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Implementation Tiers

Brain uses three implementation tiers. The tier choice for each feature is deliberate. It’s about matching the tool to the problem — using a full agent for a deterministic task wastes tokens and adds hallucination risk; using a skill for multi-step reasoning produces inconsistent results.

Tier 1 — Simple LLM + skill

A skill.md file with a clear prompt and small input/output contract. Stateless, deterministic-leaning, fast to iterate. Use for:
  • Generate a quotation with a fixed markup
  • Ask for missing client fields
  • Draft a quotation email
  • Summarize a single email
  • Classify an email topic
Pros: fast to build, easy to iterate, low engineering complexity, ideal for MVP. Cons: not suited for long-running tasks; limited state management; harder to coordinate multiple steps.

Tier 2 — LangGraph workflow

A multi-step state machine with explicit nodes for AI steps, tool calls, and human approval gates. Each transition is observable and resumable. Use for:
  • Email-to-style creation (intake → classify → extract → duplicate-check → approve → write)
  • Client creation approval flow
  • Duplicate check workflow
  • Quotation generation workflow
  • Any human-in-the-loop pipeline
Pros: clear states, good for human-in-the-loop, easy to debug, supports branching logic, strong observability. Cons: more engineering setup; requires workflow design up front; less flexible than full agent autonomy.

Tier 3 — Full agent with tools and environment

A reasoning loop with multiple tools, document access, image analysis, and the ability to plan multi-step actions. Used when the task can’t be reduced to a deterministic flow. Use for:
  • Tech pack → BOM (parse PDFs, parse Excel, vision analysis, garment template matching)
  • Manager lifecycle queries (multi-source retrieval, structured output)
  • Pricing intelligence (external search + internal history + client profile)
  • End-to-end oversight agent (continuous monitoring, risk classification, alerting)
Pros: handles complex analysis, multi-tool, multimodal; more autonomous. Cons: higher hallucination risk, requires stricter guardrails, needs strong observability, needs source attribution, more expensive to run.

Tier recommendation by feature

How tiers interact

A high-level workflow (Tier 2) often calls lower-level skills (Tier 1) as steps and delegates complex sub-problems to agents (Tier 3). For example:
Each tier is the right tool for a different shape of problem.
  • Runtime — what hosts all three tiers
  • Workflows — see each feature’s tier choice in context