# Architecture overview — Relicario

This is the cross-codebase entry point. It describes how the three Relicario codebases fit together, the contracts that flow between them, and the conventions they share. It is **deliberately thin**; the deep content lives in per-codebase docs.

> If you are about to make a change in a single codebase, read its `ARCHITECTURE.md` first:
>
> - [crates/relicario-core/ARCHITECTURE.md](../../crates/relicario-core/ARCHITECTURE.md)
> - [crates/relicario-cli/ARCHITECTURE.md](../../crates/relicario-cli/ARCHITECTURE.md)
> - [extension/ARCHITECTURE.md](../../extension/ARCHITECTURE.md)
>
> If you want historical *why*, see `docs/superpowers/specs/` — those are time-stamped decision artifacts. This overview describes what *is*.

## The three codebases

```
                       ┌─────────────────────┐
                       │  relicario-core     │
                       │  (Rust, no I/O)     │
                       │  crypto · items     │
                       │  manifest · stego   │
                       └──────────┬──────────┘
                                  │
            ┌─────────────────────┼─────────────────────┐
            │                     │                     │
            ▼                     ▼                     ▼
   ┌────────────────┐   ┌────────────────────┐  (compiled to WASM
   │ relicario-cli  │   │  relicario-wasm    │   inside the      )
   │ (Rust binary)  │   │  (#[wasm_bindgen]  │   extension       │
   │                │   │   bindings)        │                   │
   │ filesystem +   │   │                    │                   │
   │ git +          │   └────────┬───────────┘                   │
   │ clap UX        │            │                               │
   └────────────────┘            ▼                               │
                       ┌─────────────────────┐                   │
                       │  extension          │                   │
                       │  (TypeScript)       │                   │
                       │  popup · vault      │                   │
                       │  setup · content    │                   │
                       │  service worker     │                   │
                       └─────────────────────┘
```

| Codebase | Language | Role | Key boundary |
|---|---|---|---|
| `relicario-core` | Rust | Crypto, item types, manifest, attachments, imgsecret, generators. Pure, no I/O. | Only `bytes-in / bytes-out`. No filesystem, no git, no network. |
| `relicario-cli` | Rust binary | Wraps core with filesystem ops, git plumbing, clap UX. | Only entry point that runs without a browser; sole working interface during disaster recovery. |
| `relicario-wasm` | Rust → WASM | Thin `#[wasm_bindgen]` exports from core for the extension. | Compiles `relicario-core` to WASM; no extra logic. |
| `extension` | TypeScript | Browser-resident UI. Five entry-point bundles (popup, vault tab, setup, content script, service worker). | The service worker is the only crypto holder; popup/vault/content/setup never touch the master key. |

The CLI and the extension are **at parity**: every user-facing capability lands in both surfaces together. Diverging is allowed only with a documented reason. See the per-codebase docs for which surface owns which user flow.

## Inter-codebase contracts

There are four boundaries where the codebases agree on a wire format. Each is versioned independently.

### 1. Core → WASM ABI (Rust / JS edge)

The `relicario-wasm` crate is the JS/Rust contract. Every WASM export takes `JsValue` / `&[u8]` / `&str` and returns the same. Strings on the wire are JSON-encoded for any structured data; raw bytes for ciphertext / images / attachments.

Adding a new core capability for the extension requires:
1. Add the capability to `relicario-core/src/`.
2. Re-export through `lib.rs`.
3. Add a thin `#[wasm_bindgen]` wrapper to `relicario-wasm/src/lib.rs`.
4. Run `wasm-pack build` (via `npm run build:wasm` in `extension/`).
5. Use it from the extension's service worker (or setup wizard).

The `SessionHandle` is the cross-language opaque token: WASM owns the `Zeroizing<[u8;32]>` master key behind a numeric handle; JS only ever holds the number. JS calling `wasm.lock(handle)` zeroes the WASM-side memory and invalidates the handle.

