What are the strengths of this model?

Specialized in code generation, completion, and debugging. Strong understanding of programming languages and syntax. Can generate efficient and context-aware code snippets.

What are the weaknesses of this model?

May struggle with highly niche or legacy programming frameworks. Limited knowledge outside the software development domain. Code security best practices may require verification.

What are the best use cases?

Assisting developers with writing and optimizing code. Automating repetitive coding tasks and boilerplate. Code review, refactoring, and documentation generation.

ByteDance SeedProprietary

ByteDance Seed2.1 Pro

Name: ByteDance Seed2.1 Pro
Author: ByteDance Seed

Compare this model

A coder model developed by ByteDance's Seed team.

Share:X Hatena LINE

Parameters

Undisclosed

Context Window

License

Proprietary

Release Date

2026-06-23

API Pricing

Input Price (per 1M tokens)

Output Price (per 1M tokens)

Billing Mode: standard

Strengths

•Specialized in code generation, completion, and debugging.
•Strong understanding of programming languages and syntax.
•Can generate efficient and context-aware code snippets.

Weaknesses

•May struggle with highly niche or legacy programming frameworks.
•Limited knowledge outside the software development domain.
•Code security best practices may require verification.

Use Cases

•Assisting developers with writing and optimizing code.
•Automating repetitive coding tasks and boilerplate.
•Code review, refactoring, and documentation generation.

Deep Analysis

HLE

55.7%

expert-level exam; close to frontier small models

SciCode

59.8%

scientific computation; beats GPT-5.5 (58.4%)

Terminal-Bench 2.1

71%

agentic terminal use; strong for a proprietary model

SWE-Pro

57.5%

software engineering; near GPT-5.5 (58.6%)

Price

$0.89 / $4.45 per 1M

Volcengine/Doubao; Turbo half price; versus GLM-5.1 $1.40/$4.40

Context Window

262.1K tokens

multimodal; smaller than 1M frontier window

Strengths

・Cheap relative to the frontier: $0.89/$4.45 per 1M undercuts GLM-5.1 and sits far below US frontier rates while beating GPT-5.5 on SciCode (59.8 vs 58.4) and NL2Repo (47.0 vs 45.1).
・Strong agentic and coding profile: Terminal-Bench 2.1 71%, SWE-Pro 57.5%, MCP Atlas 83.8%, OSWorld 78.8% - real, not marketing, numbers.
・Seed-Evolving ships weekly model updates under one Model ID, turning model delivery from fixed versions into continuous online evolution.

Weaknesses

・262.1K context is well below the 1M frontier window, so long-document and very long agent runs need chunking or a different model.
・Proprietary weights - no on-prem control, unlike the open Chinese models (Qwen, GLM, DeepSeek) it is often compared against.
・Lower name recognition outside China; most benchmarks are vendor- or aggregator-reported and Western independent runs are still thin.

Competitor Comparison

Model	Arena	SWE	GPQA	Price
GPT-5.5	frontier	58.6% (SWE-Pro)	N/A	premium US rate
Qwen3.8-2.4T-A95B	open	N/A	N/A	$2 / $6 per 1M (1M ctx)
GLM-5.1	open	N/A	N/A	$1.40 / $4.40 per 1M

Overview

Doubao-Seed-2.1 is ByteDance's Seed family flagship, with the Pro variant opened on Volcengine on June 24, 2026. Pro and Turbo are both deep-thinking models with a uniform 256K context window, upgraded complex coding delivery, long agent execution and multimodal vision. On ByteDance's disclosed benchmarks the flagship Pro beats or nears GPT-5.5 on several code and development evals. Pricing is the headline: Pro is $0.89 per million input and $4.45 per million output tokens (Turbo halves that). On SciCode the Pro scores 59.8% versus GPT-5.5's 58.4%, and on NL2Repo-Bench 47.0% versus 45.1%; on SWE-Pro it reaches 57.5%, close to GPT-5.5's 58.6% and above Gemini-3.1-Pro's 54.2%. Volcengine also ships Seed-Evolving, a weekly rolling upgrade under one Model ID.

