ByteDance Seed: Seed 1.8
Seed 1.8 is a reasoning model from ByteDance Seed released on Dec 28, 2025. It reads text and images and writes text, with a 256K token context window and up to 64K tokens per reply.
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It costs $0.1188 per million input tokens and $1.19 per million output tokens. Cached input bills at $0.0238, 80% less than fresh input.
It supports tool calling, structured JSON output and prompt caching.
3 providers serve it, including Volcengine Ark, Ofox and Requesty.
- Modalities
- In / out price
- $0.1188 / $1.19 per 1M
- Context
- 256K
- Max output
- 64K
- Released
- Dec 28, 2025
- Knowledge cutoff
- n/a
- Tool calling
- Structured output
- Reasoning
- Prompt caching
- Open weights
- Free to use
Seed 1.8 pricing
USD, as listed on Oct 15, 2026. Most bills are input heavy, so the cached input rate matters as much as the headline price.
| Input | $0.1188 / 1M tokens | |
|---|---|---|
| Output | $1.19 / 1M tokens | |
| Cached input (read) | $0.0238 / 1M tokens | 80% off input |
| Prompts over 32K | $0.1781 in, $2.37 out | long context rate |
| Prompts over 128K | $0.3562 in, $3.56 out | long context rate |
Seed 1.8 providers
3 providers serve it, including Volcengine Ark, Ofox and Requesty. Each host sets its own price and limits, so the cheapest one is not always the one with the longest context.
| Provider | Input /M | Output /M | Cache read /M | Context | Max output |
|---|---|---|---|---|---|
| Volcengine Ark | $0.1188 | $1.19 | $0.0238 | 256K | 64K |
| Ofox | $0.12 | $0.29 | $0.023 | 256K | 64K |
| Requesty | $0.25 | $2 | $0.05 | 256K | 256K |
What Seed 1.8 costs per month
Pick a workload close to yours or type your own volumes.
Supported request parameters
What you can set when you call Seed 1.8 through an OpenAI compatible API.
- Tools
tools - Structured outputs
structured_outputs - Reasoning
reasoning - Temperature
temperature
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Seed 1.8 questions
How much does the Seed 1.8 API cost?
$0.1188 per million input tokens and $1.19 per million output tokens, with cached input at $0.0238. Prompts over 32K tokens bill at $0.1781 input and $2.37 output. The estimator on this page turns that into a monthly bill for your own workload.
What is the context window of Seed 1.8?
256,000 tokens of input, and it can write up to 64,000 tokens in one reply. As a rough guide, a million tokens is around 750,000 English words.
Which providers serve Seed 1.8?
3 providers serve it, including Volcengine Ark, Ofox and Requesty. Prices differ by host, so the Providers table on this page lists each one with its input and output price.
Does Seed 1.8 support tool calling?
Yes. It accepts tool definitions and can return JSON that matches a schema, which is what an agent needs to call your APIs.
Is Seed 1.8 open source?
No. ByteDance Seed serves it through an API only, so you cannot download the weights or host it yourself.
When was Seed 1.8 released?
Dec 28, 2025.
Catalog data from models.dev (MIT licensed), refreshed daily, last on Oct 15, 2026. The summary is written from these facts.
Building on Seed 1.8?
I test your real tasks on it and the two closest alternatives, then ship the agent on whichever wins on cost and accuracy.
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