diff --git a/doc/manual/src/notifications.md b/doc/manual/src/notifications.md
index 94070771..8d824177 100644
--- a/doc/manual/src/notifications.md
+++ b/doc/manual/src/notifications.md
@@ -8,6 +8,12 @@ Notifications are passed from `hydra-queue-runner` to `hydra-notify` through Pos
 
 Note that the notification format is subject to change and should not be considered an API. Integrate with `hydra-notify` instead of listening directly.
 
+### `cached_build_finished`
+
+* **Payload:** Exactly two values, tab separated: The ID of the evaluation which contains the finished build, followed by the ID of the finished build.
+* **When:** Issued directly after an evaluation completes, when that evaluation includes this finished build.
+* **Delivery Semantics:** At most once per evaluation.
+
 ### `build_queued`
 
 * **Payload:** Exactly one value, the ID of the build.
diff --git a/src/lib/Hydra/Event.pm b/src/lib/Hydra/Event.pm
index 99e1a2de..9feb532a 100644
--- a/src/lib/Hydra/Event.pm
+++ b/src/lib/Hydra/Event.pm
@@ -2,6 +2,7 @@ package Hydra::Event;
 
 use strict;
 use warnings;
+use Hydra::Event::CachedBuildFinished;
 use Hydra::Event::BuildFinished;
 use Hydra::Event::BuildQueued;
 use Hydra::Event::BuildStarted;
@@ -12,6 +13,7 @@ my %channels_to_events = (
   build_started => \&Hydra::Event::BuildStarted::parse,
   step_finished => \&Hydra::Event::StepFinished::parse,
   build_finished => \&Hydra::Event::BuildFinished::parse,
+  cached_build_finished => \&Hydra::Event::CachedBuildFinished::parse,
 );
 
 
diff --git a/src/lib/Hydra/Event/CachedBuildFinished.pm b/src/lib/Hydra/Event/CachedBuildFinished.pm
new file mode 100644
index 00000000..dc0f188b
--- /dev/null
+++ b/src/lib/Hydra/Event/CachedBuildFinished.pm
@@ -0,0 +1,59 @@
+package Hydra::Event::CachedBuildFinished;
+
+use strict;
+use warnings;
+
+sub parse :prototype(@) {
+    if (@_ != 2) {
+        die "cached_build_finished: payload takes two arguments, but ", scalar(@_), " were given";
+    }
+
+    my @failures = grep(!/^\d+$/, @_);
+    if (@failures > 0) {
+        die "cached_build_finished: payload arguments should be integers, but we received the following non-integers:", @failures;
+    }
+
+    my ($evaluation_id, $build_id) = map int, @_;
+    return Hydra::Event::CachedBuildFinished->new($evaluation_id, $build_id);
+}
+
+sub new {
+    my ($self, $evaluation_id, $build_id) = @_;
+    return bless {
+        "evaluation_id" => $evaluation_id,
+        "build_id" => $build_id,
+        "evaluation" => undef,
+        "build" => undef,
+    }, $self;
+}
+
+sub interestedIn {
+    my ($self, $plugin) = @_;
+    return int(defined($plugin->can('cachedBuildFinished')));
+}
+
+sub load {
+    my ($self, $db) = @_;
+
+    if (!defined($self->{"build"})) {
+        $self->{"build"} = $db->resultset('Builds')->find($self->{"build_id"})
+            or die "build $self->{'build_id'} does not exist\n";
+    }
+
+    if (!defined($self->{"evaluation"})) {
+        $self->{"evaluation"} = $db->resultset('JobsetEvals')->find($self->{"evaluation_id"})
+            or die "evaluation $self->{'evaluation_id'} does not exist\n";
+    }
+}
+
+sub execute {
+    my ($self, $db, $plugin) = @_;
+
+    $self->load($db);
+
+    $plugin->cachedBuildFinished($self->{"evaluation"}, $self->{"build"});
+
+    return 1;
+}
+
+1;
diff --git a/src/lib/Hydra/Plugin.pm b/src/lib/Hydra/Plugin.pm
index acefc663..5742b3fb 100644
--- a/src/lib/Hydra/Plugin.pm
+++ b/src/lib/Hydra/Plugin.pm
@@ -36,6 +36,12 @@ sub instantiate {
 #     my ($self, $build) = @_;
 # }
 
