# DSL Guide

Master the Symbi DSL for building policy-aware, secure AI agents.



---

## Overview

The Symbi DSL is a domain-specific language designed for creating autonomous, policy-aware agents. It combines traditional programming constructs with advanced security features, cryptographic operations, and declarative policy definitions.

### Key Features

- **Security-First Design**: Built-in policy enforcement and audit capabilities
- **Declarative Policies**: Express security requirements as code
- **Cryptographic Operations**: Native support for encryption, signing, and proofs
- **Inter-Agent Communication**: Built-in messaging and collaboration patterns
- **Type Safety**: Strong typing with security-aware type annotations

---

## Language Syntax

### Basic Structure

Every Symbi program consists of optional metadata and agent definitions:

```rust
metadata {
    version: "1.0.0"
    author: "developer"
    description: "Example agent"
}

agent process_data(input: DataSet) -> Result {
    // Agent implementation
}
```

> **Planned feature** — Import syntax is planned for a future release.
>
> ```rust
> import data_processing as dp;
> import security_utils;
> ```

### Comments

```rust
// Single-line comment
# Hash-style comment (also supported)

/*
 * Multi-line comment
 * Supports markdown formatting
 */
```

---

## Metadata Blocks

Metadata provides essential information about your agent:

```rust
metadata {
    version: "1.2.0"
    author: "ThirdKey Security Team"
    description: "Healthcare data analysis agent with HIPAA compliance"
    license: "Proprietary"
    tags: ["healthcare", "hipaa", "analysis"]
}
```

Metadata pairs accept either `=` or `:` as the separator.

### Metadata Fields

| Field | Type | Required | Description |
|-------|------|----------|-------------|
| `version` | String | Yes | Semantic version of the agent |
| `author` | String | Yes | Agent author or organization |
| `description` | String | Yes | Brief description of agent functionality |
| `license` | String | No | License identifier |
| `tags` | Array[String] | No | Classification tags |

Managed-CLI agents (Mode B) recognize these additional metadata keys, read by `symbi run` to spawn a governed Claude Code subprocess (see `agents/code_reviewer.symbi`):

| Field | Type | Description |
|-------|------|-------------|
| `executor` | String | Set to `"claude_code"` to run the agent as a governed Claude Code subprocess instead of the reasoning loop |
| `model` | String | Model passed to the subprocess (e.g. `"claude-sonnet-4-5"`) |
| `allowed_tools` | String | Comma-separated tool allowlist for the subprocess (e.g. `"Read,Grep,Glob"`) |
| `system_prompt` | String | Extra system prompt appended for the subprocess |

---

## Agent Definitions

### Basic Agent Structure

```rust
agent agent_name(param1: Type1, param2: Type2) -> ReturnType {
    capabilities: [capability1, capability2]
    
    policy policy_name {
        // Policy rules
    }
    
    with configuration_options {
        // Agent implementation
    }
}
```

### Agent Parameters

Support for various parameter types:

```rust
agent complex_agent(
    // Basic types
    name: String,
    age: int,
    active: bool,
    
    // Optional parameters
    email: Optional<String>,
    
    // Complex types
    data: Array<Record>,
    config: Map<String, Value>,
    
    // Security-aware types
    sensitive_data: EncryptedData<PersonalInfo>,
    credentials: SecureString
) -> ProcessingResult {
    // Implementation
}
```

### Capabilities Declaration

Declare what your agent can do:

```rust
agent data_processor(input: DataSet) -> Analysis {
    capabilities: [
        data_analysis,          // Core data processing
        statistical_modeling,   // Advanced analytics
        report_generation,      // Output formatting
        audit_logging           // Compliance tracking
    ]
    
    // Implementation
}
```

---

## Policy Definitions

Policies define security and compliance rules that are enforced at runtime.

