diff --git a/packages/markerikson-stack-client-prototype/react.d.ts b/packages/markerikson-stack-client-prototype/react.d.ts
new file mode 100644
index 00000000000..3c70a19a4c4
--- /dev/null
+++ b/packages/markerikson-stack-client-prototype/react.d.ts
@@ -0,0 +1,17 @@
+import "react";
+
+declare module "react" {
+  type TransitionCallback = () => void;
+
+  // The following hooks are only available in the experimental react release.
+  export function startTransition(TransitionCallback): void;
+  export function useDeferredValue(value: T): T;
+  export function useTransition(): [
+    isPending: boolean,
+    startTransition: (TransitionCallback) => void
+  ];
+
+  // Unstable Suspense cache API
+  export function unstable_getCacheForType<T>(resourceType: () => T): T;
+  export function unstable_useCacheRefresh(): () => void;
+}
diff --git a/packages/markerikson-stack-client-prototype/src/app/api.ts b/packages/markerikson-stack-client-prototype/src/app/api.ts
index 0467a1c5775..8820ae374be 100644
--- a/packages/markerikson-stack-client-prototype/src/app/api.ts
+++ b/packages/markerikson-stack-client-prototype/src/app/api.ts
@@ -13,22 +13,31 @@ import { Dictionary } from "lodash";
 import groupBy from "lodash/groupBy";
 // eslint-disable-next-line no-restricted-imports
 import { client } from "protocol/socket";
+import type { ReplayClientInterface } from "shared/client/types";
 
-interface SourceGroups {
+let sessionId: SessionId;
+let replayClient: ReplayClientInterface;
+
+export const setReplayClient = (_sessionId: SessionId, _replayClient: ReplayClientInterface) => {
+  sessionId = _sessionId;
+  replayClient = _replayClient;
+};
+
+export interface SourceGroups {
   src: newSource[];
   node_modules: newSource[];
   other: newSource[];
 }
 
-const reIsJsSourceFile = /(js|ts)x?$/;
+const reIsJsSourceFile = /(js|ts)x?(\?[\w\d]+)*$/;
 
 const CACHE_DATA_PERMANENTLY = 10 * 365 * 24 * 60 * 60;
 
 export const api = createApi({
   baseQuery: fakeBaseQuery(),
   endpoints: build => ({
-    getSources: build.query<SourceGroups, SessionId>({
-      queryFn: async (sessionId: SessionId) => {
+    getSources: build.query<SourceGroups, void>({
+      queryFn: async () => {
         const sources: newSource[] = [];
 
         // Fetch the sources
@@ -60,8 +69,8 @@ export const api = createApi({
       },
       keepUnusedDataFor: CACHE_DATA_PERMANENTLY,
     }),
-    getSourceText: build.query<string, { sessionId: SessionId; sourceId: string }>({
-      queryFn: async ({ sessionId, sourceId }) => {
+    getSourceText: build.query<string, string>({
+      queryFn: async sourceId => {
         const demoSourceText = await client.Debugger.getSourceContents(
           {
             sourceId,
@@ -72,11 +81,8 @@ export const api = createApi({
       },
       keepUnusedDataFor: CACHE_DATA_PERMANENTLY,
     }),
-    getSourceHitCounts: build.query<
-      Dictionary<HitCount[]>,
-      { sessionId: SessionId; sourceId: string }
-    >({
-      queryFn: async ({ sessionId, sourceId }) => {
+    getSourceHitCounts: build.query<Dictionary<HitCount[]>, string>({
+      queryFn: async sourceId => {
         const { lineLocations } = await client.Debugger.getPossibleBreakpoints(
           {
             sourceId,
@@ -98,32 +104,30 @@ export const api = createApi({
       },
       keepUnusedDataFor: CACHE_DATA_PERMANENTLY,
     }),
-    getLineHitPoints: build.query<PointDescription[], { location: Location; sessionId: SessionId }>(
-      {
-        queryFn: async ({ location, sessionId }) => {
-          const data = await new Promise<PointDescription[]>(async resolve => {
-            const { analysisId } = await client.Analysis.createAnalysis(
-              {
-                mapper: "",
-                effectful: false,
-              },
-              sessionId
-            );
-
-            client.Analysis.addLocation({ analysisId, location }, sessionId);
-            client.Analysis.findAnalysisPoints({ analysisId }, sessionId);
-            client.Analysis.addAnalysisPointsListener(({ points }) => {
-              resolve(points);
-              client.Analysis.releaseAnalysis({ analysisId }, sessionId);
-            });
+    getLineHitPoints: build.query<PointDescription[], Location>({
+      queryFn: async location => {
+        const data = await new Promise<PointDescription[]>(async resolve => {
+          const { analysisId } = await client.Analysis.createAnalysis(
+            {
+              mapper: "",
+              effectful: false,
+            },
+            sessionId
+          );
+
+          client.Analysis.addLocation({ analysisId, location }, sessionId);
+          client.Analysis.findAnalysisPoints({ analysisId }, sessionId);
+          client.Analysis.addAnalysisPointsListener(({ points }) => {
+            resolve(points);
+            client.Analysis.releaseAnalysis({ analysisId }, sessionId);
           });
+        });
 
