Consolidated. This note's findings now live in ../MIN-STUDIES.md §3, 4. The original is kept for its measurements; do not re-derive from it.

The three units

Young, 2026-10-10: the architecture, stated plainly.

All agents communicate via A2A. The tool is the Opencode CLI — the Arms.

🎯 We are focused on the Heart Unit.

1. ✅ Verified against the registry — it matches exactly

Checked, not assumed. cortex/registry/agents.yaml:

So the registry already encodes this correctly. No change needed — and that is the point of having one source: the statement and the file agree.

2. 🔴 Two docs describe it differently, and they are now corrected

The registry was right and the prose was thin. Two places understated what V3 is:

Why this matters beyond tidiness: V2's own record states it plainly — "SolOSV2 is the Heart Unit's system: the fleet agents that execute" — and V3 is the successor to exactly that. A design that never says whose system it is invites the wrong thing to be built into it. The brain workers were retired precisely because a Brain agent running as a Heart worker was a contradiction (2026-10-10); the docs should make that hard to reintroduce.

So the correction is load-bearing, not cosmetic: Brain runs on Hermes. Heart runs on SolOSV3. V3 is Heart's system, and a Brain agent inside it is a category error.

3. The picture

        PULSE HOST                          LAB HOST
   ┌──────────────────┐          ┌──────────────────────────────┐
   │  1. PULSE        │          │  2. BRAIN       3. HEART     │
   │  on Hermes       │◄────────►│  on Hermes      on SolOSV3   │
   │                  │   A2A    │                              │
   │  Eva · Eve · Tam │          │  Min · Mira · Sol            │
   │  8441-8443       │          │  8311-8313      Ace · Alpha  │
   └──────────────────┘          │                 Atlas · Echo │
                                 │                 Nova         │
                                 │                 8301-8305    │
                                 └──────────────────────────────┘
                                          │
                                          ▼
                                   Opencode CLI (Arms)

Two units share the LAB host and both speak A2A — so the A2A boundary is the only interface between Brain and Heart. That is why the A2A work is the spine and why its defects matter more than any other.

4. 🔴 And the A2A reality, measured — Brain's peers are still misaddressed

All agents communicate via A2A — so the addresses are load-bearing. Checked live in Brain's own config (~/.hermes/profiles/min/config.yaml):

8 peers configured, 8 misaddressed:

And three form a rotation — sol → min → mira → sol. So a call to sol reaches min, and returns success from the wrong agent.

This is the defect the whole Stage 1 exists to prevent, and it is live right now. It is latent only because nothing is calling (all Heart ports return HTTP 000 — nothing listening).

Stage 1.3's proof is exactly this: "a2a_call ace returns ace's identity." Until the peers derive from the registry, every A2A call in the fleet is a coin flip that reports heads.

5. Current state of the three units

So: Brain is up, Arms is up, and Heart is the thing we are building. That matches the focus statement exactly.

6. What this fixes in the plan

Nothing in the plan changes — the registry already agreed. Two things are sharpened:

1. Scope now states whose system V3 is, so a Brain-in-Heart component is visibly wrong rather than merely discouraged.
2. The A2A misaddress is confirmed live and 8/8, which raises Stage 1's priority: it is the one defect that is already present in the running system, not a risk for later.

Not established

• Pulse was not probed. Its host is separate and out of LAB scope; the 8441-8443 ports were checked on LAB and return HTTP 000, which is expected.
• The A2A misaddress was read from config, not exercised — no call was made to a wrong peer, because nothing is listening to receive one. The rotation is inferred from the port map, which is how the original defect was found.
• Heart's runtime does not exist, so "all agents communicate via A2A" is currently true of Brain only.