fix(server): fulfill empty embedding for trashed docs (#13461)

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

## Summary by CodeRabbit

- New Features
  - None
- Bug Fixes
- Ensures a placeholder embedding is always created when content is
empty or after deletion, reducing errors and improving Copilot
stability.
- Refactor
- Centralized empty-embedding handling for consistent behavior across
workflows.
- Standardized embedding dimension configuration to a single source for
reliability.
- Chores
- Simplified internal embedding module surface and imports for
maintainability.

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

packages/backend/server/src/models/copilot-context.ts

@@ -19,6 +19,8 @@ import {
 
 type UpdateCopilotContextInput = Pick<CopilotContext, 'config'>;
 
+export const EMBEDDING_DIMENSIONS = 1024;
+
 /**
  * Copilot Job Model
  */
@@ -290,10 +292,24 @@ export class CopilotContextModel extends BaseModel {
     `;
   }
 
+  async fulfillEmptyEmbedding(workspaceId: string, docId: string) {
+    const emptyEmbedding = {
+      index: 0,
+      content: '',
+      embedding: Array.from({ length: EMBEDDING_DIMENSIONS }, () => 0),
+    };
+    await this.models.copilotContext.insertWorkspaceEmbedding(
+      workspaceId,
+      docId,
+      [emptyEmbedding]
+    );
+  }
+
   async deleteWorkspaceEmbedding(workspaceId: string, docId: string) {
     await this.db.aiWorkspaceEmbedding.deleteMany({
       where: { workspaceId, docId },
     });
+    await this.fulfillEmptyEmbedding(workspaceId, docId);
   }
 
   async matchWorkspaceEmbedding(

packages/backend/server/src/plugins/copilot/embedding/client.ts

@@ -7,7 +7,11 @@ import {
   CopilotProviderNotSupported,
 } from '../../../base';
 import { CopilotFailedToGenerateEmbedding } from '../../../base/error/errors.gen';
-import { ChunkSimilarity, Embedding } from '../../../models';
+import {
+  ChunkSimilarity,
+  Embedding,
+  EMBEDDING_DIMENSIONS,
+} from '../../../models';
 import { PromptService } from '../prompt';
 import {
   type CopilotProvider,
@@ -16,11 +20,7 @@ import {
   ModelInputType,
   ModelOutputType,
 } from '../providers';
-import {
-  EMBEDDING_DIMENSIONS,
-  EmbeddingClient,
-  type ReRankResult,
-} from './types';
+import { EmbeddingClient, type ReRankResult } from './types';
 
 const EMBEDDING_MODEL = 'gemini-embedding-001';
 const RERANK_PROMPT = 'Rerank results';

packages/backend/server/src/plugins/copilot/embedding/index.ts

@@ -1,4 +1,4 @@
 export { getEmbeddingClient, MockEmbeddingClient } from './client';
 export { CopilotEmbeddingJob } from './job';
 export type { Chunk, DocFragment } from './types';
-export { EMBEDDING_DIMENSIONS, EmbeddingClient } from './types';
+export { EmbeddingClient } from './types';

packages/backend/server/src/plugins/copilot/embedding/job.ts

@@ -20,7 +20,7 @@ import { CopilotStorage } from '../storage';
 import { readStream } from '../utils';
 import { getEmbeddingClient } from './client';
 import type { Chunk, DocFragment } from './types';
-import { EMBEDDING_DIMENSIONS, EmbeddingClient } from './types';
+import { EmbeddingClient } from './types';
 
 @Injectable()
 export class CopilotEmbeddingJob {
@@ -392,19 +392,6 @@ export class CopilotEmbeddingJob {
     return controller.signal;
   }
 
-  private async fulfillEmptyEmbedding(workspaceId: string, docId: string) {
-    const emptyEmbedding = {
-      index: 0,
-      content: '',
-      embedding: Array.from({ length: EMBEDDING_DIMENSIONS }, () => 0),
-    };
-    await this.models.copilotContext.insertWorkspaceEmbedding(
-      workspaceId,
-      docId,
-      [emptyEmbedding]
-    );
-  }
-
   @OnJob('copilot.embedding.docs')
   async embedPendingDocs({
     contextId,
@@ -466,13 +453,19 @@ export class CopilotEmbeddingJob {
             this.logger.warn(
               `Doc ${docId} in workspace ${workspaceId} has no summary, fulfilling empty embedding.`
             );
-            await this.fulfillEmptyEmbedding(workspaceId, docId);
+            await this.models.copilotContext.fulfillEmptyEmbedding(
+              workspaceId,
+              docId
+            );
           }
         } else {
           this.logger.warn(
             `Doc ${docId} in workspace ${workspaceId} has no fragment, fulfilling empty embedding.`
           );
-          await this.fulfillEmptyEmbedding(workspaceId, docId);
+          await this.models.copilotContext.fulfillEmptyEmbedding(
+            workspaceId,
+            docId
+          );
         }
       }
     } catch (error: any) {
@@ -490,7 +483,10 @@ export class CopilotEmbeddingJob {
           `Doc ${docId} in workspace ${workspaceId} has no content, fulfilling empty embedding.`
         );
         // if the doc is empty, we still need to fulfill the embedding
-        await this.fulfillEmptyEmbedding(workspaceId, docId);
+        await this.models.copilotContext.fulfillEmptyEmbedding(
+          workspaceId,
+          docId
+        );
         return;
       }
 

packages/backend/server/src/plugins/copilot/embedding/types.ts

@@ -98,8 +98,6 @@ export type Chunk = {
   content: string;
 };
 
-export const EMBEDDING_DIMENSIONS = 1024;
-
 export abstract class EmbeddingClient {
   async configured() {
     return true;