diff --git a/.circleci/config.yml b/.circleci/config.yml
deleted file mode 100644
index a826375..0000000
--- a/.circleci/config.yml
+++ /dev/null
@@ -1,144 +0,0 @@
-version: 2.1
-
-jobs:
-  build:
-    docker:
-      - image: cimg/elixir:1.15.5-erlang-26.0.2
-        environment:
-          MIX_ENV: test
-    steps:
-      - checkout
-      - run:
-          name: Install tools
-          command: |
-            mix local.hex --force && \
-            mix local.rebar --force
-      - restore_cache:
-          keys:
-            - v2-mix-cache-{{ .Branch }}-{{ checksum "mix.lock" }}
-            - v2-mix-cache-{{ .Branch }}
-            - v2-mix-cache
-      - run:
-          name: Get dependencies
-          command: mix deps.get
-      - save_cache:
-          key: v2-mix-cache-{{ .Branch }}-{{ checksum "mix.lock" }}
-          paths:
-            - deps
-      - restore_cache:
-          keys:
-            - v4-build-cache-{{ .Branch }}
-            - v4-build-cache
-      - run:
-          name: Compile
-          command: mix do deps.compile, compile --warnings-as-errors, dialyzer --plt
-      - save_cache:
-          key: v4-build-cache-{{ .Branch }}
-          paths:
-            - _build
-      - persist_to_workspace:
-          root: ~/
-          paths:
-            - .mix
-            - project/_build
-            - project/deps
-
-  test:
-    docker:
-      - image: cimg/elixir:1.15.5-erlang-26.0.2
-        environment:
-          MIX_ENV: test
-      - image: cimg/postgres:14.6
-    steps:
-      - checkout
-      - attach_workspace:
-          at: ~/
-      - run:
-          name: Run tests
-          command: mix test --cover --export-coverage default
-      - run:
-          name: Check coverage
-          command: mix test.coverage
-      - store_test_results:
-          path: /tmp/test/results.xml
-
-  lint:
-    docker:
-      - image: cimg/elixir:1.15.5-erlang-26.0.2
-        environment:
-          MIX_ENV: test
-    steps:
-      - checkout
-      - attach_workspace:
-          at: ~/
-      - run:
-          name: Check formatting
-          command: mix format --check-formatted --dry-run
-      - run:
-          name: Check for retired dependencies
-          command: mix hex.audit
-      - run:
-          name: Check unused dependencies
-          command: mix deps.unlock --check-unused
-      - run:
-          name: Check outdated dependencies
-          command: mix hex.outdated --within-requirements || true
-      - run:
-          name: Credo
-          command: mix credo --all
-      - run:
-          name: Dialyzer
-          command: mix dialyzer
-      - run:
-          name: Check documentation
-          command: mix doctor
-
-  security:
-    docker:
-      - image: cimg/elixir:1.15.5-erlang-26.0.2
-        environment:
-          MIX_ENV: test
-    steps:
-      - checkout
-      - attach_workspace:
-          at: ~/
-      - run:
-          name: Audit dependencies
-          command: mix deps.audit
-      - run:
-          name: Sobelow
-          command: mix sobelow --config
-
-  slscan:
-    docker:
-      - image: shiftleft/sast-scan:maven385
-    environment:
-      FETCH_LICENSE: "true"
-    working_directory: /tmp/shiftleft-scan
-    steps:
-      - checkout
-      - run:
-          name: Scan
-          command: scan --no-error
-      - store_artifacts:
-          path: reports
-          destination: sast-scan-reports
-
-workflows:
-  test:
-    jobs:
-      - build
-      - test:
-          requires:
-            - build
-      - lint:
-          requires:
-            - build
-      - security:
-          requires:
-            - build
-      - slscan:
-          filters:
-            branches:
-              only:
-                - master
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
new file mode 100644
index 0000000..5969888
--- /dev/null
+++ b/.github/workflows/ci.yml
@@ -0,0 +1,93 @@
+name: CI
+on:
+  push:
+    branches: [main,master]
+  pull_request:
+    branches: [main,master]
+jobs:
+  test:
+    name: Test (Elixir ${{ matrix.elixir }} | OTP ${{ matrix.otp }})
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - elixir: 1.18.x
+            otp: 27
+            os: ubuntu-22.04
+          - elixir: 1.19.x
+            otp: 28
+            os: ubuntu-22.04
+    env:
+      MIX_ENV: test
+    steps:
+      - name: Setup Elixir
+        uses: erlef/setup-beam@v1
+        with:
+          elixir-version: ${{ matrix.elixir }}
+          otp-version: ${{ matrix.otp }}
+
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Cache dependencies
+        uses: actions/cache@v4
+        id: cache-deps
+        with:
+          path: |
+            deps
+            _build
+          key: |
+            mix-${{ runner.os }}-${{ matrix.elixir }}-${{ matrix.otp }}-${{ hashFiles('**/mix.lock') }}
+          restore-keys: |
+            mix-${{ runner.os }}-${{ matrix.elixir }}-${{ matrix.otp }}-
+      - name: Install dependencies
+        run: mix deps.get
+
+      - name: Compile
+        run: mix compile
+
+      - name: Check for unused packages
+        run: mix deps.unlock --check-unused
+
+      - run: mix format --check-formatted
+
+      - run: mix credo --strict
+
+      - run: mix dialyzer
+
+      - name: Check for abandonded packages
+        run: mix hex.audit
+
+      - name: Check outdated dependencies
+        run: mix hex.outdated --within-requirements || true
+
+      - name: Check for vulnerable packages
+        run: mix hex.audit
+
+      - name: Run tests
+        run: mix test
+
+      - name: Run tests (with coverage)
+        run: mix test --cover --export-coverage default
+
+      - name: Scan for security vulnerabilities
+        run: mix sobelow --exit --threshold medium
+
+  publish:
+    name: Publish (Dry Run)
+    runs-on: ubuntu-22.04
+    steps:
+      - uses: actions/checkout@v4
+      - uses: erlef/setup-beam@v1
+        with:
+          elixir-version: 1.18
+          otp-version: 27
+      - name: Fetch dependencies
+        run: mix deps.get
+      - name: Compile
+        run: mix compile
+      - name: Publish package
+        env:
+          HEX_API_KEY: ${{ secrets.HEX_API_KEY }}
+        run: mix hex.publish --organization ${{ vars.HEX_ORG }} --dry-run --replace --yes
diff --git a/README.md b/README.md
index 888a8e6..7b01eab 100644
--- a/README.md
+++ b/README.md
@@ -1,7 +1,7 @@
 # Zexbox
 
 [![Hex.pm](https://img.shields.io/hexpm/v/zexbox.svg)](https://hex.pm/packages/zexbox)
-[![CircleCI](https://dl.circleci.com/status-badge/img/gh/Intellection/zexbox/tree/master.svg?style=shield)](https://dl.circleci.com/status-badge/redirect/gh/Intellection/zexbox/tree/master)
+[![CI](https://github.com/Intellection/zexbox/actions/workflows/ci.yml/badge.svg)](https://github.com/Intellection/zexbox/actions/workflows/ci.yml)
 [![Documentation](https://img.shields.io/badge/documentation-gray)](https://hexdocs.pm/zexbox/api-reference.html)
 
 ## Installation
@@ -16,6 +16,8 @@ end
 
 ## LaunchDarkly Feature Flags
 
+The Zexbox library provides an idiomatic Elixir wrapper around the LaunchDarkly Erlang SDK with support for contexts, multi-contexts, and all modern LaunchDarkly features.
+
 ### Configuration
 
 Configuration is fairly simple, with the only required piece of configuration being the `sdk_key`. For production environments we recommend also including `:email` as a private attribute:
@@ -80,7 +82,35 @@ end
 
 Stopping a client with a custom tag can be done using the `Zexbox.Flags.stop/1` function.
 
