diff --git a/MQTT_IMPLEMENTATION.md b/MQTT_IMPLEMENTATION.md
index e5c8b849..f813e068 100644
--- a/MQTT_IMPLEMENTATION.md
+++ b/MQTT_IMPLEMENTATION.md
@@ -109,6 +109,8 @@ The MQTT bridge uses a slot-based architecture with up to 6 concurrent connectio
 | `meshat.se` | mqtts://mqtt.meshat.se:8883 | Username/password (fixed in firmware) | MQTT over TLS |
 | `eastidahomesh` | wss://broker.eastidahomesh.net:443 | None | WSS |
 | `coloradomesh` | wss://mqtt.meshcore.coloradomesh.org:1883 | JWT (Ed25519) | WSS |
+| `meshcore-ca-1` | mqtt1.meshcore.ca:443 | JWT (Ed25519) | WSS |
+| `meshcore-ca-2` | mqtt2.meshcore.ca:443 | JWT (Ed25519) | WSS |
 | `custom` | User-configured | Username/Password | MQTT or WSS |
 | `none` | (disabled) | — | — |
 
@@ -207,11 +209,37 @@ You can flash the merged firmware using either the web flasher or the command li
 - `MQTT_WIFI_TX_POWER` - WiFi TX power level (default: `WIFI_POWER_11dBm`)
 - ~~`MQTT_WIFI_POWER_SAVE_DEFAULT`~~ - Removed; all builds now default to `none` (no power save)
 
+#### Compile-time fresh-install defaults (`src/helpers/MQTTDefaults.h`)
+
+Optional PlatformIO `build_flags` override defaults written when `/mqtt_prefs` is first created. They do **not** change existing saved prefs on upgrade or reflash (unless `/mqtt_prefs` is erased).
+
+| Macro | Default | Notes |
+|-------|---------|-------|
+| `MQTT_DEFAULT_SLOT1_PRESET` … `MQTT_DEFAULT_SLOT6_PRESET` | slots 1–2: `analyzer-us` / `analyzer-eu`; slots 3–6: `none` | Must be a built-in preset name, `none`, or `custom` |
+| `MQTT_DEFAULT_IATA` | (empty) | e.g. `'"YYZ"'` |
+| `MQTT_DEFAULT_TIMEZONE` | (empty) | e.g. `'"America/Toronto"'` |
+| `MQTT_DEFAULT_TIMEZONE_OFFSET` | `0` | Fallback hours when TZ string is empty |
+
+Example community build:
+
+```ini
+build_flags =
+  -D MQTT_DEFAULT_SLOT1_PRESET='"meshcore-ca-1"'
+  -D MQTT_DEFAULT_SLOT2_PRESET='"meshcore-ca-2"'
+  -D MQTT_DEFAULT_IATA='"YYZ"'
+  -D MQTT_DEFAULT_TIMEZONE='"America/Toronto"'
+  -D MQTT_DEFAULT_TIMEZONE_OFFSET=-5
+```
+
+WiFi SSID/password are not compile-time configurable (operators set them per device via CLI).
+
+Legacy `get mqtt.analyzer_us` / `set mqtt.analyzer_us` still refer to the preset name `analyzer-us`, not “whatever slot 1 default is”.
+
 ## Default Configuration
 
-The MQTT bridge comes with the following defaults for fresh installs:
+The MQTT bridge comes with the following defaults for fresh installs (unless overridden by the macros above):
 - **Origin**: Device name (set automatically from `set name`)
-- **IATA**: (blank — must be configured for MeshCore-style topic presets such as Analyzer and TennMesh)
+- **IATA**: (blank — must be configured for MeshCore-style topic presets such as Analyzer and TennMesh, unless `MQTT_DEFAULT_IATA` is set at build time)
 - **Status Messages**: Enabled
 - **Packet Messages**: Enabled
 - **Raw Messages**: Disabled
@@ -224,8 +252,8 @@ The MQTT bridge comes with the following defaults for fresh installs:
 - **WiFi SSID**: (blank — must be configured)
 - **WiFi Password**: (blank — optional for open networks)
 - **WiFi Power Save**: `none` (no power save)
-- **Timezone**: (blank — uses UTC until configured)
-- **Timezone Offset**: 0 (fallback, no offset)
+- **Timezone**: (blank — uses UTC until configured, unless `MQTT_DEFAULT_TIMEZONE` is set at build time)
+- **Timezone Offset**: 0 (fallback, no offset, unless `MQTT_DEFAULT_TIMEZONE_OFFSET` is set)
 - **Repeat (forwarding)**: On (set `repeat off` for receive-only observers)
 
