Moving the agent plane behind presets left two readers on the wrong side of the host/agent line. `dsh-token-meter` was disabled on the host and mounted inside each preset's `compaction` realm, but its three projection units register into the process-wide `sessionProjections` table. A unit registered from one preset answers for every session, so whether a `minimal` session showed a context meter depended on whether some other session had mounted `standard` since boot, and a process that only ever ran `minimal` showed none. The meter takes no configuration, keys every fold by Session, and registers no tool or prompt section, so it returns to the host composition and leaves the presets' `isolate` map; the realm and `compact-basic` stay, because what a preset chooses is whether its agent compacts, not whether its tokens are counted. Nothing named an agent that joined no preset. The join is a scope-parent link, and without it the tools, prompt-section, and skill views resolve the empty global layer: the agent publishes, the turn runs, and the model receives nothing. `AgentPresets` now logs one warning per such agent while a roster is configured, and the invariant companion fails outright — at `system-prompt/assemble` rather than at publication, because an unjoined agent is legal until it addresses a model and `recompose` binds exactly such an agent. The warning stays advisory: a synchronous `agent/created` throw vetoes publication, and the ACP bridge, SDK server, and headless bundle all create an unjoined agent today. Three limits are recorded rather than fixed: projection key presence is not a per-session capability signal, a superseded standing generation is never reclaimed, and a `cordis_mount` temporary plugin belongs to the composition rather than the session that mounted it. Fixes #2203
session/ — durable session data plane
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The durable family around core/session's live in-memory service: the persistence seam with its storage backends and checkpoint policy, the projection seam that serves whole log-derived values, log-backed titles, and outbound session telemetry. All product packages. session-query/ remains a sibling group: the read/tool surface is consumed independently of persistence internals.
Persistence
Durable session persistence, semantic checkpoint policy, and the shipped storage backends.
| Package | Role | ctx key |
|---|---|---|
session-persistence/ |
Defines the persistence service and shared write coordination | ctx.sessionPersistence |
session-checkpoint-policy/ |
Applies semantic durability checkpoints | wraps ctx.llm and ctx.tools |
session-persistence-jsonl/ |
Persists sessions in JSONL files | registers on ctx.sessionPersistence |
session-persistence-sqlite/ |
Persists sessions in SQLite | registers on ctx.sessionPersistence |
The session-persistence decision records the persistence design.
Projection
Serves current, log-derived per-session state to client carriers.
| Package | Role | ctx key |
|---|---|---|
session-projection/ |
Defines and drives session projection units | ctx.sessionProjections |
session-projection-cache/ |
Persists and restores projection checkpoints | ctx.sessionProjectionCache |
Titles
Derives durable session titles from the session log, with an optional model-backed provider.
| Package | Role | ctx key |
|---|---|---|
session-title/ |
Owns title state, fallback behavior, provider registration, and refresh | ctx.sessionTitle |
session-title-llm/ |
Provides shared model-backed title generation | — |
session-title-first-message-llm/ |
Titles a session from its first eligible human message | registers on ctx.sessionTitle |
session-title-all-messages-llm/ |
Titles a session from all eligible human messages | registers on ctx.sessionTitle |
Deployments may register one model-backed provider; the service retains a deterministic fallback when none is present.
Telemetry
Projects session activity into outbound telemetry and delegates delivery to a configured reporting backend. The telemetry decision records the reporting boundary; the mode decision records immediate, feedback-gated, and disabled delivery.
| Package | Role |
|---|---|
session-telemetry/ |
Defines capture, redaction, projection, and live or on-demand backend delivery. |
session-telemetry-otel/ |
Delivers telemetry through OpenTelemetry logs in FULL, FEEDBACK_ONLY, or DISABLED mode. |
The subsystem references: persistence.md, session-projection.md, session-title.md, and telemetry.md. Only one title provider may register at a time; the demo spine mounts the fallback service and leaves both model providers out of default composition.