diff --git a/docs/development-progress-log.md b/docs/development-progress-log.md
index 1dcf994..2f96345 100644
--- a/docs/development-progress-log.md
+++ b/docs/development-progress-log.md
@@ -335,6 +335,15 @@ end
 - show custom fields in member overview per default
 - can be set to false in the settings for the specific custom field
 
+---
+
+**Onboarding / Public Join (Issue #308) – Subtask 1: JoinRequest resource and public policies**
+- JoinRequest Ash resource (`lib/membership/join_request.ex`) per concept §2.3.2: email, confirmation_token_hash, status, submitted_at, source, schema_version, payload, approved_at, rejected_at, reviewed_by_user_id
+- Migration `20260220120000_add_join_requests.exs` with unique index on `confirmation_token_hash` for idempotency
+- Public policies: `:confirm` and `:read` allowed with `actor: nil`; generic `:create` requires HasPermission
+- Domain interface: `confirm_join_request/2`, `list_join_requests/1`, `get_join_request/2`, `update_join_request/2`, `destroy_join_request/1`
+- Tests: `test/mv/membership/join_request_test.exs` – public create/read with nil, idempotency, validations (no UI/email yet)
+
 ## Implementation Decisions
 
 ### Architecture Patterns
diff --git a/docs/onboarding-join-concept.md b/docs/onboarding-join-concept.md
index 9c09da7..1959c1b 100644
--- a/docs/onboarding-join-concept.md
+++ b/docs/onboarding-join-concept.md
@@ -168,12 +168,12 @@ The feature is split into a small number of well-bounded subtasks. **Resend conf
 
 ### Prio 1 – Public Join (4 subtasks)
 
-#### 1. JoinRequest resource and public policies
+#### 1. JoinRequest resource and public policies ✅
 
 - **Scope:** Ash resource `JoinRequest` per §2.3.2 (email, payload/schema_version, status, submitted_at, approved_at, rejected_at, reviewed_by_user_id, source, optional abuse metadata); migration; idempotency key (e.g. unique_index on confirmation_token_hash).
 - **Policies:** Explicit public actions (e.g. `confirm`) allowed with `actor: nil`; no system-actor fallback, no undocumented `authorize?: false`.
 - **Boundary:** No UI, no emails, no pre-confirmation logic – only resource, persistence, and “creatable with nil actor”.
-- **Done:** Resource and migration in place; tests for create/read with `actor: nil` and for idempotency (same token twice → no second record).
+- **Done:** Resource and migration in place; tests in `test/mv/membership/join_request_test.exs` for create/read with `actor: nil` and for idempotency (same token twice → no second record).
 
