diff --git a/src/api/routes/v3/staking-bonds.ts b/src/api/routes/v3/staking-bonds.ts
index e40625bc36..ead54b72e8 100644
--- a/src/api/routes/v3/staking-bonds.ts
+++ b/src/api/routes/v3/staking-bonds.ts
@@ -51,6 +51,7 @@ export const StakingBondsRoutes: FastifyPluginAsync<
         limit: req.query.limit ?? getPagingQueryLimit(ResourceType.Tx),
         cursor: req.query.cursor,
       });
+      const poxConstants = await fastify.db.getPoxConstants();
       await reply.send({
         limit: results.limit,
         total: results.total,
@@ -59,7 +60,9 @@ export const StakingBondsRoutes: FastifyPluginAsync<
           previous: results.prev_cursor,
           current: results.current_cursor,
         },
-        results: results.results.map(r => serializeDbBondSummary(r, results.burn_block_height)),
+        results: results.results.map(r =>
+          serializeDbBondSummary(r, results.burn_block_height, poxConstants)
+        ),
       });
     }
   );
@@ -86,7 +89,9 @@ export const StakingBondsRoutes: FastifyPluginAsync<
       if (!bond) {
         throw new NotFoundError('Bond not found');
       }
-      await reply.send(serializeDbBond(bond, bond.burn_block_height));
+      await reply.send(
+        serializeDbBond(bond, bond.burn_block_height, await fastify.db.getPoxConstants())
+      );
     }
   );
 
@@ -118,6 +123,7 @@ export const StakingBondsRoutes: FastifyPluginAsync<
         limit: req.query.limit ?? getPagingQueryLimit(ResourceType.Tx),
         cursor: req.query.cursor,
       });
+      const poxConstants = await fastify.db.getPoxConstants();
       await reply.send({
         limit: results.limit,
         total: results.total,
@@ -126,7 +132,7 @@ export const StakingBondsRoutes: FastifyPluginAsync<
           previous: results.prev_cursor,
           current: results.current_cursor,
         },
-        results: results.results.map(r => serializeDbBondEvent(r)),
+        results: results.results.map(r => serializeDbBondEvent(r, poxConstants)),
       });
     }
   );
diff --git a/src/api/schemas/v3/entities/bonds.ts b/src/api/schemas/v3/entities/bonds.ts
index 5f91ab8671..f31b642e41 100644
--- a/src/api/schemas/v3/entities/bonds.ts
+++ b/src/api/schemas/v3/entities/bonds.ts
@@ -82,10 +82,20 @@ export const BondSchedulePointSchema = Type.Object({
 });
 export type BondSchedulePoint = Static<typeof BondSchedulePointSchema>;
 
-export const BondScheduleSchema = Type.Object({
-  activation: BondSchedulePointSchema,
-  unlock: BondSchedulePointSchema,
-});
+export const BondScheduleSchema = Type.Object(
+  {
+    enrollment_cutoff: BondSchedulePointSchema,
+    activation: BondSchedulePointSchema,
+    unlock: BondSchedulePointSchema,
+  },
+  {
+    description:
+      "The bond's lifecycle timeline. Each point is the first Bitcoin height of a new phase: " +
+      '`enrollment_cutoff` is the first height at which `register-for-bond` is rejected (the ' +
+      'prepare phase before activation, so enrollment is open strictly before it), `activation` ' +
+      'is the first height the bond is active, and `unlock` the first height it is unlocked.',
+  }
+);
 export type BondSchedule = Static<typeof BondScheduleSchema>;
 
 export const BondSummarySchema = Type.Object({
diff --git a/src/api/serializers/v3/bonds.ts b/src/api/serializers/v3/bonds.ts
index c1e55bbe81..4011719298 100644
--- a/src/api/serializers/v3/bonds.ts
+++ b/src/api/serializers/v3/bonds.ts
@@ -13,6 +13,7 @@ import {
   DbBondLockupType,
   DbPrincipalBondPositionStatus,
 } from '../../../datastore/common.js';
+import { getBondEnrollmentCutoff, PoxConstants } from '../../../datastore/pox-constants.js';
 import {
   Pox5EventAddToAllowlist,
   Pox5EventAnnounceL1EarlyExit,
@@ -59,12 +60,20 @@ function serializeBondStatus(summary: DbBondSummary, currentBurnBlockHeight: num
 /**
  * Serializes a database bond summary to a API bond summary.
