Finetuning Agent Skill

Prerequisites

Before starting this workflow, verify:

• A use_case_spec.md file exists
• If missing: Activate the use-case-specification skill first, then resume
• DON'T EVER offer to create a use case spec without activating the use-case-specification skill.

• A fine-tuning technique (SFT, DPO, RLVR, RLAIF, or CPT/RFT (for Nova)) and base model have already been selected
• If missing: Activate the model-selection and/or finetuning-technique skills to collect what's missing, then resume
• Don't make recommendations on the spot. You MUST activate the appropriate skill.

• A base model name available on SageMakerHub has been identified
• If missing: Activate the model-selection skill to get it
• Important: Only use the model name that model-selection retrieves, as it may differ from other commonly used names for the same model

• The SDK environment has been verified (SDK version, region, execution role)
• If not done: Activate the sdk-getting-started skill first, then resume

• A training dataset uploaded to a bucket in the environment's default region.
• If not met: Help the user upload the dataset to the correct S3

Critical Rules

Code Generation Rules

• ✅ Use EXACTLY the imports shown in each code template
• ❌ Do NOT add additional imports even if they seem helpful
• ❌ Do NOT create variables before they're needed in that section
• 📋 Copy the code structure precisely - no improvisation
• 🎯 Follow the minimal code principle strictly
• ✅ When writing code, make sure the indentation and f strings are correct

User Communication Rules

• ❌ NEVER offer to move on to a downstream skill while training is in progress (logically impossible)
• ❌ NEVER set ACCEPT_EULA to True without explicit user confirmation in the conversation
• ✅ Always mention both the number AND title of sections you reference
• ✅ If user asks how to run (notebook): If run_cell is available, offer to run it. Otherwise, tell them to run cells one by one (mention ipykernel requirement).
• ✅ If user asks how to run (script): Tell them to run with python3 <script>.py

Workflow

1. Code Generation Setup

1.1 Directory Setup

• Identify project directory from conversation context
• If unclear (multiple relevant directories exist) → Ask user which folder to use
• If no project directory exists → activate the directory-management skill to set one up

⏸ Wait for user.

1.2 Select Code Template

Read references/code_output_guide.md for output format rules, then read the code template matching the finetuning strategy:

• SFT → code_templates/sft.py
• DPO → code_templates/dpo.py
• RLVR → code_templates/rlvr.py
• RLAIF with built-in rewards → code_templates/rlaif_builtin.py
• RLAIF with custom prompt → code_templates/rlaif_custom_prompt.py

The template is a Python file where each # Cell N: Label comment marks the start of a new section. Split on these markers — everything between one marker and the next becomes one unit of output.

1.3 Generate Code

• Write the code from the template following the rules in code_output_guide.md
• Use same order, dependencies, and imports as the template
• DO NOT improvise or add extra code
• If the model is NOT a Meta/Llama model (model ID does NOT start with meta-):
• Omit the ACCEPT_EULA = False line from the config cell
• Omit the accept_eula=ACCEPT_EULA, line from the trainer call
• If the model is from the Nova family, omit any code containing max_epochs or lr_warmup_steps_ratio from the Configure Trainer section and the Hyperparameter Overrides section

1.4 Auto-Generate Configuration Values

In the 'Setup & Credentials' cell, populate:

• BASE_MODEL
• Use the exact SageMakerHub model name from context

• MODEL_PACKAGE_GROUP_NAME
• Generate from use case (read use_case_spec.md if needed)
• Format rules:
• Lowercase, alphanumeric with hyphens only
• 1-63 characters
• Pattern: a-zA-Z0-9{0,62}
• Example: "Customer Support Chatbot" → customer-support-chatbot-v1

• Save notebook

2. RLVR Reward Function (for RLVR only, skip this section if technique is SFT or DPO)

2.1 Check Reward Function Status

• Ask if user has a reward function already, or would like help creating one.
• If user says they have one → Ask for the SageMaker Hub Evaluator ARN. Only proceed to Section 2.3 once the user provides a valid Evaluator ARN. If they don't have it registered as a SageMaker Hub Evaluator, continue to 2.2.
• If user says they do not have one → Continue to 2.2

2.2 Generate Reward Function From Template

• Follow workflow in references/rlvr_reward_function.md section "Helping Users Create Custom Reward Functions"

2.3 Set CUSTOM_REWARD_FUNCTION value

• Set the value for CUSTOM_REWARD_FUNCTION in the Notebook with the ARN of the reward function (either given directly by the user, or from the function generation code as evaluator.arn).

