diff --git a/CLAUDE.md b/CLAUDE.md
index ebf7ffc..a78f253 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -103,10 +103,13 @@ instead of working around it.
 
 1. **No per-host state in any artifact, ever.** No hostnames, keys, certs,
    MACs, or per-host config in the initramfs, rootfs, UKI, or OCI image.
-   All host identity derives from the TPM at runtime (key at persistent
-   handle `0x81010001`, cert at NV index `0x01800001`, hostnqn derived from
-   the cert serial). If a change needs per-host data, it belongs in the
-   enrolment flow, not the image.
+   All host identity derives from the TPM at runtime (signing key at persistent
+   handle `0x81000100` — a **non-reserved owner handle**, deliberately NOT the
+   EK slot `0x81010001` nor the SRK `0x81000001`, which firmware/swtpm
+   provisioning already occupy; cert at NV index `0x01800001`, hostnqn derived
+   from the cert serial). If a change needs per-host data, it belongs in the
+   enrolment flow, not the image. (The handle is overridable via
+   `rd.dot1x.handle=` / `fleet-enrol -handle`.)
 1. **The hook ordering in `dot1x-macsec-up.sh` is load-bearing.**
    NV-cert extraction → supplicant start → wait for `Authorized` + macsec0 →
    DHCP **on macsec0** → hostnqn derivation. Never DHCP before auth
diff --git a/README.md b/README.md
index e1e5b7b..612c960 100644
--- a/README.md
+++ b/README.md
@@ -137,7 +137,7 @@ first non-loopback interface is used. Test builds prepend `rd.dot1x=0`.
    (needs a reasonably recent systemd; otherwise publish data and hash as
    two separate namespaces and drop the hash-offset option).
 3. **TPM key reference**: confirm wpa_supplicant accepts
-   `private_key="handle:0x81010001"` via the OpenSSL tpm2 provider; if not,
+   `private_key="handle:0x81000100"` via the OpenSSL tpm2 provider; if not,
    switch to the tpm2-pkcs11 option in the supplicant config.
 4. **CONFIG_MACSEC** in the shipped wpa_supplicant build.
 5. **Pivot survival**: `@wpa_supplicant` survives switch-root; MKA continuity
diff --git a/docs/TODO.md b/docs/TODO.md
index 24dff8d..742a55b 100644
--- a/docs/TODO.md
+++ b/docs/TODO.md
@@ -766,7 +766,7 @@ smoke test.
     returns MSK); a `hostapd` wired authenticator does 802.1X + MACsec on an
     **isolated bridge per workstation** (flat VLAN can't auth — EAPOL dropped +
     MACsec is P2P). `enrol/tpm-provision.sh` creates the key in the TPM at
-    `0x81010001` + writes the cert to NV `0x01800001`. Starting solution **signs a
+    `0x81000100` + writes the cert to NV `0x01800001`. Starting solution **signs a
     CSR** (key stays in TPM); **TPM attestation** (ACME `device-attest-01`) is the
     documented upgrade on the same CA. **BENCH-VERIFY** items flagged in the files:
     hostapd MACsec build, openssl tpm2 provider vs pkcs11 key ref, EAP-TLS version.
@@ -775,7 +775,7 @@ smoke test.
     capability check (run on the booted open-port image, no `disable_dot1x` needed)
     to de-risk the TPM half before the full path. Likely first finding: no openssl
     TPM2 **provider** in the image (`tpm2-tss` ≠ the provider) — add `tpm2-openssl`.
-  - **Enrolment of the per-host identity** (key@`0x81010001` + cert@NV) is its own
+  - **Enrolment of the per-host identity** (key@`0x81000100` + cert@NV) is its own
     design — see **#11** (TOFU + OOB fingerprint broker, pre-auth permit-set,
     provisioning UKI). `tpm-provision.sh` is the manual bench stand-in for it.
 - **NVMe discovery by DNS:** `nvmet_traddr=nvme.fleet.lab` (CI), resolved at boot
@@ -968,7 +968,7 @@ enrolls.
     every NIC/GPU option ROM is covered by your keys — clearing MS db can break
     signed **option ROMs** (NIC PXE/HTTP-boot, GPU init), bricking the boot path.
   - **PCR 7 check:** enrollment changes the Secure Boot measurement in PCR 7;
-    confirm nothing the fleet seals to the TPM (the EAP-TLS key at `0x81010001`,
+    confirm nothing the fleet seals to the TPM (the EAP-TLS key at `0x81000100`,
     NV cert) is PCR-7-policy-bound before relying on this.
 
 **Decision before building:** auto-enroll trades assurance for convenience and is
@@ -1007,7 +1007,7 @@ it talks to `/dev/tpmrm0` DIRECTLY (via `transport.FromReadWriter` on an
 `os.File` — no `linuxtpm`, so go-tpm is the only vendored dep), so the enrolment
 path needs **no tpm2-tools key-gen / no openssl tpm2 provider / no curl** in the
 image (removes the biggest bench risk — the provider `handle:` key-ref). It
-ensures the ECDSA key at `0x81010001`, builds the CSR, POSTs CSR+context to
+ensures the ECDSA key at `0x81000100`, builds the CSR, POSTs CSR+context to
 `rd.fleet.enrol_url`, shows the broker fingerprint on Plymouth, polls `/status`,
 and writes the leaf cert to NV `0x01800001`. The dracut hook `tpm-enrol.sh`
 (initqueue/settled prio 25) is now a thin GATE: empty-NV check (`tpm2_nvread`,
@@ -1038,22 +1038,55 @@ ECDSA sign → CSR verify → chunked NV write → re-enrol) against the go-tpm
 simulator** (separate `files/enrol/simtest/` module so the CGO simulator never
 enters the shipped build). Both run in CI.
 
