diff --git a/src/gpu_rent/civitai.py b/src/gpu_rent/civitai.py
index c7e5649..b05153d 100644
--- a/src/gpu_rent/civitai.py
+++ b/src/gpu_rent/civitai.py
@@ -80,6 +80,19 @@ def pick_primary_file(version: dict) -> dict | None:
     return None
 
 
+def file_size_bytes(info: dict) -> int | None:
+    """Civitai ``sizeKB`` (float) → bytes, or None."""
+    raw = info.get("sizeKB")
+    if raw is None:
+        raw = info.get("sizeKb")
+    if raw is None:
+        return None
+    try:
+        return int(round(float(raw) * 1024.0))
+    except (TypeError, ValueError):
+        return None
+
+
 def pick_preview_image(version: dict) -> tuple[str, str] | None:
     """First usable Civitai preview → (url, sidecar_suffix) for SwarmUI.
 
diff --git a/src/gpu_rent/provision.py b/src/gpu_rent/provision.py
index 6b980e1..879280d 100644
--- a/src/gpu_rent/provision.py
+++ b/src/gpu_rent/provision.py
@@ -11,7 +11,12 @@ from pathlib import Path
 
 import httpx
 
-from gpu_rent.civitai import fetch_model_version, pick_preview_image, pick_primary_file
+from gpu_rent.civitai import (
+    fetch_model_version,
+    file_size_bytes,
+    pick_preview_image,
+    pick_primary_file,
+)
 from gpu_rent.config import Config
 from gpu_rent.errors import CloudError, GpuRentError
 from gpu_rent.manifests import (
@@ -480,6 +485,9 @@ def seed_civitai(cfg: Config, host: str, log: Log) -> None:
                 f"{stem}.swarm.json": json.dumps(swarm, ensure_ascii=False, indent=2),
             },
         }
+        size_b = file_size_bytes(info)
+        if size_b:
+            job["size"] = size_b
         preview = pick_preview_image(version)
         if preview:
             preview_url, preview_suffix = preview
diff --git a/src/gpu_rent/remote/civitai_fetch.py b/src/gpu_rent/remote/civitai_fetch.py
index 1afd18b..baea0ef 100644
--- a/src/gpu_rent/remote/civitai_fetch.py
+++ b/src/gpu_rent/remote/civitai_fetch.py
@@ -4,6 +4,7 @@ from __future__ import annotations
 
 import hashlib
 import json
+import os
 import sys
 import time
 import urllib.parse
@@ -91,15 +92,65 @@ def sha256_path(path: Path) -> str:
     return digest.hexdigest()
 
 
-def should_skip(dest: Path, expect_sha: str) -> tuple[bool, str]:
-    """Return (skip, reason). Existing file with matching sha — or any non-empty if no sha."""
+def sha_sidecar_path(dest: Path) -> Path:
+    """Beside weight: name.safetensors.sha256 (avoids stem collisions)."""
+    return Path(str(dest) + ".sha256")
+
+
+def write_sha_sidecar(dest: Path, digest: str) -> None:
+    try:
+        sha_sidecar_path(dest).write_text(digest.lower().strip() + "\n", encoding="utf-8")
+    except OSError:
+        pass
+
+
+def read_sha_sidecar(dest: Path) -> str:
+    side = sha_sidecar_path(dest)
+    if not side.is_file():
+        return ""
+    try:
+        return side.read_text(encoding="utf-8").strip().split()[0].lower()
+    except (OSError, IndexError):
+        return ""
+
+
+def should_skip(
+    dest: Path,
+    expect_sha: str,
+    *,
+    expect_size: int | None = None,
+    verify_sha: bool = False,
+) -> tuple[bool, str]:
+    """Return (skip, reason).
+
+    Re-up must stay fast: prefer size + sha sidecar over hashing 10+ GB weights.
+    Full SHA only when ``verify_sha`` or size unknown.
+    """
     if not dest.is_file() or dest.stat().st_size <= 0:
         return False, ""
+    size = dest.stat().st_size
     expect = (expect_sha or "").lower()
+    # sizeKB from Civitai is float → allow small rounding slack
+    if expect_size is not None and expect_size > 0:
+        if abs(size - int(expect_size)) > 4096:
+            return False, f"размер {size} != {expect_size} — перекачиваю"
     if not expect:
         return True, "уже есть"
+    recorded = read_sha_sidecar(dest)
+    if recorded and recorded == expect:
+        return True, "уже есть (sha sidecar)"
+    if (
+        expect_size is not None
+        and expect_size > 0
+        and abs(size - int(expect_size)) <= 4096
+        and not verify_sha
+    ):
+        # Trust size match; persist expected hash so next skip is sidecar-fast.
+        write_sha_sidecar(dest, expect)
+        return True, "уже есть (size ok)"
     got = sha256_path(dest).lower()
     if got == expect:
+        write_sha_sidecar(dest, got)
         return True, "уже есть (sha ok)"
     return False, "sha не совпал — перекачиваю"
 
