Simon Willison releases datasette-apps 0.2a0.

Developer Simon Willison has launched datasette-apps 0.2a0, an update designed to improve how AI models build and modify applications using Datasette Agent. This release introduces two primary tools aimed at giving automated agents greater control and verification capabilities during the creation process. The first is app_list(), tracked as issue number 36, which allows an agent to retrieve a list of all applications the user has permission to modify. This enables the agent to seamlessly locate and edit existing projects.

The second and more technically novel addition is the app_debug() tool, tracked under issue number 33. This utility allows an AI agent to open a newly created or edited application invisibly to perform automated testing. It achieves this by rendering the application inside a sandboxed iframe styled with opacity: 0 and pointer-events: none. Because the iframe is completely hidden and ignores user interactions, the agent can run custom JavaScript inside the sandbox without disrupting the user. This mechanism relies on the context.browser_task() function, which was recently introduced in datasette-agent 0.4a0.

For software practitioners and AI developers, these updates represent a significant step toward reliable, agentic web development. Instead of blindly generating code and hoping it works, an agent can now perform smoke tests, verify that the application loads correctly, and even measure the physical dimensions of rendered page elements. This automated feedback loop reduces the need for human intervention during the prototyping phase.

These agentic capabilities align with other recent developments in the ecosystem, such as using Claude Fable 5 to build a Raccoon Heist game in a single attempt on August 5, 2026. Willison also noted a new release of the LLM tool on August 4, 2026, which added support for reasoning traces and server-side tools, alongside his ongoing work with stateless Model Context Protocol tools like mcp-explorer and datasette-mcp on July 31, 2026.