+# # Called when build $build is a finished build, and is
+# part evaluation $evaluation
+# sub cachedBuildFinished {
+#     my ($self, $evaluation, $build) = @_;
+# }
+
 # # Called when build $build has started.
 # sub buildStarted {
 #     my ($self, $build) = @_;
diff --git a/src/script/hydra-notify b/src/script/hydra-notify
index 3c929764..6bc736e9 100755
--- a/src/script/hydra-notify
+++ b/src/script/hydra-notify
@@ -96,6 +96,7 @@ my $listener = Hydra::PostgresListener->new($dbh);
 $listener->subscribe("build_finished");
 $listener->subscribe("build_queued");
 $listener->subscribe("build_started");
+$listener->subscribe("cached_build_finished");
 $listener->subscribe("hydra_notify_dump_metrics");
 $listener->subscribe("step_finished");
 
diff --git a/t/Event/CachedBuildFinished.t b/t/Event/CachedBuildFinished.t
new file mode 100644
index 00000000..442f1991
--- /dev/null
+++ b/t/Event/CachedBuildFinished.t
@@ -0,0 +1,111 @@
+use strict;
+use warnings;
+use Setup;
+
+my %ctx = test_init();
+
+require Hydra::Schema;
+require Hydra::Model::DB;
+use Hydra::Event;
+use Hydra::Event::CachedBuildFinished;
+
+use Test2::V0;
+use Test2::Tools::Exception;
+use Test2::Tools::Mock qw(mock_obj);
+
+my $db = Hydra::Model::DB->new;
+hydra_setup($db);
+
+subtest "Parsing" => sub {
+    like(
+        dies { Hydra::Event::parse_payload("cached_build_finished", "") },
+        qr/takes two arguments/,
+        "empty payload"
+    );
+    like(
+        dies { Hydra::Event::parse_payload("cached_build_finished", "abc123") },
+        qr/takes two arguments/,
+        "missing the build ID"
+    );
+
+    like(
+        dies { Hydra::Event::parse_payload("cached_build_finished", "123\t456\t789\t012\t345") },
+        qr/takes two arguments/,
+        "too many arguments"
+    );
+    like(
+        dies { Hydra::Event::parse_payload("cached_build_finished", "abc123\tdef456") },
+        qr/should be integers/,
+        "evaluation ID should be an integer"
+    );
+    like(
+        dies { Hydra::Event::parse_payload("cached_build_finished", "123\tabc123") },
+        qr/should be integers/,
+        "build ID should be an integer"
+    );
+    is(
+        Hydra::Event::parse_payload("cached_build_finished", "123\t456"),
+        Hydra::Event::CachedBuildFinished->new(123, 456),
+        "one dependent build"
+    );
+};
+
+my $project = $db->resultset('Projects')->create({name => "tests", displayname => "", owner => "root"});
+my $jobset = createBaseJobset("basic", "basic.nix", $ctx{jobsdir});
+ok(evalSucceeds($jobset),               "Evaluating jobs/basic.nix should exit with return code 0");
+is(nrQueuedBuildsForJobset($jobset), 3, "Evaluating jobs/basic.nix should result in 3 builds");
+
+subtest "interested" => sub {
+    my $event = Hydra::Event::CachedBuildFinished->new(123, 456);
+
+    subtest "A plugin which does not implement the API" => sub {
+        my $plugin = {};
+        my $mock = mock_obj $plugin => ();
+
+        is($event->interestedIn($plugin), 0, "The plugin is not interesting.");
+    };
+
+    subtest "A plugin which does implement the API" => sub {
+        my $plugin = {};
+        my $mock = mock_obj $plugin => (
+            add => [
+                "cachedBuildFinished" => sub {}
+            ]
+        );
+
+        is($event->interestedIn($plugin), 1, "The plugin is interesting.");
+    };
+};
+
+subtest "load" => sub {
+    my ($build) = $db->resultset('Builds')->search({ }, { limit => 1 })->single;
+    my $evaluation = $build->jobsetevals->search({}, { limit => 1 })->single;
+
+    my $event = Hydra::Event::CachedBuildFinished->new($evaluation->id, $build->id);
+
+    $event->load($db);
+    is($event->{"evaluation"}->id, $evaluation->id, "The evaluation record matches.");
+    is($event->{"build"}->id, $build->id, "The build record matches.");
+
+    # Create a fake "plugin" with a cachedBuildFinished sub, the sub sets this
+    # global passedEvaluation and passedBuild variables for verifying.
+    my $passedEvaluation;
+    my $passedBuild;
+    my $plugin = {};
+    my $mock = mock_obj $plugin => (
+        add => [
+            "cachedBuildFinished" => sub {
+                my ($self, $evaluation, $build) = @_;
+                $passedEvaluation = $evaluation;
+                $passedBuild = $build;
+            }
+        ]
+    );
+
+    $event->execute($db, $plugin);
+
+    is($passedEvaluation->id, $evaluation->id, "The plugin's cachedBuildFinished hook is called with a matching evaluation");
+    is($passedBuild->id, $build->id, "The plugin's cachedBuildFinished hook is called with a matching build");
+};
+
+done_testing;