diff --git a/packages/llm_gateway/tests/test_pricing.py b/packages/llm_gateway/tests/test_pricing.py
new file mode 100644
index 0000000..63d37c5
--- /dev/null
+++ b/packages/llm_gateway/tests/test_pricing.py
@@ -0,0 +1,29 @@
+"""pricing 单元测试（CR-M2-1：未知模型缺价应可观测）。"""
+
+from __future__ import annotations
+
+import structlog
+from ww_llm_gateway.pricing import cost_minor
+
+
+def test_known_model_computes_positive_cost() -> None:
+    # Arrange / Act
+    cost, currency = cost_minor("deepseek", "deepseek-chat", 1_000_000, 1_000_000)
+
+    # Assert
+    assert cost > 0
+    assert currency == "USD"
+
+
+def test_unknown_model_warns_and_still_returns_zero_cost() -> None:
+    # CR-M2-1：未知 (provider, model) 成本仍计 0（照常记账），但必须发结构化 warning
+    # 点名该 model——缺价条目应在成本账路径可见，而非静默吞成 0。
+    with structlog.testing.capture_logs() as logs:
+        cost, currency = cost_minor("mystery", "ghost-model", 1000, 2000)
+
+    assert cost == 0
+    assert currency == "USD"
+    warning = next(entry for entry in logs if entry["event"] == "pricing_unknown_model")
+    assert warning["log_level"] == "warning"
+    assert warning["provider"] == "mystery"
+    assert warning["model"] == "ghost-model"
diff --git a/packages/llm_gateway/ww_llm_gateway/pricing.py b/packages/llm_gateway/ww_llm_gateway/pricing.py
index e866c8b..7bbde2b 100644
--- a/packages/llm_gateway/ww_llm_gateway/pricing.py
+++ b/packages/llm_gateway/ww_llm_gateway/pricing.py
@@ -9,6 +9,10 @@ from __future__ import annotations
 import math
 from dataclasses import dataclass
 
+import structlog
+
+log = structlog.get_logger(__name__)
+
 
 @dataclass(frozen=True)
 class Price:
@@ -26,6 +30,9 @@ _PRICING: dict[tuple[str, str], Price] = {
 def cost_minor(provider: str, model: str, input_tokens: int, output_tokens: int) -> tuple[int, str]:
     price = _PRICING.get((provider, model))
     if price is None:
+        # 缺价条目应在成本账路径可见（CR-M2-1）：成本仍计 0（照常记账不阻断调用），
+        # 但发 warning 点名该 (provider, model)，否则漏配价格会静默吞成 0 成本。
+        log.warning("pricing_unknown_model", provider=provider, model=model)
         return 0, "USD"
     cost = math.ceil(
         input_tokens / 1_000_000 * price.in_per_mtok