# RED BEAR OS BUILD SYSTEM — PROJECT KNOWLEDGE BASE

**Generated:** 2026-04-12 (P1/P2 complete) · Updated: 2026-06 (source ownership migration)
**Toolchain:** Rust nightly (edition 2024)
**Architecture:** Microkernel OS in Rust, ~38k files, ~294k LoC Rust
**Target Hardware**: AMD64 bare metal, with AMD and Intel machines treated as equal-priority Red Bear OS targets

## OVERVIEW

Red Bear OS build system orchestrator — builds and packages ~100+ Git repositories
into a bootable Redox image. Uses a Makefile + Rust "cookbook" tool + TOML configs.
Languages: Rust (core), C (ported packages), TOML (config), Make (build orchestration).

RedBearOS is a **full fork** of Redox OS with direct source ownership.
Red Bear maintains its own git forks of every patched component under `local/sources/`.
Sources are directly editable — no patches, no indirection. Changes are committed
to the appropriate fork repo. Durable Red Bear state belongs in `local/sources/`,
`local/recipes/`, `local/docs/`, and tracked Red Bear configs.

The current baseline is **Red Bear OS 0.1.0** (Redox snapshot at build-system commit `f55acba68`).

## FULL FORK PRINCIPLE

**Red Bear OS is a FULL FORK. We do not depend on Redox. We reuse Redox code only
when needed — and when we do, we fork it into our own repos.**

This means:

| Rule | Explanation |
|---|---|
| **Own your dependencies** | Every crate and library Red Bear uses must have its source accessible in `local/sources/` or `local/recipes/`. No depending on upstream crates that we cannot fix ourselves. |
| **No waiting for upstream** | If a dependency breaks, we fix it in our fork. We do not file issues and wait. |
| **Frozen snapshots only** | Upstream Redox is a reference, not a live dependency. We baseline on frozen snapshots and never auto-pull. |
| **Upstream gitlab URLs are temporary** | Any recipe pointing at `gitlab.redox-os.org` (91 currently) must eventually be forked to `local/sources/` or pinned to a frozen archive. Exceptions: unmodified upstream packages with pinned revisions. |
| **Our code, our fixes** | When crate APIs change (e.g., `libredox 0.1.0` → `0.1.17` broke `call_ro`/`call_wo` signatures), we update OUR fork's code. We don't revert our code to match old APIs — we fix forward. |
| **Durable state** | All source modifications are committed to `local/sources/<component>/`. No edits in `recipes/*/source/` survive a rebuild. |

**Concretely:**
- `local/recipes/drivers/redox-driver-sys/` is OUR fork. We fix compilation errors there.
- `local/sources/kernel/` is OUR kernel. We don't pull from `gitlab.redox-os.org/redox-os/kernel`.
- If a Cargo dependency breaks, we fork the dependency crate to `local/sources/` and pin our Cargo.toml to our fork.
- The Linux kernel in `local/reference/` is read-only reference — never a dependency.

### Safe to Pull from Upstream (Redox System Internals)

These are Redox-specific libraries, tools, and protocols that form the stable ABI
between the kernel and userspace. We do NOT modify these — we pull them from upstream
with pinned revisions. Forking them would create divergence from the Redox ABI and
cause silent breakage.

**Crates (pulled via Cargo, NOT via recipe git URLs):**

| Crate | Why safe | Notes |
|---|---|---|
| `redox_syscall` | Syscall numbers, types, flags — must match kernel ABI | Maintained by Redox; we never modify syscall numbers |
| `redox-scheme` | Scheme protocol (`SchemeSync`, `SchemeAsync` traits) | Stable protocol; our daemons implement it |
| `libredox` | High-level syscall wrappers (`call_ro`, `call_wo`) | Thin wrapper; if it breaks we fork it |
| `pkgar` / `pkgar-core` / `pkgar-keys` | Package format (archive, signing, manifest) | Stable ABI; used by installer and repo tool |
| `redox-pkg` | Package dependency resolution | Used by cookbook; we don't modify |
| `redox_installer` | Filesystem image creation | **We forked this** — ext4 + GRUB support |
| `redoxer` | Cross-compilation wrapper | Build tool; we use it as-is |

**Recipes (gitlab URLs — safe to pull from upstream):**

| Recipe | Why safe | Notes |
|---|---|---|
| `core/pkgar` | Package format tools | Matches `pkgar` crate ABI |
| `core/ion` | Shell | We don't modify shells |
| `core/dash` | POSIX shell | Redox port, we don't modify |
| `core/coreutils` | Core utilities | From uutils; we don't modify |
| `core/extrautils` | Extra utilities | Redox-specific; we don't modify |
| `core/findutils` | File search | We don't modify |
| `core/netdb` | Network database | Redox-specific |
| `core/netutils` | Network utilities | Redox-specific |
| `core/pkgutils` | Package utilities | Redox-specific |
| `core/profiled` | Profiler daemon | Redox-specific |
| `core/strace` | Syscall tracer | Redox-specific |
| `core/contain` | Container runtime | Redox-specific |
| `gui/orbital` | Legacy display server | We use Wayland; not modified |
| `gui/orbdata` | Legacy display data | Not modified |
| `gui/orbterm` | Legacy terminal | Not modified |
| `gui/orbutils` | Legacy display utils | Not modified |
| `dev/redoxer` | Cross-compilation wrapper | Build tool |
| `kernel/kernel` | Sub-recipe | Main kernel is OUR fork in `local/sources/kernel/` |

**Rule of thumb:** If it defines the Redox ABI (syscall numbers, scheme protocol,
package format), we pull from upstream. If we add features to it, we fork it.

### What We MUST Fork (things we modify)

| Component | Our fork | Why forked |
|---|---|---|
| Kernel | `local/sources/kernel/` | ACPI, x2APIC, MSI/MSI-X, scheduling, branding |
| relibc | `local/sources/relibc/` | eventfd, signalfd, timerfd, waitid, SysV IPC |
| Base (drivers) | `local/sources/base/` | acpid, pcid, inputd, ps2d, xhcid migrations |
| Bootloader | `local/sources/bootloader/` | UEFI alloc fix, branding, GPT offset |
| Installer | `local/sources/installer/` | ext4 + GRUB bootloader integration |
| Mesa | `local/recipes/libs/mesa/` | virgl disk cache, GBM dumb prime export |
| libdrm | `local/recipes/libs/libdrm/` | ioctl bridge, PCI info, device enumeration |
| QtBase | `local/recipes/qt/qtbase/` | futex redox support, wayland guards |
| redox-driver-sys | `local/recipes/drivers/redox-driver-sys/` | Hardware quirks system |
| linux-kpi | `local/recipes/drivers/linux-kpi/` | GPU + Wi-Fi compatibility headers |
| redox-drm | `local/recipes/gpu/redox-drm/` | Intel + AMD display drivers |

