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routstr-core/tests/unit/test_cache_pricing.py
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2026-06-27 22:53:35 +02:00

348 lines
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Python

"""Tests for cache-aware pricing of cached input tokens.
Specifies two things:
1. ``backfill_cache_pricing`` — when the OpenRouter model feed omits cache
rates (it does for most DeepSeek models and e.g. openai/gpt-4o), they are
filled from litellm's bundled cost map instead of silently billing cache
reads at the full input rate. Existing OpenRouter values are never
overwritten, and provider fees apply to backfilled rates like any other.
2. ``calculate_cost`` — cached tokens are billed at the cache rates from the
model's sats_pricing; the full input rate remains only as the documented
last resort when no cache rate could be resolved anywhere.
"""
import os
from unittest.mock import Mock, patch
import litellm
import pytest
os.environ.setdefault("UPSTREAM_BASE_URL", "http://test")
os.environ.setdefault("UPSTREAM_API_KEY", "test")
os.environ.setdefault("LIGHTNING_ADDRESS", "test@stm.to")
from routstr.core.settings import settings
from routstr.payment.cost_calculation import CostData, calculate_cost
from routstr.payment.models import (
Architecture,
Model,
Pricing,
backfill_cache_pricing,
)
from routstr.upstream import GenericUpstreamProvider
def _make_model(model_id: str, pricing: Pricing) -> Model:
return Model(
id=model_id,
name=model_id,
created=0,
description="",
context_length=64000,
architecture=Architecture(
modality="text->text",
input_modalities=["text"],
output_modalities=["text"],
tokenizer="Other",
instruct_type=None,
),
pricing=pricing,
)
# ============================================================================
# backfill_cache_pricing — litellm as fallback source for missing cache rates
# ============================================================================
def test_backfill_deepseek_cache_read_from_litellm() -> None:
"""deepseek/deepseek-chat has no input_cache_read on OpenRouter; litellm
knows the real rate (10x cheaper than input)."""
pricing = Pricing(prompt=2.8e-07, completion=4.2e-07)
result = backfill_cache_pricing("deepseek/deepseek-chat", pricing)
expected = litellm.model_cost["deepseek/deepseek-chat"][
"cache_read_input_token_cost"
]
assert result.input_cache_read == expected
assert result.input_cache_read < pricing.prompt # sanity: it's a discount
def test_backfill_strips_vendor_prefix_for_litellm_lookup() -> None:
"""OpenRouter ids are vendor-prefixed (openai/gpt-4o); litellm keys most
non-DeepSeek models without the prefix (gpt-4o)."""
pricing = Pricing(prompt=2.5e-06, completion=1e-05)
result = backfill_cache_pricing("openai/gpt-4o", pricing)
expected = litellm.model_cost["gpt-4o"]["cache_read_input_token_cost"]
assert result.input_cache_read == expected
def test_backfill_case_insensitive_lookup() -> None:
"""A generic upstream may report a mixed-case id
(deepseek-ai/DeepSeek-V4-Flash); litellm keys are lowercase. The
case-insensitive fallback still resolves the cache rate."""
pricing = Pricing(prompt=1.4e-07, completion=2.8e-07)
result = backfill_cache_pricing("deepseek-ai/DeepSeek-V4-Flash", pricing)
expected = litellm.model_cost["deepseek-v4-flash"][
"cache_read_input_token_cost"
]
assert result.input_cache_read == expected
assert result.input_cache_read < pricing.prompt # sanity: it's a discount
def test_backfill_fills_cache_write_rate() -> None:
"""Anthropic cache writes cost more than input (1.25x); billing them at
the input rate undercharges. litellm carries the write rate."""
pricing = Pricing(prompt=3e-06, completion=1.5e-05)
result = backfill_cache_pricing("anthropic/claude-sonnet-4-5", pricing)
expected = litellm.model_cost["claude-sonnet-4-5"][
"cache_creation_input_token_cost"
]
assert result.input_cache_write == expected
assert result.input_cache_write > pricing.prompt # sanity: write premium
def test_backfill_never_overwrites_openrouter_rates() -> None:
"""When OpenRouter provides a cache rate, it is authoritative."""
