# Mesh Beacon Module — Function, Settings, and Client Interface Spec Status: draft, tracks firmware branch `feat/mesh-beacon`. Audience: firmware reviewers (Part 1) and client-app developers — Android / Apple / Web / Python (Part 2). The Mesh Beacon module lets a node periodically **advertise the existence of a mesh** to nodes that are not yet on it — broadcasting a short human-readable message plus an optional "join offer" (a channel, region, and modem preset). It is the mechanism behind invitations like _"Join us on NarrowSlow"_: a node sitting on one preset/region can shout an invitation that listeners on other presets/regions can hear and surface to their user. The module is deliberately **advisory**. The firmware never auto-joins an advertised channel or auto-switches preset/region in response to a received beacon — it delivers the information to the client app and stops there. All "should I act on this?" decisions belong to the client and, ultimately, the user. --- ## Part 1 — Function and settings choices ### 1.1 Two roles in one module | Role | Class | Active when | What it does | | --------------- | --------------------------- | ---------------------------- | ------------------------------------------------------------------------------------------------------------------------- | | **Broadcaster** | `MeshBeaconBroadcastModule` | `FLAG_BROADCAST_ENABLED` set | Periodically transmits `MESH_BEACON_APP` packets on the configured radio settings. | | **Listener** | `MeshBeaconListenerModule` | `FLAG_LISTEN_ENABLED` set | Receives `MESH_BEACON_APP` packets and caches the offer for the client (the packet itself flows to the client unchanged). | The boolean toggles live in a single `flags` bitfield (see [§1.8](#18-settings-reference-moduleconfigmeshbeaconconfig-tag-17)) — broadcasting and listening can be enabled independently on the same node. The whole module compiles out under the `MESHTASTIC_EXCLUDE_BEACON` build flag. ### 1.2 Wire message Beacons travel on a dedicated port number: ```protobuf MESH_BEACON_APP = 37 // meshtastic/portnums.proto ENCODING: protobuf (meshtastic.MeshBeacon) ``` ```protobuf message MeshBeacon { string message = 1; // human-readable text, max 100 bytes (buffer 101) ChannelSettings offer_channel = 2; // optional advertised channel (name + PSK + slot) Config.LoRaConfig.RegionCode offer_region = 3; // optional advertised region (UNSET = none) optional Config.LoRaConfig.ModemPreset offer_preset = 4; // optional advertised preset } ``` `.options` size caps (enforced at generation and on send): `message ≤ 100`, `offer_channel.name ≤ 12`, `offer_channel.psk ≤ 32`. The three `offer_*` fields together describe _"there is a reachable mesh on this region+preset, here is the channel to use."_ Any subset may be present; an empty message with a populated offer (or vice-versa) is valid. ### 1.3 Transmission behaviour Every outgoing beacon packet is stamped uniformly (`sendBeacon` → `stampPacket`): - `to = NODENUM_BROADCAST` - `from = local node` (see [§1.6](#16-broadcast_send_as_node-currently-disabled) for the disabled spoof path) - **`hop_limit = 0`** — beacons are **zero-hop**. They are never rebroadcast by the mesh; only direct RF neighbours hear them. This is the primary spam-control mechanism. (`hop_start` is normally `0` too, but `FLAG_LEGACY_SPLIT` raises it to `1` for old-firmware compatibility — see [§1.5](#15-legacy-split-flag_legacy_split).) - `priority = BACKGROUND`, `want_ack = false`. Broadcasting is additionally gated at runtime by: - airtime utilisation (`isTxAllowedAirUtil()`), and - device role — **`CLIENT_HIDDEN` never broadcasts**. #### Interval `broadcast_interval_secs` controls cadence. The floor is **3600 s (1 hour)** (`default_mesh_beacon_min_broadcast_interval_secs`); `0` means "use default". Values below the floor are silently raised, both at config-set time (AdminModule) and at runtime. The cadence is **reboot-safe**. Each broadcast's time is persisted to flash via `TransmitHistory` (keyed by `MESH_BEACON_APP`), and the broadcaster reads it back on boot — so a node that reboots (or crash-loops) won't re-broadcast until a full interval has elapsed since its last real send, rather than firing ~30 s after every boot. The timestamp is written **before** the transmit, so a brown-out during the high-current LoRa TX still counts as "sent." This mirrors `NodeInfoModule` / `PositionModule`. #### Radio switching for TX A beacon's whole point is often to reach a mesh on a _different_ preset/region/channel than the broadcaster currently runs. Before transmitting a beacon tagged with target radio settings, the module temporarily reconfigures the radio (`reconfigureForBeaconTX`), sends, then restores the prior config. Per-packet target settings are held in an 8-entry **sidecar table** keyed by packet ID — chosen so the `MeshPacket` proto carries no extra per-packet radio fields, and normal (non-beacon) traffic is never touched. Two safety guards run before any radio switch (`beaconTxConfigInvalid`): 1. **An unlicensed node never keys up on a licensed-only (ham) region.