PROTOCOL.md

cis2-conformance stdin/stdout protocol

This documents the exact wire contract a third-party binary must implement to be checked by cis2-conformance (source: src/bin/cis2_conformance.rs in this repo — reading that source is NOT required to implement a conforming binary; this document is the full contract). No knowledge of this repo's Rust code, src/math.rs, or src/main.rs is required either; only this document and tests/conformance/README.md (which documents the per-op field layout of each vector file).

Running the checker

cargo run --release --bin cis2-conformance -- /path/to/your-binary

or, against an already-built cis2-conformance:

cis2-conformance /path/to/your-binary

This runs every tests/conformance/vectors/*.txt / *.expected pair against your-binary, invoking your-binary once per vector, and prints a PASS/FAIL line per vector plus a final summary. Exit code is 0 if every vector passed, 1 otherwise (including if your-binary fails to launch, times out, or produces unparseable output on any vector).

Per-vector invocation

For each <name>.txt file under tests/conformance/vectors/:

1. cis2-conformance spawns your-binary with one argument: the vector's op= value (e.g. your-binary rmsnorm, your-binary attention_block). This lets an implementation dispatch without having to inspect the input first, but is redundant with the op= line inside the input itself (both are provided; a conforming binary MUST accept either identically-valued source, or ignore argv and parse op= from stdin — both are conformant, since they are guaranteed to agree).
2. cis2-conformance writes the entire raw byte content of <name>.txt to your-binary's stdin, unmodified (same key=value text format documented in tests/conformance/README.md), then closes stdin (EOF).
3. your-binary MUST:
   • Parse the key=value lines per tests/conformance/README.md's general format and the specific field layout documented there for that vector's op= value.
   • Compute the primitive named by op=, per the cited spec_ref= section of docs/CIS2_SPEC_v0.2.md, exactly (bit-for-bit — no tolerance, no "close enough": every operation in the cited section must be reproduced in the exact order and association specified, including strict left-to-right reduction (§5.1/§5.3), no fused-multiply-add, and the pinned transcendental routes (§6)).
   • Write to stdout, before exiting, exactly one line of the form:

     out_sha256=<64 lowercase hex chars>
     

     computed as SHA-256 over the concatenation of each output element's 4 raw IEEE-754 binary32 bytes, little-endian, in index order — the same convention tests/conformance/README.md and src/math.rs::table_digest use (out_sha256 in each .expected file is exactly this digest).
   • Optionally also write a second line out_bits=<comma-separated 0x-prefixed 32-bit hex> (same convention as .expected's out_bits) — cis2-conformance will report it in diagnostic output on a mismatch if present, but only out_sha256 is checked for pass/fail.
   • Exit with status 0 on success. Any nonzero exit status is treated as a FAIL for that vector regardless of stdout content.
4. your-binary MUST NOT read any file from disk, make any network call, or depend on any state outside its own stdin — every input the computation needs is in the .txt content on stdin. This is what makes the suite runnable against an arbitrary black-box binary with no shared filesystem layout assumptions.
5. cis2-conformance compares your-binary's out_sha256= line (trimmed, case-insensitively) against the pinned out_sha256= field of <name>.expected. Match is PASS; anything else (missing line, mismatch, nonzero exit, timeout, unparseable stdout) is FAIL, with a diagnostic printed to cis2-conformance's own stdout.

Example: one full stdin blob

For rmsnorm_v1, your-binary rmsnorm receives on stdin exactly the byte content of tests/conformance/vectors/rmsnorm_v1.txt (see that file), and must write to stdout:

out_sha256=f712eda3e8b49d3d84639db584c134fe265f7994a21dede9f401d7be9bc5e60c

(optionally preceded or followed by an out_bits=... line), then exit 0.

Timeouts

cis2-conformance allows each vector invocation up to 10 seconds wall-clock before treating it as a FAIL (timeout). Every vector in this suite is small (hand-sized inputs, no model weights), so a conforming implementation should return in well under a second; the timeout exists only to keep a hung or blocking candidate binary from stalling the whole run.

What this does NOT cover

This protocol checks individual normative primitives in isolation (one RMSNorm call, one RoPE table, one exp_pinned evaluation, one attention block, one matvec) — it is deliberately narrower than the full end-to-end §13.1 witness digest in EXPECTED_DIGESTS.md, which requires loading the actual SmolLM2-135M weights and running a full forward pass. Passing every vector here is necessary but not sufficient evidence of full-model conformance.