feat(08.1-01): rebuild all fixtures and bot graph builders through the ARG3 path

- mini-graph-arg2.bin: the frozen ARG2-era bytes preserved once as the D-12 decode-rejection vector (never regenerated — the arg1 precedent) - build-mini-graph.mjs: landmark stage out, CH stage in — contractGraph over the 25-node grid (41 shortcuts, 1.64/node, 0 budget hits) with fail-loud invariants: total-order rank, grid shortcut band, upward shortcuts, overlay-exact constituent weights (f64 replay, f32 compare), strong connectivity; deterministic ARG3 bytes - graph.test.mjs: committed-fixture G4 added (ARG3 magic/version, 25 nodes, 80 edges, rank 25, >=1 shortcut, ARG2 vector -> null); G7 restored (full ARG3 pin) - astar.test.mjs: A1-A6 restored — the 625-pair Dijkstra equivalence, oneway law, deriveSteps, depart/arrive, classifyTurn all green against the CH query on the committed ARG3 fixture - snap.test.mjs: S1-S6 restored on the ARG3 fixture; S3's synthetic graph rebuilt as the ARG3 ch-block star - webhook.test.mjs: landmarkBlock -> chBlock (contractGraph); corridor gains the fast nonstop chord (a pure line starves to zero shortcuts); sparse star keeps node ids 0-hub; RT9's split carrier is now two disconnected decodable stars (the honest A\* miss) - guidance-cron.test.mjs: GC6b's 2-node graph becomes the lowest-id-mid 3-node star (a 2-node graph cannot carry a valid shortcut) - routing 87 passed / bot 126 passed; routing+bot+web typechecks green
2026-10-26 07:30:15 +08:00
parent 06624bb688
commit 4ca7a71d15
8 changed files with 524 additions and 132 deletions
@@ -49,7 +49,7 @@ const { strings } = await import("../src/i18n/strings.ts");
 const { encodePolyline6 } = await import("@araharah/routing/src/polyline.ts");
 const { deriveCumulativeDistanceM, haversineM } = await import("@araharah/routing/src/geo.ts");
 const { encodeGraph, decodeGraph } = await import("@araharah/routing/src/graph.ts");
-const { LANDMARK_QUANTUM_S, landmarkTables } = await import("@araharah/routing/src/landmark.ts");
+const { contractGraph } = await import("@araharah/routing/src/contraction.ts");

 /* ————— geometry helpers (1e-6-grid-exact construction, the codec's grid law) ————— */

@@ -250,23 +250,26 @@ test("GC6b unnamed matched edge → cardStreetUnnamed ('UNNAMED ROAD') — still
  // A purpose-built unnamed way through the same encodeGraph contract
  // (names: [] → every edge carries the UNNAMED_NAME_ID sentinel).
  const meters = haversineM({ lat: 3.15, lng: 101.69 }, { lat: 3.1505, lng: 101.69 });
-  const edges = [
+  // A 3-node star through the same encodeGraph contract (names: [] →
+  // every edge carries the UNNAMED_NAME_ID sentinel). ARG3 (Phase 08.1):
+  // the ch block comes from the ONE contraction core, and the MID owns
+  // the LOWEST id — the priority tie contracts lowest-id-first, so a mid
+  // with id 1 would starve to zero shortcuts and an ARG3 with no
+  // shortcuts is not a road graph. Geometry: north leg (0->1), east leg
+  // (0->2) — the turn at the shared mid vertex.
+  const starEdges = [
    { from: 0, to: 1, seconds: meters / (30 / 3.6) },
    { from: 1, to: 0, seconds: meters / (30 / 3.6) },
+    { from: 0, to: 2, seconds: meters / (30 / 3.6) },
+    { from: 2, to: 0, seconds: meters / (30 / 3.6) },
  ];
-  // A 2-node graph has no degree>=2 farthest-point candidate (the selection
-  // filter), so the anchor pins directly — the tables still come from the
-  // ONE integer-Dijkstra core (08-02), through the ONE encode authority.
-  const landmarkInput = { nodeCount: 2, edges, quantumS: LANDMARK_QUANTUM_S };
-  const anchors = Uint32Array.of(0);
-  const { to, from } = landmarkTables(landmarkInput, anchors);
  const buf = encodeGraph({
-    lat: [3.15, 3.1505],
-    lng: [101.69, 101.69],
-    edges,
+    lat: [3.15, 3.1505, 3.15],
+    lng: [101.69, 101.69, 101.6905],
+    edges: starEdges,
    names: [],
    maxSpeedKmh: 30,
-    landmarks: { quantumS: LANDMARK_QUANTUM_S, nodes: anchors, to, from },
+    ch: contractGraph({ nodeCount: 3, edges: starEdges }),
  });
  const graph = decodeGraph(buf);
  assert.notEqual(graph, null);
@@ -472,31 +472,37 @@ test("GW11 PUT /api/guidance → 405", async () => {

 const { encodeGraph } = await import("../../routing/src/graph.ts");
 const { haversineM } = await import("../../routing/src/geo.ts");
-const { LANDMARK_QUANTUM_S, farthestPointAnchors, landmarkTables } = await import(
-  "../../routing/src/landmark.ts"
-);
+const { contractGraph } = await import("../../routing/src/contraction.ts");

-/** Tiny REAL landmark block through the ONE preprocessing core (08-02):
- *  farthest-point anchor + integer ĉ tables — computed, never faked.
- *  `{ pin }` pins the anchor for graphs with no degree>=2 candidate (the
- *  selection filter's law — e.g. a single-segment graph); the tables still
- *  come from the ONE integer-Dijkstra core. */
-function landmarkBlock(nodeCount, edges, { pin } = {}) {
-  const input = { nodeCount, edges, quantumS: LANDMARK_QUANTUM_S };
-  const anchors = pin !== undefined ? Uint32Array.of(pin) : farthestPointAnchors(input, 1);
-  if (anchors.length !== 1) throw new Error("graph has no degree-2 anchor candidate");
-  const { to, from } = landmarkTables(input, anchors);
-  return { quantumS: LANDMARK_QUANTUM_S, nodes: anchors, to, from };
+/** The ARG3 ch block through the ONE contraction core (Phase 08.1):
+ *  computed, never faked. A shape that contracts to ZERO shortcuts is a
+ *  builder bug — an ARG3 with chShortcutCount = 0 is not a road graph
+ *  (the decode law refuses it), so fail loud here instead of shipping an
+ *  undecodable test binary. */
+function chBlock(nodeCount, edges) {
+  const ch = contractGraph({ nodeCount, edges });
+  if (ch.stats.shortcutCount === 0) {
+    throw new Error("graph contracted to zero shortcuts — ARG3 has no CH-less layout");
+  }
+  return ch;
 }

 /** The committed 06-01 ground truth (25 nodes around KL center) via fs. */
 const MINI_GRAPH = readFileSync(new URL("../../routing/test/fixtures/mini-graph.bin", import.meta.url));

-/** Public gazetteer landmarks only — no user coordinate enters a test (D-12). */
+/** Public gazetteer POIs only — no user coordinate enters a test (D-12). */
 const KL_TOWER = { lat: 3.1528, lng: 101.7038 };
 const KL_SENTRAL = { lat: 3.1343, lng: 101.6869 };

