Claude Opus 4.6 vs Gemini 3.1 Pro: Definitive Comparison (2026)
By Loïc Jané · Founder, Fleece AI
Gemini 3.1 Pro vs Claude Opus 4.6: The Definitive Comparison
At a Glance: On Google's published comparison, Gemini 3.1 Pro leads on agentic and reasoning benchmarks (APEX-Agents 33.5% vs 29.8%, MCP Atlas 69.2% vs 59.5%, ARC-AGI-2 77.1% vs 68.8%) at less than half the price ($2 vs $5 per million input tokens). Claude Opus 4.6 leads on SWE-Bench Verified (80.8% vs 80.6%), supports computer use, and writes twice as much in one response (128K vs 65K output tokens). On Scale's independent MCP-Atlas leaderboard, re-scored in April 2026, the gap is much smaller: 78.2% vs 76.8%.
Update (October 2026): Gemini 3.1 Pro is still Google's latest Pro model and is still labelled Preview; Google's Gemini Pro page says "3.5 Pro coming soon". On Anthropic's side, Claude Opus 4.6 is now a legacy model. Anthropic recommends Claude Opus 5.5 ($4/$20 per million tokens) for most workloads, lists Claude Fable 5.1 ($10/$50) for the hardest reasoning work, and its Sonnet tier is now Claude Sonnet 5.5 ($2/$10). Terminal-Bench is now at version 4.0, so the scores below describe the February 2026 matchup, not today's leaderboards. On Fleece AI, Claude Opus 4.6 is no longer selectable for new agents (agents already pinned to it keep running); the Business plan offers Claude Opus 5.5, 4.8 and 4.7. Gemini is not offered.
Two frontier models led agentic AI in February 2026: Google's Gemini 3.1 Pro and Anthropic's Claude Opus 4.6. Anthropic released Opus 4.6 on February 5, 2026. Google's API docs list Gemini 3.1 Pro Preview as last updated in February 2026. This Claude Opus 4.6 vs Gemini 3.1 Pro comparison measures both on published benchmarks — APEX-Agents, SWE-Bench, ARC-AGI-2, MCP Atlas — then compares prices. They were built for the same job: complex reasoning and multi-step tool use. They take different routes to it.
For a full overview of all frontier models, see our Best AI Models for Automation 2026 comparison. For the measurement details behind each score, see AI Agent Benchmarks 2026 Explained.
Benchmark Comparison
Google published all of these scores side by side on its Gemini Pro page: Gemini 3.1 Pro at high thinking against Claude Opus 4.6 at max thinking. They are vendor-reported numbers, run by Google.
| Benchmark | Gemini 3.1 Pro | Claude Opus 4.6 | Winner |
|---|---|---|---|
| APEX-Agents (professional tasks) | 33.5% | 29.8% | Gemini 3.1 Pro |
| ARC-AGI-2 (reasoning) | 77.1% | 68.8% | Gemini 3.1 Pro |
| MCP Atlas (tool coordination) | 69.2% | 59.5% | Gemini 3.1 Pro |
| BrowseComp (web research) | 85.9% | 84.0% | Gemini 3.1 Pro |
| Terminal-Bench 2.0 (Terminus-2 harness) | 68.5% | 65.4% | Gemini 3.1 Pro |
| SWE-Bench Verified (coding) | 80.6% | 80.8% | Claude Opus 4.6 |
| τ2-bench Retail (customer-service tools) | 90.8% | 91.9% | Claude Opus 4.6 |
| GDPval-AA (knowledge work, Elo) | 1317 | 1606 | Claude Opus 4.6 |
Source: Google DeepMind, Gemini Pro model page, retrieved 2026-10-13. Vendor-reported by Google.
Gemini 3.1 Pro wins 5 of these 8 rows. Claude Opus 4.6 wins 3. The SWE-Bench and τ2-bench gaps are about one point, which is within normal run-to-run noise.
Anthropic's own launch figures for Opus 4.6 are higher in places because it used different harnesses: 81.42% on SWE-bench Verified (with a prompt modification, averaged over 25 trials), 86.8% on BrowseComp (with a multi-agent harness) and 62.7% on MCP Atlas at high effort. Anthropic also said Opus 4.6 had the highest Terminal-Bench 2.0 score at its release on February 5 — two weeks before Gemini 3.1 Pro. Source: Anthropic, Introducing Claude Opus 4.6, retrieved 2026-10-13.
The independent MCP-Atlas leaderboard
Scale's MCP-Atlas leaderboard runs every model itself. In April 2026 Scale upgraded the scoring judge, added retries for transient tool errors and replaced the 20-turn limit with a 100-tool-call budget, then re-scored every model. Under that method the two models are close.
| MCP-Atlas (Scale leaderboard, all 1,000 tasks) | Pass rate |
|---|---|
| Gemini 3.1 Pro (high) | 78.2% |
| Claude Opus 4.6 (max) | 76.8% |
| Gemini 3 Pro (preview) | 70.3% |
Source: Scale Labs, MCP-Atlas leaderboard, retrieved 2026-10-13. Leaderboard-run, April 2026 methodology.
