diff --git a/agent99-control-plane.ps1 b/agent99-control-plane.ps1
index fe2163d56..b7176a386 100644
--- a/agent99-control-plane.ps1
+++ b/agent99-control-plane.ps1
@@ -5011,6 +5011,26 @@ function Update-AgentProblemKnowledge {
   }
 }
 
+function Get-AgentCompletionCallbackIncidentId {
+  param(
+    [object]$Result,
+    [string]$FallbackAlertId = ""
+  )
+
+  $identity = Get-AgentObjectValue $Result "identity" $null
+  $canonicalIncidentId = [string](Get-AgentObjectValue $identity "incident_id" "")
+  foreach ($candidate in @($canonicalIncidentId, $FallbackAlertId)) {
+    if ($candidate -and $candidate.Length -le 30) {
+      return $candidate
+    }
+  }
+
+  $surrogateSource = if ($canonicalIncidentId) { $canonicalIncidentId } else { $FallbackAlertId }
+  if (-not $surrogateSource) { return $null }
+  $digest = Get-AgentSha256Hex $surrogateSource
+  return "INC-AG99-$($digest.Substring(0, 21).ToUpperInvariant())"
+}
+
 function Get-AgentCompletionCallbackSettings {
   if (-not $Config.PSObject.Properties["completionCallback"] -or -not $Config.completionCallback) {
     return [pscustomobject]@{ enabled = $false }
@@ -5072,6 +5092,7 @@ function Invoke-AgentCompletionCallback {
     $outcomeState = [string](Get-AgentObjectValue $outcome "state" (Get-AgentObjectValue $Result "outcomeState" "failed"))
     $resultId = [string](Get-AgentObjectValue $Result "id" "unknown")
     $alertId = [string](Get-AgentObjectValue $Result "alertId" "")
+    $callbackIncidentId = Get-AgentCompletionCallbackIncidentId $Result $alertId
     $correlationKey = [string](Get-AgentObjectValue $Result "correlationKey" "")
     $callbackId = Convert-AgentSafeKey "agent99:$resultId`:$outcomeState"
     $evidencePath = [string](Get-AgentObjectValue $Result "evidence" "")
@@ -5084,7 +5105,7 @@ function Invoke-AgentCompletionCallback {
       run_id = $resultId
       trace_id = if ($correlationKey) { $correlationKey } else { $resultId }
       work_item_id = if ($alertId) { "agent99-incident:$alertId" } else { "agent99-command:$resultId" }
-      alert_id = if ($alertId) { $alertId } else { $null }
+      alert_id = $callbackIncidentId
       correlation_key = if ($correlationKey) { $correlationKey } else { $null }
       source = [string](Get-AgentObjectValue $Result "source" "agent99")
       mode = [string](Get-AgentObjectValue $Result "mode" "Status")
diff --git a/agent99-synthetic-tests.ps1 b/agent99-synthetic-tests.ps1
index a9c243a21..7f479f933 100644
--- a/agent99-synthetic-tests.ps1
+++ b/agent99-synthetic-tests.ps1
@@ -42,6 +42,7 @@ foreach ($functionName in @(
   "Get-AgentIncidentCardModel",
   "Format-AgentTelegramText",
   "Format-AgentTelegramCaption",
+  "Get-AgentCompletionCallbackIncidentId",
   "Convert-AgentRecoveryReadback",
   "Get-HostSshUser",
   "Get-AgentSshTransportConfig",
@@ -60,6 +61,18 @@ foreach ($functionName in @(
     $formatFunctions[$functionName] = $true
   }
 }
+
+if ($formatFunctions.ContainsKey("Get-AgentCompletionCallbackIncidentId")) {
+  $canonicalIncident = Get-AgentCompletionCallbackIncidentId ([pscustomobject]@{
+    identity = [pscustomobject]@{ incident_id = "INC-20260714-A1B2C3" }
+  }) "awoooi-agent99-ae36a454-c9eb-5f2d-9e35-be852b3eac9b"
+  $surrogateIncident = Get-AgentCompletionCallbackIncidentId $null "awoooi-agent99-ae36a454-c9eb-5f2d-9e35-be852b3eac9b"
+  Add-SyntheticCheck "callback:canonical_incident_identity" ($canonicalIncident -eq "INC-20260714-A1B2C3") "canonical dispatch identity wins over external alert id"
+  Add-SyntheticCheck "callback:bounded_incident_surrogate" ($surrogateIncident -match '^INC-AG99-[A-F0-9]{21}$' -and $surrogateIncident.Length -eq 30) "long external identity is deterministic and schema-bounded"
+} else {
+  Add-SyntheticCheck "callback:canonical_incident_parser" $false "Get-AgentCompletionCallbackIncidentId not found"
+}
+
 if ($formatFunctions.ContainsKey("Format-AgentTelegramText")) {
   $perfCard = Format-AgentTelegramText "warning" "performance_warning" "test" ([pscustomobject]@{
     host = "192.168.0.120"
diff --git a/apps/api/tests/test_agent99_control_plane_outcome_contract.py b/apps/api/tests/test_agent99_control_plane_outcome_contract.py
index b5136d97c..fabffea4b 100644
--- a/apps/api/tests/test_agent99_control_plane_outcome_contract.py
+++ b/apps/api/tests/test_agent99_control_plane_outcome_contract.py
@@ -102,6 +102,17 @@ def test_agent99_posts_fenced_outcome_to_production_ingestion() -> None:
         assert field in source
 
 
+def test_agent99_completion_callback_uses_bounded_canonical_incident_id() -> None:
+    source = _CONTROL_PLANE.read_text(encoding="utf-8")
+
+    assert "function Get-AgentCompletionCallbackIncidentId" in source
+    assert 'Get-AgentObjectValue $identity "incident_id" ""' in source
+    assert 'return "INC-AG99-' in source
+    assert "$callbackIncidentId = Get-AgentCompletionCallbackIncidentId" in source
+    assert "alert_id = $callbackIncidentId" in source
+    assert "alert_id = if ($alertId)" not in source
+
+
 def test_agent99_backupcheck_reads_offsite_and_escrow_without_mutation() -> None:
     source = _CONTROL_PLANE.read_text(encoding="utf-8")
     readback = source[