@@ -186,6 +237,12 @@ def main() -> int:
         if HF_TOKEN_PATH.is_file()
         else ""
     )
+    verify_sha = (os.environ.get("GPU_RENT_VERIFY_SHA") or "").strip().lower() in {
+        "1",
+        "true",
+        "yes",
+        "on",
+    }
     jobs = json.loads(JOBS_PATH.read_text(encoding="utf-8"))
     total = len(jobs)
     failed = 0
@@ -194,6 +251,11 @@ def main() -> int:
     for index, job in enumerate(jobs, start=1):
         dest = Path(job["dest"])
         expect = (job.get("sha256") or "").lower()
+        expect_size = job.get("size")
+        try:
+            expect_size_n = int(expect_size) if expect_size is not None else None
+        except (TypeError, ValueError):
+            expect_size_n = None
         prefix = f"[{index}/{total}]"
         auth = str(job.get("auth") or "civitai").lower()
         if auth == "hf":
@@ -202,7 +264,9 @@ def main() -> int:
         else:
             token = civitai_token
             auth_host = "civitai"
-        skip, reason = should_skip(dest, expect)
+        skip, reason = should_skip(
+            dest, expect, expect_size=expect_size_n, verify_sha=verify_sha
+        )
         if skip:
             skipped += 1
             size = dest.stat().st_size if dest.is_file() else 0
@@ -234,6 +298,7 @@ def main() -> int:
                 if got != expect:
                     dest.unlink(missing_ok=True)
                     raise RuntimeError(f"sha256 {got} != {expect}")
+                write_sha_sidecar(dest, got)
             for extra_name, extra_text in (job.get("sidecars") or {}).items():
                 extra = dest.parent / extra_name
                 extra.write_text(extra_text, encoding="utf-8")
diff --git a/src/gpu_rent/remote/install_swarm_comfy.py b/src/gpu_rent/remote/install_swarm_comfy.py
index 636f3d2..b5c9711 100644
--- a/src/gpu_rent/remote/install_swarm_comfy.py
+++ b/src/gpu_rent/remote/install_swarm_comfy.py
@@ -11,6 +11,7 @@ import base64
 import hashlib
 import json
 import os
+import re
 import socket
 import struct
 import subprocess
@@ -28,6 +29,7 @@ DLBACKEND = DATA / "dlbackend"
 COMFY_ROOT = DLBACKEND / "ComfyUI"
 COMFY_VENV = COMFY_ROOT / "venv" / "bin" / "python"
 SETTINGS = DATA / "Data" / "Settings.fds"
+BACKENDS_FDS = DATA / "Data" / "Backends.fds"
 # Comfy clone + torch can take 20–40+ min on a cold disk.
 INSTALL_TIMEOUT = float(os.environ.get("GPU_RENT_COMFY_INSTALL_TIMEOUT") or "3600")
 
@@ -255,6 +257,87 @@ def recover_errored_backends(*, wait_sec: float = 180.0) -> str:
     return last
 
