What's the difference between Gemini 3.5 Flash, GPT-5.5, and Claude Opus 4.7?

Three different bets in May 2026. Gemini 3.5 Flash (Google, launched May 19) is a small-but-frontier-class agentic model — fastest output (4x baseline) and cheapest of the three. GPT-5.5 (OpenAI) is the strongest all-rounder with the best Terminal-Bench score (78.2%) and the new ChatGPT default. Claude Opus 4.7 (Anthropic) is still the highest-quality coding model — leads SWE-bench Pro at 64.3%. Pick by workload.

Which model is best for coding?

Claude Opus 4.7 for code quality on long-horizon tasks (SWE-bench Pro: 64.3% vs GPT-5.5 58.6% vs Gemini 3.5 Flash 55.1%). GPT-5.5 for terminal-style agentic coding (Terminal-Bench 2.1: 78.2% vs 76.2% Flash vs 66.1% Opus). Gemini 3.5 Flash for running thousands of cheap agentic loops — same context as Pro tier, 4x output speed, lowest cost.

Which is fastest and cheapest?

Gemini 3.5 Flash, by a clear margin. Google quotes up to 4x faster output tokens per second than other frontier models. API pricing is Flash-tier — meaningfully below GPT-5.5 and well below Claude Opus 4.7. For high-volume agentic loops where you make thousands of calls, Flash changes the unit economics.

Which has the largest context window?

Gemini 3.5 Flash, with a 1,000,000-token input context and 64K output. GPT-5.5 has roughly a 400K context window. Claude Opus 4.7 has 200K. If you're processing whole codebases or long documents in a single call, Gemini 3.5 Flash leads on context length and is also the cheapest of the three.

Quick Answer

Gemini 3.5 Flash vs GPT-5.5 vs Claude Opus 4.7 (May 2026)

Published: May 20, 2026

Gemini 3.5 Flash vs GPT-5.5 vs Claude Opus 4.7 (May 2026)

Three frontier-class models, three different jobs. Gemini 3.5 Flash launched May 19, 2026 at Google I/O and immediately changed the price-performance frontier. Here’s how it actually compares to GPT-5.5 and Claude Opus 4.7.

Last verified: May 20, 2026

TL;DR table

	Gemini 3.5 Flash	GPT-5.5	Claude Opus 4.7
Vendor	Google DeepMind	OpenAI	Anthropic
Released	May 19, 2026	April 2026	April 2026
Tier	Flash (small + fast)	Flagship	Flagship
SWE-bench Pro	55.1%	58.6%	64.3%
Terminal-Bench 2.1	76.2%	78.2%	66.1%
Input context	1,000,000	~400K	200K
Output tokens	64K	~100K	64K
Output speed	~4x baseline	baseline	baseline
Strength	Speed + cost + context	Versatility + agentic terminal	Code quality + long-horizon reasoning
API price tier	Cheapest	Mid	Most expensive
Where it’s default	Gemini app, AI Mode, Antigravity 2.0	ChatGPT, Codex, Atlas	Claude.ai, Claude Code

What each one is

Gemini 3.5 Flash — the speed-first agentic model

Google’s headline launch from I/O 2026 (May 19). Positioned as “frontier-class agentic and coding model” in a Flash-tier package. The pitch: outperforms last-gen Pro (Gemini 3.1 Pro) on most benchmarks while running 4x faster and at Flash-tier API prices.

Why it matters now: it’s the default model in Antigravity 2.0, Gemini Spark, AI Mode in Google Search, and the Gemini app. Even if you don’t choose it, you’re probably using it.

GPT-5.5 — the all-rounder

OpenAI’s current flagship, default in ChatGPT and the engine behind ChatGPT Atlas (agentic browser), Codex 2 (cloud coding), and GPT-5.5 Instant (low-latency consumer mode). Strongest versatile model in the lineup — solid coding, strong reasoning, best terminal-style agentic execution per Terminal-Bench 2.1.

Claude Opus 4.7 — the code quality leader

Anthropic’s frontier model, released April 2026. Still the highest-scoring single model on SWE-bench Pro and the default model behind Claude Code, the Claude Agent SDK, and Managed Agents. For long-horizon coding (refactors, migrations, multi-file changes), Opus 4.7 is still the one to reach for.

Benchmark deep dive

Coding — SWE-bench Pro (single attempt)

Model	Score
Claude Opus 4.7	64.3%
GPT-5.5	58.6%
Gemini 3.5 Flash	55.1%
Gemini 3.1 Pro	~50%

Read this carefully. Opus 4.7 wins on the gold-standard coding benchmark. But Flash beating 3.1 Pro at the Flash tier is the real story — Google’s small model is now matching last year’s flagships.

