diff --git a/AGENTS.md b/AGENTS.md
index 85aed7e..b4b2129 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -38,6 +38,7 @@ This repository owns the published `@elydora/sdk` package, its `elydora` CLI, lo
 - Avoid compatibility shims without a named public or user configuration contract.
 - Keep private keys and API tokens out of process arguments and generated setup commands. Accept them through hidden terminal input or owner-only credential files.
 - Persist credential-bearing files through owner-only same-directory temporary files and atomic rename.
+- Resolve every agent runtime directory as one physical child of `~/.elydora`; reject separators, traversal segments, and symbolic-link directories before writes.
 
 ## Verification
 
diff --git a/README.md b/README.md
index 4e60b4e..4c41fc7 100644
--- a/README.md
+++ b/README.md
@@ -51,7 +51,7 @@ npx elydora install \
   --kid agent-456-key-v1
 ```
 
-The CLI reads the private key and optional API token through hidden terminal prompts. For non-interactive installation, store each secret in an owner-only file and pass `--private_key_file <path>` and `--token_file <path>`. Secret values are rejected as command-line arguments because process listings and shell history can expose them.
+The CLI reads the private key and optional API token through hidden terminal prompts. For non-interactive installation, store each secret in an owner-only file and pass `--private_key_file <path>` and `--token_file <path>`. Secret values are rejected as command-line arguments because process listings and shell history can expose them. Agent IDs map to one physical directory directly under `~/.elydora`; path separators and traversal segments are rejected.
 
 ### Commands
 
diff --git a/src/cli.ts b/src/cli.ts
index f1d48cf..3a71910 100644
--- a/src/cli.ts
+++ b/src/cli.ts
@@ -4,7 +4,11 @@ import path from 'node:path';
 import os from 'node:os';
 import { resolveInstallSecrets } from './cli-secrets.js';
 import { derivePublicKey } from './crypto.js';
-import { ensurePrivateDirectory, writePrivateFile } from './secure-files.js';
+import {
+  ensurePrivateDirectory,
+  resolvePrivateChildDirectory,
+  writePrivateFile,
+} from './secure-files.js';
 import { SUPPORTED_AGENTS } from './plugins/registry.js';
 import type { AgentPlugin, InstallConfig } from './plugins/base.js';
 import { generateHookScript, generateGuardScript } from './plugins/hook-template.js';
@@ -102,6 +106,7 @@ async function cmdInstall(args: string[]): Promise<void> {
 
   const agentId = values.agent_id;
   if (!agentId) die('--agent_id is required');
+  const agentDir = resolvePrivateChildDirectory(ELYDORA_DIR, agentId);
 
   const kid = values.kid;
   if (!kid) die('--kid is required');
@@ -123,7 +128,6 @@ async function cmdInstall(args: string[]): Promise<void> {
   console.log(`Verifying private key... Public key: ${publicKey.slice(0, 12)}...`);
 
   // Create ~/.elydora/{agentId}/ directory
-  const agentDir = path.join(ELYDORA_DIR, agentId);
   await ensurePrivateDirectory(ELYDORA_DIR);
   await ensurePrivateDirectory(agentDir);
 
@@ -194,6 +198,7 @@ async function cmdUninstall(args: string[]): Promise<void> {
   }
 
   let agentId = values.agent_id;
+  if (agentId) resolvePrivateChildDirectory(ELYDORA_DIR, agentId);
 
   // If --agent_id not provided, scan ~/.elydora/*/config.json for matching agent_name
   if (!agentId) {
@@ -228,12 +233,8 @@ async function cmdUninstall(args: string[]): Promise<void> {
   await plugin.uninstall(agentId);
 
   // Remove entire agent directory
-  const agentDir = path.join(ELYDORA_DIR, agentId);
-  try {
