Meta: Muse Spark 1.3

Spark 1.3 is a point release whose one notable row in the catalog is the license line, and that row is notable for having stalled. Released 2 September 2026, it is Meta's reasoning model for long-running agent work: the OpenRouter listing positions it for "long-running agentic, multi-agent, and coding workflows," built to track information across extended tasks and request confirmation when needed. It keeps the family's million-token window — a context window of 1048576tokensopenrouter-models, last checked 2026-09-14 — and the row lists $1.25per million tokensopenrouter-models, last checked 2026-09-14 input against $4.25per million tokensopenrouter-models, last checked 2026-09-14 output, with $0.15per million tokensopenrouter-models, last checked 2026-09-14 on a cache read.

The detail worth reading twice is what the llm-releases card records under License and Weights: Open weights · Meta license (weights pending); weights not releasedsource, accessed 2026-09-03. The listing first appeared on a Spark flagship with Muse Spark 1.2's card on 5 August 2026 — the 1.1 card read Proprietary — and one full flagship release later the Weights field still has not moved. It is a listing, not a release: nothing is downloadable, and the pending state is the checkable fact — if the weights land, the line's flagship is open again; if they do not, the flag stays a dated record of an open-sourcing hope unfulfilled.

One limitation sits on the card before you pipe audio into it. OpenRouter's notice for this row says "Audio understanding in Muse Spark 1.3 is currently not fully supported, and response quality for requests including audio content may be degraded."