## BUILD SYSTEM DURABILITY — THE CARDINAL RULE

**SOURCE LIVES IN `local/sources/<component>/`. EDIT THERE. `recipes/*/source/` IS A SYMLINK
TO `local/sources/` — DO NOT EDIT THROUGH THE SYMLINK (git operations won't work). DO NOT
EDIT FILES IN `recipes/*/source/` DIRECTLY — GO TO `local/sources/<component>/` INSTEAD.**

This is the #1 mistake AI agents and new contributors make. It has caused repeated work loss
in this project. The rule is:

| What you want to do | Where to do it |
|---|---|
| Change a kernel source file | Edit `local/sources/kernel/` and commit |
| Change an init or daemon source file | Edit `local/sources/base/` and commit |
| Change relibc | Edit `local/sources/relibc/` and commit |
| Change a driver | Edit `local/sources/<component>/` and commit |
| Add a new package | Create a recipe in `local/recipes/<category>/<name>/` |
| Change build config | Edit `config/redbear-*.toml` |
| Add documentation | Write to `local/docs/` |

### How the build system works

```
repo cook <package>
  ├── repo fetch <package>
  │   ├── For local sources: symlink local/sources/<pkg>/ → recipes/<pkg>/source/
  │   ├── For git sources: clone/fetch from git URL → recipes/<pkg>/source/
  │   └── Source tree is ready for build (no patch step)
  ├── Cargo/cmake/configure build
  └── Stage artifacts into sysroot
```

The `source/` directory is a symlink to `local/sources/` for Red Bear-owned
components, or a git clone for upstream packages. There are no patches —
the source IS the source.

### Two-layer architecture

```
Layer 1: Ephemeral (destroyed on clean/fetch/rebuild)
  recipes/<pkg>/source/       ← symlink to local/sources/ or git clone
  build/                      ← build outputs
  target/                     ← cargo target dir

Layer 2: Durable (survives clean/fetch/rebuild/release provisioning)
  local/sources/<pkg>/        ← Red Bear source forks (git repos, directly editable)
  local/recipes/<pkg>/        ← custom recipe directories
  config/redbear-*.toml       ← Red Bear OS build configs
  local/docs/                 ← planning and integration docs
```

### The correct workflow for any source change

1. **Edit the source** in `local/sources/<component>/`
2. **Build**: `./target/release/repo cook <package>`
3. **Test**: `make qemu CONFIG_NAME=redbear-mini`
4. **Commit**: `git -C local/sources/<component>/ commit -m "..."`

### Common anti-patterns

| Anti-pattern | Why it fails |
|---|---|
| Editing files in `recipes/<pkg>/source/` | Those are symlinks to `local/sources/`. Git operations must happen in the actual repo. |
| Creating new patch files in `local/patches/` | `local/patches/` is historical only. Changes go as git commits in `local/sources/<component>/`. |
| Hand-writing patches | No patches exist. Use standard git workflow. |
| Expecting `source/` changes to survive `make clean` | `make clean` deletes `source/` directories |
| Running `repo cook` without `--allow-protected` for core packages | Protected recipes (kernel, relibc, base) are offline-only by default |

### Recipe source configuration

Red Bear-owned recipes use the `Local` source type, pointing at the fork repo:

```toml
[source]
path = "../../../local/sources/base"
```

Non-forked recipes use standard git or tar sources — no patches needed.

### Rules

1. **`REPO_OFFLINE` defaults to `1`** (offline). Set `REPO_OFFLINE=0` to explicitly allow online
   fetching for non-protected development recipes only.
2. **`REDBEAR_RELEASE`** unconditionally forces offline mode — no network access during release
   builds, even with `REPO_OFFLINE=0`.
3. **Protected recipes** (kernel, relibc, base, bootloader, all Red Bear custom recipes) are
   **always offline** — they use archived sources from `sources/redbear-<release>/`.
4. **`GNU_CONFIG_GET`** (wget for `config.sub`) is gated by `COOKBOOK_OFFLINE` — no download
   when offline.
5. **Manual scripts** (`fetch-firmware.sh`, `fetch-all-sources.sh`, `provision-release.sh`)
   may pull from upstream but MUST be explicitly invoked by the user. They are never called by
   `make all` or `make live`.
6. **Toolchain downloads** (`mk/prefix.mk`) are the only ungated network access — they download
   the cross-compiler toolchain from `static.redox-os.org`. These are one-time prerequisites,
   not per-recipe source fetches.

### What Counts as a Silent Upstream Pull

Any of the following that runs without the user explicitly requesting it:
- `git clone`, `git fetch`, `git pull` against any remote
- `wget` or `curl` downloading source code or build artifacts
- Any HTTP request to `gitlab.redox-os.org`, `github.com`, `static.redox-os.org`, or any other
  upstream hosting service (note: Red Bear OS does not use GitHub — see Repository Hosting below)

### What Does NOT Count

- Toolchain setup (`make prefix`) — one-time cross-compiler download
- QEMU firmware for non-x86 targets (`mk/qemu.mk` ARM/Raspberry Pi U-Boot) — not used in
  standard x86_64 builds
- `make fetch` — explicit user action, gated by `REDBEAR_RELEASE`

### Enforcement

- Violations are bugs. If you find a script or build target that silently pulls from upstream,
  fix it immediately: add an offline gate, or move the fetch to a manual-only script.
- The cookbook tool (`src/cook/fetch.rs`) enforces offline mode for protected recipes regardless
  of `COOKBOOK_OFFLINE`.
- `COOKBOOK_OFFLINE=true` is the default in the Rust cookbook config parser when the environment
  variable is not set.

