diff --git a/internal/engine.cm b/internal/engine.cm
index 318255fb..e0c7211d 100644
--- a/internal/engine.cm
+++ b/internal/engine.cm
@@ -223,6 +223,15 @@ globalThis.use = shop.use
 globalThis.json = use('json')
 var time = use('time')
 
+var pronto = use('pronto')
+globalThis.fallback = pronto.fallback
+globalThis.parallel = pronto.parallel
+globalThis.race = pronto.race
+globalThis.sequence = pronto.sequence
+globalThis.time_limit = pronto.time_limit
+globalThis.requestorize = pronto.requestorize
+globalThis.objectify = pronto.objectify
+
 var config = {
   ar_timer: 60,
   actor_memory:0,
diff --git a/pronto.cm b/pronto.cm
new file mode 100644
index 00000000..a6165893
--- /dev/null
+++ b/pronto.cm
@@ -0,0 +1,427 @@
+// pronto.cm
+// Extremism in the pursuit of parallelism is no vice.
+// Based on Douglas Crockford's parseq, adapted for Cell.
+// Time is in seconds.
+
+var os = use('os')
+var $_ = os.$_
+
+function make_reason(factory, excuse, evidence) {
+  def reason = new Error(`pronto.${factory}${excuse ? ': ' + excuse : ''}`)
+  reason.evidence = evidence
+  return reason
+}
+
+function is_requestor(fn) {
+  return typeof fn == 'function' && (fn.length == 1 || fn.length == 2)
+}
+
+function check_requestors(list, factory) {
+  if (!Array.isArray(list) || list.some(r => !is_requestor(r)))
+    throw make_reason(factory, 'Bad requestor array.', list)
+}
+
+function check_callback(cb, factory) {
+  if (typeof cb != 'function' || cb.length != 2)
+    throw make_reason(factory, 'Not a callback.', cb)
+}
+
+// fallback(requestor_array)
+// Tries each requestor in order until one succeeds.
+function fallback(requestor_array) {
+  def factory = 'fallback'
+  if (!Array.isArray(requestor_array) || requestor_array.length == 0)
+    throw make_reason(factory, 'Empty requestor array.')
+  check_requestors(requestor_array, factory)
+
+  return function fallback_requestor(callback, value) {
+    check_callback(callback, factory)
+    let index = 0
+    let current_cancel = null
+    let cancelled = false
+
+    function cancel(reason) {
+      cancelled = true
+      if (current_cancel) {
+        try { current_cancel(reason) } catch (_) {}
+        current_cancel = null
+      }
+    }
+
+    function try_next() {
+      if (cancelled) return
+      if (index >= requestor_array.length) {
+        callback(null, make_reason(factory, 'All requestors failed.'))
+        return
+      }
+
+      def requestor = requestor_array[index]
+      index += 1
+
+      try {
+        current_cancel = requestor(function(val, reason) {
+          if (cancelled) return
+          current_cancel = null
+          if (val != null) {
+            callback(val)
+          } else {
+            try_next()
+          }
+        }, value)
+      } catch (ex) {
+        try_next()
+      }
+    }
+
+    try_next()
+    return cancel
+  }
+}
+
+// parallel(requestor_array, throttle, need)
+// Runs requestors in parallel, collecting all results.
+function parallel(requestor_array, throttle, need) {
+  def factory = 'parallel'
+  if (!Array.isArray(requestor_array))
+    throw make_reason(factory, 'Not an array.', requestor_array)
+  check_requestors(requestor_array, factory)
+
+  def length = requestor_array.length
+  if (length == 0)
+    return function(callback, value) { callback([]) }
+
+  if (need == null) need = length
+  if (typeof need != 'number' || need < 0 || need > length)
+    throw make_reason(factory, 'Bad need.', need)
+
+  if (throttle != null && (typeof throttle != 'number' || throttle < 1))
+    throw make_reason(factory, 'Bad throttle.', throttle)
+
+  return function parallel_requestor(callback, value) {
+    check_callback(callback, factory)
+    def results = new Array(length)
+    def cancel_list = new Array(length)
+    let next_index = 0
+    let successes = 0
+    let failures = 0
+    let finished = false
+
+    function cancel(reason) {
+      if (finished) return
+      finished = true
+      cancel_list.forEach(c => {
+        try { if (typeof c == 'function') c(reason) } catch (_) {}
+      })
+    }
+
+    function start_one() {
+      if (finished || next_index >= length) return
+      def idx = next_index
+      next_index += 1
+      def requestor = requestor_array[idx]
+
+      try {
+        cancel_list[idx] = requestor(function(val, reason) {
+          if (finished) return
+          cancel_list[idx] = null
+
+          if (val != null) {
+            results[idx] = val
+            successes += 1
+            if (successes >= need) {
+              finished = true
+              cancel(make_reason(factory, 'Finished.'))