Capabilities Comparison
| Feature | Gemini 3.1 Pro | Claude Opus 4.6 |
|---|---|---|
| Provider | Google DeepMind | Anthropic |
| Released | February 2026 (Preview) | February 5, 2026 |
| Context Window | 1M tokens (1,048,576) | 1M tokens (beta at launch, standard pricing today) |
| Output Tokens | 65K (65,536) | 128K |
| Thinking/Reasoning | Thinking levels: low, medium, high (default high) | Adaptive thinking with effort levels |
| Computer Use | Not listed in the 3.1 Pro model card | Yes |
| Agent Teams | — | Research preview in Claude Code |
| Customtools Variant | Yes (gemini-3.1-pro-preview-customtools) | No |
| MCP Support | Yes | Yes (Anthropic created MCP) |
Sources: Gemini 3.1 Pro Preview model page, Gemini thinking docs, Anthropic launch post and Claude models overview, all retrieved 2026-10-13.
Pricing Comparison
| Metric (per million tokens) | Gemini 3.1 Pro | Claude Opus 4.6 |
|---|---|---|
| Input (prompts up to 200K) | $2.00 | $5.00 |
| Output (prompts up to 200K) | $12.00 | $25.00 |
| Input / output (prompts over 200K) | $4.00 / $18.00 | $5.00 / $25.00 (same rate across 1M) |
| Cached input | $0.20 | $0.50 |
| Batch input / output | $1.00 / $6.00 | $2.50 / $12.50 |
Sources: Gemini API pricing (Standard and Batch tiers) and Claude API pricing, retrieved 2026-10-13. At launch, Anthropic charged $10/$37.50 for Opus 4.6 prompts over 200K tokens; that premium has since been dropped.
Gemini 3.1 Pro is 2.5x cheaper on input and about 2x cheaper on output for normal-length prompts. For high-volume agent workloads, that gap compounds.
Both vendors price a cache hit at 10% of the base input rate, so caching does not change the ratio: $0.20 for Gemini against $0.50 for Opus 4.6. Both also halve prices on their Batch APIs. Anthropic states that the batch and caching discounts stack, which puts cached batch input on Opus 4.6 at about $0.25 per million tokens. The one place the gap narrows is very long prompts: above 200K tokens Gemini doubles its input rate to $4, while Opus 4.6 stays at $5.
What Changed Between Generations
Gemini 3.1 Pro was a large step over Gemini 3 Pro on Google's own table: APEX-Agents went from 18.4% to 33.5%, MCP Atlas from 54.1% to 69.2%, and ARC-AGI-2 from 31.1% to 77.1%, at the same $2/$12 list price. Claude Opus 4.6 raised Opus output capacity to 128K tokens and introduced a 1M-token context window (in beta at launch), which changed which jobs can finish in a single pass — reports, batch code review and long refactors no longer need mid-task stitching. If you are migrating from Gemini 3 Pro or Opus 4.5, re-run your own workload benchmarks before switching: per-workflow results often differ from suite numbers.
When to Choose Gemini 3.1 Pro
- Multi-app workflows: the higher APEX-Agents and MCP Atlas scores point to better end-to-end task completion, and the customtools endpoint is tuned to prioritize your own tools
- Large document processing: 1M-token context window, useful for contract analysis and legal document review
- Cost-sensitive deployments: 2.5x cheaper per input token
- Google Cloud environments: available through Vertex AI
- High-volume automation: lower cost per workflow execution
When to Choose Claude Opus 4.6
- Coding-heavy workflows: a narrow lead on SWE-Bench Verified, and strong on large codebase refactoring and multi-file edits
- Long-form output: 128K output tokens (about 2x Gemini 3.1 Pro's 65K)
- Computer use / GUI automation: supported by Opus 4.6, not listed for Gemini 3.1 Pro
- Knowledge work: a large lead on GDPval-AA in Google's own table
- Very long prompts: one flat rate across the full 1M-token window
- Today, most of these reasons point to its successor, Claude Opus 5.5, which costs less ($4/$20) than Opus 4.6
Normalized Cost per Task
Published per-token prices are only comparable once they are normalized by the tokens a workflow actually consumes. Gemini 3.1 Pro is cheaper on both sides at normal prompt lengths — $2 vs $5 input and $12 vs $25 output per million tokens — so it wins on raw per-run cost for most short tool-calling loops. Claude Opus 4.6's larger output budget lets longer results finish in one pass, which can avoid a second call. Note also that Claude 4.7 and later models use a newer tokenizer that Anthropic says produces about 30% more tokens for the same text, so compare cost per task, not cost per token, when you look at newer Claude models.
