Harness composer control never renders in the hub-client posture — the effect chain's server.current guard never fires #1799

Acceptance Criteria

• The root cause is named precisely: which guard, in which file of the effect chain, and why it is never-true in the hub-client posture — recorded in the slice's return, not guessed.
• A test drives the control's mount path in the hub-client posture (the framed app's server context as P4 builds it) and fails on the old guard, passes on the fix.
• In the local posture the control's behavior is unchanged (fetch fires, control mounts, "route absent → stays hidden" degradation holds).
• The live panel's reply-path and stream-cycle instrumentation (unbranched, baked into the live dist) is absorbed into source or reverted for any file this slice touches — never left orphaned in a rebuilt dist.
• Zero new failures in the app suite (the known lane baseline stands).
• Post-deploy confirmation (the director's probe, after the deploy decision): pickers.mjs shows the /amicode/harness request firing and the control rendered.

Testing Decisions

The unit/integration test in the app package is the slice's gate; the macbook probe is the director's post-deploy end-to-end confirmation (the live dist does not change until a deploy decision). Extend the existing control/composer suites — reuse-first.

Key Decisions

• The fix is posture-correct, not guard-deleted: the control must render for the hub-client posture; if the guard existed to protect a posture-specific state, replace it with the correct posture check — never delete a guard to make a widget appear.
• The probe repro may be run read-only from the hub (ssh -o BatchMode=yes macbook, the harness dir, node at /opt/homebrew/bin/node) to observe the RED state; it cannot show green until the deploy.

Constraints & Invariants

• No engine changes; no new routes; no deploys (the live plane is HITL — Aaron's).
• The "route absent → stays hidden" degradation contract holds: when the engine does NOT serve /amicode/harness, the control must stay hidden gracefully (the stock-engine case).

Prior Art

• The #1549 harness exception at the panel origin (the extension proxies GET/POST /amicode/harness to the engine when bound) — the route-reachability half already works.
• The P4 hub-client posture (feat(extension): the hub-host client posture — amicode.hubServerUrl spawns nothing, the panel becomes one server (#1760 P4) #1784) — how the framed app's server context differs from the local posture.
• The S2 precedent for absorbing unbranched dist instrumentation (question-reply markers → owned telemetry, S2: the question inbox — every pending question, answerable without opening the session #1786).

Source

Filed from the 2026-10-14 batch approval, riding with #1798's Phase A. Suspected guard: server.current in the posture-era framed app.

Notes

The probe script pickers.mjs and its sibling harness live on macbook at /tmp/opencode/panel-probe/ — page errors that mention aarmoniqs (typo'd directory param) are probe bugs, not server bugs.