fix(server): sse abort behavior (#13153)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

* **Bug Fixes**
* Improved handling of aborted client connections during streaming,
ensuring that session messages accurately reflect if a request was
aborted.
* Enhanced consistency and reliability across all streaming endpoints
when saving session messages after streaming.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/backend/server/src/plugins/copilot/controller.ts

@@ -299,6 +299,13 @@ export class CopilotController implements BeforeApplicationShutdown {
       this.ongoingStreamCount$.next(this.ongoingStreamCount$.value + 1);
 
       const { signal, onConnectionClosed } = getSignal(req);
+      let endBeforePromiseResolve = false;
+      onConnectionClosed(isAborted => {
+        if (isAborted) {
+          endBeforePromiseResolve = true;
+        }
+      });
+
       const { messageId, reasoning, webSearch } = ChatQuerySchema.parse(query);
 
       const source$ = from(
@@ -322,10 +329,11 @@ export class CopilotController implements BeforeApplicationShutdown {
             shared$.pipe(
               reduce((acc, chunk) => acc + chunk, ''),
               tap(buffer => {
-                onConnectionClosed(isAborted => {
                 session.push({
                   role: 'assistant',
-                    content: isAborted ? '> Request aborted' : buffer,
+                  content: endBeforePromiseResolve
+                    ? '> Request aborted'
+                    : buffer,
                   createdAt: new Date(),
                 });
                 void session
@@ -336,7 +344,6 @@ export class CopilotController implements BeforeApplicationShutdown {
                       err
                     )
                   );
-                });
               }),
               ignoreElements()
             )
@@ -384,6 +391,13 @@ export class CopilotController implements BeforeApplicationShutdown {
       this.ongoingStreamCount$.next(this.ongoingStreamCount$.value + 1);
 
       const { signal, onConnectionClosed } = getSignal(req);
+      let endBeforePromiseResolve = false;
+      onConnectionClosed(isAborted => {
+        if (isAborted) {
+          endBeforePromiseResolve = true;
+        }
+      });
+
       const { messageId, reasoning, webSearch } = ChatQuerySchema.parse(query);
 
       const source$ = from(
@@ -407,14 +421,15 @@ export class CopilotController implements BeforeApplicationShutdown {
             shared$.pipe(
               reduce((acc, chunk) => acc.concat([chunk]), [] as StreamObject[]),
               tap(result => {
-                onConnectionClosed(isAborted => {
                 const parser = new StreamObjectParser();
                 const streamObjects = parser.mergeTextDelta(result);
                 const content = parser.mergeContent(streamObjects);
                 session.push({
                   role: 'assistant',
-                    content: isAborted ? '> Request aborted' : content,
+                  content: endBeforePromiseResolve
-                    streamObjects: isAborted ? null : streamObjects,
+                    ? '> Request aborted'
+                    : content,
+                  streamObjects: endBeforePromiseResolve ? null : streamObjects,
                   createdAt: new Date(),
                 });
                 void session
@@ -425,7 +440,6 @@ export class CopilotController implements BeforeApplicationShutdown {
                       err
                     )
                   );
-                });
               }),
               ignoreElements()
             )
@@ -477,6 +491,13 @@ export class CopilotController implements BeforeApplicationShutdown {
       this.ongoingStreamCount$.next(this.ongoingStreamCount$.value + 1);
 
       const { signal, onConnectionClosed } = getSignal(req);
+      let endBeforePromiseResolve = false;
+      onConnectionClosed(isAborted => {
+        if (isAborted) {
+          endBeforePromiseResolve = true;
+        }
+      });
+
       const source$ = from(
         this.workflow.runGraph(params, session.model, {
           ...session.config.promptConfig,
@@ -526,10 +547,11 @@ export class CopilotController implements BeforeApplicationShutdown {
                 return acc;
               }, ''),
               tap(content => {
-                onConnectionClosed(isAborted => {
                 session.push({
                   role: 'assistant',
-                    content: isAborted ? '> Request aborted' : content,
+                  content: endBeforePromiseResolve
+                    ? '> Request aborted'
+                    : content,
                   createdAt: new Date(),
                 });
                 void session
@@ -540,7 +562,6 @@ export class CopilotController implements BeforeApplicationShutdown {
                       err
                     )
                   );
-                });
               }),
               ignoreElements()
             )
@@ -604,6 +625,13 @@ export class CopilotController implements BeforeApplicationShutdown {
       this.ongoingStreamCount$.next(this.ongoingStreamCount$.value + 1);
 
       const { signal, onConnectionClosed } = getSignal(req);
+      let endBeforePromiseResolve = false;
+      onConnectionClosed(isAborted => {
+        if (isAborted) {
+          endBeforePromiseResolve = true;
+        }
+      });
+
       const source$ = from(
         provider.streamImages(
           {
@@ -639,11 +667,10 @@ export class CopilotController implements BeforeApplicationShutdown {
             shared$.pipe(
               reduce((acc, chunk) => acc.concat([chunk]), [] as string[]),
               tap(attachments => {
-                onConnectionClosed(isAborted => {
                 session.push({
                   role: 'assistant',
-                    content: isAborted ? '> Request aborted' : '',
+                  content: endBeforePromiseResolve ? '> Request aborted' : '',
-                    attachments: isAborted ? [] : attachments,
+                  attachments: endBeforePromiseResolve ? [] : attachments,
                   createdAt: new Date(),
                 });
                 void session
@@ -654,7 +681,6 @@ export class CopilotController implements BeforeApplicationShutdown {
                       err
                     )
                   );
-                });
               }),
               ignoreElements()
             )