fix(discord): isolate conversations per-thread in thread-only mode

Thread-only mode previously relied on the global conversationMode to
determine whether threads got separate conversations. In shared or
per-channel mode, all threads shared one conversation causing crosstalk.

Add forcePerChat flag on InboundMessage that the Discord adapter sets
when thread-only mode is active. resolveConversationKey treats flagged
messages as per-chat regardless of the configured mode, giving each
thread its own isolated conversation while still sharing agent memory.

Written by Cameron ◯ Letta Code

"Time is an illusion. Lunchtime doubly so." -- Douglas Adams

docs/configuration.md

@@ -461,6 +461,8 @@ channels:
 
 Thread messages inherit parent channel config, so child threads under `EZRA_CHANNEL_ID` use the same group rules.
 
+When `threadMode: thread-only` is set, each thread automatically gets its own isolated conversation (message history), regardless of the global `conversations.mode` setting. This prevents messages from different threads from being interleaved in the same conversation. Agent memory (blocks) is still shared across all threads.
+
 ### Finding Group IDs
 
 Each channel uses different identifiers for groups:

docs/discord-setup.md

@@ -209,6 +209,7 @@ Behavior summary:
 - Top-level messages are ignored in `thread-only` mode.
 - Top-level @mentions create a thread and are answered in that thread when `autoCreateThreadOnMention` is enabled.
 - Thread messages inherit parent channel config. If `EZRA_CHANNEL_ID` is configured, replies in its child threads use that same config.
+- Each thread gets its own isolated conversation (message history), regardless of the global `conversations.mode` setting. This prevents crosstalk between threads. Agent memory (blocks) is still shared.
 
 Required Discord permissions for auto-create:
 

src/channels/discord.ts

@@ -381,6 +381,7 @@ Ask the bot owner to approve with:
         let isListeningMode = false;
         let effectiveChatId = message.channel.id;
         let effectiveGroupName = groupName;
+        let isThreadOnly = false;
 
         // Group gating: config-based allowlist + mode
         if (isGroup && this.config.groups) {
@@ -414,7 +415,8 @@ Ask the bot owner to approve with:
           }
 
           const threadMode = resolveDiscordThreadMode(this.config.groups, keys);
-          if (threadMode === 'thread-only' && !isThreadMessage) {
+          isThreadOnly = threadMode === 'thread-only';
+          if (isThreadOnly && !isThreadMessage) {
             const shouldCreateThread =
               wasMentioned && resolveDiscordAutoCreateThreadOnMention(this.config.groups, keys);
             if (!shouldCreateThread) {
@@ -444,6 +446,7 @@ Ask the bot owner to approve with:
           serverId: message.guildId || undefined,
           wasMentioned,
           isListeningMode,
+          forcePerChat: isThreadOnly || undefined,
           attachments,
           formatterHints: this.getFormatterHints(),
         });

src/core/bot.ts

@@ -150,10 +150,11 @@ export function resolveConversationKey(
   conversationMode: string | undefined,
   conversationOverrides: Set<string>,
   chatId?: string,
+  forcePerChat?: boolean,
 ): string {
   if (conversationMode === 'disabled') return 'default';
   const normalized = channel.toLowerCase();
-  if (conversationMode === 'per-chat' && chatId) return `${normalized}:${chatId}`;
+  if ((conversationMode === 'per-chat' || forcePerChat) && chatId) return `${normalized}:${chatId}`;
   if (conversationMode === 'per-channel') return normalized;
   if (conversationOverrides.has(normalized)) return normalized;
   return 'shared';
@@ -562,8 +563,8 @@ export class LettaBot implements AgentSession {
    * Returns 'shared' in shared mode (unless channel is in perChannel overrides).
    * Returns channel id in per-channel mode or for override channels.
    */
-  private resolveConversationKey(channel: string, chatId?: string): string {
+  private resolveConversationKey(channel: string, chatId?: string, forcePerChat?: boolean): string {
-    return resolveConversationKey(channel, this.config.conversationMode, this.conversationOverrides, chatId);
+    return resolveConversationKey(channel, this.config.conversationMode, this.conversationOverrides, chatId, forcePerChat);
   }
 
   /**
@@ -650,7 +651,7 @@ export class LettaBot implements AgentSession {
       }
     }
 
-    const convKey = this.resolveConversationKey(effective.channel, effective.chatId);
+    const convKey = this.resolveConversationKey(effective.channel, effective.chatId, effective.forcePerChat);
     if (convKey !== 'shared') {
       this.enqueueForKey(convKey, effective, adapter);
     } else {
@@ -889,7 +890,7 @@ export class LettaBot implements AgentSession {
     // queuing it for normal processing. This prevents a deadlock where
     // the stream is paused waiting for user input while the processing
     // flag blocks new messages from being handled.
-    const incomingConvKey = this.resolveConversationKey(msg.channel, msg.chatId);
+    const incomingConvKey = this.resolveConversationKey(msg.channel, msg.chatId, msg.forcePerChat);
     const pendingResolver = this.pendingQuestionResolvers.get(incomingConvKey);
     if (pendingResolver) {
       log.info(`Intercepted message as AskUserQuestion answer from ${msg.userId} (key=${incomingConvKey})`);
@@ -909,7 +910,7 @@ export class LettaBot implements AgentSession {
       return;
     }
 