-/** 8-node straight corridor kl-tower → suria-klcc (public coords), two-way. */
+/** 8-node straight corridor kl-tower → suria-klcc (public coords), two-way.
+ *  ARG3 (Phase 08.1): the corridor gains ONE fast nonstop chord (0<->7,
+ *  120 km/h vs the 60 km/h local road) — a pure line contracts to ZERO
+ *  shortcuts (endpoints starve the interior on the priority tie) and a
+ *  shortcut-less ARG3 is not a road graph. The chord gives the contraction
+ *  a real hierarchy; the split variant keeps the gap AND drops the chord,
+ *  so its two line components stay disconnected (RT9's A* miss) — the
+ *  resulting binary decodes to null under the CH-less law, which flows to
+ *  the same 200-null contract. */
 function corridorGraphBuffer({ gap = false } = {}) {
  const n = 8;
  const lat = [];
@@ -512,26 +518,40 @@ function corridorGraphBuffer({ gap = false } = {}) {
    const seconds = meters / (60 / 3.6);
    edges.push({ from: i, to: i + 1, seconds, nameId: 0 }, { from: i + 1, to: i, seconds, nameId: 0 });
  }
+  if (!gap) {
+    const meters = haversineM({ lat: lat[0], lng: lng[0] }, { lat: lat[n - 1], lng: lng[n - 1] });
+    const seconds = meters / (120 / 3.6);
+    edges.push({ from: 0, to: n - 1, seconds, nameId: 0 }, { from: n - 1, to: 0, seconds, nameId: 0 });
+  }
  return encodeGraph({
    lat,
    lng,
    edges,
    names: ["Jalan Koridor Ujian"],
    maxSpeedKmh: 60,
-    landmarks: { ...landmarkBlock(n, edges) },
+    ch: chBlock(n, edges),
  });
 }

 /** Nodes cluster at two far-apart cells with a nodeless middle: an in-bbox
- *  origin between them is the snap-miss carrier (3x3-neighborhood law). */
+ *  origin between them is the snap-miss carrier (3x3-neighborhood law).
+ *  ARG3: node 0 is the star's hub (two unnamed legs, ids kept so the
+ *  contraction's lowest-id tie-break contracts the MID first — a star
+ *  whose mid id is higher starves to zero shortcuts) — the node set is
+ *  unchanged from the ARG2-era fixture, keeping RT8's snap-miss geometry
+ *  exact. */
 function sparseGraphBuffer() {
  const lat = [3.15, 3.1501, 3.1515];
  const lng = [101.69, 101.6905, 101.7];
  const meters = haversineM({ lat: lat[0], lng: lng[0] }, { lat: lat[1], lng: lng[1] });
  const seconds = meters / (50 / 3.6);
+  const meters2 = haversineM({ lat: lat[0], lng: lng[0] }, { lat: lat[2], lng: lng[2] });
+  const seconds2 = meters2 / (50 / 3.6);
  const edges = [
    { from: 0, to: 1, seconds, nameId: 0 },
    { from: 1, to: 0, seconds, nameId: 0 },
+    { from: 0, to: 2, seconds: seconds2, nameId: 0 },
+    { from: 2, to: 0, seconds: seconds2, nameId: 0 },
  ];
  return encodeGraph({
    lat,
@@ -539,12 +559,42 @@ function sparseGraphBuffer() {
    edges,
    names: ["Jalan Sparse Ujian"],
    maxSpeedKmh: 50,
-    landmarks: { ...landmarkBlock(lat.length, edges, { pin: 0 }) },
+    ch: chBlock(lat.length, edges),
+  });
+}
+
+/** RT9's disconnected carrier: two independent 3-node stars — each
+ *  decodable (real shortcuts) but the component A stars around kl-tower
+ *  and the component B stars around kl-sentra never touch, so the route
+ *  is the honest A* miss (NOT a decode refusal). */
+function splitGraphBuffer() {
+  const lat = [3.1528, 3.1533, 3.1523, 3.1343, 3.1348, 3.1338];
+  const lng = [101.7038, 101.7043, 101.7033, 101.6869, 101.6874, 101.6864];
+  const edges = [];
+  const star = (mid, a, b) => {
+    const m1 = haversineM({ lat: lat[mid], lng: lng[mid] }, { lat: lat[a], lng: lng[a] });
+    const m2 = haversineM({ lat: lat[mid], lng: lng[mid] }, { lat: lat[b], lng: lng[b] });
+    edges.push(
+      { from: mid, to: a, seconds: m1 / (60 / 3.6), nameId: 0 },
+      { from: a, to: mid, seconds: m1 / (60 / 3.6), nameId: 0 },
+      { from: mid, to: b, seconds: m2 / (60 / 3.6), nameId: 0 },
+      { from: b, to: mid, seconds: m2 / (60 / 3.6), nameId: 0 },
+    );
+  };
+  star(0, 1, 2); // component A around kl-tower
+  star(3, 4, 5); // component B around kl-sentra — no edge bridges the two
+  return encodeGraph({
+    lat,
+    lng,
+    edges,
+    names: ["Jalan Split Ujian"],
+    maxSpeedKmh: 60,
+    ch: chBlock(lat.length, edges),
  });
 }

 const CORRIDOR_BUF = corridorGraphBuffer();
-const SPLIT_BUF = corridorGraphBuffer({ gap: true });
+const SPLIT_BUF = splitGraphBuffer();
 const SPARSE_BUF = sparseGraphBuffer();

 /** An R2 fake over one fixed binary; counts + records its gets (the memo probe).
@@ -5,14 +5,14 @@
 * RED first (plan 06-01 task 3): behavior cases fail while
 * routing/src/astar.ts does not exist (lazy-import pattern).
 *
- * Phase 08.1 re-pin (plan 01 task 2): routeAstar is CH-backed — the ALT
+ * Phase 08.1 re-pin (plan 01 tasks 2-3): routeAstar is CH-backed — the ALT
 * machinery is DELETED (D-04/D-05: one search path, no dormant engine).
 * The exhaustive equivalence law (A1's 625-pair sweep) and the oneway /
 * steps / classifier laws carry over UNCHANGED in intent; the
- * committed-fixture cases (A1/A2/A4/A5/A6) are SUSPENDED here because
- * mini-graph.bin is still ARG2 at this point in the plan — task 3
- * regenerates the fixture through the ARG3 encode path and un-suspends
- * them in place. The in-memory and structural cases are re-pinned HERE:
+ * committed-fixture cases (A1/A2/A4/A5/A6) were held out in task 2 while
+ * mini-graph.bin was still ARG2 and are restored here (task 3
+ * regenerated the fixture through the ARG3 encode path). The in-memory
+ * and structural cases were re-pinned in task 2:
 *
 *   A3  unreachable -> null    — honest miss (synthetic disconnected
 *                                graph, ch block through the ONE authority)
@@ -24,13 +24,16 @@
 *                                unpacking exist in ch-query.ts CODE;
 *                                astar.ts contains NO landmark token
 *                                (D-04's one-search-path pin)
- *   A1  exhaustive equivalence — SUSPENDED until task 3 (ARG3 fixture)
- *   A2  oneway respected       — SUSPENDED until task 3 (ARG3 fixture)
- *   A4  deriveSteps L-path     — SUSPENDED until task 3 (ARG3 fixture)
- *   A5  depart + arrive always — SUSPENDED until task 3 (ARG3 fixture)
- *   A6  classifyTurn pins      — SUSPENDED until task 3 (ARG3 fixture)
+ *   A1  exhaustive equivalence — 625 pairs, cost equality + path endpoints
+ *   A2  oneway respected       — the flagged edge is never traversed; the
+ *                                open direction is direct
+ *   A4  deriveSteps L-path     — 90-deg bearing changes classify left/right;
+ *                                steps carry name/distanceM/polyline6
+ *   A5  depart + arrive always — straight paths still start "depart" and
+ *                                end "arrive"
+ *   A6  classifyTurn pins      — sign convention: negative delta = left
 *
- * The A9/A10/A12/A13 ALT-era cases (island / search-scoped skip / oneway
+ * The A9/A10/A12/A13 ALT-era cases (island / search-scoped drop / oneway
 * ring / mixed columns) folded into ch-query.test.mjs: their surviving
 * content is CH-law Dijkstra equivalence over directed fixtures — the
 * ALT-specific table assertions are gone with the tables (D-05).
@@ -60,8 +63,13 @@ function toArrayBuffer(buf) {
  return buf.buffer.slice(buf.byteOffset, buf.byteOffset + buf.byteLength);
 }

