diff --git a/test/lib/commands/ci.js b/test/lib/commands/ci.js
index 8dc0f1d3cc149..6db01d7b6ec7a 100644
--- a/test/lib/commands/ci.js
+++ b/test/lib/commands/ci.js
@@ -308,3 +308,142 @@ t.test('should use --workspace flag', async t => {
   assert.packageMissing('node_modules/abbrev@1.1.0')
   assert.packageInstalled('node_modules/lodash@1.1.1')
 })
+
+// Issue #8726 - npm ci fails because npm install produces an out-of-sync lockfile
+// https://github.com/npm/cli/issues/8726
+//
+// Root cause: an optional peerDependency at an exact version causes buildIdealTree() to resolve a different version than what's in the lockfile.
+//
+// Pattern (mirrors real-world addons-linter / htmlhint / node-fetch scenario):
+//   - scanner@1.0.0 has optional peerDep: fetcher@1.0.0 (exact version)
+//   - hint@1.0.0 has regular dep: fetcher@^1.0.0 (semver range)
+//   - npm install resolves fetcher to 1.1.0 (latest matching ^1.0.0)
+//   - npm ci's buildIdealTree sees fetcher@1.1.0 doesn't satisfy the exact peerDep "1.0.0", treats it as a problem edge, resolves fetcher to 1.0.0
+//   - validateLockfile: lockfile has 1.1.0, ideal tree has 1.0.0 → MISMATCH
+
+t.test('issue-8726: npm ci with optional peerDep causing lockfile version mismatch', async t => {
+  // Pre-built lockfile locks fetcher@1.1.0 (what npm install would pick).
+  // scanner has optional peerDep fetcher@1.0.0 (exact version).
+  // buildIdealTree should respect the lockfile version, but the bug causes it to resolve fetcher to 1.0.0, failing validateLockfile.
+  const { npm, registry } = await loadMockNpm(t, {
+    config: { audit: false, 'ignore-scripts': true },
+    strictRegistryNock: false,
+    prefixDir: {
+      'linter-tarball': {
+        'package.json': JSON.stringify({
+          name: 'linter',
+          version: '1.0.0',
+          dependencies: { scanner: '1.0.0' },
+        }),
+      },
+      'scanner-tarball': {
+        'package.json': JSON.stringify({
+          name: 'scanner',
+          version: '1.0.0',
+          peerDependencies: { fetcher: '1.0.0' },
+          peerDependenciesMeta: { fetcher: { optional: true } },
+        }),
+      },
+      'hint-tarball': {
+        'package.json': JSON.stringify({
+          name: 'hint',
+          version: '1.0.0',
+          dependencies: { fetcher: '^1.0.0' },
+        }),
+      },
+      'fetcher-1.0.0-tarball': {
+        'package.json': JSON.stringify({ name: 'fetcher', version: '1.0.0' }),
+      },
+      'fetcher-1.1.0-tarball': {
+        'package.json': JSON.stringify({ name: 'fetcher', version: '1.1.0' }),
+      },
+      'package.json': JSON.stringify({
+        name: 'test-package',
+        version: '1.0.0',
+        devDependencies: {
+          linter: '1.0.0',
+          hint: '1.0.0',
+        },
+      }),
+      'package-lock.json': JSON.stringify({
+        name: 'test-package',
+        version: '1.0.0',
+        lockfileVersion: 3,
+        requires: true,
+        packages: {
+          '': {
+            name: 'test-package',
+            version: '1.0.0',
+            devDependencies: { linter: '1.0.0', hint: '1.0.0' },
+          },
+          'node_modules/linter': {
+            version: '1.0.0',
+            resolved: 'https://registry.npmjs.org/linter/-/linter-1.0.0.tgz',
+            dev: true,
+            dependencies: { scanner: '1.0.0' },
+          },
+          'node_modules/scanner': {
+            version: '1.0.0',
+            resolved: 'https://registry.npmjs.org/scanner/-/scanner-1.0.0.tgz',
+            dev: true,
+            peerDependencies: { fetcher: '1.0.0' },
+            peerDependenciesMeta: { fetcher: { optional: true } },
+          },
+          'node_modules/hint': {
+            version: '1.0.0',
+            resolved: 'https://registry.npmjs.org/hint/-/hint-1.0.0.tgz',
+            dev: true,
+            dependencies: { fetcher: '^1.0.0' },
+          },
+          'node_modules/fetcher': {
+            version: '1.1.0',
+            resolved: 'https://registry.npmjs.org/fetcher/-/fetcher-1.1.0.tgz',
+            dev: true,
+          },
+        },
+      }),
+    },
+  })
+
+  // With the fix, buildIdealTree no longer treats the invalid peerOptional edge as a problem, so npm ci proceeds to reification and needs tarballs.
