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Comparisons

OpenAI GPT-OSS 120B vs GLM 5.3 Flash

On provider list prices, GLM 5.3 Flash costs $0.15 per million input tokens against $0.15 for OpenAI GPT-OSS 120B: effectively level. Output is $0.50 against $0.60 (1.2x).

OpenAI GPT-OSS 120BG GLM 5.3 Flash
LabOpenAIZ.ai
AccessOpen weightsOpen weights
Context window128K tokens1M tokens
List price, input$0.15 / M tokens$0.15 / M tokens
List price, output$0.6 / M tokens$0.5 / M tokens
Cached inputn/a$0.03 / M tokens
LicenseCustom licenseNot listed
Fine-tunableYesYes

Specifications and provider list prices from the Allocate catalog, checked 2026-07-21.

What the numbers say

Take 1,000,000 requests a month at 1,200 input and 350 output tokens each. That workload costs $355 a month on GLM 5.3 Flash and $390 on OpenAI GPT-OSS 120B at list: a gap of $35.

GLM 5.3 Flash reads 1M tokens per request against 128K for OpenAI GPT-OSS 120B, 8.0x the window. That decides which one can take whole documents without splitting them.

OpenAI GPT-OSS 120B$0.15$0.60
GLM 5.3 Flash$0.15$0.50
InputOutput

Choose OpenAI GPT-OSS 120B for

  • Training toward a model you own
OpenAI GPT-OSS 120B details

Choose GLM 5.3 Flash for

  • The longer context window (1M vs 128K tokens)
  • Published cached-input pricing ($0.03 per M tokens)
GLM 5.3 Flash details

Common questions

Which is cheaper, OpenAI GPT-OSS 120B or GLM 5.3 Flash?

GLM 5.3 Flash, on this workload shape. At list prices it is $0.15/$0.50 per million tokens in and out against $0.15/$0.60 for OpenAI GPT-OSS 120B. Billed on Allocate: $0.16/$0.54 against $0.16/$0.64.

Which has the bigger context window?

GLM 5.3 Flash: 1,048,576 tokens (1M) against 131,072 (128K) for OpenAI GPT-OSS 120B.

Can I fine-tune OpenAI GPT-OSS 120B or GLM 5.3 Flash?

Both publish open weights (OpenAI GPT-OSS 120B: Custom license; GLM 5.3 Flash: Not listed), so both can be fine-tuned. On Allocate the trained weights stay inside your boundary and belong to you.

Related comparisons

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Run the numbers on your workload

LLM price comparisonAgent cost calculatorOpenAI GPT-OSS 120BGLM 5.3 Flash

Or don’t choose. On Allocate a route name is the contract: point yours at one model today, swap to the other tomorrow, and compare them on your live traffic with per-token metering.

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