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ADR-0095: SWI-Prolog is built from pinned source into a fixed project-owned prefix, and the runtime path leaves guix

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The record

Status: Accepted · Date: 2026-10-12 · Ruled: 2026-10-12 (Mohamed: "agreed")

Context

• The directive. Mohamed, 2026-10-12, verbatim: "why do we need guix, assignment, research installing it guix free".

• Evidence. A read-only measurement on this host, committed as plans/research/2026-10-12-guix-free-toolchain/. It holds REPORT.md, the build scripts, the notes and the logs (2d7dbbcad). Repo facts are from origin/master 22363abb2, which is also what /opt/orchestrata runs.

• What guix supplies to this project. Nothing else is invoked.

  From guix	Used by
  SWI-Prolog 9.3.8, plus its closure (gmp, ncurses, zlib, glibc libm, libgcc_s)	env/toolchain.env:41 (SWIPL=/home/mohamed/.guix-profile/bin/swipl) → the janus build and its RUNPATH; the prod kernel (the only prod unit mapping SWI); 13 bare-swipl call sites; the test container through read-only /gnu/store and ~/.guix-profile mounts (provision_app_container.sh:54-56,93-96,288, infra/terraform/test_fleet.tf:88-103)
  age / age-keygen 1.3.2	scripts/secrets_cli.py, external-tools gate
  direnv 2.37.1	.claude/hooks/ast-incremental-refresh.sh:97, deploy/install-claude-config.sh:189
  incusd 6.15	/etc/systemd/system/incus.service (untracked); runs every Incus fleet

• The cost of the current arrangement. ADR-0091 keeps the SWI path alive against guix gc. Even so, a garbage-collected store path took prod governance down 13:00→22:51 on 2026-10-11 (env/toolchain.env:27-29).

• Measured guix-free (REPORT.md §2-§4).

  • SWI 9.3.8 builds from tag V9.3.8 (dfe256b5434fd62af33aeff162f9127dd365125d plus 7 pinned submodule commits). It needs only distro gcc 14.2.1, cmake and ninja, and no sudo. Packages clib;http;nlp;plunit;sgml;ssl;zlib; real 0m41.851s; 9.9 MB.
  • It loads the same 26 libraries as guix's 9.3.8, with identical output.
  • janus rebuilt with scripts/build_janus_ft.py and setup.py unchanged shows 0 guix paths under /usr/bin/ldd. The real tests pass: tests/core/test_janus_bootstrap.py 28, test_prolog_worker_parallel.py 3, toolchain guards 14, test_build_janus_ft.py 24.
  • age and direnv are published as static upstream binaries whose sha256 equals the GitHub digest.
  • incusd has no OpenMandriva package and no upstream daemon binary.
  • There is no published 9.3.8 tarball (404). The pin is the git tag plus submodule commits.

• A live hazard measured on the way. janus takes its SWI home from the first swipl on PATH. With a 10.0.2 swipl first, a 9.3.8 janus aborts: boot.prc: incompatible VM-signature, rc 134 (REPORT.md §3.10, case E). This is the crash provision_app_container.sh:211-217 recorded on 2026-08-29. Setting SWI_HOME_DIR, or putting the 9.3.8 bin first, prevents it (cases F and G).

Decision (proposed)

1. Own the SWI build.
   • Build SWI-Prolog 9.3.8 from the pinned tag and submodules into a fixed, versioned, read-only prefix outside every deploy root: /opt/orchestrata-toolchain/swipl-9.3.8.
   • Set CMAKE_INSTALL_PREFIX to that final path, with the REPORT.md §3.3 flags.
   • Mirror the source archive and record its sha256 in a committed pin file.
   • A committed toolchain script builds and verifies the prefix (version, pin, checksum). The installers refuse to proceed when it is absent or does not match.
2. Declare it. env/toolchain.env SWIPL names the prefix's bin/swipl. janus is rebuilt everywhere; scripts/_janus_patched/setup.py keeps its absolute RUNPATH.
3. Make the SWI home unambiguous.
   • Every unit and container override puts the prefix bin first on PATH.
   • The kernel unit also sets SWI_HOME_DIR to the prefix's lib/swipl.
   • A test asserts the home janus resolves equals the declared prefix.
4. age and direnv come from the pinned upstream static binaries (sha256 in REPORT.md §2). The install hints in pyproject.toml:146,148 and scripts/install_janus_ft.sh:207 are updated.
5. Test container.
   • The same prefix sits at the same path in the container, copied in the way D44 copies the code.
   • The guixstore and guixprofile devices, their allow-list entries and GUIX_PATH_PREFIX are removed.
   • The Arch swi-prolog package no longer decides anything, because the prefix bin comes first.
6. incusd stays on guix as a scoped exception until a separate ADR decides its source. No guix-free option was measured for it.
7. SWI 10.x is a separate, measured upgrade. REPORT.md §3.11 shows the janus tests also pass on 10.0.2, with two observed behaviour differences.

If accepted, this supersedes ADR-0091 for SWI-Prolog.

Alternatives rejected

• An OpenMandriva package. None exists for swi-prolog, age or direnv.
• Each environment's distro swipl. The host has none. The container has 10.0.2 while janus is built for 9.3.8, which aborts (case E). The copied venv also needs identical paths.
• $ORIGIN RUNPATH for a relocatable prefix. Measured rc 134 and rc 127 unless every process sets SWI_HOME_DIR, because SWI finds its home from PATH or its compiled-in prefix.
• conda-forge. It has no 9.3.8 and would add a second package manager.
• PyPI. It has no SWI distribution.
• Keep guix with GC roots (ADR-0091). That is the arrangement that failed in prod on 2026-10-11, and it keeps the container tied to the host's store.

Consequences

• Prod, dev and the test fleet resolve SWI from one project-owned path that no package manager can collect.
• A soname change in OpenMandriva's gmp.so.10, ncursesw.so.6, z.so.1 or ssl.so.3 forces a toolchain rebuild. The floors are GLIBC_2.34 and OPENSSL_3.0.0.
• The guix entries in the systemd user manager's PATH become dead entries. Guix remains on the host for incusd until that ADR.
• Not yet measured:
  • the test container end to end;
  • an incusd source build;
  • the janus wheel's byte-reproducibility (two builds differed in the wheel archive, while the .so matched).
• The file-level change list is in REPORT.md §5.

Provenance

• Directive: Mohamed, 2026-10-12 (quoted verbatim in Context).
• Evidence: plans/research/2026-10-12-guix-free-toolchain/REPORT.md and its logs (2d7dbbcad), produced by a read-only research agent. The agent made no repo, unit or container changes.
• Recommendation: accept.
• Related: ADR-0089, ADR-0091, ADR-0092 (the plugin venv; REPORT.md §5 notes a janus-in-lock implication).
• Ruling: Mohamed, 2026-10-12, after a three-line summary (fixed-prefix build of the pinned 9.3.8; age and direnv from pinned upstream binaries; incusd stays on guix pending its own ADR): "agreed".
• ADR-0091 is superseded in part. Its guix-profile source and RUNPATH give way to this prefix. Its SWIPL declaration, its declaration-only build input and its version and RUNPATH checks stand, now pointed at this prefix.

Related ADRs

• Supersedes: ADR-0091
• Also mentioned: ADR-0089, ADR-0092

Rulings cited

None.

Specs cited

None (or no spec page exists for the ones named).