# Changelog 68: Router Error Firewall

**Date:** 2025-12-01
**Type:** Feature
**Task:** TASK-039-14

## Summary

Implemented the Error Firewall for the Router Supervisor, providing operation validation and blocking/fixing invalid operations.

## Changes

### New Files

- `server/router/application/engines/error_firewall.py` - Main implementation
- `tests/unit/router/application/test_error_firewall.py` - 44 unit tests

### Features

1. **Firewall Actions**
   - ALLOW - Let operation proceed
   - BLOCK - Prevent execution
   - MODIFY - Change parameters
   - AUTO_FIX - Add pre-steps to fix

2. **Default Rules**
   - Mode violations (mesh in OBJECT mode, etc.)
   - Selection requirements (extrude without selection)
   - Parameter bounds (bevel too large, subdivide too many)
   - Object existence (delete without objects)

3. **Rule Management**
   - Register/enable/disable rules
   - Simple condition syntax for rule matching
   - Wildcard tool pattern matching

### Condition Syntax

```python
"mode == 'OBJECT'"              # Mode check
"no_selection"                  # No geometry selected
"no_objects"                    # Scene is empty
"param:width > dimension_ratio:0.5"  # Parameter check
```

### API

```python
firewall = ErrorFirewall(config=RouterConfig())
result = firewall.validate(tool_call, context)
if result.action == FirewallAction.BLOCK:
    raise BlockedOperationError(result.message)
```

## Related

- Part of Phase 3: Tool Processing Engines
- Implements `IFirewall` interface