Benchmarks & Performance

Detailed Comparison

Seed 2.1 Pro is best read as the cheap, China-hosted answer to GPT-5.5-class coding. At $0.89/$4.45 it undercuts GLM-5.1 ($1.40/$4.40) and sits far below US frontier rates while matching or beating GPT-5.5 on specific code evals. | Feature | Seed 2.1 Pro | GPT-5.5 | Qwen3.8-2.4T-A95B | | :--- | :--- | :--- | :--- | | **Price (in/out)** | $0.89 / $4.45 | premium | $2 / $6 | | **Context** | 262.1K | ~1M | 1M | | **SciCode** | 59.8% | 58.4% | N/A | | **SWE-Pro** | 57.5% | 58.6% | N/A | | **Weights** | proprietary | proprietary | open | **The call.** For China-region or cost-sensitive coding/agent workloads, Seed 2.1 Pro is a credible GPT-5.5 alternative at a fraction of the price. For 1M-context or on-prem needs, Qwen/GLM/DeepSeek open weights still win.

Community Feedback

The API opening drew attention because the Pro variant's code benchmarks land at or above GPT-5.5 on several rows, something few non-US models claim. Aggregator threads (AnotherWrapper) framed Seed 2.1 Pro as ~8% cheaper than GLM-5.1 per million tokens with comparable scores. * **What landed.** SciCode 59.8% and SWE-Pro 57.5% beating GPT-5.5 on the first and near on the second; Seed-Evolving's continuous-update model was called a smart delivery shift. * **What drew pushback.** The 262.1K context ceiling versus 1M frontier windows; and that most numbers are vendor- or aggregator-reported with thin Western independent verification. * **Positioning.** Read alongside Doubao Seed 2.1 Lite entering docs, sheets and slides (October 10), ByteDance is pushing Seed across both consumer and enterprise surfaces.

Use Cases

**1. Cost-sensitive coding agents** * Example: a Chinese-region dev shop running thousands of code-gen and repo tasks daily. * Why Seed 2.1 Pro: SciCode 59.8% and SWE-Pro 57.5% at $0.89/$4.45, far below US frontier rates. **2. Enterprise document and multimodal workflows** * Example: contract and spreadsheet analysis with vision input across 262K context. * Why Seed 2.1 Pro: MMMU-Pro 82.7% and ByteDance's enterprise Volcengine integration. **3. Long agent execution** * Example: multi-step browser/desktop agents (OSWorld 78.8%, MCP Atlas 83.8%). * Why Seed 2.1 Pro: strong agent scores at a low per-token price. **When to pick something else** * 1M-context or on-prem control: Qwen3.8 / GLM-5.x / DeepSeek open weights. * Highest absolute frontier reasoning: GPT-5.5 or Claude Opus 5.5.

Latest News

**API opening (June 24, 2026).** ByteDance's Volcengine launched the Doubao-Seed-2.1 series with Pro and Turbo deep-thinking variants and a uniform 256K context window, upgrading complex coding delivery, long agent execution and multimodal vision. Pro pricing is 6 yuan / 30 yuan per million tokens (Turbo halves it); Seed-Evolving ships weekly rolling upgrades under one Model ID. **Benchmarks vs GPT-5.5.** On SciCode 59.8% vs 58.4%, NL2Repo-Bench 47.0% vs 45.1%, and SWE-Pro 57.5% (near GPT-5.5's 58.6%, above Gemini-3.1-Pro 54.2%). On October 10 ByteDance pushed Seed 2.1 Lite into docs, sheets and presentations tasks.

Pricing is the headline: Pro is $0.89 per million input and $4.45 per million output tokens (Turbo halves that). On SciCode the Pro scores 59.8% versus GPT-5.5's 58.4%, and on NL2Repo-Bench 47.0% versus 45.1%; on SWE-Pro it reaches 57.5%, close to GPT-5.5's 58.6% and above Gemini-3.1-Pro's 54.2%. Volcengine also ships Seed-Evolving, a weekly rolling upgrade under one Model ID.

Sources

Analysis generated: 2026-10-13