### Policy Structure

```rust
policy policy_name {
    allow: action_list if condition
    deny: action_list if condition
    require: requirement_list
    audit: audit_specification
}
```

### Access Control Policies

```rust
policy medical_data_access {
    allow: ["read", "analyze"] if user.role == "doctor"
    allow: ["read"] if user.role == "nurse" 
    deny: ["export", "print"] if data.contains_pii == true
    require: [
        user.clearance >= "medical_professional",
        session.mfa_verified == true,
        audit_trail = true
    ]
}
```

### Data Classification Policies

```rust
policy data_classification {
    allow: process(data) if data.anonymized == true
    deny: store(data) if data.classification == "restricted"
    audit: all_operations with digital_signature
}
```

### Complex Policy Logic

```rust
policy dynamic_access_control {
    allow: read(resource) if (
        user.department == resource.owner_department ||
        user.role == "administrator" ||
        (user.role == "auditor" && current_time.business_hours)
    )
    
    deny: write(resource) if (
        resource.locked == true ||
        user.last_training < 30d ||
        system.maintenance_mode == true
    )
    
    require: approval("supervisor") for operations on sensitive_data
}
```

---

## Type System

### Primitive Types

The DSL uses simplified type names (`int`, `float`) rather than Rust-specific types (`i64`, `f64`) to remain accessible to non-Rust developers. At compile time, `int` maps to `i64` and `float` maps to `f64`.

```rust
// Basic types
let name: String = "Alice";
let count: int = 42;        // compiles to i64
let rate: float = 3.14;     // compiles to f64
let active: bool = true;
```

### Collection Types

```rust
// Arrays
let numbers: Array<int> = [1, 2, 3, 4, 5];
let names: Array<String> = ["Alice", "Bob", "Charlie"];

// Maps
let config: Map<String, String> = {
    "host": "localhost",
    "port": "8080",
    "ssl": "true"
};

// Sets
let unique_ids: Set<String> = {"id1", "id2", "id3"};
```

### Security-Aware Types

```rust
// Encrypted types
let secret: EncryptedString = encrypt("sensitive_data", key);
let secure_number: Encrypted<int> = encrypt(42, key);

// Private data with differential privacy
let private_data: PrivateData<float> = PrivateData::new(value, epsilon=1.0);

// Verifiable results with zero-knowledge proofs
let verified_result: VerifiableResult<Analysis> = VerifiableResult {
    value: analysis,
    proof: generate_proof(analysis),
    signature: sign(analysis)
};
```

### Custom Types

```rust
// Type aliases
type UserId = String;
type EncryptedPersonalInfo = EncryptedData<PersonalInfo>;
```

> **Planned feature** — `struct` and `enum` definitions are planned for a future release. Currently, only `type` aliases are supported.
>
> ```rust
> // Struct definitions (planned)
> struct PersonalInfo {
>     name: String,
>     email: EncryptedString,
>     phone: Optional<String>,
>     birth_date: Date
> }
>
> // Enum definitions (planned)
> enum SecurityLevel {
>     Public,
>     Internal,
>     Confidential,
>     Restricted
> }
> ```

---

## Execution Context

Configure how your agent executes with the `with` clause:

### Memory Management

```rust
agent persistent_agent(data: DataSet) -> Result {
    with memory = "persistent", storage = "encrypted" {
        // Agent state persists across sessions
        store_knowledge(data);
        return process_with_history(data);
    }
}

agent ephemeral_agent(query: String) -> Answer {
    with memory = "ephemeral", cleanup = "immediate" {
        // Agent state is discarded after execution
        return quick_answer(query);
    }
}
```

### Privacy Settings

```rust
agent privacy_preserving_agent(sensitive_data: PersonalInfo) -> Statistics {
    with privacy = "differential", epsilon = 1.0 {
        // Add differential privacy noise
        let noisy_stats = compute_statistics(sensitive_data);
        return add_privacy_noise(noisy_stats, epsilon);
    }
}
```

### Security Configuration

```rust
agent high_security_agent(classified_data: ClassifiedInfo) -> Report {
    with 
        security = "maximum",
        sandbox = "firecracker",
        encryption = "homomorphic",
        requires = "top_secret_clearance"
    {
        // High-security processing
        return process_classified(classified_data);
    }
}
```

---

## Built-in Functions

### Data Processing

```rust
// Validation functions
if (validate_input(data)) {
    // Process valid data
}

// Data transformation
let cleaned_data = sanitize(raw_data);
let normalized = normalize(cleaned_data);
```

### Cryptographic Operations

```rust
// Encryption/Decryption
let encrypted = encrypt(plaintext, public_key);
let decrypted = decrypt(ciphertext, private_key);

// Digital signatures
let signature = sign(message, private_key);
let valid = verify(message, signature, public_key);

// Zero-knowledge proofs
let proof = prove(statement);
let verified = verify_proof(proof, public_statement);
```

### Audit and Logging

```rust
// Audit logging
audit_log("operation_started", {
    "operation": "data_processing",
    "user": user.id,
    "timestamp": now()
});

// Security events
security_event("policy_violation", {
    "policy": "data_access",
    "user": user.id,
    "resource": resource.id
});
```

---

## Inter-Agent Communication

### Direct Messaging

```rust
agent coordinator(task: Task) -> Result {
    with communication = "secure" {
        // Send task to specialized agent
        let result = agent security_analyzer.analyze(task);
        
        if (result.safe) {
            let processed = agent data_processor.process(task);
            return processed;
        } else {
            return reject("Security check failed");
        }
    }
}
```

### Publish-Subscribe Pattern

```rust
agent event_publisher(event: Event) -> Confirmation {
    with communication = "broadcast" {
        // Broadcast event to all subscribers
        broadcast(EventNotification {
            type: event.type,
            data: event.data,
            timestamp: now()
        });
        
        return Confirmation { sent: true };
    }
}

agent event_subscriber() -> Void {
    with communication = "subscribe" {
        // Subscribe to specific events
        let events = subscribe(EventNotification);
        
        for event in events {
            process_event(event);
        }
    }
}
```

### Secure Communication

```rust
agent secure_collaborator(request: SecureRequest) -> SecureResponse {
    with 
        communication = "encrypted",
        authentication = "mutual_tls"
    {
        // Establish secure channel
        let channel = establish_secure_channel(request.source);
        
        // Send encrypted response
        let response = process_request(request);
        return encrypt_response(response, channel.key);
    }
}
```

---

## Error Handling

### Try-Catch Blocks

```rust
agent robust_processor(data: DataSet) -> Result {
    try {
        let validated = validate_data(data);
        let processed = process_data(validated);
        return Ok(processed);
    } catch (ValidationError e) {
        audit_log("validation_failed", e.details);
        return Error("Invalid input data");
    } catch (ProcessingError e) {
        audit_log("processing_failed", e.details);
        return Error("Processing failed");
    }
}
```

### Error Recovery

```rust
agent fault_tolerant_agent(input: Input) -> Result {
    let max_retries = 3;
    let retry_count = 0;
    
    while (retry_count < max_retries) {
        try {
            return process_with_fallback(input);
        } catch (TransientError e) {
            retry_count += 1;
            sleep(exponential_backoff(retry_count));
        } catch (PermanentError e) {
            return Error(e.message);
        }
    }
    
    return Error("Max retries exceeded");
}
```

---

## Advanced Features

### Conditional Compilation

> **Planned feature** — Conditional compilation is planned for a future release.

```rust
agent development_agent(data: DataSet) -> Result {
    capabilities: [development, testing]

    #if debug {
        debug_log("Processing data: " + data.summary);
    }

    #if feature.enhanced_security {
        policy strict_security {
            require: multi_factor_authentication
            audit: all_operations with timestamps
        }
    }

    // Implementation
}
```

### Macros and Code Generation

> **Planned feature** — Macro definitions are planned for a future release.

```rust
// Define reusable policy template
macro secure_data_policy($classification: String) {
    policy secure_access {
        allow: read(data) if user.clearance >= $classification
        deny: export(data) if data.contains_pii
        audit: all_operations with signature
    }
}

agent classified_processor(data: ClassifiedData) -> Report {
    // Use the macro
    secure_data_policy!("secret");

    // Implementation
}
```

### Integration with External Systems

```rust
agent api_integrator(request: APIRequest) -> APIResponse {
    capabilities: [api_access, data_transformation]
    
    policy api_access {
        allow: call(external_api) if api.rate_limit_ok
        require: valid_api_key
        audit: all_api_calls with response_codes
    }
    
    with 
        timeout = 30.seconds,
        retry_policy = "exponential_backoff"
    {
        let response = call_external_api(request);
        return transform_response(response);
    }
}
```

---

## Best Practices

### Security Guidelines

1. **Always define policies** for data access and operations
2. **Use encrypted types** for sensitive data
3. **Implement audit logging** for compliance
4. **Validate all inputs** before processing
5. **Use least privilege principle** in policy definitions

### Performance Optimization

1. **Use ephemeral memory** for short-lived agents
2. **Batch operations** when possible
3. **Implement proper error handling** with retries
4. **Monitor resource usage** in execution context
5. **Use appropriate data types** for your use case

