diff --git a/packages/taskflow-core/src/schema.ts b/packages/taskflow-core/src/schema.ts
index 1a7fb4f..caf622d 100644
--- a/packages/taskflow-core/src/schema.ts
+++ b/packages/taskflow-core/src/schema.ts
@@ -51,6 +51,8 @@ export type CacheScope = (typeof CACHE_SCOPES)[number];
 const CACHE_FINGERPRINT_PREFIXES = ["git:", "glob:", "glob!:", "file:", "env:"] as const;
 /** Phase types that must NOT be cached across runs (a fresh result is required each run). */
 const CACHE_CROSS_RUN_BLOCKED_TYPES = ["gate", "approval", "loop", "tournament", "script"] as const;
+/** `cwd` is a literal path / workspace keyword, not an interpolated field. */
+const CWD_PLACEHOLDER_RE = /\{[a-zA-Z0-9_-]+(?:\.[a-zA-Z0-9_-]+)*\}/;
 
 const ParallelTaskSchema = Type.Object(
 	{
@@ -649,6 +651,11 @@ export function validateTaskflow(def: unknown, opts: ValidationOptions = {}): Va
 				errors.push(`Phase '${p.id}': '${key}' must be a string, got ${typeof v}`);
 			}
 		}
+		if (typeof p.cwd === "string" && CWD_PLACEHOLDER_RE.test(p.cwd)) {
+			errors.push(
+				`Phase '${p.id}': 'cwd' does not support interpolation placeholders (${p.cwd}). Use a literal path, or a reserved workspace keyword ('temp', 'dedicated', 'worktree').`,
+			);
+		}
 		// dependsOn / from entries are string phase-id refs that flow into the graph
 		// helpers and nodeId(); a non-string entry would crash the renderer.
 		for (const key of ["dependsOn", "from"] as const) {
diff --git a/packages/taskflow-core/test/schema.test.ts b/packages/taskflow-core/test/schema.test.ts
index 48495f5..7d5fd6b 100644
--- a/packages/taskflow-core/test/schema.test.ts
+++ b/packages/taskflow-core/test/schema.test.ts
@@ -71,6 +71,31 @@ test("validateTaskflow: new phase types and fields", () => {
 	);
 });
 
+test("validateTaskflow: cwd must be a literal path or workspace keyword (no interpolation)", () => {
+	const withArgs = validateTaskflow({
+		name: "x",
+		phases: [{ id: "p", type: "agent", task: "t", cwd: "{args.repo_dir}" }],
+	});
+	assert.equal(withArgs.ok, false);
+	assert.match(withArgs.errors.join("\n"), /cwd.*does not support interpolation placeholders/i);
+
+	const withSteps = validateTaskflow({
+		name: "x",
+		phases: [{ id: "p", type: "agent", task: "t", cwd: "{steps.plan.output}" }],
+	});
+	assert.equal(withSteps.ok, false);
+	assert.match(withSteps.errors.join("\n"), /cwd.*does not support interpolation placeholders/i);
+
+	assert.equal(
+		validateTaskflow({ name: "x", phases: [{ id: "p", type: "agent", task: "t", cwd: "./repo" }] }).ok,
+		true,
+	);
+	assert.equal(
+		validateTaskflow({ name: "x", phases: [{ id: "p", type: "agent", task: "t", cwd: "worktree" }] }).ok,
+		true,
+	);
+});
+
 test("validateTaskflow: duplicate ids and unknown deps", () => {
 	const dup = { name: "x", phases: [{ id: "p", type: "agent", task: "t" }, { id: "p", type: "agent", task: "t" }] };
 	assert.equal(validateTaskflow(dup).ok, false);