diff --git a/.github/workflows/qgate.yml b/.github/workflows/qgate.yml
index 27b95802..7393f578 100644
--- a/.github/workflows/qgate.yml
+++ b/.github/workflows/qgate.yml
@@ -62,7 +62,7 @@ jobs:
           retention-days: 14
 
       - name: Install cargo-cyclonedx
-        run: cargo install cargo-cyclonedx --locked
+        run: cargo install cargo-cyclonedx --version 0.5.9 --locked
 
       - name: Generate CycloneDX SBOM
         run: |
@@ -72,6 +72,10 @@ jobs:
           echo "SBOM files:"
           find . -name '*.cdx.json' -print
 
+      - name: Validate CycloneDX SBOM anchors
+        shell: pwsh
+        run: ./scripts/sbom-validate-check.ps1 -Path target/sbom.cdx.json
+
       - name: Upload CycloneDX SBOM
         uses: actions/upload-artifact@043fb46d1a93c77aae656e7c1c64a875d1fc6a0a # v7.0.1
         with:
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index bc4b1051..855de6cb 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -436,7 +436,7 @@ jobs:
           cat SHA256SUMS
 
       - name: install cargo-cyclonedx
-        run: cargo install cargo-cyclonedx --locked
+        run: cargo install cargo-cyclonedx --version 0.5.9 --locked
 
       - name: create CycloneDX SBOM
         run: |
@@ -449,6 +449,10 @@ jobs:
               -printf '%P\n' | sort | xargs -r sha256sum > SHA256SUMS
           )
 
+      - name: validate release CycloneDX SBOM anchors
+        shell: pwsh
+        run: ./scripts/sbom-validate-check.ps1 -Path artifacts/session-ledger.cdx.json
+
       - name: attest Release assets
         id: provenance
         if: github.repository == 'KooshaPari/SessionLedger'
diff --git a/.github/workflows/security.yml b/.github/workflows/security.yml
index fd457ce4..833a4248 100644
--- a/.github/workflows/security.yml
+++ b/.github/workflows/security.yml
@@ -131,6 +131,16 @@ jobs:
         shell: pwsh
         run: ./scripts/cargo-nonet-check.ps1 -SelfCheck
 
+  # Blocking C04 L32 SBOM policy evidence — hermetic SelfCheck only.
+  sbom-policy:
+    name: SBOM policy SelfCheck
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7
+      - name: SBOM policy + CycloneDX anchor SelfCheck
+        shell: pwsh
+        run: ./scripts/sbom-validate-check.ps1 -SelfCheck
+
   # Hard C02 L22 envelope-crypto CI evidence — blocking PR workflow in
   # .github/workflows/envelope-crypto.yml (envelope-crypto-check.ps1 -SelfCheck).
   # Does not claim in-tree KMS, sealed secrets, KEK wrap, or OKF/audit encryption.
diff --git a/CHANGELOG.md b/CHANGELOG.md
index ad516f5a..971ba7ad 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -12,6 +12,8 @@ Follows [Keep a Changelog](https://keepachangelog.com/); versioning is [SemVer](
 
 ### Added
 
+- SBOM schema validation + pinned cargo-cyclonedx (C04 L32): `docs/ops/sbom-policy.json`, `scripts/sbom-validate-check.ps1 -SelfCheck`, post-generation validation in `qgate.yml`/`release.yml`, blocking `security.yml` SBOM policy job, `tests/sbom_validate.rs`.
+
 - Wave-42 scope (396/402): consolidated `WAVE42_SCOPE.md` + `docs/ops/WAVE42_PERT.md` — five parallel carry-forward lanes (`w42-signing-check-bound`, `w42-sbom-validate`, `w42-slsa-promote`, `w42-alloc-gate-promote`, `w42-first-run-cta`) from Wave-41 deferred gaps.
 