### Code Organization

1. **Group related policies** in the same block
2. **Use descriptive capability names**
3. **Document complex policy logic** with comments
4. **Separate concerns** into different agents
5. **Reuse common patterns** with shared policy definitions

---

## Examples

### Healthcare Data Processor

```rust
metadata {
    version: "2.1.0"
    author: "Medical AI Team"
    description: "HIPAA-compliant patient data analyzer"
    tags: ["healthcare", "hipaa", "privacy"]
}

agent medical_analyzer(patient_data: EncryptedPatientRecord) -> MedicalInsights {
    capabilities: [
        medical_analysis,
        privacy_preservation,
        audit_logging,
        report_generation
    ]
    
    policy hipaa_compliance {
        allow: analyze(data) if user.medical_license.valid
        deny: export(data) if data.contains_identifiers
        require: [
            user.hipaa_training.completed,
            session.secure_connection,
            audit_trail = true
        ]
    }

    with
        memory = "encrypted",
        privacy = "differential",
        security = "high",
        requires = "medical_clearance"
    {
        try {
            let decrypted = decrypt(patient_data, medical_key);
            let anonymized = anonymize_data(decrypted);
            let insights = analyze_medical_data(anonymized);
            
            audit_log("analysis_completed", {
                "patient_id_hash": hash(decrypted.id),
                "insights_generated": insights.count,
                "timestamp": now()
            });
            
            return insights;
        } catch (DecryptionError e) {
            security_event("decryption_failed", e.details);
            return Error("Unable to process patient data");
        }
    }
}
```

### Financial Transaction Monitor

```rust
agent fraud_detector(transaction: Transaction) -> FraudAssessment {
    capabilities: [fraud_detection, risk_analysis, real_time_processing]
    
    policy financial_compliance {
        allow: analyze(transaction) if user.role == "fraud_analyst"
        deny: store(transaction.details) if transaction.amount > 10000
        require: [
            user.financial_license.valid,
            system.compliance_mode.active,
            real_time_monitoring = true
        ]
        audit: all_decisions with reasoning
    }
    
    with 
        memory = "ephemeral",
        timeout = 500.milliseconds,
        priority = "high"
    {
        let risk_score = calculate_risk(transaction);
        let historical_pattern = analyze_pattern(transaction.account_id);
        
        if (risk_score > 0.8 || historical_pattern.suspicious) {
            alert_fraud_team(transaction, risk_score);
            return FraudAssessment {
                risk_level: "high",
                recommended_action: "block_transaction",
                confidence: risk_score
            };
        }
        
        return FraudAssessment {
            risk_level: "low",
            recommended_action: "approve",
            confidence: 1.0 - risk_score
        };
    }
}
```

---

## Formatting

`symbi fmt` rewrites `.symbi` files into a canonical layout — useful in pre-commit hooks, CI, and editor save actions.

```bash
symbi fmt agents/api_aggregator.symbi          # rewrite in place
symbi fmt --check agents/*.symbi               # CI gate (exit 2 if changes needed)
cat broken.symbi | symbi fmt --stdin           # editor integration
```

The formatter parses the source with tree-sitter, validates that it has no syntax errors, and emits a canonical pretty-print. If parsing fails it leaves the file untouched and exits non-zero.

Style highlights:

- 4-space indent
- Single blank line between top-level items; a leading line comment is attached to the next item with no blank-line separator
- `metadata` pairs use `key: value,` with a trailing comma to minimise diff churn
- `with` attributes render as `with k = v, k = v { ... }` with a single space around `=` and a single space + comma between attributes
- `capabilities: [a, b, c]` on a single line

v1 covers `metadata`, `agent`, `capabilities`, and `with` blocks. Other top-level constructs (policies, schedules, channels, memories, webhooks, free-standing functions) round-trip via trimmed verbatim source while later releases extend coverage.

---

## Next Steps

- **[DSL Specification](dsl-specification.md)** - Full language specification reference
- **[Runtime Architecture](/runtime-architecture)** - Understand how agents execute
- **[Security Model](/security-model)** - Learn about security implementation
- **[API Reference](/api-reference)** - Complete function and type reference
- **[Examples](https://github.com/thirdkeyai/symbiont/tree/main/examples)** - More complete examples

Ready to build your first agent? Check out our [getting started guide](/getting-started) or explore the [runtime examples](https://github.com/thirdkeyai/symbiont/tree/main/crates/runtime/examples).