 ## CLI Commands
diff --git a/examples/simple_repeater/MyMesh.cpp b/examples/simple_repeater/MyMesh.cpp
index ab43809c..f13353e4 100644
--- a/examples/simple_repeater/MyMesh.cpp
+++ b/examples/simple_repeater/MyMesh.cpp
@@ -979,29 +979,13 @@ MyMesh::MyMesh(mesh::MainBoard &board, mesh::Radio &radio, mesh::MillisecondCloc
   _prefs.gps_interval = 0;
   _prefs.advert_loc_policy = ADVERT_LOC_PREFS;
 
-  // MQTT defaults (mqtt_origin empty => effective origin follows node_name at publish time)
+  // MQTT slot/IATA/timezone defaults come from /mqtt_prefs via loadPrefs (see MQTTDefaults.h)
   _prefs.mqtt_origin[0] = '\0';
-  StrHelper::strncpy(_prefs.mqtt_iata, "SEA", sizeof(_prefs.mqtt_iata));
-  _prefs.mqtt_status_enabled = 1;    // enabled
-  _prefs.mqtt_packets_enabled = 1;   // enabled
-  _prefs.mqtt_raw_enabled = 0;       // disabled
-  _prefs.mqtt_tx_enabled = 2;        // advert: own adverts only (matches MQTTPrefs default)
-  _prefs.mqtt_rx_enabled = 1;        // RX packets enabled by default
-  _prefs.mqtt_status_interval = 300000; // 5 minutes
 
-  // WiFi defaults
+  // WiFi defaults (user-configured via CLI; placeholders until set)
   StrHelper::strncpy(_prefs.wifi_ssid, "ssid_here", sizeof(_prefs.wifi_ssid));
   StrHelper::strncpy(_prefs.wifi_password, "password_here", sizeof(_prefs.wifi_password));
 
-  // Timezone defaults (Pacific Time with DST support)
-  StrHelper::strncpy(_prefs.timezone_string, "America/Los_Angeles", sizeof(_prefs.timezone_string));
-  _prefs.timezone_offset = -8; // fallback
-
-  // MQTT slot presets (analyzer-us and analyzer-eu enabled by default)
-  StrHelper::strncpy(_prefs.mqtt_slot_preset[0], "analyzer-us", sizeof(_prefs.mqtt_slot_preset[0]));
-  StrHelper::strncpy(_prefs.mqtt_slot_preset[1], "analyzer-eu", sizeof(_prefs.mqtt_slot_preset[1]));
-  StrHelper::strncpy(_prefs.mqtt_slot_preset[2], "none", sizeof(_prefs.mqtt_slot_preset[2]));
-
   _prefs.adc_multiplier = 0.0f; // 0.0f means use default board multiplier
 
 #if defined(USE_SX1262) || defined(USE_SX1268)
diff --git a/examples/simple_room_server/MyMesh.cpp b/examples/simple_room_server/MyMesh.cpp
index 47ca52d4..e401fd5d 100644
--- a/examples/simple_room_server/MyMesh.cpp
+++ b/examples/simple_room_server/MyMesh.cpp
@@ -692,28 +692,12 @@ MyMesh::MyMesh(mesh::MainBoard &board, mesh::Radio &radio, mesh::MillisecondCloc
   _prefs.bridge_baud = 115200;  // baud rate
   _prefs.bridge_channel = 1;    // channel 1
 
