fix(coin-tezos): reserve the reported fee when computing send-max

Author: amaslakov

.changeset/lucky-otters-wander.md

@@ -0,0 +1,5 @@
+---
+"@ledgerhq/coin-tezos": minor
+---
+
+Fix Tezos send-max reporting insufficient funds when the minFees floor exceeds the estimated fee

libs/coin-modules/coin-tezos/src/logic/estimateFees.test.ts

@@ -812,11 +812,51 @@ describe("estimateFees", () => {
     });
 
     expect(result.fees).toBe(BigInt(minFees));
-    // max = spendable(10000) - suggestedFee(100) - (DUST_MARGIN(500) - (DUST_MARGIN*0.1 + opSize(200)))
-    //     = 9900 - (500 - 250) = 9650
-    expect(result.amount).toBe(9650n);
+    // max = spendable(10000) - mainOpFee(500) - (DUST_MARGIN(500) - (DUST_MARGIN*0.1 + opSize(200)))
+    //     = 9500 - (500 - 250) = 9250
+    expect(result.amount).toBe(9250n);
   });
 
+  // Regression for LIVE-28506: the max must reserve the fee that is actually reported, so that
+  // `amount + estimatedFees` always fits the spendable balance. Reserving the raw taquito
+  // suggestion instead made every send-max fail validation once `minFees` exceeded it by more
+  // than the dust margin — at any balance.
+  it.each([
+    // balance, minFees, suggestedFeeMutez, burnFeeMutez, expected amount
+    [10000n, 2000, 100, 0, 7750n],
+    [10000n, 100, 2000, 0, 7750n],
+    // recipient allocation burn (277 bytes * COST_PER_BYTE), minus taquito's 20-byte pad
+    [100000n, 2000, 100, 69250, 33500n],
+  ])(
+    "useAllAmount send reserves the reported fee (balance=%i, minFees=%i, suggested=%i, burn=%i)",
+    async (balance, minFees, suggestedFeeMutez, burnFeeMutez, expectedAmount) => {
+      mockTezosToolkit.estimate.transfer.mockResolvedValue({
+        suggestedFeeMutez,
+        gasLimit: 1500,
+        storageLimit: 0,
+        burnFeeMutez,
+        opSize: 200,
+      });
+      (coinConfig.getCoinConfig as jest.Mock).mockReturnValue({
+        fees: { ...defaultFeesConfig, minFees },
+      });
+
+      const result = await estimateFees({
+        account: { ...revealedAccount, balance },
+        transaction: {
+          mode: "send",
+          recipient: "tz1VSUr8wwNhLAzempoch5d6nLRSNtxK8LBr",
+          amount: 0n,
+          useAllAmount: true,
+        },
+      });
+
+      expect(result.amount).toBe(expectedAmount);
+      // the invariant validateIntent's balance-coverage check relies on
+      expect(result.amount! + result.estimatedFees).toBeLessThanOrEqual(balance);
+    },
+  );
+
   it("useAllAmount send excludes staked and unstaked funds from the max", async () => {
     const balance = 10000n;
     const stakedBalance = 3000n;

libs/coin-modules/coin-tezos/src/logic/estimateFees.ts

@@ -183,11 +183,15 @@ export async function estimateFees({
 
     // NOTE: send-max only applies to native XTZ transfer, not FA2
     if (transaction.useAllAmount && transaction.mode === "send") {
+      // Reserve `mainOpFee`, not the raw taquito suggestion: `estimatedFees` below reports the
+      // `minFees` floor, so subtracting the (lower) suggestion here yields an amount whose
+      // `amount + estimatedFees` exceeds the spendable balance, and validateIntent then rejects
+      // the very max it was handed (LIVE-28506).
       // NOTE: from https://github.com/ecadlabs/taquito/blob/master/integration-tests/__tests__/contract/empty-implicit-account-into-new-implicit-account.spec.ts#L37
       const totalFees =
         estimate.burnFeeMutez > 0
-          ? estimate.suggestedFeeMutez + estimate.burnFeeMutez - 20 * COST_PER_BYTE // 20 is storage buffer
-          : estimate.suggestedFeeMutez;
+          ? mainOpFee + estimate.burnFeeMutez - 20 * COST_PER_BYTE // 20 is storage buffer
+          : mainOpFee;
       const maxAmount = spendableForMax - (totalFees + Number(revealFee));
       // NOTE: from https://github.com/ecadlabs/taquito/blob/a70c64c4b105381bb9f1d04c9c70e8ef26e9241c/integration-tests/contract-empty-implicit-account-into-new-implicit-account.spec.ts#L33
       // Temporary fix, see https://gitlab.com/tezos/tezos/-/issues/1754
@@ -196,6 +200,14 @@ export async function estimateFees({
       const incr = DUST_MARGIN_MUTEZ * MINIMAL_FEE_PER_GAS_MUTEZ + Number(estimate.opSize);
       const maxMinusBuff = maxAmount - (DUST_MARGIN_MUTEZ - incr);
       estimation.amount = maxMinusBuff > 0 ? BigInt(maxMinusBuff) : 0n;
+      log("tezos-send-max", "send-max fee inputs", {
+        minFees,
+        mainOpFee,
+        suggestedFeeMutez: estimate.suggestedFeeMutez,
+        burnFeeMutez: estimate.burnFeeMutez,
+        opSize: Number(estimate.opSize),
+        revealFee: Number(revealFee),
+      });
     } else if (transaction.useAllAmount && transaction.mode === "stake") {
       estimation.amount = computeMaxStakeAmount(
         BigInt(account.balance),