Bug Description

When memory-core dreaming is enabled, the Dream Diary narrative subagent creates a new session on every run instead of reusing an existing one. The session key includes a millisecond timestamp, making it unique each time:

// dreaming-narrative.ts
function buildNarrativeSessionKey(params) {
    const workspaceHash = createHash("sha1").update(params.workspaceDir).digest("hex").slice(0, 12);
    return `dreaming-narrative-${params.phase}-${workspaceHash}-${params.nowMs}`;
    //                                                 ^^^^^^ unique per run
}

This causes unbounded session accumulation in the session store.

Impact

• Over 4 days (Apr 12–16), 251 orphan dreaming sessions accumulated on the main agent
• Each session consumed ~19K tokens, totaling ~4.8M tokens wasted
• The session store index grew from ~4 entries to 255, with no automatic cleanup of the index entries
• While orphan transcript files get cleaned up after 5 minutes (DREAMING_ORPHAN_MIN_AGE_MS), the session store entries persist indefinitely

Reproduction

1. Enable dreaming: plugins.entries.memory-core.config.dreaming.enabled = true
2. Let the dreaming cron run (default: 0 3 * * *) or trigger dreaming manually
3. Observe session count growing by 2 per run (light + rem phases)

Expected Behavior

The narrative subagent should reuse a single session (or at most one per phase: dreaming-narrative-light and dreaming-narrative-rem) rather than creating a new session each time.

Environment

• OpenClaw version: 2026.4.14 (323493f)
• OS: macOS 26.3.1 (arm64)
• Node: v24.14.0

Suggested Fix

Remove nowMs from the session key, or use a fixed key per agent+phase combination:

function buildNarrativeSessionKey(params) {
    const workspaceHash = createHash("sha1").update(params.workspaceDir).digest("hex").slice(0, 12);
    return `dreaming-narrative-${params.phase}-${workspaceHash}`;
}

The existing orphan cleanup logic already handles transcript files — but the session store entries also need cleanup if unique keys are intentional.