amduat/tier1/fps-1.md

FPS/1 — Functional Primitive Surface

Status: Approved Owner: Architecture Version: 1.0.0 SoT: Yes Last Updated: 2026-02-21 Tags: [primitives, determinism, bytes]

Document ID: FPS/1 Layer: L1 — Deterministic functional primitives over payload bytes

Depends on (normative):

• ASL/1-CORE — Artifact, Reference, hash identity
• HASH/ASL1 — hash family registry
• ADR-006 — deterministic error semantics
• ADR-015 — CAS rejection governance (alignment)

Informative references:

• SRS §12 — Functional Primitive Surface summary

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0. Conventions

The key words MUST, MUST NOT, REQUIRED, SHOULD, and MAY are to be interpreted as in RFC 2119.

FPS/1 defines pure, deterministic operations over canonical byte payloads. The primitives are functional: identical inputs MUST produce identical outputs.

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1. CID Derivation

All primitives produce exactly one output payload and one CID.

The CID for a payload is derived as:

cid = algo_id || H("CAS:OBJ\0" || payload)

• algo_id is an ASL/1-CORE hash identifier.
• For v1, algo_id defaults to HASH/ASL1 SHA-256.
• The domain separator MUST be exactly "CAS:OBJ\0".

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2. Primitives (Normative)

2.1 put

put(payload_bytes) -> CID

Canonical write; identity only. Storage durability is out of scope here.

Errors: ERR_IO_FAILURE, ERR_NORMALIZATION

2.2 get

get(CID) -> payload_bytes

Fetch canonical bytes from a conformant store.

Errors: ERR_CID_NOT_FOUND

2.3 slice

slice(CID, offset, length) -> CID

Extract a contiguous byte range.

Errors: ERR_SLICE_RANGE

2.4 concatenate

concatenate([CID1, ..., CIDn]) -> CID

Join payloads in order.

Errors: ERR_EMPTY_INPUTS

2.5 reverse

reverse(CID, level) -> CID

Reverse payload order at a specified granularity:

• bit — reverse all bits in the payload
• byte — reverse byte order
• word — reverse 2-byte units
• long — reverse 4-byte units

Errors: ERR_REV_ALIGNMENT, ERR_INVALID_LEVEL

2.6 splice

splice(CID_a, offset, CID_b) -> CID

Insert payload b into a at offset.

Errors: ERR_SPLICE_RANGE

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3. Determinism & Closure

• Identical inputs MUST produce identical outputs.
• Inputs are immutable.
• Outputs MUST be valid inputs to any FPS/1 primitive.

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4. Conformance Vectors

The canonical vectors live in:

/amduat/tests/fixtures/conformance/fps_1/

Vectors are required for each primitive and include output bytes and CID.