# PeerSpeak Versioning Standard

PeerSpeak is a full-mesh P2P voice app. Its "API contract" is not a library
surface — it is the **wire protocol** two nodes use to talk. So versioning here
tracks one question above all others:

> **Can a node on build X talk to a node on build Y?**

There are two distinct version layers. Keep them straight.

---

## Layer 1 — Release version (`Cargo.toml`)

The human-facing label you put on a build ("install this one").

**Scheme: SemVer, pre-1.0 (`0.MINOR.PATCH`).**

While we are pre-1.0 (friends-only, no stability promise yet):

| Change | Bump | Example |
| --- | --- | --- |
| **Breaking wire/protocol change** — peers on the old build can no longer interoperate; *everyone must update* | **MINOR** | `0.4.2 → 0.5.0` |
| Compatible change — bug fix, internal refactor, or a feature that does **not** change the wire (UI, local-only behavior, additive logic that old peers ignore safely) | **PATCH** | `0.4.2 → 0.4.3` |

- **Reaching `1.0.0`:** when PeerSpeak is first shared beyond the trusted-friends
  circle (a "public" release), and we are willing to commit to wire stability.
  After 1.0, MAJOR = wire break, MINOR = compatible feature, PATCH = fix (normal
  SemVer).
- Bump `version` in `Cargo.toml` as part of the change that warrants it, in the
  same commit. The number in `Cargo.toml` is the source of truth; surface it in
  the UI (e.g. an About/Settings line) so a user can read their build.

**Rule of thumb:** if you find yourself writing "all peers must rebuild" or
"breaking gossip wire change" in a commit message (as S2 and W4 did), that is a
**MINOR** bump, and it must also bump the relevant protocol version in Layer 2.

---

## Layer 2 — Protocol compatibility (the one that actually breaks calls)

Wire incompatibility must **fail fast and legibly** — never as a silent
signature/decode error that looks like a bug or an attack. We achieve this by
embedding a protocol version into each transport plane, so incompatible peers
are rejected at connect/subscribe time instead of mid-conversation.

PeerSpeak has **three independent planes**, each versioned **separately** — bump
only the plane whose wire format actually changed (audio rarely changes; gossip
changes often; they must not be forced to bump together).

### ALPN naming convention

All peerspeak ALPNs use the form **`peerspeak/<plane>/<N>`** where `<N>` is that
plane's protocol version (an integer, starts at `1`). iroh refuses a connection
whose ALPN does not match exactly, so two peers on different `<N>` for a plane
simply cannot open that connection → we map that to a clean "peer is running an
incompatible version" instead of garbage.

| Plane | ALPN / mechanism | Bump when… |
| --- | --- | --- |
| **Audio** | ALPN `peerspeak/audio/<N>` | the Opus/datagram framing, sequencing, or audio-handshake changes |
| **Friends/presence** | ALPN `peerspeak/friends/<N>` | the `ControlMsg` / presence ping-pong shape changes |
| **Gossip** | *(see below — cannot use a custom ALPN)* | `GossipPayload` / `GossipMessage` / `PeerState` shape, signing, or freshness rules change |

### Gossip is special

The gossip plane runs over **iroh-gossip's own `GOSSIP_ALPN`**, which we do not
control, so we cannot version it via the ALPN. Instead, the gossip protocol
version is bound in **two** places:

1. **Topic namespacing (primary, fail-fast):** the room's `topic_id` is a random
   32 bytes carried in the ticket, but the topic we actually *subscribe* to is
   `protocol::versioned_topic(topic_id)` — a deterministic, dependency-free
   transform that folds `GOSSIP_PROTO` into the bytes. Peers on different gossip
   versions therefore derive **different subscription topics from the same ticket**
   and never share a swarm — the same isolation a versioned ALPN gives the other
   planes. The ticket format and the room identity (`topic_id`) are unchanged; only
   the subscribed topic is namespaced. (The transform is for *isolation*, not
   security — cryptographic separation is the signature domain below.)
2. **Signature domain (cryptographic separation):** the signing domain string
   (`peerspeak-gossip-v<N>`, bound into every signed payload) carries the version,
   so two versions that somehow met on a topic would fail each other's verification
   rather than misread it.

Bumping the gossip version = bump `protocol::GOSSIP_PROTO` (drives
`versioned_topic`) **and** `protocol::GOSSIP_SIG_DOMAIN` together (a unit test in
`protocol.rs` asserts the domain string matches `GOSSIP_PROTO`, so they can't drift).

### Single source of truth for protocol versions

All protocol versions, ALPNs, the gossip signature domain, and `versioned_topic`
live in **`src/protocol.rs`**. Every call site derives from there (e.g.
`crate::protocol::AUDIO_ALPN`); **never hand-write an ALPN literal inline.** A
unit test asserts each ALPN/domain string matches its integer version so a bump
can't half-apply.

---

## "I changed X — what do I bump?" (quick reference)

| You changed… | Layer 2 (plane version) | Layer 1 (`Cargo.toml`) |
| --- | --- | --- |
| Opus framing / audio datagram layout | `peerspeak/audio/N` → `N+1` | MINOR |
| `ControlMsg` / presence shape | `peerspeak/friends/N` → `N+1` | MINOR |
| `GossipPayload`/`PeerState`/signing | `GOSSIP_PROTO_VERSION` + sig domain → next | MINOR |
| UI, local config, recording, a fix that doesn't touch any wire | nothing | PATCH |
| An *additive* gossip field that old peers safely ignore | judgement call — if old peers misbehave without it, treat as breaking (MINOR + gossip bump); if truly ignorable, PATCH | PATCH or MINOR |

When in doubt about "is this additive-safe?", assume **breaking** and bump. A
false MINOR bump costs a coordinated rebuild; a false PATCH costs silent broken
calls in the field.

---

## Release checklist (per build handed to anyone)

1. Decide MINOR vs PATCH from the table above; bump `Cargo.toml`.
2. If MINOR for a wire reason, confirm the matching Layer-2 plane version(s) were
   bumped in the same change.
3. Note the version + "breaking?" in the commit / handoff.
4. Tag the commit (`v0.x.y`) so a given binary maps to a known commit.
5. Rebuild **every** peer that must interoperate (e.g. dopedart, staged friend
   releases) when the bump was a MINOR/wire break.

---

## Current baseline (standard adopted + migrated, 2026-06-18, `0.2.0`)

- `Cargo.toml`: **`0.2.0`** — the MINOR bump for the (deliberately breaking)
  migration to this standard. **All peers must run ≥ `0.2.0` to interoperate**
  (the ALPNs and gossip topics changed); the pre-standard `0.1.0`-era build
  (e.g. an un-resynced dopedart) cannot talk to a `0.2.0` peer — by design, and it
  now fails cleanly at the handshake instead of silently.
- Protocol versions (all at `1`): `peerspeak/audio/1`, `peerspeak/friends/1`,
  gossip `peerspeak-gossip-v1` + `versioned_topic`. All sourced from
  `src/protocol.rs`.
- **Remaining nicety (not blocking):** surface `env!("CARGO_PKG_VERSION")` in the
  UI (an About/Settings line) and/or log it at startup, so a running build is
  self-identifying in the field. Small follow-up.
