MechInterp Validation Suite

MechInterp Validation Suite

Run comprehensive credibility checks on feature interpretations to ensure findings are robust and not artifacts.

Purpose

The validation suite skill:

• Tests stability of analysis results across data splits
• Creates null distributions to assess significance
• Generates validation reports with pass/​fail criteria
• Helps identify unreliable interpretations early

When to Use

Use this skill when:

• A hypothesis reaches high confidence (>0.7) and needs validation
• You want to verify that a pattern is real, not noise
• Before finalizing feature labels or interpretations
• As part of a standard research checkpoint

Validation Tests

1. Split-Half Stability

Tests if analysis results are consistent across random splits of the data.

What it measures: Correlation of token frequency rankings between two halves Pass criterion: Mean correlation > 0.7

from splatnlp.mechinterp.schemas import ExperimentSpec, ExperimentType
from splatnlp.mechinterp.experiments import get_runner_for_type
from splatnlp.mechinterp.skill_helpers import load_context

# Create split-half spec
spec = ExperimentSpec(
    type=ExperimentType.SPLIT_HALF,
    feature_id=18712,
    model_type="ultra",
    variables={
        "n_splits": 10,
        "metric": "token_frequency_correlation"
    }
)

# Run validation
ctx = load_context("ultra")
runner = get_runner_for_type(spec.type)
result = runner.run(spec, ctx)

# Check results
mean_corr = result.aggregates.custom["mean_correlation"]
passed = result.aggregates.custom["stability_passed"]
print(f"Split-half correlation: {mean_corr:.3f} ({'PASS' if passed else 'FAIL'})")

2. Shuffle Null Test

Creates a null distribution by shuffling activations to test if observed patterns are significant.

What it measures: Whether top-token concentration exceeds null expectation Pass criterion: p-value < 0.05

spec = ExperimentSpec(
    type=ExperimentType.SHUFFLE_NULL,
    feature_id=18712,
    model_type="ultra",
    variables={
        "n_shuffles": 100
    }
)

result = runner.run(spec, ctx)

p_value = result.aggregates.custom["p_value"]
significant = result.aggregates.custom["significant"]
print(f"Shuffle null p-value: {p_value:.4f} ({'SIGNIFICANT' if significant else 'NOT SIGNIFICANT'})")

Running Full Validation Suite

from splatnlp.mechinterp.schemas import ExperimentSpec, ExperimentType
from splatnlp.mechinterp.experiments import get_runner_for_type
from splatnlp.mechinterp.skill_helpers import load_context
from splatnlp.mechinterp.state.io import SPECS_DIR, RESULTS_DIR
from datetime import datetime
import json

def run_validation_suite(feature_id: int, model_type: str = "ultra"):
    """Run all validation tests for a feature."""
    ctx = load_context(model_type)
    results = {}

    # Test 1: Split-half stability
    split_spec = ExperimentSpec(
        type=ExperimentType.SPLIT_HALF,
        feature_id=feature_id,
        model_type=model_type,
        variables={"n_splits": 10}
    )
    runner = get_runner_for_type(split_spec.type)
    split_result = runner.run(split_spec, ctx)
    results["split_half"] = {
        "mean_correlation": split_result.aggregates.custom.get("mean_correlation"),
        "passed": split_result.aggregates.custom.get("stability_passed", 0) == 1
    }

    # Test 2: Shuffle null
    null_spec = ExperimentSpec(
        type=ExperimentType.SHUFFLE_NULL,
        feature_id=feature_id,
        model_type=model_type,
        variables={"n_shuffles": 100}
    )
    runner = get_runner_for_type(null_spec.type)
    null_result = runner.run(null_spec, ctx)
    results["shuffle_null"] = {
        "p_value": null_result.aggregates.custom.get("p_value"),
        "passed": null_result.aggregates.custom.get("significant", 0) == 1
    }

    # Overall pass/​fail
    all_passed = all(r["passed"] for r in results.values())

    return {
        "feature_id": feature_id,
        "model_type": model_type,
        "tests": results,
        "overall_passed": all_passed,
        "timestamp": datetime.now().isoformat()
    }

# Run suite
validation = run_validation_suite(18712, "ultra")
print(f"\nValidation Suite for Feature {validation['feature_id']}:")
print(f"  Split-half: {validation['tests']['split_half']['mean_correlation']:.3f} "
      f"({'PASS' if validation['tests']['split_half']['passed'] else 'FAIL'})")
print(f"  Shuffle null: p={validation['tests']['shuffle_null']['p_value']:.4f} "
      f"({'PASS' if validation['tests']['shuffle_null']['passed'] else 'FAIL'})")
print(f"\nOVERALL: {'PASS' if validation['overall_passed'] else 'FAIL'}")

Interpretation Guide

Split-Half Results

Shuffle Null Results

Workflow Integration

1. Conduct research: Build hypotheses, gather evidence
2. Reach confidence threshold: When hypothesis confidence > 0.7
3. Run validation suite: Execute this skill
4. Update state: Mark hypothesis as validated (or not)
5. Document: Add validation results to evidence

from splatnlp.mechinterp.state import ResearchStateManager
from splatnlp.mechinterp.schemas.research_state import HypothesisStatus

# After validation passes
manager = ResearchStateManager(18712, "ultra")
manager.update_hypothesis(
    "h001",
    status=HypothesisStatus.SUPPORTED,
    confidence_absolute=0.9
)
manager.add_evidence(
    experiment_id="validation_suite",
    result_path="/​mnt/​e/​mechinterp_runs/​results/​validation.json",
    summary="Passed split-half (r=0.85) and shuffle null (p<0.01)",
    strength=EvidenceStrength.STRONG,
    supports=["h001"]
)

CLI Usage

cd /​root/​dev/​SplatNLP

# Run split-half validation
poetry run python -m splatnlp.mechinterp.cli.runner_cli \
    --spec-path specs/​split_half_spec.json

# Run shuffle null validation
poetry run python -m splatnlp.mechinterp.cli.runner_cli \
    --spec-path specs/​shuffle_null_spec.json

See Also

• mechinterp-state: Update hypotheses after validation
• mechinterp-summarizer: Document validation results
• mechinterp-runner: Execute validation experiments