diff --git a/src/db/repositories.ts b/src/db/repositories.ts
index 1890d68381..242296373b 100644
--- a/src/db/repositories.ts
+++ b/src/db/repositories.ts
@@ -320,15 +320,23 @@ export async function upsertPullRequestFromGitHub(
   const db = getDb(env.DB);
   const syncedAt = nowIso();
   const lastSeenOpenAt = pr.state === "open" ? (options.seenOpenAt ?? syncedAt) : null;
-  const linkedIssuesJson = jsonString(record.linkedIssues);
-  const observedLinkedIssueClaimedAt = record.linkedIssues.length > 0 ? syncedAt : null;
   const existingClaimRows = await db
     .select({ linkedIssuesJson: pullRequests.linkedIssuesJson, linkedIssueClaimedAt: pullRequests.linkedIssueClaimedAt })
     .from(pullRequests)
     .where(and(eq(pullRequests.repoFullName, repoFullName), eq(pullRequests.number, pr.number)))
     .limit(1);
+  // A sparse GitHub payload (e.g. a narrower webhook event's embedded pull_request sub-object, as opposed to a
+  // full `GET /pulls/{n}` read) can omit `body` entirely (`undefined`) rather than reporting it as explicitly
+  // empty (`null`/`""`) — `GitHubPullRequestPayload.body` is typed `string | null` precisely because a caller
+  // may not have it at all. Re-deriving linked issues from an ABSENT body would silently wipe an
+  // already-correctly-claimed linked issue (and reset its claim timestamp via resolveLinkedIssueClaimedAt's own
+  // `linkedIssues.length === 0` branch) on any such upsert. Fall back to whatever is already stored in that
+  // case; only a genuinely observed (possibly empty) body updates the claim. (#linked-issue-sparse-payload-preserve)
+  const linkedIssues = pr.body === undefined && existingClaimRows[0] ? parseLinkedIssuesJson(existingClaimRows[0].linkedIssuesJson) : record.linkedIssues;
+  const linkedIssuesJson = pr.body === undefined && existingClaimRows[0] ? existingClaimRows[0].linkedIssuesJson : jsonString(linkedIssues);
+  const observedLinkedIssueClaimedAt = linkedIssues.length > 0 ? syncedAt : null;
   const linkedIssueClaimedAt = resolveLinkedIssueClaimedAt(
-    record.linkedIssues,
+    linkedIssues,
     linkedIssuesJson,
     existingClaimRows[0],
     observedLinkedIssueClaimedAt,
@@ -375,7 +383,7 @@ export async function upsertPullRequestFromGitHub(
         updatedAt: syncedAt,
       },
     });
-  return { ...record, linkedIssueClaimedAt };
+  return { ...record, linkedIssues, linkedIssueClaimedAt };
 }
 
 function resolveLinkedIssueClaimedAt(
diff --git a/test/unit/db-parsers.test.ts b/test/unit/db-parsers.test.ts
index 533cd9a9ee..6b27e4968d 100644
--- a/test/unit/db-parsers.test.ts
+++ b/test/unit/db-parsers.test.ts
@@ -9,6 +9,7 @@ import {
   getRepoAuthorPullRequestHistory,
   getLatestScoringModelSnapshot,
   getFreshOfficialMinerDetection,
+  getPullRequest,
   listPullRequests,
   listPullRequestDetailSyncStates,
   listRepoSyncSegments,
@@ -363,6 +364,47 @@ describe("database row parser hardening", () => {
     expect(resynced?.lastRegatedAt).toBe(stamped); // but the marker survived
   });
 
+  it("REGRESSION: a sparse sync (payload.body absent) does NOT wipe an already-claimed linked issue (#linked-issue-sparse-payload-preserve)", async () => {
+    const env = createTestEnv();
+    // A full sync (e.g. pull_request.opened) correctly claims the linked issue.
+    await upsertPullRequestFromGitHub(env, "owner/repo", { number: 7, title: "Fix the bug", state: "open", user: { login: "bob" }, head: { sha: "a1" }, labels: [], body: "Closes #42" });
+    const claimed = await getPullRequest(env, "owner/repo", 7);
+    expect(claimed?.linkedIssues).toEqual([42]);
+    expect(typeof claimed?.linkedIssueClaimedAt).toBe("string");
+
+    // A NARROWER event's embedded pull_request sub-object (e.g. a pull_request_review payload shape) can omit
+    // `body` entirely -- `undefined`, not an explicit empty string/null. This upsert must not re-derive an
+    // empty linkedIssues from the absent body and clobber the already-correct claim.
+    const resynced = await upsertPullRequestFromGitHub(env, "owner/repo", { number: 7, title: "Fix the bug", state: "open", user: { login: "bob" }, head: { sha: "a1" }, labels: [] });
+    expect(resynced.linkedIssues).toEqual([42]); // the function's own return value is corrected too
+    expect(resynced.linkedIssueClaimedAt).toBe(claimed?.linkedIssueClaimedAt); // claim timestamp is untouched
+
+    const stored = await getPullRequest(env, "owner/repo", 7);
+    expect(stored?.linkedIssues).toEqual([42]);
+    expect(stored?.linkedIssueClaimedAt).toBe(claimed?.linkedIssueClaimedAt);
+  });
+
+  it("a genuinely empty body (explicit null/\"\", not absent) DOES clear a previously-claimed linked issue", async () => {
+    const env = createTestEnv();
+    await upsertPullRequestFromGitHub(env, "owner/repo", { number: 8, title: "Fix the bug", state: "open", user: { login: "bob" }, head: { sha: "a1" }, labels: [], body: "Closes #42" });
+    // The contributor genuinely deleted their PR description -- GitHub reports this as body: null, a real signal
+    // distinct from a sparse payload's absent field, and it must still update the stored claim.
+    const cleared = await upsertPullRequestFromGitHub(env, "owner/repo", { number: 8, title: "Fix the bug", state: "open", user: { login: "bob" }, head: { sha: "a1" }, labels: [], body: null });
+    expect(cleared.linkedIssues).toEqual([]);
+    const stored = await getPullRequest(env, "owner/repo", 8);
+    expect(stored?.linkedIssues).toEqual([]);
+    expect(stored?.linkedIssueClaimedAt).toBeNull();
+  });
+
+  it("a sparse sync on a brand-new PR (no existing row to preserve) falls through to the empty default", async () => {
+    const env = createTestEnv();
+    // No prior row exists for PR #9 -- the sparse-preserve branch has nothing to preserve, so this must behave
+    // exactly as it always has: derive from the (absent) body, yielding no linked issues.
+    const created = await upsertPullRequestFromGitHub(env, "owner/repo", { number: 9, title: "New PR", state: "open", user: { login: "bob" }, labels: [] });
+    expect(created.linkedIssues).toEqual([]);
+    expect(created.linkedIssueClaimedAt).toBeNull();
+  });
+
   it("countRecentDeadLetters counts github_app.dlq_dead_lettered audits since a cutoff, independent of any ops flag (#1276)", async () => {
     const env = createTestEnv();
     await recordAuditEvent(env, { eventType: "github_app.dlq_dead_lettered", actor: "gittensory", targetKey: "dlq:github-webhook:a", outcome: "error", createdAt: "2026-06-24T10:00:00.000Z" });