  * @param summary - The database bond summary to serialize.
+ * @param currentBurnBlockHeight - The Bitcoin height of the chain tip, for the bond's status.
+ * @param poxConstants - The network's PoX constants, for the bond's enrollment cutoff.
  * @returns The API bond summary.
  */
 export function serializeDbBondSummary(
   summary: DbBondSummary,
-  currentBurnBlockHeight: number
+  currentBurnBlockHeight: number,
+  poxConstants: PoxConstants
 ): BondSummary {
+  const enrollmentCutoff = getBondEnrollmentCutoff(
+    poxConstants,
+    summary.bond_start_height,
+    summary.first_reward_cycle
+  );
   return {
     index: summary.bond_index,
     pox_version: 'pox5',
@@ -80,6 +89,10 @@ export function serializeDbBondSummary(
       registered_count: summary.registered_count,
     },
     schedule: {
+      enrollment_cutoff: {
+        bitcoin_height: enrollmentCutoff.bitcoinHeight,
+        pox_cycle: enrollmentCutoff.poxCycle,
+      },
       activation: {
         bitcoin_height: summary.bond_start_height,
         pox_cycle: summary.first_reward_cycle,
@@ -111,11 +124,17 @@ export function serializeDbBondSummary(
 /**
  * Serializes a database bond to a API bond.
  * @param bond - The database bond to serialize.
+ * @param currentBurnBlockHeight - The Bitcoin height of the chain tip, for the bond's status.
+ * @param poxConstants - The network's PoX constants, for the bond's enrollment cutoff.
  * @returns The API bond.
  */
-export function serializeDbBond(bond: DbBond, currentBurnBlockHeight: number): Bond {
+export function serializeDbBond(
+  bond: DbBond,
+  currentBurnBlockHeight: number,
+  poxConstants: PoxConstants
+): Bond {
   return {
-    ...serializeDbBondSummary(bond, currentBurnBlockHeight),
+    ...serializeDbBondSummary(bond, currentBurnBlockHeight, poxConstants),
     transaction: {
       tx_id: bond.tx_id,
       block: {
@@ -138,9 +157,10 @@ export function serializeDbBond(bond: DbBond, currentBurnBlockHeight: number): B
  * same vocabulary as the bond, allowlist, and registration entities (grouped `{ btc, stx }` string
  * amounts, integer heights and cycles) instead of passing the raw synthetic event fields through,
  * and carry only what the event uniquely records — details available on a resource endpoint (e.g.
- * a registration's proven L1 lockup outputs) are not repeated here.
+ * a registration's proven L1 lockup outputs) are not repeated here. The PoX constants derive the
+ * `setup-bond` schedule's enrollment cutoff, which the event itself does not record.
