Merge remote-tracking branch 'origin/master' into feature/subagent-policy-inheritance

# Conflicts:
#	packages/core/session/README.i18n.yaml
#	packages/session-persistence/session-persistence-jsonl/README.i18n.yaml
#	packages/session-persistence/session-persistence-jsonl/README.md
#	packages/session-persistence/session-persistence-jsonl/README.zh.md

packages/session-persistence/session-persistence-jsonl/src/index.ts

@@ -27,6 +27,7 @@ import { ensureDurableDirectoryWin32, publishNewFileWin32 } from './win32.ts'
 
 export type { JsonlCompression } from './format.ts'
 
+const DEFAULT_PACK_CHUNKS = true
 const DEFAULT_COMPRESSION: JsonlCompression = 'zstd'
 
 /** Loader schema for the JSONL artifact's physical encoding. */
@@ -48,10 +49,9 @@ export interface Config {
   /**
    * Write runs of consecutive `assistant/chunk` delta events as packed
    * `text-chunks`/`reasoning-chunks`/`tool-call-chunks` rows (lossless,
-   * ~60% smaller logs measured on a real session). Off by default while
-   * snapshot fixtures stay in the one-event-per-line layout: recording with
-   * packing on rewrites every golden `session.jsonl`. READING packed rows is
-   * unconditional — a log's layout never depends on this switch.
+   * ~60% smaller logs measured on a real session). Defaults to true; false
+   * keeps one `SessionEvent` per line for diagnostics. Reading packed rows is
+   * unconditional: a log's layout never depends on this switch.
    */
   packChunks?: boolean
   /** Physical encoding; defaults to checksummed Zstandard frames. */
@@ -80,7 +80,7 @@ export class SessionPersistenceJsonl extends SessionPersistence implements Persi
 
   static Config: z<Config> = z.object({
     root: z.string().required(),
-    packChunks: z.boolean().default(false),
+    packChunks: z.boolean().default(DEFAULT_PACK_CHUNKS),
     compression: JsonlCompressionSchema,
   })
 
@@ -101,9 +101,8 @@ export class SessionPersistenceJsonl extends SessionPersistence implements Persi
     super(ctx)
     // Resolve once so later process.cwd() changes cannot split one backend across roots.
     this.root = resolve(config.root)
-    // schemastery (static Config) applied the default before construction;
-    // the cast records that runtime fact for exactOptionalPropertyTypes.
-    this.packChunks = (config as Required<Config>).packChunks
+    // Programmatic wrappers may construct the backend without Schemastery normalization.
+    this.packChunks = config.packChunks ?? DEFAULT_PACK_CHUNKS
     this.compression = config.compression ?? DEFAULT_COMPRESSION
     this.assertUsableRoot()
     this.coordinator = new PersistenceCoordinator<JsonlTornMarker>(this.ctx, this)