diff --git a/src/specify_cli/__init__.py b/src/specify_cli/__init__.py
index 0bbf42ad5..e360812c4 100644
--- a/src/specify_cli/__init__.py
+++ b/src/specify_cli/__init__.py
@@ -1211,6 +1211,7 @@ def init(
 
             ensure_constitution_from_template(project_path, tracker=tracker)
 
+            _git_ext_freshly_installed = False
             if not no_git:
                 tracker.start("git")
                 git_messages = []
@@ -1245,6 +1246,7 @@ def init(
                                 bundled_path, get_speckit_version()
                             )
                             git_messages.append("extension installed")
+                            _git_ext_freshly_installed = True
                     else:
                         git_has_error = True
                         git_messages.append("bundled extension not found")
@@ -1356,6 +1358,21 @@ def init(
     console.print(tracker.render())
     console.print("\n[bold green]Project ready.[/bold green]")
 
+    if _git_ext_freshly_installed:
+        console.print()
+        console.print(
+            Panel(
+                "The [bold]git[/bold] extension is currently enabled by default, "
+                "but starting with [bold]v1.0.0[/bold] it will require explicit opt-in.\n\n"
+                "To opt in after v1.0.0:\n"
+                "  • [cyan]specify init --extension git[/cyan]\n"
+                "  • [cyan]specify extension add git[/cyan]  (post-init)",
+                title="[yellow]⚠ Upcoming Change: git Extension[/yellow]",
+                border_style="yellow",
+                padding=(1, 2),
+            )
+        )
+
     # Agent folder security notice
     agent_config = AGENT_CONFIG.get(selected_ai)
     if agent_config:
diff --git a/tests/extensions/git/test_git_extension.py b/tests/extensions/git/test_git_extension.py
index 098caf53b..f82b17fb0 100644
--- a/tests/extensions/git/test_git_extension.py
+++ b/tests/extensions/git/test_git_extension.py
@@ -587,3 +587,79 @@ def test_check_feature_branch_rejects_malformed_timestamp(self, tmp_path: Path):
             capture_output=True, text=True,
         )
         assert result.returncode != 0
+
+
+# ── Deprecation Notice Tests ──────────────────────────────────────────────────
+
+
+class TestGitExtDeprecationNotice:
+    """Tests for the v1.0.0 deprecation notice shown during specify init."""
+
+    def test_deprecation_notice_shown_on_fresh_install(self, tmp_path: Path):
+        """specify init shows the git extension deprecation notice on first install."""
+        from typer.testing import CliRunner
+        from unittest.mock import patch, MagicMock
+        from specify_cli import app
+
+        project_dir = tmp_path / "test-project"
+        runner = CliRunner()
+
+        mock_registry = MagicMock()
+        mock_registry.is_installed.return_value = False
+
+        mock_manager = MagicMock()
+        mock_manager.registry = mock_registry
+
+        with patch("specify_cli.extensions.ExtensionManager", return_value=mock_manager):
+            result = runner.invoke(
+                app,
+                ["init", str(project_dir), "--ai", "claude", "--ignore-agent-tools", "--script", "sh"],
+                catch_exceptions=False,
+            )
+
+        assert result.exit_code == 0, result.output
+        assert "Upcoming Change: git Extension" in result.output
+        assert "v1.0.0" in result.output
+        assert "specify init --extension git" in result.output
+
+    def test_deprecation_notice_not_shown_when_already_installed(self, tmp_path: Path):
+        """specify init does NOT show the deprecation notice when git extension is already installed."""
+        from typer.testing import CliRunner
+        from unittest.mock import patch, MagicMock
+        from specify_cli import app
+
+        project_dir = tmp_path / "test-project"
+        runner = CliRunner()
+
+        mock_registry = MagicMock()
+        mock_registry.is_installed.return_value = True
+
+        mock_manager = MagicMock()
+        mock_manager.registry = mock_registry
+
+        with patch("specify_cli.extensions.ExtensionManager", return_value=mock_manager):
+            result = runner.invoke(
+                app,
+                ["init", str(project_dir), "--ai", "claude", "--ignore-agent-tools", "--script", "sh"],
+                catch_exceptions=False,
+            )
+
+        assert result.exit_code == 0, result.output
+        assert "Upcoming Change: git Extension" not in result.output
+
+    def test_deprecation_notice_not_shown_with_no_git_flag(self, tmp_path: Path):
+        """specify init does NOT show the deprecation notice when --no-git is passed."""
+        from typer.testing import CliRunner
+        from specify_cli import app
+
+        project_dir = tmp_path / "test-project"
+        runner = CliRunner()
+
+        result = runner.invoke(
+            app,
+            ["init", str(project_dir), "--ai", "claude", "--ignore-agent-tools", "--no-git", "--script", "sh"],
+            catch_exceptions=False,
+        )
+
+        assert result.exit_code == 0, result.output
+        assert "Upcoming Change: git Extension" not in result.output