fix(auth): explicit re-authorize when the OAuth callback state was lost (#1808) (#1810)

* fix(auth): offer explicit re-authorize when callback state is lost (#1808)

A `/oauth/callback` that arrives with no recorded SEP-2352 discovery state
made the SDK throw `AuthorizationServerMismatchError` and the Inspector
dead-ended, surfacing the raw SDK text with no path forward.

The SDK folds two very different failures into that one error class, so
`core/auth/issuerBinding.ts` classifies them structurally: a recoverable
"lost authorization state" (the SDK puts prose, not an issuer URL, in the
`recordedIssuer` slot) versus a genuine cross-AS `issuer_mismatch`. Only
the first gets a recovery affordance.

Web: the callback failure now raises a dedicated banner ("Authorization
state was lost" / "Authorize again") whose action clears the stale OAuth
state for that server and starts a fresh authorization. A genuine
mismatch stays a red, non-dismissible security notification with both
issuers named and no one-click retry.

Node runners (CLI/TUI): the same classification rewrites the callback
rejection into the shared actionable copy instead of the SDK text.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016S7h83UKNQ7kvSiFDNksCt

* fix(auth): detect the SDK mismatch error via isInstance (#1808)

The callback-leg classifier gated on `err.mcpBrand`, but the SDK declares
that brand in a `static {}` block, so it lives on the constructor and is
never reachable from an instance. The predicate always returned false, so
`findIssuerBindingFailure()` never matched and the #1808 recovery banner
was inert in production — the callback dead-ended exactly as before.

Use the SDK's own `AuthorizationServerMismatchError.isInstance()`, which is
cross-copy safe by construction (it consults a `Symbol.for()`-keyed brand
set), with a `name` fallback for a serialization boundary. Correct the
module doc, which cited cross-bundle safety as the reason to avoid
`instanceof` — the very thing the SDK's branded `hasInstance` provides.

Every fixture now constructs a real `AuthorizationServerMismatchError`
instead of a hand-rolled object with an own `mcpBrand`, which is why a
green `npm run ci` hid this. Adds a test pinning the brand's placement so
the feature cannot silently go inert again.

Review follow-ups: drop the unused `isLostAuthorizationStateError`, remove
the duplicated banner title default, resolve the banner title/action label
where the banner is raised, keep the clear-failure notification open, and
bound remote-supplied issuers in user-facing copy.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016S7h83UKNQ7kvSiFDNksCt

---------

Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>
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Cliff Hall 2026-07-27 18:08:31 -04:00 • committed by GitHub
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3 changed files with 1003 additions and 7 deletions

