Problem

When an agent wakes up in a session, its context window is built from the current session's JSONL transcript. Two mechanisms destroy or compress older messages:

1. Daily reset (default 4am): mints a new sessionId → the agent starts with zero messages. Previous conversation is gone from context entirely.
2. Compaction: summarizes older messages into a compact entry → the agent sees a lossy summary instead of the actual messages.

This means the agent has no guarantee of seeing the last N actual messages from the conversation. A session that was active yesterday evening starts fresh at 4am with zero raw messages. A long-running session that compacted may have replaced recent-ish messages with a summary.

For personal assistant use cases (and many others), the agent needs continuity: the last N messages should always be present in the context window as raw messages, not summaries, regardless of when they were sent.

Desired Behavior

A configurable session.minTailMessages (or similar) that guarantees the agent always sees at least the last N raw messages in its context window:

1. Across compaction: compaction should never summarize the last N messages. The summary covers everything before the tail.
2. Across daily/idle reset: when a new session is created, the last N messages from the previous session's transcript should be carried forward as seed messages into the new session's context (not as a summary, but as actual user/assistant message pairs).
3. Configurable N: default could be ~20-50 messages. Users with large context windows might want more.

Example

Session A (yesterday): 200 messages, last message at 23:45
  ↓ daily reset at 04:00
Session B (today): starts with last N messages from Session A as context seed
  → Agent immediately knows what was discussed yesterday evening

Compaction behavior change

Currently compaction summarizes everything older than the internal keepRecentMessages threshold. With this feature:

• minTailMessages acts as a floor: compaction must preserve at least N raw messages
• The compaction summary covers messages before the tail
• This is different from the existing internal keep-recent logic because it's a user-facing guarantee, not an implementation detail

Reset behavior change

Currently, session reset = clean slate. With this feature:

• On reset (daily, idle, or manual /new), read the last N messages from the outgoing session's JSONL
• Inject them as seed context into the new session (either as actual JSONL entries or as a structured "previous context" block)
• The agent sees continuity without needing to read files or rely on session-memory dumps

Configuration

// openclaw.json
{
  session: {
    // Minimum raw messages preserved in context (survives compaction + reset)
    minTailMessages: 30,
    
    // Optional: carry forward across resets (default: true when minTailMessages > 0)
    carryForwardOnReset: true,
  }
}

Interaction with existing features

• Pre-reset memory flush ([Feature]: Pre-reset agentic memory flush — /new and daily reset should get the same memory flush as compaction #45608): complementary. The flush lets the agent write durable notes; minTailMessages ensures it can read recent conversation. Both are needed.
• Compaction: minTailMessages sets a floor on what compaction can touch. The existing compaction logic already has a concept of "recent messages to keep" — this makes it explicit and configurable.
• Session pruning: unaffected (pruning only touches tool results, not user/assistant messages).
• Context engine plugins: the assemble() method should respect minTailMessages as a contract. Plugins can exceed it but not go below.

Why this matters

Personal assistants, coding agents, and any long-running agent benefit from conversational continuity. Today, the daily reset creates an artificial amnesia boundary that forces users to either:

• Disable daily resets (sessions grow unbounded)
• Accept that the agent forgets everything each morning
• Build workarounds (memory files, boot scripts)

minTailMessages provides a clean middle ground: bounded sessions with guaranteed recent context.

Edge cases

• N exceeds context window: cap at what fits after system prompt + tools
• Short sessions: if session has fewer than N messages, carry all of them
• Manual /new: respect carryForwardOnReset setting (user might want a truly clean slate — could add /new --clean to override)
• Compaction model: the compaction summary should still reference that the tail messages exist, to avoid the summary contradicting the raw messages