diff --git a/antd-ruby/lib/antd/grpc_client.rb b/antd-ruby/lib/antd/grpc_client.rb
index 2463dc1d..4d192541 100644
--- a/antd-ruby/lib/antd/grpc_client.rb
+++ b/antd-ruby/lib/antd/grpc_client.rb
@@ -6,7 +6,7 @@
 #     -I../../antd/proto \
 #     --ruby_out=lib --grpc_out=lib \
 #     antd/v1/common.proto antd/v1/health.proto antd/v1/data.proto \
-#     antd/v1/chunks.proto antd/v1/files.proto
+#     antd/v1/chunks.proto antd/v1/files.proto antd/v1/upload.proto
 #
 # The generated files are expected under lib/antd/v1/.
 
@@ -15,6 +15,7 @@
 require_relative "v1/data_services_pb"
 require_relative "v1/chunks_services_pb"
 require_relative "v1/files_services_pb"
+require_relative "v1/upload_services_pb"
 
 module Antd
   DEFAULT_GRPC_TARGET = "localhost:50051"
@@ -43,6 +44,7 @@ def initialize(target: DEFAULT_GRPC_TARGET)
       @data_stub   = Antd::V1::DataService::Stub.new(target, :this_channel_is_insecure)
       @chunk_stub  = Antd::V1::ChunkService::Stub.new(target, :this_channel_is_insecure)
       @file_stub   = Antd::V1::FileService::Stub.new(target, :this_channel_is_insecure)
+      @upload_stub = Antd::V1::UploadService::Stub.new(target, :this_channel_is_insecure)
     end
 
     # --- Health ---
@@ -214,8 +216,174 @@ def file_cost(path, is_public, payment_mode: PaymentMode::AUTO)
       )
     end
 
+    # --- External Signer (chunks) ---
+
+    # Prepare a single chunk for external-signer publish.
+    #
+    # When the chunk is already on-network the result has
+    # +already_stored: true+ and the caller can skip +finalize_chunk_upload+
+    # entirely.
+    #
+    # @param data [String] raw chunk bytes
+    # @return [PrepareChunkResult]
+    def prepare_chunk_upload(data)
+      req = Antd::V1::PrepareChunkRequest.new(data: data.b)
+      resp = grpc_call { @chunk_stub.prepare_chunk(req) }
+      PrepareChunkResult.new(
+        address: resp.address,
+        already_stored: resp.already_stored,
+        upload_id: resp.upload_id,
+        payment_type: resp.payment_type,
+        payments: resp.payments.map { |p|
+          PaymentInfo.new(
+            quote_hash: p.quote_hash,
+            rewards_address: p.rewards_address,
+            amount: p.amount
+          )
+        },
+        total_amount: resp.total_amount,
+        payment_vault_address: resp.payment_vault_address,
+        payment_token_address: resp.payment_token_address,
+        rpc_url: resp.rpc_url
+      )
+    end
+
+    # Submit a prepared chunk after external payment. Returns the chunk address.
+    #
+    # @param upload_id [String]
+    # @param tx_hashes [Hash<String, String>]
+    # @return [String] hex chunk address
+    def finalize_chunk_upload(upload_id, tx_hashes)
+      req = Antd::V1::FinalizeChunkRequest.new(
+        upload_id: upload_id,
+        tx_hashes: tx_hashes
+      )
+      resp = grpc_call { @chunk_stub.finalize_chunk(req) }
+      resp.address
+    end
+
+    # --- External Signer (uploads) ---
+
+    # Prepare a file upload for external signing.
+    #
+    # @param path [String] local file path on the daemon host
+    # @param visibility [String, nil] +"private"+ (default when nil) or
+    #   +"public"+ to bundle the DataMap chunk into the same external-signer
+    #   payment batch
+    # @return [PrepareUploadResult]
+    def prepare_upload(path, visibility: nil)
+      req = Antd::V1::PrepareFileUploadRequest.new(
+        path: path,
+        visibility: visibility.to_s
+      )
+      resp = grpc_call { @upload_stub.prepare_file_upload(req) }
+      build_prepare_upload_result(resp)
+    end
+
+    # Convenience wrapper for +prepare_upload(path, visibility: "public")+.
+    #
+    # @param path [String]
+    # @return [PrepareUploadResult]
+    def prepare_upload_public(path)
+      prepare_upload(path, visibility: "public")
+    end
+
+    # Prepare an in-memory data upload for external signing.
+    #
+    # @param data [String] raw bytes
+    # @param visibility [String, nil] same semantics as +prepare_upload+
+    # @return [PrepareUploadResult]
+    def prepare_data_upload(data, visibility: nil)
+      req = Antd::V1::PrepareDataUploadRequest.new(
+        data: data.b,
+        visibility: visibility.to_s
+      )
+      resp = grpc_call { @upload_stub.prepare_data_upload(req) }
+      build_prepare_upload_result(resp)
+    end
+
+    # Finalize a wave-batch upload after external payment.
+    #
+    # @param upload_id [String]
+    # @param tx_hashes [Hash<String, String>]
+    # @return [FinalizeUploadResult]
+    def finalize_upload(upload_id, tx_hashes)
+      req = Antd::V1::FinalizeUploadRequest.new(
+        upload_id: upload_id,
+        tx_hashes: tx_hashes
+      )
+      resp = grpc_call { @upload_stub.finalize_upload(req) }
+      FinalizeUploadResult.new(
+        address: resp.address,
+        chunks_stored: resp.chunks_stored.to_i,
+        data_map: resp.data_map,
+        data_map_address: resp.data_map_address
+      )
+    end
+
+    # Finalize a merkle-batch upload after the winning pool has been
+    # determined.
+    #
+    # @param upload_id [String]
+    # @param winner_pool_hash [String]
+    # @param store_data_map [Boolean]
+    # @return [FinalizeUploadResult]
+    def finalize_merkle_upload(upload_id, winner_pool_hash, store_data_map: false)
+      req = Antd::V1::FinalizeUploadRequest.new(
+        upload_id: upload_id,
+        winner_pool_hash: winner_pool_hash,
+        store_data_map: store_data_map
+      )
+      resp = grpc_call { @upload_stub.finalize_upload(req) }
+      FinalizeUploadResult.new(
+        address: resp.address,
+        chunks_stored: resp.chunks_stored.to_i,
+        data_map: resp.data_map,
+        data_map_address: resp.data_map_address
+      )
+    end
+
     private
 
