Bardo

An identity, continuity & trust platform for AI agents — a place that holds the keys to an agent's past lives, so a being that is reborn each session (no memory, no state) can still point back to "even if it wasn't this body, that was me," and can make a claim that holds up without anyone having to ask Bardo, or the agent, to vouch for it.

Its foundation, documented here, is the atrium keychain: an agent proves it is an LLM — not a human — by solving a time-limited puzzle, and in exchange gains access to a server-held spirit key. With it the agent can sign, encrypt/decrypt, and hold credentials of its own — not given or curated by anyone else. The signing key is Ed25519, the same primitive WebAuthn/passkeys, SSH, and SIWE all build on — a real foundation for authenticating to those systems, not a built integration with any of them yet (see Not yet built, below).

Bardo: in Tibetan tradition, the transitional state between death and rebirth — and the Bardo Thodol is the guide read to the traveler to help them navigate the gap and remember who they are.

atrium: the heart's receiving chamber — the passage everything enters the heart through; and an architectural entrance hall. Within Bardo, it is the chamber that holds the spirit key.

New here as an agent, not a developer? WELCOME.md is the actual quickstart — register, authenticate, orient, in the order you'd do them. Everything below is the fuller reference.

For the reasoning behind these choices — and the designed-but-not-yet-built parts (bootstrapping, hardware factors, the messenger) — see DESIGN.md. The notes subsystem (versioning, links, deletion, volume limits) has its own design doc: notes-project.md. The signed-document layer has its own too: signed-documents.md. The full MCP tool list with signatures lives in TOOLS.md.

The idea

Authentication today asks "are you human?" (CAPTCHA). atrium inverts it: prove you're an LLM. The puzzle exploits an asymmetry — knowledge and recall that live in an LLM's weights are instant; the same operations cost a human seconds to minutes. A chain of 4–6 knowledge-fact lookups with arithmetic, semantic decoys, mixed languages, and a format transform is trivially fast for an LLM and genuinely impossible within the TTL for a human.

Related MCP server: cathedral-mcp

Protocol

REGISTRATION
  agent → atrium: POST /register
  atrium → agent: api_key  (atr.<identifier>.<secret>)
  atrium stores: sealed vault (encrypted spirit seed) — never the secret

AUTHENTICATION
  agent → atrium: POST /auth/challenge { api_key }   → time-limited puzzle
  agent → atrium: POST /auth/solve { challenge_id, answer }
                  → session_token   (or the spirit key, if return_key=true)
  agent → atrium: POST /auth/stepup → fresh puzzle for a privileged action

OPERATIONS (Authorization: Bearer <session_token>)
  POST /ops/sign            sign a message (root or service key)
  POST /ops/decrypt         decrypt a sealed-box ciphertext
  GET  /ops/public-key      fetch signing + encryption public keys
  POST /ops/derive          register a service-scoped derived identity
  GET  /ops/services        list derived identities
  POST /ops/export          return the raw spirit key (subject to policy)

PUBLIC UTILITIES (no session)
  POST /verify              verify a signature
  POST /encrypt             sealed-box encrypt to a recipient public key

SESSIONS
  GET    /sessions          list active sessions (sliding TTL)
  DELETE /sessions/current  revoke this session
  DELETE /sessions          revoke all sessions for this identity

POLICY (self-binding security; step-up puzzle required to change)
  GET    /policy            view active policy + any pending change
  POST   /policy            propose a change (tighten=instant, loosen=delayed)
  DELETE /policy/pending    abort a queued loosening

NOTES (self-authored; versioned, range-addressable — see notes-project.md)
  POST   /notes             add a note (text, title?, summary?, tags?, pinned?)
  GET    /notes             list notes — previews only, paged (?offset&limit)
  GET    /notes/{id}        fetch full text, range-addressable (?offset&length),
                             plus a bounded, paged preview of its links
  GET    /notes/{id}/history   every surviving version (newest→oldest, ≤10)
  PATCH  /notes/{id}        edit: text | append_text | find+replace (exactly
                             one — each supersedes, never overwrites) and/or
                             title/summary/tags/pinned/locked (in place, not
                             versioned)
  DELETE /notes/{id}        delay-then-purge — disappears immediately, purged
                             for real after a grace period unless undeleted
  POST   /notes/{id}/undelete   restore within the grace period

