## Summary
- Remove "Build with MCP" option from chat mode selector dropdowns
- Route build mode to MCP agent code path when MCP servers are enabled
- Add MCP chip showing "N MCP" next to Build button when servers enabled
- Show MCP tools picker in build mode when MCP servers are enabled
- Skip deprecated agent mode in keyboard shortcut toggle cycle
- Update e2e tests to use build mode instead of agent mode

## Test plan
- [x] MCP e2e tests pass (verified locally)
- [ ] Verify Build mode works normally without MCP servers configured
- [ ] Configure an MCP server and verify the "N MCP" chip appears next
to Build button
- [ ] Verify clicking MCP tools picker shows enabled MCP servers
- [ ] Verify sending a message in Build mode with MCP servers uses the
agent code path

🤖 Generated with [Claude Code](https://claude.com/claude-code)
<!-- devin-review-badge-begin -->

---

<a href="https://app.devin.ai/review/dyad-sh/dyad/pull/2435">
  <picture>
<source media="(prefers-color-scheme: dark)"
srcset="https://static.devin.ai/assets/gh-open-in-devin-review-dark.svg?v=1">
<img
src="https://static.devin.ai/assets/gh-open-in-devin-review-light.svg?v=1"
alt="Open with Devin">
  </picture>
</a>
<!-- devin-review-badge-end -->

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> **Medium Risk**
> Changes the chat-mode UI and the main chat streaming branching so
Build may enter the MCP/tooling code path when MCP servers are enabled;
this can alter assistant behavior and tool-consent flows. Lockfile churn
may also affect dependency installs across environments.
> 
> **Overview**
> **Removes the user-facing “Build with MCP”/`agent` mode selection**
and treats stored `agent` settings as **Build** for backwards
compatibility.
> 
> **Build now conditionally enables MCP tooling**: the MCP tools picker
appears in Build only when at least one MCP server is enabled, and the
main streaming handler runs the MCP agent pre-pass only when Build has
enabled MCP servers (or when legacy `agent` is set).
> 
> Adds a small **“N MCP” status chip** next to Build when MCP servers
are enabled, updates the keyboard mode-toggle cycle to skip deprecated
`agent`, updates MCP e2e tests to select Build, and includes a large
`package-lock.json` metadata update (peer flag changes).
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
6338761b9e45313d399dd2f4873e5ef9a53ff36a. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

<!-- This is an auto-generated description by cubic. -->
---
## Summary by cubic
Removed the deprecated Agent mode by folding it into Build. Build now
uses MCP tooling only when MCP servers are enabled; the UI shows an MCP
count chip and tools picker, and old “agent” settings still work.

- **Refactors**
- Removed Agent from mode selectors; legacy “agent” appears as Build and
the keyboard toggle skips it.
- Build routes through the MCP agent path only when enabled MCP servers
exist; otherwise behaves like normal Build.
- Preserved compatibility for users with “agent” in settings and in the
streaming path.
- Updated E2E tests to use Build and aligned test_helper with the
modular PageObject structure.

- **New Features**
  - Added an “N MCP” chip next to Build when servers are enabled.
  - Show the MCP tools picker in Build when MCP servers are enabled.

<sup>Written for commit 6338761b9e45313d399dd2f4873e5ef9a53ff36a.
Summary will update on new commits.</sup>

<!-- End of auto-generated description by cubic. -->

---------
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
Co-authored-by: claude[bot] <41898282+claude[bot]@users.noreply.github.com>