-Evaluating a flag can be achieved by simply calling the `Zexbox.Flags.variation/3` function.
+### Using Contexts
+
+Contexts are the recommended way to evaluate feature flags. They provide type safety and support for multi-entity targeting:
+
+```elixir
+alias Zexbox.Flags.Context
+
+# Simple user context
+context = Context.new("user-123")
+Zexbox.Flags.variation("my-flag", context, false)
+
+# Context with attributes
+context =
+  Context.new("user-123")
+  |> Context.set("email", "user@example.com")
+  |> Context.set("plan", "enterprise")
+  |> Context.set_private_attributes(["email"])
+
+Zexbox.Flags.variation("premium-feature", context, false)
+
+# Multi-context (target based on user AND organization)
+user = Context.new("user-123", "user")
+org = Context.new("org-456", "organization")
+multi = Context.new_multi([user, org])
+
+Zexbox.Flags.variation("enterprise-feature", multi, false)
+```
+
+**Backward Compatibility**: Raw maps are still supported:
 
 ```elixir
 Zexbox.Flags.variation(
@@ -90,6 +120,8 @@ Zexbox.Flags.variation(
 )
 ```
 
+For more details, see the [Context Module Guide](CONTEXT_MODULE_GUIDE.md).
+
 ## Logging
 
 Default logging can be attached to your controllers by calling `Zexbox.Logging.attach_controller_logs!` in the `start/2` function of your `Application` module:
diff --git a/test/zexbox/metrics/client_test.exs b/test/zexbox/metrics/client_test.exs
index fd585d0..44617e5 100644
--- a/test/zexbox/metrics/client_test.exs
+++ b/test/zexbox/metrics/client_test.exs
@@ -5,11 +5,6 @@ defmodule Zexbox.Metrics.ClientTest do
   alias Zexbox.Metrics.{Client, Connection, Series}
   alias Zexbox.Metrics.ContextRegistry
 
-  setup_all do
-    ensure_registry_started()
-    :ok
-  end
-
   @map %{
     measurement: "my_measurement",
     fields: %{
@@ -21,6 +16,11 @@ defmodule Zexbox.Metrics.ClientTest do
   }
 
   describe "write_metric/1" do
+    setup do
+      start_supervised!(ContextRegistry)
+      :ok
+    end
+
     test_with_mock "writes the metric when given a series", Connection,
       write: fn metrics -> {:ok, metrics} end do
       series = struct(Series, @map)
@@ -60,11 +60,4 @@ defmodule Zexbox.Metrics.ClientTest do
       Zexbox.Metrics.enable_for_process()
     end
   end
-
-  defp ensure_registry_started do
-    case Process.whereis(ContextRegistry) do
-      nil -> {:ok, _pid} = ContextRegistry.start_link()
-      _pid -> :ok
-    end
-  end
 end
diff --git a/test/zexbox/metrics/context_registry_test.exs b/test/zexbox/metrics/context_registry_test.exs
index 26c6d00..3e70128 100644
--- a/test/zexbox/metrics/context_registry_test.exs
+++ b/test/zexbox/metrics/context_registry_test.exs
@@ -3,12 +3,14 @@ defmodule Zexbox.Metrics.ContextRegistryTest do
 
   alias Zexbox.Metrics.ContextRegistry
 
-  setup_all do
-    ensure_registry_started()
-    :ok
-  end
-
   describe "register/1, unregister/1, disabled?/1" do
+    setup do
+      # Start a supervised ContextRegistry for each test
+      # This ensures a clean state and proper cleanup
+      start_supervised!(ContextRegistry)
+      :ok
+    end
+
     test "registers and unregisters a pid" do
       pid = self()
 
