Update 4.2.0 release notes

Author: cdonnachie

doc/release-notes/release-notes-4.2.0.md

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+# Avian Core 4.2.0 Release Notes
+
+## Overview
+
+Avian Core 4.2.0 "Longbottom Leaf" is a maintenance and modernization release focused on improving build infrastructure, dependency freshness, GUI responsiveness, and wallet performance ahead of new feature development.
+
+**This is the final release of the 4.2.0 series, following three release candidates (RC1, RC2, RC3).**
+
+---
+
+## Significant Changes
+
+### Build Infrastructure & Dependencies
+
+- **Qt Framework Upgrade**: 5.7.0 → 5.12.11 (LTS)
+
+  - Improved stability and performance on modern systems
+  - Better cross-platform compatibility
+  - Enhanced security patches from upstream
+
+- **Updated Dependencies**: All depends system packages updated to current, secure versions
+
+  - Ensures long-term stability and security
+
+- **CI/CD Modernization**: GitHub Actions now builds binaries for:
+  - Windows (x64)
+  - Linux (x64)
+  - macOS (x64)
+  - aarch64 (ARM 64-bit)
+  - arm32v7 (ARM 32-bit)
+
+### Network & Protocol
+
+- **Protocol Version Bump**
+
+  - Ensures compatibility with 4.1.x and newer nodes only
+  - Pre-4.1 wallets will no longer connect, preventing sync slowdowns and network inconsistencies
+
+- **getblocktemplate Update**: Improved compliance with BIP22 specification
+
+- **Chain Parameters**: PoW hash calculation now uses chain-specific parameters correctly
+
+### GUI Improvements
+
+- **Enhanced Startup Experience**
+
+  - Splash screen now remains visible with real-time progress updates
+  - Prevents UI blocking during wallet loading
+  - Defers network initialization to speed up GUI construction
+  - Displays RC version information on splash screen when applicable
+
+- **UTXO Consolidation GUI Refactor**
+  - Consolidation now runs on background thread using QtConcurrent::run()
+  - Prevents UI freezing during long batch operations
+  - Progress dialog fully responsive and cancelable
+  - Uses QMetaObject::invokeMethod for thread-safe UI updates
+
+### New RPC Commands
+
+#### `getblockstats`
+
+Returns comprehensive block-level statistics including:
+
+- Transaction counts, sizes, and weights
+- Fee information (min, max, average, percentiles)
+- Input/output counts
+- Segwit transaction statistics
+- Developer fee tracking
+- **New**: `powtype` field indicating the block's PoW algorithm (x16rt, minotaurx, or x16r for genesis)
+
+Usage:
+
+```
+getblockstats <hash_or_height> [stats]
+```
+
+#### `listwatchonly`
+
+Lists all imported watch-only addresses with their labels and metadata.
+
+Usage:
+
+```
+listwatchonly
+```
+
+#### `removewatchonly`
+
+Removes a watch-only address from wallet storage and address book.
+
+Usage:
+
+```
+removewatchonly <address>
+```
+
+#### `getnodeaddresses`
+
+Lists known peer node addresses for network diagnostics.
+
+Usage:
+
+```
+getnodeaddresses [count]
+```
+
+#### `getindexinfo`
+
+Displays the status of active blockchain indexes.
+
+Usage:
+
+```
+getindexinfo
+```
+
+### Wallet & UTXO Management
+
+#### New UTXO Consolidation System
+
+Consolidates small UTXOs into larger ones to reduce future transaction costs and improve wallet performance.
+
+**RPC Command**: `consolidateutxos`
+
+```
+consolidateutxos <address> [min_utxos] [max_batches] [min_amount] [max_amount]
+```
+
+Parameters:
+
+- `address`: Destination address for consolidated outputs
+- `min_utxos`: Minimum UTXOs required before consolidation (default: 2000)
+- `max_batches`: Maximum number of batches to process (default: unlimited)
+- `min_amount`: Minimum UTXO amount to include (default: 0.01 AVN)
+- `max_amount`: Maximum UTXO amount to include (default: 25 AVN)
