diff --git a/src/main/comfybuilder/index.ts b/src/main/comfybuilder/index.ts
index dddfb3a25..9ce101b12 100644
--- a/src/main/comfybuilder/index.ts
+++ b/src/main/comfybuilder/index.ts
@@ -12,7 +12,7 @@
  * const client = new ComfyBuilderClient({ baseUrl, auth: tokenStoreAdapter })
  * const builds = await client.listBuilds()                     // render tiles
  * const { artifacts } = await client.getVersion(versionId)
- * const artifact = selectArtifactForHost(artifacts, { os: hostOs(), gpu })
+ * const artifact = selectArtifactForHost(artifacts, { os: hostOs(), arch: process.arch, gpu })
  * await installArtifact({ artifact, client, installPath, cacheDir, onProgress })
  * const launch = buildLaunchSpec(installPath, { launchArgs })
  * ```
diff --git a/src/main/comfybuilder/targets.test.ts b/src/main/comfybuilder/targets.test.ts
index 40ef4fd6b..951d32303 100644
--- a/src/main/comfybuilder/targets.test.ts
+++ b/src/main/comfybuilder/targets.test.ts
@@ -31,28 +31,40 @@ describe('hostOs', () => {
 
 describe('selectArtifactForHost', () => {
   it.each<[string, Host, string | null]>([
-    ['exact os+gpu (windows/nvidia)', { os: 'windows', gpu: 'nvidia' }, 'windows-nvidia'],
-    ['cpu fallback (windows host, cpu gpu)', { os: 'windows', gpu: 'cpu' }, 'windows-cpu'],
-    ['os filter rejects a mac nvidia host', { os: 'mac', gpu: 'nvidia' }, null],
-    ['no artifact for the host os (mac)', { os: 'mac', gpu: 'mps' }, null],
-    ['linux nvidia', { os: 'linux', gpu: 'nvidia' }, 'linux-nvidia']
+    [
+      'exact os+gpu (windows/nvidia)',
+      { os: 'windows', arch: 'x64', gpu: 'nvidia' },
+      'windows-nvidia'
+    ],
+    [
+      'cpu fallback (windows host, cpu gpu)',
+      { os: 'windows', arch: 'x64', gpu: 'cpu' },
+      'windows-cpu'
+    ],
+    ['os filter rejects a mac nvidia host', { os: 'mac', arch: 'arm64', gpu: 'nvidia' }, null],
+    ['no artifact for the host os (mac)', { os: 'mac', arch: 'arm64', gpu: 'mps' }, null],
+    ['linux nvidia', { os: 'linux', arch: 'x64', gpu: 'nvidia' }, 'linux-nvidia']
   ])('%s', (_name, host, expectedId) => {
     expect(selectArtifactForHost(catalog, host)?.id ?? null).toBe(expectedId)
   })
 
   it('prefers exact gpu over the cpu fallback', () => {
     const both = [art('linux', 'cpu'), art('linux', 'nvidia')]
-    expect(selectArtifactForHost(both, { os: 'linux', gpu: 'nvidia' })?.gpu).toBe('nvidia')
+    expect(selectArtifactForHost(both, { os: 'linux', arch: 'x64', gpu: 'nvidia' })?.gpu).toBe(
+      'nvidia'
+    )
   })
 
   it('ignores non-ready artifacts', () => {
     const notReady = [art('linux', 'nvidia', { status: 'building' })]
-    expect(selectArtifactForHost(notReady, { os: 'linux', gpu: 'nvidia' })).toBeNull()
+    expect(selectArtifactForHost(notReady, { os: 'linux', arch: 'x64', gpu: 'nvidia' })).toBeNull()
   })
 
   it('an nvidia host still installs a cpu-only build', () => {
     const cpuOnly = [art('windows', 'cpu')]
-    expect(selectArtifactForHost(cpuOnly, { os: 'windows', gpu: 'nvidia' })?.gpu).toBe('cpu')
+    expect(selectArtifactForHost(cpuOnly, { os: 'windows', arch: 'x64', gpu: 'nvidia' })?.gpu).toBe(
+      'cpu'
+    )
   })
 
   it('prefers the matching accelVariant among same-gpu builds', () => {
@@ -61,20 +73,40 @@ describe('selectArtifactForHost', () => {
