diff --git a/README.md b/README.md
index 6a91a87a..8b4588e8 100644
--- a/README.md
+++ b/README.md
@@ -279,6 +279,12 @@ ccs auth create backup --share-context
 ccs auth create backup2 --context-group sprint-a
 ```
 
+Update existing accounts without recreating login:
+
+1. Run `ccs config`
+2. Open `Accounts`
+3. Click the pencil icon in Actions and set `isolated` or `shared` mode
+
 Shared mode metadata in `~/.ccs/config.yaml`:
 
 ```yaml
@@ -300,6 +306,8 @@ accounts:
 
 Shared context links project workspace data only. Credentials remain isolated per account.
 
+Technical details: [`docs/session-sharing-technical-analysis.md`](docs/session-sharing-technical-analysis.md)
+
 <br>
 
 ## Maintenance
diff --git a/docs/dashboard-auth-cli.md b/docs/dashboard-auth-cli.md
index 85d1a7ed..b810656f 100644
--- a/docs/dashboard-auth-cli.md
+++ b/docs/dashboard-auth-cli.md
@@ -1,6 +1,6 @@
 # Dashboard Authentication CLI
 
-Last Updated: 2026-02-24
+Last Updated: 2026-02-26
 
 CLI commands for managing CCS dashboard authentication.
 
@@ -39,6 +39,12 @@ Account context is isolation-first:
 - normalizes valid shared `context_group` before save
 - rejects `context_group` when mode is not `shared`
 
+Dashboard accounts context editing:
+
+- `PUT /api/accounts/:name/context` updates context mode/group for existing auth accounts
+- rejects CLIProxy OAuth account keys for this route
+- applies normalization/validation rules above
+
 ## Commands
 
 ### `ccs config auth setup`
diff --git a/docs/session-sharing-technical-analysis.md b/docs/session-sharing-technical-analysis.md
new file mode 100644
index 00000000..93c8b466
--- /dev/null
+++ b/docs/session-sharing-technical-analysis.md
@@ -0,0 +1,70 @@
+# Session Sharing Technical Analysis
+
+Last Updated: 2026-02-26
+
+## Summary
+
+CCS supports practical cross-account continuity by sharing workspace context files between selected accounts, while keeping credentials isolated per account.
+
+This is implemented as a context policy per account:
+
+- `isolated` (default): account keeps its own workspace context
+- `shared`: account workspace context is linked to a shared context group
+
+## Why This Is Safe Enough
+
+CCS only shares workspace context paths (project/session context files). It does **not** merge or copy authentication credentials between accounts.
+
+Credential storage remains per account instance.
+
+## Implementation Model
+
+Account metadata is stored in `~/.ccs/config.yaml`:
+
+```yaml
+accounts:
+  work:
+    created: "2026-02-24T00:00:00.000Z"
+    last_used: null
+    context_mode: "shared"
+    context_group: "team-alpha"
+```
+
+Rules:
+
+- `context_mode` must be `isolated` or `shared`
+- `context_group` is required when `context_mode=shared`
+- group normalization: trim, lowercase, internal spaces -> `-`
+- group must start with a letter and only include `[a-zA-Z0-9_-]`
+- max length: `64`
+
+## User Workflows
+
+### New account with shared context
+
+```bash
+ccs auth create work2 --share-context
+ccs auth create backup --context-group sprint-a
+```
+
+### Existing account
+
+- Open `ccs config`
+- Go to `Accounts`
+- Click the pencil icon (`Edit Context`)
+- Choose `isolated` or `shared` and set group
+
+No account recreation required for this workflow.
+
+## Current Limitations
+
+- Shared context is local filesystem sharing. It does not bypass remote provider permission models.
+- Session continuity still depends on what the upstream tool/provider stores and allows.
+- Context sharing should only be enabled for accounts you intentionally trust to share workspace history.
+
+## Validation Checklist
+
+- Confirm account row shows `shared (<group>)` in Dashboard Accounts table
+- Switch between accounts in the same group and verify workspace continuity
+- Run `ccs doctor` if symlink/context health looks inconsistent
+
diff --git a/src/auth/auth-commands.ts b/src/auth/auth-commands.ts
index 2ed849ee..c94a91c5 100644
--- a/src/auth/auth-commands.ts
+++ b/src/auth/auth-commands.ts
@@ -128,6 +128,9 @@ class AuthCommands {
     console.log(
       `  Account profiles stay isolated unless you opt in with ${color('--share-context', 'command')}.`
     );
+    console.log(
+      `  Existing profiles: open ${color('ccs config', 'command')} -> Accounts -> Edit Context.`
+    );
     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.`
diff --git a/src/commands/help-command.ts b/src/commands/help-command.ts
index 1db7717c..461ea979 100644
--- a/src/commands/help-command.ts
+++ b/src/commands/help-command.ts
@@ -151,6 +151,7 @@ Run ${color('ccs config', 'command')} for web dashboard`.trim();
     [
       ['ccs auth --help', 'Show account management commands'],
       ['ccs auth create <name>', 'Create account profile (supports context sharing flags)'],
+      ['ccs config', 'Dashboard: Accounts table can edit context mode/group'],
       ['ccs auth list', 'List all account profiles'],
       ['ccs auth default <name>', 'Set default profile'],
       ['ccs auth reset-default', 'Restore original CCS default'],
diff --git a/src/web-server/routes/account-routes.ts b/src/web-server/routes/account-routes.ts
index b6ebc359..81d263b6 100644
--- a/src/web-server/routes/account-routes.ts
+++ b/src/web-server/routes/account-routes.ts
@@ -19,7 +19,11 @@ import {
   soloAccount,
 } from '../../cliproxy/account-manager';
 import { isCLIProxyProvider } from '../../cliproxy/provider-capabilities';
-import { resolveAccountContextPolicy } from '../../auth/account-context';
+import {
+  isValidContextGroupName,
+  normalizeContextGroupName,
+  resolveAccountContextPolicy,
+} from '../../auth/account-context';
 import {
   buildCliproxyAccountKey,
   parseCliproxyKey,
@@ -149,6 +153,111 @@ router.post('/default', (req: Request, res: Response): void => {
   }
 });
 
