Pick Claude Sonnet 4.6 for best value in the claude family or everyday professional work. Pick Fugu Ultra v2.0 for sakana's own evaluation reports best-or-joint-best results on 5 of 8 benchmarks tested, including a 74.3 on the deepswe coding-repair benchmark or claims to outperform flagship models like gpt-6 astra and claude fable 5.1 despite its underlying orchestration pool reportedly excluding both of them. On a tight budget at scale, Claude Sonnet 4.6 is the value pick.
Claude Sonnet 4.6 (Anthropic) and Fugu Ultra v2.0 (Sakana AI) are two of the models people most often weigh against each other in 2026. Claude Sonnet 4.6 is opus-class quality at lower cost; superseded as the default Sonnet by Claude Sonnet 5 (June 2026). Fugu Ultra v2.0 is sakana AI's flagship multi-agent orchestration model, claiming best-or-joint-best results on 5 of 8 self-reported benchmarks against monolithic frontier models — $5/$30 per million tokens. Their biggest split is price, and the breakdown below shows exactly how that plays out for your workload.
Key differences
Price: Claude Sonnet 4.6 is about 1.7× cheaper on input ($3/$15 per 1M tokens vs $5/$30 per 1M tokens) — modest, but it adds up at steady volume.
Context window: both advertise 1M (~1,500 pages). Tie on paper — test on your own long inputs, since usable recall varies by model.
Recency: Fugu Ultra v2.0 is the newer model by about 7 months (released September 10, 2026), usually meaning fresher training data and capabilities.
Specifications
Spec
Claude Sonnet 4.6
Fugu Ultra v2.0
Provider
Anthropic (US)
Sakana AI (Global)
Released
February 17, 2026
September 10, 2026
Context window
1M (~1,500 pages)
1M tokens (~1,500 pages)
Price (in/out)
$3/$15 per 1M tokens
$5/$30 per 1M tokens
Open weight?
No — API only
No — API only
Modalities
text, image, code
text
SWE-Bench Verified
79.6%
Not published
MRCR v2 @ 1M
Not published
Not published
Who wins what
Best value in the Claude family: Claude Sonnet 4.6 — At $3/$15 per 1M tokens it undercuts Fugu Ultra v2.0 ($5/$30 per 1M tokens), and that gap compounds at volume.
Everyday professional work: Claude Sonnet 4.6 — Opus-class quality at lower cost; superseded as the default Sonnet by Claude Sonnet 5 (June 2026) — and it runs cheaper at $3/$15 per 1M tokens.
Long-document analysis: Claude Sonnet 4.6 — Claude Sonnet 4.6 lists long-document analysis among its strengths; Fugu Ultra v2.0 does not.
Sakana's own evaluation reports best-or-joint-best results on 5 of 8 benchmarks tested, including a 74.3 on the DeepSWE coding-repair benchmark: Fugu Ultra v2.0 — Sakana AI's flagship multi-agent orchestration model, claiming best-or-joint-best results on 5 of 8 self-reported benchmarks against monolithic frontier models — $5/$30 per million tokens — and it is the newer of the two.
Claims to outperform flagship models like GPT-6 Astra and Claude Fable 5.1 despite its underlying orchestration pool reportedly excluding both of them: Fugu Ultra v2.0 — Fugu Ultra v2.0 lists claims to outperform flagship models like GPT-6 Astra and Claude Fable 5.1 despite its underlying orchestration pool reportedly excluding both of them among its strengths; Claude Sonnet 4.6 does not.
1M-token context window: Fugu Ultra v2.0 — Fugu Ultra v2.0 lists 1M-token context window among its strengths; Claude Sonnet 4.6 does not.
Lowest cost at scale: Claude Sonnet 4.6 — At $3/$15 per 1M tokens, it is the cheaper of the two — the gap dominates the bill on high-volume workloads.
Which should you pick?
A cost-sensitive startup shipping high volume: Claude Sonnet 4.6 — At $3/$15 per 1M tokens it undercuts Fugu Ultra v2.0, and on millions of tokens that margin decides the monthly bill.
