refactor(webui): extract event projection helpers

tests/utils/test_webui_event_projection_equivalence.py

@@ -0,0 +1,65 @@
+"""Shared characterization cases for live and persisted WebUI projection."""
+
+from __future__ import annotations
+
+import json
+from pathlib import Path
+from typing import Any
+
+from nanobot.webui.transcript import replay_transcript_to_ui_messages
+
+_FIXTURE_PATH = (
+    Path(__file__).parents[2]
+    / "webui"
+    / "src"
+    / "tests"
+    / "fixtures"
+    / "live-replay-event-projection.json"
+)
+_SEMANTIC_MESSAGE_FIELDS = (
+    "role",
+    "content",
+    "kind",
+    "traces",
+    "toolEvents",
+    "fileEdits",
+    "images",
+    "media",
+    "cliApps",
+    "mcpPresets",
+    "sessionMentions",
+    "reasoning",
+    "latencyMs",
+    "source",
+    "turnId",
+    "turnPhase",
+    "turnSeq",
+)
+
+
+def _normalize_projection(messages: list[dict[str, Any]]) -> list[dict[str, Any]]:
+    segment_aliases: dict[str, str] = {}
+    normalized: list[dict[str, Any]] = []
+    for message in messages:
+        row = {
+            field: message[field]
+            for field in _SEMANTIC_MESSAGE_FIELDS
+            if field in message and message[field] is not None
+        }
+        segment_id = message.get("activitySegmentId")
+        if isinstance(segment_id, str) and segment_id:
+            row["activitySegmentId"] = segment_aliases.setdefault(
+                segment_id,
+                f"segment-{len(segment_aliases) + 1}",
+            )
+        normalized.append(row)
+    return normalized
+
+
+def test_replay_matches_shared_live_projection_before_canonical_revision_migration() -> None:
+    """Lock the known-equivalent subset without defining the future snapshot protocol."""
+    fixture = json.loads(_FIXTURE_PATH.read_text(encoding="utf-8"))
+
+    for case in fixture["cases"]:
+        actual = replay_transcript_to_ui_messages(case["transcript"])
+        assert _normalize_projection(actual) == case["expected"], case["name"]