[BUG] Desktop (macOS) 1.28929.0: pinned sessions in the Claude Code sidebar accumulate duplicate entries over time

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

In the Claude Code sidebar of the Claude Desktop app on macOS, a single pinned session gradually appears multiple times within the Pinned section. This is not the expected Pinned/Recents overlap — all copies are inside the Pinned section itself.

Scope: this has been observed only in the Claude Code sidebar. Pinned items elsewhere in the desktop app do not show this behavior.

The duplication is progressive: it starts as two entries and grows to three, four, and beyond the longer the app stays open. A full app restart clears it, but the copies reappear and accumulate again over the following period of use.

Two observations that narrow this down:

• Unpinning removes exactly one copy per click. The remaining copies stay pinned. This indicates the sidebar holds genuinely distinct list entries rather than rendering one entry repeatedly.
• A restart resets the count to one. The persisted pin set therefore appears to be correct; the duplication looks like it accumulates in the in-memory pinned list at runtime.

Taken together, this suggests a pin-sync/refresh handler in the Claude Code sidebar that appends to the pinned list instead of upserting by session ID, so every sync cycle adds another entry for an already-pinned session.

Environment

• Claude Desktop: 1.28929.0 (d1a6bc), build 2026-08-11T18:58:06.000Z
• OS: macOS 26.6.1 (25G76) Apple M4
• Surface: Claude Code sidebar in the Claude Desktop app — Pinned section

What Should Happen?

Expected: each pinned session appears exactly once in the Pinned section.

Actual: pinned sessions appear two or more times, with the number of copies increasing the longer the app runs. Unpinning removes one copy per click. Restarting the app resets each session to a single entry, after which the duplicates begin accumulating again.

Error Messages/Logs

Steps to Reproduce

1. Open the Claude Code sidebar in the Claude Desktop app (macOS).
2. Pin one or more Claude Code sessions.
3. Leave the app running and continue normal use.
4. Observe the Pinned section of the Claude Code sidebar over time.

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.209 (Claude Code)

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

Possibly related, though distinct: #78317 (pins fail to persist across relaunch, Windows), #69811 (pinned sessions stop reordering by activity), #79810 (sidebar groups lost on account switch). These all point at the same pin/sidebar state-sync layer.