fix: increase stdoutDrainTimeout from 100ms to 500ms

Resolves intermittent "completed without agent_message output" errors
when Claude CLI exits before all stdout data is read.

- internal/executor/executor.go:43
- internal/app/app.go:27
- Add benchmark script for stability testing

Generated with SWE-Agent.ai

Co-Authored-By: SWE-Agent.ai <noreply@swe-agent.ai>

codeagent-wrapper/internal/app/app.go

@@ -24,7 +24,7 @@ const (
 	stdoutCloseReasonWait  = "wait-done"
 	stdoutCloseReasonDrain = "drain-timeout"
 	stdoutCloseReasonCtx   = "context-cancel"
-	stdoutDrainTimeout     = 100 * time.Millisecond
+	stdoutDrainTimeout     = 500 * time.Millisecond
 )
 
 // Test hooks for dependency injection

codeagent-wrapper/internal/executor/executor.go

@@ -40,7 +40,7 @@ const (
 	stdoutCloseReasonWait  = "wait-done"
 	stdoutCloseReasonDrain = "drain-timeout"
 	stdoutCloseReasonCtx   = "context-cancel"
-	stdoutDrainTimeout     = 100 * time.Millisecond
+	stdoutDrainTimeout     = 500 * time.Millisecond
 )
 
 // Hook points (tests can override inside this package).

codeagent-wrapper/scripts/benchmark_claude.sh

@@ -0,0 +1,43 @@
+#!/bin/bash
+# Benchmark script for Claude CLI stability test
+# Tests if the stdoutDrainTimeout fix resolves intermittent failures
+
+set -euo pipefail
+
+RUNS=${1:-100}
+FAIL_COUNT=0
+SUCCESS_COUNT=0
+TIMEOUT_COUNT=0
+
+echo "Running $RUNS iterations..."
+echo "---"
+
+for i in $(seq 1 $RUNS); do
+    result=$(timeout 30 codeagent --backend claude --skip-permissions 'say OK' 2>&1) || true
+
+    if echo "$result" | grep -q 'without agent_message'; then
+        ((FAIL_COUNT++))
+        echo "[$i] FAIL: without agent_message"
+    elif echo "$result" | grep -q 'timeout'; then
+        ((TIMEOUT_COUNT++))
+        echo "[$i] TIMEOUT"
+    elif echo "$result" | grep -q 'OK\|ok'; then
+        ((SUCCESS_COUNT++))
+        printf "\r[$i] OK                    "
+    else
+        ((FAIL_COUNT++))
+        echo "[$i] FAIL: unexpected output"
+        echo "$result" | head -3
+    fi
+done
+
+echo ""
+echo "---"
+echo "Results ($RUNS runs):"
+echo "  Success: $SUCCESS_COUNT ($(echo "scale=1; $SUCCESS_COUNT * 100 / $RUNS" | bc)%)"
+echo "  Fail:    $FAIL_COUNT ($(echo "scale=1; $FAIL_COUNT * 100 / $RUNS" | bc)%)"
+echo "  Timeout: $TIMEOUT_COUNT ($(echo "scale=1; $TIMEOUT_COUNT * 100 / $RUNS" | bc)%)"
+
+if [ $FAIL_COUNT -gt 0 ]; then
+    exit 1
+fi