# Stack Decisions

The recommended 2026 production stack, with the reasoning for each call.

## Use

| Layer             | Choice                                                                                                                                 | Why                                                                                             |
| ----------------- | -------------------------------------------------------------------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------- |
| Framework         | **LangGraph 1.0 + Deep Agents**                                                                                                        | State machine + durable checkpointing + observability. Survives process kills, resumes mid-run. |
| Harness reference | **Claude Agent SDK**                                                                                                                   | Same harness as Claude Code: CLAUDE.md + Skills + sub-agents + hooks + filesystem-as-memory.    |
| Observability     | **LangSmith** (LangGraph-native) / **Braintrust** (framework-agnostic, CI gating) / **Arize Phoenix** (open-source, OTEL-native, free) | Pick one. You cannot improve what you cannot trace.                                             |

## Avoid in production

| Avoid                            | Reason                                                 |
| -------------------------------- | ------------------------------------------------------ |
| CrewAI in production             | Fast demo, fragile at scale. Fine for hackathons only. |
| OpenAI Swarm                     | Their own README says "not production-ready".          |
| OpenAI Assistants API            | Sunsetting mid-2026.                                   |
| No-code agent platforms          | Throwaway prototypes only.                             |
| Custom vector store (by default) | Measure recall first — most apps don't need one.       |

## The decision rule

1. What is the **simplest** thing that solves this problem?
2. What does it look like at **10×** current scale (not 100×)?
3. What is the **cost of being wrong** — easy to change, or locked in?

Start with a monolith. Start serverless. Buy everything that isn't your core
product (auth, email, payments). Split into services only when parts genuinely
need to scale independently.

> Update with benchmark-backed comparisons only — see CONTRIBUTING.md.

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_Reference for "Become An AI Engineer 26". See SKILL.md → The Stack._