Summary

When aggressive session pruning removes agent:main:main from sessions, the Control UI session picker no longer shows the primary session. Heartbeat ticks keep agent:main:main:heartbeat alive, so that becomes the only visible session in the picker. The webchat input then routes user messages directly into the heartbeat-suffixed session — resulting in human↔AI conversation accumulating in a background session rather than the intended main session.

When the next heartbeat tick fires, the Control UI swaps to a newer heartbeat sessionId, effectively clobbering the conversation view mid-chat.

Steps to Reproduce

1. Configure session maintenance with aggressive pruning:

   maintenance: { mode: "enforce", pruneAfter: "3d", maxEntries: 50 }

2. Configure heartbeat with isolatedSession: true, model: "anthropic/claude-haiku-4-5", lightContext: true, target unset (defaults to "none").
3. Wait for daily session reset (or trigger prune) — agent:main:main gets pruned from sessions.json.
4. Heartbeat ticks continue to run, keeping agent:main:main:heartbeat alive.
5. Open Control UI webchat. Observe session picker.
6. Type a user message in the chat input.

Expected Behavior

• The session picker should always surface agent:main:main (or auto-create it if missing/pruned).
• Webchat input should be bound to the primary (main:main) session by default.
• Heartbeat-suffixed sessions (:heartbeat) should be hidden from the picker, or clearly labeled as "background" / read-only, so users cannot accidentally route input into them.

Actual Behavior

• Session picker only showed main:heartbeat (no main:main).
• User typed messages; webchat routed input into agent:main:main:heartbeat.
• Hours of human↔AI conversation accumulated in the heartbeat session.
• On the next heartbeat tick, Control UI swapped to a newer heartbeat sessionId, appearing to clobber the conversation view.

Environment

• OpenClaw version: 2026.4.27 (cbc2ba0)
• Channel: webchat (Control UI)
• Heartbeat config: every: "1h", model: "anthropic/claude-haiku-4-5", lightContext: true, isolatedSession: true, target not set
• Session maintenance config (at time of issue): mode: "enforce", pruneAfter: "3d", maxEntries: 50

Workaround

Relax session pruning so agent:main:main is never pruned (e.g., increase pruneAfter / maxEntries, or exempt the primary session from pruning rules).

Related Issues

• [Bug]: webchat heartbeat with target "last" skips with no-target and blocks background execution #66813 — heartbeat target: "last" skipping with no-target (related but distinct)