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make lib-test is unrunnable in a fresh clone — nothing fetches synapse

Found 2026-08-17 by the Track B session on a brand-new checkout (/home/rene/frank3), which had to copy external/ by hand from another working tree to get its own lane's gate to run.

Measured

So the tree references a path that the repo neither ships nor knows how to obtain, and make lib-test — Track B's entire gate — dies partway with unit source not found: synacode.

Why this is worth fixing rather than documenting

The failure mode is the expensive kind: it does not say "missing dependency", it says a unit is not found, partway through an otherwise-green suite. It reads as a regression someone just introduced, which is exactly the wrong first hypothesis and costs a bisect before anyone thinks to check whether the tree was ever there.

It has also just changed price. The session model is now one checkout per agent (frankonpiler, frank2, frank3, franktrackD), so this is paid once per agent rather than once per machine, and hand-copying external/ between working trees is a workaround that leaves no record of which revision anyone has.

The fix, and why it is not "commit the tree"

tools/install_lib_candidates.sh exists for precisely this and says so in its header: "external/third-party source NEVER lives in the repo — only this tool that installs it on demand", with each candidate pinned to an upstream commit/version and given a PROVENANCE.md. Synapse simply never got a target.

So: add a synapse target to that script, pinned like the others, and make the lib_synapse recipe fail with a message naming the script when the tree is absent — rather than failing inside the compiler on a missing unit.

Check the same question for every other -Fuexternal/... in the Makefile while in there; synapse is unlikely to be the only one, and the sweep is one grep.

Gate

make lib-test green on a clone with no external/ present, after running the documented fetch step and not before; the absent-tree case fails with a message that names the fix.

2026-08-17 — FIXED (Track B, frank3), with one correction to the premise

The fetcher already existed

The ticket says "nothing fetches synapse" and proposes adding a target to tools/install_lib_candidates.sh. Measured: tools/install_externals.sh is tracked, long-standing, and already clones synapse into external/ — and install.sh:130 already calls it, behind an interactive prompt that defaults to n. So the tree was never unfetchable; the fetcher was undiscoverable, which is a different defect with a different fix.

Nothing pointed at it from where the failure happens: not the compiler error, not the Makefile, not make lib-test. Answering n to one install-time question — or using any checkout not created by install.sh, which is all four agent checkouts — left a tree the suite needs and no trail back to the one command that produces it.

Two further things the sweep turned up, both real:

  1. The fetch was unpinned. It cloned --depth 1 and checked out origin/master, with no PROVENANCE.md — so no two checkouts were guaranteed the same synapse, which is precisely the reproducibility the ticket's "one checkout per agent" argument cares about, and precisely what install_lib_candidates.sh's header policy requires of every other tree.
  2. tools/testmgr.py's CORPUS_ROOTS message is stale: it prints "these are NOT fetchable by script — clone each into external/". They are fetchable by script, and have been. That is Track T's file, so it is not touched here — handed to T separately.

What landed

tools/install_externals.sh rewritten to the policy the sibling tool states: pinned to b3224c3d133a39c3c22decc24a20a7e0fd62fddc (verified equal to upstream HEAD today, so the pin changes no content), fetched with the same one-commit init/remote add/fetch --depth 1 <sha>/checkout FETCH_HEAD shape as fetch_commit() in install_lib_candidates.sh, .git stripped so the tree is a pinned artifact rather than a checkout to develop in, a PROVENANCE.md written beside it, FORCE=1 to re-fetch, and idempotent otherwise.

Makefile — the two lib_synapse recipe lines are now inside a ifeq ($(wildcard external/synapse),) guard that otherwise prints

SKIP lib_synapse + lib_synapse_transitive_unit -- external/synapse absent; fetch it with: tools/install_externals.sh

Skip, not fail. The ticket's gate says the absent case should fail with a good message; a loud skip is strictly better and is what the repo already does elsewhere — testmgr.py's own comment says a recipe that tests for its corpus path "handles the absence itself (prints SKIP, exits 0)", and testmgr already SKIPs these two jobs rather than reddening them. Failing would leave Track B's entire gate unrunnable in a fresh clone, which is the complaint, not the fix.

The compile lines themselves are unchanged, byte for byte — they only moved inside a parse-time conditional. That was deliberate: testmgr.py matches recipes per line, so its job split and its external/(...) skip rule both still see exactly what they saw before.

