diff --git a/openhands/resolver/interfaces/github.py b/openhands/resolver/interfaces/github.py
index 46cceb68a4f7..d9cd66c53eba 100644
--- a/openhands/resolver/interfaces/github.py
+++ b/openhands/resolver/interfaces/github.py
@@ -22,28 +22,28 @@ def __init__(self, owner: str, repo: str, token: str, username: str | None = Non
         self.clone_url = self.get_clone_url()
         self.headers = self.get_headers()
 
-    def set_owner(self, owner: str):
+    def set_owner(self, owner: str) -> None:
         self.owner = owner
 
-    def get_headers(self):
+    def get_headers(self) -> dict[str, str]:
         return {
             'Authorization': f'token {self.token}',
             'Accept': 'application/vnd.github.v3+json',
         }
 
-    def get_base_url(self):
+    def get_base_url(self) -> str:
         return f'https://api.github.com/repos/{self.owner}/{self.repo}'
 
-    def get_authorize_url(self):
+    def get_authorize_url(self) -> str:
         return f'https://{self.username}:{self.token}@github.com/'
 
-    def get_branch_url(self, branch_name: str):
+    def get_branch_url(self, branch_name: str) -> str:
         return self.get_base_url() + f'/branches/{branch_name}'
 
-    def get_download_url(self):
+    def get_download_url(self) -> str:
         return f'{self.base_url}/issues'
 
-    def get_clone_url(self):
+    def get_clone_url(self) -> str:
         username_and_token = (
             f'{self.username}:{self.token}'
             if self.username
@@ -51,10 +51,10 @@ def get_clone_url(self):
         )
         return f'https://{username_and_token}@github.com/{self.owner}/{self.repo}.git'
 
-    def get_graphql_url(self):
+    def get_graphql_url(self) -> str:
         return 'https://api.github.com/graphql'
 
-    def get_compare_url(self, branch_name: str):
+    def get_compare_url(self, branch_name: str) -> str:
         return f'https://github.com/{self.owner}/{self.repo}/compare/{branch_name}?expand=1'
 
     def get_converted_issues(
@@ -186,7 +186,7 @@ def branch_exists(self, branch_name: str) -> bool:
         print(f'Branch {branch_name} exists: {exists}')
         return exists
 
-    def get_branch_name(self, base_branch_name: str):
+    def get_branch_name(self, base_branch_name: str) -> str:
         branch_name = base_branch_name
         attempt = 1
         while self.branch_exists(branch_name):
@@ -194,7 +194,7 @@ def get_branch_name(self, base_branch_name: str):
             branch_name = f'{base_branch_name}-try{attempt}'
         return branch_name
 
-    def reply_to_comment(self, pr_number: int, comment_id: str, reply: str):
+    def reply_to_comment(self, pr_number: int, comment_id: str, reply: str) -> None:
         # Opting for graphql as REST API doesn't allow reply to replies in comment threads
         query = """
             mutation($body: String!, $pullRequestReviewThreadId: ID!) {
@@ -221,15 +221,18 @@ def reply_to_comment(self, pr_number: int, comment_id: str, reply: str):
         )
         response.raise_for_status()
 
-    def get_pull_url(self, pr_number: int):
+    def get_pull_url(self, pr_number: int) -> str:
         return f'https://github.com/{self.owner}/{self.repo}/pull/{pr_number}'
 
     def get_default_branch_name(self) -> str:
         response = requests.get(f'{self.base_url}', headers=self.headers)
         response.raise_for_status()
-        return response.json()['default_branch']
+        data = response.json()
+        return str(data['default_branch'])
 
-    def create_pull_request(self, data=dict) -> dict:
+    def create_pull_request(self, data: dict[str, Any] | None = None) -> dict[str, Any]:
+        if data is None:
+            data = {}
         response = requests.post(
             f'{self.base_url}/pulls', headers=self.headers, json=data
         )
@@ -240,9 +243,9 @@ def create_pull_request(self, data=dict) -> dict:
             )
         response.raise_for_status()
         pr_data = response.json()
-        return pr_data
+        return dict(pr_data)
 
-    def request_reviewers(self, reviewer: str, pr_number: int):
+    def request_reviewers(self, reviewer: str, pr_number: int) -> None:
         review_data = {'reviewers': [reviewer]}
         review_response = requests.post(
             f'{self.base_url}/pulls/{pr_number}/requested_reviewers',
@@ -254,7 +257,7 @@ def request_reviewers(self, reviewer: str, pr_number: int):
                 f'Warning: Failed to request review from {reviewer}: {review_response.text}'
             )
 
-    def send_comment_msg(self, issue_number: int, msg: str):
+    def send_comment_msg(self, issue_number: int, msg: str) -> None:
         """Send a comment message to a GitHub issue or pull request.
 
