Why Simulink Copilot Authentication Error (Error: AUTH_0701) occurs when using Simulink Copilot?

I am using MATLAB R2026a in a desktop environment and encounters an error when launching Simulink Copilot.

* MATLAB Copilot works without any issues

* When starting Simulink Copilot and write question, the following error occurs:

Your session has expired or authentication has failed. Please sign in again and restart Simulink Copilot. If the issue persists, please check your MathWorks account credentials. (Error: AUTH_0701)

Answer 1

[MathWorks Support Team]

The most likely cause of the Simulink Copilot authentication error in this case is related to the proxy configuration.

In the logs you shared, we observed the following errors:

• The connection to login.mathworks.com was interrupted during communication
• An error indicating that “the connection was forcibly closed by the remote host”

These types of errors typically occur when a connection is attempted directly in an environment where network access is required to go through a proxy, resulting in the request being rejected.

Items to Be Confirmed

We would appreciate it if you could verify the proxy settings using the following steps and then recheck the behavior of Simulink Copilot.

Please execute the following command in the Command Prompt (cmd):

curl -v https://login.mathworks.com/authenticationws/service/v4/tokens

How to interpret the results:

• If an HTTP response is returned (e.g., 400 / 405) → The server is reachable (communication via proxy may be working)
• If a connection error occurs → There may be a broader network issue (please consult your network administrator)

Run the following commands in the Command Prompt (cmd):

echo %HTTPS_PROXY%
echo %HTTP_PROXY%

Interpretation:

• If a proxy address is displayed → Proxy is already configured
• If nothing is displayed or the variable name itself is returned → Proxy is not configured

Please execute the following commands in the command prompt:

System-level proxy (WinHTTP)

netsh winhttp show proxy

User-level proxy (browser settings, etc.)

reg query "HKCU\Software\Microsoft\Windows\CurrentVersion\Internet Settings" /v Proxy

PAC file configuration

reg query "HKCU\Software\Microsoft\Windows\CurrentVersion\Internet Settings" /v AutoConfigURL

If a PAC file is configured, please also execute:

bitsadmin /util /getieproxy currentuser
bitsadmin /util /getieproxy localsystem

Based on the retrieved proxy information, please set the following environment variables:

• HTTPS_PROXY
• HTTP_PROXY

Example:

setx HTTPS_PROXY "http://proxy.example.com:8080" /M
setx HTTP_PROXY "http://proxy.example.com:8080" /M

• Restart the application after configuring the environment variables
• Then verify the behavior of Simulink Copilot again

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