diff --git a/server/src/__tests__/issues-service.test.ts b/server/src/__tests__/issues-service.test.ts
index b21c603e2eb..05ea80c4e94 100644
--- a/server/src/__tests__/issues-service.test.ts
+++ b/server/src/__tests__/issues-service.test.ts
@@ -355,6 +355,110 @@ describeEmbeddedPostgres("issueService.list participantAgentId", () => {
     expect(result.map((issue) => issue.id)).toEqual([commentMatchId, descriptionMatchId]);
   });
 
+  it("filters issue lists to the full descendant tree for a root issue", async () => {
+    const companyId = randomUUID();
+    const rootId = randomUUID();
+    const childId = randomUUID();
+    const grandchildId = randomUUID();
+    const siblingId = randomUUID();
+
+    await db.insert(companies).values({
+      id: companyId,
+      name: "Paperclip",
+      issuePrefix: `T${companyId.replace(/-/g, "").slice(0, 6).toUpperCase()}`,
+      requireBoardApprovalForNewAgents: false,
+    });
+
+    await db.insert(issues).values([
+      {
+        id: rootId,
+        companyId,
+        title: "Root",
+        status: "todo",
+        priority: "medium",
+      },
+      {
+        id: childId,
+        companyId,
+        parentId: rootId,
+        title: "Child",
+        status: "todo",
+        priority: "medium",
+      },
+      {
+        id: grandchildId,
+        companyId,
+        parentId: childId,
+        title: "Grandchild",
+        status: "todo",
+        priority: "medium",
+      },
+      {
+        id: siblingId,
+        companyId,
+        title: "Sibling",
+        status: "todo",
+        priority: "medium",
+      },
+    ]);
+
+    const result = await svc.list(companyId, { descendantOf: rootId });
+
+    expect(new Set(result.map((issue) => issue.id))).toEqual(new Set([childId, grandchildId]));
+  });
+
+  it("combines descendant filtering with search", async () => {
+    const companyId = randomUUID();
+    const rootId = randomUUID();
+    const childId = randomUUID();
+    const grandchildId = randomUUID();
+    const outsideMatchId = randomUUID();
+
+    await db.insert(companies).values({
+      id: companyId,
+      name: "Paperclip",
+      issuePrefix: `T${companyId.replace(/-/g, "").slice(0, 6).toUpperCase()}`,
+      requireBoardApprovalForNewAgents: false,
+    });
+
+    await db.insert(issues).values([
+      {
+        id: rootId,
+        companyId,
+        title: "Root",
+        status: "todo",
+        priority: "medium",
+      },
+      {
+        id: childId,
+        companyId,
+        parentId: rootId,
+        title: "Relevant parent",
+        status: "todo",
+        priority: "medium",
+      },
+      {
+        id: grandchildId,
+        companyId,
+        parentId: childId,
+        title: "Needle grandchild",
+        status: "todo",
+        priority: "medium",
+      },
+      {
+        id: outsideMatchId,
+        companyId,
+        title: "Needle outside",
+        status: "todo",
+        priority: "medium",
+      },
+    ]);
+
+    const result = await svc.list(companyId, { descendantOf: rootId, q: "needle" });
+
+    expect(result.map((issue) => issue.id)).toEqual([grandchildId]);
+  });
+
   it("accepts issue identifiers through getById", async () => {
     const companyId = randomUUID();
     const issueId = randomUUID();
diff --git a/server/src/routes/issues.ts b/server/src/routes/issues.ts
index aef722aa3af..ee7b5088acc 100644
--- a/server/src/routes/issues.ts
+++ b/server/src/routes/issues.ts
@@ -831,6 +831,7 @@ export function issueRoutes(
       workspaceId: req.query.workspaceId as string | undefined,
       executionWorkspaceId: req.query.executionWorkspaceId as string | undefined,
       parentId: req.query.parentId as string | undefined,
+      descendantOf: req.query.descendantOf as string | undefined,
       labelId: req.query.labelId as string | undefined,
       originKind: req.query.originKind as string | undefined,
       originId: req.query.originId as string | undefined,
diff --git a/server/src/services/issues.ts b/server/src/services/issues.ts
index 013d0e9b51b..5046ba09233 100644
--- a/server/src/services/issues.ts
+++ b/server/src/services/issues.ts
@@ -106,6 +106,7 @@ export interface IssueFilters {
   workspaceId?: string;
   executionWorkspaceId?: string;
   parentId?: string;
+  descendantOf?: string;
   labelId?: string;
   originKind?: string;
   originId?: string;
@@ -1396,6 +1397,29 @@ export function issueService(db: Db) {
             AND ${issueComments.body} ILIKE ${containsPattern} ESCAPE '\\'
         )
       `;
+      if (filters?.descendantOf) {
+        const descendantIds: string[] = [];
+        const seen = new Set<string>([filters.descendantOf]);
+        let frontier = [filters.descendantOf];
+
+        while (frontier.length > 0) {
+          const children = await db
+            .select({ id: issues.id })
+            .from(issues)
+            .where(and(eq(issues.companyId, companyId), inArray(issues.parentId, frontier)));
+
+          frontier = [];
+          for (const child of children) {
+            if (seen.has(child.id)) continue;
+            seen.add(child.id);
+            descendantIds.push(child.id);
+            frontier.push(child.id);
+          }
+        }
+
+        if (descendantIds.length === 0) return [];
+        conditions.push(inArray(issues.id, descendantIds));
+      }
       if (filters?.status) {
         const statuses = filters.status.split(",").map((s) => s.trim());
         conditions.push(statuses.length === 1 ? eq(issues.status, statuses[0]) : inArray(issues.status, statuses));
diff --git a/ui/src/api/issues.test.ts b/ui/src/api/issues.test.ts
index a32add42e68..dedbfa9cd73 100644
--- a/ui/src/api/issues.test.ts
+++ b/ui/src/api/issues.test.ts
@@ -24,6 +24,14 @@ describe("issuesApi.list", () => {
     );
   });
 
