diff --git a/NAMESPACE b/NAMESPACE
index 0a50a48c..f70b3089 100644
--- a/NAMESPACE
+++ b/NAMESPACE
@@ -37,6 +37,8 @@ S3method(get_queue_size,wrap)
 S3method(get_queue_size_selected,simmer)
 S3method(get_resources,simmer)
 S3method(get_resources,wrap)
+S3method(get_seized,simmer)
+S3method(get_seized_selected,simmer)
 S3method(get_selected,simmer)
 S3method(get_server_count,simmer)
 S3method(get_server_count,wrap)
@@ -54,7 +56,9 @@ S3method(now,wrap)
 S3method(peek,simmer)
 S3method(peek,wrap)
 S3method(release,trajectory)
+S3method(release_all,trajectory)
 S3method(release_selected,trajectory)
+S3method(release_selected_all,trajectory)
 S3method(renege_abort,trajectory)
 S3method(renege_if,trajectory)
 S3method(renege_in,trajectory)
@@ -112,6 +116,8 @@ export(get_queue_count_selected)
 export(get_queue_size)
 export(get_queue_size_selected)
 export(get_resources)
+export(get_seized)
+export(get_seized_selected)
 export(get_selected)
 export(get_server_count)
 export(get_server_count_selected)
@@ -128,7 +134,9 @@ export(monitor_mem)
 export(now)
 export(peek)
 export(release)
+export(release_all)
 export(release_selected)
+export(release_selected_all)
 export(renege_abort)
 export(renege_if)
 export(renege_in)
diff --git a/NEWS.md b/NEWS.md
index 05a34b02..5d19e0c6 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -6,12 +6,17 @@
   arrivals, i.e., those dropped from a resource (due to preemption, resource
   shrinkage or a rejected `seize`) or those that `leave` a trajectory (#178
   addressing #177).
+- New `release_all()` and `release_selected_all()` activities automatically
+  retrieve the amount of resources seized and release it (#180 addressing #25).
+- New `get_seized()` and `get_seized_selected()` getters allow an arrival to
+  retrieve the amount of resources seized (#180 addressing #179).
 
 ## Minor changes and fixes:
 
 - Fix performance issues in data sources (#176).
 - Update CITATION.
 - Fix monitored activity for preempted arrivals (as part of #178).
+- Fix seizes/releases with a null amount (as part of #180).
 
 # simmer 4.1.0
 
diff --git a/R/RcppExports.R b/R/RcppExports.R
index 44d7da63..d70aa936 100644
--- a/R/RcppExports.R
+++ b/R/RcppExports.R
@@ -25,6 +25,14 @@ Release__new_func <- function(resource, amount) {
     .Call(`_simmer_Release__new_func`, resource, amount)
 }
 
+ReleaseAll__new <- function(resource) {
+    .Call(`_simmer_ReleaseAll__new`, resource)
+}
+
+ReleaseAll__new_void <- function() {
+    .Call(`_simmer_ReleaseAll__new_void`)
+}
+
 ReleaseSelected__new <- function(id, amount) {
     .Call(`_simmer_ReleaseSelected__new`, id, amount)
 }
@@ -33,6 +41,10 @@ ReleaseSelected__new_func <- function(id, amount) {
     .Call(`_simmer_ReleaseSelected__new_func`, id, amount)
 }
 
+ReleaseSelectedAll__new <- function(id) {
+    .Call(`_simmer_ReleaseSelectedAll__new`, id)
+}
+
 SetCapacity__new <- function(resource, value, mod) {
     .Call(`_simmer_SetCapacity__new`, resource, value, mod)
 }
@@ -365,6 +377,14 @@ get_queue_count_selected_ <- function(sim_, id) {
     .Call(`_simmer_get_queue_count_selected_`, sim_, id)
 }
 
+get_seized_ <- function(sim_, names) {
+    .Call(`_simmer_get_seized_`, sim_, names)
+}
+
+get_seized_selected_ <- function(sim_, id) {
+    .Call(`_simmer_get_seized_selected_`, sim_, id)
+}
+
 get_selected_ <- function(sim_, id) {
     .Call(`_simmer_get_selected_`, sim_, id)
 }
diff --git a/R/simmer-class.R b/R/simmer-class.R
index c4f01085..dc55ef89 100644
--- a/R/simmer-class.R
+++ b/R/simmer-class.R
@@ -250,7 +250,7 @@ Simmer <- R6Class("simmer",
     get_prioritization = function() get_prioritization_(private$sim_obj),
 
     get_capacity = function(resources, id=0) {
-      check_args(resources=c("string vector", "NULL"), id="numeric")
+      check_args(resources=c("string vector", "NULL"), id="number")
       ret <- switch(
         binarise(is.null(resources)),
         get_capacity_(private$sim_obj, resources),
@@ -260,7 +260,7 @@ Simmer <- R6Class("simmer",
     },
 
     get_queue_size = function(resources, id=0) {
-      check_args(resources=c("string vector", "NULL"), id="numeric")
+      check_args(resources=c("string vector", "NULL"), id="number")
       ret <- switch(
         binarise(is.null(resources)),
         get_queue_size_(private$sim_obj, resources),
@@ -270,7 +270,7 @@ Simmer <- R6Class("simmer",
     },
 
     get_server_count = function(resources, id=0) {
-      check_args(resources=c("string vector", "NULL"), id="numeric")
+      check_args(resources=c("string vector", "NULL"), id="number")
       switch(
         binarise(is.null(resources)),
         get_server_count_(private$sim_obj, resources),
@@ -279,7 +279,7 @@ Simmer <- R6Class("simmer",
     },
 
     get_queue_count = function(resources, id=0) {
-      check_args(resources=c("string vector", "NULL"), id="numeric")
+      check_args(resources=c("string vector", "NULL"), id="number")
       ret <- switch(
         binarise(is.null(resources)),
         get_queue_count_(private$sim_obj, resources),
@@ -287,8 +287,17 @@ Simmer <- R6Class("simmer",
       )
     },
 
