diff --git a/tools/cli/installers/lib/core/installer.js b/tools/cli/installers/lib/core/installer.js
index 4512cd6d..5d3b0033 100644
--- a/tools/cli/installers/lib/core/installer.js
+++ b/tools/cli/installers/lib/core/installer.js
@@ -1599,10 +1599,15 @@ If AgentVibes party mode is enabled, immediately trigger TTS with agent's voice:
           const sourceModulePath = getSourcePath(`modules/${moduleName}`);
           const sourceAgentPath = path.join(sourceModulePath, 'agents');
 
-          // Copy sidecar files
-          const sidecarFiles = copyAgentSidecarFiles(sourceAgentPath, agentSidecarDir, yamlPath);
+          // Copy sidecar files (preserve existing, add new)
+          const sidecarResult = copyAgentSidecarFiles(sourceAgentPath, agentSidecarDir, yamlPath);
 
-          console.log(chalk.dim(`  Copied sidecar to: ${agentSidecarDir}`));
+          if (sidecarResult.copied.length > 0) {
+            console.log(chalk.dim(`  Copied ${sidecarResult.copied.length} new sidecar file(s) to: ${agentSidecarDir}`));
+          }
+          if (sidecarResult.preserved.length > 0) {
+            console.log(chalk.dim(`  Preserved ${sidecarResult.preserved.length} existing sidecar file(s)`));
+          }
         }
 
         // Remove the source YAML file - we can regenerate from installer source if needed
@@ -2645,8 +2650,12 @@ If AgentVibes party mode is enabled, immediately trigger TTS with agent's voice:
             const agentSidecarDir = path.join(resolvedSidecarFolder, finalAgentName);
             await fs.ensureDir(agentSidecarDir);
 
-            // Find and copy sidecar folder
-            const sidecarFiles = copyAgentSidecarFiles(agent.path, agentSidecarDir, agent.yamlFile);
+            // Copy sidecar files (preserve existing, add new)
+            const sidecarResult = copyAgentSidecarFiles(agent.path, agentSidecarDir, agent.yamlFile);
+
+            if (sidecarResult.copied.length > 0 || sidecarResult.preserved.length > 0) {
+              console.log(chalk.dim(`  Sidecar: ${sidecarResult.copied.length} new, ${sidecarResult.preserved.length} preserved`));
+            }
           }
 
           // Update manifest CSV
diff --git a/tools/cli/installers/lib/modules/manager.js b/tools/cli/installers/lib/modules/manager.js
index 70e07f6a..b9252370 100644
--- a/tools/cli/installers/lib/modules/manager.js
+++ b/tools/cli/installers/lib/modules/manager.js
@@ -750,10 +750,16 @@ class ModuleManager {
           const agentSidecarDir = path.join(resolvedSidecarFolder, agentName);
           await fs.ensureDir(agentSidecarDir);
 
-          // Copy sidecar files
-          const sidecarFiles = copyAgentSidecarFiles(path.dirname(sourceYamlPath), agentSidecarDir, sourceYamlPath);
+          // Copy sidecar files (preserve existing, add new)
+          const sidecarResult = copyAgentSidecarFiles(path.dirname(sourceYamlPath), agentSidecarDir, sourceYamlPath);
+          const totalFiles = sidecarResult.copied.length + sidecarResult.preserved.length;
 
-          console.log(chalk.dim(`    Copied sidecar to: ${agentSidecarDir}`));
+          if (sidecarResult.copied.length > 0) {
+            console.log(chalk.dim(`    Copied ${sidecarResult.copied.length} new sidecar file(s) to: ${agentSidecarDir}`));
+          }
+          if (sidecarResult.preserved.length > 0) {
+            console.log(chalk.dim(`    Preserved ${sidecarResult.preserved.length} existing sidecar file(s)`));
+          }
         }
 
         console.log(
diff --git a/tools/cli/lib/agent/installer.js b/tools/cli/lib/agent/installer.js
index 9f11b588..d79abd23 100644
--- a/tools/cli/lib/agent/installer.js
+++ b/tools/cli/lib/agent/installer.js
@@ -337,6 +337,7 @@ function copySidecarFiles(sourceDir, targetDir, excludeYaml) {
  */
 function copyAgentSidecarFiles(sourceDir, targetSidecarDir, excludeYaml) {
   const copied = [];
+  const preserved = [];
 
   // Find folders with "sidecar" in the name
   const entries = fs.readdirSync(sourceDir, { withFileTypes: true });
@@ -345,31 +346,42 @@ function copyAgentSidecarFiles(sourceDir, targetSidecarDir, excludeYaml) {
     if (entry.isDirectory() && entry.name.toLowerCase().includes('sidecar')) {
       const sidecarSourcePath = path.join(sourceDir, entry.name);
 
-      // Recursively copy the sidecar folder contents
-      function copySidecarDir(src, dest) {
+      // Recursively sync the sidecar folder contents (preserve existing, add new)
+      function syncSidecarDir(src, dest) {
         if (!fs.existsSync(dest)) {
           fs.mkdirSync(dest, { recursive: true });
         }
 
-        const sidecarEntries = fs.readdirSync(src, { withFileTypes: true });
-        for (const sidecarEntry of sidecarEntries) {
-          const srcPath = path.join(src, sidecarEntry.name);
-          const destPath = path.join(dest, sidecarEntry.name);
+        // Get all files in source
+        const sourceEntries = fs.readdirSync(src, { withFileTypes: true });
 
-          if (sidecarEntry.isDirectory()) {
-            copySidecarDir(srcPath, destPath);
+        for (const sourceEntry of sourceEntries) {
+          const srcPath = path.join(src, sourceEntry.name);
+          const destPath = path.join(dest, sourceEntry.name);
+
+          if (sourceEntry.isDirectory()) {
+            // Recursively sync subdirectories
+            syncSidecarDir(srcPath, destPath);
           } else {
-            fs.copyFileSync(srcPath, destPath);
-            copied.push(destPath);
+            // Check if file already exists in destination
+            if (fs.existsSync(destPath)) {
+              // File exists - preserve it
+              preserved.push(destPath);
+            } else {
+              // File doesn't exist - copy it
+              fs.copyFileSync(srcPath, destPath);
+              copied.push(destPath);
+            }
           }
         }
       }
 
-      copySidecarDir(sidecarSourcePath, targetSidecarDir);
+      syncSidecarDir(sidecarSourcePath, targetSidecarDir);
     }
   }
 
-  return copied;
+  // Return info about what was preserved and what was copied
+  return { copied, preserved };
 }
 
 /**