fix(auth): harden shared-context isolation and config safety

README.md

@@ -59,7 +59,7 @@ Want to run the dashboard in Docker? See `docker/README.md`.
 
 The dashboard provides visual management for all account types:
 
-- **Claude Accounts**: Create isolated instances (work, personal, client)
+- **Claude Accounts**: Isolation-first by default (work, personal, client), with explicit shared context opt-in
 - **OAuth Providers**: One-click auth for Gemini, Codex, Antigravity, Kiro, Copilot
 - **API Profiles**: Configure GLM, Kimi with your keys
 - **Health Monitor**: Real-time status across all profiles
@@ -221,17 +221,45 @@ ccs work "implement feature"    # Terminal 1
 ccs  "review code"              # Terminal 2 (personal account)
 ```
 
-Need continuity between two accounts for the same project? Opt in to shared context:
+#### Account Context Modes (Isolation-First)
+
+Account profiles are isolated by default.
+
+| Mode | Default | Requirements |
+|------|---------|--------------|
+| `isolated` | Yes | No `context_group` required |
+| `shared` | No (explicit opt-in) | Valid non-empty `context_group` |
+
+Opt in to shared context when needed:
 
 ```bash
 # Share context with default group
 ccs auth create backup --share-context
 
-# Or isolate by named group (only accounts in this group share context)
+# Share context only within named group
 ccs auth create backup2 --context-group sprint-a
 ```
 
-Isolation remains the default. Shared context only links project workspace data; credentials stay per-account.
+Shared mode metadata in `~/.ccs/config.yaml`:
+
+```yaml
+accounts:
+  work:
+    created: "2026-02-24T00:00:00.000Z"
+    last_used: null
+    context_mode: "shared"
+    context_group: "team-alpha"
+```
+
+`context_group` rules:
+
+- lowercase letters, numbers, `_`, `-`
+- must start with a letter
+- max length `64`
+- non-empty after normalization
+- normalized by trim + lowercase + whitespace collapse (`" Team Alpha "` -> `"team-alpha"`)
+
+Shared context links project workspace data only. Credentials remain isolated per account.
 
 <br>
 

docs/codebase-summary.md

@@ -1,8 +1,8 @@
 # CCS Codebase Summary
 
-Last Updated: 2026-02-04
+Last Updated: 2026-02-24
 
-Comprehensive overview of the modularized CCS codebase structure following the Phase 9 modularization effort (Settings, Analytics, Auth Monitor splits + Test Infrastructure), v7.1 Remote CLIProxy feature, v7.2 Kiro + GitHub Copilot (ghcp) OAuth providers, v7.14 Hybrid Quota Management, and v7.34 Image Analysis Hook.
+Comprehensive overview of the modularized CCS codebase structure following the Phase 9 modularization effort (Settings, Analytics, Auth Monitor splits + Test Infrastructure), v7.1 Remote CLIProxy feature, v7.2 Kiro + GitHub Copilot (ghcp) OAuth providers, v7.14 Hybrid Quota Management, v7.34 Image Analysis Hook, and account-context validation hardening.
 
 ## Repository Structure
 
@@ -201,6 +201,19 @@ src/
 | Services | `web-server/`, `api/` | HTTP server, API services |
 | Utilities | `utils/`, `management/` | Helpers, diagnostics |
 
+### Account Context Metadata Flow
+
+- Source fields: `accounts.<name>.context_mode` and `accounts.<name>.context_group` in `~/.ccs/config.yaml`.
+- Runtime policy resolver: `src/auth/account-context.ts`.
+- Metadata storage normalization: `src/auth/profile-registry.ts`.
+- API write validation: `PUT /api/config` in `src/web-server/routes/config-routes.ts`.
+- Rules:
+  - mode is isolation-first (`isolated` default, `shared` opt-in)
+  - shared mode requires non-empty valid `context_group`
+  - `context_group` is normalized (trim + lowercase + whitespace collapse to `-`)
+  - API route rejects `context_group` when mode is not `shared`
+  - registry normalization drops malformed persisted `context_group` values
+
 ### Target Adapter Module
 
 The targets module provides an extensible interface for dispatching profiles to different CLI implementations.

docs/dashboard-auth-cli.md

@@ -1,6 +1,6 @@
 # Dashboard Authentication CLI
 
-Last Updated: 2026-02-04
+Last Updated: 2026-02-24
 
 CLI commands for managing CCS dashboard authentication.
 
@@ -10,6 +10,35 @@ The CCS dashboard (`ccs config`) can be protected with username/password authent
 
 Authentication is **disabled by default** for backward compatibility. Use the CLI to configure and enable it.
 
+## Account Context Modes (Related Feature)
+
+Dashboard auth and account context metadata are separate:
+
+- `dashboard_auth`: protects dashboard access with username/password
+- `accounts.<name>.context_mode/context_group`: controls isolated vs shared account context
+
+Account context is isolation-first:
+
+| Mode | Default | Requirement |
+|------|---------|-------------|
+| `isolated` | Yes | No `context_group` required |
+| `shared` | No (opt-in) | Valid non-empty `context_group` |
+
+`context_group` normalization and validation:
+
+- trim + lowercase + collapse internal whitespace to `-`
+- allowed characters: lowercase letters, numbers, `_`, `-`
+- must start with a letter
+- max length: 64
+- shared mode requires non-empty value after normalization
+
+`PUT /api/config` behavior for account context:
+
+- rejects invalid unified payloads
+- rejects explicit `context_mode: shared` with invalid/empty `context_group`
+- normalizes valid shared `context_group` before save
+- rejects `context_group` when mode is not `shared`
+
 ## Commands
 
 ### `ccs config auth setup`
@@ -162,6 +191,10 @@ export CCS_DASHBOARD_PASSWORD_HASH='$2b$10$...'
 
 Check `session_timeout_hours` in config. Default is 24 hours.
 
+### "Invalid ... context_group ..."
+
+This error comes from `PUT /api/config` when an account explicitly sets shared mode with an invalid group. Use a canonical group value (for example: `team-alpha`).
