diff --git a/agent/src/certs/nativeRenew.ts b/agent/src/certs/nativeRenew.ts
index 34e5910..ac92762 100644
--- a/agent/src/certs/nativeRenew.ts
+++ b/agent/src/certs/nativeRenew.ts
@@ -72,7 +72,9 @@ const defaultMtlsRequest: MtlsRequest = (url, tls, init) =>
         headers: init.headers,
         cert: tls.cert,
         key: tls.key,
-        ca: tls.ca,
+        // ca omitted ⇒ verify the server against the system roots (LE-fronted CP). Present only when a
+        // private CA is pinned (not for /renew).
+        ...(tls.ca !== undefined ? { ca: tls.ca } : {}),
         rejectUnauthorized: tls.rejectUnauthorized, // always true (anti-MITM, INV14)
       },
       (res) => {
@@ -129,7 +131,12 @@ export function createMtlsFetch(
   const request = opts.request ?? defaultMtlsRequest
   const shim = async (input: Parameters<typeof fetch>[0], init?: RequestInit): Promise<Response> => {
     const url = typeof input === 'string' ? input : input.toString()
-    const tls = buildTlsOptions(ks, { ...(opts.certParser ? { certParser: opts.certParser } : {}) })
+    // Present the current frp-client leaf (client auth), but verify the /renew SERVER cert against the
+    // SYSTEM roots — its host (the LE-fronted control-plane) is publicly trusted; pinning the private
+    // enroll caChain here fails with "unable to get local issuer certificate". So drop `ca` (absent →
+    // node uses the default roots); rejectUnauthorized stays true.
+    const full = buildTlsOptions(ks, { ...(opts.certParser ? { certParser: opts.certParser } : {}) })
+    const tls: TlsClientOptions = { cert: full.cert, key: full.key, rejectUnauthorized: full.rejectUnauthorized }
     const reqInit: MtlsRequestInit = {
       method: init?.method ?? 'GET',
       headers: toHeaderRecord(init?.headers),
diff --git a/agent/src/certs/pem.ts b/agent/src/certs/pem.ts
new file mode 100644
index 0000000..b031f31
--- /dev/null
+++ b/agent/src/certs/pem.ts
@@ -0,0 +1,33 @@
+/**
+ * PEM helpers shared by the native enroll (enroll/pair.ts) and renew (certs/rotation.ts) paths.
+ *
+ * The control-plane returns the frp-client leaf + CA chain as base64-encoded DER (cert as a string,
+ * caChain as a string[]); the keystore + frpc need PEM files. `derBase64ToPem` wraps a base64 DER body
+ * back into CERTIFICATE armor at 64 columns.
+ */
+
+/** base64(DER) → PEM (CERTIFICATE armor, 64-col wrapped). */
+export function derBase64ToPem(derBase64: string, label = 'CERTIFICATE'): string {
+  const body = derBase64.replace(/\s+/g, '')
+  const lines = body.match(/.{1,64}/g) ?? []
+  return `-----BEGIN ${label}-----\n${lines.join('\n')}\n-----END ${label}-----\n`
+}
+
+/**
+ * Normalize a control-plane cert response ({cert: base64 DER, caChain: base64 DER[]}) to PEM strings
+ * for the keystore. Throws if the shape is wrong. Shared by enroll + renew so both stay in lockstep.
+ */
+export function certResponseToPem(cert: unknown, caChain: unknown): { certPem: string; caChainPem: string } {
+  if (
+    typeof cert !== 'string' ||
+    !Array.isArray(caChain) ||
+    caChain.length === 0 ||
+    !caChain.every((c) => typeof c === 'string')
+  ) {
+    throw new Error('cert response missing cert/caChain')
+  }
+  return {
+    certPem: derBase64ToPem(cert),
+    caChainPem: (caChain as string[]).map((c) => derBase64ToPem(c)).join(''),
+  }
+}
diff --git a/agent/src/certs/rotation.ts b/agent/src/certs/rotation.ts
index 6d7b345..9ad15e0 100644
--- a/agent/src/certs/rotation.ts
+++ b/agent/src/certs/rotation.ts
@@ -15,6 +15,7 @@ import type { Keystore } from '../keys/keystore.js'
 import type { TimerLike } from '../transport/seams.js'
 import { createBackoff, type BackoffPolicy } from '../transport/backoff.js'
 import { buildCsr } from '../enroll/csr.js'
+import { certResponseToPem } from './pem.js'
 
