Problem

Webhook hook mappings (e.g., Gmail Pub/Sub) create a new session per event via sessionKey templating:

{
  "sessionKey": "hook:gmail:{{messages[0].id}}",
  ...
}

These sessions accumulate forever with no built-in cleanup mechanism. Over time this leads to:

• Hundreds/thousands of orphaned session entries in sessions.json
• Orphaned transcript .jsonl files consuming disk space
• In my case: 358 sessions / 44MB before manual cleanup

Proposed Solution

Add a cleanup option to webhook mappings, similar to what sessions_spawn already supports:

{
  "match": { "path": "gmail" },
  "action": "agent",
  "sessionKey": "hook:gmail:{{messages[0].id}}",
  "cleanup": "delete",  // <-- new option
  ...
}

Options could mirror sessions_spawn:

• "delete" — remove session + transcript after completion
• "keep" — current behavior (default for backwards compat)

Current Workaround

I'm running a cron job that periodically cleans up *:hook:* sessions older than 5 minutes:

jq 'with_entries(select(
  (.key | contains(":hook:") | not) or 
  (($now - (.value.updatedAt // 0)) <= $maxAge)
))' sessions.json

This works but is hacky and requires external maintenance.

Context

• Webhook hooks are typically fire-and-forget (email triage, notifications, etc.)
• Session history has no value after the single turn completes
• The sessions_spawn precedent shows this pattern is already understood