# Implementation Plan: 007 Messaging NATS Replacement

> For the complete documentation index, see [llms.txt](https://deploy-preview-472--lucky-concha-f3599f.netlify.app/llms.txt).

## Scope

*   Transition from `005-postgres-database-replacement` to `006-messaging-nats-replacement`.
*   Replace messaging component and protocol while preserving baseline business behavior.
*   Keep runtime model on Docker Compose + NGINX ingress (no Kubernetes dependency in this state).

## Technical Approach

1.  Define architecture deltas:
    *   remove Socket.IO `trade-feed` messaging role,
    *   introduce `nats-broker`,
    *   define backend and frontend messaging paths.
2.  Define event/subject mapping for baseline flows (new trade, account updates, position updates).
3.  Define compose and ingress snippets for NATS TCP + WS exposure.
4.  Define backend migration rules:
    *   publish/subscribe client changes per service.
5.  Define frontend migration rules:
    *   switch from Socket.IO subscription model to `nats.ws` consumer model (or documented gateway fallback if needed).
6.  Define conformance + smoke checks for messaging compatibility and runtime operability.

## Deliverables

1.  Requirements and contracts deltas under `requirements/` and `contracts/`.
2.  `fidelity-profile.md` for state-level technical profile updates.
3.  Updated architecture, topology, and migration guidance documents under `system/`.
4.  Component and conformance docs for NATS messaging behavior.
5.  Generation hook and smoke-test stubs for follow-on implementation.

## Exit Criteria

*   Architecture and migration intent are fully specified and reviewable.
*   Runtime wiring examples (compose + ingress) are explicit.
*   A clear path exists to implement generation/runtime scripts for state `006`.
*   State is ready for implementation phase and subsequent publish to `code/generated-state-006-messaging-nats-replacement`.