fix(webapp): stamp Session.chatSnapshotStoragePath at row creation

Address CodeRabbit findings on PR #3679:
- Stamp `chatSnapshotStoragePath` once at session create + upsert-create
  paths so the new presign route only reads. Drops the lazy backfill
  branch (and its empty `.catch()`) from the route.
- Return `json(...)` for the 405 in the action handler so Remix doesn't
  coerce the plain object into a 200 with a misleading body.
- Extract `chatSnapshotStoragePathForSession(friendlyId)` next to the
  other session-addressing helpers so creation and the GET fallback
  agree on the canonical path.

Author: ericallam

apps/webapp/app/routes/api.v1.sessions.$sessionId.snapshot-url.ts

@@ -1,28 +1,30 @@
 import type { ActionFunctionArgs } from "@remix-run/server-runtime";
 import { json } from "@remix-run/server-runtime";
 import { z } from "zod";
-import { $replica, prisma } from "~/db.server";
-import { env } from "~/env.server";
+import { $replica } from "~/db.server";
 import { authenticateApiRequest } from "~/services/apiAuth.server";
-import { resolveSessionByIdOrExternalId } from "~/services/realtime/sessions.server";
+import {
+  chatSnapshotStoragePathForSession,
+  resolveSessionByIdOrExternalId,
+} from "~/services/realtime/sessions.server";
 import { createLoaderApiRoute } from "~/services/routeBuilders/apiBuilder.server";
 import { generatePresignedUrl } from "~/v3/objectStore.server";
 
 const ParamsSchema = z.object({
   sessionId: z.string(),
 });
 
-// Canonical key for new sessions, prefixed with the default protocol so
-// PUT/GET resolve to the same store on multi-provider deployments.
-function defaultSnapshotKey(sessionId: string): string {
-  const path = `sessions/${sessionId}/snapshot.json`;
-  const protocol = env.OBJECT_STORE_DEFAULT_PROTOCOL;
-  return protocol ? `${protocol}://${path}` : path;
+// `chatSnapshotStoragePath` is stamped on every new Session at row creation
+// (see api.v1.sessions.ts). The fallback handles sessions created before
+// the column existed — read against the currently-configured default
+// protocol and compute the same path the SDK uploaded under.
+function snapshotKey(session: { friendlyId: string; chatSnapshotStoragePath: string | null }) {
+  return session.chatSnapshotStoragePath ?? chatSnapshotStoragePathForSession(session.friendlyId);
 }
 
 export async function action({ request, params }: ActionFunctionArgs) {
   if (request.method.toUpperCase() !== "PUT") {
-    return { status: 405, body: "Method Not Allowed" };
+    return json({ error: "Method Not Allowed" }, { status: 405 });
   }
 
   const auth = await authenticateApiRequest(request);
@@ -40,31 +42,16 @@ export async function action({ request, params }: ActionFunctionArgs) {
     return json({ error: "Session not found" }, { status: 404 });
   }
 
-  // Reuse the stored path on subsequent writes; persist on first write so
-  // future default-protocol changes don't strand existing snapshots.
-  const key = session.chatSnapshotStoragePath ?? defaultSnapshotKey(parsed.sessionId);
-
   const signed = await generatePresignedUrl(
     auth.environment.project.externalRef,
     auth.environment.slug,
-    key,
+    snapshotKey(session),
     "PUT"
   );
   if (!signed.success) {
     return json({ error: `Failed to generate presigned URL: ${signed.error}` }, { status: 500 });
   }
 
-  if (session.chatSnapshotStoragePath === null) {
-    await prisma.session
-      .updateMany({
-        where: { id: session.id, chatSnapshotStoragePath: null },
-        data: { chatSnapshotStoragePath: key },
-      })
-      .catch(() => {
-        // Best-effort; concurrent writers may have already set it.
-      });
-  }
-
   return json({ presignedUrl: signed.url });
 }
 
@@ -76,18 +63,15 @@ export const loader = createLoaderApiRoute(
     findResource: async (params, auth) =>
       resolveSessionByIdOrExternalId($replica, auth.environment.id, params.sessionId),
   },
-  async ({ params, authentication, resource: session }) => {
+  async ({ authentication, resource: session }) => {
     if (!session) {
       return json({ error: "Session not found" }, { status: 404 });
     }
 
-    // Stored path wins; fall back to computed default for pre-column sessions.
-    const key = session.chatSnapshotStoragePath ?? defaultSnapshotKey(params.sessionId);
-
     const signed = await generatePresignedUrl(
       authentication.environment.project.externalRef,
       authentication.environment.slug,
-      key,
+      snapshotKey(session),
       "GET"
     );
     if (!signed.success) {

apps/webapp/app/routes/api.v1.sessions.ts

@@ -17,7 +17,10 @@ import {
   ensureRunForSession,
   type SessionTriggerConfig,
 } from "~/services/realtime/sessionRunManager.server";
-import { serializeSession } from "~/services/realtime/sessions.server";
+import {
+  chatSnapshotStoragePathForSession,
+  serializeSession,
+} from "~/services/realtime/sessions.server";
 import { SessionsRepository } from "~/services/sessionsRepository/sessionsRepository.server";
 import {
   anyResource,
@@ -181,6 +184,7 @@ const { action } = createActionApiRoute(
             environmentType: authentication.environment.type,
             organizationId: authentication.environment.organizationId,
             streamBasinName: authentication.environment.organization.streamBasinName,
+            chatSnapshotStoragePath: chatSnapshotStoragePathForSession(friendlyId),
           },
           update: { triggerConfig: triggerConfigJson },
         });
@@ -201,6 +205,7 @@ const { action } = createActionApiRoute(
             environmentType: authentication.environment.type,
             organizationId: authentication.environment.organizationId,
             streamBasinName: authentication.environment.organization.streamBasinName,
+            chatSnapshotStoragePath: chatSnapshotStoragePathForSession(friendlyId),
           },
         });
       }

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

@@ -1,6 +1,20 @@
 import type { PrismaClient, Session } from "@trigger.dev/database";
 import type { SessionItem } from "@trigger.dev/core/v3";
 import { $replica } from "~/db.server";
+import { env } from "~/env.server";
+
+/**
+ * Canonical storage URI for a session's chat.agent snapshot. Stamped on
+ * `Session.chatSnapshotStoragePath` at row creation so PUT/GET presigns
+ * resolve to the same store even if `OBJECT_STORE_DEFAULT_PROTOCOL`
+ * changes later. The protocol prefix (when set) is what makes
+ * generic-packets PUT and GET agree on the target provider.
+ */
+export function chatSnapshotStoragePathForSession(friendlyId: string): string {
+  const path = `sessions/${friendlyId}/snapshot.json`;
+  const protocol = env.OBJECT_STORE_DEFAULT_PROTOCOL;
+  return protocol ? `${protocol}://${path}` : path;
+}
 
 /**
  * Prefix that {@link SessionId.generate} attaches to every Session friendlyId.