diff --git a/layers/registry/server/utils/github-client.ts b/layers/registry/server/utils/github-client.ts
index 576f7209..f017b9bd 100644
--- a/layers/registry/server/utils/github-client.ts
+++ b/layers/registry/server/utils/github-client.ts
@@ -363,6 +363,7 @@ interface RepoSummaryGql {
   createdAt: string
   isArchived: boolean
   isFork: boolean
+  isPrivate: boolean
   defaultBranchRef: {
     name: string
     target: { oid: string, tree: { oid: string } } | null
@@ -370,7 +371,7 @@ interface RepoSummaryGql {
 }
 
 const REPO_SUMMARY_FIELDS = `databaseId name nameWithOwner url owner{login}
-      description stargazerCount forkCount pushedAt createdAt isArchived isFork
+      description stargazerCount forkCount pushedAt createdAt isArchived isFork isPrivate
       defaultBranchRef{name target{... on Commit{oid tree{oid}}}}`
 
 export interface RepoSummary {
@@ -385,12 +386,11 @@ export interface RepoSummary {
 }
 
 /**
- * Parse one GraphQL Repository into a summary, or null without a Repository
- * ID. The schema allows a null ID, and a Repository without one cannot be
- * followed across a move.
+ * Parse one public GraphQL Repository. Reject missing IDs or visibility.
+ * Its numeric ID confirms identity across moves.
  */
 function repoSummaryFromGql(r: RepoSummaryGql): RepoSummary | null {
-  if (typeof r.databaseId !== 'number')
+  if (typeof r.databaseId !== 'number' || typeof r.isPrivate !== 'boolean' || r.isPrivate)
     return null
   const branch = r.defaultBranchRef?.name || 'main'
   const meta: RepoMeta = {
@@ -398,6 +398,7 @@ function repoSummaryFromGql(r: RepoSummaryGql): RepoSummary | null {
     full_name: r.nameWithOwner,
     html_url: r.url,
     owner: { login: r.owner.login },
+    private: false,
     default_branch: branch,
     description: r.description,
     stargazers_count: r.stargazerCount,
@@ -443,7 +444,7 @@ export async function getRepoSummary(
     return { status: notFound ? 404 : 502, data: null, rateLimit: out.rateLimit, notModified: false }
   }
   const r = out.data?.repository
-  if (!r)
+  if (!r || r.isPrivate === true)
     return { status: 404, data: null, rateLimit: out.rateLimit, notModified: false }
   // A Repository without an ID fails like any other malformed answer.
   const summary = repoSummaryFromGql(r)
diff --git a/test/unit/discovery-size-guard-not-modified.test.ts b/test/unit/discovery-size-guard-not-modified.test.ts
index 711e3bb0..6f3607f8 100644
--- a/test/unit/discovery-size-guard-not-modified.test.ts
+++ b/test/unit/discovery-size-guard-not-modified.test.ts
@@ -47,6 +47,7 @@ function summaryResponse() {
           createdAt: '2026-01-01T00:00:00Z',
           isArchived: false,
           isFork: false,
+          isPrivate: false,
           defaultBranchRef: { name: 'main', target: { oid: 'commit', tree: { oid: 'tree-sha' } } },
         },
       },
diff --git a/test/unit/github-repo-identity.test.ts b/test/unit/github-repo-identity.test.ts
index 6b56539c..336a73f3 100644
--- a/test/unit/github-repo-identity.test.ts
+++ b/test/unit/github-repo-identity.test.ts
@@ -1,9 +1,35 @@
 import { afterEach, describe, expect, it, vi } from 'vitest'
 import { getRepoSummary } from '../../layers/registry/server/utils/github-client'
+import { readRepositoryPurposeEvidence } from '../../layers/registry/server/utils/repository-purpose-effect'
 
 describe('github repository identity', () => {
   afterEach(() => vi.unstubAllGlobals())
 
