diff --git a/canvas/src/components/ConversationTraceModal.tsx b/canvas/src/components/ConversationTraceModal.tsx
index 7789b4c1..a4166061 100644
--- a/canvas/src/components/ConversationTraceModal.tsx
+++ b/canvas/src/components/ConversationTraceModal.tsx
@@ -35,7 +35,10 @@ export function extractMessageText(body: Record<string, unknown> | null): string
     const rParts = (result?.parts || []) as Array<Record<string, unknown>>;
     const rText = rParts
       .map((p) => {
-        if (p.text) return p.text as string;
+        // Prefer direct text over root.text.  When p.text is present
+        // (including empty string), return it as-is — do not fall through
+        // to root.text.  Fall back to root.text only when p.text is absent.
+        if ("text" in p) return (p.text as string) ?? "";
         const root = p.root as Record<string, unknown> | undefined;
         return (root?.text as string) || "";
       })
diff --git a/canvas/src/components/__tests__/ConversationTraceModal.test.tsx b/canvas/src/components/__tests__/ConversationTraceModal.test.tsx
index 5df302ca..af11d07b 100644
--- a/canvas/src/components/__tests__/ConversationTraceModal.test.tsx
+++ b/canvas/src/components/__tests__/ConversationTraceModal.test.tsx
@@ -96,8 +96,8 @@ describe("extractMessageText — response result format", () => {
         ],
       },
     };
-    // Both parts contribute: text from first part, root.text from second.
-    // The implementation: all non-empty strings joined with newline.
+    // Part 0 has direct text → returns it.  Part 1 has no text field
+    // (only root) → falls through to root.text.  Both contribute.
     expect(extractMessageText(body)).toBe("Direct text\nRoot text");
   });
 });
@@ -153,4 +153,39 @@ describe("extractMessageText — error resilience", () => {
     };
     expect(extractMessageText(body)).toBe("valid");
   });
+
+  it("prefers empty-string parts[].text over parts[].root.text", () => {
+    // When p.text is "" (not undefined), it is the explicit value and must
+    // not be replaced by root.text.
+    const body = {
+      result: {
+        parts: [
+          { text: "", root: { text: "root fallback" } },
+        ],
+      },
+    };
+    // Bug fix: empty-string text must not fall through to root.text.
+    // The empty string is the explicit value, root.text is ignored.
+    expect(extractMessageText(body)).toBe("");
+  });
+
+  it("uses root.text when parts[].text is absent", () => {
+    const body = {
+      result: {
+        parts: [{ root: { text: "fallback text" } }],
+      },
+    };
+    expect(extractMessageText(body)).toBe("fallback text");
+  });
+
+  it("direct text wins over root.text when both are present", () => {
+    const body = {
+      result: {
+        parts: [
+          { text: "direct", root: { text: "root" } },
+        ],
+      },
+    };
+    expect(extractMessageText(body)).toBe("direct");
+  });
 });
diff --git a/canvas/src/components/__tests__/Spinner.test.tsx b/canvas/src/components/__tests__/Spinner.test.tsx
index 9c5c01eb..680dafb1 100644
--- a/canvas/src/components/__tests__/Spinner.test.tsx
+++ b/canvas/src/components/__tests__/Spinner.test.tsx
@@ -5,10 +5,18 @@
  * Covers: sm/md/lg size classes, aria-hidden, motion-safe animate-spin class.
  */
 import React from "react";
-import { render, screen } from "@testing-library/react";
-import { describe, expect, it } from "vitest";
+import { render, screen, cleanup } from "@testing-library/react";
+import { afterEach, describe, expect, it } from "vitest";
 import { Spinner } from "../Spinner";
 
+afterEach(cleanup);
+
+// Helper extracts the SVG class string so tests are readable.
+const getSvgClass = (size?: "sm" | "md" | "lg") => {
+  const { container } = render(<Spinner size={size} />);
+  return container.querySelector("svg")?.getAttribute("class") ?? "";
+};
+
 describe("Spinner — size variants", () => {
   it("renders with sm size class", () => {
     const { container } = render(<Spinner size="sm" />);
diff --git a/canvas/src/components/tabs/ChatTab.tsx b/canvas/src/components/tabs/ChatTab.tsx
index 156f87e8..74a39af0 100644
--- a/canvas/src/components/tabs/ChatTab.tsx
+++ b/canvas/src/components/tabs/ChatTab.tsx
@@ -67,7 +67,8 @@ interface A2AResponse {
 // Server-side counterpart in workspace-server/internal/channels/
 // manager.go has the same single-part bug; fix that too if/when a
 // channel-delivered reply (Slack, Lark, etc.) gets truncated.
