diff --git a/sovereign-transaction-guard.js b/sovereign-transaction-guard.js
new file mode 100644
index 000000000..3725697e6
--- /dev/null
+++ b/sovereign-transaction-guard.js
@@ -0,0 +1,104 @@
+'use strict';
+
+const { ethers } = require('ethers');
+
+/**
+ * SovereignTransactionGuard
+ * 
+ * Implements a Transactional State Machine to prevent nonce collisions
+ * and gas-limit hallucinations in high-concurrency AI agent environments.
+ * 
+ * Part of the Sovereign Settlement architecture.
+ */
+class SovereignTransactionGuard {
+  constructor(provider, wallet) {
+    this.provider = provider;
+    this.wallet = wallet;
+    this.pendingNonces = new Map(); // nonce -> { tx, timestamp, status }
+    this.lock = false;
+  }
+
+  async acquireLock() {
+    while (this.lock) {
+      await new Promise(resolve => setTimeout(resolve, 100));
+    }
+    this.lock = true;
+  }
+
+  releaseLock() {
+    this.lock = false;
+  }
+
+  /**
+   * synchronizedSubmit
+   * Ensures atomic nonce increment and gas verification.
+   */
+  async synchronizedSubmit(txRequest) {
+    await this.acquireLock();
+    try {
+      // 1. Nonce Synchronization
+      // Use the max of (on-chain nonce, local tracking nonce) to prevent collisions
+      const onChainNonce = await this.wallet.getNonce();
+      const trackedNonce = this.getLatestTrackedNonce();
+      const nonce = onChainNonce > trackedNonce ? onChainNonce : trackedNonce + 1;
+
+      // 2. Gas Hallucination Guard
+      // Agents often estimate gas poorly. We perform a strict dry-run and add a 20% safety buffer.
+      const estimatedGas = await this.provider.estimateGas({
+        ...txRequest,
+        nonce: nonce
+      });
+      
+      const gasLimit = (estimatedGas * 120n) / 100n; // 20% buffer
+
+      // 3. Transaction Construction
+      const tx = {
+        ...txRequest,
+        nonce: nonce,
+        gasLimit: gasLimit
+      };
+
+      // 4. State Update
+      this.pendingNonces.set(nonce, { 
+        tx, 
+        timestamp: Date.now(), 
+        status: 'pending' 
+      });
+
+      // 5. Execution
+      const response = await this.wallet.sendTransaction(tx);
+      
+      // Update status to confirmed
+      this.pendingNonces.set(nonce, { ...this.pendingNonces.get(nonce), status: 'confirmed' });
+      
+      return response;
+    } catch (error) {
+      console.error('[SovereignGuard] Transaction Failure:', error);
+      throw error;
+    } finally {
+      this.releaseLock();
+    }
+  }
+
+  getLatestTrackedNonce() {
+    if (this.pendingNonces.size === 0) return -1;
+    return Math.max(...this.pendingNonces.keys());
+  }
+
+  /**
+   * recoverStaleNonces
+   * Cleans up nonces that never confirmed or were skipped.
+   */
+  async recoverStaleNonces() {
+    await this.acquireLock();
+    const currentNonce = await this.wallet.getNonce();
+    for (const [nonce, data] of this.pendingNonces) {
+      if (nonce < currentNonce && data.status === 'pending') {
+        this.pendingNonces.delete(nonce);
+      }
+    }
+    this.releaseLock();
+  }
+}
+
+module.exports = { SovereignTransactionGuard };