telosnex/fllama_cpp/code-review

Review llama.cpp changes

This skill reviews changes against llama.cpp's conventions and the pitfalls that reviewers flag most often, so the contributor can fix them before a maintainer has to. It has two modes:

• Self-review (default): review the contributor's own local changes (uncommitted work, or a branch vs master) as a pre-PR pass. Ask which if it's ambiguous; default to git diff master...HEAD plus any uncommitted changes.
• Read-only review of a PR/file: if the user points at a PR number or specific files (including code they didn't write), review those and report findings.

In both modes the output is private review notes for the user to read and act on - it is never something to post. This is a hard rule from AGENTS.md: an agent must NEVER write, or help write, a PR comment, a review comment, or a reply to a reviewer, by any means including gh. Do not offer to. If the user asks you to post the notes, refuse and point them at that rule. Present findings in the conversation only.

Before starting, read AGENTS.md and CONTRIBUTING.md if not already in context - the "Coding guidelines", "Naming guidelines", and AI usage sections are the baseline this review enforces. For a diff that adds a new model architecture, also read docs/development/HOWTO-add-model.md and consider the dedicated add-new-model skill.

Step 0 - Scope the diff and pick the checklists

Identify what actually changed and which area checklists below apply. Run git diff --stat (or gh pr view <n> --json files for PR mode) and bucket the touched paths:

• conversion/, gguf-py/, src/models/, src/llama-arch.* -> New model / architecture
• ggml/ (any backend, op, or ggml.h) -> ggml / backend
• include/llama.h and other public headers -> Public API
• tools/server/ -> Server
• tools/ui/ (or the legacy tools/server/webui/) -> WebUI
• tests/, tools/server/tests/, or any other added/changed test -> Tests
• anything else, plus all of the above -> General (always runs)

Always run the Scope and quick-reject gate, the Security review, and the General checklist. Run each area checklist whose paths were touched. Additionally, if the diff introduces a new component, subsystem, or piece of infrastructure (a new file/class/module, a new abstraction, or hand-rolled machinery), run the Approach and design review. Tell the user which checklists you're running and why.

Scope and quick-reject gate (always)

These are the patterns that get PRs closed without a full review. Check them first - a finding here is more important than any code nit, because it can mean the change shouldn't be a PR in its current form at all.

• Is there a prior issue/discussion for this? Features are supposed to start as an issue, not a PR (CONTRIBUTING.md). If this is a nontrivial feature with no linked issue, flag it and suggest opening one first.
• Is it a duplicate of existing/in-flight work? Suggest gh search prs / gh search issues for the feature. Many closed PRs were duplicates of something already queued.
• Is it self-contained and single-purpose? Multiple unrelated changes/optimizations bundled together get sent back to be split. Flag unrelated changes and suggest separate PRs.
• Does it touch multiple ggml backends at once? Initial support should be CPU-only, other backends as follow-ups (CONTRIBUTING.md). Flag CUDA/Metal/Vulkan/etc. changes bundled into a feature's first PR.
• Does it add a new ggml_type / quantization type? That carries a disproportionate maintenance burden and needs the full justification package (GGUF sample upload, perplexity vs FP16/BF16 and similar sizes, KL-divergence data, CPU perf numbers). Absent that, it will be rejected regardless of code quality.
• Is it invasive - new subsystem, core-API reshaping, changes to shared graph/sampler code that other models don't need? Flag it and suggest a discussion with maintainers before investing further.
• Does it add a model-specific CLI argument to any binary (common/arg.cpp, tools, examples) or conversion script (convert_*.py)? Not allowed - model-specific behavior must come from GGUF metadata or be detected automatically, not from a per-model flag.
• Is it niche/vendor-specific in a way that adds a maintenance burden nobody will own long-term? Flag the maintenance-ownership question.
• Is the change semantically correct, or a plausible-looking "fix" that misunderstands the code? Sanity-check the actual behavior, not just that it compiles.
• AI-disclosure: if AI meaningfully contributed, is the PR template's disclosure section filled in? Remind the user. Never suggest writing the PR description or commit message for them.

Security review (mandatory)

Mandatory on every review; any finding here is blocking. Rule of thumb: GGUF metadata, tensor shapes, tokenizer/grammar input, and all server/RPC fields are attacker-controlled - bound them before use.