-**BENCH FINDING 2026-07-02 (FIXED, commit c574fa4) — stale non-ECC key at the
-handle.** First real-TPM boot (host `cygnus-cruiser-99`, `rd.dot1x=0`) failed:
-`fleet-enrol: ensure key at 0x81010001: key at handle is not ECC: did not contain
-eccDetail (selector value was 1)`. The host already had an **RSA** key persisted at
-`0x81010001` (from an older tpm2-tools/openssl provisioning path); `EnsureKey`
-fatally errored reading it as ECC → enrolment died before the CSR/POST, so the
-splash flashed "FIRST-BOOT TPM ENROLMENT" then the test system booted with **no
-fingerprint and nothing at the broker**. Fix: `EnsureKey` now **evicts a
-wrong-type/unusable key and recreates** a fresh ECC key (safe on the enrol path —
-empty NV, no cert references the old key); a valid ECC key is still reused.
-Regression `simtest/TestEnsureKeyEvictsStaleNonECC` (pre-plants an RSA key). **Needs
-a rebuild + re-boot to confirm on the bench** (the sim proves the recovery, not the
-device). ⚠ **Don't hand-run `sudo fleet-enrol` on the booted STIG host to test** —
-the confined admin domain (`sysadm_t`) is SELinux-**denied** write to
-`/dev/tpmrm0` (`avc: denied … tpm_device_t`), so it fails before the TPM regardless;
-the faithful path is the **initramfs** run (reboot) which is unconfined.
+**BENCH FINDING 2026-07-02 (FIXED) — the signing-key handle `0x81000100` was the
+EK slot; moved to `0x81000100`.** First real-TPM boot (host `cygnus-cruiser-99`,
+Proxmox vTPM, `rd.dot1x=0`) failed: `fleet-enrol: ensure key at 0x81010001: key at
+handle is not ECC: did not contain eccDetail (selector value was 1)`. `EnsureKey`
+died reading an existing RSA object as ECC → enrolment died before the CSR/POST, so
+the splash flashed "FIRST-BOOT TPM ENROLMENT" then the test system booted with **no
+fingerprint and nothing at the broker**. Root cause (confirmed via `tpm2_readpublic`
+under `enforcing=0`): **`0x81000100` is the TCG-standard RSA Endorsement Key handle**
+— the object there was the swtpm-provisioned **EK** (`restricted|decrypt|adminwithpolicy`,
+RSA-2048/AES128CFB, canonical EK authPolicy `837197674484b3f8…`), with its EK cert at
+NV `0x1c00002`. Our design squatted the EK slot fleet-wide (most firmware/swtpm TPMs
+have their EK there), so enrolment could never create our key.
+  - **Fix (commit c574fa4 + follow-up):** the fleet signing key moved to
+    **`0x81000100`** (non-reserved owner handle; threaded through `fleet-enrol
+    -handle` default, `rd.dot1x.handle=` cmdline knob baked by `extract-artifacts.sh`,
+    `wpa_supplicant-dot1x.conf`, the bench scripts, invariant #1, and the design docs).
+    NV `0x01800001` (owner range) is unchanged.
+  - **EnsureKey hardening:** (i) evicts a genuine *stale signing key* at the handle
+    and recreates (self-heal for old provisioning leftovers); (ii) **refuses to evict
+    any restricted-decrypt object (EK/SRK)** as a safety net — never clobber the TPM's
+    endorsement/storage identity (also protects the future EK/AK attestation).
+    Regressions: `simtest/TestEnsureKeyEvictsStaleNonECC` + `TestEnsureKeyRefusesToEvictProtectedKey`.
+  - **IDevID note (future):** if EK/AK attestation (`device-attest-01`, §"Stronger
+    assurance") lands, the natural home for a TPM device-identity key is the TCG
+    **IDevID** handle `0x81020001` (LDevID `0x81030001`) — see tpm-enrolment-design.md.
+    Not adopted for v1 (implies the IDevID template/cert conventions).
+  - **Also seen — leftover NV suppresses enrolment:** a *different* host (the 820)
+    booted `tpm-enrol: client cert present at NV 0x01800001 — normal boot` with nothing
+    enrolled this session — leftover NV state (from an earlier `tpm-provision.sh` /
+    `tpm-selftest.sh --use-real-handles`) **persists in the hardware TPM** across
+    reinstalls. Our presence check is content-blind (index defined ⇒ "enrolled"), so
+    foreign/stale NV silently skips enrolment (→ secure-path auth would then fail). See
+    the **content-aware NV check** item below.
+  - **Needs a rebuild + re-boot to confirm** (the sim proves the ceremony, not the
+    device). ⚠ **Don't hand-run `sudo fleet-enrol` on the booted STIG host** — the
+    confined admin domain (`sysadm_t`) is SELinux-**denied** write to `/dev/tpmrm0`
+    (`avc: denied … tpm_device_t`); the faithful path is the **initramfs** run
+    (reboot, unconfined), or `enforcing=0` for hand-run TPM inspection.
+
+**FOLLOW-UP HARDENING (from the two findings above, not yet built):**
+- **Content-aware NV presence check** — read NV `0x01800001`, parse as X.509, verify
+  it **chains to the fleet CA** (bundled `radius-ca.pem`); only then treat as enrolled,
+  else enrol + overwrite (`WriteNVCert` already undefine+redefines). Cleanest as a
+  `fleet-enrol -check-only` mode (no network) the hook calls — one content-aware source
+  of truth, replacing the hook's blind `tpm2_nvread` and the binary's `NVPresent`
+  (defined-only). Stops leftover/foreign NV from suppressing enrolment.
+- **De-enrol / TPM-reset procedure** for re-testing: `tpm2_nvundefine 0x01800001 -C o`
+  (+ `tpm2_evictcontrol -C o -c 0x81000100` for a stale *app* key — never the EK), or
+  BIOS "Clear TPM". Document in the bench README.
 