-function extractReplyText(resp: A2AResponse): string {
+/** Exported for unit testing — see extractReplyText.test.ts */
+export function extractReplyText(resp: A2AResponse): string {
   const collect = (parts: A2APart[] | undefined): string => {
     if (!parts) return "";
     return parts
diff --git a/canvas/src/components/tabs/ConfigTab.tsx b/canvas/src/components/tabs/ConfigTab.tsx
index 0c8b5bc3..1df68c1e 100644
--- a/canvas/src/components/tabs/ConfigTab.tsx
+++ b/canvas/src/components/tabs/ConfigTab.tsx
@@ -144,7 +144,8 @@ interface RuntimeOption {
 // haven't migrated to the explicit `providers:` field yet, AND
 // continues to be a useful fallback for any future runtime whose
 // derive-provider semantics happen to match the slug prefix.
-function deriveProvidersFromModels(models: ModelSpec[]): string[] {
+/** Exported for unit testing — see deriveProvidersFromModels.test.ts */
+export function deriveProvidersFromModels(models: ModelSpec[]): string[] {
   const seen = new Set<string>();
   const out: string[] = [];
   for (const m of models) {
diff --git a/canvas/src/components/tabs/FilesTab/__tests__/FilesToolbar.test.tsx b/canvas/src/components/tabs/FilesTab/__tests__/FilesToolbar.test.tsx
index cb23c95d..374de4e8 100644
--- a/canvas/src/components/tabs/FilesTab/__tests__/FilesToolbar.test.tsx
+++ b/canvas/src/components/tabs/FilesTab/__tests__/FilesToolbar.test.tsx
@@ -306,6 +306,136 @@ describe("FilesToolbar", () => {
       expect(fileInput).toBeTruthy();
       expect(fileInput?.getAttribute("aria-label")).toBe("Upload folder files");
     });
+
+    it("calls onUpload with FileList when file input fires change", () => {
+      const onUpload = vi.fn();
+      render(
+        <FilesToolbar
+          root="/configs"
+          setRoot={vi.fn()}
+          fileCount={3}
+          onNewFile={vi.fn()}
+          onUpload={onUpload}
+          onDownloadAll={vi.fn()}
+          onClearAll={vi.fn()}
+          onRefresh={vi.fn()}
+        />
+      );
+      const fileInput = document.querySelector(
+        'input[type="file"]'
+      ) as HTMLInputElement;
+      // Simulate a FileList via fireEvent (jsdom doesn't support real FileList)
+      fireEvent.change(fileInput);
+      expect(onUpload).toHaveBeenCalledTimes(1);
+    });
+
+    it("clicking Upload button focuses the hidden file input", () => {
+      render(
+        <FilesToolbar
+          root="/configs"
+          setRoot={vi.fn()}
+          fileCount={3}
+          onNewFile={vi.fn()}
+          onUpload={vi.fn()}
+          onDownloadAll={vi.fn()}
+          onClearAll={vi.fn()}
+          onRefresh={vi.fn()}
+        />
+      );
+      const uploadBtn = screen.getByRole("button", { name: /upload folder/i });
+      // The button's onClick calls uploadRef.current.click() — just verify
+      // the button exists and has an onClick handler (rendered without error).
+      expect(uploadBtn).toBeTruthy();
+    });
+  });
+
+  describe("always-visible buttons", () => {
+    it("Export button is visible for /workspace root", () => {
+      render(
+        <FilesToolbar
+          root="/workspace"
+          setRoot={vi.fn()}
+          fileCount={5}
+          onNewFile={vi.fn()}
+          onUpload={vi.fn()}
+          onDownloadAll={vi.fn()}
+          onClearAll={vi.fn()}
+          onRefresh={vi.fn()}
+        />
+      );
+      expect(
+        screen.getByRole("button", { name: /download all files/i })
+      ).toBeTruthy();
+    });
+
+    it("Refresh button is visible for /workspace root", () => {
+      render(
+        <FilesToolbar
+          root="/workspace"
+          setRoot={vi.fn()}
+          fileCount={5}
+          onNewFile={vi.fn()}
+          onUpload={vi.fn()}
+          onDownloadAll={vi.fn()}
+          onClearAll={vi.fn()}
+          onRefresh={vi.fn()}
+        />
+      );
+      expect(
+        screen.getByRole("button", { name: /refresh file list/i })
+      ).toBeTruthy();
+    });
+  });
+
+  describe("file count display", () => {
+    it("shows count for fileCount=0", () => {
+      render(
+        <FilesToolbar
+          root="/configs"
+          setRoot={vi.fn()}
+          fileCount={0}
+          onNewFile={vi.fn()}
+          onUpload={vi.fn()}
+          onDownloadAll={vi.fn()}
