[DBA-136] Highlight new build in chat (chromedevtools)

src/databao_cli/commands/build.py

@@ -1,12 +1,14 @@
 from databao_context_engine import BuildDatasourceResult, DatabaoContextDomainManager
 
 from databao_cli.project.layout import ProjectLayout
+from databao_cli.ui.project_utils import write_build_sentinel
 
 
 def build_impl(project_layout: ProjectLayout, domain: str, should_index: bool) -> list[BuildDatasourceResult]:
     dce_project_dir = project_layout.domains_dir / domain
     results: list[BuildDatasourceResult] = DatabaoContextDomainManager(domain_dir=dce_project_dir).build_context(
         datasource_ids=None, should_index=should_index
     )
+    write_build_sentinel(dce_project_dir)
 
     return results

src/databao_cli/ui/app.py

@@ -18,7 +18,12 @@
 from databao_cli.ui.components.status import AppStatus, set_status, status_context
 from databao_cli.ui.models.chat_session import ChatSession
 from databao_cli.ui.models.settings import LLMSettings
-from databao_cli.ui.project_utils import DatabaoProjectStatus, databao_project_status, has_build_output
+from databao_cli.ui.project_utils import (
+    DatabaoProjectStatus,
+    databao_project_status,
+    get_build_fingerprint,
+    has_build_output,
+)
 from databao_cli.ui.services.storage import get_cache_dir
 
 logger = logging.getLogger(__name__)
@@ -128,6 +133,7 @@ def _initialize_agent(project: ProjectLayout) -> Agent | None:
         _agent = create_agent(**kwargs)  # type: ignore[arg-type]
 
         st.session_state.agent = _agent
+        st.session_state.build_fingerprint = get_build_fingerprint(project.root_domain_dir)
 
         return _agent
 
@@ -185,6 +191,8 @@ def invalidate_agent(status_message: str = "Reloading project...") -> None:
     """
     st.session_state.databao_project = None
     st.session_state.agent = None
+    st.session_state.pop("build_fingerprint", None)
+    st.session_state.pop("new_build_available", None)
     _clear_all_chat_threads()
     set_status(AppStatus.INITIALIZING, status_message)
 
@@ -320,6 +328,11 @@ def init_session_state() -> None:
     if "build_error" not in st.session_state:
         st.session_state.build_error = None
 
+    if "build_fingerprint" not in st.session_state:
+        st.session_state.build_fingerprint = None
+    if "new_build_available" not in st.session_state:
+        st.session_state.new_build_available = False
+
 
 def _create_new_chat() -> None:
     """Create a new chat and navigate to it."""

src/databao_cli/ui/components/chat.py

@@ -7,6 +7,7 @@
 
 from databao_cli.ui.components.results import render_execution_result
 from databao_cli.ui.models.chat_session import ChatMessage
+from databao_cli.ui.project_utils import get_build_fingerprint
 from databao_cli.ui.services import (
     check_query_completion,
     get_query_phase,
@@ -510,6 +511,47 @@ def _process_pending_overwrite(chat: "ChatSession") -> None:
     start_background_query(chat, pending)
 
 
+@st.fragment(run_every=5.0)
+def _new_build_polling_fragment() -> None:
+    """Poll for new build output every 5 seconds.
+
+    Compares the current build fingerprint on disk with the one recorded
+    when the agent was loaded. Sets a session-state flag when a newer
+    build is detected so the banner can be shown.
+    """
+    if st.session_state.get("new_build_available"):
+        return
+
+    stored = st.session_state.get("build_fingerprint")
+    if stored is None:
+        return
+
+    project = st.session_state.get("databao_project")
+    if project is None:
+        return
+
+    current = get_build_fingerprint(project.root_domain_dir)
+    if current > stored:
+        st.session_state.new_build_available = True
+        st.rerun()
+
+
+def _render_new_build_banner() -> None:
+    """Show a banner when a new build is available with a reload action."""
+    if not st.session_state.get("new_build_available"):
+        return
+
+    from databao_cli.ui.app import invalidate_agent
+
+    col_msg, col_btn = st.columns([5, 1])
+    with col_msg:
+        st.warning("A new build is available. Reload to use the latest context.")
+    with col_btn:
+        if st.button("Reload", key="new_build_reload_btn", type="primary"):
+            invalidate_agent("Reloading with new build...")
+            st.rerun()
+
+
 def render_chat_interface(chat: "ChatSession") -> None:
     """Render the complete chat interface.
 
@@ -522,6 +564,9 @@ def render_chat_interface(chat: "ChatSession") -> None:
     """
     _process_pending_overwrite(chat)
 
