Routing Paths

This page covers how MeshCore Open represents, selects, validates, and stores routing paths in the UI and data layer.

Path Routing

MeshCore supports variable-length multi-byte routing paths so the app can scale from small meshes to very large node sets.

Hash Width and Multi-Byte Paths

The device capability determines the hash width (number of bytes per hop):

Width	Max Unique Nodes	Typical Use
1 byte	256	Single-byte node IDs
2 bytes	65,536	Medium meshes
3 bytes	16.7M	Large networks
4 bytes	4.3G	Very large meshes / future-proofing

Device Capability Detection

On device connection, the app reads the firmware capability to set pathHashByteWidth:

// Read from device info response (offset 81)
final modeRaw = firmwareBytes.length >= 82
    ? (firmwareBytes[81] & 0xFF)
    : 0;
final mode = modeRaw.clamp(0, 3);
_pathHashByteWidth = mode + 1; // 1, 2, 3, or 4 bytes per hop

The connector reads a single-mode byte and clamps to 0..3, so the supported hop width is 1..4 bytes. UI code also clamps widths when rendering (typically to 1..4) so 4-byte hops are handled end-to-end in the current codebase.

Path Data Structure

Paths in messages and storage consist of:

pathLength (model/storage): Hop count (number of hops). Negative values (e.g. -1) are used as a flood sentinel.
On-air path_len byte: A packed byte that encodes hop count + hash width and is decoded into pathLength + pathBytes when parsing frames.
pathBytes: Raw bytes of the path (concatenated hop prefixes), grouped by pathHashByteWidth.
hopCount: Derived display value computed from bytes and width: (byteCount + hashByteWidth - 1) ~/ hashByteWidth.
Example: With pathHashByteWidth=2, a 3-hop path has 6 bytes (pathBytes.length = 6) and pathLength = 3:
pathBytes = [0xA1, 0xA2, 0xB1, 0xB2, 0xC1, 0xC2]
Hops: [0xA1A2], [0xB1B2], [0xC1C2]

Hop Count Calculation

Convert path byte length to hop count:

int hopCount = (byteCount + hashByteWidth - 1) ~/ hashByteWidth;

Use this consistently when displaying hop counts in UI. Do not treat pathLength as a hop count when the path uses multi-byte hop hashes.

Path Usage in Different Message Types

Direct messages: Extract path from decrypted payload to trace sender route.
Channel messages: Decrypt hop-by-hop routing chain from payload; the header carries the encoded byte length for the path blob, not the derived hop count.
Contact storage: Path length in byte 32, raw path bytes in bytes 33-96, grouped by detected pathHashByteWidth.

UI Hop Count Display

⚠️ Important: In screens like "Channel Message Path", prefer the actual decoded pathBytes hop count over pathLength metadata:

// Preferred: use actual observed path length
final effectiveHopCount = (pathBytes.length + width - 1) ~/ width;

// Avoid: using encoded byte length as if it were a hop count
// pathLength is bytes; converting it twice causes inflated counts

Example scenario:

Radio header reports pathLength: 32 bytes
Decoded path bytes: [0xAB, 0xCD] (2 bytes = 1 hop with width=2)
Display: "1 hop" (from pathBytes), not "32 hops" (which would double-count the encoded length)

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