docs(plc): add soft-PLC architecture + CODESYS/Yocto lifecycle diagram

A CODESYS controller is not a monolithic appliance — it's a SoC + Linux +
software runtime + control app, built along two independent tracks (the Yocto
device platform by the OEM, the IEC 61131-3 control application by the machine
builder). Add an "Anatomy" section to the PLC guide: the classic-vs-soft-PLC
table, a Mermaid diagram of the two development tracks converging on the running
device with the artifact→scan mapping, and a callout on where Yocto fits (the
firmware layer, its own artifact). Explains why PlcSps is a composite target.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

docs/.vitepress/config.mts

@@ -44,7 +44,6 @@ export default withMermaid(defineConfig({
         items: [
           { text: 'Glossary', link: '/reference/glossary' },
           { text: 'Tools & Scanners', link: '/reference/tools' },
-          { text: 'PLC Runtime Landscape', link: '/reference/plc-runtimes' },
         ],
       },
     ],

docs/guide/plc.md

@@ -11,6 +11,72 @@ the control application *and* the device it runs on.
 | A device firmware image | Firmware SBOM / CVE (opt-in) |
 | A reachable endpoint (WebVisu, OPC UA) | DAST / pentest (opt-in) |
 
+## Anatomy: a soft PLC is a SoC + Linux + runtime
+
+A CODESYS controller is **not** a monolithic appliance like a classic Siemens
+S7. It is **PC-based ("soft") control** — commodity silicon running a
+general-purpose Linux, with a **software PLC runtime** as just another process:
+
+| Classic PLC (e.g. Siemens S7) | Soft PLC (CODESYS-on-Yocto, OpenPLC-on-Raspbian) |
+| --- | --- |
+| Proprietary hardware + firmware | Commodity SoC (x86 / ARM) |
+| Proprietary OS | General-purpose Linux (a **Yocto** image, or Raspbian) |
+| Proprietary runtime | Software runtime (**CODESYS Control**, or OpenPLC) |
+| STEP7 / TIA project | IEC 61131-3 control app (ST / LD / FBD / SFC) |
+
+Because of this, the device is built along **two independent tracks**, by
+different people, on different timelines, and shipped separately. It also
+inherits the **entire Linux / IT attack surface on top of** the OT / control
+one — which is exactly why a PLC/SPS target is treated as a **composite**:
+Certifai ingests one artifact per layer and scans each with the right pipeline.
+
+```mermaid
+flowchart TB
+    subgraph TA["Track A · Device platform — built by the hardware OEM / vendor"]
+        direction LR
+        A1["Yocto / OpenEmbedded<br/>BSP + RT kernel"] --> A2["Bake in the CODESYS<br/>Control for Linux runtime"] --> A3["bitbake → device image<br/>.wic / .tar + manifest"]
+    end
+    subgraph TB2["Track B · Control application — built by the machine builder / customer"]
+        direction LR
+        B1["CODESYS IDE<br/>ST / LD / FBD / SFC + WebVisu"] --> B2["Reference CODESYS +<br/>vendor libraries"] --> B3["Compile → download<br/>to device (gateway 11740)"]
+    end
+
+    A3 --> DEV(["Running soft-PLC device<br/>SoC + Linux + runtime + control app<br/>Modbus · OPC UA · EtherNet/IP · WebVisu"])
+    B3 --> DEV
+
+    subgraph CERT["What Certifai scans — one layer per artifact"]
+        direction LR
+        S1["Firmware layer<br/>FirmwareStatic · SBOM · CVE"]
+        S2["Control-logic layer<br/>PLC SAST — ST + FBD/LD"]
+        S3["Control-app SBOM<br/>libraries + runtime → CVE"]
+        S4["Running layer<br/>ICS probe · DAST (WebVisu)"]
+    end
+
+    A3 -. firmware image .-> S1
+    B1 -. PLCopen XML / ST via git .-> S2
+    B2 -. projectarchive (zip) .-> S3
+    DEV -. live URL / provisioned .-> S4
+
+    classDef yocto fill:#fde68a,stroke:#b45309,color:#111
+    classDef codesys fill:#bfdbfe,stroke:#1d4ed8,color:#111
+    classDef dev fill:#e9d5ff,stroke:#7e22ce,color:#111
+    classDef cert fill:#bbf7d0,stroke:#15803d,color:#111
+    class A1,A2,A3 yocto
+    class B1,B2,B3 codesys
+    class DEV dev
+    class S1,S2,S3,S4 cert
+```
+
+::: tip Where Yocto fits
+Yocto is **Track A** — the *build system* for the device platform. It produces
+the Linux image and bakes in the CODESYS runtime, so it is the **firmware
+layer**, entirely separate from the control application. Hand it to Certifai as
+its own **firmware image** artifact (scanned by the firmware pipeline, not the
+PLC pipeline). The device OS need not be Yocto — Raspbian/Debian/Buildroot, or
+even an RTOS / bare-metal, are all possible — but Yocto is the common,
+product-grade industrial choice.
+:::
+
 ## Two ways to deliver the project
 
