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painlessMesh v1.8.6 Release Notes

Release Date: November 12, 2025
Type: Patch Release
Breaking Changes: None - 100% Backward Compatible

🎯 Executive Summary

Version 1.8.6 fixes a critical issue in the bridge failover mechanism where mesh networks would remain bridgeless indefinitely when all nodes started without a designated initial bridge. This release introduces automatic bridge election monitoring that ensures meshes always establish internet connectivity when configured for bridge failover.

🐛 Bug Fixes

Bridge Failover Auto-Election (Issue #117)

Problem: The bridge failover example didn't work when all nodes had INITIAL_BRIDGE=false. The mesh would start but never elect a bridge, leaving the network without internet connectivity indefinitely.

Symptoms:

--- Bridge Status ---
I am bridge: NO
Internet available: NO
Known bridges: 0
No primary bridge available!
--------------------

Root Cause: Bridge elections only triggered when an existing bridge lost connectivity. When the mesh had no bridge from startup, no election was ever initiated.

Solution: Added periodic monitoring task (30-second interval) that:

  • Detects absence of healthy bridges in the mesh
  • Triggers bridge election after 60-second startup grace period
  • Uses randomized election delay (1-3 seconds) to prevent thundering herd
  • Respects all existing safeguards (election state, cooldown, router visibility)

Behavior Changes:

Scenario Before v1.8.6 After v1.8.6
No initial bridge Mesh stays bridgeless forever Election triggered after 60s, best RSSI node becomes bridge
Pre-designated bridge Works normally Works normally (unchanged)
Bridge failure Election triggered Election triggered (unchanged)

Backward Compatibility: Fully backward compatible. Pre-designated bridge mode continues to work exactly as before.

Core Changes: src/arduino/wifi.hpp

📝 Documentation Improvements

Bridge Failover Example Clarification

Enhanced documentation for examples/bridge_failover/ to clearly explain two deployment modes:

Auto-Election Mode (New Documentation)

  • All nodes start with INITIAL_BRIDGE=false
  • After 60-second startup grace period, monitoring begins
  • Best RSSI node automatically elected as bridge
  • Ideal for dynamic deployments where optimal bridge selection matters

Pre-Designated Mode (Existing)

  • One node starts with INITIAL_BRIDGE=true
  • Traditional setup with guaranteed initial bridge
  • Ideal for fixed deployments with known bridge location

Updated files:

  • examples/bridge_failover/bridge_failover.ino - Enhanced header comments
  • examples/bridge_failover/README.md - Comprehensive mode documentation

🔧 Housekeeping

  • Synchronized package-lock.json version to 1.8.5

🔄 Upgrade Guide

From v1.8.5 to v1.8.6

This is a seamless upgrade with no breaking changes:

  1. Update Package Version:

    # PlatformIO
pio pkg update alteriom/AlteriomPainlessMesh@^1.8.6

# NPM
npm update @alteriom/painlessmesh

# Arduino Library Manager
# Update through IDE's Library Manager

  2. No Code Changes Required - All existing code works without modification

  3. Optional: Enable Auto-Election Mode

    // For auto-election mode, set all nodes to:
#define INITIAL_BRIDGE false

// Network will automatically elect bridge after 60s startup

🎯 Use Cases

This release is particularly valuable for:

1. Dynamic Mesh Networks

  • Mobile or portable mesh deployments
  • Networks where node positions change
  • Optimal bridge selection based on WiFi signal strength

2. Fault-Tolerant Deployments

  • Meshes that must establish connectivity without manual intervention
  • Systems requiring automatic bridge recovery
  • IoT deployments with minimal human oversight

3. Development & Testing

  • Quick prototyping without pre-configuring bridge nodes
  • Testing scenarios with varying network topologies
  • Validation of bridge election algorithms

📊 Technical Details

Monitoring Task Implementation

// Periodic check every 30 seconds
this->addTask(30000, TASK_FOREVER, [this]() {
  // Skip if: not enabled, already bridge, or in startup grace period
  if (!bridgeFailoverEnabled || !routerCredentialsConfigured) return;
  if (this->isBridge() || millis() < 60000) return;
  
  // Check for healthy bridge
  bool hasHealthyBridge = false;
  for (const auto& bridge : this->getBridges()) {
    if (bridge.isHealthy(bridgeTimeoutMs) && bridge.internetConnected) {
      hasHealthyBridge = true;
      break;
    }
  }
  
  // Trigger election with randomized delay if no bridge found
  if (!hasHealthyBridge) {
    uint32_t delay = random(1000, 3000);
    this->addTask(delay, TASK_ONCE, [this]() {
      this->startBridgeElection();
    });
  }
});

Safeguards

  1. 60-second startup grace period - Allows network to stabilize
  2. Randomized election delay - Prevents simultaneous elections
  3. Respects election state - Won't trigger if election already in progress
  4. Cooldown period - Enforces 60-second minimum between elections
  5. Router visibility check - Only nodes that can see router participate

🙏 Credits

Special thanks to @woodlist for reporting Issue #117 and providing detailed logs that helped identify the root cause.

📦 Distribution

This release is available through:

  • GitHub Releases: v1.8.6
  • NPM: npm install @alteriom/painlessmesh@1.8.6
  • PlatformIO: alteriom/AlteriomPainlessMesh@^1.8.6
  • Arduino Library Manager: Search for "AlteriomPainlessMesh"

📚 Additional Resources

🐛 Found a Bug?

Please report issues at: https://github.com/Alteriom/painlessMesh/issues

Full Changelog: v1.8.5...v1.8.6

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