** (The reverse — a licensed node operating in a non-ham region — is allowed. The switch only touches preset/region/channel, never `owner.is_licensed`.) 2. **The preset must be valid for the target region** (`validateConfigLora`). If either fails, the radio is **not** switched and the radio driver **drops** the packet rather than letting it fall through onto the current config. #### Channel encryption on an override channel Encryption keys off the **primary** channel slot, and the radio-thread channel switch happens _after_ encryption. So when a beacon goes out on an override channel (different name/PSK), the module installs the beacon channel into the primary slot for the synchronous duration of `send()`, then restores it (`sendBeaconPacket`). This guarantees the packet is encrypted with the beacon channel's key and stamped with its hash — not the primary's. Meshtastic threading is cooperative, so there is no preemption between swap and restore. ### 1.4 Where beacons are sent: single-target and multi-target The broadcaster can send to one set of radio settings or to several. **Single- and multi-target are equal options — neither is preferred and neither is legacy.** Pick whichever matches the deployment. - **Single-target:** the scalar `broadcast_on_preset` / `broadcast_on_region` / `broadcast_on_channel` fields describe one destination. Used when `broadcast_targets` is empty. - **Multi-target:** `broadcast_targets` (repeated `BroadcastTarget`) describes several. When non-empty it takes over from the scalar `broadcast_on_*` fields, and the broadcaster sends **one beacon copy per entry**. Each `BroadcastTarget` is `{ optional preset, region, optional channel_index }`, where `channel_index` references a slot in the node's own channel table (the channel must already be configured locally — its key is needed to encrypt the beacon). Within one cycle, targets that resolve to the **same** effective preset/region/channel are de-duplicated — only the first is transmitted — so an accidentally repeated entry costs no extra airtime. #### Same-settings vs. other-settings Independent of single/multi, each destination can either reuse the node's **own current radio settings** or specify **different** ones: - **Same-settings ("message of the day"):** leave the preset / region / channel unset. They fall back to the running config, so the beacon goes out on the node's current mesh with **no radio switch** — a plain periodic broadcast to whoever is already on this preset/region. - **Other-settings (cross-mesh invite):** set a preset / region / channel that differs from the running config. The radio is temporarily switched for that copy's TX, then restored (see [§1.3](#radio-switching-for-tx)). Both modes support both styles: a single-target beacon with no `broadcast_on_*` overrides is a message-of-the-day on the current mesh; a multi-target list can mix one entry on the current settings with others on different presets/regions. ### 1.5 Legacy split (`FLAG_LEGACY_SPLIT`) This one flag controls **two** independent legacy-compatibility behaviours. Both are about making beacons usable by firmware that predates this module. **(a) Text/offer packet split.** A combined `MESH_BEACON_APP` packet carries both the text and the offer, but old firmware only decodes `TEXT_MESSAGE_APP` and would never show the text. When `FLAG_LEGACY_SPLIT` is set **and both text and offer content are present**, the broadcaster emits **two** packets on the same beacon radio settings instead of one: - **Packet A** — `MESH_BEACON_APP` carrying the **offer only** (no text). - **Packet B** — `TEXT_MESSAGE_APP` carrying the **text only**. This is an independent two-packet decision, not an either/or: offer-only and text-only payloads still go out as a single packet in their respective cases; only the both-present case splits. **(b) `hop_start = 1` override.