fix(protocol): align terminal receipt conformance

fixtures/conformance/gateway-input-feedback-v1.tsv

@@ -9,6 +9,7 @@ valid-controller	1	gateway_input	hex=5647493105110200030004ffff00010002000300040
 valid-controller-release	1	gateway_input	hex=5647493105110200000000000000000000000000000000	valid
 valid-idr	1	gateway_feedback	hex=5647463100010000	valid
 valid-fec	1	gateway_feedback	hex=56474631000200150000002a000500030002000a000200080002140001	valid
+valid-terminal-receipt	1	gateway_feedback	hex=5647463100030000	valid
 valid-termination	1	gateway_feedback	hex=564746310110000400000001	valid
 valid-rumble	1	gateway_feedback	hex=56474631011100050112345678	valid
 valid-hdr	1	gateway_feedback	hex=564746310112000101	valid
@@ -18,5 +19,9 @@ invalid-input-reserved	1	gateway_input	hex=564749310203010101	invalid:reserved
 invalid-input-utf8	1	gateway_input	hex=564749310402c328	invalid:utf8
 invalid-input-length	1	gateway_input	hex=564749310104010200	invalid:length
 invalid-feedback-direction	1	gateway_feedback	hex=5647463101020000	invalid:direction
-invalid-feedback-type	1	gateway_feedback	hex=5647463100030000	invalid:type
+invalid-terminal-receipt-direction	1	gateway_feedback	hex=5647463101030000	invalid:direction
+invalid-terminal-receipt-body	1	gateway_feedback	hex=5647463100030001ff	invalid:length
+invalid-terminal-receipt-truncated	1	gateway_feedback	hex=56474631000300	invalid:truncated
+invalid-terminal-receipt-length	1	gateway_feedback	hex=5647463100030001	invalid:length
+invalid-feedback-type	1	gateway_feedback	hex=5647463100040000	invalid:type
 invalid-feedback-length	1	gateway_feedback	hex=5647463101100003000000	invalid:length

fixtures/manifest.json

@@ -9,5 +9,5 @@
     "fixtures/conformance/gateway-input-feedback-v1.tsv",
     "fixtures/conformance/tunnel-v1.tsv"
   ],
-  "corpus_sha256": "69d5b12a533ff0d9786784b99aecc8a74a7ec2c6855b75c52e46ecff5bd3e6c5"
+  "corpus_sha256": "0eb9e905e77069c0bd67182b40e7f9b1b41041d5290b0e3b2152abf83ce32eae"
 }

frames/gateway-input-feedback-v1.md

@@ -53,8 +53,9 @@ is the following exact envelope:
 | 6 | 2 | payload length | exact payload byte count |
 | 8 | N | payload | exact type-specific body |
 
-The client-to-gateway types are `0x01` IDR request (empty) and `0x02` FEC
-status: `frame_index` (u32), `highest_received_sequence` (u16),
+The client-to-gateway types are `0x01` IDR request (empty), `0x02` FEC
+status, and `0x03` terminal receipt (empty). FEC status contains
+`frame_index` (u32), `highest_received_sequence` (u16),
 `next_contiguous_sequence` (u16), `missing_before_highest` (u16),
 `total_data_packets` (u16), `total_parity_packets` (u16),
 `received_data_packets` (u16), `received_parity_packets` (u16),
@@ -63,6 +64,10 @@ status: `frame_index` (u32), `highest_received_sequence` (u16),
 the provider's unsequenced ENet FEC delivery; it does not put it on the reliable
 provider input path.
 
+The terminal receipt is valid only from client to gateway with an exact
+zero-byte payload. Session-state authorization remains a gateway responsibility;
+the Protocol grammar defines only its fixed wire shape.
+
 The gateway-to-client types are `0x10` host termination (`exit_code` u32),
 `0x11` rumble (`controller` u8, `low_frequency` u16,
 `high_frequency` u16), and `0x12` HDR mode (`enabled` exactly `0` or `1`). The

openspec/changes/archive/2026-07-30-gateway-terminal-receipt/tasks.md

@@ -5,5 +5,5 @@
 
 ## 2. Immutable release
 
-- [ ] 2.1 Publish one new never-reused immutable Protocol version after final contract verification
-- [ ] 2.2 Resolve the version from separate empty consumer caches and record exact checksums
+- [x] 2.1 Publish one new never-reused immutable Protocol version after final contract verification
+- [x] 2.2 Resolve the version from separate empty consumer caches and record exact checksums

