fix(ai-openai): deduplicate response.output items to prevent invalid JSON concatenation#6178
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IMax153 merged 2 commits intoEffect-TS:mainfrom Apr 17, 2026
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…JSON concatenation
OpenAI's Responses API intermittently returns duplicate OutputMessage
items in response.output with identical IDs and content. When this
happens, all text parts are pushed and later concatenated, producing
invalid JSON like {"a":1}{"a":1} that fails schema parsing.
Skip duplicate output items by tracking seen IDs before processing.
This handles the known OpenAI API bug documented at:
https://community.openai.com/t/1306731
Fixes Effect-TS#6146
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Summary
generateObjectintermittently fails with aparseJsonerror when OpenAI's Responses API returns duplicateOutputMessageitems inresponse.output.Root Cause
OpenAI's Responses API has a known bug where it intermittently returns duplicate
OutputMessageitems with identical IDs and content inresponse.output. The current code iterates over all output items and pushes everyoutput_textas a text part. When these duplicate parts are later concatenated (viatext.join("")), the result is invalid JSON:This causes schema parsing to fail with
Unexpected non-whitespace character after JSON.Fix
Track seen output item IDs in a
Setand skip duplicates before processing. This is a defensive measure against the documented OpenAI API behavior:Changes
OpenAiLanguageModel.ts: AddseenOutputIdsSet to deduplicateresponse.outputitems by ID before processingFixes #6146
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