feat(exam): candidate exam-taking experience (Phase 4)

New portal feature apps/portal/src/app/features/exam-attempt/, following
the repo's existing folder convention (pages/<Page>/index.tsx, components/,
types/, hooks/ — matches the payments feature's hooks/ precedent):

- types/exam-attempt.ts — response/local-state shapes
- hooks/useExamAttempt.ts — all API orchestration: load (registration +
  attempt), start/resume, per-question autosave (immediate on MCQ select,
  debounced+flushed-on-navigation for essay text), local countdown seeded
  from the server's serverTime/remainingSeconds, submit, and resync from
  the server whenever a write is refused as expired/already-submitted
- components/ExamInstructions, ExamTimer, ExamQuestionNav,
  ExamQuestionDisplay, ExamCompletion — one concern per file, not a single
  page dump
- pages/ExamAttemptPage — thin view layer over the hook

Flow: /exams (existing) gets a 'Take exam' action on eligible registration
rows → /exams/:examId/take, which shows instructions before an attempt
exists, the live exam screen while IN_PROGRESS, and a no-score completion
screen once SUBMITTED/EXPIRED (never fabricates a result — grading
doesn't exist yet).

Security note: RequirePermission on the route and disabled inputs after
local timeout are UI conveniences only. Every save/submit is independently
re-checked by the backend's ownership + applyExpiry() on each call: a
client that skipped the UI entirely and hit the API directly would be
bound by exactly the same rules.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

apps/portal/src/app/features/exam-attempt/components/ExamCompletion.tsx

@@ -0,0 +1,50 @@
+import { Button, Card, Stack, Text, ThemeIcon, Title } from '@mantine/core';
+import { IconCircleCheck, IconClockPause } from '@tabler/icons-react';
+import { useNavigate } from 'react-router-dom';
+import type { AttemptStatus } from '../types/exam-attempt';
+
+/**
+ * No score, no pass/fail, nothing evaluation-shaped — grading hasn't run.
+ * This only confirms what actually happened: the candidate submitted, or
+ * the deadline closed the attempt out first.
+ */
+export function ExamCompletion({
+  status,
+  submittedAt,
+}: {
+  status: AttemptStatus;
+  submittedAt: string | null;
+}) {
+  const navigate = useNavigate();
+  const expired = status === 'EXPIRED';
+
+  return (
+    <Stack maw={520} mx="auto" align="center" py="xl">
+      <Card withBorder radius="lg" p="xl" w="100%">
+        <Stack align="center" gap="md">
+          <ThemeIcon size={64} radius="xl" variant="light" color={expired ? 'orange' : 'teal'}>
+            {expired ? <IconClockPause size={32} /> : <IconCircleCheck size={32} />}
+          </ThemeIcon>
+          <Title order={3} ta="center">
+            {expired ? 'Time expired' : 'Exam submitted'}
+          </Title>
+          <Text ta="center" c="dimmed">
+            {expired
+              ? 'The scheduled time ran out. Your saved answers were recorded as your final submission.'
+              : 'Your answers have been recorded.'}
+            {' '}Your result will appear on the Examinations page once marking, moderation and
+            approval are complete — it is not available yet.
+          </Text>
+          {submittedAt && (
+            <Text fz="xs" c="dimmed">
+              {expired ? 'Closed' : 'Submitted'} at {new Date(submittedAt).toLocaleString()}
+            </Text>
+          )}
+          <Button variant="light" onClick={() => navigate('/exams')}>
+            Back to Examinations
+          </Button>
+        </Stack>
+      </Card>
+    </Stack>
+  );
+}

