diff --git a/.gitea/workflows/verify.yml b/.gitea/workflows/verify.yml
index 5322f75..a82d159 100644
--- a/.gitea/workflows/verify.yml
+++ b/.gitea/workflows/verify.yml
@@ -35,6 +35,7 @@ jobs:
           file dist/verse-gateway-linux-* | tee dist/file.txt
           go version -m dist/verse-gateway-linux-amd64 > dist/go-version-amd64.txt
           go version -m dist/verse-gateway-linux-arm64 > dist/go-version-arm64.txt
+          make gateway-sbom DIST_DIR=dist
       - uses: christopherhx/gitea-upload-artifact@81f940d004763f986ba3582c007fd842dd5cb0d7 # v4
         with:
           name: verse-gateway-linux-${{ gitea.sha }}
diff --git a/Makefile b/Makefile
index a625d13..c079728 100644
--- a/Makefile
+++ b/Makefile
@@ -1,8 +1,10 @@
-.PHONY: format-check module-verify build vet test openspec gateway-linux verify
+.PHONY: format-check module-verify build vet test openspec gateway-linux gateway-sbom verify
 
 GO ?= go
 OPENSPEC ?= openspec
 DIST_DIR ?= dist
+SOURCE_REVISION ?= $(shell git rev-parse HEAD)
+SOURCE_DATE ?= $(shell git show -s --format=%cI HEAD)
 
 format-check:
 	@test -z "$$(gofmt -l $$(find gateway -type f -name '*.go' -print))"
@@ -27,4 +29,12 @@ gateway-linux:
 	CGO_ENABLED=0 GOOS=linux GOARCH=amd64 GOWORK=off $(GO) build -mod=readonly -trimpath -buildvcs=false -ldflags=-buildid= -o "$(DIST_DIR)/verse-gateway-linux-amd64" ./cmd/verse-gateway
 	CGO_ENABLED=0 GOOS=linux GOARCH=arm64 GOWORK=off $(GO) build -mod=readonly -trimpath -buildvcs=false -ldflags=-buildid= -o "$(DIST_DIR)/verse-gateway-linux-arm64" ./cmd/verse-gateway
 
+gateway-sbom:
+	$(GO) run ./cmd/verse-gateway-sbom \
+		-source-revision "$(SOURCE_REVISION)" \
+		-source-date "$(SOURCE_DATE)" \
+		-artifact "amd64=$(DIST_DIR)/verse-gateway-linux-amd64" \
+		-artifact "arm64=$(DIST_DIR)/verse-gateway-linux-arm64" \
+		-output "$(DIST_DIR)/verse-gateway.spdx.json"
+
 verify: format-check module-verify build vet test openspec
diff --git a/cmd/verse-gateway-sbom/main.go b/cmd/verse-gateway-sbom/main.go
new file mode 100644
index 0000000..db7d197
--- /dev/null
+++ b/cmd/verse-gateway-sbom/main.go
@@ -0,0 +1,376 @@
+package main
+
+import (
+	"bufio"
+	"crypto/sha256"
+	"debug/buildinfo"
+	"encoding/hex"
+	"encoding/json"
+	"errors"
+	"flag"
+	"fmt"
+	"io"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"reflect"
+	"regexp"
+	"sort"
+	"strings"
+	"time"
+)
+
+const (
+	dataPlaneModulePath = "git.sechmachine.io.vn/sechmachine/VerseVDI-Data-Plane"
+	protocolModulePath  = "git.sechmachine.io.vn/sechmachine/VerseVDI-Protocol"
+)
+
+type artifactFlags []string
+
+func (values *artifactFlags) String() string { return strings.Join(*values, ",") }
+func (values *artifactFlags) Set(value string) error {
+	*values = append(*values, value)
+	return nil
+}
+
+type goModule struct {
+	Path    string
+	Version string
+	Sum     string
+}
+
+type gatewayArtifact struct {
+	Architecture string
+	Filename     string
+	SHA256       string
+	Size         int64
+}
+
+type sbomInput struct {
+	SourceRevision   string
+	Created          time.Time
+	ProtocolGoModSum string
+	Modules          []goModule
+	Artifacts        []gatewayArtifact
+}
+
+type spdxDocument struct {
+	SPDXVersion       string             `json:"spdxVersion"`
