Treat literal 'null'/'none' strings as absent for optional tool args

Models routinely pass the literal string "null" or "none" instead of
omitting an optional argument. Taken at face value it becomes a filter
that matches nothing, so tools like list_notes / list_reports /
list_requests silently return no results.

Coerce such values to None in the central argument-coercion layer, but
only for parameters the schema allows to be null (or that are absent from
a declared "required" list), so required strings keep the literal value.
The list/filter helpers normalize the same values too, so a direct call
can't regress.

strix/agents/factory.py

@@ -36,6 +36,7 @@ from strix.tools.notes.tools import (
     list_notes,
     update_note,
 )
+from strix.tools.nullish import is_nullish
 from strix.tools.output_store import bound_and_store, bound_text
 from strix.tools.proxy.tools import (
     list_requests,
@@ -164,6 +165,28 @@ def _schema_types(spec: dict[str, Any]) -> set[str]:
     return types
 
 
+def _allows_null(spec: dict[str, Any]) -> bool:
+    raw = spec.get("type")
+    if raw == "null" or (isinstance(raw, list) and "null" in raw):
+        return True
+    return any(
+        isinstance(variant, dict) and _allows_null(variant) for variant in spec.get("anyOf") or ()
+    )
+
+
+def _is_nullable(key: str, spec: dict[str, Any], schema: dict[str, Any]) -> bool:
+    """Whether ``key`` may be ``None``.
+
+    Strict schemas list every property as required, so nullability shows up as a
+    ``null`` type variant; without a declared one, fall back to the property
+    being absent from a declared ``required`` list.
+    """
+    if _allows_null(spec):
+        return True
+    required = schema.get("required")
+    return isinstance(required, list) and key not in required
+
+
 def _decode_structured(value: str, types: set[str]) -> Any:
     stripped = value.strip()
     if not stripped:
@@ -178,9 +201,14 @@ def _decode_structured(value: str, types: set[str]) -> Any:
     return decoded if isinstance(decoded, wanted) else value
 
 
-def _coerce_argument(value: Any, spec: dict[str, Any]) -> Any:
+def _coerce_argument(value: Any, spec: dict[str, Any], *, nullable: bool = False) -> Any:
+    if value is None:
+        return value
+    if nullable and is_nullish(value):
+        # The model's stand-in for "no value"; as a filter it matches nothing.
+        return None
     types = _schema_types(spec)
-    if not types or value is None:
+    if not types:
         return value
     if isinstance(value, list | dict) and "string" in types and not types & {"array", "object"}:
         return json.dumps(value, ensure_ascii=False)
@@ -205,7 +233,7 @@ def _coerce_arguments(raw_input: str, schema: dict[str, Any]) -> str:
         spec = properties.get(key)
         if not isinstance(spec, dict):
             continue
-        coerced = _coerce_argument(value, spec)
+        coerced = _coerce_argument(value, spec, nullable=_is_nullable(key, spec, schema))
         if coerced is not value:
             payload[key] = coerced
             changed = True

strix/tools/notes/tools.py

@@ -14,6 +14,8 @@ from typing import Any
 
 from agents import RunContextWrapper, function_tool
 
+from strix.tools.nullish import clean_optional, is_nullish
+
 
 logger = logging.getLogger(__name__)
 
@@ -111,6 +113,10 @@ def _filter_notes(
     tags: list[str] | None = None,
     search_query: str | None = None,
 ) -> list[dict[str, Any]]:
+    category = clean_optional(category)
+    search_query = clean_optional(search_query)
+    tags = [tag for tag in tags if not is_nullish(tag)] if tags else None
+
     filtered: list[dict[str, Any]] = []
     for note_id, note in _notes_storage.items():
         if category and note.get("category") != category:

strix/tools/nullish.py

@@ -0,0 +1,23 @@
+"""Nullish argument values passed by models in place of omitting an argument.
+
+Models frequently send the literal string ``"null"`` / ``"none"`` for an
+optional filter argument instead of leaving it out. Taken at face value it is
+a filter that matches nothing, so the call quietly returns no results.
+"""
+
+from __future__ import annotations
+
+
+NULLISH_STRINGS = frozenset({"null", "none", "nil", "undefined"})
+
+
+def is_nullish(value: object) -> bool:
+    """Whether ``value`` is a string standing in for "no value"."""
+    return isinstance(value, str) and value.strip().lower() in NULLISH_STRINGS
+
+
+def clean_optional(value: str | None) -> str | None:
+    """Normalize an optional filter argument: nullish or blank becomes ``None``."""
+    if value is None or is_nullish(value):
+        return None
+    return value.strip() or None

strix/tools/proxy/tools.py

@@ -14,6 +14,7 @@ from typing import TYPE_CHECKING, Any, Literal
 from agents import RunContextWrapper, function_tool
 
 from strix.runtime.caido_handle import CaidoBootstrapHandle
+from strix.tools.nullish import clean_optional
 from strix.tools.proxy import caido_api
 