-  // MQTT defaults (same as repeater; empty mqtt_origin follows node_name when publishing)
+  // MQTT slot/IATA/timezone defaults come from /mqtt_prefs via loadPrefs (see MQTTDefaults.h)
   _prefs.mqtt_origin[0] = '\0';
-  StrHelper::strncpy(_prefs.mqtt_iata, "SEA", sizeof(_prefs.mqtt_iata));
-  _prefs.mqtt_status_enabled = 1;    // enabled
-  _prefs.mqtt_packets_enabled = 1;   // enabled
-  _prefs.mqtt_raw_enabled = 0;       // disabled
-  _prefs.mqtt_tx_enabled = 2;        // advert: own adverts only (matches MQTTPrefs default)
-  _prefs.mqtt_rx_enabled = 1;        // RX packets enabled by default
-  _prefs.mqtt_status_interval = 300000; // 5 minutes
-  
-  // WiFi defaults (same as repeater)
+
+  // WiFi defaults (user-configured via CLI; placeholders until set)
   StrHelper::strncpy(_prefs.wifi_ssid, "ssid_here", sizeof(_prefs.wifi_ssid));
   StrHelper::strncpy(_prefs.wifi_password, "password_here", sizeof(_prefs.wifi_password));
-  
-  // Timezone defaults (same as repeater - Pacific Time with DST support)
-  StrHelper::strncpy(_prefs.timezone_string, "America/Los_Angeles", sizeof(_prefs.timezone_string));
-  _prefs.timezone_offset = -8; // fallback
-  
-  // MQTT slot presets (analyzer-us and analyzer-eu enabled by default)
-  StrHelper::strncpy(_prefs.mqtt_slot_preset[0], "analyzer-us", sizeof(_prefs.mqtt_slot_preset[0]));
-  StrHelper::strncpy(_prefs.mqtt_slot_preset[1], "analyzer-eu", sizeof(_prefs.mqtt_slot_preset[1]));
-  StrHelper::strncpy(_prefs.mqtt_slot_preset[2], "none", sizeof(_prefs.mqtt_slot_preset[2]));
 
   next_post_idx = 0;
   next_client_idx = 0;
diff --git a/src/helpers/CommonCLI.cpp b/src/helpers/CommonCLI.cpp
index 64a11aa4..6d214306 100644
--- a/src/helpers/CommonCLI.cpp
+++ b/src/helpers/CommonCLI.cpp
@@ -17,6 +17,7 @@
 #endif
 #ifdef WITH_MQTT_BRIDGE
 #include "bridges/MQTTBridge.h"
+#include "MQTTDefaults.h"
 
 // Helper function to calculate total size of MQTT fields for file format compatibility
 // Uses NodePrefs struct to get accurate field sizes
@@ -449,25 +450,7 @@ void CommonCLI::savePrefs(FILESYSTEM* fs) {
 #ifdef WITH_MQTT_BRIDGE
 // Set default values for MQTT preferences (used when file doesn't exist or is corrupted)
 static void setMQTTPrefsDefaults(MQTTPrefs* prefs) {
-  memset(prefs, 0, sizeof(MQTTPrefs));
-  // Set sensible defaults matching MQTTBridge expectations
-  prefs->mqtt_status_enabled = 1;    // enabled by default
-  prefs->mqtt_packets_enabled = 1;   // enabled by default
-  prefs->mqtt_raw_enabled = 0;       // disabled by default
-  prefs->mqtt_tx_enabled = 2;        // advert: own adverts only, by default
-  prefs->mqtt_rx_enabled = 1;        // RX packets enabled by default
-  prefs->mqtt_status_interval = 300000; // 5 minutes default
-  // Slot presets: analyzer-us and analyzer-eu enabled by default, rest = none
-  strncpy(prefs->mqtt_slot_preset[0], "analyzer-us", sizeof(prefs->mqtt_slot_preset[0]) - 1);
-  prefs->mqtt_slot_preset[0][sizeof(prefs->mqtt_slot_preset[0]) - 1] = '\0';
-  strncpy(prefs->mqtt_slot_preset[1], "analyzer-eu", sizeof(prefs->mqtt_slot_preset[1]) - 1);
-  prefs->mqtt_slot_preset[1][sizeof(prefs->mqtt_slot_preset[1]) - 1] = '\0';
-  for (int i = 2; i < MAX_MQTT_SLOTS; i++) {
-    strncpy(prefs->mqtt_slot_preset[i], "none", sizeof(prefs->mqtt_slot_preset[i]) - 1);
-    prefs->mqtt_slot_preset[i][sizeof(prefs->mqtt_slot_preset[i]) - 1] = '\0';
-  }
-  prefs->wifi_power_save = 1; // Default to none (0=min, 1=none, 2=max)
-  // String fields are already zero-initialized by memset
+  applyMQTTDefaults(prefs);
 }
 
