BoundaryML/baml · error · EngineError

Function call with ID {call_id} not found

Error message

Function call with ID {call_id} not found

What it means

`EngineError::FunctionCallNotFound` is raised when the engine is asked about a function call whose `CallId` it does not track. Call IDs are engine-scoped handles; an unknown ID means the call was never registered, already completed and was reaped, or belongs to a different engine instance.

Source

Thrown at baml_language/crates/bex_engine/src/lib.rs:801

            .active_calls
            .lock()
            .unwrap_or_else(std::sync::PoisonError::into_inner);
        map.remove(&self.call_id);
        let no_active_calls = map.values().all(|call| call.pending);
        drop(map);
        if no_active_calls {
            self.engine.lifecycle_changed.notify_waiters();
        }
    }
}

/// Errors that can occur during engine execution.
#[derive(Debug, PartialEq, Error, Clone)]
pub enum EngineError {
    #[error("BAML engine is shutting down")]
    ShuttingDown,

    #[error("Function call with ID {call_id} not found")]
    FunctionCallNotFound { call_id: CallId },

    #[error("Future with ID {future_id} not found")]
    FutureNotFound { future_id: FutureId },

    #[error("Function not found: {name}")]
    FunctionNotFound { name: String },

    /// Function exists, but its `FunctionKind` is not invokable as an
    /// engine entry point. Only bytecode functions can be called via
    /// [`BexEngine::call_function`] / [`BexEngine::call_function_bound_args`]:
    /// native (`$rust_function`) entries would re-enter the VM through
    /// `YieldToCall` with no bytecode frame to return to. Sysops + builtins
    /// reach their natives from inside a calling bytecode body.
    #[error("Function `{name}` is not invokable as an entry point (kind: {kind})")]
    NotInvokableAsEntry { name: String, kind: String },

    #[error("VM internal error: {0}")]

View on GitHub (pinned to bd85ce9dee)

Solutions

1. Use only `CallId`s returned by this engine instance in this session.
2. Check that the call has not already completed and been cleaned up.
3. Re-issue the call to obtain a fresh ID instead of reusing a stale one.

Example fix

// before
let result = engine.call_result(stale_call_id).await?;
// after
let call_id = engine.call_function("f", args).await?;
let result = engine.call_result(call_id).await?;

// track CallIds only from the live engine instance; drop after completion

// rust
match engine.call_result(call_id).await {
    Err(EngineError::FunctionCallNotFound { .. }) => /* re-issue the call */,
    other => other?,
}

When it happens

Trigger: Looking up, awaiting, or cancelling a call with a fabricated, expired, or foreign `CallId` via the engine's call-tracking APIs.

Common situations: Persisting a call ID across engine restarts; awaiting a call after it completed and its record was dropped; mixing IDs between two engine instances in tests.

Understand the failure class

Background: Record Not Found Errors: "not found", RecordNotFound, and "was not found" — what they mean and how to fix them — this error's family across 28 libraries.

Related errors

• BAML engine is shutting down
• Function not found: {name}
• engine is not current with the latest sources; wait for the
• LSP client sent exit before completing shutdown
• Future with ID {future_id} not found

AI-assisted analysis of BoundaryML/baml@bd85ce9dee (2026-09-12). Data as JSON: /api/errors/c6230c2dccc42078. Report an issue: GitHub.