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"""Per-run token usage accumulation, keyed by model name.
RAGAS 0.4.3's `ragas.metrics.collections` + instructor code path does not
expose real token counts (`ragas/cost.py` only serves the legacy langchain
`evaluate()` path). This module provides a context-scoped accumulator that
the HTTP response hook in `rag_eval.metrics.factory` feeds into, so token
counts survive across the AsyncOpenAI client caching used by InlineScorer
(see docs/superpowers/specs/2026-07-02-token-usage-tracking-design.md).
"""
from __future__ import annotations
from contextlib import contextmanager
from contextvars import ContextVar
from dataclasses import dataclass, field
from typing import Iterator
@dataclass
class TokenUsageTracker:
"""Accumulates input/output token counts and call counts, grouped by model name."""
_totals: dict[str, dict[str, int]] = field(default_factory=dict)
def record(self, model: str, input_tokens: int, output_tokens: int) -> None:
"""Add one API call's usage to the running total for `model`."""
key = model or "unknown"
bucket = self._totals.setdefault(
key, {"input_tokens": 0, "output_tokens": 0, "calls": 0}
)
bucket["input_tokens"] += int(input_tokens)
bucket["output_tokens"] += int(output_tokens)
bucket["calls"] += 1
def as_dict(self) -> dict[str, dict[str, int]]:
"""Return a plain-dict snapshot: {model: {input_tokens, output_tokens, calls}}."""
return {model: dict(usage) for model, usage in self._totals.items()}
def merge_into(self, existing: dict[str, dict[str, int]]) -> dict[str, dict[str, int]]:
"""Return a new dict combining `existing` accumulated totals with this tracker's totals.
Used by session-scoped scoring (one call at a time) to keep a running
total across multiple calls instead of overwriting with just the latest call.
Does not mutate `existing`.
"""
merged: dict[str, dict[str, int]] = {
model: dict(usage) for model, usage in existing.items()
}
for model, usage in self.as_dict().items():
bucket = merged.setdefault(
model, {"input_tokens": 0, "output_tokens": 0, "calls": 0}
)
bucket["input_tokens"] += usage["input_tokens"]
bucket["output_tokens"] += usage["output_tokens"]
bucket["calls"] += usage["calls"]
return merged
_current_tracker: ContextVar[TokenUsageTracker | None] = ContextVar(
"_current_tracker", default=None
)
@contextmanager
def track_token_usage() -> Iterator[TokenUsageTracker]:
"""Activate a fresh TokenUsageTracker for the duration of the `with` block.
Any AsyncOpenAI client with `attach_usage_hook()` applied that makes a
call while this context is active will have its usage recorded here.
Safe to nest; the innermost tracker is active within its own block.
"""
tracker = TokenUsageTracker()
token = _current_tracker.set(tracker)
try:
yield tracker
finally:
_current_tracker.reset(token)
def get_current_tracker() -> TokenUsageTracker | None:
"""Return the currently active tracker, or None if no `track_token_usage()` block is active."""
return _current_tracker.get()