From 9c429d83ae78411a705bb941de4c7258e818f962 Mon Sep 17 00:00:00 2001
From: Garry Tan <garrytan@gmail.com>
Date: Sat, 4 Apr 2026 21:00:27 -0700
Subject: [PATCH] feat: add gstack-settings-hook for atomic Claude Code hook
 management

DRY helper for adding/removing SessionStart hooks in ~/.claude/settings.json.
Handles missing files, deduplication, malformed JSON, and atomic writes
(.tmp + rename) to prevent corruption on crash or disk-full.

Part of team-install-mode feature (credit: Jared Friedman).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
---
 bin/gstack-settings-hook | 82 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 82 insertions(+)
 create mode 100755 bin/gstack-settings-hook

diff --git a/bin/gstack-settings-hook b/bin/gstack-settings-hook
new file mode 100755
index 00000000..93a537f0
--- /dev/null
+++ b/bin/gstack-settings-hook
@@ -0,0 +1,82 @@
+#!/usr/bin/env bash
+# gstack-settings-hook — add/remove SessionStart hooks in Claude Code settings.json
+#
+# Usage:
+#   gstack-settings-hook add <hook-command>     # add SessionStart hook
+#   gstack-settings-hook remove <hook-command>  # remove SessionStart hook
+#
+# Requires: bun (already a gstack hard dependency)
+# Writes atomically: .tmp + rename to prevent corruption on crash/disk-full.
+
+set -euo pipefail
+
+ACTION="${1:-}"
+HOOK_CMD="${2:-}"
+SETTINGS_FILE="${GSTACK_SETTINGS_FILE:-$HOME/.claude/settings.json}"
+
+if [ -z "$ACTION" ] || [ -z "$HOOK_CMD" ]; then
+  echo "Usage: gstack-settings-hook {add|remove} <hook-command>" >&2
+  exit 1
+fi
+
+if ! command -v bun >/dev/null 2>&1; then
+  echo "Error: bun is required but not installed." >&2
+  exit 1
+fi
+
+case "$ACTION" in
+  add)
+    bun -e "
+      const fs = require('fs');
+      const settingsPath = '$SETTINGS_FILE';
+      const hookCmd = $(printf '%s' "$HOOK_CMD" | bun -e "process.stdout.write(JSON.stringify(require('fs').readFileSync('/dev/stdin','utf8')))");
+
+      let settings = {};
+      try { settings = JSON.parse(fs.readFileSync(settingsPath, 'utf8')); } catch {}
+
+      if (!settings.hooks) settings.hooks = {};
+      if (!settings.hooks.SessionStart) settings.hooks.SessionStart = [];
+
+      // Dedup: check if hook command already registered
+      const exists = settings.hooks.SessionStart.some(entry =>
+        entry.hooks && entry.hooks.some(h => h.command && h.command.includes('gstack-session-update'))
+      );
+
+      if (!exists) {
+        settings.hooks.SessionStart.push({
+          hooks: [{ type: 'command', command: hookCmd }]
+        });
+      }
+
+      const tmp = settingsPath + '.tmp';
+      fs.writeFileSync(tmp, JSON.stringify(settings, null, 2) + '\n');
+      fs.renameSync(tmp, settingsPath);
+    " 2>/dev/null
+    ;;
+  remove)
+    [ -f "$SETTINGS_FILE" ] || exit 0
+    bun -e "
+      const fs = require('fs');
+      const settingsPath = '$SETTINGS_FILE';
+
+      let settings = {};
+      try { settings = JSON.parse(fs.readFileSync(settingsPath, 'utf8')); } catch { process.exit(0); }
+
+      if (settings.hooks && settings.hooks.SessionStart) {
+        settings.hooks.SessionStart = settings.hooks.SessionStart.filter(entry =>
+          !(entry.hooks && entry.hooks.some(h => h.command && h.command.includes('gstack-session-update')))
+        );
+        if (settings.hooks.SessionStart.length === 0) delete settings.hooks.SessionStart;
+        if (Object.keys(settings.hooks).length === 0) delete settings.hooks;
+      }
+
+      const tmp = settingsPath + '.tmp';
+      fs.writeFileSync(tmp, JSON.stringify(settings, null, 2) + '\n');
+      fs.renameSync(tmp, settingsPath);
+    " 2>/dev/null
+    ;;
+  *)
+    echo "Unknown action: $ACTION (expected add or remove)" >&2
+    exit 1
+    ;;
+esac