diff --git a/pkg/providers/anthropic/provider.go b/pkg/providers/anthropic/provider.go
index d4ceaab2c..4330163df 100644
--- a/pkg/providers/anthropic/provider.go
+++ b/pkg/providers/anthropic/provider.go
@@ -10,6 +10,7 @@ import (
 	"github.com/anthropics/anthropic-sdk-go"
 	"github.com/anthropics/anthropic-sdk-go/option"
 
+	"github.com/sipeed/picoclaw/pkg/providers/common"
 	"github.com/sipeed/picoclaw/pkg/providers/protocoltypes"
 )
 
@@ -42,7 +43,7 @@ func NewProvider(token string) *Provider {
 }
 
 func NewProviderWithBaseURL(token, apiBase string) *Provider {
-	baseURL := normalizeBaseURL(apiBase)
+	baseURL := common.NormalizeAnthropicBaseURL(apiBase, defaultBaseURL, false)
 	client := anthropic.NewClient(
 		option.WithAuthToken(token),
 		option.WithBaseURL(baseURL),
@@ -385,20 +386,3 @@ func parseResponse(resp *anthropic.Message) *LLMResponse {
 		},
 	}
 }
-
-func normalizeBaseURL(apiBase string) string {
-	base := strings.TrimSpace(apiBase)
-	if base == "" {
-		return defaultBaseURL
-	}
-
-	base = strings.TrimRight(base, "/")
-	if before, ok := strings.CutSuffix(base, "/v1"); ok {
-		base = before
-	}
-	if base == "" {
-		return defaultBaseURL
-	}
-
-	return base
-}
diff --git a/pkg/providers/anthropic_messages/provider.go b/pkg/providers/anthropic_messages/provider.go
index 1e865b709..dcc31b6f9 100644
--- a/pkg/providers/anthropic_messages/provider.go
+++ b/pkg/providers/anthropic_messages/provider.go
@@ -16,6 +16,7 @@ import (
 	"strings"
 	"time"
 
+	"github.com/sipeed/picoclaw/pkg/providers/common"
 	"github.com/sipeed/picoclaw/pkg/providers/protocoltypes"
 )
 
@@ -51,7 +52,7 @@ func NewProvider(apiKey, apiBase, userAgent string) *Provider {
 
 // NewProviderWithTimeout creates a provider with custom request timeout.
 func NewProviderWithTimeout(apiKey, apiBase, userAgent string, timeoutSeconds int) *Provider {
-	baseURL := normalizeBaseURL(apiBase)
+	baseURL := common.NormalizeAnthropicBaseURL(apiBase, defaultBaseURL, true)
 	timeout := defaultRequestTimeout
 	if timeoutSeconds > 0 {
 		timeout = time.Duration(timeoutSeconds) * time.Second
@@ -161,7 +162,7 @@ func buildRequestBody(
 	options map[string]any,
 ) (map[string]any, error) {
 	// max_tokens is required and guaranteed by agent loop
-	maxTokens, ok := asInt(options["max_tokens"])
+	maxTokens, ok := common.AsInt(options["max_tokens"])
 	if !ok {
 		return nil, fmt.Errorf("max_tokens is required in options")
 	}
@@ -173,7 +174,7 @@ func buildRequestBody(
 	}
 
 	// Set temperature from options
-	if temp, ok := asFloat(options["temperature"]); ok {
+	if temp, ok := common.AsFloat(options["temperature"]); ok {
 		result["temperature"] = temp
 	}
 
@@ -361,61 +362,6 @@ func parseResponseBody(body []byte) (*LLMResponse, error) {
 	}, nil
 }
 
-// normalizeBaseURL ensures the base URL is properly formatted.
-// It removes /v1 suffix if present (to avoid duplication) and always appends /v1.
-// This handles edge cases like "https://api.example.com/v1/proxy" correctly.
-func normalizeBaseURL(apiBase string) string {
-	base := strings.TrimSpace(apiBase)
-	if base == "" {
-		return defaultBaseURL
-	}
-
-	// Remove trailing slashes
-	base = strings.TrimRight(base, "/")
-
-	// Remove /v1 suffix if present (will be re-added)
-	// This prevents duplication for URLs like "https://api.example.com/v1/proxy"
-	if before, ok := strings.CutSuffix(base, "/v1"); ok {
-		base = before
-	}
-
-	// Ensure we don't have an empty string after cutting
-	if base == "" {
-		return defaultBaseURL
-	}
-
-	// Add /v1 suffix (required by Anthropic Messages API)
-	return base + "/v1"
-}
-
-// Helper functions for type conversion
-
-func asInt(v any) (int, bool) {
-	switch val := v.(type) {
-	case int:
-		return val, true
-	case float64:
-		return int(val), true
-	case int64:
-		return int(val), true
-	default:
-		return 0, false
-	}
-}
-
-func asFloat(v any) (float64, bool) {
-	switch val := v.(type) {
-	case float64:
-		return val, true
-	case int:
-		return float64(val), true
-	case int64:
-		return float64(val), true
-	default:
-		return 0, false
-	}
-}
-
 // Anthropic API response structures
 
