BoundaryML/baml · critical · RuntimeError

Failed to initialize BAML logger: {e:#}

Error message

Failed to initialize BAML logger: {e:#}

What it means

Raised by the magnus #[init] entry point of the ruby_ffi extension when baml_log::init() fails while loading the Baml native module. The extension aborts loading and surfaces a Ruby RuntimeError: 'Failed to initialize BAML logger: {e:#}'. Because it happens at require time, the entire Baml module is unavailable.

Source

Thrown at engine/language_client_ruby/ext/ruby_ffi/src/lib.rs:325

        baml_runtime::RuntimeCliDefaults {
            output_type: baml_types::GeneratorOutputType::RubySorbet,
        },
    ) {
        Ok(exit_code) => Ok(exit_code.into()),
        Err(e) => Err(Error::new(
            ruby.exception_runtime_error(),
            format!(
                "{:?}",
                e.context("error while invoking baml-cli".to_string())
            ),
        )),
    }
}

#[magnus::init(name = "ruby_ffi")]
fn init(ruby: &Ruby) -> Result<()> {
    baml_log::init().map_err(|e| {
        Error::new(
            ruby.exception_runtime_error(),
            format!("Failed to initialize BAML logger: {e:#}"),
        )
    })?;

    let module = ruby.define_module("Baml")?.define_module("Ffi")?;

    module.define_module_function("invoke_runtime_cli", function!(invoke_runtime_cli, 2))?;

    // must be kept in sync with the magnus::wrap annotation
    let runtime_class = module.define_class("BamlRuntime", class::object())?;
    runtime_class.define_singleton_method(
        "from_directory",
        function!(BamlRuntimeFfi::from_directory, 2),
    )?;
    runtime_class
        .define_singleton_method("from_files", function!(BamlRuntimeFfi::from_files, 3))?;
    runtime_class.define_method(

View on GitHub (pinned to bd85ce9dee)

Solutions

1. Check the {e:#} detail in the message for the exact logger failure reason.
2. Verify the BAML_LOG / RUST_LOG env var, if set, is a valid log filter (e.g. 'info', 'debug', 'baml=debug').
3. Ensure the process can write to the log output location (writable HOME/TMPDIR in containers).
4. Unset BAML_LOG to fall back to defaults and retry requiring the gem.
5. Upgrade the baml gem; older versions had stricter logger init behavior.

Example fix

// before
ENV["BAML_LOG"] = "verbose"
require "baml"

// after
ENV["BAML_LOG"] = "debug" # valid level: trace|debug|info|warn|error
require "baml"

valid = %w[trace debug info warn error off]
if (lvl = ENV['BAML_LOG']) && !valid.include?(lvl.split(/[=,]/).first)
  raise "invalid BAML_LOG level: #{lvl}"
end
require 'tmpdir'
raise 'no writable tmp dir' unless File.writable?(Dir.tmpdir)

begin
  require 'baml'
rescue RuntimeError => e
  raise unless e.message.start_with?('Failed to initialize BAML logger')
  ENV.delete('BAML_LOG')
  require 'baml'
end

When it happens

Trigger: Requiring 'baml' / the ruby_ffi native extension in an environment where the BAML logger cannot initialize: BAML_LOG env var set to an invalid level, unwritable log file path/directory, or a logger-internal initialization error.

Common situations: Deploying to a read-only filesystem or container where the default log location is not writable; setting BAML_LOG to a bogus filter string; conflicting log initialization when another native extension already set a global logger.

Related errors

• Engine not initialized. Call create_baml_runtime first.
• Project not initialized
• panic(initErr)
• failed to get logs: %w
• No LLM response: {}

AI-assisted analysis of BoundaryML/baml@bd85ce9dee (2026-09-12). Data as JSON: /api/errors/d8493f9316abf5b4. Report an issue: GitHub.