diff --git a/tools/extract_all.py b/tools/extract_all.py
index eeef697..04108a5 100644
--- a/tools/extract_all.py
+++ b/tools/extract_all.py
@@ -75,10 +75,25 @@ def free_bytes(path: Path) -> int:
     return shutil.disk_usage(path).free
 
 
-def extract(archive: Path, dest: Path) -> tuple[bool, str]:
-    """7z x into dest. Empty -p avoids interactive prompts (no password)."""
-    dest.mkdir(parents=True, exist_ok=True)
-    cmd = ["7z", "x", "-y", "-p", f"-o{dest}", str(archive)]
+def extract(archive: Path, dest: Path) -> tuple[bool, str, Path]:
+    """7z x into dest. Empty -p avoids interactive prompts (no password).
+
+    Returns (ok, error, dest_used): on a name collision (the archive stem
+    exists as a *file*, e.g. 'model.stl.zip' next to 'model.stl') the
+    destination gets a '_dup' suffix instead of crashing.
+    """
+    actual = dest
+    for _ in range(5):
+        try:
+            actual.mkdir(parents=True, exist_ok=True)
+            break
+        except FileExistsError:
+            actual = dest.with_name(dest.name + "_dup")
+        except (NotADirectoryError, FileExistsError) as exc:
+            return False, f"cannot create destination {actual}: {exc}", dest
+    else:
+        return False, f"cannot create destination {dest} (repeated collisions)", dest
+    cmd = ["7z", "x", "-y", "-p", f"-o{actual}", str(archive)]
     try:
         # 7z prints legacy-encoded inner filenames (non-UTF8 bytes); decode
         # tolerantly or the whole run crashes (seen with byte 0x87).
@@ -87,15 +102,15 @@ def extract(archive: Path, dest: Path) -> tuple[bool, str]:
             encoding="utf-8", errors="replace", timeout=EXTRACT_TIMEOUT,
         )
     except subprocess.TimeoutExpired:
-        return False, f"extraction timed out after {EXTRACT_TIMEOUT}s"
+        return False, f"extraction timed out after {EXTRACT_TIMEOUT}s", actual
     except OSError as exc:
-        return False, f"7z failed to run: {exc}"
+        return False, f"7z failed to run: {exc}", actual
     if proc.returncode in (0, 1):  # 0 ok, 1 warnings (e.g. minor CRC)
         if proc.returncode == 1:
             log.warning("7z reported warnings extracting %s", archive.name)
-        return True, ""
+        return True, "", actual
     tail = "\n".join((proc.stdout or "").splitlines()[-5:])
-    return False, f"7z exit {proc.returncode}: {tail}"
+    return False, f"7z exit {proc.returncode}: {tail}", actual
 
 
 def move_to_broken(path: Path, out_root: Path, src_root: Path, note: str) -> Path:
@@ -126,16 +141,16 @@ def expand_nested(dest: Path, out_root: Path, manifest, src_root: Path,
             if free_bytes(out_root) < MIN_FREE_BYTES:
                 log.error("Out of disk space - skipping %s (kept in place)", p)
                 continue
-            ok, err = extract(p, stem_dir)
+            ok, err, actual = extract(p, stem_dir)
             if not ok:
                 log.error("FAILED nested extraction %s: %s", p, err)
                 move_to_broken(p, out_root, out_root, err)
                 continue
-            manifest.write(f"{json_line(p.relative_to(out_root), stem_dir)}\n")
-            done.add(str(stem_dir.relative_to(out_root)))
+            manifest.write(f"{json_line(p.relative_to(out_root), actual)}\n")
+            done.add(str(actual.relative_to(out_root)))
             p.unlink()  # archive copy consumed
             done_count += 1
-            queue.append(stem_dir)
+            queue.append(actual)
     return done_count
 
 
@@ -174,17 +189,17 @@ def process_root(src_root: Path, out_root: Path, manifest, done: set[str]) -> tu
                 log.error("Out of disk space - skipping archive %s", f)
                 failed += 1
                 continue
-            ok, err = extract(f, dest)
+            ok, err, actual = extract(f, dest)
             if not ok:
                 log.error("FAILED %s: %s", rel, err)
                 move_to_broken(f, out_root, src_root, err)
                 failed += 1
                 continue
-            manifest.write(f"{json_line(Path(idx) / rel, dest)}\n")
-            done.add(str(dest_rel))
+            manifest.write(f"{json_line(Path(idx) / rel, actual)}\n")
+            done.add(str(actual.relative_to(out_root)))
             extracted += 1
-            log.info("Extracted %s -> %s", rel, dest_rel)
-            expand_nested(dest, out_root, manifest, src_root, done)
+            log.info("Extracted %s -> %s", rel, actual.relative_to(out_root))
+            expand_nested(actual, out_root, manifest, src_root, done)
         else:
             link_dest = out_root / idx / rel
             if link_dest.exists():
@@ -233,16 +248,16 @@ def sweep(out_root: Path, manifest, done: set[str]) -> int:
         if free_bytes(out_root) < MIN_FREE_BYTES:
             log.error("Out of disk space - sweep skipping %s", p)
             continue
-        ok, err = extract(p, stem_dir)
+        ok, err, actual = extract(p, stem_dir)
         if not ok:
             log.error("FAILED sweep extraction %s: %s", p, err)
             move_to_broken(p, out_root, out_root, err)
             continue
-        manifest.write(f"{json_line(p.relative_to(out_root), stem_dir)}\n")
-        done.add(str(stem_dir.relative_to(out_root)))
+        manifest.write(f"{json_line(p.relative_to(out_root), actual)}\n")
+        done.add(str(actual.relative_to(out_root)))
         p.unlink()
         swept += 1
-        expand_nested(stem_dir, out_root, manifest, out_root, done)
+        expand_nested(actual, out_root, manifest, out_root, done)
     return swept