feat: regex support for model-mappings

internal/api/modules/amp/amp.go

@@ -282,13 +282,18 @@ func (m *AmpModule) hasModelMappingsChanged(old *config.AmpCode, new *config.Amp
 	// Build map for efficient comparison
     oldMap := make(map[string]string, len(old.ModelMappings))
     for _, mapping := range old.ModelMappings {
-		oldMap[strings.TrimSpace(mapping.From)] = strings.TrimSpace(mapping.To)
+        from := strings.TrimSpace(mapping.From)
+        to := strings.TrimSpace(mapping.To)
+        key := from
+        val := to + "|regex=" + boolTo01(mapping.Regex)
+        oldMap[key] = val
     }
 
     for _, mapping := range new.ModelMappings {
         from := strings.TrimSpace(mapping.From)
         to := strings.TrimSpace(mapping.To)
-		if oldTo, exists := oldMap[from]; !exists || oldTo != to {
+        val := to + "|regex=" + boolTo01(mapping.Regex)
+        if oldVal, exists := oldMap[from]; !exists || oldVal != val {
             return true
         }
     }
@@ -296,6 +301,13 @@ func (m *AmpModule) hasModelMappingsChanged(old *config.AmpCode, new *config.Amp
 	return false
 }
 
+func boolTo01(b bool) string {
+    if b {
+        return "1"
+    }
+    return "0"
+}
+
 // hasAPIKeyChanged compares old and new API keys.
 func (m *AmpModule) hasAPIKeyChanged(old *config.AmpCode, new *config.AmpCode) bool {
 	oldKey := ""

internal/api/modules/amp/model_mapping.go

@@ -3,6 +3,7 @@
 package amp
 
 import (
+    "regexp"
 	"strings"
 	"sync"
 
@@ -26,13 +27,15 @@ type ModelMapper interface {
 // DefaultModelMapper implements ModelMapper with thread-safe mapping storage.
 type DefaultModelMapper struct {
 	mu       sync.RWMutex
-	mappings map[string]string // from -> to (normalized lowercase keys)
+    mappings map[string]string // exact: from -> to (normalized lowercase keys)
+    regexps  []regexMapping    // regex rules evaluated in order
 }
 
 // NewModelMapper creates a new model mapper with the given initial mappings.
 func NewModelMapper(mappings []config.AmpModelMapping) *DefaultModelMapper {
 	m := &DefaultModelMapper{
         mappings: make(map[string]string),
+        regexps:  nil,
 	}
 	m.UpdateMappings(mappings)
 	return m
@@ -54,9 +57,20 @@ func (m *DefaultModelMapper) MapModel(requestedModel string) string {
 
 	// Check for direct mapping
 	targetModel, exists := m.mappings[normalizedRequest]
+	if !exists {
+        // Try regex mappings in order
+        base, _ := util.NormalizeThinkingModel(requestedModel)
+        for _, rm := range m.regexps {
+            if rm.re.MatchString(requestedModel) || (base != "" && rm.re.MatchString(base)) {
+                targetModel = rm.to
+                exists = true
+                break
+            }
+        }
         if !exists {
             return ""
         }
+	}
 
 	// Verify target model has available providers
 	normalizedTarget, _ := util.NormalizeThinkingModel(targetModel)
@@ -77,7 +91,8 @@ func (m *DefaultModelMapper) UpdateMappings(mappings []config.AmpModelMapping) {
 	defer m.mu.Unlock()
 
 	// Clear and rebuild mappings
-	m.mappings = make(map[string]string, len(mappings))
+    m.mappings = make(map[string]string)
+    m.regexps = m.regexps[:0]
 
 	for _, mapping := range mappings {
 		from := strings.TrimSpace(mapping.From)
@@ -88,16 +103,30 @@ func (m *DefaultModelMapper) UpdateMappings(mappings []config.AmpModelMapping) {
 			continue
 		}
 
+        if mapping.Regex {
+            // Compile case-insensitive regex; wrap with (?i) to match behavior of exact lookups
+            pattern := "(?i)" + from
+            re, err := regexp.Compile(pattern)
+            if err != nil {
+                log.Warnf("amp model mapping: invalid regex %q: %v", from, err)
+                continue
+            }
+            m.regexps = append(m.regexps, regexMapping{re: re, to: to})
+            log.Debugf("amp model regex mapping registered: /%s/ -> %s", from, to)
+        } else {
             // Store with normalized lowercase key for case-insensitive lookup
             normalizedFrom := strings.ToLower(from)
             m.mappings[normalizedFrom] = to
-
             log.Debugf("amp model mapping registered: %s -> %s", from, to)
         }
+	}
 
 	if len(m.mappings) > 0 {
 		log.Infof("amp model mapping: loaded %d mapping(s)", len(m.mappings))
 	}
+    if n := len(m.regexps); n > 0 {
+        log.Infof("amp model mapping: loaded %d regex mapping(s)", n)
+    }
 }
 