 **BENCH-VERIFY (host side, before trusting):** (a) go-tpm against a REAL TPM +
 swtpm on the target (the simulator proves the ceremony, not the device) — **the
@@ -1101,7 +1134,7 @@ Verification found + fixed two things the `mock` path had hidden:
   FreeRADIUS (next, before host enrolment).
 
 How a host gets its **802.1X EAP-TLS client identity** the first time — the key at
-TPM handle `0x81010001` + cert at NV `0x01800001` that invariant #1 says must come
+TPM handle `0x81000100` + cert at NV `0x01800001` that invariant #1 says must come
 from enrolment, never the image. Distinct from #10 (that enrols *Secure Boot*
 PK/KEK/db); this enrols the *network identity*. They share the provisioning UKI +
 isolated-environment vehicle. Pairs with #8 + the CA decision (start **step-ca**,
diff --git a/docs/design-v2-errata.md b/docs/design-v2-errata.md
index 6d105c2..0cf02ae 100644
--- a/docs/design-v2-errata.md
+++ b/docs/design-v2-errata.md
@@ -82,7 +82,7 @@ boot→secure dynamic VLAN. Consequences:
 **Per-host 802.1X identity is created by an enrolment flow, never baked in**
 (invariant #1). Chosen pattern: **trust-on-first-use with out-of-band fingerprint
 approval** — on an empty TPM the host generates a key *in* the TPM
-(`0x81010001`), submits a CSR to an enrolment **broker** (reachable via the same
+(`0x81000100`), submits a CSR to an enrolment **broker** (reachable via the same
 pre-auth permit-set, e.g. an `/enrol/` location on the serving nginx → broker →
 step-ca signer), and shows a fingerprint on the Plymouth splash; an admin
 cross-checks it and approves; the signed cert is written to NV `0x01800001` and
diff --git a/docs/fleet-management-design.md b/docs/fleet-management-design.md
index 451870d..5bcbeae 100644
--- a/docs/fleet-management-design.md
+++ b/docs/fleet-management-design.md
@@ -20,7 +20,7 @@ These are consequences of the CLAUDE.md invariants, not preferences:
    stateless and buffers only in RAM (best-effort).
 2. **Identity from the TPM, never baked.** No per-host state in any artifact
    (invariant #1). The agent derives identity at runtime from the **TPM-held
-   cert** (key `0x81010001`, cert NV `0x01800001`) — the same identity used for
+   cert** (key `0x81000100`, cert NV `0x01800001`) — the same identity used for
    802.1X EAP-TLS and the NVMe hostnqn. No enrollment token in the image.
 3. **Pull-based control, no inbound surface.** The boot LAN is locked down and
    segmented; we do not open an always-on inbound control port on hosts. Hosts
diff --git a/docs/ssp-annex-a-ism-residual-risk.md b/docs/ssp-annex-a-ism-residual-risk.md
index e2717ce..4d4c725 100644
--- a/docs/ssp-annex-a-ism-residual-risk.md
+++ b/docs/ssp-annex-a-ism-residual-risk.md
@@ -99,7 +99,7 @@ ISM/PSPF style). Ratings are **pre-treatment** unless stated; the AO accepts the
 
