diff --git a/src/hooks/atlas/index.test.ts b/src/hooks/atlas/index.test.ts
index 533bd2ffe..2db8a5ef1 100644
--- a/src/hooks/atlas/index.test.ts
+++ b/src/hooks/atlas/index.test.ts
@@ -66,6 +66,20 @@ describe("atlas hook", () => {
   })
 
   describe("tool.execute.after handler", () => {
+    test("should handle undefined output gracefully (issue #1035)", async () => {
+      // #given - hook and undefined output (e.g., from /review command)
+      const hook = createAtlasHook(createMockPluginInput())
+
+      // #when - calling with undefined output
+      const result = await hook["tool.execute.after"](
+        { tool: "delegate_task", sessionID: "session-123" },
+        undefined as unknown as { title: string; output: string; metadata: Record<string, unknown> }
+      )
+
+      // #then - returns undefined without throwing
+      expect(result).toBeUndefined()
+    })
+
     test("should ignore non-delegate_task tools", async () => {
       // #given - hook and non-delegate_task tool
       const hook = createAtlasHook(createMockPluginInput())
diff --git a/src/hooks/atlas/index.ts b/src/hooks/atlas/index.ts
index bd20168be..786ba4004 100644
--- a/src/hooks/atlas/index.ts
+++ b/src/hooks/atlas/index.ts
@@ -663,6 +663,11 @@ export function createAtlasHook(
       input: ToolExecuteAfterInput,
       output: ToolExecuteAfterOutput
     ): Promise<void> => {
+      // Guard against undefined output (e.g., from /review command - see issue #1035)
+      if (!output) {
+        return
+      }
+
       if (!isCallerOrchestrator(input.sessionID)) {
         return
       }
diff --git a/src/hooks/claude-code-hooks/index.ts b/src/hooks/claude-code-hooks/index.ts
index da4d62080..2ff745558 100644
--- a/src/hooks/claude-code-hooks/index.ts
+++ b/src/hooks/claude-code-hooks/index.ts
@@ -237,6 +237,11 @@ export function createClaudeCodeHooksHook(
       input: { tool: string; sessionID: string; callID: string },
       output: { title: string; output: string; metadata: unknown }
     ): Promise<void> => {
+      // Guard against undefined output (e.g., from /review command - see issue #1035)
+      if (!output) {
+        return
+      }
+
       const claudeConfig = await loadClaudeHooksConfig()
       const extendedConfig = await loadPluginExtendedConfig()
 
diff --git a/src/index.ts b/src/index.ts
index 7319ec34e..3d83bc66b 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -657,6 +657,10 @@ const OhMyOpenCodePlugin: Plugin = async (ctx) => {
     },
 
     "tool.execute.after": async (input, output) => {
+      // Guard against undefined output (e.g., from /review command - see issue #1035)
+      if (!output) {
+        return;
+      }
       await claudeCodeHooks["tool.execute.after"](input, output);
       await toolOutputTruncator?.["tool.execute.after"](input, output);
       await contextWindowMonitor?.["tool.execute.after"](input, output);