diff --git a/packages/eth-json-rpc-middleware/src/block-ref-rewrite.test.ts b/packages/eth-json-rpc-middleware/src/block-ref-rewrite.test.ts
new file mode 100644
index 00000000000..66c44a918dd
--- /dev/null
+++ b/packages/eth-json-rpc-middleware/src/block-ref-rewrite.test.ts
@@ -0,0 +1,247 @@
+import type { PollingBlockTracker } from '@metamask/eth-block-tracker';
+import { JsonRpcEngine } from '@metamask/json-rpc-engine';
+import type { JsonRpcRequest } from '@metamask/utils';
+
+import { createBlockRefRewriteMiddleware } from './block-ref-rewrite';
+
+describe('createBlockRefRewriteMiddleware', () => {
+  it('throws an error when blockTracker is not provided', () => {
+    expect(() => {
+      createBlockRefRewriteMiddleware();
+    }).toThrow('BlockRefRewriteMiddleware - mandatory "blockTracker" option is missing.');
+  });
+
+  it('throws an error when blockTracker is explicitly undefined', () => {
+    expect(() => {
+      createBlockRefRewriteMiddleware({ blockTracker: undefined });
+    }).toThrow('BlockRefRewriteMiddleware - mandatory "blockTracker" option is missing.');
+  });
+
+  it('skips processing when method does not have a block reference parameter', async () => {
+    const mockBlockTracker = buildMockBlockTracker();
+    const getLatestBlockSpy = jest.spyOn(mockBlockTracker, 'getLatestBlock');
+    const middleware = createBlockRefRewriteMiddleware({
+      blockTracker: mockBlockTracker,
+    });
+
+    const engine = new JsonRpcEngine();
+    engine.push(middleware);
+    
+    const originalRequest: JsonRpcRequest = {
+      id: 1,
+      jsonrpc: '2.0',
+      method: 'eth_chainId', // This method doesn't have a block reference
+      params: [],
+    };
+
+    await engine.handle(originalRequest);
+
+    // blockTracker should not be called for methods without block reference
+    expect(getLatestBlockSpy).not.toHaveBeenCalled();
+  });
+
+  it('skips processing when block reference is not "latest"', async () => {
+    const mockBlockTracker = buildMockBlockTracker();
+    const getLatestBlockSpy = jest.spyOn(mockBlockTracker, 'getLatestBlock');
+    const middleware = createBlockRefRewriteMiddleware({
+      blockTracker: mockBlockTracker,
+    });
+
+    const engine = new JsonRpcEngine();
+    engine.push(middleware);
+    
+    const originalRequest: JsonRpcRequest = {
+      id: 1,
+      jsonrpc: '2.0',
+      method: 'eth_getBalance',
+      params: ['0x1234567890abcdef', '0x123'], // Specific block number, not "latest"
+    };
+
+    await engine.handle(originalRequest);
+
+    // blockTracker should not be called when block reference is not "latest"
+    expect(getLatestBlockSpy).not.toHaveBeenCalled();
+  });
+
+  it('rewrites "latest" block reference to actual block number for eth_getBalance', async () => {
+    const mockBlockTracker = buildMockBlockTracker();
+    jest.spyOn(mockBlockTracker, 'getLatestBlock').mockResolvedValue('0xabc123');
+    const middleware = createBlockRefRewriteMiddleware({
+      blockTracker: mockBlockTracker,
+    });
+
+    const engine = new JsonRpcEngine();
+    engine.push(middleware);
+    
+    // Mock a middleware that captures the request after modification
+    let capturedRequest: JsonRpcRequest | undefined;
+    engine.push(async (req, _res, next) => {
+      capturedRequest = { ...req };
+      return next();
+    });
+    
+    const originalRequest: JsonRpcRequest = {
+      id: 1,
+      jsonrpc: '2.0',
+      method: 'eth_getBalance',
+      params: ['0x1234567890abcdef', 'latest'],
+    };
+
+    await engine.handle(originalRequest);
+
+    expect(mockBlockTracker.getLatestBlock).toHaveBeenCalled();
+    expect(capturedRequest?.params).toEqual(['0x1234567890abcdef', '0xabc123']);
+  });
+
+  it('rewrites "latest" block reference to actual block number for eth_getStorageAt', async () => {
+    const mockBlockTracker = buildMockBlockTracker();
+    jest.spyOn(mockBlockTracker, 'getLatestBlock').mockResolvedValue('0xdef456');
+    const middleware = createBlockRefRewriteMiddleware({
+      blockTracker: mockBlockTracker,
+    });
+
+    const engine = new JsonRpcEngine();
+    engine.push(middleware);
+    
+    let capturedRequest: JsonRpcRequest | undefined;
+    engine.push(async (req, _res, next) => {
+      capturedRequest = { ...req };
+      return next();
+    });
+    
+    const originalRequest: JsonRpcRequest = {
+      id: 1,
+      jsonrpc: '2.0',