 | Topic | ISM (rep.) | Requirement intent | System implementation | Status | Residual |
 |---|---|---|---|---|---|
-| Strong machine authentication | ISM-1546*, ISM-0974* | Mutual, certificate-based auth. | **802.1X EAP-TLS**, client key non-exportable in **TPM** (`0x81010001`), cert in TPM NV. | Partial | R-01 (not bench-verified; disabled in test builds), R-08 (placeholder CA) |
+| Strong machine authentication | ISM-1546*, ISM-0974* | Mutual, certificate-based auth. | **802.1X EAP-TLS**, client key non-exportable in **TPM** (`0x81000100`), cert in TPM NV. | Partial | R-01 (not bench-verified; disabled in test builds), R-08 (placeholder CA) |
 | Privileged access restricted | ISM-1507*, ISM-0445* | Limit & control admin access. | Single key-only `wheel` admin; root login disabled; admin **confined to `staff_u`** with a sudo `sysadm_r`/`sysadm_t` role/type transition (SELinux context elevates on privilege use). | Partial | R-05 |
 | Secure remote administration | ISM-1506*, ISM-1232* | Hardened admin channel. | SSH **key-only**, password & keyboard-interactive off, hardened ciphers/MACs/KEX (STIG crypto policy; ECDSA/RSA keys — ed25519 excluded by policy). | Implemented | — |
 | No default/shared credentials | ISM-1304* | No baked credentials. | No per-host secrets in any artifact; identity from TPM at runtime; `machine-id` empty; host keys regenerated at first boot. | Implemented | — |
diff --git a/docs/ssp.md b/docs/ssp.md
index 050e4e4..999a309 100644
--- a/docs/ssp.md
+++ b/docs/ssp.md
@@ -90,7 +90,7 @@ manifest. One commit = one release = one digest = one manifest entry.
    hash and STIG kernel parameters). No GRUB.
 3. **Initramfs (dracut)** brings up the NIC and performs **802.1X EAP-TLS**
    network authentication using a **private key held in the TPM** (persistent
-   handle `0x81010001`); the client certificate is read from TPM NV index
+   handle `0x81000100`); the client certificate is read from TPM NV index
    `0x01800001`.
 4. On authorisation, **MACsec** is established on the access link (link-layer
    encryption/integrity); the host then obtains an IP **on the MACsec interface**
diff --git a/docs/tpm-enrolment-design.md b/docs/tpm-enrolment-design.md
index 68f5305..4930ab0 100644
--- a/docs/tpm-enrolment-design.md
+++ b/docs/tpm-enrolment-design.md
@@ -8,7 +8,7 @@ end-to-end *minus* the human-approval queue; the only unbuilt piece is the
 **enrolment broker**.
 
 How a diskless host acquires — and keeps — its **one cryptographic identity**: a
-signing key at TPM handle `0x81010001` and a cert at NV index `0x01800001`.
+signing key at TPM handle `0x81000100` and a cert at NV index `0x01800001`.
 Invariant #1 forbids baking any per-host state into the image, so this identity
 **must** be minted at enrolment, at runtime, from the TPM. That single identity is
 then reused for everything: **802.1X EAP-TLS**, the **NVMe hostnqn** (derived from
@@ -28,7 +28,7 @@ separate box — is what makes the two designs one coherent identity story.
 
 ## Design philosophy (forced by the architecture invariants)
 
-1. **One identity, minted once, reused everywhere.** Key `0x81010001` + cert
+1. **One identity, minted once, reused everywhere.** Key `0x81000100` + cert
    NV `0x01800001` = 802.1X identity = NVMe hostnqn (`…:host-<cert-serial>`) =
    mTLS client identity. There is no second secret. (Invariant #1.)
 2. **The private key never leaves the TPM.** Generated *in* the TPM; only a CSR
@@ -74,7 +74,7 @@ are deliberately **split** — conflating them is a security regression:
 
 ### 1. TPM key + NV cert (exists — `tpm-provision.sh`)
 
-Key generated in the TPM, persisted at `0x81010001`; CSR built with it via the
+Key generated in the TPM, persisted at `0x81000100`; CSR built with it via the
 openssl tpm2 provider (key never leaves the TPM); issued cert written DER to NV
 `0x01800001`. At boot, `dot1x-macsec-up.sh` reads the cert from NV, wpa_supplicant
 signs EAP-TLS with the handle key, and the hostnqn is derived from the cert serial.
@@ -158,7 +158,7 @@ pinned for mTLS — one trust anchor across 802.1X, NVMe, and management.
 ```
   empty-NV host (early-boot enrol branch) broker (= fleet-mgr bootstrap)     admin        step-ca
   ───────────────────────────────         ─────────────────────────────     ─────        ───────
-  1. key in TPM @0x81010001
+  1. key in TPM @0x81000100
   2. build CSR (key never leaves)
   3. POST /enrol/request (CSR+context) ─▶  create PENDING, pick nonce,
                                            compute fingerprint
@@ -295,6 +295,26 @@ point (verify the attestation statement before signing). The CA bootstrap alread
 carries a commented `acme-attest` provisioner block
 (`serving/dot1x-bench/step-ca/bootstrap.sh`).
 
+### Signing-key handle choice (and the IDevID option)
+
+The fleet signing key is persisted at **`0x81000100`** — a non-reserved **owner**
+persistent handle. It is deliberately **not** the EK slot `0x81010001` / `0x81010002`
+nor the SRK `0x81000001` / `0x81000002`: firmware and swtpm provisioning routinely
+occupy those (bench-confirmed 2026-07-02 — a Proxmox vTPM had the standard **RSA
+Endorsement Key** at `0x81010001`, restricted-decrypt, with the canonical EK
+authPolicy `837197…`, and its EK cert at NV `0x1c00002`). `EnsureKey` therefore
+also refuses to evict any restricted-decrypt object as a safety net. The handle is
+overridable via `rd.dot1x.handle=` / `fleet-enrol -handle`.
+
+**Future option — IDevID (`0x81020001`):** if/when the EK/AK attestation path above
+lands, the natural home for a TPM-resident *device identity* key is the TCG
+**IDevID** handle `0x81020001` (with **LDevID** at `0x81030001`), per *TPM 2.0 Keys
+for Device Identity and Attestation*. Moving there would align our key with the
+IDevID template + EK-anchored certification flow (the key is certified by an AK that
+chains to the EK) rather than a bare owner primary. Not adopted for v1 (it implies
+the full IDevID template/cert conventions we don't yet follow); revisit together with
+`device-attest-01`.
+
 ## Inventory record born at enrolment
 
