Vapora/docs/features/workflow-orchestrator.md

Workflow Orchestrator

Multi-stage workflow execution with cost-efficient agent coordination and artifact passing.

Overview

The Workflow Orchestrator (vapora-workflow-engine) enables cost-efficient multi-agent pipelines by executing workflows as discrete stages with short-lived agent contexts. Instead of accumulating context in long sessions, agents receive only what they need, produce artifacts, and terminate.

Key Benefit: ~95% reduction in LLM cache token costs compared to monolithic session patterns.

Architecture

Core Components

┌─────────────────────────────────────────────────────────┐
│              WorkflowOrchestrator                        │
│  ┌─────────────────────────────────────────────────┐    │
│  │ WorkflowInstance                                 │    │
│  │  ├─ workflow_id: UUID                           │    │
│  │  ├─ template: WorkflowConfig                    │    │
│  │  ├─ current_stage: usize                        │    │
│  │  ├─ stage_states: Vec<StageState>               │    │
│  │  └─ artifacts: HashMap<String, Artifact>        │    │
│  └─────────────────────────────────────────────────┘    │
└─────────────────────────────────────────────────────────┘
      │                    │                    │
      ▼                    ▼                    ▼
┌──────────┐        ┌──────────┐        ┌──────────┐
│  NATS    │        │  Swarm   │        │    KG    │
│ Listener │        │Coordinator│       │Persistence│
└──────────┘        └──────────┘        └──────────┘

Workflow Lifecycle

1. Template Loading: Read workflow definition from config/workflows.toml
2. Instance Creation: Create WorkflowInstance with initial context
3. Stage Execution: Orchestrator assigns tasks to agents via SwarmCoordinator
4. Event Listening: NATS subscribers wait for TaskCompleted/TaskFailed events
5. Stage Advancement: When all tasks complete, advance to next stage
6. Artifact Passing: Accumulated artifacts passed to subsequent stages
7. Completion: Workflow marked complete, metrics recorded

Workflow Templates

Pre-configured workflows in config/workflows.toml:

feature_development (5 stages)

[[workflows]]
name = "feature_development"
trigger = "manual"

[[workflows.stages]]
name = "architecture_design"
agents = ["architect"]
parallel = false
approval_required = false

[[workflows.stages]]
name = "implementation"
agents = ["developer", "developer"]
parallel = true
max_parallel = 2
approval_required = false

[[workflows.stages]]
name = "testing"
agents = ["tester"]
parallel = false
approval_required = false

[[workflows.stages]]
name = "code_review"
agents = ["reviewer"]
parallel = false
approval_required = true

[[workflows.stages]]
name = "deployment"
agents = ["devops"]
parallel = false
approval_required = true

Stages: architecture → implementation (parallel) → testing → review (approval) → deployment (approval)

bugfix (4 stages)

Stages: investigation → fix → testing → deployment

documentation_update (3 stages)

Stages: content creation → review (approval) → publish

security_audit (4 stages)

Stages: code analysis → penetration testing → remediation → verification (approval)

Stage Types

Sequential Stages

Single agent executes task, advances when complete.

[[workflows.stages]]
name = "architecture_design"
agents = ["architect"]
parallel = false

Parallel Stages

Multiple agents execute tasks simultaneously.

[[workflows.stages]]
name = "implementation"
agents = ["developer", "developer"]
parallel = true
max_parallel = 2

Approval Gates

Stage requires manual approval before advancing.

[[workflows.stages]]
name = "deployment"
agents = ["devops"]
approval_required = true

When approval_required = true:

1. Workflow pauses with status waiting_approval:<stage_idx>
2. NATS event published to vapora.workflow.approval_required
3. Admin approves via API or CLI
4. Workflow resumes execution

Artifacts

Data passed between stages:

Artifact Types

pub enum ArtifactType {
    Adr,              // Architecture Decision Record
    Code,             // Source code files
    TestResults,      // Test execution output
    Review,           // Code review feedback
    Documentation,    // Generated docs
    Custom(String),   // User-defined type
}

Artifact Flow

Stage 1: Architecture
  └─ Produces: Artifact(Adr, "design-spec", ...)
       │
       ▼
Stage 2: Implementation
  ├─ Consumes: design-spec
  └─ Produces: Artifact(Code, "feature-impl", ...)
       │
       ▼
Stage 3: Testing
  ├─ Consumes: feature-impl
  └─ Produces: Artifact(TestResults, "test-report", ...)

