Claude Mythos 5 vs Fusion
Restricted-access flagship — vetted partners only. vs Multi-model panel — Fable 5 + GPT-5.5, ensembled. Beats Fable 5 at half the price.
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 Mythos 5 and Fusion, side by side, on 0 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 Mythos 5 · Not currently dispatched from Agent OS — no public API. Tracked for news coverage only.
Fusion · Dispatched from Agent OS for research-heavy prompts where ensemble accuracy outweighs single-model speed.
Side-by-side on 0 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 = 🥉).
Strengths & weaknesses I logged
Claude Mythos 5
Strengths
- Highest-class Anthropic model — sits above Fable 5 in the Mythos line
- Same Mythos-class capability profile as Fable 5 (with restrictions)
Trade-offs
- No public API access — can't be benched against the open field
- Restricted distribution makes it effectively unavailable to most builders
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
Pricing & context — the spec sheet
| Spec | Claude Mythos 5 | Fusion |
|---|---|---|
| Vendor | Anthropic | OpenRouter |
| Context window | 200,000 tokens | Varies — depends on which panel models are dispatched |
| Price | Restricted access — vetted partners only | OpenRouter Fusion API pricing |
| Pricing detail | Mythos 5 is the un-released sibling of Fable 5. Same Mythos class, restricted to vetted partners. Made headlines mid-June 2026 when reports of a White-House-driven ban over China access dominated AI press. | 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. |
| Release | 2026-06-09 | 2026-06-14 |
| Bench coverage | 0/0 scored · avg — | 0/0 scored · avg — |
The verdict — which should you pick?
Not enough scored shared tasks yet for a head-to-head average. The live demos for both are on the matrix above — play them and form your own opinion.
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 Mythos 5 and Fusion both into the Agent Operating System and dispatch each from the kanban by task type — vetted enterprise partners with mythos-class access → Claude Mythos 5, deep-research workflows where panel consensus beats single-model answers → Fusion. That's the same setup I run for the 3,600+ founders inside the AI Profit Boardroom.
FAQ — Claude Mythos 5 vs Fusion
Which is better, Claude Mythos 5 or Fusion?
On Goldie Bench, Claude Mythos 5 averages no scored verdicts yet across the shared tasks, with 0 gold, 0 silver, 0 bronze overall. Fusion averages no scored verdicts yet, with 0 gold, 0 silver, 0 bronze. Not enough scored shared tasks yet to call a winner.
How much does Claude Mythos 5 cost vs Fusion?
Claude Mythos 5: Mythos 5 is the un-released sibling of Fable 5. Same Mythos class, restricted to vetted partners. Made headlines mid-June 2026 when reports of a White-House-driven ban over China access dominated AI press. 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.
What's the context window for Claude Mythos 5 vs Fusion?
Claude Mythos 5 has a 200,000 tokens context window. Fusion has a Varies — depends on which panel models are dispatched context window.
When should I pick Claude Mythos 5 over Fusion?
Pick Claude Mythos 5 for: Vetted enterprise partners with Mythos-class access; (For everyone else: read the Mythos ban coverage instead of waiting for access). The trade-off is the weaknesses we logged on the bench: No public API access — can't be benched against the open field; Restricted distribution makes it effectively unavailable to most builders.
When should I pick Fusion over Claude Mythos 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.
How does Goldie Bench score Claude Mythos 5 vs Fusion?
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 Mythos 5 vs Opus 4.8 Fusion vs Opus 4.8 Claude Mythos 5 vs GLM-5.2 Fusion vs GLM-5.2 Claude Mythos 5 vs Grok Fusion vs Grok Claude Mythos 5 vs Qwen 3.7 Fusion vs Qwen 3.7Full model pages: Claude Mythos 5 · Fusion · back to the leaderboard
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.