fix(api): open the public no-credential routes to any CORS origin

[JSONbored]

Summary

• `/health`, `/v1/public/stats`, and `/v1/public/github/repos/:owner/:repo/stats` are unauthenticated, cookie-free, aggregate-only endpoints, but sat behind the same strict exact-match CORS allowlist as every authenticated route.
• Confirmed live via Loki: browserless's visual-review capture of PR previews was hitting real CORS errors calling these from a fresh `-loopover-ui.<sub>.workers.dev` preview build. Cloudflare assigns a random hostname per deploy (`ui-preview-deploy.yml`), so a static exact-match allowlist can never enumerate them by design.</sub>
• Deliberately scoped narrow. I initially considered just widening the CORS origin allowlist to any `.workers.dev`/`.pages.dev` origin (there's precedent for trusting that suffix elsewhere in this codebase, `src/review/visual/shot.ts`'s SSRF-guarded screenshot host allowlist) -- but this app's global CORS middleware also sets `Access-Control-Allow-Credentials: true`, and this app has real HttpOnly session cookies. Widening the credentialed allowlist itself would let any third party hosted on that same shared platform ride an authenticated user's session cross-origin. That's a real security regression I caught before shipping, not a hypothetical.
• Instead this adds a separate, credential-free CORS branch for exactly these 3 known-public routes (mirrors the existing `handleStats` `"*"`-with-no-credentials pattern already used for a comparable public feed), gated by a new `isPublicNoCredentialRoute()` path check. Every other route's CORS behavior -- the strict allowlist + credentials -- is completely unchanged.

Test plan

• New `test/unit/routes-cors.test.ts`: confirms the 3 public routes (including a GET with dynamic path segments, and an OPTIONS preflight) open to an arbitrary `.workers.dev`/`.pages.dev` origin with no credentials header
• REGRESSION: an authenticated route from the same unlisted preview origin gets NO CORS headers at all (still protected)
• REGRESSION: a genuinely allowlisted origin on a non-public route still gets the credentialed treatment, unchanged
• Confirms a public-but-not-in-the-3-route-list endpoint (`/v1/public/subnet-interface`) correctly does NOT get the open treatment -- only the routes that were actually failing
• Updated the 2 existing `test/integration/api.test.ts` assertions that expected the old reflected-origin behavior for `/health` and the GitHub-repo-stats route
• Full `npm run test:ci` gate green

[superagent-security]

Superagent didn't find any vulnerabilities or security issues in this PR.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.60%. Comparing base (7ee0670) to head (7f84431).
⚠️ Report is 29 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

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##             main    #6401   +/-   ##
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  Coverage   95.60%   95.60%           
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  Files         601      601           
  Lines       47310    47320   +10     
  Branches    15050    15054    +4     
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+ Hits        45232    45242   +10     
  Misses       1291     1291           
  Partials      787      787           

Flag	Coverage Δ
shard-1	43.93% <16.66%> (-0.10%)	⬇️
shard-2	36.93% <100.00%> (+0.28%)	⬆️
shard-3	32.29% <61.11%> (-0.24%)	⬇️
shard-4	34.65% <11.11%> (+0.07%)	⬆️
shard-5	31.43% <11.11%> (-0.16%)	⬇️
shard-6	45.42% <94.44%> (+0.45%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
src/api/routes.ts	94.50% <100.00%> (+0.02%)	⬆️

[loopover-orb]

Warning

⏸️ LoopOver review result - manual review recommended

_{Review updated: 2026-07-16 07:03:55 UTC}

3 files · 1 AI reviewer · 2 blockers · CI green · clean

⏸️ Suggested Action - Manual Review

Review summary
This PR splits the global CORS middleware into two branches: a wildcard, credential-free branch for three known-public, unauthenticated GET routes (health, public stats, per-repo stats), and the existing strict allowlist+credentials branch for everything else. The isPublicNoCredentialRoute check is a tight allowlist of exact/regex path matches, credentials are never set in the new branch, and the accompanying tests cover the 3 public routes, an OPTIONS preflight, and two regression cases confirming non-public and authenticated routes are unaffected. The security reasoning (avoiding widening the credentialed allowlist to a shared-hostname suffix) is sound and the change is narrowly scoped to the stated problem.

