diff --git a/CopilotCodeReviewV1/index.ts b/CopilotCodeReviewV1/index.ts
index dfe0726..c029940 100644
--- a/CopilotCodeReviewV1/index.ts
+++ b/CopilotCodeReviewV1/index.ts
@@ -73,6 +73,19 @@ async function run(): Promise<void> {
         // Get Azure DevOps authentication settings
         const useSystemAccessToken = tl.getBoolInput('useSystemAccessToken', false);
         const azureDevOpsPat = tl.getInput('azureDevOpsPat');
+        const onPremise = tl.getBoolInput('onPremise', false);
+        const systemCollectionUri = tl.getVariable('System.CollectionUri') ||
+            process.env['SYSTEM_COLLECTIONURI'] ||
+            '';
+
+        process.env['AZUREDEVOPS_ONPREMISE'] = onPremise ? 'true' : 'false';
+
+        if (onPremise && !systemCollectionUri) {
+            tl.setResult(tl.TaskResult.Failed,
+                'On-Premise mode is enabled, but System.CollectionUri is not available. ' +
+                'Ensure the pipeline provides $(System.CollectionUri) or disable On-Premise mode.');
+            return;
+        }
         
         // Determine which token and auth type to use
         let azureDevOpsToken: string;
@@ -106,19 +119,30 @@ async function run(): Promise<void> {
         let project = tl.getInput('project');
         let repository = tl.getInput('repository');
 
-        // Auto-detect organization from System.CollectionUri if not provided
-        // CollectionUri format: https://dev.azure.com/orgname/ or https://orgname.visualstudio.com/
-        if (!organization) {
-            const collectionUri = tl.getVariable('System.CollectionUri');
-            if (collectionUri) {
-                const devAzureMatch = collectionUri.match(/https:\/\/dev\.azure\.com\/([^\/]+)/);
-                const vstsMatch = collectionUri.match(/https:\/\/([^\.]+)\.visualstudio\.com/);
-                if (devAzureMatch) {
-                    organization = devAzureMatch[1];
-                    console.log(`Auto-detected organization from CollectionUri: ${organization}`);
-                } else if (vstsMatch) {
-                    organization = vstsMatch[1];
-                    console.log(`Auto-detected organization from CollectionUri: ${organization}`);
+        // Auto-detect organization/collection from System.CollectionUri if not provided
+        // CollectionUri format examples:
+        //   https://dev.azure.com/orgname/
+        //   https://orgname.visualstudio.com/
+        //   https://tfs.contoso.com/tfs/DefaultCollection/
+        if (!organization && systemCollectionUri) {
+            const devAzureMatch = systemCollectionUri.match(/https:\/\/dev\.azure\.com\/([^\/]+)/);
+            const vstsMatch = systemCollectionUri.match(/https:\/\/([^\.]+)\.visualstudio\.com/);
+            if (devAzureMatch) {
+                organization = devAzureMatch[1];
+                console.log(`Auto-detected organization from CollectionUri: ${organization}`);
+            } else if (vstsMatch) {
+                organization = vstsMatch[1];
+                console.log(`Auto-detected organization from CollectionUri: ${organization}`);
+            } else {
+                try {
+                    const url = new URL(systemCollectionUri);
+                    const segments = url.pathname.split('/').filter(Boolean);
+                    if (segments.length > 0) {
+                        organization = segments[segments.length - 1];
+                        console.log(`Auto-detected collection from CollectionUri: ${organization}`);
+                    }
+                } catch {
+                    // Ignore parse errors; organization may be provided explicitly
                 }
             }
         }
diff --git a/CopilotCodeReviewV1/package-lock.json b/CopilotCodeReviewV1/package-lock.json
index 576db04..a0e061a 100644
--- a/CopilotCodeReviewV1/package-lock.json
+++ b/CopilotCodeReviewV1/package-lock.json
@@ -1,12 +1,12 @@
 {
     "name": "copilot-code-review-task",
-    "version": "1.0.12",
+    "version": "1.4.2",
     "lockfileVersion": 3,
     "requires": true,
     "packages": {
         "": {
             "name": "copilot-code-review-task",
-            "version": "1.0.12",
+            "version": "1.4.2",
             "license": "MIT",
             "dependencies": {
                 "azure-pipelines-task-lib": "^4.17.3",
diff --git a/CopilotCodeReviewV1/scripts/Add-AzureDevOpsPRComment.ps1 b/CopilotCodeReviewV1/scripts/Add-AzureDevOpsPRComment.ps1
index 56293e9..d79fd8b 100644
--- a/CopilotCodeReviewV1/scripts/Add-AzureDevOpsPRComment.ps1
+++ b/CopilotCodeReviewV1/scripts/Add-AzureDevOpsPRComment.ps1
@@ -131,6 +131,9 @@ param(
     [int]$IterationId
 )
 