+
 ## See Also
 
 - [Dashboard Auth Feature](https://ccs.kaitran.ca/features/dashboard-auth) - Full documentation

src/auth/account-context.ts

@@ -38,7 +38,7 @@ const CONTEXT_GROUP_PATTERN = /^[a-zA-Z][a-zA-Z0-9_-]*$/;
  * Normalize context group names so paths and config stay consistent.
  */
 export function normalizeContextGroupName(value: string): string {
-  return value.trim().toLowerCase();
+  return value.trim().toLowerCase().replace(/\s+/g, '-');
 }
 
 /**

src/auth/auth-commands.ts

@@ -14,6 +14,7 @@
 import ProfileRegistry from './profile-registry';
 import { InstanceManager } from '../management/instance-manager';
 import { initUI, header, subheader, color, dim, warn, fail } from '../utils/ui';
+import { MAX_CONTEXT_GROUP_LENGTH } from './account-context';
 import packageJson from '../../package.json';
 
 // Import command handlers from modular structure
@@ -127,6 +128,10 @@ class AuthCommands {
     console.log(
       `  Account profiles stay isolated unless you opt in with ${color('--share-context', 'command')}.`
     );
+    console.log(`  Shared context groups are normalized (trim + lowercase) and spaces become "-".`);
+    console.log(
+      `  ${color('context_group', 'path')} must be non-empty and <= ${MAX_CONTEXT_GROUP_LENGTH} chars in shared mode.`
+    );
     console.log('');
   }
 

src/auth/commands/create-command-env.ts

@@ -0,0 +1,57 @@
+const AMBIENT_PROVIDER_PREFIXES = [
+  'ANTHROPIC_',
+  'OPENAI_',
+  'GOOGLE_',
+  'GEMINI_',
+  'MINIMAX_',
+  'QWEN_',
+  'DEEPSEEK_',
+  'KIMI_',
+  'AZURE_',
+  'OLLAMA_',
+  'OPENROUTER_',
+  'XAI_',
+  'MISTRAL_',
+  'COHERE_',
+  'PERPLEXITY_',
+  'TOGETHER_',
+  'FIREWORKS_',
+];
+const AMBIENT_PROVIDER_EXACT_KEYS = new Set([
+  'OPENROUTER_API_KEY',
+  'OPENROUTER_KEY',
+  'XAI_API_KEY',
+  'MISTRAL_API_KEY',
+  'COHERE_API_KEY',
+]);
+const AMBIENT_PROVIDER_SUFFIXES = [
+  '_API_KEY',
+  '_AUTH_TOKEN',
+  '_ACCESS_TOKEN',
+  '_SECRET_KEY',
+  '_API_TOKEN',
+  '_BEARER_TOKEN',
+  '_SESSION_TOKEN',
+];
+
+export function stripAmbientProviderCredentials(env: NodeJS.ProcessEnv): NodeJS.ProcessEnv {
+  const sanitized: NodeJS.ProcessEnv = { ...env };
+
+  for (const envKey of Object.keys(sanitized)) {
+    const normalizedKey = envKey.toUpperCase();
+
+    if (normalizedKey === 'CLAUDE_CONFIG_DIR') {
+      continue;
+    }
+
+    if (
+      AMBIENT_PROVIDER_PREFIXES.some((prefix) => normalizedKey.startsWith(prefix)) ||
+      AMBIENT_PROVIDER_EXACT_KEYS.has(normalizedKey) ||
+      AMBIENT_PROVIDER_SUFFIXES.some((suffix) => normalizedKey.endsWith(suffix))
+    ) {
+      delete sanitized[envKey];
+    }
+  }
+
+  return sanitized;
+}

src/auth/commands/create-command.ts

@@ -20,52 +20,12 @@ import {
 import { exitWithError } from '../../errors';
 import { ExitCode } from '../../errors/exit-codes';
 import { CommandContext, parseArgs } from './types';
+import { stripAmbientProviderCredentials } from './create-command-env';
 
 function sanitizeProfileNameForInstance(name: string): string {
   return name.replace(/[^a-zA-Z0-9_-]/g, '-').toLowerCase();
 }
 
-const AMBIENT_PROVIDER_PREFIXES = [
-  'ANTHROPIC_',
-  'OPENAI_',
-  'GOOGLE_',
-  'GEMINI_',
-  'MINIMAX_',
-  'QWEN_',
-  'DEEPSEEK_',
-  'KIMI_',
-  'AZURE_',
-  'OLLAMA_',
-];
-const AMBIENT_PROVIDER_EXACT_KEYS = new Set([
-  'OPENROUTER_API_KEY',
-  'OPENROUTER_KEY',
-  'XAI_API_KEY',
-  'MISTRAL_API_KEY',
-  'COHERE_API_KEY',
-]);
-const AMBIENT_PROVIDER_SUFFIXES = ['_API_KEY', '_AUTH_TOKEN', '_ACCESS_TOKEN', '_SECRET_KEY'];
-
-function stripAmbientProviderCredentials(env: NodeJS.ProcessEnv): NodeJS.ProcessEnv {
-  const sanitized: NodeJS.ProcessEnv = { ...env };
-
-  for (const envKey of Object.keys(sanitized)) {
-    if (envKey === 'CLAUDE_CONFIG_DIR') {
-      continue;
-    }
-
-    if (
-      AMBIENT_PROVIDER_PREFIXES.some((prefix) => envKey.startsWith(prefix)) ||
-      AMBIENT_PROVIDER_EXACT_KEYS.has(envKey) ||
-      AMBIENT_PROVIDER_SUFFIXES.some((suffix) => envKey.endsWith(suffix))
-    ) {
-      delete sanitized[envKey];
-    }
-  }
-
-  return sanitized;
-}
-
 /**
  * Handle the create command
  */
@@ -74,9 +34,14 @@ export async function handleCreate(ctx: CommandContext, args: string[]): Promise
   const { profileName, force, shareContext, contextGroup, unknownFlags } = parseArgs(args);
 
   if (unknownFlags && unknownFlags.length > 0) {
-    const unknownList = unknownFlags.join(', ');
+    const unknownList = unknownFlags.map((flag) => `"${flag}"`).join(', ');
     console.log(fail(`Unknown option(s): ${unknownList}`));
     console.log('');
+    console.log(
+      `Usage: ${color('ccs auth create <profile> [--force] [--share-context] [--context-group <name>]', 'command')}`
+    );
+    console.log(`Help:  ${color('ccs auth --help', 'command')}`);
+    console.log('');
     exitWithError(`Unknown option(s): ${unknownList}`, ExitCode.PROFILE_ERROR);
   }
 
@@ -135,15 +100,17 @@ export async function handleCreate(ctx: CommandContext, args: string[]): Promise
   const contextPolicy = resolvedContext.policy;
   const contextMetadata = policyToAccountContextMetadata(contextPolicy);
   const useUnifiedConfig = isUnifiedMode();
-  const createdProfile = useUnifiedConfig ? !existsUnified : !existsLegacy;
+  const profileExistedBeforeCreate = existsLegacy || existsUnified;
-  const previousLegacyProfile: ProfileMetadata | undefined =
+  const createdUnifiedProfile = useUnifiedConfig && !existsUnified;
-    !useUnifiedConfig && existsLegacy ? ctx.registry.getProfile(profileName) : undefined;
