[writingdeveloper]

Symptom (reported with a screenshot): on Windows, quitting or running Update all with two or more sessions open sometimes shows a Microsoft Visual C++ Runtime Library dialog:

Assertion failed!
Program: …node-pty-prebuilt-multiarch\build\Release\conpty.node
File: …conpty.cc  Line: 106
Expression: remove_pty_baton(baton->id)

Other times DevDeck stays alive after its window is gone, or exits with 0xC0000005.

Cause: in conpty.cc, each terminal's exit thread calls remove_pty_baton(). That function edits the global std::vector ptyHandles without a lock. When two terminals end together, the two threads race on the vector. @homebridge/node-pty-prebuilt-multiarch adds a mutex only in 0.15.0-beta (0.14.1 stable does not have it).

Fix: PtyHost.kill ends terminals one at a time. The next kill starts once the previous exit has reached JS, by which point its thread has finished with the vector, or after 4 s. The default shutdown budget scales with the number of terminals (1.5 s each, at least 5 s).

Evidence:

• A harness quit trace showed the hang happening after Node's exit 0, during native teardown.
• qa/claude-update.mjs stops all sessions at once twice, at Update all and at quit:
  • before: 3/20 and 3/32 runs hung or crashed at quit
  • after: 0/50
• vitest: 1511 passed, including a new test that terminals end one after another and that a missing exit holds the next one up for at most 4 s.

🤖 Generated with Claude Code

https://claude.ai/code/session_016NLGwiBY5uEivJqERQzcoY