 - P95 baseline refresh (C00 L6 / C08 L74): `bench-gate.ps1 -UpdateBaseline` writes `p95_source` per benchmark; `perf-baseline.json` refreshed from Criterion `sample.json` (replaces provisional mean×1.15 values).
diff --git a/SECURITY.md b/SECURITY.md
index f8f0b282..c490f4c3 100644
--- a/SECURITY.md
+++ b/SECURITY.md
@@ -66,6 +66,7 @@ Critical supply-chain or remote-code issues may be accelerated at maintainer dis
 - Secret scanning runs with gitleaks and TruffleHog (dual-scan) in the same workflow on PRs and pushes to `main` (plus a weekly scheduled full scan). Gitleaks uploads SARIF to GitHub code scanning when `security-events` write is available. Local pre-commit hooks use gitleaks only.
 - Dependency updates: [`renovate.json`](renovate.json) groups Cargo and GitHub Actions PRs and automerges **patch** (and Actions digest) updates after required CI checks pass. Weekly Dependabot ([`.github/dependabot.yml`](.github/dependabot.yml)) remains as a secondary CVE/update surface until Renovate is the sole bot. Prefer reviewing Renovate majors manually.
 - CycloneDX SBOMs are produced in the qgate path as `target/sbom.cdx.json` and per-crate `*.cdx.json` artifacts (see [`.github/workflows/qgate.yml`](.github/workflows/qgate.yml) header comments). Packaging notes: [`packaging/README.md`](packaging/README.md).
+- SBOM policy SSOT: [`docs/ops/sbom-policy.json`](docs/ops/sbom-policy.json) pins `cargo-cyclonedx` and documents validation via [`scripts/sbom-validate-check.ps1`](scripts/sbom-validate-check.ps1).
 