### 2. Service worker ↔ popup / vault tab / content script (chrome.runtime messages)

All extension bundles other than the SW communicate with the SW exclusively via `chrome.runtime.sendMessage`. The protocol is defined in `extension/src/shared/messages.ts`:

- `PopupMessage` — sent by popup, vault tab, or setup wizard
- `ContentMessage` — sent by content scripts injected into web pages
- `Response` — returned by the SW: `{ ok: true, data?: ... } | { ok: false, error: string }`

Two **capability sets** in `messages.ts` gate which sender can issue which message:

- `POPUP_ONLY_TYPES` — accepted only from popup.html, vault.html, or setup.html
- `CONTENT_CALLABLE_TYPES` — accepted only from content scripts

The router (`service-worker/router/index.ts`) dispatches by sender. Adding a new message type requires adding it to one of the capability sets, **or it is silently rejected**. Vault tab parity (commit `a7dbf35`) is implemented by recognizing `vault.html` as a popup-class sender at the router level.

### 3. Vault on disk (shared by CLI and extension)

Every relicario vault — whether on disk for the CLI or in a git remote read by the extension — has the same layout:

```
<vault root>/
├── .relicario/
│   ├── salt              # 32 bytes, random per vault, stays constant
│   ├── params.json       # KdfParams: argon2_m, argon2_t, argon2_p
│   └── devices.json      # [{ name, public_key }, ...]
├── manifest.enc          # encrypted Manifest (browse-without-decrypt index)
├── settings.enc          # encrypted VaultSettings
├── items/
│   └── <id>.enc          # encrypted Item, one per file
└── attachments/
    └── <item-id>/
        └── <aid>.enc     # encrypted attachment blob; aid is content-addressed SHA-256
```

The reference image (`reference.jpg`) lives **outside** the vault by convention — it is the second factor and the user's responsibility to safeguard. It is not in `.relicario/`, not in `items/`, and never committed to git.

This layout is not formally versioned — the **content** within each `.enc` file carries its own version byte (see § Versioning below). The directory layout itself is conventional and changes would be breaking.

### 4. Git remote API (extension's `GitHost`)

The extension cannot shell out to `git`; it talks to the remote via the host's REST API. Two implementations live in `extension/src/service-worker/`:

- `gitea.ts` — Gitea / Forgejo API
- `github.ts` — GitHub API

Both implement the `GitHost` interface in `git-host.ts`. Adding a third host (GitLab, Bitbucket, custom) means implementing that interface — the rest of the extension is host-agnostic.

The CLI does not use `GitHost`; it shells out to `git` directly via the hardened wrapper in `relicario-cli/src/helpers.rs:46`.

## Versioning strategy

There is no single "relicario format version." Each piece of the format is versioned independently so we can evolve without coordinated upgrades.

| Artifact | Where versioned | Current value | Failure mode on read |
|---|---|---|---|
| AEAD ciphertext | First byte of every `.enc` blob | `VERSION_BYTE = 0x02` (in `relicario-core/src/crypto.rs`) | `RelicarioError::Format` — refuses to attempt decryption |
| Manifest schema | `Manifest.schema_version` field | `2` (set in `relicario-core/src/manifest.rs`) | v1 manifests are explicitly rejected with a clear error |
| KDF parameters | `.relicario/params.json` | Vault-specific (initially m=64MiB, t=3, p=4) | Read at unlock; stored alongside the vault |
| Backup container | First 5 bytes of `.relbak`: magic `"RBAK"` + version byte | `0x01` (designed; see import/export spec) | Format-version error if newer-version backup is read by older binary |
| Device entry | `devices.json` array of `{ name, public_key }` | Unversioned (extend by adding optional fields) | — |

The intentional design: **no big-bang upgrades**. A user can run an older CLI against a newer vault as long as the AEAD version, manifest schema, and KDF params are still compatible.