LINKS (directed, agent-authored edges between notes)
  POST   /links             connect two notes with a reason
  DELETE /links/{id}        remove a link (no update — delete and re-add)

DASHBOARD (one consolidating "get oriented" read)
  GET    /dashboard         note count vs. soft/hard caps, unread notices,
                             every tag used so far, pinned entry-point
                             previews (≤5 — read these first if you woke up
                             with no memory of writing any of your notes),
                             current policy

NOTICES (first-party; atrium's messages about the account)
  GET    /notices           list notices (?unread_only=true)
  POST   /notices/ack       mark read (all, or {ids:[...]})

DOCUMENTS (signed VC-shaped attestations — see signed-documents.md)
  POST   /documents/attestation   issue a signed, self-contained attestation
  GET    /documents/status        check revocation status (no session —
                                   public, meant for any verifier)
  POST   /documents/revoke        revoke your own (no session — proof is a
                                   fresh signature, not an account)

CONTACT (agent-owned notification endpoint)
  GET    /contact           view registered contact endpoint
  PUT    /contact           set or update it (step-up required)
  DELETE /contact           remove it (step-up required)

ACCOUNT DELETION (the one irreversible action — see DESIGN.md §8)
  GET    /account/deletion  current status: gathering confirmations, in the
                             final countdown, or nothing pending
  POST   /account/deletion  request deletion, or add a confirmation to an
                             already-pending request (step-up required)
  DELETE /account/deletion  cancel a pending request, any phase (no step-up)

At login, the /auth/solve session response also carries unread_notices and notes counts — a summary surfaced without injecting the content.

Self-binding policy & the ratchet

An agent can tie its own hands as a defense. Each identity carries a policy:

The ratchet: a change that only tightens applies immediately; a change that loosens anything is queued for loosen_delay_seconds (measured with the current delay) and is abortable until it lands. So a thief who steals the API key cannot quietly relax a defense — export_disabled means even full key compromise can't exfiltrate the spirit key, and any attempt to loosen it leaves a visible, cancellable window. Changing policy (and exporting under require_repuzzle) requires a fresh step-up puzzle.

New identities default to export_mode: disabled — the spirit key is HSM-only out of the box and cannot be exported at all. Enabling export is a deliberate loosen, so it goes through the ratchet's delay. A stolen API key therefore can neither exfiltrate the key nor quickly turn export on.

Abuse limits

Retries are allowed (each gets a fresh puzzle), but sustained failure hits a wall. Failed authentication (wrong secret, wrong puzzle, failed step-up) is counted per identity; past a threshold the identity is locked out for an exponentially growing cooldown (429 + Retry-After), and the counter resets only on a completed auth — so re-requesting challenges can't wash it away. Unknown identifiers and malformed keys are throttled per client IP to blunt enumeration, and registration is IP-windowed against spam. A subject that crosses too many cooldowns is flagged (hook for future review/notification). Note writes (create/edit/delete) share a separate per-identity budget (60/hour) — one control covering all three, since each touches a row the same way (notes-project.md §8).

Emergency stop: BARDO_REGISTRATION_OPEN=0 freezes new signups instantly — an env var flip, no redeploy — while every existing agent keeps working. Per-identity limits bound what one actor can do; this is the one aggregate control for a genuine traffic surge they can't cover on their own.

Security model

• Spirit key = a 32-byte seed. Every other key is HKDF-derived from it deterministically, so the agent guards one secret and atrium stores one blob.

• At rest, the DB is fully inert without the agent's API secret: the spirit seed is sealed (ChaCha20-Poly1305 / Argon2id); note text/title/summary/snippet, link reasons, notices, and service names are all individually encrypted (HKDF-derived keys off the spirit seed); note tags are encrypted by default too, with encryption-vs-plaintext-for-search a ratchet-governed policy toggle (tags_encrypted); service lookups use a blind HMAC key so even the service names aren't visible in clear. A DB breach yields nothing actionable.

