SKILL: Aggregated Change Signal Return

Domain: extensions-mcp Trigger: Apply when a headless setup flow can change state through several mechanisms but callers only need one final answer about whether they must refresh downstream registries. Source Pattern: Distilled from reviewed extension lifecycle and source-reconciliation patterns.

Core Method

Aggregate every state-changing branch inside the headless install flow into one caller-facing signal. Seed registration, marketplace reconciliation, and delisting can each materially change the runtime even if the others do nothing, so the function should accumulate them into a single boolean that tells the caller whether a follow-up refresh is required. This keeps the internal branching detailed while exposing a minimal external contract.

Key Rules

• Initialize the change signal from the earliest state-changing step instead of only from the main reconcile path.
• Fold every later state mutation into the same signal, even if it comes from cleanup or enforcement rather than install.
• Keep the caller contract narrow: one signal that means "refresh downstream state now," not a grab bag of internal counters.
• Update the signal only on genuine state changes so callers do not refresh on no-op runs.

Example Application

If a headless extension bootstrap registers seeds, installs missing registries, and removes delisted plugins, return one extensionsChanged boolean that becomes true if any of those paths modified the effective plugin set. The caller can then refresh command discovery once, regardless of which branch caused the change.

Anti-Patterns (What NOT to do)

• Do not expose only install counts when cleanup or seed registration can also require a downstream refresh.
• Do not make callers reconstruct change state from several independent metrics when the callee already knows the full picture.