fix: support QBT_SID_<port> session cookie in network agent proxy

[lucasliet]

Problem

The Network Agent proxy fails against qBittorrent 5.2.x. Every agent request is rejected with:

{"error":"missing SID"}

Root cause

qBittorrent 5.2.x changed the session cookie name from SID to QBT_SID_<port> (e.g. QBT_SID_8081):

Set-Cookie: QBT_SID_8081=<token>; Path=/; HttpOnly

But src/server/routes/proxy.ts extracts the token assuming the cookie is named exactly SID:

const sid = cookie?.match(/SID=([^;]+)/)?.[1] || ''

For QBT_SID_8081=<token> this yields '', so the agent receives X-QBT-SID: (empty) and replies missing SID.

The login/cookie flow in src/server/utils/qbt.ts is correct — only the token extraction before calling the agent is wrong.

Fix

Replace the regex with a helper that selects the cookie whose name contains SID and returns its value:

export function extractQbtSessionToken(cookie: string | null | undefined): string {
	if (!cookie) return ''

	const sessionCookie = cookie
		.split(';')
		.map((part) => part.trim())
		.find((part) => {
			const equalsIndex = part.indexOf('=')
			return equalsIndex > 0 && part.slice(0, equalsIndex).includes('SID')
		})

	const equalsIndex = sessionCookie?.indexOf('=') ?? -1
	if (equalsIndex < 0) return ''

	return sessionCookie!.slice(equalsIndex + 1)
}

Compatibility

The agent only needs the session value (sent as X-QBT-SID), not the cookie name, so accepting any *SID*-named cookie is correct. Verified against:

Cookie	Result
SID=abc (legacy, < 5.2)	abc
QBT_SID_8081=abc (5.2.x)	abc
QBT_SID_443=abc	abc
QBT_SID_12345=abc	abc
theme=dark (no SID)	'' (rejected)
theme=dark; SID=abc (multi-cookie)	abc

• The name check is case-sensitive (includes('SID')) on purpose: qBittorrent always emits uppercase SID, and case-insensitive matching would false-positive on names like resident.
• Uses indexOf('=') + slice instead of split('=', 2) so values containing = (e.g. base64 padding) are preserved.

Testing

Added __tests__/server/proxy.test.ts (16 cases). Full suite passes (356/356), tsc --noEmit and eslint clean.

Verified with qBittorrent v5.2.2 returning Set-Cookie: QBT_SID_8081=<token>.