+# Shared URL helpers
+. "$PSScriptRoot\AzureDevOpsUrl.ps1"
+
 #region Helper Functions
 
 function Get-AuthorizationHeader {
@@ -229,7 +232,11 @@ function Format-AzureDevOpsFilePath {
 #region Main Logic
 
 $headers = Get-AuthorizationHeader -Token $Token -AuthType $AuthType
-$baseUrl = "https://dev.azure.com/$Organization/$Project/_apis/git/repositories/$Repository/pullrequests/$Id"
+$baseUrls = Get-AzureDevOpsBaseUrls -Project $Project -Organization $Organization
+if ($null -eq $baseUrls) {
+    exit 1
+}
+$baseUrl = "$($baseUrls.ApiBaseUrl)/git/repositories/$Repository/pullrequests/$Id"
 $apiVersion = "api-version=7.1"
 
 # First, verify the PR exists
@@ -401,7 +408,7 @@ else {
 }
 
 # Provide link to the PR
-$webUrl = "https://dev.azure.com/$Organization/$Project/_git/$Repository/pullrequest/$Id"
+$webUrl = "$($baseUrls.WebBaseUrl)/_git/$Repository/pullrequest/$Id"
 Write-Host "`nView PR: $webUrl" -ForegroundColor Cyan
 
 #endregion
diff --git a/CopilotCodeReviewV1/scripts/AzureDevOpsUrl.ps1 b/CopilotCodeReviewV1/scripts/AzureDevOpsUrl.ps1
new file mode 100644
index 0000000..4571dc2
--- /dev/null
+++ b/CopilotCodeReviewV1/scripts/AzureDevOpsUrl.ps1
@@ -0,0 +1,60 @@
+<#
+.SYNOPSIS
+    Shared helpers for building Azure DevOps REST and web base URLs.
+
+.DESCRIPTION
+    Centralizes URL construction for Azure DevOps Services and Server (on-prem).
+    Uses $env:AZUREDEVOPS_ONPREMISE to determine whether to use on-prem URLs.
+#>
+
+function Get-AzureDevOpsBaseUrls {
+    [CmdletBinding()]
+    param(
+        [Parameter(Mandatory = $true)]
+        [string]$Project,
+
+        [Parameter(Mandatory = $false)]
+        [string]$Organization,
+
+        [Parameter(Mandatory = $false)]
+        [switch]$Silent
+    )
+
+    $onPremise = $false
+    if ($env:AZUREDEVOPS_ONPREMISE -match '^(?i:true|1|yes)$') {
+        $onPremise = $true
+    }
+
+    $collectionUri = $null
+    if ($onPremise) {
+        $collectionUri = $env:SYSTEM_COLLECTIONURI
+        if ([string]::IsNullOrWhiteSpace($collectionUri)) {
+            if (-not $Silent) {
+                Write-Error "SYSTEM_COLLECTIONURI is required when On-Premise mode is enabled."
+            }
+            return $null
+        }
+        $collectionUri = $collectionUri.Trim()
+        if (-not $collectionUri.EndsWith('/')) {
+            $collectionUri += '/'
+        }
+    }
+    else {
+        if ([string]::IsNullOrWhiteSpace($Organization)) {
+            if (-not $Silent) {
+                Write-Error "Organization is required when On-Premise mode is disabled."
+            }
+            return $null
+        }
+    }
+
+    $apiBaseUrl = if ($onPremise) { "$collectionUri$Project/_apis" } else { "https://dev.azure.com/$Organization/$Project/_apis" }
+    $webBaseUrl = if ($onPremise) { "$collectionUri$Project" } else { "https://dev.azure.com/$Organization/$Project" }
+
+    return [PSCustomObject]@{
+        ApiBaseUrl   = $apiBaseUrl
+        WebBaseUrl   = $webBaseUrl
+        OnPremise    = $onPremise
+        CollectionUri = $collectionUri
+    }
+}
diff --git a/CopilotCodeReviewV1/scripts/Delete-CopilotComment.ps1 b/CopilotCodeReviewV1/scripts/Delete-CopilotComment.ps1
index b81d168..bca0700 100644
--- a/CopilotCodeReviewV1/scripts/Delete-CopilotComment.ps1
+++ b/CopilotCodeReviewV1/scripts/Delete-CopilotComment.ps1
@@ -49,6 +49,9 @@ param(
     [int]$CommentId
 )
 
+# Shared URL helpers
+. "$PSScriptRoot\AzureDevOpsUrl.ps1"
+
 # Wrap entire script in try/catch for silent failure
 try {
     # Read credentials from environment variables
@@ -61,7 +64,6 @@ try {
 
     # Validate required environment variables
     if ([string]::IsNullOrEmpty($token) -or 
-        [string]::IsNullOrEmpty($organization) -or 
         [string]::IsNullOrEmpty($project) -or 
         [string]::IsNullOrEmpty($repository) -or 
         [string]::IsNullOrEmpty($prId)) {
@@ -90,7 +92,11 @@ try {
     }
 
     # Build the API URL for deleting a comment
-    $baseUrl = "https://dev.azure.com/$organization/$project/_apis"
+    $baseUrls = Get-AzureDevOpsBaseUrls -Project $project -Organization $organization -Silent
+    if ($null -eq $baseUrls) {
+        exit 0
+    }
+    $baseUrl = $baseUrls.ApiBaseUrl
     $uri = "$baseUrl/git/repositories/$repository/pullrequests/$prId/threads/$ThreadId/comments/$CommentId`?api-version=7.1"
 
     # Send DELETE request
diff --git a/CopilotCodeReviewV1/scripts/Get-AzureDevOpsPR.ps1 b/CopilotCodeReviewV1/scripts/Get-AzureDevOpsPR.ps1
index fe5c3b6..d578a5e 100644
--- a/CopilotCodeReviewV1/scripts/Get-AzureDevOpsPR.ps1
+++ b/CopilotCodeReviewV1/scripts/Get-AzureDevOpsPR.ps1
@@ -86,6 +86,9 @@ param(
     [string]$OutputFile
 )
 
+# Shared URL helpers
+. "$PSScriptRoot\AzureDevOpsUrl.ps1"
+
 #region Helper Functions
 
 function Write-Output-Line {
@@ -275,7 +278,11 @@ $script:OutputToFile = -not [string]::IsNullOrEmpty($OutputFile)
 $script:OutputBuilder = [System.Text.StringBuilder]::new()
 
 $headers = Get-AuthorizationHeader -Token $Token -AuthType $AuthType
-$baseUrl = "https://dev.azure.com/$Organization/$Project/_apis"
+$baseUrls = Get-AzureDevOpsBaseUrls -Project $Project -Organization $Organization
+if ($null -eq $baseUrls) {
+    exit 1
+}
+$baseUrl = $baseUrls.ApiBaseUrl
 $apiVersion = "api-version=7.1"
 
 # If a specific PR ID is provided, get detailed information
@@ -487,7 +494,7 @@ if ($Id -gt 0) {
     }
     
     Write-Output-Line "`n[Links]" -ForegroundColor Yellow
-    $webUrl = "https://dev.azure.com/$Organization/$Project/_git/$($pr.repository.name)/pullrequest/$($pr.pullRequestId)"
+    $webUrl = "$($baseUrls.WebBaseUrl)/_git/$($pr.repository.name)/pullrequest/$($pr.pullRequestId)"
     Write-Output-Line "  Web URL: $webUrl"
     
     Write-Output-Line ("`n" + ("=" * 80)) -ForegroundColor DarkGray
diff --git a/CopilotCodeReviewV1/scripts/Get-AzureDevOpsPRChanges.ps1 b/CopilotCodeReviewV1/scripts/Get-AzureDevOpsPRChanges.ps1
index d3ea18f..72d1732 100644
--- a/CopilotCodeReviewV1/scripts/Get-AzureDevOpsPRChanges.ps1
+++ b/CopilotCodeReviewV1/scripts/Get-AzureDevOpsPRChanges.ps1
@@ -73,6 +73,9 @@ param(
     [string]$OutputFile
 )
 
