fix: preserve subagent thread routing (#1241)

Thanks @gnarco.

Co-authored-by: gnarco <gnarco@users.noreply.github.com>

src/infra/outbound/agent-delivery.ts

@@ -22,6 +22,7 @@ export type AgentDeliveryPlan = {
   resolvedChannel: GatewayMessageChannel;
   resolvedTo?: string;
   resolvedAccountId?: string;
+  resolvedThreadId?: string | number;
   deliveryTargetMode?: ChannelOutboundTargetMode;
 };
 
@@ -29,6 +30,7 @@ export function resolveAgentDeliveryPlan(params: {
   sessionEntry?: SessionEntry;
   requestedChannel?: string;
   explicitTo?: string;
+  explicitThreadId?: string | number;
   accountId?: string;
   wantsDelivery: boolean;
 }): AgentDeliveryPlan {
@@ -46,6 +48,7 @@ export function resolveAgentDeliveryPlan(params: {
     entry: params.sessionEntry,
     requestedChannel: requestedChannel === INTERNAL_MESSAGE_CHANNEL ? "last" : requestedChannel,
     explicitTo,
+    explicitThreadId: params.explicitThreadId,
   });
 
   const resolvedChannel = (() => {
@@ -89,6 +92,7 @@ export function resolveAgentDeliveryPlan(params: {
     resolvedChannel,
     resolvedTo,
     resolvedAccountId,
+    resolvedThreadId: baseDelivery.threadId,
     deliveryTargetMode,
   };
 }

src/infra/outbound/targets.test.ts

@@ -124,10 +124,12 @@ describe("resolveSessionDeliveryTarget", () => {
       channel: "whatsapp",
       to: "+1555",
       accountId: "acct-1",
+      threadId: undefined,
       mode: "implicit",
       lastChannel: "whatsapp",
       lastTo: "+1555",
       lastAccountId: "acct-1",
+      lastThreadId: undefined,
     });
   });
 
@@ -146,10 +148,12 @@ describe("resolveSessionDeliveryTarget", () => {
       channel: "telegram",
       to: undefined,
       accountId: undefined,
+      threadId: undefined,
       mode: "implicit",
       lastChannel: "whatsapp",
       lastTo: "+1555",
       lastAccountId: undefined,
+      lastThreadId: undefined,
     });
   });
 
@@ -169,10 +173,12 @@ describe("resolveSessionDeliveryTarget", () => {
       channel: "telegram",
       to: "+1555",
       accountId: undefined,
+      threadId: undefined,
       mode: "implicit",
       lastChannel: "whatsapp",
       lastTo: "+1555",
       lastAccountId: undefined,
+      lastThreadId: undefined,
     });
   });
 
@@ -192,10 +198,12 @@ describe("resolveSessionDeliveryTarget", () => {
       channel: "slack",
       to: undefined,
       accountId: undefined,
+      threadId: undefined,
       mode: "implicit",
       lastChannel: "whatsapp",
       lastTo: "+1555",
       lastAccountId: undefined,
+      lastThreadId: undefined,
     });
   });
 });

src/infra/outbound/targets.ts

@@ -35,16 +35,19 @@ export type SessionDeliveryTarget = {
   channel?: DeliverableMessageChannel;
   to?: string;
   accountId?: string;
+  threadId?: string | number;
   mode: ChannelOutboundTargetMode;
   lastChannel?: DeliverableMessageChannel;
   lastTo?: string;
   lastAccountId?: string;
+  lastThreadId?: string | number;
 };
 
 export function resolveSessionDeliveryTarget(params: {
   entry?: SessionEntry;
   requestedChannel?: GatewayMessageChannel | "last";
   explicitTo?: string;
+  explicitThreadId?: string | number;
   fallbackChannel?: DeliverableMessageChannel;
   allowMismatchedLastTo?: boolean;
   mode?: ChannelOutboundTargetMode;
@@ -54,6 +57,7 @@ export function resolveSessionDeliveryTarget(params: {
     context?.channel && isDeliverableMessageChannel(context.channel) ? context.channel : undefined;
   const lastTo = context?.to;
   const lastAccountId = context?.accountId;
+  const lastThreadId = context?.threadId;
 
   const rawRequested = params.requestedChannel ?? "last";
   const requested = rawRequested === "last" ? "last" : normalizeMessageChannel(rawRequested);
@@ -68,6 +72,10 @@ export function resolveSessionDeliveryTarget(params: {
     typeof params.explicitTo === "string" && params.explicitTo.trim()
       ? params.explicitTo.trim()
       : undefined;
+  const explicitThreadId =
+    params.explicitThreadId != null && params.explicitThreadId !== ""
+      ? params.explicitThreadId
+      : undefined;
 
   let channel = requestedChannel === "last" ? lastChannel : requestedChannel;
   if (!channel && params.fallbackChannel && isDeliverableMessageChannel(params.fallbackChannel)) {
@@ -84,16 +92,19 @@ export function resolveSessionDeliveryTarget(params: {
   }
 
   const accountId = channel && channel === lastChannel ? lastAccountId : undefined;
+  const threadId = channel && channel === lastChannel ? lastThreadId : undefined;
   const mode = params.mode ?? (explicitTo ? "explicit" : "implicit");
 
   return {
     channel,
     to,
     accountId,
+    threadId: explicitThreadId ?? threadId,
     mode,
     lastChannel,
     lastTo,
     lastAccountId,
+    lastThreadId,
   };
 }