-          return { data };
-        },
-      }
-    ),
-    getPause: build.query<createPauseResult, { point: PointDescription; sessionId: SessionId }>({
-      queryFn: async ({ point, sessionId }) => {
+        return { data };
+      },
+    }),
+    getPause: build.query<createPauseResult, PointDescription>({
+      queryFn: async point => {
         const pause = await client.Session.createPause({ point: point.point }, sessionId);
         return { data: pause };
       },
diff --git a/packages/markerikson-stack-client-prototype/src/app/hooks.ts b/packages/markerikson-stack-client-prototype/src/app/hooks.ts
index b6b61d34e28..f2f7f18a78c 100644
--- a/packages/markerikson-stack-client-prototype/src/app/hooks.ts
+++ b/packages/markerikson-stack-client-prototype/src/app/hooks.ts
@@ -1,9 +1,9 @@
 // eslint-disable-next-line no-restricted-imports
-import { TypedUseSelectorHook, useDispatch, useSelector } from "react-redux";
+import { TypedUseSelectorHook, useDispatch, useSelector, useStore } from "react-redux";
 
-import type { AppDispatch, AppState } from "./store";
+import type { AppDispatch, AppState, AppStore } from "./store";
 
 // Use throughout your app instead of plain `useDispatch` and `useSelector`
-export const useAppDispatch = () => useDispatch<AppDispatch>();
-
+export const useAppDispatch: () => AppDispatch = useDispatch;
+export const useAppStore: () => AppStore = useStore;
 export const useAppSelector: TypedUseSelectorHook<AppState> = useSelector;
diff --git a/packages/markerikson-stack-client-prototype/src/app/store.ts b/packages/markerikson-stack-client-prototype/src/app/store.ts
index 86cfd359d10..e5131d2b4a1 100644
--- a/packages/markerikson-stack-client-prototype/src/app/store.ts
+++ b/packages/markerikson-stack-client-prototype/src/app/store.ts
@@ -15,8 +15,8 @@ export function makeStore() {
 
 const store = makeStore();
 
+export type AppStore = typeof store;
 export type AppState = ReturnType<typeof store.getState>;
-
 export type AppDispatch = typeof store.dispatch;
 
 export type AppThunk<ReturnType = void> = ThunkAction<
diff --git a/packages/markerikson-stack-client-prototype/src/components/Initializer.tsx b/packages/markerikson-stack-client-prototype/src/components/Initializer.tsx
index 4503646712c..caa2d727a15 100644
--- a/packages/markerikson-stack-client-prototype/src/components/Initializer.tsx
+++ b/packages/markerikson-stack-client-prototype/src/components/Initializer.tsx
@@ -6,6 +6,7 @@ import { ReplayClientContext } from "shared/client/ReplayClientContext";
 
 import asyncInitializeClient from "../client/asyncInitializeClient";
 import { SessionContext, SessionContextType } from "../contexts/SessionContext";
+import { setReplayClient } from "../app/api";
 