 
@@ -167,6 +168,10 @@ async def list_requests(
     if client is None:
         return _no_client()
 
+    httpql_filter = clean_optional(httpql_filter)
+    after = clean_optional(after)
+    scope_id = clean_optional(scope_id)
+
     try:
         connection = await _call(
             client,
@@ -472,6 +477,8 @@ async def list_sitemap(
     client = await _ctx_client(ctx)
     if client is None:
         return _no_client()
+    scope_id = clean_optional(scope_id)
+    parent_id = clean_optional(parent_id)
     try:
         payload = await _call(
             client,

strix/tools/reporting/tool.py

@@ -16,6 +16,8 @@ from typing import Any
 
 from agents import RunContextWrapper, function_tool
 
+from strix.tools.nullish import clean_optional
+
 
 logger = logging.getLogger(__name__)
 
@@ -1605,12 +1607,12 @@ def _do_list_reports(
     caller_agent_id: str | None = None,
 ) -> dict[str, Any]:
     errors: list[str] = []
-    severity = (severity or "").strip().lower() or None
+    severity = (clean_optional(severity) or "").lower() or None
     if severity and severity not in _VALID_SEVERITIES:
         errors.append(
             f"Invalid severity: {severity!r}. Must be one of: {sorted(_VALID_SEVERITIES)}"
         )
-    finding_class = (finding_class or "").strip().lower() or None
+    finding_class = (clean_optional(finding_class) or "").lower() or None
     if finding_class and finding_class not in _VALID_FINDING_CLASSES:
         errors.append(
             f"Invalid finding_class: {finding_class!r}. "
@@ -1640,8 +1642,8 @@ def _do_list_reports(
             r,
             severity=severity,
             finding_class=finding_class,
-            target=(target or "").strip() or None,
-            search=(search or "").strip() or None,
+            target=clean_optional(target),
+            search=clean_optional(search),
         )
     ]
     matched.sort(key=lambda r: (_report_severity_rank(r), str(r.get("id", ""))))

tests/test_agent_factory_tool_arguments.py

@@ -9,6 +9,8 @@ import pytest
 from agents.tool import FunctionTool
 
 from strix.agents import factory
+from strix.tools.notes.tools import list_notes
+from strix.tools.reporting.tool import list_reports
 
 
 def _capturing_tool(captured: dict[str, str], schema: dict[str, Any]) -> FunctionTool:
@@ -144,3 +146,76 @@ async def test_coercion_is_applied_once_per_tool() -> None:
     tool = factory._with_coerced_arguments(_capturing_tool(captured, _ARRAY))
 
