diff --git a/src/ClaudeDo.Worker/Runner/StreamAnalyzer.cs b/src/ClaudeDo.Worker/Runner/StreamAnalyzer.cs
index 89060b6..6b683d0 100644
--- a/src/ClaudeDo.Worker/Runner/StreamAnalyzer.cs
+++ b/src/ClaudeDo.Worker/Runner/StreamAnalyzer.cs
@@ -86,7 +86,7 @@ public sealed class StreamAnalyzer
         TokensIn = _tokensIn,
         TokensOut = _tokensOut,
         ApiRetryCount = _apiRetryCount,
-        Blocks = _blocks,
+        Blocks = _blocks.Distinct().ToList(),
     };
 
     private string? FallbackResult()
diff --git a/src/ClaudeDo.Worker/Runner/TaskRunner.cs b/src/ClaudeDo.Worker/Runner/TaskRunner.cs
index 102a54b..1c12b5b 100644
--- a/src/ClaudeDo.Worker/Runner/TaskRunner.cs
+++ b/src/ClaudeDo.Worker/Runner/TaskRunner.cs
@@ -380,7 +380,7 @@ public sealed class TaskRunner
             global = await settingsRepo.GetAsync(ct);
         }
 
-        var systemFile = PromptFiles.ReadOrNull(PromptKind.System);
+        var systemFile = PromptFiles.ReadOrDefault(PromptKind.System);
 
         var instructions = MergeInstructions(
             systemFile, global.DefaultClaudeInstructions, listConfig?.SystemPrompt, task.SystemPrompt);
diff --git a/tests/ClaudeDo.Worker.Tests/Runner/StreamAnalyzerTests.cs b/tests/ClaudeDo.Worker.Tests/Runner/StreamAnalyzerTests.cs
index 371f952..27c8406 100644
--- a/tests/ClaudeDo.Worker.Tests/Runner/StreamAnalyzerTests.cs
+++ b/tests/ClaudeDo.Worker.Tests/Runner/StreamAnalyzerTests.cs
@@ -152,4 +152,15 @@ public sealed class StreamAnalyzerTests
         analyzer.ProcessLine("""{"type":"result","result":"done","session_id":"s1"}""");
         Assert.Empty(analyzer.GetResult().Blocks);
     }
+
+    [Fact]
+    public void Duplicate_Marker_In_Assistant_And_Result_Is_Collected_Once()
+    {
+        var analyzer = new StreamAnalyzer();
+        analyzer.ProcessLine("""{"type":"assistant","message":{"content":[{"type":"text","text":"CLAUDEDO_BLOCKED: no creds"}]}}""");
+        analyzer.ProcessLine("""{"type":"result","result":"summary\nCLAUDEDO_BLOCKED: no creds","session_id":"s1"}""");
+        var result = analyzer.GetResult();
+        Assert.Single(result.Blocks);
+        Assert.Equal("no creds", result.Blocks[0]);
+    }
 }