# Function Contracts and System Invariants
## Contract-Based Development Framework
The Agent Orchestration Platform employs **Design by Contract** principles to ensure system reliability, security, and correctness. All critical operations are governed by formal contracts that specify preconditions, postconditions, and system invariants.
## Core Contract Principles
### **Security-First Contracts**
All contracts prioritize security validation and threat prevention:
- **Input Validation**: Comprehensive whitelist-based validation for all external inputs
- **Authorization Checks**: Role-based access validation for all operations
- **Resource Limits**: Enforcement of system resource constraints
- **Audit Requirements**: Mandatory audit logging for all security-sensitive operations
### **State Consistency Contracts**
System state must remain consistent across all operations:
- **Immutable State**: Agent and session state objects are immutable
- **Atomic Operations**: Complex operations are atomic with rollback capabilities
- **Concurrent Safety**: Thread-safe operations with proper synchronization
- **Persistence Guarantees**: State persistence with integrity verification
## Agent Management Contracts
### **Agent Creation Contract**
```python
@require(lambda session_id: session_exists(session_id))
@require(lambda agent_name: is_valid_agent_name(agent_name))
@require(lambda session_id, agent_name: not agent_exists_in_session(session_id, agent_name))
@require(lambda session_id: session_has_capacity(session_id))
@ensure(lambda result: result.agent_id is not None)
@ensure(lambda result: agent_process_is_running(result.agent_id))
@ensure(lambda result: iterm_tab_exists(result.iterm_tab_id))
@ensure(lambda result: audit_log_contains_creation_event(result.agent_id))
def create_agent(session_id: SessionId, agent_name: str, **kwargs) -> AgentCreationResult:
"""
Create new Claude Code agent with comprehensive validation.
Preconditions:
- Session must exist and be accessible
- Agent name must follow Agent_# format and be unique within session
- Session must have capacity for additional agents
Postconditions:
- Agent ID is generated and unique system-wide
- Claude Code process is running and responsive
- iTerm2 tab exists and is associated with agent
- Creation event logged in audit trail
Invariants:
- Total system agents ≤ MAX_TOTAL_AGENTS (32)
- Session agents ≤ MAX_AGENTS_PER_SESSION (8)
- Agent name uniqueness within session maintained
- Resource limits enforced for new agent process
"""
```
### **Agent Deletion Contract**
```python
@require(lambda agent_id: agent_exists(agent_id))
@require(lambda agent_id: caller_has_delete_permission(agent_id))
@ensure(lambda agent_id: not agent_exists(agent_id))
@ensure(lambda agent_id: not agent_process_running(agent_id))
@ensure(lambda agent_id: not iterm_tab_exists_for_agent(agent_id))
@ensure(lambda agent_id: audit_log_contains_deletion_event(agent_id))
def delete_agent(agent_id: AgentId, force: bool = False) -> AgentDeletionResult:
"""
Remove agent with complete cleanup and resource reclamation.
Preconditions:
- Agent must exist in system
- Caller must have deletion permissions
Postconditions:
- Agent removed from all system records
- Claude Code process terminated gracefully
- iTerm2 tab closed and resources cleaned
- Deletion event logged with full context
Invariants:
- No orphaned processes remain after deletion
- All agent resources properly reclaimed
- Session agent count decremented correctly
- Audit trail maintains complete deletion history
"""
```
## Session Management Contracts
### **Session Creation Contract**
```python
@require(lambda root_path: path_exists_and_accessible(root_path))
@require(lambda root_path: path_within_allowed_boundaries(root_path))
@require(lambda session_name: is_valid_session_name(session_name))
@require(lambda session_name: not session_name_exists(session_name))
@ensure(lambda result: session_exists(result.session_id))
@ensure(lambda result: session_directory_structure_created(result.session_id))
@ensure(lambda result: security_context_established(result.session_id))
@ensure(lambda result: audit_log_contains_session_creation(result.session_id))
def create_session(root_path: Path, session_name: str, **kwargs) -> SessionCreationResult:
"""
Create new session with codebase association and security boundaries.
Preconditions:
- Root path must exist and be accessible
- Root path must be within allowed filesystem boundaries
- Session name must be unique and follow naming conventions
Postconditions:
- Session created with unique identifier
- Directory structure initialized with proper permissions
- Security context established with filesystem boundaries
- Session creation logged in audit trail
Invariants:
- Total sessions ≤ MAX_SESSIONS (16)
- Session directory boundaries enforced
- Security context properly configured
- Git integration initialized if repository detected
"""
```
### **Session Status Contract**
```python
@require(lambda session_id: session_exists(session_id) if session_id else True)
@require(lambda caller: caller_has_read_permission())
@ensure(lambda result: all_agent_statuses_current(result))
@ensure(lambda result: resource_metrics_accurate(result))
@ensure(lambda result: health_data_consistent(result))
def get_session_status(session_id: Optional[SessionId] = None) -> SessionStatusResult:
"""
Retrieve comprehensive status information for session(s).
