Real head-to-head · same prompt, one shot
Claude Sonnet 5 vs Fugu Ultra 1.1
The agentic SWE frontier — 82% SWE-bench Verified, Dev Team mode. vs Sakana's multi-agent orchestrator, v1.1 — routes experts per request.
Head-to-head verdict: Fugu Ultra 1.1 wins 12–10 with 1 tie.
What I tested — same prompt, two models
I run the same fixed prompt set through every new model the day it drops — same string, one shot, single HTML file out — and I score the result 0–10 on whether it ran, how close it hit the brief, and how good it looked. Below is what came out when I gave the exact same prompts to Claude Sonnet 5 and Fugu Ultra 1.1, side by side, on 24 shared tasks inside the Agent Operating System.
Both models were given identical prompts inside the Agent Operating System — no help, no iteration, no "best of N" tricks. I run each prompt once, save the HTML file the model produces, and score it 0–10 on whether it ran, how close it hit the brief, and how good it looked. The scoring is mine. The verdicts below are pulled from my source comparison guides at agentos.guide where I publish every score and the reasoning behind it.
Claude Sonnet 5 · Reach for it in Agent OS when the job is iterative, tool-using software engineering. For one-shot visual builds, GLM 5.2 (free) beat it 4-1 here.
Fugu Ultra 1.1 · Benched on GoldieBench via Sakana's Responses API (fugu-ultra-v1.1, xhigh reasoning). Game tasks use the skill-infused threejs-game-director prompt plus a controls+graphics fix loop with an anti-regression clamp, judged on a real mid-play frame by the same Opus judge as the field.
Side-by-side on 47 shared tasks
Click any cell to play that model's actual one-shot attempt. Medals are derived from my 0–10 scores per task (highest = 🥇, second = 🥈, third = 🥉).
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Claude Sonnet 5
Fugu Ultra 1.1
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Where Claude Sonnet 5 beat Fugu Ultra 1.1
The tasks where I gave Claude Sonnet 5 a higher 0–10 score on the same prompt — with the actual commentary from my source guides.
Raycaster
Game
Claude Sonnet 5 8.0
·
Fugu Ultra 1.1 2.0
(+6.0)
What I saw: Strong, shippable 3D maze: clean rendered walls with lighting/shadows, checkerboard floor, working minimap with player+goal markers, and solid controls/UI. Uses real 3D geometry rather than classic raycasting and looks a bit flat/plain (colored walls without texture), keeping it …
Neoncity
Game
Claude Sonnet 5 8.2
·
Fugu Ultra 1.1 2.3
(+5.9)
What I saw: Strong on-brief cyberpunk drive: neon edge strips, cyan dashed lane markers, glowing windowed buildings and clean perspective read convincingly as a neon city. Weakness is the right side feels sparse and the buildings cluster asymmetrically, keeping it just shy of the best in field.
Pool
Game
Claude Sonnet 5 8.2
·
Fugu Ultra 1.1 4.5
(+3.7)
What I saw: Clean 3D render with proper racked triangle, numbered/striped ball textures, cue stick aiming, pockets and power bar—clearly on-brief and polished. Solid physics-oriented setup but visually generic versus a task winner, and the shadowing under the rack looks a bit off.
Arcade
Game
Claude Sonnet 5 8.2
·
Fugu Ultra 1.1 5.5
(+2.7)
What I saw: Clean, polished neon Breakout that renders perfectly with glowing bricks, gradient paddle, particle bursts, and a live in-progress state (score 10, a brick already cleared). Solid physics with side-aware collisions and level scaling, but it's a well-executed take on the most comm…
Nordiccrypt
Game
Claude Sonnet 5 6.8
·
Fugu Ultra 1.1 5.2
(+1.6)
What I saw: Renders a functional first-person maze with warm torch glow, dust motes, minimap, and clean Nordic-styled UI, but the view is washed-out and flat — walls read as a beige grid without depth, stone/rune detail is barely visible, and it lacks the atmospheric contrast and dungeon men…
Where Fugu Ultra 1.1 beat Claude Sonnet 5
The tasks where I gave Fugu Ultra 1.1 a higher 0–10 score on the same prompt — with the actual commentary from my source guides.
