diff --git a/server/src/__tests__/activity-log-retention.test.ts b/server/src/__tests__/activity-log-retention.test.ts
index b435d90778a..a6a36f7f1ff 100644
--- a/server/src/__tests__/activity-log-retention.test.ts
+++ b/server/src/__tests__/activity-log-retention.test.ts
@@ -38,6 +38,7 @@ describe("capActivityDetails", () => {
     });
     expect(capped?._paperclipOriginalBytes).toBeGreaterThan(MAX_ACTIVITY_DETAILS_BYTES);
     expect(capped?._paperclipPreview).toEqual(expect.stringContaining("start-"));
+    expect(/[\uD800-\uDBFF]$/.test(String(capped?._paperclipPreview))).toBe(false);
     expect(Buffer.byteLength(JSON.stringify(capped), "utf8")).toBeLessThanOrEqual(
       MAX_ACTIVITY_DETAILS_BYTES,
     );
@@ -161,7 +162,7 @@ describeEmbeddedPostgres("activity log retention", () => {
       action: "test.oversized",
       entityType: "company",
       entityId: companyId,
-      details: { output: "x".repeat(MAX_ACTIVITY_DETAILS_BYTES * 2) },
+      details: { output: "😀".repeat(MAX_ACTIVITY_DETAILS_BYTES) },
     });
 
     const row = await db
diff --git a/server/src/index.ts b/server/src/index.ts
index f312dd9d135..083626115b9 100644
--- a/server/src/index.ts
+++ b/server/src/index.ts
@@ -827,7 +827,7 @@ export async function startServer(): Promise<StartedServer> {
   let prepareHotRestartShutdown: ((signal: "SIGINT" | "SIGTERM") => Promise<{ skipDrain: boolean }>) | null = null;
   let heartbeatSchedulerStopped = false;
   let heartbeatSchedulerInterval: ReturnType<typeof setInterval> | null = null;
-  const stopActivityLogRetention = startActivityLogRetention(db as any);
+  const stopActivityLogRetention = startActivityLogRetention(db);
   const heartbeatSchedulerInFlight = new Set<Promise<void>>();
   const trackHeartbeatSchedulerWork = (work: Promise<unknown>) => {
     let tracked: Promise<void>;
diff --git a/server/src/services/activity-log.ts b/server/src/services/activity-log.ts
index 63a53603b58..7340156f42e 100644
--- a/server/src/services/activity-log.ts
+++ b/server/src/services/activity-log.ts
@@ -99,7 +99,15 @@ export function capActivityDetails(
     }
   }
 
-  return buildMarker(serialized.slice(0, low));
+  const finalCodeUnit = serialized.charCodeAt(low - 1);
+  const nextCodeUnit = serialized.charCodeAt(low);
+  const splitsSurrogatePair = finalCodeUnit >= 0xd800
+    && finalCodeUnit <= 0xdbff
+    && nextCodeUnit >= 0xdc00
+    && nextCodeUnit <= 0xdfff;
+  const previewEnd = splitsSurrogatePair ? low - 1 : low;
+
+  return buildMarker(serialized.slice(0, previewEnd));
 }
 
 export async function resolveResponsibleUserIdForActivity(db: Db, input: LogActivityInput) {
diff --git a/ui/src/context/CompanyContext.test.tsx b/ui/src/context/CompanyContext.test.tsx
index 43beef5b533..799f56d2345 100644
--- a/ui/src/context/CompanyContext.test.tsx
+++ b/ui/src/context/CompanyContext.test.tsx
@@ -39,6 +39,7 @@ function makeCompany(id: string): Company {
     budgetMonthlyCents: 0,
     spentMonthlyCents: 0,
     attachmentMaxBytes: 10 * 1024 * 1024,
+    activityLogRetentionDays: null,
     defaultResponsibleUserId: null,
     requireBoardApprovalForNewAgents: false,
     feedbackDataSharingEnabled: false,
diff --git a/ui/storybook/fixtures/paperclipData.ts b/ui/storybook/fixtures/paperclipData.ts
index 5f6bae12977..f739e81794a 100644
--- a/ui/storybook/fixtures/paperclipData.ts
+++ b/ui/storybook/fixtures/paperclipData.ts
@@ -43,6 +43,7 @@ export const storybookCompanies: Company[] = [
     budgetMonthlyCents: 250_000,
     spentMonthlyCents: 67_500,
     attachmentMaxBytes: 10 * 1024 * 1024,
+    activityLogRetentionDays: null,
     defaultResponsibleUserId: "user-board",
     requireBoardApprovalForNewAgents: true,
     feedbackDataSharingEnabled: true,
@@ -67,6 +68,7 @@ export const storybookCompanies: Company[] = [
     budgetMonthlyCents: 180_000,
     spentMonthlyCents: 39_500,
     attachmentMaxBytes: 10 * 1024 * 1024,
+    activityLogRetentionDays: null,
     defaultResponsibleUserId: "user-board",
     requireBoardApprovalForNewAgents: false,
     feedbackDataSharingEnabled: false,
@@ -91,6 +93,7 @@ export const storybookCompanies: Company[] = [
     budgetMonthlyCents: 90_000,
     spentMonthlyCents: 91_200,
     attachmentMaxBytes: 10 * 1024 * 1024,
+    activityLogRetentionDays: null,
     defaultResponsibleUserId: "user-board",
     requireBoardApprovalForNewAgents: true,
     feedbackDataSharingEnabled: false,