 - Advisory scanning: `cargo audit` job in .github/workflows/security.yml.
 - SBOM upload: qgate uploads `sbom-cyclonedx` artifact from `target/sbom.cdx.json`.
diff --git a/docs/ops/fixtures/sbom-valid-minimal.cdx.json b/docs/ops/fixtures/sbom-valid-minimal.cdx.json
new file mode 100644
index 00000000..4ad18f0a
--- /dev/null
+++ b/docs/ops/fixtures/sbom-valid-minimal.cdx.json
@@ -0,0 +1,20 @@
+{
+  "bomFormat": "CycloneDX",
+  "specVersion": "1.5",
+  "version": 1,
+  "metadata": {
+    "component": {
+      "type": "application",
+      "name": "session-ledger-fixture",
+      "version": "0.0.0-selfcheck"
+    }
+  },
+  "components": [
+    {
+      "type": "library",
+      "name": "serde",
+      "version": "1.0.0",
+      "purl": "pkg:cargo/serde@1.0.0"
+    }
+  ]
+}
diff --git a/docs/ops/sbom-policy.json b/docs/ops/sbom-policy.json
new file mode 100644
index 00000000..04f85cc8
--- /dev/null
+++ b/docs/ops/sbom-policy.json
@@ -0,0 +1,17 @@
+{
+  "schema_version": 1,
+  "purpose": "Pinned cargo-cyclonedx installer + CycloneDX SBOM validation policy (C04 L32)",
+  "cargo_cyclonedx_version": "0.5.9",
+  "cargo_install_command": "cargo install cargo-cyclonedx --version 0.5.9 --locked",
+  "workspace_sbom_path": "target/sbom.cdx.json",
+  "release_sbom_path": "artifacts/session-ledger.cdx.json",
+  "required_fields": [
+    "bomFormat",
+    "specVersion",
+    "version",
+    "metadata"
+  ],
+  "verify_command": "./scripts/sbom-validate-check.ps1 -SelfCheck",
+  "validate_command": "./scripts/sbom-validate-check.ps1 -Path target/sbom.cdx.json",
+  "update_policy": "Bump cargo_cyclonedx_version and workflow install lines together; refresh fixtures if specVersion changes."
+}
diff --git a/scripts/sbom-validate-check.ps1 b/scripts/sbom-validate-check.ps1
new file mode 100644
index 00000000..6fd0045f
--- /dev/null
+++ b/scripts/sbom-validate-check.ps1
@@ -0,0 +1,181 @@
+<#
+.SYNOPSIS
+  Validate CycloneDX SBOM policy anchors and optional SBOM JSON files.
+
+.DESCRIPTION
+  SelfCheck verifies docs/ops/sbom-policy.json, pinned cargo-cyclonedx install
+  lines in qgate.yml + release.yml, and classification fixtures. -Path mode
+  validates bomFormat/specVersion/metadata anchors on a generated .cdx.json.
+
+.PARAMETER SelfCheck
+  Hermetic policy + fixture smoke (no cargo-cyclonedx required).
+
+.PARAMETER Path
+  CycloneDX JSON file to validate (post-generation in CI).
+
+.EXAMPLE
+  pwsh ./scripts/sbom-validate-check.ps1 -SelfCheck
+  pwsh ./scripts/sbom-validate-check.ps1 -Path target/sbom.cdx.json
+#>
+[CmdletBinding()]
+param(
+    [switch]$SelfCheck,
+    [string]$Path = ""
+)
+
+Set-StrictMode -Version Latest
+$ErrorActionPreference = "Stop"
+
+$repoRoot = Split-Path -Parent $PSScriptRoot
+$policyPath = Join-Path $repoRoot "docs/ops/sbom-policy.json"
+$validFixture = Join-Path $repoRoot "docs/ops/fixtures/sbom-valid-minimal.cdx.json"
+$qgateWorkflow = Join-Path $repoRoot ".github/workflows/qgate.yml"
+$releaseWorkflow = Join-Path $repoRoot ".github/workflows/release.yml"
+$securityWorkflow = Join-Path $repoRoot ".github/workflows/security.yml"
+$securityDoc = Join-Path $repoRoot "SECURITY.md"
+$selfPath = Join-Path $repoRoot "scripts/sbom-validate-check.ps1"
+$wrapperTest = Join-Path $repoRoot "tests/sbom_validate.rs"
+
+function Assert-File {
+    param(
+        [Parameter(Mandatory = $true)][string]$FilePath,
+        [Parameter(Mandatory = $true)][string]$Label
+    )
+    if (-not (Test-Path -LiteralPath $FilePath -PathType Leaf)) {
+        throw "Missing $Label at '$FilePath'."
+    }
+}
+
+function Write-Check {
+    param([string]$Label, [bool]$Ok)
+    $mark = if ($Ok) { "PASS" } else { "FAIL" }
+    Write-Host "  [$mark] $Label"
+    return $Ok
+}
+
+function Assert-Contains {
+    param(
+        [Parameter(Mandatory = $true)][string]$Doc,
+        [Parameter(Mandatory = $true)][string]$Needle,
+        [Parameter(Mandatory = $true)][string]$Label,
+        [string]$Context = "document"
+    )
+    $ok = $Doc.Contains($Needle)
+    [void](Write-Check -Label $Label -Ok $ok)
+    if (-not $ok) {
+        throw "$Context missing required anchor: '$Needle'"
+    }
+}
+
+function Test-CycloneDxSbom {
+    param(
+        [Parameter(Mandatory = $true)][string]$FilePath
+    )
+
+    Assert-File -FilePath $FilePath -Label "CycloneDX SBOM"
+    $raw = Get-Content -LiteralPath $FilePath -Raw
+    if ([string]::IsNullOrWhiteSpace($raw)) {
+        throw "SBOM at '$FilePath' is empty."
+    }
+
+    try {
+        $bom = $raw | ConvertFrom-Json
+    }
+    catch {
+        throw "SBOM at '$FilePath' is not valid JSON: $($_.Exception.Message)"
+    }
+
+    if ($bom.bomFormat -ne "CycloneDX") {
+        throw "SBOM at '$FilePath' bomFormat must be CycloneDX (got '$($bom.bomFormat)')."
+    }
+    if ($bom.specVersion -notmatch '^1\.[0-9]+$') {
+        throw "SBOM at '$FilePath' specVersion must be CycloneDX 1.x (got '$($bom.specVersion)')."
+    }
+    if ($null -eq $bom.version -or [int]$bom.version -lt 1) {
+        throw "SBOM at '$FilePath' version must be a positive integer."
+    }
+    if ($null -eq $bom.metadata) {
+        throw "SBOM at '$FilePath' missing metadata object."
