server/index.js

import express from "express";
import cors from "cors";
import dotenv from "dotenv";
import { spawnSync } from "node:child_process";
import { readFileSync } from "node:fs";
import path from "node:path";
import OpenAI from "openai";
import { zodTextFormat } from "openai/helpers/zod";
import { z } from "zod";

function loadEnv() {
  dotenv.config({ path: "../.env" });
  dotenv.config({ path: ".env" });
}

loadEnv();

const app = express();
const port = Number(process.env.PORT || 8791);
const appRoot = process.cwd();
const pythonBin =
  process.env.PYTHON_SIM_BIN ||
  "/Users/sanju/.cache/codex-runtimes/codex-primary-runtime/dependencies/python/bin/python3";

app.use(cors());
app.use(express.json({ limit: "1mb" }));

const FeatureSchema = z.object({
  type: z.enum([
    "rib",
    "lightening_hole",
    "boss",
    "fillet_marker",
    "hook_curve",
    "clamp_jaw",
    "stator_ring",
    "stator_tooth",
    "seat_panel",
    "chair_leg",
    "chair_back",
    "chair_crossbar",
    "decorative_curve",
    "generic_panel",
    "support_tube",
    "curved_tube",
    "flat_foot",
    "armrest",
    "headrest",
    "tabletop",
    "table_leg"
  ]),
  x: z.number(),
  y: z.number(),
  x2: z.number(),
  y2: z.number(),
  width: z.number(),
  height: z.number(),
  radius: z.number(),
  note: z.string()
});

const ToolActionParamSchema = z
  .object({
    family: z.string().optional(),
    material: z.string().optional(),
    type: z.string().optional(),
    x: z.number().optional(),
    y: z.number().optional(),
    x2: z.number().optional(),
    y2: z.number().optional(),
    width: z.number().optional(),
    height: z.number().optional(),
    radius: z.number().optional(),
    note: z.string().optional(),
    point_mm: z.array(z.number()).optional(),
    vector_n: z.array(z.number()).optional(),
    length_mm: z.number().optional(),
    width_mm: z.number().optional(),
    thickness_mm: z.number().optional(),
    start: z.array(z.number()).optional(),
    end: z.array(z.number()).optional(),
    id: z.string().optional()
  })
  .passthrough();

const ToolActionSchema = z.object({
  tool: z.enum([
    "create_design_family",
    "set_material",
    "set_envelope",
    "add_feature",
    "add_mount_hole",
    "add_rib",
    "add_lightening_hole",
    "set_load",
    "observe_design",
    "measure_clearance",
    "check_constraints",
    "visual_snapshot",
    "critique_geometry",
    "export_cadquery",
    "run_fea",
    "commit_design"
  ]),
  params: ToolActionParamSchema
});

const ToolPlanSchema = z.object({
  family: z.enum(["ribbed_cantilever_bracket", "wall_hook", "torque_clamp", "motor_stator", "chair", "bike_fixture", "table", "freeform_object"]),
  rationale: z.string(),
  actions: z.array(ToolActionSchema).min(5).max(20)
});

const ScadResponseSchema = z.object({
  rationale: z.string(),
  scad_code: z.string()
});

const CadQueryResponseSchema = z.object({
  rationale: z.string(),
  cadquery_code: z.string(),
  expected_features: z.array(z.string()).default([])
});

const DesignSchema = z.object({
  title: z.string(),
  rationale: z.string(),
  material: z.enum(["aluminum_6061", "aluminum_7075", "pla", "petg", "steel_1018"]),
  load_newtons: z.number(),
  load_point_x_mm: z.number(),
  load_point_y_mm: z.number(),
  base_length_mm: z.number(),
  base_width_mm: z.number(),
  base_thickness_mm: z.number(),
  fixed_holes: z.array(
    z.object({
      x: z.number(),
      y: z.number(),
      radius: z.number()
    })
  ),
  features: z.array(FeatureSchema),
  expected_failure_mode: z.string(),
  action_plan: z.array(z.string())
});

const materials = {
  aluminum_6061: { densityGcm3: 2.7, yieldMpa: 276, youngMpa: 69000, thermalWmK: 167 },
  aluminum_7075: { densityGcm3: 2.81, yieldMpa: 503, youngMpa: 71700, thermalWmK: 130 },
  pla: { densityGcm3: 1.24, yieldMpa: 55, youngMpa: 3500, thermalWmK: 0.13 },
  petg: { densityGcm3: 1.27, yieldMpa: 50, youngMpa: 2100, thermalWmK: 0.2 },
  steel_1018: { densityGcm3: 7.87, yieldMpa: 370, youngMpa: 200000, thermalWmK: 51 }
};

const allowedToolNames = new Set([
  "create_design_family",
  "set_material",
  "set_envelope",
  "add_feature",
  "add_mount_hole",
  "add_rib",
  "add_lightening_hole",
  "set_load",
  "observe_design",
  "measure_clearance",
  "check_constraints",
  "visual_snapshot",
  "critique_geometry",
  "export_cadquery",
  "run_fea",
  "commit_design"
]);

const allowedFamilies = new Set(["ribbed_cantilever_bracket", "wall_hook", "torque_clamp", "motor_stator", "chair", "bike_fixture", "table", "freeform_object"]);
const allowedFeatureTypes = new Set([
  "rib",
  "lightening_hole",
  "boss",
  "fillet_marker",
  "hook_curve",
  "clamp_jaw",
  "stator_ring",
  "stator_tooth",
  "seat_panel",
  "chair_leg",
  "chair_back",
  "chair_crossbar",
  "decorative_curve",
  "generic_panel",
  "support_tube",
  "curved_tube",
  "flat_foot",
  "armrest",
  "headrest",
  "tabletop",
  "table_leg"
]);
const materialAliases = {
  aluminum: "aluminum_6061",
  "6061": "aluminum_6061",
  "6061 aluminum": "aluminum_6061",
  aluminium: "aluminum_6061",
  steel: "steel_1018",
  mild_steel: "steel_1018",
  mildsteel: "steel_1018",
  plastic: "pla"
};

function clamp(value, min, max) {
  return Math.max(min, Math.min(max, value));
}

function distance(x1, y1, x2, y2) {
  return Math.hypot(x2 - x1, y2 - y1);
}

function solveLinearSystem(matrix, vector) {
  const n = vector.length;
  const a = matrix.map((row, i) => [...row, vector[i]]);

  for (let col = 0; col < n; col += 1) {
    let pivot = col;
    for (let row = col + 1; row < n; row += 1) {
      if (Math.abs(a[row][col]) > Math.abs(a[pivot][col])) pivot = row;
    }
    if (Math.abs(a[pivot][col]) < 1e-9) {
      throw new Error("FEA stiffness matrix is singular; the design is under-constrained.");
    }
    [a[col], a[pivot]] = [a[pivot], a[col]];

    const divisor = a[col][col];
    for (let j = col; j <= n; j += 1) a[col][j] /= divisor;

    for (let row = 0; row < n; row += 1) {
      if (row === col) continue;
      const factor = a[row][col];
      for (let j = col; j <= n; j += 1) a[row][j] -= factor * a[col][j];
    }
  }

  return a.map((row) => row[n]);
}

function matMul(a, b) {
  return a.map((row) => b[0].map((_, col) => row.reduce((sum, value, i) => sum + value * b[i][col], 0)));
}

function transpose(matrix) {
  return matrix[0].map((_, col) => matrix.map((row) => row[col]));
}

function frameElementStiffness(E, A, I, L, c, s) {
  const EA_L = (E * A) / L;
  const EI = E * I;
  const L2 = L * L;
  const L3 = L2 * L;
  const k = [
    [EA_L, 0, 0, -EA_L, 0, 0],
    [0, (12 * EI) / L3, (6 * EI) / L2, 0, (-12 * EI) / L3, (6 * EI) / L2],
    [0, (6 * EI) / L2, (4 * EI) / L, 0, (-6 * EI) / L2, (2 * EI) / L],
    [-EA_L, 0, 0, EA_L, 0, 0],
    [0, (-12 * EI) / L3, (-6 * EI) / L2, 0, (12 * EI) / L3, (-6 * EI) / L2],
    [0, (6 * EI) / L2, (2 * EI) / L, 0, (-6 * EI) / L2, (4 * EI) / L]
  ];

  const t = [
    [c, s, 0, 0, 0, 0],
    [-s, c, 0, 0, 0, 0],
    [0, 0, 1, 0, 0, 0],
    [0, 0, 0, c, s, 0],
    [0, 0, 0, -s, c, 0],
    [0, 0, 0, 0, 0, 1]
  ];

  return matMul(transpose(t), matMul(k, t));
}

function frameLocalStiffness(E, A, I, L) {
  const EA_L = (E * A) / L;
  const EI = E * I;
  const L2 = L * L;
  const L3 = L2 * L;
  return [
    [EA_L, 0, 0, -EA_L, 0, 0],
    [0, (12 * EI) / L3, (6 * EI) / L2, 0, (-12 * EI) / L3, (6 * EI) / L2],
    [0, (6 * EI) / L2, (4 * EI) / L, 0, (-6 * EI) / L2, (2 * EI) / L],
    [-EA_L, 0, 0, EA_L, 0, 0],
    [0, (-12 * EI) / L3, (-6 * EI) / L2, 0, (12 * EI) / L3, (-6 * EI) / L2],
    [0, (6 * EI) / L2, (2 * EI) / L, 0, (-6 * EI) / L2, (4 * EI) / L]
  ];
}

function buildFrameModel(design, material, volumeAdjustments) {
  const length = clamp(design.base_length_mm, 30, 240);
  const width = clamp(design.base_width_mm, 10, 120);
  const thickness = clamp(design.base_thickness_mm, 1, 30);
  const loadX = clamp(Math.abs(design.load_point_x_mm), 5, length);
  const loadZ = thickness / 2;
  const nodeMap = new Map();
  const nodes = [];
  const elements = [];

  function node(x, z, label) {
    const key = `${x.toFixed(3)}:${z.toFixed(3)}`;
    if (nodeMap.has(key)) return nodeMap.get(key);
    const id = nodes.length;
    nodes.push({ id, x, z, label });
    nodeMap.set(key, id);
    return id;
  }

  const stations = new Set([0, loadX, length]);
  for (const feature of design.features || []) {
    stations.add(clamp(feature.x, 0, length));
    if (feature.type === "rib") stations.add(clamp(feature.x2, 0, length));
  }
  const xs = [...stations].sort((a, b) => a - b);

  const holeArea = (design.fixed_holes || []).reduce((sum, hole) => sum + Math.PI * Math.pow(clamp(hole.radius, 1, 10), 2), 0);
  const lighteningArea = (design.features || [])
    .filter((feature) => feature.type === "lightening_hole")
    .reduce((sum, feature) => sum + Math.PI * Math.pow(clamp(feature.radius, 1, width / 3), 2), 0);
  const areaReduction = clamp((holeArea + lighteningArea) / Math.max(length * width, 1), 0, 0.55);
  const baseArea = Math.max(width * thickness * (1 - areaReduction), width * thickness * 0.35);
  const baseI = Math.max((width * Math.pow(thickness, 3)) / 12 * Math.pow(1 - areaReduction, 1.8), (width * Math.pow(thickness, 3)) / 12 * 0.2);

  for (let i = 0; i < xs.length - 1; i += 1) {
    const n1 = node(xs[i], thickness / 2, "base");
    const n2 = node(xs[i + 1], thickness / 2, "base");
    if (Math.abs(xs[i + 1] - xs[i]) > 0.5) {
      elements.push({ n1, n2, A: baseArea, I: baseI, c: thickness / 2, label: "base plate beam" });
    }
  }

  for (const feature of design.features || []) {
    if (feature.type !== "rib") continue;
    const x1 = clamp(feature.x, 0, length);
    const x2 = clamp(feature.x2, 0, length);
    const ribHeight = clamp(feature.height, 1, 60);
    const ribWidth = clamp(feature.width, 1, 20);
    const z1 = thickness / 2;
    const z2 = thickness / 2 + ribHeight;
    const n1 = node(x1, z1, feature.note || "rib foot");
    const n2 = node(x2, z2, feature.note || "rib crown");
    const A = Math.max(ribWidth * ribHeight, 1);
    const I = Math.max((ribWidth * Math.pow(ribHeight, 3)) / 12, 1);
    elements.push({ n1, n2, A, I, c: ribHeight / 2, label: feature.note || "rib frame element" });
  }

  for (const feature of design.features || []) {
    if (feature.type !== "boss") continue;
    const x = clamp(feature.x, 0, length);
    const height = clamp(feature.height, 1, 40);
    const radius = clamp(feature.radius, 1, 20);
    const n1 = node(x, thickness / 2, "boss base");
    const n2 = node(x, thickness / 2 + height, "boss top");
    const A = Math.PI * radius * radius;
    const I = (Math.PI * Math.pow(radius, 4)) / 4;
    elements.push({ n1, n2, A, I, c: radius, label: feature.note || "load boss" });
  }

  const fixedNode = node(0, thickness / 2, "fixed edge");
  const loadNode = node(loadX, loadZ, "load point");

  return {
    nodes,
    elements,
    fixedNode,
    loadNode,
    load: Math.abs(design.load_newtons),
    material,
    volumeAdjustments,
    length,
    width,
    thickness
  };
}

function runFrameFea(design, material, volumeAdjustments) {
  const model = buildFrameModel(design, material, volumeAdjustments);
  const dofCount = model.nodes.length * 3;
  const K = Array.from({ length: dofCount }, () => Array(dofCount).fill(0));
  const F = Array(dofCount).fill(0);

  for (const element of model.elements) {
    const n1 = model.nodes[element.n1];
    const n2 = model.nodes[element.n2];
    const dx = n2.x - n1.x;
    const dz = n2.z - n1.z;
    const L = Math.max(Math.hypot(dx, dz), 1e-6);
    const c = dx / L;
    const s = dz / L;
    const kg = frameElementStiffness(material.youngMpa, element.A, element.I, L, c, s);
    const dofs = [element.n1 * 3, element.n1 * 3 + 1, element.n1 * 3 + 2, element.n2 * 3, element.n2 * 3 + 1, element.n2 * 3 + 2];
    for (let i = 0; i < 6; i += 1) {
      for (let j = 0; j < 6; j += 1) K[dofs[i]][dofs[j]] += kg[i][j];
    }
  }