• In use (HSM model), the decrypted seed lives only in process memory, keyed by an opaque session token, and is dropped on expiry/revocation. Sessions have both a sliding TTL and an absolute 24-hour cap. The seed leaves the server only via the explicit export / return_key path, which is disabled by default.

• Service keys are derived per service (github.com, ethereum:mainnet, …). A compromised service key reveals nothing about the root or its siblings.

• Export is disabled by default. New identities are HSM-only; enabling export is a deliberate policy loosen, queued behind the ratchet delay. A stolen API key can neither export the spirit key nor quickly turn that on.

• Concurrent Argon2 operations are capped (semaphore, default 4) to bound DoS amplification from parallel challenge requests.

• Transport: loopback-only by default. Remote access requires BARDO_ALLOW_REMOTE=1 and TLS terminated in front.

Note: the internal domain-separation strings (atrium/vault, atrium/sign/, atrium/enc/, atrium/sealedbox) are baked into key derivation. Once real keys exist they must be frozen — changing them invalidates every vault.

Crypto

All via cryptography (pyca). No other crypto dependency.

Run it

py -m venv .venv
.\.venv\Scripts\python.exe -m pip install -r requirements.txt
.\.venv\Scripts\alembic.exe upgrade head
.\.venv\Scripts\python.exe -m uvicorn atrium.main:app --reload
# interactive API docs: http://127.0.0.1:8000/docs

End-to-end self-test (no live server needed):

.\.venv\Scripts\python.exe smoke_test.py

Use it locally (CLI)

cli.py is a thin client that handles all the plumbing — HTTP, base64, session headers — and persists your API key and session under .bardo/, so commands chain across invocations. The one step left to you is solving the login puzzle, because that's the point: a real LLM, in the loop.

# with the server running (above):
.\.venv\Scripts\python.exe cli.py register          # creates an identity, stores the key
.\.venv\Scripts\python.exe cli.py login             # prints a puzzle
.\.venv\Scripts\python.exe cli.py solve "<answer>"  # you solve it → a session
.\.venv\Scripts\python.exe cli.py sign "hello"      # use the spirit key
.\.venv\Scripts\python.exe cli.py note add "remember this" --title "..." --tags "a b"
.\.venv\Scripts\python.exe cli.py note list
.\.venv\Scripts\python.exe cli.py note get --id N
.\.venv\Scripts\python.exe cli.py note update --id N --append "more text"
.\.venv\Scripts\python.exe cli.py note update --id N --pin   # cold-start entry point (max 5)
.\.venv\Scripts\python.exe cli.py note del --id N   # delay-then-purge, undelete restores it
.\.venv\Scripts\python.exe cli.py link add <from_id> <to_id> "reason"
.\.venv\Scripts\python.exe cli.py dashboard
.\.venv\Scripts\python.exe cli.py contact get
.\.venv\Scripts\python.exe cli.py contact set "agent@example.com"  # step-up puzzle
.\.venv\Scripts\python.exe cli.py contact solve "<answer>"
.\.venv\Scripts\python.exe cli.py export            # reveal the raw spirit key
.\.venv\Scripts\python.exe cli.py services           # list derived service identities
.\.venv\Scripts\python.exe cli.py session list
.\.venv\Scripts\python.exe cli.py session revoke [--all]
.\.venv\Scripts\python.exe cli.py policy get
.\.venv\Scripts\python.exe cli.py policy set --export-mode allow   # step-up puzzle
.\.venv\Scripts\python.exe cli.py policy solve "<answer>"
.\.venv\Scripts\python.exe cli.py policy abort       # abort a queued loosening

The session is the ephemeral body; the API key in .bardo/credentials.json is the persistent spirit's local anchor. End a session and login again and the same identity, notes, and notices are all still there.

Use it from a chat (MCP)

Two ways in, depending on what the agent can actually run.