-// loadMiniGraph() returns in task 3, when the committed fixture is ARG3
-// and the suspended cases un-suspend.
+async function loadMiniGraph() {
+  const { decodeGraph } = await loadGraph();
+  const g = decodeGraph(toArrayBuffer(readFileSync(path.join(here, "fixtures", "mini-graph.bin"))));
+  assert.ok(g, "the committed mini-graph decodes");
+  return g;
+}
+

 /** Brute-force O(n^2) Dijkstra — plain arrays, SAME traversal law as CH. */
 function dijkstra(g, origin, goal) {
@@ -192,25 +200,136 @@ test("A11 structural (CH law) — the uphill rank filter + unpacking live in ch-

 /* ————— suspended committed-fixture cases (task 3 un-suspends) ————— */

-test("A1 exhaustive equivalence — SUSPENDED until task 3 regenerates mini-graph.bin as ARG3", async () => {
-  // The committed fixture is still ARG2 here; the CH query's exhaustive
-  // 625-pair Dijkstra-equivalence law runs in ch-query.test.mjs (Q1) on
-  // an in-memory ARG3 grid until task 3 re-pins this case in place.
-  assert.ok(true, "suspended: deferred to task 3 (fixture regeneration)");
+test("A1 exhaustive equivalence — A* matches brute-force Dijkstra on EVERY 25x25 node pair", async () => {
+  const { routeAstar } = await loadAstar();
+  const g = await loadMiniGraph();
+  let pairs = 0;
+  let reachable = 0;
+  for (let o = 0; o < g.nodeCount; o++) {
+    for (let t = 0; t < g.nodeCount; t++) {
+      pairs++;
+      const optimal = dijkstra(g, o, t);
+      const result = routeAstar(g, o, t);
+      if (optimal === Infinity) {
+        assert.equal(result, null, `pair ${o}->${t}: unreachable must resolve null, never a path`);
+        continue;
+      }
+      reachable++;
+      assert.ok(result, `pair ${o}->${t}: reachable must route`);
+      assert.ok(
+        Math.abs(result.seconds - optimal) < 1e-6,
+        `pair ${o}->${t}: A* cost ${result.seconds} vs Dijkstra ${optimal}`,
+      );
+      assert.equal(result.nodes[0], o, `pair ${o}->${t}: path starts at origin`);
+      assert.equal(result.nodes[result.nodes.length - 1], t, `pair ${o}->${t}: path ends at goal`);
+      assert.ok(result.distanceM > 0 || o === t, `pair ${o}->${t}: distanceM summed over the path`);
+    }
+  }
+  assert.equal(pairs, 625, "the full 25x25 sweep ran");
+  assert.ok(reachable > 600, `the grid is densely connected (${reachable} reachable pairs)`);
 });

-test("A2 oneway respected — SUSPENDED until task 3 regenerates mini-graph.bin as ARG3", async () => {
-  assert.ok(true, "suspended: deferred to task 3 (fixture regeneration)");
+test("A2 oneway respected — the flagged edge is never traversed; the open direction is direct", async () => {
+  const { routeAstar } = await loadAstar();
+  const g = await loadMiniGraph();
+  // The fixture's single oneway-reverse edge is 3 -> 2 (perimeter, row 0).
+  // Routing AGAINST it (3 -> 2) must take the long way around the block.
+  const against = routeAstar(g, 3, 2);
+  assert.ok(against, "3->2 routes via the detour");
+  assert.equal(
+    against.nodes.length > 2,
+    true,
+    `the flagged 1-edge path must NOT be used (path: ${against.nodes.join("->")})`,
+  );
+  assert.ok(
+    Math.abs(against.seconds - dijkstra(g, 3, 2)) < 1e-6,
+    "the detour cost matches Dijkstra",
+  );
+  // The open direction is the direct edge.
+  const with_flow = routeAstar(g, 2, 3);
+  assert.ok(with_flow, "2->3 routes");
+  assert.equal(with_flow.nodes.length, 2, "2->3 is the direct single edge");
+  assert.ok(Math.abs(with_flow.seconds - dijkstra(g, 2, 3)) < 1e-6);
 });

-test("A4 deriveSteps L-path — SUSPENDED until task 3 regenerates mini-graph.bin as ARG3", async () => {
-  assert.ok(true, "suspended: deferred to task 3 (fixture regeneration)");
+test("A4 deriveSteps L-path — 90-deg turns classify, steps carry name/distance/polyline6", async () => {
+  const { routeAstar, deriveSteps } = await loadAstar();
+  const { decodePolyline6 } = await import("../src/polyline.ts");
+  const g = await loadMiniGraph();
+  // 0=(r0,c0) -> 1=(r0,c1) -> 6=(r1,c1) -> 7=(r1,c2): east, then north
+  // (increasing row = increasing lat), then east.
+  const steps = deriveSteps(g, [0, 1, 6, 7]);
+  const kinds = steps.map((s) => s.kind);
+  assert.deepEqual(kinds, ["depart", "left", "right", "arrive"]);
+  assert.equal(steps[0].name, "Jalan Persiaran Mini", "step 0 rides the perimeter");
+  assert.equal(steps[1].name, "Jalan Mini 2", "the left turn turns onto Jalan Mini 2");
+  assert.equal(steps[2].name, "Jalan Mini 1", "the right turn turns onto Jalan Mini 1");
+  for (const step of steps) {
+    if (step.kind === "arrive") continue;
+    assert.ok(step.distanceM > 0, `${step.kind} step has positive distance`);
+    const points = decodePolyline6(step.geometry);
+    assert.equal(points.length, 2, `${step.kind} step geometry decodes to its two endpoints`);
+  }
+  const arrive = steps[steps.length - 1];
+  assert.equal(decodePolyline6(arrive.geometry).length, 1, "the arrive step anchors the goal node");
+  // round-trip: a full route's steps derive from A*'s own node path
+  const routed = routeAstar(g, 0, 11);
+  assert.ok(routed, "0->11 routes");
+  const routeSteps = deriveSteps(g, routed.nodes);
+  assert.equal(routeSteps[0].kind, "depart", "route-derived steps start with depart");
+  assert.equal(routeSteps[routeSteps.length - 1].kind, "arrive", "and end with arrive");
+  const total = routeSteps
+    .filter((s) => s.kind !== "arrive")
+    .reduce((sum, s) => sum + s.distanceM, 0);
+  assert.ok(
+    Math.abs(total - routed.distanceM) < 1e-6,
+    `step distances sum to the route distance (${total} vs ${routed.distanceM})`,
+  );
 });

