feat(anpr): poll snapshots until a confident plate, so auto-exit works

The ANPR bridge took ONE snapshot at the camera's vehicle-alarm instant — but the
alarm fires as the car APPROACHES, so that frame's plate is small/blurry/half-in-
frame and ANPR returns a low-confidence misread ('111'@0.20). The manual test reads
the SAME car at ~100% because by then it's STOPPED at the barrier, well-framed. So
subscriber auto-exit silently never fired (read below the 0.85 floor → ignored).

Fix (the car-stops-at-the-barrier insight): the bridge now PULLS A FRESH FRAME every
ANPR_POLL_MS (1000) and re-runs ANPR until one clears VISION_ENTRY_MIN_CONFIDENCE, or
ANPR_POLL_WINDOW_MS (8000) elapses (drove off / non-subscriber → give up cleanly).
- One loop per camera (#polling set) — the camera's ~1Hz alarm re-fires JOIN the
  running loop instead of spawning N concurrent loops.
- Fresh camera.captureSnapshot each tick, NOT captureSnapshotShared (its 1.5s TTL
  would re-serve the same bad approach frame).
- Camera-level debounce stamp moved to AFTER a successful emit (suppresses re-fires
  for ANPR_DEBOUNCE_MS once we've acted), not before the loop.

VERIFIED on hardware (DS-2CD1047G3H-LIU exit lane): 7 garbage approach frames →
AA890XX@0.999 at the barrier → signed vehicle_exit. Still advisory + fail-soft; a
barrier never opens on a low-confidence read. anpr-entry.test.ts +1 (poll
escalation low→low→high); 169 server tests green. Documented in
lane-presence-and-anpr-entry + the lpr-camera camera-fault writeup.

Claude-Session: https://claude.ai/code/session_01Xcm6ikLgGoCxxHrxtjkk5V

apps/server/src/anpr-entry.test.ts

@@ -33,9 +33,16 @@ beforeEach(() => {
   captureSnapshot.mockClear();
   delete process.env.VISION_ENTRY_MIN_CONFIDENCE;
   delete process.env.ANPR_DEBOUNCE_MS;
+  // Poll-until-confident loop: keep the window + interval tiny so a below-floor / no-plate
+  // case gives up in ~one tick instead of the 8s production window (tests stay fast). Each
+  // bridge reads these in its constructor, so set them before `new AnprBridge`.
+  process.env.ANPR_POLL_MS = "1";
+  process.env.ANPR_POLL_WINDOW_MS = "5";
 });
 afterEach(() => {
   vi.restoreAllMocks();
+  delete process.env.ANPR_POLL_MS;
+  delete process.env.ANPR_POLL_WINDOW_MS;
 });
 
 /** A camera bound to an entry relay; `anpr` toggles the opt-in flag. */
@@ -128,6 +135,31 @@ describe("AnprBridge", () => {
     expect(reads).toEqual([]);
   });
 
+  it("POLLS until confident: low-confidence approach frames, then a clean stop-at-barrier frame", async () => {
+    // The car APPROACHES (garbage reads) then STOPS at the barrier (clean read) — the bridge
+    // must re-pull until one frame clears the floor, not give up on the first bad frame.
+    const cam = seedCamera({ anpr: true });
+    // analyze escalates: 0.20, 0.20, then 0.97 on the 3rd pull → that one emits.
+    const confs = [0.2, 0.2, 0.97];
+    let i = 0;
+    const vision = {
+      enabled: true,
+      analyze: vi.fn(async () => ({
+        plate: { text: "AA111BB", confidence: confs[Math.min(i++, confs.length - 1)] },
+        plates: [],
+        lowConfidence: false,
+        modelVersion: "test",
+        tookMs: 1,
+      })),
+    } as unknown as VisionClient;
+    const bridge = new AnprBridge(db, vision, fakeSubFlow(SUB_MATCH), silentLogger());
+
+    const reads = await captureReads(() => bridge.onVehicleDetected(cam));
+    expect(reads).toHaveLength(1);
+    expect(reads[0]).toMatchObject({ value: "AA111BB", kind: "plate" });
+    expect(captureSnapshot.mock.calls.length).toBeGreaterThanOrEqual(3); // re-pulled fresh frames
+  });
+
   it("does NOT emit for a plate matching no subscription — records an advisory anpr-skip", async () => {
     const cam = seedCamera({ anpr: true });
     const vision = fakeVision({ plate: "ZZ999ZZ", confidence: 0.97 });

