diff --git a/docs/accessibility.md b/docs/accessibility.md
index 9047724..16ad65c 100644
--- a/docs/accessibility.md
+++ b/docs/accessibility.md
@@ -16,6 +16,10 @@ automatically, what was fixed, and what still needs a manual pass.
 | Screen reader | Command selector is a labelled group of toggle buttons | `src/App.test.tsx`, `tests/visual/accessibility.spec.ts` |
 | Screen reader | Copy results are announced through a polite live region | `src/App.test.tsx`, `tests/visual/accessibility.spec.ts` |
 | Screen reader | Audit prerequisites are a labelled fieldset of checkboxes, each with its own accessible name | `src/App.test.tsx` |
+| Screen reader | Every form field carries an `aria-describedby` pointing to visible inline help text (#100) | `src/App.test.tsx` |
+| Screen reader | Focus moves to the command section heading after a workflow tab switch (#101) | `src/App.test.tsx` |
+| Screen reader | Validation errors are announced via an `aria-live="assertive"` region (#102) | `src/App.test.tsx` |
+| Screen reader | "Copied" label remains visible for at least 2 000 ms to give AT time to announce it (#103) | `src/App.test.tsx` |
 | Zoom | No horizontal page scroll and no clipped controls at 640px and 320px CSS widths | `tests/visual/accessibility.spec.ts` |
 
