ADR-029: Model Audition Mechanism

Status: ACCEPTED (Revised per Council Review 2025-12-24) Date: 2025-12-24 Decision Makers: Engineering, Architecture Depends On: ADR-028 (Dynamic Candidate Discovery), ADR-027 (Frontier Tier) Council Review: Reasoning tier (gpt-5.2-pro, claude-opus-4.5, gemini-3-pro-preview, grok-4.1-fast)

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Context

When new models are discovered via ADR-028, they lack performance history. The system cannot accurately score them because:

1. No latency measurements exist
2. No quality observations from past sessions
3. No availability/reliability data

Cold Start Problem: New models are either never selected (no history → low score) or selected blindly (no data to validate quality).

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Decision

Implement a volume-based audition mechanism with Shadow Mode integration and explicit state machine progression.

Model Lifecycle State Machine (Council Requirement)

Critical Feedback: Time-based graduation is unreliable. A model used once in 30 days isn't "proven."

┌─────────────────────────────────────────────────────────────────────────────┐
│                        Model Lifecycle State Machine                         │
├─────────────────────────────────────────────────────────────────────────────┤
│                                                                             │
│   ┌──────────┐    10 sessions    ┌───────────┐    25 sessions    ┌──────┐  │
│   │  SHADOW  │ ─────────────────▶│ PROBATION │ ─────────────────▶│ EVAL │  │
│   │          │    (min 3 days)   │           │    (min 7 days)   │      │  │
│   └──────────┘                   └───────────┘                   └──────┘  │
│        │                              │                              │      │
│        │ 3+ failures                  │ 5+ failures                  │      │
│        ▼                              ▼                              ▼      │
│   ┌──────────────────────────────────────────────────────────────────────┐ │
│   │                           QUARANTINE                                  │ │
│   │           (Cooldown: 24h shadow, then retry from SHADOW)              │ │
│   └──────────────────────────────────────────────────────────────────────┘ │
│                                                                             │
│   ┌──────┐    50 sessions    ┌──────┐                                      │
│   │ EVAL │ ─────────────────▶│ FULL │  (Normal selection, full authority)  │
│   │      │   (quality ≥75th  │      │                                      │
│   └──────┘    percentile)    └──────┘                                      │
│                                                                             │
└─────────────────────────────────────────────────────────────────────────────┘

State Definitions

from enum import Enum, auto
from dataclasses import dataclass
from datetime import datetime
from typing import Optional

class AuditionState(Enum):
    """Model audition lifecycle states."""
    SHADOW = auto()      # Non-binding votes, observation only
    PROBATION = auto()   # Limited selection, paired with proven models
    EVALUATION = auto()  # Weighted selection, building confidence
    FULL = auto()        # Normal selection, full voting authority
    QUARANTINE = auto()  # Temporarily excluded due to failures


@dataclass
class AuditionStatus:
    """Tracks model's audition progress."""
    model_id: str
    state: AuditionState
    session_count: int = 0
    first_seen: Optional[datetime] = None
    last_seen: Optional[datetime] = None
    consecutive_failures: int = 0
    quality_percentile: Optional[float] = None
    quarantine_until: Optional[datetime] = None

    def days_tracked(self) -> int:
        """Days since first session."""
        if self.first_seen is None:
            return 0
        return (datetime.utcnow() - self.first_seen).days


@dataclass(frozen=True)
class GraduationCriteria:
    """Criteria for state transitions (volume-based)."""
    # SHADOW → PROBATION
    shadow_min_sessions: int = 10
    shadow_min_days: int = 3
    shadow_max_failures: int = 3

    # PROBATION → EVALUATION
    probation_min_sessions: int = 25
    probation_min_days: int = 7
    probation_max_failures: int = 5

    # EVALUATION → FULL
    eval_min_sessions: int = 50
    eval_min_quality_percentile: float = 0.75  # Must be in top 25%

    # QUARANTINE
    quarantine_cooldown_hours: int = 24

State Transition Logic

def evaluate_state_transition(
    status: AuditionStatus,
    criteria: GraduationCriteria
) -> Optional[AuditionState]:
    """
    Determine if model should transition states.
    Volume-based graduation per Council recommendation.
    """
    now = datetime.utcnow()

    # Check quarantine expiry
    if status.state == AuditionState.QUARANTINE:
        if status.quarantine_until and now >= status.quarantine_until:
            return AuditionState.SHADOW  # Retry from shadow
        return None  # Stay quarantined