+  const createdLegacyProfile = !useUnifiedConfig && !existsLegacy;
-  const previousUnifiedProfile =
+  const previousLegacyProfile: ProfileMetadata | undefined = existsLegacy
-    useUnifiedConfig && existsUnified
+    ? ctx.registry.getProfile(profileName)
-      ? ctx.registry.getAllAccountsUnified()[profileName]
+    : undefined;
-      : undefined;
+  const previousUnifiedProfile = existsUnified
+    ? ctx.registry.getAllAccountsUnified()[profileName]
+    : undefined;
   const previousContextPolicy =
-    !createdProfile && (previousUnifiedProfile || previousLegacyProfile)
+    profileExistedBeforeCreate && (previousUnifiedProfile || previousLegacyProfile)
       ? resolveAccountContextPolicy(previousUnifiedProfile || previousLegacyProfile)
       : undefined;
 
@@ -160,22 +127,21 @@ export async function handleCreate(ctx: CommandContext, args: string[]): Promise
   const rollbackMetadata = (): void => {
     try {
       if (useUnifiedConfig) {
-        if (createdProfile) {
+        if (createdUnifiedProfile) {
           if (ctx.registry.hasAccountUnified(profileName)) {
             ctx.registry.removeAccountUnified(profileName);
           }
         } else if (previousUnifiedProfile) {
           ctx.registry.updateAccountUnified(profileName, previousUnifiedProfile);
         }
-        return;
+      } else {
-      }
+        if (createdLegacyProfile) {
-
+          if (ctx.registry.hasProfile(profileName)) {
-      if (createdProfile) {
+            ctx.registry.deleteProfile(profileName);
-        if (ctx.registry.hasProfile(profileName)) {
+          }
-          ctx.registry.deleteProfile(profileName);
+        } else if (previousLegacyProfile) {
+          ctx.registry.updateProfile(profileName, previousLegacyProfile);
         }
-      } else if (previousLegacyProfile) {
-        ctx.registry.updateProfile(profileName, previousLegacyProfile);
       }
     } catch {
       // Best-effort rollback to avoid leaving stale accounts after failed login.
@@ -190,7 +156,7 @@ export async function handleCreate(ctx: CommandContext, args: string[]): Promise
 
     rollbackMetadata();
 
-    if (createdProfile) {
+    if (!profileExistedBeforeCreate) {
       try {
         ctx.instanceMgr.deleteInstance(profileName);
       } catch {

src/auth/profile-registry.ts

@@ -8,6 +8,7 @@ import {
 } from '../config/unified-config-loader';
 import type { AccountConfig } from '../config/unified-config-types';
 import { getCcsDir } from '../utils/config-manager';
+import { isValidContextGroupName, normalizeContextGroupName } from './account-context';
 
 /**
  * Profile Registry (Simplified)
@@ -51,13 +52,31 @@ export class ProfileRegistry {
     this.profilesPath = path.join(getCcsDir(), 'profiles.json');
   }
 
+  private normalizeContextGroupValue(value: unknown): string | undefined {
+    if (typeof value !== 'string') {
+      return undefined;
+    }
+
+    const normalized = normalizeContextGroupName(value);
+    if (normalized.length === 0 || !isValidContextGroupName(normalized)) {
+      return undefined;
+    }
+
+    return normalized;
+  }
+
   private normalizeLegacyProfileMetadata(metadata: ProfileMetadata): ProfileMetadata {
     const normalized: ProfileMetadata = { ...metadata };
 
     if (normalized.context_mode !== 'shared') {
       delete normalized.context_group;
-    } else if (!normalized.context_group || normalized.context_group.trim().length === 0) {
+    } else {
-      delete normalized.context_group;
+      const normalizedGroup = this.normalizeContextGroupValue(normalized.context_group);
+      if (normalizedGroup) {
+        normalized.context_group = normalizedGroup;
+      } else {
+        delete normalized.context_group;
+      }
     }
 
     return normalized;
@@ -68,8 +87,13 @@ export class ProfileRegistry {
 
     if (normalized.context_mode !== 'shared') {
       delete normalized.context_group;
-    } else if (!normalized.context_group || normalized.context_group.trim().length === 0) {
+    } else {
-      delete normalized.context_group;
+      const normalizedGroup = this.normalizeContextGroupValue(normalized.context_group);
+      if (normalizedGroup) {
+        normalized.context_group = normalizedGroup;
+      } else {
+        delete normalized.context_group;
+      }
     }
 
     return normalized;

src/management/instance-manager.ts

@@ -8,8 +8,8 @@
 
 import * as fs from 'fs';
 import * as path from 'path';
-import { createHash } from 'crypto';
 import SharedManager from './shared-manager';
+import ProfileContextSyncLock from './profile-context-sync-lock';
 import { AccountContextPolicy, DEFAULT_ACCOUNT_CONTEXT_MODE } from '../auth/account-context';
 import { getCcsDir } from '../utils/config-manager';
 
@@ -18,13 +18,13 @@ import { getCcsDir } from '../utils/config-manager';
  */
 class InstanceManager {
   private readonly instancesDir: string;
-  private readonly locksDir: string;
   private readonly sharedManager: SharedManager;
+  private readonly contextSyncLock: ProfileContextSyncLock;
 
   constructor() {
     this.instancesDir = path.join(getCcsDir(), 'instances');
-    this.locksDir = path.join(this.instancesDir, '.locks');
     this.sharedManager = new SharedManager();
+    this.contextSyncLock = new ProfileContextSyncLock(this.instancesDir);
   }
 
   /**
@@ -37,7 +37,7 @@ class InstanceManager {
     const instancePath = this.getInstancePath(profileName);
 
     // Serialize context sync operations per profile across processes.