+  it('hides a private repository even when the read credential can access it', async () => {
+    vi.stubGlobal('fetch', vi.fn(async () => Response.json({
+      data: { repository: { databaseId: 1, isPrivate: true, name: 'private', nameWithOwner: 'acme/private', owner: { login: 'acme' }, defaultBranchRef: null } },
+    })))
+    expect(await getRepoSummary('acme', 'private', {})).toMatchObject({ status: 404, data: null })
+  })
+
+  it('fails closed when the source omits repository visibility', async () => {
+    vi.stubGlobal('fetch', vi.fn(async () => Response.json({
+      data: { repository: { databaseId: 1, name: 'unknown', nameWithOwner: 'acme/unknown', owner: { login: 'acme' }, defaultBranchRef: null } },
+    })))
+    expect(await getRepoSummary('acme', 'unknown', {})).toMatchObject({ status: 502, data: null })
+  })
+
+  it('stops purpose evidence before reading any private tree or file', async () => {
+    const fetch = vi.fn(async () => Response.json({
+      data: { repository: { databaseId: 1, isPrivate: true, name: 'private', owner: { login: 'acme' }, defaultBranchRef: null } },
+    }))
+    vi.stubGlobal('fetch', fetch)
+    await expect(readRepositoryPurposeEvidence({ owner: 'acme', repo: 'private' }, {}))
+      .rejects
+      .toThrow('Repository purpose source unavailable: 404')
+    expect(fetch).toHaveBeenCalledTimes(1)
+  })
+
   it('returns GitHub canonical identity when an old repository name resolves', async () => {
     const fetch = vi.fn(async () => Response.json({
       data: {
@@ -20,6 +46,7 @@ describe('github repository identity', () => {
           createdAt: '2025-01-01T00:00:00Z',
           isArchived: false,
           isFork: false,
+          isPrivate: false,
           defaultBranchRef: {
             name: 'main',
             target: { oid: 'commit', tree: { oid: 'tree' } },
diff --git a/test/unit/github-repo-summary-batch.test.ts b/test/unit/github-repo-summary-batch.test.ts
index a4272b6d..b5a47998 100644
--- a/test/unit/github-repo-summary-batch.test.ts
+++ b/test/unit/github-repo-summary-batch.test.ts
@@ -22,6 +22,7 @@ function repository(owner: string, name: string, tree: string) {
     createdAt: '2025-01-01T00:00:00Z',
     isArchived: false,
     isFork: false,
+    isPrivate: false,
     defaultBranchRef: { name: 'main', target: { oid: 'c'.repeat(40), tree: { oid: tree } } },
   }
 }
@@ -54,6 +55,15 @@ afterEach(() => {
 })
 
 describe('getRepoSummariesBatch', () => {
+  it('omits a readable private repository while preserving the public neighbor', async () => {
+    vi.stubGlobal('fetch', vi.fn(async () => Response.json({ data: {
+      r0: { ...repository('acme', 'private', 'private-tree'), isPrivate: true },
+      r1: repository('acme', 'public', 'public-tree'),
+    } })))
+    const result = await getRepoSummariesBatch([{ owner: 'acme', repo: 'private' }, { owner: 'acme', repo: 'public' }], bindings)
+    expect(result).toMatchObject({ _tag: 'read', summaries: [null, { meta: { full_name: 'acme/public' } }] })
+  })
+
   it('reads 230 repositories in three queries, in request order', async () => {
     const fetchMock = vi.fn(graphqlAnswer)
     vi.stubGlobal('fetch', fetchMock)
diff --git a/test/unit/registry-github-app-credential.test.ts b/test/unit/registry-github-app-credential.test.ts
index 9177965b..5cbb6409 100644
--- a/test/unit/registry-github-app-credential.test.ts
+++ b/test/unit/registry-github-app-credential.test.ts
@@ -584,6 +584,7 @@ async function stubGithub(options: StubOptions) {
         createdAt: '2026-01-01T00:00:00Z',
         isArchived: false,
         isFork: false,
+        isPrivate: false,
         defaultBranchRef: { name: 'main', target: { oid: 'a'.repeat(40), tree: { oid: 'b'.repeat(40) } } },
       })
       if ('owner' in body.variables) {
diff --git a/test/unit/sync-prefetch.test.ts b/test/unit/sync-prefetch.test.ts
index 07d198e6..9c170215 100644
--- a/test/unit/sync-prefetch.test.ts
+++ b/test/unit/sync-prefetch.test.ts
@@ -43,6 +43,7 @@ function graphqlAnswer(_input: unknown, init?: RequestInit): Response {
       createdAt: '2025-01-01T00:00:00Z',
       isArchived: false,
       isFork: false,
+      isPrivate: false,
       defaultBranchRef: { name: 'main', target: { oid: 'c'.repeat(40), tree: { oid: tree } } },
     }
   }