Sentinel Fingerprint — Desktop vs OmniRoute

Part of openai-research. Sources: desktop renderer (sPr, 24 slots) and OmniRoute (buildPrekeyConfig, 18 slots).

The OmniRoute codebase documents: "Sentinel's prekey check inspects whether config[5]/config[6] reference a real chatgpt.com deployment (DPL hash + a script URL from the HTML)" — which is why it scrapes the public site HTML every hour.

Slot-by-slot comparison

Slot	Desktop (sPr)	OmniRoute (buildPrekeyConfig)
0	screen.width + screen.height	pick([3000, 4000, 3120, 4160])
1	new Date().toString()	same
2	performance.memory.jsHeapSizeLimit (real, ~2.2GB)	4294705152 fixed
3	Math.random() → solver mutates = counter	0 → solver mutates = counter
4	navigator.userAgent (real Chromium webview)	configured UA
5	pick(real webview script srcs)	scriptSrc REAL from the site (scraped)
6	match c/[^/]*/_ in scripts, else data-build	DPL hash REAL from the site (scraped)
7-8	navigator.language / languages	"en-US" / "en-US,en"
9	Math.random() → solver mutates = time	0 → solver mutates = time
10	cPr() (random navigator prototype property + value)	pick(NAVIGATOR_KEYS) (e.g. webdriver−false)
11-12	pick(keys(document)) / pick(keys(window))	same
13	performance.now()	same
14	uuid	randomUUID()
15	search params join	""
16	hardwareConcurrency	pick([8, 16, 24, 32])
17	performance.timeOrigin	Date.now() - perfNow (epoch offset)
18-23	flags: ai/createPRNG/cache/data/solana/dump/InstallTrigger in window	— (absent)

Structural divergences

1. Hash: desktop = FNV-1a 32-bit murmur-finalized; OmniRoute = SHA3-512. Mutually exclusive — the server accepts one or the other per client/route. Primary source (desktop) = FNV-1a.
2. Prekey: desktop composes gAAAAAC + base64(fingerprint) without PoW; OmniRoute solves its own PoW (empty seed, target 0fffff, 100k iterations).
3. Slots 5/6 (deployment): OmniRoute documents server-side validation against the real site deployment (DPL + script URL). The desktop sends local webview scripts + the data-build from index.html. RESOLVED at runtime (2026-08-26): the placeholder <!-- PROD_BUILD_TAG_HERE --> IS the value that leaves the client (real fingerprint, slot 6 — see sentinel-fallback-validation) and the server accepted it (lenient or not enforced for the desktop client).
4. Size: 24 slots on desktop vs 18 on OmniRoute.

Probe corrections applied (openai-chat-submode-flow.ts)

Fingerprint aligned to the desktop: slot 5 = a real webview chunk (index-rLYmMQgS.js — the only script in the index), slot 6 = the data-build attribute value (value TBD by runtime check), slot 2 = real Electron heap size, slots 10-12 = plausible navigator/document/window properties, slots 18-23 = zeros (flags absent outside a browser).

TypeScript types (the two builders)

// ── desktop (renderer sPr) ───────────────────────────────────────────────
export interface DesktopFingerprintBuilder {
  (): FingerprintArrayV24            // see sentinel-fallback-validation types
  /** gAAAAAC + base64(fingerprint) — WITHOUT PoW. The prekey. */
  prekey: (fingerprint: FingerprintArrayV24) => string
  /** FNV-1a 32-bit murmur-finalized — the desktop hash family. */
  hash: (input: string) => string
}
export interface FingerprintArrayV24 extends Array<unknown> { [k: number]: unknown }

// ── OmniRoute (buildPrekeyConfig) ────────────────────────────────────────
export interface OmniRouteConfig {
  slots: [
    number,             // pick([3000, 4000, 3120, 4160])
    string,              // new Date().toString()
    number,              // 4294705152 FIXED (vs real heap — a detectable deviation)
    number,              // counter (solver-mutated)
    string,              // configured UA
    string,              // real scriptSrc SCRAPED from the site
    string,              // DPL hash SCRAPED from the site
    string,              // 'en-US'
    string,              // 'en-US,en'
    number,              // time (solver-mutated)
    string,              // pick(NAVIGATOR_KEYS)
    unknown, unknown,    // keys(document)/keys(window)
    number,              // performance.now()
    string,              // randomUUID()
    string,              // ''
    number,              // pick([8, 16, 24, 32])
    number,              // Date.now() - perfNow (epoch offset)
  ]  // 18 slots (vs 24 desktop)
  PoW: 'SHA3-512'        // 100k iterations, target '0fffff' — DIFFERENT family from desktop
  prekey: string
}
export interface OmniRouteHash {
  (input: string): string      // SHA3-512 — mutually exclusive with the desktop's FNV-1a
}

Cross-references

• chat-submode-protocol — where the fingerprint enters the protocol
• vendor-analysis — the OmniRoute SHA3-512 PoW diverges from the desktop