fix: isolate Slack thread sessions (#758)

docs/channels/slack.md

@@ -269,6 +269,11 @@ By default, Clawdbot replies in the main channel. Use `channels.slack.replyToMod
 
 The mode applies to both auto-replies and agent tool calls (`slack sendMessage`).
 
+### Thread session isolation
+Slack thread sessions are isolated by default. Configure with:
+- `channels.slack.thread.historyScope`: `thread` (default) keeps per-thread history; `channel` shares history across the channel.
+- `channels.slack.thread.inheritParent`: `false` (default) starts a clean thread session; `true` copies the parent channel transcript into the thread session.
+
 ### Manual threading tags
 For fine-grained control, use these tags in agent responses:
 - `[[reply_to_current]]` — reply to the triggering message (start/continue thread).

docs/gateway/configuration.md

@@ -1050,6 +1050,10 @@ Slack runs in Socket Mode and requires both a bot token and app token:
       reactionNotifications: "own", // off | own | all | allowlist
       reactionAllowlist: ["U123"],
       replyToMode: "off",           // off | first | all
+      thread: {
+        historyScope: "thread",     // thread | channel
+        inheritParent: false
+      },
       actions: {
         reactions: true,
         messages: true,
@@ -1083,6 +1087,10 @@ Reaction notification modes:
 - `all`: all reactions on all messages.
 - `allowlist`: reactions from `channels.slack.reactionAllowlist` on all messages (empty list disables).
 
+Thread session isolation:
+- `channels.slack.thread.historyScope` controls whether thread history is per-thread (`thread`, default) or shared across the channel (`channel`).
+- `channels.slack.thread.inheritParent` controls whether new thread sessions inherit the parent channel transcript (default: false).
+
 Slack action groups (gate `slack` tool actions):
 | Action group | Default | Notes |
 | --- | --- | --- |