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fix(perplexity): stop double-billing reasoning tokens in manual cost fallback #30488

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Sameerlite merged 3 commits into from
Jun 17, 2026
Merged

fix(perplexity): stop double-billing reasoning tokens in manual cost fallback #30488

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7f42f4b
fix(perplexity): stop double-billing reasoning tokens in manual cost …
Anuj7411 Jun 15, 2026
e03fcca
style(perplexity): drop redundant type annotation on else branch to s…
Anuj7411 Jun 16, 2026
489d6f4
fix(perplexity): update integration test expected costs for non-doubl…
Anuj7411 Jun 16, 2026
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17 changes: 12 additions & 5 deletions litellm/llms/perplexity/cost_calculator.py
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Original file line number Diff line number Diff line change
Expand Up @@ -58,11 +58,8 @@ def _safe_float_cast(

## CALCULATE OUTPUT COST
output_cost_per_token = _safe_float_cast(model_info.get("output_cost_per_token"))
completion_cost: float = (usage.completion_tokens or 0) * output_cost_per_token

## ADD REASONING TOKENS COST (if present)
reasoning_tokens = getattr(usage, "reasoning_tokens", 0) or 0
# Also check completion_tokens_details if reasoning_tokens is not directly available
if (
reasoning_tokens == 0
and hasattr(usage, "completion_tokens_details")
Expand All @@ -73,9 +70,19 @@ def _safe_float_cast(
)

reasoning_cost_value = model_info.get("output_cost_per_reasoning_token")

# `completion_tokens` includes `reasoning_tokens` per the OpenAI/Perplexity usage
# convention (codified for the central path in PR #18607). When a reasoning rate is
# configured we subtract before the output-rate multiplication so the reasoning
# tokens are not billed twice.
if reasoning_tokens > 0 and reasoning_cost_value is not None:
reasoning_cost_per_token = _safe_float_cast(reasoning_cost_value)
completion_cost += reasoning_tokens * reasoning_cost_per_token
non_reasoning_completion_tokens = max(
0, (usage.completion_tokens or 0) - reasoning_tokens
)
completion_cost: float = non_reasoning_completion_tokens * output_cost_per_token
completion_cost += reasoning_tokens * _safe_float_cast(reasoning_cost_value)
else:
completion_cost = (usage.completion_tokens or 0) * output_cost_per_token

## ADD SEARCH QUERIES COST (if present)
num_search_queries = 0
Expand Down
94 changes: 66 additions & 28 deletions tests/test_litellm/llms/perplexity/test_perplexity_cost_calculator.py
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Original file line number Diff line number Diff line change
@@ -1,7 +1,7 @@
"""
Test file for Perplexity cost calculator functionality.

Tests the cost calculation for Perplexity models including citation tokens,
Tests the cost calculation for Perplexity models including citation tokens,
search queries, and reasoning tokens.
"""

Expand All @@ -21,7 +21,11 @@
from litellm.llms.perplexity.cost_calculator import (
cost_per_token as perplexity_cost_per_token,
)
from litellm.types.utils import Usage, PromptTokensDetailsWrapper
from litellm.types.utils import (
CompletionTokensDetailsWrapper,
Usage,
PromptTokensDetailsWrapper,
)
from litellm.utils import get_model_info


Expand Down Expand Up @@ -135,13 +139,14 @@ def test_reasoning_tokens_from_direct_attribute(self):
model="sonar-deep-research", usage=usage
)

# Expected costs:
# Input: 100 tokens * $2e-6 = $0.0002
# Output: 50 tokens * $8e-6 = $0.0004
# Reasoning: 20 tokens * $3e-6 = $0.00006
# Total completion cost: $0.00046
# `completion_tokens` includes `reasoning_tokens` per the OpenAI/Perplexity
# convention codified in PR #18607. Non-reasoning portion = 50 - 20 = 30.
# Input: 100 tokens * $2e-6 = $0.0002
# Output (text): 30 tokens * $8e-6 = $0.00024
# Reasoning: 20 tokens * $3e-6 = $0.00006
# Total completion cost = $0.0003
expected_prompt_cost = 100 * 2e-6
expected_completion_cost = (50 * 8e-6) + (20 * 3e-6)
expected_completion_cost = ((50 - 20) * 8e-6) + (20 * 3e-6)

assert math.isclose(prompt_cost, expected_prompt_cost, rel_tol=1e-6)
assert math.isclose(completion_cost, expected_completion_cost, rel_tol=1e-6)
Expand All @@ -159,13 +164,10 @@ def test_reasoning_tokens_from_completion_tokens_details(self):
model="sonar-deep-research", usage=usage
)