apps/portal/src/app/features/exam-attempt/components/ExamInstructions.tsx

@@ -0,0 +1,94 @@
+import { Alert, Badge, Button, Card, Group, Stack, Text, Title } from '@mantine/core';
+import { IconAlertCircle, IconClock, IconInfoCircle, IconPlayerPlay } from '@tabler/icons-react';
+import type { Bilingual } from '@ema-platform/api';
+import type { EstimatedTime, RegistrationWithExam } from '../types/exam-attempt';
+
+function formatDuration(time: EstimatedTime | null | undefined): string {
+  if (!time) return 'Not configured';
+  const parts = [
+    time.days ? `${time.days}d` : null,
+    time.hours ? `${time.hours}h` : null,
+    time.minutes ? `${time.minutes}m` : null,
+  ].filter(Boolean);
+  return parts.length ? parts.join(' ') : '0m';
+}
+
+export function ExamInstructions({
+  registration,
+  localized,
+  showDate,
+  starting,
+  onStart,
+}: {
+  registration: RegistrationWithExam;
+  localized: (value: Bilingual | undefined) => string;
+  showDate: (value: string | null | undefined) => string;
+  starting: boolean;
+  onStart: () => void;
+}) {
+  const exam = registration.exam;
+  const canStart = exam?.status === 'ACTIVE';
+
+  return (
+    <Stack maw={720} mx="auto" gap="md">
+      <Title order={2}>{localized(exam?.title) || 'Examination'}</Title>
+      <Text c="dimmed">{localized(exam?.certification?.name)}</Text>
+
+      <Card withBorder radius="md" p="lg">
+        <Stack gap="sm">
+          <Group justify="space-between">
+            <Text fz="sm" c="dimmed">Admission number</Text>
+            <Text fz="sm" fw={600} ff="monospace">{registration.admissionNumber}</Text>
+          </Group>
+          <Group justify="space-between">
+            <Text fz="sm" c="dimmed">Session date</Text>
+            <Text fz="sm">{showDate(exam?.date)}{exam?.venue ? ` · ${exam.venue}` : ''}</Text>
+          </Group>
+          <Group justify="space-between">
+            <Text fz="sm" c="dimmed">Duration</Text>
+            <Badge variant="light" leftSection={<IconClock size={12} />}>
+              {formatDuration(exam?.givenTime)}
+            </Badge>
+          </Group>
+          <Group justify="space-between">
+            <Text fz="sm" c="dimmed">Attempt</Text>
+            <Badge variant="light" color={registration.kind === 'RETAKE' ? 'orange' : 'blue'}>
+              {registration.kind === 'RETAKE'
+                ? `Retake · sitting ${registration.attemptNumber}`
+                : 'First sitting'}
+            </Badge>
+          </Group>
+        </Stack>
+      </Card>
+
+      {exam?.direction && localized(exam.direction) && (
+        <Alert icon={<IconInfoCircle size={16} />} color="blue" variant="light" title="Instructions">
+          {localized(exam.direction)}
+        </Alert>
+      )}
+
+      <Alert icon={<IconAlertCircle size={16} />} color="yellow" variant="light">
+        Once started, the timer cannot be paused. Answers are saved automatically as you go, but
+        the exam ends the moment the deadline passes, whether or not you have submitted.
+      </Alert>
+
+      {!canStart && (
+        <Alert color="gray" variant="light">
+          This session is not currently open for candidates to begin.
+        </Alert>
+      )}
+
+      <Group justify="flex-end">
+        <Button
+          size="md"
+          leftSection={<IconPlayerPlay size={16} />}
+          loading={starting}
+          disabled={!canStart}
+          onClick={onStart}
+        >
+          Start exam
+        </Button>
+      </Group>
+    </Stack>
+  );
+}

apps/portal/src/app/features/exam-attempt/components/ExamQuestionDisplay.tsx

@@ -0,0 +1,118 @@
+import { Badge, Button, Group, Paper, Radio, Stack, Text, Textarea } from '@mantine/core';
+import { IconAlertCircle, IconCheck, IconRefresh } from '@tabler/icons-react';
+import type { Bilingual } from '@ema-platform/api';
+import type { CandidateQuestion, SaveState } from '../types/exam-attempt';
+
+function SaveIndicator({ state, onRetry }: { state: SaveState; onRetry: () => void }) {
+  if (state === 'saving') {
+    return <Text fz="xs" c="dimmed">Saving…</Text>;
+  }
+  if (state === 'saved') {
+    return (
+      <Group gap={4}>
+        <IconCheck size={13} color="var(--mantine-color-teal-6)" />
+        <Text fz="xs" c="teal">Saved</Text>
+      </Group>
+    );
+  }
+  if (state === 'error') {
+    return (
+      <Group gap={6}>
+        <IconAlertCircle size={13} color="var(--mantine-color-red-6)" />
+        <Text fz="xs" c="red">Not saved</Text>
+        <Button
+          size="compact-xs"
+          variant="light"
+          color="red"
+          leftSection={<IconRefresh size={12} />}
+          onClick={onRetry}
+        >
+          Retry
+        </Button>
+      </Group>
+    );
+  }
+  return null;
+}
+
+/**
+ * Renders one question — never the answer key, because the API response
+ * this reads from (`CandidateQuestion`/`CandidateOption`) has no such field
+ * to render even by mistake.
+ */
+export function ExamQuestionDisplay({
+  question,
+  index,
+  total,
+  localized,
+  selectedOptionId,
+  answerText,
+  saveState,
+  disabled,
+  onSelectOption,
+  onChangeText,
+  onRetry,
+}: {
+  question: CandidateQuestion;
+  index: number;
+  total: number;
+  localized: (value: Bilingual | undefined) => string;
+  selectedOptionId: string | null | undefined;
+  answerText: string | null | undefined;
+  saveState: SaveState;
+  disabled: boolean;
+  onSelectOption: (optionId: string) => void;
+  onChangeText: (text: string) => void;
+  onRetry: () => void;
+}) {
+  return (
+    <Paper withBorder radius="md" p="lg">
+      <Group justify="space-between" mb="sm">
+        <Badge variant="light" color="gray">
+          Question {index + 1} of {total} · {question.points} pts
+        </Badge>
+        <SaveIndicator state={saveState} onRetry={onRetry} />
+      </Group>
+
+      <Text fz="md" fw={500} mb="lg">
+        {localized(question.title)}
+      </Text>
+
+      {question.form === 'CHOICE' ? (
+        <Radio.Group
+          value={selectedOptionId ?? ''}
+          onChange={onSelectOption}
+        >
+          <Stack gap="sm">
+            {question.options
+              .slice()
+              .sort((a, b) => a.order - b.order)
+              .map((option) => (
+                <Radio.Card
+                  key={option.id}
+                  value={option.id}
+                  disabled={disabled}
+                  p="sm"
+                  radius="md"
+                >
+                  <Group wrap="nowrap" gap="sm">
+                    <Radio.Indicator disabled={disabled} />
+                    <Text fz="sm">{localized(option.text)}</Text>
+                  </Group>
+                </Radio.Card>
+              ))}
+          </Stack>
+        </Radio.Group>
+      ) : (
+        <Textarea
+          placeholder="Write your answer"
+          minRows={8}
+          autosize
+          disabled={disabled}
+          value={answerText ?? ''}
+          onChange={(event) => onChangeText(event.currentTarget.value)}
+        />
+      )}
+    </Paper>
+  );
+}