 void CommonCLI::loadMQTTPrefs(FILESYSTEM* fs) {
diff --git a/src/helpers/MQTTDefaults.h b/src/helpers/MQTTDefaults.h
new file mode 100644
index 00000000..cf58b997
--- /dev/null
+++ b/src/helpers/MQTTDefaults.h
@@ -0,0 +1,98 @@
+#pragma once
+
+#ifdef WITH_MQTT_BRIDGE
+
+#include <string.h>
+#include <MeshCore.h>
+#include "CommonCLI.h"
+#include "MQTTPresets.h"
+
+// Compile-time defaults for fresh /mqtt_prefs (override via platformio build_flags).
+// Example:
+//   -D MQTT_DEFAULT_SLOT1_PRESET='"meshcore-ca-1"'
+//   -D MQTT_DEFAULT_IATA='"YYZ"'
+//   -D MQTT_DEFAULT_TIMEZONE='"America/Toronto"'
+//   -D MQTT_DEFAULT_TIMEZONE_OFFSET=-5
+
+#ifndef MQTT_DEFAULT_SLOT1_PRESET
+#define MQTT_DEFAULT_SLOT1_PRESET "analyzer-us"
+#endif
+#ifndef MQTT_DEFAULT_SLOT2_PRESET
+#define MQTT_DEFAULT_SLOT2_PRESET "analyzer-eu"
+#endif
+#ifndef MQTT_DEFAULT_SLOT3_PRESET
+#define MQTT_DEFAULT_SLOT3_PRESET "none"
+#endif
+#ifndef MQTT_DEFAULT_SLOT4_PRESET
+#define MQTT_DEFAULT_SLOT4_PRESET "none"
+#endif
+#ifndef MQTT_DEFAULT_SLOT5_PRESET
+#define MQTT_DEFAULT_SLOT5_PRESET "none"
+#endif
+#ifndef MQTT_DEFAULT_SLOT6_PRESET
+#define MQTT_DEFAULT_SLOT6_PRESET "none"
+#endif
+
+#ifndef MQTT_DEFAULT_IATA
+#define MQTT_DEFAULT_IATA ""
+#endif
+
+#ifndef MQTT_DEFAULT_TIMEZONE
+#define MQTT_DEFAULT_TIMEZONE ""
+#endif
+
+#ifndef MQTT_DEFAULT_TIMEZONE_OFFSET
+#define MQTT_DEFAULT_TIMEZONE_OFFSET 0
+#endif
+
+static inline void mqttDefaultSlotPreset(char* dest, size_t dest_size, const char* preset) {
+  const char* resolved = MQTT_PRESET_NONE;
+  if (preset && preset[0] != '\0') {
+    if (strcmp(preset, MQTT_PRESET_NONE) == 0 ||
+        strcmp(preset, MQTT_PRESET_CUSTOM) == 0 ||
+        findMQTTPreset(preset) != nullptr) {
+      resolved = preset;
+    } else {
+      MESH_DEBUG_PRINTLN("MQTT: invalid default preset '%s', using none", preset);
+    }
+  }
+  strncpy(dest, resolved, dest_size - 1);
+  dest[dest_size - 1] = '\0';
+}
+
+static inline void applyMQTTDefaults(MQTTPrefs* prefs) {
+  memset(prefs, 0, sizeof(MQTTPrefs));
+  prefs->mqtt_status_enabled = 1;
+  prefs->mqtt_packets_enabled = 1;
+  prefs->mqtt_raw_enabled = 0;
+  prefs->mqtt_tx_enabled = 2;
+  prefs->mqtt_rx_enabled = 1;
+  prefs->mqtt_status_interval = 300000;
+  prefs->wifi_power_save = 1;
+
+  mqttDefaultSlotPreset(prefs->mqtt_slot_preset[0], sizeof(prefs->mqtt_slot_preset[0]),
+                        MQTT_DEFAULT_SLOT1_PRESET);
+  mqttDefaultSlotPreset(prefs->mqtt_slot_preset[1], sizeof(prefs->mqtt_slot_preset[1]),
+                        MQTT_DEFAULT_SLOT2_PRESET);
+  mqttDefaultSlotPreset(prefs->mqtt_slot_preset[2], sizeof(prefs->mqtt_slot_preset[2]),
+                        MQTT_DEFAULT_SLOT3_PRESET);
