Skill — Fine-Tuning Workflow

When this skill activates

Any task involving LLM fine-tuning, training dataset preparation, LoRA/QLoRA adaptation, model evaluation during training, or model deployment with A/B testing.

Mandatory actions when this skill is active

Before writing any code

1. Define the fine-tuning objective (style adaptation, domain knowledge, task specialization).
2. Audit training data quality (deduplication, format consistency, bias check).
3. Establish baseline metrics with the un-tuned model.

During implementation

• Run evaluation on held-out validation set at regular intervals during training.
• Implement early stopping on quality degradation.
• Track training metrics: loss, eval metrics, learning rate schedule.

After implementation

• Compare fine-tuned model against baseline on the eval suite.
• Deploy with canary traffic (shadow or A/B testing).
• Document the model card with training details and performance.

Dataset Preparation

Data Requirements by Objective

Data Format (Instruction Tuning)

{"messages": [
  {"role": "system", "content": "You are a helpful coding assistant."},
  {"role": "user", "content": "Write a function to reverse a string in Python."},
  {"role": "assistant", "content": "def reverse_string(s: str) -> str:\n    return s[::-1]"}
]}

Data Quality Checklist

• [ ] Deduplicated (no exact or near-duplicate examples).
• [ ] Consistent format across all examples.
• [ ] Balanced across categories/topics.
• [ ] No PII or sensitive data (unless intentional and consented).
• [ ] Correct and high-quality responses (garbage in = garbage out).
• [ ] Diverse inputs (length, complexity, edge cases).

Data Cleaning Pipeline

1. Deduplication: hash-based exact dedup + embedding-based semantic dedup.
2. Format validation: ensure all examples match expected schema.
3. Quality filtering: remove low-quality examples (too short, incoherent).
4. Balance check: verify distribution across categories.
5. Contamination check: ensure eval data not in training set.

Training Approaches

Full Fine-Tuning

• Updates all model parameters.
• Use for: significant behavior changes, large datasets.
• Cost: high (full model in GPU memory, long training time).
• Risk: catastrophic forgetting of base model capabilities.

LoRA (Low-Rank Adaptation)

• Adds small trainable matrices alongside frozen base model.
• Use for: most fine-tuning tasks (efficient, less forgetting).
• Cost: low (only adapter weights in GPU memory).
• Benefit: merge adapter with base model for zero-overhead inference.

QLoRA (Quantized LoRA)

• Base model quantized to 4-bit, LoRA adapters in 16-bit.
• Use for: large models on limited GPU memory.
• Cost: very low (fits 70B model on single GPU for training).
• Trade-off: slight quality reduction from quantization.

Key Hyperparameters

Evaluation During Training

Validation Set

• Hold out 10-20% of data as validation (never train on it).
• Evaluate every N steps (e.g., every 100 steps or every epoch).
• Track: validation loss, task-specific metrics.

Early Stopping

• Stop training if validation metric doesn't improve for N evaluations.
• Prevents overfitting (model memorizes training data).
• Save checkpoint at best validation score, not last step.

Evaluation Metrics

Model Deployment

Deployment Pipeline

Train → Evaluate → Register → Shadow Test → Canary → Full Rollout

Model Registry

• Version every model with: training data hash, hyperparameters, eval scores.
• Store model artifacts in versioned storage (S3, GCS, MLflow).
• Link to training run for full reproducibility.

Shadow Traffic Testing

• Deploy new model alongside production model.
• Route production traffic to both (only serve old model's response).
• Compare outputs offline (quality, latency, error rate).
• Promote to canary only if shadow results are satisfactory.

Canary Rollout

• Route 5% of traffic to new model.
• Monitor: quality metrics, latency p99, error rate, user feedback.
• If metrics are good after 24-48 hours: increase to 25% → 50% → 100%.
• Rollback instantly if any metric degrades.

A/B Testing

Experiment Design

• Split users randomly (not requests — same user should see same model).
• Define primary metric (quality score, user satisfaction, task completion).
• Define guardrail metrics (latency, error rate, cost).
• Run for statistical significance (typically 1-2 weeks).

Analysis

• Compare primary metric between control (old model) and treatment (new model).
• Verify guardrail metrics haven't degraded.
• Check for segment effects (does new model help some users but hurt others?).
• Document results and decision in model card.

Model Versioning (Model Card)

model_card:
  name: customer-support-assistant-v3
  base_model: llama-3-8b
  adapter: LoRA (rank 32)
  training_data:
    source: customer_support_conversations_2024
    examples: 5,432
    hash: sha256:def456...
  hyperparameters:
    learning_rate: 2e-5
    epochs: 3
    batch_size: 16
    lora_rank: 32
  evaluation:
    held_out_accuracy: 0.89
    human_preference_win_rate: 0.72
    latency_p99_ms: 340
  deployed_at: 2024-01-20
  parent_version: customer-support-assistant-v2

Self-check before task completion

Before marking a task done when this skill was active:

• [ ] Did I read the full SKILL.md before starting? (Not just the triggers)
• [ ] Is training data deduplicated, validated, and quality-checked?
• [ ] Is evaluation running on held-out validation set during training?
• [ ] Is early stopping configured to prevent overfitting?
• [ ] Are baseline metrics established for comparison?
• [ ] Is the model versioned with full training lineage?
• [ ] Is deployment using canary/A/B testing (not instant full rollout)?