# Seed 1.8 (251228)

> ByteDance Seed reasoning model that combines multimodal understanding, tool calling and structured output.

## Key facts

- Model author: ByteDance
- Input: $0.25 per 1M tokens (starting tier)
- Output: $2.00 per 1M tokens (starting tier)
- Cached input: $0.05 per 1M tokens
- Context window: 256,000 tokens
- Maximum output: 64,000 tokens
- Input modalities: image, text
- Output modalities: text
- Capabilities: reasoning, tools, vision
- Released: 2025-12-28
- Model IDs: `byteplus/seed-1-8-251228`
- Model page: https://www.realrelay.ai/model/bytedance/seed-1-8-251228

## Overview

Seed 1.8 (251228) is a reasoning model from the ByteDance Seed team. BytePlus lists it with deep reasoning, text generation, multimodal understanding, tool calling and structured output. It reads text and images, can think through a task before answering, and can return answers in a defined format for programmatic use.

It has a 256K-token context window and can generate up to 64K output tokens. It accepts text and image input and returns text. It was released on December 28, 2025.

## Capabilities

Seed 1.8 (251228) supports reasoning, tool calling and vision. images can accompany a text prompt, and the reply comes back as text.

Structured output lets it return responses in a fixed format, which helps when the results feed directly into other software.

## Pricing

Seed 1.8 (251228) is priced from $0.25 per 1M input tokens and from $2.00 per 1M output tokens. Pricing is tiered, so these figures are the starting tier. Cache reads are billed from $0.05 per 1M tokens.

Seed 1.8 (251228) is available through RealRelay's OpenAI-compatible API.

## Use cases

Use Seed 1.8 (251228) for assistants that combine image understanding with tool calls, such as reading a chart or screenshot and then querying a system for related data.

Its structured output and large context window also suit document processing, where long text is read in one request and key fields come back in a format that code can parse.

## Call it

OpenAI-compatible chat completions:

```bash
curl https://www.realrelay.ai/v1/chat/completions \
  -H "Authorization: Bearer $REALRELAY_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"model": "byteplus/seed-1-8-251228", "messages": [{"role": "user", "content": "Hello"}]}'
```

## FAQ

### What is Seed 1.8 (251228)?

Seed 1.8 (251228) is a reasoning model from the ByteDance Seed team with multimodal understanding, tool calling and structured output. It accepts text and image input and returns text.

### How much does Seed 1.8 (251228) cost?

Seed 1.8 (251228) is priced from $0.25 per 1M input tokens and from $2.00 per 1M output tokens, and the figures are the starting tier of tiered pricing. Cache reads are billed from $0.05 per 1M tokens.

### What is the context window of Seed 1.8 (251228)?

Seed 1.8 (251228) has a 256K-token context window and can generate up to 64K output tokens.

### What inputs and outputs does Seed 1.8 (251228) support?

Seed 1.8 (251228) accepts text and image input and returns text.

### Does Seed 1.8 (251228) support structured output?

Yes. BytePlus lists structured output for Seed 1.8 (251228), together with deep reasoning, multimodal understanding and tool calling.

### When was Seed 1.8 (251228) released?

Seed 1.8 (251228) was released on December 28, 2025.

### How do I call Seed 1.8 (251228) via the API?

Send requests to RealRelay's OpenAI-compatible API with the model ID byteplus/seed-1-8-251228 to use Seed 1.8 (251228).