Real-World Use Case Comparison
| Use Case | Better Model | Why |
|---|---|---|
| Email summarize + post to Slack | Gemini 3.1 Pro | Multi-tool workflow, cost efficient |
| Code review across PR diffs | Claude Opus 4.6 | SWE-Bench lead, long output |
| Weekly cross-app report | Gemini 3.1 Pro | APEX-Agents leader, large context |
| Contract analysis (50+ pages) | Claude Opus 4.6 | 128K output for detailed analysis |
| Real-time data sync (hourly) | Neither — use a Flash-tier model such as Gemini 3.8 Flash | Speed and cost matter most |
| GUI-based web scraping | Claude Opus 4.6 | Computer use support |
| Research digest from arXiv | Claude Opus 4.6 | Deep reasoning + long output |
| CRM + email + calendar automation | Gemini 3.1 Pro | Multi-MCP coordination leader |
Try Claude Opus on Fleece AI — Start your 4-day trial with GLM 5.3 Flash, Kimi K3 and GPT-5.2, then upgrade to Business for Claude Opus 5.5, 4.8 and 4.7. Fleece AI does not offer Gemini.
The Verdict
Gemini 3.1 Pro is the better choice for most agentic workflow automation: on Google's published comparison it leads on professional tasks (APEX-Agents), tool coordination (MCP Atlas) and abstract reasoning (ARC-AGI-2), at less than half the price. On Scale's independent MCP-Atlas leaderboard its lead is small, so test both on your own workflows.
Claude Opus 4.6 is the better choice for coding agents, computer use and workflows that need very long outputs (128K tokens). At launch, Anthropic positioned it as its most capable model; that role has since passed to Claude Opus 5.5, with Claude Fable 5.1 above it for the hardest reasoning work.
On Fleece AI, GLM 5.3 Flash is the default model and GPT-5.2 is available on every plan, with Claude Opus (5.5, 4.8 and 4.7) available on the Business plan for deep analysis workflows. Outside Fleece AI, if you need a middle ground between cost and capability, Anthropic's Sonnet tier — Claude Sonnet 4.6 in February, Claude Sonnet 5.5 today at $2/$10 per million tokens — is priced below Opus. The choice between Gemini 3.1 Pro and Claude Opus 4.6 depends on whether your workflows prioritize multi-app orchestration (Gemini) or code generation and long outputs (Claude). Match the model to the workload, not the marketing.
Frequently Asked Questions
Is Gemini 3.1 Pro really better than Claude Opus 4.6?
On Google's published benchmarks (APEX-Agents, MCP Atlas, ARC-AGI-2, BrowseComp, Terminal-Bench 2.0), yes — Gemini 3.1 Pro leads. Claude Opus 4.6 leads narrowly on SWE-Bench Verified and τ2-bench Retail, clearly on GDPval-AA, and supports computer use. On Scale's independent MCP-Atlas leaderboard the two are within 1.4 points. Neither model dominates every category.
Why is Gemini 3.1 Pro so much cheaper?
Google prices it at $2/$12 per million tokens for prompts up to 200K tokens, against $5/$25 for Claude Opus 4.6. That is a pricing decision, not a disclosed cost difference. Gemini 3.1 Pro kept the $2/$12 list price of Gemini 3 Pro while scoring much higher on Google's benchmark table.
Can I use both models together?
Yes. Many developers use Gemini 3.1 Pro for high-volume tool-calling workflows and a Claude Opus model for complex analysis and coding tasks. On Fleece AI, you can set a different model per agent and per workflow.
Can I use both models in Fleece AI?
Not both. Fleece AI does not offer Gemini models. Claude Opus 4.6 is no longer selectable for new agents (agents already pinned to it keep running); the Business plan offers Claude Opus 5.5, 4.8 and 4.7 and GPT-5.6 Sol, and Enterprise adds Claude Fable 5. Starter includes GLM 5.3 Flash (the default), Kimi K3, Qwen 3.8 Max, DeepSeek V4.1 Flash, GPT-5.2, GPT-5.6 Luna and Mistral Medium 3.5, and Pro adds GPT-5.6 Terra.
Is there a newer Gemini Pro model than 3.1 Pro?
Not as of October 13, 2026. Gemini 3.1 Pro Preview is the newest Pro model on Google's API pricing page, and Google's Gemini Pro page says "3.5 Pro coming soon" without a date.
Related Articles
- Claude Opus 5.5 Review — Anthropic's current recommended model
- Claude Opus 4.6 Review — the model in this comparison
- Best AI Model for Tool Calling 2026 — tool calling benchmark comparison
- AI Agent Benchmarks 2026 Explained — what each benchmark measures
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