fix(kg): validate ISO-8601 date formats at MCP boundary

tool_kg_query (as_of), tool_kg_add (valid_from), and tool_kg_invalidate
(ended) accepted any string and forwarded it to SQLite without format
validation. Parameterized queries prevent SQL injection, but invalid
date strings silently produce empty result sets — callers cannot
distinguish "no fact at this time" from "your date format was
unrecognized." This is especially painful for natural-language LLM
callers that synthesize dates like "March 2026" or "Jan 2025".

Add sanitize_iso_date() in config.py alongside the other input
validators. It accepts YYYY, YYYY-MM, and YYYY-MM-DD forms; passes
through None/empty; and raises ValueError with a field-named message
on anything else. Call it from the three kg MCP tool wrappers before
values reach the storage layer so the caller gets a clear error
instead of a silent miss.

Closes #1164

Author: arnoldwender

mempalace/config.py

@@ -71,6 +71,34 @@ def sanitize_kg_value(value: str, field_name: str = "value") -> str:
     return value
 
 
+# ISO-8601 date validator for knowledge-graph temporal parameters
+# (as_of, valid_from, valid_to, ended). Parameterized queries already
+# prevent SQL injection, but unvalidated date strings silently miss
+# every row — callers cannot distinguish "no fact at this time" from
+# "your date format was unrecognized." Accept YYYY, YYYY-MM, YYYY-MM-DD.
+_ISO_DATE_RE = re.compile(r"^\d{4}(?:-(?:0[1-9]|1[0-2])(?:-(?:0[1-9]|[12]\d|3[01]))?)?$")
+
+
+def sanitize_iso_date(value, field_name: str = "date"):
+    """Validate an ISO-8601 date string, accepting None or empty as-is.
+
+    Accepts ``YYYY``, ``YYYY-MM``, or ``YYYY-MM-DD``. Raises ValueError
+    on any other non-empty input so the MCP layer can surface a clear
+    error to the caller instead of silently returning empty results.
+    """
+    if value is None or value == "":
+        return value
+    if not isinstance(value, str):
+        raise ValueError(f"{field_name} must be a string")
+    value = value.strip()
+    if not _ISO_DATE_RE.match(value):
+        raise ValueError(
+            f"{field_name}={value!r} is not a valid ISO-8601 date "
+            f"(expected YYYY, YYYY-MM, or YYYY-MM-DD)"
+        )
+    return value
+
+
 def sanitize_content(value: str, max_length: int = 100_000) -> str:
     """Validate drawer/diary content length."""
     if not isinstance(value, str) or not value.strip():

mempalace/mcp_server.py

@@ -55,6 +55,7 @@
     sanitize_kg_value,
     sanitize_name,
     sanitize_content,
+    sanitize_iso_date,
 )
 from .version import __version__  # noqa: E402
 from .backends.chroma import ChromaBackend, ChromaCollection  # noqa: E402
@@ -844,6 +845,7 @@ def tool_kg_query(entity: str, as_of: str = None, direction: str = "both"):
     """Query the knowledge graph for an entity's relationships."""
     try:
         entity = sanitize_kg_value(entity, "entity")
+        as_of = sanitize_iso_date(as_of, "as_of")
     except ValueError as e:
         return {"error": str(e)}
     if direction not in ("outgoing", "incoming", "both"):
@@ -860,6 +862,7 @@ def tool_kg_add(
         subject = sanitize_kg_value(subject, "subject")
         predicate = sanitize_name(predicate, "predicate")
         object = sanitize_kg_value(object, "object")
+        valid_from = sanitize_iso_date(valid_from, "valid_from")
     except ValueError as e:
         return {"success": False, "error": str(e)}
 
@@ -885,6 +888,7 @@ def tool_kg_invalidate(subject: str, predicate: str, object: str, ended: str = N
         subject = sanitize_kg_value(subject, "subject")
         predicate = sanitize_name(predicate, "predicate")
         object = sanitize_kg_value(object, "object")
+        ended = sanitize_iso_date(ended, "ended")
     except ValueError as e:
         return {"success": False, "error": str(e)}
     _wal_log(

tests/test_config.py

@@ -3,7 +3,7 @@
 import tempfile
 
 import pytest
-from mempalace.config import MempalaceConfig, sanitize_kg_value, sanitize_name
+from mempalace.config import MempalaceConfig, sanitize_iso_date, sanitize_kg_value, sanitize_name
 