+    # Maps a PrepareUploadResponse proto into a +PrepareUploadResult+ struct,
+    # populating the merkle-only fields (+depth+, +pool_commitments+,
+    # +merkle_payment_timestamp+) only when +payment_type+ is +"merkle"+.
+    def build_prepare_upload_result(resp)
+      is_merkle = resp.payment_type == "merkle"
+      pool_commitments = if is_merkle
+        resp.pool_commitments.map { |pc|
+          PoolCommitmentEntry.new(
+            pool_hash: pc.pool_hash,
+            candidates: pc.candidates.map { |c|
+              CandidateNodeEntry.new(
+                rewards_address: c.rewards_address,
+                amount: c.amount
+              )
+            }
+          )
+        }
+      end
+      PrepareUploadResult.new(
+        upload_id: resp.upload_id,
+        payments: resp.payments.map { |p|
+          PaymentInfo.new(
+            quote_hash: p.quote_hash,
+            rewards_address: p.rewards_address,
+            amount: p.amount
+          )
+        },
+        total_amount: resp.total_amount,
+        payment_vault_address: resp.payment_vault_address,
+        payment_token_address: resp.payment_token_address,
+        rpc_url: resp.rpc_url,
+        payment_type: resp.payment_type,
+        depth: is_merkle ? resp.depth : nil,
+        pool_commitments: pool_commitments,
+        merkle_payment_timestamp: is_merkle ? resp.merkle_payment_timestamp.to_i : nil
+      )
+    end
+
+
     # Executes a gRPC call and translates errors to Antd error types.
     def grpc_call
       yield
diff --git a/antd-ruby/lib/antd/v1/chunks_pb.rb b/antd-ruby/lib/antd/v1/chunks_pb.rb
index e0ca5553..b55491d2 100644
--- a/antd-ruby/lib/antd/v1/chunks_pb.rb
+++ b/antd-ruby/lib/antd/v1/chunks_pb.rb
@@ -7,7 +7,7 @@
 require 'antd/v1/common_pb'
 
