fix(thinking): improve model lookup and validation

internal/registry/model_registry.go

@@ -132,6 +132,21 @@ func GetGlobalRegistry() *ModelRegistry {
 	return globalRegistry
 }
 
+// LookupModelInfo searches the dynamic registry first, then falls back to static model definitions.
+//
+// This helper exists because some code paths only have a model ID and still need Thinking and
+// max completion token metadata even when the dynamic registry hasn't been populated.
+func LookupModelInfo(modelID string) *ModelInfo {
+	modelID = strings.TrimSpace(modelID)
+	if modelID == "" {
+		return nil
+	}
+	if info := GetGlobalRegistry().GetModelInfo(modelID); info != nil {
+		return info
+	}
+	return LookupStaticModelInfo(modelID)
+}
+
 // SetHook sets an optional hook for observing model registration changes.
 func (r *ModelRegistry) SetHook(hook ModelRegistryHook) {
 	if r == nil {

internal/runtime/executor/antigravity_executor.go

@@ -1458,7 +1458,7 @@ func generateProjectID() string {
 //   - For Claude models: removing thinkingConfig if budget < minimum allowed
 func normalizeAntigravityThinking(model string, payload []byte, isClaude bool) []byte {
 	payload = util.StripThinkingConfigIfUnsupported(model, payload)
-	modelInfo := registry.GetGlobalRegistry().GetModelInfo(model)
+	modelInfo := registry.LookupModelInfo(model)
 	if modelInfo == nil || modelInfo.Thinking == nil {
 		return payload
 	}
@@ -1501,7 +1501,7 @@ func antigravityEffectiveMaxTokens(model string, payload []byte) (max int, fromM
 	if maxTok := gjson.GetBytes(payload, "request.generationConfig.maxOutputTokens"); maxTok.Exists() && maxTok.Int() > 0 {
 		return int(maxTok.Int()), false
 	}
-	if modelInfo := registry.GetGlobalRegistry().GetModelInfo(model); modelInfo != nil && modelInfo.MaxCompletionTokens > 0 {
+	if modelInfo := registry.LookupModelInfo(model); modelInfo != nil && modelInfo.MaxCompletionTokens > 0 {
 		return modelInfo.MaxCompletionTokens, true
 	}
 	return 0, false
@@ -1510,7 +1510,7 @@ func antigravityEffectiveMaxTokens(model string, payload []byte) (max int, fromM
 // antigravityMinThinkingBudget returns the minimum thinking budget for a model.
 // Falls back to -1 if no model info is found.
 func antigravityMinThinkingBudget(model string) int {
-	if modelInfo := registry.GetGlobalRegistry().GetModelInfo(model); modelInfo != nil && modelInfo.Thinking != nil {
+	if modelInfo := registry.LookupModelInfo(model); modelInfo != nil && modelInfo.Thinking != nil {
 		return modelInfo.Thinking.Min
 	}
 	return -1

internal/thinking/apply.go

@@ -68,9 +68,11 @@ func IsUserDefinedModel(modelInfo *registry.ModelInfo) bool {
 //
 // Passthrough behavior (returns original body without error):
 //   - Unknown provider (not in providerAppliers map)
-//   - modelInfo is nil (model not found in registry)
 //   - modelInfo.Thinking is nil (model doesn't support thinking)
 //
+// Note: Unknown models (modelInfo is nil) are treated as user-defined models: we skip
+// validation and still apply the thinking config so the upstream can validate it.
+//
 // Example:
 //
 //	// With suffix - suffix config takes priority
@@ -87,15 +89,13 @@ func ApplyThinking(body []byte, model string, provider string) ([]byte, error) {
 	}
 
 	// 2. Parse suffix and get modelInfo
-	// First try dynamic registry, then fall back to static lookup
 	suffixResult := ParseSuffix(model)
 	baseModel := suffixResult.ModelName
-	modelInfo := registry.GetGlobalRegistry().GetModelInfo(baseModel)
-	if modelInfo == nil {
-		modelInfo = registry.LookupStaticModelInfo(baseModel)
-	}
+	modelInfo := registry.LookupModelInfo(baseModel)
 
