PSA: DeepSeek v4 pro API calls will silently route to V4.1 flash from Sept 14
TangeloOk9486 · reddit · 2026-09-12
A r/LocalLLaMA PSA warns that since the Sept 10 release, DeepSeek v4 flash and vision exp preview have retired and alias to V4.1 flash — and from Sept 14, v4 pro will also route to V4.1 flash (billed at flash rates). V4.1 flash is a 552B encoder-decoder model with reported gains on agentic/coding tasks but possible regressions on knowledge-heavy work without tools. API users with hardcoded v4 pro will see outputs shift without changing a line, while third-party hosts of the open weights let you pin versions. The author suggests running your eval set against flash and diffing against v4 pro outputs before the reroute hits production.
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