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Claude Sonnet 5.5 vs Gemini 3.8 Flash
Of the 6 public leaderboards that rate both, Claude Sonnet 5.5 scores higher on 5 and Gemini 3.8 Flash on 1. On the ArtificialWatch Index, which takes the median of each model's percentile across the boards that score it, Claude Sonnet 5.5 is at 83.3 and Gemini 3.8 Flash at 41.3 (out of 100). On each maker's API, Claude Sonnet 5.5 costs $2 / $10 per 1M tokens (input / output) and Gemini 3.8 Flash $0.75 / $3.75.
Scores as published by each board; table composed November 13, 2026.
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Leaderboard by leaderboard
| Board | Claude Sonnet 5.5 | Gemini 3.8 Flash | Higher |
|---|---|---|---|
| LMArena Elo (community votes) | 1,772.3 | 1,583.5 | Claude Sonnet 5.5 |
| LiveBench global average (0-100) | 77 | 57.3 | Claude Sonnet 5.5 |
| SimpleBench AVG@5 % (private set) | 75.9 | 82.4 | Gemini 3.8 Flash |
| Vals AI Vals Index accuracy % · weighted finance + coding tasks | 70.9 | 56 | Claude Sonnet 5.5 |
| Artificial Analysis intelligence index · measured runs only | 54.5 | 30.8 | Claude Sonnet 5.5 |
| Epoch AI Epoch Capabilities Index (ECI) · many benchmarks on one scale | 166.6 | 158.8 | Claude Sonnet 5.5 |
Raw scores are each board's own scale, so compare within a row, not across rows. Full table: the bench index.
For coding
On the ArtificialWatch coding index, Claude Sonnet 5.5 is at 65.1 (#16 of 48) and Gemini 3.8 Flash at 44.4 (#22). Claude Sonnet 5.5 scores higher on 2 of the 3 coding boards that rate both and Gemini 3.8 Flash on 1.
| Coding board | Claude Sonnet 5.5 | Gemini 3.8 Flash |
|---|---|---|
| LMArena · Coding | 1,500.9 | 1,510.1 |
| LiveBench · Coding | 77.2 | 73.3 |
| Vals Vibe Code Bench | 92.4 | 78.7 |
Claude Sonnet 5.5 at a glance
- Developer
- Anthropic
- Status
- Live since September 28, 2026
- API price
- $2 input / $10 output per 1M tokens · Anthropic, claude-sonnet-5-5
- Context window
- 1M tokens
Live — Sep 28 · $2/$10 per MTok, the same as Sonnet 5 · cache reads $0.20 at launch, halved to $0.10 on Oct 7, writes $2.50 · in the API, the Claude apps, AWS, Google Cloud and Azure the same day · 1M ctx / 128K out · knowledge cutoff Jun 2026 · Artificial Analysis Intelligence Index 56 at max effort, #3 of 216 reasoning models (read Sep 28) · Anthropic's own table: Terminal-Bench 4.0 70.6% (Opus 5.5 66.4%), OSWorld 2.1 80.1% (Opus 5.5 81.8%) · our sweep caught claude-sonnet-5-5 at 17:54 UTC and fired at 17:55.
Claude Sonnet 5.5 ships at Sonnet 5's price, and the first independent number puts it #3 among reasoning models
2026-09-28 · Claude Sonnet 5.5 is live. Our sweep read the id claude-sonnet-5-5 at 17:54:45 UTC on September 28 and the alert went out at 17:55:45, 60 seconds later, to 314 inboxes and one phone. OpenRouter listed it nine minutes after that.
Claude Sonnet 5.5: named by Anthropic, reportedly in partner testing, priced 89% by Sep 30
2026-09-27 · Anthropic has named Claude Sonnet 5.5 but has not dated it. Everything past the name is reported, not confirmed - and the one number that moves every day says it is close.
Gemini 3.8 Flash at a glance
- Developer
- Status
- Live since September 2, 2026
- API price
- $0.75 input / $3.75 output per 1M tokens · Google, gemini-3.8-flash
- Context window
- 1.05M tokens
Live — GA Sep 2 · $0.75/$3.75 per 1M introductory through Dec 31, identical to 3.7 · 1M in / 64K out · 'our most intelligent Flash model' · 20 days after 3.7.
Gemini 3.8 Flash is GA — same price as 3.7, twenty days later
2026-09-02 · Google released Gemini 3.8 Flash today. The Gemini API changelog for September 2 reads: "Gemini 3.8 Flash generally available (GA): Released gemini-3.8-flash, our most intelligent Flash model, engineered for long-horizon software engineering, autonomous agents, and complex enterprise workflows."
Claude Sonnet 5.5 vs Gemini 3.8 Flash: quick answers
Which is better, Claude Sonnet 5.5 or Gemini 3.8 Flash?
It depends on what you measure. Of the 6 public leaderboards that rate both, Claude Sonnet 5.5 scores higher on 5 and Gemini 3.8 Flash on 1. Claude Sonnet 5.5's widest lead is on Vals AI; Gemini 3.8 Flash's widest lead is on SimpleBench. On the ArtificialWatch Index, which takes the median of each model's percentile across the boards that score it, Claude Sonnet 5.5 is at 83.3 and Gemini 3.8 Flash at 41.3 (out of 100).
Which is newer, Claude Sonnet 5.5 or Gemini 3.8 Flash?
Claude Sonnet 5.5. It went live on September 28, 2026, 26 days after Gemini 3.8 Flash (September 2, 2026).
Which is cheaper, Claude Sonnet 5.5 or Gemini 3.8 Flash?
Gemini 3.8 Flash is cheaper on both input and output. On each vendor's own API, Claude Sonnet 5.5 is $2 input / $10 output per million tokens and Gemini 3.8 Flash is $0.75 input / $3.75 output per million tokens. Prices as published in the models.dev catalog, as of 2026-11-12.
Which has the bigger context window, Claude Sonnet 5.5 or Gemini 3.8 Flash?
Gemini 3.8 Flash, at 1.05M tokens against Claude Sonnet 5.5's 1M, as each vendor lists it.
How do Claude Sonnet 5.5 and Gemini 3.8 Flash compare for coding?
On the ArtificialWatch coding index, Claude Sonnet 5.5 is at 65.1 (#16 of 48) and Gemini 3.8 Flash at 44.4 (#22). Claude Sonnet 5.5 scores higher on 2 of the 3 coding boards that rate both and Gemini 3.8 Flash on 1.
Who makes Claude Sonnet 5.5 and Gemini 3.8 Flash?
Claude Sonnet 5.5 is from Anthropic; Gemini 3.8 Flash is from Google.
Where do these numbers come from?
Each score is the leaderboard's own published figure, read by ArtificialWatch (table composed November 13, 2026). Boards measure different things, so raw scores are only comparable within a row.
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Also: the bench index · API pricing · what a workload costs on each · the wire