From 266fb90e45c58cd5a6aac0deb8b91a6f16029aba Mon Sep 17 00:00:00 2001
From: samialabri <sami.alabri@gmail.com>
Date: Sat, 17 Oct 2026 23:49:48 +0900
Subject: [PATCH] Onboarding core: setup payloads, enrollment tickets,
 scan-to-join (docs/10)

* kv-proto: ticket and join wire types, LoginFinish.ticket, b64_opt.
* kv-crypto: pairing.rs (HPKE AuthPSK seal/open with the QR secret as PSK, SAS code).
* kv-sync: onboarding.rs (kestrove://setup/v1 and kestrove://join/v1 codec with
  strict validation), ApiClient ticket/join calls and login_with_ticket, test
  server support for tickets and rendezvous.
* kv-ffi: parse/encode_setup_payload, setup_payload_for_kit, add_device_payload,
  revoke_enrollment_ticket, login_with_setup, join_start/poll/cancel,
  join_approve/send. The Secret Key is kept locally, HPKE-sealed to enc_pk.
* Tests: codec round trips and rejections, AuthPSK tamper cases, end-to-end
  Add-device QR and scan-to-join between two clients, forged bundles, bound
  tickets; live test extended with scan-to-join.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
---
 Cargo.lock                         |   1 +
 crates/kv-crypto/src/lib.rs        |   1 +
 crates/kv-crypto/src/pairing.rs    | 157 +++++++++++++++
 crates/kv-ffi/Cargo.toml           |   1 +
 crates/kv-ffi/src/lib.rs           |  83 +++++++-
 crates/kv-ffi/src/onboarding.rs    | 296 ++++++++++++++++++++++++++++
 crates/kv-ffi/src/tests.rs         | 200 +++++++++++++++++++
 crates/kv-ffi/tests/live_server.rs |  26 ++-
 crates/kv-proto/src/lib.rs         | 138 +++++++++++++
 crates/kv-sync/src/client.rs       |  74 ++++++-
 crates/kv-sync/src/lib.rs          |   2 +
 crates/kv-sync/src/onboarding.rs   | 300 +++++++++++++++++++++++++++++
 crates/kv-sync/src/test_server.rs  | 145 +++++++++++++-
 crates/kv-sync/src/wire.rs         |   2 +
 14 files changed, 1409 insertions(+), 17 deletions(-)
 create mode 100644 crates/kv-crypto/src/pairing.rs
 create mode 100644 crates/kv-ffi/src/onboarding.rs
 create mode 100644 crates/kv-sync/src/onboarding.rs

diff --git a/Cargo.lock b/Cargo.lock
index 3d04d69..e91dabe 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1347,6 +1347,7 @@ dependencies = [
 name = "kv-ffi"
 version = "0.1.0"
 dependencies = [
+ "base64 0.22.1",
  "ciborium",
  "hkdf",
  "kv-crypto",
diff --git a/crates/kv-crypto/src/lib.rs b/crates/kv-crypto/src/lib.rs
index 55fb5db..7eb056f 100644
--- a/crates/kv-crypto/src/lib.rs
+++ b/crates/kv-crypto/src/lib.rs
@@ -9,6 +9,7 @@ pub mod aad;
 pub mod aead;
 pub mod kdf;
 pub mod keys;
+pub mod pairing;
 pub mod seal;
 pub mod secret_key;
 
diff --git a/crates/kv-crypto/src/pairing.rs b/crates/kv-crypto/src/pairing.rs
new file mode 100644
index 0000000..16c1ae6
--- /dev/null
+++ b/crates/kv-crypto/src/pairing.rs
@@ -0,0 +1,157 @@
+//! Scan-to-join encryption (kestrove-spec/docs/10 §4): HPKE (RFC 9180) in AuthPSK mode with the suite of
+//! [`crate::seal`], plus the short authentication string both screens show.
+//!
+//! * The joining device's ephemeral key and the PSK (`qr_secret`) travel only through the QR code, so the
+//!   server can neither read nor forge a bundle.
+//! * Auth mode binds the bundle to the approving device's ephemeral key from the `hello`, which the code
+//!   is computed over.
+
+use hpke::{
+    aead::ChaCha20Poly1305, kdf::HkdfSha256, kem::X25519HkdfSha256, Deserializable, Kem as KemTrait, OpModeR, OpModeS,
+    PskBundle, Serializable,
+};
+use kv_proto::{Alg, Envelope, FORMAT_VERSION};
+use rand_core::OsRng;
+use sha2::{Digest, Sha256};
+use uuid::Uuid;
+use zeroize::Zeroizing;
+
+use crate::{CryptoError, Result};
+
+type Kem = X25519HkdfSha256;
+const INFO: &[u8] = b"kestrove/v1/join";
+const SAS_LABEL: &[u8] = b"kestrove/v1/join/sas";
+/// Length of `qr_secret`, the HPKE PSK.
+pub const PSK_LEN: usize = 32;
+
+/// An ephemeral X25519 key for one join attempt (either side).
+pub struct PairingKeypair {
+    sk: <Kem as KemTrait>::PrivateKey,
+    pk: <Kem as KemTrait>::PublicKey,
+}
+
+impl PairingKeypair {
+    pub fn generate() -> Self {
+        let (sk, pk) = Kem::gen_keypair(&mut OsRng);
+        Self { sk, pk }
+    }
+
+    pub fn public_bytes(&self) -> [u8; 32] {
+        self.pk.to_bytes().into()
+    }
+}
+
+fn aad(rid: &[u8]) -> Vec<u8> {
+    let mut aad = INFO.to_vec();
+    aad.push(0);
+    aad.extend_from_slice(rid);
+    aad
+}
+
+fn public(bytes: &[u8]) -> Result<<Kem as KemTrait>::PublicKey> {
+    <Kem as KemTrait>::PublicKey::from_bytes(bytes).map_err(|_| CryptoError::Malformed)
+}
+
+/// Approving device: seals `plaintext` to the joining device's key from the QR.
+pub fn seal(
+    sender: &PairingKeypair,
+    recipient_pub: &[u8],
+    psk: &[u8],
+    rid: &[u8],
+    plaintext: &[u8],
+) -> Result<Envelope> {
+    if psk.len() != PSK_LEN {
+        return Err(CryptoError::Malformed);
+    }
+    let mode = OpModeS::AuthPsk((sender.sk.clone(), sender.pk.clone()), PskBundle { psk, psk_id: rid });
+    let (encapped, ct) = hpke::single_shot_seal::<ChaCha20Poly1305, HkdfSha256, Kem, _>(
+        &mode,
+        &public(recipient_pub)?,
+        INFO,
+        plaintext,
+        &aad(rid),
+        &mut OsRng,
+    )
+    .map_err(|_| CryptoError::Encrypt)?;
+    Ok(Envelope {
+        v: FORMAT_VERSION,
+        alg: Alg::HpkeX25519ChaCha,
+        kid: Uuid::nil(),
+        n: vec![],
+        ct,
+        enc: encapped.to_bytes().to_vec(),
+    })
+}
+
+/// Joining device: opens a bundle from the sender whose key arrived in the `hello`.
+pub fn open(
+    recipient: &PairingKeypair,
+    sender_pub: &[u8],
+    psk: &[u8],
+    rid: &[u8],
+    env: &Envelope,
+) -> Result<Zeroizing<Vec<u8>>> {
+    if env.v != FORMAT_VERSION || env.alg != Alg::HpkeX25519ChaCha {
+        return Err(CryptoError::Unsupported);
+    }
+    let encapped = <Kem as KemTrait>::EncappedKey::from_bytes(&env.enc).map_err(|_| CryptoError::Malformed)?;
+    let mode = OpModeR::AuthPsk(public(sender_pub)?, PskBundle { psk, psk_id: rid });
+    hpke::single_shot_open::<ChaCha20Poly1305, HkdfSha256, Kem>(
+        &mode,
+        &recipient.sk,
+        &encapped,
+        INFO,
+        &env.ct,
+        &aad(rid),
+    )
+    .map(Zeroizing::new)
+    .map_err(|_| CryptoError::Decrypt)
+}
+
+/// The 6-digit code both screens show: `SHA-256(label || 0x00 || rid || D_pub || P_pub)`, first 4 bytes as a
+/// big-endian u32, mod 10^6, formatted `"123 456"`.
+pub fn sas(rid: &[u8], joining_pub: &[u8], approving_pub: &[u8]) -> String {
+    let mut h = Sha256::new();
+    h.update(SAS_LABEL);
+    h.update([0]);
+    h.update(rid);
+    h.update(joining_pub);
+    h.update(approving_pub);
+    let d = h.finalize();
+    let n = u32::from_be_bytes([d[0], d[1], d[2], d[3]]) % 1_000_000;
+    format!("{:03} {:03}", n / 1000, n % 1000)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn seal_open_and_tamper() {
+        let (desk, phone) = (PairingKeypair::generate(), PairingKeypair::generate());
+        let (psk, rid) = ([3u8; 32], b"rendezvous-id-16");
+        let env = seal(&phone, &desk.public_bytes(), &psk, rid, b"setup payload").unwrap();
+        assert_eq!(&**open(&desk, &phone.public_bytes(), &psk, rid, &env).unwrap(), b"setup payload");
+
+        // Wrong PSK (no QR), wrong sender (server swapped the hello), other rendezvous, other recipient.
+        assert!(open(&desk, &phone.public_bytes(), &[4u8; 32], rid, &env).is_err());
+        assert!(open(&desk, &PairingKeypair::generate().public_bytes(), &psk, rid, &env).is_err());
+        assert!(open(&desk, &phone.public_bytes(), &psk, b"another-rid-0000", &env).is_err());
+        assert!(open(&PairingKeypair::generate(), &phone.public_bytes(), &psk, rid, &env).is_err());
+        let mut bad = env.clone();
+        bad.ct[0] ^= 1;
+        assert!(open(&desk, &phone.public_bytes(), &psk, rid, &bad).is_err());
+        assert!(seal(&phone, &desk.public_bytes(), &[1u8; 16], rid, b"x").is_err(), "short psk");
+        assert!(seal(&phone, &[0u8; 5], &psk, rid, b"x").is_err());
+    }
+
+    #[test]
+    fn sas_is_stable_and_order_sensitive() {
+        // kestrove-spec/vectors/onboarding.json
+        assert_eq!(sas(&[1; 16], &[2; 32], &[3; 32]), "238 148");
+        assert_ne!(sas(&[1; 16], &[2; 32], &[3; 32]), sas(&[1; 16], &[3; 32], &[2; 32]));
+        let code = sas(&[1; 16], &[2; 32], &[3; 32]);
+        assert_eq!(code.len(), 7);
+        assert!(code.chars().enumerate().all(|(i, c)| if i == 3 { c == ' ' } else { c.is_ascii_digit() }));
+    }
+}
diff --git a/crates/kv-ffi/Cargo.toml b/crates/kv-ffi/Cargo.toml
index fb2d959..dc56391 100644
--- a/crates/kv-ffi/Cargo.toml
+++ b/crates/kv-ffi/Cargo.toml
@@ -22,6 +22,7 @@ kv-store.workspace = true
 kv-sync.workspace = true
 kv-import.workspace = true
 serde.workspace = true
+base64.workspace = true
 hkdf.workspace = true
 sha2.workspace = true
 tokio = { workspace = true }
diff --git a/crates/kv-ffi/src/lib.rs b/crates/kv-ffi/src/lib.rs
index a87d53c..93366f5 100644
--- a/crates/kv-ffi/src/lib.rs
+++ b/crates/kv-ffi/src/lib.rs
@@ -36,6 +36,10 @@ mod passkeys;
 pub use passkeys::{kestrove_aaguid, PasskeyAssertion, PasskeyRegistration, PasskeySummary};
 mod import;
 pub use import::{DuplicateHandling, ImportFormat, ImportOptions, ImportPreview, ImportReport};
+mod onboarding;
+pub use onboarding::{
+    encode_setup_payload, parse_setup_payload, AddDevicePayload, JoinConfirm, JoinProgress, JoinSession, SetupInfo,
+};
 
