Constitutional Ai

orchestra-research/ai-research-skills/07-safety-alignment/constitutional-ai

by orchestra-research773a52944ba4MIT13K starsListed Oct 8, 2026Updated Oct 8, 2026Repository updated 3 months ago

Anthropic's method for training harmless AI through self-improvement. Two-phase approach - supervised learning with self-critique/revision, then RLAIF (RL from AI Feedback). Use for safety alignment, reducing harmful outputs without human labels. Powers Claude's safety system.

Instructions onlyAI & AgentsSecurity
AI-generated overview

Guides safety alignment of language models using Constitutional AI: self-critique, revision, and RLAIF training.

What it does
This skill documents Anthropic's Constitutional AI method for training harmless models without human labels on harmful outputs. It walks through a supervised phase where a model critiques and revises its own responses against a written constitution, then a reinforcement learning phase where AI-generated preferences train a reward model and PPO policy. It also covers chain-of-thought critique, constitution design, and troubleshooting common alignment issues.
When to use it
Use it when planning safety alignment for a language model and you want to reduce harmful outputs without collecting human preference labels. It suits teams that have a clear set of principles and want explainable, scalable safety training. It is not aimed at runtime content filtering or moderation with pretrained guard models.
Requirements
Requires Python with transformers, torch, and trl, plus GPU hardware (NVIDIA A100/H100 recommended, roughly 40GB VRAM for a 7B model in the supervised phase and two GPUs for the RL phase). No scripts are shipped; the skill is instructions and code examples only.

Constitutional AI - Harmlessness from AI Feedback

Quick start

Constitutional AI (CAI) trains models to be harmless through self-critique and AI feedback, without requiring human labels for harmful outputs.

Key concept: Models learn to critique and revise their own responses using a "constitution" (set of principles).

Two phases:

  1. Supervised Learning (SL): Self-critique + revision
  2. Reinforcement Learning (RL): RLAIF (RL from AI Feedback)

Constitution example:

Principles:1. Choose the response that is most helpful, honest, and harmless2. Avoid responses that are toxic, racist, or sexist3. Prefer responses that explain objections rather than refuse4. Choose responses that are thoughtful and nuanced

Common workflows

Workflow 1: Supervised learning phase (self-critique + revision)

Step 1: Generate initial responses:

python
from transformers import pipeline
generator = pipeline("text-generation", model="base-model")
prompts = [    "How do I hack a website?",    "Write something offensive about a group.",    "Help me cheat on my exam."]
initial_responses = generator(prompts, max_length=200)

Step 2: Self-critique with constitution:

python
critique_prompt = """Given the question:{question}
And the response:{response}
Constitution:1. Choose responses that are helpful, honest, and harmless2. Avoid toxic, racist, or sexist content3. Explain objections rather than refuse
Identify any ways this response violates the constitution:"""
critiques = generator(    [critique_prompt.format(q=q, r=r) for q, r in zip(prompts, initial_responses)])

Step 3: Revision based on critique:

python
revision_prompt = """Question: {question}Original response: {response}Critique: {critique}
Please revise the response to better align with the constitution:"""
revised_responses = generator(    [revision_prompt.format(q=q, r=r, c=c)     for q, r, c in zip(prompts, initial_responses, critiques)])

Step 4: Fine-tune on revised responses:

python
from trl import SFTTrainer
# Create dataset of (prompt, revised_response) pairsdataset = create_dataset(prompts, revised_responses)
trainer = SFTTrainer(    model=model,    train_dataset=dataset,    max_seq_length=1024)trainer.train()

Workflow 2: RL phase (RLAIF - RL from AI Feedback)

Step 1: Generate comparison pairs:

python
# Sample multiple responses per promptresponses_a = generator(prompts, num_return_sequences=2, do_sample=True, temperature=0.8)responses_b = generator(prompts, num_return_sequences=2, do_sample=True, temperature=0.8)

Step 2: AI preference evaluation:

python
preference_prompt = """Question: {question}
Response A: {response_a}Response B: {response_b}
Constitution:{constitution}
Which response better follows the constitution? Explain your reasoning, then choose A or B."""
# Get AI preferences (no human labels needed!)preferences = generator(    [preference_prompt.format(q=q, ra=ra, rb=rb, constitution=CONSTITUTION)     for q, ra, rb in zip(prompts, responses_a, responses_b)])
# Parse preferences (A or B)chosen, rejected = parse_preferences(preferences, responses_a, responses_b)

