Merge remote-tracking branch 'origin/master' into codex/skill-system

# Conflicts:
#	docs/event-producer-consumer.md

docs/core-data-structures/core.md

@@ -28,6 +28,8 @@ Everything else is documented on a **sub-page**, not here. The rule that draws t
 
 > Type definitions on this page are pasted **verbatim** from source and drift-checked by `pnpm run verify-type-equiv` (see [development.md](../development.md#documenting-types-verbatim-ts-type-equiv)). Inline JSDoc is omitted for readability; follow the source link for the full contracts.
 
+FIXME(catalog-verbs): the drift gate covers only the nouns (the pasted type shapes); every method surface on these pages is hand-written prose. core-data-structures should probably also generate the *verbs* — the public methods of the cataloged classes — so a signature change cannot silently outdate the catalog.
+
 ## The `…Map → derived-union` pattern
 
 Almost every extensible sum type in the harness follows one shape: an interface keyed by a discriminant tag (the `…Map`), from which the union is derived with `keyof`. Plugins add variants by **declaration merging** — no edit to the owning package.
@@ -184,6 +186,21 @@ interface ToolSchema {
 
 The model-facing `ToolSchema` is the wire shape; the registered `ToolDefinition` that produces it (schema + `execute`) is on [tools.md](tools.md).
 
+### The request envelope: `LlmCallConfig` and the logged header
+
+Requests are built by the loop, not shaped per call: the non-content half of a request — the `EpochHeader`: this call configuration plus the rendered system prompt and assembled tool schemas — is logged session state (`request/header` snapshot and delta events, [session.md](session.md#the-request-header-events-requestheader-and-requestheader-delta)), so every conversation request is a pure function of the session log ([reconstructability RFC](../rfc/implemented/architecture/2026-07-05-reconstructable-requests.md)). The `agent/request` waterfall receives a frozen `LlmCallConfig` seed and a listener returns a replacement to switch model or sampling — the loop logs whatever the request actually uses. Loop-built requests arrive at `llm/stream` deep-frozen; mutation throws.
+
+FIXME(call-config-shape): revisit the exact definition of this type — which fields are genuinely epoch-level for cache purposes (`model` certainly; the sampling scalars sit here out of caution), and where provider-specific extras (reasoning options, extra body params) belong when an adapter needs them.
+
+```ts type-equiv
+interface LlmCallConfig {
+  model: string
+  temperature?: number
+  maxTokens?: number
+  stop?: string[]
+}
+```
+
 ## Sessions
 
 A `Session` is an **append-only log** of typed `SessionEvent`s — the single source of truth. The LLM message history is *derived* from the log (`deriveMessages()`), not stored separately. The event vocabulary derives from `SessionEventMap`:
@@ -212,7 +229,7 @@ type SessionEvent<T extends SessionEventType = SessionEventType> = {
 }[T]
 ```
 
-The thirteen event variants (`turn/start`, `turn/end`, `step/start`, `step/end`, `user/message`, `prompt/blocked`, `context/message`, `assistant/chunk`, `assistant/message`, `tool/call`, `tool/result`, `steering/message`, `todo/write`), the `deriveMessages()` projection rules, the `TurnTrigger`/`TurnEndReason` reasons, and the turn-enclosure invariant are on **[session.md](session.md)**. How the log is made durable — the `SessionPersistence` seam, JSONL/SQLite backends, the `session/flush` checkpoint, crash recovery, and `SessionHeader` — is on **[persistence.md](persistence.md)**.
+The fifteen event variants (`turn/start`, `turn/end`, `step/start`, `step/end`, `user/message`, `prompt/blocked`, `context/message`, `assistant/chunk`, `assistant/message`, `tool/call`, `tool/result`, `steering/message`, `todo/write`, `request/header`, `request/header-delta`), the `deriveMessages()` projection rules, the `TurnTrigger`/`TurnEndReason` reasons, and the turn-enclosure invariant are on **[session.md](session.md)**. How the log is made durable — the `SessionPersistence` seam, JSONL/SQLite backends, the `session/flush` checkpoint, crash recovery, and `SessionHeader` — is on **[persistence.md](persistence.md)**.
 
 ## The agent handle