refactor: use existing resolveSymLink function for AGENTS.md symlink support

- Remove duplicate inline symlink resolution logic
- Reuse existing resolveSymLink function with MAX_DEPTH protection
- Adapt loadAgentRulesFile to work with resolveSymLink's fileInfo interface
- Fix test to properly mock fs.stat for resolved symlink targets
- All tests pass (36/36)

Author: daniel-lxs

src/core/prompts/sections/__tests__/custom-instructions.spec.ts

@@ -687,6 +687,18 @@ describe("addCustomInstructions", () => {
 			return Promise.reject({ code: "ENOENT" })
 		})
 
+		// Mock stat to indicate the resolved target is a file
+		statMock.mockImplementation((filePath: PathLike) => {
+			const pathStr = filePath.toString()
+			const normalizedPath = pathStr.replace(/\\/g, "/")
+			if (normalizedPath.endsWith("actual-agents-file.md")) {
+				return Promise.resolve({
+					isFile: vi.fn().mockReturnValue(true),
+				})
+			}
+			return Promise.reject({ code: "ENOENT" })
+		})
+
 		// Mock readFile to return content from the resolved path
 		readFileMock.mockImplementation((filePath: PathLike) => {
 			const pathStr = filePath.toString()

src/core/prompts/sections/custom-instructions.ts

@@ -224,19 +224,27 @@ async function loadAgentRulesFile(cwd: string): Promise<string> {
 		const agentsPath = path.join(cwd, "AGENTS.md")
 		let resolvedPath = agentsPath
 
-		// Check if the file is a symlink and resolve it if necessary
+		// Check if AGENTS.md exists and handle symlinks
 		try {
 			const stats = await fs.lstat(agentsPath)
 			if (stats.isSymbolicLink()) {
-				const linkTarget = await fs.readlink(agentsPath)
-				resolvedPath = path.resolve(path.dirname(agentsPath), linkTarget)
+				// Create a temporary fileInfo array to use with resolveSymLink
+				const fileInfo: Array<{ originalPath: string; resolvedPath: string }> = []
+
+				// Use the existing resolveSymLink function to handle symlink resolution
+				await resolveSymLink(agentsPath, fileInfo, 0)
+
+				// Extract the resolved path from fileInfo
+				if (fileInfo.length > 0) {
+					resolvedPath = fileInfo[0].resolvedPath
+				}
 			}
 		} catch (err) {
-			// If we can't check symlink status, just use the original path
-			resolvedPath = agentsPath
+			// If lstat fails (file doesn't exist), return empty
+			return ""
 		}
 
-		// Read the file content
+		// Read the content from the resolved path
 		const content = await safeReadFile(resolvedPath)
 		if (content) {
 			return `# Agent Rules Standard (AGENTS.md):\n${content}`