OpenAI compatible API · Attested · Public status

Doubao Seed 1.8 vs Z.ai: GLM 5.3 Flash

Z.ai: GLM 5.3 Flash has the lower published input-plus-output rate, more Credits provider routes and the larger context window. There is not enough recent probe data to compare speed. Compare price, speed, context, and privacy.

Verify gateway

Onebase URL to migrate

100sof models and routes

0prompt or output logs. Always.

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

Z.ai: GLM 5.3 Flash has the lower published input-plus-output rate, more Credits provider routes and the larger context window. There is not enough recent probe data to compare speed.

$2.37375/1MDoubao Seed 1.8 cheapest route

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

not enough dataDoubao Seed 1.8 fastest measured p50 TTFT

636 msZ.ai: GLM 5.3 Flash fastest measured p50 TTFT via together

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.

Doubao Seed 1.8Z.ai: GLM 5.3 Flash

Model idbytedance/doubao-seed-1.8-251228z-ai/glm-5.3-flash

Publisher BytePlus ModelArk Z.AI

AI IQ — IQ 120#42

Context262,144 tokens1,048,576 tokens

Credits provider routes134

Cheapest route$2.37375/1M$0.32705/1M

Cached input$0.05275/1M$0.01266/1M to $0.076488/1M

Privacy postureprovider posture varieshas Confidential route (E2EE + ZDR)

Fastest measured p50 TTFTnot enough data636 ms via together

Highest measured throughputnot enough datanot enough data

Recent route uptime rangenot enough data0.00% to 100.00%

Modes chat chat

Doubao Seed 1.8 routes

Overview1 Credits routes

Z.ai: GLM 5.3 Flash routes

Overview34 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.trustedrouter.com/v1",
    api_key="sk-tr-v1-..."
)

response = client.chat.completions.create(
    model="bytedance/doubao-seed-1.8-251228",
    messages=messages,
)

Questions

Which should I use, Doubao Seed 1.8 or Z.ai: GLM 5.3 Flash?

Z.ai: GLM 5.3 Flash has the lower published input-plus-output rate, more Credits provider routes and the larger context window. There is not enough recent probe data to compare speed.

Is Doubao Seed 1.8 or Z.ai: GLM 5.3 Flash cheaper?

The current cheapest TrustedRouter route is $2.37375/1M for Doubao Seed 1.8 and $0.32705/1M for Z.ai: GLM 5.3 Flash. The comparison uses current catalog prices and updates as provider pricing changes.

Is Doubao Seed 1.8 or Z.ai: GLM 5.3 Flash faster?

Current measured p50 time to first token is not enough data for Doubao Seed 1.8 and 636 ms 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 Doubao Seed 1.8 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 bytedance/doubao-seed-1.8-251228 and z-ai/glm-5.3-flash. This makes side-by-side evals possible without maintaining two provider integrations.