{
  "module": "thermodynamics",
  "version": "1.0",
  "purpose": "Constraint-first substrate grammar for temperature, entropy, free energy, flows, and equilibrium.",
  "rtt_regime": "R1",

  "hooks": {
    "state_initialization": {
      "description": "Initialize thermodynamic state variables without mechanical interpretation.",
      "variables": ["T", "S", "F", "U", "V", "P"],
      "constraints": ["S >= 0", "T >= 0", "F = U - T*S"]
    },

    "constraint_surface": {
      "description": "Defines allowable configurations via entropy and free energy surfaces.",
      "inputs": ["S", "F", "T"],
      "outputs": ["allowed_region"],
      "rules": [
        "dS >= 0",
        "F minimized at equilibrium",
        "flows follow gradients of potentials"
      ]
    },

    "gradient_flow": {
      "description": "Generates flows from gradients of temperature or free energy.",
      "inputs": ["T(x)", "F(x)"],
      "outputs": ["Q_dot", "flow_field"],
      "equations": [
        "Q_dot = -k * grad(T)",
        "flow = -grad(F)"
      ]
    },

    "equilibrium_detection": {
      "description": "Detects fixed-point structures where gradients vanish.",
      "inputs": ["F(x)", "S(x)"],
      "outputs": ["equilibrium_state"],
      "conditions": [
        "grad(F) = 0",
        "dS/dt = 0"
      ]
    },

    "entropy_production": {
      "description": "Computes irreversibility and monotonic structure.",
      "inputs": ["S(t)"],
      "outputs": ["I"],
      "equations": [
        "I = dS/dt",
        "I >= 0"
      ]
    },

    "ensemble_selection": {
      "description": "Selects macrostate constraints for simulation.",
      "ensembles": {
        "microcanonical": ["U fixed", "V fixed", "N fixed"],
        "canonical": ["T fixed", "V fixed", "N fixed"],
        "grand_canonical": ["T fixed", "V fixed", "mu fixed"]
      }
    },

    "partition_function_extension": {
      "description": "Optional R2 statistical mechanics extension.",
      "inputs": ["energy_levels", "T"],
      "outputs": ["Z"],
      "equations": [
        "Z = sum(exp(-E_i / T))"
      ]
    },

    "open_system_evolution": {
      "description": "Handles environment coupling and decoherence-like entropy flow.",
      "inputs": ["system_state", "environment_state"],
      "outputs": ["updated_state"],
      "rules": [
        "S_total >= S_system + S_environment",
        "flows exchange via gradients"
      ]
    }
  }
}