From 35c4eb33731b61188798d1983052e7f4e9dfdb22 Mon Sep 17 00:00:00 2001
From: Ricardo Guilherme Schmidt <3esmit@gmail.com>
Date: Mon, 29 Jun 2026 13:55:59 -0300
Subject: [PATCH] fix(stablecoin): bound redemption controller price

---
 artifacts/stablecoin-idl.json                 |  6 ++--
 .../methods/guest/src/bin/stablecoin.rs       |  2 ++
 .../stablecoin/src/redemption_controller.rs   | 30 +++++++++++++++++--
 3 files changed, 33 insertions(+), 5 deletions(-)

diff --git a/artifacts/stablecoin-idl.json b/artifacts/stablecoin-idl.json
index d07fbee..b2e88be 100644
--- a/artifacts/stablecoin-idl.json
+++ b/artifacts/stablecoin-idl.json
@@ -118,9 +118,9 @@
       "accounts": [
         {
           "name": "controller",
-          "writable": false,
+          "writable": true,
           "signer": false,
-          "init": false
+          "init": true
         },
         {
           "name": "stablecoin_definition",
@@ -175,7 +175,7 @@
       "accounts": [
         {
           "name": "controller",
-          "writable": false,
+          "writable": true,
           "signer": false,
           "init": false
         },
diff --git a/programs/stablecoin/methods/guest/src/bin/stablecoin.rs b/programs/stablecoin/methods/guest/src/bin/stablecoin.rs
index 1fcd50d..d651540 100644
--- a/programs/stablecoin/methods/guest/src/bin/stablecoin.rs
+++ b/programs/stablecoin/methods/guest/src/bin/stablecoin.rs
@@ -128,6 +128,7 @@ mod stablecoin {
     #[instruction]
     pub fn initialize_redemption_controller(
         ctx: ProgramContext,
+        #[account(init)]
         controller: AccountWithMetadata,
         stablecoin_definition: AccountWithMetadata,
         price_feed: AccountWithMetadata,
@@ -172,6 +173,7 @@ mod stablecoin {
     #[instruction]
     pub fn update_redemption_controller(
         ctx: ProgramContext,
+        #[account(mut)]
         controller: AccountWithMetadata,
         price_feed: AccountWithMetadata,
         current_timestamp: u64,
diff --git a/programs/stablecoin/src/redemption_controller.rs b/programs/stablecoin/src/redemption_controller.rs
index f0783f6..a42081e 100644
--- a/programs/stablecoin/src/redemption_controller.rs
+++ b/programs/stablecoin/src/redemption_controller.rs
@@ -276,12 +276,13 @@ fn compute_next_controller_state(
 
 fn apply_redemption_rate(redemption_price: u128, redemption_rate: i128, elapsed: u64) -> u128 {
     let drift = redemption_rate.saturating_mul(i128::from(elapsed));
-    if drift >= 0 {
+    let next_price = if drift >= 0 {
         redemption_price.saturating_add(u128::try_from(drift).unwrap_or(u128::MAX))
     } else {
         let decrease = u128::try_from(drift.saturating_neg()).unwrap_or(u128::MAX);
         redemption_price.saturating_sub(decrease).max(1)
-    }
+    };
+    next_price.min(i128_max_as_u128())
 }
 
 fn price_error(redemption_price: u128, market_price: u128) -> i128 {
@@ -582,6 +583,31 @@ mod tests {
         assert_eq!(updated.last_update_timestamp, 105);
     }
 
+    #[test]
+    fn controller_clamps_redemption_price_to_i128_max() {
+        let mut controller = controller_state();
+        controller.redemption_price = i128_max_as_u128() - 5;
+        controller.redemption_rate = 10;
+        controller.proportional_gain = 0;
+
+        let updated = compute_next_controller_state(&controller, i128_max_as_u128(), 101);
+
+        assert_eq!(updated.redemption_price, i128_max_as_u128());
+        assert_eq!(updated.redemption_rate, 0);
+    }
+
+    #[test]
+    fn controller_clamps_existing_redemption_price_above_i128_max() {
+        let mut controller = controller_state();
+        controller.redemption_price = i128_max_as_u128() + 5;
+        controller.redemption_rate = -1;
+        controller.proportional_gain = 0;
+
+        let updated = compute_next_controller_state(&controller, 1, 101);
+
+        assert_eq!(updated.redemption_price, i128_max_as_u128());
+    }
+
     #[test]
     fn controller_clamps_accumulated_error_and_redemption_rate() {
         let mut controller = controller_state();