension within the browser instead of a script running in a separate runtime or, worse, in a separate region.
I tried this myself - my conclusion was the overhead of parsing a screenshot, generating an action, and being limited to headful mode is much less efficient than reading accessibility trees & generating CDP commands.
basically, browser automation is a closer-to-the-metal abstraction than computer use, allows more flexibility, and ends up being much cheaper at scale!
If agents need to run on the desktop or logged into a user's real browser, the alternative would be Ui.Vision MCP. But stagehand is designed for backend use, so apples and oranges.
Exactly, as Stagehand now runs inside the browser, you'll save on the round trip.
Also, enabling batch actions will further accelerate your test suite.
seems really cool! although, one question i have is why not keep agent() alongside the new primatives? it seems v4 removed agent() entirely rather than offering it with all of act(), observe(), extract().
Looks very useful, and I like the caching idea which I think makes it interesting for self-healing CI tests.
How does it determine when a cached act() fails and has to be re-evaluated by the LLM? And in particular, if the cache is saved in the cloud (Browserbase?), won't this lead to a lot of cache churn if used in CI pipelines where different versions of the site are running against the same cache?
Also, is there a technical reason why the cache couldn't just be a local file that's checked in along with the script but must be provided by Browserbase? If it was, devs could heal failing tests locally using LLM calls, while CI runs entirely deterministically.
Where would the control come from? Software installed on the client's computer, or software installed connecting to an AI agent, or something else, something more external, something more interactive?
Yes, we install a small piece of software on their computers because we also separately control GUI of legacy windows apps. But we also need to control web based apps as well.
35 comments
[ 1.6 ms ] story [ 10.7 ms ] threadEvery action performed requires a round trip between your script and the browser (short when running locally but increased when running in the cloud). We also saw multiple posts complaining about the eager token appetite of Playwright MCP.
For this reason, we rebuilt Stagehand from the ground up and shipped v4, where Stagehand controls the browser from an extension automatically loaded upon your browser startup.
Stagehand v4 comes with batch command support, dedicated token-efficient methods `act()` and `extract()`, and a brand new architecture making it 2x faster than Playwright and 80% more token efficient.
You can see for yourself by looking at our benchmarks, comparing its performance across a dozen models (frontier and open weights) and tools (Codex, Claude Code, and more): https://www.stagehand.dev/evals
Ask me anything!
1) Does it have full Chrome Devtools support? Like, able to diagnose where a fetch() came from, what script sets a cookie? 2) How hard would it be to set up in an AWS Lambda (I can run Playwright without needing to run a container, which saves a lot of startup time/cost)?
Always interesting to see forward work on these kinds of tools which get used so foundationally billions of times a day.
How does stagehand deal with complex http/websocket request/response and or console message filtering? https://docs.stagehand.dev/v4/reference/page#on E.g. I would like a script that tracks all communication that matches a specific filter (implemented as an anonymous function/lambda). This filter may look at patterns in the url, but sometimes needs to do a deeper inspection of also the payload (if the url does not carry enough information in itself).
I've found playwright to be prohibitively slow at this, not only because of the round-trip latency, but just the simple fact that it needs to pump the complete response to my filter function, which then proceeds to read only a couple of bytes to make the filtering decision. There are a lot of cases where I am only interested in around 1% of the total requests processed by the filter, which makes this behaviour massively wasteful.
Ideally I would like to run this filter in the browser as well. From the documentation, I don't see this use-case is currently supported. Are there any plans along these lines? :)
basically, browser automation is a closer-to-the-metal abstraction than computer use, allows more flexibility, and ends up being much cheaper at scale!
[0]: https://github.com/bensyverson/sleepyhollow
How does it determine when a cached act() fails and has to be re-evaluated by the LLM? And in particular, if the cache is saved in the cloud (Browserbase?), won't this lead to a lot of cache churn if used in CI pipelines where different versions of the site are running against the same cache?
Also, is there a technical reason why the cache couldn't just be a local file that's checked in along with the script but must be provided by Browserbase? If it was, devs could heal failing tests locally using LLM calls, while CI runs entirely deterministically.
On the act/extract/observe evals it shows promising results being extremely efficient
- act: 4.3x faster, 97% fewer LLM calls. Pass rate: 97.5% -> 98.3%. - heldout: 4.1x faster, 78% fewer LLM calls. Pass rate: 87.5% -> 97.5%. - observe: 11.1x faster, 69% fewer LLM calls. Pass rate: 75.0% -> 83.3%. - extract: 8.7x faster, 75% fewer LLM calls. Pass rate unchanged at 92%.
cost effectively 0