BoundaryML/baml · error

run started record omitted target

Error message

run started record omitted target

What it means

This io::Error (InvalidData) is thrown by TryFrom<pb::RunStartedV1> for RunStartedRecord when the decoded protobuf message has no `target` field set. In proto3, optional message fields decode to None when absent, and the record type requires a target (which function/test is being run), so conversion fails fast rather than constructing a record with an unusable target.

Source

Thrown at baml_language/crates/bex_events/src/value/record.rs:406

            reason: match value.reason {
                CaptureLossReason::QueueFull => {
                    crate::value::pb::CaptureLossReason::QueueFull as i32
                }
            },
            skipped_count: value.skipped_count,
            call: value.call.map(Into::into),
            message: value.message.clone(),
            timestamp_ms: value.timestamp_ms,
        }
    }
}

impl TryFrom<crate::value::pb::RunStartedV1> for RunStartedRecord {
    type Error = io::Error;

    fn try_from(value: crate::value::pb::RunStartedV1) -> Result<Self, Self::Error> {
        let target = value.target.ok_or_else(|| {
            io::Error::new(
                io::ErrorKind::InvalidData,
                "run started record omitted target",
            )
        })?;
        let time_anchor = value.time_anchor.ok_or_else(|| {
            io::Error::new(
                io::ErrorKind::InvalidData,
                "run started record omitted time anchor",
            )
        })?;
        Ok(Self {
            request: RunRequestSummary {
                project_id: ProjectId(value.project_id),
                project_generation: ProjectGeneration(value.project_generation),
                target: run_target_from_proto(target)?,
                args_summary: value.args_summary,
                options_summary: value.options_summary,
            },

View on GitHub (pinned to bd85ce9dee)

Solutions

  1. Ensure the producer sets target (set_target(pb::RunTargetV1{...})) on every RunStartedV1 before serializing
  2. Check which emitter wrote the event and fix it to populate the required field
  3. Regenerate or repair the corrupted event-stream segment so the field is present
  4. Handle the Err case at decode time and skip/report the malformed record instead of panicking

Example fix

// before
let rec = RunStartedRecord::try_from(msg)?; // msg.target unset -> InvalidData
// after
msg.target = Some(pb::RunTargetV1 { target: Some(run_target_v1::Target::Function(...)) });
let rec = RunStartedRecord::try_from(msg)?;
Defensive patterns

Strategy: validation

Validate before calling

fn is_valid(msg: &pb::RunStartedV1) -> bool { msg.target.is_some() }
// only call try_from when true

Type guard

fn has_target(msg: &pb::RunStartedV1) -> Option<&pb::RunTargetV1> { msg.target.as_ref() }

Try / catch

match RunStartedRecord::try_from(msg) {
    Ok(rec) => rec,
    Err(e) if e.kind() == io::ErrorKind::InvalidData => { log::warn!("malformed run-started: {e}"); return; },
    Err(e) => return Err(e),
}

Prevention

When it happens

Trigger: Calling RunStartedRecord::try_from(pb_run_started) where the RunStartedV1 message was built without set_target(), or a serialized event was truncated/mutated so the target oneof is missing on decode.

Common situations: A producer of bex_events upgraded its protobuf schema and stopped populating target; hand-crafted test fixtures that only fill in time_anchor; a partial write/corruption of the event stream dropping the field.

Understand the failure class

Background: "missing required argument" and "the following required arguments were not provided": what required-argument errors mean and how to fix them — this error's family across 20 libraries.

Related errors

AI-assisted analysis of BoundaryML/baml@bd85ce9dee (2026-09-12). Data as JSON: /api/errors/51c2a276e787c132. Report an issue: GitHub.