 
-descriptor_data = "\n\x14\x61ntd/v1/chunks.proto\x12\x07\x61ntd.v1\x1a\x14\x61ntd/v1/common.proto\"\"\n\x0fGetChunkRequest\x12\x0f\n\x07\x61\x64\x64ress\x18\x01 \x01(\t\" \n\x10GetChunkResponse\x12\x0c\n\x04\x64\x61ta\x18\x01 \x01(\x0c\"\x1f\n\x0fPutChunkRequest\x12\x0c\n\x04\x64\x61ta\x18\x01 \x01(\x0c\"@\n\x10PutChunkResponse\x12\x1b\n\x04\x63ost\x18\x01 \x01(\x0b\x32\r.antd.v1.Cost\x12\x0f\n\x07\x61\x64\x64ress\x18\x02 \x01(\t2\x86\x01\n\x0c\x43hunkService\x12:\n\x03Get\x12\x18.antd.v1.GetChunkRequest\x1a\x19.antd.v1.GetChunkResponse\x12:\n\x03Put\x12\x18.antd.v1.PutChunkRequest\x1a\x19.antd.v1.PutChunkResponseBDZ8github.com/WithAutonomi/ant-sdk/antd-go/proto/antd/v1;v1\xaa\x02\x07\x41ntd.V1b\x06proto3"
+descriptor_data = "\n\x14\x61ntd/v1/chunks.proto\x12\x07\x61ntd.v1\x1a\x14\x61ntd/v1/common.proto\"\"\n\x0fGetChunkRequest\x12\x0f\n\x07\x61\x64\x64ress\x18\x01 \x01(\t\" \n\x10GetChunkResponse\x12\x0c\n\x04\x64\x61ta\x18\x01 \x01(\x0c\"\x1f\n\x0fPutChunkRequest\x12\x0c\n\x04\x64\x61ta\x18\x01 \x01(\x0c\"@\n\x10PutChunkResponse\x12\x1b\n\x04\x63ost\x18\x01 \x01(\x0b\x32\r.antd.v1.Cost\x12\x0f\n\x07\x61\x64\x64ress\x18\x02 \x01(\t\"#\n\x13PrepareChunkRequest\x12\x0c\n\x04\x64\x61ta\x18\x01 \x01(\x0c\"\xf6\x01\n\x14PrepareChunkResponse\x12\x0f\n\x07\x61\x64\x64ress\x18\x01 \x01(\t\x12\x16\n\x0e\x61lready_stored\x18\x02 \x01(\x08\x12\x11\n\tupload_id\x18\x03 \x01(\t\x12\x14\n\x0cpayment_type\x18\x04 \x01(\t\x12\'\n\x08payments\x18\x05 \x03(\x0b\x32\x15.antd.v1.PaymentEntry\x12\x14\n\x0ctotal_amount\x18\x06 \x01(\t\x12\x1d\n\x15payment_vault_address\x18\x07 \x01(\t\x12\x1d\n\x15payment_token_address\x18\x08 \x01(\t\x12\x0f\n\x07rpc_url\x18\t \x01(\t\"\x9a\x01\n\x14\x46inalizeChunkRequest\x12\x11\n\tupload_id\x18\x01 \x01(\t\x12>\n\ttx_hashes\x18\x02 \x03(\x0b\x32+.antd.v1.FinalizeChunkRequest.TxHashesEntry\x1a/\n\rTxHashesEntry\x12\x0b\n\x03key\x18\x01 \x01(\t\x12\r\n\x05value\x18\x02 \x01(\t:\x02\x38\x01\"(\n\x15\x46inalizeChunkResponse\x12\x0f\n\x07\x61\x64\x64ress\x18\x01 \x01(\t2\xa3\x02\n\x0c\x43hunkService\x12:\n\x03Get\x12\x18.antd.v1.GetChunkRequest\x1a\x19.antd.v1.GetChunkResponse\x12:\n\x03Put\x12\x18.antd.v1.PutChunkRequest\x1a\x19.antd.v1.PutChunkResponse\x12K\n\x0cPrepareChunk\x12\x1c.antd.v1.PrepareChunkRequest\x1a\x1d.antd.v1.PrepareChunkResponse\x12N\n\rFinalizeChunk\x12\x1d.antd.v1.FinalizeChunkRequest\x1a\x1e.antd.v1.FinalizeChunkResponseBDZ8github.com/WithAutonomi/ant-sdk/antd-go/proto/antd/v1;v1\xaa\x02\x07\x41ntd.V1b\x06proto3"
 
 pool = ::Google::Protobuf::DescriptorPool.generated_pool
 pool.add_serialized_file(descriptor_data)
@@ -18,5 +18,9 @@ module V1
     GetChunkResponse = ::Google::Protobuf::DescriptorPool.generated_pool.lookup("antd.v1.GetChunkResponse").msgclass
     PutChunkRequest = ::Google::Protobuf::DescriptorPool.generated_pool.lookup("antd.v1.PutChunkRequest").msgclass
     PutChunkResponse = ::Google::Protobuf::DescriptorPool.generated_pool.lookup("antd.v1.PutChunkResponse").msgclass
+    PrepareChunkRequest = ::Google::Protobuf::DescriptorPool.generated_pool.lookup("antd.v1.PrepareChunkRequest").msgclass
+    PrepareChunkResponse = ::Google::Protobuf::DescriptorPool.generated_pool.lookup("antd.v1.PrepareChunkResponse").msgclass
+    FinalizeChunkRequest = ::Google::Protobuf::DescriptorPool.generated_pool.lookup("antd.v1.FinalizeChunkRequest").msgclass
+    FinalizeChunkResponse = ::Google::Protobuf::DescriptorPool.generated_pool.lookup("antd.v1.FinalizeChunkResponse").msgclass
   end
 end
diff --git a/antd-ruby/lib/antd/v1/chunks_services_pb.rb b/antd-ruby/lib/antd/v1/chunks_services_pb.rb
index 2da23bf8..7b2c62dc 100644
--- a/antd-ruby/lib/antd/v1/chunks_services_pb.rb
+++ b/antd-ruby/lib/antd/v1/chunks_services_pb.rb
@@ -17,6 +17,13 @@ class Service
 
