BoundaryML/baml · error · BamlError

internal error

Error message

internal error: {0}

What it means

BamlError::Internal is the catch-all variant for unexpected internal errors in the Rust BAML bindings — situations that indicate a bug in BAML rather than user error. It renders as "internal error: <detail>" via thiserror. The crate docs note it is intentionally minimal until more specific variants are added.

Solutions

1. Read the wrapped detail string — it usually names the unexpected value or state.
2. Update the baml crate and regenerate the client to align versions.
3. If reproducible with minimal input, file a bug at https://github.com/BoundaryML/baml/issues.

matches!(err, BamlError::Internal(_))

match runtime.call_function("MyFunc", &inputs) {
    Err(BamlError::Internal(detail)) => {
        log::error!("baml internal error: {detail}");
        // escalate / report bug
    }
    r => r?,
}

When it happens

Trigger: Any code path in languages/rust/baml that constructs BamlError::Internal(String), typically from panics converted to errors, unmatched enum arms, or invariant violations surfaced through the public runtime API.

Common situations: Using a pre-release Rust binding where core functionality is incomplete; feeding BAML values/shapes the runtime doesn't recognize; version mismatch between the generated client and the baml runtime crate.

Understand the failure class

Background: "This is a bug, please report it": internal invariant violations, unreachable panics, and SNH errors explained — this error's family across 47 libraries.

Related errors

• ======================================== BAML Internal…
• internal error: cannot convert value
• internal error: cannot convert value
• {0}
• BAML Generate failed - Project has errors.

AI-assisted analysis of BoundaryML/baml@bd85ce9dee (2026-09-12). Data as JSON: /api/errors/8b0404af2449d2c5. Report an issue: GitHub.

Appendix: source

Thrown at languages/rust/baml/src/error.rs:10

use std::collections::HashMap;

/// BAML runtime errors
///
/// Note: This is intentionally minimal. Expand with specific variants
/// (`InitError`, `CallError`, etc.) once the core functionality works.
#[derive(Debug, thiserror::Error, Clone)]
pub enum BamlError {
    /// Internal/unexpected errors - bugs in BAML that should never happen
    #[error("internal error: {0}")]
    Internal(String),

    /// Type check errors - expected runtime failures (type mismatches)
    #[error("type error: expected {expected}, got {got}")]
    TypeCheck { expected: String, got: String },
}

/// Trait for types that can report their full type name for error messages.
/// Used by `BamlValue` variants to provide descriptive "got" values.
pub trait FullTypeName {
    fn full_type_name(&self) -> String;
}

impl BamlError {
    /// Create an internal error for unexpected bugs
    pub fn internal(msg: impl Into<String>) -> Self {
        BamlError::Internal(msg.into())
    }

View on GitHub (pinned to bd85ce9dee)