+	DataLicense       string             `json:"dataLicense"`
+	SPDXID            string             `json:"SPDXID"`
+	Name              string             `json:"name"`
+	DocumentNamespace string             `json:"documentNamespace"`
+	CreationInfo      spdxCreationInfo   `json:"creationInfo"`
+	DocumentComment   string             `json:"documentComment"`
+	Packages          []spdxPackage      `json:"packages"`
+	Relationships     []spdxRelationship `json:"relationships"`
+}
+
+type spdxCreationInfo struct {
+	Created  string   `json:"created"`
+	Creators []string `json:"creators"`
+}
+
+type spdxPackage struct {
+	Name             string         `json:"name"`
+	SPDXID           string         `json:"SPDXID"`
+	VersionInfo      string         `json:"versionInfo"`
+	DownloadLocation string         `json:"downloadLocation"`
+	FilesAnalyzed    bool           `json:"filesAnalyzed"`
+	PackagePurpose   string         `json:"primaryPackagePurpose"`
+	Checksums        []spdxChecksum `json:"checksums,omitempty"`
+	LicenseConcluded string         `json:"licenseConcluded"`
+	LicenseDeclared  string         `json:"licenseDeclared"`
+	CopyrightText    string         `json:"copyrightText"`
+	Comment          string         `json:"comment,omitempty"`
+	ExternalRefs     []spdxRef      `json:"externalRefs,omitempty"`
+}
+
+type spdxChecksum struct {
+	Algorithm     string `json:"algorithm"`
+	ChecksumValue string `json:"checksumValue"`
+}
+
+type spdxRef struct {
+	Category string `json:"referenceCategory"`
+	Type     string `json:"referenceType"`
+	Locator  string `json:"referenceLocator"`
+	Comment  string `json:"comment,omitempty"`
+}
+
+type spdxRelationship struct {
+	Element string `json:"spdxElementId"`
+	Type    string `json:"relationshipType"`
+	Related string `json:"relatedSpdxElement"`
+}
+
+func main() {
+	var artifacts artifactFlags
+	sourceRevision := flag.String("source-revision", "", "full clean source commit")
+	sourceDate := flag.String("source-date", "", "UTC RFC3339 source date")
+	goSumPath := flag.String("go-sum", "go.sum", "Go checksum file")
+	output := flag.String("output", "", "SPDX JSON output")
+	flag.Var(&artifacts, "artifact", "linux architecture and binary path, for example amd64=dist/verse-gateway-linux-amd64")
+	flag.Parse()
+
+	if *output == "" {
+		fatal(errors.New("output is required"))
+	}
+	created, err := time.Parse(time.RFC3339, *sourceDate)
+	if err != nil {
+		fatal(errors.New("source-date must be RFC3339"))
+	}
+	created = created.UTC()
+	if err := verifyCleanRevision(*sourceRevision); err != nil {
+		fatal(err)
+	}
+	inspected, modules, err := inspectArtifacts(artifacts)
+	if err != nil {
+		fatal(err)
+	}
+	protocolVersion := ""
+	for _, module := range modules {
+		if module.Path == protocolModulePath {
+			protocolVersion = module.Version
+		}
+	}
+	goModSum, err := readGoModSum(*goSumPath, protocolModulePath, protocolVersion)
+	if err != nil {
+		fatal(err)
+	}
+	encoded, err := buildSPDX(sbomInput{
+		SourceRevision: *sourceRevision, Created: created, ProtocolGoModSum: goModSum,
+		Modules: modules, Artifacts: inspected,
+	})
+	if err != nil {
+		fatal(err)
+	}
+	if err := os.WriteFile(*output, encoded, 0o644); err != nil {