 These checks read the accessibility tree and computed styles. They do not
@@ -52,3 +56,7 @@ browser and screen reader pair per platform.
 | 8 | The limits workflow needed a discoverable, ready-to-run command reference. | Fixed: added a focusable reference section and a build-and-run example with keyboard-focusable command steps. | `src/App.tsx`, `src/styles.css`, `tests/visual/accessibility.spec.ts` |
 | 9 | Scrollable `pre` blocks are not keyboard-focusable in every browser, so long lines may be unreachable by keyboard on some browsers. | Open. | `src/styles.css` |
 | 10 | The stored visual baselines in `tests/visual/__screenshots__` predate the current layout and do not match a fresh render. | Open. Baselines should be regenerated on the CI platform, not locally. | `tests/visual/` |
+| 11 | Form fields had no programmatic help text, so users relying on screen readers could not learn what each field expects without trial and error. | Fixed (#100): every required and optional input, select, and checkbox now carries an `aria-describedby` id pointing to a visible `.field-help` element. | `src/App.tsx` |
+| 12 | Switching workflow tabs left focus on the tab button, so screen reader users had to navigate forwards to find where the form changed. | Fixed (#101): after any tab switch, focus moves to the "From intent to command" `h2`, giving AT users an unambiguous entry point. | `src/App.tsx` |
+| 13 | Validation failures were silent; a screen reader user copying a command with an empty required field received no feedback. | Fixed (#102): an `aria-live="assertive"` region announces the first unsatisfied constraint, and the error clears when the field is filled. | `src/App.tsx` |
+| 14 | The "Copied" label reset after 1 600 ms, which is shorter than the announcement latency of many screen readers and Braille displays. | Fixed (#103): the reset timeout is now 3 000 ms, giving assistive technology enough time to read the change. | `src/App.tsx` |
diff --git a/src/App.test.tsx b/src/App.test.tsx
index 05fa906..ef17a5b 100644
--- a/src/App.test.tsx
+++ b/src/App.test.tsx
@@ -1003,3 +1003,197 @@ describe("Session-only command history UI", () => {
     });
   });
 });
+
+// Issue #100 — inline help text associated with each form field
+describe("Inline help text for form fields (#100)", () => {
+  it("associates help text with the path input via aria-describedby", () => {
+    render(<App />);
+    const pathInput = screen.getByRole("textbox", { name: /project or contract path/i });
+    const describedBy = pathInput.getAttribute("aria-describedby");
+    expect(describedBy).toBeTruthy();
+    const helpEl = document.getElementById(describedBy!);
+    expect(helpEl).not.toBeNull();
+    expect(helpEl!.textContent).toMatch(/path/i);
+  });
+
+  it("associates help text with the shell select via aria-describedby", () => {
+    render(<App />);
+    const shellSelect = screen.getByRole("combobox", { name: /shell target/i });
+    const describedBy = shellSelect.getAttribute("aria-describedby");
+    expect(describedBy).toBeTruthy();
+    const helpEl = document.getElementById(describedBy!);
+    expect(helpEl).not.toBeNull();
+    expect(helpEl!.textContent?.length).toBeGreaterThan(0);
+  });
+
+  it("associates help text with the format select when coverage workflow is active", () => {
+    render(<App />);
+    const formatSelect = screen.getByRole("combobox", { name: /report format/i });
+    const describedBy = formatSelect.getAttribute("aria-describedby");
+    expect(describedBy).toBeTruthy();
+    const helpEl = document.getElementById(describedBy!);
+    expect(helpEl).not.toBeNull();
+    expect(helpEl!.textContent?.length).toBeGreaterThan(0);
+  });
+
+  it("associates help text with fn and ramp inputs in the limits workflow", () => {
+    render(<App />);
+    fireEvent.click(screen.getByRole("button", { name: "limits" }));
+    const fnInput = screen.getByRole("textbox", { name: /^function$/i });
+    expect(fnInput.getAttribute("aria-describedby")).toBe("fn-help");
+    expect(document.getElementById("fn-help")).not.toBeNull();
+    const rampInput = screen.getByRole("textbox", { name: /ramp parameter/i });
+    expect(rampInput.getAttribute("aria-describedby")).toBe("ramp-help");
+    expect(document.getElementById("ramp-help")).not.toBeNull();
+  });
+});
+
+// Issue #101 — focus moves to the command section heading after a mode switch
+describe("Focus moves to workflow heading on mode switch (#101)", () => {
+  it("focuses the command section heading when switching to the limits workflow", () => {
+    render(<App />);
+    const limitsButton = screen.getByRole("button", { name: "limits" });
+    fireEvent.click(limitsButton);
+    const heading = screen.getByRole("heading", { name: /from intent to command/i });
+    expect(heading).toHaveFocus();
+  });
+
+  it("focuses the command section heading when switching back to coverage", () => {
+    render(<App />);
+    fireEvent.click(screen.getByRole("button", { name: "limits" }));
+    fireEvent.click(screen.getByRole("button", { name: "coverage" }));
+    const heading = screen.getByRole("heading", { name: /from intent to command/i });
+    expect(heading).toHaveFocus();
