No module named 'transformers' in ComfyUI

Fix ComfyUI No module named transformers errors in the active Python environment and understand when the failure comes from ComfyUI's core text stack.

If ComfyUI stops with ModuleNotFoundError: No module named 'transformers', do not assume it is only a plugin problem.

In current ComfyUI builds, this error can come from ComfyUI's own text and tokenizer stack. In the tested portable repair lab, the traceback ran through comfy\sd1_clip.py and failed on from transformers import CLIPTokenizer before the server started.

Fast answer

For the GitHub Windows portable package:

.\python_embeded\python.exe -s -m pip show transformers tokenizers
Get-Content ComfyUI\requirements.txt | Select-String "transformers|tokenizers"
.\python_embeded\python.exe -s -m pip install transformers
.\python_embeded\python.exe -s ComfyUI\main.py --windows-standalone-build

If the next startup fails on another core package, keep fixing the first new blocker in the same environment instead of switching to unrelated package commands.

What The Real Log Looked Like

In the repaired lab, the relevant part of the traceback looked like this:

File "...\ComfyUI\comfy\sd1_clip.py", line 3, in <module>
  from transformers import CLIPTokenizer
ModuleNotFoundError: No module named 'transformers'

That is not a random custom node path. It is ComfyUI's own model and tokenizer import path.

Quick Diagnosis

What You See	Meaning	First Action
`No module named 'transformers'` from `comfy\sd1_clip.py`	Core text/tokenizer dependency missing	Install `transformers` in ComfyUI's active Python
`pip show transformers` works in system Python but ComfyUI still fails	Wrong Python environment	Use `python_embeded\python.exe` or the active venv
Local `requirements.txt` lists `transformers>=...` and `tokenizers>=...`	ComfyUI expects this package family	Repair it from the same environment
Installing `transformers` exposes a new missing package	Wider dependency drift	Keep following the new first blocker
Server already starts and only a plugin fails on `transformers`	Could be plugin-specific	Still install into the same ComfyUI Python first

Step 1: Check The Local Requirement Line

In the tested lab, ComfyUI\requirements.txt included:

transformers>=4.50.3
tokenizers>=0.13.3

Check your local copy:

Get-Content ComfyUI\requirements.txt | Select-String "transformers|tokenizers"

That tells you whether your ComfyUI code already expects the package.

Step 2: Install In The Python That Launches ComfyUI

For Windows portable:

.\python_embeded\python.exe -s -m pip install transformers

For a manual venv:

python -m pip install transformers

In the tested lab, this also pulled the adjacent package family automatically, including tokenizers, huggingface-hub, and regex.

If you are using ComfyUI Desktop or another managed launcher, install through that app's environment, not a separate terminal Python.

Step 3: Restart And Read The Next Blocker

Relaunch ComfyUI:

.\python_embeded\python.exe -s ComfyUI\main.py --windows-standalone-build

In the lab, transformers was not the last missing package. After that import was repaired, the next first blocker became:

ModuleNotFoundError: No module named 'torchsde'

That is normal in a broken portable environment. The right move is not to guess ten more packages. The right move is to fix the next first blocker in the same Python.

Step 4: Distinguish Core Failure From Plugin Failure

If the traceback points into:

ComfyUI\comfy\sd1_clip.py
ComfyUI\comfy\supported_models.py
ComfyUI\comfy\sd.py

then the missing transformers import is part of ComfyUI's own text stack.

If the traceback points into a custom node folder under custom_nodes, it may be plugin-specific. Even then, the repair still belongs in the same Python environment that launches ComfyUI.

What Not To Do

do not install transformers into system Python when ComfyUI uses python_embeded
do not start by downgrading Torch, NumPy, or Pillow when the first visible error is only a missing transformers import
do not assume a plugin error means core ComfyUI is healthy until you read the traceback path
do not keep installing packages without restarting and reading the new first blocker

How Wonderful Launcher Helps

When a tokenizer or model-stack import fails, the hard part is often proving which Python actually launched ComfyUI and whether the traceback came from core code or a plugin. Wonderful Launcher helps by keeping that environment boundary visible.

Source References

Windows portable repair lab, May 18, 2026: traceback failed on from transformers import CLIPTokenizer in ComfyUI\comfy\sd1_clip.py
Same lab ComfyUI\requirements.txt: transformers>=4.50.3 and tokenizers>=0.13.3
Same lab next blocker after repair: ModuleNotFoundError: No module named 'torchsde'

You can fix it manually, or download Wonderful Launcher for Windows to diagnose plugin errors, missing dependencies, and broken ComfyUI environments without reinstalling.

Download free for Windows

Keep reading:Start from the No module named hub Fix Torch missing errors Confirm the active Python

You can fix it manually, or download Wonderful Launcher for Windows to diagnose plugin errors, missing dependencies, and broken ComfyUI environments without reinstalling.

Download free for Windows

Did this fix your issue?

Your answer helps prioritize verified ComfyUI repairs.

If ComfyUI stops with ModuleNotFoundError: No module named 'transformers', do not assume it is only a plugin problem.

