From ae0ae68e14e8bac44bef8f7ca83c8bfc01fc1d56 Mon Sep 17 00:00:00 2001
From: roboomp <omp@can.ac>
Date: Tue, 30 Jun 2026 20:21:10 +0000
Subject: [PATCH] fix(lsp): included ruff-only roots for venv lookup

Extended Python local-bin gating to Ruff-only root marker files so Windows virtualenv Scripts launchers are found before PATH fallback.

Fixes #3916
---
 packages/coding-agent/src/lsp/config.ts       |  2 +-
 .../test/tools/lsp-regressions.test.ts        | 28 +++++++++++++++++++
 2 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/packages/coding-agent/src/lsp/config.ts b/packages/coding-agent/src/lsp/config.ts
index 7e4b99658..be6d8949c 100644
--- a/packages/coding-agent/src/lsp/config.ts
+++ b/packages/coding-agent/src/lsp/config.ts
@@ -209,7 +209,7 @@ export function hasRootMarkers(cwd: string, markers: string[]): boolean {
  * Local bin directories to check before $PATH, ordered by priority.
  * Each entry maps a root marker to the bin directory to check.
  */
-const PYTHON_ROOT_MARKERS = ["pyproject.toml", "requirements.txt", "setup.py", "Pipfile"];
+const PYTHON_ROOT_MARKERS = ["pyproject.toml", "requirements.txt", "setup.py", "Pipfile", "ruff.toml", ".ruff.toml"];
 
 const LOCAL_BIN_PATHS: Array<{ markers: string[]; binDir: string }> = [
 	// Node.js - check node_modules/.bin/
diff --git a/packages/coding-agent/test/tools/lsp-regressions.test.ts b/packages/coding-agent/test/tools/lsp-regressions.test.ts
index f9bc59cc8..aa324b3d7 100644
--- a/packages/coding-agent/test/tools/lsp-regressions.test.ts
+++ b/packages/coding-agent/test/tools/lsp-regressions.test.ts
@@ -1101,6 +1101,34 @@ describe("lsp regressions", () => {
 		}
 	});
 
+	it("detects Ruff in Windows virtualenv Scripts directories for Ruff-only roots", async () => {
+		const originalPlatform = process.platform;
+		Object.defineProperty(process, "platform", { value: "win32", configurable: true, writable: true });
+		const whichSpy = vi.spyOn(Bun, "which").mockReturnValue(null);
+
+		try {
+			for (const marker of ["ruff.toml", ".ruff.toml"] as const) {
+				const tempDir = TempDir.createSync("@omp-lsp-win32-ruff-marker-");
+				try {
+					await Bun.write(path.join(tempDir.path(), marker), "");
+					const scriptsDir = path.join(tempDir.path(), ".venv", "Scripts");
+					await fs.promises.mkdir(scriptsDir, { recursive: true });
+					const localRuff = path.join(scriptsDir, "ruff.exe");
+					await Bun.write(localRuff, "");
+
+					const config = loadConfig(tempDir.path());
+					expect(config.servers.ruff?.resolvedCommand).toBe(localRuff);
+				} finally {
+					tempDir.removeSync();
+				}
+			}
+			expect(whichSpy).not.toHaveBeenCalledWith("ruff");
+		} finally {
+			Object.defineProperty(process, "platform", { value: originalPlatform, configurable: true, writable: true });
+			vi.restoreAllMocks();
+		}
+	});
+
 	it("detects tlaplus files for LSP startup and language ids", async () => {
 		const tempDir = TempDir.createSync("@omp-lsp-tlaplus-");
 		const specPath = path.join(tempDir.path(), "Spec.tla");