diff --git a/CLAUDE.md b/CLAUDE.md
index 5bd6995..ed721e0 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -97,7 +97,7 @@ Shared interactive I/O: `ask` / `choose` / `form` / `confirm` with pluggable bac
 
 Click app + readline REPL. Entry: `plyngent` / `python -m plyngent`.
 
-- **`plyngent chat`**: provider/model (flags or interactive; Tab via readline in `prompting`); sessions store `provider_name`/`model` and restore on resume; SQLite via `[database]` (file DB under user data if unset/`:memory:`); workspace-bound; resume latest for cwd/`--workspace` by default (`--new` / `--session`). One-shot: `-p/--prompt` and non-TTY stdin; exit codes 0/1/2/3; `--yes` (YOLO on), `--stream/--no-stream`, `--quiet`. Root `--log-level`.
+- **`plyngent chat`**: provider/model (flags or interactive; Tab via readline in `prompting`); sessions store `provider_name`/`model` and restore on resume; SQLite via `[database]` (file DB under user data when url unset; explicit `url = ":memory:"` kept + warn); workspace-bound; resume latest for cwd/`--workspace` by default (`--new` / `--session`). One-shot: `-p/--prompt` and non-TTY stdin; exit codes 0/1/2/3; `--yes` (YOLO on), `--stream/--no-stream`, `--quiet`. Root `--log-level`.
 - Slash: Click group in `cli/slash.py` + `awaitlet` for async work; Tab completer from registry + ParamType `shell_complete`. Multiline `"""` … `"""`; `/edit` via `$EDITOR`. `/yolo on|off|once` for soft destructive confirms. `/model --persist` / `/models --persist` write model catalog entries into TOML. `/todos` for human show/push/pop/clear of the todo stack.
 - Explicit `/resume` or `--session` from another workspace prompts: **keep** / **update** / **abort**.
 - Failed/cancelled turns: user kept; **committed tool rounds kept** (side effects not re-run on `/retry`); only unfinished assistant rolled back; Ctrl+C cancels; TTY confirms off-loop; auto-retry 10s/20s/30s then `/retry`.
diff --git a/README.md b/README.md
index da6a46f..5e26bfa 100644
--- a/README.md
+++ b/README.md
@@ -140,7 +140,7 @@ max_context_tokens = 200000
 
 Supported provider presets today: `openai` (default if `preset` is omitted; default models `gpt-5.4` / `gpt-5.4-mini` / `gpt-5.4-nano` when `models` is omitted), `openai-compatible`, `deepseek` (OpenAI convention; default models `deepseek-v4-flash` and `deepseek-v4-pro` if `models` is omitted). Anthropic presets are modeled in config but not wired in the runtime client yet.
 
-If `[database]` is omitted (or SQLite `url` is empty/`":memory:"`), chat uses a durable file under the user data dir (e.g. `~/.local/share/plyngent/chat.db` on Linux).
+If `[database]` is omitted (or SQLite `url` is unset/empty), chat uses a durable file under the user data dir (e.g. `~/.local/share/plyngent/chat.db` on Linux). Set `url = ":memory:"` for a true in-memory SQLite (CLI warns; no file; useful for tests).
 
 ## Chat
 
diff --git a/doc/plyngent.example.toml b/doc/plyngent.example.toml
index 0873dd8..13470d4 100644
--- a/doc/plyngent.example.toml
+++ b/doc/plyngent.example.toml
@@ -2,11 +2,13 @@
 # Copy to the path shown by: plyngent config path
 # Then set access_key_or_token and adjust models.
 
-# Optional. If omitted (or SQLite url is empty / ":memory:"), the CLI uses a
-# durable file under the platform user data dir (e.g. ~/.local/share/plyngent/chat.db).
+# Optional. If omitted (or SQLite url unset/empty), the CLI uses a durable file under
+# the platform user data dir (e.g. ~/.local/share/plyngent/chat.db).
+# url = ":memory:" → true in-memory SQLite (CLI warns; useful for tests).
 # [database]
 # implementation = "sqlite"
 # url = "/path/to/chat.db"
+# # url = ":memory:"
 
 [agent]
 system_prompt = "You are a careful coding assistant. Prefer small, verified edits."
diff --git a/src/plyngent/cli/app.py b/src/plyngent/cli/app.py
index 205649a..5ed3a3b 100644
--- a/src/plyngent/cli/app.py
+++ b/src/plyngent/cli/app.py
@@ -82,12 +82,21 @@ def _warn_recoverable_providers(recoverable: Mapping[str, object]) -> None:
 
 def _database_config(store: ConfigStore, *, quiet: bool = False) -> DatabaseConfig:
     raw = dict(store.database)
-    # Prefer a durable file DB so sessions survive CLI restarts.
-    if raw.get("url") in {None, "", ":memory:"} and raw.get("implementation", "sqlite") == "sqlite":
+    url = raw.get("url")
+    impl = raw.get("implementation", "sqlite")
+    # Unset/empty → durable user-data chat.db so interactive sessions persist.
+    # Explicit ``:memory:`` is kept as-is (ephemeral; warn so it is not accidental).
+    if impl == "sqlite" and url in {None, ""}:
         db_path = user_data_path("plyngent", ensure_exists=True) / _DEFAULT_DB_FILENAME
         raw = {**raw, "implementation": "sqlite", "url": str(db_path)}
         if not quiet:
             click.secho(f"using database: {db_path}", fg="bright_black", err=True)
+    elif not quiet and impl == "sqlite" and url == ":memory:":
+        click.secho(
+            "warning: database url is :memory: — sessions are not persisted to disk",
+            fg="yellow",
+            err=True,
+        )
     return msgspec.convert(raw, DatabaseConfig)
 
 
diff --git a/src/plyngent/cli/editor.py b/src/plyngent/cli/editor.py
index 603c669..0ea9744 100644
--- a/src/plyngent/cli/editor.py
+++ b/src/plyngent/cli/editor.py
@@ -18,10 +18,12 @@ _MINIMAL_CONFIG = """\
 # plyngent configuration
 # edit providers below
 
