diff --git a/Cargo.toml b/Cargo.toml
index 015e9c4..1aa4fec 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -5,7 +5,7 @@ members = [
 ]
 
 [workspace.package]
-version = "0.0.1"
+version = "0.1.1"
 edition = "2021"
 license = "MIT"
 authors = ["CambrianTech <joel@cambriantech.com>"]
diff --git a/npm/core/package.json b/npm/core/package.json
index 43c7ae1..6680f4f 100644
--- a/npm/core/package.json
+++ b/npm/core/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@positron/core",
-  "version": "0.0.1",
+  "version": "0.1.1",
   "description": "Positron wire contract — TypeScript types generated from positron-core's Rust structs (single source of truth).",
   "license": "MIT",
   "repository": {
diff --git a/npm/core/src/generated/ServerMessage.ts b/npm/core/src/generated/ServerMessage.ts
index 2720855..30f77af 100644
--- a/npm/core/src/generated/ServerMessage.ts
+++ b/npm/core/src/generated/ServerMessage.ts
@@ -4,4 +4,12 @@ import type { StateEnvelope } from "./StateEnvelope";
 /**
  * Substrate → client frames.
  */
-export type ServerMessage = { "type": "state" } & StateEnvelope;
+export type ServerMessage = { "type": "state" } & StateEnvelope | { "type": "command_failed", 
+/**
+ * Echo of [`CommandEnvelope::correlation_id`].
+ */
+correlation_id: string, 
+/**
+ * Human-readable failure reason (consumer-displayable).
+ */
+error: string, };
diff --git a/npm/core/src/generated/StateLayer.ts b/npm/core/src/generated/StateLayer.ts
index 9d95c59..44a29ed 100644
--- a/npm/core/src/generated/StateLayer.ts
+++ b/npm/core/src/generated/StateLayer.ts
@@ -4,5 +4,10 @@
  * Update-cadence classification for a state change (see `DESIGN.md`
  * § "The 4 state layers"). Renderers and observers subscribe at the
  * layer their target can sustain; the substrate enforces.
+ *
+ * `Ord` exists so layer sets can live in `BTreeSet`/sorted
+ * collections; the ordering is declaration order and carries NO
+ * semantic meaning (Semantic is not "more than" Persistent). Do not
+ * write cadence logic against `<`/`>`.
  */
 export type StateLayer = "ephemeral" | "session" | "persistent" | "semantic";
diff --git a/positron-core/src/lib.rs b/positron-core/src/lib.rs
index 625329b..2db4eb7 100644
--- a/positron-core/src/lib.rs
+++ b/positron-core/src/lib.rs
@@ -34,9 +34,10 @@
 //!
 //! ## Versioning
 //!
-//! v0.0.x — contract design + reference renderers. Breaking changes
-//! allowed. v1.0 is the first stable contract; consumers should pin
-//! to a major-version range from there.
+//! v0.x — contract design + reference renderers; wire-shape changes
+//! allowed pre-1.0 but must regenerate the npm types in-commit (CI
+//! enforces). v1.0 is the first stable contract; consumers should
+//! pin to a major-version range from there.
 
