fix(webapp): keep session runs off the legacy realtime streams backend

.server-changes/session-run-streams-version.md

@@ -0,0 +1,6 @@
+---
+area: webapp
+type: fix
+---
+
+Run-scoped realtime streams written inside a chat session run now use the same streams backend as the session itself, instead of falling back to the older one.

apps/webapp/app/services/realtime/sessionRunManager.server.ts

@@ -8,6 +8,7 @@ import { logger } from "~/services/logger.server";
 import { CancelTaskRunService } from "~/v3/services/cancelTaskRun.server";
 import { TriggerTaskService } from "~/v3/services/triggerTask.server";
 import { isFinalRunStatus } from "~/v3/taskStatus";
+import { determineRealtimeStreamsVersion } from "./v1StreamsGlobal.server";
 
 /**
  * Schema for `Session.triggerConfig` (stored as JSONB). The wire-format
@@ -275,6 +276,12 @@ export async function ensureRunForSession(
  * Trigger a single run for a session. Builds `TriggerTaskRequestBody`
  * by shallow-merging `payloadOverrides` over `config.basePayload` and
  * threading `config`'s machine/queue/tags through the trigger options.
+ *
+ * A session's own channels are always v2, so the run is stamped to match
+ * rather than inheriting the `realtimeStreamsVersion` column default. Without
+ * this, run-scoped `streams.*` calls inside a session run resolve to v1 while
+ * the session it belongs to is on v2. `determineRealtimeStreamsVersion`
+ * degrades to v1 where v2 streams are not configured.
  */
 async function triggerSessionRun(params: {
   session: Pick<Session, "id" | "taskIdentifier">;
@@ -310,6 +317,7 @@ async function triggerSessionRun(params: {
   const result = await service.call(session.taskIdentifier, environment, body, {
     triggerSource: "session",
     triggerAction: "trigger",
+    realtimeStreamsVersion: determineRealtimeStreamsVersion("v2"),
   });
 
   if (!result) {

apps/webapp/test/realtimeServices.replicaLag.test.ts

@@ -412,6 +412,7 @@ describe("realtime-svc — replica-lag guards", () => {
       // previousRunId forwarded to the triggered run is the calling run's cuid (documented fallback).
       expect(triggerState.calls).toHaveLength(1);
       expect(triggerState.calls[0]!.body.payload.previousRunId).toBe(callingRunId);
+      expect(triggerState.calls[0]!.options.realtimeStreamsVersion).toBeDefined();
       expect(replica.wasHit("taskRun")).toBe(true);
 
       // Proof the null was lag-induced: the primary holds the resolvable friendlyId (≠ the cuid).