fix(ai): use errorMode 'text' in approval continuation to preserve tool error messages#13056
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aayush-kapoor merged 2 commits intovercel:mainfrom Mar 4, 2026
Merged
fix(ai): use errorMode 'text' in approval continuation to preserve tool error messages#13056aayush-kapoor merged 2 commits intovercel:mainfrom
aayush-kapoor merged 2 commits intovercel:mainfrom
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…ion flow
When a tool with needsApproval throws an error during execution, the error
message was silently lost. The approval continuation path in both streamText
and generateText used errorMode: 'text' ? 'json' : 'none' (bug: 'json'
should be 'text'). JSON.stringify(new Error('msg')) returns '{}' because
Error properties are non-enumerable, so the model received '{}' instead of
the actual error message.
The fix aligns the approval continuation path with the normal multi-step
flow and to-response-messages.ts which correctly use errorMode: 'text',
causing getErrorMessage() to extract the message string.
Fixes vercel#13048
haroldfabla2-hue
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Mar 4, 2026
When a tool with needsApproval throws an error during execution, the error
message was being lost because errorMode 'json' routes to createToolModelOutput
which does JSON.stringify(new Error('msg')) resulting in '{}' since Error
properties are non-enumerable.
This fix changes 'json' to 'text' in both generateText and streamText to
align with the normal multi-step flow that correctly uses getErrorMessage.
Closes vercel#13056
aayush-kapoor
approved these changes
Mar 4, 2026
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just made some minor test fixes + added changeset
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@aayush-kapoor thank you! :) yeah.. changeset this is painfull for me hahah. everytime forgot it.. |
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Problem
When a tool with
needsApprovalthrows an error during execution, the error message is silently lost. The model receives{}instead of the actual error text, causing it to hallucinate success.Closes #13048
Root Cause
The approval continuation path in both
streamTextandgenerateTextused:errorMode: 'json'routes tocreateToolModelOutputwhich doestoJSONValue(error)→JSON.stringify(new Error('msg'))→'{}'becauseErrorproperties (message,stack) are non-enumerable.The normal multi-step flow and
to-response-messages.tscorrectly useerrorMode: 'text'which callsgetErrorMessage(error)to extract the message string.Fix
Change
'json'→'text'in both locations to align with the normal flow:Tests
Added test cases for both
generateTextandstreamTextthat verify when an approvedneedsApprovaltool throws, the model receives{ type: 'error-text', value: 'tool execution failed' }instead of{ type: 'error-json', value: {} }.