DeepSeek V4.1 Flash-1017: what changed, and how to use it over the API
On October 17, DeepSeek shipped V4.1-Flash-1017 — not a new generation, an updated checkpoint of V4.1 Flash. Same architecture (552B MoE, causal encoder–decoder), same 1M-token context, same native image input, same price bracket — but refreshed post-training, and DeepSeek reports gains on all eleven benchmarks it publishes, with the biggest jumps on terminal and program-automation agent work.
If you use the Core Pool, there is nothing to migrate: we rolled the 1017 build out to the pool the same day, the model id is still deepseek-v4.1-flash, and your existing keys already serve it. Unlimited, flat-rate access starts from $22/mo ($18.70/mo billed annually) — live pricing on /pools.
The update, measured
Section titled “The update, measured”Same model, new checkpoint. This is DeepSeek’s own reported before/after (vendor harness — no independent verification of these specific numbers yet):
Full vendor-stated table for the 1017 build, next to the September checkpoint it replaces:
| Benchmark | Flash-1017 | Flash (Sep) |
|---|---|---|
| Terminal-Bench 4.0 | 42.3 | 31.2 |
| HLE (no tools) | 42.6 | 36.8 |
| ProgramBench | 29.1 | 20.3 |
| Apex Bench v1.1 | 72.1 | 64.6 |
| Automation-Bench v1.0.6 | 60.5 | 54.8 |
| Agents’ Last Exam | 35.4 | 31.8 |
| DeepSWE v1.1 | 77.0 | 74.2 |
| NL2Repo-Bench | 68.2 | 65.4 |
| Chartography (with tools) | 83.0 | 78.9 |
| BabyVision (with tools) | 92.5 | 89.6 |
| ZeroBench-main (with tools) | 51.0 | 49.0 |
The pattern mirrors what the 0731 retrain did for V4 Flash: the architecture and price stay put while agentic reliability — long terminal sessions, multi-step program edits, tool-driven research — takes the jump. The weights are open under MIT: deepseek-ai/DeepSeek-V4.1-Flash-1017.
What this means if you subscribe
Section titled “What this means if you subscribe”- Nothing to change. The Core Pool serves the 1017 build since October 17 under the same id,
deepseek-v4.1-flash, on the same subscriptions and keys. - Same flat rate. Time-block subscriptions are unaffected — your cost does not scale with tokens, so a stronger checkpoint at the same price is pure upside.
- Same limits. 1M-token context and image input are unchanged; see the model page for current specifics.
Call DeepSeek V4.1 Flash-1017
Section titled “Call DeepSeek V4.1 Flash-1017”curl https://api.cheapestinference.com/v1/chat/completions \ -H "Authorization: Bearer sk-..." \ -H "Content-Type: application/json" \ -d '{ "model": "deepseek-v4.1-flash", "messages": [{"role": "user", "content": "What build are you?"}] }'It also works over the Anthropic-style endpoint (/anthropic/v1/messages) and with any OpenAI- or Anthropic-compatible SDK or agent — point the base URL at https://api.cheapestinference.com and use your subscriber key. Setup guides: getting started, DeepSeek V4.1 Flash model page.
Is there an unlimited DeepSeek V4.1 Flash-1017 API plan? Yes — the Core Pool serves it on unlimited, flat-rate 8-hour daily time blocks from $22/mo ($18.70/mo billed annually), with no token caps.