chore(main): release 0.4.0

To ensure we can tune things when other threads may have priority,
preventing UART processing in time for the studio UI requirements,
adjust our default UART thread priority, and allow overriding as needed.

.release-please-manifest.json

@@ -1 +1 @@
-{".":"0.3.0"}
+{".":"0.4.0"}

CHANGELOG.md

@@ -1,5 +1,100 @@
 # Changelog
 
+## [0.4.0](https://github.com/zmkfirmware/zmk/compare/v0.3.0...v0.4.0) (2026-03-20)
+
+
+### ⚠ BREAKING CHANGES
+
+* Move to zephyr v4.1 ([#3060](https://github.com/zmkfirmware/zmk/issues/3060))
+* **core:** Allow layer behaviors to "lock" layers on (https://github.com/zmkfirmware/zmk/pull/2717)
+
+### Features
+
+* Add double tap to enter bootloader functionality ([c06fa48](https://github.com/zmkfirmware/zmk/commit/c06fa48ce59e016105d79c20942d085314502d8d))
+* Add nBOOT_SEL bit setup for STM32 G0/C0 targets ([f85ec7e](https://github.com/zmkfirmware/zmk/commit/f85ec7e7a24be10f1cf59025a192569dc0b33167))
+* Add ZMK_BOARD_COMPAT Kconfig symbol, and check for it ([a23aa00](https://github.com/zmkfirmware/zmk/commit/a23aa009d7a07d67fe5609caca7372e16610f238))
+* Allow layer behaviors to "lock" layers on (https://github.com/zmkfirmware/zmk/pull/2717) ([5138c6f](https://github.com/zmkfirmware/zmk/commit/5138c6fb14783b756c5a3e61581625c700f3555b))
+* **behaviors:** Add retention boot mode to reset. ([c06fa48](https://github.com/zmkfirmware/zmk/commit/c06fa48ce59e016105d79c20942d085314502d8d))
+* **ble:** Use appearance set in the BT_DEVICE_APPEARANCE config ([#3115](https://github.com/zmkfirmware/zmk/issues/3115)) ([ad7fbfe](https://github.com/zmkfirmware/zmk/commit/ad7fbfef920d9907ca8f143e273fa9eb7d84b25a))
+* **boards/shields:** Add settings for Rpi Pico and add tester_rpi_pico shield ([#2900](https://github.com/zmkfirmware/zmk/issues/2900)) ([ccf20a1](https://github.com/zmkfirmware/zmk/commit/ccf20a1f5c1534a197d32279abbe0eaf651099d8))
+* **boards:** add support for nrf52840dongle_nrf52840 ([#3011](https://github.com/zmkfirmware/zmk/issues/3011)) ([c7fae18](https://github.com/zmkfirmware/zmk/commit/c7fae18ae122b2465080507380dd55d096edd666))
+* **core:** (Optionally) use Zephyr keyboard input devices ([c06fa48](https://github.com/zmkfirmware/zmk/commit/c06fa48ce59e016105d79c20942d085314502d8d))
+* **core:** mapper for magic bootloader values. ([c06fa48](https://github.com/zmkfirmware/zmk/commit/c06fa48ce59e016105d79c20942d085314502d8d))
+* **display:** Add thread name to dedicated display queue. ([c06fa48](https://github.com/zmkfirmware/zmk/commit/c06fa48ce59e016105d79c20942d085314502d8d))
+* **docs:** Update New Behavior Guide ([#3107](https://github.com/zmkfirmware/zmk/issues/3107)) ([e34793e](https://github.com/zmkfirmware/zmk/commit/e34793e8c7193bc868b95ec38d78f67956f759cb))
+* **endpoints:** add "no endpoint" value ([6e7e0de](https://github.com/zmkfirmware/zmk/commit/6e7e0de2b621073392816b284ab4931bee709ee8))
+* **endpoints:** add "no endpoint" value ([#3140](https://github.com/zmkfirmware/zmk/issues/3140)) ([6e7e0de](https://github.com/zmkfirmware/zmk/commit/6e7e0de2b621073392816b284ab4931bee709ee8))
+* **layouts:** Add physical layout for Redox shield ([61de01a](https://github.com/zmkfirmware/zmk/commit/61de01abb00a73349a188ef2e10ad1cd040d31b3))
+* Move to zephyr v4.1 ([#3060](https://github.com/zmkfirmware/zmk/issues/3060)) ([c06fa48](https://github.com/zmkfirmware/zmk/commit/c06fa48ce59e016105d79c20942d085314502d8d))
