fix(deps): a cold home can install gcc again, and CI can see it when it cannot (2026.8.10.2) - #526
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…it cannot (2026.8.10.2) 2026.8.10.1 began filling `dependency_store_roots` on every install, and shipped libxpkg 0.0.55 in the same release. Either alone is inert; together they executed a path where `dep_install_dir` gated on how specific the QUERY was rather than on whether the ANSWER was unique. Six of the seven call sites in xim-pkgindex returned nil: gcc and meson could not install on any cold home -- new machines, cold CI caches, `fresh-install`, and every downstream mcpp build -- while godot silently fell back to the host's GL and the graphics banner reported `unknown`. The fix is libxpkg 0.0.56 (`resolved_dep` judges ambiguity, which its own uniqueness guard already decided, and matches the version half as the RANGE a recipe actually writes). This commit takes that dependency and adds the thing that was missing on this side: a way to notice. **E2E-79, and why it has to be cold.** A warm home skips the install, so the config hook never runs -- which is exactly why every lane here stayed green while the released binary could not install a toolchain. The first detector was a downstream repo's cache miss. This test is that detector, in-tree: a consumer declares a namespaced ranged coordinate, the resolver places the dependency, and the hook must find it. Verified against both builds -- it fails on libxpkg 0.0.55 with "this is #524" and passes on 0.0.56. It also pins the other half of the contract, with a second consumer that asks for something it never declared: that must fail, name the coordinate, and say it is not a declared dependency. "Cannot answer" and "is not installed" made the same nil for a whole release, and that is what sent the bug report looking for a missing glibc that was sitting on disk. **`.agents/tools/repro-dep-install-dir.sh`** replays all seven real call shapes against any libxpkg revision offline -- no network, no install, no home touched. It reads the file out of git, and takes `worktree` for an uncommitted one, because otherwise a fix that is not yet committed tests as if it did not exist. Root cause, blast radius and the #525 analysis: `.agents/docs/2026-08-10-issue-524-525-root-cause-and-fix-design.md` Task graph and cross-repo order: `.agents/plans/2026-08-10-issue-524-525-implementation.md` Refs #524, #525
… costs The cross-build lane went red on main, not just here. mcpp 2026.8.10.1's host toolchain post-install fixup binds `glibc@2.39` while the resolver installs 2.44 -- latest since xim-pkgindex#582 -- and refuses to fall back. Established by re-running ONE unchanged run id across the index bump that made mcpp 2026.8.10.1 latest (xim-pkgindex#588, 01:55Z): the same commit passed with mcpp 2026.8.8.4 at 19:09 and failed with 2026.8.10.1 at 03:41. Same workflow, same runner image. Also reproduces locally against UNMODIFIED libxpkg 0.0.55, which is what rules out this branch as the cause. Filed as mcpp-community/mcpp#406. The pin is temporary and it is not free: this job takes the latest mcpp on purpose, to be the canary for exactly this. Pinning it muzzles the canary, so the comment names the removal condition rather than sitting there as an unexplained version. Until #406 lands, breakage against the newest mcpp is invisible on this lane. Also adds the 2026.8.10.2 release notes.
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Fixes #524. Ships the client half of #525's fix chain.
What happened
2026.8.10.1 began filling
dependency_store_rootson every install, and shipped libxpkg 0.0.55 in the same release. Either alone is inert; together they executed a path wheredep_install_dirgated on how specific the query was rather than on whether the answer was unique.Six of the seven call sites in xim-pkgindex returned nil. gcc and meson could not install on any cold home — new machines, cold CI caches,
fresh-install, and every downstream mcpp build. godot silently fell back to the host's GL; the graphics banner reportedunknown.The resolution fix is libxpkg 0.0.56 (openxlings/libxpkg#40). This PR takes that dependency, bumps the version, and adds the thing that was missing on this side: a way to notice.
Why CI could not see it
A warm home skips the install, so the config hook never runs. Every lane here stayed green while the released binary could not install a toolchain — the first detector was a downstream repo's cache miss.
E2E-79 is that detector, in-tree: a consumer declares a namespaced ranged coordinate, the resolver places the dependency, and the hook must find it on a genuinely cold home. Verified against both builds:
It also pins the other half of the contract with a second consumer that asks for something it never declared: that must fail, name the coordinate, and say it is not a declared dependency. "Cannot answer" and "is not installed" produced the same nil for a whole release — that is what sent the bug report looking for a missing glibc that was sitting on disk.
Offline reproduction
.agents/tools/repro-dep-install-dir.shreplays all seven real call shapes against any libxpkg revision — no network, no install, no home touched.It takes
worktreeexplicitly because every other form reads the file out of git, and an uncommitted fix otherwise tests as if it were not there — which reads as "my fix does nothing" rather than "I forgot to commit".Documents
.agents/docs/2026-08-10-issue-524-525-root-cause-and-fix-design.md.agents/plans/2026-08-10-issue-524-525-implementation.mdRelease order
libxpkg 0.0.56 must be published before this merges —
mcpp.lock's hash is recomputed from the published artifact.Companion: openxlings/xim-pkgindex#589.