+# Shared URL helpers
+. "$PSScriptRoot\AzureDevOpsUrl.ps1"
+
 #region Helper Functions
 
 function Write-Output-Line {
@@ -186,7 +189,11 @@ $script:OutputToFile = -not [string]::IsNullOrEmpty($OutputFile)
 $script:OutputBuilder = [System.Text.StringBuilder]::new()
 
 $headers = Get-AuthorizationHeader -Token $Token -AuthType $AuthType
-$baseUrl = "https://dev.azure.com/$Organization/$Project/_apis/git/repositories/$Repository/pullrequests/$Id"
+$baseUrls = Get-AzureDevOpsBaseUrls -Project $Project -Organization $Organization
+if ($null -eq $baseUrls) {
+    exit 1
+}
+$baseUrl = "$($baseUrls.ApiBaseUrl)/git/repositories/$Repository/pullrequests/$Id"
 $apiVersion = "api-version=7.1"
 
 # Verify the PR exists
@@ -299,7 +306,7 @@ else {
 Write-Output-Line ("`n" + ("=" * 80)) -ForegroundColor DarkGray
 
 # Provide link to the PR
-$webUrl = "https://dev.azure.com/$Organization/$Project/_git/$Repository/pullrequest/$Id"
+$webUrl = "$($baseUrls.WebBaseUrl)/_git/$Repository/pullrequest/$Id"
 Write-Host "`nView PR: $webUrl" -ForegroundColor Cyan
 if ($script:OutputToFile) {
     $script:OutputBuilder.AppendLine("`nView PR: $webUrl") | Out-Null
diff --git a/CopilotCodeReviewV1/scripts/Update-CopilotComment.ps1 b/CopilotCodeReviewV1/scripts/Update-CopilotComment.ps1
index e84f5dd..76129cc 100644
--- a/CopilotCodeReviewV1/scripts/Update-CopilotComment.ps1
+++ b/CopilotCodeReviewV1/scripts/Update-CopilotComment.ps1
@@ -69,6 +69,9 @@ param(
     [string]$Content
 )
 
+# Shared URL helpers
+. "$PSScriptRoot\AzureDevOpsUrl.ps1"
+
 # Wrap entire script in try/catch for silent failure
 try {
     # Validate that at least one update is requested
@@ -93,7 +96,6 @@ try {
 
     # Validate required environment variables
     if ([string]::IsNullOrEmpty($token) -or 
-        [string]::IsNullOrEmpty($organization) -or 
         [string]::IsNullOrEmpty($project) -or 
         [string]::IsNullOrEmpty($repository) -or 
         [string]::IsNullOrEmpty($prId)) {
@@ -121,7 +123,11 @@ try {
         }
     }
 
-    $baseUrl = "https://dev.azure.com/$organization/$project/_apis"
+    $baseUrls = Get-AzureDevOpsBaseUrls -Project $project -Organization $organization -Silent
+    if ($null -eq $baseUrls) {
+        exit 0
+    }
+    $baseUrl = $baseUrls.ApiBaseUrl
 
     # Update thread status if specified
     if (-not [string]::IsNullOrEmpty($Status)) {
diff --git a/CopilotCodeReviewV1/task.json b/CopilotCodeReviewV1/task.json
index 7226ba3..4e53c75 100644
--- a/CopilotCodeReviewV1/task.json
+++ b/CopilotCodeReviewV1/task.json
@@ -37,6 +37,14 @@
             "defaultValue": false,
             "helpMarkDown": "When enabled, uses the pipeline's System.AccessToken (OAuth) instead of a PAT. This is the Microsoft-recommended authentication method for Azure DevOps Services. **Note**: The Build Service identity must have 'Contribute to pull requests' permission on the repository. Not supported for Azure DevOps Server (on-prem)."
         },
+        {
+            "name": "onPremise",
+            "type": "boolean",
+            "label": "On-Premise (Azure DevOps Server)",
+            "required": false,
+            "defaultValue": false,
+            "helpMarkDown": "Enable for Azure DevOps Server (on-prem). When enabled, the task uses $(System.CollectionUri) as the API base URL."
+        },
         {
             "name": "organization",
             "type": "string",
@@ -127,4 +135,4 @@
             "allowed": []
         }
     }
-}
\ No newline at end of file
+}