Fix provider-prefixed model routing

.gitignore

@@ -1 +1,4 @@
 dist
+.env
+out
+api.json

autorouter.go

@@ -553,6 +553,7 @@ var knownProviderPrefixes = map[string]bool{
 	"perplexity": true,
 	"bedrock":    true,
 	"azure":      true,
+	"mistral":    true,
 }
 
 func stripProviderPrefix(model string) (stripped string, hasPrefix bool) {
@@ -562,7 +563,11 @@ func stripProviderPrefix(model string) (stripped string, hasPrefix bool) {
 	}
 	prefix := model[:idx]
 	if knownProviderPrefixes[prefix] {
-		return model[idx+1:], true
+		stripped = model[idx+1:]
+		if strings.HasPrefix(stripped, prefix+"/") {
+			stripped = strings.TrimPrefix(stripped, prefix+"/")
+		}
+		return stripped, true
 	}
 	return model, false
 }

autorouter_test.go

@@ -292,8 +292,10 @@ func TestStripProviderPrefix(t *testing.T) {
 		{"fireworks prefix", "fireworks/accounts/fireworks/models/llama", "accounts/fireworks/models/llama", true},
 		{"xai prefix", "xai/grok-1", "grok-1", true},
 		{"perplexity prefix", "perplexity/sonar-small", "sonar-small", true},
+		{"repeated perplexity prefix", "perplexity/perplexity/sonar", "sonar", true},
 		{"bedrock prefix", "bedrock/anthropic.claude-3", "anthropic.claude-3", true},
 		{"azure prefix", "azure/gpt-4-deployment", "gpt-4-deployment", true},
+		{"mistral prefix", "mistral/codestral-2508", "codestral-2508", true},
 		{"multiple slashes preserved", "openai/gpt-4/turbo", "gpt-4/turbo", true},
 		{"empty string", "", "", false},
 		{"slash only - not a provider", "/", "/", false},

detection.go

@@ -84,7 +84,7 @@ func DetectProviderFromModel(model string) string {
 	if idx := strings.Index(model, "/"); idx >= 0 {
 		prefix := model[:idx]
 		switch prefix {
-		case "openai", "anthropic", "googleai", "groq", "fireworks", "xai", "perplexity", "bedrock", "azure":
+		case "openai", "anthropic", "googleai", "groq", "fireworks", "xai", "perplexity", "bedrock", "azure", "mistral":
 			return prefix
 		}
 	}

detection_test.go

@@ -138,6 +138,7 @@ func TestDetectProviderFromModel(t *testing.T) {
 		{"perplexity/sonar prefix", "perplexity/sonar-small", "perplexity"},
 		{"bedrock/claude prefix", "bedrock/anthropic.claude-3", "bedrock"},
 		{"azure/gpt-4 prefix", "azure/gpt-4", "azure"},
+		{"mistral/codestral prefix", "mistral/codestral-2508", "mistral"},
 		{"unknown/ prefix returns unknown", "unknown/model", ""},
 		{"single slash only", "/", ""},
 	}

interceptors/billing_test.go

@@ -285,6 +285,7 @@ func TestDetectProvider(t *testing.T) {
 		{"gemini-1.5-flash", "googleai"},
 		{"llama-3-70b", "openai_compatible"},
 		{"mixtral-8x7b", "openai_compatible"},
+		{"mistral/codestral-2508", "mistral"},
 		{"unknown-model", ""},
 	}