diff --git a/tools/cli/installers/lib/core/ide-config-manager.js b/tools/cli/installers/lib/core/ide-config-manager.js
index 56aa8812..4a0aa232 100644
--- a/tools/cli/installers/lib/core/ide-config-manager.js
+++ b/tools/cli/installers/lib/core/ide-config-manager.js
@@ -68,7 +68,9 @@ class IdeConfigManager {
       sortKeys: false,
     });
 
-    await fs.writeFile(configPath, yamlContent, 'utf8');
+    // Ensure POSIX-compliant final newline
+    const content = yamlContent.endsWith('\n') ? yamlContent : yamlContent + '\n';
+    await fs.writeFile(manifestPath, content, 'utf8');
   }
 
   /**
diff --git a/tools/cli/installers/lib/core/installer.js b/tools/cli/installers/lib/core/installer.js
index 21137d1b..24f746cc 100644
--- a/tools/cli/installers/lib/core/installer.js
+++ b/tools/cli/installers/lib/core/installer.js
@@ -906,8 +906,9 @@ class Installer {
           }
         }
 
-        // Write the clean config file
-        await fs.writeFile(configPath, header + yamlContent, 'utf8');
+        // Write the clean config file with POSIX-compliant final newline
+        const content = header + yamlContent;
+        await fs.writeFile(configPath, content.endsWith('\n') ? content : content + '\n', 'utf8');
 
         // Track the config file in installedFiles
         this.installedFiles.push(configPath);
@@ -1195,8 +1196,9 @@ class Installer {
         // DO NOT replace {project-root} - LLMs understand this placeholder at runtime
         // const processedContent = xmlContent.replaceAll('{project-root}', projectDir);
 
-        // Write the built .md file to bmad/{module}/agents/
-        await fs.writeFile(mdPath, xmlContent, 'utf8');
+        // Write the built .md file to bmad/{module}/agents/ with POSIX-compliant final newline
+        const content = xmlContent.endsWith('\n') ? xmlContent : xmlContent + '\n';
+        await fs.writeFile(mdPath, content, 'utf8');
         this.installedFiles.push(mdPath);
 
         // Remove the source YAML file - we can regenerate from installer source if needed
@@ -1213,7 +1215,9 @@ class Installer {
         if (content.includes('<agent') && !content.includes('<activation')) {
           // Inject the activation block using XML handler
           content = this.xmlHandler.injectActivationSimple(content);
-          await fs.writeFile(agentPath, content, 'utf8');
+          // Ensure POSIX-compliant final newline
+          const finalContent = content.endsWith('\n') ? content : content + '\n';
+          await fs.writeFile(agentPath, finalContent, 'utf8');
         }
       }
     }
@@ -1294,8 +1298,9 @@ class Installer {
       // DO NOT replace {project-root} - LLMs understand this placeholder at runtime
       // const processedContent = xmlContent.replaceAll('{project-root}', projectDir);
 
-      // Write the built .md file
-      await fs.writeFile(targetMdPath, xmlContent, 'utf8');
+      // Write the built .md file with POSIX-compliant final newline
+      const content = xmlContent.endsWith('\n') ? xmlContent : xmlContent + '\n';
+      await fs.writeFile(targetMdPath, content, 'utf8');
 
       // Display result
       if (customizedFields.length > 0) {
@@ -1387,8 +1392,9 @@ class Installer {
         // DO NOT replace {project-root} - LLMs understand this placeholder at runtime
         // const processedContent = xmlContent.replaceAll('{project-root}', projectDir);
 
-        // Write the rebuilt .md file
-        await fs.writeFile(targetMdPath, xmlContent, 'utf8');
+        // Write the rebuilt .md file with POSIX-compliant final newline
+        const content = xmlContent.endsWith('\n') ? xmlContent : xmlContent + '\n';
+        await fs.writeFile(targetMdPath, content, 'utf8');
 
         // Display result with customizations if any
         if (customizedFields.length > 0) {
@@ -2005,6 +2011,11 @@ class Installer {
 
       configContent += processedTemplate;
 
+      // Ensure POSIX-compliant final newline
+      if (!configContent.endsWith('\n')) {
+        configContent += '\n';
+      }
+
       await fs.writeFile(configPath, configContent, 'utf8');
       this.installedFiles.push(configPath); // Track agent config files
       createdCount++;
diff --git a/tools/cli/installers/lib/core/manifest-generator.js b/tools/cli/installers/lib/core/manifest-generator.js
index 9996e637..8a926b40 100644
--- a/tools/cli/installers/lib/core/manifest-generator.js
+++ b/tools/cli/installers/lib/core/manifest-generator.js
@@ -469,7 +469,9 @@ class ManifestGenerator {
       sortKeys: false,
     });
 
-    await fs.writeFile(manifestPath, yamlStr);
+    // Ensure POSIX-compliant final newline
+    const content = yamlStr.endsWith('\n') ? yamlStr : yamlStr + '\n';
+    await fs.writeFile(manifestPath, content);
     return manifestPath;
   }
 
diff --git a/tools/cli/installers/lib/core/manifest.js b/tools/cli/installers/lib/core/manifest.js
index 7410450f..e0cf1cd8 100644
--- a/tools/cli/installers/lib/core/manifest.js
+++ b/tools/cli/installers/lib/core/manifest.js
@@ -35,7 +35,9 @@ class Manifest {
       sortKeys: false,
     });
 
-    await fs.writeFile(manifestPath, yamlContent, 'utf8');
+    // Ensure POSIX-compliant final newline
+    const content = yamlContent.endsWith('\n') ? yamlContent : yamlContent + '\n';
+    await fs.writeFile(manifestPath, content, 'utf8');
     return { success: true, path: manifestPath, filesTracked: 0 };
   }
 
@@ -104,7 +106,9 @@ class Manifest {
       sortKeys: false,
     });
 
-    await fs.writeFile(manifestPath, yamlContent, 'utf8');
+    // Ensure POSIX-compliant final newline
+    const content = yamlContent.endsWith('\n') ? yamlContent : yamlContent + '\n';
+    await fs.writeFile(manifestPath, content, 'utf8');
 
     return manifest;
   }
diff --git a/tools/cli/lib/config.js b/tools/cli/lib/config.js
index ade23e9e..b3ab9cb5 100644
--- a/tools/cli/lib/config.js
+++ b/tools/cli/lib/config.js
@@ -33,7 +33,9 @@ class Config {
     });
 
     await fs.ensureDir(path.dirname(configPath));
-    await fs.writeFile(configPath, yamlContent, 'utf8');
+    // Ensure POSIX-compliant final newline
+    const content = yamlContent.endsWith('\n') ? yamlContent : yamlContent + '\n';
+    await fs.writeFile(configPath, content, 'utf8');
   }
 
   /**
diff --git a/tools/cli/lib/yaml-format.js b/tools/cli/lib/yaml-format.js
index 553e72ae..66dbe3d9 100755
--- a/tools/cli/lib/yaml-format.js
+++ b/tools/cli/lib/yaml-format.js
@@ -64,7 +64,8 @@ async function formatYamlContent(content, filename) {
       noRefs: true,
       sortKeys: false, // Preserve key order
     });
-    return formatted;
+    // Ensure POSIX-compliant final newline
+    return formatted.endsWith('\n') ? formatted : formatted + '\n';
   } catch (error) {
     console.error(chalk.red(`❌ YAML syntax error in ${filename}:`), error.message);
     console.error(chalk.yellow(`💡 Try manually fixing the YAML structure first`));