Clear the OpenTUI transcript on /new and /clear

Backend session rotation still ran, but the painted stream stayed on screen
after the Ink App path went away. Emit session.clear from the runner, wipe the
shell log in the product host, and cancel live sub-agents so orphans do not
keep burning tokens under the old session.

Author: TheGreatAxios

src/tui/product-host.test.ts

@@ -203,6 +203,26 @@ describe("mountProductHost", () => {
     }
   })
 
+  test("session.clear wipes the painted transcript (CL-5612)", async () => {
+    const { host, emitter } = await mountHeadless()
+    try {
+      emitter.emit("event", { type: "user", text: "old prompt" })
+      emitter.emit("event", { type: "assistant", text: "old reply" })
+      expect(host.shell.streamLog.length).toBe(2)
+
+      emitter.emit("session.clear")
+      expect(host.shell.streamLog).toEqual([])
+      expect(host.shell.streamLogBase).toBe(0)
+      expect(host.shell.lineCount).toBe(0)
+
+      // Subsequent turns land on the empty transcript.
+      emitter.emit("event", { type: "user", text: "fresh prompt" })
+      expect(host.shell.streamLog).toEqual([{ role: "user", text: "fresh prompt" }])
+    } finally {
+      host.dispose()
+    }
+  })
+
   test("permission.gate opens the overlay and resolves through the emitter's resolve callback", async () => {
     const { host, emitter } = await mountHeadless()
     try {
@@ -253,6 +273,7 @@ describe("mountProductHost", () => {
     expect(emitter.listenerCount("event")).toBe(1)
     expect(emitter.listenerCount("history.hydrate")).toBe(1)
     expect(emitter.listenerCount("session.title")).toBe(1)
+    expect(emitter.listenerCount("session.clear")).toBe(1)
     expect(emitter.listenerCount("permission.gate")).toBe(1)
     expect(emitter.listenerCount("operator.gate")).toBe(1)
 
@@ -263,6 +284,7 @@ describe("mountProductHost", () => {
     expect(emitter.listenerCount("event")).toBe(0)
     expect(emitter.listenerCount("history.hydrate")).toBe(0)
     expect(emitter.listenerCount("session.title")).toBe(0)
+    expect(emitter.listenerCount("session.clear")).toBe(0)
     expect(emitter.listenerCount("permission.gate")).toBe(0)
     expect(emitter.listenerCount("operator.gate")).toBe(0)
   })

src/tui/product-host.ts

@@ -39,6 +39,7 @@ import type { PaletteCommand } from "./command-catalog.js"
 import {
   appendObserveStreamRow,
   appendStreamRow,
+  clearTranscript,
   createAppShell,
   paintChrome,
   setChromeZones,
@@ -425,6 +426,7 @@ export async function mountProductHost(
     disposeGates()
     config.eventEmitter.off("history.hydrate", onHistory)
     config.eventEmitter.off("session.title", onTitle)
+    config.eventEmitter.off("session.clear", onSessionClear)
     config.eventEmitter.off("hook", onHook)
     config.eventEmitter.off("mcp.status", onMcpStatus)
     config.eventEmitter.off("permission.grant", onPermissionGrant)
@@ -534,6 +536,14 @@ export async function mountProductHost(
     }
   }
 
+  // /clear and /new rotate the backend session in the runner; the host must
+  // wipe the painted transcript so the screen matches a brand-new session.
+  // The Ink App used to own this unconditionally — OpenTUI regressed it.
+  function onSessionClear(): void {
+    if (disposed) return
+    clearTranscript(shell)
+  }
+
   let currentModels = config.models ?? []
   let currentDescribeModel = config.describeModel
   let openModels: (() => void) | undefined
@@ -629,6 +639,7 @@ export async function mountProductHost(
   config.eventEmitter.on("event", onEvent)
   config.eventEmitter.on("history.hydrate", onHistory)
   config.eventEmitter.on("session.title", onTitle)
+  config.eventEmitter.on("session.clear", onSessionClear)
   config.eventEmitter.on("hook", onHook)
   config.eventEmitter.on("mcp.status", onMcpStatus)
   config.eventEmitter.on("permission.grant", onPermissionGrant)

src/tui/runner.ts

@@ -1657,10 +1657,16 @@ export async function runTUI(initialConfig: Config): Promise<number> {
   // abort handles → child agent.close) before clearing the session store so
   // /clear does not leave orphaned child reactors burning tokens.
   const newSession = (): void => {
-    // The App clears its transcript unconditionally on /clear, so the backend
-    // rotation is always enqueued regardless of contention; the queue serialises
-    // it behind any in-progress op. Sub-agents nest under the new session
-    // automatically because getWorkdirBase reads the live sessionId.
+    // Wipe the painted transcript immediately. The product host listens for
+    // session.clear; the Ink App used to clear its own stream unconditionally
+    // and that path never moved to OpenTUI.
+    emitter.emit("session.clear");
+    // Cancel live workers before rotation so /clear does not leave orphaned
+    // child reactors burning tokens under the old session id.
+    subAgentSessions.cancelAll("Session cleared");
+    // Backend rotation is always enqueued regardless of contention; the queue
+    // serialises it behind any in-progress op. Sub-agents nest under the new
+    // session automatically because getWorkdirBase reads the live sessionId.
     void enqueueOp(async () => {
       try {
         // Tear the old agent down and dispose the recorder before workdir is

src/tui/shell.ts

@@ -2326,6 +2326,43 @@ export function truncateStreamRows(shell: AppShell, length: number): void {
   paintChrome(shell)
 }
 
+/**
+ * Empty the visible transcript for a fresh session (/clear, /new).
+ *
+ * Backend session rotation lives in the runner; this is only the on-screen wipe
+ * the OpenTUI host must own after the Ink App path went away. Observe mode is
+ * dropped first so a child view cannot keep painting into a cleared parent.
+ * Retention base resets so the screen matches a brand-new session, not a window
+ * over an empty retained log with a stale eviction marker.
+ */
+export function clearTranscript(shell: AppShell): void {
+  if (shell.observe !== null) {
+    // Drop observe without the "left observe" system row — the whole log is
+    // about to go and a farewell row would only flash then vanish.
+    shell.observe = null
+    shell.parentStreamLog = null
+    shell.parentStreamLogBase = null
+    let guard = 4
+    while (guard-- > 0 && focusOwner(shell.focus) === "observe") {
+      shell.focus = popFocus(shell.focus)
+    }
+    const frames = shell.focus.frames.filter((f) => f.target !== "observe")
+    if (frames.length !== shell.focus.frames.length) {
+      shell.focus = { frames }
+    }
+    setChromeZones(shell, { agents: null })
+    applyFocus(shell)
+  }
+  shell.streamLog.length = 0
+  shell.streamLogBase = 0
+  shell.lineCount = 0
+  shell.parentStreamLog = null
+  shell.parentStreamLogBase = null
+  repaintTranscriptWindow(shell)
+  paintChrome(shell)
+}
+
+
 /**
  * Identifies a transcript child as the eviction notice rather than a row.
  * Identity, not position or state, is the source of truth: `streamLogBase`