** When `FLAG_LEGACY_SPLIT` is set, **every** beacon packet it sends (combined, split-A, or split-B; even same-settings ones) is stamped with `hop_start = 1` while `hop_limit` stays `0`. Pre-2.7.20 firmware drops `hop_start == 0` packets in a pre-decryption check before it can read the bitfield, so `hop_start = 1` lets those nodes accept the beacon — and it remains genuinely zero-hop (`hop_limit = 0` still prevents any rebroadcast). > **Side effect for clients:** with `hop_start = 1, hop_limit = 0`, receivers compute > `hops_away = hop_start − hop_limit = 1`, so a legacy-split beacon reads as **1 hop away** even > though it arrived over direct RF. Without legacy-split it reads as direct (0). Don't treat a > beacon's `hops_away` as a reliable distance signal. ### 1.6 `broadcast_send_as_node` (currently disabled) The schema reserves `broadcast_send_as_node` (field 3) to send beacons _as_ another node ID. **The firmware application of this field is currently commented out pending review**, so beacons always go out as the local node today. The access-control rule is, however, already enforced in AdminModule and should be treated as canonical: > A remote admin may only set `broadcast_send_as_node` to **their own** node ID > (`mp.from`). Any other value is rejected and reset to the stored value. Design note for when it is re-enabled: it is a _node-ID_ spoof only — it rewrites `from` but forges no signature. Once `from` is not us, the packet is no longer `isFromUs()`, so the router skips XEdDSA signing and receivers get an unsigned packet attributed to another node. ### 1.7 Reception behaviour (listener) When `FLAG_LISTEN_ENABLED` is **off**, the router drops incoming `MESH_BEACON_APP` packets up front (`Router::handleReceived`, same pattern as a disabled NeighborInfo module) — so they reach neither the modules nor the phone. When it is **on**, the packet flows normally and the listener's `wantPacket` accepts it (`has_mesh_beacon` + `FLAG_LISTEN_ENABLED` + `portnum == MESH_BEACON_APP`). On a valid beacon (`handleReceivedProtobuf`): 1. **Offer → cache.** Any offer (`offer_channel` / `offer_region` / `offer_preset`) is stored in the static `lastReceivedOffer` (sender, channel, region, preset, `received_at`). `received_at` is `0` if the node has no RTC fix yet — **consumers must not treat `0` as a valid timestamp.** 2. **Never auto-applied.** The firmware does not switch channel/preset/region from a received offer. Acting on it is the client app's job. 3. The handler returns `CONTINUE` (not `STOP`), so the original `MESH_BEACON_APP` packet **flows to the client unchanged** through the normal FromRadio path (see Part 2). The client reads the `message` field directly from that packet — there is no separate copy. The firmware deliberately does **not** unwrap a combined beacon's text into a synthesized `TEXT_MESSAGE_APP`, and does **not** fire `EVENT_RECEIVED_MSG`: a beacon is an advisory broadcast, not a personal message, so it must not duplicate the text or wake the device from sleep. If a broadcaster needs non-beacon-aware clients to see the text, it uses `FLAG_LEGACY_SPLIT`, which sends a real `TEXT_MESSAGE_APP` over RF (see [§1.5](#15-legacy-split-flag_legacy_split)). ### 1.8 Settings reference (`ModuleConfig.MeshBeaconConfig`, tag 17) | # | Field | Type | Meaning / constraints | | --- | ------------------------- | ------------------------ | ------------------------------------------------------------------------------------------------------ | | 1 | `flags` | uint32 (bitfield) | Bitwise-OR of `Flags` values (listen / broadcast / legacy-split toggles). See enum below. | | 3 | `broadcast_send_as_node` | uint32 | Send-as node ID. **Application disabled in firmware.** Remote admin may only set to own node ID. | | 4 | `broadcast_message` | string | Text in each broadcast. **Hard-capped at 100 bytes.** | | 5 | `broadcast_offer_channel` | ChannelSettings | Channel advertised in `offer_channel`. | | 6 | `broadcast_offer_region` | RegionCode | Region advertised in `offer_region`. Must be a known region or it is cleared. | | 7 | `broadcast_offer_preset` | optional ModemPreset | Preset advertised in `offer_preset`. Validated against offer region (else cleared). | | 8 | `broadcast_on_channel` | ChannelSettings | Channel to transmit on (single-target). Empty name → preset display name. | | 9 | `broadcast_on_region` | RegionCode | Region to transmit on (single-target). | | 10 | `broadcast_on_preset` | optional ModemPreset | Preset to transmit on (single-target). Validated against on-region (else this + `on_channel` cleared). | | 11 | `broadcast_interval_secs` | uint32 | Cadence. **Min 3600**, default 3600; `0` = default. | | 13 | `broadcast_targets` | repeated BroadcastTarget | Multi-target list; when non-empty overrides the