Reasoning Doesn't Work for Claude Models through Vertex Provider

Description

Hey, I'm using Claude Opus 4.5 through GCP Vertex AI, and noticed that for some reason, the reasoning doesn't work for me, even when reasoning is set to "high".

I initially thought it was perhaps hidden (I'm new to using OpenCode), but the responses I'm getting are way too fast for that, and I've tried toggling /thinking on and off, but it made no difference.

I also tried using a custom configuration on the config:

    "provider": {
        "google-vertex-anthropic": {
            "models": {
                "claude-opus-4-5@20251101": {
                    "variants": {
                        "test": {
                            "max_tokens": 64000,
                            "thinking": {
                                "type": "enabled",
                                "budget_tokens": 32000
                            }
                        }
                    }
                },
            },
        },
    },

But even using this "test" mode (which was successfully added) didn't change anything.
I also tested Claude Sonnet 4.5 and Opus 4 to check if it's specific to Opus 4.5, but those had the same issue.

I'll add that I used the same Vertex project with Roo Code and it used reasoning without any issues, so this shouldn't be an issue / limitation on my side.

I know this is not a lot of information to work with. If you need any additional information to help you debug this - please let me know how I can help.

Plugins

None

OpenCode version

v1.1.28

Steps to reproduce

No response

Screenshot and/or share link

https://opncd.ai/share/ha0A4Lmq

Operating System

macOS / Windows 11 (2 different devices, same issue)

Terminal

Windows Terminal / iTerm / OpenCode Desktop

This issue might be a duplicate of existing issues. Please check:

No reasoning at all through Github Copilot provider #6864: No reasoning at all through Github Copilot provider (similar reasoning not being retrieved even with proper config)
No Chain of Thought retrieved if Provider lacks support, despite thinkmode config #6768: No Chain of Thought retrieved if Provider lacks support, despite 'thinkmode' config (reasoning config being ignored by provider)
[BUG/FEATURE]: Desktop GUI - Thinking process disappears and cannot be viewed in detail #8789: Desktop GUI - Thinking process disappears and cannot be viewed in detail (thinking content not persisting)
Incorrect model IDs for Vertex Anthropic #9565: Incorrect model IDs for Vertex Anthropic (Vertex Anthropic provider configuration issues)
Bug: Shared state between google-vertex and google-vertex-anthropic providers causes auth conflict #7514: Bug: Shared state between google-vertex and google-vertex-anthropic providers (Vertex AI provider conflicts)

Feel free to ignore if none of these address your specific case.

this should be fairly straight forward to fix, i hope will look

fix(provider): add thinking presets for Google Vertex Anthropic

Thanks for the issue and the fix! I tried with OpenCode v1.1.34 and I'm still not seeing thinking with Claude Opus 4.5 via Vertex Anthropic (with /thinking enabled and variant set to high).

I think the npm string in #9953 should be @ai-sdk/google-vertex instead of @ai-sdk/google-vertex/anthropic based on the models.dev data?

$ jq '."google-vertex-anthropic" | {id, npm, name}' ~/.cache/opencode/models.json

{
  "id": "google-vertex-anthropic",
  "npm": "@ai-sdk/google-vertex",
  "name": "Vertex (Anthropic)"
}

@rekram1-node

@rekram1-node I also just tested v1.1.34 and reasoning is still not working.
cc @zerone0x

Opened #10442.
Tested locally and I can see thinking properly using Opus on Vertex following these changes :)

@rekram1-node

Hey @rekram1-node, just tested version 1.1.36 - reasoning still doesn't work on Vertex.
I suspect that this is because of this line I initially added that was removed before merging, which was part of the fix.

if (provider.id === "google-vertex-anthropic") return "@ai-sdk/google-vertex/anthropic"

I'd also recommend keeping the tests (or at least some of them), since they probably would've helped noticing that problem by failing if someone removes this line.

Please merge

Just tested, and can confirm reasoning works now for Anthropic models through Vertex, following the merge of anomalyco/models.dev#717 and running opencode models --refresh.

Thanks!

@MichaelYochpaz

thanks for ur prs @MichaelYochpaz apologies for delays it is super hard to see things rn due to sheer volume

Same here, confirming that thinking is working now for Anthropic Vertex models. Thanks all for pushing this through! ❤️

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Reasoning Doesn't Work for Claude Models through Vertex Provider #9894

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Reasoning Doesn't Work for Claude Models through Vertex Provider #9894

Description

Description

Plugins

OpenCode version

Steps to reproduce

Screenshot and/or share link

Operating System

Terminal

Activity

github-actions commented on Jan 21, 2026

rekram1-node commented on Jan 22, 2026

koverholt commented on Jan 23, 2026

MichaelYochpaz commented on Jan 23, 2026

MichaelYochpaz commented on Jan 24, 2026

MichaelYochpaz commented on Jan 26, 2026

r-bit-rry commented on Jan 27, 2026

MichaelYochpaz commented on Jan 31, 2026

rekram1-node commented on Jan 31, 2026

koverholt commented on Jan 31, 2026

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