fix(lsp): sanitize expanded generic output

(cherry picked from commit 1260d0633a5fb533c492f272ee500fec60c46e22)

packages/coding-agent/src/lsp/render.ts

@@ -582,7 +582,7 @@ function renderGeneric(text: string, lines: string[], expanded: boolean, theme:
 		for (let i = 0; i < lines.length; i++) {
 			const isLast = i === lines.length - 1;
 			const branch = isLast ? theme.tree.last : theme.tree.branch;
-			output += `\n ${theme.fg("dim", branch)} ${lines[i]}`;
+			output += `\n ${theme.fg("dim", branch)} ${truncateToWidth(replaceTabs(lines[i]), TRUNCATE_LENGTHS.CONTENT)}`;
 		}
 		return output.split("\n");
 	}

packages/coding-agent/test/tools/lsp-regressions.test.ts

@@ -16,6 +16,7 @@ import {
 	sortAndValidateTextEdits,
 } from "@oh-my-pi/pi-coding-agent/lsp/edits";
 import { renderCall, renderResult } from "@oh-my-pi/pi-coding-agent/lsp/render";
+import { renderResult as renderLocalResult } from "../../src/lsp/render";
 import {
 	type CodeAction,
 	type CreateFile,
@@ -1354,6 +1355,22 @@ describe("lsp regressions", () => {
 		expect(resultText.replace(/\s+/g, " ")).toContain("too many arguments in call");
 	});
 
+	it("sanitizes expanded generic error output (#7041)", async () => {
+		const theme = await getThemeByName("dark");
+		expect(theme).toBeDefined();
+		const result = renderLocalResult(
+			{
+				content: [{ type: "text", text: `Error:\nserver\tstderr ${"x".repeat(200)}` }],
+			},
+			{ expanded: true, isPartial: false },
+			theme!,
+		);
+
+		const lines = sanitizeText(result.render(300).join("\n")).split("\n");
+		expect(lines.join("\n")).not.toContain("\t");
+		expect(lines.join("\n")).not.toContain("x".repeat(100));
+	});
+
 	for (const dynamicRegistration of [false, true]) {
 		it(`reports pull diagnostics advertised through ${dynamicRegistration ? "dynamic registration" : "server capabilities"}`, async () => {
 			const tempDir = TempDir.createSync("@omp-lsp-pull-diags-");