 	// 3. Model capability check
+	// Unknown models are treated as user-defined so thinking config can still be applied.
+	// The upstream service is responsible for validating the configuration.
 	if IsUserDefinedModel(modelInfo) {
 		return applyUserDefinedModel(body, modelInfo, provider, suffixResult)
 	}

internal/thinking/provider/claude/apply.go

@@ -53,18 +53,11 @@ func init() {
 //	  }
 //	}
 func (a *Applier) Apply(body []byte, config thinking.ThinkingConfig, modelInfo *registry.ModelInfo) ([]byte, error) {
-	if modelInfo == nil {
+	if thinking.IsUserDefinedModel(modelInfo) {
 		return applyCompatibleClaude(body, config)
 	}
 	if modelInfo.Thinking == nil {
-		if modelInfo.Type == "" {
-			modelID := modelInfo.ID
-			if modelID == "" {
-				modelID = "unknown"
-			}
-			return nil, thinking.NewThinkingErrorWithModel(thinking.ErrThinkingNotSupported, "thinking not supported for this model", modelID)
-		}
-		return applyCompatibleClaude(body, config)
+		return body, nil
 	}
 
 	// Only process ModeBudget and ModeNone; other modes pass through

internal/thinking/provider/codex/apply.go

@@ -44,18 +44,11 @@ func init() {
 //	  }
 //	}
 func (a *Applier) Apply(body []byte, config thinking.ThinkingConfig, modelInfo *registry.ModelInfo) ([]byte, error) {
-	if modelInfo == nil {
+	if thinking.IsUserDefinedModel(modelInfo) {
 		return applyCompatibleCodex(body, config)
 	}
 	if modelInfo.Thinking == nil {
-		if modelInfo.Type == "" {
-			modelID := modelInfo.ID
-			if modelID == "" {
-				modelID = "unknown"
-			}
-			return nil, thinking.NewThinkingErrorWithModel(thinking.ErrThinkingNotSupported, "thinking not supported for this model", modelID)
-		}
-		return applyCompatibleCodex(body, config)
+		return body, nil
 	}
 
 	// Only handle ModeLevel and ModeNone; other modes pass through unchanged.

internal/thinking/provider/gemini/apply.go

@@ -59,18 +59,11 @@ func init() {
 //	  }
 //	}
 func (a *Applier) Apply(body []byte, config thinking.ThinkingConfig, modelInfo *registry.ModelInfo) ([]byte, error) {
-	if modelInfo == nil {
+	if thinking.IsUserDefinedModel(modelInfo) {
 		return a.applyCompatible(body, config)
 	}
 	if modelInfo.Thinking == nil {
-		if modelInfo.Type == "" {
-			modelID := modelInfo.ID
-			if modelID == "" {
-				modelID = "unknown"
-			}
-			return nil, thinking.NewThinkingErrorWithModel(thinking.ErrThinkingNotSupported, "thinking not supported for this model", modelID)
-		}
-		return a.applyCompatible(body, config)
+		return body, nil
 	}
 
 	if config.Mode != thinking.ModeBudget && config.Mode != thinking.ModeLevel && config.Mode != thinking.ModeNone && config.Mode != thinking.ModeAuto {

internal/thinking/provider/gemini/apply_test.go

@@ -381,26 +381,21 @@ func TestGeminiApplyConflictingFields(t *testing.T) {
 	}
 }
 
-// TestGeminiApplyThinkingNotSupported tests error handling when modelInfo.Thinking is nil.
+// TestGeminiApplyThinkingNotSupported tests passthrough handling when modelInfo.Thinking is nil.
 func TestGeminiApplyThinkingNotSupported(t *testing.T) {
 	applier := NewApplier()
 	config := thinking.ThinkingConfig{Mode: thinking.ModeBudget, Budget: 8192}
+	body := []byte(`{"generationConfig":{"thinkingConfig":{"thinkingBudget":8192}}}`)
 