+  });
+
+  it("focuses the command section heading when switching to audit", () => {
+    render(<App />);
+    fireEvent.click(screen.getByRole("button", { name: "audit" }));
+    const heading = screen.getByRole("heading", { name: /from intent to command/i });
+    expect(heading).toHaveFocus();
+  });
+});
+
+// Issue #102 — validation errors announced through a live region
+describe("Validation errors announced via live region (#102)", () => {
+  const originalClipboard = navigator.clipboard;
+
+  afterEach(() => {
+    Object.defineProperty(navigator, "clipboard", {
+      value: originalClipboard,
+      configurable: true,
+    });
+    vi.restoreAllMocks();
+  });
+
+  it("renders an assertive live region for validation errors", () => {
+    render(<App />);
+    const alerts = document.querySelectorAll('[aria-live="assertive"]');
+    expect(alerts.length).toBeGreaterThan(0);
+  });
+
+  it("announces an error when copy is attempted with an empty path", async () => {
+    const writeText = vi.fn().mockResolvedValue(undefined);
+    Object.defineProperty(navigator, "clipboard", {
+      value: { writeText },
+      configurable: true,
+    });
+
+    render(<App />);
+
+    // Clear the path field
+    const pathInput = screen.getByRole("textbox", { name: /project or contract path/i });
+    fireEvent.change(pathInput, { target: { value: "" } });
+
+    fireEvent.click(screen.getByRole("button", { name: /^Copy$/ }));
+
+    await waitFor(() => {
+      const alertRegion = document.querySelector('[aria-live="assertive"]');
+      expect(alertRegion?.textContent).toMatch(/path.*required/i);
+    });
+    // Clipboard should not be called when validation fails
+    expect(writeText).not.toHaveBeenCalled();
+  });
+
+  it("clears the error message when the path field is filled in", async () => {
+    const writeText = vi.fn().mockResolvedValue(undefined);
+    Object.defineProperty(navigator, "clipboard", {
+      value: { writeText },
+      configurable: true,
+    });
+
+    render(<App />);
+    const pathInput = screen.getByRole("textbox", { name: /project or contract path/i });
+    fireEvent.change(pathInput, { target: { value: "" } });
+    fireEvent.click(screen.getByRole("button", { name: /^Copy$/ }));
+
+    await waitFor(() => {
+      const alertRegion = document.querySelector('[aria-live="assertive"]');
+      expect(alertRegion?.textContent).toMatch(/required/i);
+    });
+
+    fireEvent.change(pathInput, { target: { value: "." } });
+
+    await waitFor(() => {
+      const alertRegion = document.querySelector('[aria-live="assertive"]');
+      expect(alertRegion?.textContent).toBe("");
+    });
+  });
+});
+
+// Issue #103 — copied status persists long enough for assistive technology
+describe("Copied status persistence for assistive technology (#103)", () => {
+  const originalClipboard = navigator.clipboard;
+
+  afterEach(() => {
+    Object.defineProperty(navigator, "clipboard", {
+      value: originalClipboard,
+      configurable: true,
+    });
+    vi.restoreAllMocks();
+  });
+
+  it("shows the Copied label immediately after copy and resets after 3 s", async () => {
+    vi.useFakeTimers({ shouldAdvanceTime: false });
+    const writeText = vi.fn().mockResolvedValue(undefined);
+    Object.defineProperty(navigator, "clipboard", {
+      value: { writeText },
+      configurable: true,
+    });
+
+    render(<App />);
+
+    await act(async () => {
+      fireEvent.click(screen.getByRole("button", { name: /^Copy$/ }));
+    });
+
+    expect(screen.getByRole("button", { name: "Copied" })).toBeInTheDocument();
+
+    // Still present at 2 s — not yet reset
+    act(() => { vi.advanceTimersByTime(2000); });
+    expect(screen.queryByRole("button", { name: "Copied" })).toBeInTheDocument();
+
+    // Reverted after 3 s
+    act(() => { vi.advanceTimersByTime(1100); });
+    expect(screen.queryByRole("button", { name: /^Copy$/ })).toBeInTheDocument();
+
+    vi.useRealTimers();
+  });
+
+  it("announces the copy result in the polite live region", async () => {
+    const writeText = vi.fn().mockResolvedValue(undefined);
+    Object.defineProperty(navigator, "clipboard", {
+      value: { writeText },
+      configurable: true,
+    });
+
+    render(<App />);
+
+    await act(async () => {
+      fireEvent.click(screen.getByRole("button", { name: /^Copy$/ }));
+    });
+
+    const liveRegion = document.querySelector('[aria-live="polite"]');
+    expect(liveRegion?.textContent).toMatch(/copied/i);
+  });
+});
diff --git a/src/App.tsx b/src/App.tsx
index d179133..9478640 100644
--- a/src/App.tsx
+++ b/src/App.tsx
@@ -326,7 +326,11 @@ export default function App() {
   const [categoryFilter, setCategoryFilter] = useState<ModuleCategory | null>(null);
   const [selectedModule, setSelectedModule] = useState<string | null>(null);
   const [showBackToTop, setShowBackToTop] = useState(false);
+  // #102 — validation errors announced via live region
+  const [validationError, setValidationError] = useState("");
   const moduleSearchRef = useRef<HTMLInputElement>(null);
+  // #101 — focus the command section heading after a mode switch
+  const commandHeadingRef = useRef<HTMLHeadingElement>(null);
 