 #![forbid(unsafe_code)]
 #![warn(missing_docs)]
diff --git a/positron-core/src/session.rs b/positron-core/src/session.rs
index 81cf982..7e8df1a 100644
--- a/positron-core/src/session.rs
+++ b/positron-core/src/session.rs
@@ -68,14 +68,19 @@
 //!
 //! ## Deliberate v0 omissions
 //!
-//! There is no ack/error frame in [`ServerMessage`], so
-//! `CommandEnvelope::correlation_id` has nothing protocol-level to
-//! correlate with yet — command *results* currently surface as new
-//! state (the substrate acts, state changes, the change streams
-//! down). A `Result`/`Error` frame keyed by `correlation_id` is the
-//! expected v0.x addition once a consumer actually needs
-//! request-shaped feedback; adding a `ServerMessage` variant is
-//! additive and non-breaking for tagged unions.
+//! There is no success-ack frame in [`ServerMessage`]: a successful
+//! command's acknowledgement IS the state change it causes (the
+//! unidirectional model). Failures are different — a failed command
+//! with no reporting channel is a silent failure, so
+//! [`ServerMessage::CommandFailed`] exists (v0.1.1). A full
+//! `Result` frame for request-shaped success feedback remains a
+//! v0.x candidate. **Forward compatibility rule:** consumers MUST
+//! treat a `ServerMessage` whose `type` they do not recognize as
+//! skip-and-log, never connection-fatal — that is what makes variant
+//! additions non-breaking for deployed clients, not the union shape
+//! alone. (Rust consumers of the typed enum surface unknown variants
+//! as a deserialize error on that frame; apply the same rule — log,
+//! skip the frame, keep the connection.)
 //!
 //! The exact-equality skip has one residual ABA case: a client whose
 //! `last_seen` revision N came from a pre-restart substrate may meet
@@ -157,6 +162,24 @@ pub enum ServerMessage {
     /// "which phase am I in" bookkeeping. If a client must
     /// distinguish, the revision diff already tells it.
     State(StateEnvelope),
+    /// A command could not be executed. Failures are LOUD — a
+    /// rejected [`CommandEnvelope`] must never vanish silently.
+    /// Success deliberately has no ack frame: a successful command's
+    /// acknowledgement IS the state change it causes, streaming down
+    /// as `State` (the unidirectional model). Consumers correlate via
+    /// the `correlation_id` they sent.
+    ///
+    /// **Delivery scope:** the substrate MUST send this frame ONLY to
+    /// the connection that sent the failing command — never broadcast.
+    /// Other clients neither need another client's failures nor should
+    /// see their details.
+    CommandFailed {
+        /// Echo of [`CommandEnvelope::correlation_id`].
+        #[ts(type = "string")]
+        correlation_id: uuid::Uuid,
+        /// Human-readable failure reason (consumer-displayable).
+        error: String,
+    },
 }
 
 #[cfg(test)]
@@ -194,6 +217,19 @@ mod tests {
         assert_eq!(serde_json::from_str::<ClientMessage>(&json).unwrap(), cmd);
     }
 
+    /// Failures are loud and the tag is pinned; success has no ack
+    /// frame by design (the state change is the ack).
+    #[test]
+    fn command_failed_round_trips_with_pinned_tag() {
+        let fail = ServerMessage::CommandFailed {
+            correlation_id: Uuid::from_u128(7),
+            error: "chat/send: room not found".into(),
+        };
+        let json = serde_json::to_string(&fail).unwrap();
+        assert!(json.starts_with(r#"{"type":"command_failed""#), "{json}");
+        assert_eq!(serde_json::from_str::<ServerMessage>(&json).unwrap(), fail);
+    }
+
     #[test]
     fn server_state_frame_round_trips() {
         let state = ServerMessage::State(StateEnvelope {
diff --git a/positron-core/src/wire.rs b/positron-core/src/wire.rs
index f377725..13afa96 100644
--- a/positron-core/src/wire.rs
+++ b/positron-core/src/wire.rs
@@ -26,7 +26,14 @@ use uuid::Uuid;
 /// Update-cadence classification for a state change (see `DESIGN.md`
 /// § "The 4 state layers"). Renderers and observers subscribe at the
 /// layer their target can sustain; the substrate enforces.
-#[derive(Debug, Clone, Copy, PartialEq, Eq, Default, Serialize, Deserialize, TS)]
+///
+/// `Ord` exists so layer sets can live in `BTreeSet`/sorted
+/// collections; the ordering is declaration order and carries NO
+/// semantic meaning (Semantic is not "more than" Persistent). Do not
+/// write cadence logic against `<`/`>`.
+#[derive(
+    Debug, Clone, Copy, PartialEq, Eq, Hash, PartialOrd, Ord, Default, Serialize, Deserialize, TS,
+)]
 #[serde(rename_all = "snake_case")]
 #[ts(export)]
 pub enum StateLayer {