diff --git a/.gitattributes b/.gitattributes
new file mode 100644
index 0000000..27805f0
--- /dev/null
+++ b/.gitattributes
@@ -0,0 +1,3 @@
+# -*- mode: gitattributes; -*-
+
+dist/** linguist-vendored
diff --git a/.gitignore b/.gitignore
index 485dee6..33a4b1c 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1 +1,4 @@
 .idea
+.DS_Store
+node_modules
+
diff --git a/apis/relay/builder/blocks.yaml b/apis/relay/builder/blocks.yaml
index b4315b5..7eef599 100644
--- a/apis/relay/builder/blocks.yaml
+++ b/apis/relay/builder/blocks.yaml
@@ -1,5 +1,5 @@
 post:
-  operationId: "submitBlock"
+  operationId: "blocks_submit"
   summary: Submit a new block to the relay.
   description: |
     * Blocks can be submitted as JSON or SSZ, and optionally GZIP encoded. To be
@@ -61,10 +61,9 @@ post:
       content:
         application/json:
           schema:
-            allOf:
-              - $ref: "../../../relay-oapi.yaml#/components/schemas/ErrorMessage"
-              - example:
-                  code: 400
-                  message: "payload for this slot was already delivered"
+            $ref: "../../../relay-oapi.yaml#/components/schemas/ErrorMessage"
+          example:
+            code: 400
+            message: "payload for this slot was already delivered"
     "500":
       $ref: "../../../relay-oapi.yaml#/components/responses/InternalError"
diff --git a/apis/relay/builder/headers.yaml b/apis/relay/builder/headers.yaml
new file mode 100644
index 0000000..cbf92bd
--- /dev/null
+++ b/apis/relay/builder/headers.yaml
@@ -0,0 +1,66 @@
+post:
+  operationId: "submitHeader"
+  summary: Submit optimistic header to the relay.
+  description: |
+    * Headers can be submitted as JSON or SSZ, and optionally GZIP encoded. To be
+      clear, there are four options: JSON, JSON+GZIP, SSZ, SSZ+GZIP. If JSON, the
+      content type should be `application/json`. If SSZ, the content type should
+      be `application/octet-stream`.
+    
+    * To enable GZIP compression for the request body, the HTTP content encoding 
+      should be `gzip`. Compression is optional.
+    
+    * The relay will check that the builder has enough collateral to cover the 
+      value of the bid. Otherwise the relay will not accept the optimistic header.
+
+    * The relay will need the rest of payload via the optimistic v2 endpoint. If 
+      not received in time, the relay will penalize the builder's collateral.
+    
+    * For accountability, builder signature is over the SSZ encoded `message`.
+    
+    * The `message`, which does not include the transactions, will be made
+      public via the data API, allowing anyone to verify the builder signature.
+  tags:
+    - Builder
+  parameters:
+    - name: cancellations
+      in: query
+      required: false
+      description: If set to 1, opt into bid cancellations.
+      schema:
+        $ref: "../../../relay-oapi.yaml#/components/schemas/Uint64"
+  requestBody:
+    description: A signed bid with an execution header.
+    required: true
+    content:
+      application/json:
+        schema:
+          oneOf:
+            - $ref: "../../../relay-oapi.yaml#/components/schemas/Bellatrix.SubmitHeaderRequest"
+            - $ref: "../../../relay-oapi.yaml#/components/schemas/Capella.SubmitHeaderRequest"
+            - $ref: "../../../relay-oapi.yaml#/components/schemas/Deneb.SubmitHeaderRequest"
+        examples:
+          bellatrix:
+            $ref: "../../../relay-oapi.yaml#/components/examples/Bellatrix.SubmitHeaderRequest"
+          capella:
+            $ref: "../../../relay-oapi.yaml#/components/examples/Capella.SubmitHeaderRequest"
+          deneb:
+            $ref: "../../../relay-oapi.yaml#/components/examples/Deneb.SubmitHeaderRequest"
+      application/octet-stream:
+        schema:
+          description: "SSZ serialized request. Use content type header to indicate that SSZ data is contained in the request body."
+  responses:
+    "200":
+      description: Success response.
+    "400":
+      description: Error response.
