diff --git a/frontend/src/components/tab-navigation.test.ts b/frontend/src/components/tab-navigation.test.ts
new file mode 100644
index 0000000..06f8dd3
--- /dev/null
+++ b/frontend/src/components/tab-navigation.test.ts
@@ -0,0 +1,22 @@
+import { describe, expect, it } from "vitest";
+import { tabIndexForKey } from "./tab-navigation";
+
+describe("tab keyboard navigation", () => {
+  it("wraps through horizontal and vertical arrow keys", () => {
+    expect(tabIndexForKey("ArrowRight", 0, 3)).toBe(1);
+    expect(tabIndexForKey("ArrowDown", 2, 3)).toBe(0);
+    expect(tabIndexForKey("ArrowLeft", 0, 3)).toBe(2);
+    expect(tabIndexForKey("ArrowUp", 2, 3)).toBe(1);
+  });
+
+  it("jumps to the first or last tab with Home and End", () => {
+    expect(tabIndexForKey("Home", 2, 3)).toBe(0);
+    expect(tabIndexForKey("End", 0, 3)).toBe(2);
+  });
+
+  it("ignores unsupported keys and invalid tab positions", () => {
+    expect(tabIndexForKey("Enter", 1, 3)).toBeNull();
+    expect(tabIndexForKey("ArrowRight", -1, 3)).toBeNull();
+    expect(tabIndexForKey("ArrowRight", 0, 0)).toBeNull();
+  });
+});
diff --git a/frontend/src/components/tab-navigation.ts b/frontend/src/components/tab-navigation.ts
new file mode 100644
index 0000000..c3bc411
--- /dev/null
+++ b/frontend/src/components/tab-navigation.ts
@@ -0,0 +1,8 @@
+export function tabIndexForKey(key: string, currentIndex: number, tabCount: number): number | null {
+  if (tabCount <= 0 || currentIndex < 0 || currentIndex >= tabCount) return null;
+  if (key === "Home") return 0;
+  if (key === "End") return tabCount - 1;
+  if (key === "ArrowRight" || key === "ArrowDown") return (currentIndex + 1) % tabCount;
+  if (key === "ArrowLeft" || key === "ArrowUp") return (currentIndex - 1 + tabCount) % tabCount;
+  return null;
+}
diff --git a/frontend/src/topics/build/lab.tsx b/frontend/src/topics/build/lab.tsx
index 7fab29f..9009f69 100644
--- a/frontend/src/topics/build/lab.tsx
+++ b/frontend/src/topics/build/lab.tsx
@@ -1,4 +1,4 @@
-import { type FormEvent, useMemo, useState } from "react";
+import { type FormEvent, type KeyboardEvent, useMemo, useState } from "react";
 import {
   buildFileFixtures,
   buildLabHappyPath,
@@ -10,6 +10,7 @@ import {
 } from "./content";
 import { createInitialBuildState, isBuildLabComplete, runBuildEvent } from "./simulator";
 import { TopicCompletionCard, TopicLabShell, TopicStatusFeedback, type TopicStatusTone } from "../../components/TopicShell";
+import { tabIndexForKey } from "../../components/tab-navigation";
 
 interface BuildHistoryEntry {
   command?: string;
@@ -56,6 +57,18 @@ function buildFileLines(state: BuildLabState, fileId: BuildFileId): readonly str
   return file.lines;
 }
 
