fix: support stable prerender concurrency

[ScriptedAlchemy]

Summary\n- accept stable prerender.concurrency alongside unstable_concurrency\n- validate the stable config key with focused coverage\n\n## Verification\n- pnpm test:core tests/prerender.test.ts\n- pnpm build

[pkg-pr-new]

Open in StackBlitz

pnpm add https://pkg.pr.new/rsbuild-plugin-react-router@f8acb7d

commit: f8acb7d

[github-actions]

Benchmark Results

Compared PR head f8acb7d against base fe514bc.

Total median wall time: 16.46s -> 16.44s (-0.2%, 1.00x speedup)
Compiler ready median: 14.34s -> 14.44s (+0.7%)
Route load median: 1.90s -> 1.88s (-1.0%)

Benchmark	Base total	Head total	Delta	Head ready	Head routes	Speedup	Head RSS p95
large-355-ssr-esm	16.46s	16.44s	-0.2%	14.44s	1.88s	1.00x	-

Profile: large; mode: dev; iterations: 3; warmup: 0.
Workflow run

[coderabbitai]

Warning

Review limit reached

@ScriptedAlchemy, we couldn't start this review because you've reached your PR review rate limit.

More reviews will be available in 8 minutes and 57 seconds. Learn how PR review limits work.

To continue reviewing without waiting, enable usage-based billing in the billing tab.

⌛ How to resolve this issue?

After more reviews become available, a review can be triggered using the @coderabbitai review command as a PR comment. Alternatively, push new commits to this PR.

To avoid repeated limits, reduce automatic review volume by pausing incremental auto-reviews earlier, using label-based review opt-in, excluding WIP or generated PR titles, or requesting reviews manually when the PR is ready. If your team needs uninterrupted high-volume reviews, an organization admin can enable usage-based credits.

🚦 How do rate limits work?

CodeRabbit enforces per-developer PR review limits for each organization. Most developers receive the normal plan review availability.

For paid Pro and Pro+ PR reviews, CodeRabbit uses adaptive limits for sustained high-volume activity. When a developer's recent PR review activity reaches the 95th percentile or higher among CodeRabbit users, additional reviews become available more gradually as earlier reviews age out of the rolling window.

Please see our Fair Usage Limits Policy for further information.

ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: a938e305-659d-4eb3-85b8-25997aebe0ac

📥 Commits

Reviewing files that changed from the base of the PR and between 0278cb2 and f8acb7d.

⛔ Files ignored due to path filters (1)

• pnpm-lock.yaml is excluded by !**/pnpm-lock.yaml

📒 Files selected for processing (8)

• .changeset/stable-prerender-concurrency.md
• package.json
• src/index.ts
• src/modify-browser-manifest.ts
• src/prerender.ts
• src/react-router-config.ts
• tests/prerender.test.ts
• tests/react-router-config.test.ts

📝 Walkthrough

Walkthrough

PrerenderConfigObject gains an optional concurrency?: number field as a stable alias for unstable_concurrency. getPrerenderConcurrency() now reads from concurrency first, falling back to unstable_concurrency via nullish coalescing. validatePrerenderConfig() applies the same dual-key extraction and validates the resolved value as a positive integer, reporting errors under the prerender.concurrency message format. Tests are extended to cover both keys, the default value, and validation of an invalid (0) concurrency.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly summarizes the main change: adding support for stable prerender concurrency.
Description check	✅ Passed	The description matches the code changes and verification steps in the pull request.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch codex/stable-prerender-concurrency

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands.}

[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@src/prerender.ts`:
- Around line 184-197: The validation in prerender config currently reports only
`prerender.concurrency`, even when the invalid value came from
`unstable_concurrency`. Update the logic around the `concurrency` resolution in
`src/prerender.ts` so the error message uses the actual provided key from
`PrerenderConfigObject` (`concurrency` or `unstable_concurrency`). Keep the
existing positive-integer check, but make the returned string reference the key
that was set to make the message actionable.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: 45d66636-7f7e-4297-849d-920acfb2d8cc

📥 Commits

Reviewing files that changed from the base of the PR and between fe514bc and 0278cb2.

📒 Files selected for processing (2)

• src/prerender.ts
• tests/prerender.test.ts