+              callback(results)
+              return
+            }
+          } else {
+            failures += 1
+            if (failures > length - need) {
+              cancel(reason)
+              callback(null, reason || make_reason(factory, 'Too many failures.'))
+              return
+            }
+          }
+
+          start_one()
+        }, value)
+      } catch (ex) {
+        failures += 1
+        if (failures > length - need) {
+          cancel(ex)
+          callback(null, ex)
+          return
+        }
+        start_one()
+      }
+    }
+
+    def concurrent = throttle ? Math.min(throttle, length) : length
+    for (let i = 0; i < concurrent; i++) start_one()
+
+    return cancel
+  }
+}
+
+// race(requestor_array, throttle, need)
+// Runs requestors in parallel, returns first success(es).
+function race(requestor_array, throttle, need) {
+  def factory = 'race'
+  if (!Array.isArray(requestor_array) || requestor_array.length == 0)
+    throw make_reason(factory, 'Empty requestor array.')
+  check_requestors(requestor_array, factory)
+
+  def length = requestor_array.length
+  if (need == null) need = 1
+  if (typeof need != 'number' || need < 1 || need > length)
+    throw make_reason(factory, 'Bad need.', need)
+
+  if (throttle != null && (typeof throttle != 'number' || throttle < 1))
+    throw make_reason(factory, 'Bad throttle.', throttle)
+
+  return function race_requestor(callback, value) {
+    check_callback(callback, factory)
+    def results = new Array(length)
+    def cancel_list = new Array(length)
+    let next_index = 0
+    let successes = 0
+    let failures = 0
+    let finished = false
+
+    function cancel(reason) {
+      if (finished) return
+      finished = true
+      cancel_list.forEach(c => {
+        try { if (typeof c == 'function') c(reason) } catch (_) {}
+      })
+    }
+
+    function start_one() {
+      if (finished || next_index >= length) return
+      def idx = next_index
+      next_index += 1
+      def requestor = requestor_array[idx]
+
+      try {
+        cancel_list[idx] = requestor(function(val, reason) {
+          if (finished) return
+          cancel_list[idx] = null
+
+          if (val != null) {
+            results[idx] = val
+            successes += 1
+            if (successes >= need) {
+              cancel(make_reason(factory, 'Winner.'))
+              if (need == 1) {
+                callback(val)
+              } else {
+                callback(results)
+              }
+              return
+            }
+          } else {
+            failures += 1
+            if (failures > length - need) {
+              cancel(reason)
+              callback(null, reason || make_reason(factory, 'All failed.'))
+              return
+            }
+          }
+
+          start_one()
+        }, value)
+      } catch (ex) {
+        failures += 1
+        if (failures > length - need) {
+          cancel(ex)
+          callback(null, ex)
+          return
+        }
+        start_one()
+      }
+    }
+
+    def concurrent = throttle ? Math.min(throttle, length) : length
+    for (let i = 0; i < concurrent; i++) start_one()
+
+    return cancel
+  }
+}
+
+// sequence(requestor_array)
+// Runs requestors one at a time, passing result to next.
+function sequence(requestor_array) {
+  def factory = 'sequence'
+  if (!Array.isArray(requestor_array))
+    throw make_reason(factory, 'Not an array.', requestor_array)
+  check_requestors(requestor_array, factory)
+
+  if (requestor_array.length == 0)
+    return function(callback, value) { callback(value) }
+
+  return function sequence_requestor(callback, value) {
+    check_callback(callback, factory)
+    let index = 0
+    let current_cancel = null
+    let cancelled = false
+
+    function cancel(reason) {
+      cancelled = true
+      if (current_cancel) {
+        try { current_cancel(reason) } catch (_) {}
+        current_cancel = null
+      }
+    }
+
+    function run_next(val) {
+      if (cancelled) return
+      if (index >= requestor_array.length) {
+        callback(val)
+        return
+      }
+
+      def requestor = requestor_array[index]
+      index += 1
+
+      try {
+        current_cancel = requestor(function(result, reason) {
+          if (cancelled) return
+          current_cancel = null
+          if (result == null) {
+            callback(null, reason)
+          } else {
+            run_next(result)
+          }
+        }, val)
+      } catch (ex) {
+        callback(null, ex)
+      }
+    }
+
+    run_next(value)
+    return cancel
+  }
+}
+
+// time_limit(requestor, seconds)
+// Wraps a requestor with a time limit.
