Failed to load '{}': {e} To improve iteration speed, some f

Error message

Failed to load '{}': {e}

To improve iteration speed, some files are not embedded but loaded at runtime, at the cost of making the binary non-portable. To fix this, build with codegen_embed.

What it means

Error "Failed to load '{}': {e} To improve iteration speed, some files are not embedded but loaded at runtime, at the cost of making the binary non-portable. To fix this, build with codegen_embed." thrown in oven-sh/bun.

Source

Thrown at src/bun_core/util.rs:2960

#[doc(hidden)]
pub fn __runtime_embed_load(kind: EmbedKind, sub: &'static str) -> String {
    // SAFETY: CODEGEN_PATH/BASE_PATH originate from `option_env!` (`&'static str`
    // → bytes), so the bytes are valid UTF-8 by construction.
    let from = |b: &'static [u8]| unsafe { ::core::str::from_utf8_unchecked(b) };
    let mut p = match kind {
        EmbedKind::Codegen | EmbedKind::CodegenEager => {
            ::std::path::PathBuf::from(from(crate::build_options::CODEGEN_PATH))
        }
        EmbedKind::Src | EmbedKind::SrcEager => {
            let mut b = ::std::path::PathBuf::from(from(crate::build_options::BASE_PATH));
            b.push("src");
            b
        }
    };
    p.push(sub);
    ::std::fs::read_to_string(&p).unwrap_or_else(|e| {
        panic!(
            "Failed to load '{}': {e}\n\nTo improve iteration speed, some files are not embedded but loaded at runtime, at the cost of making the binary non-portable. To fix this, build with codegen_embed.",
            p.display(),
        )
    })
}

/// Per-call-site embedded file.
/// `$root` must be one of the bare idents `Codegen` /
/// `CodegenEager` / `Src` / `SrcEager` and `$sub_path` a string literal.
///
/// The `cfg(bun_codegen_embed)` split lives **inside** the macro so call
/// sites never repeat the `#[cfg]`/`#[cfg(not)]` pair (which is error-prone
/// — a missed pair leaves a release binary that panics with "Failed to load
/// '<build-machine-path>/…'"). Under the cfg, the file is `include_str!`-ed
/// at compile time; otherwise it's read once at runtime into a per-site
/// `OnceLock<String>` for fast iteration.
///
/// `Src` paths are relative to `<repo>/src/`; `Codegen` paths are relative

View on GitHub (pinned to 8c5296ac45)

When it happens

Trigger: Thrown at src/bun_core/util.rs:2960 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of oven-sh/bun@8c5296ac45 (2026-08-16). Data as JSON: /api/errors/e9a528fa4ac52750. Report an issue: GitHub.