+    }
+    if ($null -eq $bom.metadata.component -or [string]::IsNullOrWhiteSpace([string]$bom.metadata.component.name)) {
+        throw "SBOM at '$FilePath' missing metadata.component.name."
+    }
+    if ($null -eq $bom.components) {
+        throw "SBOM at '$FilePath' missing components array."
+    }
+    if ($bom.components -isnot [System.Array]) {
+        throw "SBOM at '$FilePath' components must be an array."
+    }
+
+    return $true
+}
+
+function Invoke-SelfCheck {
+    Write-Host "SBOM policy check (C04 L32)"
+    Write-Host "Mode: SelfCheck (policy JSON + workflow pins + fixtures; no cargo-cyclonedx)"
+
+    Assert-File -FilePath $policyPath -Label "sbom policy JSON"
+    Assert-File -FilePath $validFixture -Label "valid SBOM fixture"
+    Assert-File -FilePath $qgateWorkflow -Label "qgate workflow"
+    Assert-File -FilePath $releaseWorkflow -Label "release workflow"
+    Assert-File -FilePath $securityWorkflow -Label "security workflow"
+    Assert-File -FilePath $securityDoc -Label "SECURITY.md"
+    Assert-File -FilePath $selfPath -Label "sbom validate script"
+    Assert-File -FilePath $wrapperTest -Label "sbom_validate.rs wrapper"
+
+    $policy = Get-Content -LiteralPath $policyPath -Raw | ConvertFrom-Json
+    $version = [string]$policy.cargo_cyclonedx_version
+    if ([string]::IsNullOrWhiteSpace($version)) {
+        throw "sbom-policy.json missing cargo_cyclonedx_version."
+    }
+    [void](Write-Check -Label "sbom-policy cargo_cyclonedx_version present" -Ok $true)
+
+    $installNeedle = "cargo install cargo-cyclonedx --version $version --locked"
+    $qgate = Get-Content -LiteralPath $qgateWorkflow -Raw
+    $release = Get-Content -LiteralPath $releaseWorkflow -Raw
+    $security = Get-Content -LiteralPath $securityWorkflow -Raw
+    $secDoc = Get-Content -LiteralPath $securityDoc -Raw
+
+    Assert-Contains -Doc $qgate -Needle $installNeedle -Label "qgate pinned cargo-cyclonedx install" -Context ".github/workflows/qgate.yml"
+    Assert-Contains -Doc $release -Needle $installNeedle -Label "release pinned cargo-cyclonedx install" -Context ".github/workflows/release.yml"
+    Assert-Contains -Doc $qgate -Needle "sbom-validate-check.ps1" -Label "qgate SBOM validate step" -Context ".github/workflows/qgate.yml"
+    Assert-Contains -Doc $security -Needle "sbom-validate-check.ps1 -SelfCheck" -Label "security.yml SBOM SelfCheck job" -Context ".github/workflows/security.yml"
+    Assert-Contains -Doc $secDoc -Needle "sbom-policy.json" -Label "SECURITY.md sbom policy cross-link" -Context "SECURITY.md"
+
+    Write-Host "Fixture validation:"
+    [void](Test-CycloneDxSbom -FilePath $validFixture)
+    [void](Write-Check -Label "valid minimal fixture passes schema anchors" -Ok $true)
+
+    $invalid = Join-Path ([System.IO.Path]::GetTempPath()) "sbom-invalid-selfcheck.cdx.json"
+    '{"version":1}' | Set-Content -LiteralPath $invalid -Encoding utf8
+    $failed = $false
+    try {
+        [void](Test-CycloneDxSbom -FilePath $invalid)
+    }
+    catch {
+        $failed = $true
+    }
+    finally {
+        Remove-Item -LiteralPath $invalid -ErrorAction SilentlyContinue
+    }
+    if (-not $failed) {
+        throw "Expected invalid SBOM fixture to fail validation."
+    }
+    [void](Write-Check -Label "invalid fixture rejected" -Ok $true)
+
+    Write-Host "SBOM validate SelfCheck passed (C04 L32 pinned cargo-cyclonedx + schema anchors)."
+    exit 0
+}
+
+if ($SelfCheck) {
+    Invoke-SelfCheck
+}
+
+if ([string]::IsNullOrWhiteSpace($Path)) {
+    throw "Specify -Path <file.cdx.json> or -SelfCheck."
+}
+
+$resolved = $ExecutionContext.SessionState.Path.GetUnresolvedProviderPathFromPSPath($Path)
+[void](Test-CycloneDxSbom -FilePath $resolved)
+Write-Host "CycloneDX SBOM validation passed for $resolved."
+exit 0
diff --git a/tests/sbom_validate.rs b/tests/sbom_validate.rs
new file mode 100644
index 00000000..38578bea
--- /dev/null
+++ b/tests/sbom_validate.rs
@@ -0,0 +1,32 @@
+//! Hermetic `SelfCheck` for SBOM policy + `CycloneDX` anchors (C04 L32).
+//!
+//! Local: `pwsh ./scripts/sbom-validate-check.ps1 -SelfCheck`
+
+use std::path::PathBuf;
+use std::process::Command;
+
+fn repo_root() -> PathBuf {
+    PathBuf::from(env!("CARGO_MANIFEST_DIR"))
+}
+
+#[test]
+fn sbom_validate_self_check_validates_policy_and_fixtures() {
+    let script = repo_root().join("scripts/sbom-validate-check.ps1");
+    assert!(script.is_file(), "expected SBOM validate script at {}", script.display());
+
+    let output = Command::new("pwsh")
+        .args(["-NoProfile", "-File", script.to_str().expect("utf-8 script path"), "-SelfCheck"])
+        .output()
+        .unwrap_or_else(|error| panic!("failed to spawn pwsh for SelfCheck: {error}"));
+
+    let stdout = String::from_utf8_lossy(&output.stdout);
+    let stderr = String::from_utf8_lossy(&output.stderr);
+    assert!(
+        output.status.success(),
+        "sbom-validate-check.ps1 -SelfCheck failed\nstdout:\n{stdout}\nstderr:\n{stderr}"
+    );
+    assert!(
+        stdout.contains("SBOM validate SelfCheck passed"),
+        "expected SelfCheck success line, got:\n{stdout}"
+    );
+}