diff --git a/AGENTS.md b/AGENTS.md
index 5c724c0e7..6ecd3740b 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -20,7 +20,7 @@
 - Logging/output: use `dev.jbang.util.Util` helpers (e.g., `infoMsg`, `verboseMsg`).
 - Commits: use conventional/semantic format — `feat:`, `fix:`, `build:`, `docs:`, etc. PR titles follow the same convention.
 - Startup scripts live in `src/main/scripts/`: `jbang` (bash), `jbang.cmd` (CMD), `jbang.ps1` (PowerShell). The CMD script delegates downloads and JDK installs to `jbang.ps1`. Changes affecting downloads or bootstrap must be applied consistently across all three. Behavior (e.g., retry backoff) must be consistent across tools — watch for tool-specific quirks like `curl --retry-delay 0` meaning exponential backoff while `wget --waitretry=0` meaning no delay.
-- Environment variables follow `JBANG_*` naming. New env vars must have defaults in all three scripts, be documented in the reference table in `installation.adoc` ("Startup Script Environment Variables"), and behave identically across platforms.
+- Environment variables follow `JBANG_*` naming. New env vars must have defaults in each script that actually uses them (e.g., `jbang.cmd` delegates downloads to `jbang.ps1`, so download-related vars only need defaults in `jbang` and `jbang.ps1`). Document new vars in `installation.adoc` ("Startup Script Environment Variables") and ensure consistent behavior across platforms.
 - Documentation is AsciiDoc under `docs/modules/ROOT/pages/` (e.g., `installation.adoc`, `troubleshooting.adoc`).
 - Test infrastructure: `BaseTest` includes WireMock for HTTP mocking (records/replays requests). `BaseIT` provides `shell()` helpers for running CLI commands. Use `assumeTrue` for conditionally skipping tests (e.g., `assumeTrue(isCommandAvailable("bash"))` or `assumeTrue(isCommandAvailable("pwsh"))`).
 - Script tests should run the real scripts from `src/main/scripts/` — not synthetic copies or extracted functions. Use env var overrides (e.g., `JBANG_DOWNLOAD_URL`) to point real scripts at WireMock.
diff --git a/src/main/scripts/jbang b/src/main/scripts/jbang
index d8effa46d..12d66433f 100755
--- a/src/main/scripts/jbang
+++ b/src/main/scripts/jbang
@@ -9,6 +9,11 @@
 # The Java version to install when it's not installed on the system yet
 javaVersion=${JBANG_DEFAULT_JAVA_VERSION:-17}
 
+# Base URL for downloading JBang releases.
+# Override for testing or corporate mirrors.
+# Example: JBANG_DOWNLOAD_BASEURL=http://localhost:18080
+jbangDownloadBaseUrl=${JBANG_DOWNLOAD_BASEURL:-https://github.com/jbangdev/jbang/releases}
+
 # Number of retry attempts for downloads (curl/wget)
 downloadRetry=${JBANG_DOWNLOAD_RETRY:-5}
 downloadRetryDelay=${JBANG_DOWNLOAD_RETRY_DELAY:-0}
@@ -25,20 +30,35 @@ script_dir() {
 }
 
 download() {
-  if [ -x "$(command -v curl)" ]; then
-    curl -sLf --retry "$downloadRetry" --retry-delay "$downloadRetryDelay" -o "$2" "$1"
-    retval=$?
-  elif [ -x "$(command -v wget)" ]; then
+  local attempt=0
+  local maxAttempts=$((downloadRetry + 1))
+  while true; do
+    attempt=$((attempt + 1))
+    if [ -x "$(command -v curl)" ]; then
+      curl -sLf -o "$2" "$1"
+      retval=$?
+    elif [ -x "$(command -v wget)" ]; then
+      wget -q -O "$2" "$1"
+      retval=$?
+    else
+      echo "Error: curl or wget not found, please make sure one of them is installed" 1>&2
+      exit 1
+    fi
+    if [ $retval -eq 0 ] || [ $attempt -ge $maxAttempts ]; then
+      break
+    fi
     if [ "$downloadRetryDelay" -gt 0 ] 2>/dev/null; then
-      wget -q --tries="$downloadRetry" --waitretry="$downloadRetryDelay" -O "$2" "$1"
+      sleepSeconds=$downloadRetryDelay
     else
-      wget -q --tries="$downloadRetry" -O "$2" "$1"
+      # Exponential backoff: 1, 2, 4, 8, ...
+      sleepSeconds=$((1 << (attempt - 1)))
     fi
-    retval=$?
-  else
-    echo "Error: curl or wget not found, please make sure one of them is installed" 1>&2
-    exit 1
-  fi
+    echo "Download $attempt/$maxAttempts failed. Retry in $sleepSeconds second(s)..." 1>&2
+    if [ $attempt -eq 1 ]; then
+      echo "(Set JBANG_DOWNLOAD_RETRY=0 to disable retries)" 1>&2
+    fi
+    sleep $sleepSeconds
+  done
 }
 
 unpack() {
@@ -258,15 +278,15 @@ if [[ -z "$binaryPath" ]]; then
 fi
 if [[ -z "$binaryPath" && -z "$jarPath" ]]; then
   if [[ ! -f "$JBDIR/bin/jbang.jar" || ! -f "$JBDIR/bin/jbang" ]]; then
-    echo "Downloading JBang $JBANG_DOWNLOAD_VERSION..." 1>&2
     mkdir -p "$TDIR/urls"
     if [ -n "$JBANG_DOWNLOAD_URL" ]; then
       jburl="$JBANG_DOWNLOAD_URL";
     elif [ -z "$JBANG_DOWNLOAD_VERSION" ]; then
-      jburl="https://github.com/jbangdev/jbang/releases/latest/download/jbang.tar";
+      jburl="${jbangDownloadBaseUrl}/latest/download/jbang.tar";
     else
-      jburl="https://github.com/jbangdev/jbang/releases/download/v$JBANG_DOWNLOAD_VERSION/jbang.tar";
+      jburl="${jbangDownloadBaseUrl}/download/v$JBANG_DOWNLOAD_VERSION/jbang.tar";
     fi
+    echo "Downloading JBang ${JBANG_DOWNLOAD_VERSION:-latest} from $jburl..." 1>&2
     download "$jburl" "$TDIR/urls/jbang.tar"
     if [ $retval -ne 0 ]; then echo "Error downloading JBang from $jburl" 1>&2; exit $retval; fi
     echo "Installing JBang..." 1>&2
diff --git a/src/main/scripts/jbang.ps1 b/src/main/scripts/jbang.ps1
index 2cc5a2142..d613ef9a6 100644
--- a/src/main/scripts/jbang.ps1
+++ b/src/main/scripts/jbang.ps1
@@ -60,6 +60,11 @@ if (-not (Test-Path env:JBANG_DIR)) { $JBDIR="$env:userprofile\.jbang" } else {
 if (-not (Test-Path env:JBANG_CACHE_DIR)) { $TDIR="$JBDIR\cache" } else { $TDIR=$env:JBANG_CACHE_DIR }
 if (-not (Test-Path env:JBANG_USE_NATIVE)) { $env:JBANG_USE_NATIVE="false" }
 
+# Base URL for downloading JBang releases.
+# Override for testing or corporate mirrors.
+# Example: $env:JBANG_DOWNLOAD_BASEURL='http://localhost:18080'
+if (-not (Test-Path env:JBANG_DOWNLOAD_BASEURL)) { $jbangDownloadBaseUrl='https://github.com/jbangdev/jbang/releases' } else { $jbangDownloadBaseUrl=$env:JBANG_DOWNLOAD_BASEURL }
+
 # Number of retry attempts for downloads
 if (-not (Test-Path env:JBANG_DOWNLOAD_RETRY)) { $downloadRetry=5 } else { $downloadRetry=[int]$env:JBANG_DOWNLOAD_RETRY }
 if (-not (Test-Path env:JBANG_DOWNLOAD_RETRY_DELAY)) { $downloadRetryDelay=0 } else { $downloadRetryDelay=[int]$env:JBANG_DOWNLOAD_RETRY_DELAY }
@@ -82,7 +87,10 @@ function Invoke-Download {
                 # Exponential backoff: 1, 2, 4, 8, ...
                 $sleepSeconds = [Math]::Pow(2, $attempt - 1)
             }
-            [Console]::Error.WriteLine("Download attempt $attempt/$($downloadRetry + 1) failed, retrying in $sleepSeconds second(s)...")
+            [Console]::Error.WriteLine("Download $attempt/$($downloadRetry + 1) failed. Retry in $sleepSeconds second(s)...")
+            if ($attempt -eq 1) {
+                [Console]::Error.WriteLine("(Set JBANG_DOWNLOAD_RETRY=0 to disable retries)")
+            }
             Start-Sleep -Seconds $sleepSeconds
         }
     }
@@ -142,11 +150,12 @@ if (-not $binaryPath -and -not $jarPath) {
     if (Test-Path env:JBANG_DOWNLOAD_URL) {
         $jburl=$env:JBANG_DOWNLOAD_URL
     } elseif (-not (Test-Path env:JBANG_DOWNLOAD_VERSION)) {
-        $jburl="https://github.com/jbangdev/jbang/releases/latest/download/jbang.zip"
+        $jburl="$jbangDownloadBaseUrl/latest/download/jbang.zip"
     } else {
-        $jburl="https://github.com/jbangdev/jbang/releases/download/v$env:JBANG_DOWNLOAD_VERSION/jbang.zip";
+        $jburl="$jbangDownloadBaseUrl/download/v$env:JBANG_DOWNLOAD_VERSION/jbang.zip";
     }
-    [Console]::Error.WriteLine("Downloading JBang $env:JBANG_DOWNLOAD_VERSION...")
+    $dlVersion = if ($env:JBANG_DOWNLOAD_VERSION) { $env:JBANG_DOWNLOAD_VERSION } else { 'latest' }
+    [Console]::Error.WriteLine("Downloading JBang $dlVersion from $jburl...")
     $ok = Invoke-Download "$jburl" "$TDIR\urls\jbang.zip"
     if (-not ($ok)) {
       [Console]::Error.WriteLine("Error downloading JBang from $jburl to $TDIR\urls\jbang.zip")