refactor(observability): pure-types contracts/logging + Span body channel; verbatim before/after -> LogRecord.body (273 tests)

contracts/logging.ts reduced to pure types; createLogger (+ helpers) moved to kernel/src/logging/ — @dispatch/kernel still exports it (host-bin/tool-read-file unaffected).

Span body channel (Option A): Logger.span / Span.child / Span.end accept an optional body string -> SpanOpenRecord.body / SpanCloseRecord.body. Large verbatim payloads now use body, not stringified attributes (store-fat-serve-thin; attributes stay thin/queryable for D9).

before: run-turn emits a 'prompt' span with the verbatim messages+tools in body (small scalars in attrs). after: provider.request span carries the verbatim request in body; attrs thin, auth self-redacted.

Verified: tsc -b clean, 273 tests, biome 0 warnings/0 infos. Live boot: prompt + provider.request bodies present and correlated (shared turnId); request.body no longer in attributes; auth-key leak count = 0.

2 files changed, 12 insertions, 283 deletions

diff --git a/packages/kernel/src/contracts/index.ts b/packages/kernel/src/contracts/index.ts
index e4eba87..a4c965a 100644
--- a/packages/kernel/src/contracts/index.ts
+++ b/packages/kernel/src/contracts/index.ts
@@ -81,7 +81,6 @@ export type {
 	SpanOpenRecord,
 	SpanStatus,
 } from "./logging.js";
-export { createLogger } from "./logging.js";
 export type {
 	FinishEvent,
 	ProviderContract,
diff --git a/packages/kernel/src/contracts/logging.ts b/packages/kernel/src/contracts/logging.ts
index 8e1eef3..a8bab7c 100644
--- a/packages/kernel/src/contracts/logging.ts
+++ b/packages/kernel/src/contracts/logging.ts
@@ -1,9 +1,9 @@
 /**
  * Logging contract — structured, correlated, span-capable Logger/Span ABI.
  *
- * The kernel owns types + pure record-builders. NO I/O — the LogSink is
- * injected by the host-bin. Logger/Span mint records and call sink.emit;
- * sink errors are swallowed (D7 — the turn is sovereign).
+ * PURE TYPES ONLY — no implementations. The createLogger factory lives in
+ * ../logging/logger.js. The kernel owns types + pure record-builders.
+ * NO I/O — the LogSink is injected by the host-bin.
  *
  * Key properties:
  * - P3-safe: correlation flows via explicit child()/span() values, no ambient.
@@ -11,6 +11,7 @@
  * - D3: spans emitted incrementally (open at span(), close at end()).
  * - D6: extensionId auto-stamped by host, not caller-supplied.
  * - Flat scalar attributes (serializable D3, queryable D9).
+ * - Optional `body` field on spans for large verbatim payloads (store-fat-serve-thin).
  */
 
 // --- Levels ---
@@ -53,12 +54,16 @@ export interface Span {
 		reason?: string,
 	) => void;
 	/** Open a child span nested under this one. */
-	readonly child: (name: string, attrs?: Attributes) => Span;
+	readonly child: (name: string, attrs?: Attributes, body?: string) => Span;
 	/**
 	 * Close this span. Records duration + status. Optionally records an
-	 * error and/or additional attributes.
+	 * error, additional attributes, and/or a body payload.
 	 */
-	readonly end: (outcome?: { readonly err?: unknown; readonly attrs?: Attributes }) => void;
+	readonly end: (outcome?: {
+		readonly err?: unknown;
+		readonly attrs?: Attributes;
+		readonly body?: string;
+	}) => void;
 }
 
 // --- Logger ---
@@ -80,7 +85,7 @@ export interface Logger {
 	 */
 	readonly child: (ctx: Partial<LogContext> & { readonly attrs?: Attributes }) => Logger;
 	/** Open a new span. Emits a `span-open` record immediately (D3). */
-	readonly span: (name: string, attrs?: Attributes) => Span;
+	readonly span: (name: string, attrs?: Attributes, body?: string) => Span;
 }
 
