Doubao Seed 1.6

Doubao Seed 1.6 is a family of general-purpose foundation models developed by the ByteDance Seed research team and released through Volcano Engine on 11 June 2025 at the company's Force Original Power Conference in Beijing.^[3][4] The family powers the consumer-facing Doubao chatbot app along with assorted AI features inside TikTok, Douyin, CapCut, and ByteDance's enterprise products. Three core variants shipped together at launch, Doubao-Seed-1.6, Doubao-Seed-1.6-Thinking, and Doubao-Seed-1.6-Flash, with a fourth Doubao-Seed-1.6-Vision model following in August and a derived Seed-1.6-Embedding model arriving on 28 June 2025.^[2]

The family uses a sparse mixture-of-experts (MoE) architecture with 230 billion total parameters and roughly 23 billion active parameters per forward pass.^[1] It supports a 256K-token context window across all variants. The most widely discussed technical innovation in the release is Adaptive Chain-of-Thought (AdaCoT), a training and inference scheme that lets the model decide on its own whether to use extended reasoning for a given prompt. Doubao Seed 1.6 also introduced ByteDance's first integrated vision-language reasoning capability at scale, allowing the same model to handle text, images, and short video clips without routing to a separate vision pipeline.

At launch, Volcano Engine cut Seed 1.6 prices by roughly two thirds compared with Doubao 1.5, pushing the input price down to 0.8 yuan per million tokens in the 0 to 32K input range.^[3] By the end of 2025 the consumer Doubao app, which runs on the Seed 1.6 backbone, had grown to over 226 million monthly active users and become the most popular AI-native application in mainland China, ahead of DeepSeek V4 and Alibaba's Qwen-powered Tongyi assistant.^[12]

Background

The ByteDance Seed team

ByteDance set up an internal research group focused on large foundation models in early 2023, branding it as the Seed team. The unit operates out of Beijing, Shanghai, and Singapore, and ships its work primarily through Volcano Engine, the cloud and AI platform business that ByteDance spun out as a separate brand in 2020. The Seed team's first publicly numbered language model was Doubao Pro, released in May 2024 alongside the Doubao consumer app. That release was followed by Doubao 1.5 in January 2025, which introduced a mixture-of-experts backbone and a reasoning-tuned 1.5-Pro Deep Thinking variant. Seed 1.6 is the sixth major numbered version line and the first to ship adaptive reasoning, multimodal understanding, and the new family naming convention together.

ByteDance has historically published more research about its multimodal and video work than about its text models. The Seed team's earlier papers include Seed-Thinking-v1.5 (the reasoning-tuned variant of Doubao 1.5), Seedream (text-to-image), and Seedance (text-to-video), and the team launched the SuperGPQA open benchmark covering 285 academic disciplines in mid-2025.^[13] Seed 1.6 was disclosed in a technical blog post on the seed.bytedance.com site rather than in a full research paper, a pattern that has drawn some criticism from Western researchers who note the lack of formal model cards or published evaluations for the production text models.

Doubao app history

The Doubao chatbot app first appeared in August 2023 as Cici overseas and as Doubao in mainland China. ByteDance promoted it aggressively inside Douyin and through paid acquisition, and by January 2025 it had passed 78 million monthly active users to become the largest AI assistant in China.^[15] The arrival of DeepSeek R1 in January 2025 briefly pushed Doubao into second place, but ByteDance regained the top spot by mid-2025 once Seed 1.6 was deployed and the company rolled out features such as five-second video creation, podcast generation, and Douyin integration.^[12] Doubao reached over 157 million MAUs by August 2025 according to QuestMobile, and 226 million by year-end. During Lunar New Year 2026, daily active users briefly surpassed 100 million, roughly four times the level in early February.

Seed 1.6 sits underneath all of these consumer features. The Flash variant is used for fast chat completions and real-time voice; the Thinking variant powers deep reasoning modes such as the homework helper and the science Q&A flow; the Vision variant handles photo-based queries, including ID verification, receipt parsing, and grade-school problem solving from photographed worksheets.

Seed 1.6 family versions

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All three chat-completion variants share the same 256K context window, the same vision and tool-calling capabilities, and the same training data pipeline. The differences are model size at inference time and the default thinking-mode setting. Doubao-Seed-1.6-Lite was added later in October 2025 as an additional cost tier sitting between Flash and the full model.

Architecture

ByteDance has not released the full Seed 1.6 model weights, and the technical blog stops short of disclosing the exact MoE configuration. The figures the Seed team has published are:

• Total parameters: 230 billion across all experts.
• Active parameters per token: approximately 23 billion (a 10 to 1 sparsity ratio).
• Context window: 256K tokens, extended progressively from a 32K base during training.
• Tokenizer: ByteDance's in-house tokenizer, optimised for Chinese and English. Exact vocabulary size is not disclosed.^[1]

Training proceeded in three stages, summarised in the Seed team's introduction-to-techniques post:

1. Text-only pre-training. A web, books, papers, and code corpus, with what the team calls "data quality optimisation," a phrase the team uses for deduplication, filtering, and rebalancing. Chinese and English are the dominant languages.
2. Multimodal mixed continual training (MMCT). The team added image-text and video-text pairs and increased the share of discipline-specific and reasoning content. This is when vision capability is grafted onto the language backbone.
3. Long-context continual training (LongCT). Sequence length was extended progressively from 32K up to the final 256K window.^[1]

Reinforcement learning is used during post-training. The Seed-Thinking-v1.5 paper (the predecessor to Seed 1.6-Thinking) describes a verifiable-reward RL setup similar to DeepSeek's R1 pipeline, and Seed 1.6-Thinking is built on the same general approach with parallel decoding added at inference time.^[14] Parallel decoding is a training-free technique that lets the model use more thinking tokens before producing a final answer, which the team claims significantly improves performance on challenging tasks.

The vision tower for Seed 1.6-Vision is integrated into the same backbone rather than running as a separate model. The Vision variant additionally implements tool calling for image operations including cropping, selection, scaling, rotation, and annotation, exposed through Volcano Engine's Responses API.^[5]

Adaptive Chain-of-Thought (AdaCoT)

The core algorithmic contribution in Seed 1.6 is AdaCoT, which the Seed team describes as letting the model automatically decide whether to engage in extended chain-of-thought reasoning based on the difficulty of each prompt.^[1] AdaCoT operates in three modes:

• FullCoT. The model always reasons step by step before producing a final answer.
• NoCoT. The model produces a direct answer without intermediate reasoning.
• AdaCoT. The model decides per prompt whether to enter reasoning mode.

Reported triggering rates for AdaCoT vary by benchmark difficulty:

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The Seed team argues that AdaCoT cuts roughly 60 percent of token overhead on moderate workloads compared with always running full chain-of-thought, while preserving accuracy on harder problems where reasoning is necessary.^[1] From a pricing perspective, this is also what makes the headline 0.8 yuan per million input tokens figure feasible: most everyday Doubao queries never trigger thinking mode, so the average cost per user query stays low.

Capabilities

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The family is notably strong on Chinese-language tasks. The Seed-1.6-Embedding model holds a CMTEB score of 75.62, a Chinese multilingual text embedding benchmark, which the team reports as a state-of-the-art result at launch.^[2]

Benchmarks

ByteDance has published a smaller set of benchmark numbers than competitors such as DeepSeek V4 or Qwen 3, focusing on showcase results rather than full leaderboard tables. The following table lists what has been disclosed in official Seed team materials or covered consistently in reputable reporting.