-    await fsp.rm(agentDir, { recursive: true, force: true });
-  } catch {
-    // Already removed
-  }
+  const agentDir = resolvePrivateChildDirectory(ELYDORA_DIR, agentId);
+  await fsp.rm(agentDir, { recursive: true, force: true });
 
   console.log(`Elydora audit hook uninstalled for ${registryEntry.name}.`);
 }
diff --git a/src/secure-files.ts b/src/secure-files.ts
index 9dc19c6..08235e7 100644
--- a/src/secure-files.ts
+++ b/src/secure-files.ts
@@ -8,11 +8,46 @@ function isMissingFile(error: unknown): boolean {
 
 export async function ensurePrivateDirectory(directory: string): Promise<void> {
   await fsp.mkdir(directory, { recursive: true, mode: 0o700 });
+  const metadata = await fsp.lstat(directory);
+  if (!metadata.isDirectory() || metadata.isSymbolicLink()) {
+    throw new Error(`Private directory path is not a physical directory: ${directory}`);
+  }
   if (process.platform !== 'win32') {
     await fsp.chmod(directory, 0o700);
   }
 }
 
+export function resolvePrivateChildDirectory(root: string, childName: string): string {
+  const isWindowsDeviceName = /^(?:con|prn|aux|nul|com[1-9¹²³]|lpt[1-9¹²³])(?:\.|$)/i.test(childName);
+  if (
+    childName.length === 0
+    || /[<>:"|?*\u0000-\u001f]/.test(childName)
+    || childName.includes('/')
+    || childName.includes('\\')
+    || childName === '.'
+    || childName === '..'
+    || childName.endsWith('.')
+    || childName.endsWith(' ')
+    || isWindowsDeviceName
+  ) {
+    throw new Error(`Invalid agent ID for local storage: ${JSON.stringify(childName)}`);
+  }
+
+  const resolvedRoot = path.resolve(root);
+  const candidate = path.resolve(resolvedRoot, childName);
+  const relative = path.relative(resolvedRoot, candidate);
+  if (
+    relative.length === 0
+    || path.isAbsolute(relative)
+    || relative === '..'
+    || relative.startsWith(`..${path.sep}`)
+    || relative.includes(path.sep)
+  ) {
+    throw new Error(`Agent ID escapes the local storage directory: ${JSON.stringify(childName)}`);
+  }
+  return candidate;
+}
+
 export async function writePrivateFile(filePath: string, contents: string): Promise<void> {
   const directory = path.dirname(filePath);
   await ensurePrivateDirectory(directory);
diff --git a/test/cli-security.test.mjs b/test/cli-security.test.mjs
index 897672e..eda1f7a 100644
--- a/test/cli-security.test.mjs
+++ b/test/cli-security.test.mjs
@@ -102,6 +102,38 @@ test('CLI rejects legacy secret arguments before writing files', async () => {
   }
 });
 
+test('CLI rejects agent IDs that escape the credential directory', async () => {
+  const invalidAgentIds = [
+    '../escape',
+    '..\\escape',
+    'C:escape',
+    'agent.',
+    'agent ',
+    'CON',
+    'COM¹.log',
+    '.',
+    '..',
+  ];
+  for (const agentId of invalidAgentIds) {
+    const homeDir = await mkdtemp(path.join(os.tmpdir(), 'elydora-node-cli-'));
+    try {
+      const result = await runCli([
+        'install',
+        '--agent', 'opencode',
+        '--org_id', 'org-1',
+        '--agent_id', agentId,
+        '--kid', 'key-1',
+      ], homeDir);
+
+      assert.equal(result.code, 1);
+      assert.match(result.stderr, /(Invalid agent ID for local storage|Agent ID escapes)/);
+      await assert.rejects(stat(path.join(homeDir, '.elydora')), { code: 'ENOENT' });
+    } finally {
+      await rm(homeDir, { recursive: true, force: true });
+    }
+  }
+});
+
 test('CLI installs from owner-only files and protects persisted credentials', async () => {
   const homeDir = await mkdtemp(path.join(os.tmpdir(), 'elydora-node-cli-'));
   const privateKeyFile = path.join(homeDir, 'private-key');