diff --git a/CHANGELOG.md b/CHANGELOG.md
index 3005569..213734a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,10 @@
 # Hermes Web UI -- Changelog
 
+## [v0.50.118] — 2026-04-20
+
+### Fixed
+- **CLI sessions: silent failure now logged** — `get_cli_sessions()` no longer swallows DB errors silently. If `state.db` is missing the `source` column (older hermes-agent) or has any other schema/lock issue, a warning is now logged with the DB path and a hint to upgrade hermes-agent. This makes "Show CLI sessions in sidebar has no effect" diagnosable from the server log instead of requiring code archaeology. (#634)
+
 ## [v0.50.117] — 2026-04-20
 
 ### Fixed
diff --git a/api/models.py b/api/models.py
index 2f9c989..87d9c41 100644
--- a/api/models.py
+++ b/api/models.py
@@ -297,6 +297,21 @@ def get_cli_sessions() -> list:
         with sqlite3.connect(str(db_path)) as conn:
             conn.row_factory = sqlite3.Row
             cur = conn.cursor()
+            # Introspect schema to handle older hermes-agent versions that
+            # may not have a 'source' column. Without this check the query raises
+            # OperationalError which is silently swallowed, causing the empty-list bug.
+            cur.execute("PRAGMA table_info(sessions)")
+            _session_cols = {row[1] for row in cur.fetchall()}
+            if 'source' not in _session_cols:
+                import logging as _logging
+                _logging.getLogger(__name__).warning(
+                    "get_cli_sessions(): state.db at %s has no 'source' column "
+                    "(older hermes-agent?). CLI sessions unavailable. "
+                    "Upgrade hermes-agent to fix this.",
+                    db_path,
+                )
+                return cli_sessions
+
             cur.execute("""
                 SELECT s.id, s.title, s.model, s.message_count,
                        s.started_at, s.source,
@@ -332,8 +347,14 @@ def get_cli_sessions() -> list:
                     'source_tag': _source,
                     'is_cli_session': True,
                 })
-    except Exception:
-        # DB schema changed, locked, or corrupted -- silently degrade
+    except Exception as _cli_err:
+        # DB schema changed, locked, or corrupted -- log warning so admins can diagnose.
+        # Still degrade gracefully (don't crash the WebUI).
+        import logging as _logging
+        _logging.getLogger(__name__).warning(
+            "get_cli_sessions() failed — check state.db schema or path (%s): %s",
+            db_path, _cli_err,
+        )
         return []
 
     return cli_sessions
diff --git a/tests/test_issue634.py b/tests/test_issue634.py
new file mode 100644
index 0000000..6f564e7
--- /dev/null
+++ b/tests/test_issue634.py
@@ -0,0 +1,75 @@
+"""
+Tests for #634: CLI sessions not visible when setting is enabled.
+
+Root cause: get_cli_sessions() swallowed all errors silently (bare except → return []).
+Users with older hermes-agent versions (missing 'source' column in state.db) got
+an empty list with no log output, making diagnosis impossible.
+
+Fixes:
+1. Schema introspection: check for 'source' column before querying, log a warning
+   if missing and return early.
+2. Exception path: log a warning instead of silently returning [].
+"""
+import pathlib
+import re
+
+MODELS_PY = pathlib.Path(__file__).parent.parent / 'api' / 'models.py'
+src = MODELS_PY.read_text(encoding='utf-8')
+
+
+class TestCliSessionsErrorSurface:
+    """get_cli_sessions() must log warnings instead of silently returning []."""
+
+    def test_schema_introspection_present(self):
+        """The function must check for the 'source' column before querying."""
+        assert "PRAGMA table_info(sessions)" in src
+
+    def test_missing_source_column_logs_warning(self):
+        """If 'source' column is absent, a warning is logged."""
+        # The warning message must mention the missing column and how to fix it
+        assert "no 'source' column" in src or "has no 'source' column" in src
+
+    def test_missing_source_column_suggests_upgrade(self):
+        """Warning message must suggest upgrading hermes-agent."""
+        assert "Upgrade hermes-agent" in src or "upgrade hermes-agent" in src.lower()
+
+    def test_exception_path_logs_warning(self):
+        """The except clause must call logger.warning, not silently pass."""
+        # Find the exception handler in get_cli_sessions
+        func_start = src.find("def get_cli_sessions()")
+        func_end = src.find("\ndef ", func_start + 1)
+        func_body = src[func_start:func_end] if func_end != -1 else src[func_start:]
+        assert "warning(" in func_body, \
+            "get_cli_sessions() exception handler must call logging.warning()"
+
+    def test_exception_path_includes_db_path(self):
+        """The warning must include the db_path for diagnosability."""
+        func_start = src.find("def get_cli_sessions()")
+        func_end = src.find("\ndef ", func_start + 1)
+        func_body = src[func_start:func_end] if func_end != -1 else src[func_start:]
+        # db_path should appear in the warning call
+        warning_pos = func_body.find("warning(")
+        warning_block = func_body[warning_pos:warning_pos + 300]
+        assert "db_path" in warning_block, \
+            "Warning must include db_path so admins can find the problematic database"
+
+    def test_still_returns_empty_on_error(self):
+        """Function must still return [] after logging (graceful degradation)."""
+        # After the warning, it should return cli_sessions (the empty list) not raise
+        func_start = src.find("def get_cli_sessions()")
+        func_end = src.find("\ndef ", func_start + 1)
+        func_body = src[func_start:func_end] if func_end != -1 else src[func_start:]
+        # Must have a 'return' after the warning call
+        warning_pos = func_body.find("_cli_err:")
+        after_warning = func_body[warning_pos:warning_pos + 400]
+        assert "return" in after_warning, \
+            "Function must return after the warning (not raise)"
+
+    def test_source_column_check_before_sql_query(self):
+        """Schema check must happen before the main SQL SELECT."""
+        pragma_pos = src.find("PRAGMA table_info(sessions)")
+        select_pos = src.find("SELECT s.id, s.title, s.model")
+        assert pragma_pos != -1, "PRAGMA check not found"
+        assert select_pos != -1, "SELECT query not found"
+        assert pragma_pos < select_pos, \
+            "Schema introspection must run before the main SQL query"