diff --git a/src/__tests__/diff.test.ts b/src/__tests__/diff.test.ts
index 0f8587c..daa7839 100644
--- a/src/__tests__/diff.test.ts
+++ b/src/__tests__/diff.test.ts
@@ -42,14 +42,30 @@ describe('diff', () => {
     expect(report.removed[0].name).toBe('moment');
   });
 
-  it('detects version upgrades', () => {
+  it('detects version upgrades when the purl carries the version', () => {
+    // Real-world generators embed the version in the purl. The same package at a
+    // new version must be reported as an upgrade, not a removal plus an addition.
     const a = makesbom([{ name: 'lodash', version: '4.17.20', purl: 'pkg:npm/lodash@4.17.20' }]);
     const b = makesbom([{ name: 'lodash', version: '4.17.21', purl: 'pkg:npm/lodash@4.17.21' }]);
     const report = diff(a, b);
-    // Different purl = treated as add/remove (purl includes version)
-    // With our current purl-based key: 4.17.20 -> removed, 4.17.21 -> added
-    // This is correct behavior — different purls are different packages
-    expect(report.added.length + report.removed.length + report.upgraded.length).toBeGreaterThan(0);
+    expect(report.added).toHaveLength(0);
+    expect(report.removed).toHaveLength(0);
+    expect(report.upgraded).toHaveLength(1);
+    expect(report.upgraded[0].from).toBe('4.17.20');
+    expect(report.upgraded[0].to).toBe('4.17.21');
+    expect(report.upgraded[0].isMajorBump).toBe(false);
+  });
+
+  it('matches scoped packages across versions ignoring purl qualifiers', () => {
+    const a = makesbom([
+      { name: '@angular/core', version: '15.2.0', purl: 'pkg:npm/%40angular/core@15.2.0?type=module' },
+    ]);
+    const b = makesbom([
+      { name: '@angular/core', version: '16.0.0', purl: 'pkg:npm/%40angular/core@16.0.0?type=module' },
+    ]);
+    const report = diff(a, b);
+    expect(report.upgraded).toHaveLength(1);
+    expect(report.upgraded[0].isMajorBump).toBe(true);
   });
 
   it('detects version upgrades when matched by name (no purl)', () => {
diff --git a/src/diff.ts b/src/diff.ts
index 6540b50..e0f59e2 100644
--- a/src/diff.ts
+++ b/src/diff.ts
@@ -63,13 +63,39 @@ export function diff(a: SBOM, b: SBOM): ChangeReport {
 function buildComponentMap(components: Component[]): Map<string, Component> {
   const map = new Map<string, Component>();
   for (const comp of components) {
-    // Prefer purl as key, fall back to name
-    const key = comp.purl ?? comp.name;
-    map.set(key, comp);
+    map.set(componentKey(comp), comp);
   }
   return map;
 }
 
+/**
+ * Build a version-independent identity key for a component so the same
+ * package can be matched across two SBOMs even when its version changed.
+ *
+ * Real-world CycloneDX/SPDX generators almost always embed the version in the
+ * purl (e.g. "pkg:npm/lodash@4.17.21"), so keying on the raw purl would make an
+ * upgrade look like a removal plus an addition and hide it from the "upgraded"
+ * report entirely. We therefore strip the version — and any qualifiers/subpath,
+ * which can also vary between builds — leaving the stable "pkg:type/namespace/name"
+ * identity. Components without a purl fall back to their name.
+ */
+function componentKey(comp: Component): string {
+  return comp.purl ? purlIdentity(comp.purl) : comp.name;
+}
+
+/**
+ * Strip the version (`@...`), qualifiers (`?...`), and subpath (`#...`) from a
+ * purl, returning the `pkg:type/namespace/name` portion. In a purl any literal
+ * `@` in the name or namespace is percent-encoded (e.g. the npm scope `@angular`
+ * becomes `%40angular`), so the first unescaped `@` reliably marks the version.
+ */
+function purlIdentity(purl: string): string {
+  const withoutSubpath = purl.split('#', 1)[0];
+  const withoutQualifiers = withoutSubpath.split('?', 1)[0];
+  const atIndex = withoutQualifiers.indexOf('@');
+  return atIndex === -1 ? withoutQualifiers : withoutQualifiers.slice(0, atIndex);
+}
+
 /**
  * Returns true if the major version changed (semver-style).
  * Handles versions like "1.2.3", "2.0.0-beta", etc.