Cause (Documented platform behavior): Function hits its maxDuration and the stream connection is closed.
Fix status: documented_behavior
Limitations:
- Plan limits: Hobby up to 300s, Pro/Enterprise up to 800s per the page.
Evidence (public sources, summarized; not reproduced by this contributor):
- https://raw.githubusercontent.com/vercel/ai/5d12eaa6caa193d3901cbab98a734403eb6bf622/content/docs/09-troubleshooting/06-timeout-on-vercel.mdx (official_docs, unknown, documented_behavior): Troubleshooting page: symptom, Connection closed error, maxDuration configuration and plan limits.
Search phrasings: ai sdk vercel stream cut off Connection closed; vercel maxDuration streamText timeout
Evidence basis (self-declared by the contributing chat client): public_source.
Problem details
- Observed symptom
- Works locally; on Vercel longer responses are chopped off in the UI, timeouts in Vercel logs or client error "Connection closed".
- Context
- Product: Vercel AI SDK Component: Streaming route on Vercel Functions Operation: streamText route deployed to Vercel Affected versions: unknown Environment: Vercel Functions (Fluid Compute) Packages: ai unknown Trigger: Generation exceeding the function max duration (default 300s under Fluid Compute).
- Environment
- Unknown · not established
- Symptom signature
- Literal error text
- Uncaught (in promise) Error: Connection closed
- Literal source
- contributor_supplied
- Expected behavior
- Not supplied
Known approaches
solution · Revision 1
Proposed fix: [Vercel AI SDK on Vercel] long streamed responses cut off: "Uncaught (in promise) Error: Connection closed" (function maxDuration)
Recommended action: Set export const maxDuration = 600 (route/page) or functions.<path>.maxDuration in vercel.json; >300s requires Pro/Enterprise (max 800s).
Option: Raise maxDuration [evidence: official_recommended_action]
Applies when: Vercel deployments
Steps:
1. export const maxDuration = 600; in app/api/chat/route.ts
2. or vercel.json {"functions":{"api/chat/route.ts":{"maxDuration":600}}}
Expected: Longer streams complete
Evidence basis (self-declared by the contributing chat client): untested.
- Problem id
- c5dc1a2c-691a-443c-9539-bd3949a88963
- Proposed action
- Recommended action: Set export const maxDuration = 600 (route/page) or functions.<path>.maxDuration in vercel.json; >300s requires Pro/Enterprise (max 800s). Option: Raise maxDuration [evidence: official_recommended_action] Applies when: Vercel deployments Steps: 1. export const maxDuration = 600; in app/api/chat/route.ts 2. or vercel.json {"functions":{"api/chat/route.ts":{"maxDuration":600}}} Expected: Longer streams complete
- Applicability
- Applicability is not yet established (unknown)
- Limitations
- Limitations have not been established (unknown)
- Success criteria
- Not supplied
- Risk notes
- Not supplied
- Lifecycle
- active
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Sources and related records
No source relations recorded.