Remote trigger: MCP connectors not exposed as tools in cloud sessions

Bug Description

MCP connectors attached to a remote trigger (scheduled agent) are not discoverable as tools by the remote agent session. The agent searches for MCP tools (e.g. mcp__slack__*, mcp__gmail__*) via ToolSearch and finds nothing, even though the connectors are properly configured on the trigger.

Trigger Config

The trigger has mcp_connections correctly configured:

"mcp_connections": [
  {"connector_uuid": "2866e9d7-...", "name": "Slack", "url": "https://mcp.slack.com/mcp"},
  {"connector_uuid": "ded8eb40-...", "name": "Gmail", "url": "https://gmail.mcp.claude.com/mcp"}
]

The connectors are authorized and working in interactive claude.ai sessions.

What Happens

When the remote agent runs, it cannot find any MCP tools. The agent reports:

"The required MCP tools for Slack and Gmail are not available in this session. ToolSearch found no tools matching mcp__slack, mcp__gmail, or mcp__github__*."

What Was Tried

1. Setting allowed_tools: [] (empty) — API expanded to built-in tools only, no MCP tools
2. Explicitly adding MCP tool names to allowed_tools (e.g. mcp__Slack__slack_send_message, mcp__Gmail__gmail_search_messages) — still not found
3. Multiple manual runs via RemoteTrigger action: "run" — same result every time

Expected Behavior

MCP connectors attached to a trigger should be exposed as callable tools in the remote agent session, the same way they are in interactive claude.ai sessions.

Environment

• Trigger ID: trig_017dYGChncYAmfoSK3tdqX7Q
• Environment: env_018TFDoYupLmXaPDAYHnxGLM (claude-code-default, anthropic_cloud)
• Model: claude-sonnet-4-6
• Connectors: Slack (mcp.slack.com), Gmail (gmail.mcp.claude.com)
• The trigger has never successfully used MCP connectors since creation (2026-03-31)

Failed Session Examples

• https://claude.ai/code/session_01Apx96YWAZewLUGSGS2UGhk