diff --git a/.jenkins_builds b/.jenkins_builds
index 1336ecd0..d013ddb5 100644
--- a/.jenkins_builds
+++ b/.jenkins_builds
@@ -5,68 +5,88 @@ pipeline {
 
   environment {
     DEVELOPER_PRIVATE_KEY = "/.ci/repertory/cert/developer.priv"
-    DEVELOPER_PUBLIC_KEY = "/.ci/repertory/cert/developer.pub"
+    DEVELOPER_PUBLIC_KEY  = "/.ci/repertory/cert/developer.pub"
     PROJECT_TEST_CONFIG_DIR = "/.ci/repertory/test"
   }
 
   options {
     disableConcurrentBuilds()
-    retry(2)
+    skipDefaultCheckout()
+    timestamps()
   }
 
   stages {
-    stage('linux_x86_64') {
+    stage('Build • Test • Deliver') {
       agent any
-
-      steps {
-        retry(2) {
-          sleep time: 5, unit: 'SECONDS'
-          sh 'scripts/make_unix.sh'
+      stages {
+        stage('Checkout') {
+          steps {
+            script {
+              int maxAttempts = 6
+              int baseDelay  = 10
+              for (int attempt = 1; attempt <= maxAttempts; attempt++) {
+                try {
+                  checkout scm
+                  break
+                } catch (err) {
+                  if (attempt == maxAttempts) { throw err }
+                  int waitSec = baseDelay * (1 << (attempt - 1))
+                  echo "Checkout failed (attempt ${attempt}/${maxAttempts}). Waiting ${waitSec}s before retry..."
+                  sleep time: waitSec, unit: 'SECONDS'
+                }
+              }
+            }
+          }
         }
-      }
-    }
 
-    stage('mingw64') {
-      agent any
-
-      steps {
-        retry(2) {
-          sleep time: 5, unit: 'SECONDS'
-          sh 'scripts/make_win32.sh'
+        stage('linux_x86_64') {
+          steps {
+            script { retryWithBackoff(2, 5) { sh 'scripts/make_unix.sh' } }
+          }
         }
-      }
-    }
 
-    stage('linux_aarch64') {
-      agent any
-
-      steps {
-        retry(2) {
-          sleep time: 5, unit: 'SECONDS'
-          sh 'scripts/make_unix.sh aarch64'
+        stage('mingw64') {
+          steps {
+            script { retryWithBackoff(2, 5) { sh 'scripts/make_win32.sh' } }
+          }
         }
-      }
-    }
 
-    stage('linux_x86_64_test') {
-      agent any
-
-      steps {
-        retry(2) {
-          sleep time: 5, unit: 'SECONDS'
-          sh 'scripts/run_tests.sh'
+        stage('linux_aarch64') {
+          steps {
+            script { retryWithBackoff(2, 5) { sh 'scripts/make_unix.sh aarch64' } }
+          }
         }
-      }
-    }
 
-    stage('deliver') {
-      agent any
+        stage('linux_x86_64_test') {
+          steps {
+            script { retryWithBackoff(2, 5) { sh 'scripts/run_tests.sh' } }
+          }
+        }
 
-      steps {
-        sh 'scripts/deliver.sh /mnt/repertory "" "" "" "" 1 1'
-        sh 'scripts/deliver.sh /mnt/repertory "" aarch64'
-        sh 'scripts/deliver.sh /mnt/repertory'
+        stage('deliver') {
+          steps {
+            script {
+              retryWithBackoff(3, 10) { sh 'scripts/deliver.sh /mnt/repertory "" "" "" "" 1 1' }
+              retryWithBackoff(3, 10) { sh 'scripts/deliver.sh /mnt/repertory "" aarch64' }
+              retryWithBackoff(3, 10) { sh 'scripts/deliver.sh /mnt/repertory' }
+            }
+          }
+        }
       }
     }
   }
 }
+
+def retryWithBackoff(int maxAttempts, int baseDelaySeconds, Closure body) {
+  for (int attempt = 1; attempt <= maxAttempts; attempt++) {
+    try {
+      body()
+      return
+    } catch (err) {
+      if (attempt == maxAttempts) { throw err }
+      int waitSec = baseDelaySeconds * (1 << (attempt - 1))
+      echo "Step failed (attempt ${attempt}/${maxAttempts}). Waiting ${waitSec}s before retry..."
+      sleep time: waitSec, unit: 'SECONDS'
+    }
+  }
+}
diff --git a/.jenkins_macos b/.jenkins_macos
index f226df07..43047334 100644
--- a/.jenkins_macos
+++ b/.jenkins_macos
@@ -4,57 +4,76 @@ pipeline {
   agent none
 
