fix(pricing): add Gemini 3.x pricing snapshots and normalize provider

agent/usage_pricing.py

@@ -382,6 +382,50 @@ class CostResult:
         pricing_version="deepseek-pricing-2026-05-12",
     ),
     # Google Gemini
+    (
+        "google",
+        "gemini-3.5-flash",
+    ): PricingEntry(
+        input_cost_per_million=Decimal("1.50"),
+        output_cost_per_million=Decimal("9.00"),
+        cache_read_cost_per_million=Decimal("0.15"),
+        source="official_docs_snapshot",
+        source_url="https://ai.google.dev/pricing",
+        pricing_version="google-pricing-2026-05-19",
+    ),
+    (
+        "google",
+        "gemini-3.1-flash-lite",
+    ): PricingEntry(
+        input_cost_per_million=Decimal("0.25"),
+        output_cost_per_million=Decimal("1.50"),
+        cache_read_cost_per_million=Decimal("0.025"),
+        source="official_docs_snapshot",
+        source_url="https://ai.google.dev/pricing",
+        pricing_version="google-pricing-2026-05-19",
+    ),
+    (
+        "google",
+        "gemini-3.1-flash-lite-preview",
+    ): PricingEntry(
+        input_cost_per_million=Decimal("0.25"),
+        output_cost_per_million=Decimal("1.50"),
+        cache_read_cost_per_million=Decimal("0.025"),
+        source="official_docs_snapshot",
+        source_url="https://ai.google.dev/pricing",
+        pricing_version="google-pricing-2026-05-19",
+    ),
+    (
+        "google",
+        "gemini-3-flash-preview",
+    ): PricingEntry(
+        input_cost_per_million=Decimal("0.50"),
+        output_cost_per_million=Decimal("3.00"),
+        cache_read_cost_per_million=Decimal("0.05"),
+        source="official_docs_snapshot",
+        source_url="https://ai.google.dev/pricing",
+        pricing_version="google-pricing-2026-05-19",
+    ),
     (
         "google",
         "gemini-2.5-pro",
@@ -546,6 +590,8 @@ def resolve_billing_route(
         return BillingRoute(provider="anthropic", model=model.split("/")[-1], base_url=base_url or "", billing_mode="official_docs_snapshot")
     if provider_name == "openai":
         return BillingRoute(provider="openai", model=model.split("/")[-1], base_url=base_url or "", billing_mode="official_docs_snapshot")
+    if provider_name in {"google", "gemini", "google-gemini", "google-ai-studio"}:
+        return BillingRoute(provider="google", model=model.split("/")[-1], base_url=base_url or "", billing_mode="official_docs_snapshot")
     if provider_name in {"minimax", "minimax-cn"}:
         return BillingRoute(provider=provider_name, model=model.split("/")[-1], base_url=base_url or "", billing_mode="official_docs_snapshot")
     if provider_name in {"custom", "local"} or (base and "localhost" in base):

tests/agent/test_usage_pricing.py

@@ -224,3 +224,66 @@ def test_deepseek_v4_pro_estimate_usage_cost():
     assert result.amount_usd is not None
     # 1M input × $1.74/M + 500K output × $3.48/M = $1.74 + $1.74 = $3.48
     assert float(result.amount_usd) == 3.48
+
+
+def test_gemini_35_flash_pricing_entry_exists():
+    """Ensure gemini-3.5-flash has a pricing entry and provider mapping works."""
+    entry = get_pricing_entry(
+        "gemini-3.5-flash",
+        provider="gemini",
+    )
+
+    assert entry is not None
+    assert entry.input_cost_per_million is not None
+    assert entry.output_cost_per_million is not None
+    assert entry.cache_read_cost_per_million is not None
+    assert float(entry.input_cost_per_million) == 1.50
+    assert float(entry.output_cost_per_million) == 9.00
+    assert float(entry.cache_read_cost_per_million) == 0.15
+
+
+def test_gemini_35_flash_estimate_usage_cost():
+    """Ensure gemini-3.5-flash sessions get a dollar estimate with mapped provider."""
+    result = estimate_usage_cost(
+        "gemini-3.5-flash",
+        CanonicalUsage(input_tokens=1000000, output_tokens=500000, cache_read_tokens=200000),
+        provider="gemini",
+    )
+
+    assert result.status == "estimated"
+    assert result.amount_usd is not None
+    # 1M input × $1.50/M + 500K output × $9.00/M + 200K cache_read × $0.15/M
+    # = $1.50 + $4.50 + $0.03 = $6.03
+    assert float(result.amount_usd) == 6.03
+
+
+def test_gemini_31_flash_lite_pricing_entry_exists():
+    """Ensure gemini-3.1-flash-lite has a pricing entry and provider mapping works."""
+    entry = get_pricing_entry(
+        "gemini-3.1-flash-lite",
+        provider="gemini",
+    )
+
+    assert entry is not None
+    assert entry.input_cost_per_million is not None
+    assert entry.output_cost_per_million is not None
+    assert entry.cache_read_cost_per_million is not None
+    assert float(entry.input_cost_per_million) == 0.25
+    assert float(entry.output_cost_per_million) == 1.50
+    assert float(entry.cache_read_cost_per_million) == 0.025
+
+
+def test_gemini_3_flash_preview_pricing_entry_exists():
+    """Ensure gemini-3-flash-preview has a pricing entry and provider mapping works."""
+    entry = get_pricing_entry(
+        "gemini-3-flash-preview",
+        provider="gemini",
+    )
+
+    assert entry is not None
+    assert entry.input_cost_per_million is not None
+    assert entry.output_cost_per_million is not None
+    assert entry.cache_read_cost_per_million is not None
+    assert float(entry.input_cost_per_million) == 0.50
+    assert float(entry.output_cost_per_million) == 3.00
+    assert float(entry.cache_read_cost_per_million) == 0.05