## STRUCTURE

```
redox-master/
├── config/          # Build configs (TOML): tracked redbear-* targets plus mainline references
├── mk/              # Makefile fragments: config.mk, repo.mk, prefix.mk, disk.mk, qemu.mk
├── recipes/         # Package recipes (TOML + source). 26 categories. See recipes/AGENTS.md
│   ├── core/        # kernel, bootloader, relibc, base drivers — See recipes/core/AGENTS.md
│   ├── wip/         # Wayland, KDE, driver WIP ports — See recipes/wip/AGENTS.md
│   ├── libs/        # Libraries: mesa, cairo, SDL, zlib, openssl, etc.
│   ├── gui/         # Legacy GUI stack packages
│   └── ...          # 21 other categories (net, dev, games, shells, etc.)
├── src/             # Cookbook Rust tooling (repo binary, cook logic)
├── docs/            # Architecture docs (6 detailed integration guides) — See docs/AGENTS.md
├── local/           # OUR CUSTOM WORK — survives mainline updates — See local/AGENTS.md
│   ├── config/      # Custom configs (my-amd-desktop.toml)
│   ├── sources/      # Red Bear source forks (git repos, directly editable)
│   │   ├── kernel/    #   Red Bear's kernel fork
│   │   ├── relibc/    #   Red Bear's C library fork
│   │   ├── base/      #   Red Bear's userspace drivers fork
│   │   └── ...        #   Additional component forks
│   ├── recipes/     # Custom recipes (AMD drivers, GPU stack, Wayland)
│   ├── patches/     # HISTORICAL — old patch files (not used by build system)
│   ├── Assets/      # Branding assets (icon, loading background)
│   ├── firmware/    # AMD GPU firmware blobs (fetched, not committed)
│   ├── scripts/     # Build/deploy scripts (fetch-firmware.sh, build-redbear.sh)
│   ├── docs/        # Red Bear integration docs (AMD roadmap, Wi-Fi/Bluetooth plans, status notes)
│   └── reference/   # External reference sources (gitignored, never deleted, always kept)
├── prefix/          # Cross-compiler toolchain (Clang/LLVM for x86_64-unknown-redox)
├── build/           # Build outputs, logs, fstools, per-arch directories
├── repo/            # Package manifests and PKGAR artifacts per architecture
├── bin/             # Cross-tool wrappers (pkg-config, llvm-config per target)
├── scripts/         # Helper scripts (backtrace, category, changelog, etc.)
├── podman/          # Podman container build support
├── .cargo/          # Cargo config: linker per target (aarch64, x86_64, i586, i686, riscv64gc)
├── Makefile         # Root orchestrator (all, live, image, rebuild, clean, qemu, gdb)
├── Cargo.toml       # Cookbook crate: binaries (repo, repo_builder), lib (cookbook)
├── rust-toolchain.toml  # nightly-2025-10-03 + rust-src + rustfmt + clippy
└── .config          # PODMAN_BUILD=0 (set to 1 for container builds)
```

## WHERE TO LOOK

| Task | Location | Notes |
|------|----------|-------|
| Add a package | `recipes/<category>/<name>/recipe.toml` | Use `template = "cargo\|cmake\|meson\|custom"` |
| Change build config | `config/<name>.toml` | Include chain: wayland→desktop→desktop-minimal→minimal→base |
| Fix kernel | `local/sources/kernel/` | Kernel is a recipe, not top-level |
| Fix a driver | `local/sources/base/src/drivers/` | All drivers are userspace daemons |
| Fix relibc (POSIX) | `local/sources/relibc/` | C library written in Rust |
| Wayland integration | `recipes/wip/wayland/` + `local/docs/WAYLAND-IMPLEMENTATION-PLAN.md` | 21 WIP recipes + local validation/ownership plan |
| KDE Plasma path | `recipes/wip/kde/` + `docs/05-KDE-PLASMA-ON-REDOX.md` | 9 WIP KDE app recipes |
| **Desktop path plan** | `local/docs/CONSOLE-TO-KDE-DESKTOP-PLAN.md` | **Canonical plan: console → HW-accelerated KDE** |
| Linux driver compat | `docs/04-LINUX-DRIVER-COMPAT.md` | linux-kpi + redox-driver-sys architecture (**GPU and Wi-Fi only — not USB**) |
| Build system internals | `src/bin/repo.rs`, `src/lib.rs`, `mk/repo.mk` | Cookbook tool in Rust |
| Cross-toolchain setup | `mk/prefix.mk`, `prefix/x86_64-unknown-redox/` | Downloads Clang/LLVM toolchain |
| Display/session surface | `config/redbear-full.toml` | Active desktop/graphics compile surface |
| GPU/graphics stack | `recipes/libs/mesa/` | OSMesa + LLVMpipe (software only) |
| GPU hardware drivers | `local/recipes/gpu/redox-drm/source/` | AMD + Intel DRM/KMS via redox-driver-sys |
| D-Bus integration | `local/docs/DBUS-INTEGRATION-PLAN.md` | Architecture, gap analysis, phased implementation for KDE Plasma D-Bus |
| Boot config | `config/*.toml` | TOML hierarchy, include-based |
| **Hardware quirks** | `local/recipes/drivers/redox-driver-sys/source/src/quirks/` | Data-driven quirk tables: compiled-in + TOML + DMI; see `local/docs/QUIRKS-SYSTEM.md` |

## BUILD COMMANDS

### Recommended Workflow (use the build script)

The canonical way to build Red Bear OS ISOs is through `local/scripts/build-redbear.sh`.
It enforces all project policies automatically:

```bash
# Build redbear-mini (text-only, recovery) — ~30 min
./local/scripts/build-redbear.sh redbear-mini

# Build redbear-full (3D desktop + SDDM + KDE) — ~90 min first build
./local/scripts/build-redbear.sh redbear-full

# Clean rebuild (discard caches, force recompile)
./local/scripts/build-redbear.sh redbear-full --no-cache
```

**What `build-redbear.sh` does automatically:**
1. **Enforces local-over-WIP**: Any `recipes/wip/` package shadowing a `local/recipes/` package is replaced with a symlink to the local version (per local/recipes/ priority policy)
2. **Verifies overlay integrity**: Checks that all recipe symlinks resolve correctly
3. **Stashes dirty submodules**: Prevents accidental commits from contaminating the build
4. **Checks firmware**: Warns if AMD GPU firmware is missing for redbear-full

**When to use `--no-cache`:**
- After changing `local/sources/{relibc,kernel,base}` (low-level packages)
- After `make clean` or `make distclean`
- When stale cached packages cause build failures

**Cascade rebuild rule:** When a low-level package changes (relibc, kernel, base),
ALL packages that transitively depend on it must be rebuilt. Use:
```bash
./local/scripts/rebuild-cascade.sh relibc    # Rebuild relibc + all dependents
./local/scripts/rebuild-cascade.sh --dry-run relibc  # Preview without rebuilding
```

### Legacy Manual Build Commands

```bash
# Prerequisites (Linux x86_64 host)
#   rustup + nightly-2025-10-03, cargo install just cbedgen, nasm, qemu-system-x86
#   See docs/06-BUILD-SYSTEM-SETUP.md for distro-specific packages

# Configuration
echo 'PODMAN_BUILD?=0' > .config          # Native build (no container)
echo 'PODMAN_BUILD?=1' > .config          # Podman container build

# Build Red Bear OS
# Supported compile targets:
#   redbear-full         desktop/graphics target (harddrive.img or live ISO)
#   redbear-mini         text-only console/recovery target (harddrive.img or live ISO)
#   redbear-grub         text-only with GRUB boot manager (live ISO)
# Desktop/graphics target: redbear-full
# Text-only targets: redbear-mini, redbear-grub
make all CONFIG_NAME=redbear-full         # Desktop/graphics target → harddrive.img
make all CONFIG_NAME=redbear-mini         # Text-only target → harddrive.img
make live CONFIG_NAME=redbear-full        # Full desktop live ISO
make live CONFIG_NAME=redbear-mini        # Text-only mini live ISO
make live CONFIG_NAME=redbear-grub        # Text-only mini live ISO with GRUB
CI=1 make all CONFIG_NAME=redbear-mini    # CI mode (disables TUI, for non-interactive)

# Run
make qemu                                 # Boot in QEMU
make qemu QEMUFLAGS="-m 4G"              # With more RAM
make live                                 # Build live ISO for real bare metal

# Single recipe
./target/release/repo cook recipes/libs/mesa     # Build one recipe
./target/release/repo fetch recipes/core/kernel   # Fetch source only
make r.mesa                                      # Make shorthand for cook
make cr.mesa                                     # Clean + rebuild

# Clean
make clean                                # Remove build artifacts
make distclean                            # Remove sources + artifacts
```

