diff --git a/docs/api-reference.md b/docs/api-reference.md
index 9bf1828..e930b1e 100644
--- a/docs/api-reference.md
+++ b/docs/api-reference.md
@@ -117,11 +117,19 @@ Response shape:
   "result": {
     "singleAgent": true,
     "multiAgent": true,
-    "providers": ["codex", "gemini", "opencode"],
+    "providerCatalog": [
+      { "providerId": "codex", "label": "Codex" },
+      { "providerId": "gemini", "label": "Gemini" },
+      { "providerId": "opencode", "label": "OpenCode" }
+    ],
     "capabilities": {
       "single_agent": true,
       "multi_agent": true,
-      "providers": ["codex", "gemini", "opencode"]
+      "providerCatalog": [
+        { "providerId": "codex", "label": "Codex" },
+        { "providerId": "gemini", "label": "Gemini" },
+        { "providerId": "opencode", "label": "OpenCode" }
+      ]
     }
   }
 }
@@ -129,8 +137,9 @@ Response shape:
 
 Notes:
 
-- `providers` comes from the synced external provider catalog registered through
-  `xworkmate.providers.sync`
+- `providerCatalog` comes from the synced external provider catalog registered
+  through `xworkmate.providers.sync`
+- provider order is bridge-owned and preserves the sync order
 - `multiAgent` is controlled by `ACP_MULTI_AGENT_ENABLED`, default `true`
 
 ### 3.2 `session.start`
@@ -293,6 +302,15 @@ Purpose:
   - selected skills
   - install suggestion / unavailable state
 
+Canonical use:
+
+- apps should use this method as the single preflight source for:
+  - effective execution target
+  - effective provider selection
+  - unavailable code / message
+- apps should not re-derive provider availability or `auto` resolution from
+  `acp.capabilities`
+
 Key input fields:
 
 - `taskPrompt`
diff --git a/internal/acp/providers_sync.go b/internal/acp/providers_sync.go
index 4d1daad..ef679d0 100644
--- a/internal/acp/providers_sync.go
+++ b/internal/acp/providers_sync.go
@@ -1,7 +1,6 @@
 package acp
 
 import (
-	"sort"
 	"strings"
 )
 
@@ -40,11 +39,15 @@ func (s *Server) syncProviders(providers []syncedProvider) map[string]any {
 	s.mu.Lock()
 	defer s.mu.Unlock()
 	s.providerCatalog = make(map[string]syncedProvider, len(providers))
+	s.providerOrder = make([]string, 0, len(providers))
 	for _, provider := range providers {
-		if strings.TrimSpace(provider.ProviderID) == "" {
+		providerID := strings.TrimSpace(provider.ProviderID)
+		if providerID == "" {
 			continue
 		}
-		s.providerCatalog[provider.ProviderID] = provider
+		provider.ProviderID = providerID
+		s.providerCatalog[providerID] = provider
+		s.providerOrder = append(s.providerOrder, providerID)
 	}
 	return map[string]any{
 		"ok":        true,
@@ -63,32 +66,58 @@ func (s *Server) syncedProviderByID(providerID string) (syncedProvider, bool) {
 }
 
 func (s *Server) availableProviders() []string {
-	providers := make(map[string]struct{})
 	s.mu.Lock()
-	for _, provider := range s.providerCatalog {
+	defer s.mu.Unlock()
+	ordered := make([]string, 0, len(s.providerOrder))
+	for _, providerID := range s.providerOrder {
+		provider, ok := s.providerCatalog[providerID]
+		if !ok {
+			continue
+		}
 		if !provider.Enabled || strings.TrimSpace(provider.Endpoint) == "" {
 			continue
 		}
-		providers[provider.ProviderID] = struct{}{}
+		ordered = append(ordered, provider.ProviderID)
 	}
-	s.mu.Unlock()
-	ordered := make([]string, 0, len(providers))
-	for providerID := range providers {
-		ordered = append(ordered, providerID)
-	}
-	sort.Strings(ordered)
 	return ordered
 }
 