       art('linux', 'nvidia', { id: 'cu128', accelVariant: 'cu128' })
     ]
     expect(
-      selectArtifactForHost(cudas, { os: 'linux', gpu: 'nvidia', accelVariant: 'cu128' })?.id
+      selectArtifactForHost(cudas, {
+        os: 'linux',
+        arch: 'x64',
+        gpu: 'nvidia',
+        accelVariant: 'cu128'
+      })?.id
     ).toBe('cu128')
   })
 
   it('is deterministic (not input-order dependent) when accel ties', () => {
     const a = art('linux', 'nvidia', { id: 'cu118', accelVariant: 'cu118' })
     const b = art('linux', 'nvidia', { id: 'cu128', accelVariant: 'cu128' })
-    const host = { os: 'linux', gpu: 'nvidia' } as const
+    const host = { os: 'linux', arch: 'x64', gpu: 'nvidia' } as const
     expect(selectArtifactForHost([a, b], host)?.id).toBe('cu128')
     expect(selectArtifactForHost([b, a], host)?.id).toBe('cu128')
   })
 })
 
 describe('compatibleArtifactsForHost', () => {
+  it.each<Host>([
+    { os: 'windows', arch: 'arm64', gpu: 'nvidia' },
+    { os: 'windows', arch: 'arm64', gpu: 'cpu' },
+    { os: 'linux', arch: 'arm64', gpu: 'nvidia' },
+    { os: 'linux', arch: 'arm64', gpu: 'cpu' },
+    { os: 'linux', arch: 'riscv64', gpu: 'cpu' },
+    { os: 'windows', arch: 'ia32', gpu: 'cpu' },
+    { os: 'mac', arch: 'arm64', gpu: 'mps' },
+    { os: 'mac', arch: 'x64', gpu: 'cpu' }
+  ])('rejects unverified architectures: $os/$arch/$gpu', (host) => {
+    const targets = [art(host.os, host.gpu), art(host.os, 'cpu')]
+    expect(compatibleArtifactsForHost(targets, host)).toEqual([])
+    expect(selectArtifactForHost(targets, host)).toBeNull()
+  })
+
   it('returns exact GPU targets before CPU fallbacks', () => {
     const targets = [
       art('windows', 'cpu', { id: 'cpu' }),
@@ -83,7 +115,7 @@ describe('compatibleArtifactsForHost', () => {
     ]
 
     expect(
-      compatibleArtifactsForHost(targets, { os: 'windows', gpu: 'nvidia' }).map(
+      compatibleArtifactsForHost(targets, { os: 'windows', arch: 'x64', gpu: 'nvidia' }).map(
         (artifact) => artifact.id
       )
     ).toEqual(['cuda-128', 'cuda-118', 'cpu'])
@@ -98,7 +130,7 @@ describe('compatibleArtifactsForHost', () => {
     ]
 
     expect(
-      compatibleArtifactsForHost(targets, { os: 'windows', gpu: 'nvidia' }).map(
+      compatibleArtifactsForHost(targets, { os: 'windows', arch: 'x64', gpu: 'nvidia' }).map(
         (artifact) => artifact.id
       )
     ).toEqual(['ready'])
diff --git a/src/main/comfybuilder/targets.ts b/src/main/comfybuilder/targets.ts
index e50a3b3fd..c1f3900bf 100644
--- a/src/main/comfybuilder/targets.ts
+++ b/src/main/comfybuilder/targets.ts
@@ -3,10 +3,23 @@
  *
  * A version fans out into per-target artifacts (os x gpu x accel). This module
  * identifies and ranks every artifact the host can run. Pure functions, no I/O;
- * the caller supplies the host GPU (Desktop already detects it).
+ * the caller supplies the host architecture and GPU (Desktop already detects them).
  */
 import type { Artifact, ArtifactGpu, ArtifactOs, Host } from './types'
 
+/**
+ * Builder's Artifact API has no CPU architecture field. Its curated base images
+ * currently ship x64 Python for Windows and Linux; macOS is not buildable.
+ * Keep unknown targets blocked until Builder exposes their architecture.