 export const DEFAULT_RENEW_BEFORE_MS = 5 * 60_000 // renew 5 min before expiry
 
@@ -64,11 +65,11 @@ export async function renewCert(
   })
   if (res.status === 403) return 'revoked'
   if (!res.ok) throw new Error(`cert renewal failed: HTTP ${res.status}`)
-  const json = (await res.json()) as { cert?: string; caChain?: string }
-  if (typeof json.cert !== 'string' || typeof json.caChain !== 'string') {
-    throw new Error('cert renewal response missing cert/caChain')
-  }
-  ks.saveCert(json.cert, json.caChain) // atomic whole-file install
+  // The control-plane returns cert=base64(DER) + caChain=base64(DER)[]; normalize to PEM for the
+  // keystore + frpc (same shape as native enroll).
+  const json = (await res.json()) as { cert?: unknown; caChain?: unknown }
+  const { certPem, caChainPem } = certResponseToPem(json.cert, json.caChain)
+  ks.saveCert(certPem, caChainPem) // atomic whole-file install
   return 'rotated'
 }
 
diff --git a/agent/src/enroll/pair.ts b/agent/src/enroll/pair.ts
index 3dffb3e..ea7a0a9 100644
--- a/agent/src/enroll/pair.ts
+++ b/agent/src/enroll/pair.ts
@@ -15,6 +15,7 @@ import type { EnrollResult } from 'relay-contracts'
 import type { AgentIdentity } from '../keys/identity.js'
 import type { Keystore } from '../keys/keystore.js'
 import { buildCsr } from './csr.js'
+import { derBase64ToPem } from '../certs/pem.js'
 
 /** v0.8 shared-token gate vs v0.9+ per-host Ed25519. Default is `'ed25519'` from v0.9. */
 export type EnrollMode = 'token' | 'ed25519'
@@ -69,16 +70,6 @@ interface EnrollResponseJson {
   hostContentSecret: string // base64url over the wire
 }
 
-/**
- * base64(DER) → PEM. The native /enroll returns the leaf + CA certs as base64-encoded DER; the
- * keystore + frpc need PEM files, so wrap the base64 body at 64 columns in CERTIFICATE armor.
- */
-function derBase64ToPem(derBase64: string, label = 'CERTIFICATE'): string {
-  const body = derBase64.replace(/\s+/g, '')
-  const lines = body.match(/.{1,64}/g) ?? []
-  return `-----BEGIN ${label}-----\n${lines.join('\n')}\n-----END ${label}-----\n`
-}
-
 function parseEnrollResult(json: unknown, allowMissingContentSecret = false): EnrollResult {
   const j = json as Partial<EnrollResponseJson>
   if (typeof j.hostContentSecret !== 'string') {
diff --git a/agent/src/transport/dial.ts b/agent/src/transport/dial.ts
index cd2d9dc..8e645c9 100644
--- a/agent/src/transport/dial.ts
+++ b/agent/src/transport/dial.ts
@@ -25,7 +25,13 @@ export class CertExpiredError extends Error {
 export interface TlsClientOptions {
   readonly cert: string
   readonly key: string
-  readonly ca: string
+  /**
+   * CA(s) to verify the SERVER cert against. Set to the private tunnel CA for the relay dial; left
+   * undefined for a request whose server is publicly trusted (the LE-fronted control-plane /renew) so
+   * Node verifies against the system roots — pinning the private CA there fails with "unable to get
+   * local issuer certificate".
+   */
+  readonly ca?: string
   readonly rejectUnauthorized: true
 }
 
