diff --git a/README.md b/README.md
deleted file mode 100644
index 57cbee0..0000000
--- a/README.md
+++ /dev/null
@@ -1,3 +0,0 @@
-# kaptan
-
-TODO
diff --git a/boards/geprc-f722-v2/README.md b/boards/geprc-f722-v2/README.md
deleted file mode 100644
index b333000..0000000
--- a/boards/geprc-f722-v2/README.md
+++ /dev/null
@@ -1,7 +0,0 @@
-# GEPRC GEP-F722-HD V2
-
-Build from the workspace root:
-
-```sh
-cargo build --release -p kaptan-geprc-f722-v2 --target thumbv7em-none-eabihf
-```
diff --git a/boards/kakute-f7-mini-v3/README.md b/boards/kakute-f7-mini-v3/README.md
deleted file mode 100644
index 938ed0b..0000000
--- a/boards/kakute-f7-mini-v3/README.md
+++ /dev/null
@@ -1,40 +0,0 @@
-# Kakute F7 Mini V3
-
-Kaptan support for the Holybro Kakute F7 Mini V3.
-
-The checked-in manufacturer manual is [Holybro_KakuteF7_Mini_V3_Manual_v1.0.pdf](Holybro_KakuteF7_Mini_V3_Manual_v1.0.pdf).
-
-## Build
-
-Build the firmware from the workspace root:
-
-```sh
-cargo build --release -p kaptan-kakute-f7-mini-v3 --target thumbv7em-none-eabihf
-```
-
-Create its DFU (device firmware update) image:
-
-```sh
-./scripts/create-dfu-image.sh target/thumbv7em-none-eabihf/release/kaptan-kakute-f7-mini-v3
-```
-
-The converter derives the `.bin` path and matching board `memory.x`, then prints the firmware size report. It uses rustup's `llvm-tools-preview` component which the workspace toolchain installs automatically.
-
-## Flash over USB DFU
-
-1. Disconnect the board from USB.
-2. Hold the `Boot` button.
-3. Connect USB, then release `Boot`. The board should enumerate as STM32 DFU.
-4. Flash the generated image:
-
-```sh
-dfu-util --alt 0 --dfuse-address 0x08000000:leave --download target/thumbv7em-none-eabihf/release/kaptan-kakute-f7-mini-v3.bin
-```
-
-## UART
-
-| USB-to-UART adapter | FC |
-| --- | --- |
-| `RX` | `T1` |
-| `GND` | `G` |
-| `TX` | `R1` |
diff --git a/docs/Makefile b/docs/Makefile
new file mode 100644
index 0000000..0877f22
--- /dev/null
+++ b/docs/Makefile
@@ -0,0 +1,12 @@
+MDBOOK ?= mdbook
+
+.PHONY: build serve test
+
+build:
+	$(MDBOOK) build
+
+serve:
+	$(MDBOOK) serve --open
+
+test:
+	$(MDBOOK) test
diff --git a/docs/book.toml b/docs/book.toml
new file mode 100644
index 0000000..536fb04
--- /dev/null
+++ b/docs/book.toml
@@ -0,0 +1,21 @@
+[book]
+title = "Kaptan Developer Manual"
+description = "Architecture, board bring-up, simulation, and contributor guidance for Kaptan."
+authors = ["Kaptan contributors"]
+language = "en"
+src = "src"
+
+[build]
+# Keep generated site files out of the Markdown source tree.
+build-dir = "../target/docs"
+create-missing = false
+
+[output.html]
+default-theme = "light"
+preferred-dark-theme = "navy"
+git-repository-url = "https://github.com/Orkavian/kaptan"
+edit-url-template = "https://github.com/Orkavian/kaptan/edit/main/{path}"
+additional-css = ["theme/kaptan.css"]
+additional-js = ["theme/kaptan.js"]
+fold = { enable = true, level = 1 }
+smart-punctuation = true
diff --git a/docs/src/SUMMARY.md b/docs/src/SUMMARY.md
new file mode 100644
index 0000000..356a602
--- /dev/null
+++ b/docs/src/SUMMARY.md
@@ -0,0 +1,13 @@
+# Summary
+
+- [Kaptan Developer Manual](index.md)
+- [Getting started](getting-started.md)
+- [Architecture](architecture.md)
+  - [Safety boundary](safety-boundary.md)
+  - [MAVLink and telemetry](mavlink.md)
+- [Boards](boards/index.md)
+  - [Kakute F7 Mini V3](boards/kakute-f7-mini-v3.md)
+  - [GEPRC GEP-F722-HD V2](boards/geprc-f722-v2.md)
+- [Host SITL](sitl.md)
+- [Development and verification](development.md)
+- [Reference](reference.md)
diff --git a/docs/src/architecture.md b/docs/src/architecture.md
new file mode 100644
index 0000000..6834f30
--- /dev/null
+++ b/docs/src/architecture.md
@@ -0,0 +1,35 @@
+# Architecture
+
+Kaptan separates immutable board configuration from platform-owned runtime
+resources and portable flight logic.