apps/server/src/anpr-entry.ts

@@ -3,7 +3,7 @@ import { devices, deviceEvents as deviceEventsTable, eq, siteConfig, type Db, ty
 import type { FastifyBaseLogger } from "fastify";
 import { deviceEvents, type DeviceReadEvent } from "./device-events.js";
 import { directionOf, type FlowDirection } from "./device-resolve.js";
-import { buildCamera, captureSnapshotShared } from "./snapshot.js";
+import { buildCamera } from "./snapshot.js";
 import type { SubscriptionFlow } from "./subscription-flow.js";
 import type { VisionClient } from "./vision-client.js";
 
@@ -49,6 +49,25 @@ function debounceMs(): number {
   return Number.isFinite(raw) && raw > 0 ? raw : 12_000;
 }
 
+/** A single alarm fires the INSTANT motion starts — the car is still approaching, so the
+ *  first frame often has a small/blurry/absent plate (a low-confidence misread). But the car
+ *  then STOPS at the barrier (waiting for it to open) — the same stationary, well-framed
+ *  moment the manual test reads at ~100%. So instead of one shot, we POLL fresh frames and
+ *  re-run ANPR until one clears the confidence floor, or the window elapses. Poll interval: */
+function pollMs(): number {
+  const raw = Number(process.env.ANPR_POLL_MS ?? 1000);
+  return Number.isFinite(raw) && raw > 0 ? raw : 1000;
+}
+
+/** Total time to keep polling for a confident read before giving up (the car drove off, or
+ *  it's a non-subscriber). Bounded so a stray car can't loop forever. */
+function pollWindowMs(): number {
+  const raw = Number(process.env.ANPR_POLL_WINDOW_MS ?? 8000);
+  return Number.isFinite(raw) && raw > 0 ? raw : 8000;
+}
+
+const sleep = (ms: number) => new Promise<void>((r) => setTimeout(r, ms));
+
 export class AnprBridge {
   readonly #db: Db;
   readonly #vision: VisionClient | null;
@@ -56,9 +75,14 @@ export class AnprBridge {
   readonly #logger: FastifyBaseLogger;
   readonly #entryMinConfidence: number;
   readonly #debounceMs: number;
+  readonly #pollMs: number;
+  readonly #pollWindowMs: number;
   /** Last-fire timestamps, keyed by deviceId (camera-level, pre-snapshot) AND by
    *  `deviceId:plate` (post-match) — both gated against #debounceMs. */
   readonly #lastFire = new Map<string, number>();
+  /** Cameras with a poll loop already in flight — a re-fired alarm (the camera pushes ~1Hz
+   *  while the car sits) must NOT start a second concurrent loop on the same camera. */
+  readonly #polling = new Set<string>();
 
   constructor(db: Db, vision: VisionClient | null, subscription: SubscriptionFlow, logger: FastifyBaseLogger) {
     this.#db = db;
@@ -67,6 +91,8 @@ export class AnprBridge {
     this.#logger = logger;
     this.#entryMinConfidence = entryMinConfidence();
     this.#debounceMs = debounceMs();
+    this.#pollMs = pollMs();
+    this.#pollWindowMs = pollWindowMs();
   }
 
   /**
@@ -86,13 +112,18 @@ export class AnprBridge {
       if (!row || !row.enabled || row.category !== "camera") return;
       if ((row.config as CameraConfig)?.anpr !== true) return; // opt-in only
 