Agentic terminal coding — Terminal-Bench 2.1

Model	Score
GPT-5.5	78.2%
Gemini 3.5 Flash	76.2%
Gemini 3.1 Pro	70.3%
Claude Opus 4.7	66.1%

GPT-5.5 leads on terminal-style agentic execution; Opus 4.7 underperforms here despite leading on code quality. The pattern is real: GPT-5.5 is the better executor, Opus 4.7 is the better planner.

Context window

Model	Input	Output
Gemini 3.5 Flash	1,000,000	64K
GPT-5.5	~400K	~100K
Claude Opus 4.7	200K	64K

If you need whole-codebase context in a single call, Flash wins by a wide margin.

Speed (output tokens / second)

Model	Relative speed
Gemini 3.5 Flash	~4x baseline
GPT-5.5	baseline
Claude Opus 4.7	baseline (or slower for very long reasoning)

This is a unit-economics fact, not a marketing claim. If your agent makes 1000 calls per task, Flash is 4x faster end-to-end.

When to use which

Job	Pick	Why
Long refactor / migration with high code quality bar	Opus 4.7	Best SWE-bench, best long-horizon planning
Build an agent that calls a model 1000+ times	Gemini 3.5 Flash	4x output speed, lowest cost, 1M context
Default chat / general-purpose work	GPT-5.5	Best all-rounder, ChatGPT ecosystem
Whole-codebase Q&A in one prompt	Gemini 3.5 Flash	1M-token input window
Browser-style agent (Atlas, Comet)	GPT-5.5	Atlas is built on it
Multi-agent fleet on Google Cloud	Gemini 3.5 Flash	Default in Antigravity 2.0, Vertex AI native
Terminal-style coding agents (Codex, Jules)	GPT-5.5 or Flash	Both top Terminal-Bench
MCP-orchestrated personal agent	Gemini 3.5 Flash	Default for Gemini Spark
Highest single-task reliability	Opus 4.7	Highest SWE-bench Pro

Pricing snapshot (approximate, May 2026)

Exact prices change weekly — check vendor pricing pages. Relative pricing tiers as of May 20, 2026:

Model	Input $/M tokens	Output $/M tokens	Cheapest?
Gemini 3.5 Flash	Flash-tier (cheapest)	Flash-tier	Yes
GPT-5.5	Mid-tier	Mid-tier	No
Claude Opus 4.7	Most expensive	Most expensive	No

For high-volume agentic workloads, Flash is often 5-10x cheaper than Opus 4.7 per equivalent task.

Where each ships

Model	Lives in
Gemini 3.5 Flash	Gemini app (default), AI Mode (default), Antigravity 2.0 (default), Gemini Spark, Vertex AI, Gemini API, Jules (free tier)
GPT-5.5	ChatGPT (default), Atlas, Codex, Azure OpenAI, ChatGPT Search, GPT-5.5 Instant
Claude Opus 4.7	Claude.ai (default), Claude Code, Claude Agent SDK, Anthropic API, AWS Bedrock, Google Vertex AI, Cursor, Windsurf

Quick decision flowchart

What matters most?

├─ Best raw code quality
│   └─► Claude Opus 4.7
│
├─ Best terminal agent execution
│   └─► GPT-5.5
│
├─ Cheapest / fastest / longest context
│   └─► Gemini 3.5 Flash
│
├─ Default chat assistant
│   └─► GPT-5.5 (ChatGPT)
│
├─ Build agent on Google Cloud
│   └─► Gemini 3.5 Flash (via Vertex AI / Antigravity)
│
└─ Don't know
    └─► Try Flash first (cheapest), upgrade only if quality misses

What’s next

Gemini 3.5 Pro — June 2026 (Google confirmed at I/O).
OpenAI DevDay — expected Q3 2026, GPT-5.6 / new modality drops likely.
Claude Opus 4.8 / Claude 5 — Anthropic has not confirmed a date but a refresh is expected before end of summer.

TL;DR

No single model wins everything in May 2026. Opus 4.7 wins code quality. GPT-5.5 wins versatility and terminal agents. Gemini 3.5 Flash wins speed, cost, and context — and is the most disruptive of the three because Google ships it as the default everywhere. If you’re not testing Flash this week, you’re probably overpaying.

Gemini 3.5 Flash vs GPT-5.5 vs Claude Opus 4.7 (May 2026)

TL;DR table

What each one is

Gemini 3.5 Flash — the speed-first agentic model

GPT-5.5 — the all-rounder

Claude Opus 4.7 — the code quality leader

Benchmark deep dive

Coding — SWE-bench Pro (single attempt)

Agentic terminal coding — Terminal-Bench 2.1

Context window

Speed (output tokens / second)

When to use which

Pricing snapshot (approximate, May 2026)

Where each ships

Quick decision flowchart

What’s next

TL;DR

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