diff --git a/plugins/ultraplan-local/lib/validators/session-state-validator.mjs b/plugins/ultraplan-local/lib/validators/session-state-validator.mjs
new file mode 100644
index 0000000..71fb5f7
--- /dev/null
+++ b/plugins/ultraplan-local/lib/validators/session-state-validator.mjs
@@ -0,0 +1,117 @@
+// lib/validators/session-state-validator.mjs
+// Validate .session-state.local.json — the contract consumed by /ultracontinue.
+// Schema v1 documented in docs/HANDOVER-CONTRACTS.md (Handover 7).
+
+import { readFileSync, existsSync } from 'node:fs';
+import { issue, fail } from '../util/result.mjs';
+
+export const SESSION_STATE_REQUIRED_TOP = [
+  'schema_version',
+  'project',
+  'next_session_brief_path',
+  'next_session_label',
+  'status',
+  'updated_at',
+];
+
+// All five statuses parse as valid; `completed` emits a warning that the
+// session is not resumable. Unknown statuses fail.
+export const SESSION_STATE_VALID_STATUSES = ['in_progress', 'partial', 'failed', 'stopped', 'completed'];
+
+// Statuses that /ultracontinue can resume from. `completed` is intentionally
+// excluded — running ultracontinue on a completed project should signal "no
+// further sessions to resume", not load stale context.
+export const SESSION_STATE_RESUMABLE_STATUSES = ['in_progress', 'partial', 'failed', 'stopped'];
+
+export function validateSessionStateContent(jsonText, opts = {}) {
+  let parsed;
+  try { parsed = JSON.parse(jsonText); }
+  catch (e) {
+    return fail(issue('SESSION_STATE_PARSE_ERROR', `Cannot parse JSON: ${e.message}`));
+  }
+  return validateSessionStateObject(parsed, opts);
+}
+
+export function validateSessionStateObject(parsed, opts = {}) {
+  const errors = [];
+  const warnings = [];
+
+  if (typeof parsed !== 'object' || parsed === null) {
+    return fail(issue('SESSION_STATE_NOT_OBJECT', 'Session-state payload is not an object'));
+  }
+
+  for (const k of SESSION_STATE_REQUIRED_TOP) {
+    if (!(k in parsed)) {
+      errors.push(issue('SESSION_STATE_MISSING_FIELD', `Required field missing: ${k}`));
+    }
+  }
+
+  if (parsed.schema_version !== undefined && parsed.schema_version !== 1) {
+    errors.push(issue(
+      'SESSION_STATE_SCHEMA_MISMATCH',
+      `schema_version ${JSON.stringify(parsed.schema_version)} not supported (expected 1)`,
+    ));
+  }
+
+  if (parsed.status !== undefined) {
+    if (!SESSION_STATE_VALID_STATUSES.includes(parsed.status)) {
+      errors.push(issue(
+        'SESSION_STATE_INVALID_STATUS',
+        `status "${parsed.status}" not in [${SESSION_STATE_VALID_STATUSES.join(', ')}]`,
+      ));
+    } else if (parsed.status === 'completed') {
+      warnings.push(issue(
+        'SESSION_STATE_NOT_RESUMABLE',
+        'status "completed" — project is done; no further sessions to resume',
+      ));
+    }
+  }
+
+  if (parsed.next_session_brief_path !== undefined) {
+    if (typeof parsed.next_session_brief_path !== 'string' || parsed.next_session_brief_path.length === 0) {
+      errors.push(issue('SESSION_STATE_INVALID_PATH', 'next_session_brief_path must be a non-empty string'));
+    }
+  }
+
+  if (parsed.updated_at !== undefined) {
+    if (typeof parsed.updated_at !== 'string' || Number.isNaN(Date.parse(parsed.updated_at))) {
+      errors.push(issue('SESSION_STATE_INVALID_TIMESTAMP', `updated_at "${parsed.updated_at}" is not a valid ISO-8601 timestamp`));
+    }
+  }
+
+  // Forward-compat: unknown top-level keys are tolerated silently.
+  // This protects future graceful-handoff v2.2 dual-writes that emit
+  // additional fields (branch, git_status, committed_by, ...).