 /**
@@ -184,278 +189,3 @@ export interface LogDeps {
 	readonly now: () => number;
 	readonly newId: () => string;
 }
-
-// --- Pure record builder (no I/O) ---
-
-/**
- * Internal state carried by a logger instance. Built by createLogger;
- * never exposed outside this module.
- */
-interface LoggerState {
-	readonly ctx: LogContext;
-	readonly attrs: Attributes | undefined;
-	readonly deps: LogDeps;
-	readonly sink: LogSink;
-}
-
-function mergeAttributes(
-	base: Attributes | undefined,
-	extra: Attributes | undefined,
-): Attributes | undefined {
-	if (base === undefined && extra === undefined) return undefined;
-	if (base === undefined) return extra;
-	if (extra === undefined) return base;
-	return { ...base, ...extra };
-}
-
-function isScalarAttr(value: unknown): value is string | number | boolean | null {
-	const t = typeof value;
-	return t === "string" || t === "number" || t === "boolean" || value === null;
-}
-
-function emitLog(state: LoggerState, level: Level, msg: string, attrs?: Attributes): void {
-	const merged = mergeAttributes(state.attrs, attrs);
-	const base = {
-		kind: "log" as const,
-		level,
-		msg,
-		timestamp: state.deps.now(),
-		extensionId: state.ctx.extensionId,
-	};
-	const record: LogLineRecord =
-		state.ctx.conversationId !== undefined ||
-		state.ctx.turnId !== undefined ||
-		state.ctx.spanId !== undefined ||
-		state.ctx.parentSpanId !== undefined ||
-		merged !== undefined
-			? {
-					...base,
-					...(state.ctx.conversationId !== undefined
-						? { conversationId: state.ctx.conversationId }
-						: {}),
-					...(state.ctx.turnId !== undefined ? { turnId: state.ctx.turnId } : {}),
-					...(state.ctx.spanId !== undefined ? { spanId: state.ctx.spanId } : {}),
-					...(state.ctx.parentSpanId !== undefined ? { parentSpanId: state.ctx.parentSpanId } : {}),
-					...(merged !== undefined ? { attributes: merged } : {}),
-				}
-			: base;
-	try {
-		state.sink.emit(record);
-	} catch {
-		// Swallow — D7: the turn is sovereign (never break the caller).
-	}
-}
-
-function buildSpanOpen(
-	state: LoggerState,
-	name: string,
-	spanId: string,
-	attrs?: Attributes,
-): SpanOpenRecord {
-	const base = {
-		kind: "span-open" as const,
-		spanId,
-		name,
-		timestamp: state.deps.now(),
-		extensionId: state.ctx.extensionId,
-	};
-	const merged = mergeAttributes(state.attrs, attrs);
-	return {
-		...base,
-		...(state.ctx.conversationId !== undefined ? { conversationId: state.ctx.conversationId } : {}),
-		...(state.ctx.turnId !== undefined ? { turnId: state.ctx.turnId } : {}),
-		...(state.ctx.parentSpanId !== undefined ? { parentSpanId: state.ctx.parentSpanId } : {}),
-		...(merged !== undefined ? { attributes: merged } : {}),
-	};
-}
-
-function buildSpanLink(
-	target: { readonly spanId: string; readonly turnId?: string },
-	reason?: string,
-): SpanLink {
-	return {
-		spanId: target.spanId,
-		...(target.turnId !== undefined ? { turnId: target.turnId } : {}),
-		...(reason !== undefined ? { reason } : {}),
-	};
-}
-
-/**
- * Create a structured Logger. Pure factory — all I/O goes through the
- * injected sink. `{ now, newId }` are injected for deterministic tests.
- *
- * @param ctx  Initial correlation context (extensionId + optional ids).
- * @param sink  Fire-and-forget record sink.
- * @param deps  Clock + id generator.
- * @param attrs  Optional default attributes (from child()).
- */
-export function createLogger(
-	ctx: LogContext,
-	sink: LogSink,
-	deps: LogDeps,
-	attrs?: Attributes,
-): Logger {
-	const state: LoggerState = { ctx, attrs, deps, sink };
-
-	function makeSpan(name: string, spanAttrs?: Attributes, parentSpanId?: string): Span {
-		const spanId = deps.newId();
-		const mergedParent = parentSpanId ?? state.ctx.spanId;
-		const spanCtx: LogContext = {
-			extensionId: ctx.extensionId,
-			...(ctx.conversationId !== undefined ? { conversationId: ctx.conversationId } : {}),
-			...(ctx.turnId !== undefined ? { turnId: ctx.turnId } : {}),
-			spanId,
-			...(mergedParent !== undefined ? { parentSpanId: mergedParent } : {}),
-		};
-
-		const openRecord = buildSpanOpen(state, name, spanId, spanAttrs);
-		const spanAttrsMutable: Record<string, string | number | boolean | null> =
-			spanAttrs !== undefined ? { ...spanAttrs } : {};
-		const links: SpanLink[] = [];
-		const openedAt = deps.now();
-
-		try {
-			sink.emit(openRecord);
-		} catch {
-			// Swallow — D7.
-		}
-
-		const spanLogger = createLogger(spanCtx, sink, deps, state.attrs);
-
-		const span: Span = {