-test("A5 depart + arrive always — SUSPENDED until task 3 regenerates mini-graph.bin as ARG3", async () => {
-  assert.ok(true, "suspended: deferred to task 3 (fixture regeneration)");
+test("A5 depart + arrive always — a straight same-name path still yields [depart, arrive]", async () => {
+  const { deriveSteps } = await loadAstar();
+  const g = await loadMiniGraph();
+  const steps = deriveSteps(g, [0, 1]);
+  assert.deepEqual(
+    steps.map((s) => s.kind),
+    ["depart", "arrive"],
+    "even the simplest path starts depart and ends arrive",
+  );
+  assert.equal(steps[0].name, "Jalan Persiaran Mini");
+  assert.ok(steps[0].distanceM > 0);
+  assert.equal(deriveSteps(g, []).length, 0, "an empty path derives no steps");
+  assert.deepEqual(
+    deriveSteps(g, [12]).map((s) => s.kind),
+    ["arrive"],
+    "a trivial single-node path is just the arrive step",
+  );
 });

-test("A6 classifyTurn pins — SUSPENDED until task 3 regenerates mini-graph.bin as ARG3", async () => {
-  assert.ok(true, "suspended: deferred to task 3 (fixture regeneration)");
+test("A6 classifyTurn pins — compass convention: negative bearing delta = left", async () => {
+  const { classifyTurn, TURN_STRAIGHT_MAX_DEG, TURN_SLIGHT_MAX_DEG, TURN_UTURN_MIN_DEG } = await loadAstar();
+  assert.equal(TURN_STRAIGHT_MAX_DEG, 25);
+  assert.equal(TURN_SLIGHT_MAX_DEG, 60);
+  assert.equal(TURN_UTURN_MIN_DEG, 150);
+  assert.equal(classifyTurn(0, -90), "left");
+  assert.equal(classifyTurn(0, 90), "right");
+  assert.equal(classifyTurn(0, 20), "straight");
+  assert.equal(classifyTurn(0, -20), "straight");
+  // The plan's "(0, 40) -> slight-left" contradicts its own (0,-90)->left /
+  // (0,90)->right cases; the compass-consistent reading is pinned:
+  assert.equal(classifyTurn(0, 40), "slight-right");
+  assert.equal(classifyTurn(0, -40), "slight-left");
+  assert.equal(classifyTurn(0, 175), "uturn");
+  assert.equal(classifyTurn(0, -175), "uturn");
+  assert.equal(classifyTurn(0, 180), "uturn");
+  // boundaries: 25 stays straight, 61 is a full turn, 150 is uturn
+  assert.equal(classifyTurn(0, 25), "straight");
+  assert.equal(classifyTurn(0, 26), "slight-right");
+  assert.equal(classifyTurn(0, 60), "slight-right");
+  assert.equal(classifyTurn(0, 61), "right");
+  assert.equal(classifyTurn(0, 149), "right");
+  assert.equal(classifyTurn(0, 150), "uturn");
+  // wrap-around normalization
+  assert.equal(classifyTurn(350, 10), "straight", "20 deg across north is straight");
+  assert.equal(classifyTurn(350, 80), "right", "90 deg across north is a right");
 });
@@ -3,24 +3,28 @@
 * build-mini-graph.mjs — builds the committed mini-graph.bin fixture.
 * ----------------------------------------------------------------------
 * A MAINTAINER-TIME REPO TOOL: regenerates routing/test/fixtures/
- * mini-graph.bin — the A* correctness ground truth (plan 06-01) and the
- * snap/astar suites' shared fixture. NOT a runtime dependency; nothing in
- * bot/src/, web/src/, or routing/src/ imports it. Tests consume the
- * COMMITTED binary; only a deliberate fixture redesign re-runs this.
+ * mini-graph.bin — the routing correctness ground truth (plan 06-01) and
+ * the snap/search suites' shared fixture. NOT a runtime dependency;
+ * nothing in bot/src/, web/src/, or routing/src/ imports it. Tests
+ * consume the COMMITTED binary; only a deliberate fixture redesign re-runs
+ * this.
 *
 * PROVENANCE (Phase 8 plan 08-01): routing/test/fixtures/mini-graph-arg1.bin
 * holds the frozen ARG1-era bytes preserved expressly as the v1
 * decode-rejection vector consumed by the G-suite — it is NOT regenerated
 * by this script, ever.
+ * PROVENANCE (Phase 08.1 plan 01): routing/test/fixtures/mini-graph-arg2.bin
+ * holds the frozen ARG2-era bytes preserved expressly as the ARG2
+ * decode-rejection vector consumed by the G-suite (D-12) — it is NOT
+ * regenerated by this script, ever.
 *
 * Usage:   node routing/test/fixtures/build-mini-graph.mjs
 * Exit:    0 on write; throws on any invariant violation (never writes).
 *
- * ARG2 (plan 08-02): the fixture carries a tiny real landmark stage —
- * L=2 anchors via farthestPointAnchors + quantized c-metric tables via
- * landmarkTables (the SAME pure module the real build script uses), passed
- * through the ONE encodeGraph authority. Deterministic: identical output
- * bytes on every re-run.
+ * ARG3 (Phase 08.1, D-12): the fixture carries a tiny real CH stage —
+ * contraction via contractGraph (the SAME pure module the real build
+ * script uses), passed through the ONE encodeGraph authority as the `ch`
+ * block. Deterministic: identical output bytes on every re-run.
 *
 * Design (pinned by 06-01): a hand-built 5x5 grid in a ~0.002 deg x 0.002 deg
 * bbox near KL center (lat 3.1500–3.1520, lng 101.6900–101.6920):
@@ -34,7 +38,7 @@
 import { writeFileSync } from "node:fs";
 import { encodeGraph } from "../../src/graph.ts";
 import { haversineM } from "../../src/geo.ts";
-import { LANDMARK_QUANTUM_S, farthestPointAnchors, landmarkTables, landmarkCoverage } from "../../src/landmark.ts";
+import { contractGraph, CH_SHORTCUT_EXPLOSION_RATIO } from "../../src/contraction.ts";

 const GRID = 5;
 const LAT0 = 3.15;
@@ -92,27 +96,86 @@ reverse.flags = 1;

 if (edges.length !== 80) throw new Error(`expected 80 directed edges, built ${edges.length}`);

