Almost a year ago, we first shared Mastra here (https://news.ycombinator.com/item?id=43103073). It’s kind of fun looking back since we were only a few months into building at the time. The HN community gave a lot of enthusiasm and some helpful feedback.
Today, we released Mastra 1.0 in stable, so we wanted to come back and talk about what’s changed.
If you’re new to Mastra, it's an open-source TypeScript agent framework that also lets you create multi-agent workflows, run evals, inspect in a local studio, and emit observability.
Since our last post, Mastra has grown to over 300k weekly npm downloads and 19.4k GitHub stars. It’s now Apache 2.0 licensed and runs in prod at companies like Replit, PayPal, and Sanity.
Agent development is changing quickly, so we’ve added a lot since February:
- Native model routing: You can access 600+ models from 40+ providers by specifying a model string (e.g., `openai/gpt-5.2-codex`) with TS autocomplete and fallbacks.
- Guardrails: Low-latency input and output processors for prompt injection detection, PII redaction, and content moderation. The tricky thing here was the low-latency part.
- Scorers: An async eval primitive for grading agent outputs. Users were asking how they should do evals. We wanted to make it easy to attach to Mastra agents, runnable in Mastra studio, and save results in Mastra storage.
- Plus a few other features like AI tracing (per-call costing for Langfuse, Braintrust, etc), memory processors, a `.network()` method that turns any agent into a routing agent, and server adapters to integrate Mastra within an existing Express/Hono server.
(That last one took a bit of time, we went down the ESM/CJS bundling rabbithole, ran into lots of monorepo issues, and ultimately opted for a more explicit approach.)
Anyway, we'd love for you to try Mastra out and let us know what you think. You can get started with `npm create mastra@latest`.
We'll be around and happy to answer any questions!
shudders in vietnam war flashbacks congrats on launch guys!!!
for those who want an independent third party endorsement, here's Brex CTO talking about Mastra in their AI engineering stack http://latent.space/p/brex
One thing to consider is that it felt clunky working with workflows and branching logic with non LLM agents. I have a strong preference for using rules based logic and heuristics first. That way, if I do need to bring in the big gun LLM models, I already have the context engineering solved. To me, an agent means anything with agency. After a couple weeks of frustration, I started using my own custom branching workflows.
One reason to use rules, they are free and 10,000x faster, with an LLM agent fallback if validation rules were not passing. Instead of running an LLM agent to solve a problem every single time, I can have the LLM write the rules once. The whole thing got messy.
Otherwise, Mastra is best in class for working with TypeScript.
I try to transfer as much work as I can out of LLMs and into deterministic steps. This includes most of the “orchestration” layer which is usually deterministic by nature.
Sprinkle a little bit of AI in the right places and you’ll get something that appears genuinely intelligent. Rely too much on AI and it’s dumb as fuck.
Make their tasks very small and simple (ideally, one step), give them only the context and tools that they need and nothing else, and provide them with feedback when they inevitably mess up (ideally, deterministically), and hope for the best.
Do you have code snippets you can share about how you wanted to write the rules? Want to understand desired grammar / syntax better.
https://github.com/mastra-ai/mastra/blob/main/book/principle...
It's especially effective when you litter it around ai company offices in SF
Another useful question to ask: since you’re likely using 1 of 3 frontier models anyway, do you believe Claude Agent SDK will increasingly become the workflow and runtime of agentic work? Or if not Claude itself, will that set the pattern for how the work is executed? If you do, why use a wrapper?
For any agent you're shipped to production though you probably want a harness that's open-source so you more fully control / can customize the experience.
I'm a happy Mastra user and I'm biased to their success. But I think linking it to an unrelated project is only going to matter to non-technical CXOs who choose technology based on names not merits. And that's not the audience Mastra needs to appeal to to be successful. Good dev tools and techs trickle from the bottom up in engineering organizations.
Most of us spent a lot of the last decade building Gatsby so it's sort of a personal identity/pride thing for us more than a marketing thing. But maybe we need to keep our identity small! Either way, thanks for saying something, worth thinking about.
It's built on top of Vercel AI elements/SDK and it seems to me that was a good decision.
My mental heuristic is:
Vercel AI SDK = library, low level
Mastra = framework
Then Vercel AI Elements gives you an optional pre built UI.
However, I read the blog post for the upcoming AI SDK 6.0 release last week, and it seems like it's shifting more towards being a framework as well. What are your thoughts on this? Are these two tools going to align further in the future?
https://vercel.com/blog/ai-sdk-6
I see each of us having different architectures. AI SDK is more low-level, and Mastra is more integrated with storage powering our studio, evals, memory, workflow suspend/resume etc.
I was hoping to actually engage with you but I guess you just came here to do marketing.
> AI SDK is more low-level
AI SDK was more low level. My question was, since the latest V6 release is moving towards higher level components, what do you think about that? How will you continue to differentiate your product if Vercel makes moves to eat your lunch?
That's almost certainly their intention here, following their highly successful Next.js playbook: start by creating low level dev tools, gradually expand the scope, make sure that all the docs and setup guides you towards deploying on their infrastructure.
For sure lots of good ideas in mastra, and happy that its JS TS first, I think you'll will continue to grow becuase of the TS first approach