-    await this.withContextSyncLock(profileName, async () => {
+    await this.contextSyncLock.withLock(profileName, async () => {
       // Lazy initialization
       if (!fs.existsSync(instancePath)) {
         this.initializeInstance(profileName, instancePath);
@@ -201,100 +201,6 @@ class InstanceManager {
     // Replace unsafe characters with dash
     return name.replace(/[^a-zA-Z0-9_-]/g, '-').toLowerCase();
   }
-
-  private getContextSyncLockPath(profileName: string): string {
-    const safeName = this.sanitizeName(profileName);
-    // Keep lock filenames deterministic while preventing normalized-name collisions.
-    const profileHash = createHash('sha1').update(profileName).digest('hex').slice(0, 8);
-    return path.join(this.locksDir, `${safeName}-${profileHash}.lock`);
-  }
-
-  private isProcessAlive(pid: number): boolean {
-    if (!Number.isInteger(pid) || pid <= 0) {
-      return false;
-    }
-
-    try {
-      process.kill(pid, 0);
-      return true;
-    } catch (error) {
-      if ((error as NodeJS.ErrnoException).code === 'EPERM') {
-        return true;
-      }
-      return false;
-    }
-  }
-
-  private tryRemoveDeadOwnerLock(lockPath: string): boolean {
-    try {
-      const lockContent = fs.readFileSync(lockPath, 'utf8').trim();
-      const lockPid = Number.parseInt(lockContent, 10);
-      if (!this.isProcessAlive(lockPid)) {
-        fs.unlinkSync(lockPath);
-        return true;
-      }
-    } catch {
-      // Best-effort stale lock cleanup.
-    }
-    return false;
-  }
-
-  private async withContextSyncLock<T>(
-    profileName: string,
-    callback: () => Promise<T>
-  ): Promise<T> {
-    const lockPath = this.getContextSyncLockPath(profileName);
-    const retryDelayMs = 50;
-    const staleLockMs = 30000;
-    const timeoutMs = staleLockMs + 5000;
-    const start = Date.now();
-
-    fs.mkdirSync(this.locksDir, { recursive: true, mode: 0o700 });
-
-    while (true) {
-      try {
-        const fd = fs.openSync(lockPath, 'wx', 0o600);
-        fs.writeFileSync(fd, `${process.pid}`);
-        fs.closeSync(fd);
-        break;
-      } catch (error) {
-        const err = error as NodeJS.ErrnoException;
-        if (err.code !== 'EEXIST') {
-          throw error;
-        }
-
-        try {
-          const lockStats = fs.statSync(lockPath);
-          if (Date.now() - lockStats.mtimeMs > staleLockMs) {
-            fs.unlinkSync(lockPath);
-            continue;
-          }
-
-          if (this.tryRemoveDeadOwnerLock(lockPath)) {
-            continue;
-          }
-        } catch {
-          // Best-effort stale lock cleanup.
-        }
-
-        if (Date.now() - start > timeoutMs) {
-          throw new Error(`Timed out waiting for profile context lock: ${profileName}`);
-        }
-
-        await new Promise((resolve) => setTimeout(resolve, retryDelayMs));
-      }
-    }
-
-    try {
-      return await callback();
-    } finally {
-      try {
-        fs.unlinkSync(lockPath);
-      } catch {
-        // Best-effort cleanup.