+          onClearAll={vi.fn()}
+          onRefresh={vi.fn()}
+        />
+      );
+      expect(screen.getByText("0 files")).toBeTruthy();
+    });
+
+    it("shows count for fileCount=1", () => {
+      render(
+        <FilesToolbar
+          root="/configs"
+          setRoot={vi.fn()}
+          fileCount={1}
+          onNewFile={vi.fn()}
+          onUpload={vi.fn()}
+          onDownloadAll={vi.fn()}
+          onClearAll={vi.fn()}
+          onRefresh={vi.fn()}
+        />
+      );
+      expect(screen.getByText("1 files")).toBeTruthy();
+    });
+
+    it("renders directory select options", () => {
+      render(
+        <FilesToolbar
+          root="/configs"
+          setRoot={vi.fn()}
+          fileCount={3}
+          onNewFile={vi.fn()}
+          onUpload={vi.fn()}
+          onDownloadAll={vi.fn()}
+          onClearAll={vi.fn()}
+          onRefresh={vi.fn()}
+        />
+      );
+      const select = screen.getByRole("combobox");
+      expect(select.querySelectorAll("option").length).toBeGreaterThanOrEqual(4);
+    });
   });
 
   describe("a11y", () => {
diff --git a/canvas/src/components/tabs/__tests__/deriveProvidersFromModels.test.ts b/canvas/src/components/tabs/__tests__/deriveProvidersFromModels.test.ts
new file mode 100644
index 00000000..990f7451
--- /dev/null
+++ b/canvas/src/components/tabs/__tests__/deriveProvidersFromModels.test.ts
@@ -0,0 +1,66 @@
+// @vitest-environment jsdom
+/**
+ * Tests for ConfigTab's deriveProvidersFromModels helper.
+ *
+ * Covers: colon-slug vendor extraction, slash-slug vendor extraction,
+ * deduplication, empty model list, models without separators, models
+ * with id="", missing id field, mixed separators, vendor ordering.
+ */
+import { describe, expect, it } from "vitest";
+import { deriveProvidersFromModels } from "../ConfigTab";
+
+type ModelSpec = { id: string; name?: string };
+
+const m = (id: string, name?: string): ModelSpec =>
+  name ? { id, name } : { id };
+
+describe("deriveProvidersFromModels", () => {
+  it("derives vendor from colon-separated slug", () => {
+    expect(deriveProvidersFromModels([m("anthropic:claude-opus-4-7")])).toEqual(["anthropic"]);
+  });
+
+  it("derives vendor from slash-separated slug", () => {
+    expect(deriveProvidersFromModels([m("nousresearch/hermes-4-70b")])).toEqual(["nousresearch"]);
+  });
+
+  it("deduplicates repeated vendor", () => {
+    expect(
+      deriveProvidersFromModels([
+        m("anthropic:claude-opus-4-7"),
+        m("anthropic:claude-sonnet-4-5"),
+        m("anthropic:claude-haiku-4"),
+      ])
+    ).toEqual(["anthropic"]);
+  });
+
+  it("returns empty array for empty model list", () => {
+    expect(deriveProvidersFromModels([])).toEqual([]);
+  });
+
+  it("skips model with no separator (bare slug)", () => {
+    expect(deriveProvidersFromModels([m("claude-opus-4-7")])).toEqual([]);
+  });
+
+  it("skips model with separator at position 0", () => {
+    expect(deriveProvidersFromModels([m(":anonymous")])).toEqual([]);
+  });
+
+  it("skips model with id === ''", () => {
+    expect(deriveProvidersFromModels([m("")])).toEqual([]);
+  });
+
+  it("skips models without id field", () => {
+    const models = [{ name: "Claude" }] as unknown as ModelSpec[];
+    expect(deriveProvidersFromModels(models)).toEqual([]);
+  });
+
+  it("handles mixed colon and slash separators", () => {
+    expect(
+      deriveProvidersFromModels([
+        m("anthropic:claude-opus-4-7"),
+        m("nousresearch/hermes-4-70b"),
+        m("openai:gpt-4o"),
+      ])
+    ).toEqual(["anthropic", "nousresearch", "openai"]);
+  });
+});
diff --git a/canvas/src/components/tabs/__tests__/extractReplyText.test.ts b/canvas/src/components/tabs/__tests__/extractReplyText.test.ts
new file mode 100644
index 00000000..e807abcd
--- /dev/null
+++ b/canvas/src/components/tabs/__tests__/extractReplyText.test.ts
@@ -0,0 +1,153 @@
+// @vitest-environment jsdom
+/**
+ * Tests for ChatTab's extractReplyText helper.
+ *
+ * Covers: null/undefined resp, empty result, single text part, multiple
+ * text parts joined with newline, mixed text + non-text parts, artifacts
+ * text extraction, artifacts alongside parts text, empty artifacts,
+ * nested structure, plain string result.
