diff --git a/graphify/__main__.py b/graphify/__main__.py
index 3b448a6..a5b1bd1 100644
--- a/graphify/__main__.py
+++ b/graphify/__main__.py
@@ -94,9 +94,16 @@ def _enforce_graph_size_cap_or_exit(gp: Path) -> None:
 def _check_skill_version(skill_dst: Path) -> None:
     """Warn if the installed skill is from an older graphify version."""
     version_file = skill_dst.parent / ".graphify_version"
-    if not version_file.exists():
+    try:
+        if not version_file.exists():
+            return
+    except OSError:
         return
-    if not skill_dst.exists():
+    try:
+        skill_exists = skill_dst.exists()
+    except OSError:
+        return
+    if not skill_exists:
         print("  warning: skill dir exists but SKILL.md is missing. Run 'graphify install' to repair.")
         return
     # A progressive SKILL.md links to its references/ sidecar. If the body points
@@ -108,7 +115,10 @@ def _check_skill_version(skill_dst: Path) -> None:
         body = ""
     if "references/" in body and not (skill_dst.parent / "references").exists():
         print("  warning: skill references/ sidecar is missing. Run 'graphify install' to repair.", file=sys.stderr)
-    installed = version_file.read_text(encoding="utf-8").strip()
+    try:
+        installed = version_file.read_text(encoding="utf-8").strip()
+    except OSError:
+        return
     if installed != __version__:
         print(f"  warning: skill is from graphify {installed}, package is {__version__}. Run 'graphify install' to update.", file=sys.stderr)
 
diff --git a/graphify/build.py b/graphify/build.py
index d8a69ac..0c47d41 100644
--- a/graphify/build.py
+++ b/graphify/build.py
@@ -165,9 +165,15 @@ def build_from_json(extraction: dict, *, directed: bool = False, root: str | Pat
     # _origin=="ast" as the canonical signal. AST nodes always win; any non-AST
     # node sharing (basename, label) with an AST node is a ghost.
     _loc_nodes: dict[tuple[str, str], str] = {}   # (basename, label) -> canonical node id
+    _loc_collisions: set[tuple[str, str]] = set()  # keys shared by 2+ AST nodes
     _noloc_nodes: dict[tuple[str, str], str] = {}  # (basename, label) -> ghost node id
 
     # Pass 1: collect canonical nodes — AST-origin nodes take precedence over LLM nodes.
+    # When 2+ AST nodes share a key (same-named symbols in same-named files across
+    # directories, e.g. render in two index.ts), the key is ambiguous: merging a
+    # ghost would pick an arbitrary winner via set-iteration order (#1257). Track
+    # those keys so Pass 2 skips them — same conservatism as
+    # _rewire_unique_stub_nodes, which only merges when exactly one real def exists.
     for nid in node_set:
         attrs = G.nodes[nid]
         label = str(attrs.get("label", "")).strip()
@@ -175,10 +181,16 @@ def build_from_json(extraction: dict, *, directed: bool = False, root: str | Pat
         basename = Path(sf).name if sf else ""
         if not label or not basename:
             continue
-        if attrs.get("source_location") or attrs.get("_origin") == "ast":
+        is_ast = attrs.get("_origin") == "ast"
+        if attrs.get("source_location") or is_ast:
             key = (basename, label)
-            # AST-origin nodes always overwrite; non-AST only written if key unseen.
-            if attrs.get("_origin") == "ast" or key not in _loc_nodes:
+            if is_ast:
+                # Two AST nodes on the same key is an ambiguous collision.
+                if key in _loc_nodes and G.nodes[_loc_nodes[key]].get("_origin") == "ast":
+                    _loc_collisions.add(key)
+                # AST-origin nodes always overwrite a prior non-AST entry.
+                _loc_nodes[key] = nid
+            elif key not in _loc_nodes:
                 _loc_nodes[key] = nid
 
     # Pass 2: find ghosts — non-AST nodes that have an AST canonical twin.
@@ -192,6 +204,8 @@ def build_from_json(extraction: dict, *, directed: bool = False, root: str | Pat
         if not label or not basename:
             continue
         key = (basename, label)
+        if key in _loc_collisions:
+            continue  # ambiguous key: no safe canonical winner, leave ghost intact
         if key in _loc_nodes and _loc_nodes[key] != nid:
             _noloc_nodes[key] = nid
     # For every ghost that has an AST counterpart, record a remap.
diff --git a/graphify/extract.py b/graphify/extract.py
index 6b48981..131cc7c 100644
--- a/graphify/extract.py
+++ b/graphify/extract.py
@@ -11565,6 +11565,14 @@ def _extract_parallel(
         cpu_cap = env_cap if env_cap is not None else (os.cpu_count() or 4)
         max_workers = min(cpu_cap, len(uncached_work))
 