single-target `broadcast_on_*` fields. | > The three boolean toggles were folded into the `flags` bitfield; field tags 2 and 12 are now > unused (the branch is unreleased, so the old tags are left as gaps rather than reserved). **`Flags` enum** (nested in `MeshBeaconConfig`; OR the values into `flags`): | Bit value | Name | Meaning | | --------- | ------------------------ | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | | 0 | `FLAG_NONE` | No options enabled. | | 1 | `FLAG_LISTEN_ENABLED` | Receive beacons; cache the offer. The packet flows to the client, which reads `message` directly. | | 2 | `FLAG_BROADCAST_ENABLED` | Periodically broadcast beacons from this node. | | 4 | `FLAG_LEGACY_SPLIT` | Legacy compatibility: (a) split text+offer into separate `TEXT_MESSAGE_APP` + `MESH_BEACON_APP` packets, and (b) stamp `hop_start = 1` on every beacon so pre-2.7.20 firmware accepts it (see [§1.5](#15-legacy-split-flag_legacy_split)). | `BroadcastTarget`: `1 preset` (optional, falls back to running config), `2 region` (`UNSET` = running config), `4 channel_index` (optional `uint32`, index into the node's channel table; if unset, the default channel for the preset is used). Tag `3` is an unused gap — it previously held an embedded `ChannelSettings`, dropped to keep `ModuleConfig` within the BLE `FromRadio` size budget. --- ## Part 2 — Client interface specification This section is what a client app needs to integrate with the beacon module. Everything goes through the **standard admin / ToRadio / FromRadio protocol** — there is no bespoke transport. ### 2.1 Capability detection The module is build-flag optional. Treat it as present when the node's `LocalModuleConfig` contains a `mesh_beacon` sub-message (`LocalModuleConfig.mesh_beacon`, tag 18). If absent, the firmware was built with `MESHTASTIC_EXCLUDE_BEACON` — hide the beacon UI. ### 2.2 Reading and writing configuration Standard module-config flow — no new admin messages: - **Read:** `AdminMessage.get_module_config_request = ModuleConfig.MeshBeaconConfig` (variant 17). Reply is `get_module_config_response` with the `mesh_beacon` payload. - **Write:** `AdminMessage.set_module_config { mesh_beacon = … }`. The on/off toggles (listen, broadcast, legacy-split) are bits in the `flags` field, not separate booleans — read/write them with the `MeshBeaconConfig.Flags` values (`FLAG_LISTEN_ENABLED = 1`, `FLAG_BROADCAST_ENABLED = 2`, `FLAG_LEGACY_SPLIT = 4`). To toggle one bit, read the current `flags`, set/clear the bit, and write the whole config back. The firmware **sanitises on write** — your value may be silently adjusted. Mirror these rules client-side so the UI doesn't disagree with the device: | Rule | Firmware behaviour | | --------------------------------------------------------------------------- | ------------------------------------------------------------------------------- | | `broadcast_message` length | Truncated to 100 bytes. | | `broadcast_interval_secs` | If non-zero and `< 3600`, raised to 3600. | | `broadcast_on_preset` invalid for `broadcast_on_region` (or current region) | Cleared, **and `broadcast_on_channel` cleared too.** | | `broadcast_offer_preset` invalid for offer/current region | Cleared. | | `broadcast_offer_region` not a known region | Cleared to `UNSET`. | | `broadcast_targets[i].region` not a known region | That entry's region cleared to `UNSET` (TX falls back to running config). | | `broadcast_targets[i].preset` invalid for that entry's region | That entry's `preset` and `channel_index` cleared. | | `broadcast_targets[i].channel_index` ≥ `MAX_NUM_CHANNELS` (8) | That entry's `channel_index` cleared (existence is **not** checked — see §2.5). | | `broadcast_send_as_node` ≠ sender's node ID (remote admin) | Rejected, reset to stored value. | Setting beacon config does **not** trigger a reboot (`shouldReboot = false`); changes take effect on the next broadcast cycle. After a successful write, **re-read** the config to display the effective (sanitised) values. ### 2.3 Receiving beacons A received beacon reaches the client as a normal `FromRadio.packet` (`MeshPacket`) — the listener returns `CONTINUE`, so the packet is **not** consumed on-device. The client must: 1. Subscribe to the FromRadio packet stream as usual. 2. For packets with `decoded.portnum == MESH_BEACON_APP (37)`, decode `decoded.payload` as a `meshtastic.MeshBeacon`. 3. Read `message`, `offer_channel`, `offer_region`, `offer_preset` (presence-checked). 4. `packet.from` is the **originating beaconer** (the firmware preserves it). > **Requires `FLAG_LISTEN_ENABLED` set in `flags`.