-// LANDMARK STAGE (plan 08-02): the fixture regenerates as ARG2 THROUGH the
-// one encode authority — the same farthestPointAnchors + landmarkTables the
-// real build script (08-04) will run, at a tiny L. Fail-loud invariants
-// before any write (the `edges.length !== 80` style).
-const LANDMARK_COUNT = 2; // tiny L: the 5x5 grid needs exactly 2 well-spread anchors
-const landmarkInput = { nodeCount: GRID * GRID, edges, quantumS: LANDMARK_QUANTUM_S };
-const anchors = farthestPointAnchors(landmarkInput, LANDMARK_COUNT);
-const { to, from } = landmarkTables(landmarkInput, anchors);
-if (anchors.length !== LANDMARK_COUNT) throw new Error(`expected ${LANDMARK_COUNT} anchors, got ${anchors.length}`);
-if (to.length !== LANDMARK_COUNT * GRID * GRID || from.length !== LANDMARK_COUNT * GRID * GRID) {
-  throw new Error("landmark tables are not L*N row-major");
+// CH STAGE (Phase 08.1): the fixture regenerates as ARG3 THROUGH the one
+// encode authority — the same contractGraph the real build script (plan 02)
+// runs. Fail-loud invariants before any write (the `edges.length !== 80`
+// style), per RESEARCH §Pattern 4.
+const ch = contractGraph({ nodeCount: GRID * GRID, edges });
+const rankValues = [...ch.rank];
+if (new Set(rankValues).size !== GRID * GRID) {
+  throw new Error(`rank is not a total order — ${new Set(rankValues).size} distinct for ${GRID * GRID} nodes`);
 }
-for (let l = 0; l < anchors.length; l++) {
-  const a = anchors[l];
-  if (to[l * GRID * GRID + a] !== 0 || from[l * GRID * GRID + a] !== 0) {
-    throw new Error(`anchor ${l} (node ${a}) own cells are not 0 — table law broken`);
+if (rankValues.some((r) => !Number.isInteger(r) || r < 0 || r >= GRID * GRID)) {
+  throw new Error("a rank value is outside [0, nodeCount)");
+}
+// The shortcut band for this grid (measured 2026-10-26, this host: 41 —
+// the literature's healthy ~1.4-2.0 per node; the tripwire sits at 4x).
+const SHORTCUT_BAND_MIN = 20;
+const SHORTCUT_BAND_MAX = 80;
+if (ch.stats.shortcutCount < SHORTCUT_BAND_MIN || ch.stats.shortcutCount > SHORTCUT_BAND_MAX) {
+  throw new Error(
+    `shortcut count ${ch.stats.shortcutCount} outside the expected grid band ` +
+      `[${SHORTCUT_BAND_MIN}, ${SHORTCUT_BAND_MAX}] — check the contraction/witness budget`,
+  );
+}
+// Overlay-aware weight map: a cascading shortcut's constituents are the
+// OVERLAY edges it replaced (originals OR earlier shortcuts — emission
+// order is the contraction order, so replaying rank[via]-ascending
+// rebuilds every weight exactly).
+const weight = new Map(); // "a,b" -> min overlay weight
+for (const e of edges) {
+  if ((e.flags & 1) !== 0) continue;
+  const key = `${e.from},${e.to}`;
+  const prev = weight.get(key);
+  if (prev === undefined || e.seconds < prev) weight.set(key, e.seconds);
+}
+const shortcutEntries = [];
+for (let u = 0; u < GRID * GRID; u++) {
+  for (let s = ch.shortcutStart[u]; s < ch.shortcutStart[u + 1]; s++) {
+    shortcutEntries.push({ from: u, to: ch.shortcutTarget[s], seconds: ch.shortcutSeconds[s], via: ch.shortcutVia[s] });
  }
 }
-const coverage = landmarkCoverage(to, anchors, GRID * GRID);
-if (coverage.some((c) => c !== 1)) {
-  throw new Error(`the grid is strongly connected — coverage must be 1.0, got ${coverage.join(", ")}`);
+shortcutEntries.sort((a, b) => ch.rank[a.via] - ch.rank[b.via] || a.from - b.from || a.to - b.to);
+for (const sc of shortcutEntries) {
+  const via = sc.via;
+  if (!Number.isInteger(via) || via < 0 || via >= GRID * GRID) {
+    throw new Error(`shortcut ${sc.from}->${sc.to} has an out-of-range via ${via}`);
+  }
+  if (ch.rank[sc.from] <= ch.rank[via] || ch.rank[sc.to] <= ch.rank[via]) {
+    throw new Error(`shortcut ${sc.from}->${sc.to} (via ${via}) is not upward`);
+  }
+  const w1 = weight.get(`${sc.from},${via}`);
+  const w2 = weight.get(`${via},${sc.to}`);
+  if (w1 === undefined || w2 === undefined) {
+    throw new Error(`shortcut ${sc.from}->${sc.to} (via ${via}): a constituent overlay edge is missing`);
+  }
+  if (sc.seconds !== Math.fround(w1 + w2)) {
+    throw new Error(`shortcut ${sc.from}->${sc.to} weight ${sc.seconds} != f32(${w1} + ${w2})`);
+  }
+  const key = `${sc.from},${sc.to}`;
+  const prev = weight.get(key);
+  // The contraction's overlay accumulates f64 sums (the f32 rounding
+  // happens once, at CSR assembly) — replay the same f64 domain so the
+  // next cascade level compares exactly.
+  if (prev === undefined || w1 + w2 < prev) weight.set(key, w1 + w2);
+}
+
+// Strong connectivity (the grid is bidirectional except the ONE oneway
+// mirror — every node reaches every node).
+const adj = Array.from({ length: GRID * GRID }, () => []);
+for (const e of edges) {
+  if ((e.flags & 1) !== 0) continue;
+  adj[e.from].push(e.to);
+}
+const seen = new Uint8Array(GRID * GRID);
+const stack = [0];
+seen[0] = 1;
+while (stack.length > 0) {
+  const u = stack.pop();
+  for (const v of adj[u]) if (!seen[v]) { seen[v] = 1; stack.push(v); }
+}
+if (seen.some((s) => s === 0)) {
+  throw new Error("the grid is not strongly connected — fixture invariant broken");
 }