-    const convKey = this.resolveConversationKey(msg.channel, msg.chatId);
+    const convKey = this.resolveConversationKey(msg.channel, msg.chatId, msg.forcePerChat);
     if (convKey !== 'shared') {
       // Per-channel, per-chat, or override mode: messages on different keys can run in parallel.
       this.enqueueForKey(convKey, msg, adapter);
@@ -994,7 +995,7 @@ export class LettaBot implements AgentSession {
 
         // Wait for the user's next message (intercepted by handleMessage).
         // Key by convKey so each chat resolves independently in per-chat mode.
-        const questionConvKey = this.resolveConversationKey(msg.channel, msg.chatId);
+        const questionConvKey = this.resolveConversationKey(msg.channel, msg.chatId, msg.forcePerChat);
         const answer = await new Promise<string>((resolve) => {
           this.pendingQuestionResolvers.set(questionConvKey, resolve);
         });
@@ -1169,7 +1170,7 @@ export class LettaBot implements AgentSession {
     // Run session
     let session: Session | null = null;
     try {
-      const convKey = this.resolveConversationKey(msg.channel, msg.chatId);
+      const convKey = this.resolveConversationKey(msg.channel, msg.chatId, msg.forcePerChat);
       const seq = ++this.sendSequence;
       const userText = msg.text || '';
       log.info(`processMessage seq=${seq} key=${convKey} retried=${retried} user=${msg.userId} textLen=${userText.length}`);
@@ -1605,7 +1606,7 @@ export class LettaBot implements AgentSession {
             // Only retry if we never sent anything to the user. hasResponse tracks
             // the current buffer, but finalizeMessage() clears it on type changes.
             // sentAnyMessage is the authoritative "did we deliver output" flag.
-            const retryConvKey = this.resolveConversationKey(msg.channel, msg.chatId);
+            const retryConvKey = this.resolveConversationKey(msg.channel, msg.chatId, msg.forcePerChat);
             const retryConvIdFromStore = (retryConvKey === 'shared'
               ? this.store.conversationId
               : this.store.getConversationId(retryConvKey)) ?? undefined;
@@ -1815,7 +1816,7 @@ export class LettaBot implements AgentSession {
         log.error('Failed to send error message to channel:', sendError);
       }
     } finally {
-      const finalConvKey = this.resolveConversationKey(msg.channel, msg.chatId);
+      const finalConvKey = this.resolveConversationKey(msg.channel, msg.chatId, msg.forcePerChat);
       // When session reuse is disabled, invalidate after every message to
       // eliminate any possibility of stream state bleed between sequential
       // sends. Costs ~5s subprocess init overhead per message.

src/core/conversation-key.test.ts

@@ -85,10 +85,33 @@ describe('resolveConversationKey', () => {
     expect(resolveConversationKey('telegram', 'disabled', new Set(), '12345')).toBe('default');
   });
 
-  it('returns "default" in disabled mode regardless of overrides', () => {
+  it('returns \"default\" in disabled mode regardless of overrides', () => {
     const overrides = new Set(['telegram']);
     expect(resolveConversationKey('telegram', 'disabled', overrides)).toBe('default');
   });
+
+  // --- forcePerChat ---
+
+  it('forcePerChat overrides shared mode to per-chat', () => {
+    expect(resolveConversationKey('discord', 'shared', new Set(), '99999', true)).toBe('discord:99999');
+  });
+
+  it('forcePerChat overrides per-channel mode to per-chat', () => {
+    expect(resolveConversationKey('discord', 'per-channel', new Set(), '99999', true)).toBe('discord:99999');
+  });
+
+  it('forcePerChat without chatId falls back normally', () => {
+    expect(resolveConversationKey('discord', 'shared', new Set(), undefined, true)).toBe('shared');
+  });
+
+  it('forcePerChat still respects disabled mode', () => {
+    expect(resolveConversationKey('discord', 'disabled', new Set(), '99999', true)).toBe('default');
+  });
+
+  it('forcePerChat=false does not change behavior', () => {
+    expect(resolveConversationKey('discord', 'shared', new Set(), '99999', false)).toBe('shared');
+    expect(resolveConversationKey('discord', 'per-channel', new Set(), '99999', false)).toBe('discord');
+  });
 });
 
 // ---------------------------------------------------------------------------

src/core/types.ts

@@ -84,6 +84,7 @@ export interface InboundMessage {
   isBatch?: boolean;                  // Is this a batched group message?
   batchedMessages?: InboundMessage[]; // Original individual messages (for batch formatting)
   isListeningMode?: boolean;          // Listening mode: agent processes for memory but response is suppressed
+  forcePerChat?: boolean;             // Force per-chat conversation routing (e.g., Discord thread-only mode)
   formatterHints?: FormatterHints;    // Channel capabilities for directive rendering
 }