constrain directory completion to child files

HARNESS_VERSION

@@ -1 +1 @@
-0.20.7
+0.20.8

src/clean_agent_preview.py

@@ -1525,14 +1525,31 @@ def artifact_completion_tool_schemas(offered_schemas, required_artifacts):
     This applies only after native execution enters its reserved artifact-write
     phase.  A JSON-Schema ``const`` gives the provider the exact destination
     instead of relying on it to recover the path from a long conversation.
-    Multiple outputs and directory targets stay unconstrained because choosing
+    Multiple outputs stay unconstrained. A sole directory target constrains the
-    one of those paths requires model intent.
+    writer to a non-empty descendant path while leaving the filename to the
+    model.
     """
     targets = [str(path or '').strip().rstrip('/') for path in required_artifacts]
-    targets = [path for path in targets if path and Path(path).suffix]
+    targets = [path for path in targets if path]
     if len(targets) != 1 or len(tuple(required_artifacts or ())) != 1:
         return offered_schemas
     target = targets[0]
+    if not Path(target).suffix:
+        bound = copy.deepcopy(offered_schemas)
+        for schema in bound:
+            function = schema.get('function') or {}
+            if canonical(function.get('name')) != 'write_file':
+                continue
+            properties = (function.get('parameters') or {}).get('properties') or {}
+            path_schema = properties.get('path')
+            if not isinstance(path_schema, dict):
+                continue
+            path_schema['pattern'] = '^' + re.escape(target + '/') + '.+'
+            path_schema['description'] = (
+                f'Write a new file inside the required directory {target}; '
+                'do not use the directory path itself.'
+            )
+        return bound
     if Path(target).suffix.lower() in _NON_TEXT_ARTIFACT_SUFFIXES:
         # ``write_file`` deliberately accepts UTF-8 text only. Keeping it in
         # a binary artifact completion round lets a forced writer choice trap
@@ -1571,14 +1588,9 @@ def artifact_completion_tool_schemas(offered_schemas, required_artifacts):
 
 
 def required_artifact_completion_tool_choice(required_artifacts, offered_schemas):
-    """Choose a writer only when the contract names an exact output file.
+    """Force the compatible writer during reserved artifact completion."""
-
-    A directory contract needs the model to choose one or more child filenames.
-    Forcing ``write_file`` there encourages an impossible write to the directory
-    path itself, so leave tool choice unconstrained for that case.
-    """
     targets = [str(path or '').strip().rstrip('/') for path in required_artifacts]
-    if not targets or any(not Path(target).suffix for target in targets):
+    if not targets:
         return None
     offered = {
         canonical((schema.get('function') or {}).get('name')):

tests/test_clean_agent_preview.py

@@ -624,7 +624,7 @@ def test_artifact_completion_schema_binds_single_required_file_without_mutating_
     assert 'const' not in source[0]['function']['parameters']['properties']['path']
 
 
-def test_artifact_completion_schema_does_not_bind_directory_or_multiple_outputs():
+def test_artifact_completion_schema_binds_directory_descendant_but_not_multiple_outputs():
     source = [{
         'type': 'function',
         'function': {
@@ -636,9 +636,14 @@ def test_artifact_completion_schema_does_not_bind_directory_or_multiple_outputs(
         },
     }]
 
-    assert artifact_completion_tool_schemas(
+    directory_bound = artifact_completion_tool_schemas(
         source, ('/workspace/results/',),
-    ) == source
+    )
+    directory_path = directory_bound[0]['function']['parameters']['properties']['path']
+    assert re.search(directory_path['pattern'], '/workspace/results/output.md')
+    assert not re.search(directory_path['pattern'], '/workspace/results')
+    assert 'inside the required directory' in directory_path['description']
+    assert 'pattern' not in source[0]['function']['parameters']['properties']['path']
     assert artifact_completion_tool_schemas(
         source, ('/workspace/a.txt', '/workspace/b.txt'),
     ) == source
@@ -679,7 +684,7 @@ def test_required_binary_artifact_forces_python_instead_of_text_writer():
     ]
 
 
-def test_required_directory_artifact_does_not_force_writer_to_directory_path():
+def test_required_directory_artifact_forces_writer_with_descendant_schema():
     offered = [
         {'type': 'function', 'function': {'name': 'bash'}},
         {'type': 'function', 'function': {'name': 'write_file'}},
@@ -687,7 +692,7 @@ def test_required_directory_artifact_does_not_force_writer_to_directory_path():
 
     assert required_artifact_completion_tool_choice(
         ('/tmp_workspace/results',), offered,
-    ) is None
+    ) == {'type': 'function', 'function': {'name': 'write_file'}}
 
 
 def test_action_promise_response_rejects_future_work_but_not_real_answers():
@@ -5328,11 +5333,14 @@ async def test_native_stream_reserves_remaining_budget_for_required_artifact(mon
     assert "web_search" not in request_contract["offered_tools"]
     assert request_contract["tool_choice"] is None
     reserved_names = [tool["function"]["name"] for tool in requests[12]["tools"]]
-    assert reserved_names == ["bash", "python", "write_file"]
+    assert reserved_names == ["write_file"]
     assert "tool_choice" not in requests[12]
+    directory_path = requests[12]["tools"][0]["function"]["parameters"]["properties"]["path"]
+    assert re.search(directory_path["pattern"], "/tmp_workspace/results/out.md")
+    assert not re.search(directory_path["pattern"], "/tmp_workspace/results")
     assert "create one or more files inside" in requests[12]["messages"][-1]["content"]
     assert "Do not pass the directory itself as a file path" in requests[12]["messages"][-1]["content"]
-    assert "bash" in executed
+    assert "bash" not in executed
     assert any(
         event.get("type") == "tool_output" and event.get("tool") == "write_file"
         and not event.get("error") for event in events

tests/test_harness_version.py

@@ -8,7 +8,7 @@ ROOT = Path(__file__).resolve().parents[1]
 def test_original_harness_version_is_canonical_semver() -> None:
     version = (ROOT / "HARNESS_VERSION").read_text(encoding="utf-8").strip()
 
-    assert version == "0.20.7"
+    assert version == "0.20.8"
     assert re.fullmatch(r"\d+\.\d+\.\d+", version)