diff --git a/bun.lock b/bun.lock
index 8a19cf54..0d63b0ce 100644
--- a/bun.lock
+++ b/bun.lock
@@ -52,6 +52,7 @@
       "version": "1.1.0",
       "dependencies": {
         "@nuxt/kit": "^4.3.0",
+        "defu": "^6.1.4",
       },
       "devDependencies": {
         "@nuxt/devtools": "^3.1.1",
diff --git a/packages/evlog/package.json b/packages/evlog/package.json
index a1d41ca1..7bf1f054 100644
--- a/packages/evlog/package.json
+++ b/packages/evlog/package.json
@@ -67,7 +67,8 @@
     "typecheck": "echo 'Typecheck handled by build'"
   },
   "dependencies": {
-    "@nuxt/kit": "^4.3.0"
+    "@nuxt/kit": "^4.3.0",
+    "defu": "^6.1.4"
   },
   "devDependencies": {
     "@nuxt/devtools": "^3.1.1",
diff --git a/packages/evlog/src/logger.ts b/packages/evlog/src/logger.ts
index 5171fa04..fc491a73 100644
--- a/packages/evlog/src/logger.ts
+++ b/packages/evlog/src/logger.ts
@@ -1,3 +1,4 @@
+import { defu } from 'defu'
 import type { EnvironmentContext, Log, LogLevel, LoggerConfig, RequestLogger, RequestLoggerOptions, SamplingConfig, TailSamplingContext, WideEvent } from './types'
 import { colors, detectEnvironment, formatDuration, getConsoleMethod, getLevelColor, isDev, matchesPattern } from './utils'
 
@@ -216,15 +217,14 @@ export function createRequestLogger(options: RequestLoggerOptions = {}): Request
 
   return {
     set<T extends Record<string, unknown>>(data: T): void {
-      context = { ...context, ...data }
+      context = defu(data, context) as Record<string, unknown>
     },
 
     error(error: Error | string, errorContext?: Record<string, unknown>): void {
       hasError = true
       const err = typeof error === 'string' ? new Error(error) : error
 
-      context = {
-        ...context,
+      const errorData = {
         ...errorContext,
         error: {
           name: err.name,
@@ -232,6 +232,7 @@ export function createRequestLogger(options: RequestLoggerOptions = {}): Request
           stack: err.stack,
         },
       }
+      context = defu(errorData, context) as Record<string, unknown>
     },
 
     emit(overrides?: Record<string, unknown> & { _forceKeep?: boolean }): WideEvent | null {
diff --git a/packages/evlog/src/types.ts b/packages/evlog/src/types.ts
index 1512ab9b..94d9d7e9 100644
--- a/packages/evlog/src/types.ts
+++ b/packages/evlog/src/types.ts
@@ -204,7 +204,7 @@ export type WideEvent = BaseWideEvent & Record<string, unknown>
  */
 export interface RequestLogger {
   /**
-   * Add context to the wide event (shallow merge)
+   * Add context to the wide event (deep merge via defu)
    */
   set: <T extends Record<string, unknown>>(context: T) => void
 
diff --git a/packages/evlog/test/logger.test.ts b/packages/evlog/test/logger.test.ts
index 7770570b..e903da33 100644
--- a/packages/evlog/test/logger.test.ts
+++ b/packages/evlog/test/logger.test.ts
@@ -140,7 +140,7 @@ describe('createRequestLogger', () => {
     expect(context.cart).toEqual({ items: 3 })
   })
 
-  it('overwrites existing keys with set()', () => {
+  it('overwrites existing primitive keys with set()', () => {
     const logger = createRequestLogger({})
 
     logger.set({ status: 'pending' })
@@ -150,6 +150,50 @@ describe('createRequestLogger', () => {
     expect(context.status).toBe('complete')
   })
 
+  it('deep merges nested objects with set()', () => {
+    const logger = createRequestLogger({})
+
+    logger.set({ user: { name: 'Alice' } })
+    logger.set({ user: { id: '123' } })
+
+    const context = logger.getContext()
+    expect(context.user).toEqual({ name: 'Alice', id: '123' })
+  })
+
+  it('deep merges multiple levels of nesting', () => {
+    const logger = createRequestLogger({})
+
+    logger.set({ order: { customer: { name: 'Alice' } } })
+    logger.set({ order: { customer: { email: 'alice@example.com' } } })
+    logger.set({ order: { total: 99.99 } })
+
+    const context = logger.getContext()
+    expect(context.order).toEqual({
+      customer: { name: 'Alice', email: 'alice@example.com' },
+      total: 99.99,
+    })
+  })
+
+  it('new values override existing values in nested objects', () => {
+    const logger = createRequestLogger({})
+
+    logger.set({ user: { status: 'pending' } })
+    logger.set({ user: { status: 'active' } })
+
+    const context = logger.getContext()
+    expect(context.user).toEqual({ status: 'active' })
+  })
+
+  it('handles arrays in nested objects', () => {
+    const logger = createRequestLogger({})
+
+    logger.set({ cart: { items: ['item1'] } })
+    logger.set({ cart: { total: 50 } })
+
+    const context = logger.getContext()
+    expect(context.cart).toEqual({ items: ['item1'], total: 50 })
+  })
+
   it('records error with error()', () => {
     const logger = createRequestLogger({})
     const error = new Error('Payment failed')
@@ -177,6 +221,25 @@ describe('createRequestLogger', () => {
     })
   })
 
+  it('deep merges errorContext with nested objects after set()', () => {
+    const logger = createRequestLogger({})
+
+    logger.set({ order: { id: '123', status: 'pending' } })
+    logger.error(new Error('Payment failed'), { order: { payment: { method: 'card' } } })
+
+    const context = logger.getContext()
+    expect(context.order).toEqual({
+      id: '123',
+      status: 'pending',
+      payment: { method: 'card' },
+    })
+    expect(context.error).toEqual({
+      name: 'Error',
+      message: 'Payment failed',
+      stack: expect.any(String),
+    })
+  })
+
   it('emits wide event on emit()', () => {
     const logger = createRequestLogger({
       method: 'GET',