diff --git a/codeflash/languages/base.py b/codeflash/languages/base.py
index b5fd583c8..e699afd2b 100644
--- a/codeflash/languages/base.py
+++ b/codeflash/languages/base.py
@@ -50,6 +50,12 @@ class IndexResult:
     error: bool
 
 
+@dataclass(frozen=True)
+class SetupError:
+    message: str
+    should_abort: bool
+
+
 @dataclass
 class HelperFunction:
     """A helper function that is a dependency of the target function.
@@ -725,8 +731,12 @@ def prepare_module(
         """Parse/validate a module before optimization."""
         ...
 
-    def setup_test_config(self, test_cfg: TestConfig, file_path: Path, current_worktree: Path | None = None) -> None:
-        """One-time project setup after language detection. Default: no-op."""
+    def setup_test_config(self, test_cfg: TestConfig, file_path: Path, current_worktree: Path | None = None) -> bool:
+        """One-time project setup after language detection. Default: no-op.
+
+        Returns True if the project is valid for optimization, False otherwise.
+        """
+        return True
 
     def adjust_test_config_for_discovery(self, test_cfg: TestConfig) -> None:
         """Adjust test config before test discovery. Default: no-op."""
diff --git a/codeflash/languages/java/support.py b/codeflash/languages/java/support.py
index 9e6149e1b..ab3818348 100644
--- a/codeflash/languages/java/support.py
+++ b/codeflash/languages/java/support.py
@@ -403,11 +403,12 @@ def load_coverage(
     ) -> None:
         return None
 
-    def setup_test_config(self, test_cfg: Any, file_path: Path, current_worktree: Path | None = None) -> None:
+    def setup_test_config(self, test_cfg: Any, file_path: Path, current_worktree: Path | None = None) -> bool:
         """Detect test framework from project build config (pom.xml / build.gradle)."""
         config = detect_java_project(test_cfg.project_root_path)
         if config is not None:
             self._test_framework = config.test_framework
+        return True
 
     def adjust_test_config_for_discovery(self, test_cfg: Any) -> None:
         """Adjust test config before test discovery for Java.
diff --git a/codeflash/languages/javascript/optimizer.py b/codeflash/languages/javascript/optimizer.py
index bc88786b1..1fe382ed2 100644
--- a/codeflash/languages/javascript/optimizer.py
+++ b/codeflash/languages/javascript/optimizer.py
@@ -3,6 +3,7 @@
 from typing import TYPE_CHECKING
 
 from codeflash.cli_cmds.console import logger
+from codeflash.languages.base import SetupError
 from codeflash.models.models import ValidCode
 
 if TYPE_CHECKING:
@@ -25,11 +26,13 @@ def prepare_javascript_module(
     return validated_original_code, None
 
 
-def verify_js_requirements(test_cfg: TestConfig) -> None:
+def verify_js_requirements(test_cfg: TestConfig) -> list[SetupError]:
     """Verify JavaScript/TypeScript requirements before optimization.
 
     Checks that Node.js, npm, and the test framework are available.
     Logs warnings if requirements are not met but does not abort.
+
+    Returns: List of setup errors if requirements are not met, empty list otherwise.
     """
     from codeflash.languages import get_language_support
     from codeflash.languages.base import Language
@@ -37,7 +40,7 @@ def verify_js_requirements(test_cfg: TestConfig) -> None:
 
     js_project_root = test_cfg.js_project_root
     if not js_project_root:
-        return
+        return [SetupError("JavaScript project root not found", should_abort=True)]
 
     try:
         js_support = get_language_support(Language.JAVASCRIPT)
@@ -47,6 +50,9 @@ def verify_js_requirements(test_cfg: TestConfig) -> None:
         if not success:
             logger.warning("JavaScript requirements check found issues:")
             for error in errors:
-                logger.warning(f"  - {error}")
+                logger.warning(f"  - {error.message}")
+            return errors
+        return []
     except Exception as e:
         logger.debug(f"Failed to verify JS requirements: {e}")
+        return [SetupError(str(e), should_abort=True)]
diff --git a/codeflash/languages/javascript/support.py b/codeflash/languages/javascript/support.py
index db96c4df1..3f5c13b9e 100644
--- a/codeflash/languages/javascript/support.py
+++ b/codeflash/languages/javascript/support.py
@@ -14,7 +14,15 @@
 
