fix(tui): stabilize compaction completion (#36435)

packages/tui/test/util/session.test.ts

@@ -2,6 +2,16 @@ import { describe, expect, test } from "bun:test"
 import type { SessionMessageInfo } from "@opencode-ai/sdk/v2"
 import { isDefaultTitle, lastAssistantWithUsage } from "../../src/util/session"
 
+const assistant = (id: string, input: number): SessionMessageInfo => ({
+  id,
+  type: "assistant",
+  agent: "build",
+  model: { id: "model", providerID: "provider" },
+  content: [],
+  tokens: { input, output: 0, reasoning: 0, cache: { read: 0, write: 0 } },
+  time: { created: 0 },
+})
+
 describe("util.session", () => {
   test("recognizes generated parent and child titles", () => {
     expect(isDefaultTitle("New session - 2026-06-06T12:34:56.789Z")).toBeTrue()
@@ -10,15 +20,6 @@ describe("util.session", () => {
   })
 
   test("tracks usage across undo and redo boundaries", () => {
-    const assistant = (id: string, input: number): SessionMessageInfo => ({
-      id,
-      type: "assistant",
-      agent: "build",
-      model: { id: "model", providerID: "provider" },
-      content: [],
-      tokens: { input, output: 0, reasoning: 0, cache: { read: 0, write: 0 } },
-      time: { created: 0 },
-    })
     const messages = [assistant("msg_z", 10), assistant("msg_a", 30)]
 
     expect(lastAssistantWithUsage(messages)?.tokens.input).toBe(30)
@@ -26,4 +27,22 @@ describe("util.session", () => {
     expect(lastAssistantWithUsage(messages, "msg_missing")).toBeUndefined()
     expect(lastAssistantWithUsage(messages)?.tokens.input).toBe(30)
   })
+
+  test("resets usage at completed compaction until the next assistant reports it", () => {
+    const compaction: SessionMessageInfo = {
+      id: "msg_compaction",
+      type: "compaction",
+      status: "completed",
+      reason: "manual",
+      summary: "Current state",
+      recent: "",
+      time: { created: 0 },
+    }
+    const messages = [assistant("msg_before", 30), compaction]
+
+    expect(lastAssistantWithUsage(messages)).toBeUndefined()
+
+    messages.push(assistant("msg_after", 5))
+    expect(lastAssistantWithUsage(messages)?.tokens.input).toBe(5)
+  })
 })