ByteDance now sells a model with no version number — and quietly swapped it on 1 August

Every large model vendor has trained the market to wait for the next number: 2.1, then 2.2, then a launch event with a table of benchmarks. ByteDance has stopped playing. Its Seed Evolving line, documented on Volcano Engine, has no version number at all. There is one permanent model ID — doubao-seed-evolving — and the company replaces what sits behind it whenever it has something better. The documentation states the deal in one line: upgrades take effect automatically, with no endpoint migration and no change to how the model is called. The technical case is real. The context window is 1,024,000 tokens, four times the 256,000 of the Seed 2.1 family, at the same list price of 6 yuan per million input tokens and 30 per million output — about 0.83 and 4.14 US dollars. Output runs to 256,000 tokens and the chain of thought to another 256,000. It is a branch model built for coding and agents: text, images, video and documents in, function calling, structured output, context caching, audio deliberately left out. The API speaks both the OpenAI and the Anthropic protocol, so it drops into Claude Code, OpenCode or Codex without a wrapper. The part worth reading twice is the changelog. ByteDance dates the current build to 1 August 2026 and describes it as better at repository-scale fixes, cross-file edits and long unattended runs, with hallucination in search results and tool calls as the area most improved. That is the entire public record of what changed. There is no model card for the previous build, no benchmark table, no way to tell whether the model answering today is the one somebody measured in July. That is the trade, and ByteDance does not discuss it. A model with no frozen version has no reproducible reference point. A published evaluation, an internal audit, a regulator's test — each describes whatever was behind the ID that week, and none of them can be re-run against the same weights later. For a developer tired of migrating prompts every quarter, that may be a fair price. For anyone who has to certify a system, or simply prove what it did last month, it is a new kind of problem. Editorial note: wujec.ai records this model as a rolling release rather than a dated one, which is why its profile carries no release date. Where a specification changes silently, we date what we checked and when.