     assert factory._with_coerced_arguments(tool) is tool
+
+
+_NULLABLE_STRING = {"category": {"anyOf": [{"type": "string"}, {"type": "null"}]}}
+_NULLABLE_STRING_TYPE_LIST = {"category": {"type": ["string", "null"]}}
+
+
+@pytest.mark.asyncio
+@pytest.mark.parametrize("schema", [_NULLABLE_STRING, _NULLABLE_STRING_TYPE_LIST])
+@pytest.mark.parametrize("value", ["null", "none", "NULL", " None ", "nil", "undefined"])
+async def test_nullish_string_on_a_nullable_parameter_becomes_none(
+    schema: dict[str, Any], value: str
+) -> None:
+    parsed = await _roundtrip(schema, {"category": value})
+
+    assert parsed["category"] is None
+
+
+@pytest.mark.asyncio
+async def test_nullish_string_on_a_required_parameter_is_untouched() -> None:
+    schema = {"content": {"type": "string"}}
+    captured: dict[str, str] = {}
+    tool = _capturing_tool(captured, schema)
+    tool.params_json_schema["required"] = ["content"]
+    wrapped = factory._with_coerced_arguments(tool)
+
+    assert await wrapped.on_invoke_tool(cast("Any", None), json.dumps({"content": "none"})) == "ok"
+    assert json.loads(captured["raw_input"])["content"] == "none"
+
+
+@pytest.mark.asyncio
+async def test_a_parameter_absent_from_required_is_treated_as_nullable() -> None:
+    captured: dict[str, str] = {}
+    tool = _capturing_tool(captured, {"category": {"type": "string"}})
+    tool.params_json_schema["required"] = []
+    wrapped = factory._with_coerced_arguments(tool)
+
+    assert await wrapped.on_invoke_tool(cast("Any", None), json.dumps({"category": "null"})) == "ok"
+    assert json.loads(captured["raw_input"])["category"] is None
+
+
+@pytest.mark.asyncio
+async def test_nullish_string_without_a_required_list_is_untouched() -> None:
+    parsed = await _roundtrip(_STRING, {"todos": "none"})
+
+    assert parsed["todos"] == "none"
+
+
+@pytest.mark.asyncio
+async def test_nullish_looking_content_is_not_coerced() -> None:
+    parsed = await _roundtrip(_NULLABLE_STRING, {"category": "none of the endpoints reflect input"})
+
+    assert parsed["category"] == "none of the endpoints reflect input"
+
+
+@pytest.mark.asyncio
+async def test_empty_string_on_a_nullable_string_parameter_is_untouched() -> None:
+    parsed = await _roundtrip(_NULLABLE_STRING, {"category": ""})
+
+    assert parsed["category"] == ""
+
+
+@pytest.mark.asyncio
+async def test_nullish_string_on_a_nullable_array_parameter_becomes_none() -> None:
+    parsed = await _roundtrip(_NULLABLE_ARRAY, {"tags": "null"})
+
+    assert parsed["tags"] is None
+
+
+def test_real_tool_schemas_declare_optional_filters_as_nullable() -> None:
+    for tool, params in ((list_notes, ("category", "search")), (list_reports, ("target",))):
+        schema = tool.params_json_schema
+        for param in params:
+            assert factory._is_nullable(param, schema["properties"][param], schema)

tests/test_list_reports.py

@@ -357,3 +357,25 @@ def test_get_report_no_state_returns_error(monkeypatch: pytest.MonkeyPatch) -> N
     result = _do_get_report("vuln-0001")
     assert result["success"] is False
     assert result["report"] is None
+
+
+@pytest.mark.parametrize("nullish", ["null", "none", "NULL", " None ", "undefined", "nil"])
+def test_list_reports_ignores_nullish_filter_strings(
+    report_state: ReportState, nullish: str
+) -> None:
+    _seed(report_state)
+    unfiltered = _do_list_reports(
+        severity=None, finding_class=None, target=None, search=None, include_details=False
+    )
+    assert unfiltered["filtered_count"] == 3
+
+    assert (
+        _do_list_reports(
+            severity=nullish,
+            finding_class=nullish,
+            target=nullish,
+            search=nullish,
+            include_details=False,
+        )
+        == unfiltered
+    )

tests/test_notes.py

@@ -101,3 +101,24 @@ def test_get_note_flags_caller_ownership() -> None:
     assert mine["note"]["agent_name"] == "Agent One"
     theirs = notes_tools._get_note_impl(note_id, caller_agent_id="agent-9")
     assert "by_you" not in theirs["note"]
+
+
+@pytest.mark.parametrize("nullish", ["null", "none", "NULL", " None ", "undefined", "nil"])
+def test_list_notes_ignores_nullish_filter_strings(nullish: str) -> None:
+    notes_tools._create_note_impl("recon", "content", category="findings", tags=["auth"])
+    notes_tools._create_note_impl("other", "content", category="general")
+
+    unfiltered = notes_tools._list_notes_impl()
+    assert unfiltered["filtered_count"] == 2
+
+    assert notes_tools._list_notes_impl(category=nullish) == unfiltered
+    assert notes_tools._list_notes_impl(search=nullish) == unfiltered
+    assert notes_tools._list_notes_impl(tags=[nullish]) == unfiltered
+
+
+def test_list_notes_still_filters_on_real_values() -> None:
+    notes_tools._create_note_impl("recon", "content", category="findings")
+    notes_tools._create_note_impl("other", "content", category="general")
+
+    result = notes_tools._list_notes_impl(category="findings")
+    assert [n["title"] for n in result["notes"]] == ["recon"]