+  const linterManifest = registry.manifest({ name: 'linter' })
+  await registry.tarball({
+    manifest: linterManifest.versions['1.0.0'],
+    tarball: path.join(npm.prefix, 'linter-tarball'),
+  })
+
+  const scannerManifest = registry.manifest({ name: 'scanner' })
+  await registry.tarball({
+    manifest: scannerManifest.versions['1.0.0'],
+    tarball: path.join(npm.prefix, 'scanner-tarball'),
+  })
+
+  const hintManifest = registry.manifest({ name: 'hint' })
+  await registry.tarball({
+    manifest: hintManifest.versions['1.0.0'],
+    tarball: path.join(npm.prefix, 'hint-tarball'),
+  })
+
+  const fetcherManifest = registry.manifest({
+    name: 'fetcher',
+    versions: ['1.0.0', '1.1.0'],
+  })
+  await registry.tarball({
+    manifest: fetcherManifest.versions['1.1.0'],
+    tarball: path.join(npm.prefix, 'fetcher-1.1.0-tarball'),
+  })
+
+  // npm ci should succeed - the lockfile is valid and the fix ensures the peerOptional edge doesn't cause a version mismatch.
+  await npm.exec('ci', [])
+
+  const installedFetcher = JSON.parse(
+    fs.readFileSync(
+      path.join(npm.prefix, 'node_modules', 'fetcher', 'package.json'), 'utf8'
+    )
+  )
+  t.equal(
+    installedFetcher.version,
+    '1.1.0',
+    'installed the locked fetcher version, not the peer dep version'
+  )
+})
diff --git a/test/lib/commands/install.js b/test/lib/commands/install.js
index 7fd5eb7f16100..584690b68b5c6 100644
--- a/test/lib/commands/install.js
+++ b/test/lib/commands/install.js
@@ -1,3 +1,4 @@
+const fs = require('node:fs')
 const tspawk = require('../../fixtures/tspawk')
 const {
   cleanCwd,
@@ -770,3 +771,272 @@ t.test('devEngines', async t => {
     t.ok(!output.includes('EBADDEVENGINES'))
   })
 })
+
+// Issue #8726 - npm install should re-resolve to satisfy peerOptional constraints
+// https://github.com/npm/cli/issues/8726
+//
+// When a lockfile has fetcher@1.1.0 but a peerOptional wants fetcher@1.0.0 (exact), npm install (save: true) should re-resolve fetcher to 1.0.0 to satisfy both the regular dep range (^1.0.0) and the exact peerOptional constraint.
+t.test('issue-8726: npm install re-resolves to satisfy peerOptional constraint', async t => {
+  const { npm, registry } = await loadMockNpm(t, {
+    config: { audit: false, 'ignore-scripts': true },
+    prefixDir: {
+      'linter-tarball': {
+        'package.json': JSON.stringify({
+          name: 'linter',
+          version: '1.0.0',
+          dependencies: { scanner: '1.0.0' },
+        }),
+      },
+      'scanner-tarball': {
+        'package.json': JSON.stringify({
+          name: 'scanner',
+          version: '1.0.0',
+          peerDependencies: { fetcher: '1.0.0' },
+          peerDependenciesMeta: { fetcher: { optional: true } },
+        }),
+      },
+      'hint-tarball': {
+        'package.json': JSON.stringify({
+          name: 'hint',
+          version: '1.0.0',
+          dependencies: { fetcher: '^1.0.0' },
+        }),
+      },
+      'fetcher-1.0.0-tarball': {
+        'package.json': JSON.stringify({ name: 'fetcher', version: '1.0.0' }),
+      },
+      'fetcher-1.1.0-tarball': {
+        'package.json': JSON.stringify({ name: 'fetcher', version: '1.1.0' }),
+      },
+      'package.json': JSON.stringify({
+        name: 'test-package',
+        version: '1.0.0',
+        devDependencies: {
+          linter: '1.0.0',
+          hint: '1.0.0',
+        },
+      }),
+      'package-lock.json': JSON.stringify({
+        name: 'test-package',
+        version: '1.0.0',
+        lockfileVersion: 3,
+        requires: true,
+        packages: {
+          '': {
+            name: 'test-package',
+            version: '1.0.0',
+            devDependencies: { linter: '1.0.0', hint: '1.0.0' },
+          },