pricing = Pricing(
prompt=2.1e-07, completion=7.9e-07, input_cache_read=1.3e-07
)
result = backfill_cache_pricing("deepseek/deepseek-chat", pricing)
assert result.input_cache_read == 1.3e-07
def test_backfill_unknown_model_unchanged() -> None:
"""Models litellm doesn't know stay untouched (last-resort fallback to
the input rate happens later, at billing time)."""
pricing = Pricing(prompt=1e-06, completion=2e-06)
result = backfill_cache_pricing("artificial-dumbness/dumb-1", pricing)
assert result.input_cache_read == 0.0
assert result.input_cache_write == 0.0
def test_provider_fee_applies_to_backfilled_cache_rates() -> None:
"""Backfill happens before the provider fee, so cache rates carry the
same markup as every other price component."""
provider = GenericUpstreamProvider(
base_url="http://upstream.example", provider_fee=2.0
)
model = _make_model(
"deepseek/deepseek-chat", Pricing(prompt=2.8e-07, completion=4.2e-07)
)
adjusted = provider._apply_provider_fee_to_model(model)
litellm_read = litellm.model_cost["deepseek/deepseek-chat"][
"cache_read_input_token_cost"
]
assert adjusted.pricing.input_cache_read == pytest.approx(litellm_read * 2.0)
assert adjusted.pricing.prompt == pytest.approx(2.8e-07 * 2.0)
def test_row_to_model_backfills_cache_rate() -> None:
"""The DB-override path (admin-configured providers, e.g. a generic
upstream) stores pricing without cache rates. ``_row_to_model`` must
backfill them from litellm just like ``_apply_provider_fee_to_model``,
otherwise cache reads bill at the full input rate."""
import json
from routstr.core.db import ModelRow
from routstr.payment.models import _row_to_model
row = ModelRow(
id="deepseek-v4-flash",
name="deepseek-v4-flash",
created=0,
description="",
context_length=1000000,
architecture=json.dumps(
{
"modality": "text",
"input_modalities": ["text"],
"output_modalities": ["text"],
"tokenizer": "unknown",
"instruct_type": None,
}
),
# Stored pricing omits input_cache_read (generic provider never sets it).
pricing=json.dumps({"prompt": 1.4e-07, "completion": 2.8e-07}),
enabled=True,
upstream_provider_id=1,
)
with patch(
"routstr.payment.models.sats_usd_price", return_value=5.0e-5
):
model = _row_to_model(row, apply_provider_fee=True, provider_fee=1.0)
litellm_read = litellm.model_cost["deepseek-v4-flash"][
"cache_read_input_token_cost"
]
assert model.pricing.input_cache_read == pytest.approx(litellm_read)
assert model.pricing.input_cache_read < model.pricing.prompt # a discount
assert model.sats_pricing is not None
assert model.sats_pricing.input_cache_read > 0
def test_row_to_model_backfills_via_forwarded_model_id() -> None:
"""An alias row (id != forwarded_model_id) must backfill cache rates from
the *forwarded* model name — the real upstream model litellm prices —
not the alias id, which litellm doesn't know."""
import json
from routstr.core.db import ModelRow
from routstr.payment.models import _row_to_model
row = ModelRow(
id="local-alias", # litellm has no such key
name="local-alias",
created=0,
description="",
context_length=1000000,
architecture=json.dumps(
{
"modality": "text",
"input_modalities": ["text"],
"output_modalities": ["text"],
"tokenizer": "unknown",
"instruct_type": None,
}
),
pricing=json.dumps({"prompt": 1.4e-07, "completion": 2.8e-07}),
enabled=True,
upstream_provider_id=1,
forwarded_model_id="deepseek-v4-flash",
)
with patch(
"routstr.payment.models.sats_usd_price", return_value=5.0e-5
):
model = _row_to_model(row, apply_provider_fee=True, provider_fee=1.0)
litellm_read = litellm.model_cost["deepseek-v4-flash"][
"cache_read_input_token_cost"
]
assert model.pricing.input_cache_read == pytest.approx(litellm_read)
assert model.pricing.input_cache_read < model.pricing.prompt
# ============================================================================
# calculate_cost — cached tokens billed at cache rates
# ============================================================================
@pytest.fixture(autouse=True)
def patch_sats_usd_price() -> None: # type: ignore[misc]
with patch("routstr.payment.cost_calculation.sats_usd_price", return_value=5.0e-5):
yield
@pytest.fixture
def model_pricing(monkeypatch: pytest.MonkeyPatch) -> Mock:
"""Model-based pricing: 1 msat per input token, 2 per output token,
0.1 per cache-read token, 1.25 per cache-write token."""