+
+```text
+board declaration
+        │
+        ▼
+F722 platform / RTIC application ──► data channel ──► MAVLink telemetry
+        │
+        ├── physical sensor drivers
+        └── motor-pin inhibit interlock
+
+portable libraries
+  math ─► navigation ─► control ─► safety
+```
+
+The board contract selects one immutable `BoardProfile`. The checked-in
+profile is `TelemetryOnly`; `ExternalControlOnly` is represented explicitly
+but rejected at validation time because it has no reviewed runtime.
+
+The data channel owns rate selection, mailbox consumption, message encoding,
+and bounded TX classification. Board code supplies physical routes and
+telemetry configuration; it does not receive generic output authority.
+
+## Ownership rules
+
+- A peripheral owner is local to the platform runtime.
+- Portable crates use typed units and validated values rather than raw wire or
+  timer representations.
+- A safety permit is epoch-bound and must be revalidated at the only nonzero
+  output boundary.
+- A failed observation or numerical check does not partially commit estimator,
+  controller, allocator, or safety state.
diff --git a/docs/src/boards/geprc-f722-v2.md b/docs/src/boards/geprc-f722-v2.md
new file mode 100644
index 0000000..8bd5d0e
--- /dev/null
+++ b/docs/src/boards/geprc-f722-v2.md
@@ -0,0 +1,14 @@
+# GEPRC GEP-F722-HD V2
+
+The GEPRC GEP-F722-HD V2 board declaration uses the ICM-42688-P on SPI3 and
+MAVLink telemetry on USART2. It declares no vertical sensor stream.
+
+Build and package from the workspace root:
+
+```sh
+cargo build --release -p kaptan-geprc-f722-v2 --target thumbv7em-none-eabihf
+./scripts/create-dfu-image.sh target/thumbv7em-none-eabihf/release/kaptan-geprc-f722-v2
+```
+
+The resulting image is telemetry-only and has the shared physical motor-pin
+inhibit boundary.
diff --git a/docs/src/boards/index.md b/docs/src/boards/index.md
new file mode 100644
index 0000000..e73c4b3
--- /dev/null
+++ b/docs/src/boards/index.md
@@ -0,0 +1,12 @@
+# Boards
+
+Board pages describe supported hardware topology, build products, and safe
+verification. They do not declare a board flight-ready.
+
+| Board | MCU family | Primary IMU | MAVLink UART |
+| --- | --- | --- | --- |
+| [Kakute F7 Mini V3](kakute-f7-mini-v3.md) | STM32F722 | MPU-6000 | USART1 |
+| [GEPRC GEP-F722-HD V2](geprc-f722-v2.md) | STM32F722 | ICM-42688-P | USART2 |
+
+All board images share the motor-pin inhibit boundary described in
+[Safety boundary](../safety-boundary.md).
diff --git a/docs/src/boards/kakute-f7-mini-v3.md b/docs/src/boards/kakute-f7-mini-v3.md
new file mode 100644
index 0000000..1e56618
--- /dev/null
+++ b/docs/src/boards/kakute-f7-mini-v3.md
@@ -0,0 +1,41 @@
+# Kakute F7 Mini V3
+
+The Holybro Kakute F7 Mini V3 board declaration uses the MPU-6000 on SPI1,
+MAVLink telemetry on USART1, and the MTF01 range/optical-flow route on UART4.
+The checked-in manufacturer datasheet is
+`boards/kakute-f7-mini-v3/datasheet.pdf`.