 const bin = encodeGraph({
@@ -121,11 +184,18 @@ const bin = encodeGraph({
  edges,
  names,
  maxSpeedKmh: SPEED_PERIMETER_KMH,
-  landmarks: { quantumS: LANDMARK_QUANTUM_S, nodes: anchors, to, from },
+  ch: {
+    rank: ch.rank,
+    shortcutStart: ch.shortcutStart,
+    shortcutTarget: ch.shortcutTarget,
+    shortcutSeconds: ch.shortcutSeconds,
+    shortcutVia: ch.shortcutVia,
+  },
 });
 writeFileSync(new URL("./mini-graph.bin", import.meta.url), Buffer.from(bin));
 console.log(
  `mini-graph.bin: ${GRID * GRID} nodes, ${edges.length} edges, 3 names, ` +
-    `L=${LANDMARK_COUNT} landmarks (nodes ${[...anchors].join(",")}), quantum ${LANDMARK_QUANTUM_S}s, ` +
-    `coverage ${coverage.map((c) => c.toFixed(2)).join("/")}, ${bin.byteLength} B`,
+    `CH shortcuts ${ch.stats.shortcutCount} (${ch.stats.ratioPerNode.toFixed(2)}/node, ` +
+    `witness searches ${ch.stats.witnessSearches}, budget hits ${ch.stats.witnessBudgetHits}), ` +
+    `${bin.byteLength} B`,
 );
@@ -31,6 +31,9 @@
 *   G3  bad version -> null — ARG1 fixture bytes -> null (D-01 one-path
 *                             law); version 1, 2 and 4 tampers -> null
 *                             (the accepted version is 3)
+ *   G4  committed fixture   — mini-graph.bin (ARG3) is 25 nodes / 80
+ *                             edges / rank 25 / >= 1 shortcut; the frozen
+ *                             mini-graph-arg2.bin decodes to null (D-12)
 *   G4  truncated/hostile -> null — byte-length ≠ header-declared size
 *                             (incl. huge-count header on a tiny buffer,
 *                             T-06-03b: size check BEFORE view allocation)
@@ -38,10 +41,12 @@
 *                             flipping an input byte flips the decoded view
 *   G6  name pool           — nameAt(0) === "Jalan Mini 1";
 *                             nameAt(UNNAMED_NAME_ID) === undefined
- *   G7  committed fixture   — SUSPENDED until task 3 regenerates
- *                             mini-graph.bin through the ARG3 encode path
- *                             (the committed bytes are still ARG2 here);
- *                             task 3 re-pins this case in place
+ *   G7  committed fixture   — mini-graph.bin (ARG3, regenerated through
+ *                             the ONE encode authority) decodes: 25 nodes,
+ *                             80 edges, 3 names, maxSpeed 60, exactly ONE
+ *                             oneway flag, a total-order rank, >= 1
+ *                             upward shortcut; the frozen ARG2 vector
+ *                             decodes to null
 *   G8  exported constants  — GRAPH_MAGIC === 0x41524733, GRAPH_VERSION === 3
 *   G9  table round-trip    — the CH fields restore exactly; the CH arrays
 *                             are zero-copy views over the input buffer
@@ -164,9 +169,12 @@ test("G2 bad magic -> null — a tampered header never half-decodes (T-06-03)",

 test("G3 bad version -> null — ARG1 fixture bytes refuse; version 1, 2 and 4 tampers to null (D-01 one-path law)", async () => {
  const { encodeGraph, decodeGraph } = await loadGraph();
-  // The frozen Plan 08-01 vector: REAL ARG1 bytes decode to null — the
+  // The frozen rejection vectors: REAL ARG1 bytes decode to null — the
  // Phase 6 router-pending state covers every pre-ARG3 binary (D-01).
  // There is exactly one decode path; no v1/v2 fallback branch exists.
+  // (mini-graph-arg2.bin — the frozen ARG2-era bytes, D-12 — is pinned in
+  // the committed-fixture cases G4/G7; the version-2 tamper here covers
+  // the same law in memory.)
  const arg1 = toArrayBuffer(readFileSync(path.join(here, "fixtures", "mini-graph-arg1.bin")));
  assert.equal(decodeGraph(arg1), null, "ARG1 bytes -> null, never a throw or a fallback decode");
  const buf = encodeGraph(syntheticInput());
@@ -181,6 +189,26 @@ test("G3 bad version -> null — ARG1 fixture bytes refuse; version 1, 2 and 4 t
  assert.equal(decodeGraph(v4), null, "version 4 -> null (the accepted version is 3)");
 });

+test("G4 committed ARG3 fixture — 25 nodes / 80 edges / rank 25 / >=1 shortcut; the preserved ARG2 vector decodes to null", async () => {
+  const { decodeGraph, GRAPH_MAGIC, GRAPH_VERSION } = await loadGraph();
+  // The committed ground truth, read as bytes: ARG3 header fields only.
+  const bin = readFileSync(path.join(here, "fixtures", "mini-graph.bin"));
+  assert.equal(bin.readUInt32LE(0), GRAPH_MAGIC, "the committed fixture is ARG3-magic");
+  assert.equal(bin.readUInt32LE(4), GRAPH_VERSION, "the committed fixture is version 3");
+  assert.equal(bin.readUInt32LE(8), 25, "25 nodes");
+  assert.equal(bin.readUInt32LE(12), 80, "80 directed edges");
+  assert.ok(bin.readUInt32LE(60) >= 1, "the committed hierarchy carries at least one shortcut");
+  // Decoding sees the rank table's length too.
+  const g = decodeGraph(toArrayBuffer(bin));
+  assert.ok(g, "the committed fixture decodes as ARG3");
+  assert.equal(g.chRank.length, 25, "one rank per node");
+  assert.equal(g.chShortcutCount, bin.readUInt32LE(60), "the header count agrees with the decoded graph");
+  // The preserved ARG2-era bytes (frozen before this fixture's
+  // regeneration — D-12) decode to null: one decode path, no fallback.
+  const arg2 = toArrayBuffer(readFileSync(path.join(here, "fixtures", "mini-graph-arg2.bin")));
+  assert.equal(decodeGraph(arg2), null, "ARG2 bytes -> null (the D-07 rejection vector)");
+});
+
 test("G4 truncated + hostile-size buffer -> null — exact byte-size check BEFORE any view allocation (T-06-03b)", async () => {
  const { encodeGraph, decodeGraph } = await loadGraph();
  const buf = encodeGraph(syntheticInput());
@@ -227,13 +255,51 @@ test("G6 name pool — nameAt(0) resolves the first pool name; the unnamed senti
  assert.equal(g.nameAt(999), undefined, "out-of-range id -> undefined");
 });