 #[derive(Debug, thiserror::Error, uniffi::Error)]
 pub enum CoreError {
@@ -279,6 +283,10 @@ struct AccountRecord {
     primary_vault: Uuid,
     #[serde(default)]
     local_unlock: Option<LocalUnlockRecord>,
+    /// The Secret Key, HPKE-sealed to `enc_pk` (docs/02 "Secrets the user holds"), so an unlocked device can
+    /// build setup payloads (docs/10). Absent on accounts created before this field until the next password unlock.
+    #[serde(default)]
+    secret_key: Option<Envelope>,
 }
 
 /// Keyset (and OPAQUE input) wrapped under the biometric-protected Local Unlock Key.
@@ -324,6 +332,8 @@ pub struct VaultCore {
     store: Arc<dyn Store>,
     inner: Mutex<Inner>,
     sync_lock: tokio::sync::Mutex<()>,
+    /// In-flight scan-to-join, on either side (docs/10 §4).
+    join: Mutex<Option<onboarding::JoinState>>,
 }
 
 fn luk_subkey(luk: &[u8], info: &[u8]) -> Result<SymKey> {
@@ -332,6 +342,17 @@ fn luk_subkey(luk: &[u8], info: &[u8]) -> Result<SymKey> {
     Ok(SymKey::from_bytes(Uuid::nil(), out))
 }
 
+fn secret_key_aad(account_id: Uuid) -> Vec<u8> {
+    let mut aad = b"kestrove/v1/local/secret-key".to_vec();
+    aad.extend_from_slice(account_id.as_bytes());
+    aad
+}
+
+/// Seals the Secret Key to the account's own encryption key, for local storage only.
+fn seal_secret_key(account_id: Uuid, enc_pk: &[u8], sk: &SecretKey) -> Result<Envelope> {
+    Ok(kv_crypto::seal::seal_to(account_id, enc_pk, sk.expose(), &secret_key_aad(account_id))?)
+}
+
 fn auth_input_aad(account_id: Uuid) -> Vec<u8> {
     let mut aad = b"kestrove/v1/local/auth-input".to_vec();
     aad.extend_from_slice(account_id.as_bytes());
@@ -407,6 +428,7 @@ impl VaultCore {
             sig_pk: keyset.sig_public().to_vec(),
             primary_vault: vault_id,
             local_unlock: None,
+            secret_key: Some(seal_secret_key(account_id, &keyset.enc.public_bytes(), &secret_key)?),
         };
         self.save_account(&account)?;
         inner.account = Some(account);
@@ -426,6 +448,12 @@ impl VaultCore {
         let auk = SymKey::from_bytes(Uuid::nil(), *derived.auk);
         let keyset = AccountKeyset::unwrap(acct.account_id, &auk, &acct.wrapped_keyset)?;
         let vault_key = self.open_vault_key(&keyset, acct.primary_vault)?;
+        if acct.secret_key.is_none() {
+            let mut acct = acct.clone();
+            acct.secret_key = Some(seal_secret_key(acct.account_id, &keyset.enc.public_bytes(), &sk)?);
+            self.save_account(&acct)?;
+            inner.account = Some(acct);
+        }
         inner.unlocked = Some(Unlocked {
             keyset: Arc::new(keyset),
             vault_key: Arc::new(vault_key),
@@ -740,8 +768,28 @@ impl VaultCore {
         secret_key: String,
         totp: Option<String>,
     ) -> Result<LoginResult> {
-        let api = self.api()?;
         let sk = SecretKey::parse(&secret_key)?;
+        self.login_inner(master_password, sk, totp, None, None).await
+    }
+
+    /// Pull, merge, push and verify every vault. Renews an expired session automatically when the
+    /// master password was used to unlock in this session; otherwise fails with `NotAuthenticated`.
+    pub async fn sync_now(&self) -> Result<SyncReport> {
+        self.sync_now_inner().await
+    }
+}
+
+impl VaultCore {
+    /// `login`, optionally presenting an enrollment ticket and checking the server holds `expect_account`.
+    async fn login_inner(
+        &self,
+        master_password: String,
+        sk: SecretKey,
+        totp: Option<String>,
+        ticket: Option<String>,
+        expect_account: Option<Uuid>,
+    ) -> Result<LoginResult> {
+        let api = self.api()?;
         let local = self.lock_inner().account.clone();
         // A single-tenant server tells a new device which account it holds; an existing device
         // keeps using the parameters it already trusts (no downgrade by the server).
@@ -752,8 +800,13 @@ impl VaultCore {
                 (pre.account_id, pre.kdf)
             }
         };
+        if expect_account.is_some_and(|want| want != account_id) {
+            return Err(CoreError::Invalid { msg: "the server holds a different account than the setup code".into() });
+        }
         let derived = kdf::derive_keys(&master_password, &sk, account_id, &kdf_params)?;
-        if self.do_login(&api, account_id, derived.auth_input.as_ref(), totp).await? == LoginResult::PendingApproval {
+        if self.do_login_ticket(&api, account_id, derived.auth_input.as_ref(), totp, ticket).await?
+            == LoginResult::PendingApproval
+        {
             return Ok(LoginResult::PendingApproval);
         }
         let auk = SymKey::from_bytes(Uuid::nil(), *derived.auk);
@@ -778,11 +831,16 @@ impl VaultCore {
                     sig_pk: info.sig_pk,
                     primary_vault: Uuid::nil(), // chosen after the first sync
                     local_unlock: None,
+                    secret_key: None,
                 }
             }
         };
         let keyset = AccountKeyset::unwrap(account_id, &auk, &acct.wrapped_keyset)?;
         let vault_key = self.open_vault_key(&keyset, acct.primary_vault)?;
+        let mut acct = acct;
+        if acct.secret_key.is_none() {
+            acct.secret_key = Some(seal_secret_key(account_id, &keyset.enc.public_bytes(), &sk)?);
+        }
         self.save_account(&acct)?;
         let mut inner = self.lock_inner();
         inner.account = Some(acct);
@@ -794,9 +852,7 @@ impl VaultCore {
         Ok(LoginResult::Ok)
     }
 
-    /// Pull, merge, push and verify every vault. Renews an expired session automatically when the
-    /// master password was used to unlock in this session; otherwise fails with `NotAuthenticated`.
-    pub async fn sync_now(&self) -> Result<SyncReport> {
+    async fn sync_now_inner(&self) -> Result<SyncReport> {
         let _guard = self.sync_lock.lock().await;
         let api = self.api()?;
         let (_, u) = self.unlocked_snapshot()?;
@@ -825,7 +881,10 @@ impl VaultCore {
             vaults_skipped: report.vaults_skipped.len() as u32,
         })
     }
+}
 
+#[uniffi::export(async_runtime = "tokio")]
+impl VaultCore {
     /// Devices enrolled on the account, including ones waiting for approval.
     pub async fn list_devices(&self) -> Result<Vec<DeviceDto>> {
         let devices = self.api()?.devices().await?;
@@ -889,6 +948,7 @@ impl VaultCore {
             store,
             inner: Mutex::new(Inner { account, server, ..Default::default() }),
             sync_lock: tokio::sync::Mutex::new(()),
+            join: Mutex::new(None),
         }))
     }
 
