diff --git a/core/util/ranges.test.ts b/core/util/ranges.test.ts
index 84d1c8d54a2..e16a33d9a15 100644
--- a/core/util/ranges.test.ts
+++ b/core/util/ranges.test.ts
@@ -301,8 +301,7 @@ describe("intersection", () => {
     expect(result).toBeNull();
   });
 
-  // TODO
-  test.skip("returns correct intersection for single line overlap", () => {
+  test("returns correct intersection for single line overlap", () => {
     rangeA = {
       start: { line: 1, character: 0 },
       end: { line: 1, character: 5 },
@@ -320,6 +319,42 @@ describe("intersection", () => {
     });
   });
 
+  test("returns correct intersection when both ranges start on the first line", () => {
+    rangeA = {
+      start: { line: 1, character: 0 },
+      end: { line: 5, character: 0 },
+    };
+
+    rangeB = {
+      start: { line: 1, character: 7 },
+      end: { line: 3, character: 2 },
+    };
+
+    const result = intersection(rangeA, rangeB);
+    expect(result).toEqual({
+      start: { line: 1, character: 7 },
+      end: { line: 3, character: 2 },
+    });
+  });
+
+  test("returns correct intersection when both ranges end on the last line", () => {
+    rangeA = {
+      start: { line: 1, character: 0 },
+      end: { line: 3, character: 8 },
+    };
+
+    rangeB = {
+      start: { line: 2, character: 0 },
+      end: { line: 3, character: 4 },
+    };
+
+    const result = intersection(rangeA, rangeB);
+    expect(result).toEqual({
+      start: { line: 2, character: 0 },
+      end: { line: 3, character: 4 },
+    });
+  });
+
   test("returns null for single line non-overlapping ranges", () => {
     rangeA = {
       start: { line: 1, character: 0 },
diff --git a/core/util/ranges.ts b/core/util/ranges.ts
index a9bf5e97242..6fdc8134089 100644
--- a/core/util/ranges.ts
+++ b/core/util/ranges.ts
@@ -32,25 +32,23 @@ export function intersection(a: Range, b: Range): Range | null {
     return null;
   }
 
-  if (startLine === endLine) {
-    const startCharacter = Math.max(a.start.character, b.start.character);
-    const endCharacter = Math.min(a.end.character, b.end.character);
-
-    if (startCharacter > endCharacter) {
-      return null;
-    }
-
-    return {
-      start: { line: startLine, character: startCharacter },
-      end: { line: endLine, character: endCharacter },
-    };
+  // A range only constrains the characters of the boundary line if it actually
+  // starts/ends there - otherwise it spans the whole line.
+  const startCharacter = Math.max(
+    ...[a.start, b.start]
+      .filter((position) => position.line === startLine)
+      .map((position) => position.character),
+  );
+  const endCharacter = Math.min(
+    ...[a.end, b.end]
+      .filter((position) => position.line === endLine)
+      .map((position) => position.character),
+  );
+
+  if (startLine === endLine && startCharacter > endCharacter) {
+    return null;
   }
 
-  const startCharacter =
-    startLine === a.start.line ? a.start.character : b.start.character;
-  const endCharacter =
-    endLine === a.end.line ? a.end.character : b.end.character;
-
   return {
     start: { line: startLine, character: startCharacter },
     end: { line: endLine, character: endCharacter },