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OmniRoute/open-sse/translator
Amirreza Kimiyaei b84059213f fix(gemini): preserve response-schema nullability across union flattening (#12310)
* fix(gemini): preserve response-schema nullability across union flattening

cleanJSONSchemaForAntigravity flattens every union spelling of nullable before
the schema reaches Gemini: flattenTypeArrays turns ["string","null"] into
"string" and flattenAnyOfOneOf drops the {"type":"null"} branch. Correct for
tool parameters, wrong for response schemas — a model with nothing to say can
no longer answer null, so it returns the string "null" or fabricates a value,
and either reaches the client as schema-conformant data. Pydantic emits the
anyOf spelling for Optional[str], so the fabricating path is the common one.

A Phase 1b walk now records Gemini's sibling-key spelling, nullable: true, on
any node whose union carries null — before Phase 2 destroys the evidence. The
key is absent from GEMINI_UNSUPPORTED_SCHEMA_KEYS so it survives sanitizing,
and flattenAnyOfOneOf's Object.assign cannot clobber a key the surviving
branch lacks. Opt-in via { preserveNullable: true }, passed only by the
responseSchema call site; the three tool-parameter call sites keep the default.

Closes #12308

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

* docs(changelog): add fragment for #12308 gemini nullable schema fix

Co-authored-by: diegosouzapw <8016841+diegosouzapw@users.noreply.github.com>

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Co-authored-by: Claude Opus 5 <noreply@anthropic.com>
Co-authored-by: diegosouzapw <8016841+diegosouzapw@users.noreply.github.com>
2026-09-18 12:21:02 -03:00
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