diff --git a/README.md b/README.md
index 4607f86..6d4131b 100644
--- a/README.md
+++ b/README.md
@@ -16,7 +16,7 @@ This repository ships that distribution (**`fiwicontrol`** on PyPI / `pip`) with
 
 A **first concrete goal** for this stack is to support **PCIe hot-swap (hot-plug) testing** in the lab: controlled **remove / restore** of the link, predictable **enumeration** and driver behavior, and **repeatable** runs across builds and rigs.
 
-That work fails if the bench is informal—wrong port, wrong power path, or no shared picture of what was connected when. FiWiControl targets that gap by combining **documented inventory** (INI + **`--verify-inventory`**), **remote automation** (**`ssh_node`**, **`python3 -m fiwicontrol.commands`** to bring up rigs), and **programmable power / USB paths** (**`fiwicontrol.power`**) so sequences are **scripted and checkable** before the PCIe harness runs. Longer term, **SPC** (below) is meant for **many hot-plug cycles**—spotting drift in failure rates or side metrics—not only general Fi‑Wi bring-up.
+That work fails if the bench is informal—wrong port, wrong power path, or no shared picture of what was connected when. FiWiControl targets that gap by combining **documented inventory** (INI + **`--verify-inventory`**), **remote automation** (**`ssh_node`**, **`python3 -m fiwicontrol.commands`** to bring up rigs), and **programmable power / USB paths** (**`fiwicontrol.power`**) so sequences are **scripted and checkable** before the PCIe harness runs. **`fiwicontrol.spc`** is aimed at **many hot-plug cycles**—spotting drift in failure rates or side metrics—not only general Fi‑Wi bring-up (see **`docs/spc.md`**).
 
 ## Lab fleet: Raspberry Pi 5 and iperf 2 (planned)
 
@@ -32,11 +32,13 @@ Expanded **ush** orchestration alongside OpenSSH—not only the **`ush`** transp
 
 ## Product differentiation
 
-We expect **advanced telemetry** (including **802.11-centric**, e.g. **ESP32**, data) and **advanced use of iperf 2 on Raspberry Pi 5** hosts—patterns **tied to rig state, inventory, and (eventually) SPC**, not ad hoc throughput screenshots—to help **differentiate** Umber Fi‑Wi products in the market.
+We expect **advanced telemetry** (including **802.11-centric**, e.g. **ESP32**, data) and **advanced use of iperf 2 on Raspberry Pi 5** hosts—patterns **tied to rig state, inventory, and SPC** (**`fiwicontrol.spc`**), not ad hoc throughput screenshots—to help **differentiate** Umber Fi‑Wi products in the market.
 
-## Statistical process control (planned)
+## Statistical process control
 
-The project is intended to grow **statistical process control (SPC)** support—for example **Hotelling**-style multivariate monitoring and **Shewhart** control charts—for lab and field metrics tied to Fi‑Wi rigs (including **high-volume PCIe hot-swap** campaigns where you need to know if the **process** is still in control). That code is **not** in the tree yet; today’s packages focus on automation, inventory, and power/USB control as described above.
+**In tree:** **`fiwicontrol.spc`** — **`ShewhartControlChart`** and **`HotellingT2`** (Phase I fit, *T*², Phase II UCL). Optional **`pip install -e ".[spc]"`**; overview **`docs/spc.md`**.
+
+**Planned:** tighter coupling with inventory / harness automation, campaign-scale reporting, and richer charting beyond these primitives.
 
 **Layout**
 
@@ -49,7 +51,8 @@ FiWiControl/
 │   ├── install.md
 │   ├── node-control-asyncio-design.md
 │   ├── power-control-and-inventory.md
-│   └── flows.md
+│   ├── flows.md
+│   └── spc.md
 ├── src/
 │   └── fiwicontrol/
 │       ├── commands/
@@ -96,6 +99,9 @@ cd ~/Code/FiWiControl
 python3 -m pip install -e ".[dev]"
 # optional: power / USB discovery (Acroname, Monsoon)
 python3 -m pip install -e ".[power]"
+# optional: async iperf flows / SPC (see docs/flows.md, docs/spc.md)
+python3 -m pip install -e ".[flows]"
+python3 -m pip install -e ".[spc]"
 ```
 
 Imports:
diff --git a/docs/install.md b/docs/install.md
index e9547c1..a393b6b 100644
--- a/docs/install.md
+++ b/docs/install.md
@@ -14,7 +14,7 @@ Use this order the first time you (or someone else) joins the project or replace
 | Step | Where | What to do |
 |------|--------|------------|
 | 1 | Workstation | **Clone** this repo and **`cd`** into it. |
-| 2 | Workstation | **Python 3.11+** and an **editable install**: **`python3 -m pip install -e ".[dev]"`**, then **`python3 -m pip install -e ".[power]"`** if you use Acroname/Monsoon or remote power tests (see **Workstation** below). |
+| 2 | Workstation | **Python 3.11+** and an **editable install**: **`python3 -m pip install -e ".[dev]"`**, then **`python3 -m pip install -e ".[power]"`** if you use Acroname/Monsoon or remote power tests. Add **`".[flows]"`** / **`".[spc]"`** when you use **`fiwicontrol.flows`** or **`fiwicontrol.spc`** (see **Workstation** below and **`docs/flows.md`** / **`docs/spc.md`**). |
 | 3 | Workstation → rig | **Passwordless SSH as root:** **`ssh -o BatchMode=yes root@192.168.1.39 true`** must exit **0** with no password prompt. On the rig, install your workstation’s **public key** in **`/root/.ssh/authorized_keys`** and ensure **`sshd`** allows **`root`** with pubkey auth. |
 | 4 | Rig (e.g. Pi) | **`git clone`** the same repo where you will run power/discovery (often **`/root/Code/FiWiControl`**). Your **`--remote-repo`** path must match. |
 | 5 | Workstation | From your clone, run **`python3 -m fiwicontrol.commands`** with the Pi IP and **`--remote-repo`** (PEP 668 / Raspberry Pi OS needs **`--break-system-packages`** or **`FIWI_REMOTE_PIP_FLAGS`**). See **Remote host setup** below (numbered subsections **3** and **4**: install **`fiwicontrol[power]`** on the rig, then align **`python3`** with **`pip`**). |
@@ -48,6 +48,19 @@ Or in one line:
 python3 -m pip install -e ".[dev,power]"
 ```
 
