fix: harden the observability fields against the verifier findings

tests/integration/test_postgres_telemetry.py

@@ -119,6 +119,105 @@ async def _fetch(dsn: str, sql: str, *args):
         await conn.close()
 
 
+_LEGACY_DDL = """
+CREATE TABLE {schema}.llm_calls (
+    call_id            TEXT PRIMARY KEY,
+    parent_call_id     TEXT,
+    session_id         TEXT,
+    model              TEXT NOT NULL,
+    provider           TEXT NOT NULL,
+    source_name        TEXT NOT NULL,
+    messages           TEXT NOT NULL,
+    response           TEXT NOT NULL,
+    thinking           TEXT NOT NULL DEFAULT '',
+    prompt_tokens      INTEGER NOT NULL,
+    completion_tokens  INTEGER NOT NULL,
+    usage_source       TEXT NOT NULL,
+    latency_ms         INTEGER NOT NULL,
+    ttft_ms            DOUBLE PRECISION,
+    max_inter_token_ms DOUBLE PRECISION,
+    cache_hit          BOOLEAN NOT NULL DEFAULT FALSE,
+    error              TEXT,
+    cost               DOUBLE PRECISION,
+    created_at         TIMESTAMPTZ NOT NULL DEFAULT now()
+)
+"""
+
+
+@pytest.fixture
+async def legacy_schema(dsn):
+    """在**自建的临时 schema** 里造一张 18 列旧表,验证补列(issue #3)。
+
+    绝不碰共享的 public.llm_calls: 用 search_path 把 recorder 指向临时 schema,
+    teardown 只 DROP 自己建的 schema。
+    """
+    import asyncpg
+
+    name = f"pgwtest_{uuid4().hex[:8]}"
+    conn = await asyncpg.connect(dsn, timeout=10)
+    try:
+        await conn.execute(f"CREATE SCHEMA {name}")
+        await conn.execute(_LEGACY_DDL.format(schema=name))
+    finally:
+        await conn.close()
+    sep = "&" if "?" in dsn else "?"
+    yield f"{dsn}{sep}options=-csearch_path%3D{name}", name
+    conn = await asyncpg.connect(dsn, timeout=10)
+    try:
+        await conn.execute(f"DROP SCHEMA {name} CASCADE")
+    finally:
+        await conn.close()
+
+
+class TestObservabilityColumns:
+    """issue #3: 两列写入可回读,且已存在的 18 列旧表会被自动补列。"""
+
+    async def test_values_round_trip(self, dsn):
+        recorder = PostgresRecorder(dsn)
+        try:
+            await _record_minimal(recorder, call_id=_cid("hit"), cached_prompt_tokens=64)
+            await _record_minimal(recorder, call_id=_cid("zero"), cached_prompt_tokens=0)
+            await _record_minimal(recorder, call_id=_cid("model"), model_reported="MiniMax-01")
+            rows = await _fetch(
+                dsn,
+                "SELECT call_id, cached_prompt_tokens, model_reported FROM llm_calls "
+                "WHERE call_id LIKE $1",
+                f"{_RUN_PREFIX}-%",
+            )
+            by_id = {r["call_id"]: r for r in rows}
+            assert by_id[_cid("hit")]["cached_prompt_tokens"] == 64
+            assert by_id[_cid("zero")]["cached_prompt_tokens"] == 0  # 真实零命中 ≠ NULL
+            assert by_id[_cid("model")]["cached_prompt_tokens"] is None
+            assert by_id[_cid("model")]["model_reported"] == "MiniMax-01"
+        finally:
+            await recorder.aclose()
+
+    async def test_legacy_table_is_upgraded_in_place(self, legacy_schema):
+        """18 列旧表不补列的话,每行写入都会被逐行 warning 丢弃(遥测静默全失)。"""
+        schema_dsn, schema = legacy_schema
+        recorder = PostgresRecorder(schema_dsn)
+        try:
+            await _record_minimal(
+                recorder, call_id=_cid("legacy"), cached_prompt_tokens=7, model_reported="m-real"
+            )
+            cols = await _fetch(
+                schema_dsn,
+                "SELECT column_name FROM information_schema.columns "
+                "WHERE table_schema = $1 AND table_name = 'llm_calls' ORDER BY ordinal_position",
+                schema,
+            )
+            # ALTER 只能追加到末尾: 与新建库的列序一致才不会分叉
+            assert [r["column_name"] for r in cols] == _EXPECTED_COLUMNS
+            rows = await _fetch(
+                schema_dsn,
+                "SELECT cached_prompt_tokens, model_reported FROM llm_calls WHERE call_id = $1",
+                _cid("legacy"),
+            )
+            assert (rows[0]["cached_prompt_tokens"], rows[0]["model_reported"]) == (7, "m-real")
+        finally:
+            await recorder.aclose()
+
+
 class TestSchema:
     async def test_schema_has_frozen_columns_in_order(self, dsn):
         recorder = PostgresRecorder(dsn)