-      }
-    }
-  }
 }
 
 export { InstanceManager };

src/management/profile-context-sync-lock.ts

@@ -0,0 +1,177 @@
+import * as fs from 'fs';
+import * as path from 'path';
+import { createHash } from 'crypto';
+
+interface ContextSyncLockPayload {
+  version: 1;
+  pid: number;
+  nonce: string;
+  acquiredAtMs: number;
+}
+
+interface ContextSyncLockSnapshot {
+  raw: string;
+  owner: { pid: number; nonce?: string } | null;
+}
+
+class ProfileContextSyncLock {
+  private readonly locksDir: string;
+
+  constructor(instancesDir: string) {
+    this.locksDir = path.join(instancesDir, '.locks');
+  }
+
+  private sanitizeName(name: string): string {
+    return name.replace(/[^a-zA-Z0-9_-]/g, '-').toLowerCase();
+  }
+
+  private getLockPath(profileName: string): string {
+    const safeName = this.sanitizeName(profileName);
+    const profileHash = createHash('sha1').update(profileName).digest('hex').slice(0, 8);
+    return path.join(this.locksDir, `${safeName}-${profileHash}.lock`);
+  }
+
+  private isProcessAlive(pid: number): boolean {
+    if (!Number.isInteger(pid) || pid <= 0) {
+      return false;
+    }
+
+    try {
+      process.kill(pid, 0);
+      return true;
+    } catch (error) {
+      if ((error as NodeJS.ErrnoException).code === 'EPERM') {
+        return true;
+      }
+      return false;
+    }
+  }
+
+  private parseContextSyncLock(raw: string): { pid: number; nonce?: string } | null {
+    const trimmed = raw.trim();
+    if (trimmed.length === 0) {
+      return null;
+    }
+
+    try {
+      const parsed = JSON.parse(trimmed) as Partial<ContextSyncLockPayload>;
+      if (typeof parsed.pid === 'number' && Number.isInteger(parsed.pid) && parsed.pid > 0) {
+        const nonce =
+          typeof parsed.nonce === 'string' && parsed.nonce.length > 0 ? parsed.nonce : undefined;
+        return { pid: parsed.pid, nonce };
+      }
+    } catch {
+      const legacyPid = Number.parseInt(trimmed, 10);
+      if (Number.isInteger(legacyPid) && legacyPid > 0) {
+        return { pid: legacyPid };
+      }
+    }
+
+    return null;
+  }
+
+  private readContextSyncLockSnapshot(lockPath: string): ContextSyncLockSnapshot | null {
+    try {
+      const raw = fs.readFileSync(lockPath, 'utf8');
+      return {
+        raw,
+        owner: this.parseContextSyncLock(raw),
+      };
+    } catch (error) {
+      if ((error as NodeJS.ErrnoException).code === 'ENOENT') {
+        return null;
+      }
+      return null;
+    }
+  }
+
+  private tryRemoveLockIfUnchanged(lockPath: string, expectedRaw: string): boolean {
+    try {
+      const currentRaw = fs.readFileSync(lockPath, 'utf8');
+      if (currentRaw !== expectedRaw) {
+        return false;
+      }
+      fs.unlinkSync(lockPath);
+      return true;
+    } catch {
+      return false;
+    }
+  }
+
+  private tryRemoveDeadOwnerLock(lockPath: string, snapshot: ContextSyncLockSnapshot): boolean {
+    if (!snapshot.owner || this.isProcessAlive(snapshot.owner.pid)) {
+      return false;
+    }
+
+    return this.tryRemoveLockIfUnchanged(lockPath, snapshot.raw);
+  }
+
+  async withLock<T>(profileName: string, callback: () => Promise<T>): Promise<T> {
+    const lockPath = this.getLockPath(profileName);
+    const retryDelayMs = 50;
+    const staleLockMs = 30000;
+    const timeoutMs = staleLockMs + 5000;
+    const start = Date.now();
+    const ownerPayload: ContextSyncLockPayload = {
+      version: 1,
+      pid: process.pid,
+      nonce: createHash('sha1')
+        .update(`${process.pid}:${Date.now()}:${Math.random()}`)
+        .digest('hex')
+        .slice(0, 16),
+      acquiredAtMs: Date.now(),
+    };
+    const ownerPayloadRaw = JSON.stringify(ownerPayload);
+
+    fs.mkdirSync(this.locksDir, { recursive: true, mode: 0o700 });
+
+    while (true) {
+      try {
+        const fd = fs.openSync(lockPath, 'wx', 0o600);
+        fs.writeFileSync(fd, ownerPayloadRaw, 'utf8');
+        fs.closeSync(fd);
+        break;
+      } catch (error) {
+        const err = error as NodeJS.ErrnoException;
+        if (err.code !== 'EEXIST') {
+          throw error;
+        }
+
+        const lockSnapshot = this.readContextSyncLockSnapshot(lockPath);
+        if (lockSnapshot) {
+          if (this.tryRemoveDeadOwnerLock(lockPath, lockSnapshot)) {
+            continue;
+          }
+
+          // For malformed lock payloads, fall back to age-based stale cleanup.
+          if (!lockSnapshot.owner) {
+            try {
+              const lockStats = fs.statSync(lockPath);
+              if (Date.now() - lockStats.mtimeMs > staleLockMs) {
+                if (this.tryRemoveLockIfUnchanged(lockPath, lockSnapshot.raw)) {
+                  continue;
+                }
+              }
+            } catch {
+              // Best-effort stale lock cleanup.
+            }
+          }
+        }
+
+        if (Date.now() - start > timeoutMs) {
+          throw new Error(`Timed out waiting for profile context lock: ${profileName}`);
+        }
+
+        await new Promise((resolve) => setTimeout(resolve, retryDelayMs));
+      }
+    }
+
+    try {
+      return await callback();
+    } finally {
+      this.tryRemoveLockIfUnchanged(lockPath, ownerPayloadRaw);
+    }
+  }
+}
+
+export default ProfileContextSyncLock;

src/management/shared-manager.ts

@@ -63,8 +63,14 @@ class SharedManager {
       const resolvedTarget = path.resolve(path.dirname(target), targetLink);
 
       // Check if target points back to our shared dir or link path
-      const sharedDir = path.join(getCcsDir(), 'shared');
+      const sharedDir = this.resolveCanonicalPath(path.join(getCcsDir(), 'shared'));
-      if (resolvedTarget.startsWith(sharedDir) || resolvedTarget === linkPath) {
+      const canonicalResolvedTarget = this.resolveCanonicalPath(resolvedTarget);
+      const canonicalLinkPath = this.resolveCanonicalPath(linkPath);
+
+      if (
+        this.isPathWithinDirectory(canonicalResolvedTarget, sharedDir) ||
+        canonicalResolvedTarget === canonicalLinkPath
+      ) {
         console.log(warn(`Circular symlink detected: ${target} → ${resolvedTarget}`));
         return true;
       }
@@ -692,17 +698,17 @@ class SharedManager {
    * Guard project merge operations to known CCS-managed roots only.
