Gemini 3 Pro vs Claude 4.5 Opus: A guide to choosing the best AI model

Gemini 3 Pro (Google/DeepMind) and Claude Opus 4.5 (Anthropic) are both 2025 frontier models focused on deep reasoning, agentic workflows, and stronger coding/multimodal capabilities. Gemini 3 Pro is positioned as Google’s broad, multimodal “reasoner + agent” with huge context windows and integrated product surfaces; Claude Opus 4.5 is Anthropic’s recalibrated Opus family member optimized for coding, token efficiency and agent orchestration at a lower API cost than prior Opus models. Below I compare features, public benchmark signals, reasoning and coding behavior, agent and multimodal strengths, price etc.

What is Gemini 3 Pro and what are its key features?

Gemini 3 Pro is Google/DeepMind’s 2025 flagship multimodal model designed for deep reasoning, long-horizon agentic tasks, and rich multimodal inputs (text, images, audio, video). It’s offered across Google surfaces (Gemini app, AI Studio, Vertex AI) and includes specialized variants (e.g., “Deep Think”) for extra deliberation.

Key technical and product features

• Multimodal understanding: explicit support for text + images + video + audio reasoning, with Gemini 3 Pro advances multimodal fidelity and interactivity.
• Agent-first capabilities: tool-calling, background agents, and integration with Google’s “Antigravity”/Agent platforms for orchestrating multi-agent coding/workflows.
• Reasoning modes: “Deep Think” or “thinking level” controls (low/high) to trade latency for deeper chain-of-thought style processing.
• Sparse Mixture-of-Experts (MoE) architecture: Gemini 3 Pro uses a sparse MoE design to scale capacity while keeping per-token compute lower — an architectural choice Google credits for its reasoning and long-context gains.

Typical use cases

• Multimodal assistance (image + text + video analysis)
• Search-grounded answers and retrieval augmented generation (RAG)
• Product integrations (Docs, Gmail, Google Search AI Mode)
• Interactive agents that need web grounding or cloud toolchains

What is Claude Opus 4.5 and what are its core features?

Claude Opus 4.5 (often written Claude Opus 4.5 or claude-opus-4-5-20251101) is Anthropic’s newest Opus-tier LLM release (announced Nov 24, 2025) optimized for heavy developer workflows, code migration/refactoring, and agentic workflows such as GitHub Copilot integrations. Anthropic positions Opus 4.5 as their most capable Opus model to date with significant improvements in coding benchmarks and alignment.

Key features

• Coding and software engineering focus: Opus 4.5 leads internal software engineering benchmarks (SWE-bench and related tests), showing strong performance on code synthesis, refactoring and long multi-step code tasks.
• Agentic/Tooling improvements: Optimized for agent workflows — lower token usage and more reliable tool calls for multi-step orchestrations (examples: GitHub Copilot integration, enterprise agent pipelines).
• Alignment & safety: Opus 4.5 improved resistance to prompt injection and more predictable safety behavior. Early reviews note Opus 4.5 as Anthropic’s strongest alignment release so far.
• Cost optimization: Anthropic cut Opus pricing to $5 per 1M input tokens / $25 per 1M output tokens, a material reduction aimed at broader adoption.

Typical use cases

• Large codebase migration & refactorings
• Enterprise agents (document search + tool chains)
• Productivity automation (Excel / Office workflows)
• Security-sensitive assistant deployments where alignment matters

Gemini 3 Pro (Preview) vs Claude Opus 4.5 — side-by-side comparison

How do their architectures and core capabilities compare?

Are their foundational architectures different?

Yes — at a high level the two adopt different scaling/architecture tradeoffs.

Gemini 3 Pro: sparse Mixture-of-Experts (MoE): Gemini 3 Pro’s model card and PDF explicitly list a sparse mixture-of-experts architecture; MoE lets the model have very large capacity (many experts) while activating only a subset per token, lowering inference cost per token and enabling very large effective parameter counts and very long context handling. This is a stated architectural decision from DeepMind/Google.

