GLM-5.3-Flash vs GPT-6 Luna vs Muse Spark 1.3

GPT-6 Luna is the better all-round choice, scoring 83/100 against GLM-5.3-Flash (77) and Muse Spark 1.3 (73). It leads on capability and price. Muse Spark 1.3 wins on inputs & features. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%. Capability uses the average of shared benchmarks (FrontierMath Tiers 1–3 and OTIS Mock AIME 2024–2025), because GPT-6 Luna has no Capabilities Index score yet.

GPT-6 Luna is cheaper at $0.10 input / $0.50 output per million tokens (official OpenAI API price). GLM-5.3-Flash costs $0.15 input / $0.50 output per million tokens (official Z.AI API price); Muse Spark 1.3 costs $1.25 input / $4.25 output per million tokens (official Meta API price). At a typical mix of three input tokens to one output token, that is $0.20 per million tokens for GPT-6 Luna versus $0.237 for GLM-5.3-Flash (1.2× as much) and $2.00 for Muse Spark 1.3 (10× as much).

Not every model here has a Capabilities Index score, so we compare the average of shared benchmarks (FrontierMath Tiers 1–3 and OTIS Mock AIME 2024–2025): GPT-6 Luna 88.9%, Muse Spark 1.3 86.8% and GLM-5.3-Flash 74.8%. On individual benchmarks: FrontierMath Tiers 1–3 — GPT-6 Luna 79.0%, Muse Spark 1.3 74.4%, GLM-5.3-Flash 55.8%; OTIS Mock AIME 2024–2025 — Muse Spark 1.3 99.2%, GPT-6 Luna 98.9%, GLM-5.3-Flash 93.9%.

There are no published SWE-bench Verified results for GLM-5.3-Flash, GPT-6 Luna and Muse Spark 1.3 yet, so there is no like-for-like coding score. On overall capability, GPT-6 Luna leads, which tends to carry over to coding, but test on your own codebase. All three support tool calling for agent workflows.

GPT-6 Luna and Muse Spark 1.3 have the largest context windows (1,050,000 and 1,048,576 tokens), against 1,000,000 for GLM-5.3-Flash. Maximum output per response: GLM-5.3-Flash up to 131,072, GPT-6 Luna up to 128,000, Muse Spark 1.3 up to 131,072 tokens.

GLM-5.3-Flash accepts text, images, PDFs and video; GPT-6 Luna accepts text, images and PDFs; Muse Spark 1.3 accepts text, images, PDFs, audio and video. Muse Spark 1.3 handles the widest range of inputs.

GLM-5.3-Flash publishes its weights and can be self-hosted; GPT-6 Luna and Muse Spark 1.3 is proprietary.

GPT-6 Luna is the newest, released Sep 22, 2026. Muse Spark 1.3 came out Sep 2, 2026; GLM-5.3-Flash came out Aug 26, 2026. Knowledge cutoff: GPT-6 Luna May 18, 2026.

Each model gets a 0–100 score on capability (50%, independent benchmark results); price (25%, blended price per million tokens (3 input : 1 output), log scale); inputs & features (15%, image, PDF, audio and video input, tool calling, structured output and reasoning); context window (10%, maximum tokens per request, log scale). Dimensions missing for any model are dropped and the remaining weights rescaled, so every model is judged on the same evidence. Specs and prices come from public model listings and the labs’ own API pages; capability scores come from independent benchmark runs. Data updated Oct 4, 2026.