    */
   private isSafeProjectsMergeSource(sourcePath: string, instanceName: string): boolean {
-    const resolvedSource = path.resolve(sourcePath);
+    const resolvedSource = this.resolveCanonicalPath(sourcePath);
-    const sharedContextRoot = path.resolve(path.join(this.sharedDir, 'context-groups'));
+    const sharedContextRoot = this.resolveCanonicalPath(
-    const instanceProjectsRoot = path.resolve(
+      path.join(this.sharedDir, 'context-groups')
+    );
+    const instanceProjectsRoot = this.resolveCanonicalPath(
       path.join(this.instancesDir, instanceName, 'projects')
     );
 
-    const isWithin = (child: string, root: string): boolean =>
-      child === root || child.startsWith(`${root}${path.sep}`);
-
     return (
-      isWithin(resolvedSource, sharedContextRoot) || isWithin(resolvedSource, instanceProjectsRoot)
+      this.isPathWithinDirectory(resolvedSource, sharedContextRoot) ||
+      this.isPathWithinDirectory(resolvedSource, instanceProjectsRoot)
     );
   }
 
@@ -736,7 +742,7 @@ class SharedManager {
     projectsPath: string,
     instanceName: string
   ): Promise<void> {
-    const sharedMemoryRoot = path.resolve(path.join(this.sharedDir, 'memory'));
+    const sharedMemoryRoot = this.resolveCanonicalPath(path.join(this.sharedDir, 'memory'));
 
     let projectEntries: fs.Dirent[] = [];
     try {
@@ -763,15 +769,20 @@ class SharedManager {
         continue;
       }
 
-      if (!path.resolve(memoryTarget).startsWith(sharedMemoryRoot)) {
+      const canonicalMemoryTarget = this.resolveCanonicalPath(memoryTarget);
+      if (!this.isPathWithinDirectory(canonicalMemoryTarget, sharedMemoryRoot)) {
         continue;
       }
 
       await fs.promises.unlink(memoryPath);
       await this.ensureDirectory(memoryPath);
 
-      if (await this.pathExists(memoryTarget)) {
+      if (await this.pathExists(canonicalMemoryTarget)) {
-        await this.mergeDirectoryWithConflictCopies(memoryTarget, memoryPath, instanceName);
+        await this.mergeDirectoryWithConflictCopies(
+          canonicalMemoryTarget,
+          memoryPath,
+          instanceName
+        );
       }
     }
   }
@@ -879,6 +890,27 @@ class SharedManager {
     return candidate;
   }
 
+  private resolveCanonicalPath(targetPath: string): string {
+    try {
+      return fs.realpathSync.native(targetPath);
+    } catch {
+      return path.resolve(targetPath);
+    }
+  }
+
+  private isPathWithinDirectory(candidatePath: string, rootPath: string): boolean {
+    const normalizeForCompare = (inputPath: string): string => {
+      const resolved = path.resolve(inputPath);
+      return process.platform === 'win32' ? resolved.toLowerCase() : resolved;
+    };
+
+    const normalizedCandidate = normalizeForCompare(candidatePath);
+    const normalizedRoot = normalizeForCompare(rootPath);
+    const relative = path.relative(normalizedRoot, normalizedCandidate);
+
+    return relative === '' || (!relative.startsWith('..') && !path.isAbsolute(relative));
+  }
+
   private async pathExists(targetPath: string): Promise<boolean> {
     try {
       await fs.promises.access(targetPath);

src/web-server/routes/account-routes.ts

@@ -206,25 +206,24 @@ router.delete('/:name', (req: Request, res: Response): void => {
       return;
     }
 
-    // Delete from appropriate config (unified and/or legacy)
+    const existsUnified = isUnifiedMode() && registry.hasAccountUnified(name);
-    let deleted = false;
+    const existsLegacy = registry.hasProfile(name);
-    if (isUnifiedMode() && registry.hasAccountUnified(name)) {
-      registry.removeAccountUnified(name);
-      deleted = true;
-    }
-    if (registry.hasProfile(name)) {
-      registry.deleteProfile(name);
-      deleted = true;
-    }
 
-    if (!deleted) {
+    if (!existsUnified && !existsLegacy) {
       res.status(404).json({ error: `Account not found: ${name}` });
       return;
     }
 
-    // Keep API delete behavior aligned with CLI remove command.
+    // Match CLI remove ordering: delete instance first, metadata second.
     instanceMgr.deleteInstance(name);
 
+    if (existsUnified) {
+      registry.removeAccountUnified(name);
+    }
+    if (existsLegacy) {
+      registry.deleteProfile(name);
+    }
+
     res.json({ success: true, deleted: name });
   } catch (error) {
     res.status(500).json({ error: (error as Error).message });

src/web-server/routes/config-routes.ts

@@ -22,7 +22,7 @@ import { isValidContextGroupName, normalizeContextGroupName } from '../../auth/a
 
 const router = Router();
 
-function validateAccountContextMetadata(config: unknown): string | null {
+function validateAndNormalizeAccountContextMetadata(config: unknown): string | null {
   if (typeof config !== 'object' || config === null) {
     return 'Invalid config payload';
   }
@@ -63,6 +63,15 @@ function validateAccountContextMetadata(config: unknown): string | null {
       if (!isValidContextGroupName(normalizedGroup)) {
         return `Invalid config.accounts.${accountName}.context_group`;
       }
+      account.context_group = normalizedGroup;
+    }
+
+    if (mode === 'shared' && typeof group === 'string' && group.trim().length === 0) {
+      return `Invalid config.accounts.${accountName}.context_group: shared mode requires a non-empty value`;
+    }
+
+    if (mode === 'isolated' && group !== undefined) {
+      delete account.context_group;
     }
   }
 
@@ -130,7 +139,7 @@ router.put('/', (req: Request, res: Response): void => {
     return;
   }
 
-  const accountContextError = validateAccountContextMetadata(config);
+  const accountContextError = validateAndNormalizeAccountContextMetadata(config);
   if (accountContextError) {
     res.status(400).json({ error: accountContextError });
     return;
@@ -150,6 +159,15 @@ router.put('/', (req: Request, res: Response): void => {
 router.post('/migrate', async (req: Request, res: Response): Promise<void> => {
