fix: add CI verification for AMM constant sync with smart contract

.github/workflows/ci.yml

@@ -1,33 +1,57 @@
 name: CI
-
 on:
   push:
     branches: [main]
   pull_request:
     branches: [main]
-
 jobs:
   ci:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
-
       - name: Setup Rust
         uses: dtolnay/rust-toolchain@stable
         with:
           components: rustfmt, clippy
-
       - name: Cache
         uses: Swatinem/rust-cache@v2
-
       - name: Format check
         run: cargo fmt --all -- --check
-
       - name: Clippy
         run: cargo clippy --all-targets --all-features -- -D warnings
-
+      - name: Verify fee constants match smart contract
+        run: |
+          curl -sf https://raw.githubusercontent.com/Nodus-protocol/Nodus-Protocol-Smart-Contract/main/src/math.rs -o /tmp/sc_math.rs
+          extract_value() {
+            grep -E "^\s*pub const ${1}:" "$2" | sed -E 's/.*=\s*([0-9_]+)\s*;.*/\1/' | tr -d '_'
+          }
+          SC_FEE_NUM=$(extract_value FEE_NUMERATOR /tmp/sc_math.rs)
+          SC_FEE_DEN=$(extract_value FEE_DENOMINATOR /tmp/sc_math.rs)
+          SC_MIN_LIQ=$(extract_value MINIMUM_LIQUIDITY /tmp/sc_math.rs)
+          CE_FEE_NUM=$(extract_value FEE_NUMERATOR src/pool/math.rs)
+          CE_FEE_DEN=$(extract_value FEE_DENOMINATOR src/pool/math.rs)
+          CE_MIN_LIQ=$(extract_value MINIMUM_LIQUIDITY src/pool/math.rs)
+          echo "Smart Contract: FEE_NUMERATOR=$SC_FEE_NUM FEE_DENOMINATOR=$SC_FEE_DEN MINIMUM_LIQUIDITY=$SC_MIN_LIQ"
+          echo "Core Engine:    FEE_NUMERATOR=$CE_FEE_NUM FEE_DENOMINATOR=$CE_FEE_DEN MINIMUM_LIQUIDITY=$CE_MIN_LIQ"
+          FAIL=0
+          if [ "$SC_FEE_NUM" != "$CE_FEE_NUM" ]; then
+            echo "::error::FEE_NUMERATOR mismatch: SmartContract=$SC_FEE_NUM CoreEngine=$CE_FEE_NUM"
+            FAIL=1
+          fi
+          if [ "$SC_FEE_DEN" != "$CE_FEE_DEN" ]; then
+            echo "::error::FEE_DENOMINATOR mismatch: SmartContract=$SC_FEE_DEN CoreEngine=$CE_FEE_DEN"
+            FAIL=1
+          fi
+          if [ "$SC_MIN_LIQ" != "$CE_MIN_LIQ" ]; then
+            echo "::error::MINIMUM_LIQUIDITY mismatch: SmartContract=$SC_MIN_LIQ CoreEngine=$CE_MIN_LIQ"
+            FAIL=1
+          fi
+          if [ "$FAIL" = "1" ]; then
+            echo "AMM constants have drifted between Smart Contract and Core Engine repos. Update src/pool/math.rs to match src/math.rs in Nodus-Protocol-Smart-Contract."
+            exit 1
+          fi
+          echo "AMM constants verified in sync with Smart Contract."
       - name: Test
         run: cargo test --all-features
-
       - name: Build
         run: cargo build --release

src/pool/math.rs

@@ -1,5 +1,18 @@
 // AMM constant-product math — mirrors src/math.rs in the Smart Contract repo.
-// Any formula change in the contract must be reflected here.
+//
+// SYNCHRONIZATION WARNING:
+// These constants MUST match `src/math.rs` in the Nodus-Protocol-Smart-Contract
+// repository exactly. CI verifies this automatically (see
+// .github/workflows/ci.yml, "Verify fee constants match smart contract" step),
+// which fetches the live Smart Contract source and fails the build on drift.
+//
+// If you change a value here, you must also change it in the Smart Contract
+// repo in the same release cycle, or swap quotes from this engine will not
+// match what the deployed contract actually executes.
+//
+// Tracking: see https://github.com/Nodus-protocol/Nodus-Protocol-Core-Engine/issues/61
+// for the longer-term fix (a shared `nodus-amm-types` crate that both repos
+// depend on, eliminating this manual sync requirement entirely).
 
 pub const FEE_NUMERATOR: u128 = 997;
 pub const FEE_DENOMINATOR: u128 = 1_000;
@@ -171,4 +184,25 @@ mod tests {
         let large = price_impact_bps(500_000, 1_000_000);
         assert!(large > small);
     }
+
+    /// Defense-in-depth: pins the expected constant values directly in a test,
+    /// so a local `cargo test` run (not just CI's network-dependent fetch step)
+    /// catches an accidental change to these numbers before it's committed.
+    /// If you are intentionally changing the fee, update this test AND the
+    /// Smart Contract repo's src/math.rs in the same PR/release.
+    #[test]
+    fn fee_constants_match_known_smart_contract_values() {
+        assert_eq!(
+            FEE_NUMERATOR, 997,
+            "FEE_NUMERATOR must match Smart Contract src/math.rs"
+        );
+        assert_eq!(
+            FEE_DENOMINATOR, 1_000,
+            "FEE_DENOMINATOR must match Smart Contract src/math.rs"
+        );
+        assert_eq!(
+            MINIMUM_LIQUIDITY, 1_000,
+            "MINIMUM_LIQUIDITY must match Smart Contract src/math.rs"
+        );
+    }
 }