Fast answer

For the GitHub Windows portable package:

.\python_embeded\python.exe -s -m pip show transformers tokenizers
Get-Content ComfyUI\requirements.txt | Select-String "transformers|tokenizers"
.\python_embeded\python.exe -s -m pip install transformers
.\python_embeded\python.exe -s ComfyUI\main.py --windows-standalone-build

If the next startup fails on another core package, keep fixing the first new blocker in the same environment instead of switching to unrelated package commands.

What The Real Log Looked Like

In the repaired lab, the relevant part of the traceback looked like this:

File "...\ComfyUI\comfy\sd1_clip.py", line 3, in <module>
  from transformers import CLIPTokenizer
ModuleNotFoundError: No module named 'transformers'

That is not a random custom node path. It is ComfyUI's own model and tokenizer import path.

Quick Diagnosis

What You See	Meaning	First Action
`No module named 'transformers'` from `comfy\sd1_clip.py`	Core text/tokenizer dependency missing	Install `transformers` in ComfyUI's active Python
`pip show transformers` works in system Python but ComfyUI still fails	Wrong Python environment	Use `python_embeded\python.exe` or the active venv
Local `requirements.txt` lists `transformers>=...` and `tokenizers>=...`	ComfyUI expects this package family	Repair it from the same environment
Installing `transformers` exposes a new missing package	Wider dependency drift	Keep following the new first blocker
Server already starts and only a plugin fails on `transformers`	Could be plugin-specific	Still install into the same ComfyUI Python first

Step 1: Check The Local Requirement Line

In the tested lab, ComfyUI\requirements.txt included:

transformers>=4.50.3
tokenizers>=0.13.3

Check your local copy:

Get-Content ComfyUI\requirements.txt | Select-String "transformers|tokenizers"

That tells you whether your ComfyUI code already expects the package.

Step 2: Install In The Python That Launches ComfyUI

For Windows portable:

.\python_embeded\python.exe -s -m pip install transformers

For a manual venv:

python -m pip install transformers

In the tested lab, this also pulled the adjacent package family automatically, including tokenizers, huggingface-hub, and regex.

If you are using ComfyUI Desktop or another managed launcher, install through that app's environment, not a separate terminal Python.

Step 3: Restart And Read The Next Blocker

Relaunch ComfyUI:

.\python_embeded\python.exe -s ComfyUI\main.py --windows-standalone-build

In the lab, transformers was not the last missing package. After that import was repaired, the next first blocker became:

ModuleNotFoundError: No module named 'torchsde'

That is normal in a broken portable environment. The right move is not to guess ten more packages. The right move is to fix the next first blocker in the same Python.

Step 4: Distinguish Core Failure From Plugin Failure

If the traceback points into:

ComfyUI\comfy\sd1_clip.py
ComfyUI\comfy\supported_models.py
ComfyUI\comfy\sd.py

then the missing transformers import is part of ComfyUI's own text stack.

If the traceback points into a custom node folder under custom_nodes, it may be plugin-specific. Even then, the repair still belongs in the same Python environment that launches ComfyUI.

What Not To Do

do not install transformers into system Python when ComfyUI uses python_embeded
do not start by downgrading Torch, NumPy, or Pillow when the first visible error is only a missing transformers import
do not assume a plugin error means core ComfyUI is healthy until you read the traceback path
do not keep installing packages without restarting and reading the new first blocker

How Wonderful Launcher Helps

Source References

Windows portable repair lab, May 18, 2026: traceback failed on from transformers import CLIPTokenizer in ComfyUI\comfy\sd1_clip.py
Same lab ComfyUI\requirements.txt: transformers>=4.50.3 and tokenizers>=0.13.3
Same lab next blocker after repair: ModuleNotFoundError: No module named 'torchsde'

You can fix it manually, or download Wonderful Launcher for Windows to diagnose plugin errors, missing dependencies, and broken ComfyUI environments without reinstalling.

Download free for Windows

Keep reading:Start from the No module named hub Fix Torch missing errors Confirm the active Python

You can fix it manually, or download Wonderful Launcher for Windows to diagnose plugin errors, missing dependencies, and broken ComfyUI environments without reinstalling.

Download free for Windows

Did this fix your issue?

Your answer helps prioritize verified ComfyUI repairs.

No module named 'transformers' in ComfyUI

What The Real Log Looked Like

Quick Diagnosis

Step 1: Check The Local Requirement Line

Step 2: Install In The Python That Launches ComfyUI

Step 3: Restart And Read The Next Blocker

Step 4: Distinguish Core Failure From Plugin Failure

What Not To Do

How Wonderful Launcher Helps

Source References

Table of Contents

No module named 'transformers' in ComfyUI

What The Real Log Looked Like

Quick Diagnosis

Step 1: Check The Local Requirement Line

Step 2: Install In The Python That Launches ComfyUI

Step 3: Restart And Read The Next Blocker

Step 4: Distinguish Core Failure From Plugin Failure

What Not To Do

How Wonderful Launcher Helps

Source References

Table of Contents