+
+## Build and package
+
+From the workspace root:
+
+```sh
+cargo build --release -p kaptan-kakute-f7-mini-v3 --target thumbv7em-none-eabihf
+./scripts/create-dfu-image.sh target/thumbv7em-none-eabihf/release/kaptan-kakute-f7-mini-v3
+```
+
+The packaging script derives the matching binary and linker layout, then
+prints the flash and RAM report.
+
+## Flash over USB DFU
+
+1. Disconnect USB.
+2. Hold the board's `Boot` button.
+3. Connect USB, then release `Boot` once the STM32 DFU device enumerates.
+4. Flash the generated image:
+
+```sh
+dfu-util --alt 0 --dfuse-address 0x08000000:leave --download target/thumbv7em-none-eabihf/release/kaptan-kakute-f7-mini-v3.bin
+```
+
+## Telemetry wiring
+
+Use a 3.3 V USB-to-UART adapter with crossed data lines and common ground:
+
+| Adapter | Flight controller |
+| --- | --- |
+| `RX` | `T1` |
+| `TX` | `R1` |
+| `GND` | `G` |
+
+This wiring is telemetry only. It does not enable motor control.
diff --git a/docs/src/development.md b/docs/src/development.md
new file mode 100644
index 0000000..ec30d3b
--- /dev/null
+++ b/docs/src/development.md
@@ -0,0 +1,42 @@
+# Development and verification
+
+## Fast host checks
+
+```sh
+cargo test --workspace --offline
+cargo clippy --workspace --all-targets --offline --exclude kaptan-geprc-f722-v2 --exclude kaptan-kakute-f7-mini-v3 -- -D warnings
+cargo clippy -p platform-stm32f7 --all-targets --offline -- -D warnings
+cargo fmt --check
+git diff --check
+```
+
+## Target checks
+
+```sh
+cargo check -p kaptan-geprc-f722-v2 --release --target thumbv7em-none-eabihf --offline
+cargo check -p kaptan-kakute-f7-mini-v3 --release --target thumbv7em-none-eabihf --offline
+```
+
+## Strict core coverage
+
+```sh
+scripts/report-test-coverage.sh
+```
+
+The strict gate requires 100% line and branch coverage for `kaptan-math`,
+`kaptan-navigation`, `kaptan-control`, and `kaptan-safety`. It isolates each
+core package's coverage artifacts, unions LCOV source-line records, and uses
+full LLVM source spans to merge generic branch instantiations without lowering
+the gate.
+
+## Simulation acceptance
+
+```sh
+python3 tools/sitl/world-structure-test.py
+python3 -m unittest tools/sitl/test_kaptan_sim.py
+tools/sitl/e2e-smoke.sh
+```
+
+The Docker smoke is intentionally separate from host unit tests because it
+builds the pinned base images, Rust binary, Gazebo plugin, and full loopback
+plant.
diff --git a/docs/src/getting-started.md b/docs/src/getting-started.md
new file mode 100644
index 0000000..7cf4576
--- /dev/null
+++ b/docs/src/getting-started.md
@@ -0,0 +1,42 @@
+# Getting started
+
+## Prerequisites
+
+Use the repository toolchain, Rust 1.90. The workspace declares the embedded
+F7 targets and `llvm-tools-preview` in `rust-toolchain.toml`.
+
+For host development, run:
+
+```sh
+cargo test --workspace --offline
+cargo clippy --workspace --all-targets --offline --exclude kaptan-geprc-f722-v2 --exclude kaptan-kakute-f7-mini-v3 -- -D warnings
+```
+
+Bare-metal board packages are not host-test targets. Check them with the
+target-specific commands in [Development and verification](development.md).
+
+## Repository layout
+
+| Path | Responsibility |
+| --- | --- |
+| `boards/` | Immutable board declarations and linker layouts. |
+| `platforms/stm32f7/` | Reviewed F722 RTIC platform and peripheral ownership. |
+| `libs/` | Typed math, estimation, control, safety, protocol, and driver crates. |
+| `tools/sitl/` | Host-only closed-loop Gazebo simulation. |
+| `docs/` | This Markdown documentation site. |
+
+Do not add board-local READMEs. Add a page here instead, then link it from
+`SUMMARY.md`.
