Explicit Identity Across Boundaries

Never rely on "latest" or "current" when crossing process or async boundaries.

Pattern

Pass explicit identifiers through the entire pipeline. "Most recent" is a race condition.

DO

• Pass --session-id $ID when spawning processes

• Store IDs in state files for later correlation

• Use full UUIDs, not partial matches

• Keep different ID types separate (don't collapse concepts)

DON'T

• Query for "most recent session" at execution time

• Assume the current context will still be current after await/spawn

• Collapse different ID types:

• session_id = Claude Code session (human-facing)

• root_span_id = Braintrust trace (query key)

• turn_span_id = Braintrust turn within session

Example

// BAD: race condition at session boundaries spawn('analyzer', ['--learn']) // defaults to "most recent"

// GOOD: explicit identity spawn('analyzer', ['--learn', '--session-id', input.session_id])

Source Sessions

• 1c21e6c8: Defined session_id vs root_span_id distinction

• 6a9f2d7a: Fixed wrong-session attribution via explicit passing

• a541f08a: Confirmed pattern prevents race at session boundaries