DeepSeek V4 API in 2026: 1M Context, OpenAI/Anthropic Compatibility, and CodeFast Open Source API Guide
DeepSeek V4 Flash and V4 Pro stand out in 2026 with 1M context, aggressive token pricing, OpenAI-format access, and Anthropic-format support. The CodeFast Open Source API package gives developers a practical low-entry-cost way to try DeepSeek, Kimi, MiniMax, and Mimo models.
· CodeFast Team
Why DeepSeek V4 API is worth watching now
As of May 28, 2026, DeepSeek's official models and pricing page highlights two V4 models: deepseek-v4-flash and deepseek-v4-pro. Both are listed with 1M context length, 384K maximum output, JSON output, tool calls, chat prefix completion, and beta FIM completion support. That combination matters for large codebase analysis, long-document processing, agentic workflows, and low-cost prototyping.
- DeepSeek V4 Flash is the lower-cost starting point for fast testing and everyday product workflows.
- DeepSeek V4 Pro is better suited for heavier reasoning, long analysis, and more critical agentic tasks.
- Official DeepSeek endpoints support both OpenAI format and Anthropic format.
- Context caching is enabled by default; repeated long prefixes can benefit from much lower cache-hit pricing.
Why the pricing stands out
DeepSeek's official pricing lists V4 Flash at $0.14 per 1M cache-miss input tokens and $0.28 per 1M output tokens. For V4 Pro, the discounted prices shown until May 31, 2026 at 15:59 UTC are $0.435 per 1M cache-miss input tokens and $0.87 per 1M output tokens; DeepSeek notes that the model's API pricing will officially adjust to one quarter of the original price after the promotion ends. This is not only a model update; it is a serious shift in open-model API economics.
This is where the CodeFast Open Source API package fits. As of June 11, 2026, the package is active again at 600 TRY for 30 days with 500 daily uses; the 1-day equivalent of the 500 daily request selection is 20 TRY. The positioning is clear: try DeepSeek, Kimi, MiniMax, and Mimo models in one package through OpenAI-compatible and Anthropic-compatible formats.
What OpenAI and Anthropic compatibility changes in practice
DeepSeek's official docs list https://api.deepseek.com for the OpenAI format and https://api.deepseek.com/anthropic for the Anthropic format. That lets existing OpenAI SDK-based apps or some Anthropic Messages clients try DeepSeek models with fewer code changes. CodeFast Open Source API follows a similar developer workflow: OpenAI-compatible chat/completions, Anthropic-compatible messages, and /v1/models for model discovery.
Provider: CodeFast Open Source API
OpenAI-compatible Base URL: https://api.codefast.app/open-source-api/v1
Anthropic-compatible Base URL: https://api.codefast.app/open-source-api/anthropic
Models endpoint: GET https://api.codefast.app/open-source-api/v1/models
Example models: deepseek/deepseek-v4-flash, deepseek/deepseek-v4-pro, moonshotai/kimi-k2.6
Cursor aliases: codefastd4flash, codefastd4pro, codefastk26, codefastm27, codefastm3, codefastmimo25, codefastmimo25pro
Usage note: listed successful model requests count as 1 use; /v1/models returns the current CodeFast Open Source model list.
Quick setup summary for CodeFast Open Source API
1M context is useful, but not free
A 1M context window lets you place a huge amount of information in one request, but it does not mean every request should send 1M tokens. Better results usually come from a more disciplined flow: keep stable system and project context consistent, split long documents, preserve repeated prefixes for cache-hit benefits, and send only the context the model actually needs.
- Large repository summaries, multi-file refactor planning, and long technical document Q&A can benefit heavily from 1M context.
- Short chatbot replies, simple classification, and small JSON transformations are often better served by V4 Flash or smaller models.
- Instead of sending everything again on every request, use summarization, retrieval, and caching on the application side to lower cost.
DeepSeek V4 Flash or V4 Pro?
- V4 Flash: the more sensible starting point for fast tests, in-product assistants, content classification, lighter coding tasks, and budget-controlled agent flows.
- V4 Pro: better for harder reasoning, long planning, sensitive code review, multi-step tool use, and tasks that need higher reliability.
- On CodeFast, the /v1/models response only shows public and supported Open Source model IDs.
Where CodeFast Open Source API makes sense
Before taking a model into production, the first need is usually fast testing: create an API key, set the base URL, try a few workflows, feel the cost, and switch models if needed. CodeFast Open Source API works well at this stage because packages, daily usage limits, and one-panel management lower the barrier to the first experiment.
- For solo developers: testing DeepSeek V4 and other open models without committing a large budget.
- For small teams: managing models, limits, and API keys from one panel.
- For agent builders: moving faster between OpenAI-compatible and Anthropic-compatible clients during testing.
When direct DeepSeek API is the better fit
Direct DeepSeek API can be a better fit for very high-volume production traffic, provider-level contracts, detailed billing, enterprise procurement, or custom compliance requirements. CodeFast has a different value: starting quickly, testing multiple open models from one panel, working with package-based cost, and lowering the buying threshold for small teams.
Bottom line: DeepSeek V4 accelerates the low-cost model access race
DeepSeek V4 API is becoming one of the most important open-model options in 2026 thanks to 1M context and very low token pricing. But choosing a good model is not enough; you still need the right endpoint, limit, package, and usage strategy. That is where CodeFast Open Source API fits: testing DeepSeek V4 and similar open-model options with lower entry cost, one-panel management, and developer-friendly endpoints.