Replace the transient `session/model-request` mux frame with ordinary durable session state. Occupancy now rides two last-wins projection fields instead of a non-replayable frame that needed removal tombstones and cross-stream fencing. The frame was the only non-replayable class on the mux stream. Because host and mux are independent SSE streams with no cross-stream order, a request emitted before a removal could arrive after `host/session-removed`, and a legitimate request for a new lifecycle reusing the same id could be fenced by a late removal. Fixing that needed a lifecycle generation on every frame; the frame itself was the problem. Removed: the `session/model-request` frame and schema, the `agent/model-request` core event, the ApiProxy measurement point, the client-side telemetry map and removal tombstone, and the synthetic `cancelled` open error used to signal reconnect through the error channel. Added: `request/context`, a log-only session event recording the registration-bound capacity of the route a request resolved to, appended beside `request/header` from the lookup that already prepared the call and skipped when the route is unchanged. Capacity stays out of `EpochHeader` because it is adapter metadata about a route, not an input the request was built from, so it must not join request reconstruction or header equality. The `contextPressure` projection pairs the newest provider-reported prompt size with the newest recorded capacity. The two are deliberately not one atomic request observation: switching models can pair a fresh capacity with the prior route's pressure until the next request reports usage. The figure is a user-facing reference, and this matches how the TUI status line has always computed occupancy.
core/ — product API spine
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The session log, system-prompt assembly, tool registry, agent vocabulary, and concrete loop that form the harness's default control spine. These are product packages — the stable surface plugins and consumers build against.
| Package | Role | ctx key |
|---|---|---|
scope/ |
Scoped-context registration primitive (scope tags, scope-filtered dispatch) | (library — no ctx key) |
session/ |
Event-sourced session log + in-memory store | ctx.sessions |
system-prompt/ |
Prompt-section + tool-schema assembly registry | ctx.systemPrompt |
tools/ |
Scoped tool registry + pre-policy, guards, around-dispatch, post-policy, and final-result observation | ctx.tools |
agent/ |
Agent interface, live registry, process-local initiator scope, agent/* event vocabulary |
ctx.agents |
agent-loop/ |
Concrete plugin implementing the public Agent contract and owning the loop driver |
ctx.agentLoop |
scope/ is the one non-service package here: a dependency-free library (createScope/scopeOf/scopeTarget) the registries and the loop build per-agent scoping on — it sits below session/ and system-prompt/ in the module graph precisely so they can consume it without a cycle.
agent-loop is the one concrete implementation of the agent seam and lives here because it is the harness's default product loop. It runs each driver inside ctx.agents.withInitiator(). Extension plugins depend on agent, including when they need the initiating Agent, and never on agent-loop directly, so the loop stays swappable.
The default composition that wires this spine into a runnable agent lives in examples/agent-spine-demo: one bundle plugin that loads the control spine plus selected default capabilities (timer + llm + sessions + fallback session titles + system-prompt + tools + agents + invariants + the local skill family + tool-bash + workspace-context + agent-loop) and forwards agent-loop's agents list as its own config. It sits in examples/ — ready-to-run demo/reference bundles — not in core/: core/ ships the swappable spine pieces, while a demo bundle picks one concrete composition of them and adds a front door.