[RFC] Standardizing OSD–PPL Interaction

Problem Statements

• Incomplete language awareness in OSD typeahead, OSD cannot reliably detect the exact PPL version and supported commands/functions for a connected cluster or engine. Lack of a machine-readable, versioned capabilities contract leads to incorrect or missing completions, stale suggestions, and confusing editor diagnostics.
• Unreliable “raw events before first reduce” on the Events page: OSD is expected to display raw events up to (but not including) the first reducing operator (e.g., dedup, stats). Without an authoritative definition or introspection of reducing boundaries, OSD uses heuristics that fail on complex pipelines (subqueries, macros, mvexpand, field mutations), causing incorrect previews and user confusion.
• Ambiguity in “raw events” for the Timeline page: The Timeline page should visualize counts over raw events using an effective timestamp field before any reducing step. OSD lacks a consistent, query-aware definition of “raw events”.
• No first-class cancellation for long-running PPL queries: Frontend needs to cancel in-flight or superseded queries (typing, tab switches, navigation). Lack of a Cancel API and stable query identifiers prevents responsive UX, wastes cluster resources, and complicates concurrency control in OSD.

No files, tests, or entry points are named. Start by reviewing the four problem statements and the existing OSD–PPL interaction to determine whether a capabilities contract, raw-event boundary definition, timeline semantics, or query-cancellation API is in scope. Done requires an agreed, versioned design rather than a single implementation change.