+* **pointing:** Handle INPUT_BTN_TOUCH codes for mouse buttons ([c06fa48](https://github.com/zmkfirmware/zmk/commit/c06fa48ce59e016105d79c20942d085314502d8d))
+* **pointing:** Release pressed keys on disconnect ([#3204](https://github.com/zmkfirmware/zmk/issues/3204)) ([24487bd](https://github.com/zmkfirmware/zmk/commit/24487bd9744f504724089f0e1cec98431a2d3333))
+* **shields:** Add Studio support to boardsource3x4 ([#3154](https://github.com/zmkfirmware/zmk/issues/3154)) ([40e06f3](https://github.com/zmkfirmware/zmk/commit/40e06f3c0084751f7ae012a71d92d5801ac3b7a0))
+* **split:** Add HID indicators and physical layout set to Wired split ([#3103](https://github.com/zmkfirmware/zmk/issues/3103)) ([7738924](https://github.com/zmkfirmware/zmk/commit/773892434931b74bdf54474b73c909779daa9471))
+
+
+### Bug Fixes
+
+* Add "optional" folder to .gitignore ([#3141](https://github.com/zmkfirmware/zmk/issues/3141)) ([c099041](https://github.com/zmkfirmware/zmk/commit/c0990410da4c0a0c3776448e8c05ca2ce8778c8a))
+* **behaviors:** correctly handle sensor rotation remainder ([#3084](https://github.com/zmkfirmware/zmk/issues/3084)) ([958fa78](https://github.com/zmkfirmware/zmk/commit/958fa788067e18c2228d016fcd826000bb8f0320))
+* **boards:** Add xiao_ble sd_partition label for nosd snippet compat ([c06fa48](https://github.com/zmkfirmware/zmk/commit/c06fa48ce59e016105d79c20942d085314502d8d))
+* **boards:** Fix pillbug board.yml to report extension ([a23aa00](https://github.com/zmkfirmware/zmk/commit/a23aa009d7a07d67fe5609caca7372e16610f238))
+* **boards:** Remove nano overlays for old nice_nano_v2 board ID. ([c06fa48](https://github.com/zmkfirmware/zmk/commit/c06fa48ce59e016105d79c20942d085314502d8d))
+* **boards:** Remove some references to old nice_nano_v2 board ID. ([c06fa48](https://github.com/zmkfirmware/zmk/commit/c06fa48ce59e016105d79c20942d085314502d8d))
+* **boards:** Retore bootloader support on XIAO BLE. ([c06fa48](https://github.com/zmkfirmware/zmk/commit/c06fa48ce59e016105d79c20942d085314502d8d))
+* **ci:** Better safeguards for ZMK variant build check ([#3277](https://github.com/zmkfirmware/zmk/issues/3277)) ([8feeb52](https://github.com/zmkfirmware/zmk/commit/8feeb52eafc716c1697cfe0515e98b78281c3543))
+* **ci:** disable nrf5340dk from being built in our CI ([#3066](https://github.com/zmkfirmware/zmk/issues/3066)) ([522971f](https://github.com/zmkfirmware/zmk/commit/522971f41d62d7e5d6664eb61c84d190781feeb9))
+* **ci:** Fix release please template bump ([#3021](https://github.com/zmkfirmware/zmk/issues/3021)) ([f3233c1](https://github.com/zmkfirmware/zmk/commit/f3233c1b60e4cb4c095572740bcbcaf7111eb804))
+* **ci:** Pin @actions/artifact to a compatible release ([#3230](https://github.com/zmkfirmware/zmk/issues/3230)) ([ada1542](https://github.com/zmkfirmware/zmk/commit/ada1542940c3a01c0866c9fe9c30f489bc087328))
+* **ci:** Prevent slash characters in artifact names. ([c06fa48](https://github.com/zmkfirmware/zmk/commit/c06fa48ce59e016105d79c20942d085314502d8d))
+* **ci:** Skip build on empty build matrix ([#3271](https://github.com/zmkfirmware/zmk/issues/3271)) ([df2e979](https://github.com/zmkfirmware/zmk/commit/df2e979d7e03ba84a503e3d90975a599d484b9e0)), closes [#3179](https://github.com/zmkfirmware/zmk/issues/3179)
+* **core:** Don't force CBPRINTF_NANO, for proper formatting. ([c06fa48](https://github.com/zmkfirmware/zmk/commit/c06fa48ce59e016105d79c20942d085314502d8d))
