Add fx integration guide, document headless MCP auth

[dprevoznik]

Summary

• Adds integrations/vercel/fx.mdx, an integration guide for connecting fx (Vercel Labs' native CLI coding agent) to Kernel's MCP server, and links it from integrations/overview.mdx, integrations/vercel/overview.mdx, and the nav.
• Documents a gap in the existing reference/mcp-server/clients/fx.mdx page: the OAuth flow kernel mcp install --target fx sets up only works in an interactive fx session. Non-interactive runs (fx ask, fx acp, CI) need a Kernel API key via fx's bearer_token_env field instead — fx rejects a literal Authorization header, so the generic API-key pattern used on other client pages doesn't apply here.

Test plan

Verified end-to-end in a scratch environment before writing anything down:

• Installed fx 0.0.7, confirmed it authenticates against the model provider with no extra setup
• Configured ~/.fx/mcp.json with bearer_token_env pointing at a Kernel API key
• Ran fx ask with a prompt to create a browser session, run execute_playwright_code against https://example.com, and delete the session — got back the correct page title and confirmed via kernel browser list that the session was cleaned up
• Confirmed the OAuth config written by kernel mcp install --target fx fails in non-interactive fx ask with the exact error now documented on the client page
• docs.json validated as JSON

Not run: mintlify broken-links (exits non-zero in this sandbox with no other output, likely a network/environment issue unrelated to this change).

---

Note

Low Risk
Documentation-only changes with no product code, auth, or data-path modifications.

Overview
Adds documentation for connecting Vercel fx to Kernel’s MCP server so fx can spin up cloud browsers, run Playwright via MCP tools, and tear sessions down.

A new integrations/vercel/fx.mdx page covers overview, setup (interactive OAuth vs headless), and an fx ask example. It’s wired into docs.json nav, integrations/overview.mdx, and integrations/vercel/overview.mdx.

The existing reference/mcp-server/clients/fx.mdx page gains a Headless and scripted use section: non-interactive runs (fx ask, fx acp, CI) can’t use /mcp auth, so users must use a Kernel API key via fx’s bearer_token_env (not a static Authorization header).

^{Reviewed by Cursor Bugbot for commit 46e4c55. Bugbot is set up for automated code reviews on this repo. Configure here.}

[mintlify]

Preview deployment for your docs. Learn more about Mintlify Previews.

Project	Status	Preview	Updated (UTC)
Kernel	🟢 Ready	View Preview	Aug 29, 2026, 9:53 PM

💡 Tip: Enable Workflows to automatically generate PRs for you.

[cursor]

Risk assessment: Very Low

Decision: Approve.

Inspected the actual diff (+80 / -1 across 5 files). This is documentation-only on a Mintlify docs site:

• New integrations/vercel/fx.mdx integration page
• One nav entry in docs.json
• Link additions in integrations/overview.mdx and integrations/vercel/overview.mdx
• New “Headless and scripted use” section on the existing reference/mcp-server/clients/fx.mdx client page (placeholder sk_..., env-var auth via bearer_token_env)

No application code, auth/billing/permissions logic, infrastructure, schema, or shared runtime paths changed. No CODEOWNERS file exists, so codeowner review is not required. No prior approval to preserve or revoke.

Safe to approve under the Very Low criteria (documentation-only, small scoped diff, no production logic or infra impact).

  

_{Sent by Cursor Automation: Assign PR reviewers}