BoundaryML/baml · error · CtypesError

Internal error

Error message

Internal error: {0}

What it means

This is an internal panic-style error from the bridge_ctypes error enum, used when the FFI boundary code reaches a state that should be impossible. The library throws it to signal a bug in the bridge (not user error), carrying a descriptive string about the invariant that was violated. If you see it, the typed bridge layer misused its own contracts.

Solutions

1. Check that your generated bindings and the native bridge library are built from the same version
2. Stop calling raw ctypes functions directly; use the generated wrapper API
3. Reproduce with a minimal snippet and file a bug report with the internal error message string
4. Clear stale build artifacts and rebuild the bridge

Example fix

// before
lib.baml_call_raw(unvalidated_buffer)
// after
from baml_bridge import Client
client = Client.from_source(src)
client.call(request)  # goes through validated generated wrappers

import ctypes_bridge_meta as meta
assert meta.__version__ == native_bridge_version(), 'binding/native version mismatch'

function isInternalError(e) {
  return e instanceof Error && e.name === 'BamlInternalError' && /Internal error:/.test(e.message);
}

try {
  result = bridge.call(req);
} catch (e) {
  if (isInternalError(e)) {
    logBugReport(e.message);
    throw new Error('Bridge internal error — report bug, check version match');
  }
  throw e;
}

When it happens

Trigger: Calling generated bridge functions when an internal invariant in the ctypes bridge is violated, e.g. a value shape or enum discriminant the conversion layer did not expect reaches the boundary.

Common situations: Usually surfaces after a version mismatch between generated bindings and the native library, or when bypassing generated wrappers and calling raw ctypes entry points directly with hand-built values.

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

• __class_getitem__
• Internal error
• nil success in InvocationResponse
• unsupported handle type
• {0}

AI-assisted analysis of BoundaryML/baml@bd85ce9dee (2026-09-12). Data as JSON: /api/errors/a0ac8937df35f2b8. Report an issue: GitHub.

Appendix: source

Thrown at baml_language/crates/bridge_ctypes/src/error.rs:39

    /// blobs can be up to the FFI decode cap (~67M chars), and embedding
    /// them in error messages bloats logs and exposes payload contents.
    #[error("Invalid bigint hex string ({len} bytes)")]
    InvalidBigint { len: usize },

    /// Carries only the input length for over-cap decimal type literals, so a
    /// hostile descriptor cannot amplify logs by echoing its full payload.
    #[error("Invalid decimal bigint literal ({len} bytes)")]
    InvalidBigintLiteral { len: usize },

    #[error(
        "Invalid InboundValue.value_type: a root union or optional does not identify one exact selected type"
    )]
    InvalidInboundValueTypeRootUnion,

    #[error("Union selected type `{selected}` is not a member of declared union `{union}`")]
    UnionSelectedTypeNotMember { selected: String, union: String },

    #[error("Internal error: {0}")]
    InternalError(String),
}

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