fix: avoid quadratic memory growth in streamText text() without breaking chunk streaming#14119
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okxint wants to merge 1 commit intovercel:mainfrom
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fix: avoid quadratic memory growth in streamText text() without breaking chunk streaming#14119okxint wants to merge 1 commit intovercel:mainfrom
okxint wants to merge 1 commit intovercel:mainfrom
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…le preserving chunk streaming For plain text output, every text-delta always changes the partial result, so we can skip the JSON.stringify comparison and publish immediately. This avoids creating O(n) intermediate string copies per chunk (~350MB of large_object_space allocations for a ~110KB response arriving in ~13k chunks). Structured outputs (object, array, choice, json) still use the existing JSON.stringify dedup path since partial JSON parsing can produce identical results across consecutive chunks.
tigent
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this issue has a PR in place #14123 - will be closing this as well would love to know how you verfied this is the right fix? how did you confirm memory usage doesn't grow quadratically with response size? |
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Summary
Follows up on #13878 which was closed because returning
undefinedfromparsePartialOutput()broke incremental chunk publishing.This PR takes a different approach — instead of suppressing partial output entirely, it avoids the expensive
JSON.stringify(result.partial)path for text-type outputs while preserving incremental text-delta chunk streaming.The original issue: for a ~110KB response arriving in ~13,000 chunks,
JSON.stringifywas called on the accumulated text string on every chunk, creating ~350MB of intermediate string copies that landed in V8's large_object_space.The fix: For plain text output, every
text-deltaalways changes the partial result, so the JSON.stringify-based dedup comparison is unnecessary. We short-circuit it and publish immediately. Structured outputs (object, array, choice, json) still use the existing JSON.stringify dedup path since partial JSON parsing can produce identical results across consecutive chunks.How did you test this?