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Independent reviews have noted that raw accuracy scores on the most-cited Western benchmarks, including GPQA Diamond, MMLU, LiveCodeBench, and SWE-bench Verified, have not been published officially for Seed 1.6 as of mid-2026.^[10] Third-party aggregators such as Artificial Analysis and OpenRouter list Seed 1.6 but mark intelligence and technical scores as "not verified" because of this gap. The Seed team has been more forthcoming with results from its own SuperGPQA benchmark, which covers 285 disciplines and was open-sourced in early 2025, but on which only ByteDance-internal numbers have been published for Seed 1.6.^[13]

API and pricing

All Seed 1.6 variants are served through Volcano Engine's Ark model platform. They are also resold by third-party gateways such as OpenRouter, ZenMux, and TokenMix, generally at the same or higher prices than the official Volcano Engine tier.

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Third-party gateway pricing for Seed 1.6 is typically quoted in US dollars per million tokens. OpenRouter lists Seed 1.6 at $0.25 input and $2.00 output per million tokens,^[7] doubao-seed-1.6-lite at roughly $0.044 input and $0.350 output, and doubao-seed-1.6-flash at $0.022 input and $0.219 output,^[8] which TokenMix has described as a price floor for Chinese frontier-tier models accessible internationally.^[9]

Volcano Engine offers a free quota for new accounts and a research tier for academic users, and ByteDance's consumer Doubao app remains free at the entry level with optional paid features. Enterprise plans bundle the Ark API with Volcano Engine's MCP service, the PromptPilot prompt-engineering tool, and the Volcano Agent platform.

Comparison to peers

The table below sets Seed 1.6 alongside the Chinese open-weights or hybrid-access frontier-tier models it is most often compared with. All figures are drawn from each model's official disclosures or major coverage, and benchmark figures are included only where vendors have published them.

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The most consistent third-party finding is that Seed 1.6 is competitive with these peers on general capability and tool use, leads on consumer reach inside China, but trails on published coding-specific benchmarks where DeepSeek and GLM tend to be ahead.^[10]

Reception

Reception inside China was largely positive. Yicai and 36Kr framed the launch primarily as a pricing event, with the 63 percent price cut versus Doubao 1.5 reported as the headline detail.^[6] Volcano Engine claimed at the conference that Doubao 1.6 had been used to drive a 417-fold increase in daily token consumption among its enterprise customers since the Doubao Pro launch in 2024, a figure that the company has repeated in subsequent investor materials.^[4]

Third-party benchmark coverage was more mixed. The AiPy Phase II LLM benchmark, published later in 2025, placed Doubao Seed 1.6 in third place with 84.6 alongside Claude Opus 4 and Claude Sonnet 4 as the only models hitting a 100 percent task success rate across the test suite, which was widely cited inside China as evidence that the model had reached parity with frontier US systems on practical agent workloads.^[11] Independent reviewers on Medium and Artificial Analysis raised the transparency gap noted above, arguing that without published numbers on standard Western coding and reasoning benchmarks it is difficult to verify Seed 1.6's positioning against GLM or DeepSeek for software engineering use.^[10]

A second strand of reception focused on the AdaCoT idea. Several Chinese-language technical blogs argued that adaptive reasoning was the more important contribution in the long run because it offered a cleaner solution to the over-thinking problem that had been visible in DeepSeek R1 and other always-on reasoning models. Western coverage was more muted, in part because the Seed 1.6 disclosure was a blog post rather than a paper and in part because the model weights remained closed.

For end users, the main visible effect of Seed 1.6 was the upgrade of the Doubao app's reasoning quality and the introduction of new capabilities, including five-second video creation through Seedance 1.0 Pro, deeper Douyin and CapCut integration, and the ability to take photos of homework or receipts and receive structured output. By the time the consumer-facing Doubao 2.0 was previewed in early 2026, Seed 1.6 had become the de facto Chinese AI backbone with the largest installed user base in the country, ahead of DeepSeek and Tongyi.^[12]

A recurring criticism, raised by Chinese-language tech writers and Western researchers, is that ByteDance keeps Seed 1.6's weights closed while leaning on the open-source community for distribution. The Seed team has open-sourced specific research artefacts (Seed-Thinking-v1.5 reference code, SuperGPQA benchmark, the older Seedance 1.0 image and video models), but not the production text models that drive Doubao.^[13] ByteDance has not publicly committed to releasing Seed 1.6 weights.