+function time_limit(requestor, seconds) {
+  def factory = 'time_limit'
+  if (!is_requestor(requestor))
+    throw make_reason(factory, 'Not a requestor.', requestor)
+  if (typeof seconds != 'number' || seconds <= 0)
+    throw make_reason(factory, 'Bad time limit.', seconds)
+
+  return function time_limit_requestor(callback, value) {
+    check_callback(callback, factory)
+    let finished = false
+    let requestor_cancel = null
+    let timer_cancel = null
+
+    function cancel(reason) {
+      if (finished) return
+      finished = true
+      if (timer_cancel) {
+        timer_cancel()
+        timer_cancel = null
+      }
+      if (requestor_cancel) {
+        try { requestor_cancel(reason) } catch (_) {}
+        requestor_cancel = null
+      }
+    }
+
+    timer_cancel = $_.delay(function() {
+      if (finished) return
+      def reason = make_reason(factory, 'Timeout.', seconds)
+      if (requestor_cancel) {
+        try { requestor_cancel(reason) } catch (_) {}
+        requestor_cancel = null
+      }
+      finished = true
+      callback(null, reason)
+    }, seconds)
+
+    try {
+      requestor_cancel = requestor(function(val, reason) {
+        if (finished) return
+        finished = true
+        if (timer_cancel) {
+          timer_cancel()
+          timer_cancel = null
+        }
+        callback(val, reason)
+      }, value)
+    } catch (ex) {
+      cancel(ex)
+      callback(null, ex)
+    }
+
+    return function(reason) {
+      if (requestor_cancel) {
+        try { requestor_cancel(reason) } catch (_) {}
+        requestor_cancel = null
+      }
+    }
+  }
+}
+
+// requestorize(unary)
+// Converts a unary function into a requestor.
+function requestorize(unary) {
+  def factory = 'requestorize'
+  if (typeof unary != 'function')
+    throw make_reason(factory, 'Not a function.', unary)
+
+  return function requestorized(callback, value) {
+    check_callback(callback, factory)
+    try {
+      def result = unary(value)
+      callback(result == null ? true : result)
+    } catch (ex) {
+      callback(null, ex)
+    }
+  }
+}
+
+// objectify(factory_fn)
+// Converts a factory that takes arrays to one that takes objects.
+function objectify(factory_fn) {
+  def factory = 'objectify'
+  if (typeof factory_fn != 'function')
+    throw make_reason(factory, 'Not a factory.', factory_fn)
+
+  return function objectified_factory(object_of_requestors, ...rest) {
+    if (typeof object_of_requestors != 'object' || Array.isArray(object_of_requestors))
+      throw make_reason(factory, 'Expected an object.', object_of_requestors)
+
+    def keys = Object.keys(object_of_requestors)
+    def requestor_array = keys.map(k => object_of_requestors[k])
+
+    def inner_requestor = factory_fn(requestor_array, ...rest)
+
+    return function(callback, value) {
+      return inner_requestor(function(results, reason) {
+        if (results == null) {
+          callback(null, reason)
+        } else if (Array.isArray(results)) {
+          def obj = {}
+          keys.forEach((k, i) => { obj[k] = results[i] })
+          callback(obj, reason)
+        } else {
+          callback(results, reason)
+        }
+      }, value)
+    }
+  }
+}
+
+return {
+  fallback,
+  parallel,
+  race,
+  sequence,
+  time_limit,
+  requestorize,
+  objectify
+}
diff --git a/tests/pronto.cm b/tests/pronto.cm
new file mode 100644
index 00000000..4dc9fac6
--- /dev/null
+++ b/tests/pronto.cm
@@ -0,0 +1,137 @@
+// Test pronto functions
+// Tests for fallback, parallel, race, sequence, time_limit, requestorize, objectify
+
+var test_count = 0
+
+function make_requestor(name, delay_seconds, should_succeed) {
+  return function(callback, value) {
+    log.console(`Starting ${name} with value: ${value}`)
+    if (delay_seconds > 0) {
+      $_.delay(function() {
+        if (should_succeed) {
+          log.console(`${name} succeeded with: ${value + 1}`)
+          callback(value + 1)
+        } else {
+          log.console(`${name} failed`)
+          callback(null, `${name} error`)
+        }
+      }, delay_seconds)
+    } else {
+      if (should_succeed) {
+        log.console(`${name} succeeded immediately with: ${value + 1}`)
+        callback(value + 1)
+      } else {
+        log.console(`${name} failed immediately`)
+        callback(null, `${name} error`)
+      }
+    }
+  }
+}
+
+return {
+  test_fallback: function() {
+    log.console("Testing fallback...")