## BUILD FLOW

```
make all
  → mk/config.mk (ARCH, CONFIG_NAME, FILESYSTEM_CONFIG)
  → mk/depends.mk (check host tools: rustup, cbedgen, nasm, just)
  → mk/prefix.mk (download/setup cross-toolchain if needed)
  → mk/fstools.mk (build cookbook repo binary + fstools)
  → mk/repo.mk (repo cook --filesystem=config/*.toml)
    → For each recipe: fetch source → build → stage into sysroot
    → Each successful build produces repo/<arch>/<name>.pkgar + <name>.toml
  → mk/disk.mk (create filesystem.img, harddrive.img, redbear-live.iso or harddrive.img)
    → redoxfs-mkfs → redox_installer → bootloader embedding
```

### Build Outputs

Every successful `repo cook <package>` produces:

| Artifact | Location | Purpose |
|----------|----------|---------|
| Package archive | `repo/x86_64-unknown-redox/<name>.pkgar` | Binary package for image assembly |
| Package manifest | `repo/x86_64-unknown-redox/<name>.toml` | Metadata, version, deps, hashes |
| Staged sysroot | `recipes/*/<name>/target/.../stage/` | Files for `repo push` |
| Source tree | `recipes/*/<name>/source/` | Symlink to local/sources/ or git clone |

**A build is not complete until the .pkgar and .toml exist in `repo/`.**

## CONVENTIONS

- **Rust edition 2024**, nightly channel
- **rustfmt.toml**: max_width=100, brace_style=SameLineWhere
- **clippy.toml**: cognitive-complexity-threshold=100, type-complexity-threshold=1000
- **Recipe format**: TOML with `[source]` + `[build]` + optional `[package]`
- **Build templates**: `cargo`, `meson`, `cmake`, `make`, `configure`, `custom`
- **WIP recipes**: Must start with `#TODO` comment explaining what's missing
- **Custom configs**: Name with `my-` prefix (git-ignored by convention)
- **CI**: GitLab CI (`.gitlab-ci.yml`) at root + per-recipe
- **Repository Hosting**: Gitea at `gitea.redbearos.org` — the ONLY git server. No GitHub.
- **Syscall ABI**: Unstable intentionally. Stability via `libredox` and `relibc`
- **Drivers**: ALL userspace daemons via scheme system. No kernel-space drivers (except serio)

## SYSTEM-CRITICAL INFRASTRUCTURE MUST BE RUST

All Red Bear OS system-critical infrastructure **must** be written in Rust. C and C++ are
acceptable only for ported upstream applications (KDE Plasma, Qt, games, third-party tools)
where the original source is not Rust.

### What counts as system-critical

| Layer | Component | Language | Status |
|-------|-----------|----------|--------|
| Kernel | microkernel | Rust | ✅ |
| C library | relibc | Rust | ✅ |
| Init | service manager | Rust | ✅ |
| Filesystems | redoxfs, ext4d, fatd | Rust | ✅ |
| Driver infrastructure | redox-driver-sys, linux-kpi headers | Rust + C headers | ✅ |
| Display/compositor | Wayland compositor | Rust | required |
| Session/auth | redbear-sessiond, redbear-authd | Rust | ✅ |
| D-Bus broker | session/system bus | Rust | ✅ |
| Network stack | TCP/IP, Wi-Fi control plane | Rust | required |
| Bluetooth stack | host/controller path | Rust | required |
| USB stack | controller drivers, hub driver | Rust | required |
| Input stack | evdev, libinput adapter | Rust | required |
| Firmware loading | scheme:firmware daemon | Rust | ✅ |
| Core utilities | shell, fileutils, process tools | Rust | required |
| Bootloader | UEFI bootloader | Rust | ✅ |
| Installer | redox_installer | Rust | ✅ |
| Build tooling | cookbook, repo binary | Rust | ✅ |

### What does NOT need to be Rust

- **Ported desktop applications**: KDE Plasma, Qt apps, KDE Frameworks — these are upstream
  C++ codebases and remain C++. The boundary is at the platform adapter layer: anything Red Bear
  writes to integrate them ( Wayland protocol bridges, D-Bus service implementations, platform
  plugins) must be Rust even if the upstream consumer is C++.
- **Ported libraries**: mesa, wayland, libxkbcommon, libinput, fontconfig, etc. — upstream C.
- **Games and end-user applications**: upstream code in any language.

### Decision rule

When writing new code for Red Bear OS, or when choosing between writing new code vs porting
existing code, the rule is:

> If the component runs below the application layer — kernel, libc, drivers, filesystems,
> compositor, session management, networking, input, USB, Bluetooth, core utilities —
> it must be written in Rust.
>
> If the component is an application or library that users would recognize as a separate
> upstream project (KDE, Qt, Firefox, etc.), it may remain in its upstream language.
>
> The integration layer between Rust infrastructure and upstream C/C++ code must be Rust.
> Platform adapters, D-Bus service implementations, Wayland protocol bridges, and plugin
> shims are infrastructure, not applications.

### Enforcement

- New recipes under `local/recipes/` for system-critical components must use `template = "cargo"`.
- C/C++ build templates (`cmake`, `meson`, `make`, `configure`) are only for ported upstream
  packages and their direct dependencies.
- If a ported C/C++ package needs a companion daemon, helper, or bridge, that companion must
  be a separate Rust recipe — not embedded C in the ported package.

### Conflicting implementations: always prefer Rust

When both a Rust implementation and a C/C++ implementation exist for the same functionality,
Red Bear OS **always** prefers the Rust implementation. This applies even when the C version is
from upstream Redox or appears more complete.

The rationale: Rust provides memory safety, type safety, and panic-based error recovery at the
language level. For an OS with no ASLR, no stack canaries, and a minimal kernel, the language
itself is the primary defense boundary. A C implementation of equivalent functionality is always
a strictly weaker choice.

Examples:

| Situation | Correct choice |
|-----------|---------------|
| relibc (Rust) vs newlib/glibc (C) | relibc — always |
| redoxfs (Rust) vs an imported C filesystem driver | redoxfs — always |
| redbear-sessiond (Rust) vs dbus-daemon (C) | redbear-sessiond — always |
| A Rust crate for a protocol vs the reference C library | Rust crate — always |
| Upstream Redox provides a Rust driver; we also have a C port | Rust driver — always |

If a Rust implementation is less feature-complete than the C alternative, the correct response
is to improve the Rust implementation — not to fall back to C.

## INSTALLER FILE LAYERING

The installer creates filesystem images in four layers. Understanding this ordering is critical
to avoid silent file overwrites.

### Layer Ordering During `install_dir()`

```
Layer 1: Config pre-install [[files]]    (postinstall = false)
Layer 2: Package staging                  (install_packages())
Layer 3: Config post-install [[files]]    (postinstall = true)
Layer 4: User/group creation              (passwd, shadow, group)
```

### Collision Implications

- **Layer 2 overwrites Layer 1** silently (same path → last writer wins). This is the bug class
  that caused the D-Bus regression: config overrides at `/usr/lib/init.d/` were overwritten by
  the `base` package staging the same paths.
- **Layer 3 overwrites Layer 2** (intentional — postinstall overrides).
- For init services, config overrides **MUST** use `/etc/init.d/` so they survive Layer 2.

### Init Service File Ownership

- **Packages own `/usr/lib/init.d/`** — default service files installed by recipe staging
- **Config overrides own `/etc/init.d/`** — override files created by `[[files]]` entries
- The init system's `config_for_dirs()` gives `/etc/init.d/` priority via BTreeMap dedup
- **Config `[[files]]` entries MUST NOT use `/usr/lib/init.d/` paths for init services**
- Run `make lint-config` to detect violations

### Collision Detection

The installer now includes a `CollisionTracker` (in `collision.rs`) that detects when package
staging overwrites config pre-install files. Init service collisions always error. Other
collisions warn by default, error in strict mode (`REDBEAR_STRICT_COLLISION=1`).

### Validation Gates

After building an image, run `make validate` to verify:
- Init service path violations (via `lint-config`)
- Override effectiveness and scheme binary existence (via `validate-init-services.sh`)
- File ownership conflicts (via `validate-file-ownership.sh`)

See `local/docs/BUILD-SYSTEM-HARDENING-PLAN.md` for the full plan.

## ANTI-PATTERNS (THIS PROJECT)

- **DO NOT** suppress errors with `as any` / `@ts-ignore` — use proper `Result` handling
- **DO NOT** use `unwrap()` / `expect()` in library/driver code — pervasive anti-pattern (~14k instances)
- **DO NOT** modify kernel syscall ABI directly — use `libredox` or `relibc`
- **DO NOT** put drivers in kernel space — all drivers are userspace daemons
- **DO NOT** hardcode `/dev/` paths — use scheme paths (`/scheme/drm/card0`)
- **DO NOT** skip required dependencies — document what's missing with `#TODO`
- **DO NOT** skip warnings — investigate, diagnose, and fix the root cause; suppressing or ignoring warnings is not acceptable when a fix is feasible
- **DO NOT** suppress build failures by disabling features — fix the root cause instead
- **DO NOT** remove BINS entries to fix build failures — fix the source or use EXISTING_BINS filtering
- **DO NOT** use the VESA display driver (`vesad`) as the primary display surface after GPU detection. vesad is only for early-boot framebuffer handoff — after redox-drm loads, the display path is `/scheme/drm/card0`. See **NO VESA POLICY** below.

## NO VESA POLICY

Red Bear OS does not use the VESA display driver as the primary display surface. All display
output goes through the DRM/KMS path via real GPU drivers:

| Environment | GPU Driver | 3D Support |
|---|---|---|
| QEMU | virtio-gpu (via redox-drm) | ✅ virgl |
| Intel hardware | Intel i915-like (via redox-drm) | ✅ Mesa i965/iris |
| AMD hardware | amdgpu (via redox-drm + linux-kpi) | ✅ Mesa radeonsi |
| Future | nouveau reimplementation (Rust, via redox-drm) | ✅ Mesa nouveau |

**vesad is allowed ONLY as an early-boot framebuffer handoff.** The bootloader sets up a linear
framebuffer before the kernel starts. vesad takes over this framebuffer so the initfs has console
output (fbcond, fbbootlogd) before real GPU drivers are available. Once redox-drm initializes and
registers `scheme:drm/card0`, vesad must hand off and NOT register `scheme:display.vesa` as the
primary display surface.

The display path for redbear-full:

```
Bootloader linear framebuffer
  → vesad (initfs, service 20): temporary FB handoff for text console
  → redox-drm (initfs, service 30): detects GPU hardware, takes over via DRM/KMS
  → redox-drm (rootfs, service 14): full DRM driver with 3D (Mesa)
  → KWin compositor: DRM/KMS master, composites desktop via /scheme/drm/card0
```

For redbear-mini: vesad handles the bootloader framebuffer for the text-only console. No GPU
driver loads — mini is text-only by design.

**After GPU detection, any code that opens `/scheme/display.vesa/` is incorrect.** The correct
display path is `/scheme/drm/card0` via the DRM scheme.

Rationale: VESA is a legacy BIOS-era standard with no hardware acceleration, no mode setting
beyond what the bootloader provides, no 3D, and no future. Red Bear OS targets real GPU
hardware with full DRM/KMS and Mesa support. vesad serves only as a bridge between bootloader
FB and the real GPU driver — it is never the final display path.

This policy also covers future GPU driver work: any new GPU support (nouveau Rust reimplementation,
ARM Mali, etc.) must go through the redox-drm + DRM/KMS path, never through VESA fallback.

## FULL 3D DESKTOP — NON-NEGOTIABLE

**Red Bear OS must ship with a fully hardware-accelerated 3D desktop on `redbear-full`.**
Software rendering fallbacks (LLVMpipe, softpipe) are NOT acceptable as the primary
render path. The Mesa build must include hardware GPU drivers and export proper CMake
configurations so Qt6/KWin can link against OpenGL/EGL/GBM.

