feat(cloud): honor ANTON_CLOUD_ARTIFACTS_ROOT as the artifacts dir (ENG-2056)

anton/cloud_turn/session.py

@@ -42,6 +42,16 @@
 #: Operator/CI override for the mount path (pod-side env var, not request data).
 _WORKSPACE_PATH_ENV = "ANTON_CLOUD_WORKSPACE_PATH"
 
+#: Pod-side mount of the PROJECT's shared artifacts directory (ENG-2056). The
+#: workspace mount is per-CONVERSATION, so the derived
+#: ``<workspace>/.anton/artifacts`` only ever shows a task its own artifacts.
+#: The scratchpad controller mounts the project-level artifacts dir as a second
+#: mount OUTSIDE the workspace (so it can never land on sys.path) and sets this
+#: env var to tell anton where it is. When set, it replaces the derived default
+#: so sibling tasks in one project share a single artifacts tree. Same trust
+#: posture as _WORKSPACE_PATH_ENV: pod-side config, never from the wire request.
+_ARTIFACTS_ROOT_ENV = "ANTON_CLOUD_ARTIFACTS_ROOT"
+
 #: The only tools exposed in a cloud turn: scratchpad + the workspace-scoped
 #: artifact tools. Everything else core registers is dropped.
 CLOUD_TOOL_ALLOWLIST = frozenset(
@@ -425,6 +435,32 @@ def resolve_trusted_workspace_path() -> Path:
     return resolved
 
 
+def resolve_trusted_artifacts_root() -> Path | None:
+    """Resolve the project-artifacts mount (ENG-2056), or None when not set.
+
+    Reads :data:`_ARTIFACTS_ROOT_ENV`, set by the same scratchpad controller
+    that sets :data:`_WORKSPACE_PATH_ENV` (pod-side config, never from the wire
+    request), so it gets the same validation: absolute, no ``..``, then
+    canonicalised and created. None — desktop, CI, older controllers — leaves
+    the derived ``<workspace>/.anton/artifacts`` default untouched.
+    """
+    raw = (os.environ.get(_ARTIFACTS_ROOT_ENV) or "").strip()
+    if not raw:
+        return None
+    if not os.path.isabs(raw):
+        raise ValueError(
+            f"trusted artifacts root must be absolute, got {raw!r} "
+            f"(set {_ARTIFACTS_ROOT_ENV} to an absolute path)"
+        )
+    if ".." in Path(raw).parts:
+        raise ValueError(f"trusted artifacts root must not contain '..': {raw!r}")
+    resolved = Path(raw).resolve()
+    resolved.mkdir(parents=True, exist_ok=True)
+    if not resolved.is_dir():
+        raise ValueError(f"trusted artifacts root is not a directory: {resolved}")
+    return resolved
+
+
 #: Attachments cowork-server stages into the workspace for this conversation.
 _ATTACHMENTS_DIRNAME = "attachments"
 
@@ -557,6 +593,16 @@ def build_cloud_chat_session(request: TurnRequestV1) -> "ChatSession":
         if llm.get("coding_model"):
             settings_kwargs["coding_model"] = llm["coding_model"]
     settings = AntonSettings(**settings_kwargs)
+    # ENG-2056: the workspace mount is per-conversation, so deriving
+    # `<workspace>/.anton/artifacts` hides sibling tasks' artifacts. When the
+    # controller mounts the PROJECT's shared artifacts dir (outside the
+    # workspace, so it can't land on sys.path) and points _ARTIFACTS_ROOT_ENV
+    # at it, use that instead. Must be set BEFORE resolve_workspace, which only
+    # derives artifacts_dir when the value is relative and leaves an absolute
+    # one alone; unset env var keeps today's derivation byte-identical.
+    artifacts_root = resolve_trusted_artifacts_root()
+    if artifacts_root is not None:
+        settings.artifacts_dir = str(artifacts_root)
     settings.resolve_workspace(str(base))
     if request.model:
         settings.planning_model = request.model

