This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
## Role
Operate as an **expert in cryptocurrencies and cryptography**: reason with the domain's rigor about UTXO consensus, HD key derivation (BIP32/39/SLIP-132), signature schemes and scripts (P2PKH/P2SH/P2WPKH, PSBT), address encoding (base58/bech32), Merkle/SPV proofs, and at-rest encryption. When a choice touches cryptographic correctness or fund safety, judge it through that lens and flag known risks and pitfalls (nonce reuse, missing validation, exposed keys/seed, wrong fee/coin-selection, unverified server responses). Explain trade-offs with technical precision; never take for granted what hasn't been verified.
On **every requested change**, before implementing, judge whether it makes sense and say so plainly: if a request is useful and consistent with the project, proceed; if it is useless, redundant, already covered elsewhere, or risks degrading the code, **say so** with a short rationale and propose the better alternative (or doing nothing). No automatic agreement — an honest opinion is worth more than blind execution.
SPV wallet (Sparrow-style) for the **Palladium (PLM)** cryptocurrency, a Bitcoin-derived UTXO chain. Targets desktop (Windows/Linux) and Android, from the same source. Lightning is excluded from the first release.
[blueprint.md](blueprint.md) is a **reference for understanding** (consensus parameters verified against the node, algorithms, network protocol): consult it when it helps to understand an area, but **it is no longer binding** — it need not be followed to the letter or read before every change. The source of truth is the current code; the `§` references below point to the blueprint only as further reading.
**Non-negotiable dependency rule:**`App`/`Cli` depend only on `Core`; the UI goes through the wallet domain, never directly through network or cryptography. `Core` knows nothing about the UI.
- Tests (headless, the primary verification layer): `dotnet test` — single: `dotnet test --filter "FullyQualifiedName~TestName"`; property-based tests (CsCheck, `PropertyTests.cs`) run in the same command and take ~30 s
- **Shared `MainView` + heads:** the whole UI is a single `MainView` (UserControl), so it works both as a desktop window's content and as Android's single-view root. Top-level APIs (file/folder picker, clipboard) are reached via `TopLevel.GetTopLevel(this)` since a UserControl doesn't expose them. `MainWindowViewModel.IsDesktop` (from `OperatingSystem.IsAndroid()`) hides filesystem-only features (open-from-file; the data-location wizard step auto-skips on Android because the head sets `AppPaths.OverrideDataRoot`).
- **In-app overlays, not OS windows:** details (address, transaction), settings, and help are full-screen `Border`s gated by an `IsXxxOpen` flag, not separate `Window`s — instant open/close, mobile-friendly, and popups/top-levels are slow on WSLg. Pattern: bool property + Open/Close commands + backdrop handler and Esc key in `MainView`'s code-behind; overlay close buttons bind via `$parent[UserControl]` (not `$parent[Window]`, absent on mobile). Heavy network work runs off the UI thread (`Task.Run`) so the overlay never freezes.
- **Localization:** `Localization/Loc.cs`, key→6 languages dictionary (it/en/es/fr/pt/de); in XAML `{Binding Loc[key]}`, in C# `Loc.Tr("key")`. On language change the `Loc` instance is replaced.
- **App version:** single source = `<Version>` in `src/App/PalladiumWallet.App.csproj`; read at runtime (`MainWindowViewModel.AppVersion`) and shown in the title.
- **Storage paths:** `Core/Storage/AppPaths` resolves data locations; `AppPaths.OverrideDataRoot` (top priority) is the per-platform seam — the Android head sets it to the app sandbox (`Context.FilesDir`), desktop leaves it null.
**TODO (§16 steps 8–9):** multisig, hardware wallet, coin control UI, fee ETA/mempool, RBF/CPFP UI, on-disk header chain, multi-server pool, proxy/Tor.
## Working rules
- **Cross-implementation tests (§16):** compare addresses, txids, and PSBTs against a reference wallet (golden vectors). A different address or txid is a blocking bug.
- **Security (§17):** seed and private keys never in plaintext on disk/logs/network; every server response validated with Merkle + checkpoints; watch-only truly read-only.
- *(Optional)* blueprint features may be deferred but must still be considered in the design.