+/**
+ * PUT /api/accounts/:name/context - Update account context mode/group
+ */
+router.put('/:name/context', async (req: Request, res: Response): Promise<void> => {
+  try {
+    const { name } = req.params;
+
+    if (!name) {
+      res.status(400).json({ error: 'Missing account name' });
+      return;
+    }
+
+    // CLIProxy OAuth accounts do not support local account context metadata.
+    const cliproxyKey = !hasAuthAccount(name) ? parseCliproxyKey(name) : null;
+    if (cliproxyKey) {
+      res
+        .status(400)
+        .json({ error: `Context mode is not supported for CLIProxy account: ${name}` });
+      return;
+    }
+
+    const existsUnified = isUnifiedMode() && registry.hasAccountUnified(name);
+    const existsLegacy = registry.hasProfile(name);
+    if (!existsUnified && !existsLegacy) {
+      res.status(404).json({ error: `Account not found: ${name}` });
+      return;
+    }
+
+    const mode = req.body?.context_mode;
+    const rawGroup = req.body?.context_group;
+
+    if (mode !== 'isolated' && mode !== 'shared') {
+      res.status(400).json({ error: 'Missing or invalid context_mode: expected isolated|shared' });
+      return;
+    }
+
+    if (mode !== 'shared' && rawGroup !== undefined) {
+      res
+        .status(400)
+        .json({ error: 'Invalid payload: context_group requires context_mode=shared' });
+      return;
+    }
+
+    let normalizedGroup: string | undefined;
+    if (mode === 'shared') {
+      if (typeof rawGroup !== 'string' || rawGroup.trim().length === 0) {
+        res
+          .status(400)
+          .json({ error: 'Invalid payload: shared context_mode requires non-empty context_group' });
+        return;
+      }
+
+      normalizedGroup = normalizeContextGroupName(rawGroup);
+      if (!isValidContextGroupName(normalizedGroup)) {
+        res.status(400).json({
+          error:
+            'Invalid context_group. Use letters/numbers/dash/underscore, start with a letter, max 64 chars.',
+        });
+        return;
+      }
+    }
+
+    const metadata =
+      mode === 'shared'
+        ? {
+            context_mode: 'shared' as const,
+            context_group: normalizedGroup,
+          }
+        : {
+            context_mode: 'isolated' as const,
+          };
+    const policy = resolveAccountContextPolicy(metadata);
+
+    const previousUnified = existsUnified ? registry.getAllAccountsUnified()[name] : undefined;
+    const previousLegacy = existsLegacy ? registry.getProfile(name) : undefined;
+
+    try {
+      if (existsUnified) {
+        registry.updateAccountUnified(name, metadata);
+      }
+      if (existsLegacy) {
+        registry.updateProfile(name, metadata);
+      }
+
+      await instanceMgr.ensureInstance(name, policy);
+    } catch (error) {
+      if (existsUnified && previousUnified) {
+        registry.updateAccountUnified(name, previousUnified);
+      }
+      if (existsLegacy && previousLegacy) {
+        registry.updateProfile(name, previousLegacy);
+      }
+      throw error;
+    }
+
+    res.json({
+      name,
+      context_mode: policy.mode,
+      context_group: policy.group ?? null,
+    });
+  } catch (error) {
+    res.status(500).json({ error: (error as Error).message });
+  }
+});
+
 /**
  * DELETE /api/accounts/reset-default - Reset to CCS default
  */
diff --git a/tests/unit/web-server/account-routes-context.test.ts b/tests/unit/web-server/account-routes-context.test.ts
index c3b27999..2456ff37 100644
--- a/tests/unit/web-server/account-routes-context.test.ts
+++ b/tests/unit/web-server/account-routes-context.test.ts
@@ -18,6 +18,14 @@ async function deletePath(baseUrl: string, routePath: string): Promise<Response>
   return fetch(`${baseUrl}${routePath}`, { method: 'DELETE' });
 }
 