+    get_seized = function(resources, id=0) {
+      check_args(resources=c("string vector", "NULL"), id="number")
+      ret <- switch(
+        binarise(is.null(resources)),
+        get_seized_(private$sim_obj, resources),
+        get_seized_selected_(private$sim_obj, id)
+      )
+    },
+
     get_selected = function(id=0) {
-      check_args(id="numeric")
+      check_args(id="number")
       get_selected_(private$sim_obj, id)
     },
 
diff --git a/R/simmer-methods.R b/R/simmer-methods.R
index dc06cad8..6f6380c7 100644
--- a/R/simmer-methods.R
+++ b/R/simmer-methods.R
@@ -40,13 +40,14 @@
 #' \code{\link{get_server_count}}, \code{\link{get_queue_count}},
 #' \code{\link{get_capacity_selected}}, \code{\link{get_queue_size_selected}},
 #' \code{\link{get_server_count_selected}}, \code{\link{get_queue_count_selected}},
+#' \code{\link{get_seized}}, \code{\link{get_seized_selected}},
 #' \code{\link{get_selected}}
 #'
 #' \item Sources: \code{\link{add_generator}}, \code{\link{add_dataframe}},
 #' \code{\link{get_sources}}, \code{\link{get_n_generated}},
 #' \code{\link{get_trajectory}}
 #'
-#' \item Globals: \code{\link{add_global}}, \code{\link{get_global}}.
+#' \item Globals: \code{\link{add_global}}, \code{\link{get_global}}
 #'
 #' \item Data retrieval: \code{\link{get_mon_arrivals}},
 #' \code{\link{get_mon_attributes}}, \code{\link{get_mon_resources}}
@@ -436,12 +437,12 @@ get_prioritization.simmer <- function(.env) .env$get_prioritization()
 
 #' Get Resource Parameters
 #'
-#' Getters for resources: server capacity/count and queue size/count.
+#' Getters for resources: server capacity/count and queue size/count, seized
+#' amount and selected resources.
 #'
 #' @inheritParams reset
+#' @inheritParams select
 #' @param resources one or more resource names.
-#' @param id selection identifier (a negative number causes the function to
-#' return the required parameter for all the selected resources).
 #'
 #' @return Return a vector (character for \code{get_selected}, numeric for the
 #' rest of them).
@@ -502,6 +503,20 @@ get_queue_count_selected <- function(.env, id=0) UseMethod("get_queue_count_sele
 #' @export
 get_queue_count_selected.simmer <- function(.env, id=0) .env$get_queue_count(NULL, id)
 
+#' @rdname get_capacity
+#' @export
+get_seized <- function(.env, resources) UseMethod("get_seized")
+
+#' @export
+get_seized.simmer <- function(.env, resources) .env$get_seized(resources)
+
+#' @rdname get_capacity
+#' @export
+get_seized_selected <- function(.env, id=0) UseMethod("get_seized_selected")
+
+#' @export
+get_seized_selected.simmer <- function(.env, id=0) .env$get_seized(NULL, id)
+
 #' @rdname get_capacity
 #' @export
 get_selected <- function(.env, id=0) UseMethod("get_selected")
diff --git a/R/trajectory-activities.R b/R/trajectory-activities.R
index 46025ae5..ddff8a1d 100644
--- a/R/trajectory-activities.R
+++ b/R/trajectory-activities.R
@@ -73,6 +73,20 @@ release_selected <- function(.trj, amount=1, id=0) UseMethod("release_selected")
 #' @export
 release_selected.trajectory <- function(.trj, amount=1, id=0) .trj$release(NA, amount, id)
 
+#' @rdname seize
+#' @export
+release_all <- function(.trj, resource) UseMethod("release_all")
+
+#' @export
+release_all.trajectory <- function(.trj, resource) .trj$release(resource, NA)
+
+#' @rdname seize
+#' @export
+release_selected_all <- function(.trj, id=0) UseMethod("release_selected_all")
+
+#' @export
+release_selected_all.trajectory <- function(.trj, id=0) .trj$release(NA, NA, id)
+
 #' Set Resource Parameters
 #'
 #' Activities for modifying a resource's server capacity or queue size, by name
diff --git a/R/trajectory-class.R b/R/trajectory-class.R
index 3d35eae7..18b4c730 100644
--- a/R/trajectory-class.R
+++ b/R/trajectory-class.R
@@ -125,11 +125,19 @@ Trajectory <- R6Class("trajectory",
     },
 
