> ## Documentation Index
> Fetch the complete documentation index at: https://docs.twill.ai/llms.txt
> Use this file to discover all available pages before exploring further.
# Verification
> Every PR ships with proof: build, tests, lint, runtime checks, and artifacts you can review.
The difference between a diff and a done task is verification. Before opening a PR, Twill checks its own work mechanically — and attaches the evidence so you don't have to take its word for it.
## What gets verified
* **Static checks** — type checking, lint, and a production build, using your repo's own tooling.
* **Tests** — your existing suite runs; new behavior gets new tests when warranted.
* **Runtime behavior** — because tasks run in a [real dev environment](/environment), the agent starts your app and exercises the change: clicking through UI flows with browser automation, calling API endpoints and capturing request/response, inspecting service logs.
"The types pass" or "the diff looks right" doesn't count as verified — the agent is required to observe the change working.
## Proof on the PR
Whatever the verification produced is attached to the pull request:
* Test and build output
* Screenshots of UI changes, before/after when relevant
* Screen recordings of flows (`.mp4`/`.webm`, rendered inline on GitHub)
* Logs from the running services
* A [live preview](/environment#live-previews) link while the task's sandbox is up
## CI auto-fix
If CI fails on a Twill-created PR, Twill notices and fixes it without being asked:
1. GitHub reports a failed check on the PR branch.
2. Twill matches the branch to its task, reads the CI logs, and pushes a fix.
3. CI re-runs. The PR gets a comment tracking each attempt.
Twill makes up to **3 fix attempts** per CI failure; the counter resets after 24 hours. This applies to PRs created by Twill while their task is still active.
