feat(observability): Phase A logging substrate — Logger/Span ABI + journal sink (250 tests)

Structured, agent-first logging captured durably to an append-only journal file.

Kernel (contracts/logging.ts): leveled/attributed Logger + Span, auto-scoped per extension (host stamps manifest.id, unspoofable), incremental span records (open/close) for crash-reconstructable traces, injected LogSink (pure record-builder). ctx.log on ToolContract; runTurn opens turn/step/tool-call spans and captures the verbatim pre-mutation prompt (the 'before') on the step span.

journal-sink (new package, bootstrap dep — not an extension): LogSink appending NDJSON to a rotating journal; pure serialize + thin fs edge; fail-safe drop, never blocks a turn. host-bin injects it via HostDeps; session-orchestrator threads host.logger (childed per turn) into runTurn.

Redaction is per-extension self-redaction (no shared helper — isolation over DRY). The out-of-process collector + SQLite store + the verbatim 'after' provider.request capture are Phase B / next (notes/observability-design.md §10/§11).

Verified: tsc -b clean, 250 tests (218→+32), biome clean. Live boot: a turn's journal holds host logs + turn/step spans (open+close) + the prompt:before record with the verbatim messages array.

Harness: ORCHESTRATOR §3 rule-scoping map; .dispatch/rules/isolation-over-dry.md; notes/observability-design.md (design D1–D10 + Phase A/B plan).

2 files changed, 6 insertions, 0 deletions

diff --git a/packages/session-orchestrator/src/extension.ts b/packages/session-orchestrator/src/extension.ts
index 8cd4c44..bfbc7ca 100644
--- a/packages/session-orchestrator/src/extension.ts
+++ b/packages/session-orchestrator/src/extension.ts
@@ -29,6 +29,7 @@ export function activate(host: HostAPI): void {
 		resolveProvider: () => selectFirstProvider(host.getProviders()),
 		resolveTools: () => [...host.getTools().values()],
 		runTurn,
+		logger: host.logger,
 	});
 
 	host.provideService(sessionOrchestratorHandle, orchestrator);
diff --git a/packages/session-orchestrator/src/orchestrator.ts b/packages/session-orchestrator/src/orchestrator.ts
index 302404e..37fc512 100644
--- a/packages/session-orchestrator/src/orchestrator.ts
+++ b/packages/session-orchestrator/src/orchestrator.ts
@@ -2,6 +2,7 @@ import type { ConversationStore } from "@dispatch/conversation-store";
 import type {
 	AgentEvent,
 	ChatMessage,
+	Logger,
 	ProviderContract,
 	RunTurnInput,
 	RunTurnResult,
@@ -30,6 +31,8 @@ export interface SessionOrchestratorDeps {
 	readonly resolveTools: () => readonly ToolContract[];
 	readonly resolveDispatch?: () => ToolDispatchPolicy;
 	readonly runTurn: (input: RunTurnInput) => Promise<RunTurnResult>;
+	/** Base logger (auto-scoped to this extension); childed per turn for span capture. */
+	readonly logger?: Logger;
 }
 
 export function createSessionOrchestrator(deps: SessionOrchestratorDeps): SessionOrchestrator {
@@ -41,6 +44,7 @@ export function createSessionOrchestrator(deps: SessionOrchestratorDeps): Sessio
 			const tools = deps.resolveTools();
 			const dispatch = deps.resolveDispatch?.() ?? defaultDispatchPolicy();
 			const turnId = generateTurnId();
+			const turnLogger = deps.logger?.child({ conversationId, turnId });
 
 			const result = await deps.runTurn({
 				provider,
@@ -50,6 +54,7 @@ export function createSessionOrchestrator(deps: SessionOrchestratorDeps): Sessio
 				emit: onEvent,
 				conversationId,
 				turnId,
+				...(turnLogger !== undefined ? { logger: turnLogger } : {}),
 				...(signal !== undefined ? { signal } : {}),
 			});