Terminal app

kernoid-tui is kernoid’s app for the terminal: mail, files, calendars and contacts, by keyboard. Like the web app it is a first-party app under the MIT licence and talks to kernoid only through JMAP – it shares no code with the server and works against any kernoid installation.

Part	What it does
Mail	the mailboxes of the account and of shared mailboxes it may use; conversations (threads) – or single emails, `t` switches – with full-text search; reading a whole conversation (HTML emails as plain text – nothing is loaded or run), attachments saved to disk, writing, replying, replying to all and forwarding (with the attachments) in your editor, attaching files, keeping drafts, flagging, marking read or unread, moving, deleting (to the trash; in the trash for good); new mail appears by itself
Files	the account’s own files, the tenant’s drives and what others share; folders, downloads and uploads of any size with progress (a file of the same name gets the upload as new content, the old one stays as a version), a file’s versions – saving an earlier one, or restoring it –, details, sharing folders with people and groups (read, edit, or edit and share – as in the web app), new folders, renaming, deleting (to the trash)
Calendar	the account’s calendars and those shared with it, two weeks at a time; repeating events as their instances, all-day events, place, participants with their answers, description; making, changing and deleting events – participants are invited by email –, answering invitations (accept, maybe, decline); events the organizer called off are shown cancelled
Contacts	the cards of the account’s address books with search; name, organisation, addresses, phone numbers, notes; making, changing and deleting contacts; writing an email to a contact

Not yet (OPEN): changing one instance of a repeating event (changes go to the whole series – kernoid’s JMAP does not take single instances yet), more than one address, phone number or organisation per contact (the editor shows the first; saving keeps only those), .ics and .vcf files, finding the server through DNS on Windows (there is no /etc/resolv.conf; give --server).

Logging in with OpenID Connect stays OPEN on purpose. A terminal app would use the device authorization grant (RFC 8628) – the app shows a code, the user confirms it in a browser – and then send the access token to JMAP. Both halves are missing on the server: kernoid’s provider has no device authorization endpoint, and JMAP, IMAP and CalDAV accept a kernoid session or HTTP Basic, not an OAuth bearer token (OAUTHBEARER is OPEN there too). An app password, revocable on its own and limited to programs, is the way until then.

Building

It lives in apps/tui/ – a Cargo workspace of its own, apart from the server’s, with its own Cargo.lock. Rust from rust-toolchain.toml; no OpenSSL (TLS through rustls, certificates checked by the operating system’s verifier).

cd apps/tui
cargo build --release --locked
./target/release/kernoid-tui --help

Logging in

The app logs in like a mail program: with the account’s address and an app password, made in the account settings (POST /v1/account/app-passwords) or by the operator (kernoid account app-password add <account> <name>). The account’s own password works too, but only for an account that needs no second factor.

kernoid-tui --address alice@firma.example --server https://login.firma.example

Server: --server (or KERNOID_SERVER) names the instance – the host that serves /.well-known/jmap. Without it, the app tries the domain of the address (https://firma.example/.well-known/jmap), and when that serves no JMAP, the servers the domain’s SRV records name (_jmap._tcp.firma.example, RFC 8620, 2.2), asked of the name servers in /etc/resolv.conf. An operator publishes, for instance, _jmap._tcp.firma.example. 3600 IN SRV 0 1 443 login.firma.example. The app sends the password only to the host it logs in to: links in the session that name another host are followed on that host.

Password: never as an argument. In this order: the environment variable KERNOID_PASSWORD, the output of --password-command (its first line), or asked for on the terminal. A command reaches the system keychain or a password manager:

# macOS keychain: store once, then let the app read it
security add-generic-password -s kernoid -a alice@firma.example -w
kernoid-tui -a alice@firma.example --password-command 'security find-generic-password -s kernoid -a alice@firma.example -w'
# Linux (libsecret): secret-tool store --label kernoid service kernoid account alice@firma.example
kernoid-tui -a alice@firma.example --password-command 'secret-tool lookup service kernoid account alice@firma.example'
# pass
kernoid-tui -a alice@firma.example --password-command 'pass show kernoid/alice'

HTTPS only: plain HTTP is allowed to this machine (localhost, *.localhost, loopback addresses) – for trying kernoid out – and elsewhere only with --allow-http, as the password would travel readable.
--check logs in, lists the accounts of the session and quits – to check the settings.

Settings file

~/.config/kernoid/tui.toml (or $XDG_CONFIG_HOME/kernoid/tui.toml, or the file KERNOID_TUI_CONFIG or --config names) saves typing; the command line wins over it.

address = "alice@firma.example"
server = "https://login.firma.example"
password_command = "security find-generic-password -s kernoid -a alice@firma.example -w"
downloads = "/Users/alice/Downloads/kernoid"   # default: the download directory
# allow_http = false

Keys

? shows them in the app.