Preconditions:
- Session must exist if specific session requested
- Caller must have read permissions
Postconditions:
- All agent statuses are current and accurate
- Resource metrics reflect real-time usage
- Health data is consistent across all components
Invariants:
- Status data is read-only and immutable
- Performance metrics within expected ranges
- Agent health status accurately reflects process state
- No sensitive information exposed without authorization
"""
```
## Communication Contracts
### **Message Sending Contract**
```python
@require(lambda agent_id: agent_exists_and_active(agent_id))
@require(lambda message: is_valid_message_content(message))
@require(lambda message: message_length_within_limits(message))
@require(lambda caller: caller_has_message_permission(agent_id))
@ensure(lambda result: message_delivered_successfully(result))
@ensure(lambda result: adder_prompt_properly_injected(result))
@ensure(lambda result: audit_log_contains_message_event(result))
def send_message_to_agent(agent_id: AgentId, message: str, **kwargs) -> MessageResult:
"""
Send message to agent with ADDER+ prompt prepending and security validation.
Preconditions:
- Agent must exist and be in active state
- Message content must be valid and within size limits
- Caller must have permission to message this agent
Postconditions:
- Message successfully delivered to agent process
- ADDER+ prompt properly prepended with agent name
- Message interaction logged in audit trail
Invariants:
- Message content properly sanitized and escaped
- Agent conversation history updated atomically
- System prompt injection maintains security context
- No unauthorized information leakage between agents
"""
```
## Security Contracts
### **Authentication Contract**
```python
@require(lambda token: token_format_valid(token))
@require(lambda token: token_not_expired(token))
@require(lambda token: token_signature_valid(token))
@ensure(lambda result: security_context_established(result))
@ensure(lambda result: permissions_properly_assigned(result))
@ensure(lambda result: audit_log_contains_auth_event(result))
def authenticate_request(token: JWTToken) -> SecurityContext:
"""
Authenticate and authorize MCP request with comprehensive validation.
Preconditions:
- Token must be properly formatted JWT
- Token must not be expired
- Token signature must be cryptographically valid
Postconditions:
- Security context established with proper permissions
- User permissions assigned based on token claims
- Authentication event logged with full context
Invariants:
- No authentication bypass possible
- Security context immutable once established
- Audit trail maintains complete authentication history
- Failed attempts properly logged and rate-limited
"""
```
### **State Encryption Contract**
```python
@require(lambda state: state_is_serializable(state))
@require(lambda key: key_is_valid_aes_key(key))
@ensure(lambda result: result_is_properly_encrypted(result))
@ensure(lambda result: integrity_tag_present(result))
@ensure(lambda result: decryption_produces_original_state(result, state))
def encrypt_agent_state(state: AgentState, key: AESKey) -> EncryptedState:
"""
Encrypt agent state with integrity protection and key validation.
Preconditions:
- State must be serializable to bytes
- Encryption key must be valid AES-256 key
Postconditions:
- State properly encrypted with AES-GCM
- Integrity tag included for tamper detection
- Decryption with same key produces original state
Invariants:
- No plaintext state stored on disk
- Encryption keys properly rotated and managed
- Integrity verification prevents tampering
- Key material never logged or exposed
"""
```
## System Invariants
### **Global System Invariants**
These conditions must hold throughout system operation:
```python
# Resource Constraints
assert len(active_agents()) <= MAX_TOTAL_AGENTS
assert all(len(session.agents) <= MAX_AGENTS_PER_SESSION for session in sessions)
assert sum(agent.memory_usage for agent in active_agents()) <= TOTAL_MEMORY_LIMIT
# Security Invariants
assert all(agent.security_context.is_valid() for agent in active_agents())
assert all(session.filesystem_boundaries_enforced() for session in sessions)
assert all(audit_entry.signature_valid() for audit_entry in audit_log)
# State Consistency
assert all(agent.persistent_state_encrypted() for agent in active_agents())
assert all(session.git_context_consistent() for session in sessions)
assert no_orphaned_processes_exist()
# Communication Integrity
assert all(message.properly_sanitized() for message in recent_messages)
assert all(agent.adder_prompt_injected() for agent in active_agents())
assert no_unauthorized_inter_agent_communication()
```
### **Agent Lifecycle Invariants**
```python
# Agent State Transitions
assert agent_state_transitions_are_valid()
assert agent_names_unique_within_session()
assert agent_processes_match_recorded_state()
# Resource Management
assert all(agent.within_resource_limits() for agent in active_agents())
assert all(agent.iterm_tab_responsive() for agent in active_agents())
assert all(agent.claude_process_healthy() for agent in active_agents())
```
### **Session Management Invariants**
```python
# Session Boundaries
assert all(session.filesystem_access_restricted() for session in sessions)
assert all(session.agent_isolation_maintained() for session in sessions)
assert session_names_globally_unique()
# State Persistence
assert all(session.state_properly_encrypted() for session in sessions)
assert all(session.recovery_data_available() for session in sessions)
assert all(session.audit_trail_complete() for session in sessions)
```
## Contract Violation Handling
### **Violation Response Strategy**
When contracts are violated, the system responds with:
1. **Immediate Failure**: Operation stops immediately to prevent system corruption
2. **Rollback Execution**: All partial changes are rolled back to maintain consistency
3. **Security Escalation**: Security violations trigger enhanced logging and alerts
4. **Recovery Initiation**: Automatic recovery procedures attempt to restore valid state
5. **Audit Logging**: All violations logged with full context for analysis
### **Contract Testing Strategy**
All contracts are validated through:
- **Property-Based Testing**: Hypothesis testing validates contracts across input ranges
- **Integration Testing**: End-to-end testing ensures contract compliance in real scenarios
- **Security Testing**: Penetration testing validates security contract enforcement
- **Performance Testing**: Load testing ensures contracts hold under system stress
This comprehensive contract system ensures the Agent Orchestration Platform maintains correctness, security, and reliability across all operations while providing clear specifications for system behavior and error handling.
