Standard Compute
Model comparison 2026

Claude Opus 5.5 vs Gemini 3.5 Flash

Claude Opus 5.5
Anthropic · Frontier · Proprietary
$8.80/1M · 1M ctx
Gemini 3.5 Flash
Google · Balanced · Proprietary
$3.75/1M · 1.0M ctx

Community vote

Pick a winner in each dimension. You can change your vote any time.

Output Quality
Correctness and depth of what it produces
Agentic Ability
Tool calls, instruction-following, and multi-step tasks
Speed
Tokens per second and time-to-first-token
Value for money
How much capability you get per dollar
Reliability
Consistent results: fewer refusals, loops and format breaks

Specs and pricing side by side

Spec
Opus 5.5
Gemini 3.5 Flash
Maker
Anthropic
Google
Blended price / 1M
$8.80
$3.75
Input / output
$4.00 in · $20 out / 1M tokens
$1.50 in · $9.00 out / 1M tokens
Context window
1M
1.0M
Open weights
No
No
Tool use
Yes
Yes
Reasoning
Yes
Yes
Output Quality
10.0
8.9
Agentic Ability
10.0
8.9
Speed
7.6
9.4
Value for money
7.4
8.7
Reliability
9.5
8.9

Pricing and capabilities synced from the OpenRouter catalogue. Scores are editorial (0–10).

Verdict: Opus 5.5 or Gemini 3.5 Flash?

Updated 2026-10-13

Choose Claude Opus 5.5 if you want the hardest coding and agent work, as the default flagship instead of Fable. Choose Gemini 3.5 Flash if you want high-throughput agents that need big context cheaply.

In our editorial scoring, Claude Opus 5.5 leads in 3 of five dimensions (output quality, agentic ability and reliability), while Gemini 3.5 Flash leads in 2. On price, Claude Opus 5.5 runs about $8.80 per 1M tokens (blended) and is proprietary; Gemini 3.5 Flash is about $3.75 and proprietary.

Where Opus 5.5 falls short
  • Twice Sonnet 5.5's price per token for a small measured gain
  • Released September 2026, so its long-run track record is still short
Full Opus 5.5 breakdown →
Where Gemini 3.5 Flash falls short
  • Below Pro on hard reasoning
  • Occasional verbosity
Full Gemini 3.5 Flash breakdown →

The agent matters as much as the model. Compare AI agents →

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Current frontier models Claude Opus 5.5 · Claude Sonnet 5.5

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