   try {
     const dryRun = req.query.dryRun === 'true';
+    if (!needsMigration()) {
+      res.json({
+        success: true,
+        migratedFiles: [],
+        warnings: [],
+        alreadyMigrated: true,
+      });
+      return;
+    }
     const result = await migrate(dryRun);
     res.json(result);
   } catch (error) {

tests/unit/account-context.test.ts

@@ -40,4 +40,15 @@ describe('account context helpers', () => {
     expect(resolved.mode).toBe('shared');
     expect(resolved.group).toBe('sprint-a');
   });
+
+  it('normalizes whitespace in explicit shared context group names', () => {
+    const result = resolveCreateAccountContext({
+      shareContext: false,
+      contextGroup: ' Team Alpha ',
+    });
+
+    expect(result.error).toBeUndefined();
+    expect(result.policy.mode).toBe('shared');
+    expect(result.policy.group).toBe('team-alpha');
+  });
 });

tests/unit/auth/profile-registry-context-normalization.test.ts

@@ -0,0 +1,92 @@
+import { afterEach, beforeEach, describe, expect, it } from 'bun:test';
+import * as fs from 'fs';
+import * as os from 'os';
+import * as path from 'path';
+import ProfileRegistry from '../../../src/auth/profile-registry';
+
+describe('profile-registry context normalization', () => {
+  let tempHome = '';
+  let originalCcsHome: string | undefined;
+  let originalUnifiedMode: string | undefined;
+
+  beforeEach(() => {
+    tempHome = fs.mkdtempSync(path.join(os.tmpdir(), 'ccs-profile-registry-context-'));
+    originalCcsHome = process.env.CCS_HOME;
+    originalUnifiedMode = process.env.CCS_UNIFIED_CONFIG;
+    process.env.CCS_HOME = tempHome;
+  });
+
+  afterEach(() => {
+    if (originalCcsHome !== undefined) process.env.CCS_HOME = originalCcsHome;
+    else delete process.env.CCS_HOME;
+
+    if (originalUnifiedMode !== undefined) process.env.CCS_UNIFIED_CONFIG = originalUnifiedMode;
+    else delete process.env.CCS_UNIFIED_CONFIG;
+
+    if (tempHome && fs.existsSync(tempHome)) {
+      fs.rmSync(tempHome, { recursive: true, force: true });
+    }
+  });
+
+  it('drops non-string legacy context_group values without throwing', () => {
+    const ccsDir = path.join(tempHome, '.ccs');
+    fs.mkdirSync(ccsDir, { recursive: true });
+    fs.writeFileSync(
+      path.join(ccsDir, 'profiles.json'),
+      JSON.stringify(
+        {
+          version: '2.0.0',
+          default: null,
+          profiles: {
+            work: {
+              type: 'account',
+              created: '2026-02-24T00:00:00.000Z',
+              last_used: null,
+              context_mode: 'shared',
+              context_group: { invalid: true },
+            },
+          },
+        },
+        null,
+        2
+      ),
+      'utf8'
+    );
+
+    const registry = new ProfileRegistry();
+    const profile = registry.getProfile('work');
+
+    expect(profile.context_mode).toBe('shared');
+    expect(profile.context_group).toBeUndefined();
+  });
+
+  it('drops non-string unified context_group values without throwing', () => {
+    process.env.CCS_UNIFIED_CONFIG = '1';
+    const ccsDir = path.join(tempHome, '.ccs');
+    fs.mkdirSync(ccsDir, { recursive: true });
+    fs.writeFileSync(
+      path.join(ccsDir, 'config.yaml'),
+      [
+        'version: 8',
+        'accounts:',
+        '  work:',
+        '    created: "2026-02-24T00:00:00.000Z"',
+        '    last_used: null',
+        '    context_mode: shared',
+        '    context_group: 123',
+        'profiles: {}',
+        'cliproxy:',
+        '  oauth_accounts: {}',
+        '  providers: {}',
+        '  variants: {}',
+      ].join('\n'),
+      'utf8'
+    );
+
+    const registry = new ProfileRegistry();
+    const accounts = registry.getAllAccountsUnified();
+
+    expect(accounts.work.context_mode).toBe('shared');
+    expect(accounts.work.context_group).toBeUndefined();
+  });
+});

tests/unit/shared-context-policy.test.ts

@@ -13,6 +13,12 @@ function getTestCcsDir(): string {
   return path.join(path.resolve(process.env.CCS_HOME), '.ccs');
 }
 
+function createDirectorySymlink(targetPath: string, linkPath: string): void {
+  const symlinkType: 'dir' | 'junction' = process.platform === 'win32' ? 'junction' : 'dir';
+  const linkTarget = process.platform === 'win32' ? path.resolve(targetPath) : targetPath;
+  fs.symlinkSync(linkTarget, linkPath, symlinkType);
+}
+
 describe('SharedManager context policy', () => {
   let tempRoot = '';
   let originalHome: string | undefined;
@@ -134,4 +140,42 @@ describe('SharedManager context policy', () => {
 
     expect(stats.isDirectory() || stats.isSymbolicLink()).toBe(true);
   });
+
+  it('skips merge when projects symlink target is outside canonical CCS roots', async () => {
+    const ccsDir = getTestCcsDir();
+    const instancePath = path.join(ccsDir, 'instances', 'work');
+    const projectsPath = path.join(instancePath, 'projects');
+    const unsafeProjectsPath = path.join(ccsDir, 'shared', 'context-groups-evil', 'projects');
+    const unsafeFile = path.join(unsafeProjectsPath, '-tmp-project', 'notes.md');
+
+    fs.mkdirSync(path.dirname(unsafeFile), { recursive: true });
+    fs.writeFileSync(unsafeFile, 'unsafe source', 'utf8');
+    fs.mkdirSync(instancePath, { recursive: true });
+    createDirectorySymlink(unsafeProjectsPath, projectsPath);
+
+    const manager = new SharedManager();
+    await manager.syncProjectContext(instancePath, { mode: 'isolated' });
+
+    expect(fs.lstatSync(projectsPath).isDirectory()).toBe(true);
+    expect(fs.existsSync(path.join(projectsPath, '-tmp-project', 'notes.md'))).toBe(false);
+  });
+
+  it('does not detach project memory symlink from lookalike shared path prefixes', async () => {
+    const ccsDir = getTestCcsDir();
+    const instancePath = path.join(ccsDir, 'instances', 'work');
+    const projectPath = path.join(instancePath, 'projects', '-tmp-project');