+    _render_new_build_banner()
+    _new_build_polling_fragment()
+
     agent: Agent | None = st.session_state.get("agent")
     hide_build_context_hint: bool = bool(st.session_state.get("_hide_build_context_hint"))
     if agent is not None and not agent.domain.is_context_built() and not chat.messages and not hide_build_context_hint:

src/databao_cli/ui/project_utils.py

@@ -1,5 +1,6 @@
 import logging
 from enum import Enum
+from pathlib import Path
 
 from databao.agent.integrations.dce import DatabaoContextApi
 
@@ -48,3 +49,33 @@ def has_build_output(project: ProjectLayout) -> bool:
         return len(dce_project.get_introspected_datasource_list()) > 0
     except Exception:
         return False
+
+
+BUILD_SENTINEL = ".build_complete"
+
+
+def get_build_fingerprint(domain_dir: Path) -> float:
+    """Return a fingerprint representing the current build state.
+
+    Reads the modification time of the sentinel file written after a
+    successful build.  Returns 0.0 if the sentinel does not exist.
+    """
+    sentinel = domain_dir / "output" / BUILD_SENTINEL
+    try:
+        return sentinel.stat().st_mtime if sentinel.is_file() else 0.0
+    except OSError:
+        logger.debug("Failed to read build sentinel", exc_info=True)
+        return 0.0
+
+
+def write_build_sentinel(domain_dir: Path) -> None:
+    """Write (or touch) the build sentinel after a successful build.
+
+    The sentinel is a zero-byte marker file whose mtime is compared by
+    ``get_build_fingerprint`` to detect new builds.
+    """
+    output_dir = domain_dir / "output"
+    output_dir.mkdir(parents=True, exist_ok=True)
+    sentinel = output_dir / BUILD_SENTINEL
+    sentinel.touch()
+    logger.debug("Wrote build sentinel: %s", sentinel)

src/databao_cli/ui/services/dce_operations.py

@@ -164,8 +164,12 @@ def verify_datasource_config(ds_type_str: str, ds_name: str, config: dict[str, A
 
 def build_context(project_dir: Path) -> list[BuildDatasourceResult]:
     """Build context for all datasources in the DCE project. This is a long-running operation."""
+    from databao_cli.ui.project_utils import write_build_sentinel
+
     manager = DatabaoContextDomainManager(domain_dir=project_dir)
-    return manager.build_context()
+    result = manager.build_context()
+    write_build_sentinel(project_dir)
+    return result
 
 
 def get_status_info(project_dir: Path) -> str:

tests/test_build_fingerprint.py

@@ -0,0 +1,91 @@
+"""Tests for build fingerprint and sentinel (DBA-136)."""
+
+import os
+from pathlib import Path
+
+import pytest
+
+from databao_cli.ui.project_utils import BUILD_SENTINEL, get_build_fingerprint, write_build_sentinel
+
+
+@pytest.fixture
+def domain_dir(tmp_path: Path) -> Path:
+    """Create a minimal domain directory structure."""
+    domain = tmp_path / "domain"
+    domain.mkdir()
+    return domain
+
+
+# -- get_build_fingerprint --
+
+
+def test_no_output_dir(domain_dir: Path) -> None:
+    """Returns 0.0 when the output directory does not exist."""
+    assert get_build_fingerprint(domain_dir) == 0.0
+
+
+def test_output_dir_without_sentinel(domain_dir: Path) -> None:
+    """Returns 0.0 when output dir exists but sentinel is missing."""
+    (domain_dir / "output").mkdir()
+    (domain_dir / "output" / "ds.yaml").write_text("tables: []")
+    assert get_build_fingerprint(domain_dir) == 0.0
+
+
+def test_fingerprint_from_sentinel(domain_dir: Path) -> None:
+    """Returns the mtime of the sentinel file."""
+    output = domain_dir / "output"
+    output.mkdir()
+    sentinel = output / BUILD_SENTINEL
+    sentinel.touch()
+    expected = sentinel.stat().st_mtime
+    assert get_build_fingerprint(domain_dir) == expected
+
+
+def test_fingerprint_changes_after_rebuild(domain_dir: Path) -> None:
+    """Fingerprint changes when sentinel is re-touched (simulating rebuild)."""
+    output = domain_dir / "output"
+    output.mkdir()
+    sentinel = output / BUILD_SENTINEL
+    sentinel.touch()
+
+    fp1 = get_build_fingerprint(domain_dir)
+
+    # Explicitly set a future mtime to avoid filesystem granularity issues.
+    future = fp1 + 10
+    os.utime(sentinel, (future, future))
+
+    fp2 = get_build_fingerprint(domain_dir)
+    assert fp2 > fp1
+
+
+# -- write_build_sentinel --
+
+
+def test_write_sentinel_creates_file(domain_dir: Path) -> None:
+    """write_build_sentinel creates the sentinel (and output dir if needed)."""
+    write_build_sentinel(domain_dir)
+    sentinel = domain_dir / "output" / BUILD_SENTINEL
+    assert sentinel.is_file()
+
+
+def test_write_sentinel_updates_mtime(domain_dir: Path) -> None:
+    """Calling write_build_sentinel again updates the sentinel mtime."""
+    write_build_sentinel(domain_dir)
+    sentinel = domain_dir / "output" / BUILD_SENTINEL
+    fp1 = sentinel.stat().st_mtime
+
+    # Set an old mtime, then re-touch via write_build_sentinel.
+    past = fp1 - 100
+    os.utime(sentinel, (past, past))
+    assert sentinel.stat().st_mtime < fp1
+
+    write_build_sentinel(domain_dir)
+    fp2 = sentinel.stat().st_mtime
+    assert fp2 >= fp1
+
+
+def test_fingerprint_round_trip(domain_dir: Path) -> None:
+    """get_build_fingerprint returns 0 before write, non-zero after."""
+    assert get_build_fingerprint(domain_dir) == 0.0
+    write_build_sentinel(domain_dir)
+    assert get_build_fingerprint(domain_dir) > 0.0