     release = function(resource, amount=1, id=0) {
-      check_args(resource=c("string", "NA"), amount=c("number", "function"), id="number")
+      if (missing(resource))
+        return(private$add_activity(ReleaseAll__new_void()))
+      check_args(
+        resource = c("string", "NA"),
+        amount = c("number", "function", "NA"),
+        id = "number"
+      )
       switch(
-        binarise(is.na(resource), is.function(amount)),
+        binarise(is.na(resource), is.na(amount), is.function(amount)),
         private$add_activity(Release__new(resource, amount)),
         private$add_activity(ReleaseSelected__new(id, amount)),
+        private$add_activity(ReleaseAll__new(resource)),
+        private$add_activity(ReleaseSelectedAll__new(id)),
         private$add_activity(Release__new_func(resource, amount)),
         private$add_activity(ReleaseSelected__new_func(id, amount))
       )
diff --git a/R/trajectory-methods.R b/R/trajectory-methods.R
index 6361b568..e3356a70 100644
--- a/R/trajectory-methods.R
+++ b/R/trajectory-methods.R
@@ -40,9 +40,10 @@
 #' \code{\link{set_prioritization}}
 #'
 #' \item Interaction with resources: \code{\link{select}}, \code{\link{seize}},
-#' \code{\link{release}}, \code{\link{seize_selected}}, \code{\link{release_selected}},
-#' \code{\link{set_capacity}}, \code{\link{set_queue_size}}, \code{\link{set_capacity_selected}},
-#' \code{\link{set_queue_size_selected}}
+#' \code{\link{release}}, \code{\link{release_all}}, \code{\link{seize_selected}},
+#' \code{\link{release_selected}}, \code{\link{release_selected_all}},
+#' \code{\link{set_capacity}}, \code{\link{set_queue_size}},
+#' \code{\link{set_capacity_selected}}, \code{\link{set_queue_size_selected}}
 #'
 #' \item Interaction with generators: \code{\link{activate}}, \code{\link{deactivate}},
 #' \code{\link{set_trajectory}}, \code{\link{set_source}}
@@ -56,8 +57,8 @@
 #' \item Asynchronous programming: \code{\link{send}}, \code{\link{trap}},
 #' \code{\link{untrap}}, \code{\link{wait}}
 #'
-#' \item Reneging: \code{\link{leave}}, \code{\link{renege_in}}, \code{\link{renege_if}},
-#' \code{\link{renege_abort}}
+#' \item Reneging: \code{\link{leave}}, \code{\link{handle_unfinished}},
+#' \code{\link{renege_in}}, \code{\link{renege_if}}, \code{\link{renege_abort}}
 #'
 #' }
 #'
diff --git a/inst/include/simmer/activity/resource.h b/inst/include/simmer/activity/resource.h
index 86f0a134..8d2d69ad 100644
--- a/inst/include/simmer/activity/resource.h
+++ b/inst/include/simmer/activity/resource.h
@@ -41,7 +41,7 @@ namespace simmer {
     Seize(int id, const T& amount, const VEC<bool>& cont,
           const VEC<REnv>& trj, unsigned short mask)
       : Fork("Seize", cont, trj),
-        internal::ResGetter("Seize", "[]", id), amount(amount), mask(mask) {}
+        internal::ResGetter("Seize", id), amount(amount), mask(mask) {}
 
     void print(unsigned int indent = 0, bool verbose = false, bool brief = false) {
       Activity::print(indent, verbose, brief);
@@ -50,8 +50,8 @@ namespace simmer {
     }
 
     double run(Arrival* arrival) {
-      return select_path(
-        arrival, get_resource(arrival)->seize(arrival, std::abs(get<int>(amount, arrival))));
+      return select_path(arrival, get_resource(arrival)->
+                         seize(arrival, std::abs(get<int>(amount, arrival))));
     }
 
   protected:
@@ -86,25 +86,41 @@ namespace simmer {
   public:
     CLONEABLE(Release<T>)
 
-    Release(const std::string& resource, const T& amount)
+    Release()
+      : Activity("Release", PRIORITY_RELEASE),
+        internal::ResGetter("Release"), amount(NONE) {}
+
+    Release(const std::string& resource, const OPT<T>& amount = NONE)
       : Activity("Release", PRIORITY_RELEASE),
         internal::ResGetter("Release", resource), amount(amount) {}
 
-    Release(int id, const T& amount)
+    Release(int id, const OPT<T>& amount = NONE)
       : Activity("Release", PRIORITY_RELEASE),
-        internal::ResGetter("Release", "[]", id), amount(amount) {}
+        internal::ResGetter("Release", id), amount(amount) {}
 
     void print(unsigned int indent = 0, bool verbose = false, bool brief = false) {
       Activity::print(indent, verbose, brief);
-      internal::print(brief, true, ARG(resource), ARG(amount));
+      if (amount)
+        internal::print(brief, true, ARG(resource), "amount: ", *amount);
+      else internal::print(brief, true, ARG(resource), "amount: ", "all");
     }
 
     double run(Arrival* arrival) {
-      return get_resource(arrival)->release(arrival, std::abs(get<int>(amount, arrival)));
+      if (Resource* res = get_resource(arrival)) {
+        if (amount)
+          return res->release(arrival, std::abs(get<int>(*amount, arrival)));
+        return res->release(arrival, res->get_seized(arrival));
+      }
+
+      foreach_ (const std::string& resource, arrival->sim->get_resources()) {
+        Resource* res = arrival->sim->get_resource(resource);
+        res->release(arrival, res->get_seized(arrival));
+      }
+      return 0;
     }
 
   protected:
-    T amount;
+    OPT<T> amount;
   };
 
   /**
@@ -120,7 +136,7 @@ namespace simmer {
         value(value), mod(mod), op(internal::get_op<double>(mod)) {}
 
     SetCapacity(int id, const T& value, char mod='N')
-      : Activity("SetCapacity"), internal::ResGetter("SetCapacity", "[]", id),
+      : Activity("SetCapacity"), internal::ResGetter("SetCapacity", id),
         value(value), mod(mod), op(internal::get_op<double>(mod)) {}
 
     void print(unsigned int indent = 0, bool verbose = false, bool brief = false) {
@@ -161,7 +177,7 @@ namespace simmer {
         value(value), mod(mod), op(internal::get_op<double>(mod)) {}
 
     SetQueue(int id, const T& value, char mod='N')
-      : Activity("SetQueue"), internal::ResGetter("SetQueue", "[]", id),
+      : Activity("SetQueue"), internal::ResGetter("SetQueue", id),
         value(value), mod(mod), op(internal::get_op<double>(mod)) {}
 
     void print(unsigned int indent = 0, bool verbose = false, bool brief = false) {
diff --git a/inst/include/simmer/activity/resource_internal.h b/inst/include/simmer/activity/resource_internal.h
index 0b1baac3..1aa1206b 100644
--- a/inst/include/simmer/activity/resource_internal.h
+++ b/inst/include/simmer/activity/resource_internal.h
@@ -29,8 +29,15 @@ namespace simmer { namespace internal {
   public:
     BASE_CLONEABLE(ResGetter)
 