         Args:
@@ -282,8 +285,8 @@ def get_context_from_external_issues_references(
         review_comments: list[str] | None,
         review_threads: list[ReviewThread],
         thread_comments: list[str] | None,
-    ):
-        pass
+    ) -> list[str]:
+        return []
 
 
 class GithubPRHandler(GithubIssueHandler):
@@ -487,7 +490,7 @@ def get_context_from_external_issues_references(
         review_comments: list[str] | None,
         review_threads: list[ReviewThread],
         thread_comments: list[str] | None,
-    ):
+    ) -> list[str]:
         new_issue_references = []
 
         if issue_body:
diff --git a/openhands/resolver/interfaces/gitlab.py b/openhands/resolver/interfaces/gitlab.py
index 52661d93032d..47519c4a4e0f 100644
--- a/openhands/resolver/interfaces/gitlab.py
+++ b/openhands/resolver/interfaces/gitlab.py
@@ -23,38 +23,38 @@ def __init__(self, owner: str, repo: str, token: str, username: str | None = Non
         self.clone_url = self.get_clone_url()
         self.headers = self.get_headers()
 
-    def set_owner(self, owner: str):
+    def set_owner(self, owner: str) -> None:
         self.owner = owner
 
-    def get_headers(self):
+    def get_headers(self) -> dict[str, str]:
         return {
             'Authorization': f'Bearer {self.token}',
             'Accept': 'application/json',
         }
 
-    def get_base_url(self):
-        project_path = quote(f'{self.owner}/{self.repo}', safe="")
+    def get_base_url(self) -> str:
+        project_path = quote(f'{self.owner}/{self.repo}', safe='')
         return f'https://gitlab.com/api/v4/projects/{project_path}'
 
-    def get_authorize_url(self):
+    def get_authorize_url(self) -> str:
         return f'https://{self.username}:{self.token}@gitlab.com/'
 
-    def get_branch_url(self, branch_name: str):
+    def get_branch_url(self, branch_name: str) -> str:
         return self.get_base_url() + f'/repository/branches/{branch_name}'
 
-    def get_download_url(self):
+    def get_download_url(self) -> str:
         return f'{self.base_url}/issues'
 
-    def get_clone_url(self):
+    def get_clone_url(self) -> str:
         username_and_token = self.token
         if self.username:
             username_and_token = f'{self.username}:{self.token}'
         return f'https://{username_and_token}@gitlab.com/{self.owner}/{self.repo}.git'
 
-    def get_graphql_url(self):
+    def get_graphql_url(self) -> str:
         return 'https://gitlab.com/api/graphql'
 
-    def get_compare_url(self, branch_name: str):
+    def get_compare_url(self, branch_name: str) -> str:
         return f'https://gitlab.com/{self.owner}/{self.repo}/-/compare/{self.get_default_branch_name()}...{branch_name}'
 
     def get_converted_issues(
@@ -189,7 +189,7 @@ def branch_exists(self, branch_name: str) -> bool:
         print(f'Branch {branch_name} exists: {exists}')
         return exists
 
-    def get_branch_name(self, base_branch_name: str):
+    def get_branch_name(self, base_branch_name: str) -> str:
         branch_name = base_branch_name
         attempt = 1
         while self.branch_exists(branch_name):
@@ -197,7 +197,7 @@ def get_branch_name(self, base_branch_name: str):
             branch_name = f'{base_branch_name}-try{attempt}'
         return branch_name
 
-    def reply_to_comment(self, pr_number: int, comment_id: str, reply: str):
+    def reply_to_comment(self, pr_number: int, comment_id: str, reply: str) -> None:
         response = requests.get(
             f'{self.base_url}/merge_requests/{pr_number}/discussions/{comment_id.split('/')[-1]}',
             headers=self.headers,
@@ -216,7 +216,7 @@ def reply_to_comment(self, pr_number: int, comment_id: str, reply: str):
             )
             response.raise_for_status()
 
-    def get_pull_url(self, pr_number: int):
+    def get_pull_url(self, pr_number: int) -> str:
         return (
             f'https://gitlab.com/{self.owner}/{self.repo}/-/merge_requests/{pr_number}'
         )
@@ -224,9 +224,12 @@ def get_pull_url(self, pr_number: int):
     def get_default_branch_name(self) -> str:
         response = requests.get(f'{self.base_url}', headers=self.headers)
         response.raise_for_status()
-        return response.json()['default_branch']
+        data = response.json()
+        return str(data['default_branch'])
 
-    def create_pull_request(self, data=dict) -> dict:
+    def create_pull_request(self, data: dict[str, Any] | None = None) -> dict[str, Any]:
+        if data is None:
+            data = {}
         response = requests.post(
             f'{self.base_url}/merge_requests', headers=self.headers, json=data
         )
@@ -243,9 +246,9 @@ def create_pull_request(self, data=dict) -> dict:
         if 'iid' in pr_data:
             pr_data['number'] = pr_data['iid']
 
-        return pr_data
+        return dict(pr_data)
 
-    def request_reviewers(self, reviewer: str, pr_number: int):
+    def request_reviewers(self, reviewer: str, pr_number: int) -> None:
         response = requests.get(
             f'https://gitlab.com/api/v4/users?username={reviewer}',
             headers=self.headers,
@@ -264,7 +267,7 @@ def request_reviewers(self, reviewer: str, pr_number: int):
                     f'Warning: Failed to request review from {reviewer}: {review_response.text}'
                 )
 
-    def send_comment_msg(self, issue_number: int, msg: str):
+    def send_comment_msg(self, issue_number: int, msg: str) -> None:
         """Send a comment message to a GitHub issue or pull request.
 
