diff --git a/bc2/core/common/azure_pricing.py b/bc2/core/common/azure_pricing.py
index b80963b..4485429 100644
--- a/bc2/core/common/azure_pricing.py
+++ b/bc2/core/common/azure_pricing.py
@@ -37,7 +37,7 @@ def estimate(
         self, call: dict[str, Any], runtime_config: dict[str, Any]
     ) -> dict[str, Any]:
         """Estimate the cost of one Azure service call."""
-        region = runtime_config.get("azure_region")
+        region = runtime_config.get("azure_region") or call.get("azure_region")
         if not region:
             raise AzurePricingUnavailable(
                 "azure_region is required to look up Azure retail pricing"
diff --git a/bc2/core/common/openai.py b/bc2/core/common/openai.py
index ee9d280..de329e9 100644
--- a/bc2/core/common/openai.py
+++ b/bc2/core/common/openai.py
@@ -598,6 +598,7 @@ def _record_response_usage(
             "model": config.openai_model
             or (reported_model if isinstance(reported_model, str) else config.model),
             "deployment": config.model if provider == "azure" else None,
+            "azure_region": _azure_region(client) if provider == "azure" else None,
             "response_id": getattr(response, "id", None),
             "status": getattr(response, "status", None),
             "usage": token_usage,
@@ -618,5 +619,17 @@ def _openai_provider(client: OpenAI | AsyncOpenAI) -> str:
     return "openai"
 
 
+def _azure_region(client: OpenAI | AsyncOpenAI) -> str | None:
+    """Infer the region suffix from an Azure OpenAI resource hostname."""
+    base_url = str(getattr(client, "base_url", ""))
+    host = (urlparse(base_url).hostname or "").lower()
+    suffix = ".openai.azure.com"
+    if not host.endswith(suffix):
+        return None
+
+    resource_name = host.removesuffix(suffix).rsplit(".", 1)[-1]
+    return resource_name.rsplit("-", 1)[-1] or None
+
+
 class OpenAIConfig(BaseModel):
     client: OpenAIClientConfig
diff --git a/bc2/core/common/test_azure_pricing.py b/bc2/core/common/test_azure_pricing.py
index 44f073e..3e45b14 100644
--- a/bc2/core/common/test_azure_pricing.py
+++ b/bc2/core/common/test_azure_pricing.py
@@ -115,6 +115,30 @@ def test_missing_region_fails_without_fetching_prices():
         )
 
 
+def test_region_falls_back_to_usage_call(monkeypatch):
+    pricing = AzureRetailPricing()
+    monkeypatch.setattr(
+        pricing,
+        "_estimate_openai_tokens",
+        lambda call, runtime_config, region: {
+            "estimated_cost": 0.0,
+            "currency": "USD",
+        },
+    )
+
+    estimate = pricing.estimate(
+        {
+            "service": "responses",
+            "model": "gpt-4.1",
+            "azure_region": "eastus",
+            "usage": {"input_tokens": 10},
+        },
+        {},
+    )
+
+    assert estimate["region"] == "eastus"
+
+
 def test_ambiguous_meter_fails_gracefully(monkeypatch):
     pricing = AzureRetailPricing()
     meters = [
diff --git a/bc2/core/common/test_openai.py b/bc2/core/common/test_openai.py
index ffb71b3..14bca4c 100644
--- a/bc2/core/common/test_openai.py
+++ b/bc2/core/common/test_openai.py
@@ -316,7 +316,7 @@ def test_invoke_completed_response_is_not_truncated():
 def test_invoke_records_response_usage():
     cfg = _build_chat_config()
     client = MagicMock()
-    client.base_url = "https://example.openai.azure.com/openai/v1/"
+    client.base_url = "https://hks-cpl-blindcharging-eastus.openai.azure.com/openai/v1/"
     client.responses.create.return_value = _mock_response(
         status="completed",
         output_text="full answer",
@@ -331,6 +331,7 @@ def test_invoke_records_response_usage():
 
     call = report["calls"][0]
     assert call["provider"] == "azure"
+    assert call["azure_region"] == "eastus"
     assert call["service"] == "responses"
     assert call["operation"] == "parse:openai"
     assert call["response_id"] == "resp_test"