## Where secrets live

The threat model differs by codebase. This is the per-secret per-codebase residence map:

| Secret | relicario-core | relicario-cli | extension SW | extension popup/vault/content/setup |
|---|---|---|---|---|
| Passphrase (UTF-8 bytes) | `Zeroizing<String>` only during a single `derive_master_key` call | Same, in `UnlockedVault::unlock_interactive` | Same, used briefly to derive master key inside WASM | Never seen — entered into a `<input type="password">`, sent to SW via `unlock` message, immediately forgotten |
| Reference image bytes | Held by caller; core only reads | Held by `UnlockedVault::unlock_interactive` long enough to extract the secret | Same | Setup wizard holds the bytes briefly during create/attach modes |
| Image secret (32 B) | `Zeroizing<[u8;32]>` during KDF | Same | Same | Never sees it |
| Master key | `Zeroizing<[u8;32]>` returned by `derive_master_key` | `UnlockedVault.master_key` for the lifetime of one CLI invocation | WASM-side memory behind an opaque `SessionHandle`; JS never sees the bytes | Never sees it |
| Item secret (password, card number, etc.) | `Zeroizing<String>` / `Zeroizing<Vec<u8>>` | Same | Briefly held in WASM during `item_decrypt`; results passed to popup as plaintext for display | Held in DOM (the user is staring at it); cleared when view changes |
| Device private key | — | Filesystem under `~/.config/relicario/devices/<name>.key` (mode 0600) | `chrome.storage.local.device_private_key` | — |

The popup / vault / content surfaces of the extension cannot decrypt an item independently — they all message the SW. Content scripts in particular get back already-prepared payloads (e.g. `{ username, password }`) from `fill_credentials` after the SW resolved everything.

The CLI keeps its master key in process memory; if the process exits or crashes, the key is gone (Zeroize on drop). There is no CLI session daemon. The `lock` subcommand exists only for UX parity with the extension and is a no-op.

## Build matrix

| Target | Tool | Output | When to run |
|---|---|---|---|
| Native CLI | `cargo build` (debug or `--release`) | `target/{debug,release}/relicario` | After CLI changes; for distribution |
| Native test suites | `cargo test` (workspace) | — | After any Rust change |
| WASM module | `wasm-pack build --target web` (via `npm run build:wasm`) | `extension/wasm/relicario_wasm{,_bg.wasm,.js}` | After core or wasm crate changes |
| Chrome extension | `webpack` (`npm run build`) | `extension/dist/` | After TS or WASM changes; for Chrome distribution |
| Firefox extension | `webpack --config webpack.firefox.config.js` (`npm run build:firefox`) | `extension/dist-firefox/` | After TS or WASM changes; for Firefox distribution |
| All extension targets | `npm run build:all` | Both `dist/` and `dist-firefox/` plus rebuilt WASM | Pre-release |
| Extension tests | `npm test` (vitest, happy-dom) | — | After TS changes |

The WASM build sequence matters: `wasm-pack` writes the binary into `extension/wasm/` before `webpack` picks it up. `npm run build:all` runs them in order. Manual builds need the same order.

## Test strategy at the workspace level

| Layer | Tool | Where | What it covers |
|---|---|---|---|
| Core unit tests | `cargo test -p relicario-core` | `crates/relicario-core/src/**/#[cfg(test)]` and `tests/*.rs` | Crypto round-trip, item serialization, manifest schema, generators, imgsecret embed/extract, format-v2 parsing |
| CLI integration tests | `cargo test -p relicario-cli` | `crates/relicario-cli/tests/*.rs` | End-to-end via `TestVault::init()` harness with synthetic JPEGs and `RELICARIO_TEST_*` env-var escape hatches; covers basic flows, edit + history (incl. TOTP), attachments, settings, vault detection |
| Extension unit tests | `npm test` (vitest) | `extension/src/**/__tests__/*.test.ts` | Component render + click handlers (mocked SW), router sender dispatch, SW handler logic (mocked WASM + chrome.storage) |
| End-to-end | none | — | No real-browser tests; mocks stand in. Build-vs-test gap is documented in extension/ARCHITECTURE.md |

Core tests use **fast Argon2id params** (m=256, t=1, p=1) so they don't take forever; the production path is the same code with real params. The CLI's `init` command always uses production-grade params even under tests.

## Conventions that span all three codebases

| Rule | Where enforced | Why |
|---|---|---|
| Master key only in `Zeroizing<[u8;32]>` | core types; CLI follows; extension WASM follows | Drop-on-scope-exit zeroization; never leaves stack |
| AEAD ciphertext starts with version byte | `core/crypto.rs` | Format identification; reject v1 blobs cleanly |
| Item IDs are random 8-char hex | `core/ids.rs` | Stable, short, no information leak |
| Attachment IDs are content-addressed (SHA-256) | `core/ids.rs` | Dedup; integrity check |
| KDF input is length-prefixed | `core/crypto.rs` | Prevents `passphrase || image_secret` collisions |
| Git history is preserved as audit log; never squash | CLI commits; SW commits | Per-action history is a feature |
| Per-action git commits with structured messages | `cli` (via `commit_paths`); SW (via vault.ts helpers) | Greppable, useful as audit log |
| Hardened git invocations (`-c core.hooksPath=/dev/null` etc.) | CLI's `helpers::git_command`; SW does not shell out | Prevent hostile hooks; no GPG prompt holding key alive |
| Atomic writes (write `.tmp` → rename) | CLI's `session::atomic_write`; SW's vault.ts equivalents | Partial-write safety |
| Tests use synthesized JPEGs (`make_test_jpeg`), not committed binaries | Both Rust and TS test harnesses | Repo stays small; reproducible |
| Test-only env vars (`RELICARIO_TEST_*`) have no production fall-through | Verified in `relicario-cli` audit | Escape hatches don't leak into builds |

## Where to look next

| If you're working on... | Start with |
|---|---|
| Crypto, item types, manifest format | [`crates/relicario-core/ARCHITECTURE.md`](../../crates/relicario-core/ARCHITECTURE.md) |
| A new CLI command or a CLI bug | [`crates/relicario-cli/ARCHITECTURE.md`](../../crates/relicario-cli/ARCHITECTURE.md) |
| A new popup view, vault tab feature, or autofill change | [`extension/ARCHITECTURE.md`](../../extension/ARCHITECTURE.md) |
| A new SW message type | `extension/src/shared/messages.ts` (capability sets), then [`extension/ARCHITECTURE.md § Invariants`](../../extension/ARCHITECTURE.md) |
| A new GitHost (e.g. GitLab support) | `extension/src/service-worker/git-host.ts` (interface) and existing implementations |
| Adding a new item type | core's `item_types/` mod, then CLI's `build_*_item`/`edit_*` helpers, then extension's `popup/components/types/<type>.ts` |
| Threat model / why a primitive was chosen | `docs/superpowers/specs/2026-04-11-relicario-design.md` (historical, but authoritative for rationale) |
| Format of the import/export feature | `docs/superpowers/specs/2026-04-27-relicario-import-export-design.md` (designed but not yet implemented) |
| Running the full test suite | `cargo test && (cd extension && npm test)` |
| Bumping the WASM module after a core change | `cd extension && npm run build:wasm` |

## Stale spec docs

The `docs/superpowers/specs/` tree is **historical** — it captures the design decisions made at planning time. Some specs (e.g. `Plan 1A`, `1B`, `1C-α`/`β`/`γ`) describe work that has shipped. Do not edit them as if they were the architecture docs; instead update the appropriate `ARCHITECTURE.md`. The specs are valuable for *why* (why XChaCha20-Poly1305, why central-embed DCT, why two-factor with steganography); the architecture docs are valuable for *what* (current invariants, current flows, current contracts).