    # Check failure thresholds (any state → QUARANTINE)
    if status.state == AuditionState.SHADOW:
        if status.consecutive_failures >= criteria.shadow_max_failures:
            return AuditionState.QUARANTINE

    if status.state == AuditionState.PROBATION:
        if status.consecutive_failures >= criteria.probation_max_failures:
            return AuditionState.QUARANTINE

    # SHADOW → PROBATION
    if status.state == AuditionState.SHADOW:
        if (status.session_count >= criteria.shadow_min_sessions
            and status.days_tracked() >= criteria.shadow_min_days):
            return AuditionState.PROBATION

    # PROBATION → EVALUATION
    if status.state == AuditionState.PROBATION:
        if (status.session_count >= criteria.probation_min_sessions
            and status.days_tracked() >= criteria.probation_min_days):
            return AuditionState.EVALUATION

    # EVALUATION → FULL
    if status.state == AuditionState.EVALUATION:
        if (status.session_count >= criteria.eval_min_sessions
            and status.quality_percentile is not None
            and status.quality_percentile >= criteria.eval_min_quality_percentile):
            return AuditionState.FULL

    return None  # No transition

Shadow Mode Integration (ADR-027)

Critical Council Feedback: Audition models must NOT influence consensus until proven.

from llm_council.voting import VotingAuthority

# State → Voting Authority mapping
STATE_VOTING_AUTHORITY = {
    AuditionState.SHADOW: VotingAuthority.ADVISORY,      # Non-binding
    AuditionState.PROBATION: VotingAuthority.ADVISORY,   # Non-binding
    AuditionState.EVALUATION: VotingAuthority.ADVISORY,  # Non-binding until FULL
    AuditionState.FULL: VotingAuthority.FULL,            # Full voting rights
    AuditionState.QUARANTINE: VotingAuthority.EXCLUDED,  # Not selected
}


def get_voting_authority(model_id: str, tracker: AuditionTracker) -> VotingAuthority:
    """Get voting authority based on audition state."""
    status = tracker.get_status(model_id)

    if status is None:
        # Unknown model - treat as new (SHADOW)
        return VotingAuthority.ADVISORY

    return STATE_VOTING_AUTHORITY.get(status.state, VotingAuthority.ADVISORY)

Selection with Audition (Revised)

Council Feedback: Code inconsistency fixed. Progressive weight replaces epsilon-greedy binary.

def select_with_audition(
    scored_candidates: List[Tuple[str, float]],
    tracker: AuditionTracker,
    count: int = 4,
) -> List[str]:
    """
    Select models with state-appropriate weighting.

    Progressive weight approach (NOT epsilon-greedy):
    - SHADOW/PROBATION: 30% selection weight
    - EVALUATION: 30-100% (scaled by session count)
    - FULL: 100% selection weight
    """
    weighted_candidates = []

    for model_id, score in scored_candidates:
        status = tracker.get_status(model_id)
        weight = get_selection_weight(status)
        weighted_score = score * weight
        weighted_candidates.append((model_id, weighted_score, weight))

    # Sort by weighted score
    weighted_candidates.sort(key=lambda x: -x[1])

    # Enforce max audition seats (protect council quality)
    selected = []
    audition_count = 0
    max_audition_seats = 1  # Only 1 audition model per session

    for model_id, weighted_score, weight in weighted_candidates:
        if len(selected) >= count:
            break

        # Is this an audition model (weight < 1.0)?
        is_audition = weight < 1.0

        if is_audition:
            if audition_count >= max_audition_seats:
                continue  # Skip, already have max audition models
            audition_count += 1

        selected.append(model_id)

    return selected


def get_selection_weight(status: Optional[AuditionStatus]) -> float:
    """
    Get selection weight based on audition state.
    Consistent with table definitions (fixes code/table mismatch).
    """
    if status is None:
        return 0.3  # New model: SHADOW weight

    if status.state == AuditionState.SHADOW:
        return 0.3

    if status.state == AuditionState.PROBATION:
        return 0.3

    if status.state == AuditionState.EVALUATION:
        # Scale from 0.3 to 1.0 based on session progress
        # At 25 sessions (EVAL entry): 0.3
        # At 50 sessions (FULL graduation): 1.0
        progress = min(1.0, (status.session_count - 25) / 25)
        return 0.3 + (0.7 * progress)

    if status.state == AuditionState.FULL:
        return 1.0

    if status.state == AuditionState.QUARANTINE:
        return 0.0  # Never select

    return 0.3  # Default: cautious


# REMOVED: Epsilon-greedy approach (inconsistent with progressive weights)

Probationary Periods (Revised - Volume-Based)