+**Flows** (async **iperf** over SSH, SciPy / Matplotlib stack) and **SPC** (**Shewhart** / **Hotelling** *T*² helpers) are separate optional extras:
+
+```bash
+python3 -m pip install -e ".[flows]"   # NumPy, SciPy, Matplotlib — see docs/flows.md
+python3 -m pip install -e ".[spc]"     # NumPy, SciPy — see docs/spc.md
+```
+
+Or combined with dev and power:
+
+```bash
+python3 -m pip install -e ".[dev,power,flows,spc]"
+```
+
 **Why this is the default:** you avoid remembering **`PYTHONPATH=src`**, IDEs and **`python -m`** behave predictably, and it matches how **`pyproject.toml`** / **`pytest`** are meant to be used.
 
 ### Without a local install (one-off)
diff --git a/docs/spc.md b/docs/spc.md
new file mode 100644
index 0000000..7d9d1ce
--- /dev/null
+++ b/docs/spc.md
@@ -0,0 +1,55 @@
+# FiWiControl SPC — Shewhart and Hotelling *T*²
+
+**Package:** **`fiwicontrol.spc`**  
+**Implementation:** **`src/fiwicontrol/spc/`** (`shewhart.py`, `hotelling.py`; lazy exports from **`fiwicontrol/spc/__init__.py`**)
+
+Small **statistical process control (SPC)** building blocks for lab metrics: a univariate **Shewhart**-style individuals chart (moving-range dispersion) and a multivariate **Hotelling *T*²** object with a Phase II upper control limit.
+
+---
+
+## Install
+
+SPC uses **NumPy** and **SciPy** (not bundled in the base **`fiwicontrol`** install):
+
+```bash
+cd ~/Code/FiWiControl
+python3 -m pip install -e ".[spc]"
+```
+
+**`import fiwicontrol.spc`** does not load **NumPy** / **SciPy** until you access **`ShewhartControlChart`** (NumPy only) or **`HotellingT2`** (both).
+
+---
+
+## Classes
+
+### `ShewhartControlChart`
+
+- **`ShewhartControlChart(k=3.0)`** — chart width in multiples of estimated sigma.
+- **`fit_individuals(x, moving_range_span=2)`** — Phase I fit from a 1-D **`numpy`** array; only **`moving_range_span=2`** is supported (average moving range of consecutive pairs, **`d₂ = 1.128`**).
+- **`limits()`** → **`(LCL, center, UCL)`** with width **`k`** sigma (default **`k=3.0`**).
+- **`is_out_of_control(value)`** — boolean vs those limits.
+
+### `HotellingT2`
+
+- **`fit(X)`** — **`X`** shape **`(m, p)`** with **`m > p + 1`**; unbiased sample covariance, inverse for *T*².
+- **`mean_`**, **`covariance_`** — fitted Phase I mean vector and covariance (after **`fit`**).
+- **`t2(x)`** — Hotelling statistic for one observation **`x`** of length **`p`** vs the fitted mean.
+- **`ucl(alpha=0.05)`** — Phase II UCL using the **`F_{p, m-p}`** distribution (**SciPy**).
+- **`is_out_of_control(x, *, alpha=0.05)`** — **`True`** if **`t2(x) > ucl(alpha=alpha)`** (**`alpha`** is keyword-only).
+
+---
+
+## Tests
+
+With **`[spc]`** installed:
+
+```bash
+python3 -m pytest tests/test_spc.py -q
+```
+
+---
+
+## See also
+
+- **`README.md`** (package list)  
+- **`docs/install.md`** (optional **`[spc]`** alongside **`[flows]`**, **`[power]`**, …)
diff --git a/src/fiwicontrol/spc/__init__.py b/src/fiwicontrol/spc/__init__.py
index 8c19eae..c0adcce 100644
--- a/src/fiwicontrol/spc/__init__.py
+++ b/src/fiwicontrol/spc/__init__.py
@@ -8,8 +8,9 @@ Install optional dependencies before importing the classes::
 
     pip install -e ".[spc]"
 
-Symbols load lazily so ``import fiwicontrol.spc`` does not import **NumPy** until
-you access a class.
+Symbols load lazily so ``import fiwicontrol.spc`` does not import **NumPy** or
+**SciPy** until you access a class (``ShewhartControlChart`` uses NumPy;
+``HotellingT2`` uses both).
 """
 
 from __future__ import annotations