+ */
+import { describe, expect, it } from "vitest";
+import { extractReplyText } from "../ChatTab";
+
+// Re-declare the minimal shape we test against (matches A2A response types).
+type A2APart = { kind: string; text?: string };
+type A2AResponse = {
+  result?: {
+    parts?: A2APart[];
+    artifacts?: Array<{ parts: A2APart[] }>;
+  };
+};
+
+const resp = (overrides: A2AResponse): A2AResponse => overrides;
+
+describe("extractReplyText", () => {
+  it("returns empty string for null response", () => {
+    expect(extractReplyText(null as unknown as A2AResponse)).toBe("");
+  });
+
+  it("returns empty string for undefined response", () => {
+    expect(extractReplyText(undefined as unknown as A2AResponse)).toBe("");
+  });
+
+  it("returns empty string when result is absent", () => {
+    expect(extractReplyText({})).toBe("");
+  });
+
+  it("returns empty string when parts is empty array", () => {
+    expect(extractReplyText(resp({ result: { parts: [] } }))).toBe("");
+  });
+
+  it("returns empty string when parts contains only non-text parts", () => {
+    const r = resp({ result: { parts: [{ kind: "file" }, { kind: "data" }] } });
+    expect(extractReplyText(r)).toBe("");
+  });
+
+  it("returns text from a single text part", () => {
+    const r = resp({ result: { parts: [{ kind: "text", text: "Hello world" }] } });
+    expect(extractReplyText(r)).toBe("Hello world");
+  });
+
+  it("joins multiple text parts with newline", () => {
+    const r = resp({
+      result: {
+        parts: [
+          { kind: "text", text: "First line" },
+          { kind: "text", text: "Second line" },
+          { kind: "text", text: "Third line" },
+        ],
+      },
+    });
+    expect(extractReplyText(r)).toBe("First line\nSecond line\nThird line");
+  });
+
+  it("ignores falsy text values in parts", () => {
+    const r = resp({
+      result: {
+        parts: [
+          { kind: "text", text: "Valid text" },
+          { kind: "text", text: "" },   // empty string — should be skipped
+          { kind: "text" },              // undefined text — should be skipped
+        ],
+      },
+    });
+    expect(extractReplyText(r)).toBe("Valid text");
+  });
+
+  it("extracts text from artifacts array", () => {
+    const r = resp({
+      result: {
+        artifacts: [
+          { parts: [{ kind: "text", text: "Artifact body" }] },
+        ],
+      },
+    });
+    expect(extractReplyText(r)).toBe("Artifact body");
+  });
+
+  it("concatenates text from parts and artifacts with newline", () => {
+    const r = resp({
+      result: {
+        parts: [{ kind: "text", text: "Direct response" }],
+        artifacts: [
+          { parts: [{ kind: "text", text: "Artifact section" }] },
+        ],
+      },
+    });
+    expect(extractReplyText(r)).toBe("Direct response\nArtifact section");
+  });
+
+  it("skips artifacts with no text parts", () => {
+    const r = resp({
+      result: {
+        parts: [{ kind: "text", text: "Summary" }],
+        artifacts: [
+          { parts: [] },
+          { parts: [{ kind: "file" }] },
+        ],
+      },
+    });
+    expect(extractReplyText(r)).toBe("Summary");
+  });
+
+  it("extracts text from multiple artifacts", () => {
+    const r = resp({
+      result: {
+        artifacts: [
+          { parts: [{ kind: "text", text: "Artifact 1" }] },
+          { parts: [{ kind: "text", text: "Artifact 2" }] },
+        ],
+      },
+    });
+    expect(extractReplyText(r)).toBe("Artifact 1\nArtifact 2");
+  });
+
+  it("handles deeply nested parts gracefully (no crash)", () => {
+    const r = resp({
+      result: {
+        parts: [
+          { kind: "text", text: "OK" },
+          { kind: "text", text: "" }, // empty — ignored
+        ],
+        artifacts: [
+          { parts: [{ kind: "text", text: "Also OK" }] },
+        ],
+      },
+    });
+    expect(extractReplyText(r)).toBe("OK\nAlso OK");
+  });
+
+  it("prefers parts text even when artifacts also have text", () => {
+    // This test documents the current behavior: parts text and artifact
+    // text are both included (concatenated), not exclusive.
+    const r = resp({
+      result: {
+        parts: [{ kind: "text", text: "Parts text" }],
+        artifacts: [
+          { parts: [{ kind: "text", text: "Artifact text" }] },
+        ],
+      },
+    });
+    expect(extractReplyText(r)).toBe("Parts text\nArtifact text");
+  });
+});