+ * Source: Comfy-Org/cloud services/comfy-builder/sandbox-images/catalog/base_images.yaml
+ * and apiserver/menus/build_targets_helpers.go.
+ */
+const BUILDER_ARCHITECTURES: Record<ArtifactOs, NodeJS.Architecture | null> = {
+  linux: 'x64',
+  windows: 'x64',
+  mac: null
+}
+
 /** The host OS as a build-target token, from Node's `process.platform`. */
 export function hostOs(): ArtifactOs {
   switch (process.platform) {
@@ -21,7 +34,7 @@ export function hostOs(): ArtifactOs {
 
 /**
  * Rank an artifact's GPU against the host's, higher is better. An exact match
- * wins; a CPU artifact is the universal fallback (every host can run it); an
+ * wins; a CPU artifact is the fallback within a matching OS and architecture; an
  * NVIDIA host tolerates a CPU build but never the reverse.
  */
 function gpuScore(artifactGpu: ArtifactGpu, hostGpu: ArtifactGpu): number {
@@ -50,6 +63,7 @@ function score(a: Artifact, host: Host): number {
 export function compatibleArtifactsForHost(artifacts: readonly Artifact[], host: Host): Artifact[] {
   return artifacts
     .filter((artifact) => artifact.status === 'ready' && artifact.os === host.os)
+    .filter((artifact) => BUILDER_ARCHITECTURES[artifact.os] === host.arch)
     .filter((artifact) => score(artifact, host) > 0)
     .sort((a, b) => {
       const scoreDifference = score(b, host) - score(a, host)
@@ -61,7 +75,7 @@ export function compatibleArtifactsForHost(artifacts: readonly Artifact[], host:
 }
 
 /**
- * Pick the best `ready` artifact for the host: OS must match, then GPU fit
+ * Pick the best `ready` artifact for the host: OS and architecture must match, then GPU fit
  * (exact, else CPU fallback), then a preferred `accelVariant`, then a
  * deterministic tie-break. Returns null when the version has no runnable
  * artifact for this machine (e.g. a windows-only build on mac).
diff --git a/src/main/comfybuilder/types.ts b/src/main/comfybuilder/types.ts
index c259b0358..9057d7d6a 100644
--- a/src/main/comfybuilder/types.ts
+++ b/src/main/comfybuilder/types.ts
@@ -57,6 +57,7 @@ export interface Artifact {
 /** The machine an install targets: which artifact to pick. */
 export interface Host {
   os: ArtifactOs
+  arch: NodeJS.Architecture
   gpu: ArtifactGpu
   /** Preferred accelerator build (e.g. `cu128`) when a gpu ships several. Optional. */
   accelVariant?: string
diff --git a/src/main/devplatform/builds.test.ts b/src/main/devplatform/builds.test.ts
index 93ec8cc7d..4d98d4381 100644
--- a/src/main/devplatform/builds.test.ts
+++ b/src/main/devplatform/builds.test.ts
@@ -3,14 +3,18 @@ import { beforeEach, describe, expect, it, vi } from 'vitest'
 import {
   listCompleteVersions,
   listBuildRows,
+  resolveHost,
   resolveHostArtifact,
   resolveHostArtifactForVersion,
   resolveSelectedHostArtifact
 } from './builds'
 import { clearVersionCache, getCachedVersions } from './versionCache'
 import type { Artifact, Build, BuildVersion, Host } from '../comfybuilder'
+import { detectGPUCached } from '../lib/gpu'
 
-const HOST: Host = { os: 'linux', gpu: 'nvidia' }
+vi.mock('../lib/gpu', () => ({ detectGPUCached: vi.fn() }))
+
+const HOST: Host = { os: 'linux', arch: 'x64', gpu: 'nvidia' }
 
 beforeEach(() => clearVersionCache())
 
@@ -46,6 +50,56 @@ function stubClient(opts: {
   }
 }
 
+describe('resolveHost', () => {
+  it('includes the process architecture alongside detected OS and GPU', async () => {
+    vi.mocked(detectGPUCached).mockResolvedValueOnce({ id: 'nvidia', label: 'NVIDIA', model: null })
+    expect(await resolveHost()).toEqual({
+      os:
