[Bug]: Deleting a parent leaves a remote child with a stale parent link and no error feedback #26766

Before submitting

• I searched existing issues and did not find a duplicate.
• I included enough detail to reproduce or investigate the problem.

Area

apps/web (also used by the desktop client)

Steps to reproduce

1. Have a thread on environment A delegate a task to environment B.
2. Delete the original parent on A, leaving the remote child available on B.
3. Open the child and click its Lineage entry labelled "Open parent agent".

These steps describe the observed incident. A fresh end-to-end reproduction has not been performed.

Expected behavior

Deleting a parent should leave a coherent state for its remote children. If children are retained, the lineage control should show that the parent is no longer available and keep the user in the child conversation when it cannot open the target.

The owner also suggested deleting all children when a parent is deleted. Please clarify whether cascading deletion is intended, including across linked environments. If retention is intentional, this report is about the stale navigation control and missing feedback, not a demand to delete retained results.

Actual behavior

The owner reports that clicking the parent entry opens a bare session, without an error explaining that the parent no longer exists. The saved parent title remains visible in the lineage row.

Read-only inspection matched the child's ID in the parent's saved remote-delegation metadata. The parent had a deletion timestamp, and the native thread-read tool returned thread_not_found with "is no longer available". Thus the target was genuinely deleted, rather than merely missing from a client shell snapshot.

Impact

Minor bug or occasional failure. The user loses their navigation context and cannot distinguish an unavailable parent from a failed link or an empty conversation.

Version or commit

Installed desktop client: 0.1.4-nightly.20261028.3841.

Source inspected: 8ff9ae1f87e2b7c62cfacffd08921ff40bb089b1.

Environment

macOS desktop client with a linked Linux environment. The affected child used Claude; provider-specific causality was not established.

Relevant source

DelegatedFromRow preserves the parent environment and thread ID, and retains the title captured at delegation. Its control is disabled only when the environment is absent. This report concerns missing failure feedback for a deleted target, rather than incorrect environment selection.

Related reports

• #16443 concerns opening an archived conversation that still exists. This parent is deleted.
• #26467 concerns the label of links to existing older settled threads. This report concerns the result of clicking a lineage entry pointing to a deleted parent.
• #23765 concerns mobile Back navigation and was closed through a mobile-specific fix.

Workaround and limits

No way to open the deleted parent was verified. Return manually to the child conversation. No restoration, code change, service restart, or fix validation was attempted. The original screenshot contains private conversation content and is intentionally omitted.