Use grep over large files.

packages/core/src/prompts/snippets.ts

@@ -167,6 +167,8 @@ export function renderCoreMandates(options?: CoreMandatesOptions): string {
 ## Context Efficiency:
 - Always scope and limit your searches to avoid context window exhaustion and ensure high-signal results. Use include to target relevant files and strictly limit results using total_max_matches and max_matches_per_file, especially during the research phase.
 - For broad discovery, use names_only=true or max_matches_per_file=1 to identify files without retrieving their context.
+- Limit unnecessary context consumption from file reads by using ${GREP_TOOL_NAME} to search large files (> 1kb) or ${READ_FILE_TOOL_NAME} with the desired offset and limit.
+- If the file is small, prefer reading the whole thing over "scrolling" through it by reading ranges repeatedly.
 
 ## Engineering Standards
 - **Contextual Precedence:** Instructions found in ${formattedFilenames} files are foundational mandates. They take absolute precedence over the general workflows and tool defaults described in this system prompt.

packages/core/src/tools/ls.test.ts

@@ -235,8 +235,8 @@ describe('LSTool', () => {
 
       expect(entries[0]).toBe('[DIR] x-dir');
       expect(entries[1]).toBe('[DIR] y-dir');
-      expect(entries[2]).toBe('a-file.txt');
-      expect(entries[3]).toBe('b-file.txt');
+      expect(entries[2]).toBe('a-file.txt (8 bytes)');
+      expect(entries[3]).toBe('b-file.txt (8 bytes)');
     });
 
     it('should handle permission errors gracefully', async () => {

packages/core/src/tools/ls.ts

@@ -241,7 +241,12 @@ class LSToolInvocation extends BaseToolInvocation<LSToolParams, ToolResult> {
 
       // Create formatted content for LLM
       const directoryContent = entries
-        .map((entry) => `${entry.isDirectory ? '[DIR] ' : ''}${entry.name}`)
+        .map((entry) => {
+          if (entry.isDirectory) {
+            return `[DIR] ${entry.name}`;
+          }
+          return `${entry.name} (${entry.size} bytes)`;
+        })
         .join('\n');
 
       let resultMessage = `Directory listing for ${resolvedDirPath}:\n${directoryContent}`;