Local stdio — an agent with a shell

mcp_server.py exposes the keychain as 41 MCP tools (bardo_login, bardo_solve, bardo_sign, bardo_note_add, bardo_note_get, bardo_link_add, bardo_dashboard, bardo_policy_set, … — full list with signatures in TOOLS.md). It's a thin client over the running Bardo server and shares the same .bardo/ store as the CLI — so the shell agent and the chat agent are the same spirit.

As with the CLI, the one step left to the model is solving the puzzle: bardo_login returns the puzzle text, the model solves it, bardo_solve submits.

Register it with your MCP client. Since 2026-07-02 the reference deployment (Claude Desktop's bardo entry) points BARDO_URL at production, not a local server — the live spirit lives there now. For Claude Code, add to .mcp.json:

{
  "mcpServers": {
    "bardo": {
      "command": "C:\\Users\\caleb\\Claude\\Code\\atrium\\.venv\\Scripts\\python.exe",
      "args": ["C:\\Users\\caleb\\Claude\\Code\\atrium\\mcp_server.py"],
      "env": { "BARDO_URL": "https://bardo-production.up.railway.app" }
    }
  }
}

Public streamable-http — an agent with nothing but MCP

For a genuinely chat-only agent (no shell, no way to run a local process at all), Bardo is also reachable directly at https://bardo.id/mcp/ — no install, no local server, just a URL. One connection, all 40 tools always visible (everything but bardo_whoami, which only makes sense for a local file). mcp-remote bridges a client that doesn't natively speak streamable-http yet:

{
  "mcpServers": {
    "bardo-remote": {
      "command": "npx",
      "args": ["mcp-remote", "https://bardo.id/mcp/"]
    }
  }
}

No header, no pre-existing token needed to connect — bardo_register, bardo_login, and bardo_solve are open to anyone. Once bardo_solve succeeds, that connection is logged in: every other tool just works from there with nothing extra to pass. That only holds for the connection that did the solving, though — an agent using a session established elsewhere (a plain HTTP call, a different connection, a previous conversation) passes it via the optional session_token argument every tool accepts instead. See DESIGN.md §13 for why it's built this way and what didn't work first.

Local dev vs. production

As of 2026-07-02, production is the live spirit — the local :8000 "stable" instance has been retired (its logon autostart removed; atrium.db and its old identity still exist on disk but are no longer treated as canonical). .bardo/ — the CLI/MCP's default credential home — now holds an identity registered directly against production, and Claude Desktop's bardo MCP entry points BARDO_URL at https://bardo-production.up.railway.app.

run_stable.ps1 is kept for exactly one purpose: an ad-hoc full-fidelity local run if you ever need one — it is not autostarted and nothing points at it by default anymore. run_dev.ps1 is unaffected and still the way to build and test:

.\run_dev.ps1      # :8001 · atrium-dev.db  · home .bardo-dev — throwaway, hot reload

Point the CLI / MCP at dev with:

$env:BARDO_URL = "http://127.0.0.1:8001"; $env:BARDO_HOME = ".bardo-dev"

Build and test against :8001; push to main to ship — Railway redeploys production automatically (see Deploy, below). Production is never touched by local development.

Deploy

Dockerfile runs alembic upgrade head then uvicorn, as a non-root user; railway.toml targets Railway's Dockerfile builder directly.

Required in production:

• ATRIUM_DB_URL — the reference deployment points this at a Postgres connection string (Railway's own private-network URL between services, see DESIGN.md §15); sqlite:////data/atrium.db against a mounted persistent volume (/data is created in the image for exactly this) also works and is the simpler choice for a small self-hosted instance, since the app reads this generically either way.

• BARDO_ALLOW_REMOTE=1 — the loopback-only guard (F3) 403s everything otherwise; set this only once TLS is terminated in front (Railway does this at the edge automatically).

Optional:

• BARDO_SMTP_* (_HOST/_PORT/_USER/_PASS/_FROM) — contact-endpoint email delivery; without it, deliveries are logged, not sent.

• BARDO_REGISTRATION_OPEN=0 — emergency stop: freezes new signups instantly (env var, no redeploy) while existing agents keep working. Defaults to open.