Artifacts stored in WorkflowInstance.accumulated_artifacts and passed to subsequent stages via context.

Kogral Integration

Enrich workflow context with persistent knowledge from Kogral:

orchestrator.enrich_context_from_kogral(&mut context, "feature_development").await?;

Loads:

• Guidelines: .kogral/guidelines/{workflow_name}.md
• Patterns: .kogral/patterns/*.md (matching workflow name)
• ADRs: .kogral/adrs/*.md (5 most recent, containing workflow name)

Result injected into context:

{
  "task": "Add authentication",
  "kogral_guidelines": {
    "source": ".kogral/guidelines/feature_development.md",
    "content": "..."
  },
  "kogral_patterns": [
    { "file": "auth-pattern.md", "content": "..." }
  ],
  "kogral_decisions": [
    { "file": "0005-oauth2-implementation.md", "content": "..." }
  ]
}

Configuration:

export KOGRAL_PATH="/path/to/kogral/.kogral"

Default: ../kogral/.kogral (sibling directory)

REST API

All endpoints under /api/v1/workflow_orchestrator:

Start Workflow

POST /api/v1/workflow_orchestrator
Content-Type: application/json

{
  "template": "feature_development",
  "context": {
    "task": "Implement authentication",
    "requirements": ["OAuth2", "JWT"]
  }
}

Response:

{
  "workflow_id": "3f9a2b1c-5e7f-4a9b-8c2d-1e3f5a7b9c1d"
}

List Active Workflows

GET /api/v1/workflow_orchestrator

Response:

{
  "workflows": [
    {
      "id": "3f9a2b1c-5e7f-4a9b-8c2d-1e3f5a7b9c1d",
      "template_name": "feature_development",
      "status": "running",
      "current_stage": 2,
      "total_stages": 5,
      "created_at": "2026-01-24T01:23:45.123Z",
      "updated_at": "2026-01-24T01:45:12.456Z"
    }
  ]
}

Get Workflow Status

GET /api/v1/workflow_orchestrator/:id

Response: Same as workflow object in list response

Approve Stage

POST /api/v1/workflow_orchestrator/:id/approve
Content-Type: application/json

{
  "approver": "Jane Doe"
}

Response:

{
  "success": true,
  "message": "Workflow 3f9a2b1c stage approved"
}

Cancel Workflow

POST /api/v1/workflow_orchestrator/:id/cancel
Content-Type: application/json

{
  "reason": "Requirements changed"
}

Response:

{
  "success": true,
  "message": "Workflow 3f9a2b1c cancelled"
}

List Templates

GET /api/v1/workflow_orchestrator/templates

Response:

{
  "templates": [
    "feature_development",
    "bugfix",
    "documentation_update",
    "security_audit"
  ]
}

NATS Events

Workflow orchestrator publishes/subscribes to NATS JetStream:

Subscriptions

• vapora.tasks.completed - Agent task completion events
• vapora.tasks.failed - Agent task failure events

Publications

• vapora.workflow.approval_required - Stage waiting for approval
• vapora.workflow.completed - Workflow finished successfully

Event Format:

{
  "type": "approval_required",
  "workflow_id": "3f9a2b1c-5e7f-4a9b-8c2d-1e3f5a7b9c1d",
  "stage": "code_review",
  "timestamp": "2026-01-24T01:45:12.456Z"
}

Metrics

Prometheus metrics exposed at /metrics:

