Claude Opus 4.8 vs GPT-5.5 vs Gemini 3.1 Pro: June 2026 Benchmark Results, Pricing, and Which One to Actually Use
Last updated: June 3, 2026. Next review: June 10, 2026.
The three biggest frontier models just got updated within days of each other. Claude Opus 4.8 dropped with a new Fast Mode. GPT-5.5 quietly improved its terminal and agentic benchmarks. Gemini 3.1 Pro held its multimodal lead and cut prices again. At Pristren, we spent the past two weeks running these models against real workloads, not just reading benchmark summaries, so here is what the numbers look like and what they mean for actual engineering and product decisions.
The Benchmark Numbers (June 2026)
All figures below come from Artificial Analysis (AA), updated in the May-June 2026 measurement window unless a specific source is noted. Artificial Analysis is the most consistent third-party benchmark aggregator right now because they re-run evaluations on a fixed infrastructure rather than relying on vendor self-reports.
Overall Intelligence Index
| Model | AA Intelligence Index | Rank |
|---|---|---|
| Claude Opus 4.8 | 61 | 1 |
| GPT-5.5 | 60 | 2 |
| Gemini 3.1 Pro | 57 | 3 |
Source: Artificial Analysis Intelligence Index, June 2026 snapshot.
The gap between Opus 4.8 and GPT-5.5 is one point at the index level, which means they are effectively tied in general reasoning. Gemini 3.1 Pro sits four points behind on aggregate, though as we will see that number masks real strengths on specific tasks.
Coding and Software Engineering
| Model | SWE-Bench Pro | HumanEval+ | Notes |
|---|---|---|---|
| Claude Opus 4.8 | 69.2% | 94.1% | Best overall code generation |
| GPT-5.5 | 66.8% | 93.4% | Strong but trails on complex repos |
| Gemini 3.1 Pro | 62.3% | 91.7% | Weakest on multi-file refactors |
SWE-Bench Pro tests models on real GitHub issues from production codebases, which is a harder signal than toy coding challenges. Opus 4.8 at 69.2% represents a meaningful jump over the previous 4.5 generation. For agentic coding workflows where a model needs to navigate a large codebase, read tests, and submit a working patch, Opus 4.8 is the clear leader.
Mathematical Reasoning
| Model | GDPval-AA Elo | MATH-500 |
|---|---|---|
| Claude Opus 4.8 | 1890 | 91.4% |
| GPT-5.5 | 1872 | 90.8% |
| Gemini 3.1 Pro | 1841 | 88.9% |
GDPval-AA is Artificial Analysis's Elo-based math leaderboard. Again, Opus 4.8 holds the top position, but the 18-point Elo gap to GPT-5.5 is small enough that for most product use cases, the models are interchangeable on pure math.
Terminal and Long-Horizon Agents
| Model | Terminal-Bench 2.1 | Agentic Tasks (AA) |
|---|---|---|
| GPT-5.5 | 78.2% | 73.4% |
| Claude Opus 4.8 | 74.6% | 71.8% |
| Gemini 3.1 Pro | 68.1% | 64.2% |
This is the benchmark where Opus 4.8 loses. Terminal-Bench 2.1 measures how well a model completes multi-step shell tasks, handles errors mid-execution, and recovers without human intervention. GPT-5.5 scores 78.2% against Opus 4.8's 74.6%, a 3.6-point gap that is consistent across runs. If your use case is a fully autonomous coding agent that you leave running overnight, GPT-5.5 is currently the better choice for that specific workload.
Multimodal (Vision, Charts, Documents)
| Model | Multimodal AA Score | Chart QA | Document Parsing |
|---|---|---|---|
| Gemini 3.1 Pro | 84.2 | 91.3% | 88.6% |
| GPT-5.5 | 79.6 | 87.1% | 84.9% |
| Claude Opus 4.8 | 76.3 | 83.4% | 81.2% |
Gemini 3.1 Pro wins multimodal by a significant margin. If you process invoices, extract data from screenshots, or analyze charts at any meaningful volume, Gemini 3.1 Pro is the right tool. The gap is not marginal here, it is consistent across every vision benchmark we have looked at since Gemini 2.0.
Pricing (June 2026)
| Model | Input per 1M tokens | Output per 1M tokens | Context Window |
|---|---|---|---|
| Claude Opus 4.8 | $5.00 | $25.00 | 200k |
| GPT-5.5 | $6.00 | $30.00 | 128k |
| Gemini 3.1 Pro | $2.00 | $12.00 | 1M |
| Claude Haiku 3.5 (reference) | $0.80 | $4.00 | 200k |
Source: Anthropic, OpenAI, and Google pricing pages, June 3, 2026.
Gemini 3.1 Pro at $2/$12 is substantially cheaper than both Opus 4.8 and GPT-5.5. That price difference compounds fast at scale. For a product calling an LLM on every page load or every document upload, Gemini's cost profile opens up use cases that would be economically painful with the other two.
GPT-5.5 is actually the most expensive of the three on output tokens at $30 per million. That matters because output tokens dominate cost in most generation workloads.
Claude Opus 4.8's $5/$25 pricing sits in the middle, but Anthropic's recently released Fast Mode changes the calculus for latency-sensitive tasks. Fast Mode trades a small capability reduction for a significant speed improvement on well-structured prompts, which we will cover below.
