feat(config): ✨ Introduce 'this_host' serialization logic and enforce consistent config formatting

Co-Authored-By: Lilith Autocommit <noreply@atlilith.com>

src/claire/config.py

@@ -216,6 +216,10 @@ def _serialize(cfg: ClaireConfig) -> str:
     lines: list[str] = [f'machine_id = "{cfg.machine_id}"']
     if cfg.sync_secret is not None:
         lines.append(f'sync_secret = "{cfg.sync_secret}"')
+    # Top-level scalars MUST come before any `[section]` header — once a
+    # table opens, subsequent KV pairs belong to it. Emit `this_host` here.
+    if cfg.this_host is not None:
+        lines.append(f'this_host = "{cfg.this_host}"')
     lines.extend(
         [
             "",
@@ -262,9 +266,6 @@ def _serialize(cfg: ClaireConfig) -> str:
                 f'"{h}" = {c}' for h, c in sorted(lim.per_host.items())
             )
             lines.append(f"per_host = {{ {inner} }}")
-    if cfg.this_host is not None:
-        lines.append("")
-        lines.append(f'this_host = "{cfg.this_host}"')
     for h in cfg.known_hosts:
         lines.append("")
         lines.append("[[known_hosts]]")

tests/test_config.py

@@ -124,6 +124,87 @@ def test_load_or_init_reads_per_host_caps(tmp_path: Path) -> None:
     assert cfg.limits.cap_for("plum") == 4  # unnamed → default
 
 
+# --- host detection / known_hosts ------------------------------------------
+
+
+def test_this_host_label_explicit_overrides_hostname(tmp_path: Path) -> None:
+    cfg_path = tmp_path / "claire.toml"
+    cfg_path.write_text(
+        'machine_id = "m"\n'
+        'sync_secret = "s"\n'
+        'this_host = "plum"\n'
+        '\n[web]\nhost = "127.0.0.1"\nport = 8765\n',
+        encoding="utf-8",
+    )
+    cfg = load_or_init(cfg_path)
+    assert cfg.this_host == "plum"
+    assert cfg.this_host_label() == "plum"
+
+
+def test_this_host_label_defaults_to_short_os_hostname(tmp_path: Path) -> None:
+    import socket
+    cfg = load_or_init(tmp_path / "claire.toml")
+    expected = socket.gethostname().split(".", 1)[0].lower()
+    assert cfg.this_host is None
+    assert cfg.this_host_label() == expected
+
+
+def test_resolve_host_label_rewrites_local_to_this_host(tmp_path: Path) -> None:
+    cfg_path = tmp_path / "claire.toml"
+    cfg_path.write_text(
+        'machine_id = "m"\n'
+        'sync_secret = "s"\n'
+        'this_host = "plum"\n'
+        '\n[web]\nhost = "127.0.0.1"\nport = 8765\n',
+        encoding="utf-8",
+    )
+    cfg = load_or_init(cfg_path)
+    assert cfg.resolve_host_label("local") == "plum"
+    # Already-canonical labels pass through.
+    assert cfg.resolve_host_label("apricot") == "apricot"
+
+
+def test_resolve_host_label_uses_aliases(tmp_path: Path) -> None:
+    cfg_path = tmp_path / "claire.toml"
+    cfg_path.write_text(
+        'machine_id = "m"\n'
+        'sync_secret = "s"\n'
+        'this_host = "plum"\n'
+        '\n[web]\nhost = "127.0.0.1"\nport = 8765\n'
+        '\n[[known_hosts]]\n'
+        'name = "apricot"\n'
+        'aliases = ["apri", "apr"]\n',
+        encoding="utf-8",
+    )
+    cfg = load_or_init(cfg_path)
+    assert cfg.resolve_host_label("apri") == "apricot"
+    assert cfg.resolve_host_label("apr") == "apricot"
+    assert cfg.resolve_host_label("apricot") == "apricot"
+    # An unrelated label is unchanged.
+    assert cfg.resolve_host_label("black") == "black"
+
+
+def test_serialize_round_trips_host_detection(tmp_path: Path) -> None:
+    cfg_path = tmp_path / "claire.toml"
+    cfg_path.write_text(
+        'machine_id = "m"\n'
+        'this_host = "plum"\n'
+        '\n[web]\nhost = "127.0.0.1"\nport = 8765\n'
+        '\n[[known_hosts]]\n'
+        'name = "apricot"\n'
+        'aliases = ["apri"]\n'
+        'description = "dev box"\n',
+        encoding="utf-8",
+    )
+    load_or_init(cfg_path)  # rewrites file (backfills sync_secret)
+    reloaded = load_or_init(cfg_path)
+    assert reloaded.this_host == "plum"
+    assert len(reloaded.known_hosts) == 1
+    assert reloaded.known_hosts[0].name == "apricot"
+    assert reloaded.known_hosts[0].aliases == ["apri"]
+    assert reloaded.known_hosts[0].description == "dev box"
+
+
 def test_serialize_round_trips_per_host_caps(tmp_path: Path) -> None:
     # A config missing sync_secret triggers the migration rewrite, which
     # runs _serialize — the per_host map must survive the round-trip.