  F[model.loadNode * 3 + 1] = -model.load;

  const fixedDofs = new Set([model.fixedNode * 3, model.fixedNode * 3 + 1, model.fixedNode * 3 + 2]);
  const freeDofs = Array.from({ length: dofCount }, (_, i) => i).filter((i) => !fixedDofs.has(i));
  const Kff = freeDofs.map((row) => freeDofs.map((col) => K[row][col]));
  const Ff = freeDofs.map((row) => F[row]);
  const Uf = solveLinearSystem(Kff, Ff);
  const U = Array(dofCount).fill(0);
  freeDofs.forEach((dof, index) => {
    U[dof] = Uf[index];
  });

  let maxStress = 0;
  let maxStrain = 0;
  const elementResults = [];
  for (const element of model.elements) {
    const n1 = model.nodes[element.n1];
    const n2 = model.nodes[element.n2];
    const dx = n2.x - n1.x;
    const dz = n2.z - n1.z;
    const L = Math.max(Math.hypot(dx, dz), 1e-6);
    const c = dx / L;
    const s = dz / L;
    const t = [
      [c, s, 0, 0, 0, 0],
      [-s, c, 0, 0, 0, 0],
      [0, 0, 1, 0, 0, 0],
      [0, 0, 0, c, s, 0],
      [0, 0, 0, -s, c, 0],
      [0, 0, 0, 0, 0, 1]
    ];
    const dofs = [element.n1 * 3, element.n1 * 3 + 1, element.n1 * 3 + 2, element.n2 * 3, element.n2 * 3 + 1, element.n2 * 3 + 2];
    const ug = dofs.map((dof) => [U[dof]]);
    const ul = matMul(t, ug).map((row) => row[0]);
    const fl = matMul(frameLocalStiffness(material.youngMpa, element.A, element.I, L), ul.map((value) => [value])).map((row) => row[0]);
    const axialStress = Math.max(Math.abs(fl[0]), Math.abs(fl[3])) / Math.max(element.A, 1);
    const bendingStress = Math.max(Math.abs(fl[2]), Math.abs(fl[5])) * element.c / Math.max(element.I, 1);
    const stress = axialStress + bendingStress;
    const strain = stress / material.youngMpa;
    maxStress = Math.max(maxStress, stress);
    maxStrain = Math.max(maxStrain, strain);
    elementResults.push({
      label: element.label,
      n1: element.n1,
      n2: element.n2,
      stress_mpa: Number(stress.toFixed(3)),
      strain_microstrain: Number((strain * 1_000_000).toFixed(1)),
      utilization: Number(clamp(stress / material.yieldMpa, 0, 1).toFixed(3))
    });
  }

  const displacements = model.nodes.map((node) => ({
    id: node.id,
    x: Number(node.x.toFixed(3)),
    z: Number(node.z.toFixed(3)),
    ux_mm: Number(U[node.id * 3].toFixed(6)),
    uz_mm: Number(U[node.id * 3 + 1].toFixed(6)),
    rotation_rad: Number(U[node.id * 3 + 2].toFixed(6)),
    magnitude_mm: Number(Math.hypot(U[node.id * 3], U[node.id * 3 + 1]).toFixed(6))
  }));
  const loadDisp = displacements[model.loadNode];

  return {
    method: "2D Euler-Bernoulli frame FEA",
    nodes: model.nodes,
    elements: model.elements,
    element_results: elementResults,
    displacements,
    max_stress_mpa: maxStress,
    max_strain: maxStrain,
    load_point_deflection_mm: Math.abs(loadDisp?.uz_mm || 0),
    force_vector_n: [0, 0, -Number(model.load.toFixed(2))]
  };
}

function invertMatrix(matrix) {
  const n = matrix.length;
  const a = matrix.map((row, i) => [...row, ...Array.from({ length: n }, (_, j) => (i === j ? 1 : 0))]);
  for (let col = 0; col < n; col += 1) {
    let pivot = col;
    for (let row = col + 1; row < n; row += 1) {
      if (Math.abs(a[row][col]) > Math.abs(a[pivot][col])) pivot = row;
    }
    if (Math.abs(a[pivot][col]) < 1e-12) throw new Error("Matrix is singular.");
    [a[col], a[pivot]] = [a[pivot], a[col]];
    const divisor = a[col][col];
    for (let j = 0; j < 2 * n; j += 1) a[col][j] /= divisor;
    for (let row = 0; row < n; row += 1) {
      if (row === col) continue;
      const factor = a[row][col];
      for (let j = 0; j < 2 * n; j += 1) a[row][j] -= factor * a[col][j];
    }
  }
  return a.map((row) => row.slice(n));
}

function determinant4(matrix) {
  const m = matrix.map((row) => [...row]);
  let det = 1;
  for (let col = 0; col < 4; col += 1) {
    let pivot = col;
    for (let row = col + 1; row < 4; row += 1) {
      if (Math.abs(m[row][col]) > Math.abs(m[pivot][col])) pivot = row;
    }
    if (Math.abs(m[pivot][col]) < 1e-12) return 0;
    if (pivot !== col) {
      [m[col], m[pivot]] = [m[pivot], m[col]];
      det *= -1;
    }
    det *= m[col][col];
    const divisor = m[col][col];
    for (let row = col + 1; row < 4; row += 1) {
      const factor = m[row][col] / divisor;
      for (let j = col; j < 4; j += 1) m[row][j] -= factor * m[col][j];
    }
  }
  return det;
}

function isotropicElasticityMatrix(E, nu = 0.33) {
  const lambda = (E * nu) / ((1 + nu) * (1 - 2 * nu));
  const mu = E / (2 * (1 + nu));
  return [
    [lambda + 2 * mu, lambda, lambda, 0, 0, 0],
    [lambda, lambda + 2 * mu, lambda, 0, 0, 0],
    [lambda, lambda, lambda + 2 * mu, 0, 0, 0],
    [0, 0, 0, mu, 0, 0],
    [0, 0, 0, 0, mu, 0],
    [0, 0, 0, 0, 0, mu]
  ];
}

function tetraElementStiffness(points, material) {
  const m = points.map((p) => [1, p.x, p.y, p.z]);
  const det = determinant4(m);
  const volume = Math.abs(det) / 6;
  if (volume < 1e-8) return null;
  const inv = invertMatrix(m);
  const b = [];
  const c = [];
  const d = [];
  for (let i = 0; i < 4; i += 1) {
    b.push(inv[1][i]);
    c.push(inv[2][i]);
    d.push(inv[3][i]);
  }

  const B = Array.from({ length: 6 }, () => Array(12).fill(0));
  for (let i = 0; i < 4; i += 1) {
    const col = 3 * i;
    B[0][col] = b[i];
    B[1][col + 1] = c[i];
    B[2][col + 2] = d[i];
    B[3][col] = c[i];
    B[3][col + 1] = b[i];
    B[4][col + 1] = d[i];
    B[4][col + 2] = c[i];
    B[5][col] = d[i];
    B[5][col + 2] = b[i];
  }

  const D = isotropicElasticityMatrix(material.youngMpa);
  const Ke = matMul(transpose(B), matMul(D, B)).map((row) => row.map((value) => value * volume));
  return { Ke, B, D, volume };
}

function inferLoadCase(prompt, design) {
  const text = String(prompt || "").toLowerCase();
  let loadPointX = clamp(Math.abs(design.load_point_x_mm), 5, design.base_length_mm);
  let loadPointY = clamp(design.load_point_y_mm || 0, -design.base_width_mm / 2, design.base_width_mm / 2);
  let loadPointZ = design.base_thickness_mm;
  const bosses = (design.features || []).filter((feature) => feature.type === "boss");
  if (bosses.length) {
    const nearestBoss = bosses
      .slice()
      .sort((a, b) => distance(a.x, a.y, loadPointX, loadPointY) - distance(b.x, b.y, loadPointX, loadPointY))[0];
    loadPointX = nearestBoss.x;
    loadPointY = nearestBoss.y;
    loadPointZ = design.base_thickness_mm + Math.max(nearestBoss.height, 1);
  }
  const staticFactor = text.includes("impact") ? 3 : text.includes("cyclic") || text.includes("fatigue") ? 1.5 : 1;
  const torqueMatch = text.match(/(\d+(?:\.\d+)?)\s*(?:n\s*[-*]?\s*m|nm|newton\s*meter)/i);
  if (torqueMatch) {
    const torqueNm = Number(torqueMatch[1]);
    const equivalentForce = (torqueNm * 1000) / Math.max(loadPointX, 1);
    return {
      type: "torque_as_force_couple_proxy",
      effective_load_n: equivalentForce * staticFactor,
      nominal_load_n: equivalentForce,
      factor: staticFactor,
      load_point: [loadPointX, loadPointY, loadPointZ],
      vector_n: [0, 0, -Number((equivalentForce * staticFactor).toFixed(2))],
      note: `${torqueNm} Nm converted to equivalent tip force using lever arm ${loadPointX} mm.`
    };
  }

  return {
    type: text.includes("chair") ? "distributed_downward_proxy" : "cantilever_tip_load",
    effective_load_n: Math.abs(design.load_newtons) * staticFactor,
    nominal_load_n: Math.abs(design.load_newtons),
    factor: staticFactor,
    load_point: [loadPointX, loadPointY, loadPointZ],
    vector_n: [0, 0, -Number((Math.abs(design.load_newtons) * staticFactor).toFixed(2))],
    note: "Defaulted to fixed left face and downward load at the free tip/load boss."
  };
}

function pointInFeatureVolume(point, design) {
  const { x, y, z } = point;
  const length = design.base_length_mm;
  const halfWidth = design.base_width_mm / 2;
  const thickness = design.base_thickness_mm;
  let solid = x >= 0 && x <= length && y >= -halfWidth && y <= halfWidth && z >= 0 && z <= thickness;

  if (solid && z <= thickness) {
    for (const hole of design.fixed_holes || []) {
      if (Math.hypot(x - hole.x, y - hole.y) < hole.radius) solid = false;
    }
    for (const feature of design.features || []) {
      if (feature.type === "lightening_hole" && Math.hypot(x - feature.x, y - feature.y) < feature.radius) solid = false;
    }
  }

  for (const feature of design.features || []) {
    if (feature.type === "boss") {
      const radius = clamp(feature.radius, 1, 20);
      const height = clamp(feature.height, 1, 40);
      if (Math.hypot(x - feature.x, y - feature.y) <= radius && z >= thickness && z <= thickness + height) solid = true;
    }

    if (feature.type === "rib") {
      const ax = feature.x;
      const ay = feature.y;
      const bx = feature.x2;
      const by = feature.y2;
      const vx = bx - ax;
      const vy = by - ay;
      const len2 = Math.max(vx * vx + vy * vy, 1);
      const t = clamp(((x - ax) * vx + (y - ay) * vy) / len2, 0, 1);
      const px = ax + t * vx;
      const py = ay + t * vy;
      const ribHeight = clamp(feature.height, 1, 60);
      const ribTop = thickness + ribHeight;
      if (Math.hypot(x - px, y - py) <= Math.max(feature.width, 1) / 2 && z >= thickness && z <= ribTop) solid = true;
    }
  }

  return solid;
}

function buildSolidMesh(design) {
  const length = clamp(design.base_length_mm, 30, 240);
  const width = clamp(design.base_width_mm, 10, 120);
  const thickness = clamp(design.base_thickness_mm, 1, 30);
  const maxFeatureHeight = (design.features || []).reduce((max, feature) => {
    if (feature.type === "rib" || feature.type === "boss") return Math.max(max, feature.height || 0);
    return max;
  }, 0);
  const height = Math.max(thickness + maxFeatureHeight, thickness * 2);
  const nx = 7;
  const ny = 5;
  const nz = 5;
  const nodes = [];
  const nodeId = new Map();
  const tets = [];

  function gridPoint(i, j, k) {
    return {
      x: (length * i) / nx,
      y: -width / 2 + (width * j) / ny,
      z: (height * k) / nz
    };
  }

  function addNode(i, j, k) {
    const key = `${i}:${j}:${k}`;
    if (nodeId.has(key)) return nodeId.get(key);
    const id = nodes.length;
    const point = gridPoint(i, j, k);
    nodes.push({ id, ...point });
    nodeId.set(key, id);
    return id;
  }

  const tetPattern = [
    [0, 1, 3, 7],
    [0, 3, 2, 7],
    [0, 2, 6, 7],
    [0, 6, 4, 7],
    [0, 4, 5, 7],
    [0, 5, 1, 7]
  ];

  for (let i = 0; i < nx; i += 1) {
    for (let j = 0; j < ny; j += 1) {
      for (let k = 0; k < nz; k += 1) {
        const center = {
          x: (gridPoint(i, j, k).x + gridPoint(i + 1, j, k).x) / 2,
          y: (gridPoint(i, j, k).y + gridPoint(i, j + 1, k).y) / 2,
          z: (gridPoint(i, j, k).z + gridPoint(i, j, k + 1).z) / 2
        };
        if (!pointInFeatureVolume(center, design)) continue;
        const corners = [
          addNode(i, j, k),
          addNode(i + 1, j, k),
          addNode(i, j + 1, k),
          addNode(i + 1, j + 1, k),
          addNode(i, j, k + 1),
          addNode(i + 1, j, k + 1),
          addNode(i, j + 1, k + 1),
          addNode(i + 1, j + 1, k + 1)
        ];
        for (const tet of tetPattern) tets.push(tet.map((idx) => corners[idx]));
      }
    }
  }

  return { nodes, tets, length, width, height };
}

function vonMisesFromStress(stress) {
  const [sx, sy, sz, txy, tyz, txz] = stress;
  return Math.sqrt(
    0.5 * ((sx - sy) ** 2 + (sy - sz) ** 2 + (sz - sx) ** 2) +
      3 * (txy ** 2 + tyz ** 2 + txz ** 2)
  );
}

function runSolidTetraFea(design, material, loadCase) {
  const mesh = buildSolidMesh(design);
  if (mesh.nodes.length < 8 || mesh.tets.length < 6) throw new Error("3D mesh has too few solid elements.");
  const dofCount = mesh.nodes.length * 3;
  const K = Array.from({ length: dofCount }, () => Array(dofCount).fill(0));
  const F = Array(dofCount).fill(0);
  const elementData = [];

  for (const tet of mesh.tets) {
    const points = tet.map((id) => mesh.nodes[id]);
    const elem = tetraElementStiffness(points, material);
    if (!elem) continue;
    const dofs = tet.flatMap((id) => [id * 3, id * 3 + 1, id * 3 + 2]);
    for (let i = 0; i < 12; i += 1) {
      for (let j = 0; j < 12; j += 1) K[dofs[i]][dofs[j]] += elem.Ke[i][j];
    }
    elementData.push({ tet, ...elem });
  }

  const [loadX, loadY, loadZ] = loadCase.load_point;
  const candidates = mesh.nodes
    .map((node) => ({
      id: node.id,
      distance: Math.hypot((node.x - loadX) / mesh.length, (node.y - loadY) / mesh.width, (node.z - loadZ) / Math.max(mesh.height, 1))
    }))
    .sort((a, b) => a.distance - b.distance)
    .slice(0, 6);
  const loadPerNode = loadCase.effective_load_n / Math.max(candidates.length, 1);
  for (const candidate of candidates) F[candidate.id * 3 + 2] -= loadPerNode;

  const fixedNodes = mesh.nodes.filter((node) => node.x <= mesh.length * 0.001);
  const fixedDofs = new Set(fixedNodes.flatMap((node) => [node.id * 3, node.id * 3 + 1, node.id * 3 + 2]));
  const freeDofs = Array.from({ length: dofCount }, (_, i) => i).filter((i) => !fixedDofs.has(i));
  const Kff = freeDofs.map((row) => freeDofs.map((col) => K[row][col]));
  const Ff = freeDofs.map((row) => F[row]);
  const Uf = solveLinearSystem(Kff, Ff);
  const U = Array(dofCount).fill(0);
  freeDofs.forEach((dof, index) => {
    U[dof] = Uf[index];
  });

  const D = isotropicElasticityMatrix(material.youngMpa);
  const elementResults = [];
  let maxVonMises = 0;
  let maxStrain = 0;
  for (const elem of elementData) {
    const dofs = elem.tet.flatMap((id) => [id * 3, id * 3 + 1, id * 3 + 2]);
    const ue = dofs.map((dof) => [U[dof]]);
    const strain = matMul(elem.B, ue).map((row) => row[0]);
    const stress = matMul(D, strain.map((value) => [value])).map((row) => row[0]);
    const vm = vonMisesFromStress(stress);
    const strainMag = Math.hypot(...strain);
    maxVonMises = Math.max(maxVonMises, vm);
    maxStrain = Math.max(maxStrain, strainMag);
    const centroid = elem.tet.reduce(
      (sum, id) => {
        const node = mesh.nodes[id];
        return { x: sum.x + node.x / 4, y: sum.y + node.y / 4, z: sum.z + node.z / 4 };
      },
      { x: 0, y: 0, z: 0 }
    );
    elementResults.push({
      centroid,
      von_mises_mpa: Number(vm.toFixed(3)),
      strain_microstrain: Number((strainMag * 1_000_000).toFixed(1)),
      utilization: Number(clamp(vm / material.yieldMpa, 0, 1).toFixed(3))
    });
  }

  const displacements = mesh.nodes.map((node) => {
    const ux = U[node.id * 3];
    const uy = U[node.id * 3 + 1];
    const uz = U[node.id * 3 + 2];
    return {
      id: node.id,
      x: Number(node.x.toFixed(3)),
      y: Number(node.y.toFixed(3)),
      z: Number(node.z.toFixed(3)),
      ux_mm: Number(ux.toFixed(6)),
      uy_mm: Number(uy.toFixed(6)),
      uz_mm: Number(uz.toFixed(6)),
      magnitude_mm: Number(Math.hypot(ux, uy, uz).toFixed(6))
    };
  });
  const maxDisplacement = displacements.reduce((max, node) => Math.max(max, node.magnitude_mm), 0);
  const loadNodeDeflection = candidates.reduce((sum, candidate) => sum + Math.abs(U[candidate.id * 3 + 2]) / candidates.length, 0);

