fix(proxy): skip empty passthrough body streams

[harlan-zw]

🔗 Linked issue

Resolves #853

❓ Type of change

• 📖 Documentation
• 🐞 Bug fix
• 👌 Enhancement
• ✨ New feature
• 🧹 Chore
• ⚠️ Breaking change

📚 Description

Empty beacon POSTs with Content-Length: 0 were forwarded with a ReadableStream body, causing Node fetch to reject and the proxy to return 502. The proxy now omits the body and duplex option for explicitly empty requests while preserving streams for nonempty opaque bodies.

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Project	Deployment	Actions	Updated (UTC)
scripts-playground	Ready	Preview	Aug 6, 2026 2:22pm

[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 Plus

Run ID: e15e5c96-9594-4126-bdd4-e9b508a8a24d

📥 Commits

Reviewing files that changed from the base of the PR and between 2db3380 and 427d4bd.

📒 Files selected for processing (2)

• packages/script/src/runtime/server/proxy-handler.ts
• test/unit/proxy-handler-body.test.ts

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📝 Walkthrough

Walkthrough

The proxy now omits the upstream body stream when the original request has content-length: 0. It sets duplex: 'half' only when the forwarded body is a ReadableStream. Unit tests capture upstream body and duplex values, verify gzip streaming, and cover empty opaque POST requests.

Estimated code review effort: 2 (Simple) | ~10 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly summarizes the main fix: skipping empty passthrough body streams.
Description check	✅ Passed	The description directly explains the empty beacon POST bug and the proxy fix.
Linked Issues check	✅ Passed	The changes prevent empty request streams, conditionally set duplex, and preserve nonempty streaming as required by issue #853.
Out of Scope Changes check	✅ Passed	The changes are limited to proxy body handling and tests for the linked issue.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/empty-proxy-body

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commit: 427d4bd