Where	Keys
Everywhere	`1`–`4` or `Tab`: Mail, Files, Calendar, Contacts · `g` or `F5`: load again (in Files also the session: stores shared since) · `?` help · `q` or `Ctrl-C` quit
Lists	`j`/`k` or arrows · `Enter` or `l` open · `h` or `←` back · `PgUp`/`PgDn`
Mail	`c` write · `/` search (`Esc` clears) · `r` reply · `R` reply to all · `f` forward · `m` move · `d` delete · `u` read/unread · `s` flag · `t` conversations or single emails · `a` next account (in the mailboxes)
Reading	`Space`/`PgDn` scroll · `n`/`p` next/previous · `A` attachments (`Enter` saves) · `Esc` back
Files	`Enter` open a folder, or a file’s versions · `←`/`Backspace` up · `d` download · `u` upload · `v` versions (`Enter` save, `r` restore) · `i` details · `S` share a folder · `n` new folder · `R` rename · `D` delete
Sharing	`a` add a person or group (by name or address) · `Enter` next level · `x` remove · `s` save · `Esc` cancel
Calendar	`[`/`]` or `←`/`→` a week back or on · `t` today · `Enter` details · `n` new · `e` edit · `D` delete · `a` accept · `m` maybe · `x` decline
Contacts	`/` search · `n` new · `e` or `Enter` edit · `D` delete · `c` write to the contact

Downloads ask where to save, starting with the download directory; a name that is taken there gets a number. A file is written as <name>.part and renamed once complete.

Writing

Messages are written in $VISUAL or $EDITOR (vi without either), as text: header lines, a blank line, the message.

From: Alice Example <alice@firma.example>
To: Bob <bob@firma.example>
Cc:
Bcc:
Subject: Plans for Friday
Attach: ~/Documents/agenda.pdf

Hi Bob, …

From is one of the addresses the account may send as. Each Attach: line names a file to attach; a forward lists the original’s attachments as Attached: lines – remove one to leave it out. Once the editor closes, the app asks: s send, d keep as a draft, e edit again, c drop. Sending stores the message in Drafts and submits it; once sent it moves to Sent (RFC 8621, 7.5). The text goes into a file of the system’s temporary directory, readable only by you, removed once the editor closed.

Conversations

The list shows a mailbox’s conversations, newest first: the people in each, the number of its messages, the subject of the newest. Opening one shows all its messages, oldest first – also those in other mailboxes, such as your replies in Sent; a reply answers the newest. Moving, deleting, flagging and marking read act on the conversation’s messages in the mailbox shown; your replies in Sent stay where they are.

Events and contacts

They are written in the editor too:

Title: Budget review
Calendar: Calendar
Start: 2026-10-29 10:00
End: 2026-10-29 11:00
All day: no
Time zone: Europe/Berlin
Repeat: none
Location: Room 2
Participants: bob@firma.example, carol@x.example

Please bring the numbers.

# lines are hints (the calendars to choose from, the repetitions). All-day events take dates (2026-10-29); the end is the last day. A new event gets this machine’s time zone. Participants are invited by email when it is saved, and hear of changes and of its deletion; changing an event keeps their answers unless its time changes. Only the organizer changes an event – those invited answer it; deleting an invitation removes it from your calendar without telling the organizer (decline for that). Contacts have Name, Email, Phone, Organization, Address book and a note after the blank line. Something the server did not take, or that could not be read, opens again with e.

Protocols

What	Protocol
Session, requests, uploads, downloads	JMAP Core (RFC 8620), HTTP Basic
Mail	JMAP Mail (RFC 8621): `Mailbox`, `Email`, `Identity`, `EmailSubmission`
Threads	`Email/query` with `collapseThreads`, `Thread/get` (RFC 8621, 3)
Files	JMAP for files (draft-ietf-jmap-filenode-19): `FileNode` with `shareWith`; kernoid’s `FileVersion/get` (`https://kernoid.dev/jmap/file-versions`); principals (RFC 9670) to find people and groups
Calendars	JMAP for Calendars (draft-ietf-jmap-calendars): `Calendar`, `CalendarEvent/query` with `expandRecurrences`, `CalendarEvent/set` with `sendSchedulingMessages` (invitations, answers, cancellations through iTIP)
Contacts	JMAP for Contacts (RFC 9610): `AddressBook`, `ContactCard` (`/set` too)
Finding the server	SRV records `_jmap._tcp` (RFC 8620, 2.2), DNS messages through hickory-proto
Push	the event source of RFC 8620, 7.3 – the app opens it again after a break (the dot next to the address shows whether it is open)