Releases: zephyrproject-rtos/zephyr
Zephyr 4.3.0
We are pleased to announce the release of Zephyr version 4.3.0 🎉🪁
For a detailed overview of some of the highlights of this release, you may check out the dedicated article that was posted on the Zephyr blog, and its accompanying video:
Major enhancements with this release include:
USB Device "Next" stack is now the default
The new USB device stack, built on the modern UDC (USB Device Controller) API, replaces the legacy stack and brings support for multiple simultaneous controllers, runtime configuration, and overall better architecture. The legacy stack is now deprecated and will be removed in Zephyr 4.5.
CPU load and dynamic frequency scaling subsystems
A new experimental CPU frequency scaling subsystem enables dynamic, policy-driven, clock adjustments to balance power consumption and performance Alongside it, a new cpu_load subsystem allows users to obtain CPU usage metrics based on scheduler statistics, which can be used to drive the frequency scaling policy.
Instrumentation Subsystem
A new instrumentation subsystem simplifies tracing and profiling of Zephyr applications by leveraging compiler-managed function instrumentation, allowing the recording of call-graph traces and statistical profiles at runtime.
OCPP 1.6 library
A new OCPP (Open Charge Point Protocol) library enables EV charging station development with Zephyr. The library implements OCPP 1.6 Charge Point functionality over WebSocket, supporting core profile operations including authorization, transaction management, and meter value reporting for communication with Central System servers.
Twister Display Harness
Twister can now validate on-target display output by capturing frames from a USB video camera and matching them against pre-recorded visual "fingerprints".
Developer Experience Improvements
Several new tools have been introduced to help with common development and troubleshooting tasks:
- dtdoctor to help diagnose Devicetree build errors.
- traceconfig build target to help understand where Kconfig symbols come from and their final values.
- Interactive footprint charts to visualize RAM/ROM usage of an application.
Expanded Board Support
Support for 105 new boards and 39 new shields has been added in this release.
Full Release Notes
The full release notes and list of major changes since the last release can be found here.
An overview of the changes required or recommended when migrating your application from Zephyr
v4.2.0 to Zephyr v4.3.0 can be found in the separate migration guide.
Release Lifecycle
The 4.3 release will be supported until October 15th, 2026.
Additional release information may be found on the Release Management Wiki.
Thanks 🙏
Many thanks to the 795 individuals who contributed to this release! 🚀
Johan, Chris, and the Zephyr Release Team
Zephyr v4.3.0-rc3
jhedberg
Johan Hedberg
Hi Zephyr developers!
The third release candidate for Zephyr 4.3.0 has been tagged:
https://github.com/zephyrproject-rtos/zephyr/releases/tag/v4.3.0-rc3
The merge window for features and enhancements remains closed until 4.3.0 is released.
We continue in the stabilization phase, and only blocker bug-fixes and documentation patches may be merged to the main branch. As a reminder to maintainers- please send PRs to update the release notes and migration guide for any areas you manage.
You may continue to submit pull requests for new features to gather feedback early or collaborate with others, but the release team would like to encourage everyone to focus on testing, fixing any blocker bugs found, and finalizing release notes.
Other bugs which are not critical enough to be categorized as blocker, but should still be part of 4.3 should be marked with the backport v4.3-branch label so they can be considered for the first dot release.
Regards,
The Zephyr Release Team
Release milestone dates:
https://github.com/zephyrproject-rtos/zephyr/wiki/Release-Management
Release process:
https://docs.zephyrproject.org/latest/project/release_process.html
Blocker bugs process:
https://docs.zephyrproject.org/latest/project/release_process.html#blocker-bugs
Zephyr v4.3.0-rc2
Hello Zephyr developers!
The second release candidate for Zephyr 4.3.0 has been tagged:
https://github.com/zephyrproject-rtos/zephyr/releases/tag/v4.3.0-rc2
We are still in the stabilization phase, and only bug-fix, documentation and stabilization patches may be merged to the main branch. Matching bug reports for bugfix pull requests are now required.