See also

• ByteDance
• Doubao
• DeepSeek V4
• Qwen 3
• GLM-4.5
• GLM-4.6
• Kimi K2
• TikTok

References

1. ByteDance Seed Team. "Introduction to Techniques Used in Seed1.6." seed.bytedance.com, June 2025. https://seed.bytedance.com/en/blog/introduction-to-techniques-used-in-seed1-6 ↩
2. ByteDance Seed Team. "Built on Seed1.6-Flash, Seed-1.6-Embedding Launched." seed.bytedance.com, 28 June 2025. https://seed.bytedance.com/en/blog/built-on-seed1-6-flash-seed-1-6-embedding-launched ↩
3. AIBase. "ByteDance Unveils DouBao 1.6 and Seedance 1.0 with Significantly Reduced Costs." 11 June 2025. https://www.aibase.com/news/18831 ↩
4. AIBase. "ByteDance Volcano Engine Launches DouBao Large Model 1.6, Setting New Records for AI Technology Innovation." 11 June 2025. https://www.aibase.com/news/18817 ↩
5. TechNode. "Volcengine's Doubao 1.6-Vision Cuts Costs by 50% with New Tool-Calling Multimodal Model." 2 October 2025. https://technode.com/2025/10/02/volcengines-doubao-1-6-vision-cuts-costs-by-50-with-new-tool-calling-multimodal-model/ ↩
6. Yicai. "ByteDance Today Released Its Latest Generation of AI Model, Doubao 1.6." 11 June 2025. https://x.com/yicaichina/status/1932655512753225921 ↩
7. OpenRouter. "ByteDance Seed: Seed 1.6." Accessed May 2026. https://openrouter.ai/bytedance-seed/seed-1.6 ↩
8. OpenRouter. "ByteDance Seed: Seed 1.6 Flash." Accessed May 2026. https://openrouter.ai/bytedance-seed/seed-1.6-flash ↩
9. TokenMix Blog. "Doubao API Setup 2026: 19 ByteDance Models." March 2026. https://dev.to/tokenmixai/doubao-api-setup-2026-19-bytedance-models-0022m-floor-python-in-5-min-2akn ↩
10. Barnacle Goose. "Analysis of ByteDance Seed 1.6 and of Seedream 4.5." Medium, December 2025. https://medium.com/@leucopsis/analysis-of-bytedance-seed-1-6-and-of-seedream-4-5-22dbdc5dac9d ↩
11. Cici. "AiPy Releases Phase II LLM Benchmark Report: Claude Leads, Grok 4 and Kimi K2 Fall Behind Doubao." Medium, late 2025. https://medium.com/@c8776402/aipy-releases-phase-ii-llm-benchmark-report-claude-leads-grok-4-and-kimi-k2-fall-behind-doubao-01d2233b8af1 ↩
12. South China Morning Post. "ByteDance Chatbot Doubao Still China's Most Popular AI App as Rival DeepSeek Loses Users." 2025. https://www.scmp.com/tech/big-tech/article/3325858/bytedance-chatbot-doubao-still-chinas-most-popular-ai-app-rival-deepseek-loses-users ↩
13. ByteDance Seed Team. "Doubao (Seed) Team Launched SuperGPQA: An Open-Source Benchmark Test Set Covering 285 Disciplines." seed.bytedance.com, early 2025. https://seed.bytedance.com/en/blog/doubao-seed-team-launched-supergpqa-an-open-source-benchmark-test-set-covering-285-disciplines ↩
14. arXiv. "Seed1.5-Thinking: Advancing Superb Reasoning Models with Reinforcement Learning." April 2025. https://arxiv.org/pdf/2504.13914 ↩
15. Doubao Wikipedia entry. "Doubao." Accessed May 2026. https://en.wikipedia.org/wiki/Doubao ↩