Merge pull request 'Spec: prefer one local model for all roles; record host sharing, park vision' (#54) from spec-shared-inference-host into main

Reviewed-on: dongar/nisse#54
Reviewed-by: Don Garrett <dgarrett@acm.org>

docs/Architecture-Build-Spec.md

@@ -1414,6 +1414,38 @@ The rest resolve when reached, not now.
   and ticket-driven ops work already require one. Whether every gated work item
   needs one (for instance, an ops question that turns into a change to make)
   is best settled once C2's step sequences are in use.
+- **Open: sharing the local inference host between agents.** Each agent keeps
+  one active work item (0.2), but `nisse-dev` and `nisse-ops` are separate agents,
+  and both send their local roles through LiteLLM to the one 24GB host. llama-swap
+  there keeps one model resident at a time. If the two agents' local roles map to
+  different models, interleaved requests reload weights on every switch (10–60 s
+  each), and each agent waits on the other's loads. LiteLLM's per-key rate limits
+  don't address this: they cap one key's throughput rather than share the host,
+  and know nothing about which model is loaded. (Measured 2026-09-28: they only
+  throttled the benchmark, and the token limiter leaked until LiteLLM restarted.)
+  - **Preferred: one local model for every local role.** No swaps at all. It
+    needs one model good enough as the dev executor and for ops' Home Assistant
+    tool calls. The executor benchmark and the ops evaluation decide whether one
+    exists. More agents are planned for other jobs, which makes one shared model
+    more valuable still, and OpenSCAD and video work would add vision (next
+    item).
+  - **Fallback: agents tag in and out.** If no single model fits, the agents
+    coordinate their use of the host rather than interleave: an agent holds the
+    host for a stretch of work on its model, then hands it over, so a swap happens
+    per hand-over rather than per request. Two models co-resident (llama-swap
+    groups), where VRAM allows, can reduce how often that's needed. How the
+    hand-over works (a lease, a queue, or priority for ops alerts) is only worth
+    designing if the preferred option fails.
+- **Parked: vision.** OpenSCAD development needs it: the language describes 3D
+  parts, and the only way to check a change is to render it and look. That work
+  may belong to `nisse-dev` or, being different enough from ordinary code, to an
+  agent of its own; undecided. Video-file management, planned for a future
+  agent, needs it too. Ordinary code work doesn't. The local candidates on
+  the 4090 host already accept images, and video as sampled frames, but the agent
+  code is text-only. Building it will need tools that return images, image content
+  in canonical events (A10) and both renderers, storage that keeps the durable log
+  (A2) small, and image tokens in the context budget. How well a model sees is
+  measured when that work starts, not before.
 
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