-    ResGetter(const std::string& activity, const std::string& resource, int id = -1)
-      : resource(resource), id(id), activity(activity) {}
+    ResGetter(const std::string& activity)
+      : resource(MakeString() << "[all]"), id(-2), activity(activity) {}
+
+    ResGetter(const std::string& activity, const std::string& resource)
+      : resource(resource), id(-1), activity(activity) {}
+
+    ResGetter(const std::string& activity, int id)
+      : resource(MakeString() << "[" << id << "]"),
+        id(std::abs(id)), activity(activity) {}
 
   protected:
     std::string resource;
@@ -38,7 +45,8 @@ namespace simmer { namespace internal {
 
     Resource* get_resource(Arrival* arrival) const {
       Resource* selected = NULL;
-      if (id < 0)
+      if (id == -2) return selected;
+      if (id == -1)
         selected = arrival->sim->get_resource(resource);
       else selected = arrival->get_resource_selected(id);
       if (!selected) Rcpp::stop("no resource selected");
diff --git a/inst/include/simmer/resource.h b/inst/include/simmer/resource.h
index 9a71a891..5036d098 100644
--- a/inst/include/simmer/resource.h
+++ b/inst/include/simmer/resource.h
@@ -59,6 +59,8 @@ namespace simmer {
     * @return  SUCCESS, ENQUEUE, REJECT
     */
     int seize(Arrival* arrival, int amount) {
+      if (!amount) return SUCCESS;
+
       int status;
       // serve now
       if (first_in_line(arrival->order.get_priority()) &&
@@ -92,6 +94,8 @@ namespace simmer {
     * @return  SUCCESS
     */
     int release(Arrival* arrival, int amount) {
+      if (!amount) return SUCCESS;
+
       remove_from_server(arrival, amount);
       arrival->unregister_entity(this);
 
@@ -158,6 +162,8 @@ namespace simmer {
     int get_server_count() const { return server_count; }
     int get_queue_count() const { return queue_count; }
 
+    virtual int get_seized(Arrival* arrival) const = 0;
+
   protected:
     int capacity;
     int queue_size;
diff --git a/inst/include/simmer/resource/priority.h b/inst/include/simmer/resource/priority.h
index 9b8aab2a..2b9fd07e 100644
--- a/inst/include/simmer/resource/priority.h
+++ b/inst/include/simmer/resource/priority.h
@@ -49,6 +49,13 @@ namespace simmer {
       server_map.clear();
     }
 
+    int get_seized(Arrival* arrival) const {
+      typename ServerMap::const_iterator search = server_map.find(arrival);
+      if (search != server_map.end())
+        return search->second->amount;
+      return 0;
+    }
+
   protected:
     T server;
     ServerMap server_map;
diff --git a/inst/include/simmer/simulator.h b/inst/include/simmer/simulator.h
index e9b4848f..bf295c27 100644
--- a/inst/include/simmer/simulator.h
+++ b/inst/include/simmer/simulator.h
@@ -154,6 +154,13 @@ namespace simmer {
     Arrival* get_running_arrival() const;
     void record_ongoing(bool per_resource) const;
 
+    VEC<std::string> get_resources() const {
+      VEC<std::string> out;
+      foreach_ (const EntMap::value_type& itr, resource_map)
+        out.push_back(itr.first);
+      return out;
+    }
+
     Batched** get_batch(Activity* ptr, const std::string& id) {
       if (id.size()) {
         if (namedb_map.find(id) == namedb_map.end())
diff --git a/man/get_capacity.Rd b/man/get_capacity.Rd
index 7db2b199..17e75380 100644
--- a/man/get_capacity.Rd
+++ b/man/get_capacity.Rd
@@ -9,6 +9,8 @@
 \alias{get_server_count_selected}
 \alias{get_queue_count}
 \alias{get_queue_count_selected}
+\alias{get_seized}
+\alias{get_seized_selected}
 \alias{get_selected}
 \title{Get Resource Parameters}
 \usage{
@@ -28,6 +30,10 @@ get_queue_count(.env, resources)
 
 get_queue_count_selected(.env, id = 0)
 
+get_seized(.env, resources)
+
+get_seized_selected(.env, id = 0)
+
 get_selected(.env, id = 0)
 }
 \arguments{
@@ -35,15 +41,15 @@ get_selected(.env, id = 0)
 
 \item{resources}{one or more resource names.}
 
-\item{id}{selection identifier (a negative number causes the function to
-return the required parameter for all the selected resources).}
+\item{id}{selection identifier for nested usage.}
 }
 \value{
 Return a vector (character for \code{get_selected}, numeric for the
 rest of them).
 }
 \description{
-Getters for resources: server capacity/count and queue size/count.
+Getters for resources: server capacity/count and queue size/count, seized
+amount and selected resources.
 }
 \seealso{
 \code{\link{get_resources}}, \code{\link{set_capacity}},
diff --git a/man/seize.Rd b/man/seize.Rd
index 5289f56d..7368dc91 100644
--- a/man/seize.Rd
+++ b/man/seize.Rd
@@ -5,6 +5,8 @@
 \alias{seize_selected}
 \alias{release}
 \alias{release_selected}
+\alias{release_all}
+\alias{release_selected_all}
 \title{Seize/Release Resources}
 \usage{
 seize(.trj, resource, amount = 1, continue = NULL, post.seize = NULL,
@@ -16,6 +18,10 @@ seize_selected(.trj, amount = 1, id = 0, continue = NULL,
 release(.trj, resource, amount = 1)
 