  */
-export function serializeDbBondEvent(event: DbBondEvent): BondEvent {
+export function serializeDbBondEvent(event: DbBondEvent, poxConstants: PoxConstants): BondEvent {
   const base = {
     bond_index: parseInt((event.data as { bond_index: string }).bond_index),
     transaction: {
@@ -162,6 +182,11 @@ export function serializeDbBondEvent(event: DbBondEvent): BondEvent {
   switch (event.name) {
     case Pox5EventName.SetupBond: {
       const data = event.data as unknown as Pox5EventSetupBond['data'];
+      const enrollmentCutoff = getBondEnrollmentCutoff(
+        poxConstants,
+        parseInt(data.bond_start_height),
+        parseInt(data.first_reward_cycle)
+      );
       return {
         ...base,
         name: Pox5EventName.SetupBond,
@@ -173,6 +198,10 @@ export function serializeDbBondEvent(event: DbBondEvent): BondEvent {
           },
           early_unlock_bytes: data.early_unlock_bytes,
           schedule: {
+            enrollment_cutoff: {
+              bitcoin_height: enrollmentCutoff.bitcoinHeight,
+              pox_cycle: enrollmentCutoff.poxCycle,
+            },
             activation: {
               bitcoin_height: parseInt(data.bond_start_height),
               pox_cycle: parseInt(data.first_reward_cycle),
diff --git a/src/datastore/pox-constants.ts b/src/datastore/pox-constants.ts
index 90a91c1691..507833c38f 100644
--- a/src/datastore/pox-constants.ts
+++ b/src/datastore/pox-constants.ts
@@ -205,6 +205,24 @@ export function getPoxCycleSchedule(c: PoxConstants, cycle: number): PoxCycleSch
   };
 }
 
+/**
+ * The first Bitcoin height at which pox-5 rejects `register-for-bond` for a bond: the start of the
+ * prepare phase that ends the cycle before the bond activates. The contract rejects registration
+ * during any prepare phase (`verify-not-prepare-phase`) and from the bond's start height on, and a
+ * bond always starts on a reward cycle boundary, so the prepare phase is what closes enrollment.
+ * Exclusive, like the bond's other schedule points: enrollment is open strictly before it.
+ */
+export function getBondEnrollmentCutoff(
+  c: PoxConstants,
+  bondStartHeight: number,
+  firstRewardCycle: number
+): { bitcoinHeight: number; poxCycle: number } {
+  return {
+    bitcoinHeight: bondStartHeight - c.preparePhaseBlockLength,
+    poxCycle: firstRewardCycle - 1,
+  };
+}
+
 /**
  * Where a reward cycle stands relative to the burn tip. `prepare_phase` is the cycle's final
  * `preparePhaseBlockLength` blocks, during which the next cycle's reward set is selected and the
diff --git a/tests/api/pox5/bond-events.test.ts b/tests/api/pox5/bond-events.test.ts
index fa1904ee0f..9e86cc5e79 100644
--- a/tests/api/pox5/bond-events.test.ts
+++ b/tests/api/pox5/bond-events.test.ts
@@ -271,6 +271,12 @@ describe('pox-5 bond events', () => {
       skipMigrations: true,
     });
     api = await startApiServer({ datastore: db, chainId: STACKS_TESTNET.chainId });
+    // A testnet-like geometry where the bond's start height (160) opens reward cycle 8.
+    await db.setPoxConstants({
+      firstBurnchainBlockHeight: 0,
+      rewardCycleLength: 20,
+      preparePhaseBlockLength: 5,
+    });
     await ingestScenario();
   });
 
@@ -375,6 +381,8 @@ describe('pox-5 bond events', () => {
       },
       early_unlock_bytes: '',
       schedule: {
+        // Derived from the PoX constants: cycle 7's prepare phase starts 5 blocks before 160.