### Why This Is Non-Negotiable

| Reason | Detail |
|--------|--------|
| **KDE Plasma requires 3D** | KWin is a hardware-composited window manager. It requires `libEGL`, `libGLESv2`, and `libgbm` from Mesa to composite the desktop. Without these, the greeter (SDDM) and desktop session (Plasma) cannot render. |
| **Qt6 Quick requires OpenGL** | Qt6Quick/QML rendering is GPU-accelerated. The QML JIT compiles shaders that execute on the GPU via OpenGL ES 2.0. Without hardware OpenGL, QML scenes render as blank or crash. |
| **No compromises on features** | Disabling OpenGL/EGL/GBM in Qt6 (`-DFEATURE_opengl=OFF`, `-DFEATURE_egl=OFF`) is a POLICY VIOLATION. These features are required by the desktop path and must be fixed, not disabled. |
| **Mesa is a hard build dependency** | mesa, libdrm, libepoxy, redox-drm are required packages in `redbear-full`. If they fail to build, the root cause must be fixed — never worked around by disabling features or removing packages. |

### Build Chain Integrity

The GPU stack depends on this build chain:

```
mesa → libdrm → libepoxy → redox-drm → qtbase → qtdeclarative → qtwayland
  → KF6 Frameworks → KWin → SDDM → KDE Plasma
```

If MESA fails to build or exports incorrect CMake configurations, the ENTIRE desktop
chain is blocked. Every package in this chain must compile and link correctly against
the Redox target.

### Mesa Build Requirements for Redox

| Requirement | Why |
|-------------|-----|
| `-Dgallium-drivers=swrast,virgl,iris,crocus` | Software + VirtIO + Intel GPU drivers |
| `-Dvulkan-drivers=swrast` | Software Vulkan (for future Vulkan-based compositing) |
| `-Degl=enabled` | EGL library (required by Qt6, KWin, SDDM) |
| `-Dgbm=enabled` | Generic Buffer Manager (required by KWin DRM backend) |
| `-Dllvm=enabled` | LLVMpipe software rasterizer (fallback, NOT primary) |
| `-Dshared-glapi=enabled` | Shared GL dispatch (required for multi-vendor GPU) |
| `-Dosmesa=true` | Off-screen Mesa (required by some Qt tests) |
| Stub headers provided | `sys/ioccom.h` must be available via sysroot or recipe CFLAGS for DRM uapi |

### Troubleshooting Mesa → Qt6 CMake Chain

When Qt6's CMake reports `Feature "opengles2": Forcing to "ON" breaks its condition`
or `Feature "egl": Forcing to "ON" breaks its condition`, the root cause is that Mesa's
CMake configuration files (installed to the sysroot) enable features that the
cross-compilation toolchain cannot satisfy at CMake time. The fix is:

1. Verify Mesa's `.pc` files (`egl.pc`, `glesv2.pc`, `gbm.pc`) are in the sysroot
2. Verify Mesa's CMake config (`lib/cmake/mesa/`) exports proper include paths
3. Check that the Redox toolchain has working EGL/GLES headers
4. If Qt6's CMake feature detection fails on the cross-compiled target, add
   `-DQT_FEATURE_opengles2=ON -DQT_FEATURE_egl=ON` explicitly (overriding the
   auto-detection) AND ensure the sysroot has the required libraries

**Never disable OpenGL/EGL as a workaround.** If Qt6 can't find mesa's CMake
configs, fix Mesa's build or Qt6's CMake detection — do not remove 3D support.

### No Package Removal Policy

The following packages are MANDATORY in `redbear-full` and must never be removed
or suppressed (ignored):

| Package | Reason |
|---------|--------|
| `mesa` | OpenGL/EGL/GBM provider — required by Qt6, KWin, SDDM |
| `libdrm` | DRM userspace library — required by mesa and redox-drm |
| `libepoxy` | OpenGL function pointer manager — required by Qt6 |
| `redox-drm` | DRM/KMS display driver — required for GPU display output |
| `qtbase` | Qt6 Core — required by entire KDE stack |
| `qtdeclarative` | Qt6 QML — required by SDDM greeter and KDE Plasma |
| `qtwayland` | Qt6 Wayland backend — required for Wayland compositing |
| `kwin` | KWin compositor — the Wayland compositor/window manager |
| `sddm` | SDDM display manager — the login screen |

If ANY of these packages fails to build, the root cause must be fixed immediately.
There is no "ignore" workaround for mandatory desktop packages.

## ZERO TOLERANCE FOR STUBS

**Red Bear OS has zero tolerance for stubs, placeholders, fake implementations, skeleton code,
unimplemented functions, or any other "make it compile" shortcut.**

### What counts as a stub

Any of the following:

- A function or method that returns a hardcoded value instead of computing the real result
- A trait implementation where methods log "not implemented" or return empty/default values
- A struct that stores fields but never uses them for real work
- A file that exists to satisfy an import but contains no real logic
- A `// TODO: implement` comment followed by a dummy return
- A driver that creates synthetic data (fake EDID, hardcoded modes) instead of querying the hardware
- A `todo!()` or `unimplemented!()` macro anywhere in non-test code

### The rule

> **As soon as a stub is detected, it must be replaced with real, sophisticated, comprehensive code
> in the same work session.** No exceptions. No "I'll come back to it." No "this is good enough for now."

A stub found in the tree is a **bug** — not a precedent to follow, not a placeholder to defer,
not an acceptable intermediate state. Every stub is technical debt that compounds daily.

### Required response to a stub

When you encounter a stub:

1. **Stop what you are doing.** The stub takes priority.
2. **Understand the interface.** Read the trait, API contract, or specification the stub is supposed to implement.
3. **Implement it comprehensively.** Real logic, real hardware communication, real error handling, real edge cases.
4. **Verify it works.** Run `cargo check`, tests, or build verification.

| Stub pattern | Required fix |
|---|---|
| `fn detect_connectors() -> Vec<ConnectorInfo> { vec![] }` | Implement real hardware enumeration with proper protocol |
| `fn handle_irq() -> Ok(None)` | Implement real interrupt handling with event dispatch |
| `synthetic_edid()` when hardware can provide real EDID | Query the device via the proper protocol |
| Hardcoded mode "1280x720" | Query the display hardware for actual supported modes |
| `_firmware: HashMap<String, Vec<u8>>` (unused parameter) | Use the firmware data in device initialization |
| `Ok(self.vblank_count.fetch_add(1, Ordering::SeqCst))` in page_flip | Submit real buffer to hardware and wait for display |
| `todo!()` / `unimplemented!()` | Replace with full implementation |

### Why this matters

Stubs are worse than missing code because they:

- **Hide missing functionality** — the system appears to work but silently does nothing
- **Block real testing** — you can't verify behavior against hardware when the code doesn't talk to hardware
- **Create false confidence** — "it compiles" becomes a substitute for "it works"
- **Compound over time** — one stub leads to another as callers assume the interface is real
- **Waste debugging time** — hours spent tracing why something "doesn't display" when the driver never sent a command

### Enforcement

- Code reviews must reject any PR containing stubs
- Any agent or developer that introduces a stub must replace it before the session ends
- If a stub cannot be replaced (missing specification, blocked dependency), document it as a known gap in `local/docs/` — but never leave it in the code as a stub. Remove the code path entirely and add a clear error message instead.

## LINUX REFERENCE SOURCE POLICY

`local/reference/linux-7.0/` (or later) contains a full Linux kernel source tree for
cross-referencing driver behavior, hardware initialization sequences, register definitions,
and error handling patterns.