+        process.platform === 'win32' ? 'windows' : process.platform === 'darwin' ? 'mac' : 'linux',
+      arch: process.arch,
+      gpu: 'nvidia'
+    })
+  })
+})
+
+describe.each(['windows', 'linux'] as const)('Managed Builds on %s ARM64', (os) => {
+  const host: Host = { os, arch: 'arm64', gpu: 'nvidia' }
+  const client = () =>
+    stubClient({
+      builds: [{ id: 'd1', name: 'Build' }],
+      versionsByBuild: { d1: [version(2, 'complete')] },
+      artifactsByVersion: {
+        v2: [
+          artifact({ id: 'cuda', os }),
+          artifact({ id: 'cpu', os, gpu: 'cpu', accelVariant: 'cpu' })
+        ]
+      }
+    })
+
+  it.each([undefined, 1])(
+    'blocks installation and updates (installed version: %s)',
+    async (installedVersion) => {
+      const installed =
+        installedVersion === undefined ? undefined : new Map([['d1', installedVersion]])
+      const [row] = await listBuildRows(client() as never, host, installed)
+      expect(row).toMatchObject({
+        state: 'platform-mismatch',
+        blockedReason: 'noArtifactForMachine'
+      })
+      expect(row?.releaseTargets).toBeUndefined()
+    }
+  )
+
+  it('rejects latest, explicitly selected, and update artifacts', async () => {
+    const api = client()
+    expect(await resolveHostArtifact(api as never, host, 'd1')).toBeNull()
+    for (const id of ['cuda', 'cpu']) {
+      expect(await resolveSelectedHostArtifact(api as never, host, 'd1', 2, id)).toBeNull()
+    }
+    expect(await resolveHostArtifactForVersion(api as never, host, 'd1', 2)).toBeNull()
+  })
+})
+
 describe('listBuildRows', () => {
   it('marks a build installable when the latest complete version has a host artifact', async () => {
     const client = stubClient({
diff --git a/src/main/devplatform/builds.ts b/src/main/devplatform/builds.ts
index 8fa57f624..60e3677b2 100644
--- a/src/main/devplatform/builds.ts
+++ b/src/main/devplatform/builds.ts
@@ -75,13 +75,13 @@ export interface ResolvedHostArtifact {
   version: number
 }
 
-/** The signed-in host's build target: OS from the platform, GPU from detection. */
+/** The signed-in host's build target: OS/architecture from Node, GPU from detection. */
 export async function resolveHost(): Promise<Host> {
   const gpu = await detectGPUCached()
   // The library targets nvidia/amd/cpu/mps; an Intel dGPU (or none) maps to the
-  // universal CPU build, which `selectArtifactForHost` treats as the fallback.
+  // CPU build, which `selectArtifactForHost` treats as the fallback on the same architecture.
   const mapped = gpu?.id === 'nvidia' || gpu?.id === 'amd' || gpu?.id === 'mps' ? gpu.id : 'cpu'
-  return { os: hostOs(), gpu: mapped }
+  return { os: hostOs(), arch: process.arch, gpu: mapped }
 }
 
 /** Latest complete version, or null. `complete` is the only terminal status in
diff --git a/src/main/lib/ipc/registerDevPlatformHandlers.test.ts b/src/main/lib/ipc/registerDevPlatformHandlers.test.ts
index effc328de..806013998 100644
--- a/src/main/lib/ipc/registerDevPlatformHandlers.test.ts
+++ b/src/main/lib/ipc/registerDevPlatformHandlers.test.ts
@@ -23,7 +23,7 @@ const mocks = vi.hoisted(() => ({
   })),
   listBuilds: vi.fn(),
   createBuildDraft: vi.fn(),
-  resolveHost: vi.fn(async () => ({ os: 'linux', gpu: 'nvidia' })),
+  resolveHost: vi.fn(async () => ({ os: 'linux', arch: 'x64', gpu: 'nvidia' })),
   resolveBuildRows: vi.fn(),
   resolveHostArtifact: vi.fn(),
   resolveSelectedHostArtifact: vi.fn(),
@@ -726,7 +726,7 @@ describe('registerDevPlatformHandlers', () => {
     expect(result).toMatchObject({ ok: true })
     expect(mocks.resolveSelectedHostArtifact).toHaveBeenCalledWith(
