diff --git a/tests/test_agent_render_ownership.py b/tests/test_agent_render_ownership.py
index 67e422b90..3246e2272 100644
--- a/tests/test_agent_render_ownership.py
+++ b/tests/test_agent_render_ownership.py
@@ -10,7 +10,7 @@ import unittest
 
 
 path = Path(__file__).resolve().parents[1] / "routes/chat_routes.py"
-tree = ast.parse(path.read_text())
+tree = ast.parse(path.read_text(encoding="utf-8"))
 node = next(n for n in tree.body if isinstance(n, ast.ClassDef) and n.name == "_AgentRenderState")
 namespace = {}
 exec(compile(ast.Module(body=[node], type_ignores=[]), str(path), "exec"), namespace)
diff --git a/tests/test_background_chat_completion_ui_static.py b/tests/test_background_chat_completion_ui_static.py
index 436da2f3d..51f5d176c 100644
--- a/tests/test_background_chat_completion_ui_static.py
+++ b/tests/test_background_chat_completion_ui_static.py
@@ -3,8 +3,8 @@ from tests.helpers.stylesheets import app_css
 
 
 ROOT = Path(__file__).resolve().parents[1]
-CHAT = (ROOT / "static/js/chat.js").read_text()
-SESSIONS = (ROOT / "static/js/sessions.js").read_text()
+CHAT = (ROOT / "static/js/chat.js").read_text(encoding="utf-8")
+SESSIONS = (ROOT / "static/js/sessions.js").read_text(encoding="utf-8")
 CSS = app_css()
 
 
diff --git a/tests/test_chat_ttft_timer_static.py b/tests/test_chat_ttft_timer_static.py
index cf1e00566..fe1b5bc60 100644
--- a/tests/test_chat_ttft_timer_static.py
+++ b/tests/test_chat_ttft_timer_static.py
@@ -2,8 +2,8 @@ from pathlib import Path
 
 
 ROOT = Path(__file__).resolve().parents[1]
-CHAT = (ROOT / "static/js/chat.js").read_text()
-RENDERER = (ROOT / "static/js/chatRenderer.js").read_text()
+CHAT = (ROOT / "static/js/chat.js").read_text(encoding="utf-8")
+RENDERER = (ROOT / "static/js/chatRenderer.js").read_text(encoding="utf-8")
 
 
 def test_processing_indicator_shows_live_ttft_timer():
diff --git a/tests/test_interrupted_resume_label_static.py b/tests/test_interrupted_resume_label_static.py
index b56119da6..5ff62a144 100644
--- a/tests/test_interrupted_resume_label_static.py
+++ b/tests/test_interrupted_resume_label_static.py
@@ -4,11 +4,11 @@ from tests.helpers.stylesheets import app_css
 
 
 ROOT = Path(__file__).resolve().parents[1]
-CHAT = (ROOT / "static/js/chat.js").read_text()
-RENDERER = (ROOT / "static/js/chatRenderer.js").read_text()
+CHAT = (ROOT / "static/js/chat.js").read_text(encoding="utf-8")
+RENDERER = (ROOT / "static/js/chatRenderer.js").read_text(encoding="utf-8")
 STYLE = app_css()
-APP = (ROOT / "static/app.js").read_text()
-INDEX = (ROOT / "static/index.html").read_text()
+APP = (ROOT / "static/app.js").read_text(encoding="utf-8")
+INDEX = (ROOT / "static/index.html").read_text(encoding="utf-8")
 
 
 def test_live_interruption_controls_have_visible_resume_labels():
diff --git a/tests/test_queued_message_merge_static.py b/tests/test_queued_message_merge_static.py
index ab73066fb..6f5805b29 100644
--- a/tests/test_queued_message_merge_static.py
+++ b/tests/test_queued_message_merge_static.py
@@ -2,7 +2,7 @@ from pathlib import Path
 
 
 ROOT = Path(__file__).resolve().parents[1]
-CHAT = (ROOT / "static/js/chat.js").read_text()
+CHAT = (ROOT / "static/js/chat.js").read_text(encoding="utf-8")
 
 
 def test_queued_stack_is_consumed_as_one_ordered_message():
diff --git a/tests/test_tab_stream_rejoin_static.py b/tests/test_tab_stream_rejoin_static.py
index ff00a014d..6ee6e81cb 100644
--- a/tests/test_tab_stream_rejoin_static.py
+++ b/tests/test_tab_stream_rejoin_static.py
@@ -2,7 +2,7 @@ from pathlib import Path
 
 
 ROOT = Path(__file__).resolve().parents[1]
-CHAT = (ROOT / "static/js/chat.js").read_text()
+CHAT = (ROOT / "static/js/chat.js").read_text(encoding="utf-8")
 
 
 def _visibility_handler() -> str:
diff --git a/tests/test_visual_report_mobile_toolbar.py b/tests/test_visual_report_mobile_toolbar.py
index e07f65054..bd3b6d931 100644
--- a/tests/test_visual_report_mobile_toolbar.py
+++ b/tests/test_visual_report_mobile_toolbar.py
@@ -5,7 +5,7 @@ from bs4 import BeautifulSoup
 from src.visual_report import generate_visual_report
 
 
-SOURCE = (Path(__file__).resolve().parents[1] / "src/visual_report.py").read_text()
+SOURCE = (Path(__file__).resolve().parents[1] / "src/visual_report.py").read_text(encoding="utf-8")
 
 
 def test_export_bookmark_is_anchored_and_expands_on_demand():
diff --git a/tests/test_web_search_tool_not_clickable_static.py b/tests/test_web_search_tool_not_clickable_static.py
index a782ffa7b..9d26d7a6f 100644
--- a/tests/test_web_search_tool_not_clickable_static.py
+++ b/tests/test_web_search_tool_not_clickable_static.py
@@ -2,8 +2,8 @@ from pathlib import Path
 
 
 ROOT = Path(__file__).resolve().parents[1]
-RENDERER = (ROOT / "static/js/chatRenderer.js").read_text()
-CHAT = (ROOT / "static/js/chat.js").read_text()
+RENDERER = (ROOT / "static/js/chatRenderer.js").read_text(encoding="utf-8")
+CHAT = (ROOT / "static/js/chat.js").read_text(encoding="utf-8")
 
 
 def test_saved_web_search_tool_icon_has_no_action_target():