apps/portal/src/app/features/exam-attempt/components/ExamQuestionNav.tsx

@@ -0,0 +1,57 @@
+import { Paper, SimpleGrid, Text, UnstyledButton } from '@mantine/core';
+import type { CandidateQuestion } from '../types/exam-attempt';
+
+export function ExamQuestionNav({
+  questions,
+  currentIndex,
+  answeredIds,
+  disabled,
+  onJump,
+}: {
+  questions: CandidateQuestion[];
+  currentIndex: number;
+  answeredIds: Set<string>;
+  disabled: boolean;
+  onJump: (index: number) => void;
+}) {
+  return (
+    <Paper withBorder radius="md" p="sm">
+      <Text fz="xs" fw={600} c="dimmed" mb="xs" tt="uppercase">
+        Questions
+      </Text>
+      <SimpleGrid cols={5} spacing={6}>
+        {questions.map((q, index) => {
+          const answered = answeredIds.has(q.id);
+          const current = index === currentIndex;
+          return (
+            <UnstyledButton
+              key={q.id}
+              disabled={disabled}
+              onClick={() => onJump(index)}
+              style={{
+                height: 34,
+                borderRadius: 6,
+                display: 'flex',
+                alignItems: 'center',
+                justifyContent: 'center',
+                fontWeight: 600,
+                fontSize: 13,
+                border: current ? '2px solid var(--mantine-color-blue-6)' : '1px solid var(--mantine-color-gray-4)',
+                background: answered
+                  ? 'var(--mantine-color-teal-1)'
+                  : 'var(--mantine-color-body)',
+                color: answered ? 'var(--mantine-color-teal-8)' : undefined,
+                opacity: disabled ? 0.5 : 1,
+              }}
+            >
+              {index + 1}
+            </UnstyledButton>
+          );
+        })}
+      </SimpleGrid>
+      <Text fz="xs" c="dimmed" mt="sm">
+        {answeredIds.size} of {questions.length} answered
+      </Text>
+    </Paper>
+  );
+}

apps/portal/src/app/features/exam-attempt/components/ExamTimer.tsx

@@ -0,0 +1,34 @@
+import { Badge, Group } from '@mantine/core';
+import { IconClock } from '@tabler/icons-react';
+
+function format(totalSeconds: number): string {
+  const s = Math.max(0, totalSeconds);
+  const h = Math.floor(s / 3600);
+  const m = Math.floor((s % 3600) / 60);
+  const sec = s % 60;
+  const pad = (n: number) => String(n).padStart(2, '0');
+  return h > 0 ? `${h}:${pad(m)}:${pad(sec)}` : `${pad(m)}:${pad(sec)}`;
+}
+
+/**
+ * Display only. `remainingSeconds` is a local countdown seeded once from the
+ * server's own clock (`AttemptSession.remainingSeconds`/`serverTime`) and
+ * ticked down client-side — the deadline it represents is enforced by the
+ * backend on every save/submit regardless of whether this number is right.
+ */
+export function ExamTimer({ remainingSeconds }: { remainingSeconds: number }) {
+  const low = remainingSeconds <= 300; // 5 minutes
+  return (
+    <Group gap={6}>
+      <Badge
+        size="lg"
+        variant="light"
+        color={low ? 'red' : 'blue'}
+        leftSection={<IconClock size={14} />}
+        ff="monospace"
+      >
+        {format(remainingSeconds)}
+      </Badge>
+    </Group>
+  );
+}