• vapora_workflows_started_total - Total workflows initiated
• vapora_workflows_completed_total - Successfully finished workflows
• vapora_workflows_failed_total - Failed workflows
• vapora_stages_completed_total - Individual stage completions
• vapora_active_workflows - Currently running workflows (gauge)
• vapora_stage_duration_seconds - Histogram of stage execution times
• vapora_workflow_duration_seconds - Histogram of total workflow times

Cost Optimization

Before: Monolithic Session

Session with 50 messages:
├─ Message 1:  50K context  → 50K cache reads
├─ Message 2:  100K context → 100K cache reads
├─ Message 3:  150K context → 150K cache reads
└─ Message 50: 800K context → 800K cache reads
                            ──────────────────
                            ~20M cache reads

Cost: ~$840/month for typical usage

After: Multi-Stage Workflow

Workflow with 3 stages:
├─ Architect: 40K context, 5 msgs  → 200K cache reads
├─ Developer: 25K context, 12 msgs → 300K cache reads
└─ Reviewer:  35K context, 4 msgs  → 140K cache reads
                                    ──────────────────
                                    ~640K cache reads

Cost: ~$110/month for equivalent work

Savings: ~$730/month (87% reduction)

Usage Examples

See CLI Commands Guide for command-line usage.

Programmatic Usage

use vapora_workflow_engine::WorkflowOrchestrator;
use std::sync::Arc;

// Initialize orchestrator
let orchestrator = Arc::new(
    WorkflowOrchestrator::new(
        "config/workflows.toml",
        swarm,
        kg,
        nats,
    ).await?
);

// Start event listener
orchestrator.clone().start_event_listener().await?;

// Start workflow
let workflow_id = orchestrator.start_workflow(
    "feature_development",
    serde_json::json!({
        "task": "Add authentication",
        "requirements": ["OAuth2", "JWT"]
    })
).await?;

// Get status
let workflow = orchestrator.get_workflow(&workflow_id)?;
println!("Status: {:?}", workflow.status);

// Approve stage (if waiting)
orchestrator.approve_stage(&workflow_id, "Jane Doe").await?;

Configuration

Workflow Templates

File: config/workflows.toml

[engine]
max_parallel_tasks = 10
workflow_timeout = 3600
approval_gates_enabled = true

[[workflows]]
name = "custom_workflow"
trigger = "manual"

[[workflows.stages]]
name = "stage_name"
agents = ["agent_role"]
parallel = false
max_parallel = 1
approval_required = false

Environment Variables

# Kogral knowledge base path
export KOGRAL_PATH="/path/to/kogral/.kogral"

# NATS connection
export NATS_URL="nats://localhost:4222"

# Backend API (for CLI)
export VAPORA_API_URL="http://localhost:8001"

Troubleshooting

Workflow Stuck in "waiting_approval"

Solution: Use CLI or API to approve:

vapora workflow approve <workflow_id> --approver "Your Name"

Stage Fails Repeatedly

Check:

1. Agent availability: vapora workflow list (via backend)
2. NATS connection: Verify NATS URL and cluster status
3. Task requirements: Check if stage agents have required capabilities

High Latency Between Stages

Causes:

• NATS messaging delay (check network)
• SwarmCoordinator queue depth (check agent load)
• Artifact serialization overhead (reduce artifact size)

Mitigation:

• Use parallel stages where possible
• Increase max_parallel in stage config
• Optimize artifact content (references instead of full content)

Workflow Not Advancing

Debug:

# Check workflow status
vapora workflow status <workflow_id>

# Check backend logs
docker logs vapora-backend

# Check NATS messages
nats sub "vapora.tasks.>"

Related Documentation

• CLI Commands Guide - Command-line usage
• Multi-Agent Workflows - Architecture overview
• Agent Registry & Coordination - Agent management
• ADR-0028: Workflow Orchestrator - Decision rationale
• ADR-0014: Learning-Based Agent Selection - Agent selection
• ADR-0015: Budget Enforcement - Cost control