diff --git a/src/index.ts b/src/index.ts
index 3bd092a2..e64cab20 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -212,11 +212,13 @@ export {
   getSigningHistory,
   exportSigningHistory,
   InMemorySigningHistoryStore,
+  DEFAULT_SIGNING_HISTORY_MAX_ENTRIES,
 } from "./wallet/signingHistory";
 export type {
   SigningRecord,
   SigningHistoryFilter,
   SigningHistoryStore,
+  InMemorySigningHistoryStoreOptions,
 } from "./wallet/signingHistory";
 
 // ─── Wallet connection throttling and abuse detection (#506) ──────────────────
diff --git a/src/tests/wallet.test.ts b/src/tests/wallet.test.ts
index 25788219..7346c1ee 100644
--- a/src/tests/wallet.test.ts
+++ b/src/tests/wallet.test.ts
@@ -36,6 +36,7 @@ import {
   InMemorySigningHistoryStore,
   getSigningHistory,
   exportSigningHistory,
+  DEFAULT_SIGNING_HISTORY_MAX_ENTRIES,
   type SigningRecord,
 } from "../wallet/signingHistory";
 import {
@@ -943,6 +944,85 @@ describe("signing history export with filters (#387)", () => {
       expect(parsed[0]).not.toHaveProperty("privateKey");
     }
   });
+
+  describe("InMemorySigningHistoryStore size limit and overflow (#743)", () => {
+    it("defaults to a maximum of 1000 entries and reports maxEntries", () => {
+      const store = new InMemorySigningHistoryStore();
+      expect(store.getMaxEntries()).toBe(1000);
+      expect(DEFAULT_SIGNING_HISTORY_MAX_ENTRIES).toBe(1000);
+      expect(store.size).toBe(0);
+    });
+
+    it("supports custom maxEntries via number or options object", () => {
+      const storeByNum = new InMemorySigningHistoryStore(50);
+      expect(storeByNum.getMaxEntries()).toBe(50);
+
+      const storeByObj = new InMemorySigningHistoryStore({ maxEntries: 250 });
+      expect(storeByObj.getMaxEntries()).toBe(250);
+
+      // Falls back to default if invalid/negative value is passed
+      const storeInvalid = new InMemorySigningHistoryStore({ maxEntries: -10 });
+      expect(storeInvalid.getMaxEntries()).toBe(DEFAULT_SIGNING_HISTORY_MAX_ENTRIES);
+
+      const storeZero = new InMemorySigningHistoryStore(0);
+      expect(storeZero.getMaxEntries()).toBe(DEFAULT_SIGNING_HISTORY_MAX_ENTRIES);
+    });
+
+    it("evicts the oldest entries in FIFO order when capacity is exceeded", () => {
+      const store = new InMemorySigningHistoryStore(3);
+
+      store.record({ txHash: "tx1", signer: "G1", timestamp: "2026-01-01T00:00:00Z", status: "success" });
+      store.record({ txHash: "tx2", signer: "G1", timestamp: "2026-01-02T00:00:00Z", status: "success" });
+      store.record({ txHash: "tx3", signer: "G1", timestamp: "2026-01-03T00:00:00Z", status: "failure" });
+
+      expect(store.size).toBe(3);
+      expect(store.query().map((r) => r.txHash)).toEqual(["tx1", "tx2", "tx3"]);
+
+      // Adding 4th record evicts oldest ("tx1")
+      store.record({ txHash: "tx4", signer: "G1", timestamp: "2026-01-04T00:00:00Z", status: "success" });
+      expect(store.size).toBe(3);
+      expect(store.query().map((r) => r.txHash)).toEqual(["tx2", "tx3", "tx4"]);
+
+      // Adding 5th record evicts oldest ("tx2")
+      store.record({ txHash: "tx5", signer: "G1", timestamp: "2026-01-05T00:00:00Z", status: "success" });
+      expect(store.size).toBe(3);
+      expect(store.query().map((r) => r.txHash)).toEqual(["tx3", "tx4", "tx5"]);
+    });
+
+    it("query() returns at most the capped count of records", () => {
+      const store = new InMemorySigningHistoryStore(5);
+
+      for (let i = 1; i <= 20; i++) {
+        store.record({
+          txHash: `tx${i}`,
+          signer: i % 2 === 0 ? "G_EVEN" : "G_ODD",
+          timestamp: `2026-01-${String(i).padStart(2, "0")}T00:00:00Z`,
+          status: "success",
+        });
+      }
+
+      // Query without filters returns at most maxEntries
+      const all = store.query();
+      expect(all).toHaveLength(5);
+      expect(all.map((r) => r.txHash)).toEqual(["tx16", "tx17", "tx18", "tx19", "tx20"]);
+
+      // Filtered queries also respect capped records
+      const evens = store.query({ signer: "G_EVEN" });
+      expect(evens.map((r) => r.txHash)).toEqual(["tx16", "tx18", "tx20"]);
+      expect(evens.length).toBeLessThanOrEqual(5);
+    });
+
+    it("clear() resets entries and size back to 0", () => {
+      const store = new InMemorySigningHistoryStore(3);
+      store.record({ txHash: "tx1", signer: "G1", timestamp: "2026-01-01T00:00:00Z", status: "success" });
+      store.record({ txHash: "tx2", signer: "G1", timestamp: "2026-01-02T00:00:00Z", status: "success" });
+
+      expect(store.size).toBe(2);
+      store.clear();
+      expect(store.size).toBe(0);
+      expect(store.query()).toHaveLength(0);
+    });
+  });
 });
 
