diff --git a/app/controllers/slack_onboarding_controller.rb b/app/controllers/slack_onboarding_controller.rb
index 4a85a84..e9f337d 100644
--- a/app/controllers/slack_onboarding_controller.rb
+++ b/app/controllers/slack_onboarding_controller.rb
@@ -25,6 +25,13 @@ def show
     @step = current_user ? current_user.slack_onboarding_step : :sign_up
   end
 
+  # The current step, as JSON. The page polls it while it waits on something
+  # that can happen elsewhere (accepting in Slack, the promotion), and reloads
+  # when the step changes.
+  def status
+    render json: { step: current_user.slack_onboarding_step }
+  end
+
   # Sends the Slack invite, or sends it again.
   def create
     unless %i[request_invite accept_invite].include?(current_user.slack_onboarding_step)
diff --git a/app/javascript/controllers/index.js b/app/javascript/controllers/index.js
index 09a2054..fe9590f 100644
--- a/app/javascript/controllers/index.js
+++ b/app/javascript/controllers/index.js
@@ -13,6 +13,9 @@ application.register("fingerprint", FingerprintController)
 import LoginFormController from "./login_form_controller"
 application.register("login-form", LoginFormController)
 
+import OnboardingStatusController from "./onboarding_status_controller"
+application.register("onboarding-status", OnboardingStatusController)
+
 import PasswordController from "./password_controller"
 application.register("password", PasswordController)
 
diff --git a/app/javascript/controllers/onboarding_status_controller.js b/app/javascript/controllers/onboarding_status_controller.js
new file mode 100644
index 0000000..bb920f3
--- /dev/null
+++ b/app/javascript/controllers/onboarding_status_controller.js
@@ -0,0 +1,34 @@
+import { Controller } from "@hotwired/stimulus"
+
+// Reloads the /slack onboarding page when the person's step changes somewhere
+// else, for example when they accept the Code of Conduct in Slack. Polls the
+// status endpoint while the tab is visible, and stops after a while.
+export default class extends Controller {
+  static values = { url: String, step: String }
+
+  connect() {
+    this.checks = 0
+    this.timer = setInterval(() => this.check(), 5000)
+  }
+
+  disconnect() {
+    clearInterval(this.timer)
+  }
+
+  async check() {
+    if (document.hidden) return
+    if (++this.checks > 120) return this.disconnect()
+
+    try {
+      const response = await fetch(this.urlValue, { headers: { Accept: "application/json" } })
+      if (!response.ok) return
+      const { step } = await response.json()
+      if (step !== this.stepValue) {
+        this.disconnect()
+        window.Turbo ? window.Turbo.visit(window.location.href, { action: "replace" }) : window.location.reload()
+      }
+    } catch {
+      // A failed check is retried on the next tick.
+    }
+  }
+}
diff --git a/app/jobs/slack_code_of_conduct_accepted_job.rb b/app/jobs/slack_code_of_conduct_accepted_job.rb
index 4286e1e..b58dfb2 100644
--- a/app/jobs/slack_code_of_conduct_accepted_job.rb
+++ b/app/jobs/slack_code_of_conduct_accepted_job.rb
@@ -8,9 +8,11 @@
 # A full member who joined before the code-of-conduct flow is already a member,
 # so only the acceptance is recorded for them.
 #
-# message is the Slack DM that asked for the acceptance, as { channel:, ts: }.
-# When it is given, the DM is replaced with a thank-you so its button can't be
-# used again.
+# Then every code-of-conduct DM the user still has (User#slack_coc_messages)
+# is replaced with a thank-you, wherever they accepted, so no live button is
+# left behind. message is the DM the acceptance came from, as
+# { channel:, ts: }. It is replaced too, which covers a Slack user with no
+# Weave account.
 class SlackCodeOfConductAcceptedJob < ApplicationJob
   queue_as :default
 
@@ -23,10 +25,16 @@ def perform(slack_user_id, message: nil)
     service = SlackService.new
     return unless service.configured?
 
-    already_member = user&.slack_member?
-    replace_message(service, message, already_member:) if message.present?
-    return if already_member
+    already_member = user&.slack_member? || false
+    promote(service, user, slack_user_id) unless already_member
+    replace_messages(service, user, message, already_member:)
+  rescue SlackService::ConfigurationError => e
+    Rails.logger.error "Slack not configured for promotion: #{e.message}"
+  end
+
+  private
 
+  def promote(service, user, slack_user_id)
     result = service.promote_to_member(slack_user_id)
     if result[:ok]
       user&.update_columns(slack_membership: "member", updated_at: Time.current)
@@ -34,16 +42,15 @@ def perform(slack_user_id, message: nil)
     else
       Rails.logger.error "Failed to promote #{slack_user_id} after CoC acceptance: #{result[:error]}"
     end
-  rescue SlackService::ConfigurationError => e
-    Rails.logger.error "Slack not configured for promotion: #{e.message}"
   end
 
-  private
-
-  def replace_message(service, message, already_member:)
-    service.mark_code_of_conduct_accepted(channel: message[:channel], ts: message[:ts], already_member:)
-  rescue => e
-    Rails.logger.error "Failed to update CoC DM #{message.inspect}: #{e.message}"
+  def replace_messages(service, user, message, already_member:)
+    messages = [*user&.take_code_of_conduct_messages!, message].compact.uniq
+    messages.each do |ref|
+      service.mark_code_of_conduct_accepted(channel: ref[:channel], ts: ref[:ts], already_member:)
+    rescue => e
+      Rails.logger.error "Failed to update CoC DM #{ref.inspect}: #{e.message}"
+    end
   end
 
 end
diff --git a/app/models/user.rb b/app/models/user.rb
index 9c70302..ec08b86 100644
--- a/app/models/user.rb
+++ b/app/models/user.rb
@@ -29,6 +29,7 @@
 #  slack_birthday           :date
 #  slack_city               :string
 #  slack_coc_accepted_at    :datetime
+#  slack_coc_messages       :jsonb            not null
 #  slack_coc_requested_at   :datetime
 #  slack_cost_center        :string
 #  slack_country            :string
@@ -502,6 +503,30 @@ def slack_onboarding_step
 
   def slack_onboarding_complete? = slack_onboarding_step == :member
 
+  # Remembers a code-of-conduct DM that has a live button, so it can be
+  # replaced once the user accepts (see SlackCodeOfConductAcceptedJob). Appends
+  # in SQL, so two DMs sent at the same time are both kept.
+  def remember_code_of_conduct_message!(channel:, ts:)
+    return if channel.blank? || ts.blank?
+
+    self.class.where(id: id).update_all( # rubocop:disable Rails/SkipsModelValidations
+      ["slack_coc_messages = slack_coc_messages || ?::jsonb", [{ channel: channel, ts: ts }].to_json]
+    )
+  end
+
+  # Returns the remembered DMs and forgets them. The row lock keeps a DM that
+  # is remembered at the same moment from being lost. (with_lock is not used:
+  # User#lock! means "lock the account".)
+  def take_code_of_conduct_messages!
+    messages = self.class.transaction do
+      rows = self.class.where(id: id)
+      taken = rows.lock.pick(:slack_coc_messages) || []
+      rows.update_all(slack_coc_messages: []) # rubocop:disable Rails/SkipsModelValidations
+      taken
+    end
+    messages.map { |message| message.symbolize_keys.slice(:channel, :ts) }
+  end
+
   # The membership a Slack user object (from users.info, users.lookupByEmail,
   # users.list or a team_join/user_change event) entitles its owner to. Guests
   # and deactivated accounts are not members.
diff --git a/app/serializers/user_serializer.rb b/app/serializers/user_serializer.rb
index 7565eb8..8a70bf4 100644
--- a/app/serializers/user_serializer.rb
+++ b/app/serializers/user_serializer.rb
@@ -29,6 +29,7 @@
 #  slack_birthday           :date
 #  slack_city               :string
 #  slack_coc_accepted_at    :datetime
+#  slack_coc_messages       :jsonb            not null
 #  slack_coc_requested_at   :datetime
 #  slack_cost_center        :string
 #  slack_country            :string
diff --git a/app/services/slack_service.rb b/app/services/slack_service.rb
index 6757176..77263c8 100644
--- a/app/services/slack_service.rb
+++ b/app/services/slack_service.rb
@@ -217,11 +217,14 @@ def post_code_of_conduct(slack_user_id, title: nil, paragraphs: nil, form: false
       web_url: Rails.application.routes.url_helpers.slack_onboarding_url(**Rails.application.config.action_mailer.default_url_options)
     )
 
