BoundaryML/baml · error

Failed to convert timestamp to EpochMsTimestamp

Error message

Failed to convert timestamp to EpochMsTimestamp

What it means

This is a panic message (via .expect) in to_rpc_event when converting a trace event's timestamp into baml_rpc::EpochMsTimestamp fails. EpochMsTimestamp::try_from only fails if the timestamp cannot be represented as epoch milliseconds (e.g. out-of-range datetime), which should be impossible for system-generated timestamps. Hitting it indicates an internal invariant violation — a corrupted or synthetic timestamp in the trace event metadata.

Source

Thrown at engine/baml-runtime/src/tracingv2/publisher/rpc_converters/mod.rs:37

    fn type_lookup(&self, name: &str) -> Option<Arc<BamlTypeId>>;
    fn function_lookup(&self, name: &str) -> Option<Arc<BamlFunctionId>>;
    fn baml_src_hash(&self) -> Option<String>;
}

pub trait IRRpcState: TypeLookup + BlobStorage {}

impl<T: TypeLookup + BlobStorage> IRRpcState for T {}

pub(crate) trait IntoRpcEvent<'a, RpcOutputType> {
    fn to_rpc_event(&'a self, lookup: &(impl IRRpcState + ?Sized)) -> RpcOutputType;
}

pub(super) fn to_rpc_event<'a>(
    event: &'a TraceEventWithMeta,
    lookup: &(impl IRRpcState + ?Sized),
) -> baml_rpc::runtime_api::BackendTraceEvent<'a> {
    let timestamp = baml_rpc::EpochMsTimestamp::try_from(event.timestamp)
        .expect("Failed to convert timestamp to EpochMsTimestamp");

    // Convert the content to RPC format
    let mut content = event.content.to_rpc_event(lookup);

    // Extract blobs from the content
    let blob_cache = lookup.blob_cache();
    extract_blobs_from_trace_data(&mut content, blob_cache, &event.call_id.to_string());

    baml_rpc::runtime_api::BackendTraceEvent {
        call_id: event.call_id.clone(),
        function_event_id: event.function_event_id.clone(),
        call_stack: event.call_stack.clone(),
        timestamp,
        content,
    }
}

// Helper function to extract blobs from TraceData

View on GitHub (pinned to bd85ce9dee)

Solutions

  1. Check system clock sanity (date/timezone) on the machine generating traces.
  2. If using a fake/mock clock, ensure it produces realistic epoch-millisecond values.
  3. Upgrade to the latest BAML version; if reproducible on current versions, file a bug with the failing timestamp value.

Example fix

// before
let ts = Utc.timestamp_opt(-100_000_000, 0).unwrap(); // invalid for EpochMsTimestamp
// after
let ts = Utc::now(); // realistic timestamp within epoch-ms range
Defensive patterns

Strategy: validation

Validate before calling

# sanity-check the clock before running BAML
import time; assert 0 < time.time() < 4102444800, "system clock invalid"

Type guard

fn is_epoch_ms_representable(t: &DateTime<Utc>) -> bool {
    let ms = t.timestamp_millis();
    (0..=i64::MAX).contains(&ms) && ms / 1000 < 253_402_300_800
}

Try / catch

// to_rpc_event panics via expect; guard at the event-construction boundary
let timestamp = EpochMsTimestamp::try_from(event.timestamp)
    .map_err(|_| anyhow!("invalid trace timestamp: {}", event.timestamp))?;

Prevention

When it happens

Trigger: A TraceEventWithMeta carries a timestamp that TryFrom<...> for EpochMsTimestamp rejects — e.g. a negative or absurdly large time value introduced by a mocked clock, corrupted metadata, or a library bug.

Common situations: Custom test harnesses injecting fake timestamps, system clock misconfiguration producing invalid times, or a genuine BAML bug during version upgrades of baml_rpc timestamp types.

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

AI-assisted analysis of BoundaryML/baml@bd85ce9dee (2026-09-12). Data as JSON: /api/errors/55a3618ad00ce89e. Report an issue: GitHub.