kandev/docs/plans/unlink-task-github-pr/task-01-backend-unlink-contract.md

id, title, status, wave, depends_on, plan, spec

id	title	status	wave	depends_on	plan	spec
01-backend-unlink-contract	Backend unlink contract	done	1		plan.md	../../specs/tasks/requirements/link-existing-task-github-issue.md

Task 01: Backend Unlink Contract

Acceptance

• One workspace-authorized endpoint detaches exactly one GitHub task-PR association, leaves sibling associations and the remote PR untouched, and fails closed for unknown or cross-workspace IDs.
• Detached associations survive restart/migration replay, disappear from all active association reads and automation inputs, are not resurrected by automatic watch discovery, and can be restored by explicit URL linking.
• A successful detach publishes a workspace-routed github.task_pr.deleted notification only after persistence succeeds.

Verification

cd apps/backend && go test ./internal/github ./internal/gateway/websocket ./pkg/websocket

Files likely touched

• apps/backend/internal/github/models.go
• apps/backend/internal/github/store.go
• apps/backend/internal/github/service_pr_watch.go or a focused sibling
• apps/backend/internal/github/controller.go
• apps/backend/internal/github/*_test.go
• apps/backend/internal/events/types.go
• apps/backend/pkg/websocket/actions.go
• apps/backend/internal/gateway/websocket/task_notifications.go
• apps/backend/internal/gateway/websocket/task_notifications_test.go

Dependencies

None.

Parallelism

Parallel-safe with Task 04 only: implementation and public-doc files are disjoint, and Task 04 does not depend on generated contracts.

Inputs

• Spec sections: What, Scenarios, Data And API, Failure Modes.
• Plan sections: Durable association detachment, Service and HTTP contract, Live update contract.
• Patterns: GitLab's workspace-scoped DeleteTaskMRForWorkspace, GitHub's ReplaceTaskPR, and workspace-routed task notification payloads.

Risks

• Existing databases and both supported SQL dialects must receive the nullable column through replay-safe migration order.
• Internal automatic association paths must not clear the tombstone intended for explicit relinking only.

Output contract

Report the behavioral tests added, files changed, exact command result, remaining risks/blockers, and update this task plus plan.md status in the same conversation.