| name | mintlify-preview-workflow |
| user-invocable | true |
| description | work on the Mintlify preview deployment GitHub Action, debug mint-preview.yml, change which PRs get previews, update the Mintlify preview-trigger API call, modify preview-URL PR comments |
Engineer skill for .github/workflows/mint-preview.yml — the workflow that creates Mintlify preview deployments for PRs.
What the action does
Two triggers, both hit the Mintlify preview API:
| Event | Preview branch | Sticky comment goes on |
|---|
pull_request (any base branch; types: opened / synchronize / reopened / ready_for_review) | github.head_ref (the PR's source branch) | The PR itself |
push to refs/heads/release/** | github.ref_name (the release branch) | First open PR whose head is the release branch, if any |
Draft PRs are skipped. Push events don't have a draft concept, so they always run.
Why call the API on PR events too? The Mintlify GitHub App may or may not produce the preview you want on its own. Calling the REST API directly is authoritative: we always get a previewUrl back and can surface it as a sticky comment. If duplicate previews become a problem we'll narrow this later, but for now the contract is: every non-draft PR event produces an API-triggered preview we can point the user at.
Concurrency: mintlify-preview-<PR#ornref> with cancel-in-progress: true — back-to-back pushes to the same branch cancel prior in-flight runs, keeping us under the 5 req/min Mintlify limit.
Mintlify API specifics (validated against https://www.mintlify.com/docs/api/preview/trigger.md)
- Endpoint:
POST https://api.mintlify.com/v1/project/preview/{projectId}
(note the {projectId} path parameter — easy to miss; earlier versions of this workflow used a wrong URL and silently 404'd)
- Auth:
Authorization: Bearer <MINTLIFY_TOKEN>
- Request body:
{"branch": "<git-branch-name>"}
- Success response: HTTP 202 with JSON
{ "statusId": "...", "previewUrl": "..." }
- Errors to handle explicitly:
400 — bad request (usually missing/empty branch)401/403 — bad token, wrong project ID, or plan doesn't include preview deployments (Pro/Enterprise only)429 — rate limit (5 req/min per org)
- Poll preview build status with
GET /v1/project/update/status/{statusId} (see https://www.mintlify.com/docs/api/update/status.md) — not wired in yet.
Required secrets
| Repo secret | Source | Notes |
|---|
MINTLIFY_KEY | Mintlify dashboard → API keys | Must be an admin API key, prefixed mint_. Inside the workflow this is mapped to the MINTLIFY_TOKEN env var before the curl call. |
MINTLIFY_PROJECT_ID | Same page | Distinct from the key. Used as the {projectId} path parameter in the API call. |
Both are validated at the top of the trigger step. A missing value fails the step; a token that doesn't start with mint_ emits a ::warning:: (the call will likely 401 but we still try, in case Mintlify changes the prefix scheme).
File map
| File | Role |
|---|
.github/workflows/mint-preview.yml | The workflow itself. All logic lives here — no helper scripts. |
Design decisions (with context for future edits)
- Why hit the API on PRs and also on pushes to
release/**? PR events cover the usual review flow. Pushes to release branches cover the long-lived-branch case where a release branch exists without a PR currently attached (e.g., between PR merges during a release cycle). Together they catch every preview-worthy change to branches we care about.
- Why find the PR from a push event? For push events, there may still be an open PR whose head is the release branch — the preview link belongs on it.
gh pr list --head <branch> fetches it; if none exists, skip the comment (no-op).
- Why sticky comment instead of new ones? Each push re-triggers the preview API; a non-sticky comment would spam the PR.
marocchino/sticky-pull-request-comment@v2 updates one comment in place via the header: mintlify-preview key.
- Why cancel in-progress? Back-to-back pushes shouldn't queue multiple API calls against the 5-req/min limit. The latest push wins.
- Why
if: pull_request == null || pull_request.draft == false? Mintlify previews cost build minutes; don't burn them on drafts. Push events have no draft concept — the pull_request == null short-circuit keeps pushes unaffected.
- Why a separate "Resolve preview branch" step? It makes the logic explicit and debuggable: one place to see which branch we're about to preview, regardless of event type. The downstream API step then has a single input source.
Playbook: common tasks
"Previews aren't showing up on release PRs"
- Open the workflow run's "Trigger Mintlify preview" step — check the HTTP status printed at the top of the response log.
- 401/403 → confirm
MINTLIFY_TOKEN and MINTLIFY_PROJECT_ID in repo secrets match the current dashboard values. Also verify the org plan includes preview deployments.
- 404 → the URL path changed upstream, or
MINTLIFY_PROJECT_ID is wrong.
- 429 → another workflow burned the org's 5-req/min budget; wait and re-run.
- 202 but no sticky comment → check the "Post sticky preview comment" step and its
marocchino action output; the issue is usually pull-requests: write permission missing or a fork PR (where secrets aren't available).
"Add previews for another base branch"
Add the new pattern to the on.pull_request.branches list and add a matching if: conditional on a step that decides whether to hit the API vs. rely on the GH App. Don't forget the step summary block.
"Want to show build status, not just 'queued'"
Mintlify returns a statusId on 202. Add a follow-up step that polls GET /v1/project/update/status/{statusId} until it reports success or failed, then update the sticky comment accordingly. Keep the poll bounded (e.g. 2 min with 10s sleep).
"Change the API trigger to include metadata (commit SHA, author, etc.)"
Re-check the current API schema — it only documents branch as a request body field. Extra fields are ignored (best case) or 400 (worst). Don't invent fields; use the PR comment body for human-readable metadata instead.
Working rules for this skill
- Don't call the preview API on every event. Preserve the draft-filter + base-branch gates. Previews cost plan budget.
- Keep secret names stable —
MINTLIFY_KEY and MINTLIFY_PROJECT_ID. Renaming breaks existing repo configuration silently. (The internal env var is MINTLIFY_TOKEN; don't conflate the two.)
- Always use the sticky-comment pattern for preview links. Non-sticky comments create PR timeline noise.
- When adding new HTTP status handling, write an explicit
::error:: annotation — debugging opaque curl failures in CI logs is miserable.
- Rate limit respect: if you add a poller for
statusId, keep its inner sleep ≥ 15s so a busy release day doesn't eat the 5-req/min budget.
- Don't add workflow triggers for
push. This is PR-scoped; pushes to branches should not fire previews on their own.
