diff --git a/packages/installer/src/__tests__/harnesses.test.ts b/packages/installer/src/__tests__/harnesses.test.ts
index f80ab25c..4639bacf 100644
--- a/packages/installer/src/__tests__/harnesses.test.ts
+++ b/packages/installer/src/__tests__/harnesses.test.ts
@@ -141,6 +141,27 @@ describe("claude harness", () => {
     expect(system.run).not.toHaveBeenCalledWith(expect.stringContaining("marketplace remove"));
   });
 
+  it("removes the copy installed from our own marketplace", async () => {
+    const system = fakeSystem({
+      run: (cmd) => (isList(cmd) ? claudeList(["sentry@sentry-plugin-marketplace"]) : ok),
+    });
+    const removed = await createClaude(system).cleanup!();
+
+    expect(system.run).toHaveBeenCalledWith(
+      "claude plugin uninstall sentry@sentry-plugin-marketplace",
+    );
+    expect(removed).toContain("sentry@sentry-plugin-marketplace");
+  });
+
+  it("leaves cleanup a no-op when only the official plugin is installed", async () => {
+    const system = fakeSystem({
+      run: (cmd) => (isList(cmd) ? claudeList(["sentry@claude-plugins-official"]) : ok),
+    });
+
+    expect(await createClaude(system).cleanup!()).toBeNull();
+    expect(system.run).not.toHaveBeenCalledWith(expect.stringContaining("uninstall"));
+  });
+
   it("surfaces stderr when install fails", async () => {
     const harness = createClaude(
       fakeSystem({ run: () => ({ ok: false, stderr: "boom", message: "exit 1" }) }),
diff --git a/packages/installer/src/harnesses/claude.ts b/packages/installer/src/harnesses/claude.ts
index 0bb01b9d..c50b9e9f 100644
--- a/packages/installer/src/harnesses/claude.ts
+++ b/packages/installer/src/harnesses/claude.ts
@@ -9,6 +9,13 @@ const INSTALL_COMMAND = `claude plugin install ${PLUGIN_ID}`;
 const UPDATE_COMMAND = `claude plugin update ${PLUGIN_ID}`;
 const UNINSTALL_COMMAND = `claude plugin uninstall ${PLUGIN_ID}`;
 
+// Our plugin reaches Claude two ways: Anthropic's official catalog above, which is
+// what the installer uses, and our own catalog under the marketplace name it
+// declares. Both resolve to the same repository, so a machine carrying both runs
+// two plugins serving the same skills.
+const OUR_MARKETPLACE = "sentry-plugin-marketplace";
+const OUR_PLUGIN_ID = `sentry@${OUR_MARKETPLACE}`;
+
 // `claude plugin list --json` emits an array of installed plugins. We only care
 // about the marketplace-qualified id of each entry.
 interface ClaudePlugin {
@@ -21,9 +28,9 @@ interface ClaudeMarketplace {
   name?: string;
 }
 
-async function isSentryInstalled(system: SystemDeps): Promise<boolean> {
+async function hasPlugin(system: SystemDeps, pluginId: string): Promise<boolean> {
   const plugins = await runJson<ClaudePlugin[]>(system, "claude plugin list --json");
-  return Array.isArray(plugins) && plugins.some((plugin) => plugin.id === PLUGIN_ID);
+  return Array.isArray(plugins) && plugins.some((plugin) => plugin.id === pluginId);
 }
 
 async function isMarketplaceRegistered(system: SystemDeps): Promise<boolean> {
@@ -52,10 +59,19 @@ export function createClaude(system: SystemDeps): Harness {
 
     detect: async () => detectOnPath(system, "claude"),
 
-    isInstalled: async () => isSentryInstalled(system),
+    isInstalled: async () => hasPlugin(system, PLUGIN_ID),
 
     canInstall: async () => ({ ok: true }),
 
+    cleanup: async (output) => {
+      if (!(await hasPlugin(system, OUR_PLUGIN_ID))) {
+        return null;
+      }
+
+      await runCommand(system, `claude plugin uninstall ${OUR_PLUGIN_ID}`, output);
+      return `Removed conflicting plugin ${OUR_PLUGIN_ID}`;
+    },
+
     install: async (output): Promise<InstallOutcome> => {
       await ensureMarketplace(system, output);
       await runCommand(system, INSTALL_COMMAND, output);