Scaffold Op

Arguments

op_name (positional) — manifest key for the op to scaffold, equal to the target cls.__name__ (e.g. CumsumFwdOp).

Contract

• Input: op_name must be present in tileops/manifest/ with status: spec-only and a non-empty source.kernel_map. source.kernel_map is manifest-level source of truth for Op→Kernel dispatch and cannot be derived by the scaffold (dispatch keys are kernel-internal conventions); adding it for a spec-only entry is a prerequisite manifest PR.
• Output: new file at the exact path declared by manifest source.op (e.g., tileops/ops/reduction/cumsum.py), containing the 17 scaffold slots; one-line from .<module> import <ClassName> added to the package __init__.py at that path's parent directory (e.g., tileops/ops/reduction/__init__.py) with a matching __all__ entry. Note: the filesystem package directory (parent of source.op) is not always the same as the manifest family field — for example, CumsumFwdOp has family: scan but lives under tileops/ops/reduction/. Always key paths off source.op, never off family. Plus a side-artefact at .foundry/plan/<op_name>/plan.json carrying the DRY_RUN self-audit (not tracked in git).
• Termination (success): python scripts/validate_manifest.py --check-op <op_name> reports no errors for this op. Warnings are allowed and passed through to the final summary.
• Termination (blocked): any validator error for op_name that the scaffold cannot fix by re-reading the playbook's slot rules. Do NOT commit; report with the failing rows from the validator.
• Constraints:
  • MUST NOT emit family-specific protocol variables (_op_kind, _kernel_key, _kernel_cls, _kernel_handles_padding, _op_name, kernel_cls).
  • MUST NOT emit optional hooks (_pad_value, _validate_dim, _pre_kernel, _post_kernel, _cache_key override).
  • MUST NOT implement the kernel itself.
  • MUST NOT modify tileops/manifest/, tests, benchmarks, or any existing op file.
  • MUST NOT extend scope to a T1 (family-base) subclass — the scaffold is T2 only.

Workflow

stateDiagram-v2
    [*] --> READ
    READ --> PRE_CHECK
    PRE_CHECK --> DRY_RUN
    PRE_CHECK --> BLOCKED: precondition failed
    DRY_RUN --> EMIT: plan.json written
    EMIT --> REGISTER
    REGISTER --> VALIDATE
    VALIDATE --> REPORT
    VALIDATE --> BLOCKED: validator error or §1 drift
    REPORT --> [*]
    BLOCKED --> [*]

DRY_RUN writes plan.json to freeze manifest-sourced facts before codegen. VALIDATE diffs the emitted file against plan.json §1 — any drift is a skill bug, not a manifest issue.

Slot scope

Emit exactly the 17 slots in ops-design-reference.md § Slot Rules: S1–S7, S12–S21. S8–S11 are reserved for T1 thin-wrapper subclasses and skipped.

Out of scope — leave empty:

These gaps surface as NotImplementedError or validator warnings; downstream skills fill them.

Steps

1. READ

Load the manifest entry for op_name:

Before running the snippet, substitute <op_name> with the requested manifest key (the skill's positional argument — agent literal substitution, not shell interpolation):

python - "<op_name>" <<'PY'
import sys
from tileops.manifest import load_manifest

op_name = sys.argv[1]
entry = load_manifest()[op_name]
print(entry)
PY

Extract: family, status, signature.inputs, signature.outputs, signature.params, signature.static_dims, signature.shape_rules, source.kernel_map, source.op, source.kernel, roofline.vars, roofline.flops, roofline.bytes.

Derive the target file path from source.op (e.g. tileops/ops/reduction/cumsum.py). The filesystem package directory is source.op's parent (e.g. tileops/ops/reduction/). Do not use the manifest family field to compute paths — it is a semantic label, and some ops have family distinct from their filesystem parent (e.g., CumsumFwdOp has family: scan but lives under reduction/). Module filename is source.op's basename without .py.

2. PRE_CHECK

• op_name present in tileops/manifest/ → proceed; otherwise BLOCKED ("op not in manifest").
• status field explicitly set to spec-only → proceed; status: implemented → BLOCKED ("op already implemented; use implement-op to migrate"); missing status or any other value → BLOCKED ("manifest entry must declare a valid top-level status; the validator treats status as required").
• source.kernel_map declared and non-empty → proceed; missing or empty → BLOCKED ("manifest entry needs source.kernel_map before scaffolding — add the dispatch map in a separate manifest PR per the trust model; the scaffold cannot invent dispatch keys because they are kernel-internal conventions"). Note: per docs/design/manifest.md, source.kernel_map is only required when status: implemented, so many existing spec-only entries lack it — these are the cases that need the manifest-PR prerequisite before scaffolding can run.
• Every value in source.kernel_map resolves to an importable symbol → proceed; otherwise BLOCKED ("kernel class not found at expected path").
• Target file source.op does NOT exist → proceed; exists → BLOCKED ("target file already present; scaffold would overwrite").

