Agent can run modern dev servers and display web output so layout issues are visible before delivery.
Supported stacks
Agent should prefer modern fast tooling when available: Bun for JavaScript, uv for Python, and normal framework dev commands for SvelteKit, React, PHP, and Ruby apps.
Preview flow
Agent installs missing dependencies when reasonable, starts the dev server, opens the preview, checks screenshots or rendered output, then fixes visible layout issues before final delivery.
- 1
Detect stack.
- 2
Install dependencies if needed.
- 3
Start the right dev server.
- 4
Open preview.
- 5
Inspect layout and console problems.
- 6
Fix and retest.
When preview fails
A preview can fail because of a missing runtime, bad command, locked port, broken dependency, or app error. Agent should inspect logs and try a reasonable fix before asking the user.
If the app cannot run, Agent should still deliver the files and explain the exact blocker.