+function buildFileSlug(fileId: BuildFileId): string {
+  return fileId.replace(/[^a-z0-9]+/gi, "-");
+}
+
+function buildTabId(fileId: BuildFileId): string {
+  return `build-file-tab-${buildFileSlug(fileId)}`;
+}
+
+function buildPanelId(fileId: BuildFileId): string {
+  return `build-file-panel-${buildFileSlug(fileId)}`;
+}
+
 export function buildLabProgress(state: BuildLabState): number {
   return Math.round((state.completedStepIds.length / buildLessonSteps.length) * 100);
 }
@@ -128,27 +141,49 @@ export function BuildLab({ onComplete }: { onComplete?: () => void }) {
               <b>workshop-build-lab</b>
               <span className="build-phase">{state.phase}</span>
             </div>
-            <div className="build-file-tabs" role="tablist" aria-label="Build fixture files">
-              {buildFileFixtures.map((file) => (
+            <div className="build-file-tabs" role="tablist" aria-orientation="horizontal" aria-label="Build fixture files">
+              {buildFileFixtures.map((file, index) => (
                 <button
                   className={selectedFile === file.id ? "active" : ""}
                   key={file.id}
                   type="button"
                   role="tab"
+                  id={buildTabId(file.id)}
+                  aria-controls={buildPanelId(file.id)}
                   aria-selected={selectedFile === file.id}
+                  tabIndex={selectedFile === file.id ? 0 : -1}
+                  onKeyDown={(event: KeyboardEvent<HTMLButtonElement>) => {
+                    const nextIndex = tabIndexForKey(event.key, index, buildFileFixtures.length);
+                    if (nextIndex === null) return;
+                    event.preventDefault();
+                    const nextFile = buildFileFixtures[nextIndex];
+                    setSelectedFile(nextFile.id);
+                    document.getElementById(buildTabId(nextFile.id))?.focus();
+                  }}
                   onClick={() => setSelectedFile(file.id)}
                 >
                   {file.name}
                 </button>
               ))}
             </div>
-            <div className="build-editor" role="region" aria-label={`${selectedFile} fixture`}>
-              {buildFileLines(state, selectedFile).map((line, index) => (
-                <div className="build-code-line" key={`${selectedFile}-${index}`}>
-                  <span>{String(index + 1).padStart(2, "0")}</span><code>{line || " "}</code>
-                </div>
-              ))}
-            </div>
+            {buildFileFixtures.map((file) => (
+              <div
+                className="build-editor"
+                id={buildPanelId(file.id)}
+                key={file.id}
+                role="tabpanel"
+                aria-labelledby={buildTabId(file.id)}
+                aria-label={`${file.id} fixture`}
+                tabIndex={0}
+                hidden={selectedFile !== file.id}
+              >
+                {buildFileLines(state, file.id).map((line, index) => (
+                  <div className="build-code-line" key={`${file.id}-${index}`}>
+                    <span>{String(index + 1).padStart(2, "0")}</span><code>{line || " "}</code>
+                  </div>
+                ))}
+              </div>
+            ))}
             <div className="build-terminal-output" role="log" aria-live="polite" aria-label="Build command output">
               {history.map((entry, index) => (
                 <div className={`terminal-entry ${entry.accepted === false ? "error" : ""}`} key={`${index}-${entry.command ?? "system"}`}>
diff --git a/frontend/src/topics/package/lab.tsx b/frontend/src/topics/package/lab.tsx
index d04b54b..416470c 100644
--- a/frontend/src/topics/package/lab.tsx
+++ b/frontend/src/topics/package/lab.tsx
@@ -1,4 +1,4 @@
-import { type FormEvent, useMemo, useState } from "react";
+import { type FormEvent, type KeyboardEvent, useMemo, useState } from "react";
 import {
   packageLabHappyPath,
   packageLessonSteps,
@@ -8,6 +8,7 @@ import {
 } from "./content";
 import { createInitialPackageState, isPackageLabComplete, runPackageEvent } from "./simulator";
 import { TopicCompletionCard, TopicLabShell, TopicStatusFeedback, type TopicStatusTone } from "../../components/TopicShell";
+import { tabIndexForKey } from "../../components/tab-navigation";
 
 interface PackageHistoryEntry {
   command?: string;
@@ -59,6 +60,18 @@ function packageFileLines(state: PackageLabState, file: PackageFile): readonly s
     : ["node_modules/", "  // 尚未安裝任何依賴"];
 }
 