+
+## Build the documentation website
+
+The manual is an [mdBook](https://rust-lang.github.io/mdBook/) project. Build
+it locally with a compatible `mdbook` binary:
+
+```sh
+make -C docs build
+```
+
+The generated static site is written to `target/docs/`. The GitHub Pages
+workflow builds that same output from `main`; enable **GitHub Actions** as the
+repository's Pages publishing source once, then deployments are automatic.
diff --git a/docs/src/index.md b/docs/src/index.md
new file mode 100644
index 0000000..3875500
--- /dev/null
+++ b/docs/src/index.md
@@ -0,0 +1,27 @@
+# Kaptan Developer Manual
+
+Kaptan is an embedded Rust flight-controller project. This manual is the
+single source of project documentation: board support, safety boundaries,
+simulation, development workflow, and design references live here as
+Markdown.
+
+The checked-in firmware is telemetry-only. It does not expose physical motor
+authority, and no document in this site should be read as a physical-flight
+release claim.
+
+## Start here
+
+- New contributors should read [Getting started](getting-started.md).
+- Board work belongs under [Boards](boards/index.md).
+- The currently supported closed-loop simulation is [Host SITL](sitl.md).
+- Before submitting changes, follow [Development and verification](development.md).
+
+## Documentation conventions
+
+Documentation is centralized in `docs/src/`; source directories do not carry
+README files. Keep pages in Markdown, add each page to `SUMMARY.md`, and place
+commands beside the assumptions and safety boundary they depend on.
+
+`TODO(configuration)` marks a required configuration contract that has not
+been implemented. It is not permission for an operator to substitute runtime
+values or bypass an immutable build-time safety decision.
diff --git a/docs/src/mavlink.md b/docs/src/mavlink.md
new file mode 100644
index 0000000..8487aa8
--- /dev/null
+++ b/docs/src/mavlink.md
@@ -0,0 +1,20 @@
+# MAVLink and telemetry
+
+Kaptan emits telemetry using MAVLink 2 framing. The production receiver does
+not promote inbound MAVLink frames to authority records:
+
+- MAVLink 1 is discarded.
+- CRC-invalid MAVLink 2 frames are discarded.
+- Signed frames are discarded because no signature verifier or persistent
+  replay state exists.
+- Unsigned MAVLink 2 frames are also discarded; a V2 CRC detects corruption,
+  not authentication.
+
+`TODO(signing)`: any future inbound authority requires verified MAVLink 2
+signing, configured source/target binding, persistent anti-replay state, and a
+provisioning/key-rotation policy as one reviewed feature.
+
+Telemetry transmission uses bounded frame classes. A critical frame may
+replace pending best-effort traffic, but never the DMA-owned active buffer.
+Completion retries preserve ordering and retain a transiently busy frame for a
+later service turn.
diff --git a/docs/src/reference.md b/docs/src/reference.md
new file mode 100644
index 0000000..fe5b1cd
--- /dev/null
+++ b/docs/src/reference.md
@@ -0,0 +1,19 @@
+# Reference
+
+## Build-time configuration
+
+Board configuration is immutable in the compiled image. Runtime parameter
+updates and ground-station tuning are not exposed by the checked-in firmware.
+
+`TODO(configuration)`: a future configuration system must validate and stage
+an entire profile while disarmed, commit it atomically, and prove that outputs
+remain inhibited throughout staging, activation, and power-loss recovery.
+
+## Simulation package reproducibility
+
+The host SITL Docker build uses digest-pinned base images and the locked Rust
+dependency graph. The signed Gazebo APT feed is not snapshot-pinned.
+
+`TODO(reproducibility)`: snapshot/version-pin the Gazebo package set and
+verify the repository signing-key fingerprint before treating the simulator
+image as byte-for-byte reproducible release input.
diff --git a/docs/src/safety-boundary.md b/docs/src/safety-boundary.md
new file mode 100644
index 0000000..86efe97
--- /dev/null
+++ b/docs/src/safety-boundary.md
@@ -0,0 +1,24 @@
+# Safety boundary
+
+Every checked-in F722 image inhibits PB0, PB1, PB4, and PB5 before normal
+board initialization. The interlock configures each pin as a low, push-pull
+GPIO output; it runs before clocks, board routing, UART setup, or RTIC tasks.