@@ -960,9 +1020,20 @@ impl VaultCore {
         account_id: Uuid,
         auth_input: &[u8],
         totp: Option<String>,
+    ) -> Result<LoginResult> {
+        self.do_login_ticket(api, account_id, auth_input, totp, None).await
+    }
+
+    async fn do_login_ticket(
+        &self,
+        api: &ApiClient,
+        account_id: Uuid,
+        auth_input: &[u8],
+        totp: Option<String>,
+        ticket: Option<String>,
     ) -> Result<LoginResult> {
         let device = self.enroll()?;
-        match api.login(account_id, auth_input, device, totp).await? {
+        match api.login_with_ticket(account_id, auth_input, device, totp, ticket).await? {
             LoginOutcome::Ok { session } => {
                 self.store.put_meta(META_SESSION, session.as_bytes())?;
                 Ok(LoginResult::Ok)
diff --git a/crates/kv-ffi/src/onboarding.rs b/crates/kv-ffi/src/onboarding.rs
new file mode 100644
index 0000000..ae23fdd
--- /dev/null
+++ b/crates/kv-ffi/src/onboarding.rs
@@ -0,0 +1,296 @@
+//! Easy onboarding (kestrove-spec/docs/10): Setup QR / Setup Code, enrollment tickets and scan-to-join.
+
+use base64::{engine::general_purpose::URL_SAFE_NO_PAD, Engine};
+use kv_crypto::{pairing, pairing::PairingKeypair, random_bytes, secret_key::SecretKey};
+use kv_proto::{DeviceEnroll, JoinState as WireJoinState};
+use kv_sync::onboarding::{JoinQr, SetupPayload};
+use sha2::{Digest, Sha256};
+use zeroize::Zeroizing;
+
+use crate::{
+    device_key_fingerprint, internal, parse_id, platform_to_dto, secret_key_aad, CoreError, LoginResult, PlatformDto,
+    Result, VaultCore,
+};
+
+/// A parsed, validated setup payload: everything a new device needs except the master password.
+#[derive(Clone, PartialEq, Eq, uniffi::Record)]
+pub struct SetupInfo {
+    /// Normalized server URL.
+    pub server_url: String,
+    /// Standard base64 SPKI pins, the format `configure_server` takes. Empty = WebPKI only.
+    pub spki_pins: Vec<String>,
+    pub account_id: String,
+    /// Display form `K1-…`. Store it like the app stores a typed Secret Key.
+    pub secret_key: String,
+    /// Enrollment ticket; `login_with_setup` presents it so no manual approval is needed.
+    pub ticket: Option<String>,
+}
+
+impl std::fmt::Debug for SetupInfo {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.debug_struct("SetupInfo")
+            .field("server_url", &self.server_url)
+            .field("spki_pins", &self.spki_pins)
+            .field("account_id", &self.account_id)
+            .field("secret_key", &"<redacted>")
+            .field("ticket", &self.ticket.as_ref().map(|_| "<redacted>"))
+            .finish()
+    }
+}
+
+/// The "Add a device" QR: a setup payload with a fresh, unbound ticket.
+#[derive(Debug, Clone, PartialEq, Eq, uniffi::Record)]
+pub struct AddDevicePayload {
+    pub payload: String,
+    /// For `revoke_enrollment_ticket` when the user cancels.
+    pub ticket_id: String,
+    /// Unix seconds; hide the QR after this.
+    pub expires_at: i64,
+}
+
+/// Shown by the joining device (desktop): a QR for a signed-in phone to scan.
+#[derive(Debug, Clone, PartialEq, Eq, uniffi::Record)]
+pub struct JoinSession {
+    pub qr: String,
+    /// Unix seconds.
+    pub expires_at: i64,
+}
+
+/// Result of `join_poll`. `code` appears once a phone has scanned the QR; show it so the user can compare.
+/// `setup` appears once the phone sent the bundle: then ask for the master password and call `login_with_setup`.
+#[derive(Debug, Clone, PartialEq, Eq, uniffi::Record)]
+pub struct JoinProgress {
+    pub code: Option<String>,
+    pub setup: Option<SetupInfo>,
+}
+
+/// Shown by the approving device after scanning: the code to compare and who is asking.
+#[derive(Debug, Clone, PartialEq, Eq, uniffi::Record)]
+pub struct JoinConfirm {
+    /// `"123 456"`. The joining device shows the same code.
+    pub code: String,
+    pub device_name: String,
+    pub platform: PlatformDto,
+    /// Same format as `DeviceDto.key_fingerprint`.
+    pub key_fingerprint: String,
+}
+
+/// Local state of an in-flight scan-to-join.
+pub(crate) enum JoinState {
+    /// This device is joining (it showed the QR).
+    Joining {
+        rendezvous_id: String,
+        read_token: String,
+        keypair: PairingKeypair,
+        qr_secret: Zeroizing<[u8; 32]>,
+        sender_pub: Option<Vec<u8>>,
+    },
+    /// This device scanned a QR and said hello; waiting for the user to confirm the code.
+    Approving { qr: JoinQr, keypair: PairingKeypair, device: DeviceEnroll },
+}
+
+fn invalid(msg: &str) -> CoreError {
+    CoreError::Invalid { msg: msg.into() }
+}
+
+fn to_info(p: SetupPayload) -> SetupInfo {
+    SetupInfo {
+        server_url: p.server_url,
+        spki_pins: p.spki_pins,
+        account_id: p.account_id.to_string(),
+        secret_key: p.secret_key.to_string(),
+        ticket: p.ticket,
+    }
+}
+
+fn from_info(i: &SetupInfo) -> Result<SetupPayload> {
+    Ok(SetupPayload {
+        server_url: i.server_url.clone(),
+        spki_pins: i.spki_pins.clone(),
+        account_id: parse_id(&i.account_id)?,
+        secret_key: Zeroizing::new(i.secret_key.clone()),
+        ticket: i.ticket.clone(),
+    })
+}
+
+/// Validates a scanned or pasted Setup Code (`kestrove://setup/v1?…`, docs/10 §2).
+#[uniffi::export]
+pub fn parse_setup_payload(payload: String) -> Result<SetupInfo> {
+    Ok(to_info(SetupPayload::parse(&payload)?))
+}
+
+/// Canonical encoding of a setup payload (for tools and tests; apps use `setup_payload_for_kit`).
+#[uniffi::export]
+pub fn encode_setup_payload(info: SetupInfo) -> Result<String> {
+    Ok(from_info(&info)?.encode()?.to_string())
+}
+
+#[uniffi::export(async_runtime = "tokio")]
+impl VaultCore {
+    /// The Setup Code for the Emergency Kit: server, pins, account id and Secret Key, no ticket.
+    /// Needs an unlocked vault and a configured server.
+    pub fn setup_payload_for_kit(&self) -> Result<String> {
+        Ok(self.setup_payload(None)?.encode()?.to_string())
+    }
+
+    /// The "Add a device" QR: issues a 10-minute, single-use, unbound enrollment ticket and returns the
+    /// payload. Show it as a secret view; on Cancel call `revoke_enrollment_ticket`.
+    pub async fn add_device_payload(&self) -> Result<AddDevicePayload> {
+        let created = self.api()?.create_ticket(None).await?;
+        let payload = self.setup_payload(Some(created.ticket))?.encode()?.to_string();
+        Ok(AddDevicePayload { payload, ticket_id: created.ticket_id.to_string(), expires_at: created.expires_at })
+    }
+
+    pub async fn revoke_enrollment_ticket(&self, ticket_id: String) -> Result<()> {
+        Ok(self.api()?.revoke_ticket(parse_id(&ticket_id)?).await?)
+    }
+
+    /// New device: configures the server and pins from `setup`, then logs in with the master password and the
+    /// Secret Key from `setup`, presenting its ticket (if any) so no manual approval is needed. Call
+    /// `set_device_signer` first. Then call `sync_now`.
+    pub async fn login_with_setup(&self, setup: SetupInfo, master_password: String) -> Result<LoginResult> {
+        let p = from_info(&setup)?;
+        if self.lock_inner().account.as_ref().is_some_and(|a| a.account_id != p.account_id) {
+            return Err(invalid("this device holds a different account"));
+        }
+        self.configure_server(p.server_url.clone(), p.spki_pins.clone())?;
+        let sk = SecretKey::parse(&p.secret_key)?;
+        self.login_inner(master_password, sk, None, p.ticket.clone(), Some(p.account_id)).await
+    }
+
+    /// Joining device (no camera): opens a rendezvous on `server_url` and returns the QR to show.
+    /// Then call `join_poll` every 2 seconds. Call `set_device_signer` first.
+    pub async fn join_start(&self, server_url: String) -> Result<JoinSession> {
+        if self.has_account() {
+            return Err(invalid("this device already has an account"));
+        }
+        // Unpinned for now: only ciphertext and public data cross this connection. The pins arrive in the bundle.
+        self.configure_server(server_url, vec![])?;
+        let api = self.api()?;
+        let created = api.join_create(self.enroll()?).await?;
+        let keypair = PairingKeypair::generate();
+        let qr_secret = Zeroizing::new(random_bytes::<32>());
+        let qr = JoinQr {
+            server_url: api.base_url().to_string(),
+            rendezvous_id: created.rendezvous_id.clone(),
+            public_key: keypair.public_bytes(),
+            qr_secret: qr_secret.clone(),
+        }
+        .encode()?;
+        *self.lock_join() = Some(JoinState::Joining {
+            rendezvous_id: created.rendezvous_id,
+            read_token: created.read_token,
+            keypair,
+            qr_secret,
+            sender_pub: None,
+        });
+        Ok(JoinSession { qr, expires_at: created.expires_at })
+    }
+
+    /// Joining device: polls the rendezvous. `NotFound` means it expired (start again).
+    pub async fn join_poll(&self) -> Result<JoinProgress> {
+        let (rid, token) = match &*self.lock_join() {
+            Some(JoinState::Joining { rendezvous_id, read_token, .. }) => (rendezvous_id.clone(), read_token.clone()),
+            _ => return Err(invalid("no join in progress")),
+        };
+        let poll = match self.api()?.join_poll(&rid, &token).await {
+            Err(kv_sync::SyncError::NotFound) => {
+                self.join_cancel();
+                return Err(CoreError::NotFound);
+            }
+            other => other?,
+        };
+        let mut guard = self.lock_join();
+        let Some(JoinState::Joining { keypair, qr_secret, sender_pub, .. }) = guard.as_mut() else {
+            return Err(invalid("join was cancelled"));
+        };
+        let rid_bytes = URL_SAFE_NO_PAD.decode(&rid).map_err(internal)?;
+        if let Some(p) = &poll.sender_pub {
+            // The code was shown for this key; a different one now means someone swapped it.
+            if sender_pub.as_ref().is_some_and(|known| known != p) {
+                *guard = None;
+                return Err(invalid("the approving device changed; start again"));
+            }
+            *sender_pub = Some(p.clone());
+        }
+        let code = sender_pub.as_ref().map(|p| pairing::sas(&rid_bytes, &keypair.public_bytes(), p));
+        if poll.state != WireJoinState::Sealed {
+            return Ok(JoinProgress { code, setup: None });
+        }
+        let (Some(bundle), Some(p)) = (&poll.bundle, sender_pub.as_ref()) else {
+            *guard = None;
+            return Err(internal("sealed rendezvous without bundle or sender key"));
+        };
+        let opened = pairing::open(keypair, p, qr_secret.as_ref(), &rid_bytes, bundle);
+        *guard = None;
+        let plaintext = opened.map_err(|_| invalid("the setup bundle could not be opened; start again"))?;
+        let text = std::str::from_utf8(&plaintext).map_err(|_| invalid("malformed setup bundle"))?;
+        Ok(JoinProgress { code, setup: Some(to_info(SetupPayload::parse(text)?)) })
+    }
+
+    /// Forgets the local join state on either side.
+    pub fn join_cancel(&self) {
+        *self.lock_join() = None;
+    }
+
+    /// Approving device (signed in, unlocked): answers a scanned join QR and returns the code to compare.
+    /// Refuses a QR for a different server. Nothing secret is sent until `join_send`.
+    pub async fn join_approve(&self, qr: String) -> Result<JoinConfirm> {
+        let qr = JoinQr::parse(&qr)?;
+        let api = self.api()?;
+        if kv_sync::transport::normalize_base_url(&qr.server_url)? != api.base_url() {
+            return Err(invalid("this computer is connecting to a different server"));
+        }
+        self.unlocked_snapshot()?;
+        let keypair = PairingKeypair::generate();
+        let hello = api.join_hello(&qr.rendezvous_id, keypair.public_bytes().to_vec()).await?;
+        let rid_bytes = URL_SAFE_NO_PAD.decode(&qr.rendezvous_id).map_err(internal)?;
+        let confirm = JoinConfirm {
+            code: pairing::sas(&rid_bytes, &qr.public_key, &keypair.public_bytes()),
+            device_name: hello.device.name.clone(),
+            platform: platform_to_dto(hello.device.platform),
+            key_fingerprint: device_key_fingerprint(&hello.device.p256_pk),
+        };
+        *self.lock_join() = Some(JoinState::Approving { qr, keypair, device: hello.device });
+        Ok(confirm)
+    }
+
+    /// Approving device, after the user confirmed the code: issues a ticket bound to the joining device's key
+    /// and sends the sealed setup bundle.
+    pub async fn join_send(&self) -> Result<()> {
+        let Some(JoinState::Approving { qr, keypair, device }) = self.lock_join().take() else {
+            return Err(invalid("no join to approve"));
+        };
+        let api = self.api()?;
+        let ticket = api.create_ticket(Some(Sha256::digest(&device.p256_pk).to_vec())).await?;
+        let payload = self.setup_payload(Some(ticket.ticket))?.encode()?;
+        let rid_bytes = URL_SAFE_NO_PAD.decode(&qr.rendezvous_id).map_err(internal)?;
