Bug

When a new skill is added (either via config allowlist or by placing it in a workspace/managed skills directory), the skillsSnapshot cached in sessions.json is not invalidated by /restart or gateway restart. The stale snapshot persists and the new skill never appears in the session prompt.

Steps to Reproduce

1. Have an existing session with a cached skillsSnapshot in sessions.json
2. Add a new skill to the workspace skills directory (e.g. <workspace>/skills/my-skill/SKILL.md)
3. Add the skill name to the agent's skills allowlist in config (if applicable)
4. Gateway restart (SIGUSR1) or /restart command
5. Send a message in the session

Expected: The skill appears in the session's available skills list
Actual: The skill does not appear. The stale skillsSnapshot from sessions.json is reused.

Evidence

• Gateway logs confirm the skill is loaded (Discord slash command count increased from 133 to 134)
• The skillsSnapshot field in sessions.json for the session does not contain the new skill
• Multiple gateway restarts and /restart commands did not clear the snapshot
• Manually deleting the skillsSnapshot key from sessions.json and restarting fixed the issue

Environment

• OpenClaw 2026.3.24
• macOS (arm64)
• Multi-agent setup with per-agent skills allowlist

Workaround

Manually delete the skillsSnapshot field from the affected session in <agentDir>/sessions/sessions.json and restart the gateway.

Suggested Fix

/restart (and gateway restart) should invalidate the skillsSnapshot so it rebuilds on the next turn. Alternatively, compare a hash of the current eligible skills against the cached snapshot and refresh if stale.