+      content:
+        application/json:
+          schema:
+            allOf:
+              - $ref: "../../../relay-oapi.yaml#/components/schemas/ErrorMessage"
+              - example:
+                  code: 400
+                  message: "payload for this slot was already delivered"
+    "500":
+      $ref: "../../../relay-oapi.yaml#/components/responses/InternalError"
diff --git a/apis/relay/builder/validators.yaml b/apis/relay/builder/validators.yaml
index 0ce39e0..0730759 100644
--- a/apis/relay/builder/validators.yaml
+++ b/apis/relay/builder/validators.yaml
@@ -1,5 +1,5 @@
 get:
-  operationId: "getValidators"
+  operationId: "validators_list"
   summary: |
     Get a list of validator registrations for validators scheduled to propose
     in the current and next epoch.
diff --git a/apis/relay/data/builder_blocks_received.yaml b/apis/relay/data/builder_blocks_received.yaml
index 8cdddbf..4e39d38 100644
--- a/apis/relay/data/builder_blocks_received.yaml
+++ b/apis/relay/data/builder_blocks_received.yaml
@@ -1,5 +1,5 @@
 get:
-  operationId: "getReceivedBids"
+  operationId: "blocks_list_received"
   summary: Get builder bid submissions.
   description: |
     * Returns a list of builder bids without execution payloads.
@@ -50,10 +50,9 @@ get:
       content:
         application/json:
           schema:
-            allOf:
-              - $ref: "../../../relay-oapi.yaml#/components/schemas/ErrorMessage"
-              - example:
-                  code: 400
-                  message: "cannot specify both slot and cursor"
+            $ref: "../../../relay-oapi.yaml#/components/schemas/ErrorMessage"
+          example:
+            code: 400
+            message: "cannot specify both slot and cursor"
     "500":
       $ref: "../../../relay-oapi.yaml#/components/responses/InternalError"
diff --git a/apis/relay/data/proposer_payload_delivered.yaml b/apis/relay/data/proposer_payload_delivered.yaml
index 013f4e5..5c8b6d6 100644
--- a/apis/relay/data/proposer_payload_delivered.yaml
+++ b/apis/relay/data/proposer_payload_delivered.yaml
@@ -1,5 +1,5 @@
 get:
-  operationId: "getDeliveredPayloads"
+  operationId: "payloads_list_delivered"
   summary: Get payloads that were delivered to proposers.
   description: |
     * Payloads become available after the relay responds to a `getPayload` request from the proposer.
@@ -68,10 +68,9 @@ get:
       content:
         application/json:
           schema:
-            allOf:
-              - $ref: "../../../relay-oapi.yaml#/components/schemas/ErrorMessage"
-              - example:
-                  code: 400
-                  message: "invalid block_hash argument"
+            $ref: "../../../relay-oapi.yaml#/components/schemas/ErrorMessage"
+          example:
+            code: 400
+            message: "invalid block_hash argument"
     "500":
       $ref: "../../../relay-oapi.yaml#/components/responses/InternalError"
diff --git a/apis/relay/data/validator_registration.yaml b/apis/relay/data/validator_registration.yaml
index e1111a5..6da3be7 100644
--- a/apis/relay/data/validator_registration.yaml
+++ b/apis/relay/data/validator_registration.yaml
@@ -1,5 +1,5 @@
 get:
-  operationId: "getValidatorRegistration"
+  operationId: "validators_get_registration"
   summary: Check that a validator is registered with the relay.
   description: |
     * Returns the latest validator registration for a given pubkey.