  return {
    method: "3D linear tetrahedral elasticity",
    nodes: mesh.nodes,
    tets: mesh.tets,
    element_results: elementResults,
    displacements,
    max_stress_mpa: maxVonMises,
    max_strain: maxStrain,
    load_point_deflection_mm: loadNodeDeflection,
    max_displacement_mm: maxDisplacement,
    force_vector_n: loadCase.vector_n,
    fixed_node_count: fixedNodes.length,
    loaded_node_count: candidates.length,
    load_case: loadCase
  };
}

function simulateDesignFallback(design, prompt = "") {
  const material = materials[design.material] || materials.aluminum_6061;
  const length = clamp(design.base_length_mm, 30, 240);
  const width = clamp(design.base_width_mm, 10, 120);
  const thickness = clamp(design.base_thickness_mm, 1, 30);
  const load = clamp(Math.abs(design.load_newtons), 1, 2000);
  const lever = clamp(Math.abs(design.load_point_x_mm), 5, length);
  const baseVolumeMm3 = length * width * thickness;

  let addedVolumeMm3 = 0;
  let removedVolumeMm3 = 0;
  let secondMoment = (width * Math.pow(thickness, 3)) / 12;
  let sectionModulus = (width * Math.pow(thickness, 2)) / 6;
  let usefulRibs = 0;

  for (const feature of design.features) {
    if (feature.type === "lightening_hole") {
      const radius = clamp(feature.radius, 1, width / 3);
      removedVolumeMm3 += Math.PI * radius * radius * thickness;
    }

    if (feature.type === "boss") {
      const radius = clamp(feature.radius, 1, 20);
      const height = clamp(feature.height, 1, 40);
      addedVolumeMm3 += Math.PI * radius * radius * height;
    }

    if (feature.type === "rib") {
      const ribLength = clamp(distance(feature.x, feature.y, feature.x2, feature.y2), 5, length * 1.4);
      const ribWidth = clamp(feature.width, 1, 20);
      const ribHeight = clamp(feature.height, 1, 60);
      const alignment = Math.abs(feature.x2 - feature.x) / Math.max(ribLength, 1);
      const effectiveness = 0.25 + 0.75 * alignment;
      addedVolumeMm3 += ribLength * ribWidth * ribHeight * 0.85;
      secondMoment += effectiveness * ribWidth * Math.pow(thickness + ribHeight, 3) / 12;
      sectionModulus += effectiveness * ribWidth * Math.pow(thickness + ribHeight, 2) / 6;
      usefulRibs += effectiveness;
    }
  }

  for (const hole of design.fixed_holes) {
    const radius = clamp(hole.radius, 1, 10);
    removedVolumeMm3 += Math.PI * radius * radius * thickness;
  }

  const volumeMm3 = Math.max(baseVolumeMm3 + addedVolumeMm3 - removedVolumeMm3, baseVolumeMm3 * 0.2);
  const massG = volumeMm3 * material.densityGcm3 / 1000;
  const momentNmm = load * lever;
  const loadCase = inferLoadCase(prompt, design);
  let fea;
  try {
    fea = runSolidTetraFea(design, material, loadCase);
  } catch (error) {
    fea = runFrameFea(design, material, { addedVolumeMm3, removedVolumeMm3 });
    fea.method = `${fea.method} fallback after 3D solve failed: ${error instanceof Error ? error.message : "unknown error"}`;
    fea.load_case = loadCase;
  }
  const stressMpa = fea.max_stress_mpa;
  const safetyFactor = material.yieldMpa / Math.max(stressMpa, 0.01);
  const strain = fea.max_strain;
  const microstrain = strain * 1_000_000;
  const deflectionMm = fea.load_point_deflection_mm;
  const surfaceAreaMm2 = 2 * (length * width + length * thickness + width * thickness) + addedVolumeMm3 / Math.max(thickness, 1);
  const thermalRiseC = (8 * lever) / Math.max(material.thermalWmK * surfaceAreaMm2 * 0.001, 0.001);
  const manufacturability = clamp(1 - invalidGeometryPenalty(design) - Math.max(0, usefulRibs - 8) * 0.02, 0, 1);
  const safetyScore = clamp((safetyFactor - 0.8) / 2.2, 0, 1);
  const stiffnessScore = clamp(1 - deflectionMm / 8, 0, 1);
  const massScore = clamp(1 - massG / 90, 0, 1);
  const thermalScore = clamp(1 - thermalRiseC / 45, 0, 1);
  const score = clamp(0.38 * safetyScore + 0.28 * stiffnessScore + 0.2 * massScore + 0.14 * manufacturability, 0, 1);

  return {
    mass_g: Number(massG.toFixed(2)),
    max_stress_mpa: Number(stressMpa.toFixed(2)),
    max_strain_microstrain: Number(microstrain.toFixed(1)),
    safety_factor: Number(safetyFactor.toFixed(2)),
    tip_deflection_mm: Number(deflectionMm.toFixed(3)),
    thermal_delta_c_proxy: Number(thermalRiseC.toFixed(2)),
    thermal_score: Number(thermalScore.toFixed(3)),
    manufacturability: Number(manufacturability.toFixed(3)),
    score: Number(score.toFixed(3)),
    force_vector_n: fea.force_vector_n,
    load_case: loadCase,
    stress_regions: fea.element_results
      .slice()
      .sort((a, b) => b.utilization - a.utilization)
      .slice(0, 4)
      .map((element) => {
        const n1 = element.centroid || fea.nodes[element.n1];
        const n2 = element.centroid || fea.nodes[element.n2];
        return {
          label: element.label || "3D tetra element",
          x: Number((((n1.x || 0) + (n2.x || 0)) / 2).toFixed(1)),
          y: Number((((n1.y || 0) + (n2.y || 0)) / 2).toFixed(1)),
          severity: element.utilization
        };
      }),
    deformation_regions: [
      { label: "free tip deflection", x: Number(lever.toFixed(1)), y: Number(design.load_point_y_mm.toFixed(1)), deflection_mm: Number(deflectionMm.toFixed(3)) }
    ],
    fea,
    verdict: score > 0.72 && safetyFactor >= 1.8 ? "promising" : "needs iteration",
    caveat: "Coarse 3D linear tetrahedral FEA for rapid design iteration. Use a finer production mesh before certifying a real part."
  };
}

function runPythonTool(command, payload) {
  const result = spawnSync(pythonBin, ["-m", "mechforge.cli", command], {
    cwd: process.cwd(),
    input: JSON.stringify(payload),
    encoding: "utf8",
    env: {
      ...process.env,
      XDG_CACHE_HOME: process.env.XDG_CACHE_HOME || ".cache",
      EZDXF_CACHE_DIR: process.env.EZDXF_CACHE_DIR || ".cache/ezdxf",
      PYTHONPATH: "python_tools"
    },
    maxBuffer: 20 * 1024 * 1024
  });

  if (result.status !== 0) {
    throw new Error(result.stderr || result.stdout || `Python tool ${command} failed.`);
  }

  return JSON.parse(result.stdout);
}

function simulateDesign(design, prompt = "") {
  let result;
  try {
    result = runPythonTool("simulate", { design, prompt });
  } catch (error) {
    const fallback = simulateDesignFallback(design, prompt);
    fallback.caveat = `Python solver failed; used JS fallback. ${error instanceof Error ? error.message : "Unknown Python tool error"}`;
    return augmentCadForgeAnalysis(fallback, design, prompt);
  }

  return augmentCadForgeAnalysis(result.analysis, design, prompt);
}

function countConnectedFeatureGroups(design) {
  const features = design?.features || [];
  if (!features.length) return 1;
  const structuralTypes = new Set([
    "rib",
    "boss",
    "hook_curve",
    "clamp_jaw",
    "seat_panel",
    "chair_leg",
    "chair_back",
    "chair_crossbar",
    "generic_panel",
    "support_tube",
    "curved_tube",
    "flat_foot",
    "armrest",
    "headrest",
    "tabletop",
    "table_leg"
  ]);
  const disconnected = features.filter((feature) => {
    if (!structuralTypes.has(feature.type)) return false;
    const x = Number(feature.x || 0);
    const y = Number(feature.y || 0);
    const x2 = Number(feature.x2 || x);
    const y2 = Number(feature.y2 || y);
    const nearBase = x >= -5 && x <= Number(design.base_length_mm || 0) + 5 && Math.abs(y) <= Number(design.base_width_mm || 0) / 2 + 12;
    const hasSpan = distance(x, y, x2, y2) > 4 || Number(feature.width || 0) > 4 || Number(feature.height || 0) > 4;
    return !nearBase || !hasSpan;
  }).length;
  return Math.max(1, disconnected + 1);
}

function pseudoOpenScadForDesign(design) {
  const lines = [
    `// CADForge pseudo-OpenSCAD generated from parametric feature actions`,
    `$fn = 48;`,
    `base_length = ${Number(design.base_length_mm || 100).toFixed(1)};`,
    `base_width = ${Number(design.base_width_mm || 45).toFixed(1)};`,
    `base_thickness = ${Number(design.base_thickness_mm || 5).toFixed(1)};`,
    ``,
    `module base_body() {`,
    `  cube([base_length, base_width, base_thickness], center=false);`,
    `}`,
    ``,
    `module feature_tree() {`,
    `  union() {`,
    `    base_body();`
  ];

  for (const feature of design.features || []) {
    const x = Number(feature.x || 0).toFixed(1);
    const y = (Number(feature.y || 0) + Number(design.base_width_mm || 0) / 2).toFixed(1);
    const w = Math.max(1, Number(feature.width || feature.radius * 2 || 4)).toFixed(1);
    const h = Math.max(1, Number(feature.height || design.base_thickness_mm || 4)).toFixed(1);
    if (feature.type === "lightening_hole") continue;
    if (feature.type === "chair_leg" || feature.type === "table_leg" || feature.type === "support_tube" || feature.type === "curved_tube") {
      lines.push(`    translate([${x}, ${y}, 0]) cylinder(h=${h}, r=${Math.max(1, Number(feature.width || 6) / 2).toFixed(1)}); // ${feature.type}: ${feature.note || ""}`);
    } else if (feature.type === "boss" || feature.type === "stator_ring") {
      lines.push(`    translate([${x}, ${y}, base_thickness]) cylinder(h=${h}, r=${Math.max(1, Number(feature.radius || 5)).toFixed(1)}); // ${feature.type}: ${feature.note || ""}`);
    } else {
      lines.push(`    translate([${x}, ${y}, base_thickness]) cube([${w}, ${w}, ${h}], center=true); // ${feature.type}: ${feature.note || ""}`);
    }
  }

  lines.push(`  }`, `}`, ``, `difference() {`, `  feature_tree();`);
  for (const hole of design.fixed_holes || []) {
    const x = Number(hole.x || 0).toFixed(1);
    const y = (Number(hole.y || 0) + Number(design.base_width_mm || 0) / 2).toFixed(1);
    lines.push(`  translate([${x}, ${y}, -1]) cylinder(h=base_thickness + 2, r=${Number(hole.radius || 2.5).toFixed(1)});`);
  }
  for (const feature of design.features || []) {
    if (feature.type !== "lightening_hole") continue;
    const x = Number(feature.x || 0).toFixed(1);
    const y = (Number(feature.y || 0) + Number(design.base_width_mm || 0) / 2).toFixed(1);
    lines.push(`  translate([${x}, ${y}, -1]) cylinder(h=base_thickness + 2, r=${Number(feature.radius || 3).toFixed(1)}); // lightening cut`);
  }
  lines.push(`}`);
  return lines.join("\n");
}

function augmentCadForgeAnalysis(analysis, design, prompt = "") {
  const features = design?.features || [];
  const componentCount = countConnectedFeatureGroups(design);
  const hasNegativeOrTinyThickness = Number(design?.base_thickness_mm || 0) < 2 || features.some((feature) => Number(feature.width || feature.radius || 1) <= 0);
  const namedParameterCount = 6 + (design?.fixed_holes || []).length * 3 + features.length * 6;
  const family = familyFromPrompt(prompt);
  const chairHasCoreFeatures =
    family !== "chair" ||
    (features.some((feature) => feature.type === "seat_panel") &&
      features.filter((feature) => feature.type === "chair_leg").length >= 4 &&
      features.some((feature) => feature.type === "chair_back"));
  const watertight = componentCount === 1 && !hasNegativeOrTinyThickness;
  const editabilityScore = Number(Math.min(1, namedParameterCount / Math.max(18, features.length * 5 || 18)).toFixed(2));
  const topologyPenalty = Math.min(0.65, Math.max(0, componentCount - 1) * 0.35 + (watertight ? 0 : 0.25));
  const chairPenalty = chairHasCoreFeatures ? 0 : 0.25;
  const cadforgeReward = Number(Math.max(0, Math.min(1, 1 - topologyPenalty - chairPenalty)).toFixed(3));
  return {
    ...analysis,
    cadforge: {
      ast_nodes: 1 + features.length + (design?.fixed_holes || []).length,
      connected_components: componentCount,
      floating_parts: Math.max(0, componentCount - 1),
      watertight_proxy: watertight,
      manifold_proxy: watertight,
      clean_feature_tree_proxy: features.every((feature) => feature.type && typeof feature.note === "string"),
      named_parameter_count: namedParameterCount,
      editability_score: editabilityScore,
      chair_core_features_passed: chairHasCoreFeatures,
      topology_penalty: Number(topologyPenalty.toFixed(3)),
      chair_requirement_penalty: Number(chairPenalty.toFixed(3)),
      reward: cadforgeReward,
      hard_fail: componentCount > 1 || !watertight || !chairHasCoreFeatures,
      pseudo_openscad: pseudoOpenScadForDesign(design)
    }
  };
}

function familyFromPrompt(prompt = "") {
  const text = String(prompt).toLowerCase();
  if (text.includes("table") || text.includes("desk") || text.includes("bench")) return "table";
  if (text.includes("stator") || text.includes("motor")) return "motor_stator";
  if (text.includes("chair") || text.includes("seat")) return "chair";
  if (text.includes("hook") || text.includes("hanging")) return "wall_hook";
  if (text.includes("clamp") || text.includes("shaft") || text.includes("torque") || text.includes("120 nm")) return "torque_clamp";
  return "freeform_object";
}

function wantsCurvyChair(prompt = "") {
  const text = String(prompt || "").toLowerCase();
  return (text.includes("chair") || text.includes("seat")) && /(\bcurv|round|organic|sweep|arched|bent|\bflow\b|flowing)/.test(text);
}

function wantsFlowerBackrest(prompt = "") {
  const text = String(prompt || "").toLowerCase();
  return (text.includes("chair") || text.includes("backrest")) && /(flower|floral|petal|blossom|rose|lotus)/.test(text);
}

function wantsAdvancedChair(prompt = "") {
  const text = String(prompt || "").toLowerCase();
  return text.includes("chair") && /(armrest|arm rest|handle|headrest|head rest|flat feet|flat foot|ergonomic|advanced)/.test(text);
}

function loadFromPrompt(prompt = "", fallback = 120) {
  const text = String(prompt || "").toLowerCase();
  const match = text.match(/(\d+(?:\.\d+)?)\s*n(?!\s*[-*]?\s*m|m)/i);
  if (match) return Number(match[1]);
  const torqueLike = text.match(/(\d+(?:\.\d+)?)\s*(?:n\s*[-*]?\s*m|nm)\b/i);
  return torqueLike ? Number(torqueLike[1]) : fallback;
}