 type anthropicMessageResponse struct {
diff --git a/pkg/providers/anthropic_messages/provider_test.go b/pkg/providers/anthropic_messages/provider_test.go
index ba9d24b66..6401d84bd 100644
--- a/pkg/providers/anthropic_messages/provider_test.go
+++ b/pkg/providers/anthropic_messages/provider_test.go
@@ -372,44 +372,6 @@ func TestParseResponseBody(t *testing.T) {
 	}
 }
 
-func TestNormalizeBaseURL(t *testing.T) {
-	tests := []struct {
-		name     string
-		apiBase  string
-		expected string
-	}{
-		{
-			name:     "empty string defaults to official API",
-			apiBase:  "",
-			expected: "https://api.anthropic.com/v1",
-		},
-		{
-			name:     "URL without /v1 gets it appended",
-			apiBase:  "https://api.example.com/anthropic",
-			expected: "https://api.example.com/anthropic/v1",
-		},
-		{
-			name:     "URL with /v1 remains unchanged",
-			apiBase:  "https://api.example.com/v1",
-			expected: "https://api.example.com/v1",
-		},
-		{
-			name:     "URL with trailing slash gets cleaned",
-			apiBase:  "https://api.example.com/anthropic/",
-			expected: "https://api.example.com/anthropic/v1",
-		},
-	}
-
-	for _, tt := range tests {
-		t.Run(tt.name, func(t *testing.T) {
-			got := normalizeBaseURL(tt.apiBase)
-			if got != tt.expected {
-				t.Errorf("normalizeBaseURL(%q) = %q, want %q", tt.apiBase, got, tt.expected)
-			}
-		})
-	}
-}
-
 func TestNewProvider(t *testing.T) {
 	provider := NewProvider("test-key", "https://api.example.com", "")
 	if provider == nil {
diff --git a/pkg/providers/common/common.go b/pkg/providers/common/common.go
index 0a702e85e..afc6877b1 100644
--- a/pkg/providers/common/common.go
+++ b/pkg/providers/common/common.go
@@ -478,6 +478,69 @@ func AsInt(v any) (int, bool) {
 	}
 }
 
+// ExtractProtocol extracts the effective protocol and model identifier from a
+// model configuration.
+//
+// The explicit Provider field takes precedence. When Provider is empty, the
+// protocol is inferred from Model. Plain model names default to "openai".
+// Provider-prefixed models strip the first slash-separated segment from the
+// returned model ID.
+//
+// The returned protocol is normalized to the provider's canonical spelling.
+// Examples:
+//   - Model "openai/gpt-4o" -> ("openai", "gpt-4o")
+//   - Model "nvidia/z-ai/glm-5.1" -> ("nvidia", "z-ai/glm-5.1")
+//   - Provider "nvidia", Model "z-ai/glm-5.1" -> ("nvidia", "z-ai/glm-5.1")
+//   - Provider "openai", Model "openai/gpt-4o" -> ("openai", "openai/gpt-4o")
+//   - Model "gpt-4o" -> ("openai", "gpt-4o")
+func ExtractProtocol(model string) (protocol, modelID string) {
+	if cfg == nil {
+		return "", ""
+	}
+
+	model := strings.TrimSpace(cfg.Model)
+	if provider := strings.TrimSpace(cfg.Provider); provider != "" {
+		return NormalizeProvider(provider), model
+	}
+	if model == "" {
+		return "", ""
+	}
+
+	protocol, rest, found := strings.Cut(model, "/")
+	if !found {
+		return "openai", model
+	}
+	protocol = strings.TrimSpace(protocol)
+	if protocol == "" {
+		return "", strings.TrimSpace(rest)
+	}
+	return NormalizeProvider(protocol), strings.TrimSpace(rest)
+}
+
+// NormalizeAnthropicBaseURL ensures the Anthropic base URL is properly formatted.
+// It removes a trailing /v1 suffix if present (to avoid duplication), then
+// re-appends /v1 when appendV1Suffix is true. An empty apiBase falls back to
+// defaultBaseURL.
+func NormalizeAnthropicBaseURL(apiBase, defaultBaseURL string, appendV1Suffix bool) string {
+	base := strings.TrimSpace(apiBase)
+	if base == "" {
+		return defaultBaseURL
+	}
+
+	base = strings.TrimRight(base, "/")
+	if before, ok := strings.CutSuffix(base, "/v1"); ok {
+		base = before
+	}
+	if base == "" {
+		return defaultBaseURL
+	}
+
+	if appendV1Suffix {
+		return base + "/v1"
+	}
+	return base
+}
+
 // AsFloat converts various numeric types to float64.
 func AsFloat(v any) (float64, bool) {
 	switch val := v.(type) {
diff --git a/pkg/providers/common/common_test.go b/pkg/providers/common/common_test.go
index a42d778f1..56c80e754 100644
--- a/pkg/providers/common/common_test.go
+++ b/pkg/providers/common/common_test.go
@@ -660,6 +660,71 @@ func TestAsFloat(t *testing.T) {
 	}
 }
 
+// --- ExtractProtocol tests ---
+
+func TestExtractProtocol(t *testing.T) {
+	tests := []struct {
+		name         string
+		model        string
+		wantProtocol string
+		wantModelID  string
+	}{
+		{"openai with prefix", "openai/gpt-4o", "openai", "gpt-4o"},
+		{"anthropic with prefix", "anthropic/claude-sonnet-4.6", "anthropic", "claude-sonnet-4.6"},
+		{"no prefix defaults to openai", "gpt-4o", "openai", "gpt-4o"},
+		{"groq with prefix", "groq/llama-3.1-70b", "groq", "llama-3.1-70b"},
+		{"empty string", "", "openai", ""},
+		{"with whitespace", "  openai/gpt-4  ", "openai", "gpt-4"},
+		{"multiple slashes", "nvidia/meta/llama-3.1-8b", "nvidia", "meta/llama-3.1-8b"},
+		{"azure with prefix", "azure/my-gpt5-deployment", "azure", "my-gpt5-deployment"},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			protocol, modelID := ExtractProtocol(tt.model)
+			if protocol != tt.wantProtocol {
+				t.Errorf("ExtractProtocol(%q) protocol = %q, want %q", tt.model, protocol, tt.wantProtocol)
+			}
+			if modelID != tt.wantModelID {
+				t.Errorf("ExtractProtocol(%q) modelID = %q, want %q", tt.model, modelID, tt.wantModelID)
+			}
+		})
+	}
+}
+
+// --- NormalizeAnthropicBaseURL tests ---
+
+func TestNormalizeAnthropicBaseURL(t *testing.T) {
+	const defaultURL = "https://api.anthropic.com"
+	const defaultURLWithV1 = "https://api.anthropic.com/v1"
+
+	tests := []struct {
+		name           string
+		apiBase        string
+		defaultBase    string
+		appendV1Suffix bool
+		expected       string
+	}{
+		{"empty with v1", "", defaultURLWithV1, true, defaultURLWithV1},
+		{"empty without v1", "", defaultURL, false, defaultURL},
+		{"URL without v1 gets it appended", "https://api.example.com/anthropic", defaultURLWithV1, true, "https://api.example.com/anthropic/v1"},
+		{"URL without v1 stays as-is", "https://api.example.com/anthropic", defaultURL, false, "https://api.example.com/anthropic"},
+		{"URL with v1 remains unchanged when appending", "https://api.example.com/v1", defaultURLWithV1, true, "https://api.example.com/v1"},
+		{"URL with v1 gets it stripped when not appending", "https://api.example.com/v1", defaultURL, false, "https://api.example.com"},
+		{"trailing slash cleaned with v1", "https://api.example.com/anthropic/", defaultURLWithV1, true, "https://api.example.com/anthropic/v1"},
+		{"trailing slash cleaned without v1", "https://api.example.com/anthropic/", defaultURL, false, "https://api.example.com/anthropic"},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := NormalizeAnthropicBaseURL(tt.apiBase, tt.defaultBase, tt.appendV1Suffix)
+			if got != tt.expected {
+				t.Errorf("NormalizeAnthropicBaseURL(%q, %q, %v) = %q, want %q",
+					tt.apiBase, tt.defaultBase, tt.appendV1Suffix, got, tt.expected)
+			}
+		})
+	}
+}
+
 // --- WrapHTMLResponseError tests ---
 
 func TestWrapHTMLResponseError(t *testing.T) {
diff --git a/pkg/providers/factory_provider.go b/pkg/providers/factory_provider.go
index 86d009811..63413b0a1 100644
--- a/pkg/providers/factory_provider.go
+++ b/pkg/providers/factory_provider.go
@@ -15,6 +15,7 @@ import (
 	anthropicmessages "github.com/sipeed/picoclaw/pkg/providers/anthropic_messages"
 	"github.com/sipeed/picoclaw/pkg/providers/azure"
 	"github.com/sipeed/picoclaw/pkg/providers/bedrock"
+	"github.com/sipeed/picoclaw/pkg/providers/common"
 )
 
