Vercel shipped [email protected] on 2026-09-30 (compare): optional SSE heartbeats keep idle UI message streams open; prune all tool content when retaining zero trailing messages; ignore pending tool approvals superseded by user messages; preserve partial reasoning tags at streamed text ends. Build migrates tsup→tsdown with gateway/provider/utils bumps.

Key Takeaways

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Finished reading? Explore benchmark rankings & pricing

Real-world SWE-bench scores & $20/mo vs API cost break-even calculator

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In-Depth Technical Analysis

Background

Agent/chat UIs lose idle SSE behind proxies, leave tool content when retain=0, and stall when user messages supersede pending tool approvals. [email protected] targets those runtime edges.

What shipped

[[email protected]](https://github.com/vercel/ai/releases/tag/[email protected]): optional SSE heartbeats; prune tool content at retain=0; ignore superseded approvals; preserve partial reasoning tags; tsup→tsdown + gateway/provider/utils bumps. Compare.

Benchmarks

No official SWE-bench numbers. Anchors: publish 2026-09-30T02:21:24Z, npm [email protected]. Measure your own idle-stream and approval regressions.

Get started

npm i [email protected]. Docs: https://ai-sdk.dev/docs/introduction