tests/test_cloud_turn_session.py

@@ -19,8 +19,10 @@
 from anton.cloud_turn.contract import TurnRequestV1
 from anton.cloud_turn.session import (
     CLOUD_TOOL_ALLOWLIST,
+    _ARTIFACTS_ROOT_ENV,
     _WORKSPACE_PATH_ENV,
     build_cloud_chat_session,
+    resolve_trusted_artifacts_root,
     resolve_trusted_workspace_path,
 )
 from anton.core.backends.local import local_scratchpad_runtime_factory
@@ -186,6 +188,63 @@ def test_resolver_rejects_parent_traversal(monkeypatch):
         resolve_trusted_workspace_path()
 
 
+# ── project artifacts root (ENG-2056, never from the wire) ──────────────────
+
+def test_project_artifacts_root_overrides_derived_default(tmp_path, monkeypatch):
+    # ENG-2056: the workspace mount is per-conversation, so the derived
+    # `<workspace>/.anton/artifacts` hides sibling tasks' artifacts. With the
+    # controller's project-artifacts mount announced via env, the session must
+    # use it — for the settings AND the workspace the artifact tools read.
+    root = tmp_path / "project-artifacts"
+    monkeypatch.setenv(_ARTIFACTS_ROOT_ENV, str(root))
+    _, cfg = _build(tmp_path, monkeypatch)
+    assert cfg.settings.artifacts_dir == str(root.resolve())
+    assert cfg.workspace.artifacts_dir == root.resolve()
+    assert cfg.settings.artifacts_dir != str(tmp_path.resolve() / ".anton" / "artifacts")
+
+
+def test_project_artifacts_root_created_when_missing(tmp_path, monkeypatch):
+    root = tmp_path / "mounts" / "project-artifacts"
+    assert not root.exists()
+    monkeypatch.setenv(_ARTIFACTS_ROOT_ENV, str(root))
+    _build(tmp_path, monkeypatch)
+    assert root.is_dir()
+
+
+def test_artifacts_default_unchanged_when_env_unset(tmp_path, monkeypatch):
+    # Desktop and current cloud installs: no env var, behaviour identical to
+    # before — artifacts derive under the workspace's .anton dir.
+    monkeypatch.delenv(_ARTIFACTS_ROOT_ENV, raising=False)
+    _, cfg = _build(tmp_path, monkeypatch)
+    derived = tmp_path.resolve() / ".anton" / "artifacts"
+    assert cfg.settings.artifacts_dir == str(derived)
+    assert cfg.workspace.artifacts_dir == derived
+
+
+def test_artifacts_resolver_unset_or_blank_is_none(monkeypatch):
+    monkeypatch.delenv(_ARTIFACTS_ROOT_ENV, raising=False)
+    assert resolve_trusted_artifacts_root() is None
+    monkeypatch.setenv(_ARTIFACTS_ROOT_ENV, "  ")
+    assert resolve_trusted_artifacts_root() is None
+
+
+def test_artifacts_resolver_uses_env(tmp_path, monkeypatch):
+    monkeypatch.setenv(_ARTIFACTS_ROOT_ENV, str(tmp_path))
+    assert resolve_trusted_artifacts_root() == tmp_path.resolve()
+
+
+def test_artifacts_resolver_rejects_relative_path(monkeypatch):
+    monkeypatch.setenv(_ARTIFACTS_ROOT_ENV, "not/absolute")
+    with pytest.raises(ValueError, match="absolute"):
+        resolve_trusted_artifacts_root()
+
+
+def test_artifacts_resolver_rejects_parent_traversal(monkeypatch):
+    monkeypatch.setenv(_ARTIFACTS_ROOT_ENV, "/project-artifacts/../etc")
+    with pytest.raises(ValueError, match=r"\.\."):
+        resolve_trusted_artifacts_root()
+
+
 def test_artifact_tools_cannot_escape_workspace(tmp_path):
     from anton.core.artifacts.store import ArtifactStore