feat(management): add support for static and plugin model definitions retrieval by channel

- Implement fallback logic in model definitions handler to query plugin host and global registry for unknown channels.
- Add sorting for registry model definitions by provider and ID to ensure consistent responses.

Closes: #6736

internal/api/handlers/management/model_definitions.go

@@ -2,9 +2,11 @@ package management
 
 import (
 	"net/http"
+	"sort"
 	"strings"
 
 	"github.com/gin-gonic/gin"
+	"github.com/router-for-me/CLIProxyAPI/v8/internal/pluginhost"
 	"github.com/router-for-me/CLIProxyAPI/v8/internal/registry"
 )
 
@@ -21,7 +23,10 @@ func (h *Handler) GetStaticModelDefinitions(c *gin.Context) {
 	}
 
 	models := registry.GetStaticModelDefinitionsByChannel(channel)
-	if models == nil {
+	if len(models) == 0 {
+		models = h.pluginModelDefinitionsByChannel(channel)
+	}
+	if len(models) == 0 {
 		c.JSON(http.StatusBadRequest, gin.H{"error": "unknown channel", "channel": channel})
 		return
 	}
@@ -31,3 +36,30 @@ func (h *Handler) GetStaticModelDefinitions(c *gin.Context) {
 		"models":  models,
 	})
 }
+
+func (h *Handler) pluginModelDefinitionsByChannel(channel string) []*registry.ModelInfo {
+	var host *pluginhost.Host
+	if h != nil {
+		h.mu.Lock()
+		host = h.pluginHost
+		h.mu.Unlock()
+	}
+	if host != nil {
+		if models := host.ModelsForProvider(channel); len(models) > 0 {
+			return models
+		}
+	}
+	models := registry.GetGlobalRegistry().GetAvailableModelsByProvider(channel)
+	if len(models) > 1 {
+		sort.Slice(models, func(i, j int) bool {
+			if models[i] == nil {
+				return models[j] != nil
+			}
+			if models[j] == nil {
+				return false
+			}
+			return models[i].ID < models[j].ID
+		})
+	}
+	return models
+}

