feat: add Google Vertex AI service account JSON authentication

[sandys]

Add support for authenticating to Google Vertex AI using service account JSON credentials, with proper credential separation from regular Google (Gemini) API keys.

Google Cloud actively makes it hard to use api keys with Vertex - with a complicated permission grant structure. The preferred mechanism is service accounts with json tokens. Not supporting it is a huge problem.

Changes:

• Add service account JSON auth flow in CLI (opencode auth login)
• Add TUI dialog for pasting service account JSON with location input
• Update provider loaders to use stored credentials with googleAuthOptions
• Explicitly set key: undefined and apiKey: null in Vertex loaders to prevent credential leakage from other providers
• Rename "Vertex" to "Google Vertex AI" consistently across UI:
  • /connect menu
  • Model selection dialog
  • Status bar below text entry
• Add comprehensive tests verifying credential separation between google, google-vertex, and google-vertex-anthropic providers

The three providers (google, google-vertex, google-vertex-anthropic) are now completely independent and can be configured simultaneously without credentials leaking between them.

for issues
#5712
#6280
#5711
#3586
#5097
#4282
#272
#553
#402
#1204

[rekram1-node]

/review

[github-actions]

Thanks for your contribution!

This PR doesn't have a linked issue. All PRs must reference an existing issue.

Please:

1. Open an issue describing the bug/feature (if one doesn't exist)
2. Add Fixes #<number> or Closes #<number> to this PR description

See CONTRIBUTING.md for details.

[aperepel]

are we going to push this over the hump? it's unblocking a big share of models used via Vertex.AI. They simply are blocked today otherwise.

[ddesmond]

+1 for this!

[marvinantoinette]

Strong +1
Service account JSON auth isn't just a nice-to-have - it's the standard authentication mechanism in most corporate GCP environments where API keys simply aren't an otion due to security policies and IAM governance. Without this, Vertex AI is effectively blocked for a significant portion of enterprise users. Would love to see this merged.

[bertPB]

Any updates on this?
This is a big blocker to adopt/trial opencode within our org

[sandys]

Im actually a little disappointed at this pr not getting attention from the opencode team - i have tweeted several times and gemini team have replied in support. Would appreciate if the opencode team clarify if their focus is to support their own paid models and third party models are no longer a focus. It is a struggle maintaining this pr through tons of opencode versions...and im not even sure if there is any real strategic interest in doing so.

…

On Mon, 23 Mar, 2026, 20:51 Bert Vanhaeke, ***@***.***> wrote: *bertPB* left a comment (anomalyco/opencode#6287) <#6287 (comment)> Any updates on this? This is a big blocker to adopt/trial opencode within our org — Reply to this email directly, view it on GitHub <#6287?email_source=notifications&email_token=AAASYU6AW7VRJ4C267KFMI34SFI5ZA5CNFSNUABFM5UWIORPF5TWS5BNNB2WEL2JONZXKZKDN5WW2ZLOOQXTIMJRGE2DKMJUHA2KM4TFMFZW63VGMF2XI2DPOKSWK5TFNZ2KYZTPN52GK4S7MNWGSY3L#issuecomment-4111451484>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAASYU2ZYQ4MAMHQ5BNEQ434SFI5ZAVCNFSM6AAAAACQFDWOE2VHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHM2DCMJRGQ2TCNBYGQ> . You are receiving this because you authored the thread.Message ID: ***@***.***>

[1n4001]

Interested in seeing this pushed across the finish line.

[naomatheus]

Is this going anywhere or has the opencode team decided to ignore this persistent issue?

[gabriel-milan]

Idk if it helps anybody, but I've been able to use it by setting the following environment variables

GOOGLE_APPLICATION_CREDENTIALS=/path/to/my/service-account.json
CLAUDE_CODE_USE_VERTEX=1
ANTHROPIC_VERTEX_PROJECT_ID=your-gcp-project-id
ANTHROPIC_VERTEX_REGION=your-vertex-region
GOOGLE_CLOUD_PROJECT=your-gcp-project-id

not really sure if they are all required but that's the setup I was using for Claude Code and it works just fine in OpenCode too