diff --git a/contracts/events/src/errors.rs b/contracts/events/src/errors.rs
index fd8959c..40eb478 100644
--- a/contracts/events/src/errors.rs
+++ b/contracts/events/src/errors.rs
@@ -15,8 +15,8 @@ pub enum Error {
     NotAdmin = 11,
     // Shared by both two-step rotations (admin and event manager): no pending
     // proposal / target mismatch (12) and pending proposal expired (13). The
-    // enum is at the 50-case XDR cap, so the manager flow reuses these rather
-    // than adding variants.
+    // manager flow reuses these because the two flows are structurally
+    // identical, not to duplicate a variant per flow.
     PendingRotationMismatch = 12,
     PendingRotationExpired = 13,
 
@@ -54,9 +54,8 @@ pub enum Error {
 
     OpAlreadySeen = 60,
 
-    // Also returned by append_submission's cap check — the enum is at
-    // the 50-case XDR cap, so the hackathon submission cap reuses this
-    // rather than adding a variant.
+    // Also returned by append_submission's cap check: the hackathon submission
+    // cap reuses this rather than adding a near-duplicate "TooManySubmissions".
     TooManyContributors = 61,
 
     CancellationNotStarted = 62,
@@ -70,9 +69,11 @@ pub enum Error {
     MigrationAlreadyApplied = 69,
 
     Paused = 70,
+    EventIdOverflow = 71,
 
     ProfileCallFailed = 80,
 
-    // Enum is at the 50-case XDR cap; consolidate before adding another.
+    // contracterror caps at 50 cases (48 used). Discriminants are not dense —
+    // 91 is a numeric label, not the case count.
     PrizeAlreadyClaimed = 91,
 }
diff --git a/contracts/events/src/event_ops.rs b/contracts/events/src/event_ops.rs
index 814cf08..8e002cb 100644
--- a/contracts/events/src/event_ops.rs
+++ b/contracts/events/src/event_ops.rs
@@ -128,7 +128,7 @@ pub fn create_event(env: &Env, params: CreateEventParams, op_id: BytesN<32>) ->
         );
     }
 
-    let id = idempotency::next_event_id(env);
+    let id = idempotency::next_event_id(env)?;
     let record = EventRecord { id, ..provisional };
     storage::set_event(env, id, &record);
     storage::set_non_owner_contribution_total(env, id, 0);
diff --git a/contracts/events/src/idempotency.rs b/contracts/events/src/idempotency.rs
index 65187b7..c052cc5 100644
--- a/contracts/events/src/idempotency.rs
+++ b/contracts/events/src/idempotency.rs
@@ -25,11 +25,13 @@ pub fn id_base(env: &Env) -> u64 {
     (seq as u64) << 32
 }
 
-pub fn next_event_id(env: &Env) -> u64 {
+pub fn next_event_id(env: &Env) -> Result<u64, Error> {
     let base = id_base(env);
-    let id = storage::get_next_event_id(env, base.saturating_add(1));
-    storage::set_next_event_id(env, id.saturating_add(1));
-    id
+    let fallback = base.checked_add(1).ok_or(Error::EventIdOverflow)?;
+    let id = storage::get_next_event_id(env, fallback);
+    let next = id.checked_add(1).ok_or(Error::EventIdOverflow)?;
+    storage::set_next_event_id(env, next);
+    Ok(id)
 }
 
 pub mod tag {
diff --git a/contracts/events/src/tests/op_id_security.rs b/contracts/events/src/tests/op_id_security.rs
index 8c7931b..87fe2be 100644
--- a/contracts/events/src/tests/op_id_security.rs
+++ b/contracts/events/src/tests/op_id_security.rs
@@ -10,6 +10,7 @@ use soroban_sdk::{
 };
 
 use crate::idempotency::{self, tag};
+use crate::storage;
 use crate::types::{CreateEventParams, Pillar, ReleaseKind, WinnerSpec};
 use crate::{EventsContract, EventsContractClient};
 
@@ -24,6 +25,7 @@ struct Ctx<'a> {
     events_id: Address,
     profile: ProfileContractClient<'a>,
     owner: Address,
+    fee_account: Address,
     applicant: Address,
     token_addr: Address,
 }
@@ -68,6 +70,7 @@ fn setup<'a>() -> Ctx<'a> {
         events_id,
         profile,
         owner,
+        fee_account,
         applicant,
         token_addr,
     }
@@ -209,6 +212,64 @@ fn events_domain_child_op_id_replay_still_rejected() {
     );
 }
 