+  it("passes descendantOf through to the company issues endpoint", async () => {
+    await issuesApi.list("company-1", { descendantOf: "issue-root-1", limit: 25 });
+
+    expect(mockApi.get).toHaveBeenCalledWith(
+      "/companies/company-1/issues?descendantOf=issue-root-1&limit=25",
+    );
+  });
+
   it("passes generic workspaceId filters through to the company issues endpoint", async () => {
     await issuesApi.list("company-1", { workspaceId: "workspace-1", limit: 1000 });
 
diff --git a/ui/src/api/issues.ts b/ui/src/api/issues.ts
index b2856513747..d7e244b25c1 100644
--- a/ui/src/api/issues.ts
+++ b/ui/src/api/issues.ts
@@ -43,6 +43,7 @@ export const issuesApi = {
       executionWorkspaceId?: string;
       originKind?: string;
       originId?: string;
+      descendantOf?: string;
       includeRoutineExecutions?: boolean;
       q?: string;
       limit?: number;
@@ -63,6 +64,7 @@ export const issuesApi = {
     if (filters?.executionWorkspaceId) params.set("executionWorkspaceId", filters.executionWorkspaceId);
     if (filters?.originKind) params.set("originKind", filters.originKind);
     if (filters?.originId) params.set("originId", filters.originId);
+    if (filters?.descendantOf) params.set("descendantOf", filters.descendantOf);
     if (filters?.includeRoutineExecutions) params.set("includeRoutineExecutions", "true");
     if (filters?.q) params.set("q", filters.q);
     if (filters?.limit) params.set("limit", String(filters.limit));
diff --git a/ui/src/lib/queryKeys.ts b/ui/src/lib/queryKeys.ts
index c345b87afc8..c61b216a2fd 100644
--- a/ui/src/lib/queryKeys.ts
+++ b/ui/src/lib/queryKeys.ts
@@ -41,6 +41,8 @@ export const queryKeys = {
       ["issues", companyId, "project", projectId] as const,
     listByParent: (companyId: string, parentId: string) =>
       ["issues", companyId, "parent", parentId] as const,
+    listByDescendantRoot: (companyId: string, rootIssueId: string) =>
+      ["issues", companyId, "descendants", rootIssueId] as const,
     listByExecutionWorkspace: (companyId: string, executionWorkspaceId: string) =>
       ["issues", companyId, "execution-workspace", executionWorkspaceId] as const,
     detail: (id: string) => ["issues", "detail", id] as const,
diff --git a/ui/src/pages/IssueDetail.tsx b/ui/src/pages/IssueDetail.tsx
index a6e1830034c..58840877519 100644
--- a/ui/src/pages/IssueDetail.tsx
+++ b/ui/src/pages/IssueDetail.tsx
@@ -1132,9 +1132,9 @@ export function IssueDetail() {
   const { data: rawChildIssues = [], isLoading: childIssuesLoading } = useQuery({
     queryKey:
       issue?.id && resolvedCompanyId
-        ? queryKeys.issues.listByParent(resolvedCompanyId, issue.id)
+        ? queryKeys.issues.listByDescendantRoot(resolvedCompanyId, issue.id)
         : ["issues", "parent", "pending"],
-    queryFn: () => issuesApi.list(resolvedCompanyId!, { parentId: issue!.id }),
+    queryFn: () => issuesApi.list(resolvedCompanyId!, { descendantOf: issue!.id }),
     enabled: !!resolvedCompanyId && !!issue?.id,
     placeholderData: keepPreviousDataForSameQueryTail<Issue[]>(issue?.id ?? "pending"),
   });
@@ -3133,7 +3133,7 @@ export function IssueDetail() {
             projectId={issue.projectId ?? undefined}
             viewStateKey={`paperclip:issue-detail:${issue.id}:subissues-view`}
             issueLinkState={resolvedIssueDetailState ?? location.state}
-            searchFilters={{ parentId: issue.id }}
+            searchFilters={{ descendantOf: issue.id }}
             baseCreateIssueDefaults={buildSubIssueDefaultsForViewer(issue, currentUserId)}
             createIssueLabel="Sub-issue"
             onUpdateIssue={handleChildIssueUpdate}