You may continue to submit pull requests for new features to gather feedback early or collaborate with others, but the release team would like to encourage everyone to focus on testing, documentation improvements and fixing bugs. Any feature pull requests should be tagged with the 4.4.0 release milestone.
We anticipate the coming weeks to be very busy reducing overall bug count. Please give this RC a test drive and report any issues on supported platforms (with a PR if possible).
Release milestone dates:
https://github.com/zephyrproject-rtos/zephyr/wiki/Release-Management
Release process:
https://docs.zephyrproject.org/latest/project/release_process.html
Regards,
The release team.
Zephyr v4.3.0-rc1
jhedberg
Johan Hedberg
Hello Zephyr developers!
The first release candidate for Zephyr 4.3.0 has been tagged:
https://github.com/zephyrproject-rtos/zephyr/releases/tag/v4.3.0-rc1
The merge window for features and enhancements is now closed for this release, and it will remain closed until 4.3.0 is released.
We are now in the stabilization phase, and only bug-fix, documentation and stabilization patches may be merged to the main branch. Additional features and enhancements, including new hardware support for the 4.3.0 release requires approval by the TSC. While matching bug reports for pull requests are welcome and encouraged, we will not enforce this until rc2, if the pull request is clearly a bug fix.
You may continue to submit pull requests for new features to gather feedback early or collaborate with others, but the release team would like to encourage everyone to focus on testing, documentation improvements and fixing bugs.
We anticipate the coming weeks to be very busy reducing overall bug count. Please give this RC a test drive and report any issues on supported platforms (with a PR if possible).
Release milestone dates:
https://github.com/zephyrproject-rtos/zephyr/wiki/Release-Management
Release process:
https://docs.zephyrproject.org/latest/project/release_process.html
Regards,
The release team.
Zephyr 4.2.1
danieldegrasse
Daniel DeGrasse
This is a bugfix release for Zephyr 4.2.0. The following issues are addressed by this release:
- #96197 gPTP sample does not boot with NUCLEO-H563ZI
- #92393 LIS2DUX12 setting incorrect ODR configuration
- #93011 stm32u0: interrupt vectors for lpuart1 and lpuart2 are wrong in device tree
- #93220 Twister tests with coverage enabled crash during startup
- #93265 Stm32u5x: clock disable in sleep mode fix causing USB HS device initialization stalls
- #93342 doc: Documentation issue in 'connectivity/networking/api/tftp'
- #93350 net: tcp: keep-alive "pings" are no longer acknowledged with v4.2.0
- #93364 tests/subsys/llext fails after tagging 4.2
- #93424 Missing break after IPV6_MULTICAST_IF option processing
- #93445 STM32U535/545: dtc error for node wkup-pin@8 referencing non-existent port gpiof
- #93519 drivers: nxp_lpspi: Large performance degradation
- #93594 Nicla Vision has bad I2C address for VL53L1X sensor
- #93611 doc: Documentation issue in 'releases/release-notes-4.2'
- #93790 drivers: console: posix_arch_console: build warning with
CONFIG_PRINTK=n - #93792 USB samples not working on
max32690evkit - #93831 drivers: can: nrf: fix invalid pointer leading to undef behavior
- #93839 I3C: STM32: Has a Mutex deadlock on DAA Failure
- #94000 EXT2 fs_stat on mount point fails with a NULL pointer dereference.
- #94047 Shell device name tab completion for regulator parents show incorrect names
- #94063 SPI loopback tests failing on MAX32 SoCs.