+		fatal(err)
+	}
+}
+
+func fatal(err error) {
+	_, _ = fmt.Fprintln(os.Stderr, err)
+	os.Exit(1)
+}
+
+func verifyCleanRevision(revision string) error {
+	if !regexp.MustCompile(`^[0-9a-f]{40}$`).MatchString(revision) {
+		return errors.New("source-revision must be a full lowercase commit")
+	}
+	head, err := exec.Command("git", "rev-parse", "HEAD").Output()
+	if err != nil || strings.TrimSpace(string(head)) != revision {
+		return errors.New("source-revision does not match HEAD")
+	}
+	status, err := exec.Command("git", "status", "--porcelain", "--untracked-files=no").Output()
+	if err != nil {
+		return fmt.Errorf("inspect source dirt: %w", err)
+	}
+	if len(status) != 0 {
+		return errors.New("tracked source tree is dirty")
+	}
+	return nil
+}
+
+func inspectArtifacts(specifications []string) ([]gatewayArtifact, []goModule, error) {
+	if len(specifications) != 2 {
+		return nil, nil, errors.New("exactly amd64 and arm64 artifacts are required")
+	}
+	var artifacts []gatewayArtifact
+	var common []goModule
+	seen := make(map[string]bool)
+	for _, specification := range specifications {
+		architecture, path, ok := strings.Cut(specification, "=")
+		if !ok || (architecture != "amd64" && architecture != "arm64") || seen[architecture] {
+			return nil, nil, errors.New("artifact must uniquely name amd64 or arm64")
+		}
+		seen[architecture] = true
+		artifact, modules, err := inspectArtifact(architecture, path)
+		if err != nil {
+			return nil, nil, err
+		}
+		if common == nil {
+			common = modules
+		} else if !reflect.DeepEqual(common, modules) {
+			return nil, nil, errors.New("artifact module inventories differ")
+		}
+		artifacts = append(artifacts, artifact)
+	}
+	sort.Slice(artifacts, func(first, second int) bool {
+		return artifacts[first].Architecture < artifacts[second].Architecture
+	})
+	return artifacts, common, nil
+}
+
+func inspectArtifact(architecture, path string) (gatewayArtifact, []goModule, error) {
+	info, err := buildinfo.ReadFile(path)
+	if err != nil {
+		return gatewayArtifact{}, nil, fmt.Errorf("read %s build metadata: %w", architecture, err)
+	}
+	settings := make(map[string]string, len(info.Settings))
+	for _, setting := range info.Settings {
+		settings[setting.Key] = setting.Value
+	}
+	if info.Path != dataPlaneModulePath+"/cmd/verse-gateway" || settings["GOOS"] != "linux" ||
+		settings["GOARCH"] != architecture || settings["CGO_ENABLED"] != "0" {
+		return gatewayArtifact{}, nil, fmt.Errorf("%s artifact build identity is invalid", architecture)
+	}
+	modules := []goModule{{Path: info.Main.Path, Version: info.Main.Version, Sum: info.Main.Sum}}
+	for _, dependency := range info.Deps {
+		if dependency.Replace != nil {
+			return gatewayArtifact{}, nil, fmt.Errorf("%s contains replaced module %s", architecture, dependency.Path)
+		}
+		modules = append(modules, goModule{Path: dependency.Path, Version: dependency.Version, Sum: dependency.Sum})
+	}
+	sort.Slice(modules, func(first, second int) bool {
+		if modules[first].Path == modules[second].Path {
+			return modules[first].Version < modules[second].Version
+		}
+		return modules[first].Path < modules[second].Path
+	})
+	file, err := os.Open(path)
+	if err != nil {
