The onboarding "Connect Withings" tap opened /api/withings/connect in a new
tab, which returned a raw JSON 400 for every brand-new account (Withings
credentials are per-user BYO with no env fallback, and the wizard never
collects them). WHOOP, Fitbit, Polar, Oura, and Strava shared the identical
raw-JSON-on-no-creds pattern on their own /connect routes, while every other
failure branch already redirected with a toast reason. All six now redirect
to /settings/integrations?<provider>=error&reason=nocreds instead, and the
wizard's Withings card checks the integrations-status envelope first: unless
credentials are already configured, the CTA reads "Set up in Settings" and
links straight to the credentials form rather than launching a doomed OAuth
handshake.
Also surfaces the BYO-developer-app requirement, which was invisible until a
user was deep inside a Settings card. The source-picker step now says
up front that device sources need a free developer app on the user's own
account; each of the six provider cards gets a compact 3-step guide with the
exact callback URL to register, shown until the user has saved their own
credentials.
Connect mints the PKCE pair, stashes the verifier on the OAuth-state row, and
sends the S256 challenge to the authorize endpoint. Callback reads the verifier
back and presents it on the token exchange, refusing cleanly when it is absent.
The connection-test probe hits the classic /1/user/-/profile.json endpoint.
Land the OAuth + credentials half of the Fitbit / Google Health provider,
cloning the WHOOP provider structure and adapting it to the Google identity
flow.
- Client OAuth half (src/lib/fitbit/client.ts): Google authorize-URL builder
(access_type=offline + prompt=consent), authorization-code exchange, token
refresh, and a profile fetch for the connection's external user id. Client
credentials ride in an HTTP Basic-auth header on the token endpoint; the
four launch Restricted read scopes are pinned in FITBIT_OAUTH_SCOPE. All
egress goes through safeFetch.
- Non-rotating refresh tokens: getValidToken refreshes at expiry-minus-five-
minutes, persists the new access token + expiry, and overwrites the stored
refresh token ONLY when the response carries a fresh one — Google keeps the
refresh token stable, unlike WHOOP.
- BYO credentials route (PUT/GET/DELETE /api/fitbit/credentials): per-user
client id/secret stored encrypted on the User columns, built field-by-field
under requireAuth.
- OAuth state + connect + callback routes: a random base64url nonce backed by
a 10-minute FitbitOAuthState ledger row carries the (nonce -> userId)
mapping; the callback validates the cookie/URL state with timingSafeEqual,
consumes the row atomically (replay/expired/cross-user reason tags),
exchanges the code, upserts the encrypted FitbitConnection, clears prior
reauth state, and enqueues the self-converging history backfill.
- Response classifier mirrors WHOOP's HTTP-status buckets; Google signals a
revoked grant with a 401, so there is no invalid_grant body special-case.
Tests cover the authorize URL, Basic-auth token exchange, the no-rotation
refresh branch (token preserved when omitted, overwritten when present), the
classifier status table, and the OAuth-state nonce mint.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Marc-André Bombeck