[bug]: FLUX model import crashes backend on Windows when filename starts with bracket tag (e.g. [FLX])

[rgrasley]

Is there an existing issue for this problem?

• I have searched the existing issues

Install method

Invoke's Launcher

Operating system

Windows

GPU vendor

Nvidia (CUDA)

GPU model

RTX 5070 Ti

GPU VRAM

16GB

Version number

v1.8.1

Browser

Brave 1.86.139

System Information

{
"version": "6.9.0",
"dependencies": {
"absl-py" : "2.3.1",
"accelerate" : "1.12.0",
"annotated-types" : "0.7.0",
"anyio" : "4.12.0",
"attrs" : "25.4.0",
"bidict" : "0.23.1",
"bitsandbytes" : "0.48.2",
"blake3" : "1.0.8",
"certifi" : "2022.12.7",
"cffi" : "2.0.0",
"charset-normalizer" : "2.1.1",
"click" : "8.3.1",
"colorama" : "0.4.6",
"coloredlogs" : "15.0.1",
"compel" : "2.1.1",
"contourpy" : "1.3.3",
"CUDA" : "12.8",
"cycler" : "0.12.1",
"Deprecated" : "1.3.1",
"diffusers" : "0.33.0",
"dnspython" : "2.8.0",
"dynamicprompts" : "0.31.0",
"einops" : "0.8.1",
"fastapi" : "0.118.3",
"fastapi-events" : "0.12.2",
"filelock" : "3.19.1",
"flatbuffers" : "25.9.23",
"fonttools" : "4.61.0",
"fsspec" : "2025.9.0",
"gguf" : "0.17.1",
"h11" : "0.16.0",
"httptools" : "0.7.1",
"huggingface-hub" : "0.36.0",
"humanfriendly" : "10.0",
"idna" : "3.4",
"importlib_metadata" : "7.1.0",
"InvokeAI" : "6.9.0",
"jax" : "0.7.1",
"jaxlib" : "0.7.1",
"Jinja2" : "3.1.6",
"kiwisolver" : "1.4.9",
"MarkupSafe" : "2.1.5",
"matplotlib" : "3.10.7",
"mediapipe" : "0.10.14",
"ml_dtypes" : "0.5.4",
"mpmath" : "1.3.0",
"networkx" : "3.5",
"numpy" : "1.26.3",
"onnx" : "1.16.1",
"onnxruntime" : "1.19.2",
"opencv-contrib-python": "4.11.0.86",
"opt_einsum" : "3.4.0",
"packaging" : "24.1",
"picklescan" : "0.0.32",
"pillow" : "11.3.0",
"prompt_toolkit" : "3.0.52",
"protobuf" : "4.25.8",
"psutil" : "7.1.3",
"pycparser" : "2.23",
"pydantic" : "2.12.5",
"pydantic-settings" : "2.12.0",
"pydantic_core" : "2.41.5",
"pyparsing" : "3.2.5",
"PyPatchMatch" : "1.0.2",
"pyreadline3" : "3.5.4",
"python-dateutil" : "2.9.0.post0",
"python-dotenv" : "1.2.1",
"python-engineio" : "4.12.3",
"python-multipart" : "0.0.20",
"python-socketio" : "5.15.0",
"PyWavelets" : "1.9.0",
"PyYAML" : "6.0.3",
"regex" : "2025.11.3",
"requests" : "2.28.1",
"safetensors" : "0.7.0",
"scipy" : "1.16.3",
"semver" : "3.0.4",
"sentencepiece" : "0.2.0",
"setuptools" : "70.2.0",
"simple-websocket" : "1.1.0",
"six" : "1.17.0",
"sounddevice" : "0.5.3",
"spandrel" : "0.4.1",
"starlette" : "0.48.0",
"sympy" : "1.14.0",
"tokenizers" : "0.22.1",
"torch" : "2.7.1+cu128",
"torchsde" : "0.2.6",
"torchvision" : "0.22.1+cu128",
"tqdm" : "4.66.5",
"trampoline" : "0.1.2",
"transformers" : "4.57.3",
"typing-inspection" : "0.4.2",
"typing_extensions" : "4.15.0",
"urllib3" : "1.26.13",
"uvicorn" : "0.38.0",
"watchfiles" : "1.1.1",
"wcwidth" : "0.2.14",
"websockets" : "15.0.1",
"wrapt" : "2.0.1",
"wsproto" : "1.3.2",
"zipp" : "3.19.2"
},
"config": {
"schema_version": "4.0.2",
"legacy_models_yaml_path": null,
"host": "0.0.0.0",
"port": 9090,
"allow_origins": [],
"allow_credentials": true,
"allow_methods": [""],
"allow_headers": [""],
"ssl_certfile": null,
"ssl_keyfile": null,
"log_tokenization": false,
"patchmatch": true,
"models_dir": "models",
"convert_cache_dir": "models\.convert_cache",
"download_cache_dir": "models\.download_cache",
"legacy_conf_dir": "configs",
"db_dir": "databases",
"outputs_dir": "D:\AI_Outputs\InvokeAI",
"custom_nodes_dir": "nodes",
"style_presets_dir": "style_presets",
"workflow_thumbnails_dir": "workflow_thumbnails",
"log_handlers": ["console"],
"log_format": "color",
"log_level": "info",
"log_sql": false,
"log_level_network": "warning",
"use_memory_db": false,
"dev_reload": false,
"profile_graphs": false,
"profile_prefix": null,
"profiles_dir": "profiles",
"max_cache_ram_gb": null,
"max_cache_vram_gb": null,
"log_memory_usage": false,
"device_working_mem_gb": 3,
"enable_partial_loading": false,
"keep_ram_copy_of_weights": true,
"ram": null,
"vram": null,
"lazy_offload": true,
"pytorch_cuda_alloc_conf": null,
"device": "auto",
"precision": "auto",
"sequential_guidance": false,
"attention_type": "auto",
"attention_slice_size": "auto",
"force_tiled_decode": false,
"pil_compress_level": 1,
"max_queue_size": 10000,
"clear_queue_on_startup": false,
"allow_nodes": null,
"deny_nodes": null,
"node_cache_size": 512,
"hashing_algorithm": "blake3_single",
"remote_api_tokens": null,
"scan_models_on_startup": false,
"unsafe_disable_picklescan": false,
"allow_unknown_models": true
},
"set_config_fields": ["outputs_dir", "legacy_models_yaml_path", "host"]
}

