diff --git a/agent99-control-plane.ps1 b/agent99-control-plane.ps1
index 050259013..b7f7edb99 100644
--- a/agent99-control-plane.ps1
+++ b/agent99-control-plane.ps1
@@ -4149,6 +4149,14 @@ function Convert-AgentSafeKey {
   return $safe
 }
 
+function Convert-AgentSafeFileName {
+  param([string]$Value)
+  $safe = [regex]::Replace(([string]$Value), "[^A-Za-z0-9_.-]", "_")
+  if (-not $safe) { return "unknown" }
+  if ($safe.Length -gt 140) { return $safe.Substring(0, 140) }
+  return $safe
+}
+
 function New-AgentOutcomeCheck {
   param(
     [string]$Name,
@@ -4896,7 +4904,8 @@ function Invoke-AgentCompletionCallback {
       }
       occurred_at = (Get-Date -Format o)
     }
-    $pendingPath = Join-Path $pendingDir "$callbackId.json"
+    $callbackFileKey = Convert-AgentSafeFileName $callbackId
+    $pendingPath = Join-Path $pendingDir "$callbackFileKey.json"
     $payload | ConvertTo-Json -Depth 10 | Set-Content -Path $pendingPath -Encoding UTF8
   }
 
@@ -4976,7 +4985,7 @@ function Invoke-AgentCompletionCallback {
     (Get-Item $pendingPath).LastWriteTime = Get-Date
   }
   $receipt.ok = [bool]($receipt.status -eq "durable_verified")
-  $safeCallbackId = Convert-AgentSafeKey $callbackIdValue
+  $safeCallbackId = Convert-AgentSafeFileName $callbackIdValue
   $receiptPath = Join-Path $EvidenceDir "agent99-CompletionCallback-$safeCallbackId-$stamp.json"
   $receipt.evidenceFile = Split-Path -Leaf $receiptPath
   $receipt | ConvertTo-Json -Depth 10 | Set-Content -Path $receiptPath -Encoding UTF8
diff --git a/apps/api/tests/test_agent99_transport_recovery_deploy_contract.py b/apps/api/tests/test_agent99_transport_recovery_deploy_contract.py
index 3d2fc4530..f850d9d70 100644
--- a/apps/api/tests/test_agent99_transport_recovery_deploy_contract.py
+++ b/apps/api/tests/test_agent99_transport_recovery_deploy_contract.py
@@ -242,6 +242,18 @@ def test_agent99_object_reader_preserves_ordered_callback_identity() -> None:
     assert "elseif ($Data -and $Data.PSObject.Properties[$Name])" in helper
 
 
+def test_agent99_callback_queue_uses_windows_safe_file_keys() -> None:
+    source = CONTROL.read_text(encoding="utf-8")
+    helper = source[source.index("function Convert-AgentSafeFileName") :]
+    helper = helper[: helper.index("function New-AgentOutcomeCheck")]
+
+    assert '"[^A-Za-z0-9_.-]"' in helper
+    assert '"[^A-Za-z0-9_.:-]"' not in helper
+    assert "$callbackFileKey = Convert-AgentSafeFileName $callbackId" in source
+    assert 'Join-Path $pendingDir "$callbackFileKey.json"' in source
+    assert "$safeCallbackId = Convert-AgentSafeFileName $callbackIdValue" in source
+
+
 def test_agent99_completion_token_is_bound_without_reusing_telegram_secret() -> None:
     api_deployment = (ROOT / "k8s/awoooi-prod/06-deployment-api.yaml").read_text()
     worker_deployment = (