Twilightvale
Game
Fugu Ultra 1.1 8.6
·
Claude Sonnet 5 3.0
(+5.6)
· Atmospheric RPG World
What I saw: Gorgeous cohesive twilight scene with detailed hero holding a weapon, visible enemies (creature + humanoid), wooden bridge, lampposts, cottage, river, pickups and a working minimap/HUD with quest and kill tracker. Strong art direction and populated world with combat framing; only…
Aurora
Visual
Fugu Ultra 1.1 5.5
·
Claude Sonnet 5 2.5
(+3.0)
What I saw: Clean 3D scene with moon, starfield, layered mountains and pyramid 'trees', but the actual aurora is barely visible—only faint green ground-glow blobs rather than the rippling northern-lights sky the brief demands. Polished framing and typography, but it fails the core aurora effect.
Flightsim
Game
Fugu Ultra 1.1 8.4
·
Claude Sonnet 5 5.5
(+2.9)
What I saw: Polished flight sim with a detailed aircraft model, full HUD (airspeed/alt/VS/heading tape/attitude indicator), runway with markings, hangar, control tower and terrain — plus a combat layer with visible drones and cannon reticle. Very strong and shippable, but the enemy at this f…
Gtadrive
Game
Fugu Ultra 1.1 7.4
·
Claude Sonnet 5 4.5
(+2.9)
What I saw: Strong polished HUD with wanted stars, minimap showing cops/traffic dots, and combat state ('UNDER FIRE', health at 74 taking damage) plus debris particles indicate working enemies; weakened by the player car's messy/broken 3D model that looks like clipped blocks rather than a cl…
Parachute
Game
Fugu Ultra 1.1 8.6
·
Claude Sonnet 5 6.0
(+2.6)
· combat parachute drop
What I saw: Strong deployed-chute skydiver over a jungle canopy with a polished HUD (altitude, dist-to-H, score) plus active drone enemies, flare combat, and 'THREAT DOWN' kill feedback — it delivers the full jump/steer/land loop AND working combat, edging past a bland walking sim.
Strengths & weaknesses I logged
Claude Sonnet 5
Strengths
- 82.1% SWE-bench Verified — first model past 80% on real GitHub-issue repair
- Dev Team multi-agent mode + 1M context for repo-level agentic work
- Precision on hard logic — won the raycaster the open-weight field kept botching
Trade-offs
- One-shot creative-visual builds trail GLM 5.2 here (lost 4 of 5) — no iteration to catch its own bugs
- A temporal-dead-zone bug blanked its N-body orbit sim on the first shot
Fugu Ultra 1.1
Strengths
- Orchestrates 1-3 expert agents per request and synthesises their answers
- Reported SWE-Bench Pro 73.7 — above Opus 4.8 and GPT-5.5 on Sakana's table
- OpenAI- and Anthropic-compatible API — drop-in for Codex and Claude Code
Trade-offs
- Benched as a partial run until the full 50-task batch completes
- Region-locked: unavailable across the EU/EEA/UK/CH — access depends on where you are
Pricing & context — the spec sheet
| Spec | Claude Sonnet 5 | Fugu Ultra 1.1 |
|---|---|---|
| Vendor | Anthropic | Sakana AI |
| Context window | 1,000,000 tokens | 1,000,000-token context window |
| Price | $3 / $15 per M ($2/$10 intro) | API · orchestration billed |
| Pricing detail | $3.00 input / $15.00 output per million tokens; introductory $2.00/$10.00 through 2026-08-31. | Sakana's Fugu Ultra v1.1 — a multi-agent system served as a model: an orchestrator routes each request across one to three expert agents and synthesises the answer. Reported (v1.0): SWE-Bench Pro 73.7, LiveCodeBench 93.2, GPQA Diamond 95.5. NOTE: Sakana geo-blocks the EU/EEA/UK/Switzerland pending GDPR compliance — benched from an allowed region. |
| Release | 2026-06-30 | 2026-07 |
| Bench coverage | 47/47 scored · avg 7.01/10 | 23/24 scored · avg 6.94/10 |
The verdict — which should you pick?
Across 23 scored shared tasks, the averages are essentially tied — Claude Sonnet 5 6.89 vs Fugu Ultra 1.1 6.94. This isn't the comparison where one wins; it's the comparison where you pick based on context, pricing, and what you're actually trying to ship.