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@ -0,0 +1,191 @@
import { describe, it, expect } from "vitest";
import { AuthorizationServerMismatchError } from "@modelcontextprotocol/client";
import { findIssuerBindingFailure } from "@inspector/core/auth/issuerBinding.js";
/**
* Builds a **real** SDK `AuthorizationServerMismatchError`.
*
* This must stay the real class rather than a look-alike plain object. The SDK
* declares `mcpBrand` in a `static {}` block, so it sits on the constructor and
* is invisible from the instance; a fabricated fixture carrying an own
* `mcpBrand` property would pass against a classifier that reads
* `err.mcpBrand` — which no real thrown error would ever satisfy.
*/
function mismatchError(
recordedIssuer: string,
currentIssuer: string,
): AuthorizationServerMismatchError {
return new AuthorizationServerMismatchError(recordedIssuer, currentIssuer);
}
/**
* Documents why the classifier must not test `err.mcpBrand`: the SDK declares
* that brand `static`, so it lives on the class and instances never carry it.
* If a future SDK moves it onto the instance, this fails and the note in
* `issuerBinding.ts` can be revisited.
*/
describe("SDK brand placement", () => {
it("keeps `mcpBrand` on the class, not the instance", () => {
const err = mismatchError("https://a.example.com", "https://b.example.com");
expect("mcpBrand" in err).toBe(false);
// The brand is defined at runtime via `Object.defineProperty` in a static
// block, so it is absent from the SDK's published type declarations — hence
// the cast to read it.
const brandOnClass = (
AuthorizationServerMismatchError as { mcpBrand?: unknown }
).mcpBrand;
expect(brandOnClass).toBe("mcp.AuthorizationServerMismatchError");
});
it("matches via `isInstance`, which survives a foreign SDK copy", () => {
const err = mismatchError("https://a.example.com", "https://b.example.com");
expect(AuthorizationServerMismatchError.isInstance(err)).toBe(true);
});
});
/**
* An error that crossed a serialization boundary: neither the SDK's
* `Symbol.for()`-keyed brand set nor the prototype survives, but `name` does.
* This is the fallback arm of the classifier's predicate.
*/
function serializedMismatchError(
recordedIssuer: string,
currentIssuer: string,
): Error {
const err = new Error(
"Authorization server changed between redirect and callback",
);
err.name = "AuthorizationServerMismatchError";
Object.assign(err, { recordedIssuer, currentIssuer });
return err;
}
const MISSING_STATE_SENTINEL =
"discoveryState was not available on the callback leg; ensure your provider persists discoveryState alongside codeVerifier";
describe("findIssuerBindingFailure", () => {
it("classifies the missing-discovery-state sentinel as recoverable", () => {
const failure = findIssuerBindingFailure(
mismatchError(MISSING_STATE_SENTINEL, "https://as.example.com"),
);
expect(failure).toEqual({
kind: "lost_authorization_state",
currentIssuer: "https://as.example.com",
});
});
it("classifies non-URL prose in the recorded slot as recoverable", () => {
const failure = findIssuerBindingFailure(
mismatchError("nothing was recorded, sorry", "https://as.example.com"),
);
expect(failure?.kind).toBe("lost_authorization_state");
});
it("classifies a non-http(s) URL in the recorded slot as recoverable", () => {
const failure = findIssuerBindingFailure(
mismatchError("urn:example:not-an-issuer", "https://as.example.com"),
);
expect(failure?.kind).toBe("lost_authorization_state");
});
it("classifies two real issuers as a genuine mismatch", () => {
const failure = findIssuerBindingFailure(
mismatchError("https://old.example.com", "https://evil.example.com"),
);
expect(failure).toEqual({
kind: "issuer_mismatch",
recordedIssuer: "https://old.example.com",
currentIssuer: "https://evil.example.com",
});
});
it("accepts a plain http issuer as a genuine mismatch", () => {
const failure = findIssuerBindingFailure(
mismatchError("http://localhost:9000", "http://localhost:9001"),
);
expect(failure?.kind).toBe("issuer_mismatch");
});
it("walks the `cause` chain", () => {
const wrapped = new Error("negotiation failed", {
cause: mismatchError(MISSING_STATE_SENTINEL, "https://as.example.com"),
});
expect(findIssuerBindingFailure(wrapped)?.kind).toBe(
"lost_authorization_state",
);
});
it("walks `data.cause` (SdkError wrapper shape)", () => {
const wrapped = Object.assign(new Error("ERA_NEGOTIATION_FAILED"), {
data: {
cause: mismatchError("https://a.example.com", "https://b.example.com"),
},
});
expect(findIssuerBindingFailure(wrapped)?.kind).toBe("issuer_mismatch");
});
it("walks multiple levels", () => {
const wrapped = new Error("outer", {
cause: new Error("inner", {
cause: mismatchError(MISSING_STATE_SENTINEL, "https://as.example.com"),
}),
});
expect(findIssuerBindingFailure(wrapped)?.kind).toBe(
"lost_authorization_state",
);
});
it("ignores a non-object `data`", () => {
const wrapped = Object.assign(new Error("outer"), { data: "nope" });
expect(findIssuerBindingFailure(wrapped)).toBeUndefined();
});
it("ignores a null `data`", () => {
const wrapped = Object.assign(new Error("outer"), { data: null });
expect(findIssuerBindingFailure(wrapped)).toBeUndefined();
});
it("terminates on a cyclic cause chain", () => {
const outer: { cause?: unknown } = new Error("outer");
outer.cause = outer;
expect(findIssuerBindingFailure(outer)).toBeUndefined();
});
it("returns undefined for unrelated errors and non-objects", () => {
expect(findIssuerBindingFailure(new Error("boom"))).toBeUndefined();
expect(findIssuerBindingFailure(undefined)).toBeUndefined();
expect(findIssuerBindingFailure(null)).toBeUndefined();
expect(findIssuerBindingFailure("string")).toBeUndefined();
});
it("ignores a matching error missing the issuer fields", () => {
const err = new Error("half-shaped");
err.name = "AuthorizationServerMismatchError";
expect(findIssuerBindingFailure(err)).toBeUndefined();
const halfShaped = new Error("only recorded");
halfShaped.name = "AuthorizationServerMismatchError";
Object.assign(halfShaped, { recordedIssuer: "https://as.example.com" });
expect(findIssuerBindingFailure(halfShaped)).toBeUndefined();
});
it("classifies a serialized error via the `name` fallback", () => {
expect(
findIssuerBindingFailure(
serializedMismatchError(
MISSING_STATE_SENTINEL,
"https://as.example.com",
),
)?.kind,
).toBe("lost_authorization_state");
});
it("ignores a different SDK error carrying the same fields", () => {
const err = Object.assign(new Error("other"), {
recordedIssuer: "https://a.example.com",
currentIssuer: "https://b.example.com",
});
err.name = "IssuerMismatchError";
expect(findIssuerBindingFailure(err)).toBeUndefined();
});
});

