feat: add X-Cagent-Model-Name header to models gateway requests

pkg/config/latest/types.go

@@ -259,6 +259,9 @@ func (a *AgentConfig) GetFallbackCooldown() time.Duration {
 
 // ModelConfig represents the configuration for a model
 type ModelConfig struct {
+	// Name is the manifest model name (map key), populated at runtime.
+	// Not serialized — set by teamloader/model_switcher when resolving models.
+	Name              string   `json:"-"`
 	Provider          string   `json:"provider,omitempty"`
 	Model             string   `json:"model,omitempty"`
 	Temperature       *float64 `json:"temperature,omitempty"`

pkg/httpclient/client.go

@@ -76,6 +76,14 @@ func WithModel(model string) Opt {
 	}
 }
 
+func WithModelName(name string) Opt {
+	return func(o *HTTPOptions) {
+		if name != "" {
+			o.Header.Set("X-Cagent-Model-Name", name)
+		}
+	}
+}
+
 func WithQuery(query url.Values) Opt {
 	return func(o *HTTPOptions) {
 		o.Query = query

pkg/httpclient/client_test.go

@@ -0,0 +1,97 @@
+package httpclient
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestWithModelName(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name      string
+		modelName string
+		wantSet   bool
+	}{
+		{
+			name:      "sets header when name is provided",
+			modelName: "my-fast-model",
+			wantSet:   true,
+		},
+		{
+			name:      "skips header when name is empty",
+			modelName: "",
+			wantSet:   false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+
+			var capturedHeaders http.Header
+			srv := httptest.NewServer(http.HandlerFunc(func(_ http.ResponseWriter, r *http.Request) {
+				capturedHeaders = r.Header
+			}))
+			defer srv.Close()
+
+			client := NewHTTPClient(WithModelName(tt.modelName))
+			req, err := http.NewRequest(http.MethodGet, srv.URL, http.NoBody)
+			require.NoError(t, err)
+
+			resp, err := client.Do(req)
+			require.NoError(t, err)
+			defer func() { _ = resp.Body.Close() }()
+
+			if tt.wantSet {
+				assert.Equal(t, tt.modelName, capturedHeaders.Get("X-Cagent-Model-Name"))
+			} else {
+				assert.Empty(t, capturedHeaders.Get("X-Cagent-Model-Name"))
+			}
+		})
+	}
+}
+
+func TestWithModel(t *testing.T) {
+	t.Parallel()
+
+	var capturedHeaders http.Header
+	srv := httptest.NewServer(http.HandlerFunc(func(_ http.ResponseWriter, r *http.Request) {
+		capturedHeaders = r.Header
+	}))
+	defer srv.Close()
+
+	client := NewHTTPClient(WithModel("gpt-4o"))
+	req, err := http.NewRequest(http.MethodGet, srv.URL, http.NoBody)
+	require.NoError(t, err)
+
+	resp, err := client.Do(req)
+	require.NoError(t, err)
+	defer func() { _ = resp.Body.Close() }()
+
+	assert.Equal(t, "gpt-4o", capturedHeaders.Get("X-Cagent-Model"))
+}
+
+func TestWithProvider(t *testing.T) {
+	t.Parallel()
+
+	var capturedHeaders http.Header
+	srv := httptest.NewServer(http.HandlerFunc(func(_ http.ResponseWriter, r *http.Request) {
+		capturedHeaders = r.Header
+	}))
+	defer srv.Close()
+
+	client := NewHTTPClient(WithProvider("openai"))
+	req, err := http.NewRequest(http.MethodGet, srv.URL, http.NoBody)
+	require.NoError(t, err)
+
+	resp, err := client.Do(req)
+	require.NoError(t, err)
+	defer func() { _ = resp.Body.Close() }()
+
+	assert.Equal(t, "openai", capturedHeaders.Get("X-Cagent-Provider"))
+}