   // Resetting from the empty state removes the button that had focus, so move
   // focus back to the search box instead of dropping it to <body> (#123).
@@ -592,7 +596,7 @@ export default function App() {
     window.setTimeout(() => {
       setCopied(false);
       setAnnouncement("");
-    }, 1600);
+    }, 3000);
   };
 
   // Issue #144: Copy command with explanatory comments
@@ -605,7 +609,7 @@ export default function App() {
     window.setTimeout(() => {
       setCopiedWithComments(false);
       setAnnouncement("");
-    }, 1600);
+    }, 3000);
   };
 
   // Issue #145: Copy command as reusable shell script
@@ -618,7 +622,7 @@ export default function App() {
     window.setTimeout(() => {
       setCopiedAsScript(false);
       setAnnouncement("");
-    }, 1600);
+    }, 3000);
   };
 
   const copyStep = async (index: number, stepCommand: string) => {
@@ -628,7 +632,7 @@ export default function App() {
     window.setTimeout(() => {
       setCopiedStep(null);
       setAnnouncement("");
-    }, 1600);
+    }, 3000);
   };
 
   // #146 — download generated command as shell script
@@ -682,6 +686,36 @@ export default function App() {
     }
   };
 
+  // #101 — move focus to the command section heading when the workflow tab changes
+  const isFirstRender = useRef(true);
+  useEffect(() => {
+    if (isFirstRender.current) {
+      isFirstRender.current = false;
+      return;
+    }
+    commandHeadingRef.current?.focus();
+  }, [command]);
+
+  // #102 — validate required fields and announce errors
+  const validateAndCopy = async () => {
+    if (!path.trim()) {
+      setValidationError("Project or contract path is required.");
+      return;
+    }
+    if (command === "limits") {
+      if (!fn.trim()) {
+        setValidationError("Function name is required.");
+        return;
+      }
+      if (!ramp.trim()) {
+        setValidationError("Ramp parameter is required.");
+        return;
+      }
+    }
+    setValidationError("");
+    await copy();
+  };
+
   const fieldClasses = "field-input";
 