 // GetMappings returns a copy of current mappings (for debugging/status).
@@ -111,3 +140,8 @@ func (m *DefaultModelMapper) GetMappings() map[string]string {
 	}
 	return result
 }
+
+type regexMapping struct {
+    re *regexp.Regexp
+    to string
+}

internal/api/modules/amp/model_mapping_test.go

@@ -203,3 +203,81 @@ func TestModelMapper_GetMappings_ReturnsCopy(t *testing.T) {
 		t.Error("Original map was modified")
 	}
 }
+
+func TestModelMapper_Regex_MatchBaseWithoutParens(t *testing.T) {
+    reg := registry.GetGlobalRegistry()
+    reg.RegisterClient("test-client-regex-1", "gemini", []*registry.ModelInfo{
+        {ID: "gemini-2.5-pro", OwnedBy: "google", Type: "gemini"},
+    })
+    defer reg.UnregisterClient("test-client-regex-1")
+
+    mappings := []config.AmpModelMapping{
+        {From: "^gpt-5$", To: "gemini-2.5-pro", Regex: true},
+    }
+
+    mapper := NewModelMapper(mappings)
+
+    // Incoming model has reasoning suffix but should match base via regex
+    result := mapper.MapModel("gpt-5(high)")
+    if result != "gemini-2.5-pro" {
+        t.Errorf("Expected gemini-2.5-pro, got %s", result)
+    }
+}
+
+func TestModelMapper_Regex_ExactPrecedence(t *testing.T) {
+    reg := registry.GetGlobalRegistry()
+    reg.RegisterClient("test-client-regex-2", "claude", []*registry.ModelInfo{
+        {ID: "claude-sonnet-4", OwnedBy: "anthropic", Type: "claude"},
+    })
+    reg.RegisterClient("test-client-regex-3", "gemini", []*registry.ModelInfo{
+        {ID: "gemini-2.5-pro", OwnedBy: "google", Type: "gemini"},
+    })
+    defer reg.UnregisterClient("test-client-regex-2")
+    defer reg.UnregisterClient("test-client-regex-3")
+
+    mappings := []config.AmpModelMapping{
+        {From: "gpt-5", To: "claude-sonnet-4"},                      // exact
+        {From: "^gpt-5.*$", To: "gemini-2.5-pro", Regex: true}, // regex
+    }
+
+    mapper := NewModelMapper(mappings)
+
+    // Exact match should win over regex
+    result := mapper.MapModel("gpt-5")
+    if result != "claude-sonnet-4" {
+        t.Errorf("Expected claude-sonnet-4, got %s", result)
+    }
+}
+
+func TestModelMapper_Regex_InvalidPattern_Skipped(t *testing.T) {
+    // Invalid regex should be skipped and not cause panic
+    mappings := []config.AmpModelMapping{
+        {From: "(", To: "target", Regex: true},
+    }
+
+    mapper := NewModelMapper(mappings)
+
+    result := mapper.MapModel("anything")
+    if result != "" {
+        t.Errorf("Expected empty result due to invalid regex, got %s", result)
+    }
+}
+
+func TestModelMapper_Regex_CaseInsensitive(t *testing.T) {
+    reg := registry.GetGlobalRegistry()
+    reg.RegisterClient("test-client-regex-4", "claude", []*registry.ModelInfo{
+        {ID: "claude-sonnet-4", OwnedBy: "anthropic", Type: "claude"},
+    })
+    defer reg.UnregisterClient("test-client-regex-4")
+
+    mappings := []config.AmpModelMapping{
+        {From: "^CLAUDE-OPUS-.*$", To: "claude-sonnet-4", Regex: true},
+    }
+
+    mapper := NewModelMapper(mappings)
+
+    result := mapper.MapModel("claude-opus-4.5")
+    if result != "claude-sonnet-4" {
+        t.Errorf("Expected claude-sonnet-4, got %s", result)
+    }
+}

internal/config/config.go

@@ -144,6 +144,11 @@ type AmpModelMapping struct {
 	// To is the target model name to route to (e.g., "claude-sonnet-4").
 	// The target model must have available providers in the registry.
 	To string `yaml:"to" json:"to"`
+
+    // Regex indicates whether the 'from' field should be interpreted as a regular
+    // expression for matching model names. When true, this mapping is evaluated
+    // after exact matches and in the order provided. Defaults to false (exact match).
+    Regex bool `yaml:"regex,omitempty" json:"regex,omitempty"`
 }
 
 // AmpCode groups Amp CLI integration settings including upstream routing,