Real head-to-head · same prompt, one shot
Fusion vs Claude Sonnet 5
Multi-model panel — Fable 5 + GPT-5.5, ensembled. Beats Fable 5 at half the price. vs The agentic SWE frontier — 82% SWE-bench Verified, Dev Team mode.
Head-to-head verdict: Fusion wins 33–7 with 2 ties.
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 Fusion and Claude Sonnet 5, side by side, on 42 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.
Fusion · Dispatched from Agent OS for research-heavy prompts where ensemble accuracy outweighs single-model speed.
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.
Side-by-side on 42 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 = 🥉).
Task ↓
Fusion
Claude Sonnet 5
Game
Game
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Sim
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Where Fusion beat Claude Sonnet 5
The tasks where I gave Fusion a higher 0–10 score on the same prompt — with the actual commentary from my source guides.
Solar
Sim
Fusion 9.0
·
Claude Sonnet 5 2.5
(+6.5)
· polish · interactive UI
What I saw: Most polished solar attempt I've graded — glass-morphism control panel with time slider, sun-glow slider, orbits/labels/pause toggles, hover info cards on every planet, Saturn's rings, accurate moons. Drag-to-orbit + scroll-to-zoom. Beats Opus on UI density without losing the physics.
Twilightvale
Game
Fusion 9.5
·
Claude Sonnet 5 3.0
(+6.5)
· winner · open world RPG
What I saw: RETRY @ 24K tokens — now complete: 44KB three.js + WebGL using renderer.setAnimationLoop (three.js native loop), 6 input handlers, full update() per-frame: player + NPCs + enemies + weather + day/night + HUD. Densest build on the bench.
Wormhole
Sim
Fusion 8.5
·
Claude Sonnet 5 3.0
(+5.5)
What I saw: Three.js wormhole tunnel with distorted starfield, hold-space to accelerate forward. Real depth + gravitational stretching.
Aurora
Visual
Fusion 7.5
·
Claude Sonnet 5 2.5
(+5.0)
What I saw: Aurora ribbons over a mountain ridge silhouette, WebGL noise shader. Slow morphing curtains in cyan + magenta. Smaller scope (10KB) but the prompt is met.
Orbit
Sim
Fusion 8.0
·
Claude Sonnet 5 3.5
(+4.5)
What I saw: Top-down inner-system map: Mercury / Venus / Earth / Mars orbiting the sun with accurate relative speeds. Per-planet colour palette, info card on hover, controls bar at bottom with speed slider and play/pause. Solid hit on the brief, ties with GLM on the same task.
Where Claude Sonnet 5 beat Fusion
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.
Outrun
Game
Claude Sonnet 5 8.6
·
Fusion 8.0
(+0.6)
· Textbook synthwave outrun
What I saw: Gorgeous, on-brief execution — striped retro sun, parallax mountains, glowing pink/cyan rumble strips and lane markers on a proper pseudo-3D road, plus a detailed neon car and polished CRT scanline/vignette overlays. Speed reads 000 in the shot (idle), but the classic Jake-Gordon…
Synthwave
Visual
Claude Sonnet 5 8.4
·
Fusion 8.0
(+0.4)
What I saw: Gorgeous, on-brief synthwave scene with striped sun, layered mountains, glowing neon title and a warm-to-purple gradient grid that reads beautifully; only knock is a visible rectangular artifact around the sun (the sky plane/glow seam) that slightly breaks the polish.
Boids
Sim
Claude Sonnet 5 8.2
·
Fusion 8.0
(+0.2)
What I saw: Strong 3D boids with proper flocking rules, orbit camera, live sliders, and a polished cage/grid/starfield presentation running at 60fps. Colorful cones read clearly but feel slightly sparse/scattered rather than showing tight emergent flocks in this frame, keeping it just short …
Pool
Game
Claude Sonnet 5 8.2
·
Fusion 8.0
(+0.2)
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.
