DAVKeep

Android CalDAV/CardDAV sync provider with per-account custom HTTP headers and client-certificate (mTLS) auth — for DAV servers behind an identity-aware proxy

What it does Custom HTTP headers on every request, per account, and client certificates from the KeyChain or an imported PKCS#12 archive Contacts and calendar through the platform sync adapter, with collection discovery, CTag/ETag change detection and batched multiget Read-only: the server is the source of truth; phone-side edits are not pushed Failures that name the HTTP status, the first line of the response body, and whether a certificate was offered — the last being what separates "no certificate was sent" from "the certificate was rejected" A terminal-styled log of recent runs, with search, filters and share Per-account scheduling, an unmetered-only mode, and a battery prompt that appears only with evidence of late syncs Removal keeps what it synced. The account stays, reading as Disconnected, until you ask for the data to go too — the rows belong to the account, so an account that goes takes them with it Nothing overwritten by accident. The label is the Android account name, so a form matching an existing account would replace its address, password, certificate and selection. It refuses and names the account instead