diff --git a/ui/src/components/ChatAgentSelector.test.tsx b/ui/src/components/ChatAgentSelector.test.tsx
new file mode 100644
index 00000000..bde7fc2c
--- /dev/null
+++ b/ui/src/components/ChatAgentSelector.test.tsx
@@ -0,0 +1,9 @@
+import { describe, it } from "vitest";
+
+describe("ChatAgentSelector", () => {
+  it.todo("renders active agent icon and name when agentId is set");
+  it.todo("renders 'Select agent' placeholder when no agent selected");
+  it.todo("lists all workspace agents in dropdown");
+  it.todo("calls onAgentChange with new agentId on selection");
+  it.todo("shows 'No agents configured' when agent list is empty");
+});
diff --git a/ui/src/components/ChatMentionPopover.test.tsx b/ui/src/components/ChatMentionPopover.test.tsx
new file mode 100644
index 00000000..c1956822
--- /dev/null
+++ b/ui/src/components/ChatMentionPopover.test.tsx
@@ -0,0 +1,8 @@
+import { describe, it } from "vitest";
+
+describe("ChatMentionPopover", () => {
+  it.todo("renders agent list filtered by query string");
+  it.todo("shows agent icon, name, and role for each item");
+  it.todo("calls onSelect with @agentName on item click");
+  it.todo("shows 'No agents found' when filter matches nothing");
+});
diff --git a/ui/src/components/ChatMessage.test.tsx b/ui/src/components/ChatMessage.test.tsx
new file mode 100644
index 00000000..2251af72
--- /dev/null
+++ b/ui/src/components/ChatMessage.test.tsx
@@ -0,0 +1,12 @@
+import { describe, it } from "vitest";
+
+describe("ChatMessage", () => {
+  it.todo("renders user message as right-aligned bubble with plain text");
+  it.todo("renders assistant message with ChatMarkdownMessage");
+  it.todo("renders ChatMessageIdentityBar for assistant messages when agentName is provided");
+  it.todo("shows edit pencil on hover for user messages");
+  it.todo("shows retry button on hover for assistant messages");
+  it.todo("hides retry button when isStreaming is true");
+  it.todo("switches to inline edit textarea on pencil click");
+  it.todo("renders ChatStreamingCursor when isStreaming is true");
+});
diff --git a/ui/src/components/ChatMessageIdentityBar.test.tsx b/ui/src/components/ChatMessageIdentityBar.test.tsx
new file mode 100644
index 00000000..de028bd6
--- /dev/null
+++ b/ui/src/components/ChatMessageIdentityBar.test.tsx
@@ -0,0 +1,8 @@
+import { describe, it } from "vitest";
+
+describe("ChatMessageIdentityBar", () => {
+  it.todo("renders agent icon at 16x16px");
+  it.todo("renders agent name in semibold text");
+  it.todo("renders timestamp in muted text");
+  it.todo("applies role-specific color from agentRoleColors");
+});
diff --git a/ui/src/components/ChatMessageList.test.tsx b/ui/src/components/ChatMessageList.test.tsx
new file mode 100644
index 00000000..71ad87ff
--- /dev/null
+++ b/ui/src/components/ChatMessageList.test.tsx
@@ -0,0 +1,9 @@
+import { describe, it } from "vitest";
+
+describe("ChatMessageList", () => {
+  it.todo("renders messages using virtualizer");
+  it.todo("auto-scrolls to bottom when new messages arrive");
+  it.todo("shows loading skeleton when isLoading");
+  it.todo("shows empty state when no messages");
+  it.todo("appends streaming message as synthetic entry");
+});
diff --git a/ui/src/components/ChatSlashCommandPopover.test.tsx b/ui/src/components/ChatSlashCommandPopover.test.tsx
new file mode 100644
index 00000000..a469d652
--- /dev/null
+++ b/ui/src/components/ChatSlashCommandPopover.test.tsx
@@ -0,0 +1,9 @@
+import { describe, it } from "vitest";
+
+describe("ChatSlashCommandPopover", () => {
+  it.todo("renders 5 slash command items when open");
+  it.todo("filters commands by typed query");
+  it.todo("calls onSelect with command string on item click");
+  it.todo("closes on Escape key");
+  it.todo("shows /search as greyed out with 'Coming soon' suffix");
+});
diff --git a/ui/src/hooks/useStreamingChat.test.ts b/ui/src/hooks/useStreamingChat.test.ts
new file mode 100644
index 00000000..26f770b5
--- /dev/null
+++ b/ui/src/hooks/useStreamingChat.test.ts
@@ -0,0 +1,9 @@
+import { describe, it } from "vitest";
+
+describe("useStreamingChat", () => {
+  it.todo("accumulates tokens from SSE data events into streamingContent");
+  it.todo("sets isStreaming=true when stream starts, false when done");
+  it.todo("clears streamingContent and invalidates query cache on done event");
+  it.todo("stop() closes the EventSource and sets isStreaming=false");
+  it.todo("handles SSE error event by closing connection");
+});