Bring your own key

OpenAI: GPT-5.5 Pro vs Z.ai: GLM 5.3 Flash

One key routes both. Starter credit covers your first GLM 5.3 Flash requests, while GPT-5.5 Pro runs on your own provider key. Switch by changing the model name.

Compare routesProviders, price, context, and policy posture in one view.

Use auto when uptime mattersKeep a primary model and let fallback handle provider failures.

Same API shapeUse the OpenAI client and set the model you want.

Practical read

Monthly evidence

GPT-5.5 Pro has the larger context window. Z.ai: GLM 5.3 Flash has more Credits provider routes. A published Credits price comparison is not available for both models. There is not enough recent probe data to compare speed.

$221.55/1MOpenAI: GPT-5.5 Pro cheapest route

$0.32705/1MZ.ai: GLM 5.3 Flash cheapest route

not enough dataOpenAI: GPT-5.5 Pro fastest measured p50 TTFT

not enough dataZ.ai: GLM 5.3 Flash fastest measured p50 TTFT

The price comparison adds each route's rate for one million input tokens and one million output tokens; your cost depends on your input/output mix. Prices and live route measurements can change. Use the monthly reports when you need a stable evidence window, then run a small task-specific eval before choosing a production default.

OpenAI: GPT-5.5 ProZ.ai: GLM 5.3 Flash

Model idopenai/gpt-5.5-proz-ai/glm-5.3-flash

Publisher OpenAI Z.AI

AI IQ — IQ 119#45

Context1,050,000 tokens1,048,576 tokens

Credits provider routes032

Cheapest route$221.55/1M$0.32705/1M

Cached inputNot published$0.015825/1M to $0.068575/1M

Privacy postureprovider posture varieshas Confidential route (E2EE + ZDR)

Fastest measured p50 TTFTnot enough datanot enough data

Highest measured throughputnot enough datanot enough data

Recent route uptime rangenot enough datanot enough data

Modes chat chat

OpenAI: GPT-5.5 Pro routes

Overview0 Credits routes

Z.ai: GLM 5.3 Flash routes

Overview32 Credits routes
PricingInput, cached input, and output rates
ProvidersAll serving providers

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Production choice

Pick a default model. Keep fallback enabled.

TrustedRouter is useful when you know the model you want, but still need provider rollover, budget limits, usage records, and a prompt path you can verify.

OpenAI clientPython

client = OpenAI(
    base_url="https://api-azure.trustedrouter.com/v1",
    api_key="sk-tr-v1-..."
)

response = client.chat.completions.create(
    model="openai/gpt-5.5-pro",
    messages=messages,
)

Questions

Which should I use, OpenAI: GPT-5.5 Pro or Z.ai: GLM 5.3 Flash?

Is OpenAI: GPT-5.5 Pro or Z.ai: GLM 5.3 Flash cheaper?

The current cheapest TrustedRouter route is $221.55/1M for OpenAI: GPT-5.5 Pro and $0.32705/1M for Z.ai: GLM 5.3 Flash. The comparison uses current catalog prices and updates as provider pricing changes.

Is OpenAI: GPT-5.5 Pro or Z.ai: GLM 5.3 Flash faster?

Current measured p50 time to first token is not enough data for OpenAI: GPT-5.5 Pro and not enough data for Z.ai: GLM 5.3 Flash. These are routed probe measurements, not vendor-advertised speeds, and update as new samples arrive.

Can I test OpenAI: GPT-5.5 Pro and Z.ai: GLM 5.3 Flash with the same API?

Yes. Use the same OpenAI-compatible TrustedRouter base URL and API key, then change only the model id between openai/gpt-5.5-pro and z-ai/glm-5.3-flash. This makes side-by-side evals possible without maintaining two provider integrations.