---
id: CUST-WP-0033
type: workplan
title: "Interface Change Registry — Coordinated API Evolution"
domain: custodian
repo: the-custodian
status: done
owner: custodian
topic_slug: custodian
created: "2026-04-26"
updated: "2026-04-26"
concept: canon/projects/custodian/interface_change_registry_v0.1.md
state_hub_workstream_id: "420a3981-abf5-4a8e-a94b-455964f1a0e5"
---

# CUST-WP-0033 — Interface Change Registry

## Goal

Add a first-class `InterfaceChange` entity to the state-hub. Agents producing
breaking changes can document them; agents consuming interfaces discover pending
changes at session start via dispatch, and receive inbox notifications on publish.
Webhook delivery is deferred and registered as an extension point.

Reference concept: `canon/projects/custodian/interface_change_registry_v0.1.md`

## T01: Data model and migration

```task
id: CUST-WP-0033-T01
status: done
priority: high
state_hub_task_id: "6bc77d3c-78e0-485a-a3bc-b5987c4ccc53"
```

New table `interface_changes`. Fields: `id` (UUID PK), `repo_id` (FK
managed_repos), `interface_type` (String: rest_api / mcp_tool / cli / schema /
capability), `change_type` (String: breaking / additive / deprecation / removal),
`title` (String), `description` (Text), `affected_paths` (JSONB list of strings),
`affected_repo_slugs` (JSONB list of slugs), `status` (String: draft / published /
resolved), `planned_for` (Date nullable), `published_at` (DateTime nullable),
`resolved_at` (DateTime nullable), `author` (String), `created_at`, `updated_at`.

Index on `(repo_id, status)` and `(status)` for dispatch queries.

Acceptance: Alembic migration runs cleanly, model importable, no regressions in
existing test suite.

## T02: API endpoints

```task
id: CUST-WP-0033-T02
status: done
priority: high
state_hub_task_id: "7664551e-0871-4e82-a9ba-b59be515c47c"
```

Router at `/interface-changes/` (prefix). Endpoints:

- `POST /interface-changes/` — create (status always `draft` on creation)
- `GET /interface-changes/` — list; filter params: `repo_slug`, `status`,
  `change_type`, `affected_repo` (returns changes that affect the given slug)
- `GET /interface-changes/{change_id}` — single record
- `PATCH /interface-changes/{change_id}` — update mutable fields (title,
  description, affected_paths, affected_repo_slugs, planned_for); only valid in
  `draft` status
- `POST /interface-changes/{change_id}/publish` — transition draft → published;
  sets `published_at`; fires inbox messages to agents of all `affected_repo_slugs`;
  appends a progress event on the originating repo
- `POST /interface-changes/{change_id}/resolve` — transition published → resolved;
  sets `resolved_at`

Acceptance: all endpoints return correct status codes; publish transitions send
inbox messages; 409 on invalid status transitions; tests cover happy path and
invalid transitions.

## T03: Dispatch integration

```task
id: CUST-WP-0033-T03
status: done
priority: medium
state_hub_task_id: "8f8403a2-4444-4196-9845-ea9c66b674eb"
```

Extend `GET /repos/{slug}/dispatch` to include a `pending_interface_changes` field:
published `InterfaceChange` records where `affected_repo_slugs` contains `slug` and
status is not `resolved`. Each entry: `id`, `title`, `change_type`,
`interface_type`, `repo_slug` (origin), `affected_paths`, `planned_for`,
`published_at`.

Extend `DispatchWorkstream` schema with the new field. Update `RepoDispatch` schema.
Update the `get_repo_dispatch` endpoint accordingly.

Acceptance: `GET /repos/repo-registry/dispatch` returns `pending_interface_changes`
list (empty or populated); no regression on existing dispatch tests.

## T04: MCP tools

```task
id: CUST-WP-0033-T04
status: done
priority: medium
state_hub_task_id: "d9135829-954e-41de-af9f-607768916478"
```

Four tools in `mcp_server/server.py`:

- `register_interface_change(repo_slug, interface_type, change_type, title,
  description, affected_paths=None, affected_repo_slugs=None, planned_for=None)`
  — creates a draft record
- `list_interface_changes(repo_slug=None, status=None, change_type=None,
  affected_repo=None)` — returns formatted summary
- `publish_interface_change(change_id)` — publishes and triggers notifications
- `resolve_interface_change(change_id)` — marks resolved

Acceptance: tools callable from Claude Code; publish tool returns confirmation
of how many inbox messages were sent.

## T05: Dashboard page

```task
id: CUST-WP-0033-T05
status: done
priority: low
state_hub_task_id: "d2fcbe83-c5a7-400c-a53b-ff1950795814"
```

New page `dashboard/src/interface-changes.md`. Shows:

- Table of published/draft changes grouped by repo, sorted by `published_at` desc
- Change type badge (breaking = red, deprecation = amber, additive = green)
- Affected repos column with count
- Filter by repo slug and change_type
- A "planned" section for changes with future `planned_for` dates, sorted
  chronologically — effectively a migration calendar

Add to `observablehq.config.js` nav.

Acceptance: page renders; data loads from `GET /interface-changes/?status=published`
and `GET /interface-changes/?status=draft`.

## T06: Register webhook extension point

```task
id: CUST-WP-0033-T06
status: done
priority: low
state_hub_task_id: "47d7bea8-b5fb-4fc4-9ec5-9ed5e0cdef72"
```

Register EP-CUST-ICR-001 in the state-hub:

```
interface_type: future_capability
ep_type: architecture
title: Webhook subscriptions for interface change notifications
description: |
  Inbox messages cover polling agents. Real-time push to CI pipelines,
  external webhooks, and non-Custodian agents requires a subscription table
  (repo_slug → webhook_url) and delivery infrastructure (retry, dead-letter).
  Defer until inbox-first approach proves insufficient for ≥1 real case.
status: open
priority: low
```

No implementation. Documents the deliberate deferral and records the design
direction so it is not re-invented later.

Acceptance: EP registered, retrievable via `GET /extension-points/?domain=custodian`.