diff --git a/docs/explanation/waves-lanes-and-worktrees.md b/docs/explanation/waves-lanes-and-worktrees.md
index 00216ab7..570eba45 100644
--- a/docs/explanation/waves-lanes-and-worktrees.md
+++ b/docs/explanation/waves-lanes-and-worktrees.md
@@ -31,6 +31,10 @@ independently in each repo.
 Everything in this document applies to both modes. Sections that describe
 workspace-specific behavior are called out explicitly.
 
+Task-marker lookup normalizes forward-slash and backslash separators before
+resolving task and worktree paths. Mixed separators therefore locate the same
+`STATUS.md` and `.DONE` files, including the archive fallback.
+
 ---
 
 ## 1) Dependency graph
diff --git a/docs/tutorials/install.md b/docs/tutorials/install.md
index e6d5c7c2..65f2c772 100644
--- a/docs/tutorials/install.md
+++ b/docs/tutorials/install.md
@@ -146,6 +146,10 @@ taskplane init
 
 Init detects the subdirectory repos and prompts you to choose which one holds the shared Taskplane config. The selected repo gets a `.taskplane/` directory with all config, and the workspace root gets a pointer file (`.pi/taskplane-pointer.json`) that tells Taskplane where to find it.
 
+The pointer's `config_path` must be relative to the selected config repo. Both
+forward-slash and backslash separators are accepted, but POSIX absolute paths,
+Windows drive-absolute paths, and UNC paths are rejected on every host platform.
+
 Files created in the config repo (e.g., `repo-a`):
 
 - `repo-a/.taskplane/taskplane-config.json`
diff --git a/extensions/taskplane/execution.ts b/extensions/taskplane/execution.ts
index 1065456b..cdf2ac2a 100644
--- a/extensions/taskplane/execution.ts
+++ b/extensions/taskplane/execution.ts
@@ -436,8 +436,12 @@ export function resolveCanonicalTaskPaths(
 	repoRoot: string,
 	isWorkspaceMode?: boolean,
 ): ResolvedTaskPaths {
-	const repoRootNorm = resolve(repoRoot).replace(/\\/g, "/");
-	const folderNorm = resolve(taskFolder).replace(/\\/g, "/");
+	// Normalize separators before native path resolution. On POSIX, a leading
+	// backslash is otherwise treated as a relative filename and prefixed with cwd.
+	const repoRootNorm = resolve(repoRoot.replace(/\\/g, "/")).replace(/\\/g, "/");
+	const folderPath = resolve(taskFolder.replace(/\\/g, "/"));
+	const folderNorm = folderPath.replace(/\\/g, "/");
+	const worktreeRoot = resolve(worktreePath.replace(/\\/g, "/"));
 
 	let resolvedFolder: string;
 
@@ -447,21 +451,21 @@ export function resolveCanonicalTaskPaths(
 		// the worktree, so the engine must look there too.
 		if (folderNorm.startsWith(repoRootNorm + "/")) {
 			const relPath = folderNorm.slice(repoRootNorm.length + 1);
-			resolvedFolder = join(worktreePath, relPath);
+			resolvedFolder = join(worktreeRoot, relPath);
 		} else {
 			// Cross-repo: task files were copied into the worktree under
 			// .taskplane-tasks/<taskDirName>/ by buildLaneEnvVars
-			const taskDirName = basename(resolve(taskFolder));
-			resolvedFolder = join(worktreePath, ".taskplane-tasks", taskDirName);
+			const taskDirName = basename(folderPath);
+			resolvedFolder = join(worktreeRoot, ".taskplane-tasks", taskDirName);
 		}
 	} else if (folderNorm.startsWith(repoRootNorm + "/")) {
 		// Repo mode: task folder is inside the repo root.
 		// Translate to equivalent path in the worktree.
 		const relativePath = folderNorm.slice(repoRootNorm.length + 1);
-		resolvedFolder = join(worktreePath, relativePath);
+		resolvedFolder = join(worktreeRoot, relativePath);
 	} else {
 		// Fallback: use absolute path directly.
-		resolvedFolder = resolve(taskFolder);
+		resolvedFolder = folderPath;
 	}
 
