Zephyr Project has released version 4.1 of its RTOS, bringing notable improvements in kernel performance, toolchain support, and hardware compatibility. While not an LTS release, it introduces key updates aimed at enhancing developer experience and system efficiency.

One of the main focuses of this release is performance. Extensive work went into addressing kernel bottlenecks and expanding benchmark coverage. Notably, Zephyr now includes an official port of the thread_metric RTOS benchmark suite, enabling consistent measurement of operations such as thread handling, interrupt processing, and synchronization.

Performance improvement since Zephyr 3.7 LTS
(click image to enlarge)

Comparative benchmarks show that Zephyr 4.1 performs significantly better than the 3.7 LTS release. For developers working with cooperative scheduling, enabling the multi-queue (MULTIQ) ready queue can further enhance performance—though at the cost of increased code size and RAM usage.

Zephyr 4.1 also performs competitively compared to other open-source RTOSes, effectively narrowing the gap with Eclipse ThreadX and outperforming FreeRTOS in several test cases.

Zephyr 4.1 adds experimental support for the IAR Embedded Workbench toolchain, a commercial development suite recognized for highly optimized output. Developers can now set ZEPHYR_TOOLCHAIN_VARIANT=iar and configure the path to their IAR installation to build Zephyr projects with IAR’s compiler. Build flags for size and speed optimizations are automatically mapped, streamlining the integration process.

Comparing other open source real-time operating systems with Zephyr
(click image to enlarge)

This early-stage support is expected to mature over time, further improving portability and code quality through enhanced compiler diagnostics.

This release also introduces experimental support for developing Zephyr applications in Rust. A new optional module allows Rust code to be used in Zephyr projects, providing access to the language’s strong memory safety and concurrency models. Interest in this integration is growing within the Zephyr community, especially among developers exploring safer embedded development approaches.

A USB MIDI 2.0 device driver has been added, enabling real-time audio and music applications. A sample application is included and compatible with most boards that support the USB device stack. Even before its official inclusion, the driver had been adopted by developers to build Zephyr-based musical instruments.

Zephyr 4.1 brings support for over 70 additional development boards. Highlights include:

• Raspberry Pi Pico 2 and Pico W: Now supported with added Wi-Fi driver support for the W variant.
• WCH CH32V003EVT: A low-cost RISC-V chip gaining popularity among makers.
• CAN+USB Boards: Boards like the canbardo, Makerbase MKS CANable V2.0, and FYSETC UCAN are now supported, ideal for USB-to-CAN adapter development using Zephyr-based firmware.

This expansion extends Zephyr’s applicability across a broader range of commercial and hobbyist projects.

Zephyr 4.1 Board Catalog Filter
(click image to enlarge)

Shell commands in Zephyr 4.1 now feature improved auto-completion, with commands like sensor get only displaying relevant devices—making interaction more efficient. Additionally, the board catalog now supports filtering by hardware capabilities such as display, SD card support, or processor architecture. Many board READMEs now include auto-generated capability summaries based on Devicetree information.

Further Information

Development for Zephyr 4.2 is already underway, with the merge window opening soon. According to the announcement, hundreds of pull requests are already in queue, reflecting strong community momentum.

For the complete list of updates, performance data, and technical documentation, visit the official Zephyr Project release notes.