 
 def test_default_config():
@@ -169,3 +169,65 @@ def test_kg_value_rejects_null_bytes():
 def test_kg_value_rejects_over_length():
     with pytest.raises(ValueError):
         sanitize_kg_value("a" * 129)
+
+
+# --- sanitize_iso_date ---
+
+
+def test_iso_date_accepts_year_only():
+    assert sanitize_iso_date("2026") == "2026"
+
+
+def test_iso_date_accepts_year_month():
+    assert sanitize_iso_date("2026-03") == "2026-03"
+
+
+def test_iso_date_accepts_full_date():
+    assert sanitize_iso_date("2026-03-15") == "2026-03-15"
+
+
+def test_iso_date_passes_through_none():
+    assert sanitize_iso_date(None) is None
+
+
+def test_iso_date_passes_through_empty_string():
+    assert sanitize_iso_date("") == ""
+
+
+def test_iso_date_strips_whitespace():
+    assert sanitize_iso_date("  2026-03-15  ") == "2026-03-15"
+
+
+def test_iso_date_rejects_natural_language():
+    with pytest.raises(ValueError):
+        sanitize_iso_date("March 2026")
+
+
+def test_iso_date_rejects_abbreviated_month():
+    with pytest.raises(ValueError):
+        sanitize_iso_date("Jan 2025")
+
+
+def test_iso_date_rejects_us_format():
+    with pytest.raises(ValueError):
+        sanitize_iso_date("03/15/2026")
+
+
+def test_iso_date_rejects_invalid_month():
+    with pytest.raises(ValueError):
+        sanitize_iso_date("2026-13")
+
+
+def test_iso_date_rejects_invalid_day():
+    with pytest.raises(ValueError):
+        sanitize_iso_date("2026-02-32")
+
+
+def test_iso_date_rejects_non_string():
+    with pytest.raises(ValueError):
+        sanitize_iso_date(20260315)
+
+
+def test_iso_date_error_names_field():
+    with pytest.raises(ValueError, match="valid_from"):
+        sanitize_iso_date("yesterday", "valid_from")

tests/test_mcp_server.py

@@ -665,6 +665,52 @@ def test_kg_stats(self, monkeypatch, config, palace_path, seeded_kg):
         result = tool_kg_stats()
         assert result["entities"] >= 4
 
+    # --- Date validation at the MCP boundary (issue #1164) ---
+
+    def test_kg_add_rejects_invalid_valid_from(self, monkeypatch, config, palace_path, kg):
+        _patch_mcp_server(monkeypatch, config, kg)
+        from mempalace.mcp_server import tool_kg_add
+
+        result = tool_kg_add(
+            subject="Alice",
+            predicate="likes",
+            object="coffee",
+            valid_from="Jan 2025",
+        )
+        assert result["success"] is False
+        assert "valid_from" in result["error"]
+        assert "ISO-8601" in result["error"]
+
+    def test_kg_query_rejects_invalid_as_of(self, monkeypatch, config, palace_path, seeded_kg):
+        _patch_mcp_server(monkeypatch, config, seeded_kg)
+        from mempalace.mcp_server import tool_kg_query
+
+        result = tool_kg_query(entity="Max", as_of="March 2026")
+        assert "error" in result
+        assert "as_of" in result["error"]
+
+    def test_kg_invalidate_rejects_invalid_ended(self, monkeypatch, config, palace_path, seeded_kg):
+        _patch_mcp_server(monkeypatch, config, seeded_kg)
+        from mempalace.mcp_server import tool_kg_invalidate
+
+        result = tool_kg_invalidate(
+            subject="Max",
+            predicate="does",
+            object="chess",
+            ended="yesterday",
+        )
+        assert result["success"] is False
+        assert "ended" in result["error"]
+
+    def test_kg_query_accepts_partial_iso_dates(self, monkeypatch, config, palace_path, seeded_kg):
+        _patch_mcp_server(monkeypatch, config, seeded_kg)
+        from mempalace.mcp_server import tool_kg_query
+
+        # YYYY and YYYY-MM are valid ISO-8601 forms — must not be rejected.
+        for value in ("2026", "2026-03", "2026-03-15"):
+            result = tool_kg_query(entity="Max", as_of=value)
+            assert "error" not in result, f"rejected valid date {value!r}: {result}"
+
 
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