+        let bundle = pairing::seal(&keypair, &qr.public_key, qr.qr_secret.as_ref(), &rid_bytes, payload.as_bytes())?;
+        Ok(api.join_send(&qr.rendezvous_id, bundle).await?)
+    }
+}
+
+impl VaultCore {
+    fn lock_join(&self) -> std::sync::MutexGuard<'_, Option<JoinState>> {
+        self.join.lock().unwrap_or_else(|p| p.into_inner())
+    }
+
+    /// This device's account as a setup payload (unlocked, server configured).
+    fn setup_payload(&self, ticket: Option<String>) -> Result<SetupPayload> {
+        let (acct, u) = self.unlocked_snapshot()?;
+        let server = self.lock_inner().server.clone().ok_or(CoreError::NotConfigured)?;
+        let sealed = acct
+            .secret_key
+            .as_ref()
+            .ok_or_else(|| invalid("unlock with the master password and Secret Key once to enable setup codes"))?;
+        let raw = u.keyset.enc.open(sealed, &secret_key_aad(acct.account_id))?;
+        let raw: [u8; 16] = raw.as_slice().try_into().map_err(|_| internal("stored Secret Key length"))?;
+        Ok(SetupPayload {
+            server_url: server.url,
+            spki_pins: server.pins,
+            account_id: acct.account_id,
+            secret_key: SecretKey::from_bytes(raw).to_display(),
+            ticket,
+        })
+    }
+}
diff --git a/crates/kv-ffi/src/tests.rs b/crates/kv-ffi/src/tests.rs
index e75306f..c30f044 100644
--- a/crates/kv-ffi/src/tests.rs
+++ b/crates/kv-ffi/src/tests.rs
@@ -355,3 +355,203 @@ async fn delete_item_seals_the_tombstone_and_forged_deletes_are_refused() {
     }
     assert_eq!(b.get_item(kept).unwrap().password.as_deref(), Some("pw1"));
 }
+
+// ---------------------------------------------------------------- onboarding (docs/10)
+
+/// A signed-in first device "a" with one item, on a server that requires approval for new devices.
+async fn phone_with_item(server: &TestServer) -> (Arc<VaultCore>, String, String) {
+    let a = VaultCore::new_in_memory();
+    let sk = a.create_account(PW.into()).unwrap();
+    connect(&a, server);
+    a.register_account(SETUP_TOKEN.into()).await.unwrap();
+    let id = a.save_item(login_item("Bank", "pw-a")).unwrap();
+    a.sync_now().await.unwrap();
+    server.state().require_approval = true;
+    (a, sk, id)
+}
+
+#[tokio::test]
+async fn kit_payload_carries_the_secret_key_and_survives_biometric_unlock() {
+    let server = TestServer::start().await;
+    let a = VaultCore::new_in_memory();
+    assert!(matches!(a.setup_payload_for_kit(), Err(CoreError::NoAccount)));
+    let sk = a.create_account(PW.into()).unwrap();
+    assert!(matches!(a.setup_payload_for_kit(), Err(CoreError::NotConfigured)));
+    a.configure_server(server.url(), vec!["47DEQpj8HBSa+/TImW+5JCeuQeRkm5NMpJWZG3hSuFU=".into()]).unwrap();
+
+    let kit = a.setup_payload_for_kit().unwrap();
+    assert!(kit.starts_with("kestrove://setup/v1?s=http%3A%2F%2F127.0.0.1"), "{kit}");
+    let info = parse_setup_payload(kit.clone()).unwrap();
+    assert_eq!((info.secret_key.as_str(), info.ticket.as_ref()), (sk.as_str(), None));
+    assert_eq!(info.account_id, a.account_id().unwrap());
+    assert_eq!(info.spki_pins, vec!["47DEQpj8HBSa+/TImW+5JCeuQeRkm5NMpJWZG3hSuFU=".to_string()]);
+    assert_eq!(encode_setup_payload(info).unwrap(), kit);
+
+    // After a biometric unlock the core still knows the Secret Key; locked, it does not.
+    let luk = a.enable_local_unlock().unwrap();
+    a.lock();
+    assert!(matches!(a.setup_payload_for_kit(), Err(CoreError::Locked)));
+    a.unlock_with_local_key(luk).unwrap();
+    assert_eq!(a.setup_payload_for_kit().unwrap(), kit);
+    assert!(matches!(parse_setup_payload("kestrove://setup/v2?s=x".into()), Err(CoreError::Invalid { .. })));
+}
+
+#[tokio::test]
+async fn add_device_qr_needs_only_the_password_and_no_approval() {
+    let server = TestServer::start().await;
+    let (a, sk, id) = phone_with_item(&server).await;
+
+    let add = a.add_device_payload().await.unwrap();
+    let setup = parse_setup_payload(add.payload.clone()).unwrap();
+    assert!(setup.ticket.is_some());
+
+    // The new device has nothing configured but its key; the QR and the password are enough.
+    let b = VaultCore::new_in_memory();
+    b.set_device_signer(
+        Arc::new(TestSigner(SoftwareSigner::generate(Uuid::new_v4()))),
+        "tablet".into(),
+        PlatformDto::Android,
+    )
+    .unwrap();
+    assert!(matches!(
+        b.login_with_setup(setup.clone(), "wrong password!!".into()).await,
+        Err(CoreError::BadCredentials)
+    ));
+    assert_eq!(b.login_with_setup(setup.clone(), PW.into()).await.unwrap(), LoginResult::Ok);
+    b.sync_now().await.unwrap();
+    assert_eq!(b.get_item(id).unwrap().password.as_deref(), Some("pw-a"));
+    // B can now produce the same Kit payload.
+    assert_eq!(parse_setup_payload(b.setup_payload_for_kit().unwrap()).unwrap().secret_key, sk);
+
+    // Single use: a third device with the same QR waits for approval.
+    let c = VaultCore::new_in_memory();
+    connect(&c, &server);
+    assert_eq!(c.login_with_setup(setup, PW.into()).await.unwrap(), LoginResult::PendingApproval);
+
+    // A cancelled QR is revoked.
+    let add = a.add_device_payload().await.unwrap();
+    a.revoke_enrollment_ticket(add.ticket_id).await.unwrap();
+    let d = VaultCore::new_in_memory();
+    connect(&d, &server);
+    let setup = parse_setup_payload(add.payload).unwrap();
+    assert_eq!(d.login_with_setup(setup, PW.into()).await.unwrap(), LoginResult::PendingApproval);
+}
+
+#[tokio::test]
+async fn scan_to_join_between_two_clients() {
+    let server = TestServer::start().await;
+    let (phone, sk, id) = phone_with_item(&server).await;
+
+    // Desktop: only knows the server URL.
+    let desktop = VaultCore::new_in_memory();
+    desktop
+        .set_device_signer(
+            Arc::new(TestSigner(SoftwareSigner::generate(Uuid::new_v4()))),
+            "Sami's MacBook".into(),
+            PlatformDto::Macos,
+        )
+        .unwrap();
+    assert!(matches!(desktop.join_poll().await, Err(CoreError::Invalid { .. })));
+    let session = desktop.join_start(format!("{}/", server.url())).await.unwrap();
+    assert!(session.qr.starts_with("kestrove://join/v1?") && session.qr.len() < 200);
+    assert_eq!(desktop.join_poll().await.unwrap(), JoinProgress { code: None, setup: None });
+
+    // Phone: a QR naming another server is refused before anything is sent.
+    let elsewhere = session.qr.replace("127.0.0.1", "localhost");
+    assert!(matches!(phone.join_approve(elsewhere).await, Err(CoreError::Invalid { .. })));
+    let confirm = phone.join_approve(session.qr.clone()).await.unwrap();
+    assert_eq!((confirm.device_name.as_str(), confirm.platform), ("Sami's MacBook", PlatformDto::Macos));
+    assert_eq!(confirm.key_fingerprint, desktop.device_key_fingerprint().unwrap());
+
+    // Both screens show the same code before anything secret moves.
+    let progress = desktop.join_poll().await.unwrap();
+    assert_eq!((progress.code.as_deref(), progress.setup.as_ref()), (Some(confirm.code.as_str()), None));
+    {
+        let st = server.state();
+        let rv = st.joins.values().next().unwrap();
+        assert!(rv.bundle.is_none() && rv.hello.is_some());
+    }
+
+    phone.join_send().await.unwrap();
+    assert!(matches!(phone.join_send().await, Err(CoreError::Invalid { .. })), "one send per approval");
+    {
+        // The server only ever holds ciphertext.
+        let st = server.state();
+        let bundle = st.joins.values().next().unwrap().bundle.as_ref().unwrap();
+        let raw = serde_json::to_string(bundle).unwrap();
+        assert!(!raw.contains("K1") && !raw.contains("kestrove://"));
+        assert_eq!(st.tickets.values().filter(|t| t.bound_key_sha256.is_some()).count(), 1);
+    }
+    let done = desktop.join_poll().await.unwrap();
+    let setup = done.setup.expect("bundle arrived");
+    assert_eq!((setup.secret_key.as_str(), setup.server_url.as_str()), (sk.as_str(), server.url().as_str()));
+    assert!(setup.ticket.is_some());
+    // One read: the rendezvous is gone.
+    assert!(matches!(desktop.join_poll().await, Err(CoreError::Invalid { .. })));
+    assert!(server.state().joins.is_empty());
+
+    // Only the master password is left to type, and no approval is needed.
+    assert_eq!(desktop.login_with_setup(setup, PW.into()).await.unwrap(), LoginResult::Ok);
+    desktop.sync_now().await.unwrap();
+    assert_eq!(desktop.get_item(id).unwrap().password.as_deref(), Some("pw-a"));
+    assert!(matches!(desktop.join_start(server.url()).await, Err(CoreError::Invalid { .. })));
+}
+
+#[tokio::test]
+async fn scan_to_join_ticket_is_bound_to_the_joining_device() {
+    let server = TestServer::start().await;
+    let (phone, _, _) = phone_with_item(&server).await;
+    let desktop = VaultCore::new_in_memory();
+    connect(&desktop, &server);
+    let session = desktop.join_start(server.url()).await.unwrap();
+    phone.join_approve(session.qr).await.unwrap();
+    desktop.join_poll().await.unwrap();
+    phone.join_send().await.unwrap();
+    let setup = desktop.join_poll().await.unwrap().setup.unwrap();
+
+    // Someone who intercepted the setup (and knows the password) on another device key still needs approval.
+    let thief = VaultCore::new_in_memory();
+    connect(&thief, &server);
+    assert_eq!(thief.login_with_setup(setup.clone(), PW.into()).await.unwrap(), LoginResult::PendingApproval);
+    assert_eq!(desktop.login_with_setup(setup, PW.into()).await.unwrap(), LoginResult::Ok);
+}
+
+#[tokio::test]
+async fn scan_to_join_rejects_a_forged_bundle() {
+    let server = TestServer::start().await;
+    let (phone, _, _) = phone_with_item(&server).await;
+    let desktop = VaultCore::new_in_memory();
+    connect(&desktop, &server);
+    // Round 1: the server keeps the phone's hello but substitutes a bundle it sealed itself (no QR secret).
+    let session = desktop.join_start(server.url()).await.unwrap();
+    phone.join_approve(session.qr.clone()).await.unwrap();
+    desktop.join_poll().await.unwrap();
+    {
+        let qr = kv_sync::onboarding::JoinQr::parse(&session.qr).unwrap();
+        let rid = base64::Engine::decode(&base64::engine::general_purpose::URL_SAFE_NO_PAD, &qr.rendezvous_id).unwrap();
+        let forger = kv_crypto::pairing::PairingKeypair::generate();
+        let forged = kv_crypto::pairing::seal(&forger, &qr.public_key, &[0u8; 32], &rid, b"x").unwrap();
+        server.state().joins.values_mut().next().unwrap().bundle = Some(forged);
+    }
+    assert!(matches!(desktop.join_poll().await, Err(CoreError::Invalid { .. })));
+    phone.join_cancel();
+
+    // Round 2: it also swaps the hello key for its own.
+    let session = desktop.join_start(server.url()).await.unwrap();
+    phone.join_approve(session.qr.clone()).await.unwrap();
+    desktop.join_poll().await.unwrap();
+    let qr = kv_sync::onboarding::JoinQr::parse(&session.qr).unwrap();
+    let forger = kv_crypto::pairing::PairingKeypair::generate();
+    let rid = base64::Engine::decode(&base64::engine::general_purpose::URL_SAFE_NO_PAD, &qr.rendezvous_id).unwrap();
+    let forged =
+        kv_crypto::pairing::seal(&forger, &qr.public_key, &[0u8; 32], &rid, b"kestrove://setup/v1?evil").unwrap();
+    {
+        let mut st = server.state();
+        let rv = st.joins.values_mut().next().unwrap();
+        rv.hello = Some((Uuid::new_v4(), forger.public_bytes().to_vec()));
+        rv.bundle = Some(forged);
+    }
+    // The swapped hello key is noticed (the code was shown for the phone's key) and nothing is accepted.
+    assert!(matches!(desktop.join_poll().await, Err(CoreError::Invalid { .. })));
+    assert!(matches!(desktop.join_poll().await, Err(CoreError::Invalid { .. })), "state cleared");
+}
diff --git a/crates/kv-ffi/tests/live_server.rs b/crates/kv-ffi/tests/live_server.rs
index 85060f1..cc6d8b2 100644
--- a/crates/kv-ffi/tests/live_server.rs
+++ b/crates/kv-ffi/tests/live_server.rs
@@ -1,13 +1,15 @@
 //! Two devices against a real, freshly started kestrove-server. Ignored by default.
 //!
 //! ```sh
-//! # in kestrove-server (empty database, so it prints SETUP_TOKEN=… on boot):
-//! KV_DATABASE=sqlite::memory: KV_BIND=127.0.0.1:8080 KV_PUBLIC_URL=http://127.0.0.1:8080 cargo run
+//! # in kestrove-server (empty database; without KV_SETUP_CODE it prints SETUP_TOKEN=… on boot instead):
+//! KV_DATABASE=sqlite::memory: KV_BIND=127.0.0.1:8080 KV_PUBLIC_URL=http://127.0.0.1:8080 \
+//!   KV_SETUP_CODE=live-test-setup-code cargo run
 //! # here:
-//! KESTROVE_SERVER_URL=http://127.0.0.1:8080 KESTROVE_SETUP_TOKEN=<token> \
+//! KESTROVE_SERVER_URL=http://127.0.0.1:8080 KESTROVE_SETUP_TOKEN=live-test-setup-code \
 //!   cargo test -p kv-ffi --test live_server -- --ignored --nocapture
 //! ```
-//! The setup token works once, so restart the server with an empty database for every run.
+//! The setup code works once, so restart the server with an empty database for every run. The run takes about
+//! four minutes because it waits out the server's rate limit on the login endpoints.
 