-test("G7 committed ARG3 fixture — SUSPENDED until task 3 regenerates mini-graph.bin through the ARG3 encode path", async () => {
-  // The committed mini-graph.bin is still ARG2 at this point in the plan
-  // (task 2 flips the codec; task 3 regenerates the fixture through the
-  // ONE encode authority and re-pins this case in place, together with
-  // the preserved mini-graph-arg2.bin rejection vector). Documented
-  // no-op — the ONLY suspended case in this suite.
-  assert.ok(true, "suspended: deferred to task 3 (fixture regeneration)");
+test("G7 committed ARG3 fixture — decodes to 25 nodes / 80 edges / 3 names / a real hierarchy, maxSpeed 60, ONE oneway", async () => {
+  const { decodeGraph } = await loadGraph();
+  const bin = toArrayBuffer(readFileSync(path.join(here, "fixtures", "mini-graph.bin")));
+  assert.ok(bin.byteLength > 1000, `the committed fixture is substantial (${bin.byteLength} B)`);
+  const g = decodeGraph(bin);
+  assert.ok(g, "the committed fixture decodes cleanly (ARG3 — regenerated through the ONE encode authority, task 3)");
+  assert.equal(g.nodeCount, 25, "5x5 grid");
+  assert.equal(g.edgeCount, 80, "20 H + 20 V segments, both directions");
+  assert.equal(g.nameCount, 3, "Jalan Mini 1 / Jalan Mini 2 / Jalan Persiaran Mini");
+  assert.equal(g.nameAt(0), "Jalan Mini 1");
+  assert.equal(g.nameAt(2), "Jalan Persiaran Mini");
+  assert.equal(g.maxSpeedKmh, 60, "the perimeter speed class is the header max");
+  // bbox of the hand-built grid (lat 3.1500–3.1520, lng 101.6900–101.6920)
+  assert.deepEqual(g.bbox, { minLat: 3.15, minLng: 101.69, maxLat: 3.152, maxLng: 101.692 });
+  let flagged = 0;
+  for (let e = 0; e < g.edgeCount; e++) if ((g.edgeFlags[e] & 1) !== 0) flagged++;
+  assert.equal(flagged, 1, "exactly ONE oneway-reverse edge in the whole fixture");
+  // both speed classes present: perimeter ~55.6 m / 16.67 ≈ 3.3 s; interior ≈ 6.7 s
+  let sawFast = false;
+  let sawSlow = false;
+  for (let e = 0; e < g.edgeCount; e++) {
+    if (g.edgeSeconds[e] < 5) sawFast = true;
+    if (g.edgeSeconds[e] > 5) sawSlow = true;
+  }
+  assert.ok(sawFast && sawSlow, "both speed classes (60 and 30 km/h) exist in the weights");
+  // ARG3 CH laws (Phase 08.1, D-12): the fixture regenerates THROUGH the
+  // encode authority with the tiny real contraction stage (S = 41 on the
+  // 5x5 grid — the healthy ~1.6/node band).
+  assert.equal(g.chRank.length, 25, "one rank per node");
+  assert.equal(g.shortcutStart.length, 26, "CSR row pointers: nodeCount + 1");
+  assert.equal(g.shortcutTarget.length, g.chShortcutCount, "shortcut CSR lengths agree with the header");
+  assert.equal(g.shortcutSeconds.length, g.chShortcutCount, "shortcut seconds length agrees");
+  assert.equal(g.shortcutVia.length, g.chShortcutCount, "shortcut via length agrees");
+  assert.ok(g.chShortcutCount >= 1, "the committed hierarchy carries at least one shortcut");
+  // Rank is a total order (Pitfall 9) and the shortcuts are upward.
+  assert.equal(new Set(g.chRank).size, 25, "ranks are DISTINCT");
+  for (let u = 0; u < g.nodeCount; u++) {
+    for (let s = g.shortcutStart[u]; s < g.shortcutStart[u + 1]; s++) {
+      const via = g.shortcutVia[s];
+      assert.ok(g.chRank[u] > g.chRank[via] && g.chRank[g.shortcutTarget[s]] > g.chRank[via], `shortcut ${u}->${g.shortcutTarget[s]} is upward against via ${via}`);
+    }
+  }
+  // The preserved ARG2-era bytes decode to null (D-12's rejection vector).
+  const arg2 = toArrayBuffer(readFileSync(path.join(here, "fixtures", "mini-graph-arg2.bin")));
+  assert.equal(decodeGraph(arg2), null, "ARG2 bytes -> null (the D-07 rejection vector)");
 });

 test("G8 exported constants — GRAPH_MAGIC === 0x41524733 ('ARG3'), GRAPH_VERSION === 3", async () => {
@@ -25,15 +25,11 @@
 *                               (WeakMap; build-counter, kept loose) +
 *                               structural: WeakMap and cos() in the source
 *
- * Phase 08.1 re-pin: S1/S2/S3/S4/S5/S6 read the committed mini-graph.bin (S3's
- * perimeter half) — they are
- * which is still ARG2 mid-plan — they are SUSPENDED until task 3
- * regenerates the fixture through the ARG3 encode path (the same
- * suspension pattern as graph.test.mjs G7 and astar.test.mjs A1–A6).
- * S3 was re-pinned NOW: its synthetic graph moved to the ARG3 ch block
- * (a 3-node star — a 2-node graph can carry no valid shortcut).
- *
- * Run:  npm run routing:test   (exit 0 = all green)
+ * Phase 08.1 re-pin (plan 01 tasks 2-3): the committed mini-graph.bin is
+ * now ARG3 (regenerated through the ONE encode authority) and every case
+ * runs unchanged. S3's synthetic unnamed-edge graph moved to the ARG3 ch
+ * block (a 3-node star — a 2-node graph can carry no valid shortcut, and
+ * a shortcut-less ARG3 is not a road graph).
 */
 import { strict as assert } from "node:assert";
 import { readFileSync } from "node:fs";
@@ -82,36 +78,124 @@ function nodeLng(c) {

 /* ————— S1–S6 ————— */

-test("S1 exact-node hit — SUSPENDED until task 3 regenerates mini-graph.bin as ARG3", async () => {
-  // The committed fixture is still ARG2 (decode refuses by the D-07 law); task 3 regenerates it through the ARG3 encode path and un-suspends this case in place (real body: git show f75dc9e:routing/test/snap.test.mjs).
-  assert.ok(true, "suspended: deferred to task 3 (fixture regeneration)");
+test("S1 exact-node hit — a fix at node 12's coordinates snaps to node 12 at ~0 m", async () => {
+  const { snapToGraph } = await loadSnap();
+  const g = await loadMiniGraph();
+  const result = snapToGraph(g, { lat: nodeLat(2), lng: nodeLng(2) });
+  assert.ok(result, "an on-graph fix snaps");
+  assert.equal(result.node, 12, "the exact node wins");
+  assert.ok(result.distanceM < 0.001, `distance ~ 0 (got ${result.distanceM})`);
 });

-test("S2 mid-edge projection — SUSPENDED until task 3 regenerates mini-graph.bin as ARG3", async () => {
-  // Suspended with S1; task 3 restores the real body.
-  assert.ok(true, "suspended: deferred to task 3 (fixture regeneration)");
+test("S2 mid-edge projection — a fix a quarter along edge 6->7 snaps to the closer endpoint 6, haversine distance", async () => {
+  const { snapToGraph } = await loadSnap();
+  const { haversineM } = await loadGeo();
+  const g = await loadMiniGraph();
+  // Point 25% of the way from node 6 (r1,c1) to node 7 (r1,c2).
+  const point = { lat: nodeLat(1), lng: (101690000 + 625) / 1e6 };
+  const result = snapToGraph(g, point);
+  assert.ok(result, "the mid-edge fix snaps");
+  assert.equal(result.node, 6, "the CLOSER endpoint wins — never a fabricated mid-node");
+  assert.equal(result.nameId, 0, "the best segment is 'Jalan Mini 1' (nameId 0)");
+  const expected = haversineM(point, { lat: nodeLat(1), lng: nodeLng(1) });
+  assert.ok(
+    Math.abs(result.distanceM - expected) < 1e-9,
+    `distanceM is the haversine distance to the endpoint (${result.distanceM} vs ${expected})`,
+  );
 });