function actionsForFamily(family, prompt = "") {
  const torqueVector = String(prompt).toLowerCase().match(/120\s*(?:n\s*[-*]?\s*m|nm)/) ? [0, 0, -1333.33] : [0, 0, -120];
  const curvyChair = wantsCurvyChair(prompt);
  const flowerBackrest = wantsFlowerBackrest(prompt);
  const base = [{ tool: "create_design_family", params: { family } }];
  if (family === "wall_hook") {
    return [
      { tool: "create_design_family", params: { family: "blank_wall_hook" } },
      { tool: "set_material", params: { material: "aluminum_6061" } },
      { tool: "add_feature", params: { type: "hook_curve", x: 12, y: 0, x2: 68, y2: 0, width: 8, height: 34, radius: 10, note: "round J hook tube" } },
      { tool: "add_feature", params: { type: "boss", x: 62, y: 0, height: 1, radius: 4, note: "hook lip/load contact proxy" } },
      { tool: "set_load", params: { point_mm: [62, 0, 7], vector_n: [0, 0, -120] } },
      { tool: "export_cadquery", params: {} },
      { tool: "run_fea", params: {} },
      { tool: "commit_design", params: {} }
    ];
  }
  if (family === "torque_clamp") {
    return [
      { tool: "create_design_family", params: { family: "blank_torque_clamp" } },
      { tool: "set_material", params: { material: "aluminum_6061" } },
      { tool: "add_feature", params: { type: "clamp_jaw", x: 34, y: -18, x2: 78, y2: -18, width: 10, height: 18, radius: 9, note: "lower clamp jaw" } },
      { tool: "add_feature", params: { type: "clamp_jaw", x: 34, y: 18, x2: 78, y2: 18, width: 10, height: 18, radius: 9, note: "upper clamp jaw" } },
      { tool: "add_feature", params: { type: "boss", x: 66, y: 0, height: 12, radius: 12, note: "shaft torque proxy" } },
      { tool: "set_load", params: { point_mm: [68, 0, 20], vector_n: torqueVector } },
      { tool: "export_cadquery", params: {} },
      { tool: "run_fea", params: {} },
      { tool: "commit_design", params: {} }
    ];
  }
  if (family === "motor_stator") {
    return [
      { tool: "create_design_family", params: { family: "blank_motor_stator" } },
      { tool: "set_material", params: { material: "steel_1018" } },
      { tool: "add_feature", params: { type: "stator_ring", x: 48, y: 0, width: 14, height: 8, radius: 34, note: "lamination ring" } },
      { tool: "add_feature", params: { type: "stator_tooth", x: 48, y: 0, width: 9, height: 18, radius: 12, note: "12 radial teeth" } },
      { tool: "add_feature", params: { type: "boss", x: 48, y: 0, height: 8, radius: 6, note: "center shaft/load proxy" } },
      { tool: "set_load", params: { point_mm: [48, 0, 12], vector_n: [0, 0, -80] } },
      { tool: "export_cadquery", params: {} },
      { tool: "run_fea", params: {} },
      { tool: "commit_design", params: {} }
    ];
  }
  if (family === "chair") {
    const chairLoad = loadFromPrompt(prompt, 700);
    return [
      { tool: "create_design_family", params: { family: "blank_chair" } },
      { tool: "set_material", params: { material: "aluminum_6061" } },
      { tool: "add_feature", params: { type: "seat_panel", x: 45, y: 0, width: 90, height: 6, radius: curvyChair ? 14 : 0, note: curvyChair ? "curved rounded waterfall seat panel" : "seat panel" } },
      { tool: "add_feature", params: { type: "chair_leg", x: 14, y: -24, x2: curvyChair ? 2 : 6, y2: curvyChair ? -36 : -32, width: curvyChair ? 7 : 6, height: 55, radius: curvyChair ? 10 : 0, note: curvyChair ? "curved splayed tubular front left leg" : "front left leg" } },
      { tool: "add_feature", params: { type: "chair_leg", x: 76, y: -24, x2: curvyChair ? 88 : 84, y2: curvyChair ? -36 : -32, width: curvyChair ? 7 : 6, height: 55, radius: curvyChair ? 10 : 0, note: curvyChair ? "curved splayed tubular front right leg" : "front right leg" } },
      { tool: "add_feature", params: { type: "chair_leg", x: 14, y: 24, x2: curvyChair ? 2 : 6, y2: curvyChair ? 38 : 32, width: curvyChair ? 7 : 6, height: 55, radius: curvyChair ? 12 : 0, note: curvyChair ? "curved rear left leg continuing into back post" : "rear left leg" } },
      { tool: "add_feature", params: { type: "chair_leg", x: 76, y: 24, x2: curvyChair ? 88 : 84, y2: curvyChair ? 38 : 32, width: curvyChair ? 7 : 6, height: 55, radius: curvyChair ? 12 : 0, note: curvyChair ? "curved rear right leg continuing into back post" : "rear right leg" } },
      { tool: "add_feature", params: { type: "chair_back", x: 45, y: curvyChair ? 35 : 31, width: 84, height: curvyChair ? 52 : 44, radius: curvyChair ? 18 : 0, note: curvyChair ? "curved arched backrest with rounded top rail" : "upright backrest panel" } },
      { tool: "add_feature", params: { type: "chair_crossbar", x: 45, y: -30, width: 84, height: 4, radius: curvyChair ? 8 : 0, note: curvyChair ? "curved front leg crossbar" : "front leg crossbar" } },
      ...(curvyChair
        ? [
            { tool: "add_feature", params: { type: "chair_crossbar", x: 45, y: 30, width: 84, height: 4, radius: 8, note: "curved rear leg crossbar" } },
            { tool: "add_feature", params: { type: "chair_crossbar", x: 12, y: 0, width: 52, height: 4, radius: 8, note: "curved left side crossbar" } },
            { tool: "add_feature", params: { type: "chair_crossbar", x: 78, y: 0, width: 52, height: 4, radius: 8, note: "curved right side crossbar" } }
          ]
        : []),
      ...(flowerBackrest
        ? [
            { tool: "add_feature", params: { type: "decorative_curve", x: 45, y: 42, width: 30, height: 30, radius: 8, note: "flower backrest center blossom" } },
            { tool: "add_feature", params: { type: "decorative_curve", x: 45, y: 42, x2: 45, y2: 42, width: 48, height: 24, radius: 6, note: "six petal flower pattern on backrest" } },
            { tool: "add_feature", params: { type: "decorative_curve", x: 45, y: 42, x2: 45, y2: 42, width: 18, height: 36, radius: 4, note: "flower stem and leaf curves on backrest" } }
          ]
        : []),
      { tool: "set_load", params: { point_mm: [45, 0, 6], vector_n: [0, 0, -chairLoad] } },
      { tool: "export_cadquery", params: {} },
      { tool: "run_fea", params: {} },
      { tool: "commit_design", params: {} }
    ];
  }
  if (family === "table") {
    const tableLoad = loadFromPrompt(prompt, 500);
    const sixLegs = /six|6/.test(String(prompt).toLowerCase());
    const legXs = sixLegs ? [10, 50, 90, 10, 50, 90] : [12, 88, 12, 88];
    const legYs = sixLegs ? [-28, -28, -28, 28, 28, 28] : [-28, -28, 28, 28];
    const legActions = legXs.map((x, index) => ({
      tool: "add_feature",
      params: {
        type: "table_leg",
        x,
        y: legYs[index],
        x2: x,
        y2: legYs[index],
        width: 6,
        height: 48,
        radius: 3,
        note: `${sixLegs ? "six-leg " : ""}table support leg ${index + 1}`
      }
    }));
    return [
      { tool: "create_design_family", params: { family: "blank_table" } },
      { tool: "set_material", params: { material: "aluminum_6061" } },
      { tool: "add_feature", params: { type: "tabletop", x: 50, y: 0, width: 100, height: 6, radius: 4, note: "rectangular small tabletop panel" } },
      ...legActions,
      { tool: "add_feature", params: { type: "support_tube", x: 10, y: -28, x2: 90, y2: -28, width: 4, height: 22, radius: 3, note: "front lower table stretcher" } },
      { tool: "add_feature", params: { type: "support_tube", x: 10, y: 28, x2: 90, y2: 28, width: 4, height: 22, radius: 3, note: "rear lower table stretcher" } },
      { tool: "set_load", params: { point_mm: [50, 0, 6], vector_n: [0, 0, -tableLoad] } },
      { tool: "export_cadquery", params: {} },
      { tool: "run_fea", params: {} },
      { tool: "commit_design", params: {} }
    ];
  }
  return [
    { tool: "create_design_family", params: { family: "blank_freeform_object" } },
    { tool: "set_material", params: { material: "aluminum_6061" } },
    { tool: "set_envelope", params: { length_mm: 100, width_mm: 70, thickness_mm: 6 } },
    { tool: "add_feature", params: { type: "generic_panel", x: 50, y: 0, width: 80, height: 6, radius: 3, note: "primary body panel inferred from prompt" } },
    { tool: "add_feature", params: { type: "support_tube", x: 15, y: -20, x2: 85, y2: -20, width: 5, height: 20, radius: 3, note: "generic structural support tube" } },
    { tool: "set_load", params: { point_mm: [50, 0, 6], vector_n: [0, 0, -loadFromPrompt(prompt, 120)] } },
    { tool: "export_cadquery", params: {} },
    { tool: "run_fea", params: {} },
    { tool: "commit_design", params: {} }
  ];
}

function toolPlannerSystemPrompt() {
  return [
    "You are a CAD construction planner for MechForge.",
    "Turn the user prompt into a sequence of small tool calls. Do not one-shot a full CAD object.",
    "Start with create_design_family using a blank family when available: blank_wall_hook, blank_torque_clamp, blank_motor_stator, blank_chair, blank_table, blank_freeform_object, or ribbed_cantilever_bracket.",
    "Then set material, add visible features one at a time, set the load at the actual visual contact point, export CadQuery, run FEA, and commit.",
    "Avoid object templates when the prompt asks for a new object. Compose it from primitive CAD features: generic_panel, support_tube, curved_tube, decorative_curve, flat_foot, tabletop, table_leg, armrest, headrest, and family-specific features only when they fit.",
    "For chairs, create a full chair: seat_panel, four chair_leg features, chair_back, and chair_crossbar.",
    "For advanced chairs, use armrest, headrest, flat_foot, curved_tube, and support_tube features instead of only the basic chair parts.",
    "For tables, use tabletop plus the requested number of table_leg features and support_tube stretchers. Do not render a table as a chair.",
    "If the user asks for a curvy, rounded, organic, arched, bent, flowing, or sweeping chair, preserve that style in radius and note fields: use nonzero radius values and notes like curved tubular leg, curved seat, arched backrest, curved crossbar.",
    "Use decorative_curve for semantic visual requirements such as flower, logo, lattice, engraving, petal, or ornamental backrest patterns. Decorative curves do not replace load-bearing structure.",
    "For stators, create stator_ring and stator_tooth; it should be a flat toothed stator, not a donut placeholder.",
    "For clamps, create clamp_jaw features around a shaft/boss.",
    "For hooks, create hook_curve and a boss/load contact at the hook tip.",
    "Use only the available tool names and feature types. The executor will expand your high-level plan into 50-300 observe/measure/check/build tool calls."
  ].join("\n");
}

function clampToolBudget(value) {
  return clamp(Number(value) || 72, 50, 300);
}

function microAction(tool, params = {}) {
  return { tool, params };
}

function applyPromptStyleToActions(actions, prompt, family) {
  if (family !== "chair") return actions;
  const curvy = wantsCurvyChair(prompt);
  const flower = wantsFlowerBackrest(prompt);
  const advanced = wantsAdvancedChair(prompt);
  let chairLegOrdinal = 0;
  let crossbarOrdinal = 0;
  const styled = actions.map((action) => {
    if (action.tool === "set_load") {
      const load = loadFromPrompt(prompt, 0);
      if (load > 0) {
        const params = { ...(action.params || {}) };
        params.vector_n = [0, 0, -load];
        params.point_mm = params.point_mm || [45, 0, 6];
        return { ...action, params };
      }
    }
    if (action.tool !== "add_feature") return action;
    const params = { ...(action.params || {}) };
    if (curvy && params.type === "seat_panel") {
      params.radius = Math.max(Number(params.radius || 0), 14);
      params.note = String(params.note || "").includes("curv") ? params.note : `curved rounded waterfall ${params.note || "seat panel"}`;
    }
    if (curvy && params.type === "chair_leg") {
      chairLegOrdinal += 1;
      params.radius = Math.max(Number(params.radius || 0), chairLegOrdinal >= 3 ? 12 : 10);
      params.width = Math.max(Number(params.width || 0), 7);
      params.note = String(params.note || "").includes("curv") ? params.note : `curved splayed tubular ${params.note || "chair leg"}`;
      if (chairLegOrdinal === 1) Object.assign(params, { x2: 2, y2: -36 });
      if (chairLegOrdinal === 2) Object.assign(params, { x2: 88, y2: -36 });
      if (chairLegOrdinal === 3) Object.assign(params, { x2: 2, y2: 38 });
      if (chairLegOrdinal === 4) Object.assign(params, { x2: 88, y2: 38 });
    }
    if (params.type === "chair_back") {
      params.radius = Math.max(Number(params.radius || 0), curvy ? 18 : 8);
      params.height = Math.max(Number(params.height || 0), curvy ? 52 : 48);
      params.y = Number.isFinite(Number(params.y)) ? Math.max(Number(params.y), 35) : 35;
      if (curvy) params.note = String(params.note || "").includes("curv") ? params.note : `curved arched ${params.note || "backrest"}`;
      if (flower && !String(params.note || "").includes("flower")) params.note = `${params.note || "backrest"} with flower pattern support`;
    }
    if (curvy && params.type === "chair_crossbar") {
      crossbarOrdinal += 1;
      params.radius = Math.max(Number(params.radius || 0), 8);
      params.note = String(params.note || "").includes("curv") ? params.note : `curved ${params.note || "crossbar"}`;
      if (crossbarOrdinal === 2 && !Number(params.y)) params.y = 30;
    }
    return { ...action, params };
  });
  if (flower && !styled.some((action) => action.tool === "add_feature" && action.params?.type === "decorative_curve")) {
    const finalIndex = styled.findIndex((action) => ["set_load", "export_cadquery", "run_fea", "commit_design"].includes(action.tool));
    const insertAt = finalIndex >= 0 ? finalIndex : styled.length;
    styled.splice(
      insertAt,
      0,
      { tool: "add_feature", params: { type: "decorative_curve", x: 45, y: 42, width: 30, height: 30, radius: 8, note: "flower backrest center blossom" } },
      { tool: "add_feature", params: { type: "decorative_curve", x: 45, y: 42, width: 48, height: 24, radius: 6, note: "six petal flower pattern on backrest" } },
      { tool: "add_feature", params: { type: "decorative_curve", x: 45, y: 42, width: 18, height: 36, radius: 4, note: "flower stem and leaf curves on backrest" } }
    );
  }
  if (advanced) {
    const finalIndex = styled.findIndex((action) => ["set_load", "export_cadquery", "run_fea", "commit_design"].includes(action.tool));
    const insertAt = finalIndex >= 0 ? finalIndex : styled.length;
    const additions = [];
    if (!styled.some((action) => action.tool === "add_feature" && action.params?.type === "armrest")) {
      additions.push(
        { tool: "add_feature", params: { type: "armrest", x: 7, y: -2, x2: 7, y2: 31, width: 7, height: 54, radius: 10, note: "left curved ergonomic armrest handle" } },
        { tool: "add_feature", params: { type: "armrest", x: 83, y: -2, x2: 83, y2: 31, width: 7, height: 54, radius: 10, note: "right curved ergonomic armrest handle" } }
      );
    }
    if (!styled.some((action) => action.tool === "add_feature" && action.params?.type === "headrest")) {
      additions.push({ tool: "add_feature", params: { type: "headrest", x: 45, y: 45, width: 56, height: 18, radius: 9, note: "separate curved headrest above backrest" } });
    }
    if (!styled.some((action) => action.tool === "add_feature" && action.params?.type === "flat_foot")) {
      additions.push(
        { tool: "add_feature", params: { type: "flat_foot", x: 4, y: -38, width: 24, height: 3, radius: 5, note: "front left flat foot pad" } },
        { tool: "add_feature", params: { type: "flat_foot", x: 86, y: -38, width: 24, height: 3, radius: 5, note: "front right flat foot pad" } },
        { tool: "add_feature", params: { type: "flat_foot", x: 4, y: 40, width: 24, height: 3, radius: 5, note: "rear left flat foot pad" } },
        { tool: "add_feature", params: { type: "flat_foot", x: 86, y: 40, width: 24, height: 3, radius: 5, note: "rear right flat foot pad" } }
      );
    }
    styled.splice(insertAt, 0, ...additions);
  }
  return styled;
}

function expandLongHorizonActions(actions, targetToolCalls = 72) {
  const target = clampToolBudget(targetToolCalls);
  const expanded = [];
  const preCommit = [];
  const finalActions = [];
  for (const action of actions) {
    if (["export_cadquery", "run_fea", "commit_design"].includes(action.tool)) finalActions.push(action);
    else preCommit.push(action);
  }

