F4b-Gemini — native structured output via responseSchema + JSON Schema translator#106
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…Type. Second slice of the F4b family (after #102 shipped OpenAI). Same shape: when SendArgs.jsonSchema is set, the Gemini adapter wires generationConfig.responseMimeType="application/json" plus a responseSchema translated from the caller's JSON Schema into Gemini's OpenAPI-subset Schema proto. What lands src/providers/gemini.ts: - GeminiRequestBody.generationConfig gains optional responseMimeType ("application/json") and responseSchema (Record<string,unknown>). - buildGeminiRequest accepts opts.jsonSchema. When supplied, body gets responseMimeType + responseSchema = jsonSchemaToGeminiSchema(...). - sendGemini threads args.jsonSchema into the builder. NEW jsonSchemaToGeminiSchema translator: - Upper-cases `type` (STRING/NUMBER/INTEGER/BOOLEAN/ARRAY/OBJECT) — Gemini's Schema proto rejects lowercase JSON Schema type names. - Recurses into properties + items. - Passes through Gemini-supported keywords: description, enum, format, nullable, required, minItems, maxItems, minimum, maximum. - Handles type-arrays (["string","null"]) → STRING + nullable:true. - Drops $schema and additionalProperties (Gemini-unsupported). - Never throws on degenerate input; degraded translation paths emit a relaxed superset and rely on F4c's tolerant parser + downstream validateSchema as the safety net. test/providers/gemini-native-json.test.ts (11 tests): builder (3): responseSchema attached when jsonSchema supplied; omitted in baseline; body remains JSON-serializable. translator (8): primitive type uppercasing; recursion into properties + items; passthrough of required/enum/format/description; type-array collapse to nullable; $schema and additionalProperties dropped; deeply nested schemas (3 levels); degenerate input doesn't throw. Scoreboard TS: 1,316 / 1,316 (+11 over PR #102's 1,305) typecheck + build: clean Defense-in-depth chain now covers OpenAI via response_format: json_schema (PR #102) Gemini via responseSchema + responseMimeType (this PR) Anthropic via tool_use input_schema (follow-up) Universal schema-in-prompt + tolerant parser (F4c) (already in main) The translation layer is intentionally permissive: when a passed schema uses constructs Gemini's Schema proto doesn't support, we strip the offending keyword and emit a looser shape. The model may then return a slightly richer-than-intended object, which validateSchema catches at the parse/validation boundary. Bias toward "native output mostly works" + parse-side defense rather than "fail the call because the schema can't be perfectly translated." Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
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Summary
Re-opened after #103 auto-closed when its base branch (#102's `feature/f4b-native-structured-output`) was deleted. Same diff as #103, rebased onto current main (which now has F4b OpenAI squashed in).
Second slice of the F4b family — when `SendArgs.jsonSchema` is set, the Gemini adapter wires `generationConfig.responseMimeType="application/json"` plus a `responseSchema` translated from the caller's JSON Schema into Gemini's OpenAPI-subset Schema proto.
What lands
Tests
11 new tests (3 builder + 8 translator) covering primitives, recursion, passthrough, type-array collapse, drop-list, 3-level nesting, degenerate input.
Scoreboard
🤖 Generated with Claude Code