+/// Calling create_event when the stored next_event_id is at u64::MAX must revert
+/// with EventIdOverflow rather than silently returning the same id forever.
+#[test]
+fn event_id_overflow_reverts() {
+    let ctx = setup();
+    let env = &ctx.env;
+
+    let token = token::Client::new(env, &ctx.token_addr);
+    let owner_balance_before = token.balance(&ctx.owner);
+    let fee_balance_before = token.balance(&ctx.fee_account);
+
+    env.as_contract(&ctx.events_id, || {
+        storage::set_next_event_id(env, u64::MAX);
+    });
+
+    let params = CreateEventParams {
+        pillar: Pillar::Bounty,
+        owner: ctx.owner.clone(),
+        token: ctx.token_addr.clone(),
+        total_budget: TOTAL_BUDGET,
+        release_kind: ReleaseKind::Single,
+        content_uri: String::from_str(env, "https://api.boundless.fi/events/overflow"),
+        title: String::from_str(env, "Overflow"),
+        deadline: Some(env.ledger().timestamp() + 86_400),
+        winner_distribution: dist_100(env),
+        fee_bps_override: None,
+        manager: None,
+    };
+
+    let err = ctx
+        .events
+        .try_create_event(&params, &BytesN::random(env))
+        .err()
+        .expect("event creation should fail when next_event_id overflows")
+        .unwrap();
+    assert_eq!(err, crate::errors::Error::EventIdOverflow);
+
+    // Verify transaction rollback: no funds moved, no event persisted.
+    assert_eq!(
+        token.balance(&ctx.owner),
+        owner_balance_before,
+        "owner balance unchanged after failed create_event"
+    );
+    assert_eq!(
+        token.balance(&ctx.fee_account),
+        fee_balance_before,
+        "fee account balance unchanged after failed create_event"
+    );
+    env.as_contract(&ctx.events_id, || {
+        let next_id = storage::get_next_event_id(env, 0);
+        assert_eq!(
+            next_id,
+            u64::MAX,
+            "next_event_id unchanged after failed create_event"
+        );
+    });
+}
+
 /// Events-side OpSeen is namespaced by the authorizing caller: a permissionless
 /// entrypoint (apply) cannot pre-mark an op_id and block a privileged one
 /// (select_winners) that reuses it. Before namespacing, the shared global
diff --git a/contracts/profile/src/earnings.rs b/contracts/profile/src/earnings.rs
index 04d59f3..c05c605 100644
--- a/contracts/profile/src/earnings.rs
+++ b/contracts/profile/src/earnings.rs
@@ -23,7 +23,7 @@ pub fn register(
     }
 
     let current = storage::get_earnings(env, &user, &token);
-    let new = current.saturating_add(amount);
+    let new = current.checked_add(amount).ok_or(Error::EarningsOverflow)?;
     storage::set_earnings(env, &user, &token, new);
 
     evt::EarningsRegistered {
diff --git a/contracts/profile/src/errors.rs b/contracts/profile/src/errors.rs
index 12884d2..662b378 100644
--- a/contracts/profile/src/errors.rs
+++ b/contracts/profile/src/errors.rs
@@ -22,6 +22,7 @@ pub enum Error {
     ReasonRequired = 13,
 
     OpAlreadySeen = 20,
+    EarningsOverflow = 21,
     Paused = 30,
 
     UpgradeNotProposed = 40,
diff --git a/contracts/profile/src/tests/earnings.rs b/contracts/profile/src/tests/earnings.rs
index b413729..4ee4c25 100644
--- a/contracts/profile/src/tests/earnings.rs
+++ b/contracts/profile/src/tests/earnings.rs
@@ -179,7 +179,7 @@ fn register_earnings_rejects_duplicate_op_id() {
 }
 
 #[test]
-fn register_earnings_saturating_add() {
+fn register_earnings_overflow_reverts() {
     let ctx = setup();
     ctx.client.set_events_contract(&events_addr(&ctx.env));
 
@@ -187,11 +187,16 @@ fn register_earnings_saturating_add() {
     let t = token(&ctx.env);
 
     ctx.client
-        .register_earnings(&u, &t, &(i128::MAX - 1), &BytesN::random(&ctx.env));
-    assert_eq!(ctx.client.get_earnings(&u, &t), i128::MAX - 1);
+        .register_earnings(&u, &t, &i128::MAX, &BytesN::random(&ctx.env));
+    assert_eq!(ctx.client.get_earnings(&u, &t), i128::MAX);
 
-    ctx.client
-        .register_earnings(&u, &t, &100_i128, &BytesN::random(&ctx.env));
+    let err = ctx
+        .client
+        .try_register_earnings(&u, &t, &1_i128, &BytesN::random(&ctx.env))
+        .err()
+        .expect("overflow should revert")
+        .unwrap();
+    assert_eq!(err, Error::EarningsOverflow);
     assert_eq!(ctx.client.get_earnings(&u, &t), i128::MAX);
 }