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omeraplak · 2026-05-31T14:18:04Z

PR Checklist

Please check if your PR fulfills the following requirements:

The commit message follows our guidelines: https://voltagent.dev/docs/community/contributing/#commit-convention

Bugs / Features

Related issue(s) linked (no issue number provided)
Tests for the changes have been added
Docs have been added / updated (not applicable; internal bug fix)
Changesets have been added https://voltagent.dev/docs/community/contributing/#creating-a-changeset

What is the current behavior?

Agent.streamText() eagerly materializes the AI SDK text, usage, and finishReason lazy result promises while constructing VoltAgent's wrapped stream result.

When a caller only consumes the stream, for example through toUIMessageStream(), and then aborts the run, those unconsumed promises can reject without handlers and emit global unhandledRejection events.

What is the new behavior?

VoltAgent preserves lazy access for text, usage, and finishReason on streamText() results. The sanitized text promise is now created only when result.text is accessed.

This keeps stream-only consumers from needing defensive .catch() handlers for fields they never read and aligns the wrapper more closely with AI SDK v6's lazy stream result contract.

fixes (issue): N/A

Notes for reviewers

Validation run locally:

pnpm --filter @voltagent/core build
pnpm --filter @voltagent/core test:single src/agent/agent.spec.ts -t "does not eagerly materialize lazy stream result promises"
pnpm exec biome check packages/core/src/agent/agent.ts packages/core/src/agent/agent.spec.ts .changeset/quiet-stream-abort.md

Summary by cubic

Fixes unhandled promise rejections when aborting Agent.streamText() by keeping text, usage, and finishReason lazy. Stream-only consumers (e.g., toUIMessageStream()) can abort safely, matching AI SDK v6’s lazy stream contract.

Bug Fixes
- Do not eagerly create result promises; expose text, usage, and finishReason as getters on the wrapper.
- Build sanitized text lazily only when result.text is accessed; contain guardrail finalizer errors so they don’t leak if text isn’t read.
- Keep guardrail-aware textStream/fullStream behavior without forcing promise creation.

^{Written for commit 18c2b11. Summary will update on new commits.}

Summary by CodeRabbit

Bug Fixes

Resolved unhandled rejection errors when aborting stream operations. Agent.streamText() now uses lazy evaluation for stream result fields, creating promises only when explicitly accessed by callers. This prevents errors that previously occurred when aborting mid-stream after consuming partial results or specific stream derivatives.

changeset-bot · 2026-05-31T14:18:08Z

🦋 Changeset detected

Latest commit: 18c2b11

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@voltagent/core	Patch

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coderabbitai · 2026-05-31T14:18:16Z

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: d1dd8718-b2f8-49a4-aa11-6a96feaf2e49

📥 Commits

Reviewing files that changed from the base of the PR and between 41cad53 and 18c2b11.

📒 Files selected for processing (3)

.changeset/quiet-stream-abort.md
packages/core/src/agent/agent.spec.ts
packages/core/src/agent/agent.ts

📝 Walkthrough

Walkthrough

Agent.streamText() now defers sanitized text promise creation until the text is accessed, preventing unhandled rejections when callers abort without consuming the result. A centralized helper produces sanitized text by awaiting guardrail finalization (if present), preferring runner-sanitized text, and applying any bailedResult override. A test validates lazy evaluation, and changeset documents the fix.

Changes

Lazy Sanitized Text Promise

Layer / File(s)	Summary
Lazy sanitized text promise helpers `packages/core/src/agent/agent.ts`	`createSanitizedTextPromise()` centralizes sanitized text production by awaiting guardrail finalization if present, preferring `runner.getSanitizedText()` when non-empty, otherwise `result.text`, then applying `bailedResult` override from `oc.systemContext`. `getSanitizedTextPromise()` lazily initializes and memoizes that promise. `sanitizedTextPromise` variable becomes `Promise<string> \| undefined` to enable on-demand creation.
Wiring lazy promise into stream lifecycle `packages/core/src/agent/agent.ts`	`onFinish` callback now awaits `getSanitizedTextPromise()` for `finalText`. The returned `StreamTextResultWithContext` wrapper's `text` getter returns `getSanitizedTextPromise()` instead of a pre-captured value, aligning consumer access with finish logic.
Lazy evaluation test validation `packages/core/src/agent/agent.spec.ts`	New test constructs a mock stream where `text`, `usage`, and `finishReason` are getters that increment counters on access. Verifies counters remain `0` immediately after `agent.streamText()`, then increment exactly once when those result properties are awaited.
Changeset documentation `.changeset/quiet-stream-abort.md`	Documents that `Agent.streamText()` no longer triggers unhandled rejections on abort by preserving AI SDK v6 lazy getter behavior and deferring sanitized text promise creation until accessed.

🎯 2 (Simple) | ⏱️ ~12 minutes

🐰 A promise deferred, no more to fear,
Lazy getters dance, rejection won't appear,
When abort comes calling, streams stay serene,
The gentlest refactor I've ever seen! ✨

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and specifically summarizes the main fix: preventing unhandled rejections during streamText abort operations by making lazy promises lazy.
Description check	✅ Passed	The PR description comprehensively covers all template sections, clearly explains the problem and solution, includes test validation, changeset confirmation, and provides detailed reviewer notes.
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.

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cloudflare-workers-and-pages · 2026-05-31T14:23:26Z

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fix(core): prevent streamText abort unhandled rejections

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cubic-dev-ai Bot reviewed May 31, 2026

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omeraplak merged commit a1b4427 into main May 31, 2026
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omeraplak deleted the fix/streamtext-abort-lazy-promises branch May 31, 2026 14:26

voltagent-bot mentioned this pull request May 31, 2026

ci(changesets): version packages #1328

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fix(core): prevent streamText abort unhandled rejections#1334

fix(core): prevent streamText abort unhandled rejections#1334
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PR Checklist

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Summary by cubic

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