E03: cheapest-tier implementers when plan carries complete code (transcription hypothesis)

skills/subagent-driven-development/SKILL.md

@@ -100,8 +100,10 @@ most expensive — which silently defeats this section.
 **Turn count beats token price.** Wall-clock and context cost scale with how
 many turns a subagent takes, and the cheapest models routinely take 2-3× the
 turns on multi-step work — costing more overall. Use a mid-tier model as the
-floor for implementers and reviewers; reserve the cheapest tier for
-single-file mechanical fixes.
+floor for reviewers and for implementers working from prose descriptions.
+When the task's plan text contains the complete code to write, the
+implementation is transcription plus testing: use the cheapest tier for
+that implementer. Single-file mechanical fixes also take the cheapest tier.
 
 **Task complexity signals (implementation tasks):**
 - Touches 1-2 files with a complete spec → cheap model