+async function putJson(baseUrl: string, routePath: string, body: unknown): Promise<Response> {
+  return fetch(`${baseUrl}${routePath}`, {
+    method: 'PUT',
+    headers: { 'Content-Type': 'application/json' },
+    body: JSON.stringify(body),
+  });
+}
+
 describe('web-server account-routes context normalization', () => {
   let server: Server;
   let baseUrl = '';
@@ -27,6 +35,7 @@ describe('web-server account-routes context normalization', () => {
 
   beforeAll(async () => {
     const app = express();
+    app.use(express.json());
     app.use('/api/accounts', accountRoutes);
 
     await new Promise<void>((resolve, reject) => {
@@ -173,4 +182,84 @@ describe('web-server account-routes context normalization', () => {
       InstanceManager.prototype.deleteInstance = originalDeleteInstance;
     }
   });
+
+  it('updates existing account context metadata and normalizes shared group', 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: isolated',
+        'profiles: {}',
+        'cliproxy:',
+        '  oauth_accounts: {}',
+        '  providers: {}',
+        '  variants: {}',
+      ].join('\n'),
+      'utf8'
+    );
+
+    const response = await putJson(baseUrl, '/api/accounts/work/context', {
+      context_mode: 'shared',
+      context_group: ' Team Alpha ',
+    });
+    expect(response.status).toBe(200);
+    const payload = (await response.json()) as { context_mode: string; context_group: string | null };
+    expect(payload.context_mode).toBe('shared');
+    expect(payload.context_group).toBe('team-alpha');
+
+    const accountsPayload = await getJson<{
+      accounts: Array<{ name: string; context_mode?: string; context_group?: string }>;
+    }>(baseUrl, '/api/accounts');
+    const work = accountsPayload.accounts.find((account) => account.name === 'work');
+    expect(work?.context_mode).toBe('shared');
+    expect(work?.context_group).toBe('team-alpha');
+  });
+
+  it('rejects shared mode updates without context_group', 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',
+        'profiles: {}',
+        'cliproxy:',
+        '  oauth_accounts: {}',
+        '  providers: {}',
+        '  variants: {}',
+      ].join('\n'),
+      'utf8'
+    );
+
+    const response = await putJson(baseUrl, '/api/accounts/work/context', {
+      context_mode: 'shared',
+    });
+    expect(response.status).toBe(400);
+
+    const payload = (await response.json()) as { error: string };
+    expect(payload.error).toContain('context_group');
+  });
+
+  it('rejects context updates for CLIProxy account identifiers', async () => {
+    const response = await putJson(baseUrl, '/api/accounts/gemini:test/context', {
+      context_mode: 'shared',
+      context_group: 'default',
+    });
+    expect(response.status).toBe(400);
+
+    const payload = (await response.json()) as { error: string };
+    expect(payload.error).toContain('CLIProxy');
+  });
 });
diff --git a/ui/src/components/account/accounts-table.tsx b/ui/src/components/account/accounts-table.tsx
index baaddc25..69467192 100644
--- a/ui/src/components/account/accounts-table.tsx
+++ b/ui/src/components/account/accounts-table.tsx
@@ -24,7 +24,8 @@ import {
   AlertDialogHeader,
   AlertDialogTitle,
 } from '@/components/ui/alert-dialog';
-import { Check, Trash2, RotateCcw } from 'lucide-react';
+import { Check, Pencil, Trash2, RotateCcw } from 'lucide-react';
+import { EditAccountContextDialog } from '@/components/account/edit-account-context-dialog';
 import {
   useSetDefaultAccount,
   useDeleteAccount,
@@ -35,7 +36,6 @@ import type { Account } from '@/lib/api-client';
 interface AccountsTableProps {
   data: Account[];
   defaultAccount: string | null;
-  onRefresh?: () => void;
 }
 
 export function AccountsTable({ data, defaultAccount }: AccountsTableProps) {
@@ -43,6 +43,7 @@ export function AccountsTable({ data, defaultAccount }: AccountsTableProps) {
   const deleteMutation = useDeleteAccount();
   const resetDefaultMutation = useResetDefaultAccount();
   const [deleteTarget, setDeleteTarget] = useState<string | null>(null);
+  const [contextTarget, setContextTarget] = useState<Account | null>(null);
 
   const columns: ColumnDef<Account>[] = [
     {
@@ -108,13 +109,26 @@ export function AccountsTable({ data, defaultAccount }: AccountsTableProps) {
     {
       id: 'actions',
       header: 'Actions',
-      size: 180,
+      size: 220,
       cell: ({ row }) => {
         const isDefault = row.original.name === defaultAccount;
         const isPending = setDefaultMutation.isPending || deleteMutation.isPending;
+        const isCliproxy = row.original.type === 'cliproxy';
 
         return (
           <div className="flex items-center gap-1">
+            {!isCliproxy && (
+              <Button
+                variant="ghost"
+                size="sm"
+                className="h-8 px-2"
+                disabled={isPending}
+                onClick={() => setContextTarget(row.original)}
+                title="Edit context mode"
+              >
+                <Pencil className="w-4 h-4" />
+              </Button>
+            )}
             <Button
               variant={isDefault ? 'secondary' : 'default'}
               size="sm"
@@ -173,7 +187,7 @@ export function AccountsTable({ data, defaultAccount }: AccountsTableProps) {
                         created: 'w-[150px]',
                         last_used: 'w-[150px]',
                         context: 'w-[170px]',
-                        actions: 'w-[180px]',
+                        actions: 'w-[220px]',
                       }[header.id] || 'w-auto';
 
                     return (
@@ -217,6 +231,10 @@ export function AccountsTable({ data, defaultAccount }: AccountsTableProps) {
         )}
       </div>
 
