BoundaryML/baml · error

error: no BAML toolchain is installed. Run: baml toolchain…

Error message

error: no BAML toolchain is installed.
Run: baml toolchain use canary
Or:  baml toolchain use nightly

What it means

The catch-all 'no toolchain installed' guard in version resolution: the selector is a channel that has no local state entry, and the selector did not come from a project baml.toml (i.e. it came from the global default or env), so there is nothing to resolve or exec. On a fresh machine with no `baml toolchain use` ever run, every invocation that needs the real toolchain hits this.

Solutions

1. Install and activate a toolchain: `baml toolchain use canary` or `baml toolchain use nightly`
2. Or install a specific version with `baml toolchain install <version>` then `baml toolchain use <version>`

When it happens

Trigger: Thrown at baml_language/crates/baml/src/main.rs:628 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of BoundaryML/baml@bd85ce9dee (2026-09-12). Data as JSON: /api/errors/2d9c9b497294dbd4. Report an issue: GitHub.

Appendix: source

Thrown at baml_language/crates/baml/src/main.rs:628

                .as_deref()
                .is_some_and(|base| base.trim_end_matches('/') != current_base)
            {
                return Err(anyhow!(
                    "channel {} was selected from a different manifest source.\nRun: baml toolchain use {} under the current manifest source.",
                    selector.selector,
                    selector.selector
                ));
            }
            return Ok(channel.active_version.clone());
        }
        return match &selector.source {
            SelectorSource::Project(path) => Err(anyhow!(
                "baml.toml [toolchain] selects channel {}, but no active concrete version is recorded locally.\nRun: baml toolchain use {}",
                selector.selector,
                selector.selector
            )
            .context(format!("project config: {}", path.display()))),
            _ => Err(anyhow!(
                "error: no BAML toolchain is installed.\nRun: baml toolchain use canary\nOr:  baml toolchain use nightly"
            )),
        };
    }
    Ok(selector.selector.clone())
}

fn missing_toolchain_error(selector: &ResolvedSelector, version: &str) -> anyhow::Error {
    let installed = installed_toolchains().join(", ");
    match &selector.source {
        SelectorSource::Project(path) => anyhow!(
            "{} [toolchain] pins version {version}, but it isn't installed.\nInstalled toolchains: {}\nRun: baml toolchain install {version}",
            path.display(),
            if installed.is_empty() {
                "(none)"
            } else {
                &installed
            }

View on GitHub (pinned to bd85ce9dee)