 type protocolMeta struct {
@@ -102,27 +103,7 @@ func createCodexAuthProvider() (LLMProvider, error) {
 //   - Provider "openai", Model "openai/gpt-4o" -> ("openai", "openai/gpt-4o")
 //   - Model "gpt-4o" -> ("openai", "gpt-4o")
 func ExtractProtocol(cfg *config.ModelConfig) (protocol, modelID string) {
-	if cfg == nil {
-		return "", ""
-	}
-
-	model := strings.TrimSpace(cfg.Model)
-	if provider := strings.TrimSpace(cfg.Provider); provider != "" {
-		return NormalizeProvider(provider), model
-	}
-	if model == "" {
-		return "", ""
-	}
-
-	protocol, rest, found := strings.Cut(model, "/")
-	if !found {
-		return "openai", model
-	}
-	protocol = strings.TrimSpace(protocol)
-	if protocol == "" {
-		return "", strings.TrimSpace(rest)
-	}
-	return NormalizeProvider(protocol), strings.TrimSpace(rest)
+	return common.ExtractProtocol(model)
 }
 
 // ResolveAPIBase returns the configured API base, or the protocol default when
diff --git a/pkg/providers/httpapi/gemini_helpers.go b/pkg/providers/httpapi/gemini_helpers.go
index 36d95cf9e..0f1e20ca5 100644
--- a/pkg/providers/httpapi/gemini_helpers.go
+++ b/pkg/providers/httpapi/gemini_helpers.go
@@ -128,12 +128,3 @@ func sanitizeSchemaForGemini(schema map[string]any) map[string]any {
 
 	return result
 }
-
-func extractProtocol(model string) (protocol, modelID string) {
-	model = strings.TrimSpace(model)
-	protocol, modelID, found := strings.Cut(model, "/")
-	if !found {
-		return "openai", model
-	}
-	return protocol, modelID
-}
diff --git a/pkg/providers/httpapi/gemini_provider.go b/pkg/providers/httpapi/gemini_provider.go
index d488d06f8..dab6acd29 100644
--- a/pkg/providers/httpapi/gemini_provider.go
+++ b/pkg/providers/httpapi/gemini_provider.go
@@ -303,7 +303,7 @@ func normalizeGeminiModel(model string) string {
 	model = strings.TrimSpace(model)
 	model = strings.TrimPrefix(model, "models/")
 	if strings.Contains(model, "/") {
-		_, modelID := extractProtocol(model)
+		_, modelID := common.ExtractProtocol(model)
 		if modelID != "" {
 			return modelID
 		}
diff --git a/pkg/providers/openai_compat/provider.go b/pkg/providers/openai_compat/provider.go
index 98a70cfd2..29667cd31 100644
--- a/pkg/providers/openai_compat/provider.go
+++ b/pkg/providers/openai_compat/provider.go
@@ -470,7 +470,9 @@ func (p *Provider) SupportsNativeSearch() bool {
 	return isNativeSearchHost(p.apiBase)
 }
 
-func isNativeSearchHost(apiBase string) bool {
+// isNativeOpenAIOrAzureEndpoint reports whether the given API base points to
+// OpenAI's own API or an Azure OpenAI deployment.
+func isNativeOpenAIOrAzureEndpoint(apiBase string) bool {
 	u, err := url.Parse(apiBase)
 	if err != nil {
 		return false
@@ -479,15 +481,14 @@ func isNativeSearchHost(apiBase string) bool {
 	return host == "api.openai.com" || strings.HasSuffix(host, ".openai.azure.com")
 }
 
+func isNativeSearchHost(apiBase string) bool {
+	return isNativeOpenAIOrAzureEndpoint(apiBase)
+}
+
 // supportsPromptCacheKey reports whether the given API base is known to
 // support the prompt_cache_key request field. Currently only OpenAI's own
 // API and Azure OpenAI support this. All other OpenAI-compatible providers
 // (Mistral, Gemini, DeepSeek, Groq, etc.) reject unknown fields with 422 errors.
 func supportsPromptCacheKey(apiBase string) bool {
-	u, err := url.Parse(apiBase)
-	if err != nil {
-		return false
-	}
-	host := u.Hostname()
-	return host == "api.openai.com" || strings.HasSuffix(host, ".openai.azure.com")
+	return isNativeOpenAIOrAzureEndpoint(apiBase)
 }