+
+  return { valid: errors.length === 0, errors, warnings, parsed };
+}
+
+export function validateSessionState(filePath, opts = {}) {
+  if (!existsSync(filePath)) {
+    return fail(issue('SESSION_STATE_NOT_FOUND', `File not found: ${filePath}`));
+  }
+  let text;
+  try { text = readFileSync(filePath, 'utf-8'); }
+  catch (e) {
+    return fail(issue('SESSION_STATE_READ_ERROR', `Cannot read ${filePath}: ${e.message}`));
+  }
+  return validateSessionStateContent(text, opts);
+}
+
+if (import.meta.url === `file://${process.argv[1]}`) {
+  const args = process.argv.slice(2);
+  const filePath = args.find(a => !a.startsWith('--'));
+  if (!filePath) {
+    process.stderr.write('Usage: session-state-validator.mjs [--json] <.session-state.local.json>\n');
+    process.exit(2);
+  }
+  const r = validateSessionState(filePath);
+  if (args.includes('--json')) {
+    process.stdout.write(JSON.stringify({ valid: r.valid, errors: r.errors, warnings: r.warnings }, null, 2) + '\n');
+  } else {
+    process.stdout.write(`session-state-validator: ${r.valid ? 'PASS' : 'FAIL'} ${filePath}\n`);
+    for (const e of r.errors) process.stderr.write(`  ERROR  [${e.code}] ${e.message}\n`);
+    for (const w of r.warnings) process.stderr.write(`  WARN   [${w.code}] ${w.message}\n`);
+  }
+  process.exit(r.valid ? 0 : 1);
+}
diff --git a/plugins/ultraplan-local/tests/validators/session-state-validator.test.mjs b/plugins/ultraplan-local/tests/validators/session-state-validator.test.mjs
new file mode 100644
index 0000000..72a67f0
--- /dev/null
+++ b/plugins/ultraplan-local/tests/validators/session-state-validator.test.mjs
@@ -0,0 +1,145 @@
+// tests/validators/session-state-validator.test.mjs
+// Unit + integration tests for lib/validators/session-state-validator.mjs.
+// Schema v1 contract — see docs/HANDOVER-CONTRACTS.md (Handover 7).
+
+import { test } from 'node:test';
+import assert from 'node:assert/strict';
+import {
+  validateSessionStateObject,
+  validateSessionStateContent,
+  validateSessionState,
+} from '../../lib/validators/session-state-validator.mjs';
+
+function goodState() {
+  return {
+    schema_version: 1,
+    project: '.claude/projects/2026-05-01-example',
+    next_session_brief_path: '.claude/projects/2026-05-01-example/brief.md',
+    next_session_label: 'Session 2: Implement validator + tests',
+    status: 'in_progress',
+    updated_at: '2026-05-01T18:00:00.000Z',
+  };
+}
+
+test('validateSessionStateObject — happy path returns valid', () => {
+  const r = validateSessionStateObject(goodState());
+  assert.equal(r.valid, true);
+  assert.deepEqual(r.errors, []);
+  assert.deepEqual(r.warnings, []);
+});
+
+test('validateSessionStateObject — missing project field', () => {
+  const s = goodState();
+  delete s.project;
+  const r = validateSessionStateObject(s);
+  assert.equal(r.valid, false);
+  assert.ok(r.errors.find(e => e.code === 'SESSION_STATE_MISSING_FIELD' && /project/.test(e.message)));
+});
+
+test('validateSessionStateObject — missing status field', () => {
+  const s = goodState();
+  delete s.status;
+  const r = validateSessionStateObject(s);
+  assert.equal(r.valid, false);
+  assert.ok(r.errors.find(e => e.code === 'SESSION_STATE_MISSING_FIELD' && /status/.test(e.message)));
+});
+
+test('validateSessionStateObject — missing next_session_brief_path', () => {
+  const s = goodState();
+  delete s.next_session_brief_path;
+  const r = validateSessionStateObject(s);
+  assert.equal(r.valid, false);
+  assert.ok(r.errors.find(e => e.code === 'SESSION_STATE_MISSING_FIELD' && /next_session_brief_path/.test(e.message)));
+});
+
+test('validateSessionStateObject — missing next_session_label', () => {