  for (const [index, action] of preCommit.entries()) {
    expanded.push(microAction("observe_design", { phase: "before", next_tool: action.tool, step_index: index + 1 }));
    if (["add_feature", "add_rib", "add_lightening_hole", "add_mount_hole"].includes(action.tool)) {
      expanded.push(microAction("check_constraints", { phase: "pre_feature", feature_type: action.params?.type || action.tool }));
    }
    expanded.push(action);
    if (["create_design_family", "set_material", "set_envelope", "add_feature", "add_rib", "add_lightening_hole", "add_mount_hole", "set_load"].includes(action.tool)) {
      expanded.push(microAction("measure_clearance", { phase: "after", previous_tool: action.tool }));
      expanded.push(microAction("critique_geometry", { phase: "after", previous_tool: action.tool }));
    }
    if (["add_feature", "set_load"].includes(action.tool)) {
      expanded.push(microAction("visual_snapshot", { view: "isometric", phase: "after", previous_tool: action.tool }));
    }
  }

  const viewCycle = ["isometric", "front", "right", "top"];
  let repairIndex = 0;
  while (expanded.length + finalActions.length < target) {
    const view = viewCycle[repairIndex % viewCycle.length];
    const phase = `polish_${repairIndex + 1}`;
    expanded.push(microAction("observe_design", { phase }));
    if (expanded.length + finalActions.length >= target) break;
    expanded.push(microAction("visual_snapshot", { phase, view }));
    if (expanded.length + finalActions.length >= target) break;
    expanded.push(microAction("check_constraints", { phase, view }));
    if (expanded.length + finalActions.length >= target) break;
    expanded.push(microAction("measure_clearance", { phase, view }));
    if (expanded.length + finalActions.length >= target) break;
    expanded.push(microAction("critique_geometry", { phase, view }));
    repairIndex += 1;
  }

  const requiredFinals = finalActions.length ? finalActions : [microAction("export_cadquery"), microAction("run_fea"), microAction("commit_design")];
  const editableBudget = Math.max(0, target - requiredFinals.length);
  const requiredOperationSet = new Set(preCommit);
  let remainingRequiredOperations = expanded.filter((action) => requiredOperationSet.has(action)).length;
  const selected = [];

  for (const action of expanded) {
    const isRequiredOperation = requiredOperationSet.has(action);
    if (isRequiredOperation) {
      selected.push(action);
      remainingRequiredOperations -= 1;
    } else if (editableBudget - selected.length - remainingRequiredOperations > 0) {
      selected.push(action);
    }
    if (selected.length >= editableBudget) break;
  }

  return [...selected, ...requiredFinals];
}

function expandActionChunk(actions, targetCount, round = 1) {
  const expanded = [];
  for (const [index, action] of actions.entries()) {
    expanded.push(microAction("observe_design", { phase: `round_${round}_before`, next_tool: action.tool, step_index: index + 1 }));
    if (["add_feature", "add_rib", "add_lightening_hole", "add_mount_hole"].includes(action.tool)) {
      expanded.push(microAction("check_constraints", { phase: `round_${round}_pre_feature`, feature_type: action.params?.type || action.tool }));
    }
    expanded.push(action);
    if (["create_design_family", "set_material", "set_envelope", "add_feature", "add_rib", "add_lightening_hole", "add_mount_hole", "set_load"].includes(action.tool)) {
      expanded.push(microAction("measure_clearance", { phase: `round_${round}_after`, previous_tool: action.tool }));
      expanded.push(microAction("critique_geometry", { phase: `round_${round}_after`, previous_tool: action.tool }));
    }
    if (["add_feature", "set_load"].includes(action.tool)) {
      expanded.push(microAction("visual_snapshot", { view: "isometric", phase: `round_${round}_after`, previous_tool: action.tool }));
    }
  }

  const viewCycle = ["isometric", "front", "right", "top"];
  let polishIndex = 0;
  while (expanded.length < targetCount) {
    const view = viewCycle[polishIndex % viewCycle.length];
    const phase = `round_${round}_reassess_${polishIndex + 1}`;
    expanded.push(microAction("observe_design", { phase, view }));
    if (expanded.length >= targetCount) break;
    expanded.push(microAction("visual_snapshot", { phase, view }));
    if (expanded.length >= targetCount) break;
    expanded.push(microAction("check_constraints", { phase, view }));
    if (expanded.length >= targetCount) break;
    expanded.push(microAction("critique_geometry", { phase, view }));
    polishIndex += 1;
  }

  const required = new Set(actions);
  let remainingRequired = expanded.filter((action) => required.has(action)).length;
  const selected = [];
  for (const action of expanded) {
    const isRequired = required.has(action);
    if (isRequired) {
      selected.push(action);
      remainingRequired -= 1;
    } else if (targetCount - selected.length - remainingRequired > 0) {
      selected.push(action);
    }
    if (selected.length >= targetCount) break;
  }
  return selected;
}

function normalizePlannedActions(plan, prompt = "") {
  const fallbackFamily = familyFromPrompt(prompt);
  const family = plan?.family || fallbackFamily;
  const featureCounts = {};
  let featureSequence = 0;
  const actions = Array.isArray(plan?.actions)
    ? plan.actions.map((action) => {
        const params = { ...(action.params || {}) };
        let ordinal = 0;
        let sequence = 0;
        if (action.tool === "add_feature") {
          featureSequence += 1;
          sequence = featureSequence;
          params.type = inferFeatureType(params, family, sequence);
          ordinal = featureCounts[params.type] = (featureCounts[params.type] || 0) + 1;
        }
        return { tool: action.tool, params: sanitizeActionParams(action.tool, params, family, ordinal, sequence) };
      })
    : [];
  if (!actions.length || actions[0].tool !== "create_design_family") {
    return actionsForFamily(fallbackFamily, prompt);
  }
  if (actions[0].params?.family && !String(actions[0].params.family).startsWith("blank_") && family !== "ribbed_cantilever_bracket") {
    actions[0].params.family = `blank_${family}`;
  }
  if (!actions.some((action) => action.tool === "export_cadquery")) actions.push({ tool: "export_cadquery", params: {} });
  if (!actions.some((action) => action.tool === "run_fea")) actions.push({ tool: "run_fea", params: {} });
  if (!actions.some((action) => action.tool === "commit_design")) actions.push({ tool: "commit_design", params: {} });
  return applyPromptStyleToActions(actions, prompt, family);
}

function featureDefaults(family, type, ordinal = 1) {
  if (family === "chair") {
    const legDefaults = [
      { x: 14, y: -24, x2: 8, y2: -28, width: 6, height: 48, radius: 0, note: "front left leg" },
      { x: 76, y: -24, x2: 82, y2: -28, width: 6, height: 48, radius: 0, note: "front right leg" },
      { x: 14, y: 24, x2: 8, y2: 30, width: 6, height: 48, radius: 0, note: "rear left leg" },
      { x: 76, y: 24, x2: 82, y2: 30, width: 6, height: 48, radius: 0, note: "rear right leg" }
    ];
    const crossbars = [
      { x: 45, y: -30, x2: 45, y2: -30, width: 84, height: 4, radius: 0, note: "front leg crossbar" },
      { x: 45, y: 30, x2: 45, y2: 30, width: 84, height: 4, radius: 0, note: "rear leg crossbar" }
    ];
    if (type === "seat_panel") return { x: 45, y: 0, x2: 45, y2: 0, width: 90, height: 6, radius: 0, note: "seat panel" };
    if (type === "chair_leg") return legDefaults[Math.min(Math.max(ordinal - 1, 0), legDefaults.length - 1)];
    if (type === "chair_back") return { x: 45, y: 31, x2: 45, y2: 31, width: 84, height: 44, radius: 0, note: "upright backrest panel" };
    if (type === "chair_crossbar") return crossbars[Math.min(Math.max(ordinal - 1, 0), crossbars.length - 1)];
    if (type === "decorative_curve") return { x: 45, y: 42, x2: 45, y2: 42, width: 34, height: 26, radius: 6, note: "decorative backrest curve" };
    if (type === "armrest") return { x: ordinal === 1 ? 8 : 82, y: 0, x2: ordinal === 1 ? 8 : 82, y2: 30, width: 7, height: 54, radius: 10, note: ordinal === 1 ? "left ergonomic armrest handle" : "right ergonomic armrest handle" };
    if (type === "headrest") return { x: 45, y: 42, x2: 45, y2: 42, width: 52, height: 18, radius: 8, note: "separate curved headrest above backrest" };
    if (type === "flat_foot") return { x: ordinal % 2 ? 10 : 80, y: ordinal <= 2 ? -34 : 34, x2: 0, y2: 0, width: 18, height: 3, radius: 4, note: "flat anti-tip foot pad" };
  }
  if (family === "table") {
    if (type === "tabletop") return { x: 50, y: 0, x2: 50, y2: 0, width: 100, height: 6, radius: 4, note: "small tabletop panel" };
    if (type === "table_leg") {
      const legs = [
        { x: 10, y: -28 }, { x: 50, y: -28 }, { x: 90, y: -28 },
        { x: 10, y: 28 }, { x: 50, y: 28 }, { x: 90, y: 28 }
      ];
      const pos = legs[Math.min(Math.max(ordinal - 1, 0), legs.length - 1)];
      return { ...pos, x2: pos.x, y2: pos.y, width: 6, height: 48, radius: 3, note: `table support leg ${ordinal}` };
    }
    if (type === "support_tube") return { x: 10, y: ordinal % 2 ? -28 : 28, x2: 90, y2: ordinal % 2 ? -28 : 28, width: 4, height: 22, radius: 3, note: "table stretcher support tube" };
  }
  if (family === "torque_clamp") {
    const jaws = [
      { x: 28, y: -18, x2: 84, y2: -18, width: 10, height: 18, radius: 9, note: "lower split clamp jaw" },
      { x: 28, y: 18, x2: 84, y2: 18, width: 10, height: 18, radius: 9, note: "upper split clamp jaw" }
    ];
    if (type === "clamp_jaw") return jaws[Math.min(Math.max(ordinal - 1, 0), jaws.length - 1)];
    if (type === "boss") return { x: 66, y: 0, x2: 66, y2: 0, width: 0, height: 12, radius: 12, note: "shaft torque proxy" };
  }
  if (family === "motor_stator") {
    if (type === "stator_ring") return { x: 48, y: 0, x2: 48, y2: 0, width: 14, height: 8, radius: 34, note: "lamination ring" };
    if (type === "stator_tooth") return { x: 48, y: 0, x2: 48, y2: 0, width: 9, height: 18, radius: 12, note: "12 radial teeth" };
    if (type === "boss") return { x: 48, y: 0, x2: 48, y2: 0, width: 0, height: 8, radius: 6, note: "center shaft proxy" };
  }
  if (family === "wall_hook") {
    if (type === "hook_curve") return { x: 12, y: 0, x2: 68, y2: 0, width: 8, height: 34, radius: 10, note: "round J hook tube" };
    if (type === "boss") return { x: 62, y: 0, x2: 62, y2: 0, width: 0, height: 1, radius: 4, note: "hook lip/load contact proxy" };
  }
  if (type === "boss") return { x: 90, y: 0, x2: 90, y2: 0, width: 0, height: 7, radius: 6, note: "load application boss" };
  if (type === "rib") return { x: 16, y: -14, x2: 88, y2: -4, width: 5, height: 18, radius: 0, note: "diagonal rib" };
  if (type === "generic_panel") return { x: 50, y: 0, x2: 50, y2: 0, width: 80, height: 6, radius: 3, note: "generic body panel" };
  if (type === "support_tube" || type === "curved_tube") return { x: 15, y: -20, x2: 85, y2: 20, width: 5, height: 22, radius: 4, note: "generic support tube" };
  if (type === "flat_foot") return { x: 10, y: -25, x2: 0, y2: 0, width: 18, height: 3, radius: 4, note: "flat foot pad" };
  return { x: 0, y: 0, x2: 0, y2: 0, width: 1, height: 1, radius: 0, note: type };
}

function inferFeatureType(params, family, sequence = 1) {
  const direct = params.type || params.feature_type;
  if (
    allowedFeatureTypes.has(direct) &&
    [
      "decorative_curve",
      "armrest",
      "headrest",
      "flat_foot",
      "generic_panel",
      "support_tube",
      "curved_tube",
      "tabletop",
      "table_leg"
    ].includes(direct)
  ) {
    return direct;
  }
  if (family === "chair") {
    if (sequence === 1) return "seat_panel";
    if (sequence >= 2 && sequence <= 5) return "chair_leg";
    if (sequence === 6) return "chair_back";
  }
  if (allowedFeatureTypes.has(direct)) return direct;
  const hint = [params.type, params.feature_type, params.part, params.name, params.note, params.id, params.description]
    .filter(Boolean)
    .join(" ")
    .toLowerCase();
  if (family === "chair") {
    if (hint.includes("flower") || hint.includes("petal") || hint.includes("decor") || hint.includes("ornament") || hint.includes("pattern") || hint.includes("logo")) return "decorative_curve";
    if (hint.includes("arm")) return "armrest";
    if (hint.includes("head")) return "headrest";
    if (hint.includes("foot") || hint.includes("feet")) return "flat_foot";
    if (hint.includes("seat")) return "seat_panel";
    if (hint.includes("leg") || hint.includes("post")) return "chair_leg";
    if (hint.includes("back")) return "chair_back";
    if (hint.includes("bar") || hint.includes("brace") || hint.includes("rail")) return "chair_crossbar";
    return "chair_crossbar";
  }
  if (family === "table") {
    if (hint.includes("top") || hint.includes("surface") || sequence === 1) return "tabletop";
    if (hint.includes("leg") || hint.includes("post")) return "table_leg";
    if (hint.includes("foot") || hint.includes("feet")) return "flat_foot";
    if (hint.includes("curve") || hint.includes("curvy")) return "curved_tube";
    return "support_tube";
  }
  if (family === "torque_clamp") {
    if (hint.includes("boss") || hint.includes("shaft")) return "boss";
    return "clamp_jaw";
  }
  if (family === "motor_stator") {
    if (hint.includes("ring")) return "stator_ring";
    if (hint.includes("boss") || hint.includes("shaft") || hint.includes("bore")) return "boss";
    return "stator_tooth";
  }
  if (family === "wall_hook") {
    if (hint.includes("boss") || hint.includes("tip") || hint.includes("load")) return "boss";
    return "hook_curve";
  }
  if (hint.includes("hole")) return "lightening_hole";
  if (hint.includes("boss")) return "boss";
  if (hint.includes("panel") || hint.includes("body") || hint.includes("blade") || hint.includes("surface")) return "generic_panel";
  if (hint.includes("curve") || hint.includes("arc") || hint.includes("handle")) return "curved_tube";
  if (hint.includes("foot") || hint.includes("feet")) return "flat_foot";
  return "support_tube";
}

function sanitizeNumber(value, fallback, allowZero = true) {
  const number = Number(value);
  if (!Number.isFinite(number)) return fallback;
  if (!allowZero && number === 0) return fallback;
  return number;
}

function sanitizeActionParams(tool, params, family, ordinal = 1, sequence = 1) {
  const clean = { ...params };
  if (tool === "set_material") {
    const raw = String(clean.material || "").toLowerCase();
    clean.material = materials[raw] ? raw : materialAliases[raw] || (family === "motor_stator" ? "steel_1018" : "aluminum_6061");
  }
  if (tool === "create_design_family") {
    const rawFamily = String(clean.family || family || "ribbed_cantilever_bracket");
    const baseFamily = rawFamily.startsWith("blank_") ? rawFamily.slice(6) : rawFamily;
    clean.family = allowedFamilies.has(baseFamily) && baseFamily !== "ribbed_cantilever_bracket" ? `blank_${baseFamily}` : "ribbed_cantilever_bracket";
  }
  if (tool === "add_feature" && !allowedFeatureTypes.has(clean.type)) {
    clean.type = inferFeatureType(clean, family, sequence);
  }
  if (tool === "add_feature") {
    const defaults = featureDefaults(family, clean.type, ordinal);
    const needsGeometryDefault =
      !Number.isFinite(Number(clean.x)) ||
      !Number.isFinite(Number(clean.width)) ||
      !Number.isFinite(Number(clean.height)) ||
      (Number(clean.x) === 0 && Number(clean.y) === 0 && Number(clean.x2 || 0) === 0 && Number(clean.y2 || 0) === 0 && Number(clean.width || 0) === 0 && Number(clean.height || 0) === 0);
    if (needsGeometryDefault) {
      Object.assign(clean, { ...defaults, note: clean.note || defaults.note });
    } else {
      clean.x = sanitizeNumber(clean.x, defaults.x, true);
      clean.y = sanitizeNumber(clean.y, defaults.y, true);
      clean.x2 = sanitizeNumber(clean.x2, defaults.x2, true);
      clean.y2 = sanitizeNumber(clean.y2, defaults.y2, true);
      clean.width = sanitizeNumber(clean.width, defaults.width, false);
      clean.height = sanitizeNumber(clean.height, defaults.height, false);
      clean.radius = sanitizeNumber(clean.radius, defaults.radius, true);
      clean.note = clean.note || defaults.note;
    }
  }
  return clean;
}