 #### 2. Pre-confirmation store and confirm flow
 
diff --git a/lib/membership/join_request.ex b/lib/membership/join_request.ex
new file mode 100644
index 0000000..466840b
--- /dev/null
+++ b/lib/membership/join_request.ex
@@ -0,0 +1,141 @@
+defmodule Mv.Membership.JoinRequest do
+  @moduledoc """
+  Ash resource for public join requests (onboarding flow).
+
+  Created only after email confirmation (double opt-in). Per concept §2.3.2:
+  - email (dedicated field), payload, schema_version, status, submitted_at, source
+  - approved_at, rejected_at, reviewed_by_user_id for audit (Step 2)
+  - confirmation_token_hash for idempotency (unique constraint)
+  """
+  use Ash.Resource,
+    domain: Mv.Membership,
+    data_layer: AshPostgres.DataLayer,
+    authorizers: [Ash.Policy.Authorizer]
+
+  postgres do
+    table "join_requests"
+    repo Mv.Repo
+  end
+
+  actions do
+    defaults [:read, :destroy]
+
+    create :create do
+      primary? true
+      accept [
+        :email,
+        :confirmation_token_hash,
+        :status,
+        :submitted_at,
+        :source,
+        :schema_version,
+        :payload,
+        :approved_at,
+        :rejected_at,
+        :reviewed_by_user_id
+      ]
+    end
+
+    create :confirm do
+      description "Public action: create JoinRequest after confirmation link click (actor: nil)"
+      accept [
+        :email,
+        :confirmation_token_hash,
+        :status,
+        :submitted_at,
+        :source,
+        :schema_version,
+        :payload
+      ]
+    end
+
+    update :update do
+      accept [:status, :approved_at, :rejected_at, :reviewed_by_user_id]
+      require_atomic? false
+    end
+  end
+
+  policies do
+    policy action(:confirm) do
+      description "Allow public confirmation (actor nil) for join flow"
+      authorize_if Ash.Policy.Check.Builtins.actor_absent()
+    end
+
+    policy action_type(:read) do
+      description "Allow read when actor nil (success page) or when user has permission"
+      authorize_if Ash.Policy.Check.Builtins.actor_absent()
+      authorize_if Mv.Authorization.Checks.HasPermission
+    end
+
+    policy action(:create) do
+      description "Generic create only for authorized users; public uses :confirm"
+      authorize_if Mv.Authorization.Checks.HasPermission
+    end
+
+    policy action_type([:update, :destroy]) do
+      authorize_if Mv.Authorization.Checks.HasPermission
+    end
+  end
+
+  attributes do
+    uuid_v7_primary_key :id
+
+    attribute :email, :string do
+      allow_nil? false
+      public? true
+    end
+
+    attribute :confirmation_token_hash, :string do
+      allow_nil? false
+      public? true
+    end
+
+    attribute :status, :string do
+      allow_nil? false
+      public? true
+      default "submitted"
+    end
+
+    attribute :submitted_at, :utc_datetime_usec do
+      allow_nil? false
+      public? true
+    end
+
+    attribute :source, :string do
+      allow_nil? false
+      public? true
+    end
+
+    attribute :schema_version, :integer do
+      allow_nil? false
+      public? true
+    end
+
+    attribute :payload, :map do
+      allow_nil? true
+      public? true
+      default %{}
+    end
+
+    attribute :approved_at, :utc_datetime_usec do
+      allow_nil? true
+      public? true
+    end
+
+    attribute :rejected_at, :utc_datetime_usec do
+      allow_nil? true
+      public? true
+    end
+
+    attribute :reviewed_by_user_id, :uuid do
+      allow_nil? true
+      public? true
+    end
+
+    timestamps()
+  end
+
+  identities do
+    identity :unique_confirmation_token_hash, [:confirmation_token_hash]
+  end
+end
diff --git a/lib/membership/membership.ex b/lib/membership/membership.ex
index 74735e4..69a8110 100644
--- a/lib/membership/membership.ex
+++ b/lib/membership/membership.ex
@@ -78,6 +78,52 @@ defmodule Mv.Membership do
       define :list_member_groups, action: :read
       define :destroy_member_group, action: :destroy
     end
+
+    resource Mv.Membership.JoinRequest do
+      define :list_join_requests, action: :read
+      define :get_join_request, action: :read, get_by: [:id]
+      define :update_join_request, action: :update
+      define :destroy_join_request, action: :destroy
+    end
+  end
+
+  # Idempotent confirm: implemented in code so duplicate token returns {:ok, existing} (concept §2.3.2)
+  @doc """
+  Creates a JoinRequest after confirmation link click (public action with actor: nil).
+
+  Idempotent: if a JoinRequest with the same `confirmation_token_hash` already exists,
+  returns `{:ok, existing}` instead of creating a duplicate (per concept §2.3.2).
+  """
+  def confirm_join_request(attrs, opts \\ []) do
+    hash = attrs[:confirmation_token_hash] || attrs["confirmation_token_hash"]
+
+    if hash do
+      case get_join_request_by_confirmation_token_hash!(hash, opts) do
+        nil -> do_confirm_join_request(attrs, opts)
+        existing -> {:ok, existing}
+      end
+    else
+      do_confirm_join_request(attrs, opts)
+    end
+  end
+
+  defp do_confirm_join_request(attrs, opts) do
+    Mv.Membership.JoinRequest
+    |> Ash.Changeset.for_create(:confirm, attrs)
+    |> Ash.create(Keyword.put(opts, :domain, __MODULE__))
+  end
+
+  defp get_join_request_by_confirmation_token_hash!(hash, opts) do
+    opts = Keyword.put(opts, :domain, __MODULE__)
+
+    Mv.Membership.JoinRequest
+    |> Ash.Query.filter(confirmation_token_hash == ^hash)
+    |> Ash.read_one(opts)
+    |> case do
+      {:ok, %Mv.Membership.JoinRequest{} = existing} -> existing
+      {:ok, nil} -> nil
+      _ -> nil
+    end
   end
 
