Merge remote-tracking branch 'origin/master' into codex/session-scoped-sandbox-roots

docs/core-data-structures/workflow.md

@@ -8,7 +8,7 @@ Source: [`packages/workflow/workflow/src/types.ts`](../../packages/workflow/work
 
 ## The start request
 
-What a caller asks for when starting a run. The tool layer builds this from the model's `{ script, meta, args }` call plus the calling agent; `meta` and `args` are plain JSON DATA (the engine shape-validates `meta` and rejects loud BEFORE anything runs — no script text is ever evaluated to obtain it). `parent` is REQUIRED — every child the script spawns is attributed to it (cwd, lineage, and depth flow through the [subagent seam](subagent.md)).
+What a caller asks for when starting a run. The ordinary workflow tool builds this from the model's `{ script, meta, args }` call plus the calling agent; specialized consumers may also select one engine-wide `subagentProvider` and lower `maxTotalAgents` for the run, but the script cannot observe or replace either policy. `meta` and `args` are plain JSON DATA (the engine shape-validates `meta` and rejects loud BEFORE anything runs — no script text is ever evaluated to obtain it). `parent` is REQUIRED — every child the script spawns is attributed to it (cwd, lineage, and depth flow through the [subagent seam](subagent.md)).
 
 ```ts type-equiv
 /**
@@ -26,6 +26,17 @@ interface WorkflowStartRequest {
   meta: WorkflowMeta
   /** Optional input exposed verbatim to the script as the `args` global. */
   args?: unknown
+  /**
+   * Optional engine-wide child-provider override for this run. The workflow
+   * script cannot observe or replace it; omission uses the engine's configured
+   * provider.
+   */
+  subagentProvider?: string
+  /**
+   * Optional per-run total-child ceiling. Implementations reject values above
+   * their deployment ceiling before publishing the run.
+   */
+  maxTotalAgents?: number
   /** The agent on whose behalf the run executes (parent of every child). */
   parent: Agent
   /** Cancels the run when aborted (the tool's `exec.signal`). */