apps/portal/src/app/features/exam-attempt/hooks/useExamAttempt.ts

@@ -0,0 +1,286 @@
+import { useCallback, useEffect, useMemo, useRef, useState } from 'react';
+import { useApiMutation, useApiQuery, extractErrorMessage } from '@ema-platform/api';
+import { notify } from '@ema-platform/ui';
+import type {
+  AttemptSession,
+  CandidateAnswer,
+  ExamAttempt,
+  RegistrationWithExam,
+  SaveState,
+} from '../types/exam-attempt';
+
+const ESSAY_DEBOUNCE_MS = 1500;
+
+type ViewState = 'loading' | 'not-started' | 'taking' | 'completed' | 'error';
+
+type LocalAnswer = { selectedOptionId?: string | null; answerText?: string | null };
+
+/**
+ * All state and API orchestration for taking one exam. Kept out of the page
+ * component so the component tree stays about rendering, not about save
+ * timers and expiry races.
+ *
+ * Nothing here is a security boundary — every write still goes through the
+ * backend's own ownership + `applyExpiry()` checks on every call. This hook
+ * only decides what to show; a client that skipped straight to calling the
+ * API directly would hit exactly the same server-side rules.
+ */
+export function useExamAttempt(examId: string | undefined) {
+  const [session, setSession] = useState<AttemptSession | null>(null);
+  const [viewState, setViewState] = useState<ViewState>('loading');
+  const [errorMessage, setErrorMessage] = useState('');
+  const [currentIndex, setCurrentIndex] = useState(0);
+  const [answers, setAnswers] = useState<Record<string, LocalAnswer>>({});
+  const [saveStates, setSaveStates] = useState<Record<string, SaveState>>({});
+  const [remainingSeconds, setRemainingSeconds] = useState(0);
+
+  const answersRef = useRef(answers);
+  answersRef.current = answers;
+  const debounceTimers = useRef<Record<string, ReturnType<typeof setTimeout>>>({});
+  const seeded = useRef(false);
+
+  const {
+    data: registrations,
+    isLoading: loadingRegistrations,
+  } = useApiQuery<RegistrationWithExam[]>({ url: '/exams/registrations/mine' });
+  const registration = registrations?.find((r) => r.exam?.id === examId);
+
+  const {
+    data: mineData,
+    isLoading: loadingMine,
+    isError: mineIsError,
+    error: mineError,
+    refetch: refetchMine,
+  } = useApiQuery<AttemptSession>(
+    { url: `/exam-attempts/mine/${examId}` },
+    { skip: !examId },
+  );
+
+  const [startTrigger, { isLoading: starting }] = useApiMutation<AttemptSession>();
+  const [answerTrigger] = useApiMutation<CandidateAnswer>();
+  const [submitTrigger, { isLoading: submitting }] = useApiMutation<ExamAttempt>();
+
+  const seedFrom = useCallback((data: AttemptSession) => {
+    setSession(data);
+    const map: Record<string, LocalAnswer> = {};
+    for (const a of data.answers) {
+      map[a.questionId] = { selectedOptionId: a.selectedOptionId, answerText: a.answerText };
+    }
+    setAnswers(map);
+    setRemainingSeconds(data.remainingSeconds);
+    setViewState(data.attempt.status === 'IN_PROGRESS' ? 'taking' : 'completed');
+  }, []);
+
+  // Seed once from the initial load — after that, local state (ticking
+  // timer, in-flight edits) is the source of truth, not this query.
+  useEffect(() => {
+    if (seeded.current) return;
+    if (loadingRegistrations || loadingMine) return;
+    seeded.current = true;
+
+    if (!registration) {
+      setViewState('error');
+      setErrorMessage('You are not registered for this examination.');
+      return;
+    }
+    if (mineData) {
+      seedFrom(mineData);
+      return;
+    }
+    if (mineIsError) {
+      const key = extractErrorMessage(mineError, '');
+      if (key === 'attempt_not_found') {
+        setViewState('not-started');
+        return;
+      }
+      setViewState('error');
+      setErrorMessage(extractErrorMessage(mineError, 'Could not load the exam.'));
+    }
+  }, [loadingRegistrations, loadingMine, registration, mineData, mineIsError, mineError, seedFrom]);
+
+  /** Authoritative resync — used after any write is refused as expired/submitted. */
+  const syncFromServer = useCallback(async () => {
+    const result = await refetchMine();
+    if (result.data) {
+      seedFrom(result.data as AttemptSession);
+    } else {
+      setViewState('error');
+      setErrorMessage(extractErrorMessage(result.error, 'The exam session ended.'));
+    }
+  }, [refetchMine, seedFrom]);
+
+  const persistAnswer = useCallback(
+    async (questionId: string, payload: LocalAnswer) => {
+      if (!session) return;
+      setSaveStates((s) => ({ ...s, [questionId]: 'saving' }));
+      try {
+        const saved = await answerTrigger({
+          url: `/exam-attempts/${session.attempt.id}/answers`,
+          method: 'POST',
+          body: { questionId, ...payload },
+        }).unwrap();
+        setAnswers((a) => ({
+          ...a,
+          [questionId]: { selectedOptionId: saved.selectedOptionId, answerText: saved.answerText },
+        }));
+        setSaveStates((s) => ({ ...s, [questionId]: 'saved' }));
