diff --git a/agent/auxiliary_client.py b/agent/auxiliary_client.py
index 0afb0add20bf6..490f84dc26720 100644
--- a/agent/auxiliary_client.py
+++ b/agent/auxiliary_client.py
@@ -1307,7 +1307,7 @@ def _read_nous_auth() -> Optional[dict]:
     try:
         if not _AUTH_JSON_PATH.is_file():
             return None
-        data = json.loads(_AUTH_JSON_PATH.read_text())
+        data = json.loads(_AUTH_JSON_PATH.read_text(encoding="utf-8"))
         if data.get("active_provider") != "nous":
             return None
         provider = data.get("providers", {}).get("nous", {})
diff --git a/agent/copilot_acp_client.py b/agent/copilot_acp_client.py
index e3c03938af40d..4b5f67ca0caaa 100644
--- a/agent/copilot_acp_client.py
+++ b/agent/copilot_acp_client.py
@@ -630,7 +630,7 @@ def _handle_server_message(
                 if block_error:
                     raise PermissionError(block_error)
                 try:
-                    content = path.read_text()
+                    content = path.read_text(encoding="utf-8")
                 except FileNotFoundError:
                     content = ""
                 line = params.get("line")
@@ -659,7 +659,7 @@ def _handle_server_message(
                         f"Write denied: '{path}' is a protected system/credential file."
                     )
                 path.parent.mkdir(parents=True, exist_ok=True)
-                path.write_text(str(params.get("content") or ""))
+                path.write_text(str(params.get("content") or ""), encoding="utf-8")
                 response = {
                     "jsonrpc": "2.0",
                     "id": message_id,
diff --git a/agent/credential_sources.py b/agent/credential_sources.py
index f99a758625746..ec25eda87d79e 100644
--- a/agent/credential_sources.py
+++ b/agent/credential_sources.py
@@ -164,7 +164,7 @@ def _remove_env_source(provider: str, removed) -> RemovalResult:
         if env_path.exists():
             env_in_dotenv = any(
                 line.strip().startswith(f"{env_var}=")
-                for line in env_path.read_text(errors="replace").splitlines()
+                for line in env_path.read_text(encoding="utf-8", errors="replace").splitlines()
             )
     except OSError:
         pass
diff --git a/agent/shell_hooks.py b/agent/shell_hooks.py
index 97ba3862120bc..c9aec296818e2 100644
--- a/agent/shell_hooks.py
+++ b/agent/shell_hooks.py
@@ -603,7 +603,7 @@ def allowlist_path() -> Path:
 def load_allowlist() -> Dict[str, Any]:
     """Return the parsed allowlist, or an empty skeleton if absent."""
     try:
-        raw = json.loads(allowlist_path().read_text())
+        raw = json.loads(allowlist_path().read_text(encoding="utf-8"))
     except (FileNotFoundError, json.JSONDecodeError, OSError):
         return {"approvals": []}
     if not isinstance(raw, dict):
diff --git a/tools/managed_tool_gateway.py b/tools/managed_tool_gateway.py
index d894dcb4b29b2..2bbc9dcff16ce 100644
--- a/tools/managed_tool_gateway.py
+++ b/tools/managed_tool_gateway.py
@@ -37,7 +37,7 @@ def _read_nous_provider_state() -> Optional[dict]:
         path = auth_json_path()
         if not path.is_file():
             return None
-        data = json.loads(path.read_text())
+        data = json.loads(path.read_text(encoding="utf-8"))
         providers = data.get("providers", {})
         if not isinstance(providers, dict):
             return None
diff --git a/tools/skills_sync.py b/tools/skills_sync.py
index a8a7265f95bf1..3127c80c8dd46 100644
--- a/tools/skills_sync.py
+++ b/tools/skills_sync.py
@@ -373,7 +373,7 @@ def _backfill_optional_provenance(quiet: bool = False) -> List[str]:
 
     lock_path = SKILLS_DIR / ".hub" / "lock.json"
     try:
-        data = json.loads(lock_path.read_text()) if lock_path.exists() else {"version": 1, "installed": {}}
+        data = json.loads(lock_path.read_text(encoding="utf-8")) if lock_path.exists() else {"version": 1, "installed": {}}
     except (json.JSONDecodeError, OSError):
         data = {"version": 1, "installed": {}}
     installed = data.setdefault("installed", {})