BoundaryML/baml · error · anyhow::Error

No call_id found. This indicates a bug in BAML. Please…

Error message

No call_id found. This indicates a bug in BAML. Please report this with a stack trace (RUST_BACKTRACE=1)

What it means

RuntimeContextManager::call_id_stack maintains a stack of active function-call IDs; when allow_empty is false and the stack is empty, it returns this anyhow error stating that no call_id was found and calling it a bug in BAML. It is thrown because code (call_function / stream_function_with_expr_events paths) expects to run inside an active function-call context but the context stack was empty.

Solutions

1. Only access ctx.call_id inside an active BAML function call (e.g. inside b.FunctionCall / ctx-manager-managed call scope).
2. Pass allow_empty=true (or use the corresponding API) if an empty stack is legitimate for your use case.
3. Check for calls from background threads/timers that run after the function call has finished; capture the call_id while the call is live instead.
4. If the error fires during a normal b.Test / b.Call with RUST_BACKTRACE=1, report it to the BAML repo as the message requests — it is meant to indicate an internal bug.

Example fix

// before (outside any call)
const ids = ctx.manager.getCallStack(); // throws: no call_id found
// after (inside a call)
await b.Test<MyFn>(/* ... */); // or call within ctx-manager-managed scope, then read ctx.call_id

// Only call when inside a managed call:
const safeCallStack = (ctx) => {
  try { return ctx.manager.getCallStack(false); } catch { return []; }
};

const hasActiveCall = (ctx) => {
  try { return ctx.manager.getCallStack(true).length > 0; } catch { return false; }
};

try {
  const ids = ctx.manager.getCallStack(false);
} catch (e) {
  if (String(e).includes('No call_id found')) {
    // not inside an active BAML call — reschedule or use allow_empty=true
  } else throw e;
}

When it happens

Trigger: Calling runtime APIs that resolve the current call_id (e.g. ctx.call_id.get_stack(false) from a client hook, or internal calls from call_function / stream_function_with_expr_events) when no function call is currently executing on that context.

Common situations: Accessing ctx.call_id inside an on_create_client / client-side callback or outside b.FunctionCall context; calling the API from a background thread or after the function call completed; Python/TS users reaching into runtime context manager APIs at the wrong lifecycle point.

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

• assertion failed
• BAML Generate failed - Project has errors.
• baml.json.serialize failed
• baml.json.serialize returned non-string value
• endsWith() method only available on strings at

AI-assisted analysis of BoundaryML/baml@bd85ce9dee (2026-09-12). Data as JSON: /api/errors/fd6313500a551133. Report an issue: GitHub.

Appendix: source

Thrown at engine/baml-runtime/src/types/context_manager.rs:76

    // pub fn call_id(&self) -> Result<uuid::Uuid> {
    //     self.context
    //         .lock()
    //         .unwrap()
    //         .last()
    //         .map(|(id, ..)| *id)
    //         .ok_or_else(|| anyhow::anyhow!("No call id found. This indicates a bug in BAML. Please report this with a stack trace (RUST_BACKTRACE=1)"))
    // }

    pub fn call_id_stack(&self, allow_empty: bool) -> Result<Vec<FunctionCallId>> {
        let res: Vec<FunctionCallId> = self
            .context
            .lock()
            .unwrap()
            .iter()
            .map(|(.., call_id)| call_id.clone())
            .collect();
        if res.is_empty() && !allow_empty {
            Err(anyhow::anyhow!("No call_id found. This indicates a bug in BAML. Please report this with a stack trace (RUST_BACKTRACE=1)"))
        } else {
            Ok(res)
        }
    }

    pub fn new(baml_src_reader: BamlSrcReader) -> Self {
        Self {
            baml_src_reader: Arc::new(baml_src_reader),
            context: Default::default(),
            global_tags: Default::default(),
        }
    }

    pub fn upsert_tags(&self, tags: HashMap<String, BamlValue>) {
        let call_id_stack = {
            let mut ctx = self.context.lock().unwrap();
            if let Some((.., last_tags, _)) = ctx.last_mut() {
                last_tags.extend(tags.clone());

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