+          'node_modules/linter': {
+            version: '1.0.0',
+            resolved: 'https://registry.npmjs.org/linter/-/linter-1.0.0.tgz',
+            dev: true,
+            dependencies: { scanner: '1.0.0' },
+          },
+          'node_modules/scanner': {
+            version: '1.0.0',
+            resolved: 'https://registry.npmjs.org/scanner/-/scanner-1.0.0.tgz',
+            dev: true,
+            peerDependencies: { fetcher: '1.0.0' },
+            peerDependenciesMeta: { fetcher: { optional: true } },
+          },
+          'node_modules/hint': {
+            version: '1.0.0',
+            resolved: 'https://registry.npmjs.org/hint/-/hint-1.0.0.tgz',
+            dev: true,
+            dependencies: { fetcher: '^1.0.0' },
+          },
+          'node_modules/fetcher': {
+            version: '1.1.0',
+            resolved: 'https://registry.npmjs.org/fetcher/-/fetcher-1.1.0.tgz',
+            dev: true,
+          },
+        },
+      }),
+    },
+  })
+
+  // Only set up mocks that npm install actually needs: tarballs for all installed packages (linter, scanner, hint, fetcher@1.0.0) and the fetcher packument (needed for re-resolution via #problemEdges).
+  // Packuments for linter/scanner/hint are NOT needed (already in lockfile).
+  // Fetcher@1.1.0 tarball is NOT needed (gets replaced by 1.0.0).
+  const linterManifest = registry.manifest({ name: 'linter' })
+  await registry.tarball({
+    manifest: linterManifest.versions['1.0.0'],
+    tarball: path.join(npm.prefix, 'linter-tarball'),
+  })
+
+  const scannerManifest = registry.manifest({ name: 'scanner' })
+  await registry.tarball({
+    manifest: scannerManifest.versions['1.0.0'],
+    tarball: path.join(npm.prefix, 'scanner-tarball'),
+  })
+
+  const hintManifest = registry.manifest({ name: 'hint' })
+  await registry.tarball({
+    manifest: hintManifest.versions['1.0.0'],
+    tarball: path.join(npm.prefix, 'hint-tarball'),
+  })
+
+  const fetcherManifest = registry.manifest({
+    name: 'fetcher',
+    versions: ['1.0.0', '1.1.0'],
+  })
+  await registry.package({ manifest: fetcherManifest })
+  await registry.tarball({
+    manifest: fetcherManifest.versions['1.0.0'],
+    tarball: path.join(npm.prefix, 'fetcher-1.0.0-tarball'),
+  })
+
+  await npm.exec('install', [])
+
+  // Read the updated lockfile and verify fetcher was re-resolved to 1.0.0
+  const lockfile = JSON.parse(
+    fs.readFileSync(path.join(npm.prefix, 'package-lock.json'), 'utf8')
+  )
+  t.equal(
+    lockfile.packages['node_modules/fetcher'].version,
+    '1.0.0',
+    'lockfile updated fetcher to satisfy peerOptional constraint'
+  )
+
+  // Also verify the installed package
+  const installedFetcher = JSON.parse(
+    fs.readFileSync(
+      path.join(npm.prefix, 'node_modules', 'fetcher', 'package.json'), 'utf8'
+    )
+  )
+  t.equal(
+    installedFetcher.version,
+    '1.0.0',
+    'installed fetcher version satisfies peerOptional constraint'
+  )
+})
+
+// Issue #8726 - fresh npm install (no lockfile) should pick a version that satisfies both the regular dep range AND the exact peerOptional constraint, even when the peerOptional holder is processed BEFORE the dep is placed.
+// https://github.com/npm/cli/issues/8726
+//
+// This test uses package names that reproduce the real-world alphabetical ordering from the original issue (addons-linter < htmlhint), which causes addons-scanner to be processed from the queue BEFORE htmlhint places node-fetcher.
+// At that point the peerOptional edge has no destination (MISSING, valid for peerOptional).
+// Later, htmlhint places node-fetcher@1.1.0 and the edge becomes INVALID.
+// The fix re-queues addons-scanner so #problemEdges can trigger re-resolution of node-fetcher to 1.0.0.
+//
+// Dependency graph:
+//   root -> addons-linter@1.0.0 -> addons-scanner@1.0.0 -> PEER_OPTIONAL node-fetcher@1.0.0
+//   root -> htmlhint@1.0.0      -> node-fetcher@^1.0.0
+//
+// Processing order (alphabetical): addons-linter, then addons-scanner (dep of addons-linter), THEN htmlhint (which places node-fetcher@1.1.0)
+t.test('issue-8726: fresh install re-queues scanner when dep placed later', async t => {
+  const { npm, registry } = await loadMockNpm(t, {
+    config: { audit: false, 'ignore-scripts': true },
+    prefixDir: {
+      'addons-linter-tarball': {
+        'package.json': JSON.stringify({
+          name: 'addons-linter',
+          version: '1.0.0',
+          dependencies: { 'addons-scanner': '1.0.0' },
+        }),
+      },
+      'addons-scanner-tarball': {
+        'package.json': JSON.stringify({
+          name: 'addons-scanner',
+          version: '1.0.0',
+          peerDependencies: { 'node-fetcher': '1.0.0' },
+          peerDependenciesMeta: { 'node-fetcher': { optional: true } },
+        }),
+      },
+      'htmlhint-tarball': {
+        'package.json': JSON.stringify({
+          name: 'htmlhint',
+          version: '1.0.0',
+          dependencies: { 'node-fetcher': '^1.0.0' },
+        }),
+      },
+      'node-fetcher-1.0.0-tarball': {
+        'package.json': JSON.stringify({ name: 'node-fetcher', version: '1.0.0' }),
+      },
+      'node-fetcher-1.1.0-tarball': {
+        'package.json': JSON.stringify({ name: 'node-fetcher', version: '1.1.0' }),
+      },
+      'package.json': JSON.stringify({
+        name: 'test-package',
+        version: '1.0.0',
+        devDependencies: {
+          'addons-linter': '1.0.0',
+          htmlhint: '1.0.0',
+        },
+      }),
+      // NO package-lock.json — this is a fresh install
+    },
+  })
+
+  // Fresh install needs packuments for all packages
+  const linterManifest = registry.manifest({
+    name: 'addons-linter',
+    packuments: [{ version: '1.0.0', dependencies: { 'addons-scanner': '1.0.0' } }],
+  })
+  await registry.package({ manifest: linterManifest })
+  await registry.tarball({
+    manifest: linterManifest.versions['1.0.0'],
+    tarball: path.join(npm.prefix, 'addons-linter-tarball'),
+  })
+
+  const scannerManifest = registry.manifest({
+    name: 'addons-scanner',
+    packuments: [{
+      version: '1.0.0',
+      peerDependencies: { 'node-fetcher': '1.0.0' },
+      peerDependenciesMeta: { 'node-fetcher': { optional: true } },
+    }],
+  })
+  await registry.package({ manifest: scannerManifest })
+  await registry.tarball({
+    manifest: scannerManifest.versions['1.0.0'],
+    tarball: path.join(npm.prefix, 'addons-scanner-tarball'),
+  })
+
+  const hintManifest = registry.manifest({
+    name: 'htmlhint',
+    packuments: [{ version: '1.0.0', dependencies: { 'node-fetcher': '^1.0.0' } }],
+  })
+  await registry.package({ manifest: hintManifest })
+  await registry.tarball({
+    manifest: hintManifest.versions['1.0.0'],
+    tarball: path.join(npm.prefix, 'htmlhint-tarball'),
+  })
+
+  const fetcherManifest = registry.manifest({
+    name: 'node-fetcher',
+    packuments: [{ version: '1.0.0' }, { version: '1.1.0' }],
+  })
+  // Packument is fetched twice: once when htmlhint resolves node-fetcher@^1.0.0 (picking 1.1.0), and again when addons-scanner is re-queued and re-resolves node-fetcher (picking 1.0.0 to satisfy the exact peerOptional spec).
+  await registry.package({ manifest: fetcherManifest, times: 2 })
+  await registry.tarball({
+    manifest: fetcherManifest.versions['1.0.0'],
+    tarball: path.join(npm.prefix, 'node-fetcher-1.0.0-tarball'),
+  })
+  // node-fetcher@1.1.0 tarball is NOT needed: it's replaced by 1.0.0 during tree building (before reification), so it's never downloaded.
+
+  await npm.exec('install', [])
+
+  // Verify the lockfile has node-fetcher@1.0.0
+  const lockfile = JSON.parse(
+    fs.readFileSync(path.join(npm.prefix, 'package-lock.json'), 'utf8')
+  )
+  t.equal(
+    lockfile.packages['node_modules/node-fetcher'].version,
+    '1.0.0',
+    'fresh install picks node-fetcher@1.0.0 satisfying peerOptional constraint'
+  )
+
+  // Also verify the installed package
+  const installedFetcher = JSON.parse(
+    fs.readFileSync(
+      path.join(npm.prefix, 'node_modules', 'node-fetcher', 'package.json'), 'utf8'
+    )
+  )
+  t.equal(
+    installedFetcher.version,
+    '1.0.0',
+    'installed node-fetcher version satisfies peerOptional constraint'
+  )
+})
diff --git a/workspaces/arborist/lib/arborist/build-ideal-tree.js b/workspaces/arborist/lib/arborist/build-ideal-tree.js
index b4319fab6bd37..a256b79049eba 100644
--- a/workspaces/arborist/lib/arborist/build-ideal-tree.js
+++ b/workspaces/arborist/lib/arborist/build-ideal-tree.js
@@ -339,7 +339,8 @@ module.exports = cls => class IdealTreeBuilder extends cls {
           filter: node => node,
           visit: node => {
             for (const edge of node.edgesOut.values()) {
-              if ((!edge.to && edge.type !== 'peerOptional') || !edge.valid) {
+              const skipPeerOptional = edge.type === 'peerOptional' && this.options.save === false
+              if (!skipPeerOptional && (!edge.to || !edge.valid)) {
                 this.#depsQueue.push(node)
                 break // no need to continue the loop after the first hit
               }
@@ -966,9 +967,17 @@ This is a one-time fix-up, please be patient...
                 continue
               }
               const { from, valid, peerConflicted } = edgeIn
-              if (!peerConflicted && !valid && !this.#depsSeen.has(from)) {
-                this.addTracker('idealTree', from.name, from.location)
-                this.#depsQueue.push(edgeIn.from)
+              if (!peerConflicted && !valid) {
+                if (this.#depsSeen.has(from) && this.options.save) {
+                  // Re-queue already-processed nodes when a newly placed dep creates an invalid edge during npm install (save=true).
+                  // This handles the case where a peerOptional dep was valid (missing) when the node was first processed, but becomes invalid when the dep is later placed by another path with a version that doesn't satisfy the peer spec.
+                  // See npm/cli#8726.
+                  this.#depsSeen.delete(from)
+                  this.#depsQueue.push(from)
+                } else if (!this.#depsSeen.has(from)) {
+                  this.addTracker('idealTree', from.name, from.location)
+                  this.#depsQueue.push(from)
+                }
               }
             }
           } else {
@@ -1165,9 +1174,13 @@ This is a one-time fix-up, please be patient...
         continue
       }
 
-      // If the edge has an error, there's a problem.
+      // If the edge has an error, there's a problem, unless it's peerOptional and we're not saving (e.g. npm ci), in which case we trust the lockfile and skip re-resolution.
+      // When saving (npm install), peerOptional invalid edges ARE treated as problems so the lockfile gets fixed.
+      // See npm/cli#8726.
       if (!edge.valid) {
-        problems.push(edge)
+        if (edge.type !== 'peerOptional' || this.options.save !== false) {
+          problems.push(edge)
+        }
         continue
       }
 
diff --git a/workspaces/arborist/test/arborist/build-ideal-tree.js b/workspaces/arborist/test/arborist/build-ideal-tree.js
index e56daa7ed76ad..aa632426c03e1 100644
--- a/workspaces/arborist/test/arborist/build-ideal-tree.js
+++ b/workspaces/arborist/test/arborist/build-ideal-tree.js
@@ -4460,3 +4460,114 @@ t.test('installLinks behavior with project-internal file dependencies', async t
     t.equal(edgeToA.to, packageA, 'the edge from b should point to package a')
   })
 })
+
+t.test('re-queue already-seen nodes when placed dep invalidates peerOptional (save=true, #8726)', async t => {
+  // Scenario: alpha has peerOptional on shared@1.0.0, beta has dep on shared@^1.0.0.
+  // With save=true, alpha is processed first (alphabetical order in DepsQueue),
+  // its peerOptional is not a problem (missing is OK for peerOptional).
+  // Beta is processed next, placing shared@1.1.0 (latest ^1.0.0).
