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Skip SSE fallback when OAuth is active #57

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7 changes: 7 additions & 0 deletions src/runtime/transport.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -163,6 +163,13 @@ export async function createClientContext(
await oauthSession?.close().catch(() => {});
throw primaryError;
}
// When OAuth is active the server already accepted a POST (returning 401),
// so it speaks Streamable HTTP. Falling back to SSE (GET) would fail with
// 405 Method Not Allowed or a fresh 401 that can never be resolved.
if (activeDefinition.auth === 'oauth') {
await oauthSession?.close().catch(() => {});
throw primaryError;
Comment on lines +169 to +171
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@chatgpt-codex-connector chatgpt-codex-connector bot Feb 4, 2026

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P2 Badge Avoid skipping SSE fallback based on auth alone

activeDefinition.auth === 'oauth' is used here to skip SSE fallback for any primary error, but auth only describes the auth mechanism, not the transport (there’s no transport field in ServerDefinition). That means an OAuth‑protected server that only exposes SSE (e.g., a POST returning 405 or a network error on the streamable endpoint) will now fail permanently instead of falling back to SSE, even though SSE may be the only supported transport. Consider gating this on a confirmed streamable‑HTTP 401 (or another capability signal) rather than the auth flag alone.

Useful? React with 👍 / 👎.

}
if (primaryError instanceof Error) {
logger.info(`Falling back to SSE transport for '${activeDefinition.name}': ${primaryError.message}`);
}
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18 changes: 18 additions & 0 deletions tests/runtime-transport.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -46,6 +46,24 @@ describe('createClientContext (HTTP)', () => {
expect(clientConnect).toHaveBeenCalledTimes(2);
});

it('does not fall back to SSE when OAuth is active', async () => {
const definition: ServerDefinition = {
...stubHttpDefinition('https://example.com/mcp'),
auth: 'oauth',
};
const { Client } = await import('@modelcontextprotocol/sdk/client/index.js');
const { StreamableHTTPClientTransport } = await import('@modelcontextprotocol/sdk/client/streamableHttp.js');

vi.spyOn(Client.prototype, 'connect').mockImplementation(async (transport) => {
expect(transport).toBeInstanceOf(StreamableHTTPClientTransport);
throw new Error('connection failed');
});

await expect(
createClientContext(definition, logger, clientInfo, { maxOAuthAttempts: 0 })
).rejects.toThrow('connection failed');
});

it.skip('promotes ad-hoc HTTP servers to OAuth after unauthorized, then retries', async () => {
const fetchSpy = vi.spyOn(globalThis, 'fetch').mockImplementation(async () => {
return new Response(null, { status: 401, statusText: 'Unauthorized' });
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