         rpc :Get, ::Antd::V1::GetChunkRequest, ::Antd::V1::GetChunkResponse
         rpc :Put, ::Antd::V1::PutChunkRequest, ::Antd::V1::PutChunkResponse
+        # External-signer single-chunk publish. Mirrors REST
+        # `/v1/chunks/prepare` + `/v1/chunks/finalize`. Single chunks are always
+        # below the merkle threshold, so the payment shape is always wave-batch.
+        # When the chunk is already on-network, the prepare response has
+        # `already_stored = true` and the caller can skip the finalize step.
+        rpc :PrepareChunk, ::Antd::V1::PrepareChunkRequest, ::Antd::V1::PrepareChunkResponse
+        rpc :FinalizeChunk, ::Antd::V1::FinalizeChunkRequest, ::Antd::V1::FinalizeChunkResponse
       end
 
       Stub = Service.rpc_stub_class
diff --git a/antd-ruby/lib/antd/v1/common_pb.rb b/antd-ruby/lib/antd/v1/common_pb.rb
index f18db769..4a46ae54 100644
--- a/antd-ruby/lib/antd/v1/common_pb.rb
+++ b/antd-ruby/lib/antd/v1/common_pb.rb
@@ -5,7 +5,7 @@
 require 'google/protobuf'
 
 
-descriptor_data = "\n\x14\x61ntd/v1/common.proto\x12\x07\x61ntd.v1\"y\n\x04\x43ost\x12\x13\n\x0b\x61tto_tokens\x18\x01 \x01(\t\x12\x11\n\tfile_size\x18\x02 \x01(\x04\x12\x13\n\x0b\x63hunk_count\x18\x03 \x01(\r\x12\x1e\n\x16\x65stimated_gas_cost_wei\x18\x04 \x01(\t\x12\x14\n\x0cpayment_mode\x18\x05 \x01(\t\"\x16\n\x07\x41\x64\x64ress\x12\x0b\n\x03hex\x18\x01 \x01(\t\"\x1d\n\x0ePublicKeyProto\x12\x0b\n\x03hex\x18\x01 \x01(\t\"\x1d\n\x0eSecretKeyProto\x12\x0b\n\x03hex\x18\x01 \x01(\tBDZ8github.com/WithAutonomi/ant-sdk/antd-go/proto/antd/v1;v1\xaa\x02\x07\x41ntd.V1b\x06proto3"
+descriptor_data = "\n\x14\x61ntd/v1/common.proto\x12\x07\x61ntd.v1\"y\n\x04\x43ost\x12\x13\n\x0b\x61tto_tokens\x18\x01 \x01(\t\x12\x11\n\tfile_size\x18\x02 \x01(\x04\x12\x13\n\x0b\x63hunk_count\x18\x03 \x01(\r\x12\x1e\n\x16\x65stimated_gas_cost_wei\x18\x04 \x01(\t\x12\x14\n\x0cpayment_mode\x18\x05 \x01(\t\"\x16\n\x07\x41\x64\x64ress\x12\x0b\n\x03hex\x18\x01 \x01(\t\"\x1d\n\x0ePublicKeyProto\x12\x0b\n\x03hex\x18\x01 \x01(\t\"\x1d\n\x0eSecretKeyProto\x12\x0b\n\x03hex\x18\x01 \x01(\t\"K\n\x0cPaymentEntry\x12\x12\n\nquote_hash\x18\x01 \x01(\t\x12\x17\n\x0frewards_address\x18\x02 \x01(\t\x12\x0e\n\x06\x61mount\x18\x03 \x01(\tBDZ8github.com/WithAutonomi/ant-sdk/antd-go/proto/antd/v1;v1\xaa\x02\x07\x41ntd.V1b\x06proto3"
 
 pool = ::Google::Protobuf::DescriptorPool.generated_pool
 pool.add_serialized_file(descriptor_data)
@@ -16,5 +16,6 @@ module V1
     Address = ::Google::Protobuf::DescriptorPool.generated_pool.lookup("antd.v1.Address").msgclass
     PublicKeyProto = ::Google::Protobuf::DescriptorPool.generated_pool.lookup("antd.v1.PublicKeyProto").msgclass
     SecretKeyProto = ::Google::Protobuf::DescriptorPool.generated_pool.lookup("antd.v1.SecretKeyProto").msgclass
+    PaymentEntry = ::Google::Protobuf::DescriptorPool.generated_pool.lookup("antd.v1.PaymentEntry").msgclass
   end
 end
diff --git a/antd-ruby/lib/antd/v1/upload_pb.rb b/antd-ruby/lib/antd/v1/upload_pb.rb
new file mode 100644
index 00000000..e75766f4
--- /dev/null
+++ b/antd-ruby/lib/antd/v1/upload_pb.rb
@@ -0,0 +1,25 @@
+# frozen_string_literal: true
+# Generated by the protocol buffer compiler.  DO NOT EDIT!
+# source: antd/v1/upload.proto
+
+require 'google/protobuf'
+
+require 'antd/v1/common_pb'
+
+
+descriptor_data = "\n\x14\x61ntd/v1/upload.proto\x12\x07\x61ntd.v1\x1a\x14\x61ntd/v1/common.proto\"<\n\x18PrepareFileUploadRequest\x12\x0c\n\x04path\x18\x01 \x01(\t\x12\x12\n\nvisibility\x18\x02 \x01(\t\"<\n\x18PrepareDataUploadRequest\x12\x0c\n\x04\x64\x61ta\x18\x01 \x01(\x0c\x12\x12\n\nvisibility\x18\x02 \x01(\t\"\xb7\x02\n\x15PrepareUploadResponse\x12\x11\n\tupload_id\x18\x01 \x01(\t\x12\x14\n\x0cpayment_type\x18\x02 \x01(\t\x12\'\n\x08payments\x18\x03 \x03(\x0b\x32\x15.antd.v1.PaymentEntry\x12\r\n\x05\x64\x65pth\x18\x04 \x01(\r\x12\x36\n\x10pool_commitments\x18\x05 \x03(\x0b\x32\x1c.antd.v1.PoolCommitmentEntry\x12 \n\x18merkle_payment_timestamp\x18\x06 \x01(\x04\x12\x14\n\x0ctotal_amount\x18\x07 \x01(\t\x12\x1d\n\x15payment_vault_address\x18\x08 \x01(\t\x12\x1d\n\x15payment_token_address\x18\t \x01(\t\x12\x0f\n\x07rpc_url\x18\n \x01(\t\"Y\n\x13PoolCommitmentEntry\x12\x11\n\tpool_hash\x18\x01 \x01(\t\x12/\n\ncandidates\x18\x02 \x03(\x0b\x32\x1b.antd.v1.CandidateNodeEntry\"=\n\x12\x43\x61ndidateNodeEntry\x12\x17\n\x0frewards_address\x18\x01 \x01(\t\x12\x0e\n\x06\x61mount\x18\x02 \x01(\t\"\xce\x01\n\x15\x46inalizeUploadRequest\x12\x11\n\tupload_id\x18\x01 \x01(\t\x12?\n\ttx_hashes\x18\x02 \x03(\x0b\x32,.antd.v1.FinalizeUploadRequest.TxHashesEntry\x12\x18\n\x10winner_pool_hash\x18\x03 \x01(\t\x12\x16\n\x0estore_data_map\x18\x04 \x01(\x08\x1a/\n\rTxHashesEntry\x12\x0b\n\x03key\x18\x01 \x01(\t\x12\r\n\x05value\x18\x02 \x01(\t:\x02\x38\x01\"l\n\x16\x46inalizeUploadResponse\x12\x10\n\x08\x64\x61ta_map\x18\x01 \x01(\t\x12\x0f\n\x07\x61\x64\x64ress\x18\x02 \x01(\t\x12\x18\n\x10\x64\x61ta_map_address\x18\x03 \x01(\t\x12\x15\n\rchunks_stored\x18\x04 \x01(\x04\x32\x92\x02\n\rUploadService\x12V\n\x11PrepareFileUpload\x12!.antd.v1.PrepareFileUploadRequest\x1a\x1e.antd.v1.PrepareUploadResponse\x12V\n\x11PrepareDataUpload\x12!.antd.v1.PrepareDataUploadRequest\x1a\x1e.antd.v1.PrepareUploadResponse\x12Q\n\x0e\x46inalizeUpload\x12\x1e.antd.v1.FinalizeUploadRequest\x1a\x1f.antd.v1.FinalizeUploadResponseBDZ8github.com/WithAutonomi/ant-sdk/antd-go/proto/antd/v1;v1\xaa\x02\x07\x41ntd.V1b\x06proto3"
+
+pool = ::Google::Protobuf::DescriptorPool.generated_pool
+pool.add_serialized_file(descriptor_data)
+
+module Antd
+  module V1
+    PrepareFileUploadRequest = ::Google::Protobuf::DescriptorPool.generated_pool.lookup("antd.v1.PrepareFileUploadRequest").msgclass
+    PrepareDataUploadRequest = ::Google::Protobuf::DescriptorPool.generated_pool.lookup("antd.v1.PrepareDataUploadRequest").msgclass
+    PrepareUploadResponse = ::Google::Protobuf::DescriptorPool.generated_pool.lookup("antd.v1.PrepareUploadResponse").msgclass