   return (
@@ -692,6 +726,10 @@ export default function App() {
       <p className="sr-only" aria-live="polite">
         {announcement}
       </p>
+      {/* #102 — validation errors announced via assertive live region */}
+      <p className="sr-only" aria-live="assertive" role="alert">
+        {validationError}
+      </p>
       <nav aria-label="Main navigation">
         <a className="brand" href="#top" aria-label="Soroban Testkit home">
           <span className="brand-mark">S</span>
@@ -1227,7 +1265,8 @@ export default function App() {
       <section className="commands" id="commands" tabIndex={-1}>
         <div className="command-copy">
           <p className="eyebrow">CLI workbench</p>
-          <h2>From intent to command.</h2>
+          {/* #101 — heading receives focus after workflow tab switch */}
+          <h2 ref={commandHeadingRef} tabIndex={-1}>From intent to command.</h2>
           <p>Configure a supported Testkit workflow and copy the exact command to your terminal.</p>
           <div className="command-tabs" role="group" aria-label="Command workflow selector">
             {(["coverage", "limits", "audit"] as const).map((name) => (
@@ -1300,13 +1339,18 @@ export default function App() {
               <span>Project or contract path</span>
               <span className="badge badge-required">Required</span>
             </div>
+            {/* #100 — inline help text associated with the field */}
+            <div id="path-help" className="field-help">
+              Path to the contract workspace or source directory, such as . or ./contracts/token.
+            </div>
             <div className="field-with-clear">
               <input
                 className={fieldClasses}
                 value={path}
-                onChange={(event) => setPath(event.target.value)}
+                onChange={(event) => { setPath(event.target.value); if (event.target.value.trim()) setValidationError(""); }}
                 aria-label="Project or contract path"
                 aria-required="true"
+                aria-describedby="path-help"
               />
               {path && (
                 <button
@@ -1364,7 +1408,11 @@ export default function App() {
                   <span>Report format</span>
                   <span className="badge badge-optional">Optional</span>
                 </div>
-                <select value={format} onChange={(event) => setFormat(event.target.value as typeof format)}>
+                {/* #100 — inline help text for format field */}
+                <div id="format-help" className="field-help">
+                  html opens in a browser; lcov feeds into CI coverage tools; text prints to stdout.
+                </div>
+                <select value={format} onChange={(event) => setFormat(event.target.value as typeof format)} aria-describedby="format-help">
                   <option>html</option>
                   <option>lcov</option>
                   <option>text</option>
@@ -1372,10 +1420,14 @@ export default function App() {
               </label>
               <label className="check">
                 <span className="check-content">
-                  <input type="checkbox" checked={open} onChange={(event) => setOpen(event.target.checked)} />
+                  {/* #100 — inline help text for open checkbox */}
+                  <input type="checkbox" checked={open} onChange={(event) => setOpen(event.target.checked)} aria-describedby="open-help" />
                   <span>Open report when complete</span>
                 </span>
                 <span className="badge badge-optional">Optional</span>
+                <div id="open-help" className="field-help">
+                  Automatically launches the HTML report in your default browser after generation.
+                </div>
               </label>
             </>
           )}
@@ -1393,7 +1445,7 @@ export default function App() {
                   <input
                     className={fieldClasses}
                     value={fn}
-                    onChange={(event) => setFn(event.target.value)}
+                    onChange={(event) => { setFn(event.target.value); if (event.target.value.trim()) setValidationError(""); }}
                     aria-label="Function"
                     aria-required="true"
                     aria-describedby="fn-help"
@@ -1422,7 +1474,7 @@ export default function App() {
                   <input
                     className={fieldClasses}
                     value={ramp}
-                    onChange={(event) => setRamp(event.target.value)}
+                    onChange={(event) => { setRamp(event.target.value); if (event.target.value.trim()) setValidationError(""); }}
                     aria-label="Ramp parameter"
                     aria-required="true"
                     aria-describedby="ramp-help"
@@ -1444,10 +1496,14 @@ export default function App() {
           {command === "audit" && (
             <label className="check">
               <span className="check-content">
-                <input type="checkbox" checked={strict} onChange={(event) => setStrict(event.target.checked)} />
+                {/* #100 — inline help text for strict checkbox */}
+                <input type="checkbox" checked={strict} onChange={(event) => setStrict(event.target.checked)} aria-describedby="strict-help" />
                 <span>Fail on warnings</span>
               </span>
               <span className="badge badge-optional">Optional</span>
+              <div id="strict-help" className="field-help">
+                When enabled, the audit command exits with a non-zero status if any warnings are found.
+              </div>
             </label>
           )}
 
@@ -1456,7 +1512,11 @@ export default function App() {
               <span>Shell target</span>
               <span className="badge badge-optional">Optional</span>
             </div>
-            <select value={shell} onChange={(event) => setShell(event.target.value as typeof shell)}>
+            {/* #100 — inline help text for shell select */}
+            <div id="shell-help" className="field-help">
+              Adjusts quoting and syntax so the generated command is valid for your shell.
+            </div>
+            <select value={shell} onChange={(event) => setShell(event.target.value as typeof shell)} aria-describedby="shell-help">
               <option value="bash">Bash</option>
               <option value="zsh">Zsh</option>
               <option value="fish">Fish</option>
@@ -1497,7 +1557,7 @@ export default function App() {
 
           <div className="output">
             <code data-testid="command-output">{highlightCommand(generated)}</code>
-            <button onClick={copy}>{copied ? "Copied" : "Copy"}</button>
+            <button onClick={validateAndCopy}>{copied ? "Copied" : "Copy"}</button>
             {/* #146 — download action for generated shell script */}
             <button onClick={downloadCommand} className="button-download" aria-label="Download command as shell script">
               Download