Taps the sign. We need new sandboxing technology for a new world. github.com/pydantic/monty

Learn to build a custom harness, folks. Mods in Claude Code, DeepSeek Harness, and now Pi Durable. What do these all have in common? Increased extensibility. Builders need coding agents and harnesses to be more malleable. Say you are building a simple agentic app for your users, a personalized headless experience, a software factory, or a domain-specific harness; you will quickly find that the generic harness won't cut it. Sometimes you need a different behavior in the UI. Sometimes you just need to easily add a new feature/plugin. Or sometimes you just want to build a completely new experience, like multiplayer support. You can build it from scratch, as I recommend. I mean, it's not that hard. But if you want to hit the ground running, where do you go? Pi Durable and DeepSeek Harness seem to want to solve that problem. Users want more customization in their harnesses. And those builders who understand how to build and maintain one will win big time from this next phase of more malleable harnesses. The battle of the best harness will be very different from the first wave of generic harnesses.

See a durable AI agent run end to end on the Temporal Agent Harness 👇 youtube.com/watch?v=z3L41NvF…

Every backend service should have a /feedback endpoint. Agents are quickly becoming the heaviest users of most APIs. When one hits a missing feature or a bug, it should be able to say so right there, in a structured way. If the request makes sense, another agent drafts the PR and a human approves it. Software that improves itself based on what its users actually tried to do speeds up recursive self improvement.

Fuck it, still early but here goes ... We've just released Monty v1 - a Python sandbox that starts in 1 millisecond, not 1.5 seconds. I just ran 10k sandboxed scripts in 674ms, something that would take a cloud sandbox > 3 hours. This removes the biggest drawback of letting agents write code. The future is fast. Even better, it's open source, you can install it from PyPI, npm or Crates now. Serviced platform coming soon. Please get in touch if you want to be a design partner! Who should try it? ⚡ if you care about startup time, use Monty ⚡ if you care about long-lived sessions, use Monty - Monty can be dumped and resumed at any external function call ⚡ if you care about accessing functions in the agent/host, use Monty - Monty makes it trivial to expose local functions into the sandbox ⚡ if you care about scale, use Monty - Monty workers use as little as 2MB of memory, meaning you can run thousands of concurrent sandboxes on a single machine ⚡ if you care about security, use Monty - we've run 3 rounds of bounty program and thousands of researchers have tried to break into our sandbox, meaning it should be secure to run untrusted code Who should avoid it? 🚫 if you like to take a coffee break while waiting for sandboxes to start, DO NOT use Monty 🚫 if you enjoy the challenge of routing API requests from sandboxes through your corporate network to access state in your agent without exposing secrets to the sandbox, DO NOT use Monty 🚫 if your agent really needs to install packages from PyPI, Monty won't help you yet (spoiler: it probably doesn't) pydantic.dev/docs/monty/get-…