feat(gemini): add Gemini 3 reasoning effort suffix support (-low/-high)

Add support for gemini-3-pro-preview-low and gemini-3-pro-preview-high
model variants via suffix parsing and normalization.

Changes:
- Add ParseGemini3ReasoningEffortSuffix to parse -low/-high suffixes
- Add Gemini3ReasoningEffortFromMetadata to read effort from metadata
- Update NormalizeGeminiThinkingModel to handle reasoning effort first
- Add injectGemini3ReasoningEffort to inject reasoning_effort into payload
- Add IsGemini3Model utility function

The -low and -high suffixes:
1. Get normalized to base model for routing
2. Store reasoning effort in metadata
3. Executor injects reasoning_effort into payload

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

Author: nestharus

internal/runtime/executor/gemini_cli_executor.go

@@ -60,10 +60,13 @@ func (e *GeminiCLIExecutor) Execute(ctx context.Context, auth *cliproxyauth.Auth
 	reporter := newUsageReporter(ctx, e.Identifier(), req.Model, auth)
 	defer reporter.trackFailure(ctx, &err)
 
+	// Inject reasoning_effort for Gemini 3 model variants
+	payload := injectGemini3ReasoningEffort(req.Model, req.Payload, req.Metadata)
+
 	from := opts.SourceFormat
 	to := sdktranslator.FromString("gemini-cli")
 	budgetOverride, includeOverride, hasOverride := util.GeminiThinkingFromMetadata(req.Metadata)
-	basePayload := sdktranslator.TranslateRequest(from, to, req.Model, bytes.Clone(req.Payload), false)
+	basePayload := sdktranslator.TranslateRequest(from, to, req.Model, bytes.Clone(payload), false)
 	if hasOverride && util.ModelSupportsThinking(req.Model) {
 		if budgetOverride != nil {
 			norm := util.NormalizeThinkingBudget(req.Model, *budgetOverride)
@@ -202,10 +205,13 @@ func (e *GeminiCLIExecutor) ExecuteStream(ctx context.Context, auth *cliproxyaut
 	reporter := newUsageReporter(ctx, e.Identifier(), req.Model, auth)
 	defer reporter.trackFailure(ctx, &err)
 
+	// Inject reasoning_effort for Gemini 3 model variants
+	payload := injectGemini3ReasoningEffort(req.Model, req.Payload, req.Metadata)
+
 	from := opts.SourceFormat
 	to := sdktranslator.FromString("gemini-cli")
 	budgetOverride, includeOverride, hasOverride := util.GeminiThinkingFromMetadata(req.Metadata)
-	basePayload := sdktranslator.TranslateRequest(from, to, req.Model, bytes.Clone(req.Payload), true)
+	basePayload := sdktranslator.TranslateRequest(from, to, req.Model, bytes.Clone(payload), true)
 	if hasOverride && util.ModelSupportsThinking(req.Model) {
 		if budgetOverride != nil {
 			norm := util.NormalizeThinkingBudget(req.Model, *budgetOverride)
@@ -780,6 +786,27 @@ func newGeminiStatusErr(statusCode int, body []byte) statusErr {
 	return err
 }
 
+// injectGemini3ReasoningEffort injects reasoning_effort for Gemini 3 model variants.
+// Checks metadata first (from normalized model), then falls back to model name suffix.
+func injectGemini3ReasoningEffort(modelName string, body []byte, metadata map[string]any) []byte {
+	if gjson.GetBytes(body, "reasoning_effort").Exists() {
+		return body
+	}
+	// First check metadata (set during model normalization)
+	if effort, ok := util.Gemini3ReasoningEffortFromMetadata(metadata); ok {
+		body, _ = sjson.SetBytes(body, "reasoning_effort", effort)
+		return body
+	}
+	// Fall back to model name suffix check
+	switch {
+	case strings.HasSuffix(modelName, "-low"):
+		body, _ = sjson.SetBytes(body, "reasoning_effort", "low")
+	case strings.HasSuffix(modelName, "-high"):
+		body, _ = sjson.SetBytes(body, "reasoning_effort", "high")
+	}
+	return body
+}
+
 // parseRetryDelay extracts the retry delay from a Google API 429 error response.
 // The error response contains a RetryInfo.retryDelay field in the format "0.847655010s".
 // Returns the parsed duration or an error if it cannot be determined.

internal/runtime/executor/gemini_executor.go

@@ -75,10 +75,13 @@ func (e *GeminiExecutor) Execute(ctx context.Context, auth *cliproxyauth.Auth, r
 	reporter := newUsageReporter(ctx, e.Identifier(), req.Model, auth)
 	defer reporter.trackFailure(ctx, &err)
 