+      } catch (error) {
+        setSaveStates((s) => ({ ...s, [questionId]: 'error' }));
+        const key = extractErrorMessage(error, '');
+        if (key === 'attempt_expired' || key === 'attempt_already_submitted') {
+          notify.error(
+            key === 'attempt_expired'
+              ? 'Time is up — this answer was not saved.'
+              : 'This attempt has already been submitted.',
+          );
+          syncFromServer();
+        }
+      }
+    },
+    [session, answerTrigger, syncFromServer],
+  );
+
+  const flush = useCallback(
+    (questionId: string) => {
+      const timer = debounceTimers.current[questionId];
+      if (!timer) return;
+      clearTimeout(timer);
+      delete debounceTimers.current[questionId];
+      const current = answersRef.current[questionId];
+      if (current) persistAnswer(questionId, current);
+    },
+    [persistAnswer],
+  );
+
+  const selectOption = useCallback(
+    (questionId: string, optionId: string) => {
+      setAnswers((a) => ({ ...a, [questionId]: { ...a[questionId], selectedOptionId: optionId } }));
+      persistAnswer(questionId, { selectedOptionId: optionId });
+    },
+    [persistAnswer],
+  );
+
+  const changeText = useCallback(
+    (questionId: string, text: string) => {
+      setAnswers((a) => ({ ...a, [questionId]: { ...a[questionId], answerText: text } }));
+      setSaveStates((s) => ({ ...s, [questionId]: 'idle' }));
+      clearTimeout(debounceTimers.current[questionId]);
+      debounceTimers.current[questionId] = setTimeout(() => {
+        delete debounceTimers.current[questionId];
+        persistAnswer(questionId, { answerText: text });
+      }, ESSAY_DEBOUNCE_MS);
+    },
+    [persistAnswer],
+  );
+
+  const goTo = useCallback(
+    (index: number) => {
+      const current = session?.questions[currentIndex];
+      if (current) flush(current.id);
+      setCurrentIndex(index);
+    },
+    [session, currentIndex, flush],
+  );
+
+  const retry = useCallback(
+    (questionId: string) => {
+      const current = answersRef.current[questionId];
+      if (current) persistAnswer(questionId, current);
+    },
+    [persistAnswer],
+  );
+
+  const start = useCallback(async () => {
+    if (!examId) return;
+    try {
+      const result = await startTrigger({
+        url: '/exam-attempts/start',
+        method: 'POST',
+        body: { examId },
+      }).unwrap();
+      seedFrom(result);
+    } catch (error) {
+      notify.error(extractErrorMessage(error, 'Could not start the exam.'));
+    }
+  }, [examId, startTrigger, seedFrom]);
+
+  const submit = useCallback(async () => {
+    if (!session) return;
+    const current = session.questions[currentIndex];
+    if (current) flush(current.id);
+    try {
+      const attempt = await submitTrigger({
+        url: `/exam-attempts/${session.attempt.id}/submit`,
+        method: 'POST',
+      }).unwrap();
+      setSession((s) => (s ? { ...s, attempt } : s));
+      setViewState('completed');
+    } catch (error) {
+      const key = extractErrorMessage(error, '');
+      if (key === 'attempt_expired' || key === 'attempt_already_submitted') {
+        syncFromServer();
+      } else {
+        notify.error(extractErrorMessage(error, 'Could not submit the exam.'));
+      }
+    }
+  }, [session, currentIndex, flush, submitTrigger, syncFromServer]);
+
+  /** Local countdown only — every write is still checked server-side regardless. */
+  useEffect(() => {
+    if (viewState !== 'taking') return;
+    const id = setInterval(() => {
+      setRemainingSeconds((s) => {
+        if (s <= 1) {
+          clearInterval(id);
+          return 0;
+        }
+        return s - 1;
+      });
+    }, 1000);
+    return () => clearInterval(id);
+  }, [viewState]);
+
+  // Time reaching zero locally: stop taking input, tell the server, then
+  // trust whatever it reports back over anything computed in the browser.
+  const timedOutRef = useRef(false);
+  useEffect(() => {
+    if (viewState !== 'taking' || remainingSeconds > 0 || timedOutRef.current) return;
+    timedOutRef.current = true;
+    notify.error("Time's up.");
+    // submit() itself resyncs from the server if this loses the race against
+    // applyExpiry() — either way the final state comes from the backend, not
+    // from this timer having reached zero.
+    submit();
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, [remainingSeconds, viewState]);
+
+  const answeredIds = useMemo(
+    () =>
+      new Set(
+        Object.entries(answers)
+          .filter(([, v]) => v.selectedOptionId || v.answerText?.trim())
+          .map(([id]) => id),
+      ),
+    [answers],
+  );
+
+  return {
+    viewState,
+    errorMessage,
+    registration,
+    session,
+    currentIndex,
+    answers,
+    saveStates,
+    answeredIds,
+    remainingSeconds,
+    starting,
+    submitting,
+    start,
+    selectOption,
+    changeText,
+    goTo,
+    retry,
+    submit,
+  };
+}

