DeepSeek Flash Fingerprint Changes Again, V5 Names Surface in Test Repo

Flash Model Fingerprint Change Detected

On October 27, multiple users observed that the system fingerprint returned by DeepSeek's official website and API for three model aliases — deepseek-flash, deepseek-v4-flash, and deepseek-v4-flash-vision-exp — had changed. The previous fingerprint was e72d3c7f663d3e1383b00b3884cb4501; the new fingerprint is bc19ba97cbe016479903222bb1578db6.

User-Reported Transition Timeline

Monitoring records indicate that at 19:07 on October 27, all three aliases switched from returning both old and new fingerprints to returning only the new fingerprint. User “雨哥向前冲” reported seeing both fingerprints at 18:21, a full cutover at 19:07, and personal requests at 21:34 returning the new value. User “实践哥 Li” confirmed the new fingerprint at 23:29 via API key. The pattern suggests a phased rollout rather than a one-off occurrence.

Repeated Testing Shows Stable Fingerprint, No Behavioral Change

X user jiangkoumo called the official API 23 times after seeing community reports; every request returned the new fingerprint, contrasting with his October 17 records of the old fingerprint. He re-ran two previous SVG generation tasks and found that output volume with reasoning remained within prior sample ranges, and the “English explanation followed by SVG code” format was unchanged. This indicates the backend identifier changed, but small-scale testing has not revealed clear behavioral differences.

Historical Reference: October 17 Flash Update

Ten days earlier, on October 17, Teortaxes reported that deepseek-flash fingerprint shifted from aeb56401… to e72d3c7f… (the fingerprint that just got replaced). On the same day, DeepSeek officially released V4.1-Flash-1017 across web, app, and API. This precedent shows that a fingerprint change can accompany a model update even when the calling name stays the same.

DeepSeek Harness Test Files Contain Mock V5 Names

In the DeepSeek Harness official repository, test files reference three constructed model names: deepseek-v5, deepseek-v5-open, and deepseek-v5-next. The deepseek-v5-open entry sets a minimum client version of 0.0.1, while deepseek-v5-next uses 99.0.0-alpha.1 to test version-gating logic. These are explicitly test mock data, not actual models served in production.

V4 Pro Status and API Incident

The deepseek-v4-pro fingerprint remains a307abda… with no synchronous change. However, DeepSeek's status page recorded a performance degradation for the V4 Pro API from 15:07 to 15:21 on October 27 (14 minutes). The proximity of this incident to the Flash fingerprint switch has led to speculation about pre-deployment adjustments for a new Pro version. Community member “Leo · Building w/ AI” shared an image allegedly from a new canary model, suggesting a possible V4.1 Pro test.

What Developers Should Watch For

If the new fingerprint corresponds to a new model checkpoint, the October 17 V4.1-Flash-1017 release highlighted improvements in project development capability, reduced task runtime, and shorter output length, with optimizations for DeepSeek Harness , CodeBuddy , and WorkBuddy frameworks. Concrete signals to monitor include:

Whether modifying the same code segment reduces invalid attempts.

Whether screenshot recognition errors decrease.

Whether multi-step tool calls complete more reliably.

These practical outcomes matter more than phrasing changes in a single response.

Current Official Status

As of October 28, DeepSeek's official changelog still lists V4.1-Flash-1017 as the latest model update, with no note about the new fingerprint. The user-provided timelines and repeat-call evidence give a detailed picture of the anomaly, but whether it represents a deployment tweak or a precursor to the next model release remains to be confirmed by further testing and official communication.