From 4b1f7b33ac42a7968c83f7659784d4729ce27abc Mon Sep 17 00:00:00 2001
From: Neil <4138956+nwparker@users.noreply.github.com>
Date: Sun, 31 May 2026 04:19:32 -0700
Subject: [PATCH] fix: release idle remote terminal multiplexers (#4101)

---
 .../remote-runtime-terminal-multiplexer.ts    | 31 +++++++++++++++--
 .../runtime/runtime-terminal-stream.test.ts   | 34 ++++++++++++++++++-
 2 files changed, 62 insertions(+), 3 deletions(-)

diff --git a/src/renderer/src/runtime/remote-runtime-terminal-multiplexer.ts b/src/renderer/src/runtime/remote-runtime-terminal-multiplexer.ts
index 4049307d3..6c3aa2f61 100644
--- a/src/renderer/src/runtime/remote-runtime-terminal-multiplexer.ts
+++ b/src/renderer/src/runtime/remote-runtime-terminal-multiplexer.ts
@@ -81,7 +81,13 @@ class RemoteRuntimeTerminalMultiplexer {
   private ready = false
   private nextStreamId = 1
 
-  constructor(private readonly environmentId: string) {}
+  constructor(
+    private readonly environmentId: string,
+    private readonly releaseIfCurrent: (
+      environmentId: string,
+      multiplexer: RemoteRuntimeTerminalMultiplexer
+    ) => void
+  ) {}
 
   async subscribeTerminal(args: {
     terminal: string
@@ -347,6 +353,10 @@ class RemoteRuntimeTerminalMultiplexer {
         stream.callbacks.onError?.(message)
       }
     }
+    // Why: a closed transport has no live streams or subscription; keeping it
+    // in the module map only retains callbacks for an environment that must
+    // reconnect through a fresh subscription anyway.
+    this.releaseIfCurrent(this.environmentId, this)
   }
 
   private closeIfIdle(): void {
@@ -357,22 +367,39 @@ class RemoteRuntimeTerminalMultiplexer {
     this.subscription = null
     this.connectPromise = null
     this.ready = false
+    this.releaseIfCurrent(this.environmentId, this)
   }
 }
 
 const multiplexers = new Map<string, RemoteRuntimeTerminalMultiplexer>()
 
+function releaseRemoteRuntimeTerminalMultiplexer(
+  environmentId: string,
+  multiplexer: RemoteRuntimeTerminalMultiplexer
+): void {
+  if (multiplexers.get(environmentId) === multiplexer) {
+    multiplexers.delete(environmentId)
+  }
+}
+
 export function getRemoteRuntimeTerminalMultiplexer(
   environmentId: string
 ): RemoteRuntimeTerminalMultiplexer {
   let multiplexer = multiplexers.get(environmentId)
   if (!multiplexer) {
-    multiplexer = new RemoteRuntimeTerminalMultiplexer(environmentId)
+    multiplexer = new RemoteRuntimeTerminalMultiplexer(
+      environmentId,
+      releaseRemoteRuntimeTerminalMultiplexer
+    )
     multiplexers.set(environmentId, multiplexer)
   }
   return multiplexer
 }
 
+export function _getRemoteRuntimeTerminalMultiplexerCountForTest(): number {
+  return multiplexers.size
+}
+
 export function resetRemoteRuntimeTerminalMultiplexersForTests(): void {
   multiplexers.clear()
 }
diff --git a/src/renderer/src/runtime/runtime-terminal-stream.test.ts b/src/renderer/src/runtime/runtime-terminal-stream.test.ts
index 0c42a7345..5f4931464 100644
--- a/src/renderer/src/runtime/runtime-terminal-stream.test.ts
+++ b/src/renderer/src/runtime/runtime-terminal-stream.test.ts
@@ -6,7 +6,10 @@ import {
   encodeTerminalStreamFrame,
   encodeTerminalStreamText
 } from '../../../shared/terminal-stream-protocol'
-import { resetRemoteRuntimeTerminalMultiplexersForTests } from './remote-runtime-terminal-multiplexer'
+import {
+  _getRemoteRuntimeTerminalMultiplexerCountForTest,
+  resetRemoteRuntimeTerminalMultiplexersForTests
+} from './remote-runtime-terminal-multiplexer'
 import {
   getRemoteRuntimePtyEnvironmentId,
   getRemoteRuntimeTerminalHandle,
@@ -106,8 +109,36 @@ describe('remote runtime terminal data subscriptions', () => {
     )
 
     expect(watcher).toHaveBeenCalledWith('live')
+    expect(_getRemoteRuntimeTerminalMultiplexerCountForTest()).toBe(1)
     dispose()
     expect(unsubscribe).toHaveBeenCalled()
+    expect(_getRemoteRuntimeTerminalMultiplexerCountForTest()).toBe(0)
+  })
+
+  it('keeps the shared terminal multiplexer until the last watcher closes', async () => {
+    const firstDispose = await subscribeToRuntimeTerminalData(
+      { activeRuntimeEnvironmentId: 'env-fallback' },
+      'remote:env-1@@terminal-1',
+      'watcher-1',
+      vi.fn()
+    )
+    const secondDispose = await subscribeToRuntimeTerminalData(
+      { activeRuntimeEnvironmentId: 'env-fallback' },
+      'remote:env-1@@terminal-2',
+      'watcher-2',
+      vi.fn()
+    )
+
+    expect(runtimeSubscribe).toHaveBeenCalledTimes(1)
+    expect(_getRemoteRuntimeTerminalMultiplexerCountForTest()).toBe(1)
+
+    firstDispose()
+    expect(unsubscribe).not.toHaveBeenCalled()
+    expect(_getRemoteRuntimeTerminalMultiplexerCountForTest()).toBe(1)
+
+    secondDispose()
+    expect(unsubscribe).toHaveBeenCalledOnce()
+    expect(_getRemoteRuntimeTerminalMultiplexerCountForTest()).toBe(0)
   })
 
   it('rejects remote terminal subscriptions when the multiplex connection fails', async () => {
@@ -123,5 +154,6 @@ describe('remote runtime terminal data subscriptions', () => {
     ).rejects.toThrow('offline')
 
     expect(sendBinary).not.toHaveBeenCalled()
+    expect(_getRemoteRuntimeTerminalMultiplexerCountForTest()).toBe(0)
   })
 })