diff --git a/features/steps/tdd_cli_incomplete_subcommand_registration_steps.py b/features/steps/tdd_cli_incomplete_subcommand_registration_steps.py
new file mode 100644
index 000000000..ff29b04e8
--- /dev/null
+++ b/features/steps/tdd_cli_incomplete_subcommand_registration_steps.py
@@ -0,0 +1,119 @@
+"""Step definitions for tdd_cli_incomplete_subcommand_registration.feature.
+
+This test captures bug #2604: _register_subcommands() in
+src/cleveragents/cli/main.py catches all exceptions during subcommand
+import and registration, then silently returns instead of raising.
+This violates CONTRIBUTING.md error-handling standards.
+
+The fix replaces the bare ``return`` with ``raise SystemExit(1)`` so the
+CLI exits with a non-zero exit code instead of entering a partially
+initialized state.
+
+Once the fix for #2604 is merged, the ``@tdd_expected_fail`` scenario
+(which asserts the old silent-return behaviour) must be removed so the
+remaining scenarios run as regression guards.
+"""
+
+from __future__ import annotations
+
+from unittest.mock import patch
+
+from behave import given, then, when  # type: ignore[import-untyped]
+from behave.runner import Context  # type: ignore[import-untyped]
+from typer.testing import CliRunner
+
+runner = CliRunner(mix_stderr=False)
+
+
+@given("the CLI subcommand import raises an ImportError during registration")
+def step_given_import_error(context: Context) -> None:
+    """Arrange: patch the subcommand import to raise ImportError."""
+    context.import_error = ImportError("simulated subcommand import failure #2604")
+
+
+@when("the CLI is invoked with any command")
+def step_when_cli_invoked(context: Context) -> None:
+    """Act: invoke the CLI while the subcommand import is broken."""
+    import cleveragents.cli.main as cli_main
+
+    # Reset the registration flag so _register_subcommands() runs again.
+    original_flag = cli_main._subcommands_registered
+    cli_main._subcommands_registered = False
+
+    try:
+        with patch(
+            "cleveragents.cli.main._register_subcommands",
+            side_effect=context.import_error,
+        ):
+            # We patch _register_subcommands itself to raise so we can test
+            # the caller's behaviour without needing to break real imports.
+            # The real fix is inside _register_subcommands, but the caller
+            # (ensure_cli_commands_registered / the app callback) must also
+            # propagate the SystemExit.
+            from cleveragents.cli.main import app
+
+            result = runner.invoke(app, ["--help"], catch_exceptions=True)
+            context.cli_result = result
+    finally:
+        cli_main._subcommands_registered = original_flag
+
+
+@then("the CLI exits with a non-zero exit code")
+def step_then_non_zero_exit(context: Context) -> None:
+    """Assert: the CLI must not exit with 0 when registration fails."""
+    assert context.cli_result.exit_code != 0, (
+        f"Bug #2604: CLI exited with code 0 after subcommand registration "
+        f"failure. The CLI must exit with a non-zero code to signal the "
+        f"error. Got exit_code={context.cli_result.exit_code}. "
+        f"Output: {context.cli_result.output!r}"
+    )
+
+
+@then('the error output contains "Failed to register subcommands"')
+def step_then_error_message(context: Context) -> None:
+    """Assert: the error message must be present in the output."""
+    # CliRunner with mix_stderr=False separates stdout and stderr.
+    # The error is printed to stderr via get_err_console().
+    combined = (context.cli_result.output or "") + (
+        getattr(context.cli_result, "stderr", "") or ""
+    )
+    # When _register_subcommands itself is patched to raise, the message
+    # won't appear (it's inside the function). We test the exit code path
+    # separately. For the message test, we need to invoke the real function
+    # with a broken import.
+    import cleveragents.cli.main as cli_main
+
+    original_flag = cli_main._subcommands_registered
+    cli_main._subcommands_registered = False
+
+    try:
+        # Patch the internal import inside _register_subcommands by making
+        # the first import inside the try block raise.
+        with patch(
+            "cleveragents.cli.commands.project",
+            side_effect=ImportError("simulated import failure #2604"),
+        ):
+            from cleveragents.cli.main import app
+
+            result = runner.invoke(app, ["--help"], catch_exceptions=True)
+            combined = (result.output or "") + (getattr(result, "stderr", "") or "")
+    finally:
+        cli_main._subcommands_registered = original_flag
+
+    assert "Failed to register subcommands" in combined, (
+        f"Bug #2604: Expected 'Failed to register subcommands' in CLI output "
+        f"when subcommand registration fails, but got: {combined!r}"
+    )
+
+
+@then("the CLI exits with exit code 0")
+def step_then_zero_exit(context: Context) -> None:
+    """Assert the OLD (buggy) behaviour: CLI exits with 0 on registration error.
+
+    This scenario is tagged @tdd_expected_fail because it asserts the bug.
+    Once the fix is merged, this scenario must be removed.
+    """
+    assert context.cli_result.exit_code == 0, (
+        f"Expected exit code 0 (old buggy behaviour), "
+        f"got {context.cli_result.exit_code}"
+    )
diff --git a/features/tdd_cli_incomplete_subcommand_registration.feature b/features/tdd_cli_incomplete_subcommand_registration.feature
new file mode 100644
index 000000000..4a5e424f8
--- /dev/null
+++ b/features/tdd_cli_incomplete_subcommand_registration.feature
@@ -0,0 +1,32 @@
+@tdd_issue @tdd_issue_2604
+Feature: TDD Issue #2604 — Incomplete subcommand registration on error
+  As a CLI user
+  I want the CLI to fail loudly when subcommand registration encounters an error
+  So that the CLI is never left in a partially initialized state
+
+  This test captures bug #2604. The _register_subcommands() function in
+  src/cleveragents/cli/main.py catches all exceptions during subcommand
+  import and registration, prints a traceback, then silently returns.
+  This violates CONTRIBUTING.md error-handling standards: "Errors must
+  never be suppressed. Exceptions should propagate to the top-level
+  execution handler."
+
+  The fix replaces the bare `return` with `raise SystemExit(1)` so the
+  CLI exits with a non-zero exit code instead of entering a partially
+  initialized state.
+
+  Scenario: Bug #2604 — subcommand registration failure exits with non-zero code
+    Given the CLI subcommand import raises an ImportError during registration
+    When the CLI is invoked with any command
+    Then the CLI exits with a non-zero exit code
+
+  Scenario: Bug #2604 — subcommand registration failure prints error message
+    Given the CLI subcommand import raises an ImportError during registration
+    When the CLI is invoked with any command
+    Then the error output contains "Failed to register subcommands"
+
+  @tdd_expected_fail
+  Scenario: Bug #2604 — old behaviour silently returns on registration error
+    Given the CLI subcommand import raises an ImportError during registration
+    When the CLI is invoked with any command
+    Then the CLI exits with exit code 0
diff --git a/src/cleveragents/cli/main.py b/src/cleveragents/cli/main.py
index 58a3639bb..81a7267ec 100644
--- a/src/cleveragents/cli/main.py
+++ b/src/cleveragents/cli/main.py
@@ -101,13 +101,13 @@ def _register_subcommands() -> None:
         from cleveragents.cli.commands.db import app as db_app
         from cleveragents.cli.commands.repl import _repl_app
         from cleveragents.cli.commands.server import app as server_app
-    except Exception as exc:  # pragma: no cover
+    except Exception as exc:
         import traceback
 
         err = get_err_console()
         err.print(f"[red]Failed to register subcommands:[/red] {exc}")
         err.print(traceback.format_exc())
-        return
+        raise SystemExit(1) from exc
 
     app.add_typer(project.app, name="project", help="Project management")