@@ -59,11 +61,4 @@ defmodule Zexbox.Metrics.ContextRegistryTest do
       eventually(predicate, attempts - 1)
     end
   end
-
-  defp ensure_registry_started do
-    case Process.whereis(ContextRegistry) do
-      nil -> {:ok, _pid} = ContextRegistry.start_link()
-      _pid -> :ok
-    end
-  end
 end
diff --git a/test/zexbox/metrics/context_test.exs b/test/zexbox/metrics/context_test.exs
index 6234bb4..b068a20 100644
--- a/test/zexbox/metrics/context_test.exs
+++ b/test/zexbox/metrics/context_test.exs
@@ -3,12 +3,12 @@ defmodule Zexbox.Metrics.ContextTest do
 
   alias Zexbox.Metrics.{Context, ContextRegistry}
 
-  setup_all do
-    ensure_registry_started()
-    :ok
-  end
-
   describe "disable_for_process/0 and enable_for_process/0" do
+    setup do
+      start_supervised!(ContextRegistry)
+      :ok
+    end
+
     test "toggles disabled? for the current process" do
       assert Context.disabled?() == false
 
@@ -34,11 +34,4 @@ defmodule Zexbox.Metrics.ContextTest do
       :ok = Zexbox.Metrics.enable_for_process()
     end
   end
-
-  defp ensure_registry_started do
-    case Process.whereis(ContextRegistry) do
-      nil -> {:ok, _pid} = ContextRegistry.start_link()
-      _pid -> :ok
-    end
-  end
 end
diff --git a/test/zexbox/metrics/metric_handler_test.exs b/test/zexbox/metrics/metric_handler_test.exs
index 850ebd9..dd845d8 100644
--- a/test/zexbox/metrics/metric_handler_test.exs
+++ b/test/zexbox/metrics/metric_handler_test.exs
@@ -5,11 +5,6 @@ defmodule Zexbox.Metrics.MetricHandlerTest do
   alias Zexbox.Metrics.{Connection, ControllerSeries, MetricHandler}
   alias Zexbox.Metrics.ContextRegistry
 
-  setup_all do
-    ensure_registry_started()
-    :ok
-  end
-
   defmodule MockClient do
     @spec write_metric(ControllerSeries.t()) :: ControllerSeries.t()
     def write_metric(metric) do
@@ -19,6 +14,8 @@ defmodule Zexbox.Metrics.MetricHandlerTest do
 
   describe "handle_event/4" do
     setup do
+      start_supervised!(ContextRegistry)
+
       event = [:phoenix, :endpoint, :stop]
 
       measurements = %{duration: 1_000_000_000}
@@ -101,10 +98,12 @@ defmodule Zexbox.Metrics.MetricHandlerTest do
     end
 
     test "captures and logs any exceptions", %{event: event, metadata: metadata} do
-      assert capture_log(fn ->
-               MetricHandler.handle_event(event, nil, metadata, nil)
-             end) =~
-               "Exception creating controller series: %KeyError"
+      log =
+        capture_log(fn ->
+          MetricHandler.handle_event(event, nil, metadata, nil)
+        end)
+
+      assert log =~ "Exception creating controller series:"
     end
 
     test "does not call Connection.write when process has disabled metrics", %{
@@ -120,11 +119,4 @@ defmodule Zexbox.Metrics.MetricHandlerTest do
       end
     end
   end
-
-  defp ensure_registry_started do
-    case Process.whereis(ContextRegistry) do
-      nil -> {:ok, _pid} = ContextRegistry.start_link()
-      _pid -> :ok
-    end
-  end
 end
diff --git a/test/zexbox/metrics/models/series_test.exs b/test/zexbox/metrics/models/series_test.exs
index fdbc8fb..26b0c50 100644
--- a/test/zexbox/metrics/models/series_test.exs
+++ b/test/zexbox/metrics/models/series_test.exs
@@ -35,7 +35,7 @@ defmodule Zexbox.Metrics.SeriesTest do
     metric = Series.new(measurement)
 
     assert metric.measurement == measurement
-    refute is_nil(metric.timestamp)
+    assert %DateTime{} = metric.timestamp
   end
 
   test "field/3" do