Add basic CLAUDE.md

CLAUDE.md

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+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Project Overview
+
+Eclair is a Scala implementation of the Lightning Network specification (BOLTs). It is a payment channel network built on Bitcoin, developed by ACINQ. The codebase uses Scala 2.13 with the Akka actor framework on Java 21.
+
+## Build Commands
+
+```bash
+./mvnw package                          # Build all modules with tests
+./mvnw package -DskipTests              # Build without tests
+./mvnw test                             # Run all tests
+./mvnw test -Dsuites=*<TestClassName>   # Run a single test class
+./mvnw -T <threads> test                # Run tests with parallelism
+./mvnw package -pl eclair-node -am -Dmaven.test.skip=true  # Build only eclair-node
+./mvnw clean install -pl eclair-core -am -Dmaven.test.skip=true  # Install eclair-core to local Maven repo
+```
+
+Scala compiler flags include `-Werror`, so warnings are treated as errors.
+
+## Module Structure
+
+- **eclair-core**: Core Lightning implementation library. Contains channel state machine, payment logic, routing, crypto, database layer, and protocol wire messages.
+- **eclair-node**: Server daemon. Entry point (`Boot.scala`), REST API (`api/`), and plugin system (`Plugin.scala`).
+- **eclair-front**: Front-end server for cluster mode deployments, handling peer connections.
+
+## Architecture
+
+Eclair uses an **Akka actor model** where nearly every entity is a separate actor:
+
+- **Switchboard** creates/manages **Peer** actors (one per p2p connection)
+- Each **Peer** manages multiple **Channel** actors (one per Lightning channel)
+- **Register** maps channel IDs to channel actors
+- **Router** handles network graph gossip (BOLT 7) and path-finding
+- **PaymentInitiator** orchestrates sending payments via **MultiPartPaymentLifecycle** → **PaymentLifecycle** actors
+- **PaymentHandler** manages receiving payments
+- **Relayer** delegates forwarding to **ChannelRelayer** (standard) or **NodeRelayer** (trampoline)
+
+The entry point for `eclair-core` is `Setup.scala`, which starts the actor system, connects to bitcoind, and creates top-level actors.
+
+Actors communicate via direct messages or a shared event stream.
+
+## Key Source Paths (eclair-core)
+
+All under `eclair-core/src/main/scala/fr/acinq/eclair/`:
+
+- `channel/` - Channel state machine (BOLT 2)
+- `payment/` - Payment send/receive/relay
+- `router/` - Network routing and gossip
+- `wire/` - Lightning protocol message codecs (scodec-based)
+- `blockchain/` - Bitcoin Core integration (RPC, ZMQ)
+- `db/` - Database layer (SQLite and PostgreSQL)
+- `io/` - Peer connection handling
+- `crypto/` - Cryptographic operations
+
+## Testing
+
+- Framework: ScalaTest. Tests are parallelized by suite (not individual tests).
+- Keep each test suite under one minute; split into smaller suites if needed.
+- Bug fixes should start with a failing test in a separate commit before the fix.
+- Tests live alongside sources in `src/test/scala/`.
+
+## Code Style
+
+- IntelliJ default Scala formatting is used (Ctrl+Alt+L to format, Ctrl+Alt+O to optimize imports).
+- No hard style rules, but code should be consistent with surrounding code.
+- Commit messages use present tense ("Fix bug" not "Fixed bug"), 50-char summary line.
+- Signed commits are required.
+
+## Key Dependencies
+
+- **Akka** 2.6.20 (actors, HTTP, streams, cluster)
+- **bitcoin-lib** 0.46 (ACINQ's Bitcoin library, Kotlin-based)
+- **scodec** (binary protocol encoding/decoding for wire messages)
+- **json4s** (JSON serialization)
+- **Kamon** (metrics/monitoring)
+- **SQLite** (default DB) / **PostgreSQL** (production option with HikariCP pooling)