From 1905221195dd62b98a55d0ecb5fd651cd83e4b2b Mon Sep 17 00:00:00 2001
From: Mao Nakamoto <41178744+maonakamoto@users.noreply.github.com>
Date: Sat, 29 Aug 2026 12:06:58 +0200
Subject: [PATCH] fix(ssh): keep the github.com connection alive through slow
 pre-push hooks
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git push opens the SSH connection to github.com before running the
pre-push hook, then leaves it fully idle for the hook's entire duration.
Under heavy concurrent machine load, hooks routinely took long enough
that GitHub's idle-connection timeout closed the SSH session mid-hook —
the push then silently failed to transfer after printing "Safe to
push," with only a stray "Connection to github.com closed by remote
host." to explain it. Reproduced 4x in one session before diagnosing
via GIT_TRACE=1. ServerAliveInterval/CountMax keep the connection alive
during that idle window.
---
 .ssh/config | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/.ssh/config b/.ssh/config
index 51d1059..ed1c6f8 100644
--- a/.ssh/config
+++ b/.ssh/config
@@ -4,3 +4,13 @@ Host github.com
     User git
     IdentityFile ~/.ssh/github_ed25519
     IdentitiesOnly yes
+    # git push opens this connection BEFORE running the pre-push hook, then
+    # leaves it fully idle for the hook's entire duration. Found 2026-08-29:
+    # under heavy concurrent machine load (~80 sessions), hooks routinely ran
+    # long enough that GitHub's idle-connection timeout killed the SSH session
+    # while the hook was still running — the push then silently failed to
+    # transfer after printing "Safe to push," with only a stray "Connection to
+    # github.com closed by remote host." in the log to explain it. Active
+    # keepalives during that idle window prevent the drop.
+    ServerAliveInterval 30
+    ServerAliveCountMax 10