[OMEGA-331] Add delete-file skill with existence check and error handling

Autotests/run_mandatory

@@ -38,5 +38,6 @@ test_prompt_grounding.py
 test_websearch_smoke.py
 test_wschat.py
 unit/test_fileio_verified_writes.py
+unit/test_fileio_verified_deletes.py
 unit/test_helper_parsing.py
 unit/test_openclaw_unit.py

Autotests/unit/test_fileio_verified_deletes.py

@@ -0,0 +1,83 @@
+"""In-process unit tests for src/fileio.py (verified file deletes).
+
+The delete-file skill returns a result string built from a read-back of the
+filesystem after the operation (does the path still exist?) -- ground truth
+the agent relays instead of a static success atom it could confabulate
+around. Failures return explicit DELETE-FAILED strings instead of raising,
+matching the WRITE-VERIFIED / WRITE-FAILED contract in
+test_fileio_verified_writes.py.
+
+No container, no network, no token -- same pattern as
+mock_websocket/test_wschat_unit.py: the module is loaded by file path.
+"""
+import importlib.util
+import logging
+import os
+import sys
+
+import pytest
+
+_REPO_ROOT = os.path.normpath(os.path.join(os.path.dirname(__file__), "..", ".."))
+_FILEIO_PATH = os.path.join(_REPO_ROOT, "src", "fileio.py")
+
+if _REPO_ROOT not in sys.path:
+    sys.path.insert(0, _REPO_ROOT)
+
+
+def _load_fileio():
+    spec = importlib.util.spec_from_file_location("fileio_under_test", _FILEIO_PATH)
+    module = importlib.util.module_from_spec(spec)
+    spec.loader.exec_module(module)
+    return module
+
+
+@pytest.fixture
+def fileio():
+    return _load_fileio()
+
+
+def test_delete_removes_existing_file_and_verifies(fileio, tmp_path, caplog):
+    caplog.set_level(logging.INFO)
+    target = tmp_path / "out.txt"
+    target.write_bytes(b"hello world")
+
+    result = fileio.delete_file(str(target))
+
+    assert not target.exists()
+    assert result == f"DELETE-VERIFIED file={target}"
+    assert "[FILE_IO] delete ok" in caplog.text
+
+
+def test_delete_missing_file_fails_without_raising(fileio, tmp_path, caplog):
+    caplog.set_level(logging.INFO)
+    target = tmp_path / "absent.txt"
+
+    result = fileio.delete_file(str(target))
+
+    assert result == f"DELETE-FAILED file={target}: file does not exist"
+    assert "[FILE_IO] delete failed" in caplog.text
+
+
+def test_delete_directory_fails_without_raising(fileio, tmp_path):
+    target = tmp_path / "a_directory"
+    target.mkdir()
+
+    result = fileio.delete_file(str(target))
+
+    assert target.exists()  # directory must be left untouched
+    assert result == f"DELETE-FAILED file={target}: path is a directory"
+
+
+def test_delete_result_path_matches_input_exactly(fileio, tmp_path):
+    # regression guard: result string must echo the path as given, not a
+    # resolved/normalized variant, so the agent can match it back to its request.
+    sub = tmp_path / "sub"
+    sub.mkdir()
+    target = tmp_path / "sub" / ".." / "out.txt"
+    real = tmp_path / "out.txt"
+    real.write_bytes(b"x")
+
+    result = fileio.delete_file(str(target))
+
+    assert not real.exists()
+    assert result == f"DELETE-VERIFIED file={target}"

src/fileio.py

@@ -94,3 +94,23 @@ def write_file_b64(path, content_b64):
         logger.error(f"[FILE_IO] write failed file={path} err=invalid base64")
         return f"WRITE-FAILED file={path}: invalid base64 ({e})"
     return _write(path, data, append=False)
+
+
+def delete_file(path):
+    path = str(path)
+    if not os.path.lexists(path):
+        logger.error(f"[FILE_IO] delete failed file={path} err=file does not exist")
+        return f"DELETE-FAILED file={path}: file does not exist"
+    if os.path.isdir(path):
+        logger.error(f"[FILE_IO] delete failed file={path} err=path is a directory")
+        return f"DELETE-FAILED file={path}: path is a directory"
+    try:
+        os.remove(path)
+    except Exception as e:  # the skill must return a result, never raise into the loop
+        logger.error(f"[FILE_IO] delete failed file={path} err={e}")
+        return f"DELETE-FAILED file={path}: {e}"
+    if os.path.exists(path):  # race: something recreated it between remove() and here
+        logger.error(f"[FILE_IO] delete verification failed file={path} still exists after remove")
+        return f"DELETE-FAILED file={path}: file still exists after removal"
+    logger.info(f"[FILE_IO] delete ok file={path}")
+    return f"DELETE-VERIFIED file={path}"

src/helper.py

@@ -30,7 +30,8 @@
     "websearch",
     "write-file",
     "get-io-policy",
-    "write-file-b64"
+    "write-file-b64",
+    "delete-file",
 }
 LLM_COMMANDS = set(STATIC_LLM_COMMANDS)
 TWO_ARG_COMMANDS = {

src/skills.metta

@@ -18,6 +18,7 @@
     "- Write base64-encoded content to file as a single line, prefer it when the content contains quotes, backslashes or multiple lines: write-file-b64 filename base64string"
     "- Append line to existing file, result read back from disk like write-file: append-file filename string"
     "- Get a list of allowed base paths for reading, writing, and updating files: get-io-policy"
+    "- Delete a file, the result is read back and verified afterward (DELETE-VERIFIED or DELETE-FAILED with reason) - relay it, never claim a deletion succeeded without it: delete-file filename"
     ;COMMUNICATION CHANNELS:
     "- Send message to user: send string"
     "- Search the web: websearch string"
@@ -119,6 +120,9 @@
 (= (append-file $file $str)
    (py-call (fileio.append_file $file $str)))
 
+(= (delete-file $path)
+   (py-call (fileio.delete_file $path)))
+
 ; Prolog-backed append used by the harness itself (memory.metta appendToHistory):
 ; it receives a (library ...) file-spec term that only the Prolog open/4 path
 ; resolves. Body is the previous append-file minus its exists_file guard: