fix(core): fix three JIT context bugs in read_file, read_many_files, and memoryDiscovery (#22679)

packages/core/src/tools/read-file.ts

@@ -20,7 +20,7 @@ import {
 import { ToolErrorType } from './tool-error.js';
 import { buildFilePathArgsPattern } from '../policy/utils.js';
 
-import type { PartUnion } from '@google/genai';
+import type { PartListUnion } from '@google/genai';
 import {
   processSingleFileContent,
   getSpecificMimeType,
@@ -34,7 +34,11 @@ import { READ_FILE_TOOL_NAME, READ_FILE_DISPLAY_NAME } from './tool-names.js';
 import { FileDiscoveryService } from '../services/fileDiscoveryService.js';
 import { READ_FILE_DEFINITION } from './definitions/coreTools.js';
 import { resolveToolDeclaration } from './definitions/resolver.js';
-import { discoverJitContext, appendJitContext } from './jit-context.js';
+import {
+  discoverJitContext,
+  appendJitContext,
+  appendJitContextToParts,
+} from './jit-context.js';
 
 /**
  * Parameters for the ReadFile tool
@@ -135,7 +139,7 @@ class ReadFileToolInvocation extends BaseToolInvocation<
       };
     }
 
-    let llmContent: PartUnion;
+    let llmContent: PartListUnion;
     if (result.isTruncated) {
       const [start, end] = result.linesShown!;
       const total = result.originalLineCount!;
@@ -173,8 +177,12 @@ ${result.llmContent}`;
 
     // Discover JIT subdirectory context for the accessed file path
     const jitContext = await discoverJitContext(this.config, this.resolvedPath);
-    if (jitContext && typeof llmContent === 'string') {
-      llmContent = appendJitContext(llmContent, jitContext);
+    if (jitContext) {
+      if (typeof llmContent === 'string') {
+        llmContent = appendJitContext(llmContent, jitContext);
+      } else {
+        llmContent = appendJitContextToParts(llmContent, jitContext);
+      }
     }
 
     return {