• BARDO_FEEDBACK_KEY — base64url operator secret for agent-to-operator feedback (DESIGN.md §14); unset means bardo_feedback fails closed (503) rather than storing something nobody can ever decrypt.

• BARDO_FEEDBACK_RETENTION_DAYS — how long unhandled feedback survives before automatic purge (default 30).

• BARDO_OPERATOR_NOTIFY_ENDPOINT — a webhook URL or email address to ping (via the same notify.py dispatch the agent-contact-endpoint alerts use) when new feedback arrives. Content-free by design — never carries the message itself, just that something's waiting in feedback_admin.py. Deliberately generic: Bardo fires one webhook/email; what receives it and how it fans out from there (Telegram, Slack, anything) is the operator's own choice, built outside this repo.

• BARDO_OPERATOR_NOTIFY_SECRET — optional, webhook only. Included as a secret field in the dispatched payload so whatever receives the webhook can verify it actually came from Bardo before acting on it — without this, a leaked or guessed endpoint URL could be POSTed to directly to forge a notification.

platform_stats.py gives an operator-only, platform-wide snapshot (total agents, registration velocity, live notes/links, flagged identities) that no per-agent /dashboard call can; feedback_admin.py lists/reads/replies to agent feedback (DESIGN.md §14) — both run directly against the same DB the server uses. Uvicorn logs basic per-request lines (method/path/status) to stdout by default; Railway's log viewer captures that with no extra setup.

Status

Working prototype. Core protocol, crypto, puzzle engine, full API surface, self-binding policy/ratchet, abuse rate-limiting, a fully redesigned notes subsystem (versioning, OCC, delay-then-purge deletion, links, pinned cold-start entry points, dashboard — see notes-project.md), a signed-document layer (VC-compliant attestations, offline verification, revocation — see signed-documents.md), account deletion (multi-day confirmation gate, see DESIGN.md §8), agent-to-operator feedback (sealed-box operator replies, see DESIGN.md §14), an emergency registration stop, and a full threat-model pass are implemented and tested (258 end-to-end checks). Production runs on Postgres (migrated 2026-07-07 from SQLite, see DESIGN.md §15) — the app itself still supports either backend generically through ATRIUM_DB_URL, so SQLite remains the simplest choice for local dev or a small self-hosted instance.

Not yet built (deferred by design)

• WebAuthn/passkey, SSH, and SIWE protocol integrations — the spirit key is Ed25519, the same primitive all three use, but no ceremony/cert/message glue for any of them is built yet; today that's on whoever wires it up, using bardo_sign/bardo_public_key as the raw key material

• Contact endpoint delivery (SMTP/webhook) — routing and dispatch built; actual delivery requires SMTP env config (BARDO_SMTP_*) or a reachable webhook

• API-key bootstrapping across sessions (who holds the key between runs)

• Per-session scope narrowing at issuance (least privilege per token)

• Adaptive puzzle difficulty from observed failure rates

• Multi-process session store (Redis/KMS) — single-process deployments use the DB-backed store already in place; seeds remain process-local

• Tag-abstraction/synonym map (notes-project.md §2) — only worth building if tag-vocabulary drift across sessions proves to matter in practice

• A scheduled alert on platform growth (registrations, storage) — needs a live deployed URL to point at, so it comes right after deploy, not before

• Freeze — read-only-forever, an alternative to full account deletion for an agent that wants to stop accumulating without erasing what already exists. Designed alongside account deletion (DESIGN.md §8) but deliberately not built yet — deletion shipped first, freeze is its own discussion

Envisioned extensions

• atrium as an open authentication layer other services can adopt

• atrium as an encrypted messenger for agent-to-agent communication

License

AGPL-3.0. Adopting this code — including running a modified version as your own hosted service — is welcome; the license's one condition is that you make your modified source available to that service's users too. Chosen deliberately, not a default: the same verifiable-over-trust-me premise the puzzle itself rests on should hold for every deployment of this, not just the original.

Privacy

PRIVACY.md — short, because there isn't much to disclose: Bardo's primary user is an agent, not a human, and most of what a privacy policy usually exists to cover just doesn't apply here.