+		return gatewayArtifact{}, nil, err
+	}
+	defer file.Close()
+	digest := sha256.New()
+	size, err := io.Copy(digest, file)
+	if err != nil {
+		return gatewayArtifact{}, nil, err
+	}
+	return gatewayArtifact{
+		Architecture: architecture, Filename: filepath.Base(path),
+		SHA256: hex.EncodeToString(digest.Sum(nil)), Size: size,
+	}, modules, nil
+}
+
+func readGoModSum(path, modulePath, version string) (string, error) {
+	file, err := os.Open(path)
+	if err != nil {
+		return "", err
+	}
+	defer file.Close()
+	prefix := modulePath + " " + version + "/go.mod "
+	scanner := bufio.NewScanner(file)
+	for scanner.Scan() {
+		if strings.HasPrefix(scanner.Text(), prefix) {
+			return strings.TrimPrefix(scanner.Text(), prefix), nil
+		}
+	}
+	if err := scanner.Err(); err != nil {
+		return "", err
+	}
+	return "", errors.New("protocol go.mod checksum is absent")
+}
+
+func buildSPDX(input sbomInput) ([]byte, error) {
+	if !regexp.MustCompile(`^[0-9a-f]{40}$`).MatchString(input.SourceRevision) || input.Created.Location() != time.UTC ||
+		input.ProtocolGoModSum == "" || len(input.Artifacts) != 2 {
+		return nil, errors.New("incomplete SPDX inputs")
+	}
+	modules := append([]goModule(nil), input.Modules...)
+	sort.Slice(modules, func(first, second int) bool {
+		if modules[first].Path == modules[second].Path {
+			return modules[first].Version < modules[second].Version
+		}
+		return modules[first].Path < modules[second].Path
+	})
+	artifacts := append([]gatewayArtifact(nil), input.Artifacts...)
+	sort.Slice(artifacts, func(first, second int) bool {
+		return artifacts[first].Architecture < artifacts[second].Architecture
+	})
+	if artifacts[0].Architecture != "amd64" || artifacts[1].Architecture != "arm64" {
+		return nil, errors.New("SPDX requires amd64 and arm64 artifacts")
+	}
+
+	sourceID := "SPDXRef-Source"
+	packages := []spdxPackage{{
+		Name: dataPlaneModulePath, SPDXID: sourceID, VersionInfo: input.SourceRevision,
+		DownloadLocation: "NOASSERTION", FilesAnalyzed: false, PackagePurpose: "SOURCE",
+		LicenseConcluded: "NOASSERTION", LicenseDeclared: "GPL-3.0-only", CopyrightText: "NOASSERTION",
+		Comment: "license_provenance=LICENSE",
+	}}
+	moduleIDs := make(map[string]string)
+	protocolFound := false
+	for _, module := range modules {
+		if module.Path == dataPlaneModulePath {
+			continue
+		}
+		if module.Path == "" || module.Version == "" || moduleIDs[module.Path] != "" {
+			return nil, errors.New("ambiguous module inventory")
+		}
+		id := "SPDXRef-Module-" + shortDigest(module.Path+"@"+module.Version)
+		moduleIDs[module.Path] = id
+		comment := "go_module_sum=" + module.Sum
+		if module.Path == protocolModulePath {
+			if module.Sum == "" {
+				return nil, errors.New("immutable Protocol checksum is absent")
+			}
+			protocolFound = true
+			comment += "; go_mod_sum=" + input.ProtocolGoModSum
+		}
+		packages = append(packages, spdxPackage{
+			Name: module.Path, SPDXID: id, VersionInfo: module.Version,
+			DownloadLocation: "NOASSERTION", FilesAnalyzed: false, PackagePurpose: "LIBRARY",
+			LicenseConcluded: "NOASSERTION", LicenseDeclared: "NOASSERTION", CopyrightText: "NOASSERTION",
+			Comment: comment,
+			ExternalRefs: []spdxRef{{
