Claude Sonnet 5.5 vs Muse Spark Open
Anthropic · US | Meta · US · Updated June 2026
Quick verdict
Pick Claude Sonnet 5.5 for terminal-bench 4.0 agentic coding jumps to 70.6%, up from claude sonnet 5's 10.3% or same $2/$10 per million token pricing as sonnet 5, with cache-read price cut 50% to $0.10/mtok as of october 7, 2026. Pick Muse Spark Open for meta's first open-weight muse model - 816b-parameter moe with 42b active, accepting text, image, video and audio input or artificial analysis intelligence index of 39, first among us open-weight models. Choose Muse Spark Open if you need self-hosting or data privacy; Claude Sonnet 5.5 if you want a managed API.
Claude Sonnet 5.5 (Anthropic) and Muse Spark Open (Meta) are two of the models people most often weigh against each other in 2026. Claude Sonnet 5.5 is anthropic's September 28, 2026 mid-tier update — same $2/$10 pricing as Sonnet 5 but a large agentic-coding jump (Terminal-Bench 4.0: 70.6% vs 10.3%). Muse Spark Open is meta's October 15, 2026 open-weight Muse Spark - an 816B/42B-active multimodal MoE with a 1M context under a gated Muse Model License. They diverge most on price and open vs. closed weights — each quantified below from the models' real specs.
Key differences at a glance
- ▸Cost model: Muse Spark Open ships open weights you can self-host (hardware cost only, no per-token fee), while Claude Sonnet 5.5 is API-metered at $2/$10 per 1M tokens. Your choice depends on whether you want zero marginal cost at the price of running infrastructure.
- ▸Context window: both advertise 1M tokens (~1,500 pages). Tie on paper — test on your own long inputs, since usable recall varies by model.
- ▸Recency: Muse Spark Open is the newer model by about 17 days (released October 15, 2026), usually meaning fresher training data and capabilities.
Side-by-side specs
| Spec | Claude Sonnet 5.5 | Muse Spark Open |
|---|---|---|
| Provider | Anthropic (US) | Meta (US) |
| Released | September 28, 2026 | October 15, 2026 |
| Context window | 1M tokens (~1,500 pages) | 1M tokens (~1,500 pages) |
| Price (in/out) | $2/$10 per 1M tokens | Open weight (self-host / free) |
| Open weight? | No — API only | Yes — self-hostable |
| Modalities | text, image, code | text, image, video, audio, code |
| SWE-Bench Verified | Not published | Not published |
| MRCR v2 @ 1M | Not published | Not published |
Who wins what
Terminal-Bench 4.0 agentic coding jumps to 70.6%, up from Claude Sonnet 5's 10.3%
Claude Sonnet 5.5
Claude Sonnet 5.5 lists terminal-Bench 4.0 agentic coding jumps to 70.6%, up from Claude Sonnet 5's 10.3% among its strengths; Muse Spark Open does not.
Same $2/$10 per million token pricing as Sonnet 5, with cache-read price cut 50% to $0.10/MTok as of October 7, 2026
Claude Sonnet 5.5
Muse Spark Open is comparatively weak here — needs about 1 TB of memory at 4-bit; no first-party per-token price confirmed
Scores close to Opus 5.5 on several benchmarks (e.g. GDPval-AA v2.1 knowledge-work Elo) at a fraction of the cost
Claude Sonnet 5.5
Muse Spark Open is comparatively weak here — weakest of the three Muse models (Wonder Full scores 56, Wonder 52)
Meta's first open-weight Muse model - 816B-parameter MoE with 42B active, accepting text, image, video and audio input
Muse Spark Open
Open weights make this possible at all — Claude Sonnet 5.5 is API-only, so it cannot leave the vendor's servers.
Artificial Analysis Intelligence Index of 39, first among US open-weight models
Muse Spark Open
Meta's October 15, 2026 open-weight Muse Spark - an 816B/42B-active multimodal MoE with a 1M context under a gated Muse Model License — and its weights are open while Claude Sonnet 5.5 is API-only.
About 143 output tokens/sec; up to 128K output tokens
Muse Spark Open
Meta's October 15, 2026 open-weight Muse Spark - an 816B/42B-active multimodal MoE with a 1M context under a gated Muse Model License — and it is the newer of the two.
Lowest cost at scale
Muse Spark Open
Its weights are open, so at volume you pay for your own hardware instead of Claude Sonnet 5.5's $2/$10 per 1M tokens.
Which should you pick?
A cost-sensitive startup shipping high volume
→ Muse Spark Open
At Open weight (self-host / free) it undercuts Claude Sonnet 5.5, and on millions of tokens that margin decides the monthly bill.