   environment {
-    DEVELOPER_PRIVATE_KEY = "${env.HOME}/.ci/repertory/cert/developer.priv"
-    DEVELOPER_PUBLIC_KEY = "${env.HOME}/.ci/repertory/cert/developer.pub"
+    DEVELOPER_PRIVATE_KEY   = "${env.HOME}/.ci/repertory/cert/developer.priv"
+    DEVELOPER_PUBLIC_KEY    = "${env.HOME}/.ci/repertory/cert/developer.pub"
     PROJECT_TEST_CONFIG_DIR = "${env.HOME}/.ci/repertory/test"
   }
 
   options {
     disableConcurrentBuilds()
-    retry(2)
+    skipDefaultCheckout()
+    timestamps()
   }
 
   stages {
-    stage('darwin_aarch64') {
+    stage('Build • Test • Deliver') {
       agent any
-
-      steps {
-        retry(2) {
-          sleep time: 5, unit: 'SECONDS'
-          sh 'scripts/make_unix.sh aarch64'
+      stages {
+        stage('Checkout') {
+          steps {
+            script {
+              int maxAttempts = 6
+              int baseDelay   = 10
+              for (int attempt = 1; attempt <= maxAttempts; attempt++) {
+                try {
+                  checkout scm
+                  break
+                } catch (err) {
+                  if (attempt == maxAttempts) { throw err }
+                  int waitSec = baseDelay * (1 << (attempt - 1))
+                  echo "Checkout failed (attempt ${attempt}/${maxAttempts}). Waiting ${waitSec}s before retry..."
+                  sleep time: waitSec, unit: 'SECONDS'
+                }
+              }
+            }
+          }
         }
-      }
-    }
 
-    stage('darwin_x86_64') {
-      agent any
-
-      steps {
-        retry(2) {
-          sleep time: 5, unit: 'SECONDS'
-          sh 'scripts/make_unix.sh x86_64'
+        stage('darwin_aarch64') {
+          steps { script { retryWithBackoff(2, 5) { sh 'scripts/make_unix.sh aarch64' } } }
         }
-      }
-    }
 
-    stage('darwin_aarch64_test') {
-      agent any
-
-      steps {
-        retry(2) {
-          sleep time: 5, unit: 'SECONDS'
-          sh 'scripts/run_tests.sh aarch64'
+        stage('darwin_x86_64') {
+          steps { script { retryWithBackoff(2, 5) { sh 'scripts/make_unix.sh x86_64' } } }
         }
-      }
-    }
 
-    stage('deliver') {
-      agent any
+        stage('darwin_aarch64_test') {
+          steps { script { retryWithBackoff(2, 5) { sh 'scripts/run_tests.sh aarch64' } } }
+        }
 
-      steps {
-        sh "scripts/deliver.sh ${env.HOME}/mnt/repertory '' aarch64"
-        sh "scripts/deliver.sh ${env.HOME}/mnt/repertory '' x86_64"
+        stage('deliver') {
+          steps {
+            script {
+              retryWithBackoff(3, 10) { sh "scripts/deliver.sh ${env.HOME}/mnt/repertory '' aarch64" }
+              retryWithBackoff(3, 10) { sh "scripts/deliver.sh ${env.HOME}/mnt/repertory '' x86_64" }
+            }
+          }
+        }
       }
     }
   }
 }
+
+def retryWithBackoff(int maxAttempts, int baseDelaySeconds, Closure body) {
+  for (int attempt = 1; attempt <= maxAttempts; attempt++) {
+    try {
+      body()
+      return
+    } catch (err) {
+      if (attempt == maxAttempts) { throw err }
+      int waitSec = baseDelaySeconds * (1 << (attempt - 1))
+      echo "Step failed (attempt ${attempt}/${maxAttempts}). Waiting ${waitSec}s before retry..."
+      sleep time: waitSec, unit: 'SECONDS'
+    }
+  }
+}