 You can either **upload** the project when onboarding, or point Certifai at a

docs/reference/plc-runtimes.md

@@ -1,97 +0,0 @@
-# PLC Runtime Landscape & Support
-
-A soft PLC is a **SoC + Linux + a software runtime + an IEC 61131-3 control app**
-(see [PLC / SPS Projects](/guide/plc)).
-The **runtime** is what defines the device — it provides the IEC engine, the
-Modbus / OPC UA / EtherNet/IP servers, and the WebVisu. This page tracks the
-runtime ecosystems Certifai may encounter.
-
-We do **not** aim to support every runtime up front. Certifai supports the
-**CODESYS family** today; everything else is a **watch-list** — when a customer
-shows up using one, we add the parser/support for it then. The dynamic OT probe
-(Modbus / OPC UA / EtherNet/IP) is **vendor-agnostic** and works regardless of
-the runtime.
-
-## Support status
-
-| Status | Meaning |
-| --- | --- |
-| ✅ **Supported** | Static analysis works today (control-logic SAST + library/runtime SBOM + CVE). |
-| 🟡 **Covered via CODESYS** | A rebranded CODESYS runtime — our CODESYS parsing applies (may need minor per-vendor tweaks). |
-| 🔭 **Watch-list** | Own project format — we add a format parser when a customer needs it. The dynamic OT probe already applies. |
-| 🧪 **Test-bench** | A free runtime we use to *reconstruct and dynamically test* a device (see epic: provision-and-test). |
-
-## 1. CODESYS and rebranded CODESYS (the largest slice)
-
-Much of the market licenses the CODESYS runtime and rebrands the IDE. If a
-customer "doesn't use CODESYS", they often do — under another name.
-
-| Product / vendor | Based on | Status |
-| --- | --- | --- |
-| **CODESYS** (3S-Smart Software Solutions) | CODESYS | ✅ Supported |
-| Schneider **EcoStruxure Machine Expert** (ex-SoMachine) | CODESYS | 🟡 Covered via CODESYS |
-| **WAGO** e!COCKPIT / PFC controllers | CODESYS | 🟡 Covered via CODESYS |
-| **ABB** AC500 / Automation Builder | CODESYS | 🟡 Covered via CODESYS |
-| **Bosch Rexroth** ctrlX / IndraLogic | CODESYS | 🟡 Covered via CODESYS |
-| **Eaton** XSoft-CODESYS, **KEBA** KeStudio, Berghof, Kontron, Festo (CPX-E), IFM, Turck, … | CODESYS | 🟡 Covered via CODESYS |
-
-## 2. Other embeddable IEC 61131-3 runtime toolkits
-
-Same model as CODESYS (an OEM licenses a runtime + IDE and bakes it into a
-device), but with **different project formats and libraries**.
-
-| Toolkit | Vendor | Status |
-| --- | --- | --- |
-| **ProConOS / MULTIPROG** | Phoenix Contact / KW-Software | 🔭 Watch-list |
-| **ISaGRAF** (also does IEC 61499) | Rockwell | 🔭 Watch-list |
-| **straton** | COPA-DATA | 🔭 Watch-list |
-| **logi.CAD** | logi.cals | 🔭 Watch-list |
-
-## 3. Fully proprietary ecosystems (own runtime + IDE + protocols)
-
-Static analysis here needs a **per-vendor project parser**; the **dynamic OT
