Most Foundry talks focus on using the platform to build agents. This one is about building for the people who build with it. I'll do a code-level walkthrough of designing and shipping Foundry Trace Inspector, a VS Code extension for debugging Foundry agents without leaving the editor — covering the actual engineering decisions:

- which Foundry API surfaces (tracing, telemetry, agent state) I hooked into and why.
- how the extension architecture handles async agent execution and streaming trace data, the UX trade-offs in surfacing multi-step agent behavior as inline decorations vs. a webview panel, and the debugging dead-ends I hit along the way.

I'll close with what I'd redesign if starting over, and a framework for evaluating whether a platform's developer experience gap is worth building tooling to fill.

Extension link: https://marketplace.visualstudio.com/items?itemName=jubinsoni.foundry-trace-inspector