diff --git a/pkg/providers/openai_compat/provider.go b/pkg/providers/openai_compat/provider.go
index aa4fa9e6d..841bd76dc 100644
--- a/pkg/providers/openai_compat/provider.go
+++ b/pkg/providers/openai_compat/provider.go
@@ -480,8 +480,9 @@ func asFloat(v any) (float64, bool) {
 
 // supportsPromptCacheKey reports whether the given API base is known to
 // support the prompt_cache_key request field. Currently only OpenAI's own
-// API supports this. All other OpenAI-compatible providers (Mistral,
-// Gemini, DeepSeek, Groq, etc.) reject unknown fields with 422 errors.
+// 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 {
-	return strings.Contains(apiBase, "api.openai.com")
+	return strings.Contains(apiBase, "api.openai.com") ||
+		strings.Contains(apiBase, "openai.azure.com")
 }
diff --git a/pkg/providers/openai_compat/provider_test.go b/pkg/providers/openai_compat/provider_test.go
index 5581146fe..6ec1e8bd9 100644
--- a/pkg/providers/openai_compat/provider_test.go
+++ b/pkg/providers/openai_compat/provider_test.go
@@ -785,6 +785,8 @@ func TestSupportsPromptCacheKey(t *testing.T) {
 	}{
 		{"https://api.openai.com/v1", true},
 		{"https://api.openai.com/v1/", true},
+		{"https://myresource.openai.azure.com/openai/deployments/gpt-4", true},
+		{"https://eastus.openai.azure.com/v1", true},
 		{"https://api.mistral.ai/v1", false},
 		{"https://generativelanguage.googleapis.com/v1beta", false},
 		{"https://api.deepseek.com/v1", false},