   # Singleton pattern: Get the single settings record
diff --git a/priv/repo/migrations/20260220120000_add_join_requests.exs b/priv/repo/migrations/20260220120000_add_join_requests.exs
new file mode 100644
index 0000000..00f764d
--- /dev/null
+++ b/priv/repo/migrations/20260220120000_add_join_requests.exs
@@ -0,0 +1,42 @@
+defmodule Mv.Repo.Migrations.AddJoinRequests do
+  @moduledoc """
+  Adds join_requests table for public join flow (onboarding concept §2.3.2).
+  """
+  use Ecto.Migration
+
+  def up do
+    create table(:join_requests, primary_key: false) do
+      add :id, :uuid, null: false, default: fragment("uuid_generate_v7()"), primary_key: true
+      add :email, :string, null: false
+      add :confirmation_token_hash, :string, null: false
+      add :status, :string, null: false
+      add :submitted_at, :utc_datetime_usec, null: false
+      add :source, :string, null: false
+      add :schema_version, :bigint, null: false
+      add :payload, :map, null: true
+      add :approved_at, :utc_datetime_usec, null: true
+      add :rejected_at, :utc_datetime_usec, null: true
+      add :reviewed_by_user_id, :uuid, null: true
+
+      add :inserted_at, :utc_datetime_usec,
+        null: false,
+        default: fragment("(now() AT TIME ZONE 'utc')")
+
+      add :updated_at, :utc_datetime_usec,
+        null: false,
+        default: fragment("(now() AT TIME ZONE 'utc')")
+    end
+
+    create unique_index(:join_requests, [:confirmation_token_hash],
+             name: "join_requests_unique_confirmation_token_hash_index"
+           )
+  end
+
+  def down do
+    drop_if_exists unique_index(:join_requests, [:confirmation_token_hash],
+                  name: "join_requests_unique_confirmation_token_hash_index"
+                )
+
+    drop table(:join_requests)
+  end
+end
diff --git a/test/mv/membership/join_request_test.exs b/test/mv/membership/join_request_test.exs
new file mode 100644
index 0000000..fa81231
--- /dev/null
+++ b/test/mv/membership/join_request_test.exs
@@ -0,0 +1,104 @@
+defmodule Mv.Membership.JoinRequestTest do
+  @moduledoc """
+  Tests for JoinRequest resource and public policies (Subtask 1: onboarding join concept).
+
+  Covers: public create/read with actor nil, idempotency of confirm (confirmation_token_hash),
+  and minimal required attributes. No framework behaviour is tested; only our policies and constraints.
+  """
+  use Mv.DataCase, async: false
+
+  alias Mv.Membership
+  alias Mv.Membership.JoinRequest
+
+  require Ash.Query
+
+  # Minimal valid attributes for the public :confirm action (per concept §2.3.2)
+  defp valid_confirm_attrs(opts \\ []) do
+    token = Keyword.get(opts, :confirmation_token_hash, "hash_#{System.unique_integer([:positive])}")
+    [
+      email: "join_#{System.unique_integer([:positive])}@example.com",
+      confirmation_token_hash: token,
+      status: "submitted",
+      submitted_at: DateTime.utc_now(),
+      source: "public_join",
+      schema_version: 1,
+      payload: %{}
+    ]
+    |> Enum.into(%{})
+  end
+
+  describe "Public policies (actor: nil)" do
+    test "confirm with actor nil succeeds" do
+      attrs = valid_confirm_attrs()
+
+      assert {:ok, %JoinRequest{} = request} =
+               Membership.confirm_join_request(attrs, actor: nil)
+
+      assert request.email == attrs.email
+      assert request.status == "submitted"
+      assert request.source == "public_join"
+    end
+
+    test "read with actor nil succeeds for created join request" do
+      attrs = valid_confirm_attrs()
+      {:ok, created} = Membership.confirm_join_request(attrs, actor: nil)
+
+      assert {:ok, %JoinRequest{} = read} =
+               Ash.get(JoinRequest, created.id, actor: nil, domain: Mv.Membership)
+
+      assert read.id == created.id
+      assert read.email == created.email
+    end
+
+    test "generic create with actor nil is forbidden" do
+      attrs = valid_confirm_attrs()
+
+      assert {:error, %Ash.Error.Forbidden{errors: [%Ash.Error.Forbidden.Policy{}]}} =
+               JoinRequest
+               |> Ash.Changeset.for_create(:create, attrs)
+               |> Ash.create(actor: nil, domain: Mv.Membership)
+    end
+  end
+
+  describe "Idempotency (confirmation_token_hash)" do
+    test "second create with same confirmation_token_hash does not create duplicate" do
+      system_actor = Mv.Helpers.SystemActor.get_system_actor()
+      token = "idempotent_token_#{System.unique_integer([:positive])}"
+      attrs1 = valid_confirm_attrs(confirmation_token_hash: token)
+      attrs2 = valid_confirm_attrs(confirmation_token_hash: token)
+      attrs2 = %{attrs2 | email: "other_#{System.unique_integer([:positive])}@example.com"}
+
+      assert {:ok, first} = Membership.confirm_join_request(attrs1, actor: nil)
+
+      # Second call with same token: idempotent return {:ok, existing} (concept §2.3.2)
+      assert {:ok, second} = Membership.confirm_join_request(attrs2, actor: nil)
+      assert second.id == first.id, "idempotent confirm must return the existing record"
+
+      count =
+        JoinRequest
+        |> Ash.Query.filter(confirmation_token_hash == ^token)
+        |> Ash.read!(actor: system_actor, domain: Mv.Membership, authorize?: false)
+        |> length()
+
+      assert count == 1, "expected exactly one JoinRequest with this confirmation_token_hash, got #{count}"
+    end
+  end
+
+  describe "Resource and validations" do
+    test "create with minimal required attributes succeeds" do
+      attrs = valid_confirm_attrs()
+
+      assert {:ok, %JoinRequest{}} = Membership.confirm_join_request(attrs, actor: nil)
+    end
+
+    test "email is required" do
+      attrs = valid_confirm_attrs() |> Map.delete(:email)
+
+      assert {:error, %Ash.Error.Invalid{errors: errors}} =
+               Membership.confirm_join_request(attrs, actor: nil)
+
+      assert Enum.any?(errors, fn e -> Map.get(e, :field) == :email end),
+             "expected an error for field :email, got: #{inspect(errors)}"
+    end
+  end
+end