fix(pricing): treat negative catalog pricing sentinels as unknown

Port from Kilo-Org/kilocode#13040: OpenRouter and OpenAI-compatible
model catalogs publish negative pricing sentinels ("-1") for
dynamically priced models such as openrouter/auto. The sentinel flowed
straight through _pricing_entry_from_metadata into PricingEntry as
-$1,000,000/M and produced large negative session costs in the usage
ledger and cost displays.

Negative pricing fields now degrade to None (unknown) via
_to_nonnegative_decimal; an all-sentinel pricing block yields no
pricing entry at all so downstream cost falls back to official-docs
pricing or 'unknown'. Zero (free models) is unaffected.

agent/usage_pricing.py

@@ -980,6 +980,23 @@ def _to_decimal(value: Any) -> Optional[Decimal]:
         return None
 
 
+def _to_nonnegative_decimal(value: Any) -> Optional[Decimal]:
+    """Parse a catalog pricing field, treating negative values as unknown.
+
+    Dynamic model catalogs use negative sentinels for "pricing varies":
+    OpenRouter publishes ``"-1"`` for auto-routed models (``openrouter/auto``),
+    and OpenAI-compatible endpoints mirror that convention. Multiplying a
+    sentinel through the usage ledger produces large NEGATIVE session costs
+    (-$1,000,000/M input on the auto router), so an unpriceable field must
+    degrade to "unknown" (None), never a signed price.
+    (Port of Kilo-Org/kilocode#13040.)
+    """
+    parsed = _to_decimal(value)
+    if parsed is None or parsed < 0:
+        return None
+    return parsed
+
+
 def _to_int(value: Any) -> int:
     try:
         return int(value or 0)
@@ -1138,15 +1155,17 @@ def _pricing_entry_from_metadata(
     if model_id not in metadata:
         return None
     pricing = metadata[model_id].get("pricing") or {}
-    prompt = _to_decimal(pricing.get("prompt"))
-    completion = _to_decimal(pricing.get("completion"))
-    request = _to_decimal(pricing.get("request"))
-    cache_read = _to_decimal(
+    # Negative values are dynamic-pricing sentinels (e.g. OpenRouter's "-1"
+    # on openrouter/auto), not real prices — treat them as unknown.
+    prompt = _to_nonnegative_decimal(pricing.get("prompt"))
+    completion = _to_nonnegative_decimal(pricing.get("completion"))
+    request = _to_nonnegative_decimal(pricing.get("request"))
+    cache_read = _to_nonnegative_decimal(
         pricing.get("cache_read")
         or pricing.get("cached_prompt")
         or pricing.get("input_cache_read")
     )
-    cache_write = _to_decimal(
+    cache_write = _to_nonnegative_decimal(
         pricing.get("cache_write")
         or pricing.get("cache_creation")
         or pricing.get("input_cache_write")

tests/agent/test_usage_pricing.py

@@ -312,3 +312,70 @@ def test_vertex_default_model_estimates_cached_usage(monkeypatch):
 
     assert result.status == "estimated"
     assert result.amount_usd is not None and result.amount_usd > 0
+
+
+def test_negative_pricing_sentinels_are_treated_as_unknown():
+    """OpenRouter publishes "-1" pricing sentinels for dynamically priced
+    models (e.g. openrouter/auto). Before this fix the sentinel flowed
+    straight into PricingEntry as -$1,000,000/M and produced large negative
+    session costs. Negative fields must degrade to None (unknown), and an
+    all-sentinel pricing block must yield no entry at all.
+    (Port of Kilo-Org/kilocode#13040.)
+    """
+    from agent.usage_pricing import _pricing_entry_from_metadata
+
+    all_sentinel = {
+        "openrouter/auto": {"pricing": {"prompt": "-1", "completion": "-1"}}
+    }
+    assert (
+        _pricing_entry_from_metadata(
+            all_sentinel,
+            "openrouter/auto",
+            source_url="https://example.test/models",
+            pricing_version="test",
+        )
+        is None
+    )
+
+
+def test_negative_pricing_fields_degrade_individually():
+    """A mixed pricing block keeps valid non-negative fields and drops only
+    the negative ones (including cache fields)."""
+    from decimal import Decimal
+
+    from agent.usage_pricing import _pricing_entry_from_metadata
+
+    mixed = {
+        "m": {
+            "pricing": {
+                "prompt": "-1",
+                "completion": "0.000002",
+                "cache_read": "-0.5",
+                "request": "-1",
+            }
+        }
+    }
+    entry = _pricing_entry_from_metadata(
+        mixed, "m", source_url="https://example.test/models", pricing_version="test"
+    )
+    assert entry is not None
+    assert entry.input_cost_per_million is None
+    assert entry.output_cost_per_million == Decimal("2.000000")
+    assert entry.cache_read_cost_per_million is None
+    assert entry.request_cost is None
+
+
+def test_zero_pricing_still_produces_entry():
+    """Zero is a legitimate price (free models) and must NOT be dropped by
+    the negative-sentinel guard."""
+    from decimal import Decimal
+
+    from agent.usage_pricing import _pricing_entry_from_metadata
+
+    free = {"f": {"pricing": {"prompt": "0", "completion": "0"}}}
+    entry = _pricing_entry_from_metadata(
+        free, "f", source_url="https://example.test/models", pricing_version="test"
+    )
+    assert entry is not None
+    assert entry.input_cost_per_million == Decimal("0")
+    assert entry.output_cost_per_million == Decimal("0")