diff --git a/app/models/remote_storage_authorization.rb b/app/models/remote_storage_authorization.rb
index 6c7ae6e..cd2c36d 100644
--- a/app/models/remote_storage_authorization.rb
+++ b/app/models/remote_storage_authorization.rb
@@ -2,6 +2,10 @@ class RemoteStorageAuthorization < ApplicationRecord
   belongs_to :user
   belongs_to :web_app, class_name: "AppCatalog::WebApp", optional: true
 
+  # The plaintext token is only ever held in memory, long enough to hand it to
+  # the client at issuance. At rest we store only its SHA256 digest.
+  attr_accessor :token
+
   # Tokens issued before user agents were recorded may have been used from any
   # number of devices, so they cannot be attributed to a single one.
   UNKNOWN_DEVICE = "Unknown device(s)"
@@ -77,8 +81,12 @@ class RemoteStorageAuthorization < ApplicationRecord
   end
 
   def delete_token_from_redis
-    key = "authorizations:#{user.cn}:#{token}"
-    redis.srem? key, redis.smembers(key)
+    value = token_digest.presence
+    value ||= read_attribute(:token) if self.class.column_names.include?("token")
+    return if value.blank?
+
+    key = "authorizations:#{user.cn}:#{value}"
+    redis.del key
   rescue => e
     Rails.logger.error e
     Sentry.capture_exception(e) if Setting.sentry_enabled?
@@ -92,10 +100,11 @@ class RemoteStorageAuthorization < ApplicationRecord
 
     def generate_token(length=16)
       self.token = SecureRandom.hex(length) if self.token.blank?
+      self.token_digest = Digest::SHA256.hexdigest(token)
     end
 
     def store_token_in_redis
-      redis.sadd "authorizations:#{user.cn}:#{token}", permissions
+      redis.sadd "authorizations:#{user.cn}:#{token_digest}", permissions
     end
 
     def schedule_token_expiry
diff --git a/app/services/remote_storage_manager/rekey_tokens.rb b/app/services/remote_storage_manager/rekey_tokens.rb
new file mode 100644
index 0000000..3f91125
--- /dev/null
+++ b/app/services/remote_storage_manager/rekey_tokens.rb
@@ -0,0 +1,111 @@
+require "digest"
+
+module RemoteStorageManager
+  # One-off, idempotent migration helper for issue #259. It backfills missing
+  # digests for authorizations created while the old plaintext code was still
+  # running, re-keys the Redis authorization sets from plaintext to digest
+  # keys, and removes any leftover non-digest keys.
+  #
+  # It only works while the plaintext `token` column still exists; after the
+  # follow-up contract migration drops it, `call` is a no-op.
+  class RekeyTokens < RemoteStorageManagerService
+    Result = Struct.new(:rekeyed, :legacy_removed, :skipped, keyword_init: true)
+
+    def call
+      return Result.new(rekeyed: 0, legacy_removed: 0, skipped: true) unless token_column?
+
+      rekeyed = 0
+
+      RemoteStorageAuthorization.find_each do |auth|
+        plaintext = persisted_token(auth)
+        next if plaintext.blank? && auth.token_digest.blank?
+
+        digest = auth.token_digest.presence || Digest::SHA256.hexdigest(plaintext)
+        auth.update_columns(token_digest: digest) if auth.token_digest.blank?
+
+        permissions = permissions_for(auth, plaintext)
+
+        redis.sadd(redis_key(auth.user.cn, digest), permissions) if permissions.present?
+        redis.del(redis_key(auth.user.cn, plaintext)) if plaintext.present?
+
+        rekeyed += 1
+      end
+
+      Result.new(rekeyed: rekeyed, legacy_removed: remove_legacy_keys, skipped: false)
+    end
+
+    private
+
+    def redis
+      @redis ||= Redis.new(url: Setting.rs_redis_url)
+    end
+
+    def token_column?
+      RemoteStorageAuthorization.column_names.include?("token")
+    end
+
+    # Reads the persisted plaintext directly, because the model's `token`
+    # accessor shadows the column after the token is moved into memory.
+    def persisted_token(auth)
+      auth.read_attribute(:token) if token_column?
+    end
+
+    def redis_key(cn, value)
+      "authorizations:#{cn}:#{value}"
+    end
+
+    def permissions_for(auth, plaintext)
+      permissions = redis.smembers(redis_key(auth.user.cn, plaintext)) if plaintext.present?
+      permissions.presence || permissions_from_db(auth)
+    end
+
+    def permissions_from_db(auth)
+      case (permissions = auth.permissions)
+      when Array then permissions.map(&:to_s)
+      when String then parse_permissions(permissions)
+      else Array(permissions).map(&:to_s)
+      end
+    end
+
+    def parse_permissions(raw)
+      parsed = parse_serialized(raw)
+      return parsed.map(&:to_s) if parsed.is_a?(Array)
+
+      raw.to_s.gsub(/[{}]/, "").split(/[,\s]+/).reject(&:empty?)
+    end
+
+    def parse_serialized(raw)
+      YAML.safe_load(raw)
+    rescue StandardError
+      begin
+        JSON.parse(raw)
+      rescue StandardError
+        nil
+      end
+    end
+
+    # Removes leftover plaintext authorization keys. Legacy plaintext tokens are
+    # 32 hex chars (SecureRandom.hex(16)); digests are 64. Matching on shape
+    # instead of a snapshot of known keys means a digest issued concurrently
+    # during the sweep is never deleted.
+    def remove_legacy_keys
+      removed = 0
+      cursor = "0"
+
+      loop do
+        cursor, keys = redis.scan(cursor, match: "authorizations:*", count: 1000)
+
+        keys.each do |key|
+          next if key.split(":", 3).last.match?(/\A[0-9a-f]{64}\z/)
+
+          redis.del(key)
+          removed += 1
+        end
+
+        break if cursor == "0"
+      end
+
+      removed
+    end
+  end
+end
diff --git a/app/services/remote_storage_manager_service.rb b/app/services/remote_storage_manager_service.rb
new file mode 100644
index 0000000..9de9a97
--- /dev/null
+++ b/app/services/remote_storage_manager_service.rb
@@ -0,0 +1,2 @@
+class RemoteStorageManagerService < ApplicationService
+end
diff --git a/db/migrate/20261104120000_add_token_digest_to_remote_storage_authorizations.rb b/db/migrate/20261104120000_add_token_digest_to_remote_storage_authorizations.rb
new file mode 100644
index 0000000..f196b02
--- /dev/null
+++ b/db/migrate/20261104120000_add_token_digest_to_remote_storage_authorizations.rb
@@ -0,0 +1,26 @@
+require "digest"
+
+class AddTokenDigestToRemoteStorageAuthorizations < ActiveRecord::Migration[8.1]
+  class MigrationRemoteStorageAuthorization < ActiveRecord::Base
+    self.table_name = "remote_storage_authorizations"
+  end
+
+  def up
+    add_column :remote_storage_authorizations, :token_digest, :string
+
+    MigrationRemoteStorageAuthorization.reset_column_information
+
+    MigrationRemoteStorageAuthorization.find_each do |auth|
+      next if auth.token.blank?
+
+      auth.update_columns(token_digest: Digest::SHA256.hexdigest(auth.token))
+    end
+
+    add_index :remote_storage_authorizations, :token_digest, unique: true
+  end
+
+  def down
+    remove_index :remote_storage_authorizations, :token_digest
+    remove_column :remote_storage_authorizations, :token_digest
+  end
+end
diff --git a/db/schema.rb b/db/schema.rb
index 4518582..b587aef 100644
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[8.1].define(version: 2026_11_02_130000) do
+ActiveRecord::Schema[8.1].define(version: 2026_11_04_120000) do
   create_table "active_storage_attachments", force: :cascade do |t|
     t.bigint "blob_id", null: false
     t.datetime "created_at", null: false
@@ -109,11 +109,13 @@ ActiveRecord::Schema[8.1].define(version: 2026_11_02_130000) do
     t.text "permissions", default: "--- []\n"
     t.string "redirect_uri"
     t.string "token"
+    t.string "token_digest"
     t.datetime "updated_at", null: false
     t.text "user_agent"
     t.integer "user_id", null: false
     t.integer "web_app_id"
     t.index ["permissions"], name: "index_remote_storage_authorizations_on_permissions"
+    t.index ["token_digest"], name: "index_remote_storage_authorizations_on_token_digest", unique: true
     t.index ["user_id"], name: "index_remote_storage_authorizations_on_user_id"
     t.index ["web_app_id"], name: "index_remote_storage_authorizations_on_web_app_id"
   end
diff --git a/lib/tasks/remote_storage.rake b/lib/tasks/remote_storage.rake
new file mode 100644
index 0000000..3af410b
--- /dev/null
+++ b/lib/tasks/remote_storage.rake
@@ -0,0 +1,12 @@
+namespace :rs do
+  desc "Backfill remoteStorage token digests and re-key Redis authorization keys (idempotent)"
+  task rekey_tokens: :environment do
+    result = RemoteStorageManager::RekeyTokens.call
+
+    if result.skipped
+      puts "remote_storage_authorizations.token column is gone; nothing to re-key."
+    else
+      puts "Re-keyed #{result.rekeyed} authorization(s); removed #{result.legacy_removed} legacy Redis key(s)."
+    end
+  end
+end
diff --git a/spec/controllers/rs/oauth_controller_spec.rb b/spec/controllers/rs/oauth_controller_spec.rb
index e06be1a..c7530a9 100644
--- a/spec/controllers/rs/oauth_controller_spec.rb
+++ b/spec/controllers/rs/oauth_controller_spec.rb
@@ -376,7 +376,9 @@ RSpec.describe Rs::OauthController, type: :controller do
         end
 
         it "redirects to the redirect_uri" do
-          expect(response).to redirect_to("https://example.com#access_token=#{@auth.token}&state=foobar123")
+          expect(response).to redirect_to(
+            %r{\Ahttps://example\.com#access_token=[a-f0-9]{32}&state=foobar123\z}
+          )
         end
       end
 
@@ -400,7 +402,7 @@ RSpec.describe Rs::OauthController, type: :controller do
         end
 
         it "updates the token" do
-          expect(@auth.reload.token).not_to be_nil
+          expect(@auth.reload.token_digest).not_to be_nil
         end
       end
 
diff --git a/spec/jobs/remote_storage_expire_authorization_job_spec.rb b/spec/jobs/remote_storage_expire_authorization_job_spec.rb
index afe0f3e..4bf458e 100644
--- a/spec/jobs/remote_storage_expire_authorization_job_spec.rb
+++ b/spec/jobs/remote_storage_expire_authorization_job_spec.rb
@@ -28,7 +28,7 @@ RSpec.describe RemoteStorageExpireAuthorizationJob, type: :job do
   }
 
   it "removes the RS authorization from redis" do
-    redis_key = "authorizations:#{@user.cn}:#{@rs_authorization.token}"
+    redis_key = "authorizations:#{@user.cn}:#{@rs_authorization.token_digest}"
     expect(redis.keys(redis_key)).to_not be_empty
 
     perform_enqueued_jobs { job }
diff --git a/spec/models/remote_storage_authorization_spec.rb b/spec/models/remote_storage_authorization_spec.rb
index 7616603..d38d25f 100644
--- a/spec/models/remote_storage_authorization_spec.rb
+++ b/spec/models/remote_storage_authorization_spec.rb
@@ -25,10 +25,22 @@ RSpec.describe RemoteStorageAuthorization, type: :model do
       expect(auth.token).to match(/[a-zA-Z0-9]+/)
     end
 
+    it "stores only the token digest" do
+      expect(auth.token_digest).to eq(Digest::SHA256.hexdigest(auth.token))
+    end
+
+    it "does not persist the plaintext token" do
+      plaintext = auth.token
+      auth.reload
+
+      expect(auth.read_attribute(:token)).to be_nil
+      expect(auth.token_digest).to eq(Digest::SHA256.hexdigest(plaintext))
+    end
+
     it "stores a token in redis" do
       auth
 
-      authorizations = redis_rs.smembers("authorizations:#{user.cn}:#{auth.token}")
+      authorizations = redis_rs.smembers("authorizations:#{user.cn}:#{auth.token_digest}")
       expect(authorizations.sort).to eq(%w(documents photos contacts:rw videos:r tasks/work:r).sort)
     end
 
@@ -56,7 +68,21 @@ RSpec.describe RemoteStorageAuthorization, type: :model do
              )
       auth.destroy!
 
-      expect(redis_rs.exists?("authorizations:#{user.cn}:#{auth.token}")).to be(false)
+      expect(redis_rs.exists?("authorizations:#{user.cn}:#{auth.token_digest}")).to be(false)
+    end
+
+    it "removes a legacy plaintext token from redis" do
+      auth = user.remote_storage_authorizations.create!(
+               permissions: %w(shares:rw),
+               client_id: "sharesome.5apps.com",
+               redirect_uri: "https://sharesome.5apps.com"
+             )
+      auth.update_columns(token: "legacytoken", token_digest: nil)
+      redis_rs.sadd("authorizations:#{user.cn}:legacytoken", %w(shares:rw))
+
+      auth.destroy!
+
+      expect(redis_rs.exists?("authorizations:#{user.cn}:legacytoken")).to be(false)
     end
 
     context "with expiry set" do
diff --git a/spec/services/remote_storage_manager/rekey_tokens_spec.rb b/spec/services/remote_storage_manager/rekey_tokens_spec.rb
new file mode 100644
index 0000000..3dbd3e9
--- /dev/null
+++ b/spec/services/remote_storage_manager/rekey_tokens_spec.rb
@@ -0,0 +1,114 @@
+require 'rails_helper'
+
+RSpec.describe RemoteStorageManager::RekeyTokens, type: :model do
+  let(:user) { create :user, cn: "ronald", ou: "kosmos.org" }
+  let(:redis) { redis_rs }
+
+  before do
+    allow_any_instance_of(AppCatalog::WebApp).to receive(:update_metadata).and_return(true)
+    allow_any_instance_of(RemoteStorageAuthorization).to receive(:remove_token_expiry_job).and_return(nil)
+
+    redis.keys("authorizations:*").each { |key| redis.del(key) }
+  end
+
+  def authorization_keys
+    redis.keys("authorizations:#{user.cn}:*")
+  end
+
+  # A row as it looked before #259: the plaintext token lives in the DB column
+  # and only the plaintext Redis key exists.
+  def legacy_authorization(token: "legacytoken", permissions: %w(documents:rw))
+    auth = create :remote_storage_authorization, user: user, permissions: permissions
+    auth.update_columns(token: token, token_digest: nil)
+
+    redis.keys("authorizations:#{user.cn}:*").each { |key| redis.del(key) }
+    redis.sadd("authorizations:#{user.cn}:#{token}", permissions)
+
+    auth
+  end
+
+  it "re-keys an authorization from the plaintext to the digest form" do
+    auth = legacy_authorization
+    digest = Digest::SHA256.hexdigest("legacytoken")
+
+    result = described_class.call
+
+    expect(result).to have_attributes(skipped: false, rekeyed: 1)
+    expect(redis.smembers("authorizations:#{user.cn}:#{digest}").sort).to eq(%w(documents:rw))
+    expect(redis.exists?("authorizations:#{user.cn}:legacytoken")).to be(false)
+    expect(auth.reload.token_digest).to eq(digest)
+  end
+
+  it "is idempotent" do
+    legacy_authorization
+    described_class.call
+
+    expect { described_class.call }.not_to raise_error
+    expect(authorization_keys.length).to eq(1)
+  end
+
+  it "backfills the digest for rows created while the old code was still running" do
+    auth = legacy_authorization
+
+    described_class.call
+
+    expect(auth.reload.token_digest).to eq(Digest::SHA256.hexdigest("legacytoken"))
+  end
+
+  it "falls back to the stored permissions when the legacy Redis key is gone" do
+    auth = create :remote_storage_authorization, user: user, permissions: %w(photos:rw)
+    auth.update_columns(token: "legacytoken", token_digest: nil)
+    authorization_keys.each { |key| redis.del(key) }
+
+    described_class.call
+
+    digest = Digest::SHA256.hexdigest("legacytoken")
+    expect(redis.smembers("authorizations:#{user.cn}:#{digest}").sort).to eq(%w(photos:rw))
+  end
+
+  it "removes leftover non-digest authorization keys" do
+    create :remote_storage_authorization, user: user
+    redis.sadd("authorizations:#{user.cn}:leftovertoken", %w(photos))
+
+    result = described_class.call
+
+    expect(result.legacy_removed).to eq(1)
+    expect(redis.exists?("authorizations:#{user.cn}:leftovertoken")).to be(false)
+  end
+
+  it "keeps digest-shaped keys that are not in the database" do
+    fresh = Digest::SHA256.hexdigest("brand-new-token")
+    redis.sadd("authorizations:#{user.cn}:#{fresh}", %w(documents:rw))
+
+    result = described_class.call
+
+    expect(redis.exists?("authorizations:#{user.cn}:#{fresh}")).to be(true)
+    expect(result.legacy_removed).to eq(0)
+  end
+
+  it "is a no-op once the plaintext token column is gone" do
+    allow(RemoteStorageAuthorization).to receive(:column_names)
+      .and_return(RemoteStorageAuthorization.column_names - ["token"])
+
+    expect(described_class.call).to have_attributes(skipped: true, rekeyed: 0)
+  end
+
+  describe "permissions parsing" do
+    subject(:service) { described_class.new }
+
+    it "parses a JSON array string" do
+      expect(service.send(:parse_permissions, '["documents:rw", "photos"]'))
+        .to eq(%w(documents:rw photos))
+    end
+
+    it "parses a YAML array string" do
+      expect(service.send(:parse_permissions, "---\n- documents:rw\n- photos\n"))
+        .to eq(%w(documents:rw photos))
+    end
+
+    it "parses a Postgres brace array string" do
+      expect(service.send(:parse_permissions, "{documents:rw,photos}"))
+        .to eq(%w(documents:rw photos))
+    end
+  end
+end