diff --git a/desktop/src/features/projects/lib/projectCloneUrl.test.mjs b/desktop/src/features/projects/lib/projectCloneUrl.test.mjs
index 6179c46a04..d3d232c54d 100644
--- a/desktop/src/features/projects/lib/projectCloneUrl.test.mjs
+++ b/desktop/src/features/projects/lib/projectCloneUrl.test.mjs
@@ -1,7 +1,11 @@
 import assert from "node:assert/strict";
 import { test } from "node:test";
 
-import { deriveRelayCloneUrl, effectiveCloneUrls } from "./projectCloneUrl.ts";
+import {
+  deriveRelayCloneUrl,
+  effectiveCloneUrls,
+  isActiveRelayCloneUrl,
+} from "./projectCloneUrl.ts";
 
 const OWNER = "a".repeat(64);
 const ORIGIN = "https://relay.example";
@@ -60,3 +64,58 @@ test("effectiveCloneUrls derives a default when none is advertised", () => {
 test("effectiveCloneUrls returns empty when no default can be derived", () => {
   assert.deepEqual(effectiveCloneUrls([], null, OWNER, "repo"), []);
 });
+
+test("isActiveRelayCloneUrl accepts the active relay repository shape", () => {
+  assert.equal(
+    isActiveRelayCloneUrl(`${ORIGIN}/git/${OWNER}/repo`, ORIGIN, OWNER),
+    true,
+  );
+  assert.equal(
+    isActiveRelayCloneUrl(
+      `${ORIGIN}/prefix/git/${OWNER}/repo`,
+      `${ORIGIN}/prefix`,
+      OWNER,
+    ),
+    true,
+  );
+  assert.equal(
+    isActiveRelayCloneUrl(`${ORIGIN}/git/${"b".repeat(64)}/fork`, ORIGIN),
+    true,
+  );
+});
+
+test("isActiveRelayCloneUrl rejects external and mismatched repositories", () => {
+  assert.equal(
+    isActiveRelayCloneUrl(
+      "https://github.com/octocat/hello.git",
+      ORIGIN,
+      OWNER,
+    ),
+    false,
+  );
+  assert.equal(
+    isActiveRelayCloneUrl(
+      `https://other-relay.example/git/${OWNER}/repo`,
+      ORIGIN,
+      OWNER,
+    ),
+    false,
+  );
+  assert.equal(
+    isActiveRelayCloneUrl(
+      `${ORIGIN}/git/${"b".repeat(64)}/repo`,
+      ORIGIN,
+      OWNER,
+    ),
+    false,
+  );
+  assert.equal(
+    isActiveRelayCloneUrl(`${ORIGIN}/git/${OWNER}/repo/extra`, ORIGIN, OWNER),
+    false,
+  );
+  assert.equal(isActiveRelayCloneUrl("not a URL", ORIGIN, OWNER), false);
+  assert.equal(
+    isActiveRelayCloneUrl(`${ORIGIN}/git/${OWNER}/repo`, null, OWNER),
+    false,
+  );
+});
diff --git a/desktop/src/features/projects/lib/projectCloneUrl.ts b/desktop/src/features/projects/lib/projectCloneUrl.ts
index 78dfb83762..6c31e24ab8 100644
--- a/desktop/src/features/projects/lib/projectCloneUrl.ts
+++ b/desktop/src/features/projects/lib/projectCloneUrl.ts
@@ -50,3 +50,50 @@ export function effectiveCloneUrls(
   const derived = deriveRelayCloneUrl(relayOrigin, owner, dtag);
   return derived ? [derived] : [];
 }
+
+/**
+ * Whether Desktop's native git workflow may operate on this clone URL.
+ *
+ * Native project mutations intentionally accept only repositories hosted by
+ * the active workspace relay. Keep the UI capability check aligned with that
+ * boundary so external NIP-34 clone URLs never offer an action the backend
+ * must reject.
+ */
+export function isActiveRelayCloneUrl(
+  cloneUrl: string | null | undefined,
+  relayOrigin: string | null | undefined,
+  expectedOwner?: string | null,
+): boolean {
+  if (
+    !cloneUrl ||
+    !relayOrigin ||
+    (expectedOwner !== undefined &&
+      expectedOwner !== null &&
+      !/^[0-9a-fA-F]{64}$/.test(expectedOwner))
+  ) {
+    return false;
+  }
+
+  try {
+    const clone = new URL(cloneUrl);
+    const relay = new URL(relayOrigin);
+    if (clone.origin !== relay.origin) return false;
+
+    const relayPath = relay.pathname.replace(/\/+$/, "");
+    if (relayPath && !clone.pathname.startsWith(`${relayPath}/`)) return false;
+
+    const segments = clone.pathname.split("/").filter(Boolean);
+    const gitIndex = segments.lastIndexOf("git");
+    const cloneOwner = segments[gitIndex + 1];
+    return (
+      gitIndex >= 0 &&
+      segments.length === gitIndex + 3 &&
+      /^[0-9a-fA-F]{64}$/.test(cloneOwner ?? "") &&
+      (!expectedOwner ||
+        cloneOwner?.toLowerCase() === expectedOwner.toLowerCase()) &&
+      Boolean(segments[gitIndex + 2])
+    );
+  } catch {
+    return false;
+  }
+}
diff --git a/desktop/src/features/projects/ui/PullRequestReviewCard.tsx b/desktop/src/features/projects/ui/PullRequestReviewCard.tsx
index c903769b7d..d00e992741 100644
--- a/desktop/src/features/projects/ui/PullRequestReviewCard.tsx
+++ b/desktop/src/features/projects/ui/PullRequestReviewCard.tsx
@@ -1,5 +1,6 @@
 import {
   Check,
+  ExternalLink,
   GitPullRequest,
   GitPullRequestDraft,
   MoreHorizontal,
@@ -10,6 +11,7 @@ import * as React from "react";
 import { toast } from "sonner";
 
 import { useIsManagedAgent } from "@/features/agent-memory/hooks";
+import { useCommunities } from "@/features/communities/useCommunities";
 import type { Project, ProjectPullRequest } from "@/features/projects/hooks";
 import { nextProjectPullRequestReviewCreatedAt } from "@/features/projects/projectPullRequests.mjs";
 import {
@@ -18,7 +20,10 @@ import {
   useUpdateProjectPullRequestStatusMutation,
 } from "@/features/projects/pullRequestReviews";
 import { useIdentityQuery } from "@/shared/api/hooks";
+import { relayHttpFromWs } from "@/shared/api/inviteHelpers";
+import { isActiveRelayCloneUrl } from "@/features/projects/lib/projectCloneUrl";
 import { normalizePubkey } from "@/shared/lib/pubkey";
+import { isSafeUrl } from "@/shared/lib/url";
 import { Button } from "@/shared/ui/button";
 import {
   Dialog,
@@ -59,6 +64,15 @@ export function PullRequestReviewCard({
   const [approvalSummary, setApprovalSummary] = React.useState("");
   const reviewDecisionInFlightRef = React.useRef(false);
   const lastReviewDecisionCreatedAtRef = React.useRef(0);
+  const { activeCommunity } = useCommunities();
+  const relayOrigin = React.useMemo(() => {
+    if (!activeCommunity?.relayUrl) return null;
+    try {
+      return relayHttpFromWs(activeCommunity.relayUrl);
+    } catch {
+      return null;
+    }
+  }, [activeCommunity?.relayUrl]);
 
   const viewerPubkey = identityQuery.data?.pubkey ?? null;
   const viewer = viewerPubkey ? normalizePubkey(viewerPubkey) : null;
@@ -75,10 +89,39 @@ export function PullRequestReviewCard({
   );
   const canReview = canReviewProjectPullRequest(project, pullRequest, viewer);
   const canApprove = canReview && !hasApproved;
-  const canMerge =
+  const canActOnOpenPullRequest =
     (isOwner || isManagedAgentOwner) &&
     pullRequest.status === "Open" &&
     Boolean(pullRequest.branchName && pullRequest.commit);
+  const nativeTargetMergeSupported = isActiveRelayCloneUrl(
+    project.cloneUrls[0],
+    relayOrigin,
+    project.owner,
+  );
+  const nativeSourceMergeSupported = isActiveRelayCloneUrl(
+    pullRequest.cloneUrls[0] ?? project.cloneUrls[0],
+    relayOrigin,
+  );
+  const nativeMergeSupported =
+    nativeTargetMergeSupported && nativeSourceMergeSupported;
+  const canMerge = canActOnOpenPullRequest && nativeMergeSupported;
+  const externalRepositoryUrl =
+    canActOnOpenPullRequest &&
+    relayOrigin &&
+    !nativeMergeSupported &&
+    isSafeUrl(project.webUrl ?? undefined)
+      ? project.webUrl
+      : null;
+  const externalRepositoryLabel = (() => {
+    if (!externalRepositoryUrl) return "Open repository";
+    try {
+      return new URL(externalRepositoryUrl).hostname === "github.com"
+        ? "Open on GitHub"
+        : "Open repository";
+    } catch {
+      return "Open repository";
+    }
+  })();
 