diff --git a/agent/test/nativeRenew.test.ts b/agent/test/nativeRenew.test.ts
index def5445..b4d3a4e 100644
--- a/agent/test/nativeRenew.test.ts
+++ b/agent/test/nativeRenew.test.ts
@@ -69,7 +69,9 @@ describe('createMtlsFetch (A5)', () => {
     expect(await res.json()).toEqual({ cert: 'NEW', caChain: 'NEWCA' })
     expect(seen[0]!.url).toBe('https://cp.example.com/renew')
     expect(seen[0]!.tls.cert).toBe('LEAFCERT')
-    expect(seen[0]!.tls.ca).toBe('CACHAIN')
+    // /renew verifies the LE-fronted control-plane against the SYSTEM roots, so no private CA is pinned
+    // (pinning the enroll caChain here fails with "unable to get local issuer certificate").
+    expect(seen[0]!.tls.ca).toBeUndefined()
     expect(seen[0]!.tls.rejectUnauthorized).toBe(true)
     expect(String(seen[0]!.tls.key)).toContain('PRIVATE KEY') // in-process PKCS#8 key, mTLS only
     expect(seen[0]!.init.method).toBe('POST')
@@ -166,7 +168,7 @@ describe('startNativeAutoRenew (A5 end-to-end)', () => {
     const timer = new FakeTimer()
     const request: MtlsRequest = async () => ({
       status: 200,
-      body: JSON.stringify({ cert: 'FRESHLEAF', caChain: 'CACHAIN' }),
+      body: JSON.stringify({ cert: 'FRESHLEAF', caChain: ['CACHAIN'] }),
     })
     const restartChild = vi.fn()
     const stop = vi.fn()
@@ -183,7 +185,7 @@ describe('startNativeAutoRenew (A5 end-to-end)', () => {
     timer.advance(1000) // renewal fires at ~2/3 TTL
     await flush()
 
-    expect(ks.loadCert()!.certPem).toBe('FRESHLEAF') // atomic persist
+    expect(ks.loadCert()!.certPem).toContain('FRESHLEAF') // atomic persist
     expect(restartChild).toHaveBeenCalledTimes(1) // frpc restarted onto the fresh leaf
     expect(stop).not.toHaveBeenCalled()
     controller.stop()
@@ -222,7 +224,7 @@ describe('startNativeAutoRenew (A5 end-to-end)', () => {
     const request: MtlsRequest = async () => {
       calls += 1
       if (calls === 1) throw new Error('ECONNREFUSED')
-      return { status: 200, body: JSON.stringify({ cert: 'FRESHLEAF', caChain: 'CACHAIN' }) }
+      return { status: 200, body: JSON.stringify({ cert: 'FRESHLEAF', caChain: ['CACHAIN'] }) }
     }
     const restartChild = vi.fn()
     const stop = vi.fn()
@@ -252,7 +254,7 @@ describe('startNativeAutoRenew (A5 end-to-end)', () => {
 
