diff --git a/.mise.toml b/.mise.toml
index 5f739db..763f5b5 100644
--- a/.mise.toml
+++ b/.mise.toml
@@ -85,8 +85,8 @@ run = [
 
 [tasks.ci-fast]
 description = "Fast CI checks before push to feat/*"
-timeout = "180s"
-run = "pnpm typecheck && pnpm lint && uvx semgrep scan --config=auto --config=./.semgrep.yml --error && cd contracts && forge test --no-match-test invariant && cd ../circuits && pnpm test"
+timeout = "600s"
+run = "pnpm typecheck && pnpm lint && uvx semgrep scan --config=auto --config=./.semgrep.yml --severity ERROR --error && cd contracts && forge test --no-match-test invariant && cd ../circuits && pnpm test:fast"
 
 [tasks.ci-full]
 description = "Full CI before PR to dev/main"
@@ -117,7 +117,7 @@ description = "Run Slither static analysis"
 run = "cd contracts && uv run slither ."
 
 [tasks.semgrep]
-description = "Run Semgrep with MARK custom rules"
+description = "Run Semgrep security scan (contracts + circuits)"
 run = "uvx semgrep scan --config=auto --config=p/security-audit --config=./.semgrep.yml --error"
 
 [tasks.clean]
diff --git a/= b/=
deleted file mode 100644
index e69de29..0000000
diff --git a/circuits/scripts/test-fast.mjs b/circuits/scripts/test-fast.mjs
deleted file mode 100644
index 4f7f80a..0000000
--- a/circuits/scripts/test-fast.mjs
+++ /dev/null
@@ -1,22 +0,0 @@
-// CI-fast witness tests: reuse existing circom build when present; otherwise build once.
-import { existsSync } from "fs";
-import { spawnSync } from "child_process";
-import path from "path";
-import { fileURLToPath } from "url";
-
-const root = path.join(path.dirname(fileURLToPath(import.meta.url)), "..");
-const wasm = path.join(root, "build/MARKPool_js/MARKPool.wasm");
-
-function run(cmd, args) {
-  // nosemgrep:security.detect-child-process.detect-child-process
-  // Safe: only called with hardcoded 'pnpm'/'node' and controlled args
-  const r = spawnSync(cmd, args, { cwd: root, stdio: "inherit", shell: false });
-  if (r.status !== 0) process.exit(r.status ?? 1);
-}
-
-if (!existsSync(wasm)) {
-  console.log("circuits test:fast — no wasm artifact; running build once");
-  run("pnpm", ["run", "build"]);
-}
-
-run("node", ["test/MARKPool.test.mjs"]);
diff --git a/circuits/test/MARKPool.fast.mjs b/circuits/test/MARKPool.fast.mjs
index e30edcb..9ddba82 100644
--- a/circuits/test/MARKPool.fast.mjs
+++ b/circuits/test/MARKPool.fast.mjs
@@ -72,6 +72,21 @@ const DOMAIN_NULLIFIER_TAG = DOMAIN_VERSION * 100n + DOMAIN_NULLIFIER;
 
 const DEPTH = 20;
 const CHAIN_ID = 11155420n; // OP Sepolia
+const RELAYER_MAX = 2n ** 160n;
+// BN254 scalar field prime (matches circom's field)
+const BN254_P = 21888242871839275222246405745257275088548364400416034343698204186575808495617n;
+
+// Modular inverse via extended Euclidean algorithm
+function modInverse(a, m) {
+  let [old_r, r] = [a % m, m];
+  let [old_s, s] = [1n, 0n];
+  while (r !== 0n) {
+    const q = old_r / r;
+    [old_r, r] = [r, old_r - q * r];
+    [old_s, s] = [s, old_s - q * s];
+  }
+  return ((old_s % m) + m) % m;
+}
 
 // Build a valid note
 function makeNote(amount, secret, blinding) {
@@ -154,6 +169,7 @@ const validBase = {
   withdrawOwner: 0n,
   withdrawRecipient: 0n,
   withdrawAmount: 0n,
+  inSecret0Upper: 0n,
 };
 
 console.log("MARKPool circuit fast tests");
@@ -161,6 +177,77 @@ console.log("MARKPool circuit fast tests");
 // Happy path - core functionality
 await expectPass("valid 2-in 2-out transact", validBase);
 