internal/api/handlers/management/model_definitions_test.go

@@ -0,0 +1,153 @@
+package management
+
+import (
+	"context"
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/gin-gonic/gin"
+	"github.com/router-for-me/CLIProxyAPI/v8/internal/config"
+	"github.com/router-for-me/CLIProxyAPI/v8/internal/pluginhost"
+	"github.com/router-for-me/CLIProxyAPI/v8/internal/registry"
+	coreauth "github.com/router-for-me/CLIProxyAPI/v8/sdk/cliproxy/auth"
+	"github.com/router-for-me/CLIProxyAPI/v8/sdk/pluginapi"
+)
+
+type staticPluginModelProvider struct {
+	provider string
+	models   []pluginapi.ModelInfo
+}
+
+func (p staticPluginModelProvider) StaticModels(context.Context, pluginapi.StaticModelRequest) (pluginapi.ModelResponse, error) {
+	return pluginapi.ModelResponse{
+		Provider: p.provider,
+		Models:   p.models,
+	}, nil
+}
+
+func (p staticPluginModelProvider) ModelsForAuth(context.Context, pluginapi.AuthModelRequest) (pluginapi.ModelResponse, error) {
+	return pluginapi.ModelResponse{}, nil
+}
+
+func invokeGetStaticModelDefinitions(t *testing.T, h *Handler, channel string) (*httptest.ResponseRecorder, struct {
+	Channel string               `json:"channel"`
+	Error   string               `json:"error"`
+	Models  []registry.ModelInfo `json:"models"`
+}) {
+	t.Helper()
+	gin.SetMode(gin.TestMode)
+	rec := httptest.NewRecorder()
+	ctx, _ := gin.CreateTestContext(rec)
+	ctx.Params = gin.Params{{Key: "channel", Value: channel}}
+	ctx.Request = httptest.NewRequest(http.MethodGet, "/v8/management/routing/model-definitions/"+channel, nil)
+	h.GetStaticModelDefinitions(ctx)
+
+	var body struct {
+		Channel string               `json:"channel"`
+		Error   string               `json:"error"`
+		Models  []registry.ModelInfo `json:"models"`
+	}
+	if errUnmarshal := json.Unmarshal(rec.Body.Bytes(), &body); errUnmarshal != nil {
+		t.Fatalf("unmarshal response body %q: %v", rec.Body.String(), errUnmarshal)
+	}
+	return rec, body
+}
+
+func TestGetStaticModelDefinitions_BuiltInChannel(t *testing.T) {
+	h := NewHandlerWithoutConfigFilePath(&config.Config{AuthDir: t.TempDir()}, nil)
+
+	rec, body := invokeGetStaticModelDefinitions(t, h, "claude")
+	if rec.Code != http.StatusOK {
+		t.Fatalf("status = %d, want %d; body = %s", rec.Code, http.StatusOK, rec.Body.String())
+	}
+	if body.Channel != "claude" {
+		t.Fatalf("channel = %q, want %q", body.Channel, "claude")
+	}
+	if len(body.Models) == 0 {
+		t.Fatal("expected non-empty models for built-in channel claude")
+	}
+}
+
+func TestGetStaticModelDefinitions_FallsBackToPluginStaticModels(t *testing.T) {
+	const provider = "workbuddy"
+	reg := registry.GetGlobalRegistry()
+	clientID := "workbuddy-cred-1.json"
+	reg.RegisterClient(clientID, provider, []*registry.ModelInfo{
+		{ID: "workbuddy-from-registry", DisplayName: "WorkBuddy Registry"},
+	})
+	t.Cleanup(func() {
+		reg.UnregisterClient(clientID)
+	})
+
+	host := pluginhost.New()
+	pluginID := "workbuddy-plugin"
+	host.RegisterPluginForTest(pluginID, pluginapi.Plugin{
+		Capabilities: pluginapi.Capabilities{
+			ModelProvider: staticPluginModelProvider{
+				provider: provider,
+				models: []pluginapi.ModelInfo{
+					{ID: "workbuddy-pro", DisplayName: "WorkBuddy Pro"},
+					{ID: "workbuddy-lite", DisplayName: "WorkBuddy Lite"},
+				},
+			},
+		},
+	})
+	host.RegisterModels(t.Context(), reg)
+	host.RegisterExecutors(coreauth.NewManager(nil, nil, nil), reg)
+
+	h := NewHandlerWithoutConfigFilePath(&config.Config{AuthDir: t.TempDir()}, nil)
+	h.SetPluginHost(host)
+
+	rec, body := invokeGetStaticModelDefinitions(t, h, "WorkBuddy")
+	if rec.Code != http.StatusOK {
+		t.Fatalf("status = %d, want %d; body = %s", rec.Code, http.StatusOK, rec.Body.String())
+	}
+	if body.Channel != provider {
+		t.Fatalf("channel = %q, want %q", body.Channel, provider)
+	}
+	if len(body.Models) != 2 || body.Models[0].ID != "workbuddy-pro" || body.Models[1].ID != "workbuddy-lite" {
+		t.Fatalf("models = %#v, want [workbuddy-pro workbuddy-lite]", body.Models)
+	}
+}
+
+func TestGetStaticModelDefinitions_FallsBackToRegistryModelsForPerAuthPlugin(t *testing.T) {
+	const provider = "qoderwork"
+	reg := registry.GetGlobalRegistry()
+	clientID := "qoderwork-cred-1.json"
+	reg.RegisterClient(clientID, provider, []*registry.ModelInfo{
+		{ID: "qwen3.8-plus-QoderWork", DisplayName: "Qwen 3.8 Plus"},
+		{ID: "qwen3.8-flash-QoderWork", DisplayName: "Qwen 3.8 Flash"},
+	})
+	t.Cleanup(func() {
+		reg.UnregisterClient(clientID)
+	})
+
+	h := NewHandlerWithoutConfigFilePath(&config.Config{AuthDir: t.TempDir()}, nil)
+	h.SetPluginHost(pluginhost.New())
+
+	rec, body := invokeGetStaticModelDefinitions(t, h, "QoderWork")
+	if rec.Code != http.StatusOK {
+		t.Fatalf("status = %d, want %d; body = %s", rec.Code, http.StatusOK, rec.Body.String())
+	}
+	if body.Channel != provider {
+		t.Fatalf("channel = %q, want %q", body.Channel, provider)
+	}
+	if len(body.Models) != 2 || body.Models[0].ID != "qwen3.8-flash-QoderWork" || body.Models[1].ID != "qwen3.8-plus-QoderWork" {
+		t.Fatalf("models = %#v, want [qwen3.8-flash-QoderWork qwen3.8-plus-QoderWork]", body.Models)
+	}
+}
+
+func TestGetStaticModelDefinitions_RejectsUnknownChannel(t *testing.T) {
+	h := NewHandlerWithoutConfigFilePath(&config.Config{AuthDir: t.TempDir()}, nil)
+	h.SetPluginHost(pluginhost.New())
+
+	rec, body := invokeGetStaticModelDefinitions(t, h, "nonexistent-provider")
+	if rec.Code != http.StatusBadRequest {
+		t.Fatalf("status = %d, want %d; body = %s", rec.Code, http.StatusBadRequest, rec.Body.String())
+	}
+	if body.Error != "unknown channel" || body.Channel != "nonexistent-provider" {
+		t.Fatalf("body = %#v, want unknown channel error for nonexistent-provider", body)
+	}
+}