[Feat] Add Gemini 4 Argon to Gemini and Vertex AI providers

[zoomote]

​Opened on behalf of @taltas. Follow up by mentioning @roomote, in the web UI, or in Discord.

Related GitHub Issue

No linked issue. This change was requested directly by a maintainer (Toray Altas) via Discord: register Google's new Gemini 4 Argon model in the relevant providers.

Description

Adds gemini-4-argon to the two provider registries that enumerate Gemini models statically:

• packages/types/src/providers/gemini.ts (Google Gemini API / AI Studio)
• packages/types/src/providers/vertex.ts (GCP Vertex AI)

The model pickers in the webview read these registries dynamically, so the new entry appears in the UI with no further wiring. Providers that fetch their catalog at runtime (OpenRouter, Requesty, Unbound, Vercel AI Gateway, Zoo Gateway) need no static entry, and their legacy fallback sets were not extended for Gemini 3.x either, so this PR follows that convention.

Metadata used (per 1M tokens, promo Global Standard tier pricing through November 30, 2026):

• Context window: 1,048,576 tokens, shared across input, thinking, and output.
• Max output: 65,536 tokens per streaming request. Long decodes up to 1,048,576 tokens go through continuation tokens.
• Thinking levels: low, medium (default), high. supportsReasoningBudget: false because thinking_budget returns an HTTP 400 error on this model.
• supportsTemperature: false because the backend ignores temperature/top_p/top_k.
• Pricing: input $2.00, output $10.00 (includes thinking tokens), cached input $0.10. From December 1, 2026 these become $4.00 / $20.00 / $0.20 (noted in code comments). Vertex non-global locations are +10%.
• Caching: implicit only, automatic for prompt prefixes of 6,144 tokens or more. Explicit context caching is not supported, so no cacheWritesPrice.

Availability verified before registering (checked today):

• Gemini Developer API: gemini-4-argon is listed on https://ai.google.dev/gemini-api/docs/models (Gemini 4, stable) and on https://ai.google.dev/gemini-api/docs/pricing (paid tier only; not on the Free tier or Google AI Pro plan).
• Vertex AI: available in the global, us, and eu locations per https://cloud.google.com/gemini-enterprise-agent-platform/models/guides/gemini-4-argon.
• OpenRouter: google/gemini-4-argon is live in the catalog API with matching pricing, 1,048,576 context, 65,536 max output, and mandatory reasoning (low/medium/high, default medium). OpenRouter is fetched dynamically in Zoo Code, so no code change was needed there.
• Vercel AI Gateway: google/gemini-4-argon is live in its /v1/models catalog. Also fetched dynamically.

The gated gemini-4-argon-cyber-permissive variant (Fairwind-approved cybersecurity workloads, default thinking HIGH) is intentionally not registered: it is access-restricted and there is no gated-variant precedent for such SKUs in these registries.

Test Procedure

• Added a describe.each block in packages/types/src/__tests__/google-models.test.ts that asserts the documented limits, thinking levels, default effort, promo pricing, and caching flags for gemini-4-argon on both the Gemini API and Vertex AI registries.
• pnpm vitest run src/__tests__/google-models.test.ts in packages/types: 8/8 passed.
• pnpm run check-types in packages/types: passed.
• Full pnpm test from the repository root: 532 test files, 10,580 tests passed. (One earlier full-suite run showed 2 flaky failures in src/__tests__/extension.spec.ts; that file passes standalone on clean main and with this change, and the rerun is green.)
• pnpm exec eslint --max-warnings=0 on the three touched files: clean.

Pre-Submission Checklist

• Issue Linked: No GitHub issue exists; change requested by a maintainer via Discord (see "Related GitHub Issue").
• Scope: My changes are focused on the linked issue (one major feature/fix per PR).
• Self-Review: I reviewed my own code with care.
• Writing Style: The PR title and description use Simplified Technical English (ASD-STE100): short sentences, plain words, active voice, one idea per sentence, no contractions.
• Testing: New and/or updated tests have been added to cover my changes (if applicable).
• Visual Snapshot (UI changes only): Not applicable. This is a data-only registry entry; no layout, theme token, or rendered-state change. Behavior is covered by Vitest.
• Documentation Impact: I checked if my changes need documentation updates (see "Documentation Updates" section below).
• Contribution Guidelines: I read and agree to the Contributor Guidelines.

Visual Snapshots

Not applicable: no layout, theme, or rendered-state change. The model picker lists the new entry dynamically from geminiModels.

Videos (interaction / animation only)

Not applicable: no new interaction flow or animation.

Documentation Updates

• No documentation updates are required.
• Yes, documentation updates are required. Paired docs PR: [Docs] Document Gemini 4 Argon on Gemini and Vertex AI provider pages Zoo-Code-Docs#66 adds a "Gemini 4 Argon" section to the Google Gemini and GCP Vertex AI provider pages.

Additional Notes

Sources: https://cloud.google.com/gemini-enterprise-agent-platform/models/guides/gemini-4-argon and https://cloud.google.com/vertex-ai/generative-ai/pricing.

Get in Touch

Toray Altas (taltas) on Discord.

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✅ All modified and coverable lines are covered by tests.

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