---
title: "Concepts Overview"
description: "The key concepts that make RStack SDLC work."
---

## The core problem RStack solves

AI coding agents fail at software delivery for predictable reasons:

- They code before requirements are clear
- They over-edit unrelated files
- They pass work as "done" without testing
- They forget previous mistakes and repeat them
- They make risky actions (deploys, deletes) without asking

RStack addresses all of these by giving the agent a structured operating model: an explicit lifecycle, team roles, approval gates, and evidence requirements.

## The team model

RStack organizes agents into three teams:

```
Orchestrator (team lead)
├── Builder team
│   ├── Backend specialists
│   ├── Frontend specialists
│   ├── DevOps specialists
│   ├── Data specialists
│   └── Docs specialists
└── Validator team
    ├── QA specialists
    ├── Security specialists
    ├── Architecture reviewers
    ├── Code reviewers
    └── Performance / accessibility reviewers
```

The **Orchestrator** routes work, manages the lifecycle, and is the only agent that communicates with the product owner (you).

**Builders** implement tasks within a scoped, gated context.

**Validators** review builder output with read-only tools. They cannot modify source files.

## The lifecycle

```
sdlc_orchestrate → sdlc_start → sdlc_clarify → sdlc_plan → sdlc_spec
       ↓
sdlc_approve (requirements, architecture)
       ↓
sdlc_build_next → sdlc_validate → (repeat)
       ↓
sdlc_approve (release-readiness)
       ↓
sdlc_memory
```

Each phase produces durable artifacts stored under `.rstack/runs/<run_id>/`.

## Asset types

<CardGroup cols={2}>
  <Card title="Agents" icon="robot" href="/concepts/orchestrator-builder-validator">
    Markdown files that define agent roles, tools, and operating contracts.
  </Card>
  <Card title="Skills" icon="wrench" href="/concepts/plugins-and-skills">
    Reusable workflow instructions that can be included in task packets.
  </Card>
  <Card title="Plugins" icon="puzzle-piece" href="/concepts/plugins-and-skills">
    Domain packs bundling agents, skills, and commands for specific areas.
  </Card>
  <Card title="Run State" icon="database" href="/concepts/state-management">
    Durable per-run artifacts: plan, specs, tasks, approvals, traceability, evidence.
  </Card>
</CardGroup>

## Asset counts

The RStack package currently ships:

| Asset type | Count |
|---|---|
| Agents | 196 |
| Skills | 68 |
| Prompts | 36 |
| Plugins | 72 |

## Pipeline routing

The orchestrator maps lifecycle tasks to the right SDLC agents:

| Pipeline stage | Agents involved |
|---|---|
| Product clarification | `00-environment`, `01-transcript` |
| Requirements | `02-requirements`, `04-planning`, `05-jira` |
| Architecture | `06-architecture`, `12-security-threat-model`, `14-cost-estimation` |
| Implementation | `07-code` |
| Testing | `08-testing` |
| Security review | `12-security-threat-model`, `13-compliance-checker` |
| Documentation | `03-documentation`, `10-summary` |
| Release readiness | `09-deployment`, `10-summary`, `11-feedback-loop` |

Each generated task includes routing metadata:

```json
{
  "pipeline_agents": ["agent.02-requirements", "agent.04-planning"],
  "specialists": ["agent.02-requirements", "plugin.backend-development"]
}
```