diff --git a/Auto Run Docs/SpecKit-web-header-analyzer-Phase-03-Header-Input.md b/Auto Run Docs/SpecKit-web-header-analyzer-Phase-03-Header-Input.md
index 65b918b..ec01181 100644
--- a/Auto Run Docs/SpecKit-web-header-analyzer-Phase-03-Header-Input.md	
+++ b/Auto Run Docs/SpecKit-web-header-analyzer-Phase-03-Header-Input.md	
@@ -31,7 +31,9 @@ This phase implements the user-facing input layer: a multi-line textarea for pas
 - [x] T016 [US1] Create main page layout in `frontend/src/app/page.tsx` with dark hacker theme (#1e1e2e background, monospace code areas, project title). Responsive from 320px to 2560px (NFR-04)
 - [x] T017 [P] [US1] Create `frontend/src/components/HeaderInput.tsx` — multi-line textarea for SMTP headers with placeholder, character count, clear button (FontAwesome icon), monospace styling, keyboard accessible (NFR-02), validation for empty and oversized >1MB input (NFR-10). Verify `HeaderInput.test.tsx` passes (TDD Green)
 - [x] T018 [P] [US1] Create `frontend/src/components/FileDropZone.tsx` — drag-and-drop zone accepting `.eml` and `.txt` files, reads client-side via File API (FR-02), populates HeaderInput on drop, shows drag-over highlight and rejection feedback, FontAwesome upload icon. Verify `FileDropZone.test.tsx` passes (TDD Green)
-- [ ] T019 [US1] Create `frontend/src/components/AnalyseButton.tsx` — primary action button with FontAwesome analyse icon, Ctrl+Enter shortcut (FR-05), disabled when input empty, loading state during analysis (NFR-05), hacker accent colour. Verify `AnalyseButton.test.tsx` passes (TDD Green)
+- [x] T019 [US1] Create `frontend/src/components/AnalyseButton.tsx` — primary action button with FontAwesome analyse icon, Ctrl+Enter shortcut (FR-05), disabled when input empty, loading state during analysis (NFR-05), hacker accent colour. Verify `AnalyseButton.test.tsx` passes (TDD Green)
+
+Note: `npx vitest run src/__tests__/AnalyseButton.test.tsx` passes; Vitest emits existing act() environment warnings.
 
 ## Completion
 
diff --git a/frontend/src/components/AnalyseButton.tsx b/frontend/src/components/AnalyseButton.tsx
new file mode 100644
index 0000000..bb4d699
--- /dev/null
+++ b/frontend/src/components/AnalyseButton.tsx
@@ -0,0 +1,52 @@
+"use client";
+
+import { useEffect, useMemo } from "react";
+import { FontAwesomeIcon } from "@fortawesome/react-fontawesome";
+import { faMagnifyingGlass, faSpinner } from "@fortawesome/free-solid-svg-icons";
+
+type AnalyseButtonProps = {
+  hasInput: boolean;
+  onAnalyse: () => void;
+  isLoading?: boolean;
+};
+
+export default function AnalyseButton({
+  hasInput,
+  onAnalyse,
+  isLoading = false,
+}: AnalyseButtonProps) {
+  const isDisabled = useMemo(() => !hasInput || isLoading, [hasInput, isLoading]);
+
+  useEffect(() => {
+    const handleShortcut = (event: KeyboardEvent) => {
+      if (!event.ctrlKey || event.key !== "Enter") {
+        return;
+      }
+
+      if (isDisabled) {
+        return;
+      }
+
+      event.preventDefault();
+      onAnalyse();
+    };
+
+    window.addEventListener("keydown", handleShortcut);
+    return () => {
+      window.removeEventListener("keydown", handleShortcut);
+    };
+  }, [isDisabled, onAnalyse]);
+
+  return (
+    <button
+      type="button"
+      className="flex w-full items-center justify-center gap-2 rounded-full bg-accent px-5 py-3 text-sm font-semibold text-background transition hover:brightness-110 focus-visible:outline focus-visible:outline-2 focus-visible:outline-offset-2 focus-visible:outline-info disabled:cursor-not-allowed disabled:opacity-60 sm:w-auto"
+      onClick={onAnalyse}
+      disabled={isDisabled}
+      aria-busy={isLoading ? "true" : undefined}
+    >
+      <FontAwesomeIcon icon={isLoading ? faSpinner : faMagnifyingGlass} spin={isLoading} />
+      {isLoading ? "Analysing..." : "Analyse Headers"}
+    </button>
+  );
+}