function sanitizeModelPlan(rawPlan, prompt = "") {
  const promptFamily = familyFromPrompt(prompt);
  const family = promptFamily !== "freeform_object"
    ? promptFamily
    : allowedFamilies.has(rawPlan?.family)
      ? rawPlan.family
      : promptFamily;
  const actions = (Array.isArray(rawPlan?.actions) ? rawPlan.actions : [])
    .filter((action) => allowedToolNames.has(action?.tool))
    .map((action) => ({ tool: action.tool, params: action.params && typeof action.params === "object" ? action.params : {} }));
  const normalizedActions = normalizePlannedActions({ family, actions }, prompt);
  if (!normalizedActions.length) {
    throw new Error("Planner returned no executable tool actions.");
  }
  return {
    family,
    rationale: typeof rawPlan?.rationale === "string" ? rawPlan.rationale : "Model-planned CAD tool sequence.",
    actions: normalizedActions,
    raw_action_count: Array.isArray(rawPlan?.actions) ? rawPlan.actions.length : 0,
    executable_action_count: normalizedActions.length
  };
}

async function planToolActionsWithModel(prompt = "") {
  loadEnv();
  const model = process.env.MODEL_NAME || "gpt-5.4";
  const systemPrompt = toolPlannerSystemPrompt();
  const userMessage = [
    prompt,
    "",
    "Return a tool plan. The environment will execute each tool call sequentially and show the trace."
  ].join("\n");
  if (!process.env.OPENAI_API_KEY) {
    return {
      source: "deterministic_fallback",
      model,
      system: systemPrompt,
      user: userMessage,
      plan: { family: familyFromPrompt(prompt), rationale: "OPENAI_API_KEY missing; used local family template.", actions: actionsForFamily(familyFromPrompt(prompt), prompt) }
    };
  }

  const client = new OpenAI({ apiKey: process.env.OPENAI_API_KEY });
  const response = await client.responses.create({
    model,
    input: [
      { role: "system", content: systemPrompt },
      {
        role: "user",
        content: [
          userMessage,
          "",
          "Return valid JSON only with this shape:",
          '{"family":"chair","rationale":"...","actions":[{"tool":"create_design_family","params":{"family":"blank_chair"}}]}'
        ].join("\n")
      }
    ]
  });
  const rawText = response.output_text || "";
  const parsedJson = JSON.parse(rawText);
  const parsedPlan = sanitizeModelPlan(parsedJson, prompt);
  return {
    source: "openai_tool_planner",
    model,
    system: systemPrompt,
    user: userMessage,
    plan: {
      ...parsedPlan,
      actions: normalizePlannedActions(parsedPlan, prompt)
    }
  };
}

function compactDesignObservation(design, analysis = null, prompt = "") {
  const features = design?.features || [];
  const featureTypes = features.reduce((acc, feature) => {
    acc[feature.type] = (acc[feature.type] || 0) + 1;
    return acc;
  }, {});
  const notes = features.map((feature) => feature.note).filter(Boolean).slice(-10);
  return {
    prompt,
    title: design?.title,
    material: design?.material,
    load_newtons: design?.load_newtons,
    dimensions_mm: design
      ? { length: design.base_length_mm, width: design.base_width_mm, thickness: design.base_thickness_mm }
      : null,
    feature_count: features.length,
    feature_types: featureTypes,
    recent_feature_notes: notes,
    analysis: analysis
      ? {
          score: analysis.score,
          safety_factor: analysis.safety_factor,
          max_stress_mpa: analysis.max_stress_mpa,
          max_displacement_mm: analysis.max_displacement_mm,
          mass_g: analysis.mass_g,
          verdict: analysis.verdict
        }
      : null,
    semantic_requirements: {
      flower_backrest: wantsFlowerBackrest(prompt),
      curvy_chair: wantsCurvyChair(prompt)
    }
  };
}

function sanitizeContinuationActions(rawPlan, prompt, currentDesign) {
  const family = familyFromPrompt(prompt);
  const existingCounts = {};
  for (const feature of currentDesign?.features || []) {
    existingCounts[feature.type] = (existingCounts[feature.type] || 0) + 1;
  }
  let featureSequence = (currentDesign?.features || []).length;
  const actions = (Array.isArray(rawPlan?.actions) ? rawPlan.actions : [])
    .filter((action) => allowedToolNames.has(action?.tool))
    .filter((action) => !["create_design_family", "export_cadquery", "run_fea", "commit_design"].includes(action.tool))
    .map((action) => {
      const params = action.params && typeof action.params === "object" ? { ...action.params } : {};
      let ordinal = 0;
      let sequence = 0;
      if (action.tool === "add_feature") {
        featureSequence += 1;
        sequence = featureSequence;
        params.type = inferFeatureType(params, family, sequence);
        ordinal = existingCounts[params.type] = (existingCounts[params.type] || 0) + 1;
      }
      return { tool: action.tool, params: sanitizeActionParams(action.tool, params, family, ordinal, sequence) };
    });
  return applyPromptStyleToActions(actions, prompt, family);
}

async function planContinuationWithModel(prompt, currentDesign, currentAnalysis, round, maxRounds) {
  loadEnv();
  const model = process.env.MODEL_NAME || "gpt-5.4";
  const systemPrompt = [
    toolPlannerSystemPrompt(),
    "",
    "You are now replanning from an existing CAD state.",
    "Return only the next few repair/improvement tool calls. Do not recreate the design family. Do not export, run FEA, or commit; the environment handles those.",
    "Prefer semantic repairs first: if the prompt asks for a flower backrest and the current state lacks decorative_curve flower/petal features, add them.",
    "Use structural repairs if safety factor is low or the chair is missing legs/back/crossbars."
  ].join("\n");
  const observation = compactDesignObservation(currentDesign, currentAnalysis, prompt);
  const userMessage = [
    `Round ${round} of ${maxRounds}.`,
    "Current CAD/environment observation:",
    JSON.stringify(observation, null, 2),
    "",
    "Return valid JSON only with this shape:",
    '{"family":"chair","rationale":"...","actions":[{"tool":"add_feature","params":{"type":"decorative_curve","x":45,"y":42,"width":30,"height":30,"radius":8,"note":"flower petal curve"}}]}'
  ].join("\n");

  if (!process.env.OPENAI_API_KEY) {
    return {
      source: "deterministic_continuation_fallback",
      model,
      system: systemPrompt,
      user: userMessage,
      plan: { family: familyFromPrompt(prompt), rationale: "OPENAI_API_KEY missing; used local continuation repair.", actions: continuationFallbackActions(prompt, currentDesign) }
    };
  }

  const client = new OpenAI({ apiKey: process.env.OPENAI_API_KEY });
  const response = await client.responses.create({
    model,
    input: [
      { role: "system", content: systemPrompt },
      { role: "user", content: userMessage }
    ]
  });
  const rawText = response.output_text || "";
  const parsedJson = JSON.parse(rawText);
  return {
    source: "openai_receding_horizon_planner",
    model,
    system: systemPrompt,
    user: userMessage,
    plan: {
      family: allowedFamilies.has(parsedJson?.family) ? parsedJson.family : familyFromPrompt(prompt),
      rationale: parsedJson?.rationale || "Continuation repair plan.",
      actions: sanitizeContinuationActions(parsedJson, prompt, currentDesign)
    }
  };
}

function continuationFallbackActions(prompt, currentDesign) {
  const actions = [];
  const features = currentDesign?.features || [];
  if (wantsFlowerBackrest(prompt) && !features.some((feature) => feature.type === "decorative_curve" && /flower|petal|blossom/i.test(feature.note || ""))) {
    actions.push(
      { tool: "add_feature", params: { type: "decorative_curve", x: 45, y: 42, width: 30, height: 30, radius: 8, note: "flower backrest center blossom" } },
      { tool: "add_feature", params: { type: "decorative_curve", x: 45, y: 42, width: 48, height: 24, radius: 6, note: "six petal flower pattern on backrest" } },
      { tool: "add_feature", params: { type: "decorative_curve", x: 45, y: 42, width: 18, height: 36, radius: 4, note: "flower stem and leaf curves on backrest" } }
    );
  }
  if (currentDesign && currentDesign.load_newtons < 1600 && /1600\s*n/i.test(prompt)) {
    actions.push({ tool: "set_load", params: { point_mm: [currentDesign.base_length_mm / 2, 0, currentDesign.base_thickness_mm], vector_n: [0, 0, -1600] } });
  }
  return actions;
}

function runToolEpisode(prompt = "", actions = null, initialDesign = null) {
  const family = familyFromPrompt(prompt);
  return runPythonTool("run-actions", {
    prompt,
    actions: actions || actionsForFamily(family, prompt),
    initial_design: initialDesign
  });
}

function summarizeSimulation(simulation) {
  if (!simulation?.element_results) return simulation;
  return {
    method: simulation.method,
    node_count: simulation.nodes?.length,
    element_count: simulation.tets?.length || simulation.elements?.length,
    max_stress_mpa: simulation.max_stress_mpa,
    max_strain_microstrain: simulation.max_strain_microstrain,
    tip_deflection_mm: simulation.tip_deflection_mm,
    max_displacement_mm: simulation.max_displacement_mm,
    safety_factor: simulation.safety_factor,
    mass_g: simulation.mass_g,
    score: simulation.score,
    force_vector_n: simulation.force_vector_n,
    load_case: simulation.load_case,
    stress_regions: simulation.stress_regions,
    verdict: simulation.verdict
  };
}

function summarizeToolResult(result) {
  if (!result?.simulation) return result || {};
  return {
    ...result,
    simulation: summarizeSimulation(result.simulation)
  };
}

function invalidGeometryPenalty(design) {
  let penalty = 0;
  for (const feature of design.features) {
    const outside =
      feature.x < 0 ||
      feature.x > design.base_length_mm ||
      feature.y < -design.base_width_mm / 2 ||
      feature.y > design.base_width_mm / 2;
    if (outside) penalty += 0.08;
    if (feature.type === "lightening_hole" && feature.radius > design.base_width_mm / 3) penalty += 0.12;
    if (feature.type === "rib" && feature.height < design.base_thickness_mm) penalty += 0.04;
  }
  return clamp(penalty, 0, 0.8);
}

const sampleDesign = {
  title: "Two-rib lightweight cantilever bracket",
  rationale:
    "A broad thin base keeps bolt spacing stable, two diagonal ribs move material toward the bending load path, and small lightening holes reduce mass away from the fixed edge.",
  material: "aluminum_6061",
  load_newtons: 120,
  load_point_x_mm: 90,
  load_point_y_mm: 0,
  base_length_mm: 105,
  base_width_mm: 44,
  base_thickness_mm: 4,
  fixed_holes: [
    { x: 12, y: -13, radius: 3 },
    { x: 12, y: 13, radius: 3 }
  ],
  features: [
    { type: "rib", x: 16, y: -14, x2: 88, y2: -4, width: 5, height: 18, radius: 0, note: "lower diagonal rib" },
    { type: "rib", x: 16, y: 14, x2: 88, y2: 4, width: 5, height: 18, radius: 0, note: "upper diagonal rib" },
    { type: "rib", x: 18, y: 0, x2: 96, y2: 0, width: 4, height: 12, radius: 0, note: "center spine rib" },
    { type: "lightening_hole", x: 52, y: -13, x2: 0, y2: 0, width: 0, height: 0, radius: 4, note: "low-stress pocket" },
    { type: "lightening_hole", x: 52, y: 13, x2: 0, y2: 0, width: 0, height: 0, radius: 4, note: "low-stress pocket" },
    { type: "boss", x: 92, y: 0, x2: 0, y2: 0, width: 0, height: 7, radius: 6, note: "load application boss" }
  ],
  expected_failure_mode: "Bending stress at the fixed edge and rib roots.",
  action_plan: ["Search the load path", "Add ribs along tension/compression lines", "Remove material from low-stress regions", "Run simulation", "Iterate dimensions"]
};

function defaultSystemPrompt() {
  return [
    "You are CADForge, a code-CAD construction agent producing constrained parametric CAD JSON.",
    "Think like an OpenSCAD/CSG feature-tree builder: primitives, transforms, booleans, then validation.",
    "Pick an identifiable family before designing: chair, truss/bracket, wall_hook, torque_clamp, motor_stator, table, or bike_fixture.",
    "Use family-specific features when appropriate: seat_panel/chair_leg/chair_back/chair_crossbar for chairs, hook_curve for hooks, clamp_jaw for clamps, stator_ring/stator_tooth for motors, and rib/lightening_hole/boss for brackets.",
    "Use millimeters and newtons. Keep coordinates inside the base plate: x from 0 to base_length_mm and y from -base_width_mm/2 to +base_width_mm/2.",
    "The environment runs a coarse 3D linear tetrahedral elasticity solve with a fixed left face and inferred load point unless the prompt specifies otherwise.",
    "Do not create floating parts. A final design should be one connected, editable, watertight/manifold CAD-like solid.",
    "For chairs, include a seat panel, four legs, crossbars, and a backrest before adding styling.",
    "Do not turn non-bracket objects into ribbed plates. A hook must visibly be a hook, a stator must be circular with teeth, and a chair must have a seat and legs.",
    "Use every numeric field in the schema. For unused feature fields, set numeric values to 0 and explain in note.",
    "Do not output markdown. Return only the structured design."
  ].join("\n");
}

function scadSystemPrompt() {
  return [
    "You are CADForge SCAD, a careful multi-step OpenSCAD code generator for functional mechanical objects.",
    "Return real OpenSCAD code, not pseudocode, and improve the candidate like an agent using verifier feedback.",
    "Use only this currently renderable subset: cube, sphere, cylinder, translate, rotate, scale, union, difference, and intersection.",
    "Use numeric constants directly. Do not use modules, variables, loops, list comprehensions, hull, minkowski, text, import, surface, or unsupported functions.",
    "Keep the candidate renderer-safe: no more than 16 visible primitives and use $fn no higher than 16.",
    "Prefer one connected solid. Avoid floating parts by making primitives overlap by 1-4 mm before union.",
    "For Markus-like chairs, include these connected semantic parts: broad seat pan, tall backrest, upper headrest-like pad, two armrests, central gas cylinder, central hub, five-star base spokes, and simple caster proxies.",
    "For a five-star base without loops, explicitly write five rotated or translated spokes. Every spoke must overlap the hub.",
    "Make the chair taller than it is wide, with the backrest connected to the seat and the column/base connected to the underside of the seat.",
    "If verifier stats report floating_parts, multiple connected_components, boundary_edges, or non_manifold_edges, fix topology before adding detail.",
    "Use difference for holes only when the cutting primitive fully passes through the target.",
    "Keep code compact and readable, but complete enough to visibly read as an office chair."
  ].join("\n");
}

function cleanScadCode(value = "") {
  return String(value)
    .replace(/^```(?:openscad|scad)?/i, "")
    .replace(/```$/i, "")
    .trim();
}