BLOCKED terminations return without writing any file.

3. DRY_RUN

Write .foundry/plan/<op_name>/plan.json with three sections:

Always proceed to EMIT. Empty open_questions is fine.

Skeleton:

{
  "locked_facts": {
    "op_name": "CumsumFwdOp",
    "module_path": "tileops/ops/reduction/cumsum.py",
    "kernel_map": {"cumulative_fwd": "CumulativeKernel"},
    "init_kwargs": [{"name": "dim", "source": "signature.params.dim", "type": "int", "default": -1}],
    "forward_inputs": ["x"],
    "static_dims": {"N": "x.shape[dim]"},
    "roofline": {"flops": "M * N", "bytes": "2 * M * N * elem_bytes"}
  },
  "agent_notes": {"docstring_summary": "...", "kernel_ctor_signature_observed": "..."},
  "open_questions": [{"tag": "needs_human_decision", "topic": "...", "detail": "..."}]
}

4. EMIT

Follow docs/design/ops-design.md § Scaffolding an Op from a Manifest Entry Steps 1-7 in order. For each scaffold slot, read the authoritative rule at docs/design/ops-design-reference.md#slot-sN before emitting.

Key slot pointers (follow the reference, do not re-derive):

If a slot's rule is ambiguous for the given manifest entry (e.g. multi-kernel kernel_map, multiple independent dtype axes, fixed-rank vs arbitrary-rank branching), STOP and surface the ambiguity in the final report instead of guessing. Do not expand scope.

5. REGISTER

Append to the __init__.py at dirname(source.op):

Add matching <ClassName> to __all__, preserving any existing sectioning.

6. VALIDATE

(a) §1 post-check — diff plan.json.locked_facts against the emitted artefacts:

• Parse source.op with ast: extract class name, base, imports, __all__, __init__ kwargs (names / defaults / types in order), forward params, default_kernel_map dict, _static_axes.
• Parse dirname(source.op)/__init__.py with both ast (presence + __all__ membership) and raw text (block placement under # --- <KernelClassName> ops --- when the file uses grouping comments; skip placement check on flat-style files).
• Any locked_facts field mismatch → BLOCKED §1 drift: <field>. Skill deviated from its own contract; fix the emitted file (or revert and restart DRY_RUN if the plan was wrong). Do NOT edit plan.json to match.

(b) Manifest validator:

python scripts/validate_manifest.py --check-op <op_name>

--check-op runs L0–L4 even on status: spec-only. Classify output:

• ERROR → BLOCKED. Copy the row to REPORT. For L2 / L3 parity failures, re-check the emitted _infer_output_shapes / _validate_dtypes against manifest shape_rules / dtype_combos first — likely a mis-emit.
• WARNING → pass through.

Never edit the manifest to silence an error. No parity_opt_out escape hatch. Demote to status: spec-only only when the implementation genuinely cannot conform.

7. REPORT

Status: SUCCESS | BLOCKED
Op: <op_name>
File: <path> (<lines>)
Package registration: <parent-of-source.op>/__init__.py (+1 import, +1 __all__)
Plan: .foundry/plan/<op_name>/plan.json

§1 drift: <none | <field>: <plan> vs <emitted>>
Validator: <N errors, M warnings>
<if BLOCKED, list each blocking error row verbatim>

Warnings:
  - <warning>

Open questions (from plan.json §3):
  needs_doc_fix:      - <topic>: <detail>
  needs_manifest_fix: - <topic>: <detail>
  needs_human_decision: - <topic>: <detail>

Not filled (downstream hand-off):
  - Kernel implementation
  - Optional hooks (family-specific)
  - Family protocol variables (family-specific)
  - _cache_key override (recommended under dynamic shapes)

SUCCESS → commit [Feat][OPS] scaffold <op_name>. BLOCKED → leave tree dirty, return. plan.json persists either way.

Non-goals

• Not a codegen engine — agent procedure. The input/output contract is codegen-compatible.
• Not a migration driver — status: implemented ops use implement-op / align-family.
• Not a kernel scaffold.

If a slot rule is internally inconsistent or cannot be followed mechanically, file a doc issue and BLOCK; do not invent slot behaviour.