**Rules:**
- **NEVER delete** the reference tree. It is gitignored but permanent.
- **ALWAYS consult** the Linux source when building or fixing drivers, daemons, or any subsystem
  that has a Linux counterpart (audio/HDA, GPU/DRM, networking, USB, PCI, ACPI, input, storage,
  filesystems, scheduler, memory management).
- **Update** the reference tree when a new stable Linux version is needed:
  `git -C local/reference/linux-7.0 fetch --depth=1 origin tag:v7.x --force`
- The reference tree is read-only for consultation purposes. No modifications.
- Location: `local/reference/` is gitignored. It survives `make clean` and `make distclean`.

## DURABILITY POLICY

Every change to an upstream-owned source tree (anything under `recipes/*/source/`) **must** be
mirrored into a durable location **in the same work session** it was made. A change that exists
only inside a fetched source tree is not preserved.

**Required actions after any source-tree edit:**

1. **Commit** your changes in the fork repo: `git -C local/sources/<component>/ commit -m "..."`.
2. **Push** if sharing: `git -C local/sources/<component>/ push`.

**Why:** `make distclean`, `make clean`, and source immutable archivedes all
discard or replace `recipes/*/source/` trees. Only `local/sources/`, `local/recipes/`,
tracked configs, `local/docs/`, and `sources/redbear-0.1.0/` survive.

**Examples of changes that require immediate committing:**

| What you edited | Where to commit |
|---|---|
| `local/sources/relibc/src/header/sys_select/mod.rs` | `git -C local/sources/relibc commit` |
| `local/sources/relibc/src/header/signal/cbindgen.toml` | same repo as above |
| `local/sources/userutils/res/issue` | `git -C local/sources/userutils commit` |
| `local/sources/kernel/src/...` | `git -C local/sources/kernel commit` |

**What does NOT need committing to fork repos:** Files that already live in `local/recipes/`, tracked `config/redbear-*.toml`,
or any path that is already git-tracked in the main repo.

**What does NOT need committing to fork repos:** Files that already live in `local/recipes/`, tracked `config/redbear-*.toml`,
or any path that is already git-tracked in the main repo.

## BUILD SYSTEM POLICIES

### Build Durability Rule — Every Build Lands in the Repo

Every successful `repo cook` produces two durable artifacts:

1. **Package in the repo**: `repo/x86_64-unknown-redox/<name>.pkgar` + `<name>.toml`
2. **Committed source**: All source modifications are committed in the appropriate `local/sources/<component>/` git repo

A build is **not complete** until the repo artifacts exist:

```bash
# After cooking, verify the package is in the repo
./target/release/repo find <package>

# Check the repo manifest exists
ls repo/x86_64-unknown-redox/<package>.toml
ls repo/x86_64-unknown-redox/<package>.pkgar
```

If a package was built but the repo artifacts are missing, the build did not complete.
Re-run `repo cook <package>` to regenerate them.

If source changes were made but not committed to `local/sources/<component>/`, commit them there.

### Cascade Rebuild Rule

When a low-level package changes (relibc, kernel, base, or any library), **all
packages that depend on it must be rebuilt**. A stale dependent silently produces
link errors, ABI mismatches, or runtime crashes.

Use the cascade rebuild script:

```bash
# Rebuild relibc and everything that depends on it
./local/scripts/rebuild-cascade.sh relibc

# Dry run: show what would be rebuilt without building
./local/scripts/rebuild-cascade.sh --dry-run relibc

# Multiple root packages
./local/scripts/rebuild-cascade.sh relibc ncurses
```

The script:
1. Finds all packages whose `recipe.toml` lists the target in `dependencies`
2. Transitively expands the reverse dependency graph (BFS)
3. Builds the root package(s) first, then dependents in order
4. Pushes all rebuilt packages to the sysroot

**When to use cascade rebuilds:**
- After changing relibc headers or ABI
- After rebuilding a shared library (ncurses, zlib, openssl, etc.)
- After kernel ABI changes that affect userspace
- After any change to a package listed in other packages' `dependencies`

**When NOT to use cascade rebuilds:**
- Standalone applications with no dependents (editors, games, utilities)
- Terminal/leaf packages that nothing depends on


## AMD-FIRST INTEGRATION PATH

See `local/docs/CONSOLE-TO-KDE-DESKTOP-PLAN.md` for the canonical desktop path plan.

**Target**: AMD64 bare metal, with AMD and Intel machines treated as equal-priority hardware targets.

**amdgpu is 6M+ lines — 18x larger than Intel i915. LinuxKPI compat approach mandatory.**

### Bare Metal Boot Status

| Component | Status | Detail |
|-----------|--------|--------|
| UEFI boot | ✅ | x86_64 bootloader functional |
| AMD CPUs | ✅ | Ryzen Threadripper 128-thread verified |
| ACPI | ✅ Boot-baseline complete | RSDP/SDT checksums, MADT types 0x4/0x5/0x9/0xA, LVT NMI, FADT shutdown/reboot, explicit `RSDP_ADDR` forwarding into `acpid`, x86 BIOS-search AML fallback, and bounded AML-backed power enumeration are present; the explicit AML bootstrap producer contract and broader robustness still remain open — see `local/docs/ACPI-IMPROVEMENT-PLAN.md` |
| ACPI shutdown | 🚧 | PM1a/PM1b S5 via `\_S5` AML exists, but shutdown robustness and bounded validation are still open |
| ACPI reboot | 🚧 | Reset register + keyboard controller fallback exist, but broader reboot correctness and bounded validation are still open |
| ACPI power | 🚧 | `\_PS0`/`\_PS3`/`\_PPC` AML methods are available and the runtime power surface performs bounded AML-backed enumeration, but bootstrap preconditions and validation are still too weak for stronger support claims; see `local/docs/ACPI-IMPROVEMENT-PLAN.md` |
| x2APIC/SMP | ✅ | Multi-core works |
| IOMMU | 🚧 | QEMU first-use proof now passes; real hardware validation still open |
| AMD GPU | 🚧 | MMIO mapped, bounded Red Bear display glue path builds, MSI-X wired; imported Linux AMD DC/TTM/core remain builds and included in redbear-full (2026-04-29); no hardware validation yet |

### Phased Roadmap (historical P0–P6)

> **Note:** The P0–P6 numbering below is the historical hardware-enablement sequence.
> The canonical current desktop path plan uses a new Phase 1–5 structure documented in
> `local/docs/CONSOLE-TO-KDE-DESKTOP-PLAN.md` (v2.0, 2026-04-16).