Anyone whose priority is best value in the claude family: Claude Sonnet 4.6 — It is specifically built for that.
Anyone whose priority is sakana's own evaluation reports best-or-joint-best results on 5 of 8 benchmarks tested, including a 74.3 on the deepswe coding-repair benchmark: Fugu Ultra v2.0 — That is its strongest area.
Claude Sonnet 4.6: where it fits
Opus-class quality at lower cost; superseded as the default Sonnet by Claude Sonnet 5 (June 2026). Released February 17, 2026 by Anthropic, it is built for best value in the Claude family, everyday professional work, long-document analysis, and coding at lower cost than Opus.
Its trade-offs are real: trails Opus on the hardest agentic tasks, and not an open-weight option. At $3 in / $15 out per million tokens, it sits in the mid price band.
Fugu Ultra v2.0: where it fits
Sakana AI's flagship multi-agent orchestration model, claiming best-or-joint-best results on 5 of 8 self-reported benchmarks against monolithic frontier models — $5/$30 per million tokens. Released September 10, 2026 by Sakana AI, it is built for sakana's own evaluation reports best-or-joint-best results on 5 of 8 benchmarks tested, including a 74.3 on the DeepSWE coding-repair benchmark, claims to outperform flagship models like GPT-6 Astra and Claude Fable 5.1 despite its underlying orchestration pool reportedly excluding both of them, and 1M-token context window.
Its trade-offs: not a single trained model — Sakana describes Fugu as "a Multi-Agent System, Delivered as One Model" that dynamically routes tasks across a pool of other models, so head-to-head benchmark framing against monolithic frontier models should be read skeptically, pricing rises to roughly $10/$45 per million tokens for prompts above 272K tokens, and benchmark comparisons against GPT-6 Astra and Claude Fable 5.1 are Sakana's own self-reported figures, not independently verified head-to-head scores. At $5 in / $30 out per million tokens, it sits in the premium price band.
The bottom line for this matchup
Claude Sonnet 4.6 and Fugu Ultra v2.0 overlap enough that the right pick depends on your specific job. Claude Sonnet 4.6 costs less per token; and each leads in its own area — Claude Sonnet 4.6 for best value in the claude family, Fugu Ultra v2.0 for sakana's own evaluation reports best-or-joint-best results on 5 of 8 benchmarks tested, including a 74.3 on the deepswe coding-repair benchmark. Rather than crowning one, run the same hard task through both once and let the results decide.
Frequently asked questions
Is Claude Sonnet 4.6 or Fugu Ultra v2.0 better for coding?
Public SWE-Bench figures are not available for Fugu Ultra v2.0, so the honest test is your own repository — run an identical real bug through both. By design, Claude Sonnet 4.6 leans toward best value in the claude family while Fugu Ultra v2.0 leans toward sakana's own evaluation reports best-or-joint-best results on 5 of 8 benchmarks tested, including a 74.3 on the deepswe coding-repair benchmark, and that positioning usually predicts which feels better on your codebase.
Which is cheaper, Claude Sonnet 4.6 or Fugu Ultra v2.0?
Claude Sonnet 4.6 is cheaper — $3/$15 per 1M tokens vs $5/$30 per 1M tokens, roughly 1.7× apart on input.
Which has the bigger context window?
Both advertise 1M (~1,500 pages). Remember advertised ≠ usable: recall typically degrades before the ceiling.
Can I use both Claude Sonnet 4.6 and Fugu Ultra v2.0 together?
Yes — a multi-model platform like LumiChats gives you Claude Sonnet 4.6, Fugu Ultra v2.0 and 40+ others under one ₹69/day pass (about $1/day), so you can draft with one and cross-check with the other instead of buying two subscriptions.
Which is newer, Claude Sonnet 4.6 or Fugu Ultra v2.0?
Fugu Ultra v2.0 — released September 10, 2026, about 7 months after Claude Sonnet 4.6.