+function packageFileSlug(file: PackageFile): string {
+  return file.replace(/[^a-z0-9]+/gi, "-");
+}
+
+function packageTabId(file: PackageFile): string {
+  return `package-file-tab-${packageFileSlug(file)}`;
+}
+
+function packagePanelId(file: PackageFile): string {
+  return `package-file-panel-${packageFileSlug(file)}`;
+}
+
 export function packageLabProgress(state: PackageLabState): number {
   return Math.round((state.completedStepIds.length / packageLessonSteps.length) * 100);
 }
@@ -130,27 +143,49 @@ export function PackageLab({ onComplete }: { onComplete?: () => void }) {
               <b>workshop-package-lab</b>
               <span className="package-phase">{state.phase}</span>
             </div>
-            <div className="package-file-tabs" role="tablist" aria-label="Package fixture files">
-              {PACKAGE_FILES.map((file) => (
+            <div className="package-file-tabs" role="tablist" aria-orientation="horizontal" aria-label="Package fixture files">
+              {PACKAGE_FILES.map((file, index) => (
                 <button
                   className={selectedFile === file ? "active" : ""}
                   key={file}
                   type="button"
                   role="tab"
+                  id={packageTabId(file)}
+                  aria-controls={packagePanelId(file)}
                   aria-selected={selectedFile === file}
+                  tabIndex={selectedFile === file ? 0 : -1}
+                  onKeyDown={(event: KeyboardEvent<HTMLButtonElement>) => {
+                    const nextIndex = tabIndexForKey(event.key, index, PACKAGE_FILES.length);
+                    if (nextIndex === null) return;
+                    event.preventDefault();
+                    const nextFile = PACKAGE_FILES[nextIndex];
+                    setSelectedFile(nextFile);
+                    document.getElementById(packageTabId(nextFile))?.focus();
+                  }}
                   onClick={() => setSelectedFile(file)}
                 >
                   {file}
                 </button>
               ))}
             </div>
-            <div className="package-editor" role="region" aria-label={`${selectedFile} fixture`}>
-              {packageFileLines(state, selectedFile).map((line, index) => (
-                <div className="package-code-line" key={`${selectedFile}-${index}`}>
-                  <span>{String(index + 1).padStart(2, "0")}</span><code>{line || " "}</code>
-                </div>
-              ))}
-            </div>
+            {PACKAGE_FILES.map((file) => (
+              <div
+                className="package-editor"
+                id={packagePanelId(file)}
+                key={file}
+                role="tabpanel"
+                aria-labelledby={packageTabId(file)}
+                aria-label={`${file} fixture`}
+                tabIndex={0}
+                hidden={selectedFile !== file}
+              >
+                {packageFileLines(state, file).map((line, index) => (
+                  <div className="package-code-line" key={`${file}-${index}`}>
+                    <span>{String(index + 1).padStart(2, "0")}</span><code>{line || " "}</code>
+                  </div>
+                ))}
+              </div>
+            ))}
             <div className="package-terminal-output" role="log" aria-live="polite" aria-label="Package command output">
               {history.map((entry, index) => (
                 <div className={`terminal-entry ${entry.accepted === false ? "error" : ""}`} key={`${index}-${entry.command ?? "system"}`}>
diff --git a/frontend/src/topics/rest/lab.tsx b/frontend/src/topics/rest/lab.tsx
index 05e4d40..6ef216e 100644
--- a/frontend/src/topics/rest/lab.tsx
+++ b/frontend/src/topics/rest/lab.tsx
@@ -1,4 +1,4 @@
-import { useMemo, useState } from "react";
+import { type KeyboardEvent, useState } from "react";
 import { TopicCompletionCard, TopicLabShell, TopicStatusFeedback, type TopicStatusTone } from "../../components/TopicShell";
 import {
   findRestCodeFile,
@@ -15,6 +15,7 @@ import {
   type RestTraceStageId,
 } from "./content";
 import { createInitialRestState, isRestLabComplete, isRestStageUnlocked, runRestEvent } from "./simulator";
+import { tabIndexForKey } from "../../components/tab-navigation";
 
 type RestCodeMode = "annotated" | "source";
 
@@ -54,6 +55,18 @@ function firstLineId(fileId: RestCodeFileId): string {
   return firstLine.id;
 }
 