monkeypatch.setattr(settings, "fixed_pricing", False)
model = Mock()
model.sats_pricing = Pricing(
prompt=0.001,
completion=0.002,
input_cache_read=0.0001,
input_cache_write=0.00125,
)
return model
@pytest.mark.asyncio
async def test_deepseek_cache_hits_billed_at_cache_rate(model_pricing: Mock) -> None:
"""The reported overcharge scenario: a 10k-token prompt with 90% cache
hits costs 2900 msats at honest rates, not the 11000 msats that billing
every prompt token at the full input rate would charge."""
response = {
"model": "deepseek-chat",
"usage": {
"prompt_tokens": 10000,
"completion_tokens": 500,
"prompt_cache_hit_tokens": 9000,
"prompt_cache_miss_tokens": 1000,
},
}
with patch("routstr.proxy.get_model_instance", return_value=model_pricing):
result = await calculate_cost(response, max_cost=100000)
assert isinstance(result, CostData)
# 1000 input @ 1 msat + 9000 cache reads @ 0.1 msat + 500 output @ 2 msat.
# input_msats folds the cache-read cost in (1000 + 900) so a dashboard
# rendering I/O/T sees input + output == total; the cache portion stays
# visible in cache_read_msats.
assert result.cache_read_msats == 900
assert result.output_msats == 1000
assert result.input_msats == 1900
assert result.input_msats + result.output_msats == result.total_msats
assert result.total_msats == 2900
@pytest.mark.asyncio
async def test_anthropic_cache_write_billed_at_write_rate(model_pricing: Mock) -> None:
"""Cache writes carry their premium rate (1.25x input here), instead of
being silently billed at the plain input rate."""
response = {
"model": "claude-sonnet-4-5",
"usage": {
"input_tokens": 300,
"output_tokens": 100,
"cache_read_input_tokens": 500,
"cache_creation_input_tokens": 2000,
},
}
with patch("routstr.proxy.get_model_instance", return_value=model_pricing):
result = await calculate_cost(response, max_cost=100000)
assert isinstance(result, CostData)
# 300 @ 1 + 500 @ 0.1 + 2000 @ 1.25 + 100 @ 2
assert result.cache_read_msats == 50
assert result.cache_creation_msats == 2500
assert result.total_msats == 3050
@pytest.mark.asyncio
async def test_missing_cache_rate_falls_back_to_input_rate(
monkeypatch: pytest.MonkeyPatch,
) -> None:
"""Documented last resort: when no cache rate could be resolved anywhere
(OpenRouter and litellm both silent), cache reads bill at the input rate —
never cheaper, never free."""
monkeypatch.setattr(settings, "fixed_pricing", False)
model = Mock()
model.sats_pricing = Pricing(prompt=0.001, completion=0.002)
response = {
"model": "dumb-1",
"usage": {
"prompt_tokens": 10000,
"completion_tokens": 500,
"prompt_cache_hit_tokens": 9000,
"prompt_cache_miss_tokens": 1000,
},
}
with patch("routstr.proxy.get_model_instance", return_value=model):
result = await calculate_cost(response, max_cost=100000)
assert isinstance(result, CostData)
# 1000 @ 1 + 9000 @ 1 (fallback) + 500 @ 2
assert result.total_msats == 11000