 use std::sync::Arc;
 
@@ -107,6 +109,22 @@ async fn two_devices_against_local_server() {
     b.sync_now().await.unwrap();
     assert!(matches!(b.get_item(temp), Err(CoreError::NotFound)));
 
+    // Scan-to-join (docs/10 §4): a third device that knows only the server URL needs no approval.
+    tokio::time::sleep(std::time::Duration::from_secs(61)).await; // rate limit again
+    let c = VaultCore::new_in_memory();
+    connect(&c, &url, "device C");
+    let session = c.join_start(url.clone()).await.unwrap();
+    let confirm = a.join_approve(session.qr).await.unwrap();
+    assert_eq!(confirm.device_name, "device C");
+    assert_eq!(c.join_poll().await.unwrap().code.as_deref(), Some(confirm.code.as_str()));
+    a.join_send().await.unwrap();
+    tokio::time::sleep(std::time::Duration::from_millis(1100)).await; // the server allows one poll per second
+    let setup = c.join_poll().await.unwrap().setup.expect("bundle");
+    assert_eq!(setup.secret_key, sk);
+    assert_eq!(c.login_with_setup(setup, pw.into()).await.unwrap(), LoginResult::Ok);
+    c.sync_now().await.unwrap();
+    assert!(c.list_items().unwrap().iter().any(|i| i.title == "Bank"));
+
     b.logout().await.unwrap();
     println!("live sync OK against {url}");
 }
diff --git a/crates/kv-proto/src/lib.rs b/crates/kv-proto/src/lib.rs
index d607128..0cc65a3 100644
--- a/crates/kv-proto/src/lib.rs
+++ b/crates/kv-proto/src/lib.rs
@@ -16,6 +16,17 @@ pub const API_VERSION: u32 = 1;
 pub const MIN_KDF_M_KIB: u32 = 64 * 1024;
 pub const MIN_KDF_T: u32 = 3;
 
+/// Enrollment tickets live this long (docs/10 §3).
+pub const TICKET_TTL_SECS: i64 = 600;
+/// At most this many unused, unexpired, unrevoked tickets at once.
+pub const MAX_LIVE_TICKETS: i64 = 5;
+/// A scan-to-join rendezvous lives this long (docs/10 §4).
+pub const JOIN_TTL_SECS: i64 = 300;
+/// Largest serialized bundle a rendezvous accepts.
+pub const JOIN_MAX_BUNDLE: usize = 4096;
+/// Header carrying the joining device's `read_token`.
+pub const HEADER_JOIN_TOKEN: &str = "kv-join-token";
+
 /// base64url (no padding) serde helper for byte fields.
 pub mod b64 {
     use base64::{engine::general_purpose::URL_SAFE_NO_PAD, Engine};
@@ -31,6 +42,25 @@ pub mod b64 {
     }
 }
 
+/// base64url (no padding) serde helper for optional byte fields (absent = `None`).
+pub mod b64_opt {
+    use base64::{engine::general_purpose::URL_SAFE_NO_PAD, Engine};
+    use serde::{Deserialize, Deserializer, Serializer};
+
+    pub fn serialize<S: Serializer>(bytes: &Option<Vec<u8>>, s: S) -> Result<S::Ok, S::Error> {
+        match bytes {
+            Some(b) => s.serialize_str(&URL_SAFE_NO_PAD.encode(b)),
+            None => s.serialize_none(),
+        }
+    }
+
+    pub fn deserialize<'de, D: Deserializer<'de>>(d: D) -> Result<Option<Vec<u8>>, D::Error> {
+        Option::<String>::deserialize(d)?
+            .map(|s| URL_SAFE_NO_PAD.decode(s).map_err(serde::de::Error::custom))
+            .transpose()
+    }
+}
+
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
 pub enum Alg {
     /// XChaCha20-Poly1305 with a 24-byte random nonce.
@@ -173,6 +203,9 @@ pub struct LoginFinish {
     /// Reserved for the TOTP enrollment path; not implemented by the server yet.
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub totp: Option<String>,
+    /// Enrollment ticket (docs/10 §3). Checked only after KE3 verifies; a valid one approves a new device.
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub ticket: Option<String>,
 }
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
@@ -301,6 +334,96 @@ pub struct Manifest {
     pub signature: Vec<u8>,
 }
 
+// ---------------------------------------------------------------- onboarding (docs/10)
+
+/// `POST /v1/devices/tickets` (signed by an approved device).
+#[derive(Debug, Clone, Default, Serialize, Deserialize)]
+pub struct TicketCreate {
+    /// Optional binding: SHA-256 of the new device's SEC1 P-256 public key.
+    #[serde(with = "b64_opt", default, skip_serializing_if = "Option::is_none")]
+    pub device_key_sha256: Option<Vec<u8>>,
+}
+
+/// Reply to `POST /v1/devices/tickets`. `ticket` is shown once; the server keeps only its hash.
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct TicketCreated {
+    pub ticket_id: Uuid,
+    /// base64url of 32 random bytes.
+    pub ticket: String,
+    /// Unix seconds.
+    pub expires_at: i64,
+}
+
+/// An entry of `GET /v1/devices/tickets` (live tickets only).
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct TicketInfo {
+    pub ticket_id: Uuid,
+    pub issued_by: Uuid,
+    /// True when bound to one device key.
+    pub bound: bool,
+    pub expires_at: i64,
+    pub created_at: i64,
+}
+
+/// `POST /v1/join`: the joining device opens a rendezvous (unauthenticated, rate limited).
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct JoinCreate {
+    pub device: DeviceEnroll,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct JoinCreated {
+    /// base64url of 16 random bytes; goes into the QR.
+    pub rendezvous_id: String,
+    /// base64url of 32 random bytes; send as `KV-Join-Token`. Never put it in the QR.
+    pub read_token: String,
+    /// Unix seconds.
+    pub expires_at: i64,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
+#[serde(rename_all = "snake_case")]
+pub enum JoinState {
+    /// Nobody has answered yet.
+    Waiting,
+    /// An approving device posted its key.
+    Hello,
+    /// The bundle is here (returned once, then the rendezvous is gone).
+    Sealed,
+}
+
+/// Reply to `GET /v1/join/{rid}`.
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct JoinPoll {
+    pub state: JoinState,
+    #[serde(with = "b64_opt", default, skip_serializing_if = "Option::is_none")]
+    pub sender_pub: Option<Vec<u8>>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub bundle: Option<Envelope>,
+    pub expires_at: i64,
+}
+
+/// `POST /v1/join/{rid}/hello` (signed by an approved device).
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct JoinHello {
+    /// X25519 public key, 32 bytes.
+    #[serde(with = "b64")]
+    pub sender_pub: Vec<u8>,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct JoinHelloResponse {
+    /// The device that opened the rendezvous: show its name, platform and key fingerprint.
+    pub device: DeviceEnroll,
+    pub expires_at: i64,
+}
+
+/// `PUT /v1/join/{rid}/bundle` (signed by the device that sent the hello).
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct JoinBundle {
+    pub bundle: Envelope,
+}
+
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct ApiError {
     pub code: String,
@@ -327,4 +450,19 @@ mod tests {
         assert!(!json.contains('+') && !json.contains('/'));
         assert_eq!(serde_json::from_str::<Envelope>(&json).unwrap(), env);
     }
+
+    #[test]
+    fn optional_bytes_and_ticket_field() {
+        let none = serde_json::to_string(&TicketCreate::default()).unwrap();
+        assert_eq!(none, "{}");
+        let some = TicketCreate { device_key_sha256: Some(vec![0xfb; 32]) };
+        let json = serde_json::to_string(&some).unwrap();
+        assert!(json.contains("-_") && !json.contains('='));
+        assert_eq!(serde_json::from_str::<TicketCreate>(&json).unwrap().device_key_sha256, some.device_key_sha256);
+        // Old clients omit `ticket`; old servers ignore it.
+        let fin: LoginFinish = serde_json::from_str(r#"{"login_id":"x","ke3":"AAAA"}"#).unwrap();
+        assert!(fin.ticket.is_none() && fin.totp.is_none());
+        let poll: JoinPoll = serde_json::from_str(r#"{"state":"waiting","expires_at":1}"#).unwrap();
+        assert_eq!((poll.state, poll.sender_pub, poll.bundle), (JoinState::Waiting, None, None));
+    }
 }
diff --git a/crates/kv-sync/src/client.rs b/crates/kv-sync/src/client.rs
index ca239e3..cc65018 100644
--- a/crates/kv-sync/src/client.rs
+++ b/crates/kv-sync/src/client.rs
@@ -6,9 +6,10 @@ use std::{
 };
 
