docs: record the GUI architecture and version lockstep; adopt GPL-3.0-or-later

1 files changed, 21 insertions, 5 deletions

diff --git a/AGENTS.md b/AGENTS.md
index ede8d67..e784624 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -51,6 +51,18 @@
 - `ServerCore::poll` must be idempotent: it settles the round, removes the
   session, and pushes once. A second poll must produce nothing.
 
+## GUI
+- The GUI is a second frontend over `ClientCore`, not a second client.
+  Frontends send `Command` and render `View`; the core owns navigation and
+  state and contains no I/O or terminal types.
+- egui lives in the `gui/` workspace member. Its dependencies must never
+  enter the TUI or server build graph: no GUI crate in the root package's
+  `[dependencies]`.
+- First contact shows the fingerprint and waits for a decision before sending
+  any credentials. A changed key is a hard stop; forgetting it is explicit.
+- The GUI is themed deliberately. Default egui styling is not an acceptable
+  look; keep a style module and a reference screen.
+
 ## Client TUI
 - `render_lines()` and `render()` must agree. If `render()` uses `\r\n`,
   count lines against the same string the cursor will erase.
@@ -98,14 +110,18 @@
 Use semantic versioning (`MAJOR.MINOR.PATCH`) in `Cargo.toml`.
 
 - **MAJOR** — breaking protocol changes (wire format, TLS trust model,
-  database schema migration that can't auto-upgrade). Clients and servers
-  at different MAJOR versions are incompatible.
-- **MINOR** — new features, new game types, new commands. Backwards
-  compatible: old clients work with new servers, new clients work with
-  old servers (they just don't see the new feature).
+  database schema migration that can't auto-upgrade).
+- **MINOR** — new features, new game types, new commands, or any change to
+  shared semantics.
 - **PATCH** — bug fixes, payout corrections, refactors that don't change
   observable behavior.
 
+Client and server are **MAJOR.MINOR lockstep**: they may differ only in the
+patch component. `HELLO <version>` is the first line after TLS; the server
+refuses a mismatch before any credentials are sent. A feature that changes
+the wire format is a MAJOR bump and a simultaneous release of both sides, not
+a compatible MINOR.
+
 Bump the version in `Cargo.toml` as the **last** step before committing
 a release-worthy change. The commit message should contain the new version
 number (e.g. `v0.2.0`).