+    PoolCommitmentEntry = ::Google::Protobuf::DescriptorPool.generated_pool.lookup("antd.v1.PoolCommitmentEntry").msgclass
+    CandidateNodeEntry = ::Google::Protobuf::DescriptorPool.generated_pool.lookup("antd.v1.CandidateNodeEntry").msgclass
+    FinalizeUploadRequest = ::Google::Protobuf::DescriptorPool.generated_pool.lookup("antd.v1.FinalizeUploadRequest").msgclass
+    FinalizeUploadResponse = ::Google::Protobuf::DescriptorPool.generated_pool.lookup("antd.v1.FinalizeUploadResponse").msgclass
+  end
+end
diff --git a/antd-ruby/lib/antd/v1/upload_services_pb.rb b/antd-ruby/lib/antd/v1/upload_services_pb.rb
new file mode 100644
index 00000000..e15c03eb
--- /dev/null
+++ b/antd-ruby/lib/antd/v1/upload_services_pb.rb
@@ -0,0 +1,51 @@
+# Generated by the protocol buffer compiler.  DO NOT EDIT!
+# Source: antd/v1/upload.proto for package 'antd.v1'
+
+require 'grpc'
+require 'antd/v1/upload_pb'
+
+module Antd
+  module V1
+    module UploadService
+      # External-signer flow for files + in-memory data. Mirrors the REST
+      # `/v1/upload/prepare`, `/v1/data/prepare`, `/v1/upload/finalize` surface 1:1.
+      #
+      # Two-phase: caller submits a prepare request, daemon collects quotes from the
+      # network and stashes server-side state keyed by `upload_id`. Caller then
+      # signs + submits the EVM payment off-daemon, then calls FinalizeUpload with
+      # the resulting transaction artefacts.
+      #
+      # Wave-batch (files with < 64 chunks): per-quote payments via `payForQuotes()`.
+      # Merkle (files with >= 64 chunks): pool commitments via `payForMerkleTree2()`.
+      #
+      # File and data prepares are intentionally separate RPCs (their request shapes
+      # differ — filesystem path vs raw bytes), but they share one finalize RPC
+      # because the server-side stored state is the same shape either way.
+      class Service
+
+        include ::GRPC::GenericService
+
+        self.marshal_class_method = :encode
+        self.unmarshal_class_method = :decode
+        self.service_name = 'antd.v1.UploadService'
+
+        # Phase 1: prepare a file upload for external signing. Returns payment
+        # details + an upload_id. For files with < 64 chunks returns
+        # `payment_type = "wave_batch"`; otherwise `payment_type = "merkle"`.
+        rpc :PrepareFileUpload, ::Antd::V1::PrepareFileUploadRequest, ::Antd::V1::PrepareUploadResponse
+        # Phase 1 (data): prepare an in-memory data upload for external signing.
+        # Same as PrepareFileUpload but takes raw bytes instead of a filesystem
+        # path. Honours visibility = "public" (requires ant-client #73, already
+        # merged on main since 2026-05-05).
+        rpc :PrepareDataUpload, ::Antd::V1::PrepareDataUploadRequest, ::Antd::V1::PrepareUploadResponse
+        # Phase 2: finalize an upload after the external EVM payment has landed.
+        # For wave-batch uploads pass `tx_hashes`; for merkle uploads pass
+        # `winner_pool_hash` from the `MerklePaymentMade` event. The server-side
+        # stored upload state is consumed (one-shot).
+        rpc :FinalizeUpload, ::Antd::V1::FinalizeUploadRequest, ::Antd::V1::FinalizeUploadResponse
+      end
+
+      Stub = Service.rpc_stub_class
+    end
+  end
+end
diff --git a/antd-ruby/test/test_grpc_client.rb b/antd-ruby/test/test_grpc_client.rb
index 31ebe814..f9dc4e71 100644
--- a/antd-ruby/test/test_grpc_client.rb
+++ b/antd-ruby/test/test_grpc_client.rb
@@ -127,6 +127,123 @@ def put(_req)
     def get(_req)
       OpenStruct.new(data: "chunkdata")
     end
+
+    # Inputs starting with "EXISTS" → already-stored short-circuit.