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@ -19,6 +19,12 @@ import {
stepUpInsufficientScopeMessage,
stepUpModalTitle,
stepUpAuthorizeActionLabel,
issuerBindingFailureCopy,
issuerMismatchMessage,
issuerMismatchTitle,
lostAuthorizationStateActionLabel,
lostAuthorizationStateMessage,
lostAuthorizationStateTitle,
} from "@inspector/core/auth/oauthUx.js";
import type { AuthChallenge } from "@inspector/core/auth/challenge.js";
@ -334,3 +340,79 @@ describe("oauthUx re-auth banner", () => {
expect(reAuthBannerMessage({})).toBe("Authentication needs attention.");
});
});
describe("oauthUx issuer-binding copy", () => {
it("explains lost authorization state in plain language, with the server name", () => {
const withName = lostAuthorizationStateMessage({ serverName: "svc" });
expect(withName).toContain('"svc"');
expect(withName).toContain("was lost");
expect(withName).toContain("Authorize again");
// Never leaks the SDK's security-flavoured wording.
expect(withName).not.toContain("discoveryState");
expect(withName).not.toContain("AuthorizationServerMismatchError");
expect(lostAuthorizationStateMessage()).toContain("this server");
expect(lostAuthorizationStateTitle()).toBe("Authorization state was lost");
expect(lostAuthorizationStateActionLabel()).toBe("Authorize again");
});
it("names both issuers for a genuine mismatch and offers no retry nudge", () => {
const message = issuerMismatchMessage({
recordedIssuer: "https://old.example.com",
currentIssuer: "https://evil.example.com",
serverName: "svc",
});
expect(message).toContain('"svc"');
expect(message).toContain("https://old.example.com");
expect(message).toContain("https://evil.example.com");
expect(message).toContain("was not exchanged");
expect(message).not.toContain("Authorize again");
expect(
issuerMismatchMessage({
recordedIssuer: "https://old.example.com",
currentIssuer: "https://evil.example.com",
}),
).toContain("this server");
expect(issuerMismatchTitle()).toBe("Authorization server mismatch");
});
it("bounds an overlong remote-supplied issuer in the mismatch copy", () => {
const overlong = `https://evil.example.com/${"a".repeat(400)}`;
const message = issuerMismatchMessage({
recordedIssuer: "https://old.example.com",
currentIssuer: overlong,
});
expect(message).not.toContain(overlong);
expect(message).toContain("…");
// The short issuer on the same call is passed through untouched.
expect(message).toContain("https://old.example.com");
});
it("issuerBindingFailureCopy dispatches on the failure kind", () => {
expect(
issuerBindingFailureCopy(
{
kind: "lost_authorization_state",
currentIssuer: "https://as.example.com",
},
{ serverName: "svc" },
),
).toEqual({
title: lostAuthorizationStateTitle(),
message: lostAuthorizationStateMessage({ serverName: "svc" }),
});
expect(
issuerBindingFailureCopy({
kind: "issuer_mismatch",
recordedIssuer: "https://old.example.com",
currentIssuer: "https://evil.example.com",
}),
).toEqual({
title: issuerMismatchTitle(),
message: issuerMismatchMessage({
recordedIssuer: "https://old.example.com",
currentIssuer: "https://evil.example.com",
}),
});
});
});