 release_selected(.trj, amount = 1, id = 0)
+
+release_all(.trj, resource)
+
+release_selected_all(.trj, id = 0)
 }
 \arguments{
 \item{.trj}{the trajectory object.}
diff --git a/man/simmer.Rd b/man/simmer.Rd
index 06bdd1db..30afa4aa 100644
--- a/man/simmer.Rd
+++ b/man/simmer.Rd
@@ -54,13 +54,14 @@ Available methods by category:
 \code{\link{get_server_count}}, \code{\link{get_queue_count}},
 \code{\link{get_capacity_selected}}, \code{\link{get_queue_size_selected}},
 \code{\link{get_server_count_selected}}, \code{\link{get_queue_count_selected}},
+\code{\link{get_seized}}, \code{\link{get_seized_selected}},
 \code{\link{get_selected}}
 
 \item Sources: \code{\link{add_generator}}, \code{\link{add_dataframe}},
 \code{\link{get_sources}}, \code{\link{get_n_generated}},
 \code{\link{get_trajectory}}
 
-\item Globals: \code{\link{add_global}}, \code{\link{get_global}}.
+\item Globals: \code{\link{add_global}}, \code{\link{get_global}}
 
 \item Data retrieval: \code{\link{get_mon_arrivals}},
 \code{\link{get_mon_attributes}}, \code{\link{get_mon_resources}}
diff --git a/man/trajectory.Rd b/man/trajectory.Rd
index 1fa70799..6f9e84c2 100644
--- a/man/trajectory.Rd
+++ b/man/trajectory.Rd
@@ -52,9 +52,10 @@ Available activities by category:
 \code{\link{set_prioritization}}
 
 \item Interaction with resources: \code{\link{select}}, \code{\link{seize}},
-\code{\link{release}}, \code{\link{seize_selected}}, \code{\link{release_selected}},
-\code{\link{set_capacity}}, \code{\link{set_queue_size}}, \code{\link{set_capacity_selected}},
-\code{\link{set_queue_size_selected}}
+\code{\link{release}}, \code{\link{release_all}}, \code{\link{seize_selected}},
+\code{\link{release_selected}}, \code{\link{release_selected_all}},
+\code{\link{set_capacity}}, \code{\link{set_queue_size}},
+\code{\link{set_capacity_selected}}, \code{\link{set_queue_size_selected}}
 
 \item Interaction with generators: \code{\link{activate}}, \code{\link{deactivate}},
 \code{\link{set_trajectory}}, \code{\link{set_source}}
@@ -68,8 +69,8 @@ Available activities by category:
 \item Asynchronous programming: \code{\link{send}}, \code{\link{trap}},
 \code{\link{untrap}}, \code{\link{wait}}
 
-\item Reneging: \code{\link{leave}}, \code{\link{renege_in}}, \code{\link{renege_if}},
-\code{\link{renege_abort}}
+\item Reneging: \code{\link{leave}}, \code{\link{handle_unfinished}},
+\code{\link{renege_in}}, \code{\link{renege_if}}, \code{\link{renege_abort}}
 
