[sentry]

This PR addresses an N+1 API call issue occurring on docs pages (/_library/$libraryId/$version/docs/$).

Problem:
When navigating to a docs page, the fetchDocsManifest server function was triggering hundreds of individual HTTP calls to GitHub's content API. This happened because buildDocsManifest (which fetchDocsManifest uses) iterates over every markdown file in a library's docs directory and fetches each one individually to extract frontmatter redirect metadata. While a cache (getCachedDocsArtifact) exists, the GitHub webhook handler (src/routes/api/github/webhook.ts) only marked these artifacts as stale, rather than proactively rebuilding them. Consequently, the first user request after a cache invalidation (or on a cold server start) would incur the full N+1 cost.

Solution:

1. Proactive Cache Warm-up: A new server-only utility, warmDocsArtifacts (src/utils/docs-warm.server.ts), is introduced. After the GitHub webhook handler marks docs artifacts stale, it now calls warmDocsArtifacts in a background task. This rebuilds both the main docs manifest and the docs path manifest immediately, ensuring the cache is warm before subsequent user requests.
2. In-flight Deduplication: buildDocsManifest now includes in-flight deduplication. If multiple concurrent requests attempt to build the same manifest (e.g., during a cold server start), only one build process will execute, and all other pending requests will await and share its result. This prevents redundant GitHub API calls in high-concurrency scenarios.

These changes ensure that docs manifests are always served from a warm cache, significantly reducing the number of outbound GitHub API calls and improving page load performance.

Fixes TANSTACK-COM-4D2

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Status	Name	Latest Commit	Preview URL	Updated (UTC)
✅ Deployment successful! View logs	tanstack-com	4ffd44e	Commit Preview URL Branch Preview URL	Oct 20 2026, 12:26 PM

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Latest commit: 4ffd44e

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[tannerlinsley]

The cache warming is worth keeping, but we can use the cache's existing request deduplication. I pushed a follow-up that also tightens validation of cached manifests.

AI review notes:
Head 4ffd44e9d962a396851f9a8716a258ee64c0b3f2 integrates current main and shares a cast-free manifest validator between normal reads and warming. The original warmer accepted { paths: [4], redirects: null }; the corrected validator rejects it, arrays of redirects, and non-string redirect targets.

The extra manifest promise map is removed. Tests against the real artifact cache show eight concurrent cold requests produce one build, eight requests after invalidation produce one rebuild, a fresh read does not rebuild, and a failed cold build can recover on the next request. Builders and stored data in these tests are fixtures; no production webhook or cache was exercised.

Full pnpm test and normal commit hooks passed: 606 unit tests passed with 4 skipped, 2,270 chat tests passed, and 20 desktop tests passed with 1 skipped, plus types and lint. New-head CI and the required server-code team review are still pending. This is pushed, not merged or deployed.