docs(mcp): document delegated OAuth admission migration

[joshua-berri]

Summary

Document the removal of anonymous admission for legacy delegated OAuth MCP routes. The upstream OAuth token still uses Authorization: Bearer <upstream-token> unchanged; LiteLLM admission is now required separately

The migration guide recommends oauth_delegate, preserves the existing legacy section anchor, shows the two-header key flow, and links OAuth-only clients to the existing authenticated DCR bridge. Public discovery is distinguished from permission to open sessions or invoke tools

The cost and public-internet pages clarify unattributed passthrough spend, the absence of identity-based budget debits, and the separate IP access controls

Breaking-change placement

The fix merged after the currently published releases. As agreed, an upcoming red Breaking Changes notice lives in the MCP guide, explicitly scoped to builds containing the backend fix. This PR does not assign a version or alter an older release note

When the containing release is assigned, its release note should include the warning below the deployment block, following the repository convention

Scope

Only docs/mcp_oauth_passthrough.md, docs/mcp_public_internet.md, and docs/mcp_cost.md change. No new pages, screenshots, dependency changes, instruction files, or unrelated formatting

Validation

npm run lint:writing passed across 1,044 Markdown files; its nine existing vocabulary warnings are outside the edited pages

python3 scripts/check-docs.py docs passed across 800 docs pages, including links, anchors, and embedded examples

npm run build passed with the locked dependencies and Node 20, matching the CI major version

Generated HTML for all three edited pages was checked: the notice renders with danger styling, the legacy migration anchor is preserved, the authenticated bridge and cost-attribution links resolve, and the two-token curl example is present

git diff --check passed. Validation applies to commit 3c59a882. Hosted writing-style and structure checks passed; the deployment and requested bot reviews are still pending

The Vercel preview requires Vercel sign-in. Generated pages were verified locally without starting a server or requesting browser access

This is documentation-only; there is no changed executable behavior requiring Python regression coverage

Existing environment warnings

npm ci reported 64 vulnerabilities in the unchanged dependency lockfile. The successful build also reports existing blog-preview, browser-data, and HTML-minifier warnings on other pages. No edited MCP page appears in those diagnostics; no unrelated content was changed and no checks were suppressed

References

Closes #1448

Backend fix: BerriAI/litellm#40923

Linear: https://linear.app/litellm-ai/issue/LIT-6970/mcp-tool-calls-on-passthrough-upstream-delegated-servers-are-recorded

[vercel]

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Project	Deployment	Actions	Updated
litellm	Ready	Preview	Sep 13, 2026 2:28am UTC

[joshua-berri]

@greptileai Please review this MCP migration documentation for accurate authentication boundaries, unchanged upstream token handling, and the upcoming breaking-change notice.

[joshua-berri]

@cursor review Please check this docs-only migration for incorrect authentication claims, broken examples, and regressions in existing MCP documentation links.

[joshua-berri]

@veria-ai Please review the security wording around legacy delegated admission, public OAuth discovery, and the distinction between authentication and unattributed spend.

[cursor]

✅ Bugbot reviewed your changes and found no new issues!

Comment @cursor review or bugbot run to trigger another review on this PR

^{Reviewed by Cursor Bugbot for commit 3c59a88. Configure here.}