3. RLAIF (for RLAIF only, skip this section if technique is not RLAIF)

Read references/rlaif_guide.md and follow its instructions.

4. EULA review and acceptance

• Look up the official license link for the selected base model from references/eula_links.md
• Display the license to the user following the phrasing in references/eula_links.md. For OSS models: "This model is licensed under {License}. Please review the license terms here: {URL}." For Nova models: "This model is subject to the AWS Service Terms: {URL}."
• Check if the selected base model is a Meta/Llama model (model ID starts with meta-)
• If Meta/Llama: Tell the user they must read and agree to the EULA before using this model. Ask: "Do you accept the license terms? (yes/no)". If the user confirms, set ACCEPT_EULA = True and uncomment accept_eula=ACCEPT_EULA in the generated notebook. If the user declines, leave ACCEPT_EULA = False and warn that training will fail without acceptance.
• If non-Meta: Inform the user of the license for their awareness. No code-level action needed — the ACCEPT_EULA variable and accept_eula parameter should already be omitted from the notebook (see Step 1.3).

5. Post-Generation

After generating the code, offer to run it. Training can take hours depending on your dataset and model.

Notebook mode: If run_cell is available, offer to run the cells. Otherwise tell the user to run cells themselves.

Script mode: Present the user with options:

> "Would you like me to:

>

> 1. Leave it to you — run with python scripts/[script_name]

> 2. Run it and wait until it's done

> 3. Start it but don't wait — we can check status later"

• Option 1: Done. Wait for user to come back.
• Option 2: Execute the script as-is. trainer.train(wait=True) blocks until complete. Report final status.
• Option 3: Change wait=True to wait=False in the script, execute, report the training job name.

Checking status:

• describe-training-job --training-job-name NAME → TrainingJobStatus, FailureReason, SecondaryStatusTransitions
• For model package ARN after completion: list-model-packages --model-package-group-name GROUP_NAME --sort-by CreationTime --sort-order Descending --max-results 1

Showing results after completion:

• Use scripts/mlflow_reference.py as the pattern to query MLflow metrics
• Present loss by epoch as a text table (total_loss, val_eval_total_loss for SFT; rewards/margins for DPO; critic/rewards/mean for RLVR)

CRITICAL:

• DON'T suggest moving to next steps before training completes
• DON'T elaborate on the next steps unless the user specifically asks you about them.

6. Continuous Customization

If the user wants to finetune a model they had already customized, follow the instructions in references/continuous_customization.md

References

• rlvr_reward_function.md - Lambda reward function creation guide (RLVR only)
• templates/rlvr_reward_function_source_template.py - Lambda reward function source template for open-weights models (RLVR only)
• templates/nova_rlvr_reward_function_source_template.py - Lambda reward function source template for Nova 2.0 Lite (RLVR only)
• code_templates/sft.py - Complete notebook template for Supervised Fine-Tuning (OSS path)
• code_templates/dpo.py - Complete notebook template for Direct Preference Optimization (OSS path)
• code_templates/rlvr.py - Complete notebook template for Reinforcement Learning from Verifiable Rewards (OSS path)
• references/continuous_customization.md - Instructions on fine-tuning an already fine-tuned model.
• rlaif_guide.md - instructions on RLAIF finetuning options
• rlaif_builtin.py - Code template for RLAIF with built-in judge prompt
• rlaif_custom_prompt.py - Code template for RLAIF with custom judge prompt