What happened

When importing a FLUX safetensors checkpoint whose filename begins with a bracketed tag (for example [FLX] flux1-dev-fp8.safetensors), the Invoke backend process crashes during model install. The crash occurs immediately after hashing completes, and the backend exits with Windows access violation code 3221225477 (0xC0000005).

Renaming the file to remove the leading bracket tag resolves the issue and allows the model to be added successfully.

This does not occur with SD / SDXL checkpoints using similar bracketed naming conventions, which suggests the issue is specific to the FLUX ingestion path.

What you expected to happen

• Model should either install successfully or fail gracefully with a validation error
• Backend should not crash due to filename format

How to reproduce the problem

1. Take a FLUX checkpoint, e.g. flux1-dev-fp8.safetensors
2. Rename it to start with a bracket tag (e.g. [FLX] flux1-dev-fp8.safetensors)
3. Add the model via Model Manager
4. Observe hashing completes
5. Backend process exits immediately afterward

Additional context

Observed behavior:

• Backend exits with code 3221225477 (0xC0000005)
• No Python traceback is shown
• Invoke UI loses backend connection

Workaround: Renaming the file to remove the leading bracket tag fixes the issue immediately

Additional notes:

• Multiple SDXL models with bracketed filename prefixes import and work correctly
• This appears to be FLUX-ingest specific
• Crash happens after hashing, likely during model registration / classification

Discord username

No response