# DeepSeek V4.1 Flash vs V4 Flash 0731: what changed and why it matters

By SeedRouter · Published 2026-09-28 · Updated 2026-09-28

DeepSeek V4.1 Flash replaced DeepSeek V4 Flash on September 10, 2026. It is not a retrained V4 Flash: it is a new architecture, it reads images natively, its cache is much smaller, and its prices are lower. DeepSeek retired V4 Flash that day. If you still call `deepseek-v4-flash` on DeepSeek's API, your requests already run on V4.1 Flash.

## What is the DeepSeek V4 Flash timeline?

From DeepSeek's [change log](https://api-docs.deepseek.com/updates):

| Date         | What happened                                                                                     |
| ------------ | ------------------------------------------------------------------------------------------------- |
| Apr 24, 2026 | DeepSeek V4 Pro and V4 Flash arrive on the API                                                    |
| Jul 31, 2026 | V4 Flash 0731: same architecture and size as the preview, re-post-trained for stronger agent work |
| Aug 16, 2026 | Peak and off-peak pricing starts, off-peak at half the peak rate                                  |
| Aug 21, 2026 | V4 Flash Vision Exp, an experimental image-reading model, is released                             |
| Sep 10, 2026 | V4.1 Flash is released; V4 Flash and V4 Flash Vision Exp are retired; prices drop                 |

## What changed in DeepSeek V4.1 Flash?

* **A new architecture.** V4.1 Flash is "the smallest model in our new architecture family", a 552B-parameter mixture-of-experts model with a causal encoder–decoder design: 8B active parameters to read input, 16B to write output.
* **Images, natively.** V4 Flash read text; images needed the separate Vision Exp model. V4.1 Flash reads images itself.
* **A smaller cache.** Its KV cache needs a quarter of the GPU memory and an eighth of the SSD storage of the previous generation. DeepSeek notes that cache-hit charges "often account for a large share of agent costs".
* **Lower prices.** DeepSeek's change log says "API prices have been reduced accordingly".

The architecture and cache figures are from DeepSeek's [release note](https://api-docs.deepseek.com/news/news260910).

## How much better does it score?

DeepSeek reported these results for each model; they are DeepSeek's own numbers:

| Benchmark          | V4 Flash 0731 | V4.1 Flash |
| ------------------ | ------------- | ---------- |
| Terminal Bench 2.1 | 82.7          | 90.6       |
| NL2Repo            | 54.2          | 65.4       |
| CyberGym           | 76.7          | 88.1       |
| Agents' Last Exam  | 25.2          | 31.8       |

V4.1 Flash is ahead on each of them, most on repository-scale coding (NL2Repo, listed as NL2Repo-Bench in the V4.1 note) and on CyberGym.

## Which model do the old names run now?

On DeepSeek's API, `deepseek-flash` is the name for V4.1 Flash. The retired names `deepseek-v4-flash` and `deepseek-v4-flash-vision-exp` are still accepted and "temporarily route to V4.1-Flash", billed at the V4.1 Flash price. DeepSeek calls this routing temporary, so switch code to the current name rather than relying on it.

On SeedRouter, the model ID is `deepseek-v4.1-flash`:

```python
completion = client.chat.completions.create(
    model="deepseek-v4.1-flash",
    messages=[{"role": "user", "content": "Hello"}],
)
```

## Do I need to change my code?

Usually only the model name. The request format is the same Chat Completions, Responses or Anthropic Messages body. Two things to check:

* **Images.** If you used V4 Flash Vision Exp for images, send the same `image_url` parts to V4.1 Flash.
* **Costs.** Rerun a sample of your traffic: V4.1 Flash reasons differently, so output token counts per request can change even though the rates went down.

## What does V4.1 Flash cost?

The current SeedRouter rates, peak and off-peak:

### DeepSeek V4.1 Flash

Current rates are temporarily unavailable. No price estimate is provided; unavailable rates must not be interpreted as free usage.

## Frequently asked questions

### Is DeepSeek V4 Flash 0731 still available?

No. DeepSeek retired V4 Flash on September 10, 2026. Its model names now run on V4.1 Flash.

### Can DeepSeek V4 Flash 0731 see images?

No, it was a text model; images needed V4 Flash Vision Exp. DeepSeek V4.1 Flash reads images natively.

### Is V4.1 Flash more expensive than V4 Flash?

No. DeepSeek lowered prices when it released V4.1 Flash. Peak and off-peak pricing continues, with off-peak at half the peak rate.

### How do I start with DeepSeek V4.1 Flash?

The [DeepSeek V4.1 Flash API guide](https://seedrouter.ai/blog/deepseek-v4-1-flash-api) shows how to get a key and make the first call.