diff --git a/src/utils/text.py b/src/utils/text.py
index f04b6e2..9ddff64 100644
--- a/src/utils/text.py
+++ b/src/utils/text.py
@@ -7,10 +7,51 @@
 
 from __future__ import annotations
 
+import logging
 from typing import List
 
 from src.config.constants import LLM_TAB_SEPARATOR
 from src.schemas.classification import Classification
+from src.utils.exceptions import ValidationError
+
+
+logger = logging.getLogger(__name__)
+
+# Maximum string length threshold (10 MB)
+MAX_STRING_LENGTH = 10 * 1024 * 1024
+
+
+# ---------------------------------------------------------------------------
+# Validation helpers
+# ---------------------------------------------------------------------------
+
+
+def validate_input_text(content: str, function_name: str) -> None:
+    """
+    Validate input text for null, empty, and size constraints.
+    
+    Raises:
+        ValidationError: If content is None, empty after stripping, or exceeds max length.
+        TypeError: If content is not a string.
+    """
+    if content is None:
+        raise ValidationError(f"{function_name}: Input text cannot be None")
+    
+    if not isinstance(content, str):
+        raise TypeError(f"{function_name}: Input must be a string, got {type(content).__name__}")
+    
+    if not content.strip():
+        raise ValidationError(f"{function_name}: Input text cannot be empty or whitespace-only")
+    
+    if len(content) > MAX_STRING_LENGTH:
+        logger.warning(
+            f"{function_name}: Input text exceeds maximum length. "
+            f"Length: {len(content)} bytes, Max: {MAX_STRING_LENGTH} bytes"
+        )
+        raise ValidationError(
+            f"{function_name}: Input text exceeds maximum allowed length "
+            f"({len(content)} > {MAX_STRING_LENGTH} bytes)"
+        )
 
 
 def attribute_unify(value: str) -> str:
@@ -45,7 +86,12 @@ def parse_raw_response_to_classifications(content: str) -> List[Classification]:
 
     Expected line format::
         SOURCE::QUERY
+    
+    Raises:
+        ValidationError: If content is None, empty, or exceeds maximum length.
     """
+    validate_input_text(content, "parse_raw_response_to_classifications")
+    
     classifications: List[Classification] = []
 
     for line in content.strip().splitlines():
@@ -99,7 +145,12 @@ def parse_raw_response_to_profiles(content: str) -> list[dict]:
         TOPIC::SUB_TOPIC::MEMO
 
     Lines before ``---`` are treated as the LLM's "thinking" and ignored.
+    
+    Raises:
+        ValidationError: If content is None, empty, or exceeds maximum length.
     """
+    validate_input_text(content, "parse_raw_response_to_profiles")
+    
     facts: list[dict] = []
 
     # Skip the thinking section (everything before '---')
@@ -150,7 +201,12 @@ def parse_raw_response_to_events(content: str) -> list[dict]:
 
     Returns:
         List of event dicts. Empty list if no events found.
+    
+    Raises:
+        ValidationError: If content is None, empty, or exceeds maximum length.
     """
+    validate_input_text(content, "parse_raw_response_to_events")
+    
     content = content.strip()
 
     if "NO_EVENT" in content.upper():
@@ -253,7 +309,12 @@ def parse_raw_response_to_event(content: str) -> dict | None:
 
     Returns:
         Dict with event data or *None* if no event was found.
+    
+    Raises:
+        ValidationError: If content is None, empty, or exceeds maximum length.
     """
+    validate_input_text(content, "parse_raw_response_to_event")
+    
     events = parse_raw_response_to_events(content)
     return events[0] if events else None
 
@@ -277,7 +338,12 @@ def parse_raw_response_to_image(content: str) -> dict:
     Returns:
         Dict with keys ``description`` (str) and ``observations`` (list of dicts).
         Each observation dict has ``category``, ``description``, and optional ``confidence``.
+    
+    Raises:
+        ValidationError: If content is None, empty, or exceeds maximum length.
     """
+    validate_input_text(content, "parse_raw_response_to_image")
+    
     content = content.strip()
 
     result: dict = {
diff --git a/tests/unit/test_utils.py b/tests/unit/test_utils.py
index 304ed78..6607a14 100644
--- a/tests/unit/test_utils.py
+++ b/tests/unit/test_utils.py
@@ -123,3 +123,208 @@ def test_xmem_error_serializes_context():
         "operation": "write",
         "details": {"id": "1"},
     }
+
+
+# ============================================================================
+# VALIDATION TESTS - Empty String, Null, and Length Constraint Checks
+# ============================================================================
+
+class TestTextValidationEmptyAndNull:
+    """Test that text parsing functions reject empty and null inputs."""
+
+    def test_parse_classifications_rejects_empty_string(self):
+        """Empty strings should raise ValidationError."""
+        with pytest.raises(ValidationError, match="cannot be empty"):
+            parse_raw_response_to_classifications("")
+
+    def test_parse_classifications_rejects_whitespace_only(self):
+        """Whitespace-only strings should raise ValidationError."""
+        with pytest.raises(ValidationError, match="cannot be empty"):
+            parse_raw_response_to_classifications("   \n\t  ")
+
+    def test_parse_classifications_rejects_none(self):
+        """None input should raise ValidationError."""
+        with pytest.raises(ValidationError, match="cannot be None"):
+            parse_raw_response_to_classifications(None)
+
+    def test_parse_profiles_rejects_empty_string(self):
+        """Empty strings should raise ValidationError."""
+        with pytest.raises(ValidationError, match="cannot be empty"):
+            parse_raw_response_to_profiles("")
+
+    def test_parse_profiles_rejects_whitespace_only(self):
+        """Whitespace-only strings should raise ValidationError."""
+        with pytest.raises(ValidationError, match="cannot be empty"):
+            parse_raw_response_to_profiles("   \n\t  ")
+
+    def test_parse_profiles_rejects_none(self):
+        """None input should raise ValidationError."""
+        with pytest.raises(ValidationError, match="cannot be None"):
+            parse_raw_response_to_profiles(None)
+
+    def test_parse_events_rejects_empty_string(self):
+        """Empty strings should raise ValidationError."""
+        with pytest.raises(ValidationError, match="cannot be empty"):
+            parse_raw_response_to_events("")
+
+    def test_parse_events_rejects_whitespace_only(self):
+        """Whitespace-only strings should raise ValidationError."""
+        with pytest.raises(ValidationError, match="cannot be empty"):
+            parse_raw_response_to_events("   \n\t  ")
+
+    def test_parse_events_rejects_none(self):
+        """None input should raise ValidationError."""
+        with pytest.raises(ValidationError, match="cannot be None"):
+            parse_raw_response_to_events(None)
+
+    def test_parse_event_rejects_empty_string(self):
+        """Empty strings should raise ValidationError."""
+        with pytest.raises(ValidationError, match="cannot be empty"):
+            parse_raw_response_to_event("")
+
+    def test_parse_event_rejects_whitespace_only(self):
+        """Whitespace-only strings should raise ValidationError."""
+        with pytest.raises(ValidationError, match="cannot be empty"):
+            parse_raw_response_to_event("   \n\t  ")
+
+    def test_parse_event_rejects_none(self):
+        """None input should raise ValidationError."""
+        with pytest.raises(ValidationError, match="cannot be None"):
+            parse_raw_response_to_event(None)
+
+    def test_parse_image_rejects_empty_string(self):
+        """Empty strings should raise ValidationError."""
+        with pytest.raises(ValidationError, match="cannot be empty"):
+            parse_raw_response_to_image("")
+
+    def test_parse_image_rejects_whitespace_only(self):
+        """Whitespace-only strings should raise ValidationError."""
+        with pytest.raises(ValidationError, match="cannot be empty"):
+            parse_raw_response_to_image("   \n\t  ")
+
+    def test_parse_image_rejects_none(self):
+        """None input should raise ValidationError."""
+        with pytest.raises(ValidationError, match="cannot be None"):
+            parse_raw_response_to_image(None)
+
+
+class TestTextValidationTypeChecks:
+    """Test that text parsing functions enforce type checks."""
+
+    def test_parse_classifications_rejects_non_string_types(self):
+        """Non-string types should raise TypeError."""
+        with pytest.raises(TypeError, match="Input must be a string"):
+            parse_raw_response_to_classifications(123)
+
+        with pytest.raises(TypeError, match="Input must be a string"):
+            parse_raw_response_to_classifications(["profile::test"])
+
+        with pytest.raises(TypeError, match="Input must be a string"):
+            parse_raw_response_to_classifications({"text": "test"})
+
+    def test_parse_profiles_rejects_non_string_types(self):
+        """Non-string types should raise TypeError."""
+        with pytest.raises(TypeError, match="Input must be a string"):
+            parse_raw_response_to_profiles(456)
+
+    def test_parse_events_rejects_non_string_types(self):
+        """Non-string types should raise TypeError."""
+        with pytest.raises(TypeError, match="Input must be a string"):
+            parse_raw_response_to_events(789)
+
+    def test_parse_image_rejects_non_string_types(self):
+        """Non-string types should raise TypeError."""
+        with pytest.raises(TypeError, match="Input must be a string"):
+            parse_raw_response_to_image(999)
+
+
+class TestTextValidationLengthConstraints:
+    """Test that text parsing functions enforce maximum length constraints."""
+
+    def test_parse_classifications_rejects_oversized_payload(self):
+        """Oversized payloads should raise ValidationError."""
+        from src.utils.text import MAX_STRING_LENGTH
+        
+        oversized = "x" * (MAX_STRING_LENGTH + 1)
+        with pytest.raises(ValidationError, match="exceeds maximum allowed length"):
+            parse_raw_response_to_classifications(oversized)
+
+    def test_parse_profiles_rejects_oversized_payload(self):
+        """Oversized payloads should raise ValidationError."""
+        from src.utils.text import MAX_STRING_LENGTH
+        
+        oversized = "x" * (MAX_STRING_LENGTH + 1)
+        with pytest.raises(ValidationError, match="exceeds maximum allowed length"):
+            parse_raw_response_to_profiles(oversized)
+
+    def test_parse_events_rejects_oversized_payload(self):
+        """Oversized payloads should raise ValidationError."""
+        from src.utils.text import MAX_STRING_LENGTH
+        
+        oversized = "x" * (MAX_STRING_LENGTH + 1)
+        with pytest.raises(ValidationError, match="exceeds maximum allowed length"):
+            parse_raw_response_to_events(oversized)
+
+    def test_parse_image_rejects_oversized_payload(self):
+        """Oversized payloads should raise ValidationError."""
+        from src.utils.text import MAX_STRING_LENGTH
+        
+        oversized = "x" * (MAX_STRING_LENGTH + 1)
+        with pytest.raises(ValidationError, match="exceeds maximum allowed length"):
+            parse_raw_response_to_image(oversized)
+
+
+class TestTextValidationRegressions:
+    """Test that valid inputs still work correctly after validation additions."""
+
+    def test_parse_classifications_valid_inputs_still_work(self):
+        """Valid classification inputs should still parse correctly."""
+        result = parse_raw_response_to_classifications(
+            "profile::I work at XMem\ncode::Explain the API"
+        )
+        assert len(result) == 2
+        assert result[0]["source"] == "profile"
+        assert result[0]["query"] == "I work at XMem"
+
+    def test_parse_profiles_valid_inputs_still_work(self):
+        """Valid profile inputs should still parse correctly."""
+        result = parse_raw_response_to_profiles(
+            "thinking\n---\nwork::company::Google\nbasic_info::name::Alice"
+        )
+        assert len(result) == 2
+        assert result[0]["topic"] == "work"
+
+    def test_parse_events_valid_inputs_still_work(self):
+        """Valid event inputs should still parse correctly."""
+        result = parse_raw_response_to_events(
+            "DATE: 05-11\nEVENT_NAME: Demo\nYEAR: 2026"
+        )
+        assert len(result) == 1
+        assert result[0]["date"] == "05-11"
+
+    def test_parse_event_valid_inputs_still_work(self):
+        """Valid single event inputs should still parse correctly."""
+        result = parse_raw_response_to_event(
+            "DATE: 05-11\nEVENT_NAME: Demo\nYEAR: 2026"
+        )
+        assert result["date"] == "05-11"
+        assert result["event_name"] == "Demo"
+
+    def test_parse_image_valid_inputs_still_work(self):
+        """Valid image inputs should still parse correctly."""
+        result = parse_raw_response_to_image(
+            "DESCRIPTION: Test image\nOBSERVATIONS:\n- [document] test"
+        )
+        assert result["description"] == "Test image"
+        assert len(result["observations"]) == 1
+
+    def test_parse_events_no_event_keyword_still_works(self):
+        """NO_EVENT keyword should still return empty list."""
+        result = parse_raw_response_to_events("NO_EVENT")
+        assert result == []
+
+    def test_parse_event_with_no_event_keyword_returns_none(self):
+        """NO_EVENT keyword should still return None for single event parser."""
+        result = parse_raw_response_to_event("NO_EVENT")
+        assert result is None
+