| Phase | Duration | Delivers |
|-------|----------|----------|
| ~~P0: Fix ACPI for AMD~~ | ~~4-6 weeks~~ | ✅ Materially complete — boots on modern AMD bare metal; see `local/docs/ACPI-IMPROVEMENT-PLAN.md` for forward work |
| ~~P1: Driver infrastructure~~ | ~~8-12 weeks~~ | ✅ Complete — redox-driver-sys + linux-kpi + firmware-loader + pcid /config + MSI-X (compiles) |
| ~~P2: AMD GPU display~~ | ~~12-16 weeks~~ | 🚧 Partial — redox-drm + bounded Red Bear AMD display glue build; imported Linux AMD DC/TTM/core remain builds and included in redbear-full (2026-04-29); Intel driver compiles, no HW validation |
| ~~P3: POSIX + input~~ | ~~4-8 weeks~~ | 🚧 Build-side work substantially complete — the relibc source fork carries the bounded fd-event, semaphore, and waitid compatibility surface needed by current downstreams, while broader runtime validation and input-stack maturity remain open |
| P4: Wayland compositor | 4-6 weeks | 🚧 Partial — libwayland/Qt6 Wayland/Mesa EGL+GBM+GLES2/Qt6 OpenGL now build, but compositor/runtime validation is still incomplete |
| ~~P5: DML2 enablement~~ | ~~partial~~ | 🚧 Historical DML2 config work landed, but the current retained AMDGPU build no longer treats imported DML2/TTM as part of the default bounded compile path; libdrm amdgpu ✅, `iommu` daemon now builds; hardware validation still open |
| P6: KDE Plasma | 12-16 weeks | 🚧 In progress — Qt6 ✅, KF6 32/32 ✅, Mesa EGL/GBM/GLES2 ✅, kf6-kcmutils ✅, kf6-kwayland ✅, kdecoration ✅, KWin 🔄 building |

### Canonical Desktop Path (current plan)

The current execution plan uses a three-track model with new Phase 1–5 numbering:
- **Phase 1:** Runtime Substrate Validation (4–6 weeks)
- **Phase 2:** Wayland Compositor Proof (4–6 weeks)
- **Phase 3:** KWin Desktop Session (6–10 weeks)
- **Phase 4:** KDE Plasma Session (8–12 weeks)
- **Phase 5:** Hardware GPU Enablement (12–20 weeks, parallel with 3–4)

See `local/docs/CONSOLE-TO-KDE-DESKTOP-PLAN.md` for full detail.

**Total to software-rendered KDE Plasma**: 22–34 weeks (~6–8 months) with 2 developers.
**Total to hardware-accelerated KDE Plasma**: 34–54 weeks (~8–13 months) with 2 developers.

### Critical Path
```
Phase 1 (runtime substrate) → Phase 2 (software compositor) → Phase 3 (KWin session) → Phase 4 (KDE Plasma)
                               Phase 5 (hardware GPU, parallel with Phases 3–4)
```

### Custom Crates (P1/P2)
1. `redox-driver-sys` — `local/recipes/drivers/redox-driver-sys/source/` — Safe Rust wrappers for scheme:memory, scheme:irq, scheme:pci + hardware quirks system (`src/quirks/`)
2. `linux-kpi` — `local/recipes/drivers/linux-kpi/source/` — C headers translating Linux kernel APIs → redox-driver-sys; includes `pci_get_quirk_flags()` C FFI for quirk queries. **GPU and Wi-Fi drivers only — linux-kpi does NOT cover USB.** It provides PCI, DMA, IRQ, DRM, networking (ieee80211/nl80211/mac80211), firmware, and related kernel infrastructure headers, but contains zero USB headers, USB device ID tables, or USB driver implementations.
3. `redox-drm` — `local/recipes/gpu/redox-drm/source/` — DRM scheme daemon (AMD + Intel drivers); consumes quirk flags for MSI/MSI-X fallback and DISABLE_ACCEL
4. `firmware-loader` — `local/recipes/system/firmware-loader/source/` — scheme:firmware for GPU blobs
5. `amdgpu` — `local/recipes/gpu/amdgpu/source/` — AMD DC C port with linux-kpi compat; can query quirks via `pci_has_quirk()` FFI
6. `redbear-sessiond` — `local/recipes/system/redbear-sessiond/source/` — Rust D-Bus session broker exposing `org.freedesktop.login1` subset for KWin (uses `zbus`)
7. `redbear-dbus-services` — `local/recipes/system/redbear-dbus-services/` — D-Bus activation `.service` files and XML policy files for system and session buses

All custom work goes in `local/` — see `local/AGENTS.md` for fork model usage.

## NOTES

- Build requires Linux x86_64 host, 8GB+ RAM, 20GB+ disk
- QEMU used for testing (make qemu). VirtualBox also supported
- The `repo` binary (cookbook CLI) may crash with TUI in non-interactive environments — use `CI=1`
- No git submodules — external repos managed via recipe source URLs and repo manifests
- Historical integration report removed (2026-04-16); see `local/docs/CONSOLE-TO-KDE-DESKTOP-PLAN.md` for current state

## WARNING POLICY

When presented with a compiler warning, linker warning, runtime warning, or test warning, the
project treats it as a signal requiring action — not as noise to be silenced or deferred.

- **Investigate** every warning. Understand what causes it and whether it indicates a real defect.
- **Fix the root cause** when feasible. Prefer comprehensive fixes over workarounds.
- **Suppress only as last resort**, with a comment explaining why the warning is known-safe and
  why suppression is the correct choice for that specific case.
- **Never ignore warnings silently.** An unexplained warning in the build is a defect in
  discipline, not just in code.

This applies to all subsystems: kernel, relibc, drivers, userspace daemons, and build tooling.

## SUBSYSTEM PRIORITY AND ORDER

Red Bear OS should treat low-level controllers, USB, Wi-Fi, and Bluetooth as first-class subsystem
targets.

For PCI interrupt plumbing, IRQ delivery quality, MSI/MSI-X follow-up, low-level controller
runtime-proof sequencing, and IOMMU/interrupt-remapping quality, the canonical current plan is:

- `local/docs/IRQ-AND-LOWLEVEL-CONTROLLERS-ENHANCEMENT-PLAN.md`

Use that file as the execution authority and current robustness judgment for PCI/IRQ work. Higher-
level summaries in `README.md`, `docs/README.md`, and this file should stay aligned with its
validation language rather than acting as competing rollout plans.

Current execution order:

1. low-level controllers / IRQ quality / runtime-proof
2. USB controller and topology maturity
3. Wi-Fi native control-plane and one bounded driver path
4. Bluetooth host/controller path
5. desktop/session compatibility layers on top of those runtime services

Current blocker emphasis:

- low-level controller quality blocks reliable USB and Wi-Fi validation
- USB maturity blocks the realistic first Bluetooth transport path
- Wi-Fi and Bluetooth should not be treated as optional polish; both remain missing subsystem work
  that must be implemented fully, but in the right order