** With listening disabled the firmware drops > received `MESH_BEACON_APP` packets in the router — before they reach the phone or any on-device > handler — the same way it drops a disabled module's packets (e.g. NeighborInfo). The node still > physically receives the RF, but the client will not see beacons over the FromRadio stream until > listening is enabled. #### Reading the text — no duplication For a beacon-aware client the text is **simply the `message` field of the `MESH_BEACON_APP` packet** you already decode for the offer (step 3 above). One packet, one field — the firmware does **not** inject a separate `TEXT_MESSAGE_APP` copy, so there is nothing to deduplicate. The only time a beacon's text arrives as a separate `TEXT_MESSAGE_APP` is when the broadcaster set `FLAG_LEGACY_SPLIT`: in that mode the `MESH_BEACON_APP` carries the **offer only** (empty `message`) and the text is sent as a normal `TEXT_MESSAGE_APP` over RF, so legacy/non-beacon-aware clients can display it. These two cases are mutually exclusive — a given beacon's text appears exactly once, either in `MESH_BEACON_APP.message` (combined) or as a `TEXT_MESSAGE_APP` (legacy-split) — so a client never needs to dedup. Render whichever it receives. ### 2.4 Acting on an offer (the core client responsibility) When a `MESH_BEACON_APP` carries offer content, present it to the user as an **invitation** — e.g. _"Node ⟨from⟩ invites you to join '⟨offer_channel.name⟩' on ⟨preset⟩/⟨region⟩."_ Then, only on explicit user confirmation, apply it by writing normal config: - `offer_channel` → add/replace a `Channel` (`set_channel`), typically as a secondary channel. - `offer_region` / `offer_preset` → `set_config { lora = … }` (`use_preset = true`, set `modem_preset` and `region`). **Note this changes the node's own radio and will drop it off its current mesh** — make that consequence explicit in the UI. **The firmware will never do any of this for the user. No silent auto-apply.** The on-device `lastReceivedOffer` cache is a firmware-internal convenience and is **not** currently exposed via an admin message — clients should source offers from the live `MESH_BEACON_APP` packet stream (§2.3), not expect a "get last offer" RPC. #### Offer trust model — read before applying - **The advertised PSK is not a secret.** `offer_channel.psk` is a public join token sent in the clear inside a broadcast; it is a convenience, not a security boundary. An operator who wants a genuinely private channel must distribute the PSK out-of-band and leave `offer_channel` unset. Surface offered channels as **public/open** to the user. - **Validate before applying.** Reject or warn if `offer_preset` is not valid for `offer_region`, and **never** apply a licensed-only (ham) region for a user who is not a licensed operator — mirror the firmware's own guard. - Beacons are **unsigned** when sent as another node (the disabled send-as path), and even normal beacons assert nothing about the sender's authority. Treat `from` as informational. ### 2.5 Configuring this node as a broadcaster To make a node advertise a mesh, write `MeshBeaconConfig` with `FLAG_BROADCAST_ENABLED` set in `flags` and at least one of: a non-empty `broadcast_message`, or offer content (`broadcast_offer_*`). With neither, the broadcaster has nothing to send and stays silent. Typical multi-region invite beacon: ```text flags = FLAG_BROADCAST_ENABLED | FLAG_LEGACY_SPLIT // broadcast on; split so legacy nodes still see the text broadcast_message = "Join us on NarrowSlow!" broadcast_offer_preset = NARROW_SLOW broadcast_offer_region = EU_N_868 broadcast_offer_channel = { name: "MyChannel", psk: <32-byte key> } broadcast_interval_secs = 3600 // channel_index points at slots in THIS node's channel table — configure those channels first. broadcast_targets = [ { preset: LONG_FAST, region: EU_868, channel_index: 0 }, { preset: NARROW_SLOW, region: EU_N_868, channel_index: 1 }, ] ``` The same fields can be baked in at build time via `userPrefs.jsonc` (`USERPREFS_MESH_BEACON_*`) — see that file for the full list, including `USERPREFS_MESH_BEACON_TARGET__*` for multi-target entries. #### Single-target vs. multi-target — equal options, different channel representation Single-target and multi-target are **equal, first-class options**. Neither is preferred, deprecated, or a "legacy" fallback — pick whichever matches the deployment (a single-target beacon with no overrides is a plain message-of-the-day; a multi-target list reaches several preset/region/channel combinations). The broadcaster uses `broadcast_targets` when