YarnOrigCtx

YarnOrigCtx tells YaRN the model’s original trained context length. The scaling factor is derived from the ratio between the target ContextSize and YarnOrigCtx. This is the most commonly set YaRN knob.

Quick reference


Type	`uint?`
Default	`null` (use model default from GGUF metadata)
Range	Positive integer; the model’s trained max context
Category	YaRN position encoding
Field on	`ContextParameters.YarnOrigCtx`

What it does

YaRN extends context by a factor ContextSize / YarnOrigCtx. If the model was trained at 8K and you target 32K, the scale factor is 32768 / 8192 = 4. YaRN’s quality depends on knowing both values accurately.

null (default) — YaRN reads the value from the GGUF metadata. This is what most presets use.
Specific integer — override. Set to the model’s actual training context length when the metadata is missing or wrong.

When to change it

Scenario	Value
Default (GGUF has correct metadata)	`null`
Custom GGUF without trained-context metadata	Set to the model’s native context
Running an older model at extended context	Set to the original training window

For a Qwen 2.5 7B model (trained at 32K) targeting 128K:

preset.ContextParameters.ContextSize = 131072;
preset.ContextParameters.RopeScalingType = RopeScalingType.Yarn;
preset.ContextParameters.YarnOrigCtx = 32768;  // Qwen2.5 training context

Example

using Aspose.LLM.Abstractions.Models;

var preset = new Qwen25Preset();
preset.ContextParameters.ContextSize = 65536;
preset.ContextParameters.RopeScalingType = RopeScalingType.Yarn;
preset.ContextParameters.YarnOrigCtx = 32768;

using var api = AsposeLLMApi.Create(preset);

Interactions

ContextSize — target; scale = ContextSize / YarnOrigCtx.
RopeScalingType — must be Yarn.
Other YaRN knobs (YarnExtFactor, YarnAttnFactor, YarnBetaFast, YarnBetaSlow) — usually null; model defaults work.

What’s next

RopeScalingType — enables YaRN.
ContextSize — the extended target.
Long context tuning — full recipe.

YarnBetaSlow AttentionType