diff --git a/config.e2e-local.yaml b/config.e2e-local.yaml
index 28c724c..d135755 100644
--- a/config.e2e-local.yaml
+++ b/config.e2e-local.yaml
@@ -82,7 +82,7 @@ token:
       symbol: "DEMO"
       decimals: 18
       instrument_id: "DEMO"
-    "0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48":
+    "0xC1A0000000000000000000000000000000000001":
       name: "USD Coin"
       symbol: "USDCx"
       decimals: 6
diff --git a/pkg/config/defaults/config.api-server.docker.yaml b/pkg/config/defaults/config.api-server.docker.yaml
index 434a0ab..125dc1b 100644
--- a/pkg/config/defaults/config.api-server.docker.yaml
+++ b/pkg/config/defaults/config.api-server.docker.yaml
@@ -86,7 +86,7 @@ token:
       symbol: "DEMO"
       decimals: 18
       instrument_id: "DEMO"
-    "0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48":
+    "0xC1A0000000000000000000000000000000000001":
       name: "USD Coin"
       symbol: "USDCx"
       decimals: 6
diff --git a/pkg/config/defaults/config.api-server.local-devnet.yaml b/pkg/config/defaults/config.api-server.local-devnet.yaml
index 15b2f66..d871983 100644
--- a/pkg/config/defaults/config.api-server.local-devnet.yaml
+++ b/pkg/config/defaults/config.api-server.local-devnet.yaml
@@ -79,7 +79,7 @@ token:
       symbol: "DEMO"
       decimals: 18
       instrument_id: "DEMO"
-    "0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48":
+    "0xC1A0000000000000000000000000000000000001":
       name: "USD Coin"
       symbol: "USDCx"
       decimals: 6
diff --git a/pkg/config/defaults/config.api-server.mainnet.yaml b/pkg/config/defaults/config.api-server.mainnet.yaml
index aaf9f48..d8ea5c4 100644
--- a/pkg/config/defaults/config.api-server.mainnet.yaml
+++ b/pkg/config/defaults/config.api-server.mainnet.yaml
@@ -48,12 +48,21 @@ canton:
 
 token:
   supported_tokens:
+    # Display-only synthetic addresses for MetaMask. The api-server's
+    # eth_call balanceOf facade keys balances by these addresses. They must
+    # NOT collide with well-known mainnet token contracts (e.g. real USDC,
+    # USDT, etc.) or MetaMask flags imports as suspected phishing.
+    "0x9907000000000000000000000000000000000001":
+      name: "PROMPT"
+      symbol: "PROMPT"
+      decimals: 18
+      instrument_id: "PROMPT"
     "0xDE30000000000000000000000000000000000001":
       name: "Demo Token"
       symbol: "DEMO"
       decimals: 18
       instrument_id: "DEMO"
-    "0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48":
+    "0xC1A0000000000000000000000000000000000001":
       name: "USD Coin"
       symbol: "USDCx"
       decimals: 6
diff --git a/pkg/config/tests/env-substitution.api.yaml b/pkg/config/tests/env-substitution.api.yaml
index ccc220f..b22ff59 100644
--- a/pkg/config/tests/env-substitution.api.yaml
+++ b/pkg/config/tests/env-substitution.api.yaml
@@ -31,7 +31,7 @@ token:
       symbol: "PROMPT"
       decimals: 18
       instrument_id: "PROMPT"
-    "0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48":
+    "0xC1A0000000000000000000000000000000000001":
       name: "USD Coin"
       symbol: "USDCx"
       decimals: 6
diff --git a/pkg/config/tests/invalid-database-url.api.yaml b/pkg/config/tests/invalid-database-url.api.yaml
index 47f1040..6b55e8f 100644
--- a/pkg/config/tests/invalid-database-url.api.yaml
+++ b/pkg/config/tests/invalid-database-url.api.yaml
@@ -31,7 +31,7 @@ token:
       symbol: "PROMPT"
       decimals: 18
       instrument_id: "PROMPT"
-    "0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48":
+    "0xC1A0000000000000000000000000000000000001":
       name: "USD Coin"
       symbol: "USDCx"
       decimals: 6
diff --git a/pkg/config/tests/minimal.api.yaml b/pkg/config/tests/minimal.api.yaml
index 17c043a..f7dd7ad 100644
--- a/pkg/config/tests/minimal.api.yaml
+++ b/pkg/config/tests/minimal.api.yaml
@@ -31,7 +31,7 @@ token:
       symbol: "PROMPT"
       decimals: 18
       instrument_id: "PROMPT"
-    "0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48":
+    "0xC1A0000000000000000000000000000000000001":
       name: "USD Coin"
       symbol: "USDCx"
       decimals: 6
diff --git a/pkg/config/tests/missing-env.api.yaml b/pkg/config/tests/missing-env.api.yaml
index ee39fb6..52ad978 100644
--- a/pkg/config/tests/missing-env.api.yaml
+++ b/pkg/config/tests/missing-env.api.yaml
@@ -31,7 +31,7 @@ token:
       symbol: "PROMPT"
       decimals: 18
       instrument_id: "PROMPT"
-    "0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48":
+    "0xC1A0000000000000000000000000000000000001":
       name: "USD Coin"
       symbol: "USDCx"
       decimals: 6
diff --git a/tests/e2e/devstack/stack/types.go b/tests/e2e/devstack/stack/types.go
index 7e63f5c..195edb6 100644
--- a/tests/e2e/devstack/stack/types.go
+++ b/tests/e2e/devstack/stack/types.go
@@ -23,9 +23,12 @@ const (
 	DemoTokenVirtualAddr = "0xDE30000000000000000000000000000000000001"
 
 	// USDCxTokenVirtualAddr is the well-known virtual EVM address mapped to the
-	// USDCx external token in the api-server configuration.
-	// #nosec G101 -- public deterministic EVM contract address, not a credential.
-	USDCxTokenVirtualAddr = "0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48"
+	// USDCx external token in the api-server configuration. Synthetic (no real
+	// on-chain meaning) so MetaMask's anti-phishing check — which compares
+	// imported token addresses against its known-mainnet-tokens registry — does
+	// not flag USDCx imports as a possible spoof of real-mainnet USDC.
+	// #nosec G101 -- synthetic placeholder EVM address, not a credential.
+	USDCxTokenVirtualAddr = "0xC1A0000000000000000000000000000000000001"
 )
 
 // CantonHolding is a minimal view of a CIP56Holding contract used by E2E tests.