openspec/changes/fix-terminal-receipt-conformance/.openspec.yaml

@@ -0,0 +1,2 @@
+schema: spec-driven
+created: 2026-07-30

openspec/changes/fix-terminal-receipt-conformance/design.md

@@ -0,0 +1,27 @@
+## Context
+
+RC8's canonical requirement names a terminal receipt, but its frame grammar, fixed fixture, and all Protocol validators reject the exact receipt accepted by Data Plane. The existing VGF1 envelope and generated conformance machinery already cover the required boundary.
+
+## Goals / Non-Goals
+
+**Goals:**
+
+- Make one fixed empty client-direction type `0x03` receipt valid in every Protocol validator.
+- Preserve all existing VGF1 direction, type, size, and payload validation.
+- Make independent clients able to construct the receipt from Protocol-owned evidence.
+
+**Non-Goals:**
+
+- No new envelope, feedback framework, transport, or acknowledgement protocol.
+- No change to gateway-to-client termination, rumble, HDR, client IDR, or FEC payloads.
+
+## Decisions
+
+- Extend the existing VGF1 grammar and fixed TSV corpus; generated and native validators remain consumers of that single contract.
+- Reserve type `0x03` only for client direction with a zero-length payload. Direction and exact-length checks remain prior trust-boundary requirements.
+- Publish the verified change as a new immutable version; RC8 remains unchanged.
+
+## Risks / Trade-offs
+
+- [A validator diverges from the fixed corpus] → Require normalized cross-language conformance in `make verify`.
+- [Receipt handling is accepted outside terminal state] → Keep state authorization in Data Plane; Protocol validates only the wire shape.

openspec/changes/fix-terminal-receipt-conformance/proposal.md

@@ -0,0 +1,23 @@
+## Why
+
+The canonical terminal-receipt requirement contradicts the fixed VGF1 grammar and every generated validator, so RC8 cannot provide an executable cross-language contract for gateway-owned terminal closure.
+
+## What Changes
+
+- Define client-direction VGF1 type `0x03` as an empty terminal receipt in the existing frame grammar.
+- Add fixed conformance vectors for valid receipt handling and invalid direction, body, truncation, length, and unknown-type cases.
+- Generate consistent Go, Rust, Swift, and Python validation behavior from the Protocol source.
+
+## Capabilities
+
+### New Capabilities
+
+None.
+
+### Modified Capabilities
+
+- `gateway-input-feedback`: Make the already-required terminal receipt executable and cross-language conformant without weakening other VGF1 validation.
+
+## Impact
+
+Protocol frame documentation, conformance fixtures, generators, generated bindings, native validator tools, and immutable Protocol consumers. RC8 remains unchanged and a new immutable Protocol version is required.

openspec/changes/fix-terminal-receipt-conformance/specs/gateway-input-feedback/spec.md

@@ -0,0 +1,27 @@
+## MODIFIED Requirements
+
+### Requirement: Bounded provider feedback control envelope
+The registered bidirectional reliable `control.ack.v1` flow SHALL define an ASCII `VGF1` envelope
+with a direction byte, type byte, big-endian payload length, and exact payload
+bytes. Only host termination, rumble, and HDR feedback SHALL be valid from the
+gateway to the client. Only IDR, FEC/loss feedback, and client-direction type
+`0x03` with an empty payload as terminal receipt SHALL be valid from the client
+to the gateway. The fixed conformance corpus and every generated or native
+Protocol validator SHALL accept that exact receipt and reject unknown types,
+wrong direction, nonempty receipt bodies, truncation, and length mismatch. The
+terminal receipt SHALL be valid only while the same session awaits receipt of
+its one terminal event and MUST NOT be forwarded to the provider. The envelope
+SHALL contain no provider address, certificate, credential, or opaque provider
+packet.
+
+#### Scenario: Host termination forwarding
+- **WHEN** the Apollo adapter receives an authenticated host termination packet
+- **THEN** the gateway forwards a bounded `VGF1` termination envelope over reliable Verse control and reports the provider state separately
+
+#### Scenario: Terminal event receipt
+- **WHEN** a client receives the reliable typed terminal event
+- **THEN** it sends the fixed empty client-direction type `0x03` receipt and the gateway owns bounded tunnel closure without forwarding the receipt to the provider
+
+#### Scenario: Unauthorized or malformed feedback
+- **WHEN** feedback is disabled by policy, has an invalid direction/type/length, contains a forbidden provider field, or sends a terminal receipt outside the awaiting-terminal state
+- **THEN** the gateway rejects it without forwarding or provider mutation