-			id: spanId,
-			log: spanLogger,
-			setAttributes(newAttrs: Attributes): void {
-				for (const [key, value] of Object.entries(newAttrs)) {
-					spanAttrsMutable[key] = value;
-				}
-			},
-			addLink(target, reason): void {
-				links.push(buildSpanLink(target, reason));
-			},
-			child(childName: string, childAttrs?: Attributes): Span {
-				return makeSpan(childName, childAttrs, spanId);
-			},
-			end(outcome?): void {
-				const closedAt = deps.now();
-				const err = outcome?.err;
-				let status: SpanStatus = "ok";
-				if (err !== undefined && err !== null) {
-					status = "error";
-					const errMsg = err instanceof Error ? err.message : String(err);
-					spanAttrsMutable["error.message"] = errMsg;
-					if (err instanceof Error && err.stack !== undefined) {
-						spanAttrsMutable["error.stack"] = err.stack;
-					}
-				}
-				if (outcome?.attrs !== undefined) {
-					for (const [key, value] of Object.entries(outcome.attrs)) {
-						spanAttrsMutable[key] = value;
-					}
-				}
-
-				const hasAttrs = Object.keys(spanAttrsMutable).length > 0;
-				const hasLinks = links.length > 0;
-				const base = {
-					kind: "span-close" as const,
-					spanId,
-					name,
-					timestamp: closedAt,
-					durationMs: closedAt - openedAt,
-					status,
-					extensionId: ctx.extensionId,
-				};
-				const closeRecord: SpanCloseRecord = {
-					...base,
-					...(ctx.conversationId !== undefined ? { conversationId: ctx.conversationId } : {}),
-					...(ctx.turnId !== undefined ? { turnId: ctx.turnId } : {}),
-					...(mergedParent !== undefined ? { parentSpanId: mergedParent } : {}),
-					...(hasAttrs ? { attributes: { ...spanAttrsMutable } } : {}),
-					...(hasLinks ? { links: [...links] } : {}),
-				};
-				try {
-					sink.emit(closeRecord);
-				} catch {
-					// Swallow — D7.
-				}
-			},
-		};
-
-		return span;
-	}
-
-	const logger: Logger = {
-		debug(msg: string, attrs?: Attributes): void {
-			emitLog(state, "debug", msg, attrs);
-		},
-		info(msg: string, attrs?: Attributes): void {
-			emitLog(state, "info", msg, attrs);
-		},
-		warn(msg: string, attrs?: Attributes): void {
-			emitLog(state, "warn", msg, attrs);
-		},
-		error(msg: string, attrs?: ErrorAttributes): void {
-			const err = attrs?.err;
-			if (err !== undefined && err !== null) {
-				// Extract scalar attributes (everything except err).
-				const scalarAttrs: Record<string, string | number | boolean | null> = {};
-				if (attrs !== undefined) {
-					for (const [key, value] of Object.entries(attrs)) {
-						if (key !== "err" && isScalarAttr(value)) {
-							scalarAttrs[key] = value;
-						}
-					}
-				}
-				const merged = mergeAttributes(
-					state.attrs,
-					Object.keys(scalarAttrs).length > 0 ? scalarAttrs : undefined,
-				);
-				const errMsg = err instanceof Error ? err.message : String(err);
-				const errorAttrs: Record<string, string | number | boolean | null> = {
-					...(merged ?? {}),
-					"error.message": errMsg,
-				};
-				if (err instanceof Error && err.stack !== undefined) {
-					errorAttrs["error.stack"] = err.stack;
-				}
-				emitLog(state, "error", msg, errorAttrs as Attributes);
-			} else {
-				// No err field — filter to scalar attributes only.
-				const scalarAttrs: Record<string, string | number | boolean | null> = {};
-				if (attrs !== undefined) {
-					for (const [key, value] of Object.entries(attrs)) {
-						if (isScalarAttr(value)) {
-							scalarAttrs[key] = value;
-						}
-					}
-				}
-				emitLog(
-					state,
-					"error",
-					msg,
-					Object.keys(scalarAttrs).length > 0 ? (scalarAttrs as Attributes) : undefined,
-				);
-			}
-		},
-		child(childCtx: Partial<LogContext> & { readonly attrs?: Attributes }): Logger {
-			const convId = childCtx.conversationId ?? ctx.conversationId;
-			const tId = childCtx.turnId ?? ctx.turnId;
-			const sId = childCtx.spanId ?? ctx.spanId;
-			const pId = childCtx.parentSpanId ?? ctx.parentSpanId;
-			const newCtx: LogContext = {
-				extensionId: ctx.extensionId,
-				...(convId !== undefined ? { conversationId: convId } : {}),
-				...(tId !== undefined ? { turnId: tId } : {}),
-				...(sId !== undefined ? { spanId: sId } : {}),
-				...(pId !== undefined ? { parentSpanId: pId } : {}),
-			};
-			const newAttrs = mergeAttributes(state.attrs, childCtx.attrs);
-			return createLogger(newCtx, sink, deps, newAttrs);
-		},
-		span(name: string, attrs?: Attributes): Span {
-			return makeSpan(name, attrs);
-		},
-	};
-
-	return logger;
-}