-probe still works** (they speak Modbus / OPC UA / EtherNet/IP, plus vendor
-protocols like S7comm / CIP).
-
-| Ecosystem | Vendor | Notes | Status |
-| --- | --- | --- | --- |
-| **TIA Portal / STEP 7** (S7-1200/1500), S7-1500 **Software Controller**, **Virtual PLC** | Siemens | Largest install base; the soft/virtual variants are Linux/container | 🔭 Watch-list |
-| **Studio 5000** (ControlLogix / CompactLogix) | Rockwell / Allen-Bradley | Strong in North America | 🔭 Watch-list |
-| **TwinCAT 3** | Beckhoff | Genuine PC-based control on Windows / TwinCAT-BSD; IEC 61131-3 **+ C++ + Simulink** | 🔭 Watch-list |
-| **Automation Studio** | B&R (ABB) | Own Automation Runtime | 🔭 Watch-list |
-| **GX Works** (MELSEC) | Mitsubishi | | 🔭 Watch-list |
-| **Sysmac Studio** (NX / NJ) | Omron | | 🔭 Watch-list |
-| **Proficy Machine Edition** (PACSystems) | Emerson / GE | | 🔭 Watch-list |
-
-## 4. Linux-native / containerized soft-PLC (the direction of travel)
-
-| Product | Vendor | Notes | Status |
-| --- | --- | --- | --- |
-| **PLCnext** | Phoenix Contact | Open, Linux-based; native runtime is eCLR (not CODESYS), but can also run CODESYS as an app | 🔭 Watch-list |
-| **ctrlX** | Bosch Rexroth | Ubuntu-core, app-store model (CODESYS runtime inside) | 🟡 Covered via CODESYS |
-| **Virtual PLC** / **CODESYS Virtual Control** | Siemens / CODESYS | Containerized PLCs (Docker / K8s) | 🟡 / 🔭 |
-
-## 5. Open-source runtimes (free — our test-bench substrates)
-
-Used to **reconstruct and dynamically test** a customer device without touching
-their network (provision-and-test).
-
-| Runtime | Standard | Notes | Status |
-| --- | --- | --- | --- |
-| **OpenPLC** | IEC 61131-3 | Modbus-centric, education/small automation; uses MatIEC | 🧪 Test-bench (current) |
-| **Beremiz + MatIEC** | IEC 61131-3 | Fuller open-source IDE; compiles ST/IL → C. Natural fidelity step-up from OpenPLC | 🧪 Test-bench (candidate) |
-| **Eclipse 4diac (FORTE)** | IEC **61499** | Distributed, event-driven — a *different paradigm* from 61131-3's scan cycle | 🔭 Watch-list |
-| **ProView** | — | Open-source process control + SCADA | 🔭 Watch-list |
-
-## How we add support for a new runtime
-
-- **Static (SAST / SBOM):** needs a parser for that runtime's **project format**
-  (and its library/package convention). This is the per-vendor work.
-- **Dynamic (ICS probe / DAST):** already **vendor-agnostic** — it targets the
-  device's OT ports and WebVisu, not the runtime's file format. So a brand-new
-  ecosystem still gets dynamic coverage on day one.
-
-::: tip Rule of thumb
-Confirm whether a "non-CODESYS" controller is actually a **rebranded CODESYS**
-runtime (Section 1) before assuming new work — most of the long tail is.
-:::