+				Category: "PACKAGE-MANAGER", Type: "purl",
+				Locator: "pkg:golang/" + module.Path + "@" + module.Version,
+			}},
+		})
+	}
+	if !protocolFound {
+		return nil, errors.New("Protocol module is absent")
+	}
+
+	var relationships []spdxRelationship
+	for _, artifact := range artifacts {
+		if artifact.Filename == "" || len(artifact.SHA256) != 64 || artifact.Size < 1 {
+			return nil, errors.New("artifact metadata is invalid")
+		}
+		id := "SPDXRef-Artifact-" + artifact.Architecture
+		packages = append(packages, spdxPackage{
+			Name: artifact.Filename, SPDXID: id, VersionInfo: input.SourceRevision,
+			DownloadLocation: "NOASSERTION", FilesAnalyzed: false, PackagePurpose: "APPLICATION",
+			Checksums:        []spdxChecksum{{Algorithm: "SHA256", ChecksumValue: artifact.SHA256}},
+			LicenseConcluded: "NOASSERTION", LicenseDeclared: "GPL-3.0-only", CopyrightText: "NOASSERTION",
+			Comment: fmt.Sprintf("GOOS=linux; GOARCH=%s; CGO_ENABLED=0; size=%d", artifact.Architecture, artifact.Size),
+		})
+		relationships = append(relationships,
+			spdxRelationship{Element: "SPDXRef-DOCUMENT", Type: "DESCRIBES", Related: id},
+			spdxRelationship{Element: id, Type: "GENERATED_FROM", Related: sourceID},
+		)
+		for _, moduleID := range moduleIDs {
+			relationships = append(relationships, spdxRelationship{Element: id, Type: "DEPENDS_ON", Related: moduleID})
+		}
+	}
+	sort.Slice(packages, func(first, second int) bool { return packages[first].SPDXID < packages[second].SPDXID })
+	sort.Slice(relationships, func(first, second int) bool {
+		left := relationships[first].Element + relationships[first].Type + relationships[first].Related
+		right := relationships[second].Element + relationships[second].Type + relationships[second].Related
+		return left < right
+	})
+	document := spdxDocument{
+		SPDXVersion: "SPDX-2.3", DataLicense: "CC0-1.0", SPDXID: "SPDXRef-DOCUMENT",
+		Name:              "verse-gateway-" + input.SourceRevision,
+		DocumentNamespace: "https://git.sechmachine.io.vn/sechmachine/VerseVDI-Data-Plane/spdx/" + input.SourceRevision,
+		CreationInfo: spdxCreationInfo{
+			Created:  input.Created.Format(time.RFC3339),
+			Creators: []string{"Tool: verse-gateway-sbom"},
+		},
+		DocumentComment: "notices=LICENSE; provenance=Go build metadata and artifact SHA-256; vulnerability_status=unscanned; signing_status=unsigned; phase3c_c_image_remediation=separate",
+		Packages:        packages, Relationships: relationships,
+	}
+	encoded, err := json.MarshalIndent(document, "", "  ")
+	if err != nil {
+		return nil, err
+	}
+	return append(encoded, '\n'), nil
+}
+
+func shortDigest(value string) string {
+	digest := sha256.Sum256([]byte(value))
+	return hex.EncodeToString(digest[:8])
+}
diff --git a/cmd/verse-gateway-sbom/main_test.go b/cmd/verse-gateway-sbom/main_test.go
new file mode 100644
index 0000000..5a65919
--- /dev/null
+++ b/cmd/verse-gateway-sbom/main_test.go
@@ -0,0 +1,82 @@
+package main
+
+import (
+	"bytes"
+	"strings"
+	"testing"
+	"time"
+)
+
+func TestBuildSPDXIsDeterministicAndTruthful(t *testing.T) {
+	input := sbomInput{
+		SourceRevision:   strings.Repeat("a", 40),
+		Created:          time.Date(2026, time.July, 30, 1, 2, 3, 0, time.UTC),
+		ProtocolGoModSum: "h1:protocol-go-mod",
+		Modules: []goModule{
+			{Path: "git.sechmachine.io.vn/sechmachine/VerseVDI-Data-Plane", Version: "(devel)"},
+			{Path: protocolModulePath, Version: "v1.0.0-phase3c-gateway-rc.9", Sum: "h1:protocol"},
+			{Path: "github.com/quic-go/quic-go", Version: "v0.61.0", Sum: "h1:quic"},
+		},
+		Artifacts: []gatewayArtifact{
+			{Architecture: "amd64", Filename: "verse-gateway-linux-amd64", SHA256: strings.Repeat("1", 64), Size: 100},
+			{Architecture: "arm64", Filename: "verse-gateway-linux-arm64", SHA256: strings.Repeat("2", 64), Size: 101},
+		},
+	}
+	first, err := buildSPDX(input)
+	if err != nil {
+		t.Fatal(err)
+	}
+	second, err := buildSPDX(input)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !bytes.Equal(first, second) {
+		t.Fatal("SPDX generation was not byte-stable")
+	}
+	text := string(first)
+	for _, required := range []string{
+		`"spdxVersion": "SPDX-2.3"`,
+		input.SourceRevision,
+		"v1.0.0-phase3c-gateway-rc.9",
+		input.ProtocolGoModSum,
+		"verse-gateway-linux-amd64",
+		"verse-gateway-linux-arm64",
+		strings.Repeat("1", 64),
+		strings.Repeat("2", 64),
+		`"licenseConcluded": "NOASSERTION"`,
+		"vulnerability_status=unscanned",
+		"signing_status=unsigned",
+	} {
+		if !strings.Contains(text, required) {
+			t.Fatalf("SPDX is missing %q", required)
+		}
+	}
+}
+
+func TestBuildSPDXRejectsAmbiguousInputs(t *testing.T) {
+	valid := sbomInput{
+		SourceRevision: strings.Repeat("a", 40), Created: time.Unix(0, 0).UTC(),
+		ProtocolGoModSum: "h1:protocol-go-mod",
+		Modules: []goModule{
+			{Path: protocolModulePath, Version: "v1.0.0-rc.9", Sum: "h1:protocol"},
+		},
+		Artifacts: []gatewayArtifact{
+			{Architecture: "amd64", Filename: "amd64", SHA256: strings.Repeat("1", 64), Size: 1},
+			{Architecture: "arm64", Filename: "arm64", SHA256: strings.Repeat("2", 64), Size: 1},
+		},
+	}
+	mutations := []func(*sbomInput){
+		func(input *sbomInput) { input.SourceRevision = "short" },
+		func(input *sbomInput) { input.Modules = nil },
+		func(input *sbomInput) { input.Artifacts[1].Architecture = "amd64" },
+	}
+	for index, mutate := range mutations {
+		input := valid
+		input.Modules = append([]goModule(nil), valid.Modules...)
+		input.Artifacts = append([]gatewayArtifact(nil), valid.Artifacts...)
+		mutate(&input)
+		if _, err := buildSPDX(input); err == nil {
+			t.Fatalf("invalid SPDX input %d was accepted", index)
+		}
+	}
+}
diff --git a/openspec/changes/deterministic-gateway-sbom/.openspec.yaml b/openspec/changes/deterministic-gateway-sbom/.openspec.yaml
new file mode 100644
index 0000000..ab39675
--- /dev/null
+++ b/openspec/changes/deterministic-gateway-sbom/.openspec.yaml
@@ -0,0 +1,2 @@
+schema: spec-driven
+created: 2026-07-30
diff --git a/openspec/changes/deterministic-gateway-sbom/design.md b/openspec/changes/deterministic-gateway-sbom/design.md
new file mode 100644
index 0000000..f06612b
--- /dev/null
+++ b/openspec/changes/deterministic-gateway-sbom/design.md
@@ -0,0 +1,28 @@
+## Context
+
+The repository already produces reproducible pure-Go Linux binaries and can read exact Go module/build metadata. A standard deterministic document is missing; adding an external SBOM tool is unnecessary for this bounded artifact.
