diff --git a/packages/commons/fdr-utils/src/__test__/__snapshots__/octoai.test.ts.snap b/packages/commons/fdr-utils/src/__test__/__snapshots__/octoai.test.ts.snap
index 9d14752e18..fea589bc6f 100644
--- a/packages/commons/fdr-utils/src/__test__/__snapshots__/octoai.test.ts.snap
+++ b/packages/commons/fdr-utils/src/__test__/__snapshots__/octoai.test.ts.snap
@@ -177,7 +177,7 @@ exports[`getNavigationRoot > octoai > gets navigation root for /api-reference/as
       "description": undefined,
       "hidden": false,
       "icon": undefined,
-      "id": "list",
+      "id": "subpackage_asset-library.list",
       "method": "GET",
       "slug": [
         "api-reference",
@@ -204,7 +204,7 @@ exports[`getNavigationRoot > octoai > gets navigation root for /api-reference/oc
       "description": "Return fields on an account",
       "hidden": false,
       "icon": undefined,
-      "id": "getAccount",
+      "id": "subpackage_account.getAccount",
       "method": "GET",
       "slug": [
         "api-reference",
diff --git a/packages/commons/fdr-utils/src/flattenApiDefinition.ts b/packages/commons/fdr-utils/src/flattenApiDefinition.ts
index 1ec33fcbab..a2de30aa14 100644
--- a/packages/commons/fdr-utils/src/flattenApiDefinition.ts
+++ b/packages/commons/fdr-utils/src/flattenApiDefinition.ts
@@ -1,6 +1,7 @@
 import { APIV1Read, DocsV1Read, FdrAPI } from "@fern-api/fdr-sdk";
 import { isNonNullish, titleCase, visitDiscriminatedUnion } from "@fern-ui/core-utils";
 import { stringifyEndpointPathParts } from "./stringifyEndpointPathParts";
+import { isSubpackage } from "./subpackage";
 
 /**
  * Flattened API Definition lightly transforms the APIV1Read.ApiDefinition into a more usable format:
@@ -200,10 +201,12 @@ function flattenPackage(
     const endpoints: FlattenedEndpointDefinition[] = [];
     const methodAndPathToEndpoint = new Map<string, FlattenedEndpointDefinition>();
 
+    const packageId = isSubpackage(currentPackage) ? currentPackage.subpackageId : "root";
+
     currentPackage.endpoints.forEach((endpoint) => {
         const flattenedEndpoint: FlattenedEndpointDefinition = {
             type: "endpoint",
-            id: endpoint.id,
+            id: endpoint.originalEndpointId ?? `${packageId}.${endpoint.id}`,
             slug: [...parentSlugs, endpoint.urlSlug],
             name: endpoint.name ?? stringifyEndpointPathParts(endpoint.path.parts),
             description: endpoint.description,
@@ -251,7 +254,7 @@ function flattenPackage(
     const websockets = currentPackage.websockets.map(
         (websocket): FlattenedWebSocketChannel => ({
             type: "websocket",
-            id: websocket.id,
+            id: `${packageId}.${websocket.id}`,
             slug: [...parentSlugs, websocket.urlSlug],
             name: websocket.name,
             description: websocket.description,
@@ -272,7 +275,7 @@ function flattenPackage(
     const webhooks = currentPackage.webhooks.map(
         (webhook): FlattenedWebhookDefinition => ({
             type: "webhook",
-            id: webhook.id,
+            id: `${packageId}.${webhook.id}`,
             slug: [...parentSlugs, webhook.urlSlug],
             name: webhook.name,
             description: webhook.description,
diff --git a/packages/ui/app/src/api-page/endpoints/EndpointContentCodeSnippets.tsx b/packages/ui/app/src/api-page/endpoints/EndpointContentCodeSnippets.tsx
index 98938df741..4fe27acfc2 100644
--- a/packages/ui/app/src/api-page/endpoints/EndpointContentCodeSnippets.tsx
+++ b/packages/ui/app/src/api-page/endpoints/EndpointContentCodeSnippets.tsx
@@ -173,7 +173,7 @@ const UnmemoizedEndpointContentCodeSnippets: React.FC<EndpointContentCodeSnippet
                             state={{
                                 type: "endpoint",
                                 api,
-                                endpointId: endpoint.slug.join("/"),
+                                endpointId: endpoint.id,
                             }}
                             // example={selectedClient.exampleCall}
                         />
diff --git a/packages/ui/app/src/api-playground/PlaygroundContext.tsx b/packages/ui/app/src/api-playground/PlaygroundContext.tsx
index 78b7ffb08b..b48630a097 100644
--- a/packages/ui/app/src/api-playground/PlaygroundContext.tsx
+++ b/packages/ui/app/src/api-playground/PlaygroundContext.tsx
@@ -1,3 +1,4 @@
+import * as Sentry from "@sentry/nextjs";
 import { useAtom } from "jotai";
 import { atomWithStorage } from "jotai/utils";
 import { mapValues, noop } from "lodash-es";
@@ -61,7 +62,7 @@ export const PlaygroundContextProvider: FC<PropsWithChildren> = ({ children }) =
     const { basePath } = useDocsContext();
     const [selectionState, setSelectionState] = useState<PlaygroundSelectionState | undefined>();
 