 }
 
diff --git a/src/RcppExports.cpp b/src/RcppExports.cpp
index 073d87c9..b136cfc7 100644
--- a/src/RcppExports.cpp
+++ b/src/RcppExports.cpp
@@ -90,6 +90,27 @@ BEGIN_RCPP
     return rcpp_result_gen;
 END_RCPP
 }
+// ReleaseAll__new
+SEXP ReleaseAll__new(const std::string& resource);
+RcppExport SEXP _simmer_ReleaseAll__new(SEXP resourceSEXP) {
+BEGIN_RCPP
+    Rcpp::RObject rcpp_result_gen;
+    Rcpp::RNGScope rcpp_rngScope_gen;
+    Rcpp::traits::input_parameter< const std::string& >::type resource(resourceSEXP);
+    rcpp_result_gen = Rcpp::wrap(ReleaseAll__new(resource));
+    return rcpp_result_gen;
+END_RCPP
+}
+// ReleaseAll__new_void
+SEXP ReleaseAll__new_void();
+RcppExport SEXP _simmer_ReleaseAll__new_void() {
+BEGIN_RCPP
+    Rcpp::RObject rcpp_result_gen;
+    Rcpp::RNGScope rcpp_rngScope_gen;
+    rcpp_result_gen = Rcpp::wrap(ReleaseAll__new_void());
+    return rcpp_result_gen;
+END_RCPP
+}
 // ReleaseSelected__new
 SEXP ReleaseSelected__new(int id, int amount);
 RcppExport SEXP _simmer_ReleaseSelected__new(SEXP idSEXP, SEXP amountSEXP) {
@@ -114,6 +135,17 @@ BEGIN_RCPP
     return rcpp_result_gen;
 END_RCPP
 }
+// ReleaseSelectedAll__new
+SEXP ReleaseSelectedAll__new(int id);
+RcppExport SEXP _simmer_ReleaseSelectedAll__new(SEXP idSEXP) {
+BEGIN_RCPP
+    Rcpp::RObject rcpp_result_gen;
+    Rcpp::RNGScope rcpp_rngScope_gen;
+    Rcpp::traits::input_parameter< int >::type id(idSEXP);
+    rcpp_result_gen = Rcpp::wrap(ReleaseSelectedAll__new(id));
+    return rcpp_result_gen;
+END_RCPP
+}
 // SetCapacity__new
 SEXP SetCapacity__new(const std::string& resource, double value, char mod);
 RcppExport SEXP _simmer_SetCapacity__new(SEXP resourceSEXP, SEXP valueSEXP, SEXP modSEXP) {
@@ -1121,6 +1153,30 @@ BEGIN_RCPP
     return rcpp_result_gen;
 END_RCPP
 }
+// get_seized_
+std::vector<int> get_seized_(SEXP sim_, const std::vector<std::string>& names);
+RcppExport SEXP _simmer_get_seized_(SEXP sim_SEXP, SEXP namesSEXP) {
+BEGIN_RCPP
+    Rcpp::RObject rcpp_result_gen;
+    Rcpp::RNGScope rcpp_rngScope_gen;
+    Rcpp::traits::input_parameter< SEXP >::type sim_(sim_SEXP);
+    Rcpp::traits::input_parameter< const std::vector<std::string>& >::type names(namesSEXP);
+    rcpp_result_gen = Rcpp::wrap(get_seized_(sim_, names));
+    return rcpp_result_gen;
+END_RCPP
+}
+// get_seized_selected_
+std::vector<int> get_seized_selected_(SEXP sim_, int id);
+RcppExport SEXP _simmer_get_seized_selected_(SEXP sim_SEXP, SEXP idSEXP) {
+BEGIN_RCPP
+    Rcpp::RObject rcpp_result_gen;
+    Rcpp::RNGScope rcpp_rngScope_gen;
+    Rcpp::traits::input_parameter< SEXP >::type sim_(sim_SEXP);
+    Rcpp::traits::input_parameter< int >::type id(idSEXP);
+    rcpp_result_gen = Rcpp::wrap(get_seized_selected_(sim_, id));
+    return rcpp_result_gen;
+END_RCPP
+}
 // get_selected_
 std::vector<std::string> get_selected_(SEXP sim_, int id);
 RcppExport SEXP _simmer_get_selected_(SEXP sim_SEXP, SEXP idSEXP) {
@@ -1311,8 +1367,11 @@ static const R_CallMethodDef CallEntries[] = {
     {"_simmer_SeizeSelected__new_func", (DL_FUNC) &_simmer_SeizeSelected__new_func, 5},
     {"_simmer_Release__new", (DL_FUNC) &_simmer_Release__new, 2},
     {"_simmer_Release__new_func", (DL_FUNC) &_simmer_Release__new_func, 2},
+    {"_simmer_ReleaseAll__new", (DL_FUNC) &_simmer_ReleaseAll__new, 1},
+    {"_simmer_ReleaseAll__new_void", (DL_FUNC) &_simmer_ReleaseAll__new_void, 0},
     {"_simmer_ReleaseSelected__new", (DL_FUNC) &_simmer_ReleaseSelected__new, 2},
     {"_simmer_ReleaseSelected__new_func", (DL_FUNC) &_simmer_ReleaseSelected__new_func, 2},
+    {"_simmer_ReleaseSelectedAll__new", (DL_FUNC) &_simmer_ReleaseSelectedAll__new, 1},
     {"_simmer_SetCapacity__new", (DL_FUNC) &_simmer_SetCapacity__new, 3},
     {"_simmer_SetCapacity__new_func", (DL_FUNC) &_simmer_SetCapacity__new_func, 3},
     {"_simmer_SetCapacitySelected__new", (DL_FUNC) &_simmer_SetCapacitySelected__new, 3},
@@ -1396,6 +1455,8 @@ static const R_CallMethodDef CallEntries[] = {
     {"_simmer_get_server_count_selected_", (DL_FUNC) &_simmer_get_server_count_selected_, 2},
     {"_simmer_get_queue_count_", (DL_FUNC) &_simmer_get_queue_count_, 2},
     {"_simmer_get_queue_count_selected_", (DL_FUNC) &_simmer_get_queue_count_selected_, 2},
+    {"_simmer_get_seized_", (DL_FUNC) &_simmer_get_seized_, 2},
+    {"_simmer_get_seized_selected_", (DL_FUNC) &_simmer_get_seized_selected_, 2},
     {"_simmer_get_selected_", (DL_FUNC) &_simmer_get_selected_, 2},
     {"_simmer_Simulator__new", (DL_FUNC) &_simmer_Simulator__new, 4},
     {"_simmer_reset_", (DL_FUNC) &_simmer_reset_, 1},
diff --git a/src/activity.cpp b/src/activity.cpp
index 3c06318f..f4bbebc1 100644
--- a/src/activity.cpp
+++ b/src/activity.cpp
@@ -60,6 +60,16 @@ SEXP Release__new_func(const std::string& resource, const Function& amount) {
   return XPtr<Release<Function> >(new Release<Function>(resource, amount));
 }
 
+//[[Rcpp::export]]
+SEXP ReleaseAll__new(const std::string& resource) {
+  return XPtr<Release<int> >(new Release<int>(resource));
+}
+
+//[[Rcpp::export]]
+SEXP ReleaseAll__new_void() {
+  return XPtr<Release<int> >(new Release<int>());
+}
+
 //[[Rcpp::export]]
 SEXP ReleaseSelected__new(int id, int amount) {
   return XPtr<Release<int> >(new Release<int>(id, amount));
@@ -70,6 +80,11 @@ SEXP ReleaseSelected__new_func(int id, const Function& amount) {
   return XPtr<Release<Function> >(new Release<Function>(id, amount));
 }
 
+//[[Rcpp::export]]
+SEXP ReleaseSelectedAll__new(int id) {
+  return XPtr<Release<int> >(new Release<int>(id));
+}
+
 //[[Rcpp::export]]
 SEXP SetCapacity__new(const std::string& resource, double value, char mod) {
   return XPtr<SetCapacity<double> >(new SetCapacity<double>(resource, value, mod));
@@ -392,20 +407,17 @@ SEXP Log__new_func(const Function& message, int level) {
 