       expect.anything(),
-      { os: 'linux', gpu: 'nvidia' },
+      { os: 'linux', arch: 'x64', gpu: 'nvidia' },
       'd1',
       7,
       'art-cpu'
diff --git a/src/main/sources/comfybuilder/index.test.ts b/src/main/sources/comfybuilder/index.test.ts
index 0e2f22b3b..69aff1cea 100644
--- a/src/main/sources/comfybuilder/index.test.ts
+++ b/src/main/sources/comfybuilder/index.test.ts
@@ -52,7 +52,7 @@ vi.mock('./modelStagingTask', () => ({
   restageBuildModelsIfNeeded: vi.fn()
 }))
 vi.mock('../../devplatform/builds', () => ({
-  resolveHost: vi.fn(async () => ({ os: 'linux', gpu: 'nvidia' })),
+  resolveHost: vi.fn(async () => ({ os: 'linux', arch: 'x64', gpu: 'nvidia' })),
   resolveHostArtifactForVersion: vi.fn(),
   listCompleteVersions: vi.fn(async () => [])
 }))
@@ -61,7 +61,11 @@ import fs, { promises as fsp } from 'fs'
 import os from 'os'
 import path from 'path'
 import { installArtifact, stageModels, resolveModelManifest, venvPython } from '../../comfybuilder'
-import { listCompleteVersions, resolveHostArtifactForVersion } from '../../devplatform/builds'
+import {
+  listCompleteVersions,
+  resolveHost,
+  resolveHostArtifactForVersion
+} from '../../devplatform/builds'
 import {
   clearVersionCache,
   getCachedVersions,
@@ -168,6 +172,22 @@ describe('comfybuilder.install wiring', () => {
     expect(releaseInstallTerminalForFsOp).toHaveBeenCalledWith('i1')
   })
 
+  it.each(['windows', 'linux'] as const)(
+    'rejects a saved %s x64 selection on ARM64 before changing the environment',
+    async (os) => {
+      vi.mocked(resolveHost).mockResolvedValueOnce({ os, arch: 'arm64', gpu: 'nvidia' })
+      await expect(
+        comfybuilder.install!(record({ artifactOs: os, status: 'failed' }), fakeTools())
+      ).rejects.toThrow('This build is not compatible with this machine.')
+      expect(installArtifact).not.toHaveBeenCalled()
+      expect(releaseInstallTerminalForFsOp).not.toHaveBeenCalled()
+      expect(rm).not.toHaveBeenCalled()
+      expect(rename).not.toHaveBeenCalled()
+      expect(writeFile).not.toHaveBeenCalled()
+      expect(startModelStaging).not.toHaveBeenCalled()
+    }
+  )
+
   it('updates code while models and user data remain at stable paths', async () => {
     access.mockImplementation(realFsp.access)
     mkdir.mockImplementation(realFsp.mkdir)
diff --git a/src/main/sources/comfybuilder/index.ts b/src/main/sources/comfybuilder/index.ts
index 20419287f..dfbca5e56 100644
--- a/src/main/sources/comfybuilder/index.ts
+++ b/src/main/sources/comfybuilder/index.ts
@@ -33,6 +33,7 @@ import type {
   ModelDescriptor
 } from '../../comfybuilder'
 import { getBuilderClient } from '../../devplatform/session'
+import { selectArtifactForHost } from '../../comfybuilder/targets'
 import {
   listCompleteVersions,
   resolveHost,
@@ -405,8 +406,13 @@ async function installEnvironment(
   },
   onTransactionStarted?: () => Promise<void>
 ): Promise<readonly ModelDescriptor[]> {
-  releaseInstallTerminalForFsOp(installation.id)
   const artifact = artifactFromRecord(installation)
+  // Retried installs carry a persisted selection and bypass catalog resolution.
+  // Revalidate before releasing terminals or touching the existing environment.
+  if (!selectArtifactForHost([artifact], await resolveHost())) {
+    throw new Error('This build is not compatible with this machine.')
+  }
+  releaseInstallTerminalForFsOp(installation.id)
   const client = getBuilderClient()
   const paths = environmentPaths(installation.installPath)
   const interrupted = await hasEnvironmentBackups(installation.installPath)