 // HACK Hack around the fact that the initSocket() function is side effectful
 // and writes to an "app" global on the window object.
@@ -25,6 +26,7 @@ export default function Initializer({ children }: { children: ReactNode }) {
     // We only need to initialize them once.
     if (!didInitializeRef.current) {
       asyncInitializeClient(replayClient).then(sessionData => {
+        setReplayClient(sessionData.sessionId, replayClient)
         setContext(sessionData);
       });
     }
diff --git a/packages/markerikson-stack-client-prototype/src/components/Loader.module.css b/packages/markerikson-stack-client-prototype/src/components/Loader.module.css
new file mode 100644
index 00000000000..a2aaa9cf9ac
--- /dev/null
+++ b/packages/markerikson-stack-client-prototype/src/components/Loader.module.css
@@ -0,0 +1,4 @@
+.Loader {
+  padding: 0.25rem;
+  background-color: yellow;
+}
\ No newline at end of file
diff --git a/packages/markerikson-stack-client-prototype/src/components/Loader.tsx b/packages/markerikson-stack-client-prototype/src/components/Loader.tsx
new file mode 100644
index 00000000000..f4e6c55511f
--- /dev/null
+++ b/packages/markerikson-stack-client-prototype/src/components/Loader.tsx
@@ -0,0 +1,5 @@
+import styles from "./Loader.module.css";
+
+export default function Loader() {
+  return <div className={styles.Loader}>Loading… ⏱️</div>;
+}
\ No newline at end of file
diff --git a/packages/markerikson-stack-client-prototype/src/features/sources/SourceContent.tsx b/packages/markerikson-stack-client-prototype/src/features/sources/SourceContent.tsx
index 15de335b094..77cd82aa341 100644
--- a/packages/markerikson-stack-client-prototype/src/features/sources/SourceContent.tsx
+++ b/packages/markerikson-stack-client-prototype/src/features/sources/SourceContent.tsx
@@ -25,14 +25,11 @@ export const SourceContent = () => {
   const selectedSourceId = useAppSelector(state => state.sources.selectedSourceId);
   const selectedPoint = useAppSelector(state => state.sources.selectedPoint);
 
-  const replayClient = useContext(ReplayClientContext);
-  const sessionId = replayClient.getSessionId()!;
-
   const { currentData: sourceText } = useGetSourceTextQuery(
-    selectedSourceId ? { sessionId, sourceId: selectedSourceId } : skipToken
+    selectedSourceId ? selectedSourceId : skipToken
   );
   const { currentData: sourceHits } = useGetSourceHitCountsQuery(
-    selectedSourceId ? { sessionId, sourceId: selectedSourceId } : skipToken
+    selectedSourceId ? selectedSourceId : skipToken
   );
 
   let closestHitPoint: HitCount | null = null;
@@ -48,17 +45,10 @@ export const SourceContent = () => {
 
   const location = closestHitPoint?.location;
   const { currentData: locationHitPoints } = useGetLineHitPointsQuery(
-    location ? { location, sessionId } : skipToken
+    location ? location : skipToken
   );
 
-  const { currentData: pause } = useGetPauseQuery(
-    selectedPoint
-      ? {
-          point: selectedPoint,
-          sessionId,
-        }
-      : skipToken
-  );
+  const { currentData: pause } = useGetPauseQuery(selectedPoint ? selectedPoint : skipToken);
 
   const domHandler = useMemo(() => {
     return EditorView.domEventHandlers({
diff --git a/packages/markerikson-stack-client-prototype/src/features/sources/SourcesList.tsx b/packages/markerikson-stack-client-prototype/src/features/sources/SourcesList.tsx
index 0bb4226b83d..fb58981d9d8 100644
--- a/packages/markerikson-stack-client-prototype/src/features/sources/SourcesList.tsx
+++ b/packages/markerikson-stack-client-prototype/src/features/sources/SourcesList.tsx
@@ -1,18 +1,14 @@
-import { useContext } from "react";
-import { ReplayClientContext } from "shared/client/ReplayClientContext";
-
-import { useGetSourcesQuery } from "../../app/api";
-import { useAppDispatch, useAppSelector } from "../../app/hooks";
+import { useAppDispatch, useAppSelector, useAppStore } from "../../app/hooks";
 
 import { sourceEntrySelected } from "./sourcesSlice";
+import { getSourceGroups } from "./sourcesCache";
 
 export const SourcesList = () => {
   const dispatch = useAppDispatch();
   const selectedSourceId = useAppSelector(state => state.sources.selectedSourceId);
+  const store = useAppStore();
 
