Index: internal/agent/coordinator.go
--- internal/agent/coordinator.go.orig
+++ internal/agent/coordinator.go
@@ -823,11 +823,11 @@ func (c *coordinator) buildAnthropicProvider(baseURL, 
 	switch {
 	case strings.HasPrefix(apiKey, "Bearer "):
 		// NOTE: Prevent the SDK from picking up the API key from env.
-		os.Setenv("ANTHROPIC_API_KEY", "")
+		os.Unsetenv("ANTHROPIC_API_KEY")
 		headers["Authorization"] = apiKey
 	case providerID == string(catwalk.InferenceProviderMiniMax) || providerID == string(catwalk.InferenceProviderMiniMaxChina):
 		// NOTE: Prevent the SDK from picking up the API key from env.
-		os.Setenv("ANTHROPIC_API_KEY", "")
+		os.Unsetenv("ANTHROPIC_API_KEY")
 		headers["Authorization"] = "Bearer " + apiKey
 	case apiKey != "":
 		// X-Api-Key header