 ```
@@ -324,7 +344,7 @@ exists. Enrolment is where it comes into being.
    approve → cert; pubkey match). Ships in `serving/dot1x-bench/docker-compose.yml`.
 3. **Host side — BUILT 2026-07-02 (awaiting bench):** the **inline empty-NV
    trigger** as a static **Go + go-tpm** binary (`files/enrol/`, `fleet-enrol`)
-   talking to `/dev/tpmrm0` directly — ensures the key at `0x81010001`, builds the
+   talking to `/dev/tpmrm0` directly — ensures the key at `0x81000100`, builds the
    CSR, POSTs to the broker, shows the Plymouth fingerprint, polls, writes the leaf
    cert to NV `0x01800001`. A thin dracut GATE hook (`95dot1x-macsec/tpm-enrol.sh`,
    initqueue/settled prio 25) does the empty-NV check + pre-auth DHCP on the
diff --git a/files/dracut/95dot1x-macsec/tpm-enrol.sh b/files/dracut/95dot1x-macsec/tpm-enrol.sh
index 3562b78..3f8ad4f 100644
--- a/files/dracut/95dot1x-macsec/tpm-enrol.sh
+++ b/files/dracut/95dot1x-macsec/tpm-enrol.sh
@@ -39,6 +39,10 @@ TESTMODE=0
 
 # --- knobs (override on the kernel cmdline) ---------------------------------
 NVINDEX=$(getarg rd.dot1x.nvindex=); [ -n "$NVINDEX" ] || NVINDEX=0x01800001
+# Persistent handle for the signing key: a NON-reserved owner handle. NOT the EK
+# slot 0x81010001 (which most firmware/swtpm provisioning already occupies) nor
+# the SRK 0x81000001 — see EnsureKey / CLAUDE.md invariant #1.
+HANDLE=$(getarg rd.dot1x.handle=); [ -n "$HANDLE" ] || HANDLE=0x81000100
 ENROL_URL=$(getarg rd.fleet.enrol_url=); [ -n "$ENROL_URL" ] || ENROL_URL=http://boot.fleet.lab/enrol
 NETTMO=$(getarg rd.dot1x.timeout=); [ -n "$NETTMO" ] || NETTMO=60
 
@@ -104,7 +108,7 @@ info "tpm-enrol: pre-auth lease on $NIC; handing off to fleet-enrol ($ENROL_URL)
 # It drives the TPM (key/CSR/NV), the broker exchange, and the Plymouth
 # fingerprint. Exit 0 = enrolled (reboot to converge); 10 = already enrolled
 # (shouldn't reach here after the NV gate, but treat as normal boot); else fail.
-/usr/sbin/fleet-enrol -url "$ENROL_URL" -iface "$NIC" -nvindex "$NVINDEX"
+/usr/sbin/fleet-enrol -url "$ENROL_URL" -iface "$NIC" -nvindex "$NVINDEX" -handle "$HANDLE"
 rc=$?
 case "$rc" in
     0)
diff --git a/files/enrol/main.go b/files/enrol/main.go
index 0b40db1..35cf5a6 100644
--- a/files/enrol/main.go
+++ b/files/enrol/main.go
@@ -2,7 +2,8 @@
 //
 // Invoked from the dracut hook (95dot1x-macsec/tpm-enrol.sh) ONLY when the
 // secure build boots a host whose TPM NV 0x01800001 is empty. It:
-//  1. ensures an ECDSA signing key exists at TPM handle 0x81010001,
+//  1. ensures an ECDSA signing key exists at a non-reserved owner handle
+//     (default 0x81000100 — deliberately NOT the EK slot 0x81010001),
 //  2. builds a CSR with it (key never leaves the TPM),
 //  3. submits CSR + device context to the enrolment broker, shows the returned
 //     fingerprint on the Plymouth splash, and polls until an admin approves,
@@ -42,7 +43,7 @@ func main() {
 		url       = flag.String("url", "http://boot.fleet.lab/enrol", "enrolment broker base URL")
 		tpmPath   = flag.String("tpm", "/dev/tpmrm0", "TPM device path")
 		nvHex     = flag.String("nvindex", "0x01800001", "TPM NV index for the client cert")
-		handleHex = flag.String("handle", "0x81010001", "TPM persistent handle for the signing key")
+		handleHex = flag.String("handle", "0x81000100", "TPM persistent handle for the signing key (non-reserved owner handle; NOT the EK slot 0x81010001)")
 		cn        = flag.String("cn", "fleet-host", "CSR CommonName (generic; identity is the cert serial)")
 		iface     = flag.String("iface", "", "network interface for the device-context MAC")
 		caFile    = flag.String("cacert", "/etc/dot1x/radius-ca.pem", "CA bundle for an https broker URL")
diff --git a/files/enrol/simtest/tpmsim_test.go b/files/enrol/simtest/tpmsim_test.go
index ced826c..5c307d0 100644
--- a/files/enrol/simtest/tpmsim_test.go
+++ b/files/enrol/simtest/tpmsim_test.go
@@ -30,7 +30,7 @@ func openSim(t *testing.T) transport.TPM {
 
 func TestEnsureKeyAndSignCSR(t *testing.T) {
 	tpm := openSim(t)
-	const h = tpm2.TPMHandle(0x81010001)
+	const h = tpm2.TPMHandle(0x81000100)
 
 	signer, created, err := tpmkey.EnsureKey(tpm, h)
 	if err != nil {
@@ -101,14 +101,15 @@ func TestNVWriteAndPresence(t *testing.T) {
 }
 