+
+## Goals / Non-Goals
+
+**Goals:**
+
+- Generate byte-stable SPDX 2.3 JSON with Go standard library encoding.
+- Describe the repository, Protocol dependency, all resolved modules, both Linux binaries, relationships, hashes, architectures, notices, and truthful licenses.
+
+**Non-Goals:**
+
+- Vulnerability scanning, signing, image remediation, public release, or inferred license conclusions.
+
+## Decisions
+
+- Use a small repository command that reads each binary with
+  `debug/buildinfo`, verifies Linux architecture and cgo settings, and compares
+  embedded module inventories before sorting every package and relationship.
+- Use fixed SPDX identifiers and a source-date timestamp supplied by the caller; reject dirty/ambiguous inputs rather than embedding current time.
+- Use `NOASSERTION` for unavailable concluded/declared license evidence and record no vulnerability result.
+
+## Risks / Trade-offs
+
+- [Go module metadata lacks complete license conclusions] → retain notices and use `NOASSERTION`.
+- [Artifact paths make output host-dependent] → encode architecture, filename, size, and digest only.
+- [A hand-built serializer could drift] → validate required SPDX fields and require byte-identical double generation.
diff --git a/openspec/changes/deterministic-gateway-sbom/proposal.md b/openspec/changes/deterministic-gateway-sbom/proposal.md
new file mode 100644
index 0000000..79b50f9
--- /dev/null
+++ b/openspec/changes/deterministic-gateway-sbom/proposal.md
@@ -0,0 +1,24 @@
+## Why
+
+The gateway has reproducible Linux binaries and a dependency inventory but no deterministic standard SBOM, while OPS-009 and the Phase 3C gateway plan require one for engineering exit.
+
+## What Changes
+
+- Generate byte-stable SPDX 2.3 JSON using repository, Go module, and artifact metadata.
+- Record exact source revision, immutable Protocol version/checksum, module relationships, Linux artifact hashes and architectures, and truthful license fields.
+- Retain notices/provenance and use `NOASSERTION` where license evidence is unavailable.
+- Keep vulnerability scanning, signing, and Phase 3C-C image remediation explicitly separate.
+
+## Capabilities
+
+### New Capabilities
+
+None.
+
+### Modified Capabilities
+
+- `gateway-deployment-artifact`: Require an inspected deterministic standard SBOM for shipped gateway binaries.
+
+## Impact
+
+Data Plane packaging tooling, deterministic tests, Makefile targets, canonical deployment-artifact OpenSpec, and evidence records. Uses Go standard library only; no new dependency. Requirements: SYS-019, P3C-002, P3C-035, OPS-009, VER-015, VER-017.
diff --git a/openspec/changes/deterministic-gateway-sbom/specs/gateway-deployment-artifact/spec.md b/openspec/changes/deterministic-gateway-sbom/specs/gateway-deployment-artifact/spec.md
new file mode 100644
index 0000000..ff6d567
--- /dev/null
+++ b/openspec/changes/deterministic-gateway-sbom/specs/gateway-deployment-artifact/spec.md
@@ -0,0 +1,12 @@
+## MODIFIED Requirements
+
+### Requirement: Artifact evidence is inspected and truthful
+Candidate evidence SHALL record exact source and immutable Protocol revisions/checksums, artifact hashes, architecture, embedded dependency inventory, container configuration when built, and the actual scanner/signing status. It SHALL include one byte-stable SPDX 2.3 JSON SBOM for the shipped Linux gateway artifacts containing the source package, resolved Go modules, dependency and generated-from relationships, artifact hashes and architectures, retained notices/provenance, and truthful license fields using `NOASSERTION` where evidence is unavailable. It MUST NOT claim a vulnerability result, signature, image architecture, deployment, or license conclusion that was not produced and inspected.
+
+#### Scenario: Deterministic gateway SBOM
+- **WHEN** the canonical SBOM command runs twice with the same clean source revision, Protocol module/checksum, module graph, source date, and Linux artifacts
+- **THEN** both SPDX JSON outputs are byte-identical and every declared artifact/module relationship and hash matches the inspected inputs
+
+#### Scenario: Supplemental scanner is unavailable
+- **WHEN** no qualifying vulnerability scanner is available in the frozen environment
+- **THEN** the artifact remains explicitly unscanned and unsigned, the deterministic SBOM/compiler/dependency/boundary evidence is retained, and no zero-finding security claim is emitted
diff --git a/openspec/changes/deterministic-gateway-sbom/tasks.md b/openspec/changes/deterministic-gateway-sbom/tasks.md
new file mode 100644
index 0000000..5816315
--- /dev/null
+++ b/openspec/changes/deterministic-gateway-sbom/tasks.md
@@ -0,0 +1,14 @@
+## 1. Red deterministic contract
+
+- [x] 1.1 Add a focused test requiring SPDX 2.3 fields, source/Protocol/module relationships, two architectures, and exact artifact hashes
+- [x] 1.2 Prove current packaging cannot produce the required standard SBOM
+
+## 2. Standard-library generator
+
+- [x] 2.1 Implement bounded deterministic SPDX JSON generation from explicit build and Go module metadata
+- [x] 2.2 Record truthful license fields, notices/provenance, unscanned status, and no signing claim
+
+## 3. Verification
+
+- [ ] 3.1 Prove byte-stable regeneration and rejection of dirty, missing, mismatched, or ambiguous inputs
+- [x] 3.2 Reconcile the deployment-artifact canonical spec and run strict validation
diff --git a/openspec/specs/gateway-deployment-artifact/spec.md b/openspec/specs/gateway-deployment-artifact/spec.md
index 22e3ddc..bcf8765 100644
--- a/openspec/specs/gateway-deployment-artifact/spec.md
+++ b/openspec/specs/gateway-deployment-artifact/spec.md
@@ -12,8 +12,26 @@ The candidate SHALL build the gateway with the normal immutable Protocol module
 - **THEN** both amd64 and arm64 outputs are byte-identical pure-Go ELF executables with matching embedded GOOS, GOARCH, and cgo settings
 
 ### Requirement: Artifact evidence is inspected and truthful
-Candidate evidence SHALL record exact source and Protocol revisions, artifact hashes, architecture, embedded dependency inventory, container configuration when built, and the actual scanner/signing status. It MUST NOT claim an SBOM, vulnerability result, signature, image architecture, or deployment that was not produced and inspected.
+Candidate evidence SHALL record exact source and immutable Protocol
+revisions/checksums, artifact hashes, architecture, embedded dependency
+inventory, container configuration when built, and the actual scanner/signing
+status. It SHALL include one byte-stable SPDX 2.3 JSON SBOM for the shipped Linux
+gateway artifacts containing the source package, resolved Go modules, dependency
+and generated-from relationships, artifact hashes and architectures, retained
+notices/provenance, and truthful license fields using `NOASSERTION` where
+evidence is unavailable. It MUST NOT claim a vulnerability result, signature,
+image architecture, deployment, or license conclusion that was not produced and
+inspected.
+
+#### Scenario: Deterministic gateway SBOM
+- **WHEN** the canonical SBOM command runs twice with the same clean source
+  revision, Protocol module/checksum, module graph, source date, and Linux
+  artifacts
+- **THEN** both SPDX JSON outputs are byte-identical and every declared
+  artifact/module relationship and hash matches the inspected inputs
 
 #### Scenario: Supplemental scanner is unavailable
 - **WHEN** no qualifying vulnerability scanner is available in the frozen environment
-- **THEN** the artifact remains explicitly unscanned, deterministic compiler/dependency/boundary evidence is retained, and no zero-finding security claim is emitted
+- **THEN** the artifact remains explicitly unscanned and unsigned, the
+  deterministic SBOM/compiler/dependency/boundary evidence is retained, and no
+  zero-finding security claim is emitted