Scheduled triggers: MCP connector tools never register in automated runs

Description

MCP connector tools (specifically Slack via claude.ai connector) are never available in automated scheduled trigger runs, but work fine when manually interacting with the same session on claude.ai.

Reproduction

1. Create a scheduled trigger with an MCP connection:

{
  "mcp_connections": [{
    "connector_uuid": "ee462478-b709-497b-9d0e-373de55cf866",
    "name": "Slack",
    "url": "https://mcp.slack.com/mcp",
    "permitted_tools": ["slack_search_channels", "slack_read_channel", "slack_read_thread"]
  }]
}

1. The Slack MCP tools are also listed in allowed_tools in the session context and ToolSearch is included.

1. When the trigger runs automatically (or via POST /run), the agent calls ToolSearch with select:mcp__Slack__slack_search_channels,... and gets "No matching deferred tools found".

1. The agent retries with sleep 5 between attempts, up to 5 times — still fails every time.

1. However, if I visit the session URL on claude.ai and manually type "try again", the ToolSearch call succeeds immediately and the Slack tools load and work perfectly.

Observed behavior

• Automated run: ToolSearch → "No matching deferred tools found" (100% failure across 6 consecutive runs)
• Manual interaction in same session: ToolSearch → tools load successfully, Slack API calls work

Expected behavior

MCP connector tools should be available in automated scheduled trigger runs without manual intervention.

Environment

• Trigger IDs: trig_01VacCxX5umUYa3VDEDV36Nj
• MCP connector: claude.ai Slack connector (ee462478-b709-497b-9d0e-373de55cf866)
• Environment: Default Anthropic Cloud (env_01CoHRoFa1MymevZrCN43dFH)
• Model: claude-sonnet-4-6

Workaround

None found. The only way to make it work is manual interaction with the session on claude.ai after the automated run starts.