Getting model not found error while trying to use Anthropic models (BYOK)

[Peedy-55]

Feedback source

None

GitHub Copilot plugin version

1.13.1-251

JetBrains IDE and version

WebStorm 2026.2 Build #WS-262.8665.259, built on July 15, 2026 Source revision: 9db502cc722e2 Licensed to Trial User Subscription is active until August 19, 2026. Runtime version: 25.0.3+9-b508.16 amd64 VM: OpenJDK 64-Bit Server VM by JetBrains s.r.o. Toolkit: sun.awt.windows.WToolkit Windows 11.0 Exception reporter ID: 19032610f5feddc-327d-44ac-a1ec-7ca7d5d3abaa JCEF version: 144.0.15-262-b37 GC: G1 Young Generation, G1 Concurrent GC, G1 Old Generation Memory: 2016MiB Cores: 8 Registry: ide.experimental.ui=true vfs.windows.use.buffered.directory.stream=false trace.state.event.service.url=https://api.jetbrains.cloud/trace-status Non-Bundled Plugins: com.intellij.kubernetes (262.8665.173) com.intellij.debugger.collections.visualizer (262.8665.173) com.github.copilot (1.13.1-251) com.intellij.plugin.adernov.powershell (2.12.0) intellij.jupyter (262.8665.339) com.intellij.notebooks.core (262.8665.270) hg4idea (262.8665.173) PerforceDirectPlugin (262.8665.176) Subversion (262.8665.339)

Platform

Microsoft Windows NT 10.0.26200.0 x64

Steps to reproduce

Add your own Anthropic key and try to get a response from any of the Claude models in ask or agent mode

Logs (optional)

idea.log

Expected behavior

Model should give response based on the prompt

Actual behavior

The following error is shown:

Model 'claude-haiku-4-5-20251001' not found on provider at https://api.anthropic.com/v1 (HTTP 404).
Check that the model is available on your provider.

Additional information

This appears to be an issue specific to WebStorm's built-in Anthropic provider preset, not a problem with the API key, model availability, or plugin installation.

Environment

• Personal machine, not on a corporate network (no proxy involved)
• GitHub Copilot plugin version: [same version confirmed working correctly in IntelliJ IDEA]
• Using own Anthropic API key (BYOK)

Symptom

Selecting Anthropic from the built-in provider dropdown and adding models (e.g. claude-haiku-4-5-20251001, claude-sonnet-4-6) resulted in:

Model '' not found on provider at https://api.anthropic.com/v1 (HTTP 404). Check that the model is available on your provider.

This occurred in both Ask mode and Agent mode in WebStorm.

Troubleshooting already performed (all failed to resolve)

• Signed out/in of GitHub
• Generated and tried a brand new Anthropic API key
• Invalidated caches and restarted
• Fully reinstalled WebStorm
• Fully reinstalled the GitHub Copilot plugin
• Set IDE proxy setting explicitly to No proxy
• Confirmed plugin version matches an installation of IntelliJ IDEA where the identical key/models work correctly with no errors

Isolation steps that confirmed the key/models were valid

Ran a direct API call against https://api.anthropic.com/v1/models using the same key. Response returned a full list of available models, including both claude-haiku-4-5-20251001 and claude-sonnet-4-6 — confirming the key has access to these models and that the models exist on Anthropic's side.

Fix found

Switching the provider configuration from the built-in Anthropic preset to a Custom Endpoint, manually entering:

• Deployment URL: https://api.anthropic.com/v1/messages
• Model ID: claude-haiku-4-5-20251001

...resolved the issue immediately using the exact same API key that failed with the built-in preset.

Conclusion

This strongly suggests WebStorm's built-in Anthropic preset is calling an incorrect or incomplete internal route (possibly missing the /v1/messages path suffix), causing a 404 even with valid credentials and valid model IDs. The same preset appears to work correctly in IntelliJ IDEA, suggesting a WebStorm-specific regression or config divergence in how the built-in Anthropic provider is wired for this IDE.

[smile37773]

Hi Dhanush Pakala (@Peedy-55),

Thanks for the very detailed report and for confirming the root cause with the Custom Endpoint workaround — that's really helpful.

I tried to reproduce this issue in WebStorm using the built-in Anthropic provider preset with a BYOK Anthropic key, but I wasn't able to reproduce the 404 error on my end. This suggests it may have already been addressed in a more recent build, or could be related to a specific environment/config state.

Could you please try the following and let us know if the issue persists?

1. Update the GitHub Copilot plugin to the latest available version (you're currently on 1.13.1-251 — please check for a newer release in the JetBrains Marketplace or via  Settings > Plugins ).
2. Fully restart WebStorm after the update (not just reload/invalidate caches).
3. Re-select the built-in Anthropic provider preset (rather than the Custom Endpoint workaround) and try the same models again ( claude-haiku-4-5-20251001 ,  claude-sonnet-4-6 ).

If the error still occurs after updating and restarting, please share:

• The exact new plugin version you're on
• A fresh  idea.log  capturing the failing request (ideally right after restart, to minimize noise)

This will help us narrow down whether this is a stale-config issue or a genuine regression specific to WebStorm. Thanks again for your thorough troubleshooting!

[Peedy-55]

Hey, it appears to be working now. I updated the version to WebStorm 2026.2.0.1. Not sure if that fixed it.

[smile37773]

Great to hear it's working now — thanks for following up and confirming!
It looks like updating to WebStorm 2026.2.0.1 resolved the issue. Since the built-in Anthropic provider preset is now working correctly with your BYOK key, I'll go ahead and close this issue.

[dileep98]

The issue still persists.
I worked with Copilot integrated with Claude yesterday. But today it's not working. I have updated the Copilot plugin, IntelliJ IDEA to 2026.2.0.1

[smile37773]

Dileep Kumar T (@dileep98) Is it the built-in Anthropic preset or a Custom Endpoint?
If the error still occurs after updating and restarting, please share:
• The exact new plugin version you're on
• A fresh idea.log capturing the failing request (ideally right after restart, to minimize noise)