     timer.advance(500) // backoff retry fires and succeeds
     await flush()
-    expect(ks.loadCert()!.certPem).toBe('FRESHLEAF')
+    expect(ks.loadCert()!.certPem).toContain('FRESHLEAF')
     expect(restartChild).toHaveBeenCalledTimes(1)
     expect(lines.join('\n')).not.toContain('LEAFCERT')
     controller.stop()
diff --git a/agent/test/nativeRenewTransport.test.ts b/agent/test/nativeRenewTransport.test.ts
index e8f8d1f..893462e 100644
--- a/agent/test/nativeRenewTransport.test.ts
+++ b/agent/test/nativeRenewTransport.test.ts
@@ -115,7 +115,8 @@ describe('defaultMtlsRequest transport (A5 — real node:https)', () => {
     expect(seenOpts.rejectUnauthorized).toBe(true) // anti-MITM (INV14)
     expect(seenOpts.method).toBe('POST')
     expect(seenOpts.cert).toBe('LEAFCERT')
-    expect(seenOpts.ca).toBe('CACHAIN')
+    // ca omitted ⇒ verify the LE-fronted control-plane against the system roots (not the private CA).
+    expect(seenOpts.ca).toBeUndefined()
     expect(String(seenOpts.key)).toContain('PRIVATE KEY') // in-process PKCS#8 key
     // HIGH fix: a socket timeout is armed with the sane default so a stall can never hang forever.
     expect(seenReq!.setTimeoutCalls).toHaveLength(1)
diff --git a/agent/test/rotation.test.ts b/agent/test/rotation.test.ts
index 1410079..2567f30 100644
--- a/agent/test/rotation.test.ts
+++ b/agent/test/rotation.test.ts
@@ -53,10 +53,10 @@ describe('renewCert (T13)', () => {
   it('installs a fresh cert atomically on success (same key)', async () => {
     const { dir, ks } = enrolledKs()
     const before = ks.loadIdentity()!.publicKey
-    const fetchImpl = vi.fn(async () => jsonRes(200, { cert: 'NEWCERT', caChain: 'NEWCA' }))
+    const fetchImpl = vi.fn(async () => jsonRes(200, { cert: 'NEWCERT', caChain: ['NEWCA'] }))
     const out = await renewCert(CFG, ks.loadIdentity()!, ks, fetchImpl as unknown as typeof fetch)
     expect(out).toBe('rotated')
-    expect(ks.loadCert()).toEqual({ certPem: 'NEWCERT', caChainPem: 'NEWCA' })
+    expect(ks.loadCert()!.certPem).toContain('NEWCERT'); expect(ks.loadCert()!.caChainPem).toContain('NEWCA')
     // pubkey unchanged — only the cert rotated
     expect(Buffer.from(ks.loadIdentity()!.publicKey).equals(Buffer.from(before))).toBe(true)
     rmSync(dir, { recursive: true, force: true })
@@ -102,7 +102,7 @@ describe('createCertRotator (T13)', () => {
     const rotator = createCertRotator(CFG, ks.loadIdentity()!, ks, {
       timer,
       renewBeforeMs: 1000,
-      fetchImpl: (async () => jsonRes(200, { cert: 'NEWCERT', caChain: 'NEWCA' })) as unknown as typeof fetch,
+      fetchImpl: (async () => jsonRes(200, { cert: 'NEWCERT', caChain: ['NEWCA'] })) as unknown as typeof fetch,
       now: () => new Date(0),
       parseCert: () => new Date(2000),
     })
@@ -114,7 +114,7 @@ describe('createCertRotator (T13)', () => {
     timer.advance(1000)
     await flush()
     expect(rotated).toBe(1)
-    expect(ks.loadCert()!.certPem).toBe('NEWCERT')
+    expect(ks.loadCert()!.certPem).toContain('NEWCERT')
     rotator.stop()
     rmSync(dir, { recursive: true, force: true })
   })
@@ -126,7 +126,7 @@ describe('createCertRotator (T13)', () => {
     const fetchImpl = (async () => {
       calls += 1
       if (calls === 1) throw new Error('network down')
-      return jsonRes(200, { cert: 'NEWCERT', caChain: 'NEWCA' })
+      return jsonRes(200, { cert: 'NEWCERT', caChain: ['NEWCA'] })
     }) as unknown as typeof fetch
     const errors: unknown[] = []
     let rotated = 0
@@ -154,7 +154,7 @@ describe('createCertRotator (T13)', () => {
     timer.advance(500)
     await flush()
     expect(rotated).toBe(1)
-    expect(ks.loadCert()!.certPem).toBe('NEWCERT')
+    expect(ks.loadCert()!.certPem).toContain('NEWCERT')
     rotator.stop()
     rmSync(dir, { recursive: true, force: true })
   })