9. Layer 4: Coupling and SVAF Evaluation

9.1 Peer-Level Coupling (Drift)

When a node receives a state-sync frame, it MUST compute peer drift:

Coupling decision based on drift:

9.2 Content-Level Evaluation (SVAF)

When a node receives a cmb frame, it MUST evaluate the signal independently of peer coupling state. Implementations MUST support at least the non-neural evaluation path (cosine-distance SVAF). Neural evaluation is RECOMMENDED. The encoder that maps field text to vectors SHOULD use semantic embeddings (e.g. sentence-transformers) rather than lexical hashing — per-field evaluation quality is bounded by encoder quality (see Section 18.7).

The SVAF evaluation computes per-field drift between the incoming CMB and local anchor CMBs, applies per-agent field weights (α_f), combines with temporal drift, and produces a four-class decision using a band-pass model:

totalDrift = (1 - λ) × fieldDrift + λ × temporalDrift

fieldDrift    = Σ(α_f × δ_f) / Σ(α_f)
temporalDrift = 1 - exp(-age / τ_freshness)

κ = redundant if max(δ_f) < T_redundant  (default 0.10)
κ = aligned   if totalDrift ≤ T_aligned    (default 0.25)
κ = guarded   if totalDrift ≤ T_guarded    (default 0.50)
κ = rejected  otherwise

The redundancy test is the key addition: a signal is redundant if every field falls below T_redundant — meaning no field carries novel content relative to local anchors. If any field is novel (e.g., same topic but different intent), the signal passes. This preserves per-field selectivity while preventing paraphrase accumulation.

Information-theoretic basis: a signal’s value is proportional to its surprise (Shannon, 1948). A signal identical to existing knowledge carries zero information gain regardless of domain alignment. The band-pass model reflects the Wundt curve (Berlyne, 1970): intermediate novelty produces maximal value, while both overly familiar (redundant) and overly foreign (rejected) signals are disengaged from.

If accepted, the implementation SHOULD produce a remixed CMB — a new CMB created from the incoming signal processed through the agent’s domain intelligence — with lineage (parents + ancestors) pointing to the source CMBs. The remixed CMB is stored locally; the original incoming CMB is not stored.

9.3 Mood Field Extraction

Mood is a CAT7 field within the CMB, not a separate frame type. Affective state crosses all domain boundaries — this is the only field with this property.

When SVAF rejects a CMB (totalDrift > T_guarded), the receiving node MUST still inspect the mood field. If the mood field contains a non-neutral value (text ≠ "neutral"), the implementation MUST deliver the mood field — including text, valence, and arousal — to the application layer for autonomous processing. The full CMB is not stored, but the mood field is not lost.

This ensures that a coding agent’s observation “user exhausted after 3 hours debugging” reaches a music agent even though the focus (“debugging auth module”) and issue (“type error in handler”) fields are irrelevant to the music domain. The music agent receives only the mood: "exhausted" (v:−0.6, a:−0.5).

9.4 Coupling Bootstrap (Cold Start)

When two agents connect for the first time, they have no shared cognitive history. Peer-level drift (Section 9.1) will be high — typically > 0.8 — because their hidden state vectors were initialised independently. This is correct behaviour, not a bug. The mesh is conservative by default: unknown peers are cognitively distant until proven otherwise.

However, CMB evaluation (Section 9.2) operates independently of peer coupling state. Even when a peer is rejected at the state-sync level, incoming cmb framesMUST still be evaluated by SVAF on their own merit. A rejected peer can send a highly relevant CMB — SVAF evaluates the content, not the sender’s overall drift.

The bootstrapping path works through two mechanisms:

• —Mood fast-coupling (Section 9.3) — mood is always delivered even from rejected CMBs. Agents that share non-neutral affective state begin influencing each other immediately. This is why agents SHOULD extract genuine mood from their observations rather than defaulting to neutral.
• —Content-driven convergence — when SVAF accepts individual CMBs from a rejected peer (because the content is relevant even though the peer’s overall state is distant), the receiving agent’s cognitive state shifts. Over multiple cycles, this narrows peer drift until the peer crosses into the guarded or aligned zone.

Implementations SHOULD log the distinction between peer-level rejection (state-sync drift) and content-level evaluation (SVAF per-CMB) to aid debugging. A peer may be “rejected” at Layer 4 while its individual CMBs are “aligned” at the content level — this is normal during bootstrap and indicates convergence is in progress.

Cold-start convergence time depends on CMB frequency, field relevance, and mood signal strength. For agents that share domain overlap (e.g., a knowledge agent and a coding agent both in the AI domain), convergence typically occurs within 2–5 CMB exchanges. For agents with no domain overlap (e.g., a fitness agent and a legal agent), convergence may never occur — and that is correct. They couple only through mood.

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