State	Sessions	Min Days	Selection Weight	Max Seats	Voting
Shadow	0-10	3	30%	1	Advisory
Probation	10-25	7	30%	1	Advisory
Evaluation	25-50	-	30-100%	1	Advisory
Full	50+	-	100%	Any	Full
Quarantine	-	-	0%	0	Excluded

Audition Safeguards

1. Shadow Mode by default - New models don't affect consensus
2. Volume-based graduation - Requires actual usage, not just time
3. Max 1 audition per council session - Limit risk exposure
4. Paired with proven models - Always have reliable responses
5. Quality gate for FULL status - Must be top 25% to graduate
6. Quarantine on failures - Automatic exclusion with cooldown
7. Consensus exclusion - Audition models excluded from tie-breaking

Configuration

council:
  model_intelligence:
    audition:
      enabled: true

      # State progression (volume-based)
      shadow:
        min_sessions: 10
        min_days: 3
        max_failures: 3

      probation:
        min_sessions: 25
        min_days: 7
        max_failures: 5

      evaluation:
        min_sessions: 50
        min_quality_percentile: 0.75

      quarantine:
        cooldown_hours: 24

      # Selection limits
      max_audition_seats: 1

Environment Variables

Variable	Type	Default	Purpose
LLM_COUNCIL_AUDITION_ENABLED	bool	true	Enable audition mechanism
LLM_COUNCIL_AUDITION_MAX_SEATS	int	1	Max audition models per session
LLM_COUNCIL_AUDITION_SHADOW_SESSIONS	int	10	Sessions before probation
LLM_COUNCIL_AUDITION_EVAL_SESSIONS	int	50	Sessions for full graduation

---

Observability (Council Requirement)

# Metrics to emit
audition.state_transition{model_id, from_state, to_state}
audition.selection{model_id, state, selected}
audition.failure{model_id, state, failure_type}
audition.quarantine{model_id, reason, cooldown_hours}
audition.graduation{model_id, quality_percentile}

# Structured logging
{
    "event": "audition_state_change",
    "model_id": "openai/gpt-5.2",
    "from_state": "PROBATION",
    "to_state": "EVALUATION",
    "session_count": 25,
    "days_tracked": 8,
    "quality_percentile": null
}

---

Consequences

Positive

• Solves cold start problem for new models
• Volume-based graduation ensures actual usage
• Shadow Mode protects consensus from unproven models
• Explicit state machine provides clear lifecycle
• Quality gate prevents low-quality model graduation

Negative

• Audition models contribute responses but not votes
• Longer path to full status (50 sessions minimum)
• Additional complexity in selection logic
• Quarantine may miss temporary issues vs systemic

Risks & Mitigations

Risk	Mitigation
Audition model pollutes context	Shadow Mode (advisory only)
Volume manipulation (spam requests)	Min days requirement alongside sessions
Good model stuck in evaluation	Clear quality percentile metric
Quarantine too aggressive	Configurable thresholds, auto-retry

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Testing Strategy

class TestAuditionMechanism:
    def test_state_transitions_volume_based(self):
        """State transitions require session count, not just time."""

    def test_shadow_mode_no_voting(self):
        """Shadow state models have ADVISORY voting authority."""

    def test_quarantine_on_failures(self):
        """Consecutive failures trigger quarantine."""

    def test_quarantine_cooldown_and_retry(self):
        """Models retry from SHADOW after cooldown."""

    def test_max_audition_seats(self):
        """Only 1 audition model selected per session."""

    def test_quality_gate_for_full(self):
        """EVALUATION → FULL requires 75th percentile quality."""

    def test_selection_weight_progression(self):
        """Weight scales 0.3 → 1.0 during EVALUATION."""

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Implementation Plan

1. Define AuditionState enum and AuditionStatus dataclass
2. Implement state transition logic with volume-based criteria
3. Add AuditionTracker with persistence (JSONL)
4. Integrate with VotingAuthority from ADR-027
5. Implement select_with_audition() with progressive weights
6. Add metrics and structured logging
7. Add configuration via YAML and env vars
8. Add comprehensive tests

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References

• ADR-027: Frontier Tier (Shadow Mode)
• ADR-028: Dynamic Candidate Discovery
• ADR-026: Dynamic Model Intelligence