+func (s *Server) availableProviderCatalog() []map[string]any {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	result := make([]map[string]any, 0, len(s.providerOrder))
+	for _, providerID := range s.providerOrder {
+		provider, ok := s.providerCatalog[providerID]
+		if !ok {
+			continue
+		}
+		if !provider.Enabled || strings.TrimSpace(provider.Endpoint) == "" {
+			continue
+		}
+		result = append(result, map[string]any{
+			"providerId": provider.ProviderID,
+			"label":      providerLabel(provider),
+		})
+	}
+	return result
+}
+
 func syncedProvidersResult(providers []syncedProvider) []map[string]any {
 	result := make([]map[string]any, 0, len(providers))
 	for _, provider := range providers {
 		result = append(result, map[string]any{
 			"providerId": provider.ProviderID,
-			"label":      provider.Label,
+			"label":      providerLabel(provider),
 			"endpoint":   provider.Endpoint,
 			"enabled":    provider.Enabled,
 		})
 	}
 	return result
 }
+
+func providerLabel(provider syncedProvider) string {
+	if label := strings.TrimSpace(provider.Label); label != "" {
+		return label
+	}
+	return provider.ProviderID
+}
diff --git a/internal/acp/providers_sync_test.go b/internal/acp/providers_sync_test.go
index 81da261..a976f51 100644
--- a/internal/acp/providers_sync_test.go
+++ b/internal/acp/providers_sync_test.go
@@ -41,19 +41,77 @@ func TestProvidersSyncUpdatesCapabilities(t *testing.T) {
 	if rpcErr != nil {
 		t.Fatalf("expected capabilities success, got %v", rpcErr)
 	}
-	providers, _ := result["providers"].([]string)
-	if len(providers) == 0 {
+	providerCatalog, ok := result["providerCatalog"].([]map[string]any)
+	if !ok || len(providerCatalog) == 0 {
 		t.Fatalf("expected synced provider in capabilities, got %#v", result)
 	}
-	found := false
-	for _, provider := range providers {
-		if provider == "claude" {
-			found = true
-			break
-		}
+	if providerCatalog[0]["providerId"] != "claude" {
+		t.Fatalf("expected claude provider after sync, got %#v", providerCatalog)
 	}
-	if !found {
-		t.Fatalf("expected claude provider after sync, got %#v", providers)
+	if providerCatalog[0]["label"] != "Claude" {
+		t.Fatalf("expected Claude label after sync, got %#v", providerCatalog)
+	}
+}
+
+func TestProvidersSyncPreservesProviderCatalogOrder(t *testing.T) {
+	server := NewServer()
+
+	_, rpcErr := server.handleRequest(shared.RPCRequest{
+		Method: "xworkmate.providers.sync",
+		Params: map[string]any{
+			"providers": []any{
+				map[string]any{
+					"providerId":          "gemini",
+					"label":               "Gemini",
+					"endpoint":            "http://127.0.0.1:9001",
+					"authorizationHeader": "Bearer gemini",
+					"enabled":             true,
+				},
+				map[string]any{
+					"providerId":          "codex",
+					"label":               "Codex",
+					"endpoint":            "http://127.0.0.1:9002",
+					"authorizationHeader": "Bearer codex",
+					"enabled":             true,
+				},
+				map[string]any{
+					"providerId":          "opencode",
+					"label":               "OpenCode",
+					"endpoint":            "http://127.0.0.1:9003",
+					"authorizationHeader": "Bearer opencode",
+					"enabled":             true,
+				},
+			},
+		},
+	}, func(map[string]any) {})
+	if rpcErr != nil {
+		t.Fatalf("expected sync success, got %v", rpcErr)
+	}
+
+	result, rpcErr := server.handleRequest(shared.RPCRequest{
+		Method: "acp.capabilities",
+		Params: map[string]any{},
+	}, func(map[string]any) {})
+	if rpcErr != nil {
+		t.Fatalf("expected capabilities success, got %v", rpcErr)
+	}
+	providerCatalog, ok := result["providerCatalog"].([]map[string]any)
+	if !ok {
+		t.Fatalf("expected providerCatalog array, got %#v", result)
+	}
+	if len(providerCatalog) != 3 {
+		t.Fatalf("expected 3 catalog entries, got %#v", providerCatalog)
+	}
+	gotOrder := []string{
+		providerCatalog[0]["providerId"].(string),
+		providerCatalog[1]["providerId"].(string),
+		providerCatalog[2]["providerId"].(string),
+	}
+	wantOrder := []string{"gemini", "codex", "opencode"}
+	for index, want := range wantOrder {
+		if gotOrder[index] != want {
+			t.Fatalf("expected provider order %#v, got %#v", wantOrder, gotOrder)
+		}
 	}
 }
 
