Installation

Start

Installation

Requirements

• Rust 1.88 or newer (edition 2024). Check with rustc --version.
• A firmware already using embassy, or a host binary using embassy-executor’s std support. The supervisor tracks these crate versions: embassy-executor 0.10, embassy-sync 0.8, embassy-time 0.5. Because embassy is pre-1.0, your application must resolve to compatible minor versions. If you use a git or patched embassy, make sure the supervisor resolves to the same revision through your [patch] section.
• No allocator needed. No unsafe in the library (#![forbid(unsafe_code)]); two optional features can emit small, documented unsafe helpers into your crate, and both are opt-in.

Add the crate

cargo add embassy-supervisor

The macros feature is on by default. It provides the supervisor_graph! declaration macro, re-exported from the crate root. Everything else the supervisor can do is opt-in:

[dependencies]
embassy-supervisor = "0.8"

[features]
# an example application feature that turns on supervisor capabilities
default = ["supervised"]
supervised = [
    "embassy-supervisor/readiness",
    "embassy-supervisor/liveness-monitor",
    "embassy-supervisor/control",
    "embassy-supervisor/pool",
]

Pick features by what your graph actually uses. Both control and pool add code to the supervisor’s driver loop that runs whether or not a graph uses it, so a graph with no runtime control and no pools should not carry either. A wrong choice is loud: declaring a pool without the feature, or calling a control verb without it, produces an error that names the feature.

The full list with defaults is in the feature reference.

Logging backends

The supervisor logs lifecycle events through an optional backend:

• defmt for on-target logging (the usual choice with embassy and RTT),
• log for hosted or std consumers.

With neither enabled the log calls compile to nothing. If you want stale reports and bring-up lines visible anywhere, enable one.

Release profile

For smaller, better optimized firmware, set this profile in the workspace root’s Cargo.toml:

[profile.release]
debug = 2
lto = "fat"
opt-level = "s"
codegen-units = 1

• lto = "fat" runs link-time optimization across the whole dependency tree, letting the compiler inline and eliminate code across crate boundaries.
• codegen-units = 1 compiles each crate as one unit instead of parallel chunks, enabling more thorough optimization at the cost of compile time.
• opt-level = "s" optimizes for size rather than speed, the usual embedded budget.
• debug = 2 keeps full debug symbols in the ELF for probe-rs and GDB. It does not change codegen, and debug sections are not flashed to the device.

Verify the toolchain

rustup target add thumbv7em-none-eabihf   # or your MCU's target
cargo build

The library itself is HAL-free, so it builds for any target embassy builds for, including x86_64-unknown-linux-gnu for host tests.

Next

Your first graph takes the crate from installed to running.