 //[[Rcpp::export]]
 int activity_get_count_(SEXP activity_) {
-  XPtr<Activity> activity(activity_);
-  return activity->count;
+  return XPtr<Activity>(activity_)->count;
 }
 
 //[[Rcpp::export]]
 void activity_print_(SEXP activity_, int indent, bool verbose) {
-  XPtr<Activity> activity(activity_);
-  return activity->print(indent, verbose);
+  return XPtr<Activity>(activity_)->print(indent, verbose);
 }
 
 //[[Rcpp::export]]
 SEXP activity_get_next_(SEXP activity_) {
-  XPtr<Activity> activity(activity_);
-  Activity* the_next = activity->get_next();
+  Activity* the_next = XPtr<Activity>(activity_)->get_next();
   if (the_next)
     return XPtr<Activity>(the_next, false);
   return R_NilValue;
@@ -413,8 +425,7 @@ SEXP activity_get_next_(SEXP activity_) {
 
 //[[Rcpp::export]]
 SEXP activity_get_prev_(SEXP activity_) {
-  XPtr<Activity> activity(activity_);
-  Activity* the_prev = activity->get_prev();
+  Activity* the_prev = XPtr<Activity>(activity_)->get_prev();
   if (the_prev)
     return XPtr<Activity>(the_prev, false);
   return R_NilValue;
@@ -430,6 +441,5 @@ void activity_chain_(SEXP first_, SEXP second_) {
 
 //[[Rcpp::export]]
 SEXP activity_clone_(SEXP activity_) {
-  XPtr<Activity> activity(activity_);
-  return XPtr<Activity>(activity->clone());
+  return XPtr<Activity>(XPtr<Activity>(activity_)->clone());
 }
diff --git a/src/monitor.cpp b/src/monitor.cpp
index 023f6086..319988ff 100644
--- a/src/monitor.cpp
+++ b/src/monitor.cpp
@@ -36,18 +36,15 @@ SEXP CsvMonitor__new(const std::string& ends_path, const std::string& releases_p
 
 //[[Rcpp::export]]
 DataFrame get_arrivals_(SEXP mon_, bool per_resource) {
-  XPtr<MemMonitor> mon(mon_);
-  return mon->get_arrivals(per_resource);
+  return XPtr<MemMonitor>(mon_)->get_arrivals(per_resource);
 }
 
 //[[Rcpp::export]]
 DataFrame get_attributes_(SEXP mon_) {
-  XPtr<MemMonitor> mon(mon_);
-  return mon->get_attributes();
+  return XPtr<MemMonitor>(mon_)->get_attributes();
 }
 
 //[[Rcpp::export]]
 DataFrame get_resources_(SEXP mon_) {
-  XPtr<MemMonitor> mon(mon_);
-  return mon->get_resources();
+  return XPtr<MemMonitor>(mon_)->get_resources();
 }
diff --git a/src/process.cpp b/src/process.cpp
index 65438172..93d1bc2b 100644
--- a/src/process.cpp
+++ b/src/process.cpp
@@ -43,8 +43,7 @@ std::vector<Environment> get_trajectory_(SEXP sim_, const std::vector<std::strin
 
 //[[Rcpp::export]]
 std::string get_name_(SEXP sim_) {
-  XPtr<Simulator> sim(sim_);
-  return sim->get_running_arrival()->name;
+  return XPtr<Simulator>(sim_)->get_running_arrival()->name;
 }
 
 //[[Rcpp::export]]
@@ -65,8 +64,7 @@ NumericVector get_attribute_(SEXP sim_, const std::vector<std::string>& keys, bo
 
 //[[Rcpp::export]]
 IntegerVector get_prioritization_(SEXP sim_) {
-  XPtr<Simulator> sim(sim_);
-  Arrival* a = sim->get_running_arrival();
+  Arrival* a = XPtr<Simulator>(sim_)->get_running_arrival();
   return IntegerVector::create(
     a->order.get_priority(), a->order.get_preemptible(), (int)a->order.get_restart()
   );
diff --git a/src/resource.cpp b/src/resource.cpp
index cb7f92ba..06eff6a1 100644
--- a/src/resource.cpp
+++ b/src/resource.cpp
@@ -35,14 +35,8 @@ template <typename T>
 VEC<T> get_param(SEXP sim_, int id, const Fn<T(Resource*)>& param) {
   XPtr<Simulator> sim(sim_);
   VEC<T> out;
-  if (id >= 0) {
-    if (Resource* r = sim->get_running_arrival()->get_resource_selected(id))
-      out.push_back(param(r));
-  } else {
-    int i = 0;
-    while (Resource* r = sim->get_running_arrival()->get_resource_selected(i++))
-      out.push_back(param(r));
-  }
+  if (Resource* r = sim->get_running_arrival()->get_resource_selected(id))
+    out.push_back(param(r));
   return out;
 }
 
@@ -86,6 +80,18 @@ std::vector<int> get_queue_count_selected_(SEXP sim_, int id) {
   return get_param<int>(sim_, id, boost::mem_fn(&Resource::get_queue_count));
 }
 
+//[[Rcpp::export]]
+std::vector<int> get_seized_(SEXP sim_, const std::vector<std::string>& names) {
+  Arrival* arrival = XPtr<Simulator>(sim_)->get_running_arrival();
+  return get_param<int>(sim_, names, BIND(&Resource::get_seized, _1, arrival));
+}
+
+//[[Rcpp::export]]
+std::vector<int> get_seized_selected_(SEXP sim_, int id) {
+  Arrival* arrival = XPtr<Simulator>(sim_)->get_running_arrival();
+  return get_param<int>(sim_, id, BIND(&Resource::get_seized, _1, arrival));
+}
+
 std::string get_name(Resource* res) { return res->name; }
 