 use kv_proto::{
-    AccountInfo, ApiError, Changes, DeviceEnroll, DeviceInfo, ItemPut, ItemRecord, KdfParams, LoginFinish,
-    LoginFinishResponse, LoginStart, LoginStartResponse, LoginStatus, Manifest, PreloginResponse,
-    RegistrationStartResponse, ServerInfo, SetupFinish, SetupStart, Vault,
+    AccountInfo, ApiError, Changes, DeviceEnroll, DeviceInfo, Envelope, ItemPut, ItemRecord, JoinBundle, JoinCreate,
+    JoinCreated, JoinHello, JoinHelloResponse, JoinPoll, KdfParams, LoginFinish, LoginFinishResponse, LoginStart,
+    LoginStartResponse, LoginStatus, Manifest, PreloginResponse, RegistrationStartResponse, ServerInfo, SetupFinish,
+    SetupStart, TicketCreate, TicketCreated, TicketInfo, Vault, HEADER_JOIN_TOKEN,
 };
 use reqwest::{Method, StatusCode};
 use serde::{de::DeserializeOwned, Serialize};
@@ -76,10 +77,25 @@ impl ApiClient {
         body: Option<Vec<u8>>,
         if_match: Option<u64>,
         signed: bool,
+    ) -> Result<(StatusCode, Vec<u8>), SyncError> {
+        self.send_ext(method, path, body, if_match, signed, None).await
+    }
+
+    async fn send_ext(
+        &self,
+        method: Method,
+        path: &str,
+        body: Option<Vec<u8>>,
+        if_match: Option<u64>,
+        signed: bool,
+        extra_header: Option<(&str, &str)>,
     ) -> Result<(StatusCode, Vec<u8>), SyncError> {
         let url = format!("{}{}", self.base, path);
         let body = body.unwrap_or_default();
         let mut req = self.http.request(method.clone(), &url);
+        if let Some((k, v)) = extra_header {
+            req = req.header(k, v);
+        }
         if !body.is_empty() {
             req = req.header("content-type", "application/json");
         }
@@ -188,12 +204,25 @@ impl ApiClient {
         auth_input: &[u8],
         device: DeviceEnroll,
         totp: Option<String>,
+    ) -> Result<LoginOutcome, SyncError> {
+        self.login_with_ticket(account_id, auth_input, device, totp, None).await
+    }
+
+    /// OPAQUE login presenting an enrollment ticket (docs/10 §3). A valid ticket approves a new device at once;
+    /// an invalid one is ignored by the server (the outcome is then `PendingApproval`).
+    pub async fn login_with_ticket(
+        &self,
+        account_id: Uuid,
+        auth_input: &[u8],
+        device: DeviceEnroll,
+        totp: Option<String>,
+        ticket: Option<String>,
     ) -> Result<LoginOutcome, SyncError> {
         let start = opaque::login_start(auth_input)?;
         let req = LoginStart { account_id, ke1: start.ke1.clone(), device };
         let resp: LoginStartResponse = self.json(Method::POST, PATH_LOGIN_START, Some(&req), None, false).await?;
         let done = start.finish(auth_input, &resp.ke2)?;
-        let fin = LoginFinish { login_id: resp.login_id, ke3: done.ke3, totp };
+        let fin = LoginFinish { login_id: resp.login_id, ke3: done.ke3, totp, ticket };
         let resp: LoginFinishResponse = match self.json(Method::POST, PATH_LOGIN_FINISH, Some(&fin), None, false).await
         {
             Err(SyncError::Server { status: 401, .. }) => return Err(SyncError::BadCredentials),
@@ -209,8 +238,45 @@ impl ApiClient {
         }
     }
 
+    /// Opens a scan-to-join rendezvous for this (not yet enrolled) device (docs/10 §4).
+    pub async fn join_create(&self, device: DeviceEnroll) -> Result<JoinCreated, SyncError> {
+        self.json(Method::POST, PATH_JOIN, Some(&JoinCreate { device }), None, false).await
+    }
+
+    /// Polls a rendezvous with its read token. `NotFound` once it expired or the bundle was read.
+    pub async fn join_poll(&self, rendezvous_id: &str, read_token: &str) -> Result<JoinPoll, SyncError> {
+        let path = format!("{PATH_JOIN}/{rendezvous_id}");
+        let (_, bytes) =
+            self.send_ext(Method::GET, &path, None, None, false, Some((HEADER_JOIN_TOKEN, read_token))).await?;
+        serde_json::from_slice(&bytes).map_err(|e| SyncError::Protocol(format!("{path}: {e}")))
+    }
+
     // ---------------------------------------------------------------- authenticated
 
+    /// Issues an enrollment ticket, optionally bound to SHA-256 of the new device's key (docs/10 §3).
+    pub async fn create_ticket(&self, device_key_sha256: Option<Vec<u8>>) -> Result<TicketCreated, SyncError> {
+        self.json(Method::POST, PATH_TICKETS, Some(&TicketCreate { device_key_sha256 }), None, true).await
+    }
+
+    pub async fn tickets(&self) -> Result<Vec<TicketInfo>, SyncError> {
+        self.json(Method::GET, PATH_TICKETS, None::<&()>, None, true).await
+    }
+
+    pub async fn revoke_ticket(&self, ticket_id: Uuid) -> Result<(), SyncError> {
+        self.no_content(Method::DELETE, &format!("{PATH_TICKETS}/{ticket_id}"), None::<&()>, true).await
+    }
+
+    /// Answers a rendezvous with this device's ephemeral key; returns the joining device's details.
+    pub async fn join_hello(&self, rendezvous_id: &str, sender_pub: Vec<u8>) -> Result<JoinHelloResponse, SyncError> {
+        let path = format!("{PATH_JOIN}/{rendezvous_id}/hello");
+        self.json(Method::POST, &path, Some(&JoinHello { sender_pub }), None, true).await
+    }
+
+    pub async fn join_send(&self, rendezvous_id: &str, bundle: Envelope) -> Result<(), SyncError> {
+        let path = format!("{PATH_JOIN}/{rendezvous_id}/bundle");
+        self.no_content(Method::PUT, &path, Some(&JoinBundle { bundle }), true).await
+    }
+
     pub async fn logout(&self) -> Result<(), SyncError> {
         let r = self.no_content(Method::POST, PATH_LOGOUT, None::<&()>, true).await;
         self.set_session(None);
diff --git a/crates/kv-sync/src/lib.rs b/crates/kv-sync/src/lib.rs
index c21ff33..59cb63a 100644
--- a/crates/kv-sync/src/lib.rs
+++ b/crates/kv-sync/src/lib.rs
@@ -9,11 +9,13 @@
 //! * [`engine`]: pull, then push with `If-Match`, then three-way field merge on 412 ([`merge`]), then manifest verify
 //!   and publish ([`manifest`]).
 //! * [`replay`]: per-item replay check on pull (the `seq` field sealed into every item version and tombstone).
+//! * [`onboarding`]: setup payloads and scan-to-join QR codes (docs/10).
 
