refactor: remove parent fork config knob

docs/.generated/config-baseline.sha256

@@ -1,4 +1,4 @@
-f40d6dea3b81c42d5af9e340f091d34b9e39321d171fade6115da594ba90522f  config-baseline.json
-40b1f91714d6f17e2718ea5d34c135550f5a39fe47f781cddc153cf3a59fe2e7  config-baseline.core.json
+0020a49cdf07b79fddfed9584f10323ef77e3ca5c7f907d441c1f2e3f45932c9  config-baseline.json
+8193fd771c9fa50e77c71ff69d41015e6dc02d140182ceea3baaa17713f04b18  config-baseline.core.json
 f42329d45c095881bd226bdb192c235980658fd250606d0c0badc2b12f12f5d3  config-baseline.channel.json
 af71b84b2411d8ccabcc6e09de0ee41f8212ff9869a6677698b6e7e3afdfaa47  config-baseline.plugin.json

docs/gateway/config-agents.md

@@ -1210,10 +1210,6 @@ See [Multi-Agent Sandbox & Tools](/tools/multi-agent-sandbox-tools) for preceden
 - **`identityLinks`**: map canonical ids to provider-prefixed peers for cross-channel session sharing. Dock commands such as `/dock_discord` use the same map to switch the active session's reply route to another linked channel peer; see [Channel docking](/concepts/channel-docking).
 - **`reset`**: primary reset policy. `daily` resets at `atHour` local time; `idle` resets after `idleMinutes`. When both configured, whichever expires first wins. Daily reset freshness uses the session row's `sessionStartedAt`; idle reset freshness uses `lastInteractionAt`. Background/system-event writes such as heartbeat, cron wakeups, exec notifications, and gateway bookkeeping can update `updatedAt`, but they do not keep daily/idle sessions fresh.
 - **`resetByType`**: per-type overrides (`direct`, `group`, `thread`). Legacy `dm` accepted as alias for `direct`.
-- **`parentForkMaxTokens`**: deprecated compatibility guard for the historical parent fork ceiling (default `100000`).
-  - Channel thread sessions and subagent `context="fork"` now use the same parent fork decision path.
-  - When the active parent branch is too large, OpenClaw starts with isolated context instead of failing or inheriting unusable history.
-  - Set `0` only if you intentionally want to disable this guard.
 - **`mainKey`**: legacy field. Runtime always uses `"main"` for the main direct-chat bucket.
 - **`agentToAgent.maxPingPongTurns`**: maximum reply-back turns between agents during agent-to-agent exchanges (integer, range: `0`–`5`). `0` disables ping-pong chaining.
 - **`sendPolicy`**: match by `channel`, `chatType` (`direct|group|channel`, with legacy `dm` alias), `keyPrefix`, or `rawKeyPrefix`. First deny wins.

docs/reference/session-management-compaction.md

@@ -148,7 +148,7 @@ Rules of thumb:
 - **Daily reset** (default 4:00 AM local time on the gateway host) creates a new `sessionId` on the next message after the reset boundary.
 - **Idle expiry** (`session.reset.idleMinutes` or legacy `session.idleMinutes`) creates a new `sessionId` when a message arrives after the idle window. When daily + idle are both configured, whichever expires first wins.
 - **System events** (heartbeat, cron wakeups, exec notifications, gateway bookkeeping) may mutate the session row but do not extend daily/idle reset freshness. Reset rollover discards queued system-event notices for the previous session before the fresh prompt is built.
-- **Parent fork policy** uses PI's active branch when creating a thread or subagent fork. If that branch is too large, OpenClaw starts the child with isolated context instead of failing or inheriting unusable history. The legacy `session.parentForkMaxTokens` key remains as a deprecated compatibility guard; set `0` only if you intentionally want to disable it.
+- **Parent fork policy** uses PI's active branch when creating a thread or subagent fork. If that branch is too large, OpenClaw starts the child with isolated context instead of failing or inheriting unusable history. The sizing policy is automatic; legacy `session.parentForkMaxTokens` config is removed by `openclaw doctor --fix`.
 
 Implementation detail: the decision happens in `initSessionState()` in `src/auto-reply/reply/session.ts`.