Claude Sonnet 4.6 vs Fugu Ultra v2.0
Anthropic · US | Sakana AI · Global · Updated June 2026
Quick verdict
Pick Claude Sonnet 4.6 for best value in the claude family or everyday professional work. Pick Fugu Ultra v2.0 for sakana's own evaluation reports best-or-joint-best results on 5 of 8 benchmarks tested, including a 74.3 on the deepswe coding-repair benchmark or claims to outperform flagship models like gpt-6 astra and claude fable 5.1 despite its underlying orchestration pool reportedly excluding both of them. On a tight budget at scale, Claude Sonnet 4.6 is the value pick.
Claude Sonnet 4.6 (Anthropic) and Fugu Ultra v2.0 (Sakana AI) are two of the models people most often weigh against each other in 2026. Claude Sonnet 4.6 is opus-class quality at lower cost; superseded as the default Sonnet by Claude Sonnet 5 (June 2026). Fugu Ultra v2.0 is sakana AI's flagship multi-agent orchestration model, claiming best-or-joint-best results on 5 of 8 self-reported benchmarks against monolithic frontier models — $5/$30 per million tokens. Their biggest split is price, and the breakdown below shows exactly how that plays out for your workload.
Key differences at a glance
▸Price: Claude Sonnet 4.6 is about 1.7× cheaper on input ($3/$15 per 1M tokens vs $5/$30 per 1M tokens) — modest, but it adds up at steady volume.
▸Context window: both advertise 1M (~1,500 pages). Tie on paper — test on your own long inputs, since usable recall varies by model.
▸Recency: Fugu Ultra v2.0 is the newer model by about 7 months (released September 10, 2026), usually meaning fresher training data and capabilities.
Side-by-side specs
Spec
Claude Sonnet 4.6
Fugu Ultra v2.0
Provider
Anthropic (US)
Sakana AI (Global)
Released
February 17, 2026
September 10, 2026
Context window
1M (~1,500 pages)
1M tokens (~1,500 pages)
Price (in/out)
$3/$15 per 1M tokens
$5/$30 per 1M tokens
Open weight?
No — API only
No — API only
Modalities
text, image, code
text
SWE-Bench Verified
79.6%
Not published
MRCR v2 @ 1M
Not published
Not published
Who wins what
Best value in the Claude family
Claude Sonnet 4.6
At $3/$15 per 1M tokens it undercuts Fugu Ultra v2.0 ($5/$30 per 1M tokens), and that gap compounds at volume.
Everyday professional work
Claude Sonnet 4.6
Opus-class quality at lower cost; superseded as the default Sonnet by Claude Sonnet 5 (June 2026) — and it runs cheaper at $3/$15 per 1M tokens.
Long-document analysis
Claude Sonnet 4.6
Claude Sonnet 4.6 lists long-document analysis among its strengths; Fugu Ultra v2.0 does not.
Sakana's own evaluation reports best-or-joint-best results on 5 of 8 benchmarks tested, including a 74.3 on the DeepSWE coding-repair benchmark
Fugu Ultra v2.0
Sakana AI's flagship multi-agent orchestration model, claiming best-or-joint-best results on 5 of 8 self-reported benchmarks against monolithic frontier models — $5/$30 per million tokens — and it is the newer of the two.
Claims to outperform flagship models like GPT-6 Astra and Claude Fable 5.1 despite its underlying orchestration pool reportedly excluding both of them
Fugu Ultra v2.0
Fugu Ultra v2.0 lists claims to outperform flagship models like GPT-6 Astra and Claude Fable 5.1 despite its underlying orchestration pool reportedly excluding both of them among its strengths; Claude Sonnet 4.6 does not.
1M-token context window
Fugu Ultra v2.0
Fugu Ultra v2.0 lists 1M-token context window among its strengths; Claude Sonnet 4.6 does not.
Lowest cost at scale
Claude Sonnet 4.6
At $3/$15 per 1M tokens, it is the cheaper of the two — the gap dominates the bill on high-volume workloads.
Which should you pick?
A cost-sensitive startup shipping high volume
→ Claude Sonnet 4.6
At $3/$15 per 1M tokens it undercuts Fugu Ultra v2.0, and on millions of tokens that margin decides the monthly bill.
Anyone whose priority is best value in the claude family
→ Claude Sonnet 4.6
It is specifically built for that.