+  const s = goodState();
+  delete s.next_session_label;
+  const r = validateSessionStateObject(s);
+  assert.equal(r.valid, false);
+  assert.ok(r.errors.find(e => e.code === 'SESSION_STATE_MISSING_FIELD' && /next_session_label/.test(e.message)));
+});
+
+test('validateSessionStateObject — missing updated_at', () => {
+  const s = goodState();
+  delete s.updated_at;
+  const r = validateSessionStateObject(s);
+  assert.equal(r.valid, false);
+  assert.ok(r.errors.find(e => e.code === 'SESSION_STATE_MISSING_FIELD' && /updated_at/.test(e.message)));
+});
+
+test('validateSessionStateObject — invalid status value rejected', () => {
+  const s = goodState();
+  s.status = 'maybe';
+  const r = validateSessionStateObject(s);
+  assert.equal(r.valid, false);
+  assert.ok(r.errors.find(e => e.code === 'SESSION_STATE_INVALID_STATUS'));
+});
+
+test('validateSessionStateObject — status completed valid but warns NOT_RESUMABLE', () => {
+  const s = goodState();
+  s.status = 'completed';
+  const r = validateSessionStateObject(s);
+  assert.equal(r.valid, true);
+  assert.deepEqual(r.errors, []);
+  assert.ok(r.warnings.find(w => w.code === 'SESSION_STATE_NOT_RESUMABLE'));
+});
+
+test('validateSessionStateObject — schema_version mismatch fails', () => {
+  const s = goodState();
+  s.schema_version = 2;
+  const r = validateSessionStateObject(s);
+  assert.equal(r.valid, false);
+  assert.ok(r.errors.find(e => e.code === 'SESSION_STATE_SCHEMA_MISMATCH'));
+});
+
+test('validateSessionStateObject — invalid timestamp rejected', () => {
+  const s = goodState();
+  s.updated_at = 'not-a-date';
+  const r = validateSessionStateObject(s);
+  assert.equal(r.valid, false);
+  assert.ok(r.errors.find(e => e.code === 'SESSION_STATE_INVALID_TIMESTAMP'));
+});
+
+test('validateSessionStateContent — malformed JSON returns SESSION_STATE_PARSE_ERROR', () => {
+  const r = validateSessionStateContent('{ broken');
+  assert.equal(r.valid, false);
+  assert.ok(r.errors.find(e => e.code === 'SESSION_STATE_PARSE_ERROR'));
+});
+
+test('validateSessionState — missing file returns SESSION_STATE_NOT_FOUND', () => {
+  const r = validateSessionState('/tmp/nonexistent-ultracontinue-test-9b2f4e.json');
+  assert.equal(r.valid, false);
+  assert.ok(r.errors.find(e => e.code === 'SESSION_STATE_NOT_FOUND'));
+});
+
+test('validateSessionState — fixture file loads and parses correctly (SC-1)', () => {
+  const r = validateSessionState('tests/fixtures/session-state/valid-in-progress.json');
+  assert.equal(r.valid, true);
+  assert.equal(r.parsed.status, 'in_progress');
+  assert.equal(typeof r.parsed.project, 'string');
+  assert.equal(typeof r.parsed.next_session_brief_path, 'string');
+  assert.equal(typeof r.parsed.next_session_label, 'string');
+});
+
+test('validateSessionState — malformed fixture returns SESSION_STATE_PARSE_ERROR (SC-3)', () => {
+  const r = validateSessionState('tests/fixtures/session-state/malformed.json');
+  assert.equal(r.valid, false);
+  assert.ok(r.errors.find(e => e.code === 'SESSION_STATE_PARSE_ERROR'));
+});
+
+test('validateSessionStateObject — forward-compat: unknown keys ignored silently', () => {
+  // Simulates graceful-handoff v2.2 dual-write with extra fields.
+  const s = {
+    ...goodState(),
+    branch: 'main',
+    git_status: { dirty: false, ahead: 0, detached: false },
+    committed_by: 'graceful-handoff',
+    last_commits: [{ sha: 'abc1234', msg: 'feat: foo' }],
+    next_steps: ['cd repo', 'git status'],
+  };
+  const r = validateSessionStateObject(s);
+  assert.equal(r.valid, true);
+  assert.deepEqual(r.errors, []);
+  assert.deepEqual(r.warnings, []);
+});