# AMDUAT-FLS/1 — Functional Linkage Surface Specification

Status: Draft | Owner: Architecture | Version: 0.1.1 | Last Updated: 2025-11-30 | SoT: Yes
Tags: [communication, linkage, deterministic]

identity_authority: amduat.programme
lineage_id: L-PENDING-FLS1
doc_code: AMDUAT-FLS/1
code_status: tentative
doc_code_aliases: []

location: /amduat/tier1/fls.md
surface: developer
internal_revision: 2
provenance_mode: full

## Scope

FLS/1 defines the deterministic interface between certified composites, enabling
canonical message exchange and ledger-based completion tracking.

## Elements

* Session Envelope — capability handshake and deterministic scheduler params
* Channel Catalogue — logical channel definitions (request/response/event)
* Message Envelope — COR/1 payload with (channel-id, ordinal, payload-cid, trace-cid)
* Termination Ledger — final ledger of ordinals and status (complete, abandoned, diverged)

## Next Steps

* Specify binary layout in DDS §9 (placeholder)
* Add behavioural requirements in SRS §3.5 for message ordering and error codes.
* Integrate into PH04 traceability register once phase starts.

## Dependencies (pinned drafts)

FLS/1 relies on upstream drafts; consumers MUST treat these versions as pinned
for this spec and handle later changes as upstream drift:

* DDS v0.x (binary layouts for envelopes/ledgers)
* FER/1 v1.x for run evidence (current)
* FCT/1 (Draft) for certification/intent (referenced, not defined here)
* FPS/1 v0.4.3 (Draft) for primitive byte operations

## Evidence (PH04)

PH04 evidence bundles capture the linkage surface scaffolding:

* `logs/ph04/evidence/fls1/`
* `logs/ph04/evidence/fls1-crs/`
* `logs/ph04/evidence/fls1-router/`

Treat these as sealed references; new work requires explicit reactivation.

## Document History

* **0.1.0 (2025-11-01):** Initial draft defining FLS/1 scope, elements, and next steps.
* **0.1.1 (2025-11-30):** Added DOCID header, pinned draft dependencies, and referenced PH04 evidence bundles.