# Muse Spark Open Muse Spark Open is Meta's open-weight multimodal reasoning model, a sparse mixture-of-experts with 816 billion total and 42 billion active parameters. It is the downloadable sibling of the hosted Muse Spark line, aimed at coding and long-horizon agentic work that you can run on your own hardware or any inference host. Its published context window is 1,048,576 tokens. The advertised input rate is $1.25 per million input tokens. The advertised output rate is $4.25 per million output tokens. - Model identifier: ` meta/muse-spark-open ` - Creator: Meta - Providers: Fireworks - Model type: Text generation - Canonical model page: [Muse Spark Open]() - API availability: Listed as serving through Impossibl. - Creator release date: 2026-10-15 ## Providers Fireworks hosts Muse Spark Open. Impossibl routes your request intelligently and handles failover automatically when a provider is down. | Provider | Endpoint location | Routes | Verified context window | Tool calling | | --- | --- | --- | --- | --- | | Fireworks | Not specified | 1 | Not verified | Not verified | The model price applies whichever provider serves the request. Endpoint locations do not guarantee inference residency. ## Specs and Capabilities - Context window: 1,048,576 tokens - Maximum output tokens: Not published in the public catalog; this is separate from the context window. - Inputs: text, image - Outputs: text - Tool calling: Not published ## API access Use ` meta/muse-spark-open ` as the model identifier through the Impossibl API. Published API endpoints: - ` /v1/chat/completions ` [API quickstart]() · [Models and billing documentation]() ## Published API prices All rates are in USD. An unpublished rate is unknown, not zero. Workspace-specific pricing, taxes, balance-purchase fees, billing adjustments, and tool charges can affect the amount paid. | Usage | Published base rate | Billing unit | | --- | --- | --- | | Input | $1.25 | per million input tokens | | Output | $4.25 | per million output tokens | | Cache read | $0.15 | per million cached input tokens | | Cache write (default retention) | Not published | per million tokens | | Cache write (one-hour retention) | Not published | per million tokens | | Audio input | Not published | per million audio input tokens | ## Benchmarks Last checked: 2026-10-19T03:22:58.358Z. Configurations are evaluated separately. API scores retain their original units. Unmeasured scores are omitted. ### Muse Spark Open (Xhigh) Source: [Evaluation source]() | Benchmark | Score | | --- | --- | | Intelligence Index | 38.87 | | Omniscience Index | 24.65 | | GPQA | 88.99% | | Humanity’s Last Exam | 43.88% | | SciCode | 58.45% | | CritPt | 14.86% | | AA-LCR | 78.33% | | GDPval Elo | 1401.12 | | GDP.pdf All-pass | 18.60% | | AutomationBench Partial | 49.71% | | MMMU-Pro | 80.92% | | legal index (API) | 44.5 | | economics index (API) | 51 | | engineering index (API) | 40.4 | | intelligence index (API) | 38.9 | | strategy and ops index (API) | 42.7 | | finance and accounting index (API) | 42.5 | Full benchmark data and breakdowns: [Complete benchmark snapshot](). ## Availability and retirement The model is listed as serving. No retirement is announced in the current public catalog. ## Frequently asked questions ### What is Muse Spark Open? Muse Spark Open is Meta's open-weight multimodal reasoning model, a sparse mixture-of-experts with 816 billion total and 42 billion active parameters. It is the downloadable sibling of the hosted Muse Spark line, aimed at coding and long-horizon agentic work that you can run on your own hardware or any inference host. Sources: [Meta AI Research: Introducing Muse Spark Open](); [OpenRouter: Muse Spark Open](); [Fireworks AI model API: muse-spark-open]() ### How much does Muse Spark Open cost? Muse Spark Open costs $1.25 per million input tokens and $4.25 per million output tokens through the Impossibl API. Cache reads cost $0.15 per million tokens. All rates are in USD. ### What is the context length of Muse Spark Open? Muse Spark Open has a 1,048,576-token context window through the Impossibl API. ### What inputs and outputs does Muse Spark Open support? Muse Spark Open accepts text and image as input. Muse Spark Open returns text. ### How do I use Muse Spark Open through an API? Muse Spark Open is available through the Impossibl API. Use meta/muse-spark-open as the model identifier with /v1/chat/completions. The quickstart explains how to create an API key and send your first request. ### When was Muse Spark Open released? Meta released Muse Spark Open on October 15, 2026. Sources: [Creator release announcement]() ## Sources and related links Prices, limits, capabilities, endpoints, and availability come from the public Impossibl catalog. Creator documentation supplies descriptions and release dates where available; it does not override the published API offering. - [Public Impossibl model catalog]() - [Full model directory as JSON]() - [Muse Spark Open: model details and pricing]() - [Model directory]() - [Meta AI Research: Introducing Muse Spark Open]() - [OpenRouter: Muse Spark Open]() - [Fireworks AI model API: muse-spark-open]()