+  // This invalidates alpha's peerOptional edge, triggering re-queue of alpha.
+  const registry = createRegistry(t, false)
+
+  const alphaPack = registry.packument({
+    name: 'alpha',
+    version: '1.0.0',
+    peerDependencies: { shared: '1.0.0' },
+    peerDependenciesMeta: { shared: { optional: true } },
+  })
+  const alphaManifest = registry.manifest({ name: 'alpha', packuments: [alphaPack] })
+  await registry.package({ manifest: alphaManifest })
+
+  const betaPack = registry.packument({
+    name: 'beta',
+    version: '1.0.0',
+    dependencies: { shared: '^1.0.0' },
+  })
+  const betaManifest = registry.manifest({ name: 'beta', packuments: [betaPack] })
+  await registry.package({ manifest: betaManifest })
+
+  const sharedPacks = registry.packuments(['1.0.0', '1.1.0'], 'shared')
+  const sharedManifest = registry.manifest({ name: 'shared', packuments: sharedPacks })
+  await registry.package({ manifest: sharedManifest, times: 2 })
+
+  const path = t.testdir({
+    'package.json': JSON.stringify({
+      name: 'test-8726-install',
+      version: '1.0.0',
+      dependencies: {
+        alpha: '1.0.0',
+        beta: '1.0.0',
+      },
+    }),
+  })
+
+  const arb = newArb(path, { save: true })
+  const tree = await arb.buildIdealTree()
+
+  t.ok(tree.children.get('alpha'), 'alpha is in the tree')
+  t.ok(tree.children.get('beta'), 'beta is in the tree')
+  t.ok(tree.children.get('shared'), 'shared is in the tree')
+})
+
+t.test('skip invalid peerOptional edges in problemEdges when save=false (#8726)', async t => {
+  // With save=false (npm ci behavior), invalid peerOptional edges should NOT be treated as problems.
+  // We use update.names to force alpha into #problemEdges while shared@1.1.0 (invalid for alpha's peerOptional spec of 1.0.0) is already in the tree from the lockfile.
+  const registry = createRegistry(t, false)
+
+  const utilPacks = registry.packuments(['1.0.0', '1.0.1'], 'util')
+  const utilManifest = registry.manifest({ name: 'util', packuments: utilPacks })
+  await registry.package({ manifest: utilManifest })
+
+  const path = t.testdir({
+    'package.json': JSON.stringify({
+      name: 'test-8726-ci',
+      version: '1.0.0',
+      dependencies: {
+        alpha: '1.0.0',
+        beta: '1.0.0',
+      },
+    }),
+    'package-lock.json': JSON.stringify({
+      name: 'test-8726-ci',
+      version: '1.0.0',
+      lockfileVersion: 3,
+      requires: true,
+      packages: {
+        '': {
+          name: 'test-8726-ci',
+          version: '1.0.0',
+          dependencies: { alpha: '1.0.0', beta: '1.0.0' },
+        },
+        'node_modules/alpha': {
+          version: '1.0.0',
+          resolved: 'https://registry.npmjs.org/alpha/-/alpha-1.0.0.tgz',
+          dependencies: { util: '^1.0.0' },
+          peerDependencies: { shared: '1.0.0' },
+          peerDependenciesMeta: { shared: { optional: true } },
+        },
+        'node_modules/beta': {
+          version: '1.0.0',
+          resolved: 'https://registry.npmjs.org/beta/-/beta-1.0.0.tgz',
+          dependencies: { shared: '^1.0.0' },
+        },
+        'node_modules/shared': {
+          version: '1.1.0',
+          resolved: 'https://registry.npmjs.org/shared/-/shared-1.1.0.tgz',
+        },
+        'node_modules/util': {
+          version: '1.0.0',
+          resolved: 'https://registry.npmjs.org/util/-/util-1.0.0.tgz',
+        },
+      },
+    }),
+  })
+
+  const arb = newArb(path, { save: false })
+  const tree = await arb.buildIdealTree({ update: { names: ['util'] } })
+
+  t.ok(tree.children.get('alpha'), 'alpha is in the tree')
+  t.ok(tree.children.get('beta'), 'beta is in the tree')
+  t.equal(tree.children.get('shared').version, '1.1.0',
+    'shared stays at 1.1.0 - peerOptional mismatch is not treated as a problem')
+  t.ok(tree.children.get('util'), 'util is in the tree')
+})