+    # Windows ProcessPoolExecutor hard-caps at 61 workers (CPython limitation
+    # tied to WaitForMultipleObjects). Clamp here so every path — auto-compute,
+    # GRAPHIFY_MAX_WORKERS, and --max-workers — stays valid on >61-core boxes
+    # (issue #1298). Guard against 0 from an empty work list.
+    if sys.platform == "win32":
+        max_workers = min(max_workers, 61)
+    max_workers = max(max_workers, 1)
+
     root_str = str(effective_root)
     work_items = [(idx, str(path), root_str) for idx, path in uncached_work]
 
diff --git a/graphify/prs.py b/graphify/prs.py
index 319892e..42943f8 100644
--- a/graphify/prs.py
+++ b/graphify/prs.py
@@ -643,9 +643,12 @@ def triage_with_opus(prs: list[PRInfo], base: str) -> None:
             print("\n")
 
         elif backend == "claude-cli":
-            import subprocess as _sp
+            import platform as _platform, shutil as _shutil, subprocess as _sp
+            _claude = "claude"
+            if _platform.system() == "Windows":
+                _claude = _shutil.which("claude.cmd") or _shutil.which("claude") or "claude"
             proc = _sp.run(
-                ["claude", "-p", "--no-session-persistence"],
+                [_claude, "-p", "--no-session-persistence"],
                 input=prompt, capture_output=True, text=True, timeout=120,
             )
             if proc.returncode != 0:
diff --git a/tests/test_build.py b/tests/test_build.py
index 9be6c12..c57d7a7 100644
--- a/tests/test_build.py
+++ b/tests/test_build.py
@@ -149,6 +149,56 @@ def test_file_type_synonym_mapping():
     assert G.nodes["n3"]["file_type"] == "concept"
 
 
+def test_ghost_merge_unique_located_node_still_merges():
+    """#1145 ghost-merge: a semantic ghost collapses into the single AST node
+    sharing its (basename, label), and edges re-point to the AST node."""
+    ext = {
+        "nodes": [
+            {"id": "ast_render", "label": "render", "file_type": "code",
+             "source_file": "src/app/index.ts", "source_location": "L10", "_origin": "ast"},
+            {"id": "ghost_render", "label": "render", "file_type": "code",
+             "source_file": "src/app/index.ts"},
+            {"id": "caller", "label": "main", "file_type": "code",
+             "source_file": "src/main.ts", "source_location": "L1", "_origin": "ast"},
+        ],
+        "edges": [{"source": "caller", "target": "ghost_render", "relation": "calls",
+                   "confidence": "EXTRACTED", "source_file": "src/main.ts", "weight": 1.0}],
+        "input_tokens": 0, "output_tokens": 0,
+    }
+    G = build_from_json(ext)
+    assert "ghost_render" not in G.nodes()
+    assert G.has_edge("caller", "ast_render")
+
+
+def test_ghost_merge_skipped_on_basename_collision():
+    """#1257: when two files with the same basename both define a symbol with the
+    same label, the (basename, label) key is ambiguous and the semantic ghost
+    must not be merged into an arbitrary one of them."""
+    ext = {
+        "nodes": [
+            {"id": "a_render", "label": "render", "file_type": "code",
+             "source_file": "src/a/index.ts", "source_location": "L10", "_origin": "ast"},
+            {"id": "b_render", "label": "render", "file_type": "code",
+             "source_file": "src/b/index.ts", "source_location": "L20", "_origin": "ast"},
+            {"id": "ghost_render", "label": "render", "file_type": "code",
+             "source_file": "src/a/index.ts"},
+            {"id": "caller", "label": "main", "file_type": "code",
+             "source_file": "src/main.ts", "source_location": "L1", "_origin": "ast"},
+        ],
+        "edges": [{"source": "caller", "target": "ghost_render", "relation": "calls",
+                   "confidence": "EXTRACTED", "source_file": "src/main.ts", "weight": 1.0}],
+        "input_tokens": 0, "output_tokens": 0,
+    }
+    G = build_from_json(ext)
+    # The ghost survives: merging it into either a_render or b_render would
+    # pick an arbitrary winner (set iteration order over node_set).
+    assert "ghost_render" in G.nodes()
+    assert G.number_of_nodes() == 4
+    assert G.has_edge("caller", "ghost_render")
+    assert not G.has_edge("caller", "a_render")
+    assert not G.has_edge("caller", "b_render")
+
+
 def test_build_merge_preserves_call_edge_direction(tmp_path):
     """Regression for #760.
 
diff --git a/tests/test_install_references.py b/tests/test_install_references.py
index 06cfd9d..0f6061a 100644
--- a/tests/test_install_references.py
+++ b/tests/test_install_references.py
@@ -150,6 +150,33 @@ def test_check_skill_version_warns_on_missing_references(tmp_path, fake_bundle,
     assert "references/ sidecar is missing" in err
 
 
+def test_check_skill_version_ignores_permission_error(tmp_path, fake_bundle, monkeypatch, capsys):
+    """Unreadable version probes should not crash startup."""
+    platform = fake_bundle
+    _install(tmp_path, platform)
+    skill_dir = tmp_path / ".claude" / "skills" / "graphify"
+    skill = skill_dir / "SKILL.md"
+
+    # Drain install output so the no-warning assertions below see only what
+    # _check_skill_version itself emits.
+    capsys.readouterr()
+
+    original_exists = Path.exists
+
+    def guarded_exists(self):
+        if self.name == ".graphify_version":
+            raise PermissionError("denied")
+        return original_exists(self)
+
+    monkeypatch.setattr(Path, "exists", guarded_exists)
+
+    mainmod._check_skill_version(skill)
+
+    out = capsys.readouterr()
+    assert out.out == ""
+    assert out.err == ""
+
+
 def test_hard_fail_when_bundle_dir_present_but_references_missing(tmp_path, monkeypatch):
     """A bundle dir that exists but has no references/ subdir is a malformed
     package: exit 1 rather than silently shipping an empty sidecar.