+* **core:** Generate correct keymap layer names for all builds ([#3047](https://github.com/zmkfirmware/zmk/issues/3047)) ([0b5a103](https://github.com/zmkfirmware/zmk/commit/0b5a103c187ad337b9f50d824667866c4d7252e1)), closes [#3045](https://github.com/zmkfirmware/zmk/issues/3045)
+* **core:** One tick kscan wait on RP2350 ([#3255](https://github.com/zmkfirmware/zmk/issues/3255)) ([9278505](https://github.com/zmkfirmware/zmk/commit/9278505975759e9cf01b4e6e8ead359b14a11400))
+* **core:** Set a system work queue stack size of 2048 by default ([c06fa48](https://github.com/zmkfirmware/zmk/commit/c06fa48ce59e016105d79c20942d085314502d8d))
+* **core:** support magic bootloader values for nRF52833 ([#3163](https://github.com/zmkfirmware/zmk/issues/3163)) ([308de56](https://github.com/zmkfirmware/zmk/commit/308de56fb938057da7648a411ce0dce780dfc3f1))
+* Disable Nordic dt-bindings header checks. ([c06fa48](https://github.com/zmkfirmware/zmk/commit/c06fa48ce59e016105d79c20942d085314502d8d))
+* **display:** Adjust stack sizes for display usage. ([c06fa48](https://github.com/zmkfirmware/zmk/commit/c06fa48ce59e016105d79c20942d085314502d8d))
+* **display:** Fix setting the small font for the mono theme. ([c06fa48](https://github.com/zmkfirmware/zmk/commit/c06fa48ce59e016105d79c20942d085314502d8d))
+* **display:** port nice!view display code ([c06fa48](https://github.com/zmkfirmware/zmk/commit/c06fa48ce59e016105d79c20942d085314502d8d))
+* **docs:** Improve ZMK setup instructions ([#3209](https://github.com/zmkfirmware/zmk/issues/3209)) ([354cff9](https://github.com/zmkfirmware/zmk/commit/354cff9c36b49eee6abbb8a61e6b927539aebbf2))
+* **docs:** Tweak layer tap example to be clearer ([#3023](https://github.com/zmkfirmware/zmk/issues/3023)) ([919bce7](https://github.com/zmkfirmware/zmk/commit/919bce7962db78139415ccf0e80fb858c89adb3d))
+* Don't enable ZMK Display by default for a few shields ([c06fa48](https://github.com/zmkfirmware/zmk/commit/c06fa48ce59e016105d79c20942d085314502d8d))
+* **endpoints:** Add endpoint setting upgrade ([6e7e0de](https://github.com/zmkfirmware/zmk/commit/6e7e0de2b621073392816b284ab4931bee709ee8))
+* Fix redundant const warning ([#3139](https://github.com/zmkfirmware/zmk/issues/3139)) ([8987f39](https://github.com/zmkfirmware/zmk/commit/8987f3979d7877114ede2f34edb5570a6b454460))
+* **hid:** initialize missing d_scroll_x field in mouse report ([#3196](https://github.com/zmkfirmware/zmk/issues/3196)) ([abce9de](https://github.com/zmkfirmware/zmk/commit/abce9deab76124d72c61a824aaa1affc3dbc1260))
+* **keymap:** Fix overflow in get/set bindings ([#3205](https://github.com/zmkfirmware/zmk/issues/3205)) ([ab46f48](https://github.com/zmkfirmware/zmk/commit/ab46f48dde8aa70e44a2fc2d2a1b81ae703d4981))
+* nice!view built-in widgets render failure from insufficient memory ([#3243](https://github.com/zmkfirmware/zmk/issues/3243)) ([536375e](https://github.com/zmkfirmware/zmk/commit/536375e45ef6d01a9c194803525bf9dd5e119421)), closes [#3219](https://github.com/zmkfirmware/zmk/issues/3219)
+* **pointing:** Refactor for changes to input API ([c06fa48](https://github.com/zmkfirmware/zmk/commit/c06fa48ce59e016105d79c20942d085314502d8d))
+* Refactor for new Zephyr PM API ([c06fa48](https://github.com/zmkfirmware/zmk/commit/c06fa48ce59e016105d79c20942d085314502d8d))
+* Remove usage of renamed Kconfig from core coverage. ([c06fa48](https://github.com/zmkfirmware/zmk/commit/c06fa48ce59e016105d79c20942d085314502d8d))
+* replace removed `K_THREAD_STACK_MEMBER` with `K_KERNEL_STACK_MEMBER` ([#3218](https://github.com/zmkfirmware/zmk/issues/3218)) ([f6c629e](https://github.com/zmkfirmware/zmk/commit/f6c629e895bbe3957ec243afb80b11e1e4b4e503))