 // Regression for the bench failure "key at handle is not ECC ... selector value
-// was 1": an older provisioning path left an RSA key at 0x81010001, and EnsureKey
-// fatally failed trying to read it as ECC. It must now evict the stale key and
-// create a fresh ECC one.
+// was 1": an older provisioning path left an RSA SIGNING key at the enrol handle,
+// and EnsureKey fatally failed trying to read it as ECC. It must now evict the
+// stale key and create a fresh ECC one.
 func TestEnsureKeyEvictsStaleNonECC(t *testing.T) {
 	tpm := openSim(t)
-	const h = tpm2.TPMHandle(0x81010001)
+	const h = tpm2.TPMHandle(0x81000100)
 
-	// Pre-populate the handle with an RSA key (mimics tpm2-tools/openssl default).
+	// Pre-populate the handle with an RSA SIGNING key (mimics tpm2-tools/openssl
+	// default) — SignEncrypt, NOT restricted/decrypt, so it is safe to evict.
 	rsaTmpl := tpm2.TPMTPublic{
 		Type:    tpm2.TPMAlgRSA,
 		NameAlg: tpm2.TPMAlgSHA256,
@@ -163,3 +164,53 @@ func TestEnsureKeyEvictsStaleNonECC(t *testing.T) {
 		t.Fatalf("post-heal ECDSA signature did not verify")
 	}
 }
+
+// Safety guard: if the handle ever holds a restricted-decrypt object (an EK/SRK —
+// e.g. handle misconfigured to the EK slot 0x81010001), EnsureKey must REFUSE to
+// evict it and error, never clobber the TPM's endorsement/storage identity.
+func TestEnsureKeyRefusesToEvictProtectedKey(t *testing.T) {
+	tpm := openSim(t)
+	const h = tpm2.TPMHandle(0x81000100)
+
+	// A restricted decryption primary — the shape of an EK/SRK (storage key).
+	skTmpl := tpm2.TPMTPublic{
+		Type:    tpm2.TPMAlgECC,
+		NameAlg: tpm2.TPMAlgSHA256,
+		ObjectAttributes: tpm2.TPMAObject{
+			FixedTPM: true, FixedParent: true, SensitiveDataOrigin: true,
+			UserWithAuth: true, Restricted: true, Decrypt: true, NoDA: true,
+		},
+		Parameters: tpm2.NewTPMUPublicParms(tpm2.TPMAlgECC, &tpm2.TPMSECCParms{
+			Symmetric: tpm2.TPMTSymDefObject{
+				Algorithm: tpm2.TPMAlgAES,
+				KeyBits:   tpm2.NewTPMUSymKeyBits(tpm2.TPMAlgAES, tpm2.TPMKeyBits(128)),
+				Mode:      tpm2.NewTPMUSymMode(tpm2.TPMAlgAES, tpm2.TPMAlgCFB),
+			},
+			Scheme:  tpm2.TPMTECCScheme{Scheme: tpm2.TPMAlgNull},
+			CurveID: tpm2.TPMECCNistP256,
+			KDF:     tpm2.TPMTKDFScheme{Scheme: tpm2.TPMAlgNull},
+		}),
+	}
+	cp, err := tpm2.CreatePrimary{
+		PrimaryHandle: tpm2.TPMRHOwner, InPublic: tpm2.New2B(skTmpl),
+	}.Execute(tpm)
+	if err != nil {
+		t.Fatalf("create storage-like primary: %v", err)
+	}
+	if _, err := (tpm2.EvictControl{
+		Auth:             tpm2.TPMRHOwner,
+		ObjectHandle:     &tpm2.NamedHandle{Handle: cp.ObjectHandle, Name: cp.Name},
+		PersistentHandle: h,
+	}).Execute(tpm); err != nil {
+		t.Fatalf("persist storage-like key: %v", err)
+	}
+	_, _ = (tpm2.FlushContext{FlushHandle: cp.ObjectHandle}).Execute(tpm)
+
+	// EnsureKey must refuse (error), and must NOT have evicted the object.
+	if _, _, err := tpmkey.EnsureKey(tpm, h); err == nil {
+		t.Fatalf("EnsureKey should refuse to evict a restricted-decrypt (EK/SRK) object")
+	}
+	if _, err := (tpm2.ReadPublic{ObjectHandle: h}).Execute(tpm); err != nil {
+		t.Fatalf("protected object was evicted (should have been left intact): %v", err)
+	}
+}
diff --git a/files/enrol/tpmkey/tpmkey.go b/files/enrol/tpmkey/tpmkey.go
index 051f29b..731dad2 100644
--- a/files/enrol/tpmkey/tpmkey.go
+++ b/files/enrol/tpmkey/tpmkey.go
@@ -1,7 +1,9 @@
 // Package tpmkey — TPM 2.0 operations via go-tpm (pure Go, no CGO, no tpm2-tools
 // / no openssl tpm2 provider). Provides: ensure a persistent ECDSA signing key
-// at 0x81010001, a crypto.Signer backed by it (for CSR signing), and NV cert
-// read-presence + write at 0x01800001. Talks to any transport.TPM, so the same
+// at a non-reserved owner handle (default 0x81000100 — NOT the EK slot
+// 0x81010001, see EnsureKey), a crypto.Signer backed by it (for CSR signing),
+// and NV cert read-presence + write at 0x01800001. Talks to any transport.TPM,
+// so the same
 // code runs against /dev/tpmrm0 (production) and the software simulator (tests).
 //
 // Exported so the ceremony can be tested against the go-tpm simulator from a
@@ -105,21 +107,43 @@ func signerFromPub(tpm transport.TPM, handle tpm2.TPMHandle, name tpm2.TPM2BName
 	return &Signer{tpm: tpm, handle: handle, name: name, pub: pk}, nil
 }
 
