Build modern British Challenger 2 style main battle tank: long low hull, large flat-sided turret with a smooth rounded front, long 120 mm rifled gun with a thermal sleeve and fume extractor, six road wheels per side, heavy side skirts, turret stowage bins and baskets, two external fuel drums on the hull rear, commander's panoramic sight (the one on sheet.jpg) as a production, REALISTIC 3D game asset in Blender, for Forge's asset library. Look at the reference
images in this directory with your image tool first: sheet.jpg. It must look like a real object from a modern
third-person game up close: never blocky, never toy-like, never flat colours.

Blender 5.2 is headless on another machine. Write bpy scripts here and run them with:
  ssh gex44 /root/blender-spike/blender-5.2.0-linux-x64/blender -b --python-exit-code 1 --python /root/fal-author/challenger2-tank-v1/<script>.py
(first `ssh gex44 mkdir -p /root/fal-author/challenger2-tank-v1`, scp scripts and any textures to gex44:/root/fal-author/challenger2-tank-v1/, scp renders back here, then
LOOK at them with your image tool). Iterate until the renders match the references: silhouette, proportions, every
named part, materials. Only one Blender job on the GPU box at a time from you.

Quality bar:
- Real dimensions in metres: 11.55 m long with the gun forward (hull 8.33 m), 3.52 m wide, 2.49 m high.
- Construction detail as geometry where it shapes the silhouette or catches light: bevelled edges everywhere (no razor
  box edges), real thickness, frames around openings, trims, rails, fittings, bolts, ropes, cables, small parts. No
  z-fighting, no gaps, nothing floating, smooth shading on round parts.
- Photographic materials: use CC0 Poly Haven textures (download 1k or 2k jpg maps from https://dl.polyhaven.org/file/
  ph-assets/Textures/jpg/<res>/<id>/<id>_<map>_<res>.jpg, maps diff, nor_gl, arm; pick ids by browsing
  https://api.polyhaven.com/assets?t=textures) mixed with node detail (rust streaks, grime, moss, edge wear, salt), then
  BAKE each material's result with Cycles to image textures (base colour, normal, ORM) so it survives glTF export.
  List every Poly Haven id you used in NOTES.md (licence evidence). No other image sources.
- Budget: 80k to 140k triangles, at most 10 materials, texture images at most 2048 px, GLB at most 12 MB.