 pub mod client;
 pub mod engine;
 pub mod manifest;
 pub mod merge;
+pub mod onboarding;
 pub mod opaque;
 pub mod replay;
 pub mod signing;
diff --git a/crates/kv-sync/src/onboarding.rs b/crates/kv-sync/src/onboarding.rs
new file mode 100644
index 0000000..1ade264
--- /dev/null
+++ b/crates/kv-sync/src/onboarding.rs
@@ -0,0 +1,300 @@
+//! Setup payloads and scan-to-join QR codes (kestrove-spec/docs/10 §2 and §4). Pure encoding and validation,
+//! no I/O.
+//!
+//! ```text
+//! kestrove://setup/v1?s=<server>&a=<account hex>&k=<Secret Key, no hyphens>[&p=<pin>]*[&t=<ticket>]
+//! kestrove://join/v1?s=<server>&r=<rendezvous id>&k=<X25519 public key>&c=<qr secret>
+//! ```
+
+use base64::{engine::general_purpose::URL_SAFE_NO_PAD, Engine};
+use kv_crypto::secret_key::SecretKey;
+use url::form_urlencoded;
+use uuid::Uuid;
+use zeroize::Zeroizing;
+
+use crate::{
+    transport::{normalize_base_url, parse_pin},
+    SyncError,
+};
+
+/// Longest payload a parser accepts (fits a version 13-M QR code with room to spare).
+pub const MAX_PAYLOAD_LEN: usize = 512;
+/// Longest server URL in a payload.
+pub const MAX_SERVER_URL_LEN: usize = 200;
+/// Most pins in one payload.
+pub const MAX_PINS: usize = 4;
+
+const SETUP_PREFIX: &str = "kestrove://setup/";
+const JOIN_PREFIX: &str = "kestrove://join/";
+const VERSION: &str = "v1";
+
+/// Everything a new device needs except the master password.
+#[derive(Clone, PartialEq, Eq)]
+pub struct SetupPayload {
+    /// Normalized base URL (as `normalize_base_url` returns it).
+    pub server_url: String,
+    /// Standard base64 SPKI SHA-256 pins, the format `configure_server` takes.
+    pub spki_pins: Vec<String>,
+    pub account_id: Uuid,
+    /// Display form `K1-XXXXXX-…`.
+    pub secret_key: Zeroizing<String>,
+    /// Enrollment ticket (base64url, 32 bytes), if any.
+    pub ticket: Option<String>,
+}
+
+impl std::fmt::Debug for SetupPayload {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.debug_struct("SetupPayload")
+            .field("server_url", &self.server_url)
+            .field("spki_pins", &self.spki_pins)
+            .field("account_id", &self.account_id)
+            .field("secret_key", &"<redacted>")
+            .field("ticket", &self.ticket.as_ref().map(|_| "<redacted>"))
+            .finish()
+    }
+}
+
+/// What the joining device shows as a QR code.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct JoinQr {
+    pub server_url: String,
+    /// base64url, 16 bytes.
+    pub rendezvous_id: String,
+    /// X25519 public key of the joining device.
+    pub public_key: [u8; 32],
+    /// HPKE PSK; only ever in the QR.
+    pub qr_secret: Zeroizing<[u8; 32]>,
+}
+
+fn bad(field: &str) -> SyncError {
+    SyncError::Config(format!("setup code: invalid {field}"))
+}
+
+fn enc(s: &str) -> String {
+    form_urlencoded::byte_serialize(s.as_bytes()).collect()
+}
+
+/// Splits `kestrove://<kind>/v1?query` into key/value pairs after checking kind, version and size.
+fn query_pairs(input: &str, prefix: &str) -> Result<Vec<(String, Zeroizing<String>)>, SyncError> {
+    let input = input.trim();
+    if input.len() > MAX_PAYLOAD_LEN {
+        return Err(SyncError::Config("setup code is too long".into()));
+    }
+    let (head, query) = input.split_once('?').ok_or_else(|| bad("format"))?;
+    let rest = head
+        .get(..prefix.len())
+        .filter(|p| p.eq_ignore_ascii_case(prefix))
+        .map(|_| &head[prefix.len()..])
+        .ok_or_else(|| SyncError::Config("not a Kestrove setup code".into()))?;
+    if rest != VERSION {
+        return Err(SyncError::Config("this code needs a newer version of Kestrove".into()));
+    }
+    Ok(form_urlencoded::parse(query.as_bytes())
+        .map(|(k, v)| (k.into_owned(), Zeroizing::new(v.into_owned())))
+        .collect())
+}
+
+/// The single value of `key`; an error if it is repeated, `None` if absent.
+fn single<'a>(pairs: &'a [(String, Zeroizing<String>)], key: &str) -> Result<Option<&'a str>, SyncError> {
+    let mut it = pairs.iter().filter(|(k, _)| k == key);
+    match (it.next(), it.next()) {
+        (None, _) => Ok(None),
+        (Some((_, v)), None) => Ok(Some(v.as_str())),
+        _ => Err(SyncError::Config(format!("setup code: repeated {key}"))),
+    }
+}
+
+fn server(pairs: &[(String, Zeroizing<String>)]) -> Result<String, SyncError> {
+    let s = single(pairs, "s")?.ok_or_else(|| bad("server"))?;
+    if s.len() > MAX_SERVER_URL_LEN {
+        return Err(bad("server"));
+    }
+    normalize_base_url(s)
+}
+
+fn b64_exact<const N: usize>(s: &str, field: &str) -> Result<[u8; N], SyncError> {
+    URL_SAFE_NO_PAD.decode(s).ok().and_then(|v| v.try_into().ok()).ok_or_else(|| bad(field))
+}
+
+impl SetupPayload {
+    /// Canonical encoding: keys in the order `s, a, k, p…, t`.
+    pub fn encode(&self) -> Result<Zeroizing<String>, SyncError> {
+        let server = normalize_base_url(&self.server_url)?;
+        if server.len() > MAX_SERVER_URL_LEN || self.spki_pins.len() > MAX_PINS {
+            return Err(SyncError::Config("server URL or pin list too long for a setup code".into()));
+        }
+        let sk = SecretKey::parse(&self.secret_key).map_err(|_| bad("Secret Key"))?;
+        let compact: Zeroizing<String> = Zeroizing::new(sk.to_display().replace('-', ""));
+        let mut out = Zeroizing::new(format!(
+            "{SETUP_PREFIX}{VERSION}?s={}&a={}&k={}",
+            enc(&server),
+            self.account_id.simple(),
+            compact.as_str()
+        ));
+        for pin in &self.spki_pins {
+            out.push_str("&p=");
+            out.push_str(&URL_SAFE_NO_PAD.encode(parse_pin(pin)?));
+        }
+        if let Some(t) = &self.ticket {
+            b64_exact::<32>(t, "ticket")?;
+            out.push_str("&t=");
+            out.push_str(t);
+        }
+        Ok(out)
+    }
+
+    /// Strict parse and validation (docs/10 §2). Unknown keys are ignored.
+    pub fn parse(input: &str) -> Result<Self, SyncError> {
+        let pairs = query_pairs(input, SETUP_PREFIX)?;
+        let server_url = server(&pairs)?;
+        let account_id = single(&pairs, "a")?
+            .filter(|a| a.len() == 32)
+            .and_then(|a| Uuid::try_parse(a).ok())
+            .ok_or_else(|| bad("account id"))?;
+        let k = single(&pairs, "k")?.ok_or_else(|| bad("Secret Key"))?;
+        let secret_key = SecretKey::parse(k).map_err(|_| bad("Secret Key"))?.to_display();
+        let pins: Vec<&str> = pairs.iter().filter(|(k, _)| k == "p").map(|(_, v)| v.as_str()).collect();
+        if pins.len() > MAX_PINS {
+            return Err(bad("pins"));
+        }
+        let spki_pins = pins
+            .into_iter()
+            .map(|p| b64_exact::<32>(p, "pin").map(|raw| base64::engine::general_purpose::STANDARD.encode(raw)))
+            .collect::<Result<_, _>>()?;
+        let ticket = single(&pairs, "t")?
+            .map(|t| b64_exact::<32>(t, "ticket").map(|raw| URL_SAFE_NO_PAD.encode(raw)))
+            .transpose()?;
+        Ok(SetupPayload { server_url, spki_pins, account_id, secret_key, ticket })
+    }
+}
+
+impl JoinQr {
+    pub fn encode(&self) -> Result<String, SyncError> {
+        let server = normalize_base_url(&self.server_url)?;
+        if server.len() > MAX_SERVER_URL_LEN {
+            return Err(bad("server"));
+        }
+        b64_exact::<16>(&self.rendezvous_id, "rendezvous id")?;
+        Ok(format!(
+            "{JOIN_PREFIX}{VERSION}?s={}&r={}&k={}&c={}",
+            enc(&server),
+            self.rendezvous_id,
+            URL_SAFE_NO_PAD.encode(self.public_key),
+            URL_SAFE_NO_PAD.encode(self.qr_secret.as_ref())
+        ))
+    }
+
+    pub fn parse(input: &str) -> Result<Self, SyncError> {
+        let pairs = query_pairs(input, JOIN_PREFIX)?;
+        let server_url = server(&pairs)?;
+        let rid = single(&pairs, "r")?.ok_or_else(|| bad("rendezvous id"))?;
+        b64_exact::<16>(rid, "rendezvous id")?;
+        let public_key = b64_exact::<32>(single(&pairs, "k")?.ok_or_else(|| bad("key"))?, "key")?;
+        let qr_secret = Zeroizing::new(b64_exact::<32>(single(&pairs, "c")?.ok_or_else(|| bad("secret"))?, "secret")?);
+        Ok(JoinQr { server_url, rendezvous_id: rid.to_owned(), public_key, qr_secret })
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    const PIN_A: &str = "47DEQpj8HBSa+/TImW+5JCeuQeRkm5NMpJWZG3hSuFU=";
+    const PIN_B: &str = "n4bQgYhMfWWaL+qgxVrQFaO/TxsrC4Is0V1sFbDwCgg=";
+
+    fn sample(ticket: bool) -> SetupPayload {
+        SetupPayload {
+            server_url: "https://kestrove.samialabri.com".into(),
+            spki_pins: vec![PIN_A.into(), PIN_B.into()],
+            account_id: Uuid::parse_str("6f1c2b9a-4e0d-4c7f-9b3a-8e2d1c0b9a87").unwrap(),
+            secret_key: SecretKey::from_bytes([0x5a; 16]).to_display(),
+            ticket: ticket.then(|| URL_SAFE_NO_PAD.encode([0xc3; 32])),
+        }
+    }
+
+    #[test]
+    fn setup_roundtrip_and_canonical_form() {
+        for with_ticket in [false, true] {
+            let p = sample(with_ticket);
+            let s = p.encode().unwrap();
+            assert!(s.starts_with(
+                "kestrove://setup/v1?s=https%3A%2F%2Fkestrove.samialabri.com&a=6f1c2b9a4e0d4c7f9b3a8e2d1c0b9a87&k=K1"
+            ));
+            assert_eq!(s.contains("&t="), with_ticket);
+            assert!(s.len() <= 300, "{} bytes", s.len());
+            assert_eq!(SetupPayload::parse(&s).unwrap(), p);
+            // Encoding is canonical: parse → encode gives the same string.
+            assert_eq!(*SetupPayload::parse(&s).unwrap().encode().unwrap(), *s);
+        }
+        // No pins; http on loopback; Secret Key with hyphens and lowercase; keys in another order; unknown keys.
+        let sk = SecretKey::from_bytes([1; 16]).to_display().to_lowercase();
+        let s = format!(
+            "KESTROVE://setup/v1?a=6f1c2b9a4e0d4c7f9b3a8e2d1c0b9a87&x=future&k={sk}&s=http%3A%2F%2F127.0.0.1%3A8080%2F"
+        );
+        let p = SetupPayload::parse(&s).unwrap();
+        assert_eq!((p.server_url.as_str(), p.spki_pins.len(), p.ticket.as_ref()), ("http://127.0.0.1:8080", 0, None));
+        assert_eq!(SecretKey::parse(&p.secret_key).unwrap().expose(), &[1; 16]);
+        // The Debug form never shows secrets.
+        let dbg = format!("{:?}", sample(true));
+        assert!(!dbg.contains("K1") && !dbg.contains(&URL_SAFE_NO_PAD.encode([0xc3; 32])));
+    }
+
+    #[test]
+    fn canonical_vector() {
+        // kestrove-spec/vectors/onboarding.json
+        const V: &str = "kestrove://setup/v1?s=https%3A%2F%2Fkestrove.samialabri.com&a=6f1c2b9a4e0d4c7f9b3a8e2d1c0b9a87&k=K12TB9D5MPJTB9D5MPJTB9D5MPJTW&p=47DEQpj8HBSa-_TImW-5JCeuQeRkm5NMpJWZG3hSuFU&p=n4bQgYhMfWWaL-qgxVrQFaO_TxsrC4Is0V1sFbDwCgg&t=w8PDw8PDw8PDw8PDw8PDw8PDw8PDw8PDw8PDw8PDw8M";
+        assert_eq!(sample(true).encode().unwrap().as_str(), V);
+        assert_eq!(SetupPayload::parse(V).unwrap(), sample(true));
+    }
+
+    #[test]
+    fn setup_rejects_malformed_input() {
+        let good = sample(true).encode().unwrap().to_string();
+        let swap = |from: &str, to: &str| good.replacen(from, to, 1);
+        let k = SecretKey::from_bytes([0x5a; 16]).to_display().replace('-', "");
+        let mut typo = k.clone();
+        typo.replace_range(5..6, if &k[5..6] == "2" { "3" } else { "2" });
+        let cases = [
+            ("empty", String::new()),
+            ("no query", "kestrove://setup/v1".into()),
+            ("other scheme", swap("kestrove://", "https://")),
+            ("join instead of setup", swap("kestrove://setup/", "kestrove://join/")),
+            ("future version", swap("/v1?", "/v2?")),
+            ("plain http", swap("https%3A", "http%3A")),
+            ("server with query", swap("samialabri.com&", "samialabri.com%3Fx%3D1&")),
+            ("account not hex", swap("&a=6f1c", "&a=zz1c")),
+            ("account with hyphens", swap("6f1c2b9a4e0d", "6f1c2b9a-4e0d")),
+            ("secret key checksum", good.replace(&k, &typo)),
+            ("missing secret key", good.replace(&format!("&k={k}"), "")),
+            ("short pin", swap("&p=47DEQ", "&p=47DE")),
+            ("short ticket", good[..good.len() - 2].to_string()),
+            ("repeated account", format!("{good}&a=6f1c2b9a4e0d4c7f9b3a8e2d1c0b9a87")),
+            ("repeated ticket", format!("{good}&t={}", URL_SAFE_NO_PAD.encode([1u8; 32]))),
+            ("too many pins", format!("{good}&p={0}&p={0}&p={0}", URL_SAFE_NO_PAD.encode([2u8; 32]))),
+            ("too long", format!("{good}&x={}", "a".repeat(400))),
+            ("non-ascii", swap("&a=", "&a=é")),
+        ];
+        for (name, input) in cases {
+            assert!(SetupPayload::parse(&input).is_err(), "{name} was accepted: {input}");
+        }
+    }
+
+    #[test]
+    fn join_qr_roundtrip_and_rejects() {
+        let qr = JoinQr {
+            server_url: "https://kestrove.samialabri.com/".into(),
+            rendezvous_id: URL_SAFE_NO_PAD.encode([7u8; 16]),
+            public_key: [8; 32],
+            qr_secret: Zeroizing::new([9; 32]),
+        };
+        let s = qr.encode().unwrap();
+        assert!(s.starts_with("kestrove://join/v1?s=https%3A%2F%2Fkestrove.samialabri.com&r="));
+        assert!(s.len() < 200, "{} bytes", s.len());
+        let back = JoinQr::parse(&s).unwrap();
+        assert_eq!(back, JoinQr { server_url: "https://kestrove.samialabri.com".into(), ..qr });
+        assert!(JoinQr::parse(&s.replace("/v1?", "/v9?")).is_err());
+        assert!(JoinQr::parse(&s.replace("&c=", "&c=AA")).is_err());
+        assert!(JoinQr::parse(&s.replace("kestrove://join/", "kestrove://setup/")).is_err());
+        assert!(SetupPayload::parse(&s).is_err());
+    }
+}
diff --git a/crates/kv-sync/src/test_server.rs b/crates/kv-sync/src/test_server.rs
index fe4159c..2063379 100644
--- a/crates/kv-sync/src/test_server.rs
+++ b/crates/kv-sync/src/test_server.rs
@@ -12,9 +12,10 @@ use std::{
 };
 