+  mqttDefaultSlotPreset(prefs->mqtt_slot_preset[3], sizeof(prefs->mqtt_slot_preset[3]),
+                        MQTT_DEFAULT_SLOT4_PRESET);
+  mqttDefaultSlotPreset(prefs->mqtt_slot_preset[4], sizeof(prefs->mqtt_slot_preset[4]),
+                        MQTT_DEFAULT_SLOT5_PRESET);
+  mqttDefaultSlotPreset(prefs->mqtt_slot_preset[5], sizeof(prefs->mqtt_slot_preset[5]),
+                        MQTT_DEFAULT_SLOT6_PRESET);
+
+  if (MQTT_DEFAULT_IATA[0] != '\0') {
+    strncpy(prefs->mqtt_iata, MQTT_DEFAULT_IATA, sizeof(prefs->mqtt_iata) - 1);
+    prefs->mqtt_iata[sizeof(prefs->mqtt_iata) - 1] = '\0';
+  }
+
+  if (MQTT_DEFAULT_TIMEZONE[0] != '\0') {
+    strncpy(prefs->timezone_string, MQTT_DEFAULT_TIMEZONE, sizeof(prefs->timezone_string) - 1);
+    prefs->timezone_string[sizeof(prefs->timezone_string) - 1] = '\0';
+  }
+  prefs->timezone_offset = MQTT_DEFAULT_TIMEZONE_OFFSET;
+}
+
+#endif // WITH_MQTT_BRIDGE
diff --git a/src/helpers/MQTTPresets.h b/src/helpers/MQTTPresets.h
index bca9516e..5ce6fb07 100644
--- a/src/helpers/MQTTPresets.h
+++ b/src/helpers/MQTTPresets.h
@@ -119,8 +119,8 @@ static const MQTTPresetDef MQTT_PRESETS[MQTT_PRESET_COUNT] = {
     { "coloradomesh",  "wss://mqtt.meshcore.coloradomesh.org:1883","mqtt.meshcore.coloradomesh.org", ISRG_ROOT_X1,  MQTT_AUTH_JWT,      MQTT_TOPIC_MESHCORE,  0,       true,   55,      nullptr,     nullptr     },
     { "dutchmeshcore-1", "wss://collector1.dutchmeshcore.nl:443/mqtt", "collector1.dutchmeshcore.nl",     GTS_ROOT_R4,  MQTT_AUTH_JWT,      MQTT_TOPIC_MESHCORE,  0,       true,   55,      nullptr,     nullptr     },
     { "dutchmeshcore-2", "wss://collector2.dutchmeshcore.nl:443/mqtt", "collector2.dutchmeshcore.nl",     GTS_ROOT_R4,  MQTT_AUTH_JWT,      MQTT_TOPIC_MESHCORE,  0,       true,   55,      nullptr,     nullptr     },
-    { "meshcore-ca-1",    "wss://mqtt1.meshcore.ca:443/mqtt",          "mqtt1.meshcore.ca",               ISRG_ROOT_X1, MQTT_AUTH_JWT,      MQTT_TOPIC_MESHCORE,  0,       true,   55,      nullptr,     nullptr     },
-    { "meshcore-ca-2",    "wss://mqtt2.meshcore.ca:443/mqtt",          "mqtt2.meshcore.ca",               ISRG_ROOT_X1, MQTT_AUTH_JWT,      MQTT_TOPIC_MESHCORE,  0,       true,   55,      nullptr,     nullptr     },
+    { "meshcore-ca-1",   "wss://mqtt1.meshcore.ca:443/mqtt",          "mqtt1.meshcore.ca",               ISRG_ROOT_X1, MQTT_AUTH_JWT,      MQTT_TOPIC_MESHCORE,  0,       true,   55,      nullptr,     nullptr     },
+    { "meshcore-ca-2",   "wss://mqtt2.meshcore.ca:443/mqtt",          "mqtt2.meshcore.ca",               ISRG_ROOT_X1, MQTT_AUTH_JWT,      MQTT_TOPIC_MESHCORE,  0,       true,   55,      nullptr,     nullptr     },
 };
 
 // Find a preset by name, returns nullptr if not found