Short answer: For a new production integration, neither exact model is a sensible starting point. Google says Gemini 3 Pro Preview was shut down on March 9, 2026. Anthropic says Claude Sonnet 4.5 remains functional but is deprecated and scheduled to retire on November 30, 2026. These status statements concern the direct Gemini Developer API and Claude API; availability through a partner or another channel may differ. (Google’s Gemini 3 Pro Preview documentation; Anthropic’s Sonnet 4.5 documentation)
If you already use Sonnet 4.5, plan and test a migration before its scheduled retirement. Google’s deprecation schedule names Gemini 3.1 Pro Preview as a recommended replacement for Gemini 3 Pro Preview. Confirm that the replacement is currently supported in your API channel before migrating. (Google’s deprecation schedule)
At a glance
| Production question | Claude Sonnet 4.5 | Gemini 3 Pro Preview |
|---|---|---|
| API status | Deprecated, still functional according to Anthropic; scheduled to retire November 30, 2026 | Google says the preview API shut down March 9, 2026 |
| Production decision | Avoid for a new long-lived integration; plan migration if already in use | The shut-down Gemini Developer API model is not available for new calls |
| Historical specifications supported by the supplied provider documentation | 200K-token context; up to 64K output tokens | The available excerpt confirms shutdown, but does not establish exact context or output limits |
| Base API rates reported on the Sonnet 4.5 model page | $3 per million input tokens; $15 per million output tokens | No current rate for the shut-down model |
The lifecycle and Sonnet figures above are provider-reported documentation claims. They do not establish that one model produces better results. The Gemini entry is a retired preview, not a currently available service. (Anthropic’s Sonnet 4.5 documentation; Google’s Gemini 3 Pro Preview documentation)
What the comparison evidence can—and cannot—tell you
A previous content-focused comparison proposed Sonnet 4.5 for consistent, brand-sensitive long-form writing and Gemini 3 Pro for research-heavy or multimodal work. That article did not provide a reproducible head-to-head test. Treat those suggestions as hypotheses for your own evaluation, not as a verified quality ranking. Search grounding can help retrieve information; it does not guarantee accuracy or eliminate the need to check important claims. (Cosmic’s comparison)
The available provider material supports a lifecycle comparison and some Sonnet 4.5 limits and rates, but it does not establish a current, like-for-like performance winner. Also, Gemini 3 Pro’s shutdown means teams cannot now run a fresh production-API comparison against it through that endpoint. If you need to assess historical outputs, use archived logs or a previously retained test set; do not treat that as evidence of current API availability.
API availability and model IDs
Anthropic reports that Claude Sonnet 4.5 is deprecated but remains functional until its scheduled November 30, 2026 retirement. That remaining service window may matter to an existing application, but it makes the model a poor default for a new long-lived integration. Check Anthropic’s model documentation and your account’s API channel before relying on a specific identifier or planning a migration. (Anthropic’s Sonnet 4.5 documentation)
Google identifies Gemini 3 Pro Preview as shut down on March 9, 2026. The model code reported in the Gemini Developer API documentation is gemini-3-pro-preview; an identifier in old sample code or a third-party wrapper does not restore access to a shut-down endpoint. (Google’s Gemini 3 Pro Preview documentation)
For migration, Google’s deprecation schedule lists Gemini 3.1 Pro Preview as the recommended replacement for Gemini 3 Pro Preview. Verify that recommendation and the current supported model in the documentation for the specific API channel you use. (Google’s deprecation schedule)
API pricing: what is comparable
Anthropic’s Sonnet 4.5 model documentation reports base rates of $3 per million input tokens and $15 per million output tokens. Treat these as the rates reported for that model, not as a price comparison with Gemini 3 Pro: Google shut down the Gemini 3 Pro Preview API, so there is no current billable rate for calling that model through the former endpoint. Check provider pricing and account terms before budgeting a deployment. (Anthropic’s Sonnet 4.5 documentation; Google’s Gemini 3 Pro Preview documentation)
Older third-party articles reported Gemini 3 Pro prices, but they are historical claims and not a usable current quote for a shut-down model. Do not substitute a successor’s price and label it Gemini 3 Pro pricing.
Sonnet 4.5 cost illustration: using the reported base rates, 10,000 input tokens and 2,000 output tokens would cost $0.06: (10,000 ÷ 1,000,000 × $3) + (2,000 ÷ 1,000,000 × $15). This is a simple rate calculation, not a comparison with Gemini 3 Pro or a full estimate of production costs.
How to choose a replacement for production
Run a small, controlled evaluation on models that are currently available in the API channel you intend to deploy. This is a proposed method, not a test performed for this comparison:
- Choose representative tasks. Include the writing, research, document, or multimodal tasks that matter to your application.
- Use consistent inputs and acceptance criteria. Define success before comparing outputs—for example, factual correctness, required details, format compliance, or successful completion of a task.
- Record human correction effort. Track pass rates and review or revision time, not just which output sounds better.
- Calculate cost per accepted output. Use current provider rates and observed token counts, then divide total spend by the number of outputs that meet your acceptance bar.
- Verify deployment conditions. Confirm model status, access, limits, and applicable terms in the provider documentation for the exact model and API channel you plan to use.
Decision: If the choice must be exactly Claude Sonnet 4.5 versus Gemini 3 Pro, lifecycle status decides the production question: Gemini 3 Pro Preview’s API is shut down, and Sonnet 4.5 is scheduled to retire on November 30, 2026. For a new integration, compare currently supported models on your actual workload and confirm the migration path in the relevant provider documentation. Historical feature claims or prices cannot establish which replacement will perform better for your application.
Sources
Claude Sonnet 4.5 — Claude Platform Docs
Gemini 3 Pro Preview — Gemini API
Gemini deprecations — Gemini API
Claude 4.5 vs Gemini Pro: Which AI is Better for Content Creation?