+function restFileSlug(fileId: RestCodeFileId): string {
+  return fileId.replace(/[^a-z0-9]+/gi, "-");
+}
+
+function restTabId(fileId: RestCodeFileId): string {
+  return `rest-file-tab-${restFileSlug(fileId)}`;
+}
+
+function restPanelId(fileId: RestCodeFileId): string {
+  return `rest-file-panel-${restFileSlug(fileId)}`;
+}
+
 export function lineForFileSelection(fileId: RestCodeFileId, stageId: RestTraceStageId): string {
   return relatedLine(fileId, stageId) ?? firstLineId(fileId);
 }
@@ -76,11 +89,6 @@ export function RestLab({ onComplete }: { onComplete?: () => void }) {
   const terminalIndex = stageIndex(scenario.terminalStageId);
   const currentIndex = stageIndex(state.activeStageId);
   const completed = isRestLabComplete(state);
-  const activeLineIds = useMemo(
-    () => selectedFile.lines.filter((line) => line.stages.includes(state.activeStageId)).map((line) => line.id),
-    [selectedFile, state.activeStageId],
-  );
-
   function dispatch(event: RestLabEvent) {
     const result = runRestEvent(state, event);
     if (!isRestLabComplete(state) && isRestLabComplete(result.state)) onComplete?.();
@@ -181,9 +189,29 @@ export function RestLab({ onComplete }: { onComplete?: () => void }) {
       <div className="rest-workbench">
         <section className="rest-code-panel" aria-label="Full stack source code">
           <header className="rest-code-toolbar">
-            <div className="rest-file-tabs" role="tablist" aria-label="程式檔案">
-              {restCodeFiles.map((file) => (
-                <button key={file.id} type="button" role="tab" aria-selected={selectedFileId === file.id} className={selectedFileId === file.id ? "active" : ""} onClick={() => changeFile(file.id)}>{file.id}</button>
+            <div className="rest-file-tabs" role="tablist" aria-orientation="horizontal" aria-label="程式檔案">
+              {restCodeFiles.map((file, index) => (
+                <button
+                  key={file.id}
+                  id={restTabId(file.id)}
+                  type="button"
+                  role="tab"
+                  aria-controls={restPanelId(file.id)}
+                  aria-selected={selectedFileId === file.id}
+                  tabIndex={selectedFileId === file.id ? 0 : -1}
+                  className={selectedFileId === file.id ? "active" : ""}
+                  onKeyDown={(event: KeyboardEvent<HTMLButtonElement>) => {
+                    const nextIndex = tabIndexForKey(event.key, index, restCodeFiles.length);
+                    if (nextIndex === null) return;
+                    event.preventDefault();
+                    const nextFile = restCodeFiles[nextIndex];
+                    changeFile(nextFile.id);
+                    document.getElementById(restTabId(nextFile.id))?.focus();
+                  }}
+                  onClick={() => changeFile(file.id)}
+                >
+                  {file.id}
+                </button>
               ))}
             </div>
             <div className="rest-mode-switch" aria-label="Code display mode">
@@ -193,23 +221,40 @@ export function RestLab({ onComplete }: { onComplete?: () => void }) {
           </header>
           <div className="rest-code-meta"><span>{selectedFile.path}</span><small>{selectedFile.language} · {selectedFile.role}</small></div>
           {fileSelectionNotice ? <p className="rest-code-notice" role="status">{fileSelectionNotice}</p> : null}
-          <div className="rest-code-lines" role="listbox" aria-label={`${selectedFile.id} 逐行程式碼`}>
-            {selectedFile.lines.map((line, index) => {
-              const isRelated = activeLineIds.includes(line.id);
-              return (
-                <button
-                  type="button"
-                  role="option"
-                  aria-selected={selectedLineId === line.id}
-                  className={`${selectedLineId === line.id ? "selected" : ""} ${isRelated ? "related" : ""}`}
-                  key={line.id}
-                  onClick={() => setSelectedLineId(line.id)}
-                >
-                  <span>{String(index + 1).padStart(2, "0")}</span><code>{line.code}</code>{codeMode === "annotated" ? <small>{line.explanation}</small> : null}
-                </button>
-              );
-            })}
-          </div>
+          {restCodeFiles.map((file) => {
+            const isSelected = selectedFileId === file.id;
+            const activeLineIds = file.lines.filter((line) => line.stages.includes(state.activeStageId)).map((line) => line.id);
+            return (
+              <div
+                className="rest-code-tabpanel"
+                id={restPanelId(file.id)}
+                key={file.id}
+                role="tabpanel"
+                aria-labelledby={restTabId(file.id)}
+                aria-label={`${file.id} 逐行程式碼`}
+                tabIndex={0}
+                hidden={!isSelected}
+              >
+                <div className="rest-code-lines" role="listbox" aria-label={`${file.id} 逐行程式碼`}>
+                  {file.lines.map((line, index) => {
+                    const isRelated = activeLineIds.includes(line.id);
+                    return (
+                      <button
+                        type="button"
+                        role="option"
+                        aria-selected={selectedLineId === line.id}
+                        className={`${selectedLineId === line.id ? "selected" : ""} ${isRelated ? "related" : ""}`}
+                        key={line.id}
+                        onClick={() => setSelectedLineId(line.id)}
+                      >
+                        <span>{String(index + 1).padStart(2, "0")}</span><code>{line.code}</code>{codeMode === "annotated" ? <small>{line.explanation}</small> : null}
+                      </button>
+                    );
+                  })}
+                </div>
+              </div>
+            );
+          })}
         </section>
 
         <aside className="rest-explanation-panel" aria-live="polite">