diff --git a/extensions/matrix/src/matrix/sdk/crypto-runtime.ts b/extensions/matrix/src/matrix/sdk/crypto-runtime.ts
index 0fbefd95cf9b..f2be358b735b 100644
--- a/extensions/matrix/src/matrix/sdk/crypto-runtime.ts
+++ b/extensions/matrix/src/matrix/sdk/crypto-runtime.ts
@@ -1,5 +1,8 @@
 // Matrix plugin module implements crypto runtime behavior.
 import "fake-indexeddb/auto";
+import { installFakeIndexedDbTransactionPruner } from "./fake-indexeddb-prune.js";
+
+installFakeIndexedDbTransactionPruner();
 
 export { MatrixCryptoBootstrapper } from "./crypto-bootstrap.js";
 export type { MatrixCryptoBootstrapResult } from "./crypto-bootstrap.js";
diff --git a/extensions/matrix/src/matrix/sdk/fake-indexeddb-prune.test.ts b/extensions/matrix/src/matrix/sdk/fake-indexeddb-prune.test.ts
new file mode 100644
index 000000000000..8b78fb606fb7
--- /dev/null
+++ b/extensions/matrix/src/matrix/sdk/fake-indexeddb-prune.test.ts
@@ -0,0 +1,126 @@
+// Matrix tests cover fake-indexeddb transaction pruning for crypto stores.
+import "fake-indexeddb/auto";
+import { afterEach, describe, expect, it } from "vitest";
+import {
+  installFakeIndexedDbTransactionPruner,
+  pruneFinishedFakeIndexedDbTransactions,
+} from "./fake-indexeddb-prune.js";
+
+function openDatabase(name: string): Promise<IDBDatabase> {
+  return new Promise((resolve, reject) => {
+    const request = indexedDB.open(name, 1);
+    request.addEventListener("upgradeneeded", () => {
+      request.result.createObjectStore("sessions", { keyPath: "key" });
+    });
+    request.addEventListener("success", () => resolve(request.result), { once: true });
+    request.addEventListener(
+      "error",
+      () => reject(request.error ?? new Error("database open failed")),
+      {
+        once: true,
+      },
+    );
+  });
+}
+
+function deleteDatabase(name: string): Promise<void> {
+  return new Promise((resolve) => {
+    const request = indexedDB.deleteDatabase(name);
+    request.addEventListener("success", () => resolve(), { once: true });
+    request.addEventListener("error", () => resolve(), { once: true });
+    request.addEventListener("blocked", () => resolve(), { once: true });
+  });
+}
+
+function putRecord(db: IDBDatabase, key: string): Promise<void> {
+  return new Promise((resolve, reject) => {
+    const transaction = db.transaction("sessions", "readwrite");
+    transaction.objectStore("sessions").put({ key, value: "payload" });
+    transaction.addEventListener("complete", () => resolve(), { once: true });
+    transaction.addEventListener(
+      "error",
+      () => reject(transaction.error ?? new Error("transaction failed")),
+      {
+        once: true,
+      },
+    );
+    transaction.addEventListener(
+      "abort",
+      () => reject(transaction.error ?? new Error("transaction aborted")),
+      {
+        once: true,
+      },
+    );
+  });
+}
+
+function rawTransactions(db: IDBDatabase): Array<{ _state?: string }> {
+  return (
+    (db as unknown as { _rawDatabase?: { transactions?: Array<{ _state?: string }> } })[
+      "_rawDatabase"
+    ]?.transactions ?? []
+  );
+}
+
+describe("Matrix fake-indexeddb transaction pruning", () => {
+  const databaseNames = new Set<string>();
+
+  afterEach(async () => {
+    for (const name of databaseNames) {
+      await deleteDatabase(name);
+    }
+    databaseNames.clear();
+  });
+
+  it("prunes finished transactions for Matrix crypto databases", async () => {
+    installFakeIndexedDbTransactionPruner();
+    const databaseName = `openclaw-matrix-prune-test-${Date.now()}::matrix-sdk-crypto`;
+    databaseNames.add(databaseName);
+    const db = await openDatabase(databaseName);
+
+    for (let i = 0; i < 5; i += 1) {
+      await putRecord(db, `key-${i}`);
+    }
+
+    expect(rawTransactions(db)).toHaveLength(0);
+    db.close();
+  });
+
+  it("prunes finished transactions for Matrix crypto metadata databases", async () => {
+    installFakeIndexedDbTransactionPruner();
+    const databaseName = `openclaw-matrix-meta-prune-test-${Date.now()}::matrix-sdk-crypto-meta`;
+    databaseNames.add(databaseName);
+    const db = await openDatabase(databaseName);
+
+    for (let i = 0; i < 5; i += 1) {
+      await putRecord(db, `key-${i}`);
+    }
+
+    expect(rawTransactions(db)).toHaveLength(0);
+    db.close();
+  });
+
+  it("does not prune unrelated fake-indexeddb databases", async () => {
+    installFakeIndexedDbTransactionPruner();
+    const databaseName = `openclaw-matrix-unrelated-prune-test-${Date.now()}`;
+    databaseNames.add(databaseName);
+    const db = await openDatabase(databaseName);
+
+    await putRecord(db, "key-1");
+
+    expect(
+      rawTransactions(db).filter((transaction) => transaction["_state"] === "finished").length,
+    ).toBeGreaterThan(0);
+    db.close();
+  });
+
+  it("keeps active transactions when pruning the raw transaction queue", () => {
+    const rawDatabase = {
+      name: "openclaw-matrix-direct-prune-test::matrix-sdk-crypto",
+      transactions: [{ _state: "finished" }, { _state: "active" }, { _state: "inactive" }],
+    };
+
+    expect(pruneFinishedFakeIndexedDbTransactions(rawDatabase)).toBe(1);
+    expect(rawDatabase.transactions).toEqual([{ _state: "active" }, { _state: "inactive" }]);
+  });
+});
diff --git a/extensions/matrix/src/matrix/sdk/fake-indexeddb-prune.ts b/extensions/matrix/src/matrix/sdk/fake-indexeddb-prune.ts
new file mode 100644
index 000000000000..55b4b0aae5b1
--- /dev/null
+++ b/extensions/matrix/src/matrix/sdk/fake-indexeddb-prune.ts
@@ -0,0 +1,119 @@
+// Matrix SDK helper mitigates fake-indexeddb finished-transaction retention.