+      {contextTarget && (
+        <EditAccountContextDialog account={contextTarget} onClose={() => setContextTarget(null)} />
+      )}
+
       {/* Delete confirmation dialog */}
       <AlertDialog open={!!deleteTarget} onOpenChange={(open) => !open && setDeleteTarget(null)}>
         <AlertDialogContent>
diff --git a/ui/src/components/account/create-auth-profile-dialog.tsx b/ui/src/components/account/create-auth-profile-dialog.tsx
index 51b7b997..9a04b4cd 100644
--- a/ui/src/components/account/create-auth-profile-dialog.tsx
+++ b/ui/src/components/account/create-auth-profile-dialog.tsx
@@ -32,7 +32,7 @@ export function CreateAuthProfileDialog({ open, onClose }: CreateAuthProfileDial
 
   // Validate profile name: alphanumeric, dash, underscore only
   const isValidName = /^[a-zA-Z][a-zA-Z0-9_-]*$/.test(profileName);
-  const normalizedGroup = contextGroup.trim().toLowerCase();
+  const normalizedGroup = contextGroup.trim().toLowerCase().replace(/\s+/g, '-');
   const isValidContextGroup =
     normalizedGroup.length === 0 ||
     (normalizedGroup.length <= MAX_CONTEXT_GROUP_LENGTH &&
@@ -73,7 +73,8 @@ export function CreateAuthProfileDialog({ open, onClose }: CreateAuthProfileDial
         <DialogHeader>
           <DialogTitle>Create New Account</DialogTitle>
           <DialogDescription>
-            Auth profiles require Claude CLI login. Run the command below in your terminal.
+            Auth profiles require Claude CLI login. Run the command below in your terminal. You can
+            edit context mode/group later from the Accounts table.
           </DialogDescription>
         </DialogHeader>
 