         Args:
@@ -292,8 +295,8 @@ def get_context_from_external_issues_references(
         review_comments: list[str] | None,
         review_threads: list[ReviewThread],
         thread_comments: list[str] | None,
-    ):
-        pass
+    ) -> list[str]:
+        return []
 
 
 class GitlabPRHandler(GitlabIssueHandler):
@@ -479,7 +482,7 @@ def get_context_from_external_issues_references(
         review_comments: list[str] | None,
         review_threads: list[ReviewThread],
         thread_comments: list[str] | None,
-    ):
+    ) -> list[str]:
         new_issue_references = []
 
         if issue_body:
diff --git a/openhands/resolver/interfaces/issue.py b/openhands/resolver/interfaces/issue.py
index 263fd8160377..ffd6a204ca7a 100644
--- a/openhands/resolver/interfaces/issue.py
+++ b/openhands/resolver/interfaces/issue.py
@@ -26,7 +26,7 @@ class Issue(BaseModel):
 
 class IssueHandlerInterface(ABC):
     @abstractmethod
-    def set_owner(self, owner: str):
+    def set_owner(self, owner: str) -> None:
         pass
 
     @abstractmethod
@@ -40,43 +40,43 @@ def get_issue_comments(
         pass
 
     @abstractmethod
-    def get_base_url(self):
+    def get_base_url(self) -> str:
         pass
 
     @abstractmethod
-    def get_branch_url(self, branch_name):
+    def get_branch_url(self, branch_name: str) -> str:
         pass
 
     @abstractmethod
-    def get_download_url(self):
+    def get_download_url(self) -> str:
         pass
 
     @abstractmethod
-    def get_clone_url(self):
+    def get_clone_url(self) -> str:
         pass
 
     @abstractmethod
-    def get_pull_url(self, pr_number: int):
+    def get_pull_url(self, pr_number: int) -> str:
         pass
 
     @abstractmethod
-    def get_graphql_url(self):
+    def get_graphql_url(self) -> str:
         pass
 
     @abstractmethod
-    def get_headers(self):
+    def get_headers(self) -> dict[str, str]:
         pass
 
     @abstractmethod
-    def get_compare_url(self, branch_name):
+    def get_compare_url(self, branch_name: str) -> str:
         pass
 
     @abstractmethod
-    def get_branch_name(self, base_branch_name: str):
+    def get_branch_name(self, base_branch_name: str) -> str:
         pass
 
     @abstractmethod
-    def get_default_branch_name(self):
+    def get_default_branch_name(self) -> str:
         pass
 
     @abstractmethod
@@ -84,23 +84,25 @@ def branch_exists(self, branch_name: str) -> bool:
         pass
 
     @abstractmethod
-    def reply_to_comment(self, pr_number: int, comment_id: str, reply: str):
+    def reply_to_comment(self, pr_number: int, comment_id: str, reply: str) -> None:
         pass
 
     @abstractmethod
-    def send_comment_msg(self, issue_number: int, msg: str):
+    def send_comment_msg(self, issue_number: int, msg: str) -> None:
         pass
 
     @abstractmethod
-    def get_authorize_url(self):
+    def get_authorize_url(self) -> str:
         pass
 
     @abstractmethod
-    def create_pull_request(self, data=dict) -> dict:
-        pass
+    def create_pull_request(self, data: dict[str, Any] | None = None) -> dict[str, Any]:
+        if data is None:
+            data = {}
+        raise NotImplementedError
 
     @abstractmethod
-    def request_reviewers(self, reviewer: str, pr_number: int):
+    def request_reviewers(self, reviewer: str, pr_number: int) -> None:
         pass
 
     @abstractmethod
@@ -112,7 +114,7 @@ def get_context_from_external_issues_references(
         review_comments: list[str] | None,
         review_threads: list[ReviewThread],
         thread_comments: list[str] | None,
-    ):
+    ) -> list[str]:
         pass
 
     @abstractmethod
diff --git a/openhands/resolver/interfaces/issue_definitions.py b/openhands/resolver/interfaces/issue_definitions.py
index 6912ab5c1e78..15a9f7cb2d77 100644
--- a/openhands/resolver/interfaces/issue_definitions.py
+++ b/openhands/resolver/interfaces/issue_definitions.py
@@ -25,7 +25,7 @@ def __init__(self, strategy: IssueHandlerInterface, llm_config: LLMConfig | None
         if llm_config is not None:
             self.llm = LLM(llm_config)
 
-    def set_strategy(self, strategy):
+    def set_strategy(self, strategy: IssueHandlerInterface) -> None:
         self._strategy = strategy
 
 
@@ -36,7 +36,7 @@ class ServiceContextPR(ServiceContext):
     def __init__(self, strategy: IssueHandlerInterface, llm_config: LLMConfig):
         super().__init__(strategy, llm_config)
 
