fix(review-4.4): tolerate additive terminal turn events

4 files changed, 19 insertions, 2 deletions

diff --git a/src/core/chunks/reducer.test.ts b/src/core/chunks/reducer.test.ts
index cba6fad..ae0aa73 100644
--- a/src/core/chunks/reducer.test.ts
+++ b/src/core/chunks/reducer.test.ts
@@ -1051,3 +1051,13 @@ describe("turnId provenance on live chunks", () => {
     expect(selectChunks(s).map((c) => c.turnId)).toEqual(["t9", undefined]);
   });
 });
+
+describe("foldEvent — additive wire compatibility", () => {
+  it.each(["turn-ended", "future-event"])("preserves transcript identity for %s", (type) => {
+    const state = foldEvent(foldEvent(initialState(), turnStart("t1")), textDelta("t1", "partial"));
+    const before = structuredClone(state);
+    const event = { type, conversationId: "c1", turnId: "t1", reason: "sealed" };
+    expect(foldEvent(state, event as Parameters<typeof foldEvent>[1])).toBe(state);
+    expect(state).toEqual(before);
+  });
+});
diff --git a/src/core/chunks/reducer.ts b/src/core/chunks/reducer.ts
index 4eb08c1..0af2ddd 100644
--- a/src/core/chunks/reducer.ts
+++ b/src/core/chunks/reducer.ts
@@ -408,6 +408,9 @@ function reduceEvent(state: TranscriptState, event: AgentEvent): TranscriptState
       // (already true from `turn-start`) is left untouched.
       return { ...state, providerRetry: event };
     }
+
+    default:
+      return state; // Forward-compatible with additive wire events.
   }
 }
 
diff --git a/src/core/wire/conformance.test.ts b/src/core/wire/conformance.test.ts
index e74a663..1c5829b 100644
--- a/src/core/wire/conformance.test.ts
+++ b/src/core/wire/conformance.test.ts
@@ -75,6 +75,7 @@ describe("classifies every AgentEvent type", () => {
     { type: "error", conversationId: "c1", turnId: "t1", message: "oops" },
     { type: "done", conversationId: "c1", turnId: "t1", reason: "complete" },
     { type: "turn-sealed", conversationId: "c1", turnId: "t1" },
+    { type: "turn-ended", conversationId: "c1", turnId: "t1", reason: "sealed" },
     { type: "steering", conversationId: "c1", turnId: "t1", text: "steer mid-turn" },
     {
       type: "provider-retry",
@@ -103,13 +104,14 @@ describe("classifies every AgentEvent type", () => {
       "error",
       "done",
       "turn-sealed",
+      "turn-ended",
       "steering",
       "provider-retry",
     ]);
   });
 
-  it("covers all 15 AgentEvent variants", () => {
-    expect(samples).toHaveLength(15);
+  it("covers all 16 AgentEvent variants", () => {
+    expect(samples).toHaveLength(16);
   });
 });
 
diff --git a/src/core/wire/conformance.ts b/src/core/wire/conformance.ts
index 855f7ea..9847081 100644
--- a/src/core/wire/conformance.ts
+++ b/src/core/wire/conformance.ts
@@ -32,6 +32,8 @@ export function assertAgentEventExhaustive(event: AgentEvent): string {
       return "done";
     case "turn-sealed":
       return "turn-sealed";
+    case "turn-ended":
+      return "turn-ended";
     case "step-complete":
       return "step-complete";
     case "steering":