function cadquerySystemPrompt() {
  return [
    "You are CADForge CadQuery, a careful Python CadQuery code generator for real mechanical CAD.",
    "Return executable CadQuery Python code, not pseudocode.",
    "Use CadQuery as cq. You may include `import cadquery as cq`, `from cadquery import exporters`, and `import math`; the runner already provides cq, exporters, and math.",
    "Do not use file IO, network, subprocesses, OS APIs, random external imports, or shell commands.",
    "Do not call exporters.export; the backend runner exports the final object.",
    "Assign the final exportable CadQuery object to a variable named `fixture`.",
    "For this web backend, prefer one `cq.Workplane`/Solid/Compound named `fixture`; do not use `cq.Assembly`, `show_object`, display-only colors, or CQ-Editor-only helpers unless the prompt explicitly asks for presentation code.",
    "Use real CadQuery features such as workplanes, sketches, extrude, revolve, cskHole, union, cut, and clean when useful.",
    "Prefer parameterized code with named dimensions at the top.",
    "For generated chair models, avoid fillet/chamfer calls unless the edge selector is guaranteed to match a solid; robust executable CAD is more important than decorative rounded edges.",
    "For generated chair models, do not use mirror(), mirrorX(), mirrorY(), loft(), sweep(), or complex open-wire profiles; build the chair from translated/rotated boxes, cylinders, simple extrusions, and boolean cuts so the code runs reliably headlessly.",
    "For chair-like objects, use a robust union of solids: five-star caster base, central gas cylinder, under-seat mechanism block, seat cushion, tall back frame/mesh panel, headrest pad, lumbar pad, and armrests. Keep it approximate but runnable; exact proprietary IKEA manufacturing geometry is not available.",
    "For wall-mounted J hooks, use the known-stable pattern: base plate as a filleted box with cskHole mounting holes, hook body as a closed 2D profile on the YZ plane extruded with both=True, triangular gussets as closed YZ profiles extruded with both=True, then fixture = base.union(hook).union(gussets).",
    "Avoid fragile sweep paths for hooks unless absolutely necessary; CadQuery threePointArc inside a closed planar profile is more reliable than sweep for this app.",
    "Do not use try/except blocks in generated code. Produce straightforward code that either runs or gives a clear verifier error.",
    "Generate a single coherent part suitable for STL export."
  ].join("\n");
}

function cleanCadqueryCode(value = "") {
  return String(value)
    .replace(/^```(?:python|py)?/i, "")
    .replace(/```$/i, "")
    .trim();
}

function repairCadqueryFilletChains(code = "") {
  return String(code)
    .replace(/\n\s*\.edges\([^)]*\)\s*\n\s*\.(?:fillet|chamfer)\([^)]*\)/g, "")
    .replace(/\n\s*\.(?:fillet|chamfer)\([^)]*\)/g, "")
    .trim();
}

function isFilletSelectionFailure(body = {}) {
  const text = `${body.error || ""}\n${body.stderr || ""}\n${body.stdout || ""}`.toLowerCase();
  return text.includes("no suitable edges") && (text.includes("fillet") || text.includes("chamfer"));
}

async function generateCadqueryWithModel({ prompt }) {
  if (!process.env.OPENAI_API_KEY) {
    throw new Error("OPENAI_API_KEY is missing. Real CadQuery generation requires a configured model API key.");
  }
  const client = new OpenAI({ apiKey: process.env.OPENAI_API_KEY });
  const response = await client.responses.parse({
    model: process.env.MODEL_NAME || "gpt-5.4",
    input: [
      { role: "system", content: cadquerySystemPrompt() },
      { role: "user", content: prompt }
    ],
    text: {
      format: zodTextFormat(CadQueryResponseSchema, "cadquery_generation")
    }
  });
  return {
    ...response.output_parsed,
    cadquery_code: cleanCadqueryCode(response.output_parsed.cadquery_code),
    model: process.env.MODEL_NAME || "gpt-5.4",
    system: cadquerySystemPrompt(),
    user: prompt
  };
}

async function generateCadqueryCodeText({ prompt, currentCode = "", reward = null, provider = "openai", model = "" }) {
  const system = [
    cadquerySystemPrompt(),
    "You are working in a code-editing CAD REPL.",
    "Return only the complete updated CadQuery Python file. Do not return explanations outside code."
  ].join("\n\n");
  const user = [
    `Task: ${prompt}`,
    currentCode ? `Current CadQuery code:\n${currentCode}` : "No current code yet. Create the first candidate.",
    reward ? `Last reward/verifier JSON:\n${JSON.stringify(reward, null, 2)}` : "",
    "Write a robust, executable, editable CadQuery candidate."
  ].filter(Boolean).join("\n\n");

  if (provider === "ollama") {
    const ollamaModel = model || process.env.OLLAMA_MODEL || "qwen3.5:0.8b";
    const response = await fetch(process.env.OLLAMA_URL || "http://localhost:11434/api/chat", {
      method: "POST",
      headers: { "Content-Type": "application/json" },
      body: JSON.stringify({
        model: ollamaModel,
        stream: false,
        messages: [
          { role: "system", content: system },
          { role: "user", content: user }
        ]
      })
    });
    const result = await response.json();
    if (!response.ok) {
      throw new Error(result.error || `Ollama request failed with status ${response.status}`);
    }
    return {
      provider: "ollama",
      model: ollamaModel,
      cadquery_code: cleanCadqueryCode(result.message?.content || result.response || "")
    };
  }

  if (!process.env.OPENAI_API_KEY) {
    throw new Error("OPENAI_API_KEY is missing. OpenAI CadQuery generation requires a configured model API key.");
  }
  const openaiModel = model || process.env.MODEL_NAME || "gpt-5.4";
  const client = new OpenAI({ apiKey: process.env.OPENAI_API_KEY });
  const response = await client.responses.create({
    model: openaiModel,
    input: [
      { role: "system", content: system },
      { role: "user", content: user }
    ]
  });
  return {
    provider: "openai",
    model: openaiModel,
    cadquery_code: cleanCadqueryCode(response.output_text || "")
  };
}

async function generateScadWithModel({ prompt, previousScad = "", renderStats = null }) {
  if (!process.env.OPENAI_API_KEY) {
    throw new Error("OPENAI_API_KEY is missing. Real SCAD generation requires a configured model API key.");
  }
  const client = new OpenAI({ apiKey: process.env.OPENAI_API_KEY });
  const user = previousScad
    ? [
        prompt,
        "",
        "Revise the existing OpenSCAD code to better satisfy the prompt, the Markus-chair target, and the verifier feedback.",
        "Treat the verifier feedback as tool output from the environment. First repair compile/topology problems, then improve chair likeness.",
        "Existing SCAD:",
        previousScad,
        "",
        `Previous render stats: ${JSON.stringify(renderStats || {})}`
      ].join("\n")
    : prompt;
  const response = await client.responses.parse({
    model: process.env.MODEL_NAME || "gpt-5.4",
    input: [
      { role: "system", content: scadSystemPrompt() },
      { role: "user", content: user }
    ],
    text: {
      format: zodTextFormat(ScadResponseSchema, "scad_generation")
    }
  });
  return {
    ...response.output_parsed,
    scad_code: cleanScadCode(response.output_parsed.scad_code),
    model: process.env.MODEL_NAME || "gpt-5.4",
    system: scadSystemPrompt(),
    user
  };
}

function feedbackPrompt(prompt, previousDesign, previousAnalysis, iteration, maxIterations) {
  if (!previousDesign) return prompt;
  return [
    prompt,
    "",
    `Iteration ${iteration} of ${maxIterations}. Improve the previous design using this verifier feedback.`,
    `Previous title: ${previousDesign.title}`,
    `Score: ${previousAnalysis.score}`,
    `Mass: ${previousAnalysis.mass_g} g`,
    `Stress: ${previousAnalysis.max_stress_mpa} MPa`,
    `Strain: ${previousAnalysis.max_strain_microstrain} microstrain`,
    `Safety factor: ${previousAnalysis.safety_factor}`,
    `Tip deflection: ${previousAnalysis.tip_deflection_mm} mm`,
    `Thermal proxy rise: ${previousAnalysis.thermal_delta_c_proxy} C`,
    `FEA method: ${previousAnalysis.fea?.method || "unknown"}`,
    `Highest-stress regions: ${JSON.stringify(previousAnalysis.stress_regions || [])}`,
    `Verdict: ${previousAnalysis.verdict}`,
    "Return a revised design. Preserve useful load-path features, reduce mass if safety factor is excessive, and improve weak areas if stress or deflection is high."
  ].join("\n");
}

async function generateDesignForModel(client, model, prompt, previousDesign = null, previousAnalysis = null, iteration = 1, maxIterations = 1, systemPrompt = defaultSystemPrompt()) {
  const userMessage = feedbackPrompt(prompt, previousDesign, previousAnalysis, iteration, maxIterations);
  const response = await client.responses.parse({
    model,
    input: [
      { role: "system", content: systemPrompt },
      { role: "user", content: userMessage }
    ],
    text: {
      format: zodTextFormat(DesignSchema, "mechanical_design")
    }
  });

  const design = response.output_parsed;
  const analysis = simulateDesign(design, prompt);
  return {
    design,
    analysis,
    model,
    trace: [
      { role: "system", content: systemPrompt },
      { role: "user", content: userMessage },
      { role: "assistant", content: design },
      { role: "tool", name: "run_python_3d_fea", content: analysis }
    ]
  };
}

async function runIterativeBenchmark(client, model, prompt, iterations, systemPrompt = defaultSystemPrompt()) {
  const trace = [];
  let previousDesign = null;
  let previousAnalysis = null;
  for (let iteration = 1; iteration <= iterations; iteration += 1) {
    const result = await generateDesignForModel(client, model, prompt, previousDesign, previousAnalysis, iteration, iterations, systemPrompt);
    trace.push({ iteration, ...result });
    previousDesign = result.design;
    previousAnalysis = result.analysis;
  }
  return {
    model,
    iterations,
    best: trace.reduce((best, item) => (item.analysis.score > best.analysis.score ? item : best), trace[0]),
    final: trace[trace.length - 1],
    trace
  };
}

app.get("/api/sample", (_req, res) => {
  res.json({ design: sampleDesign, analysis: simulateDesign(sampleDesign), source: "local_sample" });
});

app.post("/api/tool-episode", async (req, res) => {
  const prompt = String(req.body?.prompt || "").trim();
  const targetToolCalls = clampToolBudget(req.body?.target_tool_calls);
  try {
    let planner;
    try {
      planner = await planToolActionsWithModel(prompt);
    } catch (error) {
      const family = familyFromPrompt(prompt);
      planner = {
        source: "deterministic_fallback",
        model: process.env.MODEL_NAME || "gpt-5.4",
        system: toolPlannerSystemPrompt(),
        user: prompt,
        error: error instanceof Error ? error.message : "Unknown planner error",
        plan: { family, rationale: "Model planner failed; used local family template.", actions: actionsForFamily(family, prompt) }
      };
    }
    const baseActions = normalizePlannedActions(planner.plan, prompt);
    const expandedActions = expandLongHorizonActions(baseActions, targetToolCalls);
    planner = {
      ...planner,
      plan: {
        ...planner.plan,
        base_actions: baseActions,
        actions: expandedActions,
        target_tool_calls: targetToolCalls,
        executable_action_count: expandedActions.length
      }
    };
    const result = runToolEpisode(prompt, expandedActions);
    const simulation = result.last_result?.simulation || simulateDesign(result.design, prompt);
    const trace = (result.trace || []).map((item) => ({
      role: "tool",
      name: item.action?.tool || "unknown_tool",
      content: {
        step: item.step,
        params: item.action?.params || {},
        result: summarizeToolResult(item.result),
        design_snapshot: item.design || null
      }
    }));
    res.json({
      source: "python_tool_episode",
      planner,
      target_tool_calls: targetToolCalls,
      design: result.design,
      analysis: simulation,
      trace
    });
  } catch (error) {
    res.status(500).json({ error: error instanceof Error ? error.message : "Unknown Python tool episode error" });
  }
});

app.post("/api/receding-agent", async (req, res) => {
  const prompt = String(req.body?.prompt || "").trim();
  const targetToolCalls = clampToolBudget(req.body?.target_tool_calls);
  const model = process.env.MODEL_NAME || "gpt-5.4";
  try {
    let trace = [];
    const plannerRounds = [];
    let design = null;
    let analysis = null;
    const maxRounds = clamp(Math.ceil(targetToolCalls / 60), 2, 4);
    const finalActions = [microAction("export_cadquery"), microAction("run_fea"), microAction("commit_design")];
    const perRoundBudget = Math.max(12, Math.floor((targetToolCalls - finalActions.length) / maxRounds));

    let initialPlanner;
    try {
      initialPlanner = await planToolActionsWithModel(prompt);
    } catch (error) {
      const family = familyFromPrompt(prompt);
      initialPlanner = {
        source: "deterministic_fallback",
        model,
        system: toolPlannerSystemPrompt(),
        user: prompt,
        error: error instanceof Error ? error.message : "Unknown planner error",
        plan: { family, rationale: "Model planner failed; used local family template.", actions: actionsForFamily(family, prompt) }
      };
    }
    const firstBaseActions = normalizePlannedActions(initialPlanner.plan, prompt).filter((action) => !["export_cadquery", "run_fea", "commit_design"].includes(action.tool));
    const firstBuildCount = Math.min(firstBaseActions.length, Math.max(7, Math.ceil(firstBaseActions.length * 0.62)));
    const firstChunk = expandActionChunk(firstBaseActions.slice(0, firstBuildCount), perRoundBudget, 1);
    const firstResult = runToolEpisode(prompt, [...firstChunk, microAction("run_fea", { round: 1, reason: "checkpoint before replanning" })]);
    design = firstResult.design;
    analysis = firstResult.last_result?.simulation || simulateDesign(design, prompt);
    trace = trace.concat((firstResult.trace || []).map((item, index) => ({
      role: "tool",
      name: item.action?.tool || "unknown_tool",
      content: {
        step: index + 1,
        round: 1,
        params: item.action?.params || {},
        result: summarizeToolResult(item.result),
        design_snapshot: item.design || null
      }
    })));
    plannerRounds.push({
      round: 1,
      kind: "initial_plan",
      source: initialPlanner.source,
      model: initialPlanner.model,
      system: initialPlanner.system,
      user: initialPlanner.user,
      plan: { ...initialPlanner.plan, base_actions: firstBaseActions, executed_actions: firstChunk }
    });

    const remainingInitialActions = firstBaseActions.slice(firstBuildCount);
    for (let round = 2; round <= maxRounds; round += 1) {
      let continuation;
      try {
        continuation = await planContinuationWithModel(prompt, design, analysis, round, maxRounds);
      } catch (error) {
        continuation = {
          source: "deterministic_continuation_fallback",
          model,
          system: "Local fallback continuation planner.",
          user: JSON.stringify(compactDesignObservation(design, analysis, prompt), null, 2),
          error: error instanceof Error ? error.message : "Unknown continuation planner error",
          plan: { family: familyFromPrompt(prompt), rationale: "Continuation planner failed; used local semantic repair.", actions: continuationFallbackActions(prompt, design) }
        };
      }

      const carryover = round === 2 ? remainingInitialActions : [];
      const continuationActions = sanitizeContinuationActions(continuation.plan, prompt, design);
      const roundActions = [...carryover, ...continuationActions].filter((action, index, all) => {
        const key = JSON.stringify(action);
        return all.findIndex((candidate) => JSON.stringify(candidate) === key) === index;
      });
      if (!roundActions.length) {
        plannerRounds.push({ round, kind: "replan_noop", ...continuation, observation: compactDesignObservation(design, analysis, prompt) });
        continue;
      }

      const chunk = expandActionChunk(roundActions, perRoundBudget, round);
      const result = runToolEpisode(prompt, [...chunk, microAction("run_fea", { round, reason: "checkpoint after replanning" })], design);
      const offset = trace.length;
      design = result.design;
      analysis = result.last_result?.simulation || simulateDesign(design, prompt);
      trace = trace.concat((result.trace || []).map((item, index) => ({
        role: "tool",
        name: item.action?.tool || "unknown_tool",
        content: {
          step: offset + index + 1,
          round,
          params: item.action?.params || {},
          result: summarizeToolResult(item.result),
          design_snapshot: item.design || null
        }
      })));
      plannerRounds.push({
        round,
        kind: "replan",
        source: continuation.source,
        model: continuation.model,
        system: continuation.system,
        user: continuation.user,
        error: continuation.error || null,
        observation: compactDesignObservation(design, analysis, prompt),
        plan: { ...continuation.plan, carryover_actions: carryover, executed_actions: chunk }
      });
    }

    const finalChunk = finalActions;
    const finalResult = runToolEpisode(prompt, finalChunk, design);
    const offset = trace.length;
    design = finalResult.design;
    analysis = finalResult.last_result?.simulation || simulateDesign(design, prompt);
    trace = trace.concat((finalResult.trace || []).map((item, index) => ({
      role: "tool",
      name: item.action?.tool || "unknown_tool",
      content: {
        step: offset + index + 1,
        round: maxRounds + 1,
        params: item.action?.params || {},
        result: summarizeToolResult(item.result),
        design_snapshot: item.design || null
      }
    })));