-    const key = urljoin(basePath ?? "", "/api/fern-docs/resolve-api");
+    const key = urljoin(basePath ?? "/", "/api/fern-docs/resolve-api");
 
     const { data } = useSWR<Record<string, ResolvedRootPackage> | null>(key, fetcher);
     useEffect(() => {
@@ -90,14 +91,17 @@ export const PlaygroundContextProvider: FC<PropsWithChildren> = ({ children }) =
         async (newSelectionState: PlaygroundSelectionState) => {
             const matchedPackage = flattenedApis[newSelectionState.api];
             if (matchedPackage == null) {
+                Sentry.captureMessage("Could not find package for API playground selection state", "fatal");
                 return;
             }
 
             if (newSelectionState.type === "endpoint") {
                 const matchedEndpoint = matchedPackage.apiDefinitions.find(
-                    (definition) =>
-                        isEndpoint(definition) && definition.slug.join("/") === newSelectionState.endpointId,
+                    (definition) => isEndpoint(definition) && definition.id === newSelectionState.endpointId,
                 ) as ResolvedApiDefinition.Endpoint | undefined;
+                if (matchedEndpoint == null) {
+                    Sentry.captureMessage("Could not find endpoint for API playground selection state", "fatal");
+                }
                 setSelectionState(newSelectionState);
                 expandPlayground();
                 capturePosthogEvent("api_playground_opened", {
@@ -119,9 +123,11 @@ export const PlaygroundContextProvider: FC<PropsWithChildren> = ({ children }) =
                 }
             } else if (newSelectionState.type === "websocket") {
                 const matchedWebSocket = matchedPackage.apiDefinitions.find(
-                    (definition) =>
-                        isWebSocket(definition) && definition.slug.join("/") === newSelectionState.webSocketId,
+                    (definition) => isWebSocket(definition) && definition.id === newSelectionState.webSocketId,
                 ) as ResolvedApiDefinition.Endpoint | undefined;
+                if (matchedWebSocket == null) {
+                    Sentry.captureMessage("Could not find websocket for API playground selection state", "fatal");
+                }
                 setSelectionState(newSelectionState);
                 expandPlayground();
                 capturePosthogEvent("api_playground_opened", {
diff --git a/packages/ui/app/src/api-playground/PlaygroundDrawer.tsx b/packages/ui/app/src/api-playground/PlaygroundDrawer.tsx
index 9610e705a0..c97d66e895 100644
--- a/packages/ui/app/src/api-playground/PlaygroundDrawer.tsx
+++ b/packages/ui/app/src/api-playground/PlaygroundDrawer.tsx
@@ -197,14 +197,14 @@ export const PlaygroundDrawer: FC<PlaygroundDrawerProps> = ({ apis }) => {
     const matchedEndpoint =
         selectionState?.type === "endpoint"
             ? (matchedSection?.apiDefinitions.find(
-                  (definition) => isEndpoint(definition) && definition.slug.join("/") === selectionState.endpointId,
+                  (definition) => isEndpoint(definition) && definition.id === selectionState.endpointId,
               ) as ResolvedApiDefinition.Endpoint | undefined)
             : undefined;
 
     const matchedWebSocket =
         selectionState?.type === "websocket"
             ? (matchedSection?.apiDefinitions.find(
-                  (definition) => isWebSocket(definition) && definition.slug.join("/") === selectionState.webSocketId,
+                  (definition) => isWebSocket(definition) && definition.id === selectionState.webSocketId,
               ) as ResolvedApiDefinition.WebSocket | undefined)
             : undefined;
 
diff --git a/packages/ui/app/src/api-playground/PlaygroundEndpointSelectorContent.tsx b/packages/ui/app/src/api-playground/PlaygroundEndpointSelectorContent.tsx
index 51ba72a82d..a8e2c92d7c 100644
--- a/packages/ui/app/src/api-playground/PlaygroundEndpointSelectorContent.tsx
+++ b/packages/ui/app/src/api-playground/PlaygroundEndpointSelectorContent.tsx
@@ -103,7 +103,7 @@ export const PlaygroundEndpointSelectorContent = forwardRef<HTMLDivElement, Play
             setSelectionStateAndOpen({
                 type: "endpoint",
                 api: group.api,
-                endpointId: endpoint.slug.join("/"),
+                endpointId: endpoint.id,
             });
             closeDropdown?.();
         };
@@ -112,14 +112,16 @@ export const PlaygroundEndpointSelectorContent = forwardRef<HTMLDivElement, Play
             setSelectionStateAndOpen({
                 type: "websocket",
                 api: group.api,
-                webSocketId: websocket.slug.join("/"),
+                webSocketId: websocket.id,
             });
             closeDropdown?.();
         };
 
         function renderApiDefinitionPackage(apiGroup: ApiGroup) {
-            const endpoints = apiGroup.items.filter((endpoint): endpoint is SidebarNode.ApiPage =>
-                matchesEndpoint(filterValue, apiGroup, endpoint),
+            const endpoints = apiGroup.items.filter(
+                (endpoint): endpoint is SidebarNode.ApiPage =>
+                    matchesEndpoint(filterValue, apiGroup, endpoint) &&
+                    (endpoint.apiType === "endpoint" || endpoint.apiType === "websocket"),
             );
             if (endpoints.length === 0) {
                 return null;
diff --git a/packages/ui/app/src/resolver/__test__/__snapshots__/ApiDefinitionResolver.test.ts.snap b/packages/ui/app/src/resolver/__test__/__snapshots__/ApiDefinitionResolver.test.ts.snap
index 5d50698f83..dcca7b3e46 100644
--- a/packages/ui/app/src/resolver/__test__/__snapshots__/ApiDefinitionResolver.test.ts.snap
+++ b/packages/ui/app/src/resolver/__test__/__snapshots__/ApiDefinitionResolver.test.ts.snap
@@ -28,7 +28,7 @@ exports[`resolveApiDefinition > should finish resolving 1`] = `
           "errors": [],
           "examples": [],
           "headers": [],
-          "id": "getMerchants",
+          "id": "subpackage_merchants.getMerchants",
           "method": "GET",
           "path": [],
           "pathParameters": [],