+* **sensors:** Initialize sensor data to 0 before fetching. ([c06fa48](https://github.com/zmkfirmware/zmk/commit/c06fa48ce59e016105d79c20942d085314502d8d))
+* Set default transport according to enabled transports ([6e7e0de](https://github.com/zmkfirmware/zmk/commit/6e7e0de2b621073392816b284ab4931bee709ee8))
+* **shields:** Proper transparent binding in sofle raise layer ([#3238](https://github.com/zmkfirmware/zmk/issues/3238)) ([5cfc67a](https://github.com/zmkfirmware/zmk/commit/5cfc67a33402b24ab893b8d71cef1af2a869adbb))
+* **split:** correct async UART RX buffer definition ([#3193](https://github.com/zmkfirmware/zmk/issues/3193)) ([36dbf46](https://github.com/zmkfirmware/zmk/commit/36dbf467644d4b4b6b9176241d42261d27fb18f2))
+* **split:** int to pointer cast in bas proxy ([#3105](https://github.com/zmkfirmware/zmk/issues/3105)) ([ece2ce1](https://github.com/zmkfirmware/zmk/commit/ece2ce11b8c7245fbe2b4e41ec9fa7a870632e6c))
+* **split:** Properly return from command handler ([#3120](https://github.com/zmkfirmware/zmk/issues/3120)) ([d32ffb0](https://github.com/zmkfirmware/zmk/commit/d32ffb0a335ece70a9ce3dc3ce014676534ee99b))
+* **split:** Use correct Kconfig for bumping TX buffers for discovery ([#3216](https://github.com/zmkfirmware/zmk/issues/3216)) ([9490391](https://github.com/zmkfirmware/zmk/commit/9490391e1e4010c83291d437b7f9a71ace244581)), closes [#3156](https://github.com/zmkfirmware/zmk/issues/3156)
+* **studio:** Allow setting UART RPC thread priority ([#3290](https://github.com/zmkfirmware/zmk/issues/3290)) ([e4fb39d](https://github.com/zmkfirmware/zmk/commit/e4fb39d4a6514fe90d44b1570f908bddc5df0ad2))
+* **studio:** avoid decoding buffer overflow ([#3185](https://github.com/zmkfirmware/zmk/issues/3185)) ([70ab6b2](https://github.com/zmkfirmware/zmk/commit/70ab6b243a90b556d113fcdd0c8de1ef3dccdc1e))
+* **studio:** Correct `memset` usage. ([c06fa48](https://github.com/zmkfirmware/zmk/commit/c06fa48ce59e016105d79c20942d085314502d8d))
+* **studio:** Correct usage of thread analyzer API ([c06fa48](https://github.com/zmkfirmware/zmk/commit/c06fa48ce59e016105d79c20942d085314502d8d))
+* **studio:** Properly serialize GATT RPC indications. ([c06fa48](https://github.com/zmkfirmware/zmk/commit/c06fa48ce59e016105d79c20942d085314502d8d))
+* **tests:** Fix BLE test to account for Zephyr changes ([c06fa48](https://github.com/zmkfirmware/zmk/commit/c06fa48ce59e016105d79c20942d085314502d8d))
+* **underglow:** Remove use of removed Kconfig WS2812 symbol ([c06fa48](https://github.com/zmkfirmware/zmk/commit/c06fa48ce59e016105d79c20942d085314502d8d))
+* **usb:** Adjust Kconfig settings for USB. ([c06fa48](https://github.com/zmkfirmware/zmk/commit/c06fa48ce59e016105d79c20942d085314502d8d))
+* **usb:** Prevent unexpected USB disconnection caused by USB SOF ([#3070](https://github.com/zmkfirmware/zmk/issues/3070)) ([118359c](https://github.com/zmkfirmware/zmk/commit/118359c83efa0758144489fd5e12cc6f5bdbad4c))
+
+
+### Documentation
+
+* Added documentation note on locking layers ([5138c6f](https://github.com/zmkfirmware/zmk/commit/5138c6fb14783b756c5a3e61581625c700f3555b))
+
+
+### Code Refactoring
+
+* **core:** Allow layer behaviors to "lock" layers on (https://github.com/zmkfirmware/zmk/pull/2717) ([5138c6f](https://github.com/zmkfirmware/zmk/commit/5138c6fb14783b756c5a3e61581625c700f3555b))
+
 ## [0.3.0](https://github.com/zmkfirmware/zmk/compare/v0.2.1...v0.3.0) (2025-08-01)
 
