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Your seed phrase is a 24-word BIP-39 mnemonic that serves as the master key to your Cossi account. It is generated on your device during setup and is used to derive your authentication keys and vault encryption key.

Because Cossi has no server-side accounts, there is no "forgot password" flow. Your seed phrase is the only way to recover your account if you lose access to your device. Write it down on paper and store it somewhere safe. We cannot recover it for you.

No. Cossi has no server-side accounts. Your identity is your seed phrase and the cryptographic keys derived from it. No email address, phone number, or personal information is required to use Cossi.

No API key is required. Cossi runs a language model directly on your device using llama.rn. On first launch, you'll be prompted to download a model (typically 1–4 GB). Once downloaded, the AI works fully offline — no internet connection, no API calls, no cost per query.

Model download requires a Wi-Fi connection and adequate storage space. We recommend downloading over Wi-Fi and ensuring at least 2 GB of free space before starting.

Cossi supports CalDAV, which is the open standard used by Google Calendar, Apple iCloud, Fastmail, and most self-hosted calendar servers. In Settings, tap Calendar, then enter your CalDAV server URL and credentials. These credentials are stored encrypted on your device and never sent to our servers.

You can also create and manage events directly within Cossi without connecting an external calendar.

Cossi connects to your inbox using standard IMAP (for reading) and SMTP (for sending). In Settings, tap Email and enter your IMAP and SMTP server details. If you use Gmail, you will need to generate an App Password (Google requires this for third-party IMAP clients with two-factor authentication enabled).

Your email credentials are encrypted with AES-256-GCM and stored locally. Cossi connects directly to your mail server — no email is routed through our infrastructure.

No. Cossi is local-first. Your calendar, contacts, email, AI conversations, vault contents, and seed phrase never leave your device. We operate no user data servers.

The only network requests Cossi makes are:

• To your calendar server (CalDAV sync, if configured)
• To your mail server (IMAP/SMTP, if configured)
• To public blockchain RPC endpoints for wallet balance (your public address only, not your private key)
• To CoinGecko's public API for crypto price data (no account identifier sent)

Cossi uses multiple encryption layers:

• Vault: AES-256-GCM with a key derived from your seed phrase via HKDF.
• Authentication: ML-DSA-65 (CRYSTALS-Dilithium), a NIST-standardised post-quantum digital signature scheme. Your private key is generated and stored on-device; it never leaves.
• Email credentials: AES-256-GCM encrypted before being written to local storage.
• Device storage: All sensitive keys are stored in the iOS Secure Enclave via Keychain.

Install Cossi on your new device and choose "Recover account" on the onboarding screen. Enter your 24-word seed phrase. Cossi will re-derive your authentication keys and vault encryption key, giving you full access to your encrypted vault and previous configuration.

If your data was also stored on an external calendar or mail server, it will re-sync from those sources. Data that existed only on the lost device (local calendar events, contacts not synced elsewhere, vault contents) can only be recovered if you have a manual backup or your iCloud backup includes Cossi's local data.

No. Your seed phrase is the only recovery mechanism. We have no copy of it and no server-side key that could unlock your account. This is by design — it means we cannot be compelled to hand over your data because we do not have it.

If you lose your seed phrase and lose access to your device, your account and vault contents cannot be recovered. Please store your seed phrase offline in a secure location.

Cossi supports multiple on-device models available via the in-app model library (powered by llama.rn). Models range from lightweight (1.5B parameters, ~1 GB) to more capable (7B parameters, ~4 GB). The specific models available may change with app updates. You choose which model to download and use.

None of these models require an internet connection once downloaded. No query is ever sent to an external AI provider.

On-device models are smaller than cloud-based alternatives and may occasionally produce incorrect or inconsistent outputs. This is a known limitation. You can:

• Rephrase your query with more context
• Try a different model from the model library (larger models are generally more capable)
• Use the feedback option in the chat to mark a response as unhelpful — this helps us tune future prompt templates

Cossi always operates with human-in-the-loop confirmation for actions (drafts, calendar events, tasks). The AI suggesting something incorrect does not mean an action will be taken without your approval.

The AI accesses your calendar and, where relevant, email data to generate your daily brief and meeting prep briefings. This processing happens entirely on your device — the AI model runs locally and no data is sent externally. You can review and control which data Cossi surfaces in Settings.

Cossi is currently in early access. During this period, the app is available at no charge. We may introduce pricing in the future and will communicate this clearly in advance. There are no hidden fees and no AI usage charges — the model runs on your device at no per-query cost.

Not currently. Cossi does not require a subscription during early access. Future pricing, if introduced, will be communicated with adequate notice to existing users.

Cossi requires iOS 16 or later. For the best experience and on-device AI performance, iOS 17 or later is recommended. On-device AI inference requires a device with an A14 Bionic chip or newer (iPhone 12 and later).

The Cossi app itself is under 50 MB. On-device AI models require additional storage:

• Small model (1.5B): ~900 MB – 1.2 GB
• Medium model (3B): ~1.8 GB – 2.2 GB
• Large model (7B): ~3.8 GB – 4.5 GB

We recommend having at least 2 GB of free storage before downloading your first model. Models can be deleted and re-downloaded from the Model Setup screen at any time.

Try these steps in order:

• Force-quit Cossi and reopen it
• Restart your iPhone
• Check that you have adequate free storage (low storage can cause instability)
• If the crash occurs during AI inference, try switching to a smaller model in Settings → Model Setup
• If the issue persists, email us at customer_services@sianalytics.tech with your device model, iOS version, and a description of what triggers the crash

Cossi is currently iPhone-only. iPad and Android support are on our roadmap but have no confirmed release dates. If either platform is important to you, let us know at customer_services@sianalytics.tech — user demand influences our priorities.