What causes "a bin target must be available for `cargo run`" in rust-lang/cargo?

Add a binary target: create `src/main.rs` or add a `[[bin]]` section in Cargo.toml.

a bin target must be available for `cargo run`

Error message

a bin target must be available for `cargo run`

What it means

Thrown by `cargo run` when no binary target (`[bin]`) is found in the selected package(s) and no specific filter (like `--bin` or `--example`) is provided. `cargo run` requires at least one executable target to run.

Solutions

Add a binary target: create `src/main.rs` or add a `[[bin]]` section in Cargo.toml.
If you meant to test, use `cargo test` or `cargo run --example <name>` instead.
Switch to a crate that actually has a binary target.

Example fix

# Cargo.toml — add a binary target
[[bin]]
name = "my_app"
path = "src/main.rs"

# Create src/main.rs
fn main() {
    println!("Hello, world!");
}

Defensive patterns

Strategy: validation

Validate before calling

fn workspace_has_binary_target(pkg: &cargo::core::Package) -> bool {
    pkg.manifest().targets().iter().any(|t| t.is_bin())
}

Prevention

Ensure the crate has at least one `[[bin]]` target or `src/main.rs`.
Use `cargo run --example <name>` to run examples instead.
Check `cargo run` is being invoked in the right package (use `-p <pkg>`).

When it happens

Trigger: Running `cargo run` on a crate that has only a `[lib]` target and no `[bin]` targets, or where all potential binary targets have been filtered out. The `bins` vector is empty and `!options.filter.is_specific()`.

Common situations: A library-only crate with no `main.rs` or `src/bin/`; running `cargo run` in a workspace root; a crate whose binary was removed or renamed.

Related errors

AI-assisted analysis of rust-lang/cargo@eb98b54bc9 (2026-08-11). Data as JSON: /api/errors/28fe3618fb48b2ea. Report an issue: GitHub.

Appendix: source

Thrown at src/ops/cargo_run.rs:43

    let packages = options.spec.get_packages(ws)?;
    let bins: Vec<_> = packages
        .into_iter()
        .flat_map(|pkg| {
            iter::repeat(pkg).zip(pkg.manifest().targets().iter().filter(|target| {
                !target.is_lib()
                    && !target.is_custom_build()
                    && if !options.filter.is_specific() {
                        target.is_bin()
                    } else {
                        options.filter.target_run(target)
                    }
            }))
        })
        .collect();

    if bins.is_empty() {
        if !options.filter.is_specific() {
            anyhow::bail!("a bin target must be available for `cargo run`")
        } else {
            // This will be verified in `cargo_compile`.
        }
    }

    if bins.len() == 1 {
        let target = bins[0].1;
        if let TargetKind::ExampleLib(..) = target.kind() {
            anyhow::bail!(
                "example target `{}` is a library and cannot be executed",
                target.name()
            )
        }
    }

    if bins.len() > 1 {
        if !options.filter.is_specific() {
            let mut names: Vec<&str> = bins

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