 
+def sanitize_backends_fds() -> bool:
+    """Repair ExtraArgs: \\x --flag (FDS empty + appended flag). Return True if changed."""
+    path = DATA / "Data" / "Backends.fds"
+    if not path.is_file():
+        return False
+    try:
+        text = path.read_text(encoding="utf-8")
+    except OSError:
+        return False
+    new, n = re.subn(r"^(\s*ExtraArgs:\s*)\\x(\s+)", r"\1", text, flags=re.M)
+    if not n:
+        return False
+    path.write_text(new, encoding="utf-8")
+    print(f"sanitized Backends.fds ExtraArgs \\x corruption ({n} line(s))", flush=True)
+    return True
+
+
+def restart_swarmui_local() -> None:
+    print("systemctl restart swarmui (после fix Backends.fds)", flush=True)
+    try:
+        subprocess.run(
+            ["sudo", "-n", "systemctl", "restart", "swarmui"],
+            check=False,
+            timeout=120,
+        )
+    except (OSError, subprocess.TimeoutExpired) as exc:
+        print(f"WARN restart swarmui: {exc}", flush=True)
+    wait_http(time.time() + 180)
+
+
+def list_backends(sid: str) -> dict:
+    try:
+        return post(
+            "/API/ListBackends",
+            {"session_id": sid, "nonreal": False, "full_data": False},
+            timeout=30.0,
+        )
+    except Exception as exc:
+        return {"error": str(exc)}
+
+
+def add_comfy_selfstart(sid: str) -> dict:
+    return post(
+        "/API/AddNewBackend",
+        {"session_id": sid, "type_id": "comfyui_selfstart"},
+        timeout=60.0,
+    )
+
+
+def recover_empty_backends() -> str:
+    """When API says empty but venv/IsInstalled exist — fix FDS and/or AddNewBackend."""
+    changed = sanitize_backends_fds()
+    if changed:
+        restart_swarmui_local()
+        bstat, _ = backend_status_detail()
+        if bstat not in ("empty", "unknown") and not bstat.startswith("error:"):
+            print(f"after sanitize: backend_status={bstat}", flush=True)
+            return bstat
+
+    sid = get_session(time.time() + 60)
+    backends = list_backends(sid)
+    if isinstance(backends, dict) and any(
+        isinstance(v, dict) and v.get("type") for v in backends.values()
+    ):
+        bstat, _ = backend_status_detail()
+        return bstat
+
+    print("ListBackends empty — AddNewBackend comfyui_selfstart", flush=True)
+    try:
+        result = add_comfy_selfstart(sid)
+        print(f"AddNewBackend: {result}", flush=True)
+    except Exception as exc:
+        print(f"AddNewBackend FAIL: {exc}", flush=True)
+        return "empty"
+
+    # Default StartScript may be dlbackend/comfy/...; our tree is dlbackend/ComfyUI.
+    time.sleep(2)
+    bstat, _ = backend_status_detail()
+    return bstat
+
+
 def run_diagnostics() -> None:
     """Best-effort: prefer uploaded swarm_diag.py, else journalctl snippet."""
     diag = Path("/tmp/gpu-rent-swarm_diag.py")
diff --git a/src/gpu_rent/remote/tune_swarm_perf.py b/src/gpu_rent/remote/tune_swarm_perf.py
index 6b41145..f2d6d02 100644
--- a/src/gpu_rent/remote/tune_swarm_perf.py
+++ b/src/gpu_rent/remote/tune_swarm_perf.py
@@ -84,25 +84,42 @@ def find_pip() -> Path | None:
 
 
 def patch_backends_extra_args(extra: str) -> bool:
-    """Ensure ExtraArgs contains sage flag for Comfy self-start backends."""
+    """Ensure ExtraArgs contains sage flag for Comfy self-start backends.
+
+    FreneticDataSyntax encodes an empty string as ``\\x``. Appending to that
+    line corrupts the file so SwarmUI loads zero backends (ListBackends={}).
+    """
     if not extra:
         return False
     if not BACKENDS.is_file():
         print(f"no {BACKENDS} yet — skip ExtraArgs (Comfy not registered)")
         return False
     text = BACKENDS.read_text(encoding="utf-8")
-    if "--use-sage-attention" in text:
+    if "--use-sage-attention" in text and not re.search(
+        r"ExtraArgs:\s*\\x\s+--use-sage-attention", text
+    ):
         print("Backends.fds already has --use-sage-attention")
         return False
     lines = text.splitlines()
     changed = False
     out = []
     for line in lines:
-        if re.match(r"^(\s*)ExtraArgs:\s*$", line) or re.match(r"^(\s*)ExtraArgs:\s*\"\"\s*$", line):
-            indent = re.match(r"^(\s*)", line).group(1)
+        m_empty = re.match(r"^(\s*)ExtraArgs:\s*(?:\\x)?\s*$", line)
+        m_corrupt = re.match(r"^(\s*)ExtraArgs:\s*\\x\s+(.*)$", line)
+        m_val = re.match(r"^(\s*)ExtraArgs:\s+(\S.*)$", line)
+        if m_empty:
+            indent = m_empty.group(1)
             out.append(f"{indent}ExtraArgs: {extra}")
             changed = True
-        elif re.match(r"^(\s*)ExtraArgs:\s+", line) and "--use-sage-attention" not in line:
+        elif m_corrupt:
+            indent = m_corrupt.group(1)
+            rest = m_corrupt.group(2).strip()
+            if "--use-sage-attention" in rest:
+                out.append(f"{indent}ExtraArgs: {rest}")
+            else:
+                out.append(f"{indent}ExtraArgs: {rest} {extra}".strip())
+            changed = True
+        elif m_val and "--use-sage-attention" not in line:
             out.append(line.rstrip() + f" {extra}")
             changed = True
         else:
@@ -115,6 +132,24 @@ def patch_backends_extra_args(extra: str) -> bool:
     return True
 