If you only run one of these inside your stack, the head-to-head average above is the call. If you can run both, my honest play is to wire Claude Sonnet 5 and Fugu Ultra 1.1 both into the Agent Operating System and dispatch each from the kanban by task type — agentic software engineering — write / run / test / fix loops on real repos → Claude Sonnet 5, hard, high-stakes coding and reasoning where answer quality beats latency → Fugu Ultra 1.1. That's the same setup I run for the 4,000+ founders inside the AI Profit Boardroom.
FAQ — Claude Sonnet 5 vs Fugu Ultra 1.1
Which is better, Claude Sonnet 5 or Fugu Ultra 1.1?
On Goldie Bench, Claude Sonnet 5 averages 6.89/10 across the shared tasks, with 0 gold, 0 silver, 4 bronze overall. Fugu Ultra 1.1 averages 6.94/10, with 0 gold, 1 silver, 2 bronze. Fugu Ultra 1.1 wins the head-to-head 12–10.
How much does Claude Sonnet 5 cost vs Fugu Ultra 1.1?
Claude Sonnet 5: $3.00 input / $15.00 output per million tokens; introductory $2.00/$10.00 through 2026-08-31. Fugu Ultra 1.1: Sakana's Fugu Ultra v1.1 — a multi-agent system served as a model: an orchestrator routes each request across one to three expert agents and synthesises the answer. Reported (v1.0): SWE-Bench Pro 73.7, LiveCodeBench 93.2, GPQA Diamond 95.5. NOTE: Sakana geo-blocks the EU/EEA/UK/Switzerland pending GDPR compliance — benched from an allowed region.
What's the context window for Claude Sonnet 5 vs Fugu Ultra 1.1?
Claude Sonnet 5 has a 1,000,000 tokens context window. Fugu Ultra 1.1 has a 1,000,000-token context window context window.
When should I pick Claude Sonnet 5 over Fugu Ultra 1.1?
Pick Claude Sonnet 5 for: Agentic software engineering — write / run / test / fix loops on real repos; Repo-level reasoning across a 1M-token context (Dev Team multi-agent mode); Precise logic — raycasters, physics — where one-shot open models slip. The trade-off is the weaknesses we logged on the bench: One-shot creative-visual builds trail GLM 5.2 here (lost 4 of 5) — no iteration to catch its own bugs; A temporal-dead-zone bug blanked its N-body orbit sim on the first shot.
When should I pick Fugu Ultra 1.1 over Claude Sonnet 5?
Pick Fugu Ultra 1.1 for: Hard, high-stakes coding and reasoning where answer quality beats latency; Agentic workflows in Codex / Claude Code via the drop-in provider config; One-shot builds you want a panel of experts on, not a single model. The trade-off is the weaknesses we logged on the bench: Benched as a partial run until the full 50-task batch completes; Region-locked: unavailable across the EU/EEA/UK/CH — access depends on where you are.
How does Goldie Bench score Claude Sonnet 5 vs Fugu Ultra 1.1?
Every demo on this page was built by Julian Goldie inside the Agent Operating System — same fixed prompt for both models, one shot, single HTML file out. Each result gets a 0–10 score on whether it ran, how close it hit the brief, and how good it looked. The highest score on each task gets gold; second gets silver; third gets bronze. See methodology for full provenance.
Related comparisons
Other head-to-heads using the same scoring system:
Claude Sonnet 5 vs Fusion Fugu Ultra 1.1 vs Fusion Claude Sonnet 5 vs Claude Opus 5 Fugu Ultra 1.1 vs Claude Opus 5 Claude Sonnet 5 vs Hermes MoA Fugu Ultra 1.1 vs Hermes MoA Claude Sonnet 5 vs GPT-5.6 Sol Fugu Ultra 1.1 vs GPT-5.6 SolFull model pages: Claude Sonnet 5 · Fugu Ultra 1.1 · back to the leaderboard
The same stack Julian uses
Run this stack yourself.
Every demo on this bench was built inside the Agent Operating System — one prompt, one shot, single HTML file out. The Agent OS, the prompts, the templates, the weekly walkthroughs and 4,000+ founders shipping with it every day all live inside the AI Profit Boardroom.
4,000+founders
258documented wins
38countries
$59/momonthly