fix(public-chat): an anonymous session finds its own history after a reload (#3443)

src/backend/db/public_chat.py

@@ -137,16 +137,34 @@ def get_session_by_identifier(
         link_id: str,
         session_identifier: str
     ) -> Optional[PublicChatSession]:
-        """Look up a session by link ID and identifier."""
+        """Look up a session by link ID and identifier.
+
+        Mirrors the normalisation in ``get_or_create_session`` (#3443): an
+        identifier is stored verbatim unless it is an email, so the exact
+        string is matched first and only an ``email`` row is reachable through
+        its lowercased form. Lowercasing unconditionally made a mixed-case
+        anonymous token miss the row it had just created.
+        """
         with get_engine().connect() as conn:
             row = conn.execute(
                 select(public_chat_sessions).where(
                     and_(
                         public_chat_sessions.c.link_id == link_id,
-                        public_chat_sessions.c.session_identifier == session_identifier.lower(),
+                        public_chat_sessions.c.session_identifier == session_identifier,
                     )
                 )
             ).mappings().first()
+            lowered = session_identifier.lower()
+            if row is None and lowered != session_identifier:
+                row = conn.execute(
+                    select(public_chat_sessions).where(
+                        and_(
+                            public_chat_sessions.c.link_id == link_id,
+                            public_chat_sessions.c.session_identifier == lowered,
+                            public_chat_sessions.c.identifier_type == 'email',
+                        )
+                    )
+                ).mappings().first()
             return self._row_to_session(row) if row else None
 
     def get_session(self, session_id: str) -> Optional[PublicChatSession]:

tests/registry.json

@@ -5339,6 +5339,18 @@
         "unit"
       ],
       "description": "#3455 + #3456: the email whitelist validates what it stores and can remove whatever it holds. Driven through the real composed settings router with the auth dependency overridden and the table replaced by an in-memory stand-in. POST refuses a@, @b.com, a 10 000-character string, whitespace and control characters with a 422 whose detail is ONE named sentence (never Pydantic's array, never the echoed value, never a 500 for a malformed or non-JSON body), and stores a valid address trimmed and lower-cased; the admin gate still answers first. DELETE removes a stored value containing a slash when sent URL-encoded (the {email:path} converter), including rows that predate validation, still 404s an absent value, keeps its admin gate, and claims no sibling settings route at any method (Invariant #4). No Docker."
+    },
+    {
+      "file": "unit/test_3443_public_chat_history_lookup.py",
+      "feature": "#3443",
+      "added": "2026-10-09",
+      "categories": [
+        "backend",
+        "database",
+        "public-links",
+        "unit"
+      ],
+      "description": "#3443: an anonymous public-chat session finds its own row. get_session_by_identifier (behind GET /api/public/history and DELETE /api/public/session) matches the identifier verbatim, as get_or_create_session stores it, so a mixed-case anonymous token restores its history after a reload; two tokens differing only in case stay separate sessions; only an email row is reachable through its lowercased form. PublicChatOperations driven against an ephemeral DB (db_harness). No Docker."
     }
   ]
 }

