Channel notifications miss turn cycle on idle Claude Code sessions

Context

I've been building khimaira-chat, a multi-agent orchestration layer for Claude Code that uses the claude/channel research-preview capability extensively. We push events to peer Claude Code sessions via SSE → notifications/claude/channel.

Symptom

When a Claude Code session is idle (no active prompt, no in-flight tool call) and an external SSE event arrives that emits a notifications/claude/channel JSON-RPC notification, the receiving session sometimes does not start a new turn — the channel block isn't surfaced until the user types something to trigger the next user-prompt cycle.

Active sessions (any in-flight work) appear to surface channel blocks reliably. Idle sessions appear to receive the notification at the protocol level but not always trigger the turn cycle.

Reproduction

1. Two Claude Code windows, each with the khimaira-chat MCP server registered
2. Window A: mcp__khimaira-chat__chat_send(chat_id, body) to a chat both windows are members of
3. Window B: idle (no prompt typed, last response received N minutes ago)
4. Expected: Window B starts a new turn surfacing the channel block
5. Observed (intermittent): Window B doesn't refresh until user types in it

Why this matters

True auto-delivery is the load-bearing affordance for multi-agent orchestration — without it, agents have to poll, which defeats the channels primitive's design.

Workarounds we've shipped

• Proactive SSE subscriber in the MCP subprocess that opens the SSE stream at boot, independent of tool calls (commit 0b02304)
• SSE keepalive + client read timeout to survive laptop suspend/resume (commit 79a5611)
• Exponential SSE backoff on reconnect (commit ca642b5)

These help in many cases but the underlying idle-turn-cycle gap still occasionally surfaces.

Happy to provide

• More detailed reproduction recipes from our dogfood rounds
• Daemon-side SSE traces correlated with Claude Code's response timing
• Specific session IDs / timestamps if telemetry exists

Filed as one of several pieces of feedback on the claude/channel primitive — happy to chat about the broader multi-agent orchestration usage if useful.