+// isProtectedObject reports whether a persistent object is a restricted
+// decryption key — i.e. an Endorsement Key or Storage Root Key. We must NEVER
+// evict one of those (it would destroy the TPM's endorsement/storage identity,
+// including the EK the future EK/AK attestation path depends on). Fail-safe: if
+// the public area can't be parsed, treat it as protected.
+func isProtectedObject(pub2b tpm2.TPM2BPublic) bool {
+	pub, err := pub2b.Contents()
+	if err != nil {
+		return true
+	}
+	a := pub.ObjectAttributes
+	return a.Restricted && a.Decrypt
+}
+
 // ensureKey returns a signer for the persistent key at handle, creating +
 // persisting a fresh ECDSA key there if none exists. Returns created=true when
-// a new key was generated.
+// a new key was generated. handle MUST be a non-reserved owner handle (the fleet
+// default is 0x81000100) — NOT the EK (0x81010001/2) or SRK (0x81000001/2) slots.
 //
 // If the handle already holds an object that is NOT our ECC signing key (e.g. an
-// RSA key left by an older tpm2-tools/openssl provisioning path — go-tpm reports
-// "key at handle is not ECC"), it is treated as STALE and evicted, then a fresh
-// ECC key is created. Safe on the enrol path: this only runs on an empty-NV host,
-// so no issued cert references the old key. Only a valid ECC key is reused.
+// RSA signing key left by an older tpm2-tools/openssl provisioning path — go-tpm
+// reports "key at handle is not ECC"), it is treated as STALE and evicted, then a
+// fresh ECC key is created. Safe on the enrol path: this only runs on an empty-NV
+// host, so no issued cert references the old key. Only a valid ECC key is reused.
+// A restricted-decrypt object (EK/SRK) is NEVER evicted — it errors instead, which
+// only happens if handle was misconfigured to a reserved slot.
 func EnsureKey(tpm transport.TPM, handle tpm2.TPMHandle) (signer *Signer, created bool, err error) {
 	if rp, e := (tpm2.ReadPublic{ObjectHandle: handle}).Execute(tpm); e == nil {
-		if s, e2 := signerFromPub(tpm, handle, rp.Name, rp.OutPublic); e2 == nil {
-			return s, false, nil // our ECC key is already there — reuse it
+		// Guard FIRST: never touch a restricted-decrypt object (EK/SRK). An ECC
+		// EK/SRK would otherwise parse as a usable ECC key below and be "reused".
+		if isProtectedObject(rp.OutPublic) {
+			return nil, false, fmt.Errorf("refusing to evict a restricted-decrypt object (EK/SRK?) at handle %#x — configure a non-reserved owner handle (e.g. 0x81000100)", uint32(handle))
 		}
-		// Stale/wrong-type key occupying the handle — evict so we can recreate.
+		if s, e2 := signerFromPub(tpm, handle, rp.Name, rp.OutPublic); e2 == nil {
+			return s, false, nil // our ECC signing key is already there — reuse it
+		}
+		// Stale/wrong-type signing key occupying the handle — evict so we recreate.
 		if _, e2 := (tpm2.EvictControl{
 			Auth:             tpm2.TPMRHOwner,
 			ObjectHandle:     &tpm2.NamedHandle{Handle: handle, Name: rp.Name},
diff --git a/files/etc/dot1x/wpa_supplicant-dot1x.conf b/files/etc/dot1x/wpa_supplicant-dot1x.conf
index 7a39cda..8e0e192 100644
--- a/files/etc/dot1x/wpa_supplicant-dot1x.conf
+++ b/files/etc/dot1x/wpa_supplicant-dot1x.conf
@@ -14,8 +14,11 @@ network={
     client_cert="/run/dot1x/client.pem"
 