diff --git a/internal/acp/routing_test.go b/internal/acp/routing_test.go
index f5a3276..4f5915c 100644
--- a/internal/acp/routing_test.go
+++ b/internal/acp/routing_test.go
@@ -325,6 +325,66 @@ func TestExecuteSessionTaskExplicitProviderRequiresAdvertisedBridgeProvider(t *t
 	if got := response["unavailableCode"]; got != "PROVIDER_UNAVAILABLE" {
 		t.Fatalf("expected PROVIDER_UNAVAILABLE, got %#v", response)
 	}
+	if got := response["unavailableMessage"]; got != "explicit provider is unavailable" {
+		t.Fatalf("expected explicit provider unavailable message, got %#v", response)
+	}
+}
+
+func TestExecuteSessionTaskAutoRoutingUsesBridgeSyncOrderForProviderResolution(t *testing.T) {
+	workspaceDir := filepath.Join(t.TempDir(), "workspace")
+	if err := os.MkdirAll(workspaceDir, 0o755); err != nil {
+		t.Fatalf("create workspace: %v", err)
+	}
+
+	server := NewServer()
+	geminiProvider := newExternalSingleAgentProvider(t, "gemini", "gemini-output")
+	defer geminiProvider.Close()
+	codexProvider := newExternalSingleAgentProvider(t, "codex", "codex-output")
+	defer codexProvider.Close()
+	server.syncProviders([]syncedProvider{
+		{
+			ProviderID: "gemini",
+			Label:      "Gemini",
+			Endpoint:   geminiProvider.URL,
+			Enabled:    true,
+		},
+		{
+			ProviderID: "codex",
+			Label:      "Codex",
+			Endpoint:   codexProvider.URL,
+			Enabled:    true,
+		},
+	})
+
+	response, rpcErr := server.executeSessionTask(task{
+		req: shared.RPCRequest{
+			Method: "session.start",
+			Params: map[string]any{
+				"sessionId":        "session-auto-order",
+				"threadId":         "thread-auto-order",
+				"taskPrompt":       "create a powerpoint deck for launch",
+				"workingDirectory": workspaceDir,
+				"routing": map[string]any{
+					"routingMode":            "auto",
+					"preferredGatewayTarget": "local",
+					"availableSkills": []any{
+						map[string]any{
+							"id":          "pptx",
+							"label":       "PPTX",
+							"description": "slides",
+							"installed":   true,
+						},
+					},
+				},
+			},
+		},
+	})
+	if rpcErr != nil {
+		t.Fatalf("expected success, got rpc error: %v", rpcErr)
+	}
+	if got := response["resolvedProviderId"]; got != "gemini" {
+		t.Fatalf("expected resolved provider gemini from bridge order, got %#v", response)
+	}
 }
 
 func TestExecuteSessionTaskRequiresRouting(t *testing.T) {
diff --git a/internal/acp/server.go b/internal/acp/server.go
index b7cc9fc..3b133bb 100644
--- a/internal/acp/server.go
+++ b/internal/acp/server.go
@@ -50,6 +50,7 @@ type Server struct {
 	queues          map[string]chan task
 	gateway         *gatewayruntime.Manager
 	providerCatalog map[string]syncedProvider
+	providerOrder   []string
 	authService     *service.StaticTokenAuthService
 }
 
@@ -108,6 +109,7 @@ func NewServer() *Server {
 		queues:          make(map[string]chan task),
 		gateway:         gatewayruntime.NewManager(),
 		providerCatalog: make(map[string]syncedProvider),
+		providerOrder:   nil,
 		authService:     service.NewStaticTokenAuthService(strings.TrimSpace(shared.EnvOrDefault("ACP_AUTH_TOKEN", ""))),
 	}
 }
@@ -296,20 +298,20 @@ func (s *Server) handleRequest(
 	method := strings.TrimSpace(request.Method)
 	switch method {
 	case "acp.capabilities":
-		providers := s.availableProviders()
-		singleAgent := len(providers) > 0
+		providerCatalog := s.availableProviderCatalog()
+		singleAgent := len(providerCatalog) > 0
 		multiAgent := shared.BoolArg(
 			shared.EnvOrDefault("ACP_MULTI_AGENT_ENABLED", "true"),
 			true,
 		)
 		result := map[string]any{
-			"singleAgent": singleAgent,
-			"multiAgent":  multiAgent,
-			"providers":   providers,
+			"singleAgent":     singleAgent,
+			"multiAgent":      multiAgent,
+			"providerCatalog": providerCatalog,
 			"capabilities": map[string]any{
-				"single_agent": singleAgent,
-				"multi_agent":  multiAgent,
-				"providers":    providers,
+				"single_agent":    singleAgent,
+				"multi_agent":     multiAgent,
+				"providerCatalog": providerCatalog,
 			},
 		}
 		return result, nil
diff --git a/internal/acp/web_contract_test.go b/internal/acp/web_contract_test.go
index 52a41c3..2b678ca 100644
--- a/internal/acp/web_contract_test.go
+++ b/internal/acp/web_contract_test.go
@@ -125,7 +125,7 @@ func TestHandleRPCCapabilitiesStillReturnsJSONResult(t *testing.T) {
 	if got := recorder.Header().Get("Content-Type"); !strings.Contains(got, "application/json") {
 		t.Fatalf("expected application/json content type, got %q", got)
 	}
-	if !strings.Contains(recorder.Body.String(), `"providers"`) {
+	if !strings.Contains(recorder.Body.String(), `"providerCatalog"`) {
 		t.Fatalf("expected capabilities response, got %q", recorder.Body.String())
 	}
 }
diff --git a/internal/router/router.go b/internal/router/router.go
index e1248f5..690c189 100644
--- a/internal/router/router.go
+++ b/internal/router/router.go
@@ -2,7 +2,6 @@ package router
 
 import (
 	"os"
-	"sort"
 	"strings"
 
 	"xworkmate-bridge/internal/memory"
@@ -267,7 +266,6 @@ func normalizeProviders(values []string) []string {
 		unique[providerID] = struct{}{}
 		normalized = append(normalized, providerID)
 	}
-	sort.Strings(normalized)
 	return normalized
 }