diff --git a/solo/gat562_30s_mesh_kit/platformio.ini b/solo/gat562_30s_mesh_kit/platformio.ini
index 6defbc9d..3d4bd5da 100644
--- a/solo/gat562_30s_mesh_kit/platformio.ini
+++ b/solo/gat562_30s_mesh_kit/platformio.ini
@@ -15,7 +15,10 @@ board_upload.maximum_size = 712704
 ; (≈ -O3 + -ffast-math), which bloats flash by ~200 KB on this feature-rich
 ; solo build. -Os keeps every feature, fits comfortably, and is actually safer
 ; for float (no fast-math reassociation). Speed is irrelevant for the UI/mesh.
-build_unflags = -Ofast
+; The offline queue (messages held for the phone app while it's away) at 128,
+; not the board's 256: on the nRF52 the 256 x 177 B left ~5 KB of heap next to
+; the on-device UI (which keeps its own history), too little for a sign buffer.
+build_unflags = -Ofast -D OFFLINE_QUEUE_SIZE=256
 build_flags =
   ${GAT562_30S_Mesh_Kit.build_flags}
   -I examples/companion_radio/ui-new
@@ -23,7 +26,7 @@ build_flags =
   -D MAX_CONTACTS=350
   -D MAX_GROUP_CHANNELS=40
   -D BLE_PIN_CODE=123456
-  -D OFFLINE_QUEUE_SIZE=256
+  -D OFFLINE_QUEUE_SIZE=128
   -D FIRMWARE_SOLO_BUILD=1
   -D MESHCORE_VERSION='"1.17.1"'
   -D UI_SENSORS_PAGE=1
diff --git a/solo/gat562_mesh_watch13/platformio.ini b/solo/gat562_mesh_watch13/platformio.ini
index 8c7992dc..32dfe132 100644
--- a/solo/gat562_mesh_watch13/platformio.ini
+++ b/solo/gat562_mesh_watch13/platformio.ini
@@ -13,6 +13,10 @@
 extends = GAT562_Mesh_Watch13
 board_build.ldscript = boards/nrf52840_s140_v6_extrafs.ld
 board_upload.maximum_size = 712704
+; The offline queue (messages held for the phone app while it's away) at 128,
+; not the board's 256: on the nRF52 the 256 x 177 B left ~5 KB of heap next to
+; the on-device UI (which keeps its own history), too little for a sign buffer.
+build_unflags = -D OFFLINE_QUEUE_SIZE=256
 build_flags =
   ${GAT562_Mesh_Watch13.build_flags}
   -I examples/companion_radio/ui-new
@@ -20,7 +24,7 @@ build_flags =
   -D MAX_CONTACTS=350
   -D MAX_GROUP_CHANNELS=40
   -D BLE_PIN_CODE=123456
-  -D OFFLINE_QUEUE_SIZE=256
+  -D OFFLINE_QUEUE_SIZE=128
   -D DUAL_SERIAL=1
   -D FIRMWARE_SOLO_BUILD=1
   -D MESHCORE_VERSION='"1.17.1"'
diff --git a/solo/lilygo_techo_lite/platformio.ini b/solo/lilygo_techo_lite/platformio.ini
index 1d3c0af5..6c43b766 100644
--- a/solo/lilygo_techo_lite/platformio.ini
+++ b/solo/lilygo_techo_lite/platformio.ini
@@ -12,7 +12,10 @@ board_upload.maximum_size = 712704
 ; (≈ -O3 + -ffast-math), which bloats flash by ~200 KB on this feature-rich
 ; solo build. -Os keeps every feature, fits comfortably, and is actually safer
 ; for float (no fast-math reassociation). Speed is irrelevant for the UI/mesh.
-build_unflags = -Ofast
+; The offline queue (messages held for the phone app while it's away) at 128,
+; not the board's 256: on the nRF52 the 256 x 177 B left ~5 KB of heap next to
+; the on-device UI (which keeps its own history), too little for a sign buffer.
