fix(chat): avoid Windows path redaction backtracking stalls

loopx/chat.py

@@ -66,10 +66,15 @@ def _root_character_atoms(
         options = tuple((variant, True) for variant in variants) + tuple(
             (variant, True) for variant in encoded_variants
         )
+        # IGNORECASE already covers the one-character case variants. Keeping
+        # both as alternatives multiplies backtracking at each near-miss letter.
+        # Multi-character Unicode mappings still need their explicit spelling;
+        # encoded UTF-8 variants remain distinct byte sequences.
+        literal_variants = {char} | {variant for variant in variants if len(variant) > 1}
         pattern = (
             "(?i:"
             + "|".join(
-                re.escape(variant) for variant in sorted(variants | encoded_variants)
+                re.escape(variant) for variant in sorted(literal_variants | encoded_variants)
             )
             + ")"
         )

tests/test_chat_path_redaction.py

@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 import json
+import subprocess
 import sys
 from http.server import BaseHTTPRequestHandler, HTTPServer
 from pathlib import Path
@@ -20,6 +21,37 @@
 from loopx.chat_status_api import ChatStatusRequestMixin
 
 
+def test_windows_near_root_finishes_without_exponential_case_backtracking():
+    # A near miss must reach the generic private-path rule rather than explore
+    # every equivalent upper/lower-case spelling of the protected prefix. Run
+    # in a disposable process so a regression cannot stall the whole suite.
+    result = subprocess.run(
+        [sys.executable, "-c", """
+import json
+from loopx.chat import VisibleResponseStreamFilter, redact_local_paths
+root = 'Q:/' + 'a' * 32 + 'z'
+candidate = 'q:/' + 'a' * 32 + 'y/report.txt'
+stream = VisibleResponseStreamFilter(protected_paths=[root])
+visible = stream.feed(candidate[:20]) + stream.feed(candidate[20:]) + stream.finish()
+print(json.dumps({'batch': redact_local_paths(candidate, protected_paths=[root]), 'stream': visible}))
+"""],
+        cwd=Path(__file__).resolve().parents[1], capture_output=True,
+        encoding="utf-8", check=True, timeout=20,
+    )
+    assert json.loads(result.stdout) == {"batch": "[local-path]", "stream": "[local-path]"}
+
+
+@pytest.mark.parametrize("component", ["Straße", "İ", "ΐ"])
+def test_windows_root_retains_multicharacter_unicode_case_aliases(component):
+    root = f"Q:/{component}/workspace"
+    for alias in (component, component.lower(), component.upper()):
+        candidate = f"q:/{alias}/workspace/report.md"
+        for spelling in (candidate, quote(candidate, safe="/:")):
+            assert redact_local_paths(spelling, protected_paths=[root]) == "[project]"
+            stream = VisibleResponseStreamFilter(protected_paths=[root])
+            assert stream.feed(spelling[:5]) + stream.feed(spelling[5:]) + stream.finish() == "./report.md"
+
+
 @pytest.mark.parametrize(
     "root",
     [