-    def get_clone_url(self):
+    def get_clone_url(self) -> str:
         return self._strategy.get_clone_url()
 
     def download_issues(self) -> list[Any]:
@@ -266,31 +266,31 @@ class ServiceContextIssue(ServiceContext):
     def __init__(self, strategy: IssueHandlerInterface, llm_config: LLMConfig | None):
         super().__init__(strategy, llm_config)
 
-    def get_base_url(self):
+    def get_base_url(self) -> str:
         return self._strategy.get_base_url()
 
-    def get_branch_url(self, branch_name):
+    def get_branch_url(self, branch_name: str) -> str:
         return self._strategy.get_branch_url(branch_name)
 
-    def get_download_url(self):
+    def get_download_url(self) -> str:
         return self._strategy.get_download_url()
 
-    def get_clone_url(self):
+    def get_clone_url(self) -> str:
         return self._strategy.get_clone_url()
 
-    def get_graphql_url(self):
+    def get_graphql_url(self) -> str:
         return self._strategy.get_graphql_url()
 
-    def get_headers(self):
+    def get_headers(self) -> dict[str, str]:
         return self._strategy.get_headers()
 
-    def get_authorize_url(self):
+    def get_authorize_url(self) -> str:
         return self._strategy.get_authorize_url()
 
-    def get_pull_url(self, pr_number: int):
+    def get_pull_url(self, pr_number: int) -> str:
         return self._strategy.get_pull_url(pr_number)
 
-    def get_compare_url(self, branch_name: str):
+    def get_compare_url(self, branch_name: str) -> str:
         return self._strategy.get_compare_url(branch_name)
 
     def download_issues(self) -> list[Any]:
@@ -299,25 +299,27 @@ def download_issues(self) -> list[Any]:
     def get_branch_name(
         self,
         base_branch_name: str,
-    ):
+    ) -> str:
         return self._strategy.get_branch_name(base_branch_name)
 
-    def branch_exists(self, branch_name: str):
+    def branch_exists(self, branch_name: str) -> bool:
         return self._strategy.branch_exists(branch_name)
 
     def get_default_branch_name(self) -> str:
         return self._strategy.get_default_branch_name()
 
-    def create_pull_request(self, data=dict):
+    def create_pull_request(self, data: dict[str, Any] | None = None) -> dict[str, Any]:
+        if data is None:
+            data = {}
         return self._strategy.create_pull_request(data)
 
-    def request_reviewers(self, reviewer: str, pr_number: int):
+    def request_reviewers(self, reviewer: str, pr_number: int) -> None:
         return self._strategy.request_reviewers(reviewer, pr_number)
 
-    def reply_to_comment(self, pr_number, comment_id, reply):
+    def reply_to_comment(self, pr_number: int, comment_id: str, reply: str) -> None:
         return self._strategy.reply_to_comment(pr_number, comment_id, reply)
 
-    def send_comment_msg(self, issue_number: int, msg: str):
+    def send_comment_msg(self, issue_number: int, msg: str) -> None:
         return self._strategy.send_comment_msg(issue_number, msg)
 
     def get_issue_comments(
diff --git a/openhands/resolver/patching/apply.py b/openhands/resolver/patching/apply.py
index aedc521a1cd6..65db16c21a83 100644
--- a/openhands/resolver/patching/apply.py
+++ b/openhands/resolver/patching/apply.py
@@ -5,10 +5,13 @@
 import tempfile
 
 from .exceptions import HunkApplyException, SubprocessException
+from .patch import Change, diffobj
 from .snippets import remove, which
 
 
-def _apply_diff_with_subprocess(diff, lines, reverse=False):
+def _apply_diff_with_subprocess(
+    diff: diffobj, lines: list[str], reverse: bool = False
+) -> tuple[list[str], list[str] | None]:
     # call out to patch program
     patchexec = which('patch')
     if not patchexec:
@@ -63,21 +66,21 @@ def _apply_diff_with_subprocess(diff, lines, reverse=False):
     return lines, rejlines
 
 
-def _reverse(changes):
-    def _reverse_change(c):
+def _reverse(changes: list[Change]) -> list[Change]:
+    def _reverse_change(c: Change) -> Change:
         return c._replace(old=c.new, new=c.old)
 
     return [_reverse_change(c) for c in changes]
 