    res.json({
      source: "receding_horizon_agent",
      planner: {
        source: "receding_horizon",
        model,
        rounds: plannerRounds,
        target_tool_calls: targetToolCalls,
        executable_action_count: trace.length
      },
      target_tool_calls: targetToolCalls,
      design,
      analysis,
      trace
    });
  } catch (error) {
    res.status(500).json({ error: error instanceof Error ? error.message : "Unknown receding-horizon agent error" });
  }
});

app.get("/api/system-prompt", (_req, res) => {
  res.json({ system_prompt: defaultSystemPrompt() });
});

app.post("/api/generate", async (req, res) => {
  loadEnv();
  const model = process.env.MODEL_NAME || "gpt-5.4";
  const prompt = String(req.body?.prompt || "").trim();
  const systemPrompt = String(req.body?.system_prompt || defaultSystemPrompt());
  if (!prompt) {
    res.status(400).json({ error: "Prompt is required." });
    return;
  }

  if (!process.env.OPENAI_API_KEY) {
    res.status(400).json({
      error: "OPENAI_API_KEY is missing. Copy .env.example to .env and paste your key.",
      design: sampleDesign,
      analysis: simulateDesign(sampleDesign)
    });
    return;
  }

  try {
    const client = new OpenAI({ apiKey: process.env.OPENAI_API_KEY });
    const result = await generateDesignForModel(client, model, prompt, null, null, 1, 1, systemPrompt);
    res.json({ ...result, source: "openai" });
  } catch (error) {
    res.status(500).json({
      error: error instanceof Error ? error.message : "Unknown OpenAI generation error",
      design: sampleDesign,
      analysis: simulateDesign(sampleDesign)
    });
  }
});

app.post("/api/benchmark", async (req, res) => {
  loadEnv();
  const prompt = String(req.body?.prompt || "").trim();
  const systemPrompt = String(req.body?.system_prompt || defaultSystemPrompt());
  const models = Array.isArray(req.body?.models) && req.body.models.length ? req.body.models.map(String) : ["gpt-5.4"];
  const iterations = clamp(Number(req.body?.iterations || 3), 1, 5);

  if (!prompt) {
    res.status(400).json({ error: "Prompt is required." });
    return;
  }

  if (!process.env.OPENAI_API_KEY) {
    res.status(400).json({ error: "OPENAI_API_KEY is missing in root .env or experiment .env." });
    return;
  }

  try {
    const client = new OpenAI({ apiKey: process.env.OPENAI_API_KEY });
    const startedAt = Date.now();
    const results = [];
    for (const benchmarkModel of models) {
      try {
        results.push(await runIterativeBenchmark(client, benchmarkModel, prompt, iterations, systemPrompt));
      } catch (error) {
        results.push({
          model: benchmarkModel,
          error: error instanceof Error ? error.message : "Unknown model benchmark error",
          trace: []
        });
      }
    }
    res.json({
      source: "openai",
      prompt,
      iterations,
      elapsed_ms: Date.now() - startedAt,
      results
    });
  } catch (error) {
    res.status(500).json({
      error: error instanceof Error ? error.message : "Unknown benchmark error"
    });
  }
});

app.post("/api/scad-generate", async (req, res) => {
  loadEnv();
  const prompt = String(req.body?.prompt || "").trim();
  if (!prompt) {
    res.status(400).json({ error: "Prompt is required." });
    return;
  }
  try {
    const result = await generateScadWithModel({ prompt });
    res.json({ source: "openai_scad_generator", ...result });
  } catch (error) {
    res.status(500).json({ error: error instanceof Error ? error.message : "Unknown SCAD generation error" });
  }
});

app.post("/api/scad-iterate", async (req, res) => {
  loadEnv();
  const prompt = String(req.body?.prompt || "").trim();
  const previousScad = String(req.body?.scad_code || "").trim();
  if (!prompt || !previousScad) {
    res.status(400).json({ error: "Prompt and existing SCAD code are required." });
    return;
  }
  try {
    const result = await generateScadWithModel({ prompt, previousScad, renderStats: req.body?.render_stats || null });
    res.json({ source: "openai_scad_iterator", ...result });
  } catch (error) {
    res.status(500).json({ error: error instanceof Error ? error.message : "Unknown SCAD iteration error" });
  }
});

app.post("/api/cadquery/sample-hook", async (req, res) => {
  loadEnv();
  const scriptPath = path.join(appRoot, "python_tools", "cadquery_heavy_duty_hook.py");
  const outDir = path.join(appRoot, "runs", "cadquery");
  const pythonPath = path.join(appRoot, "python_tools");
  const startedAt = Date.now();
  const result = spawnSync(pythonBin, [scriptPath, "--out-dir", outDir], {
    cwd: appRoot,
    encoding: "utf8",
    timeout: 120000,
    env: {
      ...process.env,
      PYTHONPATH: pythonPath,
      XDG_CACHE_HOME: process.env.XDG_CACHE_HOME || path.join(appRoot, ".cache")
    }
  });

  if (result.error) {
    res.status(500).json({
      error: result.error.message,
      stdout: result.stdout,
      stderr: result.stderr
    });
    return;
  }

  if (result.status !== 0) {
    res.status(500).json({
      error: `CadQuery exited with status ${result.status}`,
      stdout: result.stdout,
      stderr: result.stderr
    });
    return;
  }

  try {
    const lines = String(result.stdout || "").trim().split(/\r?\n/).filter(Boolean);
    const payload = JSON.parse(lines[lines.length - 1] || "{}");
    const stl = readFileSync(payload.stl_path);
    res.json({
      source: "cadquery_sample_hook",
      elapsed_ms: Date.now() - startedAt,
      ...payload,
      stl_base64: stl.toString("base64"),
      stdout: result.stdout,
      stderr: result.stderr
    });
  } catch (error) {
    res.status(500).json({
      error: error instanceof Error ? error.message : "Failed to read CadQuery STL output.",
      stdout: result.stdout,
      stderr: result.stderr
    });
  }
});

function cadqueryResultToResponse({ result, startedAt, source }) {
  if (result.error) {
    return {
      status: 500,
      body: {
        error: result.error.message,
        stdout: result.stdout,
        stderr: result.stderr
      }
    };
  }

  if (result.status !== 0) {
    return {
      status: 500,
      body: {
        error: `CadQuery exited with status ${result.status}`,
        stdout: result.stdout,
        stderr: result.stderr
      }
    };
  }

  try {
    const lines = String(result.stdout || "").trim().split(/\r?\n/).filter(Boolean);
    const payload = JSON.parse(lines[lines.length - 1] || "{}");
    const stl = readFileSync(payload.stl_path);
    return {
      status: 200,
      body: {
        source,
        elapsed_ms: Date.now() - startedAt,
        ...payload,
        stl_base64: stl.toString("base64"),
        stdout: result.stdout,
        stderr: result.stderr
      }
    };
  } catch (error) {
    return {
      status: 500,
      body: {
        error: error instanceof Error ? error.message : "Failed to read CadQuery STL output.",
        stdout: result.stdout,
        stderr: result.stderr
      }
    };
  }
}

function parsePythonJsonStdout(stdout) {
  const text = String(stdout || "").trim();
  const start = text.indexOf("{");
  const end = text.lastIndexOf("}");
  if (start < 0 || end < start) {
    throw new Error("Python command did not return JSON.");
  }
  return JSON.parse(text.slice(start, end + 1));
}

function cadqueryEnvResponse({ result, startedAt, source }) {
  if (result.error) {
    return {
      status: 500,
      body: {
        source,
        error: result.error.message,
        stdout: result.stdout,
        stderr: result.stderr
      }
    };
  }
  if (result.status !== 0) {
    return {
      status: 500,
      body: {
        source,
        error: `CadQuery environment exited with status ${result.status}`,
        stdout: result.stdout,
        stderr: result.stderr
      }
    };
  }
  try {
    return {
      status: 200,
      body: {
        source,
        elapsed_ms: Date.now() - startedAt,
        ...parsePythonJsonStdout(result.stdout),
        stderr: result.stderr
      }
    };
  } catch (error) {
    return {
      status: 500,
      body: {
        source,
        error: error instanceof Error ? error.message : "Failed to parse CadQuery environment output.",
        stdout: result.stdout,
        stderr: result.stderr
      }
    };
  }
}

app.get("/api/cadquery/sample-code", (req, res) => {
  const scriptPath = path.join(appRoot, "python_tools", "cadquery_samples", "heavy_duty_hook_query.py");
  try {
    res.json({
      source: "cadquery_sample_code",
      cadquery_code: readFileSync(scriptPath, "utf8")
    });
  } catch (error) {
    res.status(500).json({ error: error instanceof Error ? error.message : "Could not read CadQuery sample code." });
  }
});

app.get("/api/cadquery/ideal-code", (req, res) => {
  const scriptPath = path.join(appRoot, "..", "3d-models", "ikea_markus_idealish_code.md");
  try {
    const text = readFileSync(scriptPath, "utf8");
    const match = text.match(/```(?:python|py)?\s*\n([\s\S]*?)```/i);
    res.json({
      source: "cadquery_ideal_markus_code",
      cadquery_code: match ? match[1].trim() : text.trim()
    });
  } catch (error) {
    res.status(500).json({ error: error instanceof Error ? error.message : "Could not read ideal Markus CadQuery code." });
  }
});

app.get("/api/cadquery/reference", (req, res) => {
  loadEnv();
  const scriptPath = path.join(appRoot, "python_tools", "cadquery_env.py");
  const pythonPath = path.join(appRoot, "python_tools");
  const startedAt = Date.now();
  const result = spawnSync(pythonBin, [scriptPath, "preprocess-reference"], {
    cwd: appRoot,
    encoding: "utf8",
    timeout: 240000,
    env: {
      ...process.env,
      PYTHONPATH: pythonPath,
      XDG_CACHE_HOME: process.env.XDG_CACHE_HOME || path.join(appRoot, ".cache")
    }
  });
  const response = cadqueryEnvResponse({ result, startedAt, source: "cadquery_reference_preprocess" });
  res.status(response.status).json(response.body);
});

app.post("/api/cadquery/health", async (req, res) => {
  loadEnv();
  const code = [
    "import cadquery as cq",
    "",
    "base = cq.Workplane(\"XY\").box(40, 30, 12)",
    "boss = cq.Workplane(\"XY\").circle(8).extrude(18).translate((0, 0, 6))",
    "fixture = base.union(boss).clean()"
  ].join("\n");
  const scriptPath = path.join(appRoot, "python_tools", "cadquery_code_runner.py");
  const outDir = path.join(appRoot, "runs", "cadquery-health");
  const pythonPath = path.join(appRoot, "python_tools");
  const startedAt = Date.now();
  const result = spawnSync(pythonBin, [scriptPath, "--out-dir", outDir, "--name", "cadquery_health"], {
    cwd: appRoot,
    input: JSON.stringify({ code, features: ["CadQuery import", "boolean union", "STL export"] }),
    encoding: "utf8",
    timeout: 120000,
    env: {
      ...process.env,
      PYTHONPATH: pythonPath,
      XDG_CACHE_HOME: process.env.XDG_CACHE_HOME || path.join(appRoot, ".cache")
    }
  });

  const response = cadqueryResultToResponse({ result, startedAt, source: "cadquery_backend_health" });
  if (response.status === 200) {
    response.body = {
      ...response.body,
      code,
      stl_bytes: Buffer.from(response.body.stl_base64, "base64").length
    };
  }
  res.status(response.status).json(response.body);
});

app.post("/api/cadquery/generate", async (req, res) => {
  loadEnv();
  const prompt = String(req.body?.prompt || "").trim();
  if (!prompt) {
    res.status(400).json({ error: "Prompt is required." });
    return;
  }
  try {
    const result = await generateCadqueryWithModel({ prompt });
    res.json({ source: "openai_cadquery_generator", ...result });
  } catch (error) {
    res.status(500).json({ error: error instanceof Error ? error.message : "Unknown CadQuery generation error" });
  }
});

app.post("/api/cadquery/repl-step", async (req, res) => {
  loadEnv();
  const prompt = String(req.body?.prompt || "").trim();
  const currentCode = String(req.body?.current_code || req.body?.cadquery_code || "").trim();
  const provider = String(req.body?.provider || "openai").toLowerCase() === "ollama" ? "ollama" : "openai";
  const model = String(req.body?.model || "").trim();
  const reward = req.body?.reward && typeof req.body.reward === "object" ? req.body.reward : null;
  if (!prompt) {
    res.status(400).json({ error: "Prompt is required." });
    return;
  }
  try {
    const result = await generateCadqueryCodeText({ prompt, currentCode, reward, provider, model });
    res.json({ source: "cadquery_repl_step", ...result });
  } catch (error) {
    res.status(500).json({ error: error instanceof Error ? error.message : "Unknown CadQuery REPL generation error" });
  }
});

app.post("/api/cadquery/render-code", async (req, res) => {
  loadEnv();
  const code = String(req.body?.cadquery_code || "").trim();
  const features = Array.isArray(req.body?.features) ? req.body.features.map(String) : [];
  if (!code) {
    res.status(400).json({ error: "CadQuery code is required." });
    return;
  }

  const scriptPath = path.join(appRoot, "python_tools", "cadquery_code_runner.py");
  const outDir = path.join(appRoot, "runs", "cadquery-generated");
  const pythonPath = path.join(appRoot, "python_tools");
  const startedAt = Date.now();
  const runCode = (candidateCode) =>
    spawnSync(pythonBin, [scriptPath, "--out-dir", outDir, "--name", "generated_cadquery"], {
      cwd: appRoot,
      input: JSON.stringify({ code: candidateCode, features }),
      encoding: "utf8",
      timeout: 120000,
      env: {
        ...process.env,
        PYTHONPATH: pythonPath,
        XDG_CACHE_HOME: process.env.XDG_CACHE_HOME || path.join(appRoot, ".cache")
      }
    });

  let response = cadqueryResultToResponse({ result: runCode(code), startedAt, source: "cadquery_code_runner" });
  if (response.status !== 200 && isFilletSelectionFailure(response.body)) {
    const repairedCode = repairCadqueryFilletChains(code);
    if (repairedCode && repairedCode !== code) {
      const originalFailure = response.body;
      response = cadqueryResultToResponse({ result: runCode(repairedCode), startedAt, source: "cadquery_code_runner_repaired_fillet" });
      if (response.status === 200) {
        response.body = {
          ...response.body,
          repaired: true,
          repair_note: "Removed failing fillet/chamfer edge-selection chains after CadQuery reported no suitable edges.",
          original_error: originalFailure.error,
          original_stderr: originalFailure.stderr
        };
      }
    }
  }
  res.status(response.status).json(response.body);
});

app.post("/api/cadquery/evaluate-code", async (req, res) => {
  loadEnv();
  const code = String(req.body?.cadquery_code || req.body?.code || "").trim();
  const episodeId = String(req.body?.episode_id || "api");
  const stepId = String(req.body?.step_id || `step-${Date.now()}`);
  const taskPrompt = String(req.body?.task_prompt || "");
  const rewardMode = String(req.body?.reward_mode || "full") === "fast" ? "fast" : "full";
  if (!code) {
    res.status(400).json({ error: "CadQuery code is required." });
    return;
  }

  const scriptPath = path.join(appRoot, "python_tools", "cadquery_env.py");
  const pythonPath = path.join(appRoot, "python_tools");
  const startedAt = Date.now();
  const result = spawnSync(
    pythonBin,
    [scriptPath, "evaluate", "--episode-id", episodeId, "--step-id", stepId, "--task-prompt", taskPrompt, "--reward-mode", rewardMode],
    {
      cwd: appRoot,
      input: JSON.stringify({ code }),
      encoding: "utf8",
      timeout: 240000,
      env: {
        ...process.env,
        PYTHONPATH: pythonPath,
        XDG_CACHE_HOME: process.env.XDG_CACHE_HOME || path.join(appRoot, ".cache")
      }
    }
  );
  const response = cadqueryEnvResponse({ result, startedAt, source: "cadquery_environment_evaluator" });
  if (response.status === 200 && response.body?.candidate_stl) {
    try {
      const stl = readFileSync(response.body.candidate_stl);
      response.body.stl_base64 = stl.toString("base64");
      response.body.stl_bytes = stl.length;
    } catch {
      // Evaluation still succeeded; leave render payload absent if the STL cannot be read.
    }
  }
  res.status(response.status).json(response.body);
});

app.listen(port, () => {
  console.log(`CADForge API listening on http://localhost:${port}`);
});