-# Optional: omit [database] to use ~/.local/share/plyngent/chat.db (Linux).
+# Optional: omit [database] (or leave url unset) → ~/.local/share/plyngent/chat.db.
+# url = ":memory:" keeps a true in-memory SQLite (CLI warns; nothing on disk).
 # [database]
 # implementation = "sqlite"
 # url = "/path/to/chat.db"
+# # url = ":memory:"
 
 # [agent]
 # system_prompt = "You are a careful coding assistant."
diff --git a/src/plyngent/config/models.py b/src/plyngent/config/models.py
index cdc89c5..2e319f8 100644
--- a/src/plyngent/config/models.py
+++ b/src/plyngent/config/models.py
@@ -4,10 +4,15 @@ from msgspec import Struct, field
 
 
 class DatabaseConfig(Struct, omit_defaults=True):
-    """Database connection configuration."""
+    """Database connection configuration.
+
+    ``url`` is ``None`` when unset. The CLI fills a durable user-data
+    ``chat.db`` only for unset/empty url. Explicit ``":memory:"`` is a true
+    in-memory SQLite (no rewrite).
+    """
 
     implementation: str = "sqlite"
-    url: str = ":memory:"
+    url: str | None = None
     username: str | None = None
     password: str | None = None
 
diff --git a/src/plyngent/memory/database/engine.py b/src/plyngent/memory/database/engine.py
index 47039ca..c9e6fe2 100644
--- a/src/plyngent/memory/database/engine.py
+++ b/src/plyngent/memory/database/engine.py
@@ -20,7 +20,7 @@ def build_async_url(config: DatabaseConfig) -> str:
         raise UnsupportedDatabaseError(msg)
 
     url = config.url
-    if url in {":memory:", ""}:
+    if url is None or url in {":memory:", ""}:
         return "sqlite+aiosqlite:///:memory:"
     if url.startswith("sqlite+aiosqlite://"):
         return url
diff --git a/tests/test_cli/test_app.py b/tests/test_cli/test_app.py
index d19bd6a..8f51414 100644
--- a/tests/test_cli/test_app.py
+++ b/tests/test_cli/test_app.py
@@ -1,10 +1,102 @@
-from __future__ import annotations
-
 from pathlib import Path
 
+import pytest
 from click.testing import CliRunner
 
-from plyngent.cli.app import main
+from plyngent.cli.app import _database_config, main
+from plyngent.config import load as load_config
+
+
+def test_database_config_memory_url_kept_with_warning(
+    tmp_path: Path,
+    capsys: pytest.CaptureFixture[str],
+) -> None:
+    """Explicit ``url = ":memory:"`` is not rewritten; CLI warns (when not quiet)."""
+    path = tmp_path / "mem.toml"
+    _ = path.write_text(
+        """
+[database]
+implementation = "sqlite"
+url = ":memory:"
+""",
+        encoding="utf-8",
+    )
+    store = load_config(path)
+    cfg = _database_config(store, quiet=False)
+    assert cfg.url == ":memory:"
+    assert cfg.implementation == "sqlite"
+    err = capsys.readouterr().err
+    assert ":memory:" in err
+    assert "not persisted" in err.lower() or "warning" in err.lower()
+
+
+def test_database_config_memory_url_quiet_no_warn(tmp_path: Path, capsys: pytest.CaptureFixture[str]) -> None:
+    path = tmp_path / "mem.toml"
+    _ = path.write_text(
+        """
+[database]
+implementation = "sqlite"
+url = ":memory:"
+""",
+        encoding="utf-8",
+    )
+    store = load_config(path)
+    cfg = _database_config(store, quiet=True)
+    assert cfg.url == ":memory:"
+    assert capsys.readouterr().err == ""
+
+
+def test_database_config_unset_url_uses_user_data(
+    tmp_path: Path,
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    """Unset/empty url → durable user-data chat.db."""
+    data_dir = tmp_path / "user-data"
+    _ = data_dir.mkdir()
+
+    def fake_user_data_path(*_args: object, **_kwargs: object) -> Path:
+        return data_dir
+
+    monkeypatch.setattr("plyngent.cli.app.user_data_path", fake_user_data_path)
+    path = tmp_path / "empty-url.toml"
+    _ = path.write_text(
+        """
+[database]
+implementation = "sqlite"
+""",
+        encoding="utf-8",
+    )
+    store = load_config(path)
+    cfg = _database_config(store, quiet=True)
+    assert cfg.url == str(data_dir / "chat.db")
+
+
+def test_database_config_omitted_section_uses_user_data(
+    tmp_path: Path,
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    """Omitted [database] → durable user-data chat.db (url default None)."""
+    data_dir = tmp_path / "user-data2"
+    _ = data_dir.mkdir()
+
+    def fake_user_data_path(*_args: object, **_kwargs: object) -> Path:
+        return data_dir
+
+    monkeypatch.setattr("plyngent.cli.app.user_data_path", fake_user_data_path)
+    path = tmp_path / "no-db.toml"
+    _ = path.write_text(
+        """
+[providers.local]
+preset = "openai-compatible"
+url = "http://127.0.0.1:1/v1"
+access_key_or_token = "x"
+""",
+        encoding="utf-8",
+    )
+    store = load_config(path)
+    assert store.database.get("url") is None
+    cfg = _database_config(store, quiet=True)
+    assert cfg.url == str(data_dir / "chat.db")
 
 
 def test_providers_list() -> None: