diff --git a/frontend/src/components/screens/Dashboard.tsx b/frontend/src/components/screens/Dashboard.tsx
index 8b474562..330ae0f2 100644
--- a/frontend/src/components/screens/Dashboard.tsx
+++ b/frontend/src/components/screens/Dashboard.tsx
@@ -24,7 +24,7 @@ import {
   type Assignment,
 } from "@/lib/api";
 import type { GraphNode as ApiNode, GraphEdge as ApiEdge } from "@/lib/types";
-import { apiToGraphNode, type GraphNode, type GraphEdge } from "@/lib/data";
+import { apiToGraphNode, learnHrefForNode, type GraphNode, type GraphEdge } from "@/lib/data";
 import { partitionCurrentAndArchive } from "@/lib/semesters";
 import { IS_TEST_MODE, now } from "@/lib/testMode";
 
@@ -475,13 +475,7 @@ export function Dashboard() {
           width={size.w}
           height={size.h}
           highlightId={suggestNode?.id}
-          onNodeClick={(n) => {
-            const p = new URLSearchParams();
-            p.set("topic", n.name);
-            p.set("mode", "socratic");
-            if (n.course_id) p.set("course_id", n.course_id);
-            router.push(`/learn?${p.toString()}`);
-          }}
+          onNodeClick={(n) => router.push(learnHrefForNode(n))}
         />
         {/* Courses key — sidebar layout only. Top-nav layout uses the
             full My Courses panel in the left column instead. */}
@@ -1051,7 +1045,7 @@ export function Dashboard() {
             highlightId={suggestNode?.id}
             onNodeClick={(n) => {
               setFullscreen(false);
-              router.push(`/learn?topic=${encodeURIComponent(n.name)}&mode=socratic${n.course_id ? `&course_id=${encodeURIComponent(n.course_id)}` : ""}`);
+              router.push(learnHrefForNode(n));
             }}
           />
         </div>
diff --git a/frontend/src/components/screens/Tree.tsx b/frontend/src/components/screens/Tree.tsx
index 3d985234..b5b8317f 100644
--- a/frontend/src/components/screens/Tree.tsx
+++ b/frontend/src/components/screens/Tree.tsx
@@ -14,7 +14,7 @@ import { getGraph, getCourses, getSessions, deleteGraphNode, type EnrolledCourse
 import { useToast } from "../ToastProvider";
 import { useConfirm } from "@/lib/useConfirm";
 import type { GraphNode as ApiNode, GraphEdge as ApiEdge } from "@/lib/types";
-import { apiToGraphNode, type GraphNode, type GraphEdge } from "@/lib/data";
+import { apiToGraphNode, learnHrefForNode, type GraphNode, type GraphEdge } from "@/lib/data";
 
 type Tier = "all" | "mastered" | "learning" | "struggling" | "unexplored";
 
@@ -132,11 +132,13 @@ export function Tree() {
     return n?.id;
   }, [suggest, nodes]);
 
-  const onLearn = (n: GraphNode) => router.push(
-    `/learn?topic=${encodeURIComponent(n.name)}&mode=socratic${n.course_id ? `&course_id=${encodeURIComponent(n.course_id)}` : ""}`,
-  );
+  const onLearn = (n: GraphNode) => router.push(learnHrefForNode(n));
+  // Subject-root (course) nodes have no single quiz topic — open the picker
+  // rather than seeding the course name (mirrors the tutor fix, #319). The
+  // Quiz screen only reads `topic`/`concept`, so the old `course_id` param was
+  // dead and is dropped.
   const onQuiz = (n: GraphNode) => router.push(
-    `/quiz?topic=${encodeURIComponent(n.name)}${n.course_id ? `&course_id=${encodeURIComponent(n.course_id)}` : ""}`,
+    n.is_subject_root ? "/quiz" : `/quiz?topic=${encodeURIComponent(n.name)}`,
   );
 
   const del = useConfirm(async () => {
diff --git a/frontend/src/lib/data.test.ts b/frontend/src/lib/data.test.ts
index 75959857..e6134af5 100644
--- a/frontend/src/lib/data.test.ts
+++ b/frontend/src/lib/data.test.ts
@@ -1,7 +1,8 @@
 import { describe, expect, it } from "vitest";
-import { apiToGraphNode, hashSeed, paletteFor } from "./data";
+import { apiToGraphNode, hashSeed, learnHrefForNode, paletteFor } from "./data";
 import type { GraphNode as ApiNode } from "./types";
 import type { EnrolledCourse } from "./api";
+import type { GraphNode } from "./data";
 
 function makeApiNode(over: Partial<ApiNode> = {}): ApiNode {
   return {
@@ -107,6 +108,61 @@ describe("apiToGraphNode color resolution", () => {
   });
 });
 
