Merge origin/master into codex/invariant-service-seam

# Conflicts:
#	docs/module-graph.md

packages/workflow/workflow/README.md

@@ -6,11 +6,11 @@ The workflow seam (`ctx.workflows`) executes a model-written orchestration scrip
 
 ## Service and run contract
 
-`WorkflowService.start(request): WorkflowRun` validates enough synchronously to reject a malformed meta block or unparseable script before a run exists. Once returned, `WorkflowRun.result` never rejects: execution failures resolve with `stopReason: 'error'`, and cancellation resolves with `cancelled` within the engine's bounded grace.
+`WorkflowService.start(request): WorkflowRun` validates enough synchronously to reject a malformed meta block, unparseable script, unavailable provider route, or unsupported per-run limit before a run exists. Once returned, `WorkflowRun.result` never rejects: execution failures resolve with `stopReason: 'error'`, and cancellation resolves with `cancelled` within the engine's bounded grace.
 
 A run is holder-owned. Engine-plugin unload prevents new starts but does not revoke accepted runs. The holder must call `dispose()` on every path; disposal cancels remaining work and reaches or abandons quiescence within the documented bound.
 
-`WorkflowStartRequest` contains `{ meta, script, args?, parent, signal? }`. `parent` attributes every child agent to the invoking agent. `meta` and `args` are plain data, not script fragments.
+`WorkflowStartRequest` contains `{ meta, script, args?, subagentProvider?, maxTotalAgents?, parent, signal? }`. `parent` attributes every child agent to the invoking agent. `subagentProvider` optionally routes every child in that run without exposing provider choice to the script; omission uses the engine's configured provider. `maxTotalAgents` optionally lowers the engine's deployment ceiling for one run and is likewise invisible to the script. An implementation rejects invalid routes and limits synchronously. `meta` and `args` are plain data, not script fragments.
 
 `WorkflowRun` exposes `{ id, meta, result, cancel(reason?), dispose() }`. `WorkflowResult` contains `{ value, stopReason, error?, agentsStarted }`; `value` is plain JSON data or `null`.
 

packages/workflow/workflow/src/types.ts

@@ -70,6 +70,17 @@ export 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`). */