 from codeflash.code_utils.git_utils import git_root_dir, mirror_path
 from codeflash.discovery.functions_to_optimize import FunctionToOptimize
-from codeflash.languages.base import CodeContext, FunctionFilterCriteria, HelperFunction, Language, TestInfo, TestResult
+from codeflash.languages.base import (
+    CodeContext,
+    FunctionFilterCriteria,
+    HelperFunction,
+    Language,
+    SetupError,
+    TestInfo,
+    TestResult,
+)
 from codeflash.languages.javascript.treesitter import TreeSitterAnalyzer, TreeSitterLanguage, get_analyzer_for_file
 from codeflash.languages.registry import register_language
 from codeflash.models.models import FunctionParent
@@ -1950,11 +1958,13 @@ def prepare_module(
 
         return prepare_javascript_module(module_code, module_path)
 
-    def setup_test_config(self, test_cfg: TestConfig, file_path: Path, current_worktree: Path | None) -> None:
+    def setup_test_config(self, test_cfg: TestConfig, file_path: Path, current_worktree: Path | None) -> bool:
         from codeflash.languages.javascript.optimizer import verify_js_requirements
         from codeflash.languages.javascript.test_runner import find_node_project_root
 
         test_cfg.js_project_root = find_node_project_root(file_path)
+        if test_cfg.js_project_root is None:
+            return False
         if current_worktree is not None:
             original_js_root = git_root_dir()
             worktree_node_modules = test_cfg.js_project_root / "node_modules"
@@ -1970,7 +1980,11 @@ def setup_test_config(self, test_cfg: TestConfig, file_path: Path, current_workt
                 original_root_node_modules = original_js_root / "node_modules"
                 if original_root_node_modules.exists() and not worktree_root_node_modules.exists():
                     worktree_root_node_modules.symlink_to(original_root_node_modules)
-        verify_js_requirements(test_cfg)
+        setup_errors = verify_js_requirements(test_cfg)
+        if any(e.should_abort for e in setup_errors):
+            return False
+
+        return True
 
     def adjust_test_config_for_discovery(self, test_cfg: TestConfig) -> None:
         test_cfg.tests_project_rootdir = test_cfg.tests_root
@@ -2216,7 +2230,7 @@ def get_module_path(self, source_file: Path, project_root: Path, tests_root: Pat
             rel_path = source_file.relative_to(project_root)
             return "../" + rel_path.with_suffix("").as_posix()
 
-    def verify_requirements(self, project_root: Path, test_framework: str = "jest") -> tuple[bool, list[str]]:
+    def verify_requirements(self, project_root: Path, test_framework: str = "jest") -> tuple[bool, list[SetupError]]:
         """Verify that all JavaScript requirements are met.
 
         Checks for:
@@ -2236,27 +2250,40 @@ def verify_requirements(self, project_root: Path, test_framework: str = "jest")
             Tuple of (success, list of error messages).
 
         """
-        errors: list[str] = []
+        errors: list[SetupError] = []
 
         # Check Node.js
         try:
             result = subprocess.run(["node", "--version"], check=False, capture_output=True, text=True, timeout=10)
             if result.returncode != 0:
-                errors.append("Node.js is not installed. Please install Node.js 18+ from https://nodejs.org/")
+                errors.append(
+                    SetupError(
+                        "Node.js is not installed. Please install Node.js 18+ from https://nodejs.org/",
+                        should_abort=True,
+                    )
+                )
         except FileNotFoundError:
-            errors.append("Node.js is not installed. Please install Node.js 18+ from https://nodejs.org/")
+            errors.append(
+                SetupError(
+                    "Node.js is not installed. Please install Node.js 18+ from https://nodejs.org/", should_abort=True
+                )
+            )
         except Exception as e:
-            errors.append(f"Failed to check Node.js: {e}")
+            errors.append(SetupError(f"Failed to check Node.js: {e}", should_abort=True))
 
         # Check npm
         try:
             result = subprocess.run(["npm", "--version"], check=False, capture_output=True, text=True, timeout=10)
             if result.returncode != 0:
-                errors.append("npm is not available. Please ensure npm is installed with Node.js.")
+                errors.append(
+                    SetupError("npm is not available. Please ensure npm is installed with Node.js.", should_abort=True)
+                )
         except FileNotFoundError:
-            errors.append("npm is not available. Please ensure npm is installed with Node.js.")
+            errors.append(
+                SetupError("npm is not available. Please ensure npm is installed with Node.js.", should_abort=True)
+            )
         except Exception as e:
-            errors.append(f"Failed to check npm: {e}")
+            errors.append(SetupError(f"Failed to check npm: {e}", should_abort=True))
 
         # Check test framework is installed (with monorepo support)
         # Uses find_node_modules_with_package which searches up the directory tree
@@ -2270,12 +2297,17 @@ def verify_requirements(self, project_root: Path, test_framework: str = "jest")
             local_node_modules = project_root / "node_modules"
             if not local_node_modules.exists():
                 errors.append(
-                    f"node_modules not found in {project_root}. Please run 'npm install' to install dependencies."
+                    SetupError(
+                        f"node_modules not found in {project_root}. Please run 'npm install' to install dependencies.",
+                        should_abort=True,
+                    )
                 )
             else:
                 errors.append(
-                    f"{test_framework} is not installed. "
-                    f"Please run 'npm install --save-dev {test_framework}' to install it."
+                    SetupError(
+                        f"{test_framework} is not installed. Please run 'npm install --save-dev {test_framework}' to install it.",
+                        should_abort=True,
+                    )
                 )
 
         return len(errors) == 0, errors
diff --git a/codeflash/languages/python/support.py b/codeflash/languages/python/support.py
index 596073590..34f0527b2 100644
--- a/codeflash/languages/python/support.py
+++ b/codeflash/languages/python/support.py
@@ -1044,8 +1044,9 @@ def prepare_module(
 
     pytest_cmd: str = "pytest"
 
-    def setup_test_config(self, test_cfg: TestConfig, file_path: Path, current_worktree: Path | None = None) -> None:
+    def setup_test_config(self, test_cfg: TestConfig, file_path: Path, current_worktree: Path | None = None) -> bool:
         self.pytest_cmd = test_cfg.pytest_cmd or "pytest"
+        return True
 
     def pytest_cmd_tokens(self, is_posix: bool) -> list[str]:
         import shlex
diff --git a/codeflash/optimization/optimizer.py b/codeflash/optimization/optimizer.py
index fef53a760..8c2f66db4 100644
--- a/codeflash/optimization/optimizer.py
+++ b/codeflash/optimization/optimizer.py
@@ -526,7 +526,11 @@ def run(self) -> None:
                 if funcs and funcs[0].language:
                     set_current_language(funcs[0].language)
                     self.test_cfg.set_language(funcs[0].language)
-                    current_language_support().setup_test_config(self.test_cfg, file_path, self.current_worktree)
+                    if not current_language_support().setup_test_config(
+                        self.test_cfg, file_path, self.current_worktree
+                    ):
+                        logger.error("Project setup failed — aborting optimization. Check warnings above for details.")
+                        return
                     break
 
         if self.args.all:
diff --git a/tests/test_languages/test_javascript_requirements.py b/tests/test_languages/test_javascript_requirements.py
index dc95d5584..efefda228 100644
--- a/tests/test_languages/test_javascript_requirements.py
+++ b/tests/test_languages/test_javascript_requirements.py
@@ -91,7 +91,7 @@ def test_verify_requirements_fails_without_node(self, js_support, project_with_j
 
             assert success is False
             assert len(errors) >= 1
-            node_error_found = any("Node.js" in error for error in errors)
+            node_error_found = any("Node.js" in error.message for error in errors)
             assert node_error_found is True
 
     def test_verify_requirements_fails_without_npm(self, js_support, project_with_jest):
@@ -108,7 +108,7 @@ def mock_run_side_effect(cmd, **kwargs):
             success, errors = js_support.verify_requirements(project_with_jest, "jest")
 
             assert success is False
-            npm_error_found = any("npm" in error for error in errors)
+            npm_error_found = any("npm" in error.message for error in errors)
             assert npm_error_found is True
 
     def test_verify_requirements_fails_without_node_modules(self, js_support, project_without_node_modules):
@@ -120,11 +120,11 @@ def test_verify_requirements_fails_without_node_modules(self, js_support, projec
 
             assert success is False
             assert len(errors) == 1
-            expected_error = (
+            expected_message = (
                 f"node_modules not found in {project_without_node_modules}. "
                 f"Please run 'npm install' to install dependencies."
             )
-            assert errors[0] == expected_error
+            assert errors[0].message == expected_message
 
     def test_verify_requirements_fails_without_test_framework(self, js_support, project_without_jest):
         """Test verification fails when test framework is not installed."""
@@ -135,8 +135,8 @@ def test_verify_requirements_fails_without_test_framework(self, js_support, proj
 
             assert success is False
             assert len(errors) == 1
-            expected_error = "jest is not installed. Please run 'npm install --save-dev jest' to install it."
-            assert errors[0] == expected_error
+            expected_message = "jest is not installed. Please run 'npm install --save-dev jest' to install it."
+            assert errors[0].message == expected_message
 
     def test_verify_requirements_returns_multiple_errors(self, js_support, project_without_node_modules):
         """Test that multiple errors can be returned."""
@@ -148,7 +148,7 @@ def test_verify_requirements_returns_multiple_errors(self, js_support, project_w
             assert success is False
             assert len(errors) >= 2
             # Should have errors for Node.js, npm, and node_modules
-            error_text = " ".join(errors)
+            error_text = " ".join(e.message for e in errors)
             assert "Node.js" in error_text
             assert "npm" in error_text
 
@@ -161,8 +161,8 @@ def test_verify_requirements_vitest_not_installed(self, js_support, project_with
 
             assert success is False
             assert len(errors) == 1
-            expected_error = "vitest is not installed. Please run 'npm install --save-dev vitest' to install it."
-            assert errors[0] == expected_error
+            expected_message = "vitest is not installed. Please run 'npm install --save-dev vitest' to install it."
+            assert errors[0].message == expected_message
 
     def test_verify_requirements_jest_not_installed(self, js_support, project_with_vitest):
         """Test verification fails when Jest is requested but only Vitest is installed."""
@@ -173,8 +173,46 @@ def test_verify_requirements_jest_not_installed(self, js_support, project_with_v
 
             assert success is False
             assert len(errors) == 1
-            expected_error = "jest is not installed. Please run 'npm install --save-dev jest' to install it."
-            assert errors[0] == expected_error
+            expected_message = "jest is not installed. Please run 'npm install --save-dev jest' to install it."
+            assert errors[0].message == expected_message
+
+
+class TestSetupTestConfig:
+    """Tests for JavaScriptSupport.setup_test_config() early-exit behavior."""
+
+    @pytest.fixture
+    def js_support(self):
+        return JavaScriptSupport()
+
+    def test_setup_test_config_returns_false_on_abort_error(self, js_support, tmp_path):
+        """setup_test_config returns False when verify_js_requirements reports a should_abort error."""
+        from codeflash.languages.base import SetupError
+
+        abort_error = SetupError("Node.js is not installed", should_abort=True)
+        with (
+            patch("codeflash.languages.javascript.test_runner.find_node_project_root", return_value=tmp_path.resolve()),
+            patch("codeflash.languages.javascript.optimizer.verify_js_requirements", return_value=[abort_error]),
+        ):
+            test_cfg = MagicMock()
+            result = js_support.setup_test_config(test_cfg, tmp_path.resolve(), current_worktree=None)
+            assert result is False
+
+    def test_setup_test_config_returns_true_on_no_errors(self, js_support, tmp_path):
+        """setup_test_config returns True when verify_js_requirements reports no errors."""
+        with (
+            patch("codeflash.languages.javascript.test_runner.find_node_project_root", return_value=tmp_path.resolve()),
+            patch("codeflash.languages.javascript.optimizer.verify_js_requirements", return_value=[]),
+        ):
+            test_cfg = MagicMock()
+            result = js_support.setup_test_config(test_cfg, tmp_path.resolve(), current_worktree=None)
+            assert result is True
+
+    def test_setup_test_config_returns_false_when_project_root_is_none(self, js_support, tmp_path):
+        """setup_test_config returns False when find_node_project_root returns None."""
+        with patch("codeflash.languages.javascript.test_runner.find_node_project_root", return_value=None):
+            test_cfg = MagicMock()
+            result = js_support.setup_test_config(test_cfg, tmp_path.resolve(), current_worktree=None)
+            assert result is False
 
 
 class TestVerifyRequirementsIntegration: