---
id: ADR-PFM-INT-016
title: Platform keeps customization configuration; hosts execute it
product_area: platform
module: integrations
revision: 1
status: proposed
design_intent: proposed
source_sha:
  services-platform: ad3f6a6582843008ed0f5a17b131878d15829af1
  react-console: baf6dae382d6f41dce976c7f848667ccc37e076f
decision: >-
  Keep customization declarations, handlers, bindings, preview resolution and invocation history in Platform.
  Hosts resolve and invoke through the shared library and save outcomes through the restricted
  invocation-writer role.
constrains:
  - DOM-PFM-INT-005
  - STATE-PFM-INT-013
  - WF-PFM-INT-020
  - SCR-PFM-INT-016
  - SCR-PFM-INT-017
  - SCR-PFM-INT-018
  - SVC-PFM-INT-extensions
alternatives:
  - option: Route every handler invocation through Platform.
    why_not: A central round trip would lengthen the host’s critical path and obscure its responsibility for failure.
consequences:
  - Single-answer points allow one authoritative binding within each scope.
  - Platform’s separate preview implementation can diverge from shared host resolution.
  - >-
    External event subscriptions belong to the integrations service; the withdrawn customization subscription
    facility is not revived.
origin: 'docs/proposals/extensibility/decision-log.md A2, A4, A7 (adopted autonomously; OQ-PFM-INT-001)'
supersedes: []
---

# Platform keeps customization configuration; hosts execute it

## Context

Platform handler tests do not substitute for host-owned production execution.

## Decision

Keep customization declarations, handlers, bindings, preview resolution and invocation history in Platform. Hosts resolve and invoke through the shared library and save outcomes through the restricted invocation-writer role.

## Alternatives Considered

Route every handler invocation through Platform. A central round trip would lengthen the host’s critical path and obscure its responsibility for failure.

## Consequences

Single-answer points allow one authoritative binding within each scope.

Platform’s separate preview implementation can diverge from shared host resolution.

External event subscriptions belong to the integrations service; the withdrawn customization subscription facility is not revived.