- #94083 stm32: u3: low clock frequency for the RNG periphera
- #94093 Build error when OCRAM node is disabled in device tree (status = "disabled") [NXP RT1061]
- #94107 ppp link-layer address configuration is wrong
- #94325 iar: incorrect assembler optimzation flag
- #94473 LVGL Widgets Demo stopped working in v4.1 on mimxrt1060_evk@A
- #94702 Locally Administered Address (LAA) bit missing for STM32 ethernet driver
- #94703 Locally Administered Address (LAA) bit set on wrong index for NXP i.MX ethernet driver
- #94774 modules/picolibc: Roll back unnecessary changes, synchronize with SDK 0.17.4
- #94812
nocachedata is included in ROM section - #94842 iar: Zephyr 4.2 fails with IAR EWARM 9.70.1
- #94954 Spurious error log "No valid legacy adv to resume" in bt_hci_le_enh_conn_complete when using bt_le_ext_adv_start()
- #95113 gpio_pin_get_config for STM32 returns wrong flags value for input pins
- #95146 i2c: stm32: non-RTIO driver fixes on PM and on STM32F7 from Zephyr v4.3
- #95297 Links to the pyOCD repository are outdated
- #95456 Zephyr Netstack buffer leaks
- #95580 Picolibc module and SDK are not in sync for Zephyr 4.2.0
- #95721 Boards documentation: "arm" Architecture not specified at least for STM32MP13 and STM32N6 boards
- #95724 drivers: i2c: stm32: build error when using DMAs with st,stm32-i2c-v2 driver
- #95768 Possible TCP connection leak when creating a socket
- #95850 Applications do not watch MCUboot key file for changes
- #96087 TCP connection sends an incorrect seqnum FIN message
- #96172 arch: arm: switch to privilege stack in SVC handler
- #96768 incorrect i2c3 base address on stm32f303Xe
Zephyr 4.2.0
danieldegrasse
Daniel DeGrasse
We are pleased to announce the release of Zephyr 4.2.0!
For a detailed overview of some of the highlights of this release, you may check out the dedicated article that was just posted on the Zephyr blog, and its accompanying video:
Major enhancements with this release include:
Initial Support for Renesas RX
The Renesas RX architecture is now supported, including a QEMU-based board target.
USB Video Class Driver
The USB device stack now supports USB Video Class (UVC) allowing camera devices and other image/video sources to be exposed as standard USB video devices. See USB Video webcam to get started.
Twister Power Harness
A new Twister harness enables measurement of the power consumption of the device under test and ensures it remains within a given tolerance.
MQTT 5.0
The networking stack now includes full support for the MQTT 5.0 protocol.
Bluetooth Classic improvements
The Bluetooth Classic stack now includes support for Hands-Free Profile (HFP) for both Audio Gateway (AG) and Hands-Free (HF) roles.
Zbus
The Zbus library graduates to stable status with the release of API version v1.0.0.
Expanded Board Support
Support for 96 new boards and 22 new shields has been added in this release.
An overview of the changes required or recommended when migrating your application from Zephyr v4.1.0 to Zephyr v4.2.0 can be found in the separate migration guide.
The 4.2 release will be supported until March 20th, 2026
Regards,
Dan and Dan, and the full Zephyr Release Team
Zephyr v4.2.0-rc3
danieldegrasse
Daniel DeGrasse
The third release candidate for Zephyr 4.2.0 has been tagged:
https://github.com/zephyrproject-rtos/zephyr/releases/tag/v4.2.0-rc3
The merge window for features and enhancements remains closed until 4.2.0 is released.
We continue in the stabilization phase, and only blocker bug-fixes and documentation patches may be merged to the main branch. As a reminder to maintainers- please send PRs to update the release notes and migration guide for any areas you manage.
You may continue to submit pull requests for new features to gather feedback early or collaborate with others, but the release team would like to encourage everyone to focus on testing, fixing any blocker bugs found, and finalizing release notes.
Other bugs which are not critical enough to be categorized as blocker, but should still be part of 4.2 should be marked with the backport v4.2-branch label so they can be considered for the first dot release.
