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Ecosystem review — round 5, F1 (llama.cpp on Vulkan)

Four repositories, one lane carried from an engine primitive to generated text on a machine with no GPU. Written against the measurements, not the intent.

repository change state
mcpp-index compat:spirv-headers@1.4.357.0 merged (#358), CN mirror byte-identical
mcpp two engine fixes, the example regrouping, two new checks PR #576
llama.cpp-m backend-vulkan, released as b10069.1 PR pending mcpp's release
mcpp-plugins none needed 0.2.0 already carries the glslc route

What was actually verified

Not "it built". The criteria, and what each can say no to:

  • The device computed the right thing. The device decode and the host decode of one prompt under greedy sampling produce the SAME token (471), and the offload is asserted from llama.cpp's own log FIRST -- without that, two host decodes agree trivially. A token merely inside the vocabulary is produced by a backend that computed nonsense.
  • The shaders are graph edges. 136 declared action rules for 134 vendored shaders plus the generator and the header; 134 generated sources joined the compile set; ar t libllama.a carries 134 shader objects. A build program that looped would leave the same artifacts and no edges.
  • The feature costs a CPU consumer nothing. With the lock removed, a CPU-only build writes no mcpp.lock at all: it resolves nothing.
  • The artifact's host surface. ldd outside the mcpp registry: the kernel's vDSO and the Khronos loader this ecosystem builds from source.
  • The published form. V5 section F builds a consumer that declares the dependency and the feature and nothing else. Red until the index entry lands, by construction.

The defects this round produced

Seven, none reported by a pre-existing test; six found reviewing work written in this same round.

where defect what surfaced it
mcpp engine [feature-xlings] tool installed and then invisible to xpkg_dir building the backend
mcpp engine [feature-deps] shared library compiled and then left off the link line the same build, at link
mcpp manifest the version warning predicted a failure it cannot see V5's own output
llama.cpp-m the manifest claimed a platform refusal the code did not make reading the comment against the code
llama.cpp-m a probe that failed for any other reason reported "supported" reading upstream's rule
llama.cpp-m a warning quoting a diagnostic truncated at the first newline the directive channel is line-based
llama.cpp-m -static not portable between the compilers; the clang variant that links SEGFAULTS building under --toolchain llvm@22.1.8

The two engine defects are one shape: an answer resolved and never wired to the decision that reads it. Neither had a diagnostic, and the second was quiet because of its SHAPE -- a library package's mcpp build produces an archive, and an archive resolves no symbols.

Two of my own criteria were pointed at the wrong object

Both would have shipped as green.

  • e2e 615, first draft. With a binary root it passed on both the defective and the fixed engine -- measured. A fixture built around mcpp run was a test that could not fail. The defect needs a library root whose test binary links.
  • V5 section C, first draft. It grepped resolution.json, which records the machine environment's runtime binding and names mesa-lavapipe whether or not the project asked for it. mcpp.lock records what the project resolved.

Stated rather than fixed

  • backend-vulkan needs libstdc++ on this checkpoint -- upstream destroys a std::unique_ptr<vk_memory_logger> where the class is forward-declared. Deliberately not refused: the distinction a refusal needs (which standard library the project resolved) is not something mcpp hands a build program, and the compiler's name would refuse clang with libstdc++, which works. That gap should land WITH its consumer, not as a field nobody reads.
  • ggml excludes a software Vulkan device on TYPE -- lavapipe advertises every required feature and is dropped for being eCpu. Upstream's policy, upstream's selector.
  • Two local e2e failures are machine state. Both reproduce on the binary predating every change here, and ci-linux-e2e is green on the base commit.

Verdict

The lane is complete and the evidence is behavioural at every layer. Each engine fix has a criterion that exits 1 on the previous binary and 0 on this one, measured with the two binaries side by side.

Remaining risk is entirely the release chain, whose order is forced: mcpp must be installable before llama.cpp-m's CI can be green, and llama.cpp-m must be tagged before the index can name it.