 
+def sanitize_backends_fds() -> bool:
+    """Repair ``ExtraArgs: \\x --flag`` corruption; return True if file changed."""
+    if not BACKENDS.is_file():
+        return False
+    text = BACKENDS.read_text(encoding="utf-8")
+    new, n = re.subn(
+        r"^(\s*ExtraArgs:\s*)\\x(\s+)",
+        r"\1",
+        text,
+        flags=re.M,
+    )
+    if n:
+        BACKENDS.write_text(new, encoding="utf-8")
+        print(f"sanitized Backends.fds ExtraArgs \\x corruption ({n} line(s))")
+        return True
+    return False
+
+
 def sage_already_importable(py: Path) -> bool:
     code, _ = _run(
         [str(py), "-c", "import triton, sageattention"],
diff --git a/tests/test_civitai_fetch.py b/tests/test_civitai_fetch.py
index 1f377ea..ba55034 100644
--- a/tests/test_civitai_fetch.py
+++ b/tests/test_civitai_fetch.py
@@ -1,7 +1,12 @@
 from pathlib import Path
 
-from gpu_rent.civitai import pick_preview_image
-from gpu_rent.remote.civitai_fetch import fmt_bytes, progress_line, should_skip
+from gpu_rent.civitai import file_size_bytes, pick_preview_image
+from gpu_rent.remote.civitai_fetch import (
+    fmt_bytes,
+    progress_line,
+    should_skip,
+    write_sha_sidecar,
+)
 
 
 def test_should_skip_missing(tmp_path: Path):
@@ -17,21 +22,52 @@ def test_should_skip_exists_no_sha(tmp_path: Path):
     assert "уже есть" in reason
 
 
-def test_should_skip_sha_match(tmp_path: Path):
+def test_should_skip_size_ok_fast(tmp_path: Path):
+    """Re-up must not hash multi-GB weights when size matches."""
+    dest = tmp_path / "big.safetensors"
+    data = b"x" * 10_000
+    dest.write_bytes(data)
+    expect = "deadbeef" * 8
+    skip, reason = should_skip(dest, expect, expect_size=len(data))
+    assert skip is True
+    assert "size ok" in reason
+    # sidecar written for next run
+    assert (tmp_path / "big.safetensors.sha256").is_file()
+
+
+def test_should_skip_sha_sidecar(tmp_path: Path):
+    dest = tmp_path / "a.safetensors"
+    dest.write_bytes(b"weights")
+    expect = "abcd" * 16
+    write_sha_sidecar(dest, expect)
+    skip, reason = should_skip(dest, expect, expect_size=7)
+    assert skip is True
+    assert "sidecar" in reason
+
+
+def test_should_skip_sha_match_slow(tmp_path: Path):
     dest = tmp_path / "a.safetensors"
     dest.write_bytes(b"weights")
     import hashlib
 
     digest = hashlib.sha256(b"weights").hexdigest()
-    skip, reason = should_skip(dest, digest)
+    skip, reason = should_skip(dest, digest, verify_sha=True)
     assert skip is True
     assert "sha ok" in reason
 
 
+def test_should_not_skip_bad_size(tmp_path: Path):
+    dest = tmp_path / "a.safetensors"
+    dest.write_bytes(b"weights")
+    skip, reason = should_skip(dest, "deadbeef" * 8, expect_size=99999)
+    assert skip is False
+    assert "размер" in reason
+
+
 def test_should_not_skip_bad_sha(tmp_path: Path):
     dest = tmp_path / "a.safetensors"
     dest.write_bytes(b"weights")
-    skip, reason = should_skip(dest, "deadbeef" * 8)
+    skip, reason = should_skip(dest, "deadbeef" * 8, verify_sha=True)
     assert skip is False
     assert "перекачиваю" in reason
 
@@ -80,3 +116,9 @@ def test_pick_preview_image_png_and_default():
     ] == ".preview.jpg"
     assert pick_preview_image({"images": []}) is None
     assert pick_preview_image({}) is None
+
+
+def test_file_size_bytes():
+    assert file_size_bytes({"sizeKB": 1.0}) == 1024
+    assert file_size_bytes({"sizeKB": 6775430.35}) == int(round(6775430.35 * 1024))
+    assert file_size_bytes({}) is None