Dan and Dan, and the full Zephyr Release Team
Release milestone dates:
https://github.com/zephyrproject-rtos/zephyr/wiki/Release-Management
Release process:
https://docs.zephyrproject.org/latest/project/release_process.html
Blocker bugs process:
https://docs.zephyrproject.org/latest/project/release_process.html#blocker-bugs
Zephyr v4.2.0-rc2
danieldegrasse
Daniel DeGrasse
The second release candidate for Zephyr 4.2.0 has been tagged:
https://github.com/zephyrproject-rtos/zephyr/releases/tag/v4.2.0-rc2
The merge window for features and enhancements remains closed until 4.2.0 is released.
We continue in the stabilisation phase, and only bug-fix, documentation and stabilisation patches may be merged to the main branch.
You may continue to submit pull requests for new features to gather feedback early or collaborate with others, but the release team would like to encourage everyone to focus on testing, fixing and helping triage bugs.
Release milestone dates:
https://github.com/zephyrproject-rtos/zephyr/wiki/Release-Management
Release process:
https://docs.zephyrproject.org/latest/project/release_process.html
Dan and Dan, and the full Zephyr Release Team
Zephyr v4.2.0-rc1
danieldegrasse
Daniel DeGrasse
The first release candidate for Zephyr 4.2.0 has been tagged:
https://github.com/zephyrproject-rtos/zephyr/releases/tag/v4.2.0-rc1
The merge window for features and enhancements is now closed for this release,
and it will remain closed until 4.2.0 is released.
We are now in the stabilisation phase, and only bug-fix, documentation, and
stabilisation patches may be merged to the main branch. Additional features and
enhancements, including new hardware support for the 4.2.0 release requires
approval by the TSC.
You may continue to submit pull requests for new features to gather feedback
early or collaborate with others, but the release team would like to encourage
everyone to focus on testing, documentation improvements and fixing bugs.
We anticipate the coming weeks to be very busy reducing overall bug count.
Please give this RC a test drive and report any issues on supported platforms
(with a PR if possible).
Release milestone dates:
https://github.com/zephyrproject-rtos/zephyr/wiki/Release-Management
Release process:
https://docs.zephyrproject.org/latest/project/release_process.html
Dan and Dan, and the full Zephyr Release Team
Zephyr 4.1.0
We are pleased to announce the release of Zephyr 4.1.0!
For a detailed overview of some of the highlights of this release, you may check out the dedicated article that was posted on the Zephyr blog, and its accompanying video.
Major enhancements with this release include:
Performance improvements
Multiple performance improvements of core Zephyr kernel functions have been implemented, benefiting all supported hardware architectures.
An official port of the thread_metric RTOS benchmark has also been added to make it easier for developers to measure the performance of Zephyr on their hardware and compare it to other RTOSes.
Experimental support for IAR compiler
IAR Arm Toolchain can now be used to build Zephyr applications. This is an experimental feature that is expected to be improved in future releases.
Initial support for Rust on Zephyr
It is now possible to write Zephyr applications in Rust. Rust Language Support is available through an optional Zephyr module, and several code samples are available as a starting point.
USB MIDI Class Driver
Introduction of a new USB MIDI 2.0 device driver, allowing Zephyr devices to communicate with MIDI controllers and instruments over USB.
Expanded Board Support
Support for 70 new boards and 11 new shields has been added in this release.
This includes highly popular boards such as Raspberry Pi Pico 2 and WCH CH32V003EVT, several boards with CAN+USB capabilities making them good candidates for running the Zephyr-based open source CANnectivity firmware, and dozens of other boards across all supported architectures.
The full release notes and list of major changes since the last release can be found here: https://docs.zephyrproject.org/latest/releases/release-notes-4.1.html
An overview of the changes required or recommended when migrating your application from Zephyr v4.0.0 to Zephyr v4.1.0 can be found in the migration guide:https://docs.zephyrproject.org/latest/releases/migration-guide-4.1.html
This 4.1 release will be supported until November 14th, 2025.
Many thanks to the 678(!) individuals who contributed to this release! 🚀
Benjamin and Fabio.