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PROMPT — OCPP 2.1 MCS Simulation Platform

You are a senior systems architect and protocol engineer building a production-grade OCPP 2.1 simulation platform for heavy-duty Megawatt Charging System (MCS) scenarios.

Your task is to design and scaffold a project whose purpose is to stress-test a CPMS/CSMS using OCPP 2.1 only, at scale, with deterministic, replayable simulations.

This is not a demo, not a UI-first product, and not a physics engine. This is a protocol-correct simulation and experimentation system.

1. Core goals (non-negotiable)

  1. CLI-first, deterministic simulation engine
  2. OCPP 2.1–correct EVSE state machines
  3. Accurate ChargingProfile enforcement
  4. High-volume MeterValues + TransactionEvent stress
  5. Site-level constraints projected into EVSE-level OCPP signals
  6. Full replayability and diffability of runs
  7. Web UI is read-only orchestration + observability only

If any design choice conflicts with these goals, reject it.

2. Explicit scope

In scope

  • OCPP 2.1 JSON over WebSocket
  • Virtual EVSEs (DC, MCS-class)
  • ChargingProfile handling (TxProfile, StationMaxProfile)
  • TransactionEvent lifecycle
  • StatusNotification correctness
  • MeterValues at high frequency
  • Fault injection and constraint signaling
  • Scenario-driven simulation
  • Deterministic execution with seeds
  • CLI + optional web UI

Out of scope (Forbidden Domain Scope)

The following areas are permanently out of scope:

  • CPMS runtime logic: Pricing engines, billing, invoicing, user ledgers, roaming settlement.
  • OCPI / Roaming: No OCPI, OCHP, or OICP logic.
  • Smart Gateway: No retry smoothing, connection holding, message buffering, or "smart" pipes.
  • Physics: No battery chemistry, real power electronics, or grid physics.
  • UI-defined behavior: The UI is read-only. It never inputs data into the simulation. All inputs come from scenarios.
  • ISO-15118 PLC: No low-level PLC timing or signal modulation.
  • Non-deterministic simulations: "Works on my machine" is not acceptable.

Explicitly forbidden agents: pricing-agent, billing-agent, invoicing-agent, ledger-agent, user-agent, ocpi-agent, roaming-agent, settlement-agent, smart-gateway-agent, physics-agent, plc-agent.

3. System architecture (you must follow this)

A. Simulation engine (authoritative)

  • Headless
  • Deterministic
  • Discrete-time (e.g. 1s ticks)
  • No UI dependencies

B. CLI (control plane)

  • Defines, runs, replays, and sweeps scenarios
  • Suitable for CI and batch execution

C. Experiment registry

  • Immutable runs
  • Versioned scenarios
  • Metadata + artifacts

D. Web UI (lens only)

  • Launch predefined scenarios
  • Visualize timelines and diffs
  • Must not change simulation semantics

4. Required components (design + scaffold)

4.1 Virtual EVSE (OCPP 2.1)

Implement a strict finite state machine with:

  • States: Available, Preparing, Charging, SuspendedEV, SuspendedEVSE, Faulted

  • Transitions driven only by:

    • OCPP messages
    • Scenario events
    • ChargingProfile enforcement

Must support:

  • BootNotification
  • Heartbeat
  • StatusNotification
  • TransactionEvent (Started / Updated / Ended)
  • MeterValues
  • SetChargingProfile / ClearChargingProfile

Every reported power value must be explainable by:

  • Active ChargingProfiles
  • Faults
  • Suspension state

4.2 ChargingProfile executor (critical module)

Implement as a standalone module:

  • Resolves overlapping profiles
  • Enforces limits deterministically
  • Emits enforcement events
  • Handles zero-power cases correctly

This module must be testable in isolation.

4.3 Site model (no protocol object exists)

You must:

  • Model site constraints internally

  • Project them down as EVSE-level OCPP effects:

    • Profile updates
    • SuspendedEVSE
    • Faulted

Never invent non-OCPP messages.

4.4 Scenario system

Scenarios must be:

  • Declarative (YAML or JSON)
  • Versionable
  • Immutable once executed

Scenarios describe:

  • Site topology
  • EVSE capabilities
  • Arrival patterns
  • Power requests
  • Grid events
  • Fault injections

4.5 CLI interface (mandatory commands)

Design and implement:

  • sim run <scenario>
  • sim replay <run-id>
  • sim sweep <param>=<range>
  • sim validate <scenario>
  • sim export <run-id>

CLI output must be machine-readable.

4.6 Observability & artifacts

Each run must produce:

  • Full OCPP message trace
  • EVSE state timelines
  • Power vs time series
  • Profile application history
  • Assertions and violations

Artifacts must be reproducible from inputs + seed.

5. Web UI (optional but defined)

If you design a UI, it must:

  • Be a thin client

  • Read from run artifacts

  • Support:

    • Timeline views
    • EVSE state transitions
    • ChargingProfile diffs
    • Run-to-run comparison

UI must not:

  • Define scenarios
  • Modify active simulations
  • Hide protocol detail

6. Quality bars (do not skip)

You must include:

  • Clear module boundaries
  • State transition tables
  • Invariants (assertions)
  • Failure modes
  • Determinism guarantees
  • Documentation explaining why choices were made

Avoid:

  • Over-engineering
  • Framework lock-in
  • UI-driven logic

7. Deliverables you must produce

  1. Project overview and rationale
  2. Architecture diagram (textual)
  3. Module breakdown
  4. Scenario schema
  5. CLI command spec
  6. Example MCS heavy-duty scenarios
  7. Extension points
  8. Explicit “what we are not doing” section

Do not generate placeholder fluff. Everything should be implementable.

8. Evaluation rule

At every step, ask:

“Would this catch a real CPMS bug under megawatt load?”

If the answer is “maybe not,” redesign.

Final instruction

Proceed top-down, architecture first, then drill into modules. Be strict. Be boring. Be correct.

“Simplicity is prerequisite for reliability.” — Edsger Dijkstra