+	// Inject reasoning_effort for Gemini 3 model variants
+	payload := injectGemini3ReasoningEffort(req.Model, req.Payload, req.Metadata)
+
 	// Official Gemini API via API key or OAuth bearer
 	from := opts.SourceFormat
 	to := sdktranslator.FromString("gemini")
-	body := sdktranslator.TranslateRequest(from, to, req.Model, bytes.Clone(req.Payload), false)
+	body := sdktranslator.TranslateRequest(from, to, req.Model, bytes.Clone(payload), false)
 	if budgetOverride, includeOverride, ok := util.GeminiThinkingFromMetadata(req.Metadata); ok && util.ModelSupportsThinking(req.Model) {
 		if budgetOverride != nil {
 			norm := util.NormalizeThinkingBudget(req.Model, *budgetOverride)
@@ -171,9 +174,12 @@ func (e *GeminiExecutor) ExecuteStream(ctx context.Context, auth *cliproxyauth.A
 	reporter := newUsageReporter(ctx, e.Identifier(), req.Model, auth)
 	defer reporter.trackFailure(ctx, &err)
 
+	// Inject reasoning_effort for Gemini 3 model variants
+	payload := injectGemini3ReasoningEffort(req.Model, req.Payload, req.Metadata)
+
 	from := opts.SourceFormat
 	to := sdktranslator.FromString("gemini")
-	body := sdktranslator.TranslateRequest(from, to, req.Model, bytes.Clone(req.Payload), true)
+	body := sdktranslator.TranslateRequest(from, to, req.Model, bytes.Clone(payload), true)
 	if budgetOverride, includeOverride, ok := util.GeminiThinkingFromMetadata(req.Metadata); ok && util.ModelSupportsThinking(req.Model) {
 		if budgetOverride != nil {
 			norm := util.NormalizeThinkingBudget(req.Model, *budgetOverride)

internal/util/gemini_thinking.go

@@ -64,13 +64,29 @@ func ParseGeminiThinkingSuffix(model string) (string, *int, *bool, bool) {
 }
 
 func NormalizeGeminiThinkingModel(modelName string) (string, map[string]any) {
-	baseModel, budget, include, matched := ParseGeminiThinkingSuffix(modelName)
+	// First try Gemini 3 reasoning effort normalization (-low/-high suffix)
+	workingModel := modelName
+	var metadata map[string]any
+
+	if base, effort, matched := ParseGemini3ReasoningEffortSuffix(modelName); matched {
+		workingModel = base
+		metadata = map[string]any{
+			Gemini3OriginalModelMetadataKey:   modelName,
+			Gemini3ReasoningEffortMetadataKey: effort,
+		}
+	}
+
+	// Then try thinking suffix normalization on the (possibly already normalized) model
+	baseModel, budget, include, matched := ParseGeminiThinkingSuffix(workingModel)
 	if !matched {
-		return baseModel, nil
+		return workingModel, metadata
 	}
-	metadata := map[string]any{
-		GeminiOriginalModelMetadataKey: modelName,
+
+	// Merge thinking metadata
+	if metadata == nil {
+		metadata = map[string]any{}
 	}
+	metadata[GeminiOriginalModelMetadataKey] = modelName
 	if budget != nil {
 		metadata[GeminiThinkingBudgetMetadataKey] = *budget
 	}
@@ -259,3 +275,55 @@ func ConvertThinkingLevelToBudget(body []byte) []byte {
 	}
 	return updated
 }
+
+const (
+	Gemini3ReasoningEffortMetadataKey = "gemini3_reasoning_effort"
+	Gemini3OriginalModelMetadataKey   = "gemini3_original_model"
+)
+
+// ParseGemini3ReasoningEffortSuffix parses -low or -high suffix from Gemini 3 model names.
+// Returns the base model, reasoning effort ("low" or "high"), and whether a match was found.
+func ParseGemini3ReasoningEffortSuffix(model string) (baseModel string, reasoningEffort string, matched bool) {
+	if model == "" {
+		return model, "", false
+	}
+	lower := strings.ToLower(model)
+	if !strings.HasPrefix(lower, "gemini-3-") {
+		return model, "", false
+	}
+
+	if strings.HasSuffix(lower, "-low") {
+		return model[:len(model)-len("-low")], "low", true
+	}
+	if strings.HasSuffix(lower, "-high") {
+		return model[:len(model)-len("-high")], "high", true
+	}
+	return model, "", false
+}
+
+// NormalizeGemini3ReasoningEffortModel normalizes a Gemini 3 model with -low/-high suffix.
+// Returns the base model name and metadata containing the reasoning effort.
+func NormalizeGemini3ReasoningEffortModel(modelName string) (string, map[string]any) {
+	baseModel, effort, matched := ParseGemini3ReasoningEffortSuffix(modelName)
+	if !matched {
+		return modelName, nil
+	}
+	metadata := map[string]any{
+		Gemini3OriginalModelMetadataKey:   modelName,
+		Gemini3ReasoningEffortMetadataKey: effort,
+	}
+	return baseModel, metadata
+}
+
+// Gemini3ReasoningEffortFromMetadata extracts reasoning effort from metadata.
+func Gemini3ReasoningEffortFromMetadata(metadata map[string]any) (string, bool) {
+	if len(metadata) == 0 {
+		return "", false
+	}
+	if effort, ok := metadata[Gemini3ReasoningEffortMetadataKey]; ok {
+		if s, ok := effort.(string); ok && s != "" {
+			return s, true
+		}
+	}
+	return "", false
+}