+        enrollment_cutoff: { bitcoin_height: 155, pox_cycle: 7 },
         activation: { bitcoin_height: 160, pox_cycle: 8 },
         unlock: { bitcoin_height: 410, pox_cycle: 20 },
       },
diff --git a/tests/api/pox5/bonds.test.ts b/tests/api/pox5/bonds.test.ts
index b1994ff333..4751424604 100644
--- a/tests/api/pox5/bonds.test.ts
+++ b/tests/api/pox5/bonds.test.ts
@@ -69,12 +69,17 @@ interface BondSummaryItem {
     btc_capacity: string;
   };
   registrations: { allowed_count: number; registered_count: number };
+  schedule: Record<'enrollment_cutoff' | 'activation' | 'unlock', BondSchedulePoint>;
   balances: {
     locked: { btc: string; stx: string };
     rewards: { btc: { distributed: string; accrued: string; claimed: string } };
     paid_out: { btc: string };
   };
 }
+interface BondSchedulePoint {
+  bitcoin_height: number;
+  pox_cycle: number;
+}
 interface BondDetail extends BondSummaryItem {
   transaction: { tx_id: string };
 }
@@ -223,6 +228,27 @@ describe('pox-5 bonds (simulated ingestion)', () => {
     assert.equal(normalizeTxId(bond.transaction.tx_id), normalizeTxId(SETUP_TX_ID));
   });
 
+  test('the bond schedule reports its enrollment cutoff (GET .../bonds and .../bonds/:index)', async () => {
+    // A testnet-like geometry where the bond's start height (160) opens reward cycle 8.
+    await db.setPoxConstants({
+      firstBurnchainBlockHeight: 0,
+      rewardCycleLength: 20,
+      preparePhaseBlockLength: 5,
+    });
+    const expected = {
+      // Registration closes when cycle 7's prepare phase begins, 5 blocks before activation.
+      enrollment_cutoff: { bitcoin_height: 155, pox_cycle: 7 },
+      activation: { bitcoin_height: BOND_START_HEIGHT, pox_cycle: FIRST_REWARD_CYCLE },
+      unlock: { bitcoin_height: UNLOCK_BURN_HEIGHT, pox_cycle: UNLOCK_CYCLE },
+    };
+    const list = await getJson<CursorPaginated<BondSummaryItem>>(
+      '/extended/v3/staking/bonds?limit=50'
+    );
+    assert.deepEqual(list.results.find(b => b.index === BOND_INDEX)?.schedule, expected);
+    const bond = await getJson<BondDetail>(`/extended/v3/staking/bonds/${BOND_INDEX}`);
+    assert.deepEqual(bond.schedule, expected);
+  });
+
   test('the allowlist lists alice and bob (GET .../allowlist)', async () => {
     const list = await getJson<CursorPaginated<BondAllowlistEntry>>(
       `/extended/v3/staking/bonds/${BOND_INDEX}/allowlist?limit=50`
diff --git a/tests/api/pox5/pox-constants.test.ts b/tests/api/pox5/pox-constants.test.ts
index 49f6f1e50f..75b6396861 100644
--- a/tests/api/pox5/pox-constants.test.ts
+++ b/tests/api/pox5/pox-constants.test.ts
@@ -10,6 +10,7 @@ import {
   PoxInfoClient,
   burnHeightToRewardCycle,
   ensurePoxConstants,
+  getBondEnrollmentCutoff,
   getPoxCyclePhase,
   getPoxCycleSchedule,
   poxConstantsFromNodeInfo,
@@ -301,4 +302,14 @@ describe('pox cycle arithmetic', () => {
     });
     assert.equal(getPoxCyclePhase(small, 10, 1095), 'prepare_phase');
   });
+
+  test('closes bond enrollment at the prepare phase before the bond activates', () => {
+    // A bond activating at the start of cycle 144 stops accepting registrations when cycle 143's
+    // prepare phase begins, the first height `verify-not-prepare-phase` rejects.
+    const cutoff = getBondEnrollmentCutoff(c, rewardCycleToBurnHeight(c, 144), 144);
+    assert.deepEqual(cutoff, { bitcoinHeight: 968350, poxCycle: 143 });
+    assert.equal(cutoff.bitcoinHeight, getPoxCycleSchedule(c, 143).preparePhaseStartBitcoinHeight);
+    assert.equal(getPoxCyclePhase(c, 143, cutoff.bitcoinHeight - 1), 'reward_phase');
+    assert.equal(getPoxCyclePhase(c, 143, cutoff.bitcoinHeight), 'prepare_phase');
+  });
 });