pkg/model/provider/anthropic/client.go

@@ -184,6 +184,7 @@ func NewClient(ctx context.Context, cfg *latest.ModelConfig, env environment.Pro
 				httpclient.WithProxiedBaseURL(cmp.Or(cfg.BaseURL, "https://api.anthropic.com/")),
 				httpclient.WithProvider(cfg.Provider),
 				httpclient.WithModel(cfg.Model),
+				httpclient.WithModelName(cfg.Name),
 				httpclient.WithQuery(url.Query()),
 			}
 			if globalOptions.GeneratingTitle() {

pkg/model/provider/gemini/client.go

@@ -130,6 +130,7 @@ func NewClient(ctx context.Context, cfg *latest.ModelConfig, env environment.Pro
 				httpclient.WithProxiedBaseURL(cmp.Or(cfg.BaseURL, "https://generativelanguage.googleapis.com/")),
 				httpclient.WithProvider(cfg.Provider),
 				httpclient.WithModel(cfg.Model),
+				httpclient.WithModelName(cfg.Name),
 				httpclient.WithQuery(url.Query()),
 			}
 			if globalOptions.GeneratingTitle() {

pkg/model/provider/openai/client.go

@@ -118,6 +118,7 @@ func NewClient(ctx context.Context, cfg *latest.ModelConfig, env environment.Pro
 				httpclient.WithProxiedBaseURL(cmp.Or(cfg.BaseURL, "https://api.openai.com/v1")),
 				httpclient.WithProvider(cfg.Provider),
 				httpclient.WithModel(cfg.Model),
+				httpclient.WithModelName(cfg.Name),
 				httpclient.WithQuery(url.Query()),
 			}
 			if globalOptions.GeneratingTitle() {

pkg/runtime/model_switcher.go

@@ -84,6 +84,7 @@ func (r *LocalRuntime) SetAgentModel(ctx context.Context, agentName, modelRef st
 
 	// Check if modelRef is a named model from config
 	if modelConfig, exists := r.modelSwitcherCfg.Models[modelRef]; exists {
+		modelConfig.Name = modelRef
 		// Check if this is an alloy model (no provider, comma-separated models)
 		if isAlloyModelConfig(modelConfig) {
 			providers, err := r.createProvidersFromAlloyConfig(ctx, modelConfig)
@@ -175,6 +176,7 @@ func (r *LocalRuntime) createProvidersFromInlineAlloy(ctx context.Context, model
 
 		// Check if this part exists as a named model in config
 		if modelCfg, exists := r.modelSwitcherCfg.Models[part]; exists {
+			modelCfg.Name = part
 			prov, err := r.createProviderFromConfig(ctx, &modelCfg)
 			if err != nil {
 				return nil, fmt.Errorf("failed to create provider for %q: %w", part, err)
@@ -219,6 +221,7 @@ func (r *LocalRuntime) createProvidersFromAlloyConfig(ctx context.Context, alloy
 
 		// Check if this model reference exists in the config
 		if modelCfg, exists := r.modelSwitcherCfg.Models[modelRef]; exists {
+			modelCfg.Name = modelRef
 			prov, err := r.createProviderFromConfig(ctx, &modelCfg)
 			if err != nil {
 				return nil, fmt.Errorf("failed to create provider for %q: %w", modelRef, err)

pkg/teamloader/teamloader.go

@@ -301,6 +301,7 @@ func getModelsForAgent(ctx context.Context, cfg *latest.Config, a *latest.AgentC
 				return nil, false, fmt.Errorf("model '%s' not found in configuration", name)
 			}
 		}
+		modelCfg.Name = name
 
 		// Check if thinking_budget was explicitly configured BEFORE provider defaults are applied.
 		// This is used to initialize session thinking state - thinking is only enabled by default
@@ -371,6 +372,7 @@ func getFallbackModelsForAgent(ctx context.Context, cfg *latest.Config, a *lates
 				Model:    modelName,
 			}
 		}
+		modelCfg.Name = name
 
 		// Use max_tokens from config if specified, otherwise look up from models.dev
 		maxTokens := &defaultMaxTokens