apps/portal/src/app/features/exam-attempt/pages/ExamAttemptPage/index.tsx

@@ -0,0 +1,187 @@
+import { useState } from 'react';
+import { useParams } from 'react-router-dom';
+import { Alert, Button, Center, Group, Loader, Modal, Stack, Text } from '@mantine/core';
+import { IconAlertCircle, IconSend } from '@tabler/icons-react';
+import { useLocalized } from '@ema-platform/api';
+import { useDateDisplayer } from '@ema-platform/shared';
+import { useExamAttempt } from '../../hooks/useExamAttempt';
+import { ExamInstructions } from '../../components/ExamInstructions';
+import { ExamTimer } from '../../components/ExamTimer';
+import { ExamQuestionNav } from '../../components/ExamQuestionNav';
+import { ExamQuestionDisplay } from '../../components/ExamQuestionDisplay';
+import { ExamCompletion } from '../../components/ExamCompletion';
+
+/**
+ * The candidate exam-taking screen (Phase 4). Route: `/exams/:examId/take`.
+ *
+ * All state/API orchestration lives in `useExamAttempt` — this component is
+ * the view: pick which of loading/not-started/taking/completed/error to
+ * render. Every write it triggers (start, save, submit) is re-checked by the
+ * backend regardless of what this screen currently shows; nothing here is
+ * the actual security boundary.
+ */
+export function ExamAttemptPage() {
+  const { examId } = useParams<{ examId: string }>();
+  const localized = useLocalized();
+  const showDate = useDateDisplayer();
+  const [confirmOpened, setConfirmOpened] = useState(false);
+
+  const {
+    viewState,
+    errorMessage,
+    registration,
+    session,
+    currentIndex,
+    answers,
+    saveStates,
+    answeredIds,
+    remainingSeconds,
+    starting,
+    submitting,
+    start,
+    selectOption,
+    changeText,
+    goTo,
+    retry,
+    submit,
+  } = useExamAttempt(examId);
+
+  if (viewState === 'loading') {
+    return (
+      <Center py="xl">
+        <Loader />
+      </Center>
+    );
+  }
+
+  if (viewState === 'error') {
+    return (
+      <Alert icon={<IconAlertCircle size={16} />} color="red" maw={600} mx="auto" mt="xl">
+        {errorMessage}
+      </Alert>
+    );
+  }
+
+  if (viewState === 'not-started') {
+    if (!registration) return null; // guarded by 'error' above, appeases TS
+    return (
+      <ExamInstructions
+        registration={registration}
+        localized={localized}
+        showDate={showDate}
+        starting={starting}
+        onStart={start}
+      />
+    );
+  }
+
+  if (viewState === 'completed' && session) {
+    return (
+      <ExamCompletion status={session.attempt.status} submittedAt={session.attempt.submittedAt} />
+    );
+  }
+
+  if (!session) return null; // 'taking' always has a session by construction
+
+  const question = session.questions[currentIndex];
+  const answer = answers[question.id];
+
+  return (
+    <Stack maw={1000} mx="auto" gap="md">
+      <Group justify="space-between" wrap="nowrap">
+        <Text fw={600}>{localized(registration?.exam?.title) || 'Examination in progress'}</Text>
+        <ExamTimer remainingSeconds={remainingSeconds} />
+      </Group>
+
+      <Group align="flex-start" gap="md" wrap="wrap-reverse">
+        <div style={{ flex: 1, minWidth: 280 }}>
+          <ExamQuestionDisplay
+            question={question}
+            index={currentIndex}
+            total={session.questions.length}
+            localized={localized}
+            selectedOptionId={answer?.selectedOptionId}
+            answerText={answer?.answerText}
+            saveState={saveStates[question.id] ?? 'idle'}
+            disabled={remainingSeconds <= 0}
+            onSelectOption={(optionId) => selectOption(question.id, optionId)}
+            onChangeText={(text) => changeText(question.id, text)}
+            onRetry={() => retry(question.id)}
+          />
+
+          <Group justify="space-between" mt="md">
+            <Button
+              variant="default"
+              disabled={currentIndex === 0}
+              onClick={() => goTo(currentIndex - 1)}
+            >
+              Previous
+            </Button>
+            {currentIndex < session.questions.length - 1 ? (
+              <Button onClick={() => goTo(currentIndex + 1)}>Next</Button>
+            ) : (
+              <Button
+                color="teal"
+                leftSection={<IconSend size={15} />}
+                onClick={() => setConfirmOpened(true)}
+              >
+                Submit exam
+              </Button>
+            )}
+          </Group>
+        </div>
+
+        <div style={{ width: 220, flexShrink: 0 }}>
+          <ExamQuestionNav
+            questions={session.questions}
+            currentIndex={currentIndex}
+            answeredIds={answeredIds}
+            disabled={remainingSeconds <= 0}
+            onJump={goTo}
+          />
+          <Button
+            fullWidth
+            mt="sm"
+            variant="light"
+            color="teal"
+            leftSection={<IconSend size={15} />}
+            onClick={() => setConfirmOpened(true)}
+          >
+            Submit exam
+          </Button>
+        </div>
+      </Group>
+
+      <Modal
+        opened={confirmOpened}
+        onClose={() => setConfirmOpened(false)}
+        title="Submit this exam?"
+        radius="lg"
+      >
+        <Stack>
+          <Text size="sm">
+            {answeredIds.size} of {session.questions.length} questions answered. Once submitted,
+            answers cannot be changed.
+          </Text>
+          <Group justify="flex-end">
+            <Button variant="default" onClick={() => setConfirmOpened(false)}>
+              Keep working
+            </Button>
+            <Button
+              color="teal"
+              loading={submitting}
+              onClick={async () => {
+                await submit();
+                setConfirmOpened(false);
+              }}
+            >
+              Submit
+            </Button>
+          </Group>
+        </Stack>
+      </Modal>
+    </Stack>
+  );
+}
+
+export default ExamAttemptPage;