   const handleStatusChange = React.useCallback(
     async (status: "open" | "draft" | "closed") => {
@@ -168,6 +211,7 @@ export function PullRequestReviewCard({
   const hasAvailableAction =
     canApprove ||
     canMerge ||
+    Boolean(externalRepositoryUrl) ||
     canMarkReady ||
     canConvertToDraft ||
     canClose ||
@@ -207,6 +251,24 @@ export function PullRequestReviewCard({
               pullRequest={pullRequest}
             />
           ) : null}
+          {externalRepositoryUrl ? (
+            <Button
+              asChild
+              className="h-8 gap-1.5 px-3.5"
+              size="xs"
+              type="button"
+              variant="secondary"
+            >
+              <a
+                href={externalRepositoryUrl}
+                rel="noopener noreferrer"
+                target="_blank"
+              >
+                <ExternalLink className="h-3.5 w-3.5" />
+                {externalRepositoryLabel}
+              </a>
+            </Button>
+          ) : null}
           {canMarkReady ? (
             <Button
               className="h-8 gap-1.5 px-3"
diff --git a/desktop/src/testing/e2eBridge.ts b/desktop/src/testing/e2eBridge.ts
index 355ccea9fc..78401b67e7 100644
--- a/desktop/src/testing/e2eBridge.ts
+++ b/desktop/src/testing/e2eBridge.ts
@@ -1118,6 +1118,10 @@ declare global {
     };
     /** Overrides the first mock repository owner for delegated-owner tests. */
     __BUZZ_E2E_PROJECT_OWNER_OVERRIDE__?: string;
+    /** Overrides the first mock repository clone URL for provider tests. */
+    __BUZZ_E2E_PROJECT_CLONE_URL_OVERRIDE__?: string;
+    /** Adds a web URL to the first mock repository for provider tests. */
+    __BUZZ_E2E_PROJECT_WEB_URL_OVERRIDE__?: string;
     /** Project history kinds rejected with CLOSED for aggregate-query tests. */
     __BUZZ_E2E_REJECT_PROJECT_QUERY_KINDS__?: number[];
     /** Captured aggregate project-history filters for request-count assertions. */
@@ -5135,6 +5139,15 @@ function buildMockProjectEvents(): RelayEvent[] {
       projectIndex === 0
         ? (window.__BUZZ_E2E_PROJECT_OWNER_OVERRIDE__ ?? seed.owner)
         : seed.owner;
+    const relayCloneUrl = `${getRelayHttpUrl(getConfig())}/git/${owner}/${seed.dtag}`;
+    const cloneUrl =
+      projectIndex === 0
+        ? (window.__BUZZ_E2E_PROJECT_CLONE_URL_OVERRIDE__ ?? relayCloneUrl)
+        : relayCloneUrl;
+    const webUrl =
+      projectIndex === 0
+        ? window.__BUZZ_E2E_PROJECT_WEB_URL_OVERRIDE__
+        : undefined;
     const repoAddress = `${KIND_REPO_ANNOUNCEMENT}:${owner}:${seed.dtag}`;
     const authors = [seed.owner, ...seed.contributors];
     const random = mulberry32(projectIndex + 1);
@@ -5147,7 +5160,8 @@ function buildMockProjectEvents(): RelayEvent[] {
           ["d", seed.dtag],
           ["name", seed.name],
           ["description", seed.description],
-          ["clone", `https://relay.example.com/git/${owner}/${seed.dtag}`],
+          ["clone", cloneUrl],
+          ...(webUrl ? [["web", webUrl]] : []),
           ...seed.contributors.map((pubkey) => ["p", pubkey]),
         ],
         owner,
@@ -5212,10 +5226,7 @@ function buildMockProjectEvents(): RelayEvent[] {
             ? [
                 ["h", "9a1657ac-f7aa-5db0-b632-d8bbeb6dfb50"],
                 ["branch-name", `feature/mock-${dayOffset}-${index}`],
-                [
-                  "clone",
-                  `https://relay.example.com/git/${owner}/${seed.dtag}`,
-                ],
+                ["clone", cloneUrl],
               ]
             : []),
         ];
diff --git a/desktop/tests/e2e/project-pr-review.spec.ts b/desktop/tests/e2e/project-pr-review.spec.ts
index cae9a08481..b673d7cc96 100644
--- a/desktop/tests/e2e/project-pr-review.spec.ts
+++ b/desktop/tests/e2e/project-pr-review.spec.ts
@@ -711,6 +711,41 @@ test("managed agent repository owner can merge", async ({ page }) => {
   });
 });
 
+test("external repository owner opens the provider instead of native merge", async ({
+  page,
+}) => {
+  await enableProjectsFeature(page);
+  await page.addInitScript(() => {
+    window.__BUZZ_E2E_PROJECT_CLONE_URL_OVERRIDE__ =
+      "https://github.com/block/buzz.git";
+    window.__BUZZ_E2E_PROJECT_WEB_URL_OVERRIDE__ =
+      "https://github.com/block/buzz";
+  });
+  await installMockBridge(page);
+  await openBuzzProject(page);
+
+  await page.getByRole("tab", { name: "Pull Request" }).click();
+  const aliceRow = page
+    .getByTestId("project-pull-request-row")
+    .filter({ hasText: "alice" })
+    .first();
+  await aliceRow.getByRole("button", { name: /^#/ }).click();
+
+  await expect(
+    page.getByRole("button", { name: "Merge", exact: true }),
+  ).toHaveCount(0);
+  await expect(
+    page.getByRole("link", { name: "Open on GitHub", exact: true }),
+  ).toHaveAttribute("href", "https://github.com/block/buzz");
+  const mergeCommandCount = await page.evaluate(
+    () =>
+      window.__BUZZ_E2E_COMMANDS__?.filter(
+        (command) => command === "merge_project_pull_request",
+      ).length ?? 0,
+  );
+  expect(mergeCommandCount).toBe(0);
+});
+
 test("viewer without repository ownership cannot merge", async ({ page }) => {
   await enableProjectsFeature(page);
   await page.addInitScript((owner) => {