add file AGENTS.md

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AGENTS.md

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+### Project Summary: Lightning Loop
+
+**1. Core Purpose:**
+Lightning Loop is a non-custodial service from Lightning Labs for bridging the Bitcoin mainnet (on-chain) and the Lightning Network (off-chain). It enables users to rebalance their channels—moving funds into or out of Lightning—without the need for closing and reopening them. The system is architected to be non-custodial, using atomic swaps to ensure neither the user nor the server can lose funds.
+
+**2. Architecture & Core Components:**
+The project is a client daemon (`loopd`) that connects to a user's `lnd` node and communicates with a remote Loop server via gRPC. It is composed of several distinct managers and services that handle different aspects of the swap lifecycle.
+
+*   **`loopd` (Daemon):** The main executable that bootstraps and orchestrates all other components. It initializes the database, connects to `lnd`, starts the gRPC/REST servers, and launches all the feature-specific managers (`liquidity`, `instantout`, `staticaddr`, etc.). Its lifecycle and configuration are managed in the `loopd/` and `cmd/loopd/` packages.
+
+*   **Finite State Machines (FSM):** The core logic for managing swaps is built around a robust FSM pattern (`fsm/`). Each swap type (Instant Out, Static Address Loop-in, etc.) has its own state machine that defines its lifecycle. This ensures that swaps progress through a defined set of states, with transitions triggered by on-chain or off-chain events, making the system resilient to failures and restarts.
+
+*   **Database (`loopdb/`):** Persistence is handled by a database layer that supports both `bbolt` and `PostgreSQL` (via `sqlc` for query generation). It stores swap contracts, state history, liquidity parameters, and other critical data, allowing the daemon to recover and resume operations after a restart.
+
+*   **Notification Manager (`notifications/`):** Manages a persistent gRPC subscription to the Loop server. It listens for asynchronous events, such as a `Reservation` being offered or a request to co-sign a `StaticAddress` sweep, and dispatches them to the appropriate internal manager.
+
+*   **On-Chain Transaction Management:**
+    *   **Sweeper (`sweep/`):** A utility library responsible for crafting and signing sweep transactions for various HTLC types (P2WSH, P2TR, etc.).
+    *   **Sweep Batcher (`sweepbatcher/`):** A sophisticated service that batches multiple on-chain sweeps into a single transaction to save on-chain fees. It has its own database store and logic for creating, tracking, and RBF-bumping (Replace-By-Fee) batch transactions until they are confirmed.
+
+**3. Swap Types & Features:**
+
+*   #### Standard Loop Out
+    *   **Goal:** Move funds from Lightning to an on-chain address.
+    *   **Mechanism:** The client pays an off-chain Lightning invoice to the Loop server. In return, the server sends an equivalent amount (minus fees) to the user's on-chain address via an on-chain HTLC. The client sweeps this HTLC using the same preimage from the Lightning payment, completing the atomic swap.
+
+*   #### Standard Loop In
+    *   **Goal:** Move on-chain funds into the Lightning Network.
+    *   **Mechanism:** The client sends funds to an on-chain HTLC. This HTLC is spendable by the server *if* it knows the swap preimage (which it learns by paying the client's off-chain Lightning invoice), or by the client after a timeout. Once the server sees the on-chain HTLC, it pays the invoice to "loop in" the funds and then sweeps the HTLC with the revealed preimage, often in cooperation with the client to save fees.
+
+*   #### Instant Loop-Out (`instantout/`)
+    *   **Goal:** A faster, more efficient Loop-Out that prioritizes a cooperative path.
+    *   **Mechanism:** Built on **Reservations**—on-chain UTXOs controlled by a 2-of-2 MuSig2 key between the client and server. The primary flow is a cooperative "Sweepless Sweep" that spends the reservation directly to the client's destination. A non-cooperative fallback to a standard HTLC ensures the swap remains non-custodial.
+
+*   #### Static Address (`staticaddr/`)
+    *   **Goal:** Provide a permanent, reusable on-chain address for receiving funds that can then be looped into Lightning.
+    *   **Mechanism:** The address is a P2TR (Taproot) output with a cooperative MuSig2 keyspend path and a unilateral CSV timeout scriptspend path for safety. This feature is composed of several sub-managers:
+        *   `address/`: Manages the creation and lifecycle of the static address itself.
+        *   `deposit/`: Monitors the address for new UTXOs (deposits) and manages their state (e.g., `Deposited`, `Expired`, `LoopingIn`).
+        *   `loopin/`: Orchestrates the Loop-In process for funds held at the static address.
+        *   `withdraw/`: Handles cooperative withdrawal of funds from the address back to the user's wallet without performing a swap.
+
+*   #### Liquidity Manager (`liquidity/`)
+    *   **Goal:** Automate channel liquidity management based on user-defined rules.
+    *   **Mechanism:** Periodically assesses channel balances and can suggest or automatically dispatch swaps to meet target liquidity levels. It supports detailed rules, fee budgets, and an "easyAutoloop" mode for simple balance targeting.
+
+**4. Technology & Cross-Cutting Concerns:**
+
+*   **Language:** Go
+*   **Remote Communication:** gRPC. Definitions are split between `looprpc/` (client-facing) and `swapserverrpc/` (server-facing).
+*   **Cryptography:** Extensively uses Taproot and MuSig2 for efficiency, privacy, and complex spending conditions, especially in the `instantout` and `staticaddr` features.
+*   **Labeling (`labels/`):** A utility to create and validate labels for swaps, which helps distinguish between user-initiated and automated swaps (e.g., `[reserved]: autoloop-out`).
+*   **Assets (`assets/`):** Contains logic for interacting with `tapd` (Taproot Assets Protocol Daemon), allowing Loop to facilitate swaps involving assets other than Bitcoin.