feat(providers): add extra_body config to inject custom fields into request body

Allow configuring provider-specific fields like reasoning_split for minimax via
the model config's extra_body map. These fields are merged into the request
body last, giving them precedence over default values.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

pkg/providers/factory_provider.go

@@ -93,6 +93,7 @@ func CreateProviderFromConfig(cfg *config.ModelConfig) (LLMProvider, string, err
 			cfg.Proxy,
 			cfg.MaxTokensField,
 			cfg.RequestTimeout,
+			cfg.ExtraBody,
 		), modelID, nil
 
 	case "azure", "azure-openai":
@@ -132,6 +133,7 @@ func CreateProviderFromConfig(cfg *config.ModelConfig) (LLMProvider, string, err
 			cfg.Proxy,
 			cfg.MaxTokensField,
 			cfg.RequestTimeout,
+			cfg.ExtraBody,
 		), modelID, nil
 
 	case "anthropic":
@@ -157,6 +159,7 @@ func CreateProviderFromConfig(cfg *config.ModelConfig) (LLMProvider, string, err
 			cfg.Proxy,
 			cfg.MaxTokensField,
 			cfg.RequestTimeout,
+			cfg.ExtraBody,
 		), modelID, nil
 
 	case "anthropic-messages":

pkg/providers/http_provider.go

@@ -24,12 +24,13 @@ func NewHTTPProvider(apiKey, apiBase, proxy string) *HTTPProvider {
 }
 
 func NewHTTPProviderWithMaxTokensField(apiKey, apiBase, proxy, maxTokensField string) *HTTPProvider {
-	return NewHTTPProviderWithMaxTokensFieldAndRequestTimeout(apiKey, apiBase, proxy, maxTokensField, 0)
+	return NewHTTPProviderWithMaxTokensFieldAndRequestTimeout(apiKey, apiBase, proxy, maxTokensField, 0, nil)
 }
 
 func NewHTTPProviderWithMaxTokensFieldAndRequestTimeout(
 	apiKey, apiBase, proxy, maxTokensField string,
 	requestTimeoutSeconds int,
+	extraBody map[string]any,
 ) *HTTPProvider {
 	return &HTTPProvider{
 		delegate: openai_compat.NewProvider(
@@ -38,6 +39,7 @@ func NewHTTPProviderWithMaxTokensFieldAndRequestTimeout(
 			proxy,
 			openai_compat.WithMaxTokensField(maxTokensField),
 			openai_compat.WithRequestTimeout(time.Duration(requestTimeoutSeconds)*time.Second),
+			openai_compat.WithExtraBody(extraBody),
 		),
 	}
 }

pkg/providers/openai_compat/provider.go

@@ -35,6 +35,7 @@ type Provider struct {
 	apiBase        string
 	maxTokensField string // Field name for max tokens (e.g., "max_completion_tokens" for o1/glm models)
 	httpClient     *http.Client
+	extraBody      map[string]any // Additional fields to inject into request body
 }
 
 type Option func(*Provider)
@@ -55,6 +56,12 @@ func WithRequestTimeout(timeout time.Duration) Option {
 	}
 }
 
+func WithExtraBody(extraBody map[string]any) Option {
+	return func(p *Provider) {
+		p.extraBody = extraBody
+	}
+}
+
 func NewProvider(apiKey, apiBase, proxy string, opts ...Option) *Provider {
 	p := &Provider{
 		apiKey:     apiKey,
@@ -140,6 +147,12 @@ func (p *Provider) buildRequestBody(
 		}
 	}
 
+	// Merge extra body fields configured per-provider/model.
+	// These are injected last so they take precedence over defaults.
+	for k, v := range p.extraBody {
+		requestBody[k] = v
+	}
+
 	return requestBody
 }
 

pkg/providers/openai_compat/provider_test.go

@@ -610,6 +610,90 @@ func TestProvider_RequestTimeoutOverride(t *testing.T) {
 	}
 }
 
+func TestProviderChat_ExtraBodyInjected(t *testing.T) {
+	var requestBody map[string]any
+
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if err := json.NewDecoder(r.Body).Decode(&requestBody); err != nil {
+			http.Error(w, err.Error(), http.StatusBadRequest)
+			return
+		}
+		resp := map[string]any{
+			"choices": []map[string]any{
+				{
+					"message":       map[string]any{"content": "ok"},
+					"finish_reason": "stop",
+				},
+			},
+		}
+		w.Header().Set("Content-Type", "application/json")
+		json.NewEncoder(w).Encode(resp)
+	}))
+	defer server.Close()
+
+	extraBody := map[string]any{"reasoning_split": true, "custom_field": "test"}
+	p := NewProvider("key", server.URL, "", WithExtraBody(extraBody))
+
+	_, err := p.Chat(
+		t.Context(),
+		[]Message{{Role: "user", Content: "hi"}},
+		nil,
+		"minimax/abab7",
+		nil,
+	)
+	if err != nil {
+		t.Fatalf("Chat() error = %v", err)
+	}
+
+	if got, ok := requestBody["reasoning_split"]; !ok || got != true {
+		t.Fatalf("reasoning_split = %v, want true", got)
+	}
+	if got, ok := requestBody["custom_field"]; !ok || got != "test" {
+		t.Fatalf("custom_field = %v, want test", got)
+	}
+}
+
+func TestProviderChat_ExtraBodyOverridesOptions(t *testing.T) {
+	var requestBody map[string]any
+
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if err := json.NewDecoder(r.Body).Decode(&requestBody); err != nil {
+			http.Error(w, err.Error(), http.StatusBadRequest)
+			return
+		}
+		resp := map[string]any{
+			"choices": []map[string]any{
+				{
+					"message":       map[string]any{"content": "ok"},
+					"finish_reason": "stop",
+				},
+			},
+		}
+		w.Header().Set("Content-Type", "application/json")
+		json.NewEncoder(w).Encode(resp)
+	}))
+	defer server.Close()
+
+	extraBody := map[string]any{"temperature": 0.9}
+	p := NewProvider("key", server.URL, "", WithExtraBody(extraBody))
+
+	_, err := p.Chat(
+		t.Context(),
+		[]Message{{Role: "user", Content: "hi"}},
+		nil,
+		"gpt-4o",
+		map[string]any{"temperature": 0.5},
+	)
+	if err != nil {
+		t.Fatalf("Chat() error = %v", err)
+	}
+
+	// ExtraBody takes precedence over options since it is merged last.
+	if got := requestBody["temperature"]; got != float64(0.9) {
+		t.Fatalf("temperature = %v, want 0.9 (from extraBody, overriding options)", got)
+	}
+}
+
 type roundTripperFunc func(*http.Request) (*http.Response, error)
 
 func (f roundTripperFunc) RoundTrip(r *http.Request) (*http.Response, error) {