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= Target matrix policy
== Tier definitions
* **Tier 1** — blocks merge. Every tier-1 target must pass the full
prebuilt matrix (build + validate) on every PR that touches the
prebuilt machinery. A tier-1 failure prevents the PR from merging.
* **Tier 2** — best-effort. Tested in CI but a failure doesn't block
merge; the maintainer investigates and either fixes or demotes.
* **Tier 3** — on-request. Not in the default matrix; can be built
locally via `ci/build_prebuilt.sh` but is not shipped in releases.
== Current matrix
[cols="1,1,1,2", options="header"]
|===
| Target triple | Tier | Runner | Notes
| `x86_64-unknown-linux-gnu` | 1 | `ubuntu-latest` | Broadest Linux compatibility.
| `aarch64-unknown-linux-gnu` | 1 | `ubuntu-24.04-arm` | ARM64 server.
| `aarch64-apple-darwin` | 1 | `macos-14` | Apple Silicon; `MACOSX_DEPLOYMENT_TARGET=12.0`.
| `x86_64-pc-windows-msvc` | 1 | `windows-latest` | MSVC via vcpkg; `/MT` static runtime.
| `x86_64-unknown-linux-musl` | 2 | `ubuntu-latest` (alpine) | Static libc; Alpine/Docker.
| `aarch64-unknown-linux-musl`| 2 | `ubuntu-24.04-arm` (alpine) | Static libc ARM64; PR artifact upload skipped (JS-action limitation).
|===
== Support window
* **Linux glibc**: built on the runner's system glibc (currently
Ubuntu 22.04/24.04). Consumers on older glibc (< 2.31) may need to
build from source.
* **macOS**: N-2. Currently 12 (Monterey) + 13 (Ventura) + 14 (Sonoma)
for Apple Silicon; 11 (Big Sur) + 12 + 13 for Intel.
* **Windows**: latest MSVC (VS 2025 on `windows-latest`).
* **Linux musl**: latest Alpine `alpine:latest` at build time.
== Adding a target
To propose a new target:
1. Create `ci/targets/<triple>.env` with all required fields (see
existing files for the template).
2. Add a matrix entry in `.github/workflows/prebuilt.yml` under
`target:` with `triple`, `runner`, and `container`.
3. Run `ci/test_prebuilt.sh` against a locally-built tarball and
confirm ALL CHECKS PASSED.
4. Open a PR; a maintainer reviews and assigns a tier.
== Deprecating a target
1. Announce in `CHANGELOG.md` under the next release.
2. Keep the target in CI for one release cycle (best-effort, tier 2).
3. Remove from the matrix and delete `ci/targets/<triple>.env` in the
following release.