openspec/changes/fix-terminal-receipt-conformance/tasks.md

@@ -0,0 +1,15 @@
+## 1. Red Conformance
+
+- [x] 1.1 Add fixed valid and invalid terminal-receipt vectors and prove Python, Go, Rust, and Swift reject the required valid vector
+- [x] 1.2 Add a Data Plane independent-client regression that consumes the Protocol fixed vector rather than the production encoder
+
+## 2. Contract Repair
+
+- [x] 2.1 Update the VGF1 grammar and Protocol validator sources for the exact empty client-direction type `0x03` receipt
+- [x] 2.2 Regenerate bindings normally and prove deterministic generation has no drift
+- [x] 2.3 Run complete Protocol verification and strict OpenSpec validation
+
+## 3. Immutable Release
+
+- [ ] 3.1 Verify the next version is unused locally and remotely, publish one immutable annotated tag, and verify its object and peeled commit
+- [ ] 3.2 Resolve the version from separate empty caches and pin exact fetched checksums in Data Plane and Connection Server

openspec/specs/gateway-input-feedback/spec.md

@@ -47,21 +47,16 @@ MUST NOT be forwarded to the provider. The envelope SHALL contain no provider
 address, certificate, credential, or opaque provider packet.
 
 #### Scenario: Host termination forwarding
-- **WHEN** the Apollo adapter receives an authenticated host termination
-  packet
-- **THEN** the gateway forwards a bounded `VGF1` termination envelope over
-  reliable Verse control and reports the provider state separately.
+- **WHEN** the Apollo adapter receives an authenticated host termination packet
+- **THEN** the gateway forwards a bounded `VGF1` termination envelope over reliable Verse control and reports the provider state separately
 
 #### Scenario: Terminal event receipt
 - **WHEN** a client receives the reliable typed terminal event
-- **THEN** it sends the empty terminal receipt and the gateway owns bounded
-  tunnel closure without forwarding the receipt to the provider.
+- **THEN** it sends the empty terminal receipt and the gateway owns bounded tunnel closure without forwarding the receipt to the provider
 
 #### Scenario: Unauthorized or malformed feedback
-- **WHEN** feedback is disabled by policy, has an invalid direction/type/length,
-  contains a forbidden provider field, or sends a terminal receipt outside the
-  awaiting-terminal state
-- **THEN** the gateway rejects it without forwarding or provider mutation.
+- **WHEN** feedback is disabled by policy, has an invalid direction/type/length, contains a forbidden provider field, or sends a terminal receipt outside the awaiting-terminal state
+- **THEN** the gateway rejects it without forwarding or provider mutation
 
 ### Requirement: Policy-bound text clipboard envelope
 The reliable `clipboard.text.v1` flow SHALL carry only a typed UTF-8 text

tools/go-conformance/main.go

@@ -270,12 +270,16 @@ func classifyGatewayFeedback(encoded string) string {
 				return "valid"
 			}
 			return "invalid:field"
+		case 3:
+			if len(body) == 0 {
+				return "valid"
+			}
 		default:
 			return "invalid:type"
 		}
 		return "invalid:length"
 	}
-	if kind == 1 || kind == 2 {
+	if kind == 1 || kind == 2 || kind == 3 {
 		return "invalid:direction"
 	}
 	switch kind {

tools/native_conformance.rs

@@ -143,10 +143,12 @@ fn classify_gateway_feedback(encoded: &str) -> &'static str {
             1 => "invalid:length",
             2 if valid_fec_status(body) => "valid",
             2 => "invalid:field",
+            3 if body.is_empty() => "valid",
+            3 => "invalid:length",
             _ => "invalid:type",
         };
     }
-    if kind == 1 || kind == 2 {
+    if kind == 1 || kind == 2 || kind == 3 {
         return "invalid:direction";
     }
     match kind {

tools/native_conformance.swift

@@ -101,10 +101,11 @@ func classifyGatewayFeedback(_ encoded: String) -> String {
         case 1: return body.isEmpty ? "valid" : "invalid:length"
         case 2:
             return validFECStatus(body) ? "valid" : "invalid:field"
+        case 3: return body.isEmpty ? "valid" : "invalid:length"
         default: return "invalid:type"
         }
     }
-    if kind == 1 || kind == 2 { return "invalid:direction" }
+    if kind == 1 || kind == 2 || kind == 3 { return "invalid:direction" }
     switch kind {
     case 0x10: return body.count == 4 ? "valid" : "invalid:length"
     case 0x11:

tools/validate_gateway_envelopes.py

@@ -59,8 +59,10 @@ def classify_feedback(raw: bytes) -> str:
             return "valid" if not body else "invalid:length"
         if kind == 2:
             return "valid" if valid_fec_status(body) else "invalid:field"
+        if kind == 3:
+            return "valid" if not body else "invalid:length"
         return "invalid:type"
-    if kind in (1, 2):
+    if kind in (1, 2, 3):
         return "invalid:direction"
     if kind == 0x10:
         return "valid" if len(body) == 4 else "invalid:length"