Claude Opus 4.5 on AWS Bedrock not reasoning

[badbird (Evan)]

Where does the bug appear (feature/product)?

Cursor IDE

Describe the Bug

I’m currently using cursor with AWS bedrock, however I’ve noticed the claude opus models don’t seem to reason. But with the model provided by cursor, it does reason properly. Other AWS bedrock models properly reason before answering (tested claude-sonnet-4-5-20250929-v1:0).

Steps to Reproduce

1. Setup AWS bedrock in cursor settings
2. Select the us.anthropic.claude-opus-4-5-20251101-v1:0 model
3. Ask it to make any change

Expected Behavior

It will reason before answering

Screenshots / Screen Recordings

Operating System

Windows 10/11

Current Cursor Version (Menu → About Cursor → Copy)

Version: 2.3.35 (user setup)
VSCode Version: 1.105.1
Commit: cf8353edc265f5e46b798bfb276861d0bf3bf120
Date: 2026-01-13T07:39:18.564Z
Electron: 37.7.0
Chromium: 138.0.7204.251
Node.js: 22.20.0
V8: 13.8.258.32-electron.0
OS: Windows_NT arm64 10.0.26100

For AI issues: which model did you use?

us.anthropic.claude-opus-4-5-20251101-v1:0

For AI issues: add Request ID with privacy disabled

74fff2b6-3550-4300-bce8-3a7ef45d2838

Additional Information

Originally discovered this with opus 4.5, but it also seems to affect opus 4.1
Reasoning also isn’t hidden, as the model responds near instantly

Does this stop you from using Cursor

Sometimes - I can sometimes use Cursor

[Colin]

Hey Evan!

You’re right that extended thinking for Claude Opus 4.5 via Amazon Bedrock isn’t currently supported in Cursor. I’ve flagged this with the team.

If you’d like to use Opus 4.5 with thinking enabled in the meantime, you have a couple of options:

• Use it directly through Cursor (charged against your included usage / on-demand rates)
• Add your own Anthropic API key in Cursor Settings > Models

Also worth noting: Sonnet 4.5 via Bedrock does support thinking in Cursor, so that might work depending on your use case.

[badbird (Evan)]

Hi, thanks for letting me know and the quick response.

I was trying to use opus on bedrock as we had a good amount of AWS credits expiring. I’ll resort to using Opus on my cursor subscription and sonnet on Bedrock.

Thanks again