+    var req1 = make_requestor("fallback_req1", 0.1, false)  // fails
+    var req2 = make_requestor("fallback_req2", 0.1, true)   // succeeds
+    var req3 = make_requestor("fallback_req3", 0.1, true)   // should not run
+
+    fallback([req1, req2, req3])(function(result, reason) {
+      if (result != null) {
+        log.console(`Fallback succeeded: ${result}`)
+      } else {
+        log.console(`Fallback failed: ${reason}`)
+      }
+    }, 10)
+  },
+
+  test_parallel: function() {
+    log.console("Testing parallel...")
+    var req1 = make_requestor("parallel_req1", 0.2, true)
+    var req2 = make_requestor("parallel_req2", 0.1, true)
+    var req3 = make_requestor("parallel_req3", 0.3, true)
+
+    parallel([req1, req2, req3])(function(results, reason) {
+      if (results != null) {
+        log.console(`Parallel results: ${results}`)
+      } else {
+        log.console(`Parallel failed: ${reason}`)
+      }
+    }, 100)
+  },
+
+  test_race: function() {
+    log.console("Testing race...")
+    var req1 = make_requestor("race_req1", 0.3, true)  // slow
+    var req2 = make_requestor("race_req2", 0.1, true)  // fast winner
+    var req3 = make_requestor("race_req3", 0.2, true)  // medium
+
+    race([req1, req2, req3])(function(result, reason) {
+      if (result != null) {
+        log.console(`Race winner: ${result}`)
+      } else {
+        log.console(`Race failed: ${reason}`)
+      }
+    }, 200)
+  },
+
+  test_sequence: function() {
+    log.console("Testing sequence...")
+    var req1 = make_requestor("seq_req1", 0.1, true)
+    var req2 = make_requestor("seq_req2", 0.1, true)
+    var req3 = make_requestor("seq_req3", 0.1, true)
+
+    sequence([req1, req2, req3])(function(result, reason) {
+      if (result != null) {
+        log.console(`Sequence result: ${result}`)
+      } else {
+        log.console(`Sequence failed: ${reason}`)
+      }
+    }, 1000)
+  },
+
+  test_time_limit: function() {
+    log.console("Testing time_limit...")
+    var slow_req = make_requestor("slow_req", 0.5, true)  // takes 0.5s
+    var timed_req = time_limit(slow_req, 0.2)  // 0.2s limit
+
+    timed_req(function(result, reason) {
+      if (result != null) {
+        log.console(`Time limit succeeded: ${result}`)
+      } else {
+        log.console(`Time limit failed: ${reason}`)
+      }
+    }, 100)
+  },
+
+  test_requestorize: function() {
+    log.console("Testing requestorize...")
+    var add_one = function(x) { return x + 1 }
+    var req = requestorize(add_one)
+
+    req(function(result, reason) {
+      if (result != null) {
+        log.console(`Requestorize result: ${result}`)
+      } else {
+        log.console(`Requestorize failed: ${reason}`)
+      }
+    }, 42)
+  },
+
+  test_objectify: function() {
+    log.console("Testing objectify...")
+    var req_a = make_requestor("obj_req_a", 0.1, true)
+    var req_b = make_requestor("obj_req_b", 0.1, true)
+    var req_c = make_requestor("obj_req_c", 0.1, true)
+
+    var parallel_obj = objectify(parallel)
+    var req = parallel_obj({a: req_a, b: req_b, c: req_c})
+
+    req(function(result, reason) {
+      if (result != null) {
+        log.console(`Objectify result: ${json.encode(result)}`)
+      } else {
+        log.console(`Objectify failed: ${reason}`)
+      }
+    }, 1000)
+  }
+}
\ No newline at end of file