@@ -26,10 +26,9 @@ get:
       content:
         application/json:
           schema:
-            allOf:
-              - $ref: "../../../relay-oapi.yaml#/components/schemas/ErrorMessage"
-              - example:
-                  code: 400
-                  message: "missing pubkey argument"
+            $ref: "../../../relay-oapi.yaml#/components/schemas/ErrorMessage"
+          example:
+            code: 400
+            message: "missing pubkey argument"
     "500":
       $ref: "../../../relay-oapi.yaml#/components/responses/InternalError"
diff --git a/beacon-apis b/beacon-apis
index 2e7c4aa..69d2feb 160000
--- a/beacon-apis
+++ b/beacon-apis
@@ -1 +1 @@
-Subproject commit 2e7c4aabcf60f5ae6d414866c268aff350a70e81
+Subproject commit 69d2feb12a6047c4f21e628dea8b0135b7e9013a
diff --git a/builder-specs b/builder-specs
index 5cb324e..ae1d97d 160000
--- a/builder-specs
+++ b/builder-specs
@@ -1 +1 @@
-Subproject commit 5cb324e34e173d963d1233e238bf50e4d7497653
+Subproject commit ae1d97d080a12bfb7ca248b58fb1fc6b10aed02e
diff --git a/examples/bellatrix/submit_header_request.json b/examples/bellatrix/submit_header_request.json
new file mode 100644
index 0000000..422658a
--- /dev/null
+++ b/examples/bellatrix/submit_header_request.json
@@ -0,0 +1,32 @@
+{
+  "value": {
+    "message": {
+      "slot": "1",
+      "parent_hash": "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2",
+      "block_hash": "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2",
+      "builder_pubkey": "0x93247f2209abcacf57b75a51dafae777f9dd38bc7053d1af526f220a7489a6d3a2753e5f3e8b1cfe39b56f43611df74a",
+      "proposer_fee_recipient": "0xabcf8e0d4e9587369b2301d0790347320302cc09",
+      "gas_limit": "1",
+      "gas_used": "1",
+      "value": "1"
+    },
+    "header": {
+      "parent_hash": "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2",
+      "fee_recipient": "0xabcf8e0d4e9587369b2301d0790347320302cc09",
+      "state_root": "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2",
+      "receipts_root": "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2",
+      "logs_bloom": "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000",
+      "prev_randao": "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2",
+      "block_number": "1",
+      "gas_limit": "1",
+      "gas_used": "1",
+      "timestamp": "1",
+      "extra_data": "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2",
+      "base_fee_per_gas": "1",
+      "block_hash": "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2",
+      "transactions_root": "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2"
+    },
+
+    "signature": "0x1b66ac1fb663c9bc59509846d6ec05345bd908eda73e670af888da41af171505cc411d61252fb6cb3fa0017b679f8bb2305b26a285fa2737f175668d0dff91cc1b66ac1fb663c9bc59509846d6ec05345bd908eda73e670af888da41af171505"
+  }
+}
diff --git a/examples/capella/submit_header_request.json b/examples/capella/submit_header_request.json
new file mode 100644
index 0000000..4fd326f
--- /dev/null
+++ b/examples/capella/submit_header_request.json
@@ -0,0 +1,32 @@
+{
+  "value": {
+    "message": {
+      "slot": "1",
+      "parent_hash": "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2",
+      "block_hash": "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2",
+      "builder_pubkey": "0x93247f2209abcacf57b75a51dafae777f9dd38bc7053d1af526f220a7489a6d3a2753e5f3e8b1cfe39b56f43611df74a",
+      "proposer_fee_recipient": "0xabcf8e0d4e9587369b2301d0790347320302cc09",
+      "gas_limit": "1",
+      "gas_used": "1",
+      "value": "1"
+    },
+    "header": {
+      "parent_hash": "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2",
+      "fee_recipient": "0xabcf8e0d4e9587369b2301d0790347320302cc09",
+      "state_root": "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2",
+      "receipts_root": "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2",
+      "logs_bloom": "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000",
+      "prev_randao": "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2",
+      "block_number": "1",
+      "gas_limit": "1",
+      "gas_used": "1",
+      "timestamp": "1",
+      "extra_data": "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2",