it is non-empty and the scalar `broadcast_on_*` fields when it is empty. The one **subtle implementation difference** is how each names its TX channel: | Path | TX channel is specified by | Channel name/PSK live… | | ------------- | ------------------------------------------------------- | ----------------------------------------- | | Single-target | `broadcast_on_channel` — an embedded `ChannelSettings` | …inline in the beacon config | | Multi-target | `broadcast_targets[i].channel_index` — a `uint32` index | …in the node's channel table (referenced) | This asymmetry is deliberate: embedding a full `ChannelSettings` in every one of the (up to four) targets would push `ModuleConfig` past the BLE `FromRadio` size limit, so a target references an already-configured channel-table slot instead. `broadcast_offer_channel` (the advertised join token) is **always** inline regardless of path — it is the advertisement payload and must carry the actual name/PSK. #### Configuring a multi-target broadcaster (two-step) Because a target's channel is a reference, configuring a multi-target broadcaster takes **two admin writes**, in order: 1. **Create/define each channel in the node's channel table** with the normal channel admin flow (the same `set_channel` your app already uses for adding channels): ```text AdminMessage.set_channel { index: 1, role: SECONDARY, settings: { name: "NarrowSlow", psk: , channel_num: 0 } } ``` 2. **Write the beacon config**, pointing each target at the slot index from step 1: ```text AdminMessage.set_module_config { mesh_beacon: { flags = FLAG_BROADCAST_ENABLED broadcast_targets = [ { preset: NARROW_SLOW, region: EU_N_868, channel_index: 1 } ] } } ``` Notes: - A target may **only** reference a channel that already exists locally — the node needs that channel's key to encrypt the beacon. A `channel_index` that is out of range, or points at a blank/unconfigured slot, is not an error: the beacon falls back to the node's **current/primary channel** (its name, PSK, and slot) on the target preset/region. The channel name only defaults to the preset's display name (e.g. `LongFast`) when the primary channel itself is unnamed — so the fallback is "broadcast on my home channel," **not** a freshly-synthesised default-PSK channel for that preset. - `channel_index` must be `< MAX_NUM_CHANNELS` (8); the firmware clears it on write otherwise (see §2.2 sanitise rules). This is the **only** check on write — the firmware does **not** verify that the referenced slot is actually populated, because you may legitimately write the beacon config before creating the channel. **Validating that a referenced channel exists is the client app's responsibility.** A dangling reference doesn't error; it silently falls back to the preset's default channel — so without a client-side check, the user can believe they're advertising channel _X_ while the node is really transmitting on the preset default. Before writing, confirm each `channel_index` maps to a configured `Channel`, and warn the user otherwise. - **No automatic deduplication of channels.** Neither the beacon config nor the channel table dedups by content: two `broadcast_targets` may carry the same `channel_index`, or different indices whose slots hold identical settings, and `set_channel` will happily store two slots with the same name/PSK. The broadcaster _does_ skip transmitting a target whose effective preset/region/channel duplicates an earlier one in the same cycle (so a duplicated entry wastes no airtime), but it does not rewrite or reject your config — keeping the target list free of redundant entries is up to the client. - The single-target path needs no separate `set_channel` step — its `broadcast_on_channel` is written inline in the same beacon-config message. ### 2.6 Quick reference | Concern | Value | | ---------------------- | ---------------------------------------------------------------------------------------- | | Port number | `MESH_BEACON_APP = 37` | | Wire message | `meshtastic.MeshBeacon` | | Config message | `ModuleConfig.MeshBeaconConfig` (variant tag 17) | | On/off toggles | `flags` bitfield (`MeshBeaconConfig.Flags`) | | Local config presence | `LocalModuleConfig.mesh_beacon` (tag 18) | | Min broadcast interval | 3600 s (1 h) | | Message max length | 100 bytes | | Hop behaviour | Zero-hop (`hop_limit = 0`), never rebroadcast; `hop_start = 1` under `FLAG_LEGACY_SPLIT` | | Auto-apply offers? | **Never** — client + user decide | | Offer PSK | Public join token, not a secret | | Disabled today | `broadcast_send_as_node` application |