diff --git a/lib/providers/base.mjs b/lib/providers/base.mjs
index 749b6a1..c4bacfd 100644
--- a/lib/providers/base.mjs
+++ b/lib/providers/base.mjs
@@ -24,6 +24,7 @@
  * @property {boolean} requiresTTY
  * @property {boolean} concurrentSpawnSafe
  * @property {number} maxConcurrent
+ * @property {number} [maxSpawnTimeMs] - optional integer milliseconds, default 600000
  */
 
 /**
@@ -110,13 +111,18 @@ export function validateProvider(p) {
   }
 
   if (!p.hints || typeof p.hints !== 'object') {
-    errors.push('hints must be an object with { requiresTTY, concurrentSpawnSafe, maxConcurrent }');
+    errors.push('hints must be an object with { requiresTTY, concurrentSpawnSafe, maxConcurrent, maxSpawnTimeMs }');
   } else {
     if (typeof p.hints.requiresTTY !== 'boolean') errors.push('hints.requiresTTY must be a boolean');
     if (typeof p.hints.concurrentSpawnSafe !== 'boolean') errors.push('hints.concurrentSpawnSafe must be a boolean');
     if (typeof p.hints.maxConcurrent !== 'number' || !Number.isInteger(p.hints.maxConcurrent) || p.hints.maxConcurrent < 0) {
       errors.push('hints.maxConcurrent must be a non-negative integer');
     }
+    if (p.hints.maxSpawnTimeMs !== undefined) {
+      if (typeof p.hints.maxSpawnTimeMs !== 'number' || !Number.isInteger(p.hints.maxSpawnTimeMs) || p.hints.maxSpawnTimeMs <= 0) {
+        errors.push('hints.maxSpawnTimeMs must be a positive integer (milliseconds) or omitted');
+      }
+    }
   }
 
   return { valid: errors.length === 0, errors };
diff --git a/test-features.mjs b/test-features.mjs
index 2e8325c..556fd17 100644
--- a/test-features.mjs
+++ b/test-features.mjs
@@ -521,6 +521,42 @@ describe('Provider contract validation', () => {
     assert.ok(r.errors.some(e => e.includes('maxConcurrent')));
   });
 
+  it('validateProvider rejects negative maxSpawnTimeMs', () => {
+    const r = validateProvider(makeProvider({ hints: { requiresTTY: false, concurrentSpawnSafe: true, maxConcurrent: 4, maxSpawnTimeMs: -1 } }));
+    assert.equal(r.valid, false);
+    assert.ok(r.errors.some(e => e.includes('maxSpawnTimeMs')));
+  });
+
+  it('validateProvider rejects zero maxSpawnTimeMs', () => {
+    const r = validateProvider(makeProvider({ hints: { requiresTTY: false, concurrentSpawnSafe: true, maxConcurrent: 4, maxSpawnTimeMs: 0 } }));
+    assert.equal(r.valid, false);
+    assert.ok(r.errors.some(e => e.includes('maxSpawnTimeMs')));
+  });
+
+  it('validateProvider rejects non-integer maxSpawnTimeMs (e.g., 100.5)', () => {
+    const r = validateProvider(makeProvider({ hints: { requiresTTY: false, concurrentSpawnSafe: true, maxConcurrent: 4, maxSpawnTimeMs: 100.5 } }));
+    assert.equal(r.valid, false);
+    assert.ok(r.errors.some(e => e.includes('maxSpawnTimeMs')));
+  });
+
+  it('validateProvider rejects non-number maxSpawnTimeMs (e.g., \'600\')', () => {
+    const r = validateProvider(makeProvider({ hints: { requiresTTY: false, concurrentSpawnSafe: true, maxConcurrent: 4, maxSpawnTimeMs: '600' } }));
+    assert.equal(r.valid, false);
+    assert.ok(r.errors.some(e => e.includes('maxSpawnTimeMs')));
+  });
+
+  it('validateProvider accepts omitted maxSpawnTimeMs (optional field)', () => {
+    const r = validateProvider(makeProvider({ hints: { requiresTTY: false, concurrentSpawnSafe: true, maxConcurrent: 4 } }));
+    assert.equal(r.valid, true);
+    assert.deepEqual(r.errors, []);
+  });
+
+  it('validateProvider accepts positive integer maxSpawnTimeMs (e.g., 60000)', () => {
+    const r = validateProvider(makeProvider({ hints: { requiresTTY: false, concurrentSpawnSafe: true, maxConcurrent: 4, maxSpawnTimeMs: 60000 } }));
+    assert.equal(r.valid, true);
+    assert.deepEqual(r.errors, []);
+  });
+
   it('rejects non-object input', () => {
     const r = validateProvider(null);
     assert.equal(r.valid, false);