+const MATRIX_CRYPTO_DATABASE_SUFFIXES = [
+  "::matrix-sdk-crypto",
+  "::matrix-sdk-crypto-meta",
+] as const;
+const PRUNER_INSTALLED = Symbol.for("openclaw.matrix.fakeIndexedDbTransactionPruner");
+
+type FakeIndexedDbTransaction = {
+  _state?: string;
+  addEventListener?: (type: "complete" | "abort", listener: () => void) => void;
+  db?: FakeIndexedDbDatabaseConnection;
+};
+
+type FakeIndexedDbRawDatabase = {
+  name?: string;
+  transactions?: FakeIndexedDbTransaction[];
+};
+
+type FakeIndexedDbDatabaseConnection = {
+  _rawDatabase?: FakeIndexedDbRawDatabase;
+};
+
+type FakeIndexedDbDatabasePrototype = FakeIndexedDbDatabaseConnection & {
+  transaction?: IDBDatabase["transaction"];
+  [PRUNER_INSTALLED]?: true;
+};
+
+type GlobalWithFakeIndexedDb = typeof globalThis & {
+  IDBDatabase?: {
+    prototype?: FakeIndexedDbDatabasePrototype;
+  };
+};
+
+function getRawDatabase(value: unknown): FakeIndexedDbRawDatabase | undefined {
+  if (!value || typeof value !== "object") {
+    return undefined;
+  }
+  const rawDatabase = (value as FakeIndexedDbDatabaseConnection)["_rawDatabase"];
+  if (!rawDatabase || typeof rawDatabase !== "object") {
+    return undefined;
+  }
+  return rawDatabase;
+}
+
+function isMatrixCryptoDatabase(
+  rawDatabase: FakeIndexedDbRawDatabase | undefined,
+): rawDatabase is FakeIndexedDbRawDatabase & {
+  transactions: FakeIndexedDbTransaction[];
+} {
+  if (!rawDatabase || !Array.isArray(rawDatabase.transactions)) {
+    return false;
+  }
+  const databaseName = rawDatabase.name;
+  return (
+    typeof databaseName === "string" &&
+    MATRIX_CRYPTO_DATABASE_SUFFIXES.some((suffix) => databaseName.endsWith(suffix))
+  );
+}
+
+export function pruneFinishedFakeIndexedDbTransactions(rawDatabase: unknown): number {
+  const matrixRawDatabase = rawDatabase as FakeIndexedDbRawDatabase | undefined;
+  if (!isMatrixCryptoDatabase(matrixRawDatabase)) {
+    return 0;
+  }
+
+  const transactions = matrixRawDatabase.transactions;
+  const activeTransactions = transactions.filter(
+    (transaction) => transaction?.["_state"] !== "finished",
+  );
+  const removed = transactions.length - activeTransactions.length;
+  if (removed > 0) {
+    transactions.splice(0, transactions.length, ...activeTransactions);
+  }
+  return removed;
+}
+
+export function installFakeIndexedDbTransactionPruner(): void {
+  const globalObject = globalThis as GlobalWithFakeIndexedDb;
+  const databasePrototype = globalObject.IDBDatabase?.prototype;
+  const originalTransaction = databasePrototype?.transaction;
+  if (
+    !databasePrototype ||
+    typeof originalTransaction !== "function" ||
+    databasePrototype[PRUNER_INSTALLED]
+  ) {
+    return;
+  }
+
+  Object.defineProperty(databasePrototype, PRUNER_INSTALLED, {
+    configurable: false,
+    enumerable: false,
+    value: true,
+  });
+
+  const patchedTransaction = function patchedMatrixFakeIndexedDbTransaction(
+    this: IDBDatabase & FakeIndexedDbDatabaseConnection,
+    ...args: Parameters<IDBDatabase["transaction"]>
+  ): ReturnType<IDBDatabase["transaction"]> {
+    pruneFinishedFakeIndexedDbTransactions(getRawDatabase(this));
+
+    const transaction = originalTransaction.apply(this, args) as IDBTransaction &
+      FakeIndexedDbTransaction;
+    const rawDatabase = getRawDatabase(transaction?.db) ?? getRawDatabase(this);
+    if (
+      isMatrixCryptoDatabase(rawDatabase) &&
+      typeof transaction?.addEventListener === "function"
+    ) {
+      const prune = (): void => {
+        pruneFinishedFakeIndexedDbTransactions(rawDatabase);
+      };
+      transaction.addEventListener("complete", prune);
+      transaction.addEventListener("abort", prune);
+    }
+
+    return transaction;
+  } as IDBDatabase["transaction"];
+
+  databasePrototype.transaction = patchedTransaction;
+}