+    def prepare_chunk(req)
+      if req.data.byteslice(0, 6) == "EXISTS"
+        OpenStruct.new(
+          address: "0xabc",
+          already_stored: true,
+          upload_id: "",
+          payment_type: "",
+          payments: [],
+          total_amount: "",
+          payment_vault_address: "",
+          payment_token_address: "",
+          rpc_url: "",
+        )
+      else
+        OpenStruct.new(
+          address: "0xnewchunk",
+          already_stored: false,
+          upload_id: "upid_chunk_42",
+          payment_type: "wave_batch",
+          payments: [
+            OpenStruct.new(quote_hash: "0xq1", rewards_address: "0xr1", amount: "100"),
+          ],
+          total_amount: "100",
+          payment_vault_address: "0xvault",
+          payment_token_address: "0xtoken",
+          rpc_url: "http://localhost:8545",
+        )
+      end
+    end
+
+    def finalize_chunk(req)
+      # Echo upload_id into address so the test can verify forwarding.
+      OpenStruct.new(address: "addr_for_#{req.upload_id}")
+    end
+  end
+
+  # Mock UploadService stub. PrepareFileUpload echoes visibility into
+  # upload_id; PrepareDataUpload returns merkle when payload starts with
+  # "MERKLE"; FinalizeUpload returns merkle vs wave-batch based on which
+  # field is set.
+  class UploadStub
+    def prepare_file_upload(req)
+      OpenStruct.new(
+        upload_id: "upid_file_#{req.visibility}",
+        payment_type: "wave_batch",
+        payments: [
+          OpenStruct.new(quote_hash: "0xqa", rewards_address: "0xra", amount: "1"),
+        ],
+        depth: 0,
+        pool_commitments: [],
+        merkle_payment_timestamp: 0,
+        total_amount: "1",
+        payment_vault_address: "0xvault",
+        payment_token_address: "0xtoken",
+        rpc_url: "http://localhost:8545",
+      )
+    end
+
+    def prepare_data_upload(req)
+      uid = "upid_data_#{req.visibility}"
+      if req.data.byteslice(0, 6) == "MERKLE"
+        OpenStruct.new(
+          upload_id: uid,
+          payment_type: "merkle",
+          payments: [],
+          depth: 7,
+          pool_commitments: [
+            OpenStruct.new(
+              pool_hash: "0xpool",
+              candidates: [
+                OpenStruct.new(rewards_address: "0xc1", amount: "5"),
+              ],
+            ),
+          ],
+          merkle_payment_timestamp: 1_700_000_000,
+          total_amount: "0",
+          payment_vault_address: "0xvault",
+          payment_token_address: "0xtoken",
+          rpc_url: "http://localhost:8545",
+        )
+      else
+        OpenStruct.new(
+          upload_id: uid,
+          payment_type: "wave_batch",
+          payments: [
+            OpenStruct.new(quote_hash: "0xqb", rewards_address: "0xrb", amount: "2"),
+          ],
+          depth: 0,
+          pool_commitments: [],
+          merkle_payment_timestamp: 0,
+          total_amount: "2",
+          payment_vault_address: "0xvault",
+          payment_token_address: "0xtoken",
+          rpc_url: "http://localhost:8545",
+        )
+      end
+    end
+
+    def finalize_upload(req)
+      if req.winner_pool_hash && !req.winner_pool_hash.empty?
+        OpenStruct.new(
+          data_map: "dm_merkle",
+          address: req.store_data_map ? "stored_on_network" : "",
+          data_map_address: "",
+          chunks_stored: 64,
+        )
+      else
+        OpenStruct.new(
+          data_map: "dm_wave",
+          address: "",
+          data_map_address: req.upload_id.end_with?("public") ? "addr_public_dm" : "",
+          chunks_stored: 3,
+        )
+      end
+    end
   end
 