+      method: 'eth_getStorageAt',
+      params: ['0x1234567890abcdef', '0x0', 'latest'], // blockRef is at index 2
+    };
+
+    await engine.handle(originalRequest);
+
+    expect(mockBlockTracker.getLatestBlock).toHaveBeenCalled();
+    expect(capturedRequest?.params).toEqual(['0x1234567890abcdef', '0x0', '0xdef456']);
+  });
+
+  it('rewrites "latest" block reference to actual block number for eth_getBlockByNumber', async () => {
+    const mockBlockTracker = buildMockBlockTracker();
+    jest.spyOn(mockBlockTracker, 'getLatestBlock').mockResolvedValue('0x789abc');
+    const middleware = createBlockRefRewriteMiddleware({
+      blockTracker: mockBlockTracker,
+    });
+
+    const engine = new JsonRpcEngine();
+    engine.push(middleware);
+    
+    let capturedRequest: JsonRpcRequest | undefined;
+    engine.push(async (req, _res, next) => {
+      capturedRequest = { ...req };
+      return next();
+    });
+    
+    const originalRequest: JsonRpcRequest = {
+      id: 1,
+      jsonrpc: '2.0',
+      method: 'eth_getBlockByNumber',
+      params: ['latest', true], // blockRef is at index 0
+    };
+
+    await engine.handle(originalRequest);
+
+    expect(mockBlockTracker.getLatestBlock).toHaveBeenCalled();
+    expect(capturedRequest?.params).toEqual(['0x789abc', true]);
+  });
+
+  it('treats omitted block reference as "latest" and rewrites it', async () => {
+    const mockBlockTracker = buildMockBlockTracker();
+    jest.spyOn(mockBlockTracker, 'getLatestBlock').mockResolvedValue('0x111222');
+    const middleware = createBlockRefRewriteMiddleware({
+      blockTracker: mockBlockTracker,
+    });
+
+    const engine = new JsonRpcEngine();
+    engine.push(middleware);
+    
+    let capturedRequest: JsonRpcRequest | undefined;
+    engine.push(async (req, _res, next) => {
+      capturedRequest = { ...req };
+      return next();
+    });
+    
+    const originalRequest: JsonRpcRequest = {
+      id: 1,
+      jsonrpc: '2.0',
+      method: 'eth_getBalance',
+      params: ['0x1234567890abcdef'], // No block reference provided (should default to "latest")
+    };
+
+    await engine.handle(originalRequest);
+
+    expect(mockBlockTracker.getLatestBlock).toHaveBeenCalled();
+    expect(capturedRequest?.params).toEqual(['0x1234567890abcdef', '0x111222']);
+  });
+
+  it('handles non-array params gracefully', async () => {
+    const mockBlockTracker = buildMockBlockTracker();
+    const getLatestBlockSpy = jest.spyOn(mockBlockTracker, 'getLatestBlock');
+    const middleware = createBlockRefRewriteMiddleware({
+      blockTracker: mockBlockTracker,
+    });
+
+    const engine = new JsonRpcEngine();
+    engine.push(middleware);
+    
+    const originalRequest: JsonRpcRequest = {
+      id: 1,
+      jsonrpc: '2.0',
+      method: 'eth_getBalance',
+      params: null, // Non-array params
+    };
+
+    await engine.handle(originalRequest);
+
+    // Should treat non-array params as "latest" and try to process
+    expect(getLatestBlockSpy).toHaveBeenCalled();
+  });
+
+  it('preserves original request properties except for the modified param', async () => {
+    const mockBlockTracker = buildMockBlockTracker();
+    jest.spyOn(mockBlockTracker, 'getLatestBlock').mockResolvedValue('0xffffff');
+    const middleware = createBlockRefRewriteMiddleware({
+      blockTracker: mockBlockTracker,
+    });
+
+    const engine = new JsonRpcEngine();
+    engine.push(middleware);
+    
+    let capturedRequest: JsonRpcRequest | undefined;
+    engine.push(async (req, _res, next) => {
+      capturedRequest = { ...req };
+      return next();
+    });
+    
+    const originalRequest: JsonRpcRequest = {
+      id: 42,
+      jsonrpc: '2.0',
+      method: 'eth_call',
+      params: [{ to: '0x123', data: '0x456' }, 'latest'],
+    };
+
+    await engine.handle(originalRequest);
+
+    expect(capturedRequest?.id).toBe(42);
+    expect(capturedRequest?.jsonrpc).toBe('2.0');
+    expect(capturedRequest?.method).toBe('eth_call');
+    expect(capturedRequest?.params).toEqual([{ to: '0x123', data: '0x456' }, '0xffffff']);
+  });
+});
+
+/**
+ * Constructs a mock PollingBlockTracker for use in tests.
+ *
+ * @returns The mock block tracker.
+ */
+function buildMockBlockTracker(): PollingBlockTracker {
+  return {
+    getLatestBlock: jest.fn().mockResolvedValue('0x123'),
+  } as unknown as PollingBlockTracker;
+}
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