diff --git a/CLAUDE.md b/CLAUDE.md
index 104a751ecaf..35e5a89e6e7 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -102,6 +102,22 @@ LiteLLM is a unified interface for 100+ LLM providers with two main components:
 ### UI / Backend Consistency
 - When wiring a new UI entity type to an existing backend endpoint, verify the backend API contract (single value vs. array, required vs. optional params) and ensure the UI controls match — e.g., use a single-select dropdown when the backend accepts a single value, not a multi-select
 
+### MCP OAuth / OpenAPI Transport Mapping
+- `TRANSPORT.OPENAPI` is a UI-only concept. The backend only accepts `"http"`, `"sse"`, or `"stdio"`. Always map it to `"http"` before any API call (including pre-OAuth temp-session calls).
+- FastAPI validation errors return `detail` as an array of `{loc, msg, type}` objects. Error extractors must handle: array (map `.msg`), string, nested `{error: string}`, and fallback.
+- When an MCP server already has `authorization_url` stored, skip OAuth discovery (`_discovery_metadata`) — the server URL for OpenAPI MCPs is the spec file, not the API base, and fetching it causes timeouts.
+- `client_id` should be optional in the `/authorize` endpoint — if the server has a stored `client_id` in credentials, use that. Never require callers to re-supply it.
+
+### MCP Credential Storage
+- OAuth credentials and BYOK credentials share the `litellm_mcpusercredentials` table, distinguished by a `"type"` field in the JSON payload (`"oauth2"` vs plain string).
+- When deleting OAuth credentials, check type before deleting to avoid accidentally deleting a BYOK credential for the same `(user_id, server_id)` pair.
+- Always pass the raw `expires_at` timestamp to the client — never set it to `None` for expired credentials. Let the frontend compute the "Expired" display state from the timestamp.
+- Use `RecordNotFoundError` (not bare `except Exception`) when catching "already deleted" in credential delete endpoints.
+
+### Browser Storage Safety (UI)
+- Never write LiteLLM access tokens or API keys to `localStorage` — use `sessionStorage` only. `localStorage` survives browser close and is readable by any injected script (XSS).
+- Shared utility functions (e.g. `extractErrorMessage`) belong in `src/utils/` — never define them inline in hooks or duplicate them across files.
+
 ### Database Migrations
 - Prisma handles schema migrations
 - Migration files auto-generated with `prisma migrate dev`