fix: address provider routing review feedback

packages/workflow/tool-workflow/src/index.ts

@@ -47,7 +47,7 @@ const DESCRIPTION = `Run a JavaScript workflow script that orchestrates subagent
 The workflow's identity rides the \`meta\` parameter as JSON: required \`name\` (short kebab-case) and \`description\` strings, optional \`whenToUse\` string and \`phases\` array (\`{title, detail?, provider?, model?}\`). The \`script\` parameter is the plain JavaScript body ONLY (NOT TypeScript, and NO \`export const meta\` statement — meta is a parameter, not code), running with top-level await; end with \`return <value>\` — the value must be JSON-serializable and is this tool's result.
 
 Script-body hooks:
-- \`agent(prompt, opts?): Promise<any>\` — run one subagent to completion. Without \`opts.schema\` it resolves to the child's final text; with \`opts.schema\` (an object-rooted JSON Schema using ONLY type/properties/required/additionalProperties/items/enum/const — no oneOf/pattern/format/numeric bounds) it resolves to the validated object. Resolves \`null\` when the child fails (filter with \`.filter(Boolean)\`). Other opts: \`label\` (display), \`phase\` (progress group), \`provider\` and \`model\` (paired LLM target overrides). Anything else (\`effort\`/\`isolation\`/\`agentType\`) is rejected loudly.
+- \`agent(prompt, opts?): Promise<any>\` — run one subagent to completion. Without \`opts.schema\` it resolves to the child's final text; with \`opts.schema\` (an object-rooted JSON Schema using ONLY type/properties/required/additionalProperties/items/enum/const — no oneOf/pattern/format/numeric bounds) it resolves to the validated object. Resolves \`null\` when the child fails (filter with \`.filter(Boolean)\`). Other opts: \`label\` (display), \`phase\` (progress group), and independent \`provider\`/\`model\` LLM target overrides (either may be provided alone). Anything else (\`effort\`/\`isolation\`/\`agentType\`) is rejected loudly.
 - \`pipeline(items, ...stages): Promise<any[]>\` — run each item through the stages independently with NO barrier between stages (prefer this for multi-stage work). Each stage receives \`(prev, item, index)\`. An ordinary stage throw drops that ITEM to \`null\` and skips its remaining stages.
 - \`parallel(thunks): Promise<any[]>\` — run zero-argument functions concurrently and await ALL of them (a barrier; use only when a stage genuinely needs every prior result together). A throwing thunk resolves to \`null\`.
 - \`phase(title)\` — start a progress phase; \`log(message)\` — narrate progress; \`args\` — the tool call's \`args\` input, verbatim.

packages/workflow/workflow-workerthread/src/runtime.ts

@@ -368,7 +368,7 @@ export class WorkflowExecution {
     for (const key of Object.keys(record)) {
       if (SUPPORTED_AGENT_OPTIONS.has(key)) continue
       if (DEFERRED_AGENT_OPTIONS.has(key)) {
-        throw new WorkflowError(`agent() option "${key}" is deferred and not supported by this engine (supported: label, phase, schema, model)`, 'UNSUPPORTED_OPTION')
+        throw new WorkflowError(`agent() option "${key}" is deferred and not supported by this engine (supported: label, phase, schema, provider, model)`, 'UNSUPPORTED_OPTION')
       }
       throw new WorkflowError(`agent() option "${key}" is not recognized (supported: label, phase, schema, provider, model)`, 'UNSUPPORTED_OPTION')
     }

packages/workflow/workflow-workerthread/tests/session.spec.ts

@@ -341,7 +341,7 @@ describe('runWorkerSession over an in-process MessageChannel', () => {
       ["return await agent('p', { label: 3 })", '"label" must be a string'],
       ["return await agent('p', { get label() { throw new Error('read failed') } })", 'options must be plain JSON data'],
       ["return await agent('p', { bogus: true })", '"bogus" is not recognized'],
-      ["return await agent('p', { effort: 'high' })", '"effort" is deferred'],
+      ["return await agent('p', { effort: 'high' })", '"effort" is deferred and not supported by this engine (supported: label, phase, schema, provider, model)'],
       ["return await agent('p', { schema: { type: 'object', oneOf: [] } })", 'outside the supported subset'],
       ['return await parallel([() => 1, () => 2, () => 3])', 'over the per-call cap (2)'],
       ['return await pipeline([1, 2, 3], (x) => x)', 'maxItemsPerCall'],