Fine-Tuning

Definition

Fine-tuning is further training of an existing model on your own examples so it learns a specific task, style or format.

Key takeaways

  • Fine-tuning changes a model's weights using a set of example inputs and ideal outputs.
  • It's useful when prompting alone can't get a consistent style or format.
  • It needs good training data, time and money, and the result has to be hosted somewhere.
  • Try Prompt Engineering, Few-Shot Prompting and Retrieval-Augmented Generation first. They're cheaper and faster to change.
  • luv13 doesn't offer fine-tuning. OpenAI's /v1/fine_tuning/jobs path returned 404 on 2026-09-30.

How it works

  1. Collect examples. Hundreds to thousands of input and output pairs that show exactly what you want.
  2. Train. Start from a base model and train it a bit more on your examples.
  3. Evaluate. Compare the tuned model with the original on test cases it didn't train on.
  4. Serve. Host the new weights so you can call them.

Lighter methods such as LoRA train a small add-on instead of every weight. They need far less memory and are common with Open-Weight Models.

Fine-tuning vs. other options

GoalUsually best
Answer from your documents or fresh factsRetrieval-augmented generation
Follow a format a few timesFew-shot examples in the prompt
Match a narrow style every time, at scaleFine-tuning
Teach new factsRetrieval, not fine-tuning. Tuning is poor at adding reliable facts.

On luv13

luv13 serves the models in its live list at https://api.luv13.ai/v1/models as they are. To steer them, use prompts and examples. See Endpoints for what luv13 serves.

Example

A few-shot prompt is often enough to get the style you'd otherwise fine-tune for:

curl https://api.luv13.ai/v1/chat/completions \
  -H "Authorization: Bearer $LUV13_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "luv13/glm-5.3-flash",
    "messages": [
      {"role": "system", "content": "Rewrite product names in our house style: all lowercase, words joined by dots."},
      {"role": "user", "content": "Blue Water Bottle"},
      {"role": "assistant", "content": "blue.water.bottle"},
      {"role": "user", "content": "Travel Coffee Mug"}
    ]
  }'