# Expected costs:
# Input: 100 tokens * $2e-6 = $0.0002
# Output: 50 tokens * $8e-6 = $0.0004
# Reasoning: 20 tokens * $3e-6 = $0.00006
# Total completion cost: $0.00046
# Same convention as the direct-attribute case above; reasoning is a subset of
# completion_tokens, so non-reasoning portion = 50 - 20 = 30.
expected_prompt_cost = 100 * 2e-6
expected_completion_cost = (50 * 8e-6) + (20 * 3e-6)
expected_completion_cost = ((50 - 20) * 8e-6) + (20 * 3e-6)

assert math.isclose(prompt_cost, expected_prompt_cost, rel_tol=1e-6)
assert math.isclose(completion_cost, expected_completion_cost, rel_tol=1e-6)
Expand All @@ -187,16 +189,16 @@ def test_comprehensive_cost_calculation(self):
model="sonar-deep-research", usage=usage
)

# Expected costs:
# Input: 100 tokens * $2e-6 = $0.0002
# Citation: 30 tokens * $2e-6 = $0.00006
# Total prompt cost: $0.00026
# Output: 50 tokens * $8e-6 = $0.0004
# Reasoning: 15 tokens * $3e-6 = $0.000045
# Search: 2 queries * ($0.005 / 1000) = $0.00001
# Total completion cost: $0.000455
# Expected costs (reasoning is a subset of completion_tokens):
# Input: 100 tokens * $2e-6 = $0.0002
# Citation: 30 tokens * $2e-6 = $0.00006
# Total prompt cost = $0.00026
# Output (text): (50 - 15) tokens * $8e-6 = $0.00028
# Reasoning: 15 tokens * $3e-6 = $0.000045
# Search: 2 queries * ($0.005 / 1000) = $0.00001
# Total completion cost = $0.000335
expected_prompt_cost = (100 * 2e-6) + (30 * 2e-6)
expected_completion_cost = (50 * 8e-6) + (15 * 3e-6) + (2 / 1000 * 0.005)
expected_completion_cost = ((50 - 15) * 8e-6) + (15 * 3e-6) + (2 / 1000 * 0.005)

assert math.isclose(prompt_cost, expected_prompt_cost, rel_tol=1e-6)
assert math.isclose(completion_cost, expected_completion_cost, rel_tol=1e-6)
Expand Down Expand Up @@ -306,11 +308,11 @@ def test_integration_with_completion_cost_function(self):
completion_response=response, custom_llm_provider="perplexity"
)

# Calculate expected total cost
# Calculate expected total cost (reasoning is a subset of completion_tokens)
expected_prompt_cost = (100 * 2e-6) + (15 * 2e-6) # Input + citation
expected_completion_cost = (
(50 * 8e-6) + (10 * 3e-6) + (1 / 1000 * 0.005)
) # Output + reasoning + search
((50 - 10) * 8e-6) + (10 * 3e-6) + (1 / 1000 * 0.005)
) # Output (text) + reasoning + search
expected_total = expected_prompt_cost + expected_completion_cost

assert math.isclose(total_cost, expected_total, rel_tol=1e-6)
Expand Down Expand Up @@ -353,10 +355,13 @@ def test_cost_calculation_combinations(
model="sonar-deep-research", usage=usage
)

# Calculate expected costs
# Calculate expected costs. `completion_tokens` includes `reasoning_tokens`,
# so non-reasoning portion = 50 - reasoning_tokens.
expected_prompt_cost = (100 * 2e-6) + (citation_tokens * 2e-6)
expected_completion_cost = (
(50 * 8e-6) + (reasoning_tokens * 3e-6) + (search_queries / 1000 * 0.005)
((50 - reasoning_tokens) * 8e-6)
+ (reasoning_tokens * 3e-6)
+ (search_queries / 1000 * 0.005)
)

assert math.isclose(prompt_cost, expected_prompt_cost, rel_tol=1e-6)
Expand Down Expand Up @@ -413,3 +418,36 @@ def test_falls_back_to_manual_calculation_when_no_cost_provided(self):

assert math.isclose(prompt_cost, expected_prompt, rel_tol=1e-6)
assert math.isclose(completion_cost, expected_completion, rel_tol=1e-6)

def test_reasoning_tokens_not_double_billed(self):
"""
Regression: `completion_tokens` includes `reasoning_tokens` per the
OpenAI/Perplexity usage convention (codified for the central path in PR #18607).
When `output_cost_per_reasoning_token` is configured the manual fallback must
subtract reasoning from completion before applying the output rate so the
reasoning tokens are not billed at BOTH the output rate and the reasoning rate.

