Channel splash shows 'plugin not installed' for all plugin-type channels despite channels working correctly (v2.1.145)

Description

In Claude Code v2.1.145, the startup splash always shows plugin not installed for all plugin: prefix channels, even when those channels work correctly. This affects both third-party plugins and Anthropic's own official telegram@claude-plugins-official plugin.

Reproduction

Any session with a plugin that provides channels (e.g. relay, telegram):

Listening for channel messages from: plugin:telegram@claude-plugins-official, plugin:relay@eco-relay, server:tacto-channel
Experimental · inbound messages will be pushed into this session, this carries prompt injection risks.
plugin:telegram@claude-plugins-official · plugin not installed
plugin:relay@eco-relay · plugin not installed

Note: server:tacto-channel (a direct MCP server) shows NO error. Only plugin: prefixed channels fail.

Environment

• Claude Code version: 2.1.145
• OS: Windows 11 Pro 10.0.26200
• Plugins affected: relay@eco-relay (third-party), telegram@claude-plugins-official (official)

Evidence that channels actually work

Despite the warning, channels function correctly:

• Relay <channel> messages are received and delivered between sessions
• Telegram bot daemon is running (bot.pid active)
• All MCP tools (relay_peers, relay_send, etc.) work normally

The warning is a false positive.

Investigation

We verified the following:

1. Both plugins are correctly installed — present in installed_plugins.json with correct paths
2. Both MCP servers declare channel capability correctly at runtime:

``typescript
experimental: { "claude/channel": {} }
``

1. plugin.json lacks the channels field (per the official JSON Schema at schemastore.org). We added the correct format to one plugin:

``json
"channels": [{ "server": "relay" }]
``
This did not resolve the warning, suggesting the channel loader's static check does not read this field in v2.1.145.

1. The telegram@claude-plugins-official plugin (official Anthropic plugin) has the same problem — its plugin.json also lacks channels and shows the identical error. This strongly suggests the issue is in the channel loader, not the plugins.

Expected behavior

• plugin:relay@eco-relay → no error (plugin is installed and channel works)
• plugin:telegram@claude-plugins-official → no error (official Anthropic plugin)

Actual behavior

Both show · plugin not installed despite being installed and functional.

Suggested fix

The channel loader's pre-flight check for plugin: channels should either:

1. Read the channels field from plugin.json (per the official schema) to confirm the plugin declares channel support, OR
2. Verify the plugin exists in installed_plugins.json (which it does) rather than failing the check