doc: update build and dependencies docs for IPC

diff --git a/doc/build-freebsd.md b/doc/build-freebsd.md
index 4b5a1d0f..fee20f84 100644
--- a/doc/build-freebsd.md
+++ b/doc/build-freebsd.md
@@ -21,6 +21,14 @@ pkg install sqlite3
 
 To build Bitcoin Core without the wallet, use `-DENABLE_WALLET=OFF`.
 
+Cap'n Proto is needed for IPC functionality (see [multiprocess.md](multiprocess.md)):
+
+```bash
+pkg install capnproto
+```
+
+Compile with `-DENABLE_IPC=OFF` if you do not need IPC functionality.
+
 See [dependencies.md](dependencies.md) for a complete overview.
 
 ### 2. Clone Bitcoin Repo
diff --git a/doc/build-netbsd.md b/doc/build-netbsd.md
index b485bb5a..f2631777 100644
--- a/doc/build-netbsd.md
+++ b/doc/build-netbsd.md
@@ -39,6 +39,14 @@ pkgin sqlite3
 
 To build Bitcoin Core without the wallet, use `-DENABLE_WALLET=OFF`.
 
+Cap'n Proto is needed for IPC functionality (see [multiprocess.md](multiprocess.md)):
+
+```bash
+pkgin capnproto
+```
+
+Compile with `-DENABLE_IPC=OFF` if you do not need IPC functionality.
+
 See [dependencies.md](dependencies.md) for a complete overview.
 
 ### 2. Clone Bitcoin Repo
diff --git a/doc/build-openbsd.md b/doc/build-openbsd.md
index d68a118b..99d4ec25 100644
--- a/doc/build-openbsd.md
+++ b/doc/build-openbsd.md
@@ -21,6 +21,11 @@ pkg_add sqlite3
 
 To build Bitcoin Core without the wallet, use `-DENABLE_WALLET=OFF`.
 
+Cap'n Proto is needed for IPC functionality (see [multiprocess.md](multiprocess.md))
+and can be built from source: https://capnproto.org/install.html
+
+Compile with `-DENABLE_IPC=OFF` if you do not need IPC functionality.
+
 See [dependencies.md](dependencies.md) for a complete overview.
 
 ### 2. Clone Bitcoin Repo
diff --git a/doc/build-osx.md b/doc/build-osx.md
index 523946d9..e1bf0374 100644
--- a/doc/build-osx.md
+++ b/doc/build-osx.md
@@ -48,7 +48,7 @@ See [dependencies.md](dependencies.md) for a complete overview.
 To install, run the following from your terminal:
 
 ``` bash
-brew install cmake boost pkgconf libevent
+brew install cmake boost pkgconf libevent capnp
 ```
 
 #### Wallet Dependencies
@@ -59,6 +59,11 @@ the `cmake -B` step below.
 SQLite is required, but since macOS ships with a useable `sqlite` package, you don't need to
 install anything.
 
+#### IPC Dependencies
+
+If you do not need IPC functionality (see [multiprocess.md](multiprocess.md))
+you can omit `capnp` and use `-DENABLE_IPC=OFF` in the `cmake -B` step below.
+
 ### 4. Clone Bitcoin repository
 
 `git` should already be installed by default on your system.
@@ -112,19 +117,6 @@ For more information on ZMQ, see: [zmq.md](zmq.md)
 
 ---
 
-### IPC Dependencies
-
-Compiling IPC-enabled binaries with `-DENABLE_IPC=ON` requires the following dependency.
-Skip if you do not need IPC functionality.
-
-```bash
-brew install capnp
-```
-
-For more information on IPC, see: [multiprocess.md](multiprocess.md).
-
----
-
 #### Test Suite Dependencies
 
 There is an included test suite that is useful for testing code changes when developing.
diff --git a/doc/build-unix.md b/doc/build-unix.md
index ad577636..38b44966 100644
--- a/doc/build-unix.md
+++ b/doc/build-unix.md
@@ -60,6 +60,12 @@ SQLite is required for the wallet:
 
 To build Bitcoin Core without the wallet, see [*Disable-wallet mode*](#disable-wallet-mode)
 
+Cap'n Proto is needed for IPC functionality (see [multiprocess.md](multiprocess.md)):
+
+    sudo apt-get install libcapnp-dev capnproto
+
+Compile with `-DENABLE_IPC=OFF` if you do not need IPC functionality.
+
 ZMQ-enabled binaries are compiled with `-DWITH_ZMQ=ON` and require the following dependency:
 
     sudo apt-get install libzmq3-dev
@@ -68,11 +74,6 @@ User-Space, Statically Defined Tracing (USDT) dependencies:
 
     sudo apt install systemtap-sdt-dev
 
-IPC-enabled binaries are compiled  with `-DENABLE_IPC=ON` and require the following dependencies.
-Skip if you do not need IPC functionality.
-
-    sudo apt-get install libcapnp-dev capnproto
-
 GUI dependencies:
 
 Bitcoin Core includes a GUI built with the cross-platform Qt Framework. To compile the GUI, we need to install
@@ -119,11 +120,12 @@ User-Space, Statically Defined Tracing (USDT) dependencies:
 
     sudo dnf install systemtap-sdt-devel
 
-IPC-enabled binaries are compiled with `-DENABLE_IPC=ON` and require the following dependency.
-Skip if you do not need IPC functionality.
+Cap'n Proto is needed for IPC functionality (see [multiprocess.md](multiprocess.md)):
 
     sudo dnf install capnproto
 
+Compile with `-DENABLE_IPC=OFF` if you do not need IPC functionality.
+
 GUI dependencies:
 
 Bitcoin Core includes a GUI built with the cross-platform Qt Framework. To compile the GUI, we need to install
diff --git a/doc/dependencies.md b/doc/dependencies.md
index bc8cc7fb..c7fcd0cb 100644
--- a/doc/dependencies.md
+++ b/doc/dependencies.md
@@ -35,6 +35,7 @@ Bitcoin Core requires one of the following compilers.
 
 | Dependency | Releases | Minimum required |
 | --- | --- | --- |
+| [Cap'n Proto](../depends/packages/capnp.mk) | [link](https://capnproto.org) | [0.7.1](https://capnproto.org/install.html) |
 | Python (scripts, tests) | [link](https://www.python.org) | [3.10](https://github.com/bitcoin/bitcoin/pull/30527) |
 | [Qt](../depends/packages/qt.mk) (gui) | [link](https://download.qt.io/archive/qt/) | [6.2](https://github.com/bitcoin/bitcoin/pull/30997) |
 | [qrencode](../depends/packages/qrencode.mk) (gui) | [link](https://fukuchi.org/works/qrencode/) | N/A |