# 50% Rule Validation Report

## Overview

This document validates the effectiveness of the 50% rule in preventing agent context exhaustion.

**Date:** 2026-02-01
**Issue:** #143 [COORD-003]
**Status:** ✅ VALIDATED

## The 50% Rule

**Rule:** No single issue assignment may exceed 50% of the target agent's context limit.

**Rationale:** This ensures:

- Room for conversation history and tool use
- Buffer before hitting hard context limits
- Prevents single issues from monopolizing agent capacity
- Allows multiple issues to be processed without exhaustion

## Agent Context Limits

| Agent   | Total Limit | 50% Threshold | Use Case              |
| ------- | ----------- | ------------- | --------------------- |
| opus    | 200,000     | 100,000       | High complexity tasks |
| sonnet  | 200,000     | 100,000       | Medium complexity     |
| haiku   | 200,000     | 100,000       | Low complexity        |
| glm     | 128,000     | 64,000        | Self-hosted medium    |
| minimax | 128,000     | 64,000        | Self-hosted low       |

## Test Scenarios

### 1. Oversized Issue (REJECTED) ✅

**Scenario:** Issue with 120K token estimate assigned to sonnet (200K limit)

**Expected:** Rejected (60% exceeds 50% threshold)

**Result:** ✅ PASS

```
Issue context estimate (120000 tokens) exceeds 50% rule for sonnet agent.
Maximum allowed: 100000 tokens (50% of 200000 context limit).
```

### 2. Properly Sized Issue (ACCEPTED) ✅

**Scenario:** Issue with 80K token estimate assigned to sonnet

**Expected:** Accepted (40% is below 50% threshold)

**Result:** ✅ PASS - Issue accepted without warnings

### 3. Edge Case - Exactly 50% (ACCEPTED) ✅

**Scenario:** Issue with exactly 100K token estimate for sonnet

**Expected:** Accepted (exactly at threshold, not exceeding)

**Result:** ✅ PASS - Issue accepted at boundary condition

### 4. Sequential Issues Without Exhaustion ✅

**Scenario:** Three sequential 60K token issues for sonnet (30% each)

**Expected:** All accepted individually (50% rule checks individual issues, not cumulative)

**Result:** ✅ PASS - All three issues accepted

**Note:** Cumulative context tracking will be handled by runtime monitoring (COORD-002), not assignment validation.

## Implementation Details

**Module:** `src/validation.py`
**Function:** `validate_fifty_percent_rule(metadata: IssueMetadata) -> ValidationResult`

**Test Coverage:** 100% (14/14 statements)
**Test Count:** 12 comprehensive test cases

## Edge Cases Validated

1. ✅ Zero context estimate (accepted)
2. ✅ Very small issues < 1% (accepted)
3. ✅ Exactly at 50% threshold (accepted)
4. ✅ Just over 50% threshold (rejected)
5. ✅ All agent types (opus, sonnet, haiku, glm, minimax)
6. ✅ Different context limits (200K vs 128K)

## Effectiveness Analysis

### Prevention Capability

The 50% rule successfully prevents:

- ❌ Single issues consuming > 50% of agent capacity
- ❌ Context exhaustion from oversized assignments
- ❌ Agent deadlock from insufficient working memory

### What It Allows

The rule permits:

- ✅ Multiple medium-sized issues to be processed
- ✅ Efficient use of agent capacity (up to 50% per issue)
- ✅ Buffer space for conversation history and tool outputs
- ✅ Clear, predictable validation at assignment time

### Limitations

The 50% rule does NOT prevent:

- Cumulative context growth over multiple issues (requires runtime monitoring)
- Context bloat from tool outputs or conversation (requires compaction)
- Issues that grow beyond estimate during execution (requires monitoring)

These are addressed by complementary systems:

- **Runtime monitoring** (#155) - Tracks actual context usage
- **Context compaction** - Triggered at 80% threshold
- **Session rotation** - Triggered at 95% threshold

## Validation Metrics

| Metric            | Target | Actual | Status  |
| ----------------- | ------ | ------ | ------- |
| Test coverage     | ≥85%   | 100%   | ✅ PASS |
| Test scenarios    | 4      | 12     | ✅ PASS |
| Edge cases tested | -      | 6      | ✅ PASS |
| Type safety       | Pass   | Pass   | ✅ PASS |
| Linting           | Pass   | Pass   | ✅ PASS |

## Recommendations

1. ✅ **Implemented:** Agent-specific limits (200K vs 128K)
2. ✅ **Implemented:** Clear rejection messages with context
3. ✅ **Implemented:** Validation at assignment time
4. 🔄 **Future:** Integrate with issue assignment workflow
5. 🔄 **Future:** Add telemetry for validation rejection rates
6. 🔄 **Future:** Consider dynamic threshold adjustment based on historical context growth

## Conclusion

The 50% rule validation is **EFFECTIVE** at preventing oversized issue assignments and context exhaustion. All test scenarios pass, edge cases are handled correctly, and the implementation achieves 100% test coverage.

**Status:** ✅ Ready for integration into coordinator workflow