diff --git a/scripts/ci_runner_bootstrap.ps1 b/scripts/ci_runner_bootstrap.ps1
index fa469051..bd84d483 100644
--- a/scripts/ci_runner_bootstrap.ps1
+++ b/scripts/ci_runner_bootstrap.ps1
@@ -338,7 +338,8 @@ $runnerDir   = '__RUNNER_DIR__'
 $runnerExe   = Join-Path $runnerDir 'gitea-runner.exe'
 $runnerCfg   = Join-Path $runnerDir 'config.yaml'
 $logDir      = Join-Path $runnerDir 'log'
-$log         = Join-Path $logDir 'runner-stdout.log'
+$log         = Join-Path $logDir 'runner-watchdog.log'
+$daemonLog   = Join-Path $logDir 'runner-daemon.log'
 $probeUrl    = '__GITEA_URL__/api/v1/version'
 $maxWaitSec  = 1800
 
@@ -371,7 +372,15 @@ while ($true) {
     }
 
     Log 'starting daemon'
-    & $runnerExe daemon --config $runnerCfg *>> $log
+    # MEASURED TRAP (2026-10-12, hit by this very script): in PowerShell 5.1 the
+    # *>> redirection is implemented with Out-File, whose DEFAULT ENCODING IS
+    # UTF-16LE. Appending that into a file whose other lines come from
+    # Add-Content -Encoding ascii leaves ONE FILE WITH TWO ENCODINGS, and the
+    # daemon lines read back as "t i m e = 2 0 2 6 ..." (a NUL after every byte).
+    # Never rely on a redirection's default encoding -- state it explicitly.
+    # utf8 (not ascii) because job/commit text can legitimately be non-ASCII.
+    & $runnerExe daemon --config $runnerCfg 2>&1 |
+        Out-File -FilePath $daemonLog -Append -Encoding utf8
     Log ("daemon exited, exit code {0}; restarting in 10s" -f $LASTEXITCODE)
     Start-Sleep -Seconds 10
 }
@@ -415,7 +424,8 @@ if ($StartNow) {
         Warn "Gitea is not answering at $GiteaUrl right now -- the watchdog will keep waiting"
     }
     Start-ScheduledTask -TaskName $TaskName
-    Ok "task started; watch: Get-Content '$(Join-Path $RunnerDir 'log\runner-stdout.log')' -Tail 20"
+    Ok "task started; daemon log: Get-Content '$(Join-Path $RunnerDir 'log\runner-daemon.log')' -Tail 20"
+    Ok "watchdog log: Get-Content '$(Join-Path $RunnerDir 'log\runner-watchdog.log')' -Tail 20"
     Info 'verify on the web UI: repo -> Settings -> Actions -> Runners -> win-stm32-ci should turn Idle'
 }