refactor(aws-lambda): add srvx lambda handlers

[taylorfsteele]

🔗 Linked issue

#4051

❓ Type of change

• 📖 Documentation (updates to the documentation, readme, or JSdoc annotations)
• 🐞 Bug fix (a non-breaking change that fixes an issue)
• 👌 Enhancement (improving an existing functionality like performance)
• ✨ New feature (a non-breaking change that adds functionality)
• 🧹 Chore (updates to the build process or auxiliary tools and libraries)
• ⚠️ Breaking change (fix or feature that would cause existing functionality to change)

📚 Description

Closes #4051

This PR removes the previous aws-lambda handlers in favor srvx's lambda handlers.

📝 Checklist

• I have linked an issue or discussion.
• I have updated the documentation accordingly.

[vercel]

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[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: da0684c6-a9e6-45fd-add5-9739f412a828

📥 Commits

Reviewing files that changed from the base of the PR and between dc5b6ce and a6af3e7.

📒 Files selected for processing (4)

• src/build/vite/prod.ts
• test/presets/aws-lambda.test.ts
• test/vite/lambda-ssr-fixture/app/entry-server.ts
• test/vite/lambda-ssr-fixture/vite.config.ts

✅ Files skipped from review due to trivial changes (2)

• test/vite/lambda-ssr-fixture/vite.config.ts
• test/vite/lambda-ssr-fixture/app/entry-server.ts

---

📝 Walkthrough

Walkthrough

Adds a preview command to the aws-lambda preset and rewrites both aws-lambda runtimes to use the srvx/aws-lambda adapter with streaming and preview-fallback support; adjusts Vite prod loader dispatch and expands tests/fixtures to cover streaming preview and SSR.

Changes

AWS Lambda Preset and Runtime Upgrade

Layer / File(s)	Summary
Preset Configuration src/presets/aws-lambda/preset.ts	A new preview command is added to the preset using npx srvx --prod ./.
Streaming runtime (srvx adapter) src/presets/aws-lambda/runtime/aws-lambda-streaming.ts	Rewrites streaming runtime to use srvx/aws-lambda imports, builds lambdaHandler via toLambdaHandler, implements handlerWithPreviewFallback, optional streamifyResponse wrapper, retains named handler, and adds default export { fetch: (request) => invokeLambdaHandler(...) }.
Standard runtime wrapper src/presets/aws-lambda/runtime/aws-lambda.ts	Creates exported handler via toLambdaHandler(...) and adds a default export object with fetch that delegates to invokeLambdaHandler(handler, request).
Vite prod loader dispatch src/build/vite/prod.ts	lazyService(loader) now resolves modules without forcing .default normalization and dispatches to mod.fetch or mod.default?.fetch to support both default and named fetch exports.
Tests & fixtures test/presets/aws-lambda.test.ts, test/vite/lambda-ssr-fixture/*	Expand Vitest imports, add tests for adapter default.fetch preview, add streaming and streaming-vite-ssr suites (including APIGatewayProxyEventV2 streaming test), and add fixture entry-server and vite.config for SSR streaming test.

Estimated code review effort

🎯 4 (Complex) | ⏱️ ~45 minutes

Possibly related PRs

• nitrojs/nitro#3814: Both modify the streaming Lambda handler implementation in aws-lambda-streaming.ts to address streaming behavior in the srvx-based adapter.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title follows conventional commits format with scope (aws-lambda) and concise description of the refactor.
Description check	✅ Passed	The description is directly related to the changeset, explaining it replaces aws-lambda handlers with srvx handlers to close issue #4051.
Linked Issues check	✅ Passed	The code changes fully address issue #4051 by adding preview command support and srvx lambda handlers for the aws-lambda preset.
Out of Scope Changes check	✅ Passed	All changes are directly scoped to implementing srvx lambda handlers for aws-lambda preset and adding preview support; test additions align with the feature implementation.

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[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/nitro@4052

commit: a6af3e7

[martinmiglio]

Confirming this PR fixes TSS prerender + link crawling on aws-lambda end-to-end.

Installed the pkg.pr.new build into a minimal @tanstack/react-start app with prerender: { enabled: true, crawlLinks: true } and nitro({ preset: 'aws-lambda' }):

• Before (nitro nightly 3.0.260415-beta): fails with Error: Failed to fetch /: — silent 404 from src/preview.ts:74-75 default stub because srvx's loadServerEntry has no branch for { handler }-only exports (srvx src/loader.ts:163-178).
• With this PR: 4 routes crawled, real HTML written to .output/public/{about,contact,pricing}/index.html, and .output/server/index.mjs still exports handler alongside the new default — Lambda deployment artifact intact. No regression on node-server / vercel / netlify.

Also reproduces the underlying bug without any framework: nitro-only/ — only nitro dep, nitro build + nitro preview + curl returns HTTP 404 with empty statusText for preset: "aws-lambda"; 200 for preset: "node-server".

Related: #4051 (this PR's linked issue), TanStack/router#6562 (stale, same root cause pre-#4011).

[taylorfsteele]

Hey @pi0 / any other Nitro maintainers. It's been a little bit since I opened this PR, I think I opened it when I was on alpha.2. I should have some time this month to rework this if there's anything that needs to be fixed or changed, I would love to try to get this in for the next beta release. Or if we needed to wait for more things to go into the beta before these preset-specific fixes go in that's fine too. Let me know if there's anything I can do to assist, more than happy to help.

[pi0]

Hi dear @taylorfsteele thanks for patience and help on this PR. We have recently added actual lamda compatibility to srvx via toLambdaHandler, invokeLambdaHandler (docs) which preview command can leverage it this way nitro|vite preview will work out of the box.

[taylorfsteele]

@pi0 Fantastic! I've gone ahead and updated this branch to use the srvx handlers, let me know what you think

[martinmiglio]

Re-tested the reworked PR (pkg.pr.new build, commit b2ab1cb) against the same minimal @tanstack/react-start repro from my earlier comment — aws-lambda prerender now crawls and exits cleanly. vercel and netlify also build green in the same setup. 👍