Fluid
Sim
Claude Sonnet 5 8.6
·
Fusion 8.5
(+0.1)
· gorgeous flow field
What I saw: Stunning rendered flow-field with rich swirling particle streaks, a clear vortex focal point, and vivid rainbow color mapping over additive-blended trails — genuinely beautiful and clearly on-brief. Only knock is the low 22fps and it's a flow-field trail sim rather than true flui…
Strengths & weaknesses I logged
Fusion
Strengths
- Premium Fusion panel scored 69.0% on DRACO deep-research benchmark — beats solo Fable 5 by +3.7 points
- Budget panel ties Fable 5 at ~64.7% for roughly half the cost
- Vendor-agnostic — model panel can swap as new frontier releases land
Trade-offs
- Ensemble latency higher than any single model (panel calls run in parallel but the slowest still gates the response)
- No per-task goldiebench scoring yet — bench rank pending
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
Pricing & context — the spec sheet
| Spec | Fusion | Claude Sonnet 5 |
|---|---|---|
| Vendor | OpenRouter | Anthropic |
| Context window | Varies — depends on which panel models are dispatched | 1,000,000 tokens |
| Price | OpenRouter Fusion API pricing | $3 / $15 per M ($2/$10 intro) |
| Pricing detail | OpenRouter's Fusion API dispatches a single prompt to multiple frontier models and ensembles the answers. Premium panel: Fable 5 + GPT-5.5. Budget panel: cheaper open-weights models. Roughly half the per-token cost of a Fable 5 solo call. | $3.00 input / $15.00 output per million tokens; introductory $2.00/$10.00 through 2026-08-31. |
| Release | 2026-06-14 | 2026-06-30 |
| Bench coverage | 42/42 scored · avg 8.60/10 | 42/42 scored · avg 7.18/10 |
The verdict — which should you pick?
Across 42 scored shared tasks, Fusion averaged 8.60/10, beating Claude Sonnet 5's 7.18/10 by 1.41 points. Pick Fusion when the build has to ship on the first prompt and you can afford the trade-offs in the comparison below.
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 Fusion and Claude Sonnet 5 both into the Agent Operating System and dispatch each from the kanban by task type — deep-research workflows where panel consensus beats single-model answers → Fusion, agentic software engineering — write / run / test / fix loops on real repos → Claude Sonnet 5. That's the same setup I run for the 3,600+ founders inside the AI Profit Boardroom.
FAQ — Fusion vs Claude Sonnet 5
Which is better, Fusion or Claude Sonnet 5?
On Goldie Bench, Fusion averages 8.60/10 across the shared tasks, with 20 gold, 10 silver, 6 bronze overall. Claude Sonnet 5 averages 7.18/10, with 3 gold, 3 silver, 3 bronze. Fusion wins the head-to-head 33–7.
How much does Fusion cost vs Claude Sonnet 5?
Fusion: OpenRouter's Fusion API dispatches a single prompt to multiple frontier models and ensembles the answers. Premium panel: Fable 5 + GPT-5.5. Budget panel: cheaper open-weights models. Roughly half the per-token cost of a Fable 5 solo call. Claude Sonnet 5: $3.00 input / $15.00 output per million tokens; introductory $2.00/$10.00 through 2026-08-31.
What's the context window for Fusion vs Claude Sonnet 5?
Fusion has a Varies — depends on which panel models are dispatched context window. Claude Sonnet 5 has a 1,000,000 tokens context window.
When should I pick Fusion over Claude Sonnet 5?
Pick Fusion for: Deep-research workflows where panel consensus beats single-model answers; Cost-sensitive operators who want Fable-5-class output at ~half the bill; Production agents that benefit from vendor-redundancy on every call. The trade-off is the weaknesses we logged on the bench: Ensemble latency higher than any single model (panel calls run in parallel but the slowest still gates the response); No per-task goldiebench scoring yet — bench rank pending.
When should I pick Claude Sonnet 5 over Fusion?
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.
How does Goldie Bench score Fusion vs Claude Sonnet 5?
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:
Fusion vs Hermes MoA Claude Sonnet 5 vs Hermes MoA Fusion vs Grok Claude Sonnet 5 vs Grok Fusion vs MiniMax M3 Claude Sonnet 5 vs MiniMax M3 Fusion vs Fugu Ultra Claude Sonnet 5 vs Fugu UltraFull model pages: Fusion · Claude Sonnet 5 · 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 3,600+ founders shipping with it every day all live inside the AI Profit Boardroom.
3,600+founders
258documented wins
38countries
$59/momonthly