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`src/provider/gemini.rs` — `GeminiClient` [feature: gemini]

The Google Gemini client. (~3,720 lines with tests.)

Key items

  • from_env() (GEMINI_API_KEY / GOOGLE_API_KEY) + builder including with_include_thoughts(false default).
  • Model-in-path URLs (:streamGenerateContent?alt=sse / :generateContent); key in the x-goog-api-key header, never the URL.
  • System folding into systemInstruction (inline system rejected by the API — omitted entirely when empty).
  • generationConfig — thinkingConfig.includeThoughts (opt-in) and/or responseMimeType + responseJsonSchema for formats.
  • The emitter: synthesized MessageStart (Gemini chunks carry no ids), usage latched from the latest non-empty usageMetadata (thoughts counted into output), terminal = a chunk with finishReason, emitted once (proxy re-emits guarded).

Behavior notes

  • include_thoughts(true) on a non-reasoning model = 400; match the flag to the model. Parsing routes thought: true parts to the thinking lane regardless of the flag.
  • Tool calls arrive complete (not fragmented): open → one JSON delta → close, so downstream sees the standard shape.
  • Errors: code 429/503/529 or status RESOURCE_EXHAUSTED/UNAVAILABLE → rate limit; else API error. MAX_TOKENS → MaxTokens; everything else (incl. SAFETY) → EndTurn.

Deep dive: Gemini.