+function makeGraphNode(over: Partial<GraphNode> = {}): GraphNode {
+  return {
+    id: "n1",
+    name: "Eigenvalues",
+    subject: "Linear Algebra",
+    color: "#7a874f",
+    is_subject_root: false,
+    mastery_tier: "learning",
+    mastery_score: 0.5,
+    course_id: "c1",
+    ...over,
+  };
+}
+
+describe("learnHrefForNode", () => {
+  it("seeds the topic from a concept node's name", () => {
+    const href = learnHrefForNode(makeGraphNode({ name: "Eigenvalues" }));
+    const params = new URLSearchParams(href.split("?")[1]);
+    expect(params.get("topic")).toBe("Eigenvalues");
+    expect(params.get("mode")).toBe("socratic");
+    expect(params.get("course")).toBe("c1");
+  });
+
+  it("never sends a subject-root (course) node's name as the topic (#319)", () => {
+    const href = learnHrefForNode(
+      makeGraphNode({ name: "Linear Algebra", is_subject_root: true }),
+    );
+    const params = new URLSearchParams(href.split("?")[1]);
+    expect(params.has("topic")).toBe(false);
+    // Still scoped to the course so the tutor opens filtered to it.
+    expect(params.get("course")).toBe("c1");
+    expect(params.get("mode")).toBe("socratic");
+  });
+
+  it("scopes the course via the `course` param the Learn screen reads", () => {
+    // Regression guard: the old handlers passed `course_id`, which Learn
+    // (searchParams.get("course")) silently ignored, dropping course scope.
+    const href = learnHrefForNode(makeGraphNode({ course_id: "c42" }));
+    const params = new URLSearchParams(href.split("?")[1]);
+    expect(params.get("course")).toBe("c42");
+    expect(params.has("course_id")).toBe(false);
+  });
+
+  it("omits the course param when the node has no course_id", () => {
+    const href = learnHrefForNode(makeGraphNode({ course_id: "" }));
+    const params = new URLSearchParams(href.split("?")[1]);
+    expect(params.has("course")).toBe(false);
+  });
+
+  it("honors a non-default mode", () => {
+    const href = learnHrefForNode(makeGraphNode(), "flashcards");
+    expect(new URLSearchParams(href.split("?")[1]).get("mode")).toBe("flashcards");
+  });
+});
+
 describe("hashSeed", () => {
   it("is deterministic", () => {
     expect(hashSeed("hello")).toBe(hashSeed("hello"));
diff --git a/frontend/src/lib/data.ts b/frontend/src/lib/data.ts
index 6dec524b..2f3eeb7d 100644
--- a/frontend/src/lib/data.ts
+++ b/frontend/src/lib/data.ts
@@ -66,6 +66,26 @@ export type GraphEdge = {
   strength: number;
 };
 
+// Deep-link from a knowledge-graph node into the AI Tutor (`/learn`).
+//
+// Subject-root (course) nodes carry the *course* name, which must never be
+// sent as the session topic: doing so pre-selected the course name as a topic
+// on redirect (#319). For a course node we scope the tutor to the course and
+// leave the topic empty so the learner picks a concept; concept nodes seed
+// their own name as the topic. The course is passed as `course` — the param
+// the Learn screen reads (`searchParams.get("course")`); the earlier handlers
+// passed `course_id`, which Learn silently ignored, dropping course scope.
+export function learnHrefForNode(
+  n: Pick<GraphNode, "name" | "course_id" | "is_subject_root">,
+  mode = "socratic",
+): string {
+  const p = new URLSearchParams();
+  if (!n.is_subject_root) p.set("topic", n.name);
+  p.set("mode", mode);
+  if (n.course_id) p.set("course", n.course_id);
+  return `/learn?${p.toString()}`;
+}
+
 // Adapter from the backend `ApiNode` shape to the frontend `GraphNode`
 // shape consumed by `KnowledgeGraph`. Hoisted here from Tree/Learn/
 // Dashboard so the three screens share a single source of truth.