Released 23 days after Muse Glimmer · All Meta releases
Muse Spark 1.3 is the latest release in Meta's Muse Spark line, published on September 2, 2026, by Artificial Analysis's count the fourth Muse Spark release in five months and the one Mark Zuckerberg described as Meta's largest step forward yet on coding and agent work. It works across a 1 million token context, accepts text, images, and video, and supports tool use, structured output, and selectable reasoning effort up to a max setting that Meta held back for extra safety testing at launch and has since opened up. The headline change is efficiency in agent loops: in comparisons by Meta's own engineers it finishes coding tasks with roughly a fifth fewer tool calls and a quarter fewer tokens than Muse Spark 1.2, taking fewer turns and writing less when the task does not need it. Independent testing by Artificial Analysis put the xhigh setting at 61 on its Intelligence Index, tied with GPT-5.6 Sol and a few points behind Claude Fable 5.1, with 85% on Terminal-Bench 2.1, 94% on GPQA Diamond, and 79% on the AA-LCR long-context test, a four-point drop from 1.2. Muse Spark 1.3 suits coding agents, long-running tool-driven workflows, and long-form instruction following, and Meta reports stronger adversarial robustness and better calibration on which actions are irreversible.
Call Muse Spark 1.3 Contributor on Opper with the OpenAI SDK. Sign up without a credit card. Get started
Muse Spark 1.3 Contributor runs on 2 different routes through the Opper gateway. Compare residency, zero data retention and training posture at a glance, with full data-handling detail per route below.
Each route hosting Muse Spark 1.3 Contributor has its own privacy posture, residency, and GDPR terms. Postures are maintained by Opper with a last-verification timestamp.
Content is retained: used for training by default. Trained on customer data by default. GLOBAL; unknown.
Zero data retention with abuse monitoring: prompts and outputs are kept for abuse monitoring only, for a window the provider does not state, and are not used for training. No training on customer data. GLOBAL; SCCs; DPA available.
Independent benchmark scores — composite indices for reasoning, coding, and math, plus individual eval scores where available.
Call Muse Spark 1.3 Contributor through the Opper gateway with one API key. Opper is drop-in compatible with the OpenAI, Anthropic and Google AI SDKs.
Muse Spark 1.3 Contributor is a premium model on Opper. Sign up needs no credit card: you get an API key straight away and the free models work in the playground and the API. Add a card to use premium models, pay-as-you-go with no minimum.
Copy this and paste it into a coding agent like Claude Code, Cursor or Codex and it'll wire up Opper for you.
import OpenAI from "openai";const client = new OpenAI({apiKey: process.env.OPPER_API_KEY,baseURL: "https://api.opper.ai/v3/compat",});const completion = await client.chat.completions.create({model: "meta-contributor/muse-spark-1.3-contributor",messages: [{ role: "user", content: "Hello" }],});console.log(completion.choices[0].message.content);
Side-by-side on privacy, EU hosting, pricing, and benchmarks.