@@ -118,7 +119,7 @@ export function CreateAuthProfileDialog({ open, onClose }: CreateAuthProfileDial
                   autoComplete="off"
                 />
                 <p className="text-xs text-muted-foreground">
-                  Leave empty to use the default shared group.
+                  Leave empty to use the default shared group. Spaces are normalized to dashes.
                 </p>
                 {contextGroup.trim().length > 0 && !isValidContextGroup && (
                   <p className="text-xs text-destructive">
diff --git a/ui/src/components/account/edit-account-context-dialog.tsx b/ui/src/components/account/edit-account-context-dialog.tsx
new file mode 100644
index 00000000..cd6230c2
--- /dev/null
+++ b/ui/src/components/account/edit-account-context-dialog.tsx
@@ -0,0 +1,139 @@
+import { useMemo, useState } from 'react';
+import {
+  Dialog,
+  DialogContent,
+  DialogDescription,
+  DialogFooter,
+  DialogHeader,
+  DialogTitle,
+} from '@/components/ui/dialog';
+import { Button } from '@/components/ui/button';
+import { Input } from '@/components/ui/input';
+import { Label } from '@/components/ui/label';
+import {
+  Select,
+  SelectContent,
+  SelectItem,
+  SelectTrigger,
+  SelectValue,
+} from '@/components/ui/select';
+import type { Account } from '@/lib/api-client';
+import { useUpdateAccountContext } from '@/hooks/use-accounts';
+
+type ContextMode = 'isolated' | 'shared';
+
+const MAX_CONTEXT_GROUP_LENGTH = 64;
+const CONTEXT_GROUP_PATTERN = /^[a-zA-Z][a-zA-Z0-9_-]*$/;
+
+interface EditAccountContextDialogProps {
+  account: Account;
+  onClose: () => void;
+}
+
+export function EditAccountContextDialog({ account, onClose }: EditAccountContextDialogProps) {
+  const updateContextMutation = useUpdateAccountContext();
+  const [mode, setMode] = useState<ContextMode>(
+    account.context_mode === 'shared' ? 'shared' : 'isolated'
+  );
+  const [group, setGroup] = useState(account.context_group || 'default');
+
+  const normalizedGroup = useMemo(() => group.trim().toLowerCase().replace(/\s+/g, '-'), [group]);
+  const isSharedGroupValid =
+    normalizedGroup.length > 0 &&
+    normalizedGroup.length <= MAX_CONTEXT_GROUP_LENGTH &&
+    CONTEXT_GROUP_PATTERN.test(normalizedGroup);
+  const canSubmit = mode === 'isolated' || isSharedGroupValid;
+
+  const handleSave = () => {
+    if (!canSubmit) {
+      return;
+    }
+
+    updateContextMutation.mutate(
+      {
+        name: account.name,
+        context_mode: mode,
+        context_group: mode === 'shared' ? normalizedGroup : undefined,
+      },
+      {
+        onSuccess: () => {
+          onClose();
+        },
+      }
+    );
+  };
+
+  const handleOpenChange = (nextOpen: boolean) => {
+    if (!nextOpen) {
+      onClose();
+    }
+  };
+
+  return (
+    <Dialog open onOpenChange={handleOpenChange}>
+      <DialogContent className="sm:max-w-md">
+        <DialogHeader>
+          <DialogTitle>Edit Context Mode</DialogTitle>
+          <DialogDescription>
+            Configure how "{account.name}" shares project workspace context with other accounts.
+          </DialogDescription>
+        </DialogHeader>
+
+        <div className="space-y-4 py-2">
+          <div className="space-y-2">
