fix(transcript): record the codex session model from turn_context

src/vouch/transcript.py

@@ -312,6 +312,16 @@ def flush() -> None:
                     session["git_branch"] = git["branch"]
                 continue
 
+            # codex records the turn's model on `turn_context`, not on
+            # `session_meta`, so without this the normalized transcript's model
+            # is always none for codex while the claude parser fills it. first
+            # non-empty wins (the model can change across turns; keep the first).
+            if rtype == "turn_context":
+                model = payload.get("model")
+                if isinstance(model, str) and model.strip() and session["model"] is None:
+                    session["model"] = model.strip()
+                continue
+
             if rtype != "response_item":
                 continue
             if len(messages) >= max_messages:

tests/test_session_transcript.py

@@ -213,6 +213,8 @@ def test_handler_returns_degraded_when_absent() -> None:
     {"type": "session_meta", "payload": {
         "id": "cx-1", "cwd": "/repo", "timestamp": "2026-06-22T08:01:54Z",
         "git": {"branch": "feat/x"}}},
+    {"type": "turn_context", "payload": {
+        "turn_id": "t1", "cwd": "/repo", "model": "gpt-5-codex"}},
     {"type": "response_item", "payload": {
         "type": "message", "role": "developer",
         "content": [{"type": "input_text", "text": "<permissions>boilerplate"}]}},
@@ -245,6 +247,8 @@ def test_parse_codex_pairs_calls_and_skips_boilerplate(tmp_path: Path) -> None:
     assert out["session"]["agent"] == "codex"
     assert out["session"]["cwd"] == "/repo"
     assert out["session"]["git_branch"] == "feat/x"
+    # codex carries the model on turn_context, not session_meta
+    assert out["session"]["model"] == "gpt-5-codex"
 
     roles = [m["role"] for m in out["messages"]]
     assert roles == ["user", "assistant"]  # developer message skipped