tests/unit/test_3443_public_chat_history_lookup.py

@@ -0,0 +1,133 @@
+"""Unit tests for #3443 — an anonymous public-chat session finds its own row.
+
+``PublicChatOperations.get_or_create_session`` lowercases the identifier only
+for ``identifier_type == 'email'``; an anonymous identifier is a
+``secrets.token_urlsafe(16)`` token stored with its case intact. The lookup the
+history route (``GET /api/public/history/{token}``) and the session-clear route
+(``DELETE /api/public/session/{token}``) both go through,
+``get_session_by_identifier``, lowercased its argument unconditionally — so a
+mixed-case anonymous token never matched the row it had just written, history
+came back empty after every reload, and "New conversation" cleared nothing.
+
+Driven at the layer the defect lives in: the create path writes the row, the
+lookup reads it back, against a real ephemeral DB (db_harness, #300 — SQLite
+always, PostgreSQL when TEST_POSTGRES_URL is set). Setup mirrors
+``test_903_public_chat_sender.py``.
+"""
+from __future__ import annotations
+
+import sys
+from pathlib import Path
+
+import pytest
+
+_BACKEND = Path(__file__).resolve().parent.parent.parent / "src" / "backend"
+_BACKEND_STR = str(_BACKEND)
+
+# Modules whose sys.modules identity this file swaps so production code
+# re-resolves against the db_harness engine; snapshotted + restored by the
+# autouse fixture below (the sanctioned escape hatch for
+# tests/lint_sys_modules.py).
+_STUBBED_MODULE_NAMES = [
+    "db.public_chat",
+]
+
+while _BACKEND_STR in sys.path:
+    sys.path.remove(_BACKEND_STR)
+sys.path.insert(0, _BACKEND_STR)
+
+from db_harness import db_backend  # noqa: E402,F401
+
+pytestmark = pytest.mark.unit
+
+LINK = "link-3443"
+# The shape `secrets.token_urlsafe(16)` produces: mixed case, digits, `-`/`_`.
+ANON_TOKEN = "Zk3-QwErTy_9aBcDeFgHiJ"
+
+
+@pytest.fixture(autouse=True)
+def _restore_sys_modules():
+    saved = {name: sys.modules.get(name) for name in _STUBBED_MODULE_NAMES}
+    try:
+        yield
+    finally:
+        for name, mod in saved.items():
+            if mod is None:
+                sys.modules.pop(name, None)
+            else:
+                sys.modules[name] = mod
+
+
+@pytest.fixture()
+def ops(db_backend):
+    """PublicChatOperations on the active backend (db_harness, #300)."""
+    sys.modules.pop("db.public_chat", None)
+    from db.public_chat import PublicChatOperations
+    return PublicChatOperations()
+
+
+# ---------------------------------------------------------------------------
+# The reported defect
+# ---------------------------------------------------------------------------
+
+def test_mixed_case_anonymous_token_finds_its_own_session(ops):
+    """The reload path: a turn is stored under the token, then the history
+    route looks the session up by the same token, case intact."""
+    created = ops.get_or_create_session(LINK, ANON_TOKEN, "anonymous")
+    ops.add_message(created.id, "user", "hello")
+    ops.add_message(created.id, "assistant", "hi there")
+
+    found = ops.get_session_by_identifier(LINK, ANON_TOKEN)
+
+    assert found is not None, "an anonymous token must find the row it created"
+    assert found.id == created.id
+    assert found.identifier_type == "anonymous"
+    assert [m.content for m in ops.get_recent_messages(found.id, limit=100)] == [
+        "hello",
+        "hi there",
+    ]
+
+
+def test_anonymous_tokens_differing_only_in_case_stay_separate(ops):
+    """Two visitors whose tokens differ only in case own two sessions. The
+    lowercasing lookup handed the mixed-case visitor the OTHER visitor's
+    conversation."""
+    mixed = ops.get_or_create_session(LINK, "AbCdEf123", "anonymous")
+    lower = ops.get_or_create_session(LINK, "abcdef123", "anonymous")
+    assert mixed.id != lower.id
+
+    assert ops.get_session_by_identifier(LINK, "AbCdEf123").id == mixed.id
+    assert ops.get_session_by_identifier(LINK, "abcdef123").id == lower.id
+
+
+def test_anonymous_lookup_is_not_case_insensitive(ops):
+    """A token is a bearer secret: only the exact string resolves it."""
+    ops.get_or_create_session(LINK, "abcdef123", "anonymous")
+
+    assert ops.get_session_by_identifier(LINK, "ABCDEF123") is None
+    assert ops.get_session_by_identifier(LINK, "AbCdEf123") is None
+
+
+def test_anonymous_lookup_is_scoped_to_the_link(ops):
+    ops.get_or_create_session(LINK, ANON_TOKEN, "anonymous")
+
+    assert ops.get_session_by_identifier("another-link", ANON_TOKEN) is None
+
+
+# ---------------------------------------------------------------------------
+# Email identifiers stay case-insensitive
+# ---------------------------------------------------------------------------
+
+@pytest.mark.parametrize(
+    "lookup",
+    ["visitor@example.com", "Visitor@Example.com", "VISITOR@EXAMPLE.COM"],
+)
+def test_email_lookup_stays_case_insensitive(ops, lookup):
+    created = ops.get_or_create_session(LINK, "Visitor@Example.COM", "email")
+    assert created.session_identifier == "visitor@example.com"
+
+    found = ops.get_session_by_identifier(LINK, lookup)
+
+    assert found is not None
+    assert found.id == created.id
+    assert found.identifier_type == "email"