+
+**GUI Integration**: New "Consolidate UTXO Transactions" dialog with:
+
+- Configurable limits (min/max inputs, batch size, amount ranges)
+- Real-time UTXO display and selection
+- Progress tracking and cancellation support
+- Thread-safe background processing
+
+**Improvements in RC3**:
+
+- Improved batch counting and progress accuracy
+- Pre-calculates totalUTXOFiltered before consolidation loop
+- Applies min/max filters consistently during counting
+- Accurately accounts for maxBatches limit
+- Displays precise progress (e.g., "1 of 1" when maxBatches=1)
+
+#### New Watch-Only Address Management
+
+- `listwatchonly`: Display all imported watch-only addresses with labels
+- `removewatchonly`: Completely remove watch-only addresses from wallet storage and address book
+- Automatic GUI sync via NotifyAddressBookChanged signal
+- No wallet unlock required for watch-only operations
+
+### Developer & Maintenance
+
+- **NetworkUpgrade Struct**: Added for better handling of network upgrade logic
+- **Mainnet Checkpoint Data**: Updated to the latest block
+- **Help System**: Added powhashcache details to help messages
+
+---
+
+## Bug Fixes & Performance Improvements
+
+- Fixed null pointer dereference in `getblockstats` for genesis block
+- Improved wallet RPC command filtering and accuracy
+- Performance optimizations in GUI startup sequence
+- Better error handling in batch UTXO operations
+- Fixed progress estimation for UTXO consolidation
+
+---
+
+## Testing Recommendations
+
+### For Windows Users
+
+- Test wallet startup time and responsiveness
+- Verify UTXO consolidation with test wallets containing many small outputs
+- Check splash screen progress updates during initial sync
+
+### For Linux / macOS Users
+
+- Verify cross-platform Qt 5.12.11 compatibility
+- Test RPC commands (especially new ones: getblockstats, listwatchonly, removewatchonly)
+- Confirm network syncing with mixed 4.1.x and 4.2.0 nodes
+
+### For ARM Users (aarch64 / arm32v7)
+
+- Verify binary builds and execution on ARM hardware
+- Test wallet functionality and RPC operations
+- Confirm network connectivity and syncing
+
+### For RPC Users
+
+- Test `getblockstats` with various block heights and filters
+- Verify `listwatchonly` and `removewatchonly` operations
+- Test `getnodeaddresses` and `getindexinfo`
+- Confirm UTXO consolidation batch processing
+
+---
+
+## Upgrading
+
+### From 4.1.x
+
+- Backup your wallet before upgrading
+- The protocol version bump means pre-4.1 nodes will disconnect from your node
+- You can deploy 4.2.0; it will automatically only connect to 4.1.0+ peers
+- UTXO consolidation is optional and accessed via GUI or RPC
+
+### From Older Versions
+
+- Direct upgrade from any prior version is supported
+- If you are upgrading from a version much older than 4.1.0, ensure you are on the correct chain (mainnet vs testnet)
+- If experiencing sync issues after upgrade, verify your peers and network connectivity
+- Use `-reindex` flag if you encounter blockchain validation errors
+
+---
+
+## Known Issues
+
+None known at this time. Please report any issues via GitHub Issues.
+
+---
+
+## Credits
+
+The Avian Core development team thanks all contributors, testers, and the community for their feedback throughout the RC process.
+
+---
+
+## Version Information
+
+- **Version**: 4.2.0
+- **Release Date**: [TBD]
+- **Previous Release**: 4.1.0
+- **Network**: Mainnet
+
+---
+
+## Changelog Summary
+
+- 1 new major feature (UTXO Consolidation System)
+- 5 new RPC commands (getblockstats, listwatchonly, removewatchonly, getnodeaddresses, getindexinfo)
+- 1 major dependency upgrade (Qt 5.12.11 LTS)
+- 30+ bug fixes and improvements
+- Full CI/CD modernization (5 platform builds)