 	// Check primary location
diff --git a/extensions/taskplane/workspace.ts b/extensions/taskplane/workspace.ts
index 58faddc0..3b18aba6 100644
--- a/extensions/taskplane/workspace.ts
+++ b/extensions/taskplane/workspace.ts
@@ -40,7 +40,7 @@
  * @module orch/workspace
  */
 import { readFileSync, existsSync, realpathSync } from "fs";
-import { resolve, relative, isAbsolute } from "path";
+import { resolve, relative, isAbsolute, win32 } from "path";
 import { parse as yamlParse } from "yaml";
 
 import { runGit } from "./git.ts";
@@ -226,7 +226,7 @@ export function resolvePointer(
 	const normalizedConfigPath = configPath.trim().replace(/\\/g, "/");
 
 	// Reject absolute paths (POSIX `/...` and Windows `C:/...`, `\\...`)
-	if (isAbsolute(normalizedConfigPath) || isAbsolute(configPath.trim())) {
+	if (isAbsolute(normalizedConfigPath) || win32.isAbsolute(normalizedConfigPath)) {
 		return {
 			used: false,
 			configRoot: fallbackConfigRoot,
diff --git a/extensions/tests/execution-path-resolution.test.ts b/extensions/tests/execution-path-resolution.test.ts
index a55a895a..48015222 100644
--- a/extensions/tests/execution-path-resolution.test.ts
+++ b/extensions/tests/execution-path-resolution.test.ts
@@ -542,7 +542,8 @@ function runEdgeCaseTests(): void {
 		const wtMirror = join(worktreePath, "tasks", "TP-WIN");
 		mkdirSync(wtMirror, { recursive: true });
 
-		// Use backslash-style paths (if on Windows this is natural; on unix resolve() normalizes anyway)
+		// Use backslash-style paths on every platform. POSIX resolve() does not
+		// interpret backslashes, so the task resolver must normalize them first.
 		const backslashTask = taskFolder.replace(/\//g, "\\");
 		const backslashRepo = repoRoot.replace(/\//g, "\\");
 		const backslashWt = worktreePath.replace(/\//g, "\\");
diff --git a/extensions/tests/portable-task-paths.test.ts b/extensions/tests/portable-task-paths.test.ts
new file mode 100644
index 00000000..65e4e01a
--- /dev/null
+++ b/extensions/tests/portable-task-paths.test.ts
@@ -0,0 +1,105 @@
+import { afterEach, beforeEach, describe, it } from "node:test";
+import { strict as assert } from "node:assert";
+import { existsSync, mkdirSync, mkdtempSync, rmSync, writeFileSync } from "node:fs";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+import { resolveCanonicalTaskPaths } from "../taskplane/execution.ts";
+import { resolvePointer } from "../taskplane/workspace.ts";
+import type { WorkspaceConfig } from "../taskplane/types.ts";
+
+describe("portable task and pointer paths", () => {
+	let root: string;
+	beforeEach(() => {
+		root = mkdtempSync(join(tmpdir(), "tp-portable-paths-"));
+	});
+	afterEach(() => {
+		rmSync(root, { recursive: true, force: true });
+	});
+
+	const backslashes = (path: string) => path.replace(/\//g, "\\");
+	const forwardSlashes = (path: string) => path.replace(/\\/g, "/");
+
+	function writeMarkers(folder: string) {
+		mkdirSync(folder, { recursive: true });
+		writeFileSync(join(folder, ".DONE"), "done");
+		writeFileSync(join(folder, "STATUS.md"), "completed");
+	}
+
+	function assertMarkers(result: ReturnType<typeof resolveCanonicalTaskPaths>, folder: string) {
+		assert.equal(result.taskFolderResolved, folder);
+		assert.equal(result.donePath, join(folder, ".DONE"));
+		assert.equal(result.statusPath, join(folder, "STATUS.md"));
+		assert.ok(existsSync(result.donePath));
+		assert.ok(existsSync(result.statusPath));
+	}
+
+	it("rejects Windows absolute pointer paths in the Linux CI test selection", () => {
+		mkdirSync(join(root, ".pi"));
+		const config = {
+			repos: new Map([["infra", { path: join(root, "infra") }]]),
+		} as unknown as WorkspaceConfig;
+		for (const configPath of ["C:/config", "D:\\config", "\\\\server\\share\\config"]) {
+			writeFileSync(
+				join(root, ".pi", "taskplane-pointer.json"),
+				JSON.stringify({ config_repo: "infra", config_path: configPath }),
+			);
+			const result = resolvePointer(root, config);
+			assert.equal(result?.used, false, configPath);
+			assert.match(result?.warning ?? "", /absolute paths not allowed/);
+			assert.equal(result?.configRoot, join(root, ".pi"));
+		}
+	});
+
+	for (const workspaceMode of [false, true]) {
+		it(`finds worktree markers when input separators differ (workspace=${workspaceMode})`, () => {
+			const repo = join(root, "repo");
+			const worktree = join(root, "worktree");
+			const expected = join(worktree, "tasks", "TEST-001");
+			writeMarkers(expected);
+			const result = resolveCanonicalTaskPaths(
+				backslashes(join(repo, "tasks", "TEST-001")),
+				backslashes(worktree),
+				forwardSlashes(repo),
+				workspaceMode,
+			);
+			assertMarkers(result, expected);
+		});
+	}
+
+	it("keeps external task markers at their canonical location outside workspace mode", () => {
+		const externalTask = join(root, "external", "TEST-002");
+		writeMarkers(externalTask);
+		const result = resolveCanonicalTaskPaths(
+			backslashes(externalTask),
+			join(root, "worktree"),
+			join(root, "repo"),
+		);
+		assertMarkers(result, externalTask);
+	});
+
+	it("uses the task directory name for cross-repo workspace copies", () => {
+		const worktree = join(root, "worktree");
+		const expected = join(worktree, ".taskplane-tasks", "TEST-003");
+		writeMarkers(expected);
+		const result = resolveCanonicalTaskPaths(
+			backslashes(join(root, "packet-repo", "tasks", "TEST-003")),
+			backslashes(worktree),
+			join(root, "execution-repo"),
+			true,
+		);
+		assertMarkers(result, expected);
+	});
+
+	it("finds archived markers after translating the worktree path", () => {
+		const repo = join(root, "repo");
+		const worktree = join(root, "worktree");
+		const archived = join(worktree, "tasks", "archive", "TEST-004");
+		writeMarkers(archived);
+		const result = resolveCanonicalTaskPaths(
+			backslashes(join(repo, "tasks", "TEST-004")),
+			backslashes(worktree),
+			backslashes(repo),
+		);
+		assertMarkers(result, archived);
+	});
+});
diff --git a/extensions/tests/workspace-config.integration.test.ts b/extensions/tests/workspace-config.integration.test.ts
index c9527ae8..4c49f046 100644
--- a/extensions/tests/workspace-config.integration.test.ts
+++ b/extensions/tests/workspace-config.integration.test.ts
@@ -996,9 +996,18 @@ describe("resolvePointer", () => {
 