Export contract (glTF binary .glb, Y up, metres): Gun forward toward +Z, up = +Y, +X = the tank's LEFT side, centred on X = 0; origin (0,0,0) on the ground plane at the centre of the hull footprint. Tracks touch y = 0. Turret straight ahead, gun level. Apply transforms and modifiers. No cameras, lights or
helpers in the GLB. GAME WEIGHT overrides the budget above: every texture image at most 1024 px, ORM / occlusion maps at most 512 px; share baked texture sets between parts and use tiling materials + trim textures on big surfaces. RIG. Separate named mesh nodes: Hull (everything fixed to the hull), Turret (origin ON the turret ring's vertical axis, turns about Y), Gun (child of Turret: the mantlet, origin on the trunnion axis, elevates about X), Barrel (child of Gun: the tube forward of the mantlet, origin on the bore axis where it leaves the mantlet: a game slides it back along the bore for recoil), empty Muzzle (barrel tip, child of Barrel), MG (roof machine gun, child of Turret, origin at its pivot) where the type has one, Track_L, Track_R (the track belts: their texture V coordinate runs ALONG the track, once round the loop, so a game scrolls or deforms it to animate; links modelled as geometry), every road wheel, sprocket, idler and return roller as its own node Wheel_L1..Wheel_Ln and Wheel_R1..Wheel_Rn (front to back, origin at its hub, spin about X). Crew hatches as their own nodes, origin on the hinge line, closed: Hatch_Commander, Hatch_Driver and Hatch_Loader where the type has them, with a dark crew space modelled just under each so an open hatch shows depth, not a hole to nowhere. Empty nodes (no mesh): Seat_Commander (head-out hatch point), Seat_Driver, Exhaust, Light_Head_L, Light_Head_R, Fx_Engine (centre of the engine deck: where a game puts fire and smoke), Fx_Ammo (inside the hull where the ammunition burns), Fx_Hatch (top of the commander hatch: flame jet). Lamps: material "Lamps". PAINT CONTRACT (how games get variants of one model): the main paint lives in ONE material named exactly "Paint". Its base colour TEXTURE holds only light neutral detail (near white, with grey grime, mud, dust, soot, rain streaks, panel lines, chipped edges baked in) and its baseColorFactor holds the paint colour; default factor = [0.42, 0.36, 0.24] (desert sand). A game changes that factor, so nothing else (rubber, metal, tracks, glass, lamps, weapons, interior) may use Paint. Matte military paint: no clearcoat. In nodes.json add "paints": six real paints for this model as linear RGB triples with names, the default first, chosen from: olive drab, NATO green, desert tan, field grey, winter white, dark green-black, sand, forest green, dark yellow, panzer grey, khaki brown; and render paints.png: a 3x2 grid of the same 3/4 view in those six paints (EEVEE or low-sample Cycles) to prove the recolour works. DESTRUCTIBLE TANK (library contract tank-damage/v1). Games show this tank healthy, hit, stripped of its panels, immobilised, gun knocked out, and as a burnt wreck, only by showing and hiding named nodes. So deliver TWO GLBs in the same frame, origin and scale. FILE A, challenger2-tank.glb = the healthy tank with the rig above. In it every bolt-on item is its OWN mesh node named Part_<Name>, never merged into Hull or Turret, with its origin at its own centre (a game hides it, or throws it as debris): side skirt / armour plates one node per plate (Part_Skirt_L1.. front to back, Part_Skirt_R1..), fenders and mudguards (Part_Fender_FL, _FR, _RL, _RR), stowage boxes, tool sets, fuel drums or jerrycans, exhaust mufflers and shrouds, engine deck grilles, lamp guards, spare track links, tow cable, unditching beam, antennas, smoke launchers; turret items are children of Turret (Part_Turret_<Name>: bins, bustle rack, cupola ring, sights, extra plates). Use what this type really carries: at least 14 Part_ nodes, spread over all four sides and the turret, big enough that removing them clearly changes the silhouette. UNDER every Part the Hull / Turret surface is complete and detailed (mounting brackets, bolt bosses, weld seams, unfaded paint patch; behind skirts the return rollers and upper track run): hiding a Part must never show a hole, a missing face or empty space. FILE B, challenger2-tank-damage.glb = ONLY the damage pieces (a game keeps them hidden until needed). Exactly four top-level nodes: (1) Hull_Damage, an empty at the origin, with children: Dmg_<Name> for at least 8 of the hull Parts (the SAME part in place but battle-damaged: bent, torn open, shot through with curled edges, half hanging, scorched; same origin as its Part, so a game swaps Part_X for Dmg_X); Scar_Hull_Front, Scar_Hull_L, Scar_Hull_R, Scar_Hull_Rear (hit marks for that armour face: 3 to 5 impacts each, real geometry hugging the armour 2 to 4 mm proud, no z-fighting: gouges of bright bare steel, ricochet furrows, one penetration hole with a petalled raised rim and a black inside, a soot fan around them); Track_L_Broken and Track_R_Broken (that track thrown: snapped at the front, the upper run fallen off the wheels, the loose end lying flat on the ground at y = 0 ahead of or behind the tank; a game shows it instead of Track_L / Track_R). (2) Turret_Damage, an empty exactly at the Turret origin, with children: Dmg_Turret_<Name> twins (at least 3), Scar_Turret_Front, Scar_Turret_L, Scar_Turret_R, Scar_Turret_Rear, and Gun_Broken (origin exactly at the Gun origin: the mantlet with the barrel burst and peeled open at mid length, or bent down; shown instead of Gun). (3) Wreck_Hull, at the origin: the whole hull knocked out and burnt out as ONE mesh, wheels and tracks included: paint burnt off to grey scale, rust and soot (material "Burnt", never Paint), engine deck ruptured upward, hatches blown open, several plates missing or hanging, rubber burnt off the road wheels, suspension sagged about 5 cm, tracks slack and one broken; the open turret ring well is modelled, with a dark burnt interior. (4) Wreck_Turret, origin exactly at the Turret origin (a game leaves it in place, sets it askew, or blows it off beside the hull): the burnt turret with its gun drooped to full depression and hatches open; its underside is closed, with the turret ring and basket stub modelled, because it may lie upside down. Build the damage from copies of your healthy meshes (deform, cut, boolean, decimate) so everything lines up. Budget of file B: at most 110k triangles (the wreck about 40 percent of the healthy count); materials Paint (same texture and factor as file A: the recolour must follow), Burnt, Scars (bare steel and soot), TrackSteel, Rubber; its textures at most 512 px except Paint. PROOF: render states.png, a 3x2 grid of the same 3/4 front view, built by importing BOTH exported GLBs into an empty scene: 1 healthy; 2 hit (every Scar_ node shown, six Parts swapped for their Dmg_ twins); 3 stripped (every Part_ hidden, no twins: the bare tank must still look finished); 4 immobilised (Track_L_Broken instead of Track_L, Gun_Broken instead of Gun); 5 wreck (only Wreck_Hull + Wreck_Turret); 6 wreck with Wreck_Turret blown off, lying beside the hull. LOOK at it with your image tool and fix what reads badly. In nodes.json add "damage": {"parts": [{"part", "twin" or null}], "scars": [...], "broken": {...}, "wreck": [...]} and list the nodes of both files. No national insignia, crosses, stars, roundels, flags, unit badges, serial numbers or any text: games give these to their own factions. No manufacturer logos. MOVING PARTS: never apply transforms to a moving node: each turret, gun, barrel, wheel and hatch keeps its object origin ON its own pivot (turret ring axis, gun trunnion, bore axis, wheel centre, hinge line). Check it in Blender before export: rotate each moving node 30 degrees in a test render; nothing may leave its place. Keep this directory clean: put any helper tools you install (node_modules, vendored three.js, browser checks) under /tmp, never here. Pace: deliver a first complete healthy GLB within about 30 minutes, the damage file by about 60 minutes, then use what is left of about 75 minutes to improve what the renders show is weakest. Use Cycles with the GPU (OptiX/CUDA) and modest samples for bakes and renders. 
Deliver in this directory: challenger2-tank.glb; build_challenger2-tank.py (ONE script that builds the whole asset from an empty scene,
downloads/loads its textures, bakes and exports: the GLB you deliver must come from a clean run of it); final.png
(1920x1080 Cycles render, 3/4 front view, soft daylight); side.png (orthographic side); clay.png (same view as final,
plain grey material); nodes.json (every node name with world position + overall bounding box); NOTES.md (6 lines:
what you made, triangle count, materials, texture sizes, Poly Haven ids, what still differs from the references).
Stop when you judge it matches the references and would not look out of place in a modern realistic game.