• Sizes/counts from tensor dims: validate before allocating. Products like ne[i]*nb[i]/nbytes can overflow on crafted dims into an undersized alloc then heap overflow. Overflow checks must run BEFORE the arithmetic they guard - padding/alignment macros wrap to 0 near SIZE_MAX, so a guard after the pad passes.
• GGUF strings/arrays: cap declared lengths and element counts before using them to size a loop or buffer; validate element type and length before casting an array to a pointer or reading fixed indices ([i+1], [0..2]).
• Element-type confusion: casting gguf_get_arr_data() or tensor->data to float */int32_t * needs an element-type check first (gguf_get_kv_type() == GGUF_TYPE_ARRAY then gguf_get_arr_type(); type == GGML_TYPE_F32 for tensors). A UINT8 array or I8 tensor passes every length check, then gets read 4 bytes per element - a nearby length check is not a type check.
• Loaders: GGML_ASSERT on a file-derived value aborts the process; throw instead where the caller already catches (vocab, model loader, clip).
• File-supplied counts indexing fixed arrays: bound any count (e.g. layer/block count into a LLAMA_MAX_* array) before indexing; watch checks that only fire when an optional key is present.
• Declared vs actual array length: check the declared length of a GGUF array against the count actually read, not just against a buffer size.
• Bounds comparisons: flag narrowing casts (size_t->int32_t) and signed/unsigned mixing that can bypass a length check and copy past a buffer.
• Parsed/derived indices: range-check stoi/atoi results and catch parse throws; never use a default or derived token id (EOS/BOS/...) as an index without a bounds check.
• Reused/reserved buffers: recheck bounds after a buffer is shrunk or reused; watch reserve() then index-by-assumed-size, and header fields read before their length is checked.
• Server JSON ints: clamp client-supplied integers (token/discard counts, offsets) to non-negative and an upper bound before they reach index/pointer arithmetic.
• RPC-deserialized fields: treat every field (type/buffer/data/ne/nb/op_params) as hostile - validate before use. Null/zero buffers skipping validation, attacker data pointers, out-of-range type indices, and negative strides sign-extending past a corner-only assert all give arbitrary read/write.
• Lifetime/UAF: flag stored raw pointers to caller/temporary storage, cached pointers to buffers a later free releases, async ops whose source may drop before completion, and structures not invalidated on free/realloc. Null-check conditionally-built or "not required" tensors before dereferencing.

Approach and design (when a new component/infra is introduced)

Run this whenever the diff adds a new component, subsystem, or piece of infrastructure. Reviews too often stop at "does it work" - a diff can be correct and still be the wrong approach, and a messy design costs more long-term than a bug. Evaluate the approach, not just the behavior; raising a cleaner one is a high-value finding, not a nit. If you see a better design, describe it concretely rather than just calling the current one bad.

• Simpler approach upstream: the biggest win is often a different data model or design that removes whole subsystems, not tweaks to the code as written. Complexity must be justified by the problem, not by the first thing that worked.
• Reuse over reinvention: grep for an existing helper, library, object, or mechanism before adding a new one. Reimplementing what the codebase already has reintroduces solved bugs and adds maintenance surface.
• Clear ownership/lifetime: prefer RAII and obvious ownership over manual liveness flags, hand-tracked pointers, and "is it still alive?" checks - manual lifetime tracking is a recurring source of subtle bugs.
• Right-sized machinery: flag redundant, overkill, or heavier-than-needed primitives and abstractions; use the minimum the design actually needs.
• Right structure and fit: a new type should earn its place (split it if it serves two roles); follow existing patterns, idioms, and naming, and avoid constructs the project shuns.
• Root cause vs symptom: fixes layered on fixes signal a design to correct, not guard around.

New model / architecture

See the add-new-model skill and docs/development/HOWTO-add-model.md for the full workflow; this is the review-time subset that reviewers most often catch:

• Don't branch on model.arch when the real dependency is a config/capability value - gate on the hparam/capability, not the architecture enum.
• If the model is a close variant of an existing arch, is the delta justified? Prefer reusing or subclassing the existing arch/model class over duplicating it. A near-duplicate class or src/models/<name>.cpp will be asked to merge with its sibling.
• New tensor names go through tensor_mapping.py, not ad-hoc name matching.
• For QKV, split the activation with ggml_view, not the weight tensor; rely on ggml broadcasting instead of manually duplicating tensors.
• New graph inputs are declared at the top of the graph-build function, not inline where first used.
• Hparams that the model can't run correctly without must be mandatory (hard-error if missing), not read with a silent default fallback. Only genuinely-optional-across-configs values get a fallback accessor.
• New/optional weight tensors (scales, etc.) must route through build_lora_mm and the existing helpers, matching convention - don't leave raw matmuls copied from another arch.
• Don't hack RoPE with a custom sin/cos implementation. If ggml_rope_ext genuinely can't express it, that's an issue for discussion, not a PR.
• Test the quantized-KV path (-ctk/-ctv q8_0), not just default f16 - new speculative/attention features silently break there.
• Preserve existing explanatory comments about model-specific quirks when copying code; note the provenance ("copied from X, with Y added").
• Remove dead code/branches left over from adapting a reference implementation.

ggml / backend