Claude Opus 4.5: hybrid reasoning with transformer backbone + efficiency modes. Anthropic describes Claude’s design as hybrid reasoning — modes that trade instant responses for extended, deeper reasoning — and provides mechanisms (effort/efficiency settings, context compression) to reduce token use while keeping performance. Anthropic does not publicly advertise a MoE backbone for Opus; instead the focus is on reasoning modes, alignment, and tooling (agents, file editing).

What does that mean in practice:

• Long-context & huge data ingestion: Gemini’s MoE + 1M context architecture gives it an edge for extremely large single-request inputs (e.g., 1M tokens — thousands of pages, large codebases, or long video transcripts). Claude’s Opus 4.5 sits lower (200k tokens) in standard mode but benefits from Anthropic’s context tools, summarization, and efficiency controls to handle long tasks economically.
• Specialization vs generality: Opus 4.5 is explicitly tuned and marketed for software engineering and agentic automation, often performing agentic sequences with fewer tokens. Gemini 3 Pro aims for general frontier capability across reasoning, multimodality, and parametric knowledge.

How do they implement reasoning/“thinking”?

• Anthropic (Claude Opus 4.5): hybrid reply modes (fast vs extended thinking), explicit agent/tool orchestration and developer controls like effort to tune depth vs latency. Anthropic highlights efficiency gains in multi-step engineering tasks (fewer token iterations and fewer tool call errors).
• Google (Gemini 3 Pro): internal “thinking” and Deep Think mode that invests extra internal compute for complex reasoning tasks, plus deep grounding and multimodal fusion layers to integrate video/audio/pdf inputs. Google documents explicit support for tool chaining and agentic behaviors as part of the developer toolkit.

Practical takeaway: for tasks that require rugged, repeated engineering work (long agent sessions, code migration, continuous tool use), Anthropic emphasizes robustness and lower iteration counts; for complex, multimodal research and single-shot ingestion of massive datasets, Gemini’s 1M+ context and multimodal fusion are strong advantages.

How do technical specifications and benchmarks compare?

Neither single benchmark tells the whole story — but aggregators , a consistent picture emerges: Gemini 3 Pro is marketed as the best generalist multimodal reasoner with extremely large context support; Claude Opus 4.5 is marketed as the best coder and agentic workhorse with strengthened safety.

Below are representative benchmark results reported by independent analysts and labs (context: late Nov — Dec 2025).

Benchmarks (representative numbers)

• Gemini 3 Pro : high marks across reasoning and parametric knowledge: e.g., SimpleQA Verified ~72.1%, Humanity’s Last Exam 37.5% (no tools), Terminal-Bench 54.2% on agentic coding benchmarks (figures shown by DeepMind).
• Claude Opus 4.5 : Anthropic highlights Opus 4.5’s strong SWE-bench Verified performance for software engineering and improved token efficiency vs prior Opus. Independent writeups report Opus 4.5 achieving strong scores on coding and some reasoning tasks, sometimes outperforming Gemini on specific engineering-centric benchmarks (discrepancies depend on which benchmark and configuration).
• Gemini 3 Pro looks dominant on broad multimodal knowledge and parametric benchmarks as presented by Google. Opus 4.5 appears specifically tuned to excel at real-world software engineering tests and agentic workflows and to be more token-efficient on those workflows per Anthropic’s claims.

Which model is better at agentic workflows and proxying tools?

Agentic capabilities (tool use, secure function calls, orchestrating APIs/services) are central to both vendors’ roadmaps.

Gemini 3 Pro: agents + interactive UI

Google has integrated Gemini into several agent-like UIs (Search AI Mode, Gemini CLI), and advertises agentic coding and workflow features. Gemini’s long context and multimodal reasoning make it strong for agents that need to synthesize many data sources (documents, tables, charts, images) before acting. Paid tiers give access to extended agent features. ([blog.google][1])

Claude Opus 4.5: safety-first agents with robust tool control

Anthropic built Opus 4.5 with explicit emphasis on agentic robustness and safety: its updates focus on resisting prompt injection and dangerous/tool misuse while still allowing heavy tool use. This makes Opus 4.5 attractive where you must delegate powerful actions (code execution, data access) but maintain strict safety guarantees. Opus 4.5 has better resistance to prompt attacks in many tests. ([vellum.ai][6])

How do the multimodal capabilities compare?

