BoundaryML/baml · error

the browser TypeScript bridge must own the process-wide inbo

Error message

the browser TypeScript bridge must own the process-wide inbound policy

What it means

The WASM entrypoint start() registers the process-wide inbound union ambiguity policy (SelectDefault) and expects registration to succeed. bex_project::register_inbound_union_ambiguity_policy returns Err if the policy was already set, and start() .expect()s on it: 'the browser TypeScript bridge must own the process-wide inbound policy'. It means something else in the process initialized the policy first, so the browser bridge no longer owns it.

Source

Thrown at baml_language/crates/bridge_wasm/src/lib.rs:71

mod wasm_http;
mod wasm_io;
mod wasm_io_fs;
mod wasm_io_glob;
mod wasm_random;
mod wasm_sys;
mod wasm_time;
mod wasm_vfs;

pub use lsp_wire::{LspNotification, LspRequest, LspResponse, LspResponseError};

static LOGGER_INIT: Once = Once::new();

#[wasm_bindgen(start)]
pub fn start() {
    bex_project::register_inbound_union_ambiguity_policy(
        bex_project::InboundUnionAmbiguityPolicy::SelectDefault,
    )
    .expect("the browser TypeScript bridge must own the process-wide inbound policy");
    #[cfg(feature = "console_error_panic")]
    console_error_panic_hook::set_once();
    LOGGER_INIT.call_once(|| {
        let level = if cfg!(debug_assertions) {
            log::Level::Debug
        } else {
            log::Level::Info
        };
        wasm_logger::init(wasm_logger::Config::new(level));
    });
}

/// Get the version of the `bridge_wasm` crate.
#[wasm_bindgen]
pub fn version() -> String {
    baml_version::CANONICAL_VERSION.to_string()
}

View on GitHub (pinned to bd85ce9dee)

Solutions

1. Ensure the wasm module is imported/initialized only once per process
2. Check that no other bridge or test setup registers the inbound policy before WASM start
3. Deduplicate bundle chunks so a single wasm_bindgen start runs
4. Use a fresh WASM instance per isolated runtime instead of sharing one globally

Example fix

// before
import wasm1 from 'baml_wasm_bg';
import wasm2 from 'baml_wasm_bg'; // second start() -> panic
// after
export const wasm = await import('baml_wasm_bg'); // single shared import

if (globalThis.__BAML_WASM_STARTED__) throw new Error('baml wasm already initialized in this process');
await import('baml_wasm_bg'); // single init point
globalThis.__BAML_WASM_STARTED__ = true;

When it happens

Trigger: Loading the WASM module twice into the same process/runtime, or another binding (Node bridge, tests) calling register_inbound_union_ambiguity_policy before wasm_bindgen start runs.

Common situations: Double-importing the wasm package (e.g. via two bundle chunks), SSR/test environments pre-initializing bex_project, or mixing the WASM bridge with a native bridge in the same process.

Related errors

• BAML internal error - credential provider bridges not initia
• -32002
• Package initialization failed: {0}
• {0}
• Engine not initialized. Call create_baml_runtime first.

AI-assisted analysis of BoundaryML/baml@bd85ce9dee (2026-09-12). Data as JSON: /api/errors/74ee3fbe4cf1d03c. Report an issue: GitHub.