diff --git a/docs/changelog.md b/docs/changelog.md
index 58dda54..d109857 100644
--- a/docs/changelog.md
+++ b/docs/changelog.md
@@ -1,5 +1,8 @@
 # Changelog
 
+### v0.4.2
+- FIX: Fixed serialization of extended fields (e.g., DevTools) in HarLog dump. Now all additional fields are correctly preserved when calling model_dump().
+
 ### v0.4.1
 - FIX: Removed the mistakenly added `rich` dependency from the requirements.
 
@@ -44,4 +47,4 @@
 
 ## v0.1.0
 
-- Initial release of `hario-core`.
\ No newline at end of file
+- Initial release of `hario-core`.
diff --git a/pyproject.toml b/pyproject.toml
index e86db14..41454e4 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -4,7 +4,7 @@ build-backend = "poetry.core.masonry.api"
 
 [project]
 name = "hario-core"
-version = "0.4.1"
+version = "0.4.2"
 description = "Modern, type-safe, and extensible library for parsing, transforming, and analyzing HAR (HTTP Archive) files."
 authors = [{name = "Vasiliy Pikulev", email = "pikulev.vasiliy@gmail.com"}]
 readme = "README.md"
@@ -106,7 +106,7 @@ convention = "google"
 
 [tool.poetry]
 name = "hario-core"
-version = "0.4.1"
+version = "0.4.2"
 description = "Modern, type-safe, and extensible library for parsing, transforming, and analyzing HAR (HTTP Archive) files."
 authors = ["Vasiliy Pikulev <pikulev.vasiliy@gmail.com>"]
 readme = "README.md"
diff --git a/src/hario_core/__init__.py b/src/hario_core/__init__.py
index 9fbca5a..606f5b5 100644
--- a/src/hario_core/__init__.py
+++ b/src/hario_core/__init__.py
@@ -2,7 +2,7 @@
 Hario Core package root.
 """
 
-__version__ = "0.4.1"
+__version__ = "0.4.2"
 
 from . import models, parse, transform
 
diff --git a/src/hario_core/models/extensions/chrome_devtools.py b/src/hario_core/models/extensions/chrome_devtools.py
index 67e3a0b..a70edb0 100644
--- a/src/hario_core/models/extensions/chrome_devtools.py
+++ b/src/hario_core/models/extensions/chrome_devtools.py
@@ -4,7 +4,7 @@
 
 from typing import List, Optional
 
-from pydantic import BaseModel, Field
+from pydantic import BaseModel, ConfigDict, Field
 
 from ..har_1_2 import Entry, Request, Response, Timings
 
@@ -68,6 +68,11 @@ class DevToolsWebSocketMessage(BaseModel):
 class DevToolsEntry(Entry):
     """HAR Entry object with DevTools extensions."""
 
+    model_config = ConfigDict(
+        extra="allow",
+        populate_by_name=True,
+    )
+
     initiator: Optional[DevToolsInitiator] = Field(None, alias="_initiator")
     priority: Optional[str] = Field(None, alias="_priority")
     resourceType: str = Field(alias="_resourceType")
diff --git a/src/hario_core/models/har_1_2.py b/src/hario_core/models/har_1_2.py
index 88b1309..5145ae5 100644
--- a/src/hario_core/models/har_1_2.py
+++ b/src/hario_core/models/har_1_2.py
@@ -98,7 +98,8 @@ class Entry(BaseModel):
     """HAR Entry object."""
 
     model_config = ConfigDict(
-        extra="forbid",
+        extra="allow",
+        populate_by_name=True,
     )
 
     pageref: Optional[str] = None
@@ -135,10 +136,21 @@ class Page(BaseModel):
 
 
 class HarLog(BaseModel):
-    model_config = ConfigDict(extra="forbid")  # strict: forbid vendor‑specific fields
+    model_config = ConfigDict(
+        extra="allow",
+        populate_by_name=True,
+    )
 
     version: str
     creator: Creator
     browser: Optional[Browser] = None
     pages: List[Page] = []
     entries: List[Entry]
+
+    def model_dump(self: HarLog, **kwargs: Any) -> Dict[str, Any]:
+        dump = super().model_dump(**kwargs)
+        # manually serialize entries with the actual type
+        dump["entries"] = [
+            entry.model_dump(**kwargs) for entry in self.entries if entry is not None
+        ]
+        return dump
diff --git a/tests/samples.py b/tests/samples.py
index 5a40029..96b9c5b 100644
--- a/tests/samples.py
+++ b/tests/samples.py
@@ -156,8 +156,6 @@
     }
 }
 
-CHROME_DEVTOOLS_HAR_BYTES: bytes = orjson.dumps(CHROME_DEVTOOLS_HAR)
-
 # Valid HAR 1.2
 CLEANED_HAR: Dict[str, Any] = {
     "log": {
@@ -274,6 +272,8 @@
 
 CLEANED_HAR_BYTES: bytes = orjson.dumps(CLEANED_HAR)
 
+CHROME_DEVTOOLS_HAR_BYTES: bytes = orjson.dumps(CHROME_DEVTOOLS_HAR)
+
 # Edge-case: HAR without log field (based on real HAR)
 INVALID_HAR_NO_LOG: Dict[str, Any] = {
     k: v for k, v in CHROME_DEVTOOLS_HAR.items() if k != "log"
diff --git a/tests/test_har_parser.py b/tests/test_har_parser.py
index 82c45c8..b1abb4d 100644
--- a/tests/test_har_parser.py
+++ b/tests/test_har_parser.py
@@ -240,3 +240,22 @@ def test_validate_with_invalid_entries(self, cleaned_har: Dict[str, Any]) -> Non
         har["log"]["entries"] = dict()
         with pytest.raises(ValueError):
             validate(har)
+
+    def test_har_log_model_dump_preserves_extension_fields(self) -> None:
+        """
+        Test that har_log.model_dump() preserves
+        Chrome DevTools extension fields at all levels.
+        """
+        har_log = parse(CHROME_DEVTOOLS_HAR_BYTES)
+        dumped = har_log.model_dump()
+        # Check that entries exists and is not empty
+        assert "entries" in dumped
+        assert len(dumped["entries"]) > 0
+        entry_dump = dumped["entries"][0]
+        # Check that DevTools extension fields are preserved
+        assert "initiator" in entry_dump
+        assert "connectionId" in entry_dump
+        # Check that nested fields are preserved
+        assert isinstance(entry_dump["initiator"], dict)
+        assert entry_dump["initiator"]["type"] == "parser"
+        assert "transferSize" in entry_dump["response"]