apps/portal/src/app/features/exam-attempt/types/exam-attempt.ts

@@ -0,0 +1,78 @@
+import type { Bilingual } from '@ema-platform/api';
+
+export type AttemptStatus = 'IN_PROGRESS' | 'SUBMITTED' | 'EXPIRED';
+export type QuestionForm = 'ESSAY' | 'CHOICE';
+
+export interface CandidateOption {
+  id: string;
+  text: Bilingual;
+  order: number;
+}
+
+/** Never carries a correct-answer flag — the API doesn't send one. */
+export interface CandidateQuestion {
+  id: string;
+  title: Bilingual;
+  form: QuestionForm;
+  points: number;
+  options: CandidateOption[];
+}
+
+export interface ExamAttempt {
+  id: string;
+  examId: string;
+  registrationId: string;
+  status: AttemptStatus;
+  startedAt: string;
+  expiresAt: string;
+  submittedAt: string | null;
+}
+
+export interface CandidateAnswer {
+  id: string;
+  attemptId: string;
+  questionId: string;
+  selectedOptionId: string | null;
+  answerText: string | null;
+}
+
+/** Response shape shared by POST /exam-attempts/start and GET .../mine/:examId. */
+export interface AttemptSession {
+  attempt: ExamAttempt;
+  questions: CandidateQuestion[];
+  answers: CandidateAnswer[];
+  serverTime: string;
+  remainingSeconds: number;
+}
+
+export type SaveState = 'idle' | 'saving' | 'saved' | 'error';
+
+export interface EstimatedTime {
+  days: number;
+  hours: number;
+  minutes: number;
+}
+
+/**
+ * The subset of `GET /exams/registrations/mine`'s response this feature
+ * reads — the endpoint returns the full raw exam/registration, this is
+ * just this feature's own narrow view of it (matches the sibling `exams`
+ * feature's pattern of each screen typing only what it uses).
+ */
+export interface RegistrationWithExam {
+  id: string;
+  admissionNumber: string;
+  kind: 'NEW' | 'RETAKE';
+  attemptNumber: number;
+  attendanceStatus: string;
+  exam?: {
+    id: string;
+    title: Bilingual;
+    direction?: Bilingual;
+    date: string;
+    venue: string | null;
+    status: string;
+    givenTime: EstimatedTime | null;
+    certification?: { name?: Bilingual };
+  };
+}

