diff --git a/muxplex/settings.py b/muxplex/settings.py
new file mode 100644
index 0000000..eceae8a
--- /dev/null
+++ b/muxplex/settings.py
@@ -0,0 +1,66 @@
+"""
+Server-side settings management for muxplex.
+
+Settings are stored at ~/.config/muxplex/settings.json.
+"""
+
+import json
+from pathlib import Path
+
+SETTINGS_PATH = Path.home() / ".config" / "muxplex" / "settings.json"
+
+DEFAULT_SETTINGS: dict = {
+    "default_session": None,
+    "sort_order": "manual",
+    "hidden_sessions": [],
+    "window_size_largest": False,
+    "auto_open_created": True,
+    "new_session_template": "tmux new-session -d -s {name}",
+}
+
+
+def load_settings() -> dict:
+    """Load settings from disk, merging saved values over defaults.
+
+    Returns DEFAULT_SETTINGS if the file does not exist or contains corrupt JSON.
+    Unknown keys in the file are ignored.
+    """
+    result = DEFAULT_SETTINGS.copy()
+    try:
+        text = SETTINGS_PATH.read_text()
+        data = json.loads(text)
+        for key in DEFAULT_SETTINGS:
+            if key in data:
+                result[key] = data[key]
+    except FileNotFoundError:
+        pass
+    except (json.JSONDecodeError, Exception):
+        pass
+    return result
+
+
+def save_settings(data: dict) -> None:
+    """Save settings to disk, merging *data* with defaults first.
+
+    Creates parent directories as needed. Writes JSON with indent=2 and a
+    trailing newline.
+    """
+    merged = DEFAULT_SETTINGS.copy()
+    for key in DEFAULT_SETTINGS:
+        if key in data:
+            merged[key] = data[key]
+    SETTINGS_PATH.parent.mkdir(parents=True, exist_ok=True)
+    SETTINGS_PATH.write_text(json.dumps(merged, indent=2) + "\n")
+
+
+def patch_settings(patch: dict) -> dict:
+    """Merge known keys from *patch* into the current settings, save, and return result.
+
+    Unknown keys in *patch* are silently ignored.
+    """
+    current = load_settings()
+    for key in DEFAULT_SETTINGS:
+        if key in patch:
+            current[key] = patch[key]
+    save_settings(current)
+    return current
diff --git a/muxplex/tests/test_settings.py b/muxplex/tests/test_settings.py
new file mode 100644
index 0000000..28d1d2b
--- /dev/null
+++ b/muxplex/tests/test_settings.py
@@ -0,0 +1,118 @@
+"""
+Tests for muxplex/settings.py — server-side settings management.
+7 acceptance-criteria tests defined here.
+"""
+
+import json
+
+import pytest
+
+import muxplex.settings as settings_mod
+from muxplex.settings import (
+    DEFAULT_SETTINGS,
+    load_settings,
+    patch_settings,
+    save_settings,
+)
+
+
+# ---------------------------------------------------------------------------
+# Autouse fixture: redirect SETTINGS_PATH to tmp_path
+# ---------------------------------------------------------------------------
+
+
+@pytest.fixture(autouse=True)
+def redirect_settings_path(tmp_path, monkeypatch):
+    """Redirect SETTINGS_PATH to a temporary file for all tests."""
+    fake_path = tmp_path / "settings.json"
+    monkeypatch.setattr(settings_mod, "SETTINGS_PATH", fake_path)
+    return fake_path
+
+
+# ---------------------------------------------------------------------------
+# Tests
+# ---------------------------------------------------------------------------
+
+
+def test_load_returns_defaults_when_no_file():
+    """load_settings() returns DEFAULT_SETTINGS when no file exists."""
+    result = load_settings()
+    assert result == DEFAULT_SETTINGS
+
+
+def test_load_returns_saved_values(tmp_path, monkeypatch):
+    """load_settings() merges saved values over defaults."""
+    # Write partial settings file
+    fake_path = tmp_path / "settings.json"
+    monkeypatch.setattr(settings_mod, "SETTINGS_PATH", fake_path)
+    fake_path.write_text(json.dumps({"sort_order": "alpha"}))
+
+    result = load_settings()
+
+    # Overridden value
+    assert result["sort_order"] == "alpha"
+    # Default fallback for unset key
+    assert result["default_session"] is None
+
+
+def test_save_creates_file_and_dirs(tmp_path, monkeypatch):
+    """save_settings() creates parent dirs and writes the file."""
+    nested_path = tmp_path / "a" / "b" / "settings.json"
+    monkeypatch.setattr(settings_mod, "SETTINGS_PATH", nested_path)
+
+    save_settings({"sort_order": "alpha"})
+
+    assert nested_path.exists()
+
+
+def test_save_merges_with_defaults(tmp_path, monkeypatch):
+    """save_settings() merges data with defaults before writing."""
+    fake_path = tmp_path / "settings.json"
+    monkeypatch.setattr(settings_mod, "SETTINGS_PATH", fake_path)
+
+    save_settings({"sort_order": "alpha"})
+
+    written = json.loads(fake_path.read_text())
+    # The override should be present
+    assert written["sort_order"] == "alpha"
+    # The default should also be present (merged)
+    assert "default_session" in written
+    assert "auto_open_created" in written
+
+
+def test_load_handles_corrupt_json(tmp_path, monkeypatch):
+    """load_settings() returns defaults gracefully on corrupt JSON."""
+    fake_path = tmp_path / "settings.json"
+    monkeypatch.setattr(settings_mod, "SETTINGS_PATH", fake_path)
+    fake_path.write_text("NOT VALID JSON {{{{")
+
+    result = load_settings()
+
+    assert result == DEFAULT_SETTINGS
+
+
+def test_patch_settings_merges_single_field(tmp_path, monkeypatch):
+    """patch_settings() updates a single known field and returns result."""
+    fake_path = tmp_path / "settings.json"
+    monkeypatch.setattr(settings_mod, "SETTINGS_PATH", fake_path)
+
+    result = patch_settings({"sort_order": "alpha"})
+
+    assert result["sort_order"] == "alpha"
+    # Other defaults preserved
+    assert result["auto_open_created"] is True
+
+    # Also verify persistence
+    loaded = load_settings()
+    assert loaded["sort_order"] == "alpha"
+
+
+def test_patch_settings_ignores_unknown_keys(tmp_path, monkeypatch):
+    """patch_settings() ignores keys not in DEFAULT_SETTINGS."""
+    fake_path = tmp_path / "settings.json"
+    monkeypatch.setattr(settings_mod, "SETTINGS_PATH", fake_path)
+
+    result = patch_settings({"unknown_key": "should_be_ignored", "sort_order": "alpha"})
+
+    assert "unknown_key" not in result
+    assert result["sort_order"] == "alpha"