 	// Model with nil Thinking support
 	modelInfo := &registry.ModelInfo{ID: "gemini-unknown", Thinking: nil}
 
-	_, err := applier.Apply([]byte(`{}`), config, modelInfo)
-	if err == nil {
-		t.Fatal("Apply() expected error for nil Thinking, got nil")
+	got, err := applier.Apply(body, config, modelInfo)
+	if err != nil {
+		t.Fatalf("Apply() expected nil error for nil Thinking, got %v", err)
 	}
-
-	// Verify it's the correct error type
-	thinkErr, ok := err.(*thinking.ThinkingError)
-	if !ok {
-		t.Fatalf("Apply() error type = %T, want *thinking.ThinkingError", err)
-	}
-	if thinkErr.Code != thinking.ErrThinkingNotSupported {
-		t.Fatalf("Apply() error code = %v, want %v", thinkErr.Code, thinking.ErrThinkingNotSupported)
+	if string(got) != string(body) {
+		t.Fatalf("expected body unchanged, got %s", string(got))
 	}
 }
 
@@ -462,17 +457,14 @@ func TestGeminiApplyEmptyModelID(t *testing.T) {
 	applier := NewApplier()
 	config := thinking.ThinkingConfig{Mode: thinking.ModeBudget, Budget: 8192}
 	modelInfo := &registry.ModelInfo{ID: "", Thinking: nil}
+	body := []byte(`{"generationConfig":{"thinkingConfig":{"thinkingBudget":8192}}}`)
 
-	_, err := applier.Apply([]byte(`{}`), config, modelInfo)
-	if err == nil {
-		t.Fatal("Apply() with empty modelID and nil Thinking should error")
+	got, err := applier.Apply(body, config, modelInfo)
+	if err != nil {
+		t.Fatalf("Apply() expected nil error, got %v", err)
 	}
-	thinkErr, ok := err.(*thinking.ThinkingError)
-	if !ok {
-		t.Fatalf("Apply() error type = %T, want *thinking.ThinkingError", err)
-	}
-	if thinkErr.Model != "unknown" {
-		t.Fatalf("Apply() error model = %q, want %q", thinkErr.Model, "unknown")
+	if string(got) != string(body) {
+		t.Fatalf("expected body unchanged, got %s", string(got))
 	}
 }
 

internal/thinking/provider/geminicli/apply.go

@@ -29,18 +29,11 @@ func init() {
 
 // Apply applies thinking configuration to Gemini CLI request body.
 func (a *Applier) Apply(body []byte, config thinking.ThinkingConfig, modelInfo *registry.ModelInfo) ([]byte, error) {
-	if modelInfo == nil {
+	if thinking.IsUserDefinedModel(modelInfo) {
 		return a.applyCompatible(body, config)
 	}
 	if modelInfo.Thinking == nil {
-		if modelInfo.Type == "" {
-			modelID := modelInfo.ID
-			if modelID == "" {
-				modelID = "unknown"
-			}
-			return nil, thinking.NewThinkingErrorWithModel(thinking.ErrThinkingNotSupported, "thinking not supported for this model", modelID)
-		}
-		return a.applyCompatible(body, config)
+		return body, nil
 	}
 
 	if config.Mode != thinking.ModeBudget && config.Mode != thinking.ModeLevel && config.Mode != thinking.ModeNone && config.Mode != thinking.ModeAuto {

internal/thinking/provider/geminicli/apply_test.go

@@ -208,26 +208,21 @@ func TestGeminiCLIApplyConflictingFields(t *testing.T) {
 	}
 }
 