Both models are explicitly multimodal; differences are in emphasis and integration.

Gemini 3 Pro: broad multimodality and large-context visual reasoning

Google positions Gemini 3 Pro as a top multimodal generalist: images, charts, videos and complex documents are first-class inputs. Gemini’s visual reasoning scores are often reported near the top of public leaderboards, and the model’s tight integration with Google Search and Nano Banana family helps in tasks that blend internet knowledge with image/video understanding. ([Google DeepMind][8])

Claude Opus 4.5: focused multimodality with strong document and chart understanding

Opus 4.5 supports image+text inputs and performs well on mixed tasks; Anthropic’s messaging emphasizes high accuracy on document analysis and chart understanding when tied to structured reasoning and tool flows. On some visual reasoning metrics the Opus variant trails Gemini slightly, but remains competitive and often outperforms older baselines.

How do API access and pricing compare?

Anthropic (Claude Opus 4.5)

• Model identifier: claude-opus-4-5-20251101 (Anthropic / Vertex / cloud partners publish variants).
• Pricing (official Anthropic announcement): $5 / 1M input tokens and $25 / 1M output tokens for Opus 4.5.
• Availability: Anthropic API, Anthropic apps, and CometAPI.

Google (Gemini 3 Pro Preview)

• Model access: Gemini 3 Pro is offered via Google AI Studio / Gemini Developer API and CometAPI
• Pricing: Preview pricing listed on Google docs: $2 / $12 per 1M tokens (input / output) for the <200k tier; higher rates for >200k (examples in docs show $4 / $18 for >200k).
• Subscriptions & product plans: Google AI Pro / AI Ultra subscription tiers ($19.99/mo and higher) can include priority access to Gemini 3 Pro in product integrations (Search/Docs) and extra features.

If you want to use two models simultaneously, I recommend CometAPI, which provides both Gemini 3 Pro Preview API and Claude Sonnet 4.5 API, and is priced at 20% of the official price.

Practical recommendations (which to choose, when)

If your priority is multimodal reasoning & integration with Google products

Choose Gemini 3 Pro if you need best-in-class multimodal understanding, Search grounding, and deep integration with Google AI Studio or other Google tooling. It looks especially strong where image + text + search grounding matters. ([Google AI for Developers][2])

If your priority is production coding, agentic reliability, and fewer iterations

Choose Claude Opus 4.5 if you need robust code generation, safer multi-step tool use, and fewer human corrections in operational workflows — Anthropic emphasizes improved tool reliability and fewer errors. This can translate to lower operational costs per completed task. ([anthropic.com][5])

Hybrid approach

For many teams the right approach is hybrid:

• Use Gemini 3 Pro for image-heavy, UX/prototyping, and search-grounded workflows.
• Use Opus 4.5 for backend code generation, CI/CD automation, and agentic orchestration tasks.
  Route tasks to whichever model historically produces fewer edits / lower $ per accepted output.

Conclusion

Gemini 3 Pro and Claude Opus 4.5 are both frontier models with complementary strengths. Gemini 3 Pro — with Google’s product integrations and very large context multimodality — is a top pick for research, multimedia analysis and doc+image workflows. Claude Opus 4.5 — with demonstrably leading coding performance, token efficiency on software tasks, and a heavy emphasis on agentic safety — is a top pick for engineering teams that want robust code generation and safer agent deployment. The right model for you depends on your workload, expected scale, safety posture and budget; the only reliable way to choose is to run the reproducible tests above on your actual tasks.

Developers can access Gemini 3 Pro Preview API and Claude Opus 4.5 through CometAPI. To begin, explore the model capabilities of CometAPI in the Playground and consult the API guide for detailed instructions. Before accessing, please make sure you have logged in to CometAPI and obtained the API key. CometAPI offer a price far lower than the official price to help you integrate.

Ready to Go?→ Free trial of Gemini 3 pro and Claude opus 4.5 models !