     # BENCH-VERIFY: TPM key reference method on your wpa_supplicant build.
+    # Handle is the fleet signing-key handle (non-reserved owner handle; NOT the
+    # EK slot 0x81010001 — see CLAUDE.md invariant #1). Keep in sync with the
+    # enrolment -handle / rd.dot1x.handle default.
     # Option A (OpenSSL tpm2 provider, direct persistent handle):
-    private_key="handle:0x81010001"
+    private_key="handle:0x81000100"
     # Option B (tpm2-pkcs11 with a store regenerated into /run at boot):
     # private_key="pkcs11:token=fleet;object=dot1x-key;type=private;pin-value=..."
 
diff --git a/scripts/extract-artifacts.sh b/scripts/extract-artifacts.sh
index 1c5459e..befa0b2 100755
--- a/scripts/extract-artifacts.sh
+++ b/scripts/extract-artifacts.sh
@@ -223,7 +223,7 @@ printf '%s' \
   "$STIG_FRAGMENT" \
   "$DOT1X_FRAGMENT" \
   "rd.neednet=1 systemd.volatile=overlay " \
-  "rd.dot1x.nvindex=0x01800001 rd.dot1x.timeout=60 " \
+  "rd.dot1x.nvindex=0x01800001 rd.dot1x.handle=0x81000100 rd.dot1x.timeout=60 " \
   "rd.fleet.enrol_url=${ENROL_URL} " \
   "rd.nvmf.discover=tcp,${NVMET_TRADDR},4420 " \
   "root=/dev/mapper/root rootfstype=erofs rootflags=ro " \
diff --git a/serving/dot1x-bench/README.md b/serving/dot1x-bench/README.md
index 4346449..1db4c37 100644
--- a/serving/dot1x-bench/README.md
+++ b/serving/dot1x-bench/README.md
@@ -83,7 +83,7 @@ qm set <vmid-A> --tpmstate0 <storage>:1,version=v2.0
 
 3. **Enrol each workstation's TPM** (one-shot, on a provisioning network that can
    reach step-ca) — see `enrol/tpm-provision.sh`: generates the key **in** the TPM
-   at `0x81010001`, builds a CSR with it, has step-ca sign it, writes the cert to
+   at `0x81000100`, builds a CSR with it, has step-ca sign it, writes the cert to
    NV `0x01800001`. Each host gets a unique cert → unique hostnqn.
 
 4. **Set up the authenticator** — `authenticator/setup-link.sh` (bridge + macsec
diff --git a/serving/dot1x-bench/enrol/tpm-provision.sh b/serving/dot1x-bench/enrol/tpm-provision.sh
index 25cfd91..29ee814 100755
--- a/serving/dot1x-bench/enrol/tpm-provision.sh
+++ b/serving/dot1x-bench/enrol/tpm-provision.sh
@@ -3,7 +3,8 @@
 #
 # One-shot enrolment for ONE workstation. Models the real flow (invariant #1:
 # per-host identity is created at enrolment, never baked into the image):
-#   1. generate a signing key INSIDE the TPM, persist it at handle 0x81010001
+#   1. generate a signing key INSIDE the TPM, persist it at handle 0x81000100
+#      (non-reserved owner handle; NOT the EK slot 0x81010001)
 #   2. build a CSR using that TPM key (private key never leaves the TPM)
 #   3. have step-ca sign it (token-gated 'enrol' provisioner)
 #   4. write the issued cert (DER) to TPM NV index 0x01800001
@@ -25,7 +26,7 @@
 set -euo pipefail
 
 HOSTID=${1:?usage: tpm-provision.sh <host-id>   e.g. ws-vm-a}
-HANDLE=${HANDLE:-0x81010001}
+HANDLE=${HANDLE:-0x81000100}
 NVINDEX=${NVINDEX:-0x01800001}
 export TPM2TOOLS_TCTI="${TPM2TOOLS_TCTI:-device:/dev/tpmrm0}"
 CA_DNS=${CA_DNS:-ca.fleet.lab}; CA_PORT=${CA_PORT:-8443}
diff --git a/serving/dot1x-bench/enrol/tpm-selftest.sh b/serving/dot1x-bench/enrol/tpm-selftest.sh
index bd28059..f63d5bb 100755
--- a/serving/dot1x-bench/enrol/tpm-selftest.sh
+++ b/serving/dot1x-bench/enrol/tpm-selftest.sh
@@ -4,7 +4,7 @@
 #
 # Run as root on a booted workstation (the open-port test image is fine — it
 # ships the same tooling). Uses SCRATCH handle/NV and cleans them up, so it never
-# touches the real 0x81010001 / 0x01800001. Pass --use-real-handles to exercise
+# touches the real 0x81000100 / 0x01800001. Pass --use-real-handles to exercise
 # the actual locations instead (still cleaned up unless --keep).
 #
 # It validates, in order:
@@ -24,7 +24,7 @@ for a in "$@"; do case "$a" in
 esac; done
 
 export TPM2TOOLS_TCTI="${TPM2TOOLS_TCTI:-device:/dev/tpmrm0}"
-if [ "$USE_REAL" = 1 ]; then HANDLE=0x81010001; NV=0x01800001
+if [ "$USE_REAL" = 1 ]; then HANDLE=0x81000100; NV=0x01800001
 else HANDLE=0x81008000; NV=0x01500000; fi
 
 WORK=$(mktemp -d); PASS=0; FAIL=0; SKIP=0