A team with data-privacy or self-hosting needs
→ Muse Spark Open
Open weights let you run it on your own hardware; Claude Sonnet 5.5 is API-only.
Anyone whose priority is terminal-bench 4.0 agentic coding jumps to 70.6%, up from claude sonnet 5's 10.3%
→ Claude Sonnet 5.5
It is specifically built for that.
Anyone whose priority is meta's first open-weight muse model - 816b-parameter moe with 42b active, accepting text, image, video and audio input
→ Muse Spark Open
That is its strongest area.
Claude Sonnet 5.5: where it fits
Anthropic's September 28, 2026 mid-tier update — same $2/$10 pricing as Sonnet 5 but a large agentic-coding jump (Terminal-Bench 4.0: 70.6% vs 10.3%). Released September 28, 2026 by Anthropic, it is built for terminal-Bench 4.0 agentic coding jumps to 70.6%, up from Claude Sonnet 5's 10.3%, same $2/$10 per million token pricing as Sonnet 5, with cache-read price cut 50% to $0.10/MTok as of October 7, 2026, scores close to Opus 5.5 on several benchmarks (e.g. GDPval-AA v2.1 knowledge-work Elo) at a fraction of the cost, and anthropic highlights stronger document/slide generation, spreadsheet work, and visual chart recognition (Chartography: 61.6%).
Its trade-offs are real: anthropic is explicit that Opus 5.5 'remains clearly stronger' on complex, open-ended work requiring sustained judgment, 1M-token context isn't uniformly available across every platform/plan, consistent with the rest of the 5.5 family, and mid-tier update released a week after Opus 5.5 (Sept 22) — Haiku 5.5 followed Oct 7 to complete the family. At $2 in / $10 out per million tokens, it sits in the mid price band.
Muse Spark Open: where it fits
Meta's October 15, 2026 open-weight Muse Spark - an 816B/42B-active multimodal MoE with a 1M context under a gated Muse Model License. Released October 15, 2026 by Meta, it is built for meta's first open-weight Muse model - 816B-parameter MoE with 42B active, accepting text, image, video and audio input, artificial Analysis Intelligence Index of 39, first among US open-weight models, and about 143 output tokens/sec; up to 128K output tokens.
Its trade-offs: weakest of the three Muse models (Wonder Full scores 56, Wonder 52), muse Model License: attribution required and a revenue threshold (reported as about $20M; check the license text) before a separate license is needed, and needs about 1 TB of memory at 4-bit; no first-party per-token price confirmed. As an open-weight model, its running cost is your own hardware rather than a per-token fee.
The bottom line for this matchup
The defining split here is open vs. closed. Muse Spark Open gives you weights you control — self-host it, fine-tune it, keep data in-house, pay only for hardware. Claude Sonnet 5.5 gives you a managed, always-updated API with no infrastructure to run. Teams with GPUs, privacy requirements, or huge volume often favour the open model; teams that want zero ops and the latest capabilities favour the closed one. Capability is close enough that this operational question, not the benchmark, usually decides it.
Want both Claude Sonnet 5.5 and Muse Spark Open 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.
See pricingFrequently asked questions
Is Claude Sonnet 5.5 or Muse Spark Open better for coding?
Public SWE-Bench figures are not available for either model, so the honest test is your own repository — run an identical real bug through both. By design, Claude Sonnet 5.5 leans toward terminal-bench 4.0 agentic coding jumps to 70.6%, up from claude sonnet 5's 10.3% while Muse Spark Open leans toward meta's first open-weight muse model - 816b-parameter moe with 42b active, accepting text, image, video and audio input, and that positioning usually predicts which feels better on your codebase.
Which is cheaper, Claude Sonnet 5.5 or Muse Spark Open?
Muse Spark Open is open-weight, so self-hosting means no per-token fee (you pay for hardware instead), while Claude Sonnet 5.5 is API-metered at $2/$10 per 1M tokens. For most teams without GPUs, the API model is cheaper to start; at very high volume, self-hosting can win.
Which has the bigger context window?
Both advertise 1M tokens (~1,500 pages). Remember advertised ≠ usable: recall typically degrades before the ceiling.
Can I use both Claude Sonnet 5.5 and Muse Spark Open together?
Yes — a multi-model platform like LumiChats gives you Claude Sonnet 5.5, Muse Spark Open 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 5.5 or Muse Spark Open?
Muse Spark Open — released October 15, 2026, about 17 days after Claude Sonnet 5.5.
Related comparisons
Specifications and benchmarks reflect publicly reported figures as of June 2026 and may change as providers release updates. Always verify on your own workload.