 describe("wallet connection persistence and recovery", () => {
diff --git a/src/wallet/index.ts b/src/wallet/index.ts
index 272a5a75..4d7cc5ca 100644
--- a/src/wallet/index.ts
+++ b/src/wallet/index.ts
@@ -76,11 +76,13 @@ export {
   getSigningHistory,
   exportSigningHistory,
   InMemorySigningHistoryStore,
+  DEFAULT_SIGNING_HISTORY_MAX_ENTRIES,
 } from "./signingHistory";
 export type {
   SigningRecord,
   SigningHistoryFilter,
   SigningHistoryStore,
+  InMemorySigningHistoryStoreOptions,
 } from "./signingHistory";
 export type {
   CreateSigningChallengeOptions,
diff --git a/src/wallet/signingHistory.ts b/src/wallet/signingHistory.ts
index 7cf8e5f2..073db075 100644
--- a/src/wallet/signingHistory.ts
+++ b/src/wallet/signingHistory.ts
@@ -18,6 +18,22 @@ export interface SigningHistoryFilter {
   to?: string;
 }
 
+/**
+ * Default maximum number of signing records retained by {@link InMemorySigningHistoryStore} (#743).
+ */
+export const DEFAULT_SIGNING_HISTORY_MAX_ENTRIES = 1000;
+
+/**
+ * Options for {@link InMemorySigningHistoryStore}.
+ */
+export interface InMemorySigningHistoryStoreOptions {
+  /**
+   * Maximum number of signing records to retain in memory (default: 1000).
+   * When capacity is reached, the oldest entries are evicted in FIFO order.
+   */
+  maxEntries?: number;
+}
+
 export interface SigningHistoryStore {
   record(entry: SigningRecord): void;
   query(filter?: SigningHistoryFilter): SigningRecord[];
@@ -26,9 +42,38 @@ export interface SigningHistoryStore {
 
 export class InMemorySigningHistoryStore implements SigningHistoryStore {
   private entries: SigningRecord[] = [];
+  private readonly maxEntries: number;
+
+  /**
+   * @param options - Maximum entries number or options object with `maxEntries`. Defaults to 1000.
+   */
+  constructor(options?: number | InMemorySigningHistoryStoreOptions) {
+    const rawMax = typeof options === "number" ? options : options?.maxEntries;
+    this.maxEntries =
+      typeof rawMax === "number" && Number.isFinite(rawMax) && rawMax > 0
+        ? Math.floor(rawMax)
+        : DEFAULT_SIGNING_HISTORY_MAX_ENTRIES;
+  }
+
+  /**
+   * Return the configured maximum capacity of the store.
+   */
+  getMaxEntries(): number {
+    return this.maxEntries;
+  }
+
+  /**
+   * Return the current number of retained records.
+   */
+  get size(): number {
+    return this.entries.length;
+  }
 
   record(entry: SigningRecord): void {
     this.entries.push({ ...entry });
+    if (this.entries.length > this.maxEntries) {
+      this.entries.splice(0, this.entries.length - this.maxEntries);
+    }
   }
 
   query(filter?: SigningHistoryFilter): SigningRecord[] {