Uses the exact usage shape produced by the live response fixture in
`tests/llm_translation/test_perplexity_reasoning.py`.
"""
usage = Usage(
prompt_tokens=9,
completion_tokens=20,
total_tokens=29,
completion_tokens_details=CompletionTokensDetailsWrapper(
reasoning_tokens=15
),
)

prompt_cost, completion_cost = perplexity_cost_per_token(
model="sonar-deep-research", usage=usage
)

# sonar-deep-research rates: input 2e-6, output 8e-6, reasoning 3e-6.
# Non-reasoning portion of the 20 completion tokens = 20 - 15 = 5.
# Pre-fix this asserted 20 * 8e-6 + 15 * 3e-6 = 2.05e-4 (a 2.16x overcharge).
expected_prompt = 9 * 2e-6
expected_completion = (20 - 15) * 8e-6 + 15 * 3e-6

assert math.isclose(prompt_cost, expected_prompt, rel_tol=1e-9)
assert math.isclose(completion_cost, expected_completion, rel_tol=1e-9)
26 changes: 11 additions & 15 deletions tests/test_litellm/llms/perplexity/test_perplexity_integration.py
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Original file line number Diff line number Diff line change
Expand Up @@ -104,12 +104,10 @@ def test_end_to_end_cost_calculation_with_transformation(self):
)
citation_tokens = citation_chars // 4

expected_prompt_cost = (100 * 2e-6) + (
citation_tokens * 2e-6
) # Input + citation
expected_prompt_cost = (100 * 2e-6) + (citation_tokens * 2e-6)
expected_completion_cost = (
(50 * 8e-6) + (10 * 3e-6) + (2 / 1000 * 0.005)
) # Output + reasoning + search
((50 - 10) * 8e-6) + (10 * 3e-6) + (2 / 1000 * 0.005)
)
expected_total = expected_prompt_cost + expected_completion_cost

assert math.isclose(total_cost, expected_total, rel_tol=1e-6)
Expand Down Expand Up @@ -152,11 +150,10 @@ def test_main_cost_calculator_integration(self):
usage_object=usage,
)

# Calculate expected costs
expected_prompt_cost = (200 * 2e-6) + (40 * 2e-6) # Input + citation
expected_prompt_cost = (200 * 2e-6) + (40 * 2e-6)
expected_completion_cost = (
(100 * 8e-6) + (25 * 3e-6) + (3 / 1000 * 0.005)
) # Output + reasoning + search
((100 - 25) * 8e-6) + (25 * 3e-6) + (3 / 1000 * 0.005)
)

assert math.isclose(prompt_cost, expected_prompt_cost, rel_tol=1e-6)
assert math.isclose(completion_cost_val, expected_completion_cost, rel_tol=1e-6)
Expand Down Expand Up @@ -263,15 +260,14 @@ def test_high_volume_cost_calculation(self):
custom_llm_provider="perplexity",
)

# Calculate expected cost
expected_prompt_cost = (50000 * 2e-6) + (5000 * 2e-6) # $0.11
expected_prompt_cost = (50000 * 2e-6) + (5000 * 2e-6)
expected_completion_cost = (
(25000 * 8e-6) + (10000 * 3e-6) + (100 / 1000 * 0.005)
) # $0.23
expected_total = expected_prompt_cost + expected_completion_cost # $0.34
((25000 - 10000) * 8e-6) + (10000 * 3e-6) + (100 / 1000 * 0.005)
)
expected_total = expected_prompt_cost + expected_completion_cost

assert math.isclose(total_cost, expected_total, rel_tol=1e-6)
assert total_cost > 0.3 # Sanity check for high-volume scenario
assert total_cost > 0.25

def test_transformation_preserves_existing_usage_fields(self):
"""Test that transformation doesn't overwrite existing standard usage fields."""
Expand Down
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