+build_unflags = -Ofast -D OFFLINE_QUEUE_SIZE=256
 build_flags =
   ${LilyGo_T-Echo-Lite.build_flags}
   -I src/helpers/ui
@@ -23,7 +26,7 @@ build_flags =
   ; -D QSPIFLASH=1
   -D BLE_PIN_CODE=123456
   ; -D BLE_DEBUG_LOGGING=1
-  -D OFFLINE_QUEUE_SIZE=256
+  -D OFFLINE_QUEUE_SIZE=128
   -D UI_RECENT_LIST_SIZE=9
   -D UI_SENSORS_PAGE=1
   ; -D MESH_PACKET_LOGGING=1
diff --git a/solo/promicro/platformio.ini b/solo/promicro/platformio.ini
index 05e5bdbb..cb049911 100644
--- a/solo/promicro/platformio.ini
+++ b/solo/promicro/platformio.ini
@@ -17,14 +17,17 @@ board_build.ldscript = boards/nrf52840_s140_v6_extrafs.ld
 board_upload.maximum_size = 712704
 ; -Ofast (the core's default) doesn't fit a feature-complete solo build;
 ; -Os fits with headroom.
-build_unflags = -Ofast
+; The offline queue (messages held for the phone app while it's away) at 128,
+; not the board's 256: on the nRF52 the 256 x 177 B left ~5 KB of heap next to
+; the on-device UI (which keeps its own history), too little for a sign buffer.
+build_unflags = -Ofast -D OFFLINE_QUEUE_SIZE=256
 build_flags = ${Promicro.build_flags}
   -I examples/companion_radio/ui-new
   -D MAX_CONTACTS=350
   -D MAX_GROUP_CHANNELS=40
   -D BLE_PIN_CODE=123456
   -D DUAL_SERIAL=1
-  -D OFFLINE_QUEUE_SIZE=256
+  -D OFFLINE_QUEUE_SIZE=128
   -D DISPLAY_CLASS=SSD1306Display
   -D FIRMWARE_SOLO_BUILD=1
   -D UI_SENSORS_PAGE=1
diff --git a/solo/wio-tracker-l1-eink/platformio.ini b/solo/wio-tracker-l1-eink/platformio.ini
index 3dd6d146..4e81ed88 100644
--- a/solo/wio-tracker-l1-eink/platformio.ini
+++ b/solo/wio-tracker-l1-eink/platformio.ini
@@ -11,8 +11,12 @@ extends = WioTrackerL1Eink
 ; (≈ -O3 + -ffast-math), which bloats flash by ~200 KB on this feature-rich
 ; solo build. -Os keeps every feature, fits comfortably, and is actually safer
 ; for float (no fast-math reassociation). Speed is irrelevant for the UI/mesh.
-build_unflags = -Ofast
+; The offline queue (messages held for the phone app while it's away) at 128,
+; not the board's 256: on the nRF52 the 256 x 177 B left ~5 KB of heap next to
+; the on-device UI (which keeps its own history), too little for a sign buffer.
+build_unflags = -Ofast -D OFFLINE_QUEUE_SIZE=256
 build_flags = ${WioTrackerL1Eink.build_flags}
+  -D OFFLINE_QUEUE_SIZE=128
   -D DUAL_SERIAL=1
   -D ENABLE_SCREENSHOT
   -Os
diff --git a/solo/wio-tracker-l1/platformio.ini b/solo/wio-tracker-l1/platformio.ini
index 97f69e82..ca33b6a8 100644
--- a/solo/wio-tracker-l1/platformio.ini
+++ b/solo/wio-tracker-l1/platformio.ini
@@ -10,8 +10,12 @@ extends = WioTrackerL1CompanionDual
 ; (≈ -O3 + -ffast-math), which bloats flash by ~200 KB on this feature-rich
 ; solo build. -Os keeps every feature, fits comfortably, and is actually safer
 ; for float (no fast-math reassociation). Speed is irrelevant for the UI/mesh.
-build_unflags = -Ofast
+; The offline queue (messages held for the phone app while it's away) at 128,
+; not the board's 256: on the nRF52 the 256 x 177 B left ~5 KB of heap next to
+; the on-device UI (which keeps its own history), too little for a sign buffer.
+build_unflags = -Ofast -D OFFLINE_QUEUE_SIZE=256
 build_flags = ${WioTrackerL1CompanionDual.build_flags}
+  -D OFFLINE_QUEUE_SIZE=128
   -D UI_HAS_JOYSTICK_UPDOWN=1
   -D ENABLE_SCREENSHOT
   -D DUAL_SERIAL=1