-    @client.chat_postMessage(
+    response = @client.chat_postMessage(
       channel: slack_user_id,
       text: "Please review and accept the Patchwork Labs Code of Conduct.",
       blocks: message[:blocks]
     )
+    # Remembered so that accepting anywhere (Slack or the web) replaces it.
+    User.find_by(slack_id: slack_user_id)&.remember_code_of_conduct_message!(channel: response["channel"], ts: response["ts"])
+    response
   end
 
   # Opens the code-of-conduct form from a button click. trigger_id comes from
diff --git a/app/views/slack_onboarding/show.html.erb b/app/views/slack_onboarding/show.html.erb
index ef10f24..96a060f 100644
--- a/app/views/slack_onboarding/show.html.erb
+++ b/app/views/slack_onboarding/show.html.erb
@@ -14,7 +14,12 @@
   link_class = "text-grape hover:text-ink font-medium underline decoration-dashed underline-offset-2"
 %>
 
-<div class="min-h-full flex items-center justify-center px-4 py-12">
+<%# While the next step can happen in Slack, check now and then and reload
+    when it does. %>
+<%= tag.div class: "min-h-full flex items-center justify-center px-4 py-12",
+      data: (if current_user && %i[accept_invite accept_code_of_conduct awaiting_promotion].include?(@step)
+               { controller: "onboarding-status", onboarding_status_url_value: status_slack_onboarding_path, onboarding_status_step_value: @step }
+             end) do %>
   <div class="patch patch-bound patch-tilt-l w-full max-w-lg">
     <div class="quilt-binding"></div>
 
@@ -142,4 +147,4 @@
       <% end %>
     </div>
   </div>
-</div>
+<% end %>
diff --git a/config/routes.rb b/config/routes.rb
index bd21da3..8035ea4 100644
--- a/config/routes.rb
+++ b/config/routes.rb
@@ -33,6 +33,7 @@
 #                                           GET    /(*path)                                                                                          redirect(302)
 #                                      root GET    /                                                                                                 home#index
 #   accept_code_of_conduct_slack_onboarding POST   /slack/code-of-conduct(.:format)                                                                  slack_onboarding#accept_code_of_conduct
+#                   status_slack_onboarding GET    /slack/status(.:format)                                                                           slack_onboarding#status
 #                          slack_onboarding GET    /slack(.:format)                                                                                  slack_onboarding#show
 #                                           POST   /slack(.:format)                                                                                  slack_onboarding#create
 #                                           GET    /.well-known/*path                                                                                well_known#show
@@ -359,6 +360,7 @@
   # request or resend the invite.
   resource :slack_onboarding, path: "slack", only: [:show, :create], controller: "slack_onboarding" do
     post :accept_code_of_conduct, path: "code-of-conduct"
+    get :status
   end
 
   # Well-known routes for standard compliance
diff --git a/db/migrate/20261010120000_add_slack_coc_messages_to_users.rb b/db/migrate/20261010120000_add_slack_coc_messages_to_users.rb
new file mode 100644
index 0000000..d5b0671
--- /dev/null
+++ b/db/migrate/20261010120000_add_slack_coc_messages_to_users.rb
@@ -0,0 +1,10 @@
+# frozen_string_literal: true
+
+class AddSlackCocMessagesToUsers < ActiveRecord::Migration[8.1]
+  def change
+    # The code-of-conduct DMs sent to a user that still have a live button, as
+    # [{ "channel" => ..., "ts" => ... }]. They are all replaced with a
+    # thank-you once the user accepts, from Slack or the web.
+    add_column :users, :slack_coc_messages, :jsonb, default: [], null: false
+  end
+end
diff --git a/db/schema.rb b/db/schema.rb
index 3f3e977..5a6ae88 100644
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -12,7 +12,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[8.1].define(version: 2026_10_09_140000) do
+ActiveRecord::Schema[8.1].define(version: 2026_10_10_120000) do
   # These are extensions that must be enabled in order to support this database
   enable_extension "fuzzystrmatch"
   enable_extension "pg_catalog.plpgsql"
@@ -590,6 +590,7 @@
     t.date "slack_birthday"
     t.string "slack_city"
     t.datetime "slack_coc_accepted_at"
+    t.jsonb "slack_coc_messages", default: [], null: false
     t.datetime "slack_coc_requested_at"
     t.string "slack_cost_center"
     t.string "slack_country"
diff --git a/docs/CODE_OF_CONDUCT.md b/docs/CODE_OF_CONDUCT.md
index 0079056..2854904 100644
--- a/docs/CODE_OF_CONDUCT.md
+++ b/docs/CODE_OF_CONDUCT.md
@@ -16,6 +16,8 @@ flowchart TD
 - The DM button accepts at once. When the Slack import saved a placeholder name (`NOTSET`, `Unknown`, `User`), the button opens a Slack form instead. The form has a required "I have read and accept" box, and name fields when the name is missing.
 - The email links to sign-in. After sign-in, `/` sends the member to `/slack`, which shows the same accept step and name fields.
 - The message text is in `config/locales/code_of_conduct_request.en.yml`.
+- Weave remembers every CoC DM it sends (`users.slack_coc_messages`). When the person accepts, in Slack or on `/slack`, `SlackCodeOfConductAcceptedJob` replaces all of them with a thank-you, so no live button is left.
+- While `/slack` waits on a step that can happen in Slack, it polls `GET /slack/status` every 5 seconds and reloads when the step changes.
 
 ## Runbook
 
diff --git a/spec/factories/users.rb b/spec/factories/users.rb
index 297d1bb..c404b93 100644
--- a/spec/factories/users.rb
+++ b/spec/factories/users.rb
@@ -29,6 +29,7 @@
 #  slack_birthday           :date
 #  slack_city               :string
 #  slack_coc_accepted_at    :datetime
+#  slack_coc_messages       :jsonb            not null
 #  slack_coc_requested_at   :datetime
 #  slack_cost_center        :string
 #  slack_country            :string
diff --git a/spec/jobs/slack_code_of_conduct_accepted_job_spec.rb b/spec/jobs/slack_code_of_conduct_accepted_job_spec.rb
index 8822896..8bf45a4 100644
--- a/spec/jobs/slack_code_of_conduct_accepted_job_spec.rb
+++ b/spec/jobs/slack_code_of_conduct_accepted_job_spec.rb
@@ -49,4 +49,27 @@
 
     described_class.perform_now("U123", message: { channel: "D1", ts: "1.2" })
   end
+
+  it "replaces every DM the user still has, wherever they accepted, and forgets them" do
+    user.update!(slack_membership: "member")
+    user.remember_code_of_conduct_message!(channel: "D1", ts: "1.1")
+    user.remember_code_of_conduct_message!(channel: "D1", ts: "1.2")
+    replaced = []
+    allow(service).to receive(:mark_code_of_conduct_accepted) { |**ref| replaced << ref }
+
+    described_class.perform_now("U123", message: { channel: "D1", ts: "1.2" })
+
+    expect(replaced).to eq([{ channel: "D1", ts: "1.1", already_member: true }, { channel: "D1", ts: "1.2", already_member: true }])
+    expect(user.reload.slack_coc_messages).to eq([])
+  end
+
+  it "keeps replacing the other DMs when one fails" do
+    user.update!(slack_membership: "member")
+    user.remember_code_of_conduct_message!(channel: "D1", ts: "1.1")
+    user.remember_code_of_conduct_message!(channel: "D1", ts: "1.2")
+    allow(service).to receive(:mark_code_of_conduct_accepted).with(hash_including(ts: "1.1")).and_raise(Slack::Web::Api::Errors::SlackError, "message_not_found")
+    expect(service).to receive(:mark_code_of_conduct_accepted).with(hash_including(ts: "1.2"))
+
+    described_class.perform_now("U123")
+  end
 end
diff --git a/spec/models/user_spec.rb b/spec/models/user_spec.rb
index 298cec2..3bca8a4 100644
--- a/spec/models/user_spec.rb
+++ b/spec/models/user_spec.rb
@@ -29,6 +29,7 @@
 #  slack_birthday           :date
 #  slack_city               :string
 #  slack_coc_accepted_at    :datetime
+#  slack_coc_messages       :jsonb            not null
 #  slack_coc_requested_at   :datetime
 #  slack_cost_center        :string
 #  slack_country            :string
diff --git a/spec/requests/slack_onboarding_spec.rb b/spec/requests/slack_onboarding_spec.rb
index d8e6e13..880a80f 100644
--- a/spec/requests/slack_onboarding_spec.rb
+++ b/spec/requests/slack_onboarding_spec.rb
@@ -89,6 +89,35 @@
     end
   end
 
+  describe "GET /slack/status" do
+    it "reports the current step, so the page can reload when it changes elsewhere" do
+      user.update!(slack_id: "U1", slack_membership: "member")
+      sign_in_via_magic_link(user)
+
+      get status_slack_onboarding_path
+
+      expect(response.parsed_body).to eq("step" => "accept_code_of_conduct")
+    end
+
+    it "makes the accept step check the status" do
+      user.update!(slack_id: "U1", slack_membership: "member")
+      sign_in_via_magic_link(user)
+
+      get slack_onboarding_path
+
+      expect(response.body).to include('data-controller="onboarding-status"', status_slack_onboarding_path)
+    end
+
+    it "does not check the status once the person is a full member" do
+      user.update!(slack_id: "U1", slack_membership: "member", slack_coc_accepted_at: 1.day.ago)
+      sign_in_via_magic_link(user)
+
+      get slack_onboarding_path
+
+      expect(response.body).not_to include("onboarding-status")
+    end
+  end
+
   describe "POST /slack" do
     before { sign_in_via_magic_link(user) }
 
diff --git a/spec/serializers/user_serializer_spec.rb b/spec/serializers/user_serializer_spec.rb
index 4d13374..68e8389 100644
--- a/spec/serializers/user_serializer_spec.rb
+++ b/spec/serializers/user_serializer_spec.rb
@@ -29,6 +29,7 @@
 #  slack_birthday           :date
 #  slack_city               :string
 #  slack_coc_accepted_at    :datetime
+#  slack_coc_messages       :jsonb            not null
 #  slack_coc_requested_at   :datetime
 #  slack_cost_center        :string
 #  slack_country            :string
diff --git a/spec/services/slack_service_code_of_conduct_spec.rb b/spec/services/slack_service_code_of_conduct_spec.rb
index 525fdb6..f5e6d27 100644
--- a/spec/services/slack_service_code_of_conduct_spec.rb
+++ b/spec/services/slack_service_code_of_conduct_spec.rb
@@ -30,6 +30,15 @@ def block_types(blocks) = blocks.map { |block| block[:type] }
       service.post_code_of_conduct("U1", title: "Hello", paragraphs: ["First paragraph"])
     end
 
+    it "remembers the DM, so accepting anywhere can replace it" do
+      user = create(:user, slack_id: "U1")
+      allow(client).to receive(:chat_postMessage).and_return({ "ok" => true, "channel" => "D1", "ts" => "1.2" })
+
+      service.post_code_of_conduct("U1")
+
+      expect(user.reload.slack_coc_messages).to eq([{ "channel" => "D1", "ts" => "1.2" }])
+    end
+
     it "uses the form button when asked" do
       expect(client).to receive(:chat_postMessage) do |args|
         button = args[:blocks].find { |block| block[:type] == "actions" }[:elements].first
diff --git a/test/fixtures/users.yml b/test/fixtures/users.yml
index 61376e8..5cbfbc7 100644
--- a/test/fixtures/users.yml
+++ b/test/fixtures/users.yml
@@ -33,6 +33,7 @@
 #  slack_birthday           :date
 #  slack_city               :string
 #  slack_coc_accepted_at    :datetime
+#  slack_coc_messages       :jsonb            not null
 #  slack_coc_requested_at   :datetime
 #  slack_cost_center        :string
 #  slack_country            :string
diff --git a/test/models/user_test.rb b/test/models/user_test.rb
index e974bc0..7b2be59 100644
--- a/test/models/user_test.rb
+++ b/test/models/user_test.rb
@@ -29,6 +29,7 @@
 #  slack_birthday           :date
 #  slack_city               :string
 #  slack_coc_accepted_at    :datetime
+#  slack_coc_messages       :jsonb            not null
 #  slack_coc_requested_at   :datetime
 #  slack_cost_center        :string
 #  slack_country            :string