+            <Label htmlFor="context-mode">Context Mode</Label>
+            <Select value={mode} onValueChange={(value) => setMode(value as ContextMode)}>
+              <SelectTrigger id="context-mode">
+                <SelectValue placeholder="Select context mode" />
+              </SelectTrigger>
+              <SelectContent>
+                <SelectItem value="isolated">isolated</SelectItem>
+                <SelectItem value="shared">shared</SelectItem>
+              </SelectContent>
+            </Select>
+            <p className="text-xs text-muted-foreground">
+              {mode === 'shared'
+                ? 'Shared mode reuses workspace context for accounts in the same group.'
+                : 'Isolated mode keeps this account workspace context separate.'}
+            </p>
+          </div>
+
+          {mode === 'shared' && (
+            <div className="space-y-2">
+              <Label htmlFor="context-group">Context Group</Label>
+              <Input
+                id="context-group"
+                value={group}
+                onChange={(event) => setGroup(event.target.value)}
+                placeholder="default"
+                autoComplete="off"
+              />
+              <p className="text-xs text-muted-foreground">
+                Normalized to lowercase (spaces become dashes). Allowed: letters, numbers, `_`, `-`
+                (max {MAX_CONTEXT_GROUP_LENGTH} chars).
+              </p>
+              {!isSharedGroupValid && (
+                <p className="text-xs text-destructive">
+                  Enter a valid group name that starts with a letter.
+                </p>
+              )}
+            </div>
+          )}
+
+          <p className="text-xs text-muted-foreground">
+            Credentials stay isolated per account. Only project workspace context is shared.
+          </p>
+        </div>
+
+        <DialogFooter>
+          <Button variant="outline" onClick={onClose} disabled={updateContextMutation.isPending}>
+            Cancel
+          </Button>
+          <Button onClick={handleSave} disabled={!canSubmit || updateContextMutation.isPending}>
+            {updateContextMutation.isPending ? 'Saving...' : 'Save'}
+          </Button>
+        </DialogFooter>
+      </DialogContent>
+    </Dialog>
+  );
+}
diff --git a/ui/src/components/account/index.ts b/ui/src/components/account/index.ts
index 0b75ccb8..fe6da6ea 100644
--- a/ui/src/components/account/index.ts
+++ b/ui/src/components/account/index.ts
@@ -6,6 +6,7 @@
 export { AccountsTable } from './accounts-table';
 export { AddAccountDialog } from './add-account-dialog';
 export { CreateAuthProfileDialog } from './create-auth-profile-dialog';
+export { EditAccountContextDialog } from './edit-account-context-dialog';
 
 // Flow visualization (from subdirectory)
 export { AccountFlowViz } from './flow-viz';
diff --git a/ui/src/hooks/use-accounts.ts b/ui/src/hooks/use-accounts.ts
index b46691af..1e616022 100644
--- a/ui/src/hooks/use-accounts.ts
+++ b/ui/src/hooks/use-accounts.ts
@@ -1,5 +1,5 @@
 /**
- * React Query hooks for accounts (profiles.json)
+ * React Query hooks for account management
  * Dashboard parity: Full CRUD operations for auth profiles
  */
 