Nits — 5 non-blocking

• The new branch drops `Access-Control-Allow-Headers: mcp-session-id, mcp-protocol-version` and narrows `Access-Control-Allow-Methods` to `GET, OPTIONS` (src/api/routes.ts ~961-963); confirm none of the 3 public routes are ever called with MCP headers or non-GET methods, since a future MCP client hitting these paths cross-origin would silently fail preflight.
• The new branch omits `Vary: Origin` (src/api/routes.ts ~964) even though the response is now origin-independent (`*`), which is correct, but worth a one-line comment noting that's intentional so a future editor doesn't 're-add' it by copying the else-branch pattern.
• `isPublicNoCredentialRoute` (src/api/routes.ts ~5975) is a hard-coded path list; if a 4th public route is added later it's easy to forget updating this function — consider colocating it with the route registration or referencing the route table directly.
• Consider extracting the shared header-setting logic (Allow-Methods, Max-Age) between the two branches to reduce duplication, though the current explicit duplication is arguably clearer for a security-sensitive branch.
• Add a code comment cross-reference from `requiresApiToken` to `isPublicNoCredentialRoute` (src/api/routes.ts) since both are path-classification functions for public vs protected routes and could drift out of sync.

Concerns raised — review before merging

• No linked issue detected — If this PR is intended to solve an issue, link it explicitly in the PR body.
• Maintainer requires a linked issue — Link the relevant issue (for example Closes #123) before opening the PR.

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Fix the following blocker(s) from this PR review:

1. No linked issue detected — If this PR is intended to solve an issue, link it explicitly in the PR body.

2. Maintainer requires a linked issue — Link the relevant issue (for example `Closes #123`) before opening the PR.

Decision drivers

• ❌ Code review — 2 blockers (1 reviewer)
• ❌ Gate result — Blocking (Repo-configured hard blocker found.)

Context & advisory signals — never blocks the verdict

Signal	Result	Evidence
Linked issue	⚠️ Missing	No linked issue or no-issue rationale found.
Related work	✅ No active overlap found	No same-issue or scoped active PR overlap found.
Change scope	✅ 20/20	Low review scope from cached public metadata (no linked issue context).
Validation posture	✅ 25/25	PR body includes validation/test evidence.
Contributor workload	✅ 10/10	Author activity: 42 registered-repo PR(s), 34 merged, 374 issue(s).
Contributor context	✅ Confirmed Gittensor contributor	JSONbored; Gittensor profile; 42 PR(s), 374 issue(s).
Improvement	✅ Minor	risk: clean · value: minor

Review context

• Author: JSONbored
• Role context: owner (maintainer lane)
• Public audience mode: oss maintainer
• Lane context: Repository is configured for direct PR review.
• Public profile languages: not available
• Official Gittensor activity: 42 PR(s), 374 issue(s).
• PR-specific overlap: none found.

Contributor next steps

• Start here: Treat this as maintainer-lane context rather than normal contributor-lane activity.
• Then work through the remaining 2 steps in the Signals table above.

Signal definitions

• Related work = same linked issue, overlapping active PRs, or title/path similarity.
• Change scope = cached public metadata such as size labels, draft state, and review-burden hints.
• Validation posture = whether the PR provides enough public validation/test evidence for maintainer review.
• Contributor workload = public contributor activity and cleanup pressure, not a repo-wide quality failure.
• Contributor context = public GitHub/Gittensor identity context; non-Gittensor status is not a blocker.

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_{🟩 Safe / merged · 🟦 Advisory · 🟨 Held for review · 🟥 Blocked / closed}

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