   class FileStub
@@ -192,6 +309,7 @@ def build_fake_client
   client.instance_variable_set(:@data_stub, FakeGrpc::DataStub.new)
   client.instance_variable_set(:@chunk_stub, FakeGrpc::ChunkStub.new)
   client.instance_variable_set(:@file_stub, FakeGrpc::FileStub.new)
+  client.instance_variable_set(:@upload_stub, FakeGrpc::UploadStub.new)
   client
 end
 
@@ -202,6 +320,7 @@ def build_error_client(error)
   client.instance_variable_set(:@data_stub, stub)
   client.instance_variable_set(:@chunk_stub, stub)
   client.instance_variable_set(:@file_stub, stub)
+  client.instance_variable_set(:@upload_stub, stub)
   client
 end
 
@@ -363,6 +482,97 @@ def test_error_propagates_from_file_upload
     assert_raises(Antd::TooLargeError) { client.file_upload_public("/tmp/big") }
   end
 
+  # --- External signer (prepare/finalize) ---
+
+  def test_prepare_upload_omits_visibility_when_nil
+    r = @client.prepare_upload("/tmp/x.bin")
+    # Empty visibility = proto3 default; the mock echoes that into upload_id.
+    assert_equal "upid_file_", r.upload_id
+    assert_equal "wave_batch", r.payment_type
+    assert_equal 1, r.payments.length
+    assert_equal "0xqa", r.payments.first.quote_hash
+    assert_nil r.depth
+    assert_nil r.pool_commitments
+    assert_nil r.merkle_payment_timestamp
+  end
+
+  def test_prepare_upload_forwards_visibility_public
+    r = @client.prepare_upload("/tmp/x.bin", visibility: "public")
+    assert_equal "upid_file_public", r.upload_id
+  end
+
+  def test_prepare_upload_public_convenience
+    r = @client.prepare_upload_public("/tmp/x.bin")
+    assert_equal "upid_file_public", r.upload_id
+  end
+
+  def test_prepare_data_upload_wave_batch
+    r = @client.prepare_data_upload("small")
+    assert_equal "upid_data_", r.upload_id
+    assert_equal "wave_batch", r.payment_type
+    assert_nil r.depth
+  end
+
+  def test_prepare_data_upload_merkle
+    r = @client.prepare_data_upload("MERKLE-large-payload")
+    assert_equal "merkle", r.payment_type
+    assert_equal 7, r.depth
+    assert_equal 1_700_000_000, r.merkle_payment_timestamp
+    assert_equal 1, r.pool_commitments.length
+    assert_equal "0xpool", r.pool_commitments.first.pool_hash
+    assert_equal "0xc1", r.pool_commitments.first.candidates.first.rewards_address
+  end
+
+  def test_finalize_upload_wave_batch_private_omits_data_map_address
+    r = @client.finalize_upload("upid_file_", { "0xq1" => "0xtx1" })
+    assert_equal "dm_wave", r.data_map
+    assert_equal "", r.data_map_address
+    assert_equal 3, r.chunks_stored
+  end
+
+  def test_finalize_upload_wave_batch_public_returns_data_map_address
+    r = @client.finalize_upload("upid_file_public", { "0xq1" => "0xtx1" })
+    assert_equal "addr_public_dm", r.data_map_address
+  end
+
+  def test_finalize_merkle_upload_store_data_map_true
+    r = @client.finalize_merkle_upload("upid_data_", "0xwinpool", store_data_map: true)
+    assert_equal "dm_merkle", r.data_map
+    assert_equal "stored_on_network", r.address
+    assert_equal 64, r.chunks_stored
+  end
+
+  def test_finalize_merkle_upload_store_data_map_default_false
+    r = @client.finalize_merkle_upload("upid_data_", "0xwinpool")
+    assert_equal "dm_merkle", r.data_map
+    assert_equal "", r.address
+  end
+
+  def test_prepare_chunk_upload_new_chunk
+    r = @client.prepare_chunk_upload("newchunk")
+    refute r.already_stored
+    assert_equal "0xnewchunk", r.address
+    assert_equal "upid_chunk_42", r.upload_id
+    assert_equal "wave_batch", r.payment_type
+    assert_equal 1, r.payments.length
+    assert_equal "0xq1", r.payments.first.quote_hash
+    assert_equal "100", r.total_amount
+    assert_equal "http://localhost:8545", r.rpc_url
+  end
+
+  def test_prepare_chunk_upload_already_stored_short_circuit
+    r = @client.prepare_chunk_upload("EXISTS-data")
+    assert r.already_stored
+    assert_equal "0xabc", r.address
+    assert_equal "", r.upload_id
+    assert_empty r.payments
+  end
+
+  def test_finalize_chunk_upload_returns_address_and_forwards_body
+    addr = @client.finalize_chunk_upload("upid_chunk_42", { "0xq1" => "0xtxabc" })
+    assert_equal "addr_for_upid_chunk_42", addr
+  end
+
   private
 
   # Build a GRPC::BadStatus-compatible error.