 

app/VERSION

@@ -3,7 +3,7 @@ VERSION_MAJOR = 0
 # x-release-please-end
 
 # x-release-please-start-minor
-VERSION_MINOR = 3
+VERSION_MINOR = 4
 # x-release-please-end
 
 # x-release-please-start-patch

app/src/studio/Kconfig

@@ -59,11 +59,20 @@ config ZMK_STUDIO_TRANSPORT_UART
     select RING_BUFFER
     default y if $(dt_chosen_enabled,$(DT_CHOSEN_ZMK_STUDIO_RPC_UART))
 
+if ZMK_STUDIO_TRANSPORT_UART
+
 config ZMK_STUDIO_TRANSPORT_UART_RX_STACK_SIZE
     int "RX Stack Size"
     depends on !UART_INTERRUPT_DRIVEN
     default 512
 
+config ZMK_STUDIO_TRANSPORT_UART_RX_PRIORITY
+    int "RX Thread Priority"
+    depends on !UART_INTERRUPT_DRIVEN
+    default 9
+
+endif
+
 config ZMK_STUDIO_TRANSPORT_BLE
     bool "BLE (GATT)"
     select RING_BUFFER
@@ -71,9 +80,12 @@ config ZMK_STUDIO_TRANSPORT_BLE
     depends on ZMK_BLE
     default y
 
+
 config BT_CONN_TX_MAX
     default 64 if ZMK_STUDIO_TRANSPORT_BLE
 
+if ZMK_STUDIO_TRANSPORT_BLE
+
 config ZMK_STUDIO_TRANSPORT_BLE_PREF_LATENCY
     int "BLE Transport preferred latency"
     default 10
@@ -81,6 +93,8 @@ config ZMK_STUDIO_TRANSPORT_BLE_PREF_LATENCY
       When the studio UI is connected, a lower latency can be requested in order
       to make the interactions between keyboard and studio faster.
 
+endif
+
 endmenu
 
 config ZMK_STUDIO_RPC_THREAD_STACK_SIZE

app/src/studio/uart_rpc_transport.c

@@ -65,7 +65,7 @@ static void uart_rx_main(void) {
 }
 
 K_THREAD_DEFINE(uart_transport_read_thread, CONFIG_ZMK_STUDIO_TRANSPORT_UART_RX_STACK_SIZE,
-                uart_rx_main, NULL, NULL, NULL, K_LOWEST_APPLICATION_THREAD_PRIO, 0, 0);
+                uart_rx_main, NULL, NULL, NULL, CONFIG_ZMK_STUDIO_TRANSPORT_UART_RX_PRIORITY, 0, 0);
 
 #endif