+
+There is no checked-in platform actuator route:
+
+- no DShot or PWM peripheral implementation is linked;
+- no TIM3/TIM5 motor task or DMA output path exists;
+- MAVLink input has no production authority path;
+- a future verified arm command is still acknowledged as unsupported.
+
+The protocol reference crate remains in the workspace only as a framing and
+arming-sequence reference. It does not grant hardware access or authority.
+
+Run the structural guard after any platform or board change:
+
+```sh
+cargo test -p platform-stm32f7 --test platform_safety_boundary --offline
+```
+
+This boundary is deliberately stronger than an application-level disarm flag:
+it removes the physical actuator implementation from the platform image.
diff --git a/docs/src/sitl.md b/docs/src/sitl.md
new file mode 100644
index 0000000..e7fe8d9
--- /dev/null
+++ b/docs/src/sitl.md
@@ -0,0 +1,40 @@
+# Host SITL
+
+Host SITL is Kaptan's deterministic closed-loop simulation tier. Gazebo sends
+simulated IMU and declared noisy local position/velocity observations over a
+private loopback protocol. The Rust process runs the ESKF, safety supervisor,
+trajectory, controller, and allocator, then returns four virtual motor
+fractions to Gazebo.
+
+It is a pre-bench software gate, not a physical-flight validation.
+
+## Run the closed loop
+
+```sh
+docker compose -f tools/sitl/compose.yaml up -d --build
+tools/sitl/kaptan-sim ready
+tools/sitl/kaptan-sim move 5 3 1 --wait
+tools/sitl/kaptan-sim land 0 0 --wait
+docker compose -f tools/sitl/compose.yaml down
+```
+
+For the reproducible command-path gate, use:
+
+```sh
+tools/sitl/e2e-smoke.sh
+```
+
+The smoke scenario verifies ascent, translation, descent, landing, flat-plane
+proximity, and zero applied motor fractions after landing. Its reference world
+contains only a visual landing pad; the pad has no collision geometry and
+never contributes a controller or truth observation.
+
+Open <https://app.gazebosim.org/visualization>, connect to
+`ws://localhost:9002`, and leave authorization blank to view the world.
+
+## Limits
+
+This model does not validate terrain, vision, flow/range sensing, wind,
+vibration, battery/ESC behavior, sensor latency/jitter, actuator faults, or
+physical touchdown sensing. Add those only as a reviewed sensor/contact model,
+not as a display-only shortcut.
diff --git a/docs/theme/kaptan.css b/docs/theme/kaptan.css
new file mode 100644
index 0000000..5d6a8cf
--- /dev/null
+++ b/docs/theme/kaptan.css
@@ -0,0 +1,47 @@
+:root {
+  --kaptan-ink: #142033;
+  --kaptan-blue: #1769aa;
+  --kaptan-sky: #e8f3fb;
+  --kaptan-border: #d4dfeb;
+}
+
+.content main {
+  max-width: 58rem;
+  margin: 0 auto;
+}
+
+.content h1,
+.content h2,
+.content h3 {
+  color: var(--kaptan-ink);
+  font-weight: 700;
+  letter-spacing: -0.02em;
+}
+
+.content h1 {
+  border-bottom: 3px solid var(--kaptan-blue);
+  padding-bottom: 0.45rem;
+}
+
+.content a {
+  color: var(--kaptan-blue);
+}
+
+.content table {
+  border: 1px solid var(--kaptan-border);
+  border-radius: 0.5rem;
+  overflow: hidden;
+}
+
+.content blockquote {
+  border-left-color: var(--kaptan-blue);
+  background: var(--kaptan-sky);
+}
+
+.sidebar .sidebar-scrollbox {
+  border-right: 1px solid var(--kaptan-border);
+}
+
+.nav-chapters {
+  border-top: 1px solid var(--kaptan-border);
+}
diff --git a/docs/theme/kaptan.js b/docs/theme/kaptan.js
new file mode 100644
index 0000000..dc6a94d
--- /dev/null
+++ b/docs/theme/kaptan.js
@@ -0,0 +1,5 @@
+"use strict";
+
+// Keep a small stable hook for future theme enhancements without replacing
+// mdBook's built-in navigation, search, or theme picker.
+document.documentElement.classList.add("kaptan-docs");