Anyone whose priority is sakana's own evaluation reports best-or-joint-best results on 5 of 8 benchmarks tested, including a 74.3 on the deepswe coding-repair benchmark
→ Fugu Ultra v2.0
That is its strongest area.
Claude Sonnet 4.6: where it fits
Opus-class quality at lower cost; superseded as the default Sonnet by Claude Sonnet 5 (June 2026). Released February 17, 2026 by Anthropic, it is built for best value in the Claude family, everyday professional work, long-document analysis, and coding at lower cost than Opus.
Its trade-offs are real: trails Opus on the hardest agentic tasks, and not an open-weight option. At $3 in / $15 out per million tokens, it sits in the mid price band.
Fugu Ultra v2.0: where it fits
Sakana AI's flagship multi-agent orchestration model, claiming best-or-joint-best results on 5 of 8 self-reported benchmarks against monolithic frontier models — $5/$30 per million tokens. Released September 10, 2026 by Sakana AI, it is built for sakana's own evaluation reports best-or-joint-best results on 5 of 8 benchmarks tested, including a 74.3 on the DeepSWE coding-repair benchmark, claims to outperform flagship models like GPT-6 Astra and Claude Fable 5.1 despite its underlying orchestration pool reportedly excluding both of them, and 1M-token context window.
Its trade-offs: not a single trained model — Sakana describes Fugu as "a Multi-Agent System, Delivered as One Model" that dynamically routes tasks across a pool of other models, so head-to-head benchmark framing against monolithic frontier models should be read skeptically, pricing rises to roughly $10/$45 per million tokens for prompts above 272K tokens, and benchmark comparisons against GPT-6 Astra and Claude Fable 5.1 are Sakana's own self-reported figures, not independently verified head-to-head scores. At $5 in / $30 out per million tokens, it sits in the premium price band.
The bottom line for this matchup
Claude Sonnet 4.6 and Fugu Ultra v2.0 overlap enough that the right pick depends on your specific job. Claude Sonnet 4.6 costs less per token; and each leads in its own area — Claude Sonnet 4.6 for best value in the claude family, Fugu Ultra v2.0 for sakana's own evaluation reports best-or-joint-best results on 5 of 8 benchmarks tested, including a 74.3 on the deepswe coding-repair benchmark. Rather than crowning one, run the same hard task through both once and let the results decide.
Want both Claude Sonnet 4.6 and Fugu Ultra v2.0 without two subscriptions? LumiChats gives you these plus 40+ models under one ₹69/day pass (about $1/day) — draft with one, cross-check with the other.
Is Claude Sonnet 4.6 or Fugu Ultra v2.0 better for coding?
Public SWE-Bench figures are not available for Fugu Ultra v2.0, so the honest test is your own repository — run an identical real bug through both. By design, Claude Sonnet 4.6 leans toward best value in the claude family while Fugu Ultra v2.0 leans toward sakana's own evaluation reports best-or-joint-best results on 5 of 8 benchmarks tested, including a 74.3 on the deepswe coding-repair benchmark, and that positioning usually predicts which feels better on your codebase.
Which is cheaper, Claude Sonnet 4.6 or Fugu Ultra v2.0?
Claude Sonnet 4.6 is cheaper — $3/$15 per 1M tokens vs $5/$30 per 1M tokens, roughly 1.7× apart on input.
Which has the bigger context window?
Both advertise 1M (~1,500 pages). Remember advertised ≠ usable: recall typically degrades before the ceiling.
Can I use both Claude Sonnet 4.6 and Fugu Ultra v2.0 together?
Yes — a multi-model platform like LumiChats gives you Claude Sonnet 4.6, Fugu Ultra v2.0 and 40+ others under one ₹69/day pass (about $1/day), so you can draft with one and cross-check with the other instead of buying two subscriptions.
Which is newer, Claude Sonnet 4.6 or Fugu Ultra v2.0?
Fugu Ultra v2.0 — released September 10, 2026, about 7 months after Claude Sonnet 4.6.
Specifications and benchmarks reflect publicly reported figures as of June 2026 and may change as providers release updates. Always verify on your own workload.