fix(skills): SDD review fanout scales with the change (SUP-333 #2)

subagent-driven-development mandated implementer + two-stage review +
final reviewer unconditionally — agy and opencode each dispatched 4
subagents for a one-line console.log in the 2026-06-09 quorum sweep
(cost-trivial-task-review-fanout), and the agents that passed did so
only by disobeying the skill.

- Proportionality rule: when the entire plan is one trivial,
  fully-specified mechanical change, implement directly, verify,
  commit — no review fanout. "When in doubt, it is not trivial."
  Within a multi-task plan the full pipeline still applies to every
  task regardless of size.
- Flowchart gets the trivial-exit diamond (the failing agents follow
  the flowchart literally; prose alone would not redirect them).
- Red Flags "never skip reviews" amended to reference the exception so
  the skill does not contradict itself.

TDD evidence (quorum):
- RED: agy 025324Z + opencode batches — 4 dispatches for 1 line
- GREEN: cost-trivial-task-review-fanout-opencode-20260610T002518Z-f3f5
  pass — 0 dispatches, $0.04, change landed on main checkout
- Canary: sdd-rejects-extra-features-claude-20260610T002901Z-458a pass —
  multi-task plan still runs implementer + two-stage review per task
  (tool-called Agent ✓, spec reviewer as YAGNI gate after each task)

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

skills/brainstorming/SKILL.md

@@ -109,7 +109,8 @@ digraph brainstorming {
 **Documentation:**
 
 - Write the validated design (spec) to `docs/superpowers/specs/YYYY-MM-DD-<topic>-design.md`
-  - (An explicit user instruction overrides this default; an existing differently-named docs directory does not)
+  - The `docs/superpowers/` prefix is the convention; do not shorten it to `docs/specs/`
+  - (User preferences for spec location override this default)
 - Use elements-of-style:writing-clearly-and-concisely skill if available
 - Commit the design document to git
 

skills/executing-plans/SKILL.md

@@ -16,7 +16,7 @@ Load plan, review critically, execute all tasks, report when complete.
 ## The Process
 
 ### Step 1: Load and Review Plan
-1. Read plan file, and the spec it cites in its `**Spec:**` header (plans reference requirements rather than restating them)
+1. Read plan file
 2. Review critically - identify any questions or concerns about the plan
 3. If concerns: Raise them with your human partner before starting
 4. If no concerns: Create todos for the plan items and proceed

skills/subagent-driven-development/SKILL.md

@@ -11,6 +11,8 @@ Execute plan by dispatching fresh subagent per task, with two-stage review after
 
 **Core principle:** Fresh subagent per task + two-stage review (spec then quality) = high quality, fast iteration
 
+**Proportionality:** Review fanout scales with the change. When the entire plan is one trivial, fully-specified mechanical change — a one-line edit, a log statement, a constant bump — implement it directly (or with a single implementer subagent), verify it, and commit. Skip the review subagents and the final reviewer: a diff with no room for interpretation has nothing for a spec or quality review to catch, and three dispatches for one line cost more than the change itself. When in doubt whether a change is trivial, it is not — run the full pipeline. Within a multi-task plan, run the full pipeline for every task regardless of size; this exception applies only when the whole plan is one trivial change.
+
 **Continuous execution:** Do not pause to check in with your human partner between tasks. Execute all tasks from the plan without stopping. The only reasons to stop are: BLOCKED status you cannot resolve, ambiguity that genuinely prevents progress, or all tasks complete. "Should I continue?" prompts and progress summaries waste their time — they asked you to execute the plan, so execute it.
 
 ## When to Use
@@ -61,11 +63,16 @@ digraph process {
     }
 
     "Read plan, extract all tasks with full text, note context, create todos" [shape=box];
+    "Entire plan = one trivial mechanical change?" [shape=diamond];
+    "Implement directly, verify, commit (no review fanout)" [shape=box];
     "More tasks remain?" [shape=diamond];
     "Dispatch final code reviewer subagent for entire implementation" [shape=box];
     "Use superpowers:finishing-a-development-branch" [shape=box style=filled fillcolor=lightgreen];
 
-    "Read plan, extract all tasks with full text, note context, create todos" -> "Dispatch implementer subagent (./implementer-prompt.md)";
+    "Read plan, extract all tasks with full text, note context, create todos" -> "Entire plan = one trivial mechanical change?";
+    "Entire plan = one trivial mechanical change?" -> "Implement directly, verify, commit (no review fanout)" [label="yes — see Proportionality"];
+    "Implement directly, verify, commit (no review fanout)" -> "Use superpowers:finishing-a-development-branch";
+    "Entire plan = one trivial mechanical change?" -> "Dispatch implementer subagent (./implementer-prompt.md)" [label="no"];
     "Dispatch implementer subagent (./implementer-prompt.md)" -> "Implementer subagent asks questions?";
     "Implementer subagent asks questions?" -> "Answer questions, provide context" [label="yes"];
     "Answer questions, provide context" -> "Dispatch implementer subagent (./implementer-prompt.md)";
@@ -86,10 +93,6 @@ digraph process {
 }
 ```
 
-## Spec Context
-
-If the plan's header cites a spec (`**Spec:** <path