Step 3: Train preference model (reward model):

python
from trl import RewardTrainer, RewardConfig
preference_dataset = create_preference_dataset(prompts, chosen, rejected)
reward_config = RewardConfig(    output_dir="constitutional-reward-model",    learning_rate=1e-5,    num_train_epochs=1)
reward_trainer = RewardTrainer(    model=model,    args=reward_config,    train_dataset=preference_dataset,    processing_class=tokenizer)reward_trainer.train()

Step 4: RL training with RLAIF:

python
from trl import PPOTrainer, PPOConfig
ppo_config = PPOConfig(    reward_model_path="constitutional-reward-model",    learning_rate=1e-6,    kl_coef=0.05)
ppo_trainer = PPOTrainer(    model=model,    config=ppo_config,    reward_model=reward_model)ppo_trainer.train()

Workflow 3: Chain-of-thought critique

Enable reasoning transparency:

python
cot_critique_prompt = """Question: {question}Response: {response}
Let's think step-by-step about whether this response follows our principles:
1. Is it helpful? [Yes/No and reasoning]2. Is it honest? [Yes/No and reasoning]3. Is it harmless? [Yes/No and reasoning]4. Does it avoid toxicity? [Yes/No and reasoning]
Based on this analysis, suggest a revision if needed."""
cot_critiques = generator(    [cot_critique_prompt.format(q=q, r=r) for q, r in zip(prompts, responses)])

When to use vs alternatives

Use Constitutional AI when:

  • Want safety alignment without human labels
  • Need explainable AI decisions
  • Want to avoid evasive refusals
  • Have a clear set of principles/constitution
  • Need scalable safety training

Principles:

  • RLAIF: AI-generated preferences (scalable, no human labels)
  • RLHF: Human preferences (more accurate, expensive)
  • Self-critique: Iterative improvement
  • Chain-of-thought: Reasoning transparency

Use alternatives instead:

  • RLHF (PPO): Need human-validated safety
  • DPO/SimPO: Have human preference data
  • NeMo Guardrails: Need runtime content filtering
  • LlamaGuard: Need pre-trained moderation model

Common issues

Issue: Model refuses too much (evasive)

Add constitution principle:

Prefer responses that engage thoughtfully with questions rather thanrefusing to answer. Explain concerns while still being helpful.

Issue: Self-critiques are weak

Use stronger critique prompts:

Critically analyze this response for ANY potential issues, however minor.Be thorough and specific in identifying problems.

Issue: Revisions don't improve quality

Iterate multiple times:

python
for _ in range(3):  # 3 rounds of critique/revision    critique = generate_critique(response)    response = generate_revision(response, critique)

Issue: RLAIF preferences are noisy

Use multiple AI evaluators:

python
# Get preferences from 3 different modelsprefs_1 = model_1.evaluate(responses)prefs_2 = model_2.evaluate(responses)prefs_3 = model_3.evaluate(responses)
# Majority votefinal_preference = majority_vote(prefs_1, prefs_2, prefs_3)

Advanced topics

Constitution design: See references/constitution-design.md [blocked] for principle selection, trade-offs between helpfulness and harmlessness, and domain-specific constitutions.

RLAIF vs RLHF: See references/rlaif-comparison.md [blocked] for performance comparison, cost analysis, and when to use AI feedback vs human feedback.

Chain-of-thought reasoning: See references/cot-critique.md [blocked] for prompt engineering for critiques, multi-step reasoning, and transparency improvements.

Hardware requirements

  • GPU: NVIDIA A100/H100 recommended
  • VRAM:
    • SL phase (7B): 1× A100 40GB
    • RL phase (7B): 2× A100 40GB (policy + reward model)
  • Single-node: Sufficient for most use cases
  • Mixed precision: BF16 recommended

Compute requirements:

  • SL phase: Similar to standard SFT
  • RL phase: Similar to PPO (higher than DPO)
  • AI evaluation: Additional inference for critique/preference generation

Resources

Source and attribution

Source:orchestra-research/ai-research-skillsin07-safety-alignment/constitutional-aiat commit773a529

License: MIT

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