 use kv_proto::{
-    AccountInfo, ApiError, Changes, DeviceInfo, Envelope, ItemPut, ItemRecord, KdfParams, LoginFinish,
-    LoginFinishResponse, LoginStart, LoginStartResponse, LoginStatus, Manifest, PreloginResponse,
-    RegistrationStartResponse, ServerInfo, SetupFinish, SetupStart, Vault,
+    AccountInfo, ApiError, Changes, DeviceEnroll, DeviceInfo, Envelope, ItemPut, ItemRecord, JoinBundle, JoinCreate,
+    JoinCreated, JoinHello, JoinHelloResponse, JoinPoll, JoinState, KdfParams, LoginFinish, LoginFinishResponse,
+    LoginStart, LoginStartResponse, LoginStatus, Manifest, PreloginResponse, RegistrationStartResponse, ServerInfo,
+    SetupFinish, SetupStart, TicketCreate, TicketCreated, TicketInfo, Vault, HEADER_JOIN_TOKEN,
 };
 use opaque_ke::{
     CredentialFinalization, CredentialRequest, RegistrationRequest, RegistrationUpload, ServerLogin,
@@ -54,6 +55,24 @@ pub struct Device {
     pub revoked: bool,
 }
 
+/// An enrollment ticket (docs/10 §3). Expiry is not simulated; set `expired` to test it.
+pub struct Ticket {
+    pub id: Uuid,
+    pub issuer: Uuid,
+    pub bound_key_sha256: Option<Vec<u8>>,
+    pub used_by: Option<Uuid>,
+    pub revoked: bool,
+    pub expired: bool,
+}
+
+/// A scan-to-join rendezvous (docs/10 §4). TTL and poll interval are not simulated.
+pub struct Rendezvous {
+    pub read_token: String,
+    pub device: DeviceEnroll,
+    pub hello: Option<(Uuid, Vec<u8>)>,
+    pub bundle: Option<Envelope>,
+}
+
 pub struct State {
     pub setup: ServerSetup<Suite>,
     pub setup_token: Option<String>,
@@ -61,6 +80,10 @@ pub struct State {
     pub devices: HashMap<Uuid, Device>,
     pub sessions: HashMap<String, Uuid>,
     logins: HashMap<String, (Vec<u8>, Uuid)>,
+    /// Keyed by the ticket secret.
+    pub tickets: HashMap<String, Ticket>,
+    /// Keyed by rendezvous id.
+    pub joins: HashMap<String, Rendezvous>,
     pub vaults: BTreeMap<Uuid, VaultState>,
     /// New devices need approval (else they are auto-approved).
     pub require_approval: bool,
@@ -84,6 +107,8 @@ impl State {
             devices: HashMap::new(),
             sessions: HashMap::new(),
             logins: HashMap::new(),
+            tickets: HashMap::new(),
+            joins: HashMap::new(),
             vaults: BTreeMap::new(),
             require_approval: false,
             log: vec![],
@@ -268,6 +293,9 @@ fn handle(st: &mut State, req: &Request) -> Result<ResponseTemplate, ResponseTem
             let login = ServerLogin::<Suite>::deserialize(&state).map_err(|_| err(401, "unauthorized"))?;
             let ke3 = CredentialFinalization::deserialize(&r.ke3).map_err(|_| err(401, "unauthorized"))?;
             login.finish(ke3).map_err(|_| err(401, "unauthorized"))?;
+            if let Some(secret) = &r.ticket {
+                redeem_ticket(st, secret, device);
+            }
             if !st.devices.get(&device).is_some_and(|d| d.approved) {
                 return Ok(json(
                     200,
@@ -281,6 +309,30 @@ fn handle(st: &mut State, req: &Request) -> Result<ResponseTemplate, ResponseTem
                 &LoginFinishResponse { status: LoginStatus::Ok, session: Some(session), expires_at: Some(now()) },
             ))
         }
+        ("POST", ["v1", "join"]) => {
+            let r: JoinCreate = parse(req)?;
+            let rid = random_b64::<16>();
+            let read_token = random_b64::<32>();
+            st.joins.insert(
+                rid.clone(),
+                Rendezvous { read_token: read_token.clone(), device: r.device, hello: None, bundle: None },
+            );
+            Ok(json(201, &JoinCreated { rendezvous_id: rid, read_token, expires_at: 0 }))
+        }
+        ("GET", ["v1", "join", rid]) => {
+            let token = req.headers.get(HEADER_JOIN_TOKEN).and_then(|v| v.to_str().ok()).unwrap_or_default();
+            let j = st.joins.get(*rid).filter(|j| j.read_token == token).ok_or_else(|| err(404, "not_found"))?;
+            let sender_pub = j.hello.as_ref().map(|(_, k)| k.clone());
+            if j.bundle.is_some() {
+                let j = st.joins.remove(*rid).expect("present");
+                return Ok(json(
+                    200,
+                    &JoinPoll { state: JoinState::Sealed, sender_pub, bundle: j.bundle, expires_at: 0 },
+                ));
+            }
+            let state = if sender_pub.is_some() { JoinState::Hello } else { JoinState::Waiting };
+            Ok(json(200, &JoinPoll { state, sender_pub, bundle: None, expires_at: 0 }))
+        }
         _ => {
             let device = authenticate(st, req)?;
             authed(st, req, device, &method, &segs)
@@ -288,6 +340,33 @@ fn handle(st: &mut State, req: &Request) -> Result<ResponseTemplate, ResponseTem
     }
 }
 
+fn random_b64<const N: usize>() -> String {
+    use base64::{engine::general_purpose::URL_SAFE_NO_PAD, Engine};
+    use rand_core::RngCore;
+    let mut b = [0u8; N];
+    OsRng.fill_bytes(&mut b);
+    URL_SAFE_NO_PAD.encode(b)
+}
+
+/// Approves `device` if `secret` is a live ticket valid for its key (docs/10 §3).
+fn redeem_ticket(st: &mut State, secret: &str, device: Uuid) {
+    use sha2::Digest;
+    let Some(dev) = st.devices.get(&device) else { return };
+    let key_hash = sha2::Sha256::digest(&dev.p256_pk).to_vec();
+    let Some(t) = st.tickets.get_mut(secret) else { return };
+    let issuer_ok = st.devices.get(&t.issuer).is_some_and(|d| d.approved && !d.revoked);
+    if t.used_by.is_some() || t.revoked || t.expired || !issuer_ok {
+        return;
+    }
+    if t.bound_key_sha256.as_ref().is_some_and(|b| *b != key_hash) {
+        return;
+    }
+    t.used_by = Some(device);
+    if let Some(d) = st.devices.get_mut(&device).filter(|d| !d.revoked) {
+        d.approved = true;
+    }
+}
+
 fn authed(
     st: &mut State,
     req: &Request,
@@ -296,6 +375,66 @@ fn authed(
     segs: &[&str],
 ) -> Result<ResponseTemplate, ResponseTemplate> {
     match (method, segs) {
+        ("POST", ["v1", "devices", "tickets"]) => {
+            let r: TicketCreate = parse(req)?;
+            let secret = random_b64::<32>();
+            let id = Uuid::new_v4();
+            st.tickets.insert(
+                secret.clone(),
+                Ticket {
+                    id,
+                    issuer: device,
+                    bound_key_sha256: r.device_key_sha256,
+                    used_by: None,
+                    revoked: false,
+                    expired: false,
+                },
+            );
+            Ok(json(201, &TicketCreated { ticket_id: id, ticket: secret, expires_at: 0 }))
+        }
+        ("GET", ["v1", "devices", "tickets"]) => {
+            let list: Vec<TicketInfo> = st
+                .tickets
+                .values()
+                .filter(|t| t.used_by.is_none() && !t.revoked && !t.expired)
+                .map(|t| TicketInfo {
+                    ticket_id: t.id,
+                    issued_by: t.issuer,
+                    bound: t.bound_key_sha256.is_some(),
+                    expires_at: 0,
+                    created_at: 0,
+                })
+                .collect();
+            Ok(json(200, &list))
+        }
+        ("DELETE", ["v1", "devices", "tickets", id]) => {
+            let id = Uuid::parse_str(id).map_err(|_| err(404, "not_found"))?;
+            let t = st
+                .tickets
+                .values_mut()
+                .find(|t| t.id == id && t.used_by.is_none() && !t.revoked)
+                .ok_or_else(|| err(404, "not_found"))?;
+            t.revoked = true;
+            Ok(ResponseTemplate::new(204))
+        }
+        ("POST", ["v1", "join", rid, "hello"]) => {
+            let r: JoinHello = parse(req)?;
+            let j = st.joins.get_mut(*rid).ok_or_else(|| err(404, "not_found"))?;
+            if j.hello.is_some() {
+                return Err(err(409, "conflict"));
+            }
+            j.hello = Some((device, r.sender_pub));
+            Ok(json(200, &JoinHelloResponse { device: j.device.clone(), expires_at: 0 }))
+        }
+        ("PUT", ["v1", "join", rid, "bundle"]) => {
+            let r: JoinBundle = parse(req)?;
+            let j = st.joins.get_mut(*rid).ok_or_else(|| err(404, "not_found"))?;
+            if j.bundle.is_some() || j.hello.as_ref().map(|(d, _)| *d) != Some(device) {
+                return Err(err(409, "conflict"));
+            }
+            j.bundle = Some(r.bundle);
+            Ok(ResponseTemplate::new(204))
+        }
         ("POST", ["v1", "auth", "logout"]) => {
             st.sessions.retain(|_, d| *d != device);
             Ok(ResponseTemplate::new(204))
diff --git a/crates/kv-sync/src/wire.rs b/crates/kv-sync/src/wire.rs
index 9b4fac7..efa9cd2 100644
--- a/crates/kv-sync/src/wire.rs
+++ b/crates/kv-sync/src/wire.rs
@@ -10,3 +10,5 @@ pub const PATH_LOGOUT: &str = "/v1/auth/logout";
 pub const PATH_ACCOUNT: &str = "/v1/account";
 pub const PATH_VAULTS: &str = "/v1/vaults";
 pub const PATH_DEVICES: &str = "/v1/devices";
+pub const PATH_TICKETS: &str = "/v1/devices/tickets";
+pub const PATH_JOIN: &str = "/v1/join";