microsoft/Terminal

[cont] [DefTerm] Some invocations can cause deadlocks in terminal + another GUI application in Attach mode

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#19,749 opened on Jan 15, 2026

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Area-DefAppHelp WantedIssue-BugPriority-2Product-Terminal

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Description

Windows Terminal version

No response

Windows build number

No response

Other Software

No response

Steps to reproduce

Same steps as https://github.com/microsoft/terminal/issues/14131 More here: https://github.com/microsoft/terminal/issues/14131#issuecomment-3731555688

Expected Behavior

no 5000ms timeout from SendMessageTimeoutW: SMTO_NOTIMEOUTIFNOTHUNG

Actual Behavior

5000ms because the window is newly hung (by call to system())

Contributor guide

Research direction
Investigate the SendMessageTimeoutW call in the attach mode logic and trace how the target window becomes hung due to the system() call.
Tech stack
cpp
Domain
desktop
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
4
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
Half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
C++Windows programming
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
50