-// TestGeminiCLIApplyThinkingNotSupported tests error handling when modelInfo.Thinking is nil.
+// TestGeminiCLIApplyThinkingNotSupported tests passthrough handling when modelInfo.Thinking is nil.
 func TestGeminiCLIApplyThinkingNotSupported(t *testing.T) {
 	applier := NewApplier()
 	config := thinking.ThinkingConfig{Mode: thinking.ModeBudget, Budget: 8192}
+	body := []byte(`{"request":{"generationConfig":{"thinkingConfig":{"thinkingBudget":8192}}}}`)
 
 	// Model with nil Thinking support
 	modelInfo := &registry.ModelInfo{ID: "gemini-cli-unknown", Thinking: nil}
 
-	_, err := applier.Apply([]byte(`{}`), config, modelInfo)
-	if err == nil {
-		t.Fatal("Apply() expected error for nil Thinking, got nil")
+	got, err := applier.Apply(body, config, modelInfo)
+	if err != nil {
+		t.Fatalf("Apply() expected nil error for nil Thinking, got %v", err)
 	}
-
-	// Verify it's the correct error type
-	thinkErr, ok := err.(*thinking.ThinkingError)
-	if !ok {
-		t.Fatalf("Apply() error type = %T, want *thinking.ThinkingError", err)
-	}
-	if thinkErr.Code != thinking.ErrThinkingNotSupported {
-		t.Fatalf("Apply() error code = %v, want %v", thinkErr.Code, thinking.ErrThinkingNotSupported)
+	if string(got) != string(body) {
+		t.Fatalf("expected body unchanged, got %s", string(got))
 	}
 }
 
@@ -252,17 +247,14 @@ func TestGeminiCLIApplyEmptyModelID(t *testing.T) {
 	applier := NewApplier()
 	config := thinking.ThinkingConfig{Mode: thinking.ModeBudget, Budget: 8192}
 	modelInfo := &registry.ModelInfo{ID: "", Thinking: nil}
+	body := []byte(`{"request":{"generationConfig":{"thinkingConfig":{"thinkingBudget":8192}}}}`)
 
-	_, err := applier.Apply([]byte(`{}`), config, modelInfo)
-	if err == nil {
-		t.Fatal("Apply() with empty modelID and nil Thinking should error")
+	got, err := applier.Apply(body, config, modelInfo)
+	if err != nil {
+		t.Fatalf("Apply() expected nil error, got %v", err)
 	}
-	thinkErr, ok := err.(*thinking.ThinkingError)
-	if !ok {
-		t.Fatalf("Apply() error type = %T, want *thinking.ThinkingError", err)
-	}
-	if thinkErr.Model != "unknown" {
-		t.Fatalf("Apply() error model = %q, want %q", thinkErr.Model, "unknown")
+	if string(got) != string(body) {
+		t.Fatalf("expected body unchanged, got %s", string(got))
 	}
 }
 

internal/thinking/provider/iflow/apply.go

@@ -54,15 +54,11 @@ func init() {
 //	  "reasoning_split": true
 //	}
 func (a *Applier) Apply(body []byte, config thinking.ThinkingConfig, modelInfo *registry.ModelInfo) ([]byte, error) {
-	if modelInfo == nil {
+	if thinking.IsUserDefinedModel(modelInfo) {
 		return body, nil
 	}
 	if modelInfo.Thinking == nil {
-		modelID := modelInfo.ID
-		if modelID == "" {
-			modelID = "unknown"
-		}
-		return nil, thinking.NewThinkingErrorWithModel(thinking.ErrThinkingNotSupported, "thinking not supported for this model", modelID)
+		return body, nil
 	}
 
 	if isGLMModel(modelInfo.ID) {

internal/thinking/provider/iflow/apply_test.go

@@ -75,31 +75,21 @@ func TestApplyMissingThinkingSupport(t *testing.T) {
 	tests := []struct {
 		name    string
 		modelID string
-		wantModel string
 	}{
-		{"model id", "glm-4.6", "glm-4.6"},
-		{"empty model id", "", "unknown"},
+		{"model id", "glm-4.6"},
+		{"empty model id", ""},
 	}
 