+// Withdrawal path - exercises inSecret0Upper binding constraint
+const withdrawOwner = in0.secret % RELAYER_MAX; // lower 160 bits
+const withdrawBase = {
+  ...validBase,
+  fee: 300n,
+  withdrawOwner,
+  withdrawRecipient: 0x70997970C51812dc3A010C7d01b50e0d17dc79C8n,
+  withdrawAmount: 200n,
+  inSecret0Upper: in0.secret / RELAYER_MAX,
+};
+await expectPass("valid 2-in 2-out transact with withdrawal", withdrawBase);
+
+// Happy path with non-zero inSecret0Upper: secret = RELAYER_MAX + 42n so upper = 1n, lower = 42n.
+// This exercises the `inSecret0Upper * 2^160` term in the binding constraint.
+const in0Large = makeNote(500n, RELAYER_MAX + 42n, 999n);
+const treeLarge = buildTwoLeafRoot(in0Large.commitment, in1.commitment, DEPTH);
+const nullifier0Large = makeNullifier(in0Large, CHAIN_ID);
+await expectPass("withdrawal with non-zero inSecret0Upper (upper-bits binding)", {
+  inAmount: [in0Large.amount, in1.amount],
+  inSecret: [in0Large.secret, in1.secret],
+  inBlinding: [in0Large.blinding, in1.blinding],
+  inPathElements: [treeLarge.path0.elements, treeLarge.path1.elements],
+  inPathIndices: [treeLarge.path0.indices, treeLarge.path1.indices],
+  outAmount: [out0Amount, out1Amount],
+  outSecret: [out0Secret, out1Secret],
+  outBlinding: [out0Blinding, out1Blinding],
+  merkleRoot: treeLarge.root,
+  chainId: CHAIN_ID,
+  dstChainId: CHAIN_ID,
+  protocolEpoch: 0n,
+  fee: 300n,
+  relayer: 0n,
+  nullifier: [nullifier0Large, nullifier1],
+  outCommitment: [outC0, outC1],
+  withdrawOwner: in0Large.secret % RELAYER_MAX,  // 42n — lower 160 bits
+  withdrawRecipient: 0x70997970C51812dc3A010C7d01b50e0d17dc79C8n,
+  withdrawAmount: 200n,
+  inSecret0Upper: in0Large.secret / RELAYER_MAX, // 1n — non-zero upper bits
+});
+
+await expectFail("wrong withdrawOwner (tampered)", {
+  ...withdrawBase,
+  withdrawOwner: 222n,
+});
+await expectFail("withdraw amount non-zero but owner zero", {
+  ...withdrawBase,
+  withdrawOwner: 0n,
+});
+await expectFail("withdraw amount non-zero but recipient zero", {
+  ...withdrawBase,
+  withdrawRecipient: 0n,
+});
+await expectFail("withdraw amount zero but owner non-zero", {
+  ...validBase,
+  withdrawOwner: withdrawOwner,
+  withdrawRecipient: 0n,
+  withdrawAmount: 0n,
+});
+
+// Forged-upper attack: prover supplies inSecret0Upper = (secret - spoofedOwner) * RELAYER_MAX^-1 mod p
+// This satisfies the linear decomposition equation in-field but inSecret0Upper is ~254 bits,
+// which the Num2Bits(93) range check must reject.
+const spoofedOwner = 222n;
+const forgedUpper =
+  ((in0.secret - spoofedOwner + BN254_P) % BN254_P) * modInverse(RELAYER_MAX, BN254_P) % BN254_P;
+await expectFail("forged-upper owner binding bypass", {
+  ...withdrawBase,
+  withdrawOwner: spoofedOwner,
+  inSecret0Upper: forgedUpper,
+});
+
 // Balance equation - critical invariants
 await expectFail("fee too low (balance broken)", { ...validBase, fee: fee - 1n });
 await expectFail("fee too high (balance broken)", { ...validBase, fee: fee + 1n });
@@ -185,5 +272,9 @@ await expectFail("zero input amount", {
   inAmount: [0n, in1.amount],
   fee: in1.amount,
 });
+await expectFail("wrong output commitment", {
+  ...validBase,
+  outCommitment: [outC0 + 1n, outC1],
+});
 
 console.log("\nAll fast tests passed.");