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Choose a supported base model for your training config. List the available training models with:

Training catalog

Every catalog model supports SFT and GRPO. Image and reasoning support depend on the model: The 0.8B and 4B paths are text-only for both training and serving. For the other three models, see Image inputs. Use thinking = true to enable reasoning on models with optional thinking. Custom training is supported only on Qwen/Qwen3.5-9B, text-only, on one H100. Its context and rank limits are lower than the SFT/GRPO limits below. A deployed checkpoint preserves its trained thinking mode, including on metered hosted serving with Flash 1.3.9 or later. Reasoning tokens are included in the normal output-token charge. See reasoning support. The catalog is the whole set of trainable models. A model outside it is rejected when the config is parsed, before any GPU is rented, and there is no config key that opts into an uncatalogued id. The error lists the supported ids.

Serving prices

Serving is billed per token after deployment, at the per 1M token rates below. See Billing for cached-input discounts. These are final customer rates, with no additional provider markup. Later price changes do not affect previously accepted requests. The training catalog contains these five models. Retired 2B and Qwen3.6 27B identities are rejected; Qwen3.8 27B is a distinct model, not a rename of an old adapter’s base.

DeepSeek base-model serving

deepseek-ai/DeepSeek-V4.1-Flash-1017 is available as a hosted, text-only base model through the OpenAI-compatible API. It does not support Flash training or LoRA adapters. It is separate from the training catalog in flash models list. The serving context is 32,768 tokens, including the rendered input, requested output, and 64 reserved tokens. The upstream million-token window is not exposed by this serving configuration. Thinking is optional and defaults to off; reasoning tokens count toward output usage. Check the hosted /v1/models endpoint for availability. See Chat with DeepSeek for supported request fields and an example.

Context window and LoRA rank

Every training-catalog model supports a 32768-token context for SFT, GRPO, and hosted serving. flash train enforces the applicable context and rank caps: a config whose max_context_tokens exceeds the cap, whose GRPO prompt plus max_completion_tokens cannot fit, or whose lora_rank exceeds the max rank, is rejected. Custom training is limited to 4096 tokens and rank 64.

Choosing a model

Start with 9B

Use Qwen/Qwen3.5-9B to validate your environment and dataset with a short run.

Compare on your task

Evaluate Qwen/Qwen3.8-27B and Qwen/Qwen3.6-35B-A3B on held-out data. Compare quality and the quote for your configuration before scaling up.

Pick a model, then train

Set model in your config and submit a run.