[BUG] Cowork plugins installed via marketplace are immediately removed as NOT_AVAILABLE on next sync — skills never load

Description

Plugins installed via the Cowork marketplace are accepted by the remote API ("install succeeded") but immediately marked as NOT_AVAILABLE and removed on the very next RemotePluginManager sync cycle. Skills never load, and Cowork processes are killed within ~1 second of spawning. This has been happening since March 25, 2026 — coinciding with the "Elevated connection reset errors in Cowork" incident on status.claude.com.

Environment

• Claude Desktop: macOS Darwin 25.3.0 (Apple Silicon)
• Claude Code SDK in VM: v2.1.78
• VM bundle: fb30784dadb34104626c8cf6d8f90dd47cd393cc
• Model: claude-opus-4-6

Reproduction Steps

1. Open Claude Desktop → Cowork
2. Add a marketplace (e.g. a custom Git-based marketplace or install from Browse)
3. Install any plugin (e.g. sales@benai-skills, marketing@benai-skills, obsidian@benai-skills)
4. Observe logs: install reports success
5. Wait 2-5 seconds for next sync cycle
6. Plugin is removed as NOT_AVAILABLE
7. Try to invoke any skill from the plugin → "Skill details couldn't be loaded" / process dies in ~1 second

Also tested with a full local cleanup (wiped installed_plugins.json, plugin cache, marketplaces, blocklist, VM state, Extensions Update Cache, remote_cowork_plugins, skills-plugin session data, settings.json enabledPlugins/extraKnownMarketplaces). Same result after clean reinstall.

Expected Behavior

Installed plugins should persist across sync cycles and their skills should be loadable in Cowork sessions.

Actual Behavior

Three distinct failures occurring simultaneously:

1. Plugins removed on every sync as NOT_AVAILABLE

Every sync cycle, RemotePluginManager marks and removes user-installed plugins:

2026-03-26 14:22:16 [info] [RemotePluginManager] Removed 2 user-installed plugins set to NOT_AVAILABLE
2026-03-26 14:23:14 [info] [RemotePluginManager] Removed 1 user-installed plugins set to NOT_AVAILABLE
2026-03-26 14:23:58 [info] [RemotePluginManager] Removed 1 user-installed plugins set to NOT_AVAILABLE

This happens even immediately after a successful install:

2026-03-26 14:23:47 [info] [CustomPlugins] installPlugin: remote API install succeeded for plugin marketing@benai-skills
...
2026-03-26 14:23:58 [info] [RemotePluginManager] Removed 1 user-installed plugins set to NOT_AVAILABLE

The NOT_AVAILABLE removal has been firing on every sync since at least March 25:

2026-03-25 21:10:51 [info] [RemotePluginManager] Removed 1 user-installed plugins set to NOT_AVAILABLE
2026-03-25 21:13:30 [info] [RemotePluginManager] Removed 1 user-installed plugins set to NOT_AVAILABLE
2026-03-25 21:14:15 [info] [RemotePluginManager] Removed 1 user-installed plugins set to NOT_AVAILABLE
2026-03-26 14:01:05 [info] [RemotePluginManager] Removed 1 user-installed plugins set to NOT_AVAILABLE

2. Cowork VM processes killed within ~1 second of spawning

2026-03-26 14:23:59 [info] [Spawn:vm] id=fd47f524 Spawn succeeded in 98ms
2026-03-26 14:23:59 [info] [CoworkVMProcess:fd47f524] kill called with signal: SIGTERM
2026-03-26 14:23:59 [info] [Process:fd47f524] Exited, code=0, signal=null, duration=953ms

2026-03-26 14:24:39 [info] [Spawn:vm] id=0788d033 Spawn succeeded in 102ms
2026-03-26 14:24:40 [info] [CoworkVMProcess:0788d033] kill called with signal: SIGTERM
2026-03-26 14:24:40 [info] [Process:0788d033] Exited, code=0, signal=null, duration=1031ms

The user experience is: invoke a skill → Cowork appears to start → stops after a few seconds → shows "Skill details couldn't be loaded" or nothing at all.

3. MCP server connection failure

On every session start:

2026-03-26 14:23:15 [warn] [LocalAgentModeSessionManager] Failed to query mcpServerStatus: Query closed before response received
2026-03-26 14:23:59 [warn] [LocalAgentModeSessionManager] Failed to query mcpServerStatus: Query closed before response received
2026-03-26 14:24:40 [warn] [LocalAgentModeSessionManager] Failed to query mcpServerStatus: Query closed before response received

4. LocalPluginsReader always finds 0 plugins

Despite plugins being installed via the remote API, the local reader never sees them:

2026-03-26 14:23:52 [info] [LocalPluginsReader] Found 0 local plugins
2026-03-26 14:23:52 [info] [LocalPluginsReader] Found 0 enabled local plugins (0 installed)

This repeats dozens of times per minute.

Additional Context

• This coincides with the "Elevated connection reset errors in Cowork" incident posted on status.claude.com starting March 25, 2026 at 14:33 UTC.
• The VM itself boots fine (10s startup, network connects, SDK installs). The issue is in the plugin management layer above the VM.
• Only plugin_016jbzs7aGBZSgBfSWhp4ToX (appears to be a built-in/official plugin) is ever mounted. User-installed plugins from custom marketplaces are never mounted.
• Tested with multiple plugins from different marketplaces — all exhibit the same behavior.
• Full local state reset (cache, manifests, settings, VM state, session data) does not resolve the issue — confirming this is server-side.

Logs

main.log — Plugin install → immediate removal:

14:23:47 installPlugin: remote API install succeeded for plugin marketing@benai-skills
14:23:58 RemotePluginManager: Removed 1 user-installed plugins set to NOT_AVAILABLE
14:23:58 LocalPluginsReader: Found 0 enabled local plugins (0 installed)
14:23:58 LocalAgentModeSessionManager: Using 1 remote plugins
14:23:59 Failed to query mcpServerStatus: Query closed before response received

cowork_vm_node.log — Process spawn → instant kill:

14:24:39 Spawn:vm id=0788d033 Spawn succeeded in 102ms
14:24:40 CoworkVMProcess:0788d033 kill called with signal: SIGTERM
14:24:40 Process:0788d033 Exited, code=0, duration=1031ms