The toolchain that completes the loop.

A frontend design rubric you can hand an agent. Impeccable is what we point our design skills at when an interface needs to clear the bar — concrete checks for hierarchy, density, and craft, not vibes. It pairs with Hydrant's design-skill workflow because the agent now has a written standard to ship against, instead of generating something that merely compiles.

We use Biome because it replaces ESLint, Prettier, and import-sort with a single Rust binary that runs in milliseconds. Agents don't tolerate slow feedback loops — every extra second on save adds up across a long run. Biome also has opinionated defaults, which means less config to negotiate with the model on every new repo.

Lefthook runs your linters, formatters, and tests before a commit lands — in parallel, per file, fast enough that nobody disables it. Hydrant treats commits as the unit of progress, so the hook is a real quality gate, not a ceremony. When an agent is the one running git commit at 2 a.m., the hook is what stops a broken change from reaching the branch.

Surf is the harness we use to actually open the page after a UI change — not just typecheck it. An agent driving Surf can navigate, click, screenshot, and read the console without a human in the loop. Hydrant ships with repo-scoped Surf wiring so any worktree can be validated against its own preview URL before the PR opens.

Bun replaces Node, npm, and the bundler step with one fast tool. Install times that used to be a coffee break are now a few seconds — which matters when an agent is creating worktrees, running tests, and tearing them down on every iteration. We use Bun for everything from bun dev to bun run lint, and the consistency removes a class of papercuts from the loop.

Convex gives us a typed, reactive database with serverless functions and a local backend per worktree. Schema lives in code, queries are subscriptions by default, and migrations don't require an outage. Hydrant runs on Convex because the agent loop benefits from a backend that's introspectable end-to-end — the same MCP-style affordances we expose to users, we get internally.