-  const replayClient = useContext(ReplayClientContext);
-  const sessionId = replayClient.getSessionId()!;
-  const { data } = useGetSourcesQuery(sessionId);
+  const data = getSourceGroups(store);
 
   return (
     <ul>
@@ -26,7 +22,7 @@ export const SourcesList = () => {
         const onLineClicked = () => dispatch(sourceEntrySelected(entry.sourceId));
         return (
           <li key={entry.sourceId} onClick={onLineClicked}>
-            {entryText}
+            {entryText} ({entry.kind})
           </li>
         );
       })}
diff --git a/packages/markerikson-stack-client-prototype/src/features/sources/sourcesCache.ts b/packages/markerikson-stack-client-prototype/src/features/sources/sourcesCache.ts
new file mode 100644
index 00000000000..dfd99a78dce
--- /dev/null
+++ b/packages/markerikson-stack-client-prototype/src/features/sources/sourcesCache.ts
@@ -0,0 +1,65 @@
+import { unstable_getCacheForType as getCacheForType } from "react";
+import type { AppStore } from "../../app/store";
+
+import { api, SourceGroups } from "../../app/api";
+
+/*
+ * This entire file is _mostly_ WIP PROOF OF CONCEPT!
+
+  I've been staring at Brian's `CommentsCache` and `MessagesCache`
+  trying to understand the data flow, and reverse-engineer how to 
+  create a valid Suspense cache entry.
+
+  There appear to be two key pieces to know about here:
+
+  - The `unstable_createCacheForType` API, which seems to accept a factory function
+    that holds the wrapper for a piece of data (such as a `new Map()`, or an object
+    with some field that has the actual value).  Note: per Brian, that's not needed 
+    for this cache implementation, since we don't need to invalidate the data later.
+  - React's undocumented but semi-known "throw a promise" mechanism, where we throw
+    a consistent promise reference if the data isn't yet available.  
+    (Note: the promise throwing behavior may still be subject to change? per Dan, 
+      https://github.com/facebook/react/issues/22964#issuecomment-1113649154 )
+
+  Brian's example uses synchronous "wakeables" - a plain JS object
+  with a `.then` method, plus `.resolve/reject` methods, and is doing
+  manual "pending/resolved" tracking.  This is apparently to avoid the
+  overhead of promises and microtasks.
+
+  RTKQ recently added a `getRunningOperationPromise` method, which returns
+  a consistent promise reference _if_ there's a request in flight for that
+  particular endpoint+args combination.  So, we can use that as the thrown promise.
+ */
+
+// We know there's only one cache entry, since it's a "list of things" query.
+// Create a selector to read that cache entry from the Redux store.
+const selectSourceGroupsEntry = api.endpoints.getSources.select();
+
+// Use module-scoped variables for the cache, since this is a one-shot retrieval
+let hasPromiseListenerBeenAttached = false;
+let sourceGroups: SourceGroups | null = null;
+
+export function getSourceGroups(store: AppStore): SourceGroups {
+  if (sourceGroups !== null) {
+    return sourceGroups;
+  }
+
+  let sourcesEntry: ReturnType<typeof selectSourceGroupsEntry> | undefined =
+    selectSourceGroupsEntry(store.getState());
+
+  if (!sourcesEntry || sourcesEntry.isUninitialized) {
+    store.dispatch(api.endpoints.getSources.initiate());
+    sourcesEntry = selectSourceGroupsEntry(store.getState());
+  }
+
+  const promise = api.util.getRunningOperationPromise("getSources", undefined)!;
+
+  if (!hasPromiseListenerBeenAttached) {
+    hasPromiseListenerBeenAttached = true;
+    promise.then(result => {
+      sourceGroups = result.data as SourceGroups;
+    });
+  }
+
+  throw promise;
+}
diff --git a/packages/markerikson-stack-client-prototype/src/pages/index.tsx b/packages/markerikson-stack-client-prototype/src/pages/index.tsx
index 6e899667f60..5a51f7fe1da 100644
--- a/packages/markerikson-stack-client-prototype/src/pages/index.tsx
+++ b/packages/markerikson-stack-client-prototype/src/pages/index.tsx
@@ -1,9 +1,10 @@
+import React, { Suspense, useContext } from "react";
 import type { NextPage } from "next";
 import styles from "../styles/Home.module.css";
 
 import { SessionContext } from "../contexts/SessionContext";
-import { useContext } from "react";
 
+import Loader from "../components/Loader";
 import { SourcesList } from "../features/sources/SourcesList";
 import { SourceContent } from "../features/sources/SourceContent";
 
@@ -23,7 +24,9 @@ const IndexPage: NextPage = () => {
       <div style={{ display: "flex" }}>
         <div style={{ minWidth: 300 }}>
           <h2>Sources Entries</h2>
-          <SourcesList />
+          <Suspense fallback={<Loader />}>
+            <SourcesList />
+          </Suspense>
         </div>
         <div style={{ marginLeft: 10 }}>
           <h2>Source Contents</h2>