[ENHANCEMENT] Allow 1M context for Sonnet 4 and 4.5 on Vertex AI

[nickcatal]

Problem (one or two sentences)

Per Google's Documentation, Google Vertex AI supports a 1 million context window for Sonnet 4, and has beta support for a 1 million context window for Sonnet 4.5 (GA is 200k tokens)

Context (who is affected and when)

Vertex AI Users who are using Sonnet 4 or 4.5

Desired behavior (conceptual, not technical)

It's possible to use a 1 million context window for Sonnet 4 and 4.5 in Vertex AI

Constraints / preferences (optional)

No response

Request checklist

• I've searched existing Issues and Discussions for duplicates
• This describes a specific problem with clear context and impact

Roo Code Task Links (optional)

No response

Acceptance criteria (optional)

No response

Proposed approach (optional)

No response

Trade-offs / risks (optional)

No response

[roomote]

I'm exploring a potential fix for enabling 1M context windows for Claude Sonnet 4 and 4.5 on Vertex AI, as documented in Google's specifications. Will open a PR to share progress.

[nickcatal]

@roomote any way you can create a PR here?

[roomote]

Thanks @nickcatal! I've seen your request and I'm working on enabling 1M context windows for Claude Sonnet 4 and 4.5 on Vertex AI. I'll create a PR shortly with the necessary changes.

[roomote]

Hi @nickcatal! I've created PR #8685 to enable 1M context windows for Claude Sonnet 4 and 4.5 on Vertex AI as requested.

Changes made:

• Updated claude-sonnet-4@20250514 context window from 200k to 1M tokens
• Updated claude-sonnet-4-5@20250929 context window from 200k to 1M tokens
• Added comprehensive test coverage

The PR is ready for review: #8685

This aligns with Google's Vertex AI documentation showing 1M context support for these models.