+    const memoryPath = path.join(projectPath, 'memory');
+    const unsafeMemoryTarget = path.join(ccsDir, 'shared', 'memory-evil', '-tmp-project');
+    const unsafeMemoryFile = path.join(unsafeMemoryTarget, 'MEMORY.md');
+
+    fs.mkdirSync(path.dirname(unsafeMemoryFile), { recursive: true });
+    fs.writeFileSync(unsafeMemoryFile, 'unsafe memory', 'utf8');
+    fs.mkdirSync(projectPath, { recursive: true });
+    createDirectorySymlink(unsafeMemoryTarget, memoryPath);
+
+    const manager = new SharedManager();
+    await manager.syncProjectContext(instancePath, { mode: 'isolated' });
+
+    expect(fs.lstatSync(memoryPath).isSymbolicLink()).toBe(true);
+  });
 });

tests/unit/web-server/account-routes-context.test.ts

@@ -5,6 +5,8 @@ import * as os from 'os';
 import * as path from 'path';
 import type { Server } from 'http';
 import accountRoutes from '../../../src/web-server/routes/account-routes';
+import ProfileRegistry from '../../../src/auth/profile-registry';
+import { InstanceManager } from '../../../src/management/instance-manager';
 
 async function getJson<T>(baseUrl: string, routePath: string): Promise<T> {
   const response = await fetch(`${baseUrl}${routePath}`);
@@ -12,6 +14,10 @@ async function getJson<T>(baseUrl: string, routePath: string): Promise<T> {
   return (await response.json()) as T;
 }
 
+async function deletePath(baseUrl: string, routePath: string): Promise<Response> {
+  return fetch(`${baseUrl}${routePath}`, { method: 'DELETE' });
+}
+
 describe('web-server account-routes context normalization', () => {
   let server: Server;
   let baseUrl = '';
@@ -130,4 +136,41 @@ describe('web-server account-routes context normalization', () => {
     expect(work?.context_mode).toBe('shared');
     expect(work?.context_group).toBe('default');
   });
+
+  it('does not delete metadata when instance deletion fails', async () => {
+    const ccsDir = path.join(tempHome, '.ccs');
+    fs.mkdirSync(ccsDir, { recursive: true });
+    fs.writeFileSync(
+      path.join(ccsDir, 'config.yaml'),
+      [
+        'version: 8',
+        'accounts:',
+        '  work:',
+        '    created: "2026-02-01T00:00:00.000Z"',
+        '    last_used: null',
+        '    context_mode: shared',
+        '    context_group: sprint-a',
+        'profiles: {}',
+        'cliproxy:',
+        '  oauth_accounts: {}',
+        '  providers: {}',
+        '  variants: {}',
+      ].join('\n'),
+      'utf8'
+    );
+    const registry = new ProfileRegistry();
+
+    const originalDeleteInstance = InstanceManager.prototype.deleteInstance;
+    InstanceManager.prototype.deleteInstance = () => {
+      throw new Error('simulated instance delete failure');
+    };
+
+    try {
+      const response = await deletePath(baseUrl, '/api/accounts/work');
+      expect(response.status).toBe(500);
+      expect(registry.hasAccountUnified('work')).toBe(true);
+    } finally {
+      InstanceManager.prototype.deleteInstance = originalDeleteInstance;
+    }
+  });
 });

tests/unit/web-server/config-routes-account-context.test.ts

@@ -6,6 +6,7 @@ import * as path from 'path';
 import type { Server } from 'http';
 import configRoutes from '../../../src/web-server/routes/config-routes';
 import { createEmptyUnifiedConfig } from '../../../src/config/unified-config-types';
+import { loadUnifiedConfig } from '../../../src/config/unified-config-loader';
 
 async function putJson(baseUrl: string, routePath: string, body: unknown): Promise<Response> {
   return fetch(`${baseUrl}${routePath}`, {
@@ -17,6 +18,16 @@ async function putJson(baseUrl: string, routePath: string, body: unknown): Promi
   });
 }
 
+async function postJson(baseUrl: string, routePath: string, body?: unknown): Promise<Response> {
+  return fetch(`${baseUrl}${routePath}`, {
+    method: 'POST',
+    headers: {
+      'Content-Type': 'application/json',
+    },
+    body: body === undefined ? undefined : JSON.stringify(body),
+  });
+}
+
 describe('web-server config-routes account context validation', () => {
   let server: Server;
   let baseUrl = '';
@@ -124,6 +135,26 @@ describe('web-server config-routes account context validation', () => {
     expect(payload.error).toContain('context_group');
   });
 
+  it('rejects whitespace-only shared context_group values', async () => {
+    const response = await putJson(baseUrl, '/api/config', {
+      version: 8,
+      accounts: {
+        work: {
+          created: '2026-01-01T00:00:00.000Z',
+          last_used: null,
+          context_mode: 'shared',
+          context_group: '   ',
+        },
+      },
+      profiles: {},
+      cliproxy: { oauth_accounts: {}, providers: [], variants: {} },
+    });
+
+    expect(response.status).toBe(400);
+    const payload = (await response.json()) as { error: string };
+    expect(payload.error).toContain('requires a non-empty value');
+  });
+
   it('accepts valid shared context metadata', async () => {
     const config = createEmptyUnifiedConfig();
     config.accounts.work = {
@@ -137,5 +168,24 @@ describe('web-server config-routes account context validation', () => {
     expect(response.status).toBe(200);
     const payload = (await response.json()) as { success: boolean };
     expect(payload.success).toBe(true);
+
+    const savedConfig = loadUnifiedConfig();
+    expect(savedConfig?.accounts.work.context_group).toBe('sprint-a');
+  });
+
+  it('returns alreadyMigrated when migration is not needed', async () => {
+    const response = await postJson(baseUrl, '/api/config/migrate');
+
+    expect(response.status).toBe(200);
+    const payload = (await response.json()) as {
+      success: boolean;
+      migratedFiles: string[];
+      warnings: string[];
+      alreadyMigrated?: boolean;
+    };
+    expect(payload.success).toBe(true);
+    expect(payload.migratedFiles).toEqual([]);
+    expect(payload.warnings).toEqual([]);
+    expect(payload.alreadyMigrated).toBe(true);
   });
 });