Document zero-argument contract signatures

.claude-plugin/plugin.json

@@ -21,5 +21,14 @@
   "agents": [
     "./agents/tend.md",
     "./agents/weed.md"
-  ]
+  ],
+  "lspServers": {
+    "allium": {
+      "command": "allium-lsp",
+      "args": ["--stdio"],
+      "extensionToLanguage": {
+        ".allium": "allium"
+      }
+    }
+  }
 }

README.md

@@ -230,6 +230,8 @@ The developer never mentioned invoicing or payment method capture. The Allium di
 
 When the CLI is installed, `.allium` files are validated automatically after every write or edit. Diagnostics appear inline and the model fixes issues in the same turn.
 
+**Live diagnostics in Claude Code.** The Claude Code plugin also wires the `allium-lsp` language server, so Claude receives checker errors, go-to-definition and hover for `.allium` files immediately after each edit, without a separate `allium check` invocation. The language server is **not bundled** with the plugin — install the `allium-lsp` server from the [allium-tools repo](https://github.com/juxt/allium-tools) and make sure the `allium-lsp` binary is on your `PATH`. If it isn't found, Claude Code reports `Executable not found in $PATH` in the `/plugin` Errors tab and falls back to CLI checking.
+
 ## Language governance
 
 Every change to Allium is debated by a [nine-member review panel](https://github.com/juxt/allium/blob/proposals/TEAM.md) before adoption. Each panellist represents a distinct design priority: simplicity, machine reasoning, composability, readability, formal rigour, domain modelling, developer experience, creative ambition and backward compatibility. The panel exists to surface tensions that any single perspective would miss.

skills/allium/references/language-reference.md

@@ -150,6 +150,17 @@ contract Codec {
 
 Contract bodies contain typed signatures and annotations (`@invariant`, `@guidance`). Entity, value, enum and variant declarations are prohibited inside contracts. Types referenced in signatures must be declared at module level or imported via `use`.
 
+A zero-argument operation uses an empty parameter list:
+
+```
+contract Registry {
+    list_things: () -> Set<Foo>
+    health: () -> Status
+}
+```
+
+`name: () -> ReturnType` is the only form for parameterless operations; a bare arrow (`name: -> ReturnType`) is not valid.
+
 ### Referencing contracts in surfaces
 
 Surfaces reference contracts in a `contracts:` clause. Each entry uses `demands` or `fulfils` to indicate the direction of the obligation: