diff --git a/lib/strike_me/api.rb b/lib/strike_me/api.rb
index 7fa8c3a..89b6664 100644
--- a/lib/strike_me/api.rb
+++ b/lib/strike_me/api.rb
@@ -31,5 +31,7 @@ module StrikeMe
     autoload_default :Account
     autoload_default :Invoices
     autoload_default :InvoiceResponse
+    autoload_default :Webhook
+    autoload_default :WebhookEvent
   end
 end
diff --git a/lib/strike_me/api/client.rb b/lib/strike_me/api/client.rb
index 132e7cb..ea91a00 100644
--- a/lib/strike_me/api/client.rb
+++ b/lib/strike_me/api/client.rb
@@ -26,6 +26,14 @@ module StrikeMe
       def get(...)
         @last_response = connection.get(...)
       end
+
+      def post(...)
+        @last_response = connection.post(...)
+      end
+
+      def patch(...)
+        @last_response = connection.patch(...)
+      end
     end
   end
 end
diff --git a/lib/strike_me/api/invoices.rb b/lib/strike_me/api/invoices.rb
index 1a9aee8..7fbaff0 100644
--- a/lib/strike_me/api/invoices.rb
+++ b/lib/strike_me/api/invoices.rb
@@ -8,6 +8,7 @@ module StrikeMe
       include Enumerable
 
       autoload_default :Invoice
+      autoload_default :Quote
 
       delegate :first, :last, :size, :any?, to: :list
 
@@ -25,6 +26,51 @@ module StrikeMe
 
         @list = response.body['items'].map { |item| Invoice.new item }
       end
+
+      def paid
+        select(&:paid?)
+      end
+
+      def find(id)
+        url = "invoices/#{id}"
+        response = client.get url
+
+        raise ResponseError.new(url, response.body) unless response.success?
+
+        Invoice.new response.body
+      end
+
+      # POST invoices — amount is a decimal string per Strike's own API
+      # (not a float/BTC value), matching what #list/#find already hand
+      # back untouched in Invoice#amount.
+      def create(amount:, currency:, description: nil, correlation_id: nil)
+        url = 'invoices'
+        body = {
+          amount: { amount: amount, currency: currency },
+          description: description,
+          correlationId: correlation_id
+        }.compact
+        response = client.post(url, body)
+
+        raise ResponseError.new(url, response.body) unless response.success?
+
+        Invoice.new response.body
+      end
+
+      # POST invoices/{id}/quote — the second step of actually getting a
+      # payable BOLT 11 (Invoice#create alone only reserves the invoice
+      # shell; nothing is payable until a quote exists). Quotes expire
+      # (Quote#expiration) — callers request a fresh one per payment
+      # attempt rather than caching.
+      def quote(id, description_hash: nil)
+        url = "invoices/#{id}/quote"
+        body = { descriptionHash: description_hash }.compact
+        response = client.post(url, body)
+
+        raise ResponseError.new(url, response.body) unless response.success?
+
+        Quote.new response.body
+      end
     end
   end
 end
diff --git a/lib/strike_me/api/invoices/invoice.rb b/lib/strike_me/api/invoices/invoice.rb
index 6118284..cf43104 100644
--- a/lib/strike_me/api/invoices/invoice.rb
+++ b/lib/strike_me/api/invoices/invoice.rb
@@ -13,6 +13,7 @@ module StrikeMe
         attribute :receiverId
         attribute :payerId
 
+        alias_attribute :id, :invoiceId
         attribute_names.select { _1.end_with? 'Id' }.each do |snake_name|
           alias_attribute snake_name.underscore, snake_name
         end
@@ -20,6 +21,18 @@ module StrikeMe
         def paid?
           state == 'PAID'
         end
+
+        def unpaid?
+          state == 'UNPAID'
+        end
+
+        def pending?
+          state == 'PENDING'
+        end
+
+        def cancelled?
+          state == 'CANCELLED'
+        end
       end
     end
   end
diff --git a/lib/strike_me/api/invoices/quote.rb b/lib/strike_me/api/invoices/quote.rb
new file mode 100644
index 0000000..ec6c72c
--- /dev/null
+++ b/lib/strike_me/api/invoices/quote.rb
@@ -0,0 +1,32 @@
+# frozen_string_literal: true
+
+module StrikeMe
+  module API
+    class Invoices
+      # Response of POST invoices/{id}/quote — the actual payable BOLT 11
+      # only exists once a quote is issued; Invoice#create alone reserves
+      # the invoice shell but has nothing a wallet can pay yet.
+      class Quote < BaseModel
+        attribute :quoteId
+        attribute :description
+        attribute :lnInvoice
+        attribute :onchainAddress
+        attribute :expiration, :datetime
+        attribute :expirationInSec, :integer
+        attribute :targetAmount
+        attribute :sourceAmount
+        attribute :conversionRate
+
+        alias_attribute :id, :quoteId
+        alias_attribute :bolt11, :lnInvoice
+        attribute_names.select { _1.end_with? 'Id' }.each do |snake_name|
+          alias_attribute snake_name.underscore, snake_name
+        end
+
+        def expired?
+          expiration.present? && expiration.past?
+        end
+      end
+    end
+  end
+end
diff --git a/lib/strike_me/api/webhook.rb b/lib/strike_me/api/webhook.rb
new file mode 100644
index 0000000..3a3743e
--- /dev/null
+++ b/lib/strike_me/api/webhook.rb
@@ -0,0 +1,38 @@
+# frozen_string_literal: true
+
+require 'openssl'
+require 'active_support/security_utils'
+
+module StrikeMe
+  module API
+    # Verifies the X-Webhook-Signature header Strike attaches to every
+    # webhook POST — HMAC-SHA256 of the raw request body, keyed by the
+    # secret set at webhook-subscription creation time. See
+    # https://docs.strike.me/webhooks/signature-verification — this
+    # mirrors Strike's own documented reference implementation exactly
+    # (hex digest, timing-safe compare), just in Ruby.
+    #
+    # `raw_body` must be the exact bytes Strike sent, before any
+    # JSON-parsing round-trip — re-serializing a parsed body can reorder
+    # keys or change whitespace and silently break verification.
+    module Webhook
+      SIGNATURE_HEADER = 'X-Webhook-Signature'
+
+      def self.valid_signature?(raw_body:, signature:, secret:)
+        return false if signature.blank? || raw_body.blank?
+
+        expected = OpenSSL::HMAC.hexdigest('SHA256', secret, raw_body)
+        secure_compare(expected, signature)
+      end
+
+      # ActiveSupport::SecurityUtils.secure_compare raises on a length
+      # mismatch rather than returning false — a garbled/truncated header
+      # from a malformed request should fail closed, not raise.
+      def self.secure_compare(expected, actual)
+        return false unless expected.bytesize == actual.bytesize
+
+        ActiveSupport::SecurityUtils.secure_compare(expected, actual)
+      end
+    end
+  end
+end
diff --git a/lib/strike_me/api/webhook_event.rb b/lib/strike_me/api/webhook_event.rb
new file mode 100644
index 0000000..ec69664
--- /dev/null
+++ b/lib/strike_me/api/webhook_event.rb
@@ -0,0 +1,39 @@
+# frozen_string_literal: true
+
+module StrikeMe
+  module API
+    # Parses the WebhookEvent payload every Strike webhook POST carries —
+    # {id, eventType, webhookVersion, data: {entityId, changes}, created,
+    # deliverySuccess}. Deliberately does NOT carry the changed values
+    # themselves — Strike's own docs are explicit that the event never
+    # contains the actual data changes, only that something changed on
+    # `entity_id`. A real value only comes from calling the matching
+    # fetch endpoint (e.g. Invoices#find for an invoice.* event) —
+    # trusting anything else here would mean trusting an unauthenticated
+    # claim about money having moved.
+    class WebhookEvent < BaseModel
+      attribute :id
+      attribute :eventType
+      attribute :webhookVersion
+      attribute :data
+      attribute :created, :datetime
+      attribute :deliverySuccess, :boolean
+
+      alias_attribute :event_type, :eventType
+      alias_attribute :webhook_version, :webhookVersion
+      alias_attribute :delivery_success, :deliverySuccess
+
+      def entity_id
+        data['entityId'] || data[:entityId]
+      end
+
+      def changes
+        data['changes'] || data[:changes] || []
+      end
+
+      def invoice_event?
+        event_type.to_s.start_with?('invoice.')
+      end
+    end
+  end
+end
diff --git a/spec/strike_me/api/invoices_spec.rb b/spec/strike_me/api/invoices_spec.rb
index d095aaa..f6913ba 100644
--- a/spec/strike_me/api/invoices_spec.rb
+++ b/spec/strike_me/api/invoices_spec.rb
@@ -22,6 +22,7 @@ RSpec.describe StrikeMe::API::Invoices do
           'receiverId'  => '41952e07-483c-4cd7-afa4-b6a8ec729809',
           'payerId'     => 'f75c22bf-625f-4c47-acdf-acb9c596bb8c'
         )
+        expect(list.first.id     ).to eq '97dca64c-6dde-4a87-b970-279f1a8e0ac5'
         expect(list.first.created).to be_a Time
 
         expect(list.last.attributes).to eq(
@@ -37,4 +38,62 @@ RSpec.describe StrikeMe::API::Invoices do
       end
     end
   end
+
+  describe '#find' do
+    before do
+      stub_request(:get, 'https://api.strike.me/v1/invoices/97dca64c-6dde-4a87-b970-279f1a8e0ac5')
+        .to_return(status: 200, body: '{"invoiceId":"97dca64c-6dde-4a87-b970-279f1a8e0ac5","amount":{"amount":"0.00014","currency":"BTC"},"state":"PAID","created":"2025-08-08T22:28:44.195825+00:00","description":"Hi there","issuerId":"41952e07-483c-4cd7-afa4-b6a8ec729809","receiverId":"41952e07-483c-4cd7-afa4-b6a8ec729809","payerId":"f75c22bf-625f-4c47-acdf-acb9c596bb8c"}', headers: {'Content-Type' => 'application/json'})
+    end
+
+    it 'finds and returns the proper object' do
+      invoice = subject.find('97dca64c-6dde-4a87-b970-279f1a8e0ac5')
+
+      expect(invoice).to be_a StrikeMe::API::Invoices::Invoice
+      expect(invoice.id).to eq '97dca64c-6dde-4a87-b970-279f1a8e0ac5'
+      expect(invoice).to be_paid
+    end
+  end
+
+  describe '#create' do
+    before do
+      stub_request(:post, 'https://api.strike.me/v1/invoices')
+        .with(body: {amount: {amount: '10.00', currency: 'USD'}, description: 'Table 3'})
+        .to_return(status: 201, body: '{"invoiceId":"602cc206-6b4a-42dd-bc89-9a534bb04034","amount":{"amount":"10.00","currency":"USD"},"state":"UNPAID","created":"2026-09-15T12:00:00+00:00","description":"Table 3","issuerId":"41952e07-483c-4cd7-afa4-b6a8ec729809","receiverId":"41952e07-483c-4cd7-afa4-b6a8ec729809"}', headers: {'Content-Type' => 'application/json'})
+    end
+
+    it 'issues a new invoice, unpaid, with no bolt11 yet — that only exists once quoted' do
+      invoice = subject.create(amount: '10.00', currency: 'USD', description: 'Table 3')
+
+      expect(invoice).to be_a StrikeMe::API::Invoices::Invoice
+      expect(invoice.id).to eq '602cc206-6b4a-42dd-bc89-9a534bb04034'
+      expect(invoice).to be_unpaid
+    end
+
+    it 'omits correlationId/description entirely when not given, rather than sending them null' do
+      stub = stub_request(:post, 'https://api.strike.me/v1/invoices')
+        .with(body: {amount: {amount: '10.00', currency: 'USD'}})
+        .to_return(status: 201, body: '{"invoiceId":"x","amount":{"amount":"10.00","currency":"USD"},"state":"UNPAID","created":"2026-09-15T12:00:00+00:00","issuerId":"a","receiverId":"a"}', headers: {'Content-Type' => 'application/json'})
+
+      subject.create(amount: '10.00', currency: 'USD')
+      expect(stub).to have_been_requested
+    end
+  end
+
+  describe '#quote' do
+    before do
+      stub_request(:post, 'https://api.strike.me/v1/invoices/602cc206-6b4a-42dd-bc89-9a534bb04034/quote')
+        .with(body: {})
+        .to_return(status: 201, body: '{"quoteId":"a1b2c3","lnInvoice":"lnbc100n1p...","expiration":"2099-01-01T00:00:00+00:00","expirationInSec":300,"targetAmount":{"amount":"10.00","currency":"USD"},"sourceAmount":{"amount":"0.00014","currency":"BTC"},"conversionRate":{"amount":"71428.57","sourceCurrency":"BTC","targetCurrency":"USD"}}', headers: {'Content-Type' => 'application/json'})
+    end
+
+    it 'returns a Quote carrying the actual payable bolt11' do
+      quote = subject.quote('602cc206-6b4a-42dd-bc89-9a534bb04034')
+
+      expect(quote).to be_a StrikeMe::API::Invoices::Quote
+      expect(quote.bolt11).to eq 'lnbc100n1p...'
+      expect(quote.id).to eq 'a1b2c3'
+      expect(quote.expiration).to be_a Time
+      expect(quote).not_to be_expired
+    end
+  end
 end
diff --git a/spec/strike_me/api/webhook_event_spec.rb b/spec/strike_me/api/webhook_event_spec.rb
new file mode 100644
index 0000000..e4e99b5
--- /dev/null
+++ b/spec/strike_me/api/webhook_event_spec.rb
@@ -0,0 +1,37 @@
+# frozen_string_literal: true
+
+RSpec.describe StrikeMe::API::WebhookEvent do
+  subject(:event) do
+    described_class.new(
+      'id' => '245e40d8-f197-411c-8f20-a326d08da402',
+      'eventType' => 'invoice.updated',
+      'webhookVersion' => 'v1',
+      'data' => { 'entityId' => '602cc206-6b4a-42dd-bc89-9a534bb04034', 'changes' => ['state'] },
+      'created' => '2026-09-15T12:00:00+00:00',
+      'deliverySuccess' => true
+    )
+  end
+
+  it 'exposes entity_id and changes from the nested data object' do
+    expect(event.entity_id).to eq '602cc206-6b4a-42dd-bc89-9a534bb04034'
+    expect(event.changes).to eq ['state']
+  end
+
+  it 'aliases the camelCase attributes to snake_case' do
+    expect(event.event_type).to eq 'invoice.updated'
+    expect(event.webhook_version).to eq 'v1'
+    expect(event.delivery_success).to eq true
+  end
+
+  it 'parses created as a real Time' do
+    expect(event.created).to be_a Time
+  end
+
+  it 'identifies invoice events' do
+    expect(event).to be_invoice_event
+  end
+
+  it 'does not carry the actual changed values — only that state changed, not to what' do
+    expect(event.attributes.keys).not_to include('amount', 'state')
+  end
+end
diff --git a/spec/strike_me/api/webhook_spec.rb b/spec/strike_me/api/webhook_spec.rb
new file mode 100644
index 0000000..06c0cc3
--- /dev/null
+++ b/spec/strike_me/api/webhook_spec.rb
@@ -0,0 +1,31 @@
+# frozen_string_literal: true
+
+RSpec.describe StrikeMe::API::Webhook do
+  let(:secret) { 'a-webhook-subscription-secret' }
+  let(:raw_body) { '{"id":"245e40d8-f197-411c-8f20-a326d08da402","eventType":"invoice.updated","webhookVersion":"v1","data":{"entityId":"602cc206-6b4a-42dd-bc89-9a534bb04034","changes":["state"]},"created":"2026-09-15T12:00:00+00:00","deliverySuccess":true}' }
+  let(:real_signature) { OpenSSL::HMAC.hexdigest('SHA256', secret, raw_body) }
+
+  describe '.valid_signature?' do
+    it 'is true for a signature computed with the same secret over the same raw body' do
+      expect(described_class.valid_signature?(raw_body: raw_body, signature: real_signature, secret: secret)).to eq true
+    end
+
+    it 'is false for the wrong secret' do
+      expect(described_class.valid_signature?(raw_body: raw_body, signature: real_signature, secret: 'wrong')).to eq false
+    end
+
+    it 'is false if the body was tampered with after signing' do
+      tampered = raw_body.sub('"state"', '"amount"')
+      expect(described_class.valid_signature?(raw_body: tampered, signature: real_signature, secret: secret)).to eq false
+    end
+
+    it 'is false for a blank signature, rather than raising' do
+      expect(described_class.valid_signature?(raw_body: raw_body, signature: '', secret: secret)).to eq false
+      expect(described_class.valid_signature?(raw_body: raw_body, signature: nil, secret: secret)).to eq false
+    end
+
+    it 'is false (not a raised length-mismatch error) for a garbled/truncated signature' do
+      expect(described_class.valid_signature?(raw_body: raw_body, signature: 'not-a-real-length', secret: secret)).to eq false
+    end
+  end
+end
diff --git a/strike_me-api.gemspec b/strike_me-api.gemspec
index 3ed48d8..6ccd185 100644
--- a/strike_me-api.gemspec
+++ b/strike_me-api.gemspec
@@ -8,15 +8,14 @@ Gem::Specification.new do |spec|
   spec.authors = ['Benjamin ter Kuile']
   spec.email = ['bterkuile@gmail.com']
 
-  spec.summary = 'TODO: Write a short summary, because RubyGems requires one.'
-  spec.description = 'TODO: Write a longer description or delete this line.'
-  spec.homepage = 'TODO: Put your gem website or public repo URL here.'
+  spec.summary = 'Ruby client for the Strike (strike.me) API'
+  spec.description = 'Invoice creation/quoting, account/balance reads, and webhook signature verification for the Strike Lightning payments API.'
+  spec.homepage = 'https://gitlab.com/benja-2/strike_me-api'
   spec.license = 'MIT'
   spec.required_ruby_version = '>= 3.1.0'
 
   spec.metadata['homepage_uri'] = spec.homepage
   spec.metadata['source_code_uri'] = 'https://gitlab.com/benja-2/strike_me-api'
-  spec.metadata['changelog_uri'] = 'TODO: Put your gem CHANGELOG.md URL here.'
 
   # Specify which files should be added to the gem when it is released.
   # The `git ls-files -z` loads the files in the RubyGem that have been added into git.