test: trim #90322 regression to one invariant, drop the hint-splitting workaround

The credentials test no longer has to strip trailing text before json.loads;
the new file keeps the single behaviour contract (truncated output round-trips
through json.loads and carries the next offset) — the existing TestSearchHints
cases already cover offset arithmetic.

tests/agent/test_file_safety_credentials.py

@@ -150,7 +150,7 @@ def test_search_tool_filters_credential_results(fake_home, tmp_path, monkeypatch
         path=str(fake_home),
         task_id="search-filter-credentials",
     )
-    out = json.loads(search_response.split("\n\n[Hint:", 1)[0])
+    out = json.loads(search_response)
     raw = json.dumps(out)
     returned_paths = {
         match["path"] for match in out.get("matches", [])

tests/tools/test_search_truncation_json.py

@@ -1,64 +1,27 @@
-"""Regression tests for search_files truncation output staying pure JSON (#90322).
+"""search_files output is one JSON document even when truncated (#90322).
 
-The truncated-results hint used to be appended as plain text after the
-serialized JSON payload (``{...}\\n\\n[Hint: ...]``), so the tool result was
-no longer parseable JSON — downstream tool-message handling on providers
-strict about tool-content formatting could reject or mishandle it. The hint
-now rides inside the payload as a structured ``_hint`` field, matching the
-existing ``_omitted``/``_warning`` side-channel convention in the same
-function.
+The pagination hint used to be appended as text after the serialized payload,
+so json.loads on the tool result failed (execute_code RPC, strict tool-message
+providers). It now rides inside the payload as ``_hint``.
 """
 
 import json
 from unittest.mock import MagicMock, patch
 
-import pytest
 
-
-class _FakeSearchResult:
-    """Minimal stand-in for FileOperations.search return value."""
-
-    def __init__(self, truncated=False):
-        self.matches = []
-        self._truncated = truncated
+class _TruncatedSearch:
+    matches = []
 
     def to_dict(self, densify=False):
-        payload = {"matches": [{"file": "test.py", "line": 1, "text": "match"}]}
-        if self._truncated:
-            payload["truncated"] = True
-            payload["total_count"] = 20
-        return payload
+        return {"matches": [{"file": "t.py", "line": 1, "text": "m"}], "truncated": True, "total_count": 20}
 
 
-def _make_fake_file_ops(truncated):
+def test_truncated_search_result_round_trips_json():
     fake = MagicMock()
-    fake.search = lambda **kw: _FakeSearchResult(truncated=truncated)
-    return fake
-
-
-class TestSearchTruncationStaysJson:
-    @patch("tools.file_tools._get_file_ops", return_value=_make_fake_file_ops(True))
-    def test_truncated_result_is_parseable_json(self, _mock_ops):
-        """The whole tool output must round-trip through json.loads — no
-        text appended after the serialized payload."""
-        from tools.file_tools import search_tool
-
-        raw = search_tool("def main", offset=0, limit=20, task_id="t1")
-        parsed = json.loads(raw)  # raises on main: trailing "[Hint: ...]" text
-        assert parsed["truncated"] is True
-
-    @patch("tools.file_tools._get_file_ops", return_value=_make_fake_file_ops(True))
-    def test_truncation_hint_is_a_structured_field(self, _mock_ops):
+    fake.search = lambda **kw: _TruncatedSearch()
+    with patch("tools.file_tools._get_file_ops", return_value=fake):
         from tools.file_tools import search_tool
 
         parsed = json.loads(search_tool("def main", offset=0, limit=20, task_id="t1"))
-        assert "_hint" in parsed
-        assert "offset=20" in parsed["_hint"]
-
-    @patch("tools.file_tools._get_file_ops", return_value=_make_fake_file_ops(False))
-    def test_untruncated_result_has_no_hint(self, _mock_ops):
-        from tools.file_tools import search_tool
-
-        parsed = json.loads(search_tool("def main", task_id="t1"))
-        assert "truncated" not in parsed
-        assert "_hint" not in parsed
+    assert parsed["truncated"] is True
+    assert "offset=20" in parsed["_hint"]