 
-def apply_diff(diff, text, reverse=False, use_patch=False):
-    try:
-        lines = text.splitlines()
-    except AttributeError:
-        lines = list(text)
+def apply_diff(
+    diff: diffobj, text: str | list[str], reverse: bool = False, use_patch: bool = False
+) -> list[str]:
+    lines = text.splitlines() if isinstance(text, str) else list(text)
 
     if use_patch:
-        return _apply_diff_with_subprocess(diff, lines, reverse)
+        lines, _ = _apply_diff_with_subprocess(diff, lines, reverse)
+        return lines
 
     n_lines = len(lines)
 
diff --git a/openhands/resolver/patching/exceptions.py b/openhands/resolver/patching/exceptions.py
index 30653c56da18..75159ddf6555 100644
--- a/openhands/resolver/patching/exceptions.py
+++ b/openhands/resolver/patching/exceptions.py
@@ -1,31 +1,31 @@
-class PatchingException(Exception):
-    pass
-
-
-class HunkException(PatchingException):
-    def __init__(self, msg, hunk=None):
-        self.hunk = hunk
-        if hunk is not None:
-            super(HunkException, self).__init__(
-                '{msg}, in hunk #{n}'.format(msg=msg, n=hunk)
-            )
-        else:
-            super(HunkException, self).__init__(msg)
-
-
-class ApplyException(PatchingException):
-    pass
-
-
-class SubprocessException(ApplyException):
-    def __init__(self, msg, code):
-        super(SubprocessException, self).__init__(msg)
-        self.code = code
-
-
-class HunkApplyException(HunkException, ApplyException, ValueError):
-    pass
-
-
-class ParseException(HunkException, ValueError):
-    pass
+class PatchingException(Exception):
+    pass
+
+
+class HunkException(PatchingException):
+    def __init__(self, msg: str, hunk: int | None = None) -> None:
+        self.hunk = hunk
+        if hunk is not None:
+            super(HunkException, self).__init__(
+                '{msg}, in hunk #{n}'.format(msg=msg, n=hunk)
+            )
+        else:
+            super(HunkException, self).__init__(msg)
+
+
+class ApplyException(PatchingException):
+    pass
+
+
+class SubprocessException(ApplyException):
+    def __init__(self, msg: str, code: int) -> None:
+        super(SubprocessException, self).__init__(msg)
+        self.code = code
+
+
+class HunkApplyException(HunkException, ApplyException, ValueError):
+    pass
+
+
+class ParseException(HunkException, ValueError):
+    pass
diff --git a/openhands/resolver/patching/patch.py b/openhands/resolver/patching/patch.py
index 97cb5d488293..4359e732512c 100644
--- a/openhands/resolver/patching/patch.py
+++ b/openhands/resolver/patching/patch.py
@@ -3,6 +3,7 @@
 import re
 import zlib
 from collections import namedtuple
+from typing import Iterable
 
 from . import exceptions
 from .snippets import findall_regex, split_by_regex
@@ -71,11 +72,8 @@
 old_cvs_diffcmd_header = re.compile('^diff.* (.+):(.*) (.+):(.*)$')
 
 
-def parse_patch(text):
-    try:
-        lines = text.splitlines()
-    except AttributeError:
-        lines = text
+def parse_patch(text: str | list[str]) -> Iterable[diffobj]:
+    lines = text.splitlines() if isinstance(text, str) else text
 
     # maybe use this to nuke all of those line endings?
     # lines = [x.splitlines()[0] for x in lines]
@@ -104,18 +102,15 @@ def parse_patch(text):
             yield diffobj(header=h, changes=d, text=difftext)
 
 
-def parse_header(text):
+def parse_header(text: str | list[str]) -> header | None:
     h = parse_scm_header(text)
     if h is None:
         h = parse_diff_header(text)
     return h
 
 
-def parse_scm_header(text):
-    try:
-        lines = text.splitlines()
-    except AttributeError:
-        lines = text
+def parse_scm_header(text: str | list[str]) -> header | None:
+    lines = text.splitlines() if isinstance(text, str) else text
 
     check = [
         (git_header_index, parse_git_header),
@@ -154,11 +149,8 @@ def parse_scm_header(text):
     return None
 
 
-def parse_diff_header(text):
-    try:
-        lines = text.splitlines()
-    except AttributeError:
-        lines = text
+def parse_diff_header(text: str | list[str]) -> header | None:
+    lines = text.splitlines() if isinstance(text, str) else text
 
     check = [
         (unified_header_new_line, parse_unified_header),
@@ -178,10 +170,10 @@ def parse_diff_header(text):
     return None  # no header?
 
 
-def parse_diff(text):
-    try:
+def parse_diff(text: str | list[str]) -> list[Change] | None:
+    if isinstance(text, str):
         lines = text.splitlines()
-    except AttributeError:
+    else:
         lines = text
 
     check = [
@@ -200,11 +192,8 @@ def parse_diff(text):
     return None
 
 
-def parse_git_header(text):
-    try:
-        lines = text.splitlines()
-    except AttributeError:
-        lines = text
+def parse_git_header(text: str | list[str]) -> header | None:
+    lines = text.splitlines() if isinstance(text, str) else text
 
     old_version = None
     new_version = None
@@ -275,11 +264,8 @@ def parse_git_header(text):
     return None
 
 
-def parse_svn_header(text):
-    try:
-        lines = text.splitlines()
-    except AttributeError:
-        lines = text
+def parse_svn_header(text: str | list[str]) -> header | None:
+    lines = text.splitlines() if isinstance(text, str) else text
 
     headers = findall_regex(lines, svn_header_index)
     if len(headers) == 0:
@@ -346,11 +332,8 @@ def parse_svn_header(text):
     return None
 
 
-def parse_cvs_header(text):
-    try:
-        lines = text.splitlines()
-    except AttributeError:
-        lines = text
+def parse_cvs_header(text: str | list[str]) -> header | None:
+    lines = text.splitlines() if isinstance(text, str) else text
 
     headers = findall_regex(lines, cvs_header_rcs)
     headers_old = findall_regex(lines, old_cvs_diffcmd_header)
@@ -430,11 +413,8 @@ def parse_cvs_header(text):
     return None
 
 
-def parse_diffcmd_header(text):
-    try:
-        lines = text.splitlines()
-    except AttributeError:
-        lines = text
+def parse_diffcmd_header(text: str | list[str]) -> header | None:
+    lines = text.splitlines() if isinstance(text, str) else text
 
     headers = findall_regex(lines, diffcmd_header)
     if len(headers) == 0:
@@ -454,11 +434,8 @@ def parse_diffcmd_header(text):
     return None
 
 
-def parse_unified_header(text):
-    try:
-        lines = text.splitlines()
-    except AttributeError:
-        lines = text
+def parse_unified_header(text: str | list[str]) -> header | None:
+    lines = text.splitlines() if isinstance(text, str) else text
 
     headers = findall_regex(lines, unified_header_new_line)
     if len(headers) == 0:
@@ -490,11 +467,8 @@ def parse_unified_header(text):
     return None
 
 
-def parse_context_header(text):
-    try:
-        lines = text.splitlines()
-    except AttributeError:
-        lines = text
+def parse_context_header(text: str | list[str]) -> header | None:
+    lines = text.splitlines() if isinstance(text, str) else text
 
     headers = findall_regex(lines, context_header_old_line)
     if len(headers) == 0:
@@ -526,11 +500,8 @@ def parse_context_header(text):
     return None
 
 
-def parse_default_diff(text):
-    try:
-        lines = text.splitlines()
-    except AttributeError:
-        lines = text
+def parse_default_diff(text: str | list[str]) -> list[Change] | None:
+    lines = text.splitlines() if isinstance(text, str) else text
 
     old = 0
     new = 0
@@ -582,11 +553,8 @@ def parse_default_diff(text):
     return None
 
 
-def parse_unified_diff(text):
-    try:
-        lines = text.splitlines()
-    except AttributeError:
-        lines = text
+def parse_unified_diff(text: str | list[str]) -> list[Change] | None:
+    lines = text.splitlines() if isinstance(text, str) else text
 
     old = 0
     new = 0
@@ -652,11 +620,8 @@ def parse_unified_diff(text):
     return None
 
 
-def parse_context_diff(text):
-    try:
-        lines = text.splitlines()
-    except AttributeError:
-        lines = text
+def parse_context_diff(text: str | list[str]) -> list[Change] | None:
+    lines = text.splitlines() if isinstance(text, str) else text
 
     old = 0
     new = 0
@@ -795,11 +760,8 @@ def parse_context_diff(text):
     return None
 
 
-def parse_ed_diff(text):
-    try:
-        lines = text.splitlines()
-    except AttributeError:
-        lines = text
+def parse_ed_diff(text: str | list[str]) -> list[Change] | None:
+    lines = text.splitlines() if isinstance(text, str) else text
 
     old = 0
     j = 0
@@ -878,12 +840,9 @@ def parse_ed_diff(text):
     return None
 
 
-def parse_rcs_ed_diff(text):
+def parse_rcs_ed_diff(text: str | list[str]) -> list[Change] | None:
     # much like forward ed, but no 'c' type
-    try:
-        lines = text.splitlines()
-    except AttributeError:
-        lines = text
+    lines = text.splitlines() if isinstance(text, str) else text
 
     old = 0
     j = 0
@@ -905,7 +864,7 @@ def parse_rcs_ed_diff(text):
 
                 hunk_kind = o.group(1)
                 old = int(o.group(2))
-                size = int(o.group(3))
+                size = int(o.group(3)) if o.group(3) else 0
 
                 if hunk_kind == 'a':
                     old += total_change_size + 1
@@ -926,15 +885,11 @@ def parse_rcs_ed_diff(text):
 
     if len(changes) > 0:
         return changes
-
     return None
 
 
-def parse_git_binary_diff(text):
-    try:
-        lines = text.splitlines()
-    except AttributeError:
-        lines = text
+def parse_git_binary_diff(text: str | list[str]) -> list[Change] | None:
+    lines = text.splitlines() if isinstance(text, str) else text
 
     changes: list[Change] = list()
 
diff --git a/openhands/resolver/patching/snippets.py b/openhands/resolver/patching/snippets.py
index f9d9e620d0f7..1c90f573df15 100644
--- a/openhands/resolver/patching/snippets.py
+++ b/openhands/resolver/patching/snippets.py
@@ -1,10 +1,11 @@
 # -*- coding: utf-8 -*-
 
 import os
+import re
 from shutil import rmtree
 
 
-def remove(path):
+def remove(path: str) -> None:
     if os.path.exists(path):
         if os.path.isdir(path):
             rmtree(path)
@@ -13,7 +14,7 @@ def remove(path):
 
 
 # find all indices of a list of strings that match a regex
-def findall_regex(items, regex):
+def findall_regex(items: list[str], regex: re.Pattern[str]) -> list[int]:
     found = list()
     for i in range(0, len(items)):
         k = regex.match(items[i])
@@ -24,7 +25,7 @@ def findall_regex(items, regex):
     return found
 
 
-def split_by_regex(items, regex):
+def split_by_regex(items: list[str], regex: re.Pattern[str]) -> list[list[str]]:
     splits = list()
     indices = findall_regex(items, regex)
     if not indices:
@@ -45,8 +46,8 @@ def split_by_regex(items, regex):
 
 
 # http://stackoverflow.com/questions/377017/test-if-executable-exists-in-python
-def which(program):
-    def is_exe(fpath):
+def which(program: str) -> str | None:
+    def is_exe(fpath: str) -> bool:
         return os.path.isfile(fpath) and os.access(fpath, os.X_OK)
 
     fpath, fname = os.path.split(program)
diff --git a/openhands/resolver/resolve_all_issues.py b/openhands/resolver/resolve_all_issues.py
index 6aa32396545d..7696c06d2ad2 100644
--- a/openhands/resolver/resolve_all_issues.py
+++ b/openhands/resolver/resolve_all_issues.py
@@ -6,8 +6,9 @@
 import os
 import pathlib
 import subprocess
-from typing import Awaitable, TextIO
+from typing import Any, Awaitable, TextIO
 
+from pydantic import SecretStr
 from tqdm import tqdm
 
 import openhands
@@ -25,7 +26,7 @@
 )
 
 
-def cleanup():
+def cleanup() -> None:
     print('Cleaning up child processes...')
     for process in mp.active_children():
         print(f'Terminating child process: {process.name}')
@@ -214,7 +215,7 @@ async def resolve_issues(
         # Use asyncio.gather with a semaphore to limit concurrency
         sem = asyncio.Semaphore(num_workers)
 
-        async def run_with_semaphore(task):
+        async def run_with_semaphore(task: Awaitable[Any]) -> Any:
             async with sem:
                 return await task
 
@@ -228,7 +229,7 @@ async def run_with_semaphore(task):
     logger.info('Finished.')
 
 
-def main():
+def main() -> None:
     parser = argparse.ArgumentParser(
         description='Resolve multiple issues from Github or Gitlab.'
     )
@@ -349,7 +350,7 @@ def main():
 
     llm_config = LLMConfig(
         model=my_args.llm_model or os.environ['LLM_MODEL'],
-        api_key=str(api_key) if api_key else None,
+        api_key=SecretStr(api_key) if api_key else None,
         base_url=my_args.llm_base_url or os.environ.get('LLM_BASE_URL', None),
     )
 
diff --git a/openhands/resolver/resolve_issue.py b/openhands/resolver/resolve_issue.py
index 80cddb9ed581..9a686815da38 100644
--- a/openhands/resolver/resolve_issue.py
+++ b/openhands/resolver/resolve_issue.py
@@ -10,6 +10,7 @@
 from typing import Any
 from uuid import uuid4
 
+from pydantic import SecretStr
 from termcolor import colored
 
 import openhands
@@ -18,6 +19,7 @@
 from openhands.core.logger import openhands_logger as logger
 from openhands.core.main import create_runtime, run_controller
 from openhands.events.action import CmdRunAction, MessageAction
+from openhands.events.event import Event
 from openhands.events.observation import (
     CmdOutputObservation,
     ErrorObservation,
@@ -48,7 +50,7 @@
 def initialize_runtime(
     runtime: Runtime,
     platform: Platform,
-):
+) -> None:
     """Initialize the runtime for the agent.
 
     This function is called before the runtime is used to run the agent.
@@ -192,26 +194,28 @@ async def process_issue(
     # This code looks unnecessary because these are default values in the config class
     # they're set by default if nothing else overrides them
     # FIXME we should remove them here
-    kwargs = {}
+    sandbox_config = SandboxConfig(
+        runtime_container_image=runtime_container_image,
+        enable_auto_lint=False,
+        use_host_network=False,
+        # large enough timeout, since some testcases take very long to run
+        timeout=300,
+    )
+
     if os.getenv('GITLAB_CI') == 'True':
-        kwargs['local_runtime_url'] = os.getenv('LOCAL_RUNTIME_URL', 'http://localhost')
+        sandbox_config.local_runtime_url = os.getenv(
+            'LOCAL_RUNTIME_URL', 'http://localhost'
+        )
         user_id = os.getuid() if hasattr(os, 'getuid') else 1000
         if user_id == 0:
-            kwargs['user_id'] = get_unique_uid()
+            sandbox_config.user_id = get_unique_uid()
 
     config = AppConfig(
         default_agent='CodeActAgent',
         runtime='docker',
         max_budget_per_task=4,
         max_iterations=max_iterations,
-        sandbox=SandboxConfig(
-            runtime_container_image=runtime_container_image,
-            enable_auto_lint=False,
-            use_host_network=False,
-            # large enough timeout, since some testcases take very long to run
-            timeout=300,
-            **kwargs,
-        ),
+        sandbox=sandbox_config,
         # do not mount workspace
         workspace_base=workspace_base,
         workspace_mount_path=workspace_base,
@@ -222,7 +226,7 @@ async def process_issue(
     runtime = create_runtime(config)
     await runtime.connect()
 
-    def on_event(evt):
+    def on_event(evt: Event) -> None:
         logger.info(evt)
 
     runtime.event_stream.subscribe(EventStreamSubscriber.MAIN, on_event, str(uuid4()))
@@ -524,10 +528,10 @@ async def resolve_issue(
         logger.info('Finished.')
 
 
-def main():
+def main() -> None:
     import argparse
 
-    def int_or_none(value):
+    def int_or_none(value: str) -> int | None:
         if value.lower() == 'none':
             return None
         else:
@@ -654,7 +658,7 @@ def int_or_none(value):
     api_key = my_args.llm_api_key or os.environ['LLM_API_KEY']
     llm_config = LLMConfig(
         model=my_args.llm_model or os.environ['LLM_MODEL'],
-        api_key=str(api_key) if api_key else None,
+        api_key=SecretStr(api_key) if api_key else None,
         base_url=my_args.llm_base_url or os.environ.get('LLM_BASE_URL', None),
     )
 
diff --git a/openhands/resolver/send_pull_request.py b/openhands/resolver/send_pull_request.py
index 7cbe37cfcca0..0ca032e4da97 100644
--- a/openhands/resolver/send_pull_request.py
+++ b/openhands/resolver/send_pull_request.py
@@ -5,6 +5,7 @@
 import subprocess
 
 import jinja2
+from pydantic import SecretStr
 
 from openhands.core.config import LLMConfig
 from openhands.core.logger import openhands_logger as logger
@@ -543,7 +544,7 @@ def process_all_successful_issues(
             )
 
 
-def main():
+def main() -> None:
     parser = argparse.ArgumentParser(
         description='Send a pull request to Github or Gitlab.'
     )
@@ -641,7 +642,7 @@ def main():
     api_key = my_args.llm_api_key or os.environ['LLM_API_KEY']
     llm_config = LLMConfig(
         model=my_args.llm_model or os.environ['LLM_MODEL'],
-        api_key=str(api_key) if api_key else None,
+        api_key=SecretStr(api_key) if api_key else None,
         base_url=my_args.llm_base_url or os.environ.get('LLM_BASE_URL', None),
     )
 
diff --git a/openhands/resolver/utils.py b/openhands/resolver/utils.py
index b0e25861ccb7..d08686d592e3 100644
--- a/openhands/resolver/utils.py
+++ b/openhands/resolver/utils.py
@@ -107,7 +107,7 @@ def codeact_user_response(
     return msg
 
 
-def cleanup():
+def cleanup() -> None:
     print('Cleaning up child processes...')
     for process in mp.active_children():
         print(f'Terminating child process: {process.name}')
@@ -115,7 +115,9 @@ def cleanup():
         process.join()
 
 
-def prepare_dataset(dataset: pd.DataFrame, output_file: str, eval_n_limit: int):
+def prepare_dataset(
+    dataset: pd.DataFrame, output_file: str, eval_n_limit: int
+) -> pd.DataFrame:
     assert 'instance_id' in dataset.columns, (
         "Expected 'instance_id' column in the dataset. You should define your own "
         "unique identifier for each instance and use it as the 'instance_id' column."
@@ -152,7 +154,7 @@ def prepare_dataset(dataset: pd.DataFrame, output_file: str, eval_n_limit: int):
 
 def reset_logger_for_multiprocessing(
     logger: logging.Logger, instance_id: str, log_dir: str
-):
+) -> None:
     """Reset the logger for multiprocessing.
 
     Save logs to a separate file for each process, instead of trying to write to the
@@ -208,7 +210,7 @@ def extract_issue_references(body: str) -> list[int]:
     return [int(match) for match in re.findall(pattern, body)]
 
 
-def get_unique_uid(start_uid=1000):
+def get_unique_uid(start_uid: int = 1000) -> int:
     existing_uids = set()
     with open('/etc/passwd', 'r') as passwd_file:
         for line in passwd_file:
diff --git a/openhands/resolver/visualize_resolver_output.py b/openhands/resolver/visualize_resolver_output.py
index f7081f6c76f4..ca0717d84088 100644
--- a/openhands/resolver/visualize_resolver_output.py
+++ b/openhands/resolver/visualize_resolver_output.py
@@ -4,7 +4,9 @@
 from openhands.resolver.io_utils import load_single_resolver_output
 
 
-def visualize_resolver_output(issue_number: int, output_dir: str, vis_method: str):
+def visualize_resolver_output(
+    issue_number: int, output_dir: str, vis_method: str
+) -> None:
     output_jsonl = os.path.join(output_dir, 'output.jsonl')
     resolver_output = load_single_resolver_output(output_jsonl, issue_number)
     if vis_method == 'json':