+      "base_fee_per_gas": "1",
+      "block_hash": "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2",
+      "transactions_root": "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2",
+      "withdrawals_root": "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2"
+    },
+    "signature": "0x1b66ac1fb663c9bc59509846d6ec05345bd908eda73e670af888da41af171505cc411d61252fb6cb3fa0017b679f8bb2305b26a285fa2737f175668d0dff91cc1b66ac1fb663c9bc59509846d6ec05345bd908eda73e670af888da41af171505"
+  }
+}
diff --git a/examples/deneb/submit_header_request.json b/examples/deneb/submit_header_request.json
new file mode 100644
index 0000000..3eeee6c
--- /dev/null
+++ b/examples/deneb/submit_header_request.json
@@ -0,0 +1,35 @@
+{
+  "value": {
+    "message": {
+      "slot": "1",
+      "parent_hash": "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2",
+      "block_hash": "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2",
+      "builder_pubkey": "0x93247f2209abcacf57b75a51dafae777f9dd38bc7053d1af526f220a7489a6d3a2753e5f3e8b1cfe39b56f43611df74a",
+      "proposer_fee_recipient": "0xabcf8e0d4e9587369b2301d0790347320302cc09",
+      "gas_limit": "1",
+      "gas_used": "1",
+      "value": "1"
+    },
+    "header": {
+      "parent_hash": "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2",
+      "fee_recipient": "0xabcf8e0d4e9587369b2301d0790347320302cc09",
+      "state_root": "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2",
+      "receipts_root": "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2",
+      "logs_bloom": "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000",
+      "prev_randao": "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2",
+      "block_number": "1",
+      "gas_limit": "1",
+      "gas_used": "1",
+      "timestamp": "1",
+      "extra_data": "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2",
+      "base_fee_per_gas": "1",
+      "block_hash": "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2",
+      "transactions_root": "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2",
+      "withdrawals_root": "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2"
+    },
+    "blob_kzg_commitments": [
+      "0xa94170080872584e54a1cf092d845703b13907f2e6b3b1c0ad573b910530499e3bcd48c6378846b80d2bfa58c81cf3d5"
+    ],
+    "signature": "0x1b66ac1fb663c9bc59509846d6ec05345bd908eda73e670af888da41af171505cc411d61252fb6cb3fa0017b679f8bb2305b26a285fa2737f175668d0dff91cc1b66ac1fb663c9bc59509846d6ec05345bd908eda73e670af888da41af171505"
+  }
+}
diff --git a/relay-oapi.yaml b/relay-oapi.yaml
index 7f6044d..5be2c33 100644
--- a/relay-oapi.yaml
+++ b/relay-oapi.yaml
@@ -38,6 +38,13 @@ paths:
     $ref: "./apis/relay/data/validator_registration.yaml"
 
 components:
+  securitySchemes:
+    ApiKey:
+      type: apiKey
+      in: header
+      name: X-API-Key
+      description: Optional API key for authenticated requests
+
   schemas:
     Uint64:
       $ref: "./beacon-apis/types/primitive.yaml#/Uint64"
@@ -63,10 +70,92 @@ components:
       $ref: "./types/responses.yaml#/DeliveredPayloadsResponse"
     ReceivedBlocksResponse:
       $ref: "./types/responses.yaml#/ReceivedBlocksResponse"
+    PageInfo:
+      type: object
+      properties:
+        next_cursor:
+          type: string
+          description: "Cursor for next page of results"
+        has_more:
+          type: boolean
+          description: "Whether more results exist beyond this page"
+    ValidatorsPage:
+      type: object
+      properties:
+        data:
+          $ref: "#/components/schemas/ValidatorsResponse"
+        page_info:
+          $ref: "#/components/schemas/PageInfo"
+    DeliveredPayloadsPage:
+      type: object
+      properties:
+        data:
+          $ref: "#/components/schemas/DeliveredPayloadsResponse"
+        page_info:
+          $ref: "#/components/schemas/PageInfo"
+    ReceivedBlocksPage:
+      type: object
+      properties:
+        data:
+          $ref: "#/components/schemas/ReceivedBlocksResponse"
+        page_info:
+          $ref: "#/components/schemas/PageInfo"
+    $shared.BidTrace:
+      $ref: "./types/bids.yaml#/BidTraceV2"
+    $shared.BidTraceWithTimestamp:
+      $ref: "./types/bids.yaml#/BidTraceV2WithTimestamp"
+    $shared.ValidatorRegistration:
+      $ref: "./beacon-apis/types/registration.yaml#/SignedValidatorRegistration"
+    $shared.Signature:
+      $ref: "./beacon-apis/types/primitive.yaml#/Signature"
+    $shared.Pubkey:
+      $ref: "./beacon-apis/types/primitive.yaml#/Pubkey"
+    $shared.Uint64:
+      $ref: "./beacon-apis/types/primitive.yaml#/Uint64"
+    $shared.Root:
+      $ref: "./beacon-apis/types/primitive.yaml#/Root"
+    ValidationError:
+      allOf:
+        - $ref: "#/components/schemas/ErrorMessage"
+        - type: object
+          properties:
+            field_errors:
+              type: array
+              items:
+                type: object
+                properties:
+                  field:
+                    type: string
+                    description: "Field name that caused the error"
+                  message:
+                    type: string
+                    description: "Error message for this field"
+              description: "List of field-specific validation errors"
+    AuthenticationError:
+      allOf:
+        - $ref: "#/components/schemas/ErrorMessage"
+        - type: object
+          properties:
+            error_type:
+              type: string
+              enum: ["missing_api_key", "invalid_api_key", "expired_api_key"]
+              description: "Type of authentication error"
 
   responses:
     InternalError:
       $ref: "./types/http.yaml#/InternalError"
+    ValidationError:
+      description: "Validation error response"
+      content:
+        application/json:
+          schema:
+            $ref: "#/components/schemas/ValidationError"
+    AuthenticationError:
+      description: "Authentication error response"
+      content:
+        application/json:
+          schema:
+            $ref: "#/components/schemas/AuthenticationError"
 
   examples:
     Bellatrix.SubmitBlockRequest:
diff --git a/types/bellatrix/requests.yaml b/types/bellatrix/requests.yaml
index 6b26223..3c578d7 100644
--- a/types/bellatrix/requests.yaml
+++ b/types/bellatrix/requests.yaml
@@ -14,3 +14,11 @@ Bellatrix:
         properties:
           execution_payload:
             $ref: "../../beacon-apis/types/bellatrix/execution_payload.yaml#/Bellatrix/ExecutionPayload"
+  
+  SubmitHeaderRequest:
+    allOf:
+      - $ref: '#/Bellatrix/SubmitBlockRequestCommon'
+      - type: object
+        properties:
+          header:
+            $ref: "../../beacon-apis/types/bellatrix/execution_payload.yaml#/Bellatrix/ExecutionPayloadHeader"
diff --git a/types/capella/requests.yaml b/types/capella/requests.yaml
index f28c62e..ca92a9c 100644
--- a/types/capella/requests.yaml
+++ b/types/capella/requests.yaml
@@ -6,3 +6,11 @@ Capella:
         properties:
           execution_payload:
             $ref: "../../beacon-apis/types/capella/execution_payload.yaml#/Capella/ExecutionPayload"
+
+  SubmitHeaderRequest:
+    allOf:
+      - $ref: '#/Bellatrix/SubmitBlockRequestCommon'
+      - type: object
+        properties:
+          header:
+            $ref: "../../beacon-apis/types/bellatrix/execution_payload.yaml#/Capella/ExecutionPayloadHeader"
diff --git a/types/deneb/requests.yaml b/types/deneb/requests.yaml
index 3488862..27f4865 100644
--- a/types/deneb/requests.yaml
+++ b/types/deneb/requests.yaml
@@ -3,3 +3,17 @@ Deneb:
     allOf:
       - $ref: '../bellatrix/requests.yaml#/Bellatrix/SubmitBlockRequestCommon'
       - $ref: "../../builder-specs/types/deneb/execution_payload_and_blobs_bundle.yaml#/Deneb/ExecutionPayloadAndBlobsBundle"
+
+  SubmitHeaderRequest:
+    allOf:
+      - $ref: '#/Bellatrix/SubmitBlockRequestCommon'
+      - type: object
+        properties:
+          header:
+            $ref: "../../beacon-apis/types/bellatrix/execution_payload.yaml#/Deneb/ExecutionPayloadHeader"
+          blob_kzg_commitments:
+            type: array
+            items:
+              $ref: '../../beacon-apis/types/primitive.yaml#/KZGCommitment'
+            minItems: 0
+            maxItems: 4096
\ No newline at end of file
diff --git a/wordlist.txt b/wordlist.txt
index 390a228..70895ed 100644
--- a/wordlist.txt
+++ b/wordlist.txt
@@ -13,6 +13,7 @@ gzip
 http
 https
 json
+kzg
 mev
 nodejs
 npm