-      // Camera-level debounce (pre-snapshot): a car re-firing ~1Hz must not pull a
-      // snapshot + analyze every second.
+      // Post-success debounce: once we've emitted a read for this camera, ignore the
+      // ~1Hz re-fires for #debounceMs (set on success below). A fresh alarm AFTER the
+      // window is a new presentation and may start a new poll loop.
       if (this.#debounced(deviceId)) return;
-      this.#stamp(deviceId);
+      // One poll loop per camera: the camera pushes the SAME alarm ~1Hz while the car
+      // sits at the barrier — those re-fires must JOIN the running loop, not spawn N of them.
+      if (this.#polling.has(deviceId)) return;
+      this.#polling.add(deviceId);
 
       const camera = buildCamera(row);
       if (!camera) {
+        this.#polling.delete(deviceId);
         this.#logger.warn(`anpr-bridge: camera ${deviceId} config won't build`);
         return;
       }
@@ -100,18 +131,42 @@ export class AnprBridge {
       // "both" collapses to entry purely for the capture hint (it doesn't pick the lane —
       // the gated flow infers the verb from the camera's bound relay direction).
       const direction: FlowDirection = directionOf(this.#db, row) === "exit" ? "exit" : "entry";
-      // Shared capture (deviceId-keyed): coalesces with the advisory snapshotAsync for
-      // the SAME vehicle so the single-threaded camera isn't hit twice (→ HTTP 503).
-      const shot = await captureSnapshotShared(deviceId, camera, { direction });
-      const result = await this.#vision.analyze(shot.bytes, shot.contentType);
-      if (!result || !result.plate) return; // nothing read
 
-      // Entry floor — stricter than the advisory floor (analyze() still returns the plate
-      // object with its confidence even when its own lowConfidence flag is set).
-      if (result.plate.confidence < this.#entryMinConfidence) {
+      // POLL-UNTIL-CONFIDENT. The alarm fires as the car APPROACHES (small/blurry/absent
+      // plate → low-confidence misread, e.g. '111'@0.20). But the car then STOPS at the
+      // barrier — the stationary, well-framed moment the manual test reads at ~100%. So we
+      // pull a FRESH frame every #pollMs and re-run ANPR until one clears the floor, or the
+      // #pollWindowMs window elapses (car drove off / non-subscriber). NB: a fresh pull each
+      // tick — NOT captureSnapshotShared, whose TTL would re-serve the same bad frame.
+      let result: Awaited<ReturnType<VisionClient["analyze"]>> = null;
+      const deadline = Date.now() + this.#pollWindowMs;
+      let attempts = 0;
+      try {
+        while (Date.now() < deadline) {
+          attempts++;
+          const shot = await camera.captureSnapshot({ direction });
+          const r = await this.#vision.analyze(shot.bytes, shot.contentType);
+          if (r?.plate && r.plate.confidence >= this.#entryMinConfidence) {
+            result = r;
+            break;
+          }
+          if (r?.plate) {
+            this.#logger.info(
+              `anpr-bridge: '${r.plate.text}' (${r.plate.confidence.toFixed(3)}) below floor ` +
+                `${this.#entryMinConfidence} — re-pulling (attempt ${attempts})`,
+            );
+          }
+          if (Date.now() + this.#pollMs >= deadline) break;
+          await sleep(this.#pollMs);
+        }
+      } finally {
+        this.#polling.delete(deviceId);
+      }
+
+      if (!result || !result.plate) {
         this.#logger.info(
-          `anpr-bridge: plate '${result.plate.text}' below entry floor ` +
-            `(${result.plate.confidence.toFixed(3)} < ${this.#entryMinConfidence}) — ignored`,
+          `anpr-bridge: no confident plate from ${deviceId} after ${attempts} attempt(s) ` +
+            `in ${this.#pollWindowMs}ms — gave up`,
         );
         return;
       }
@@ -140,6 +195,9 @@ export class AnprBridge {
       const plateKey = `${deviceId}:${plate}`;
       if (this.#debounced(plateKey)) return;
       this.#stamp(plateKey);
+      // Camera-level debounce stamp — now that we've emitted, suppress the camera's ~1Hz
+      // re-fires (and any new poll loop) for #debounceMs.
+      this.#stamp(deviceId);
 
       this.#logger.info(
         `anpr-bridge: subscriber plate '${plate}' (${result.plate.confidence.toFixed(3)}) → read bus`,