# PR #19271 — desktop non-loopback link-proof evidence

Target: [#19271](https://github.com/pingdotgg/t3code/pull/19271).
Candidate: 3ef9d9ec113bf383bba88aa24c6da6983934176a.
Base: 1451e7cb23034d29774338608368a15d8845df36.

## Before and after

Replacing the two production files with main while retaining the consolidated HTTP suite gives one expected failure: desktop bootstrap proof request returns 400 instead of 200. Eleven other HTTP cases pass. Production files were restored byte-for-byte. Candidate: 114/114 focused tests across ten files pass; server typecheck and changed-file lint/format pass.

PR additions went 10→8 cases across two→one existing test files. Comparable affected suites went 23→21 executions across three→two files. The one-off HTTP test file and duplicated URL-helper tests were removed. The remaining success case verifies EdDSA signature, issuer, audience, type, endpoint, challenge and origin through real auth issuance and CloudLink; negative cases preserve the boundary.

## Live server proof

Started the actual Node server CLI in desktop mode with an explicit isolated base directory under the batch worktree. No provider turn, relay, tunnel, browser or Electron app was started. Used real HTTP requests to localhost TCP port 19371 with representative Host 172.24.162.233:19371; this is a Host-header transport fixture, not actual WSL networking. Exchanged a private disposable desktop bootstrap credential through /oauth/token. Neither credentials nor proof tokens are included here.

| Request | Status |
| --- | ---: |
| Desktop bootstrap, non-loopback Host, loopback signed origin | 200 |
| Paired session with spoofed desktop subject/label/header/body flag, non-loopback Host | 400 |
| Same paired session, loopback Host | 200 |
| Desktop bootstrap, non-loopback signed origin | 400 |
| Desktop bootstrap, mismatched signed-origin port | 400 |
| Desktop bootstrap, forwarded host | 400 |
| Desktop bootstrap, forwarded protocol | 400 |
| Desktop bootstrap exchanged with relay:read only | 403 |
| Unauthenticated | 401 |

The successful proof's EdDSA signature was independently verified with Node crypto and its environment public key. Its origin was 127.0.0.1:19371, its challenge matched the request, and response cache-control was no-store. The isolated server was stopped by its captured PID after verification. An initial launch with environment-precedence overriding the bootstrap base was refused by the existing ownership lock before opening the live database. The corrected launch used explicit --base-dir. No existing server was stopped.

## Limits

No packaged Windows desktop, WSL NAT/mirrored network, external proxy, actual tunnel/relay, SSH/cloud credential integration, macOS, native Linux Electron, iOS or Android was run. Source tracing and existing auth suites support the unchanged non-desktop credential paths; paired provenance was verified live. Human review of the authenticated origin boundary remains required before landing. This is nonvisual server proof, so screenshots do not apply. No merge was performed.

Tests: GPT-6-Astra (high). Implementation/integration: GPT-6.1-Sol (high), Codex harness through T3 Code.