 //[[Rcpp::export]]
diff --git a/src/simulator.cpp b/src/simulator.cpp
index e1ca24f8..9970c4be 100644
--- a/src/simulator.cpp
+++ b/src/simulator.cpp
@@ -29,32 +29,27 @@ SEXP Simulator__new(const std::string& name, bool verbose, SEXP mon, int log_lev
 
 //[[Rcpp::export]]
 void reset_(SEXP sim_) {
-  XPtr<Simulator> sim(sim_);
-  sim->reset();
+  XPtr<Simulator>(sim_)->reset();
 }
 
 //[[Rcpp::export]]
 double now_(SEXP sim_) {
-  XPtr<Simulator> sim(sim_);
-  return sim->now();
+  return XPtr<Simulator>(sim_)->now();
 }
 
 //[[Rcpp::export]]
 DataFrame peek_(SEXP sim_, int steps) {
-  XPtr<Simulator> sim(sim_);
-  return sim->peek(steps);
+  return XPtr<Simulator>(sim_)->peek(steps);
 }
 
 //[[Rcpp::export]]
 void stepn_(SEXP sim_, unsigned int n) {
-  XPtr<Simulator> sim(sim_);
-  sim->step(n);
+  XPtr<Simulator>(sim_)->step(n);
 }
 
 //[[Rcpp::export]]
 void run_(SEXP sim_, double until) {
-  XPtr<Simulator> sim(sim_);
-  sim->run(until);
+  XPtr<Simulator>(sim_)->run(until);
 }
 
 //[[Rcpp::export]]
@@ -165,6 +160,5 @@ bool add_global_manager_(SEXP sim_, const std::string& key, double init,
 
 //[[Rcpp::export]]
 void record_ongoing_(SEXP sim_, bool per_resource) {
-  XPtr<Simulator> sim(sim_);
-  sim->record_ongoing(per_resource);
+  XPtr<Simulator>(sim_)->record_ongoing(per_resource);
 }
diff --git a/tests/testthat/test-trajectory-seize-release.R b/tests/testthat/test-trajectory-seize-release.R
index fa763527..da1271e6 100644
--- a/tests/testthat/test-trajectory-seize-release.R
+++ b/tests/testthat/test-trajectory-seize-release.R
@@ -268,3 +268,36 @@ test_that("arrivals don't jump the queue if there is room in the server (2)", {
   expect_equal(arrs_ordered$end_time, c(20, 11, 21))
   expect_equal(arrs_ordered$activity_time, c(10, 10, 10))
 })
+
+test_that("unknown amounts can be released", {
+  random <- function() sample(10, 1)
+  t <- trajectory() %>%
+    seize("res1", random) %>%
+    set_attribute("res1", function() get_seized(env, "res1")) %>%
+    seize("res2", random) %>%
+    set_attribute("res2", function() get_seized(env, "res2")) %>%
+    select("res3", id=0) %>%
+    seize_selected(random, id=0) %>%
+    set_attribute("res3", function() get_seized_selected(env, id=0)) %>%
+    select("res4", id=1) %>%
+    seize_selected(random, id=1) %>%
+    set_attribute("res4", function() get_seized_selected(env, id=1)) %>%
+    timeout(1) %>%
+    release_all("res1") %>%
+    release_selected_all(id=0) %>%
+    release_all()
+
+  env <- simmer(verbose = TRUE) %>%
+    add_resource("res1", 10) %>%
+    add_resource("res2", 10) %>%
+    add_resource("res3", 10) %>%
+    add_resource("res4", 10) %>%
+    add_generator("dummy", t, at(0), mon=2)
+
+  run(env, 1)
+  expect_true(all(get_server_count(env, paste0("res", 1:4)) > rep(0, 4)))
+  expect_equal(get_server_count(env, paste0("res", 1:4)),
+               get_mon_attributes(env)$value)
+  run(env)
+  expect_equal(get_server_count(env, paste0("res", 1:4)), rep(0, 4))
+})
diff --git a/tests/testthat/test-trajectory-select.R b/tests/testthat/test-trajectory-select.R
index b84a3322..51230665 100644
--- a/tests/testthat/test-trajectory-select.R
+++ b/tests/testthat/test-trajectory-select.R
@@ -270,7 +270,7 @@ test_that("selections can be retrieved", {
 
   expect_error(run(env))
 
-  expect_equal(get_selected(env, id=-1), c("res0", "res1"))
+  expect_equal(get_selected(env, id=-1), "res1")
   expect_equal(get_selected(env, id=0), "res0")
   expect_equal(get_selected(env, id=1), "res1")
   expect_equal(get_selected(env, id=2), character(0))
diff --git a/tests/testthat/test-trajectory.R b/tests/testthat/test-trajectory.R
index e2b5fda9..77d535f4 100644
--- a/tests/testthat/test-trajectory.R
+++ b/tests/testthat/test-trajectory.R
@@ -50,6 +50,8 @@ t0 <- trajectory(verbose = TRUE) %>%
   untrap(function() "asdf") %>%
   wait() %>%
   log_(function() "asdf") %>%
+  release_all() %>%
+  release_selected_all() %>%
   release_selected(1) %>%
   release("nurse", 1)
 
@@ -93,6 +95,8 @@ trajs <- c(
   trajectory(verbose = TRUE) %>% untrap(function() "asdf"),
   trajectory(verbose = TRUE) %>% wait(),
   trajectory(verbose = TRUE) %>% log_(function() "asdf"),
+  trajectory(verbose = TRUE) %>% release_all(),
+  trajectory(verbose = TRUE) %>% release_selected_all(),
   trajectory(verbose = TRUE) %>% release_selected(1),
   trajectory(verbose = TRUE) %>% release("nurse", 1)
 )