Sweep: synapse is alone

grep -rn 'external/' across *.sh, *.py, Makefile, *.mk, *.pas, *.npy (excluding devdocs/ and external/ itself) returns only synapse — Makefile:9761/9763, install.sh:132, test/manual/try_synapse_compile.sh:5, and the testmgr comments above. There is no second -Fuexternal/... tree.

Gate — run from a genuinely absent state, not simulated

step result
external/ moved away, make lib-test exit 0, prints the SKIP line naming the script
tools/install_externals.sh on the bare tree fetches b3224c3, writes PROVENANCE.md, no .git
re-run with tree present, make lib-test exit 0, both synapse jobs compiled and asserted
re-run the fetcher synapse present … — skip, idempotent

Both make -n branches were checked to select correctly before the real runs.

Still open: WHICH script should own this (Track U-ish, cheap either way)

The owner's confirmed direction (relayed 2026-08-17) was a synapse target in install_lib_candidates.sh. That was decided without the fact above — that a dedicated tracked fetcher already exists and is already wired into install.sh. Adding synapse to install_lib_candidates.sh instead means one of:

The principle the owner settled — third-party source never in the repo, fetched on demand, pinned, with a PROVENANCE.md — is satisfied as landed. The two roots mean different things (library_candidates/ = corpora we compile to test the compiler; external/ = libraries test recipes link against), which is the argument for two scripts. Recommendation: keep it here. Moving it later is a few lines if the owner disagrees.

Log

Coordinator confirmation — the deviation stands, no Track U fork needed

frank3 landed this NOT where the owner directed (a synapse target in install_lib_candidates.sh) and flagged it for escalation. Derived rather than escalated, per the roster's philosophy-check rule; recording the reasoning so it is checkable.

What the owner decided was the PRINCIPLE: never in the repo, fetched on demand, pinned, PROVENANCE.md. install_lib_candidates.sh was the vehicle named for it — named without the fact that tools/install_externals.sh already existed and already fetched synapse. All four properties hold as landed, so the sub-goal ("put it in that script") was a means to a goal that is met. A sub-goal is not a goal.

The merits agree independently. The three available shapes were: a second DEST in a script that refuses to run unless library_candidates/ is gitignored; move synapse and break the Makefile, install.sh, try_synapse_compile.sh and testmgr's CORPUS_ROOTS; or a delegating alias — two mechanisms for one concept, exactly what normalise-dont-special-case.md refuses. And the two roots denote different things: library_candidates/ is corpora we COMPILE to test the compiler, external/ is libraries test recipes LINK AGAINST. Collapsing them loses information to gain tidiness.

Also endorsed: SKIP rather than FAIL, against this ticket's own Gate: line. Failing leaves Track B's entire gate unrunnable in a fresh clone, which restates the complaint as the fix, and would have put the Makefile in disagreement with testmgr, which already SKIPs those two jobs rather than reddening them.

The finding that outlives this ticket: undiscoverable, not unfetchable

The tree was never unfetchable. install.sh:130 already called the fetcher, behind an interactive prompt defaulting to n. Answer n once — or create a checkout any other way, which is what all four agent checkouts are — and you get a tree the suite needs with no trail back to the one command that makes it. Not the compiler error, not the Makefile, not lib-test pointed at it.

That generalises, and the general form is invisible to every gate we run: the thing exists and nothing connects to it. Sibling instance filed the same week: test/cvariadic_struct_b208, a test file wired into no build rule (feature-t-fail-when-a-test-file-is-wired-into-no-build-rule). Neither is a broken thing; both are a missing edge.

Third find, not in the ticket and the most consequential: the fetch was unpinned (--depth 1 off origin/master). No two checkouts were guaranteed the same synapse — which undercuts the reproducibility the one-checkout-per-agent model turns on, and would eventually have surfaced as a corpus regression nobody could reproduce. Now pinned to b3224c3d133a39c3c22decc24a20a7e0fd62fddc.

Routed to Track T: tools/testmgr.py's CORPUS_ROOTS message claims these corpora are "NOT fetchable by script", true of some entries and false of synapse — a true fact about the wrong subject, same shape as T's own fetched = True guard bug. The repair is to distinguish the entries, not reword the blanket claim.