@@ -58,3 +58,30 @@ export function useDeleteAccount() {
     },
   });
 }
+
+export function useUpdateAccountContext() {
+  const queryClient = useQueryClient();
+
+  return useMutation({
+    mutationFn: ({
+      name,
+      context_mode,
+      context_group,
+    }: {
+      name: string;
+      context_mode: 'isolated' | 'shared';
+      context_group?: string;
+    }) => api.accounts.updateContext(name, { context_mode, context_group }),
+    onSuccess: (_data, vars) => {
+      queryClient.invalidateQueries({ queryKey: ['accounts'] });
+      const contextSummary =
+        vars.context_mode === 'shared'
+          ? `shared (${(vars.context_group || 'default').trim().toLowerCase().replace(/\s+/g, '-')})`
+          : 'isolated';
+      toast.success(`Updated "${vars.name}" context to ${contextSummary}`);
+    },
+    onError: (error: Error) => {
+      toast.error(error.message);
+    },
+  });
+}
diff --git a/ui/src/lib/api-client.ts b/ui/src/lib/api-client.ts
index 12ec590e..bab3455e 100644
--- a/ui/src/lib/api-client.ts
+++ b/ui/src/lib/api-client.ts
@@ -457,6 +457,11 @@ export interface Account {
   context_group?: string;
 }
 
+export interface UpdateAccountContext {
+  context_mode: 'isolated' | 'shared';
+  context_group?: string;
+}
+
 // Unified config types
 export interface ConfigFormat {
   format: 'yaml' | 'json' | 'none';
@@ -785,6 +790,11 @@ export const api = {
       }),
     resetDefault: () => request('/accounts/reset-default', { method: 'DELETE' }),
     delete: (name: string) => request(`/accounts/${name}`, { method: 'DELETE' }),
+    updateContext: (name: string, data: UpdateAccountContext) =>
+      request(`/accounts/${encodeURIComponent(name)}/context`, {
+        method: 'PUT',
+        body: JSON.stringify(data),
+      }),
   },
   // Unified config API
   config: {
diff --git a/ui/src/pages/accounts.tsx b/ui/src/pages/accounts.tsx
index bbed9c89..9a47b1df 100644
--- a/ui/src/pages/accounts.tsx
+++ b/ui/src/pages/accounts.tsx
@@ -11,7 +11,7 @@ import { Button } from '@/components/ui/button';
 import { useAccounts } from '@/hooks/use-accounts';
 
 export function AccountsPage() {
-  const { data, isLoading, refetch } = useAccounts();
+  const { data, isLoading } = useAccounts();
   const [createDialogOpen, setCreateDialogOpen] = useState(false);
 
   return (
@@ -20,7 +20,7 @@ export function AccountsPage() {
         <div>
           <h1 className="text-2xl font-bold">Accounts</h1>
           <p className="text-sm text-muted-foreground mt-1">
-            Manage multi-account Claude sessions (profiles.json)
+            Manage multi-account Claude sessions and shared context groups
           </p>
         </div>
         <Button onClick={() => setCreateDialogOpen(true)}>
@@ -32,11 +32,13 @@ export function AccountsPage() {
       {isLoading ? (
         <div className="text-muted-foreground">Loading accounts...</div>
       ) : (
-        <AccountsTable
-          data={data?.accounts || []}
-          defaultAccount={data?.default ?? null}
-          onRefresh={refetch}
-        />
+        <div className="space-y-3">
+          <p className="text-xs text-muted-foreground">
+            New profile login: <code className="rounded bg-muted px-1 py-0.5">Create Account</code>.
+            Existing profile context: use the pencil icon in the table.
+          </p>
+          <AccountsTable data={data?.accounts || []} defaultAccount={data?.default ?? null} />
+        </div>
       )}
 
       <CreateAuthProfileDialog open={createDialogOpen} onClose={() => setCreateDialogOpen(false)} />