fix(api): keep private PR titles out of other workspaces and public pages

[Zach Dunn (zachdunn)]

In plain terms

PR and issue titles are resolved with the uploads GitHub App, which is installed across many GitHub orgs and can read any repo it is installed on. Title lookups did not check who was asking, so private titles could reach people outside the repo:

• Titles endpoint. GET /v1/workspaces/:workspace/github/titles checked that the caller belongs to the workspace in the path. It did not check that the requested refs belong to that workspace. A signed-in user with any workspace (self-serve signup creates one) could request any owner/repo#n. The resolver then minted that repo's installation token and returned the title and open/closed/merged state of a private PR or issue in another tenant's repo. The ghref: KV cache had no audience dimension, so a title cached for one workspace was also returned to every other caller.
• Public file pages. The unauthenticated /public/files/... JSON (behind /f/ pages) used the same resolver. A public file tagged with a private repo's gh.ref showed that PR's current title. A private repo the home installation can read leaked the same way.

After this change, private titles resolve only for workspaces linked to the repo, and public pages show live titles only for repos verified as public.

What it does / what it is not

• resolveTitles now requires an audience:
  • public uses only the home installation. It serves a title only when repoIsPrivate returns an explicit false, and it caches under a separate ghref:pub: namespace. It never calls installationForRepo.
  • member takes the set of repos linked to the caller's workspace (github_repo_links). Those repos get the existing private-capable ladder under ghref:. Every other ref falls back to the public ladder.
• The titles route scopes by repo links, not by refs found in the workspace's files. gh.* metadata is client-writable, so anyone could tag their own file with a victim's ref. Repo links are one workspace per repo, and the first claim requires GitHub write permission (Cross-tenant authorization for the bot-comment endpoint (workspace may target any org's repo) #297), so they are a real trust boundary. Because each linked repo has one workspace, the ghref: cache needs no workspace dimension.
• If D1 fails while loading links, the route fails closed: every ref degrades to the public audience.
• /f/ pages use the public audience. The uploader's stamped gh.title still shows. Only the live overlay is restricted.
• Webhook invalidation for issues and pull_request now clears both ghref: and ghref:pub: through the shared titleCacheKeys helper.
• Behavior change: a second workspace that uses a private repo linked to a different workspace loses live titles for that repo. It still sees stamped titles. Public-repo titles work for every workspace.
• Not in this PR: if a repo goes from public to private, its ghref:pub: entries can live up to their TTL (1h open, 24h settled). Those titles were public when cached. A follow-up could invalidate on the repository privatized event.
• No changeset. The change is API-only.

Technical notes

• Repo-visibility lookups are shared within a batch, so N refs in one repo cost one /repos/:repo probe. They reuse the existing ghpriv: cache, which webhooks already prime.
• A failed home-token mint returns null on the public ladder without negative-caching, because it says nothing about the ref.
• Existing ghref: entries need no purge. Public pages no longer read that namespace, and member reads are limited to linked repos.

Test plan

• Repro tests written first and confirmed failing on main: cross-tenant installation mint, cross-tenant cache read, public page serving a member-cached private title, public page minting the repo's own installation, public page leaking a home-readable private repo
• The same tests pass with the fix, along with new unit tests for the public ladder (namespace split, no installation hop, shared visibility probe, unlinked member refs falling back to public)
• Webhook tests cover invalidation of both namespaces
• pnpm test (full suite green)
• pnpm --filter @uploads/api typecheck, oxlint on changed files, pnpm format:check
• After deploy: on a signed-in workspace, check that rail titles still resolve for a linked private repo

Summary by CodeRabbit

• Bug Fixes
  • Public pages now show live GitHub titles only for verified-public repositories; otherwise, they retain the stamped title.
  • Workspace title lookups respect linked repositories. Unlinked private repositories won’t be fetched using their own installation credentials or expose titles from member caches.
  • GitHub events now invalidate both public and member title-cache entries.

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Latest commit: 4fba9fd

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[Zach Dunn (zachdunn)]

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Status	Name	Latest Commit	Preview URL	Updated (UTC)
✅ Deployment successful! View logs	uploads-api	4fba9fd	Commit Preview URL Branch Preview URL	Oct 04 2026, 06:57 PM

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📝 Walkthrough

Walkthrough

Title resolution now separates public lookups from member lookups. Public lookups require verified repository visibility and use a separate cache namespace. Workspace routes provide linked repositories for member resolution. Webhook events invalidate both title-cache keys.

Changes

Audience-scoped title resolution

Layer / File(s)	Summary
Audience resolver and cache behavior apps/api/src/github-titles.ts, apps/api/src/github-titles.test.ts	resolveTitles now selects public or member resolution. Public lookups verify repository visibility and use the ghref:pub: cache namespace. Member lookups use the ghref: namespace and retain the installation fallback for linked repositories.
Route audience selection apps/api/src/routes/public-files.ts, apps/api/src/routes/workspace-github.ts, apps/api/test/routes-public-files.test.ts, apps/api/test/routes-workspace-github.test.ts, apps/api/src/routes/github-titles-route.test.ts	Public-file requests select the public audience. Workspace requests pass linked repositories to member resolution; unlinked repositories use public resolution. Tests cover private-title handling and repository scoping.
Dual cache invalidation apps/api/src/github-webhook.ts, apps/api/src/github-webhook.test.ts, apps/api/src/github-webhook-queue.test.ts, apps/api/src/routes/github-webhook-route.test.ts	Issue and pull-request events invalidate both title-cache keys. Webhook tests now check the public and member cache entries.

Priority: ⬆️ High

Estimated code review effort: 3 (Moderate) | ~25 minutes

Change: Bug fix

Sequence Diagram(s)

sequenceDiagram
  participant WorkspaceRoute
  participant ResolveTitles
  participant TitleCache
  participant GitHub
  WorkspaceRoute->>ResolveTitles: Pass refs, audience, and linked repositories
  ResolveTitles->>TitleCache: Read audience-specific cache key
  alt Public lookup
    ResolveTitles->>GitHub: Check repository visibility with home installation
    GitHub-->>ResolveTitles: Return repository visibility
    ResolveTitles->>GitHub: Fetch issue only when repository is verified public
  else Linked member lookup
    ResolveTitles->>GitHub: Fetch with home installation
    GitHub-->>ResolveTitles: Return issue or access failure
    ResolveTitles->>GitHub: Retry with repository installation after access failure
  end
  ResolveTitles->>TitleCache: Store title or negative result
  ResolveTitles-->>WorkspaceRoute: Return titles or null results

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Merge Risk: 🔵 Low · up to 4fba9

A public page may briefly continue showing a formerly public repository’s live title after the repository becomes private. The exposure is bounded, but it remains a privacy gap to fix or explicitly accept before merging.

Security Architecture Review

Security architecture risk: 🔵 Low · up to 4fba9

The change substantially reduces cross-workspace access to private GitHub titles. Remaining disclosure risks concern stale visibility decisions and cached titles after a repository becomes private. These risks prevent a minimal rating, but the reviewed behavior is narrower than before this change.

Retained concerns
No architecture-level concerns identified.

Security review details

Security Blast Radius

• inferred — Residual external exposure is title, kind, and open/closed/merged metadata, not repository contents or installation credentials. Any workspace member can request arbitrary refs through their own workspace; anonymous viewers can receive matching live results on public-file responses. Cache replay requires a public-namespace entry, while a stale-visibility fetch additionally requires the home installation to retain access to the now-private repository.

Security Findings and Attack Paths

• observed — The two retained findings overlap on the public-cache early return: a title cached while a repository was public can still be returned after privatization without checking current visibility. The same caller exposure existed in base, which also allowed unrestricted private-capable fetches. Head narrows that exposure rather than introducing or worsening it.
• inferred — On a public-title cache miss, a stale public visibility value can authorize a fetch after privatization. If the home installation still has access, this can expose a newly private title and cache it for the normal title TTL. The explicit-public check blocks unknown results but does not make cached visibility fresh. Base already permitted these callers to fetch the same private data without a visibility restriction.

Trust Boundaries and Controls

• observed — Workspace membership alone no longer authorizes private GitHub title resolution. Eligibility comes from repository-link records, not caller refs or file metadata. Self-serve link creation requires verified GitHub write-level permission and uses first-claim-wins semantics; unlinking is owner-scoped. Unlinked refs and failed link reads select public resolution, which never uses the repository-installation fallback.

Resilience and Maintainability Implications

• inferred — Title revocation is best-effort rather than atomic. Issue and pull-request events identify both item-specific keys, but failed deletes do not fail processing, and an in-flight resolver can write after deletion. The inspected extraction does not provide repository-wide invalidation on privatization. TTLs are recovery mechanisms, not proof of immediate revocation or a strict end-to-end stale-data bound.

Hardening Proposals

• proposed — For a stronger public-title contract, evaluate fresh repository visibility before returning positive cached titles, with explicit fail-closed behavior and an assessed GitHub rate-limit cost. Pair that policy with a strategy preventing concurrent fills or delayed events from restoring revoked results.
• proposed — Before enabling database read replication, define the required unlink and reassignment revocation semantics and use a suitably fresh authorization read. Do not treat an unconstrained replica read as proof of current repository ownership.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 64.29% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 14 functions across 11 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly summarizes the main change: preventing private pull request titles from appearing in other workspaces or on public pages.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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Inline comments:
Review comments at @apps/api/src/github-titles.ts:
- Around line 151-166: Update repoIsPrivate and the isPublicRepo callback to
support bypassing the visibility cache, then update resolvePublic to check
visibility with that option before reading the title cache or fetching a title.
Return without using or updating the title cache when the repository is not
public, and preserve the existing behavior for public repositories.

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📥 Commits

Reviewing files that changed from the base of the PR and between b0e07a4 and 4fba9fd.

📒 Files selected for processing (11)

• apps/api/src/github-titles.test.ts
• apps/api/src/github-titles.ts
• apps/api/src/github-webhook-queue.test.ts
• apps/api/src/github-webhook.test.ts
• apps/api/src/github-webhook.ts
• apps/api/src/routes/github-titles-route.test.ts
• apps/api/src/routes/github-webhook-route.test.ts
• apps/api/src/routes/public-files.ts
• apps/api/src/routes/workspace-github.ts
• apps/api/test/routes-public-files.test.ts
• apps/api/test/routes-workspace-github.test.ts

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