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@ -1,4 +1,5 @@
import { describe, it, expect, vi, afterEach } from "vitest";
import { AuthorizationServerMismatchError } from "@modelcontextprotocol/client";
import {
runRunnerInteractiveOAuth,
type RunnerInteractiveOAuthClient,
@ -249,6 +250,76 @@ describe("runRunnerInteractiveOAuth", () => {
).rejects.toThrow("token exchange failed");
});
it("rewrites a lost-authorization-state callback failure into actionable copy (#1808)", async () => {
const redirectUrlProvider = { redirectUrl: "" };
// Real SDK error — its `mcpBrand` is static, so a fabricated
// instance-branded look-alike would not exercise the real shape.
const sdkError = new AuthorizationServerMismatchError(
"discoveryState was not available on the callback leg; ensure your provider persists discoveryState alongside codeVerifier",
"https://as.example",
);
const client = mockClient({
authenticate: vi.fn(async () => {
await simulateCallback(handlers.current);
return new URL("https://as.example/authorize");
}),
completeOAuthFlow: vi.fn(async () => {
throw sdkError;
}),
});
const failure = await runRunnerInteractiveOAuth({
client,
redirectUrlProvider,
callbackListen: {
hostname: "127.0.0.1",
port: 6276,
pathname: "/oauth/callback",
},
createCallbackServer: () => createMockCallbackServer(handlers),
}).catch((err: unknown) => err);
expect(failure).toBeInstanceOf(Error);
const message = (failure as Error).message;
expect(message).toContain("Authorization state was lost");
expect(message).toContain("Authorize again");
expect(message).not.toContain("discoveryState");
expect((failure as Error).cause).toBe(sdkError);
});
it("keeps the security wording for a genuine issuer mismatch (#1808)", async () => {
const redirectUrlProvider = { redirectUrl: "" };
const sdkError = new AuthorizationServerMismatchError(
"https://old.example",
"https://evil.example",
);
const client = mockClient({
authenticate: vi.fn(async () => {
await simulateCallback(handlers.current);
return new URL("https://as.example/authorize");
}),
completeOAuthFlow: vi.fn(async () => {
throw sdkError;
}),
});
const failure = await runRunnerInteractiveOAuth({
client,
redirectUrlProvider,
callbackListen: {
hostname: "127.0.0.1",
port: 6276,
pathname: "/oauth/callback",
},
createCallbackServer: () => createMockCallbackServer(handlers),
}).catch((err: unknown) => err);
const message = (failure as Error).message;
expect(message).toContain("Authorization server mismatch");
expect(message).toContain("https://evil.example");
expect(message).not.toContain("Authorize again");
});
it("propagates OAuth callback errors from the authorization server", async () => {
const redirectUrlProvider = { redirectUrl: "" };
const client = mockClient({