apps/portal/src/app/features/exams/pages/ExamsPage/columns.tsx

@@ -1,5 +1,5 @@
 import { Badge, Button, Text } from '@mantine/core';
-import { IconFileText, IconGavel } from '@tabler/icons-react';
+import { IconFileText, IconGavel, IconPlayerPlay } from '@tabler/icons-react';
 import type { AdvancedColumn } from '@ema-platform/ui';
 import type { Bilingual } from '@ema-platform/api';
 import { PORTAL_PERMISSIONS } from '@ema-platform/auth';
@@ -19,12 +19,15 @@ const ATTENDANCE_COLOR: Record<AttendanceStatus, string> = {
   DISQUALIFIED: 'red',
 };
 
+const NOT_SITTING: AttendanceStatus[] = ['ABSENT', 'WITHDRAWN', 'DISQUALIFIED'];
+
 export function registrationColumns(deps: {
   /** Permission check from usePermissions() — hooks can't run in a cell. */
   can: (required?: string[]) => boolean;
   localized: (value: Bilingual | undefined) => string;
   showDate: (value: string | null | undefined) => string;
   onDownloadSlip: (registration: MyRegistration) => void;
+  onStartExam: (registration: MyRegistration) => void;
 }): AdvancedColumn<MyRegistration>[] {
   return [
     {
@@ -87,6 +90,25 @@ export function registrationColumns(deps: {
           </Button>
         ) : null,
     },
+    {
+      header: 'Exam',
+      cell: ({ row }) => {
+        const exam = row.original.exam;
+        const eligible =
+          exam?.status === 'ACTIVE' && !NOT_SITTING.includes(row.original.attendanceStatus);
+        if (!eligible || !deps.can([PORTAL_PERMISSIONS.APPLY_EXAM])) return null;
+        return (
+          <Button
+            size="compact-xs"
+            color="teal"
+            leftSection={<IconPlayerPlay size={13} />}
+            onClick={() => deps.onStartExam(row.original)}
+          >
+            Take exam
+          </Button>
+        );
+      },
+    },
   ];
 }
 

apps/portal/src/app/features/exams/pages/ExamsPage/index.tsx

@@ -1,4 +1,5 @@
 import { useState } from 'react';
+import { useNavigate } from 'react-router-dom';
 import {
   Badge,
   Button,
@@ -79,6 +80,7 @@ export interface MyAppeal {
  * when a mark looks wrong.
  */
 export function ExamsPage() {
+  const navigate = useNavigate();
   const showDate = useDateDisplayer();
   const localized = useLocalized();
   const [appealFor, setAppealFor] = useState<MyResult | null>(null);
@@ -243,6 +245,7 @@ export function ExamsPage() {
             localized,
             showDate,
             onDownloadSlip: downloadSlip,
+            onStartExam: (registration) => navigate(`/exams/${registration.exam?.id}/take`),
           })}
           data={pagedRegistrations.rows}
           itemCount={pagedRegistrations.itemCount}

apps/portal/src/app/router.tsx

@@ -32,6 +32,7 @@ import { SeafarerRegistrationPage } from "./features/seafarer/pages/SeafarerRegi
 import { MySeaRecordsPage } from "./features/seafarer/pages/MySeaRecordsPage";
 import { VerifyCertificatePage } from "./features/verify/pages/VerifyCertificatePage";
 import { ExamsPage } from "./features/exams/pages/ExamsPage";
+import { ExamAttemptPage } from "./features/exam-attempt/pages/ExamAttemptPage";
 
 // Phase 1 pages
 import { DocumentVaultPage } from "./features/documents/pages/DocumentVaultPage";
@@ -184,6 +185,14 @@ export const router = createBrowserRouter([
           </RequirePermission>
         ),
       },
+      {
+        path: "/exams/:examId/take",
+        element: (
+          <RequirePermission anyOf={[P.APPLY_EXAM, P.VIEW_OWN_EXAM]}>
+            <ExamAttemptPage />
+          </RequirePermission>
+        ),
+      },
       // The public-facing registry was a hardcoded mock and does not belong in
       // the applicant portal; officers browse seafarers in the backoffice.
       {