 		const result = resolvePointer(dir, wsConfig);
 		expect(result!.used).toBe(false);
-		// May be caught by absolute check or containment check
+		expect(result!.warning).toContain("absolute paths not allowed");
+	});
+
+	it("6.8d: rejects UNC config_path on every host platform", () => {
+		const dir = makeTestDir("ptr-abs-unc");
+		writePointer(
+			dir,
+			JSON.stringify({ config_repo: "infra", config_path: "\\\\server\\share\\config" }),
+		);
+		const result = resolvePointer(dir, makeWorkspaceConfig({ infra: "/fake/infra" }));
 		expect(result!.used).toBe(false);
-		expect(result!.warning).toBeDefined();
+		expect(result!.warning).toContain("absolute paths not allowed");
 	});
 
 	// ── 6.9: Valid pointer → resolved paths ─────────────────────
@@ -1031,6 +1040,16 @@ describe("resolvePointer", () => {
 		expect(result!.agentRoot).toBe(resolve(repoPath, "config", "taskplane", "agents"));
 	});
 
+	it("6.9c: accepts relative config_path with backslash separators", () => {
+		const dir = makeTestDir("ptr-relative-backslashes");
+		const repoPath = resolve(dir, "infra-repo");
+		writePointer(dir, JSON.stringify({ config_repo: "infra", config_path: "config\\taskplane" }));
+		const result = resolvePointer(dir, makeWorkspaceConfig({ infra: repoPath }));
+		expect(result!.used).toBe(true);
+		expect(result!.configRoot).toBe(resolve(repoPath, "config", "taskplane"));
+		expect(result!.agentRoot).toBe(resolve(repoPath, "config", "taskplane", "agents"));
+	});
+
 	// ── 6.10: Defense-in-depth containment check ────────────────
 
 	it("6.10: containment check catches resolved path escaping repo root", () => {