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
 			modelInfo := &registry.ModelInfo{ID: tt.modelID}
-			got, err := applier.Apply([]byte(`{"model":"`+tt.modelID+`"}`), thinking.ThinkingConfig{}, modelInfo)
-			if err == nil {
-				t.Fatalf("expected error, got nil")
+			body := []byte(`{"model":"` + tt.modelID + `"}`)
+			got, err := applier.Apply(body, thinking.ThinkingConfig{}, modelInfo)
+			if err != nil {
+				t.Fatalf("expected nil error, got %v", err)
 			}
-			if got != nil {
-				t.Fatalf("expected nil body on error, got %s", string(got))
-			}
-			thinkingErr, ok := err.(*thinking.ThinkingError)
-			if !ok {
-				t.Fatalf("expected ThinkingError, got %T", err)
-			}
-			if thinkingErr.Code != thinking.ErrThinkingNotSupported {
-				t.Fatalf("expected code %s, got %s", thinking.ErrThinkingNotSupported, thinkingErr.Code)
-			}
-			if thinkingErr.Model != tt.wantModel {
-				t.Fatalf("expected model %s, got %s", tt.wantModel, thinkingErr.Model)
+			if string(got) != string(body) {
+				t.Fatalf("expected body unchanged, got %s", string(got))
 			}
 		})
 	}

internal/thinking/provider/openai/apply.go

@@ -41,18 +41,11 @@ func init() {
 //	  "reasoning_effort": "high"
 //	}
 func (a *Applier) Apply(body []byte, config thinking.ThinkingConfig, modelInfo *registry.ModelInfo) ([]byte, error) {
-	if modelInfo == nil {
+	if thinking.IsUserDefinedModel(modelInfo) {
 		return applyCompatibleOpenAI(body, config)
 	}
 	if modelInfo.Thinking == nil {
-		if modelInfo.Type == "" {
-			modelID := modelInfo.ID
-			if modelID == "" {
-				modelID = "unknown"
-			}
-			return nil, thinking.NewThinkingErrorWithModel(thinking.ErrThinkingNotSupported, "thinking not supported for this model", modelID)
-		}
-		return applyCompatibleOpenAI(body, config)
+		return body, nil
 	}
 
 	// Only handle ModeLevel and ModeNone; other modes pass through unchanged.

internal/thinking/provider/openai/apply_test.go

@@ -57,22 +57,13 @@ func TestApplyNilModelInfo(t *testing.T) {
 func TestApplyMissingThinkingSupport(t *testing.T) {
 	applier := NewApplier()
 	modelInfo := &registry.ModelInfo{ID: "gpt-5.2"}
-	got, err := applier.Apply([]byte(`{"model":"gpt-5.2"}`), thinking.ThinkingConfig{}, modelInfo)
-	if err == nil {
-		t.Fatalf("expected error, got nil")
+	body := []byte(`{"model":"gpt-5.2"}`)
+	got, err := applier.Apply(body, thinking.ThinkingConfig{}, modelInfo)
+	if err != nil {
+		t.Fatalf("expected nil error, got %v", err)
 	}
-	if got != nil {
-		t.Fatalf("expected nil body on error, got %s", string(got))
-	}
-	thinkingErr, ok := err.(*thinking.ThinkingError)
-	if !ok {
-		t.Fatalf("expected ThinkingError, got %T", err)
-	}
-	if thinkingErr.Code != thinking.ErrThinkingNotSupported {
-		t.Fatalf("expected code %s, got %s", thinking.ErrThinkingNotSupported, thinkingErr.Code)
-	}
-	if thinkingErr.Model != "gpt-5.2" {
-		t.Fatalf("expected model gpt-5.2, got %s", thinkingErr.Model)
+	if string(got) != string(body) {
+		t.Fatalf("expected body unchanged, got %s", string(got))
 	}
 }