Which is cheaper, GPT-6 Luna and GLM-5.3?

GPT-6 Luna has the lowest input price. Per 1M input tokens: GPT-6 Luna from $0.10 and GLM-5.3 from $0.56.

Which has the larger context window, GPT-6 Luna and GLM-5.3?

GLM-5.3 has the largest context window: GPT-6 Luna 400,000 tokens and GLM-5.3 1,048,576 tokens.

Can I switch between GPT-6 Luna and GLM-5.3 without changing my code?

Yes. All of them are served through FastRouter's OpenAI-compatible API, so switching is a change of the model parameter (openai/gpt-6-luna, z-ai/glm-5.3).

GPT-6 Luna vs GLM-5.3

Side-by-side pricing per provider, context window, benchmark scores and speed, all on one OpenAI-compatible API.

GPT-6 Luna OpenAIopenai/gpt-6-luna

GLM-5.3 Z.aiz-ai/glm-5.3

Creator

OpenAI

Z.ai

Released

Sep 22, 2026

Aug 18, 2026

Context window

400K

1.05M

Max output

128K

131K

Input / 1MLowest provider price

$0.10

$0.56$0.56–$1.40 across 5

Output / 1MLowest provider price

$0.50

$2.50$2.50–$4.40 across 5

Providers

IntelligenceArtificial Analysis index

38.1

44.8

CodingArtificial Analysis index

—

74.8

Accepts

Files, Image, Text

Text

Produces

Text

Tool calling

Yes

Structured output

Yes

Reasoning

Yes

GPT-6 Luna vs GLM-5.3: summary

GPT-6 Luna and GLM-5.3 are both available through FastRouter's OpenAI-compatible API, so switching between them is a change of model id, not a new integration.

GPT-6 Luna, from OpenAI, has a 400,000-token context window, costs $0.10/1M input and $0.50/1M output tokens and scores 38.1 on the Artificial Analysis Intelligence Index.

GLM-5.3, from Z.ai, has a 1,048,576-token context window, costs from $0.56/1M input and $2.50/1M output tokens across 5 providers and scores 44.8 on the Artificial Analysis Intelligence Index.

GPT-6 Luna is the cheapest on input, 5.6× cheaper than the next model, GLM-5.3 has the largest context window and GLM-5.3 scores highest for intelligence.

Switch with one line

client = OpenAI(base_url="https://api.fastrouter.ai/api/v1", api_key="<FASTROUTER_API_KEY>") client.chat.completions.create(model="openai/gpt-6-luna", messages=[...]) # or client.chat.completions.create(model="z-ai/glm-5.3", messages=[...])

Full API docs

Frequently asked questions

More comparisons

Benchmark scores sourced from ArtificialAnalysis