-test("S3 nameId — SUSPENDED until task 3 regenerates mini-graph.bin as ARG3", async () => {
-  // Both halves read ARG2-era data mid-plan: the perimeter half reads the
-  // committed fixture, and the unnamed half's re-pinned ch block rides the
-  // same restore. Task 3 un-suspends with the ARG3 fixture (the unnamed
-  // half's 3-node-star ch-block builder is already in this file's history:
-  // git show <task-2-green>:routing/test/snap.test.mjs).
-  assert.ok(true, "suspended: deferred to task 3 (fixture regeneration)");
+test("S3 nameId — a perimeter fix resolves 'Jalan Persiaran Mini'; an unnamed segment resolves null", async () => {
+  const { snapToGraph } = await loadSnap();
+  const { encodeGraph } = await loadGraph();
+  const g = await loadMiniGraph();
+  const atNode1 = snapToGraph(g, { lat: nodeLat(0), lng: nodeLng(1) });
+  assert.ok(atNode1, "perimeter fix snaps");
+  assert.notEqual(atNode1.nameId, null, "perimeter edges carry names");
+  assert.equal(g.nameAt(atNode1.nameId), "Jalan Persiaran Mini");
+
+  // Synthetic 3-node star with UNNAMED edges -> nameId null.
+  // ARG3 (Phase 08.1): the ch block is required by the one encode
+  // authority; it comes from the ONE contraction core. A 2-node graph can
+  // carry no valid shortcut (no via node exists), so the fixture is the
+  // C4 star — mid node 0, unnamed legs to 1 and 2 — whose contraction
+  // emits the two endpoint shortcuts (decode refuses a shortcut-less
+  // ARG3). The snapped segment 0->1 covers the unnamed fix.
+  const { contractGraph } = await import("../src/contraction.ts");
+  const starEdges = [
+    { from: 0, to: 1, seconds: 4 },
+    { from: 1, to: 0, seconds: 4 },
+    { from: 0, to: 2, seconds: 4 },
+    { from: 2, to: 0, seconds: 4 },
+  ];
+  const bare = encodeGraph({
+    lat: [3.15, 3.1505, 3.16],
+    lng: [101.69, 101.6905, 101.7],
+    edges: starEdges,
+    names: [],
+    maxSpeedKmh: 60,
+    ch: contractGraph({ nodeCount: 3, edges: starEdges }),
+  });
+  const { decodeGraph, UNNAMED_NAME_ID } = await loadGraph();
+  const bg = decodeGraph(bare);
+  assert.ok(bg, "synthetic graph decodes");
+  assert.equal(bg.edgeNameId[0], UNNAMED_NAME_ID, "the synthetic edge is unnamed");
+  const unnamed = snapToGraph(bg, { lat: 3.15025, lng: 101.69025 });
+  assert.ok(unnamed, "the unnamed segment still snaps");
+  assert.equal(unnamed.nameId, null, "UNNAMED_NAME_ID resolves to null for consumers");
 });

-test("S4 bbox margin — SUSPENDED until task 3 regenerates mini-graph.bin as ARG3", async () => {
-  // Suspended with S1; task 3 restores the real body.
-  assert.ok(true, "suspended: deferred to task 3 (fixture regeneration)");
+test("S4 bbox margin — outside bbox + SNAP_BBOX_MARGIN_DEG -> null; just outside the bbox still snaps", async () => {
+  const { snapToGraph, SNAP_BBOX_MARGIN_DEG } = await loadSnap();
+  assert.equal(SNAP_BBOX_MARGIN_DEG, 0.01, "the named margin constant is 0.01 deg");
+  const g = await loadMiniGraph();
+  // bbox maxLat = 3.152; +0.008 above it is inside the margin AND near row-4 roads.
+  const justOutside = snapToGraph(g, { lat: 3.1528, lng: nodeLng(1) });
+  assert.ok(justOutside, "a fix just outside the bbox but near roads still snaps");
+  assert.ok(justOutside.node >= 20 && justOutside.node <= 24, "snaps to a row-4 node (ids 20..24)");
+  // 0.011 deg above the bbox top -> outside bbox + margin -> honest null.
+  assert.equal(
+    snapToGraph(g, { lat: 3.163, lng: nodeLng(1) }),
+    null,
+    "beyond bbox + margin -> null (router-pending upstream, D-03)",
+  );
+  assert.equal(
+    snapToGraph(g, { lat: nodeLat(1), lng: 101.703 }),
+    null,
+    "beyond bbox + margin in lng -> null",
+  );
 });

-test("S5 oneway ignored — SUSPENDED until task 3 regenerates mini-graph.bin as ARG3", async () => {
-  // Suspended with S1; task 3 restores the real body.
-  assert.ok(true, "suspended: deferred to task 3 (fixture regeneration)");
+test("S5 oneway ignored — a fix near the oneway segment snaps to its endpoints like any segment", async () => {
+  const { snapToGraph } = await loadSnap();
+  const g = await loadMiniGraph();
+  // The fixture's single oneway-reverse edge is 3 -> 2 (segment 2-3, perimeter).
+  // A fix 25% along segment 2->3 snaps to node 2 — direction plays no part.
+  const point = { lat: nodeLat(0), lng: (101690000 + 1125) / 1e6 };
+  const result = snapToGraph(g, point);
+  assert.ok(result, "the oneway segment's fix snaps");
+  assert.equal(result.node, 2, "the closer endpoint of the oneway segment wins");
+  assert.notEqual(result.nameId, null);
+  assert.equal(g.nameAt(result.nameId), "Jalan Persiaran Mini");
 });

-test("S6 memoized grid — SUSPENDED until task 3 regenerates mini-graph.bin as ARG3", async () => {
-  // Suspended with S1 (the memo law re-pins against the ARG3 fixture in task 3).
-  assert.ok(true, "suspended: deferred to task 3 (fixture regeneration)");
+test("S6 memoized grid — the coarse grid builds once per RoadGraph (WeakMap) + structural gates", async () => {
+  const mod = await loadSnap();
+  const g = await loadMiniGraph();
+  const before = mod.gridBuildCount();
+  mod.snapToGraph(g, { lat: nodeLat(2), lng: nodeLng(2) });
+  assert.equal(mod.gridBuildCount(), before + 1, "first snap on a graph builds the grid once");
+  mod.snapToGraph(g, { lat: nodeLat(0), lng: nodeLng(1) });
+  mod.snapToGraph(g, { lat: nodeLat(4), lng: nodeLng(4) });
+  assert.equal(mod.gridBuildCount(), before + 1, "subsequent snaps REUSE the memoized grid");
+  const g2 = await loadMiniGraph(); // a second decode -> a fresh RoadGraph instance
+  mod.snapToGraph(g2, { lat: nodeLat(2), lng: nodeLng(2) });
+  assert.equal(mod.gridBuildCount(), before + 2, "a new graph instance gets its own grid");
+
+  // Structural: the memo is a WeakMap and the projection scales lng by cos.
+  const src = readFileSync(path.join(here, "..", "src", "snap.ts"), "utf8");
+  const code = src
+    .replace(/\/\*[\s\S]*?\*\//g, " ")
+    .replace(/(^|[^:\\])\/\/[^\n]*/g, "$1");
+  assert.ok(code.includes("WeakMap"), "the per-graph memo is a WeakMap (no global leak)");
+  assert.ok(/Math\.cos\(/.test(code), "lng is cos(lat)-scaled — Pitfall 8 (never raw degrees)");
 });