feat(token-tracking): accumulate token usage across session_async calls

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

tests/webapp/test_session_score_manager_token_usage.py

@@ -0,0 +1,84 @@
+"""Tests that session-grouped async scoring accumulates token usage across calls."""
+from __future__ import annotations
+
+import json
+import time
+
+from webapp.models import ScoreRequest
+from webapp.services.session_score_manager import SessionScoreJobManager
+
+
+def _wait_for_call_count(mgr: SessionScoreJobManager, session_id: str, expected: int, timeout: float = 2.0):
+    deadline = time.monotonic() + timeout
+    while time.monotonic() < deadline:
+        session = mgr.get_session(session_id)
+        if session is not None and session.call_count >= expected:
+            all_done = all(j.status in ("completed", "failed") for j in session.jobs)
+            if all_done:
+                return session
+        time.sleep(0.02)
+    raise TimeoutError(f"session {session_id} did not reach {expected} completed calls in time")
+
+
+def test_session_accumulates_token_usage_across_calls(tmp_path, monkeypatch):
+    from rag_eval.metrics.token_tracker import get_current_tracker
+
+    mgr = SessionScoreJobManager(
+        output_dir=tmp_path / "score-session",
+        index_dir=tmp_path / "score-session-jobs",
+        max_workers=1,
+    )
+
+    call_usages = iter([(100, 40), (30, 10)])
+
+    def _fake_score(**kwargs):
+        tracker = get_current_tracker()
+        input_tok, output_tok = next(call_usages)
+        if tracker is not None:
+            tracker.record("gpt-5", input_tok, output_tok)
+        return {m: 0.9 for m in kwargs["metrics"]}
+
+    monkeypatch.setattr(
+        "webapp.services.inline_scorer.inline_scorer.score", _fake_score
+    )
+
+    request = ScoreRequest(question="q?", answer="a.", metrics=["answer_relevancy"])
+
+    _, run_id = mgr.submit("session-token-test", request)
+    _wait_for_call_count(mgr, "session-token-test", 1)
+    mgr.submit("session-token-test", request)
+    _wait_for_call_count(mgr, "session-token-test", 2)
+
+    run_dir = tmp_path / "score-session" / run_id
+    metadata = json.loads((run_dir / "metadata.json").read_text(encoding="utf-8"))
+    assert metadata["token_usage"] == {
+        "gpt-5": {"input_tokens": 130, "output_tokens": 50, "calls": 2}
+    }
+
+
+def test_session_first_call_writes_token_usage_from_scratch(tmp_path, monkeypatch):
+    from rag_eval.metrics.token_tracker import get_current_tracker
+
+    mgr = SessionScoreJobManager(
+        output_dir=tmp_path / "score-session",
+        index_dir=tmp_path / "score-session-jobs",
+        max_workers=1,
+    )
+
+    def _fake_score(**kwargs):
+        tracker = get_current_tracker()
+        if tracker is not None:
+            tracker.record("gpt-5", 50, 20)
+        return {m: 0.9 for m in kwargs["metrics"]}
+
+    monkeypatch.setattr(
+        "webapp.services.inline_scorer.inline_scorer.score", _fake_score
+    )
+
+    request = ScoreRequest(question="q?", answer="a.", metrics=["answer_relevancy"])
+    _, run_id = mgr.submit("session-first-call-test", request)
+    _wait_for_call_count(mgr, "session-first-call-test", 1)
+
+    run_dir = tmp_path / "score-session" / run_id
+    metadata = json.loads((run_dir / "metadata.json").read_text(encoding="utf-8"))
+    assert metadata["token_usage"] == {"gpt-5": {"input_tokens": 50, "output_tokens": 20, "calls": 1}}

webapp/services/session_score_manager.py

@@ -193,6 +193,7 @@ class SessionScoreJobManager:
 
         # Lazy imports — keep web server bootable if ragas is not installed.
         from rag_eval.advisor import run_advisor
+        from rag_eval.metrics.token_tracker import track_token_usage
         from rag_eval.metrics.weights import compute_weighted_score
         from rag_eval.reporting.writers import write_run_artifacts
         from rag_eval.settings import EvaluationSettings
@@ -215,6 +216,7 @@ class SessionScoreJobManager:
 
         try:
             # --- Scoring (can run concurrently for the same session) ----------
+            with track_token_usage() as usage_tracker:
                 if effective:
                     raw_scores = inline_scorer.score(
                         question=request.question,
@@ -250,6 +252,14 @@ class SessionScoreJobManager:
                 run_dir = self._output_dir / run_id
                 run_dir.mkdir(parents=True, exist_ok=True)
 
+                # Merge this call's token usage into the session's running total, so
+                # repeated calls accumulate instead of overwriting (mirrors the
+                # scores.csv append-only accumulation below).
+                existing_metadata = self._read_metadata(run_dir)
+                merged_token_usage = usage_tracker.merge_into(
+                    existing_metadata.get("token_usage", {})
+                )
+
                 # Read all existing rows, then append the new one
                 existing_rows = self._read_score_rows(run_dir)
                 call_number = len(existing_rows) + 1
@@ -312,6 +322,7 @@ class SessionScoreJobManager:
                     valid_samples=valid_samples,
                     invalid_samples=[],
                     score_rows=all_rows,
+                    token_usage=merged_token_usage,
                 )
 
                 write_run_artifacts(result)
@@ -376,6 +387,16 @@ class SessionScoreJobManager:
         except (OSError, ValueError):
             return []
 
+    def _read_metadata(self, run_dir: Path) -> dict[str, Any]:
+        """Read this session's existing metadata.json, returning {} if absent/unreadable."""
+        metadata_path = run_dir / "metadata.json"
+        if not metadata_path.is_file():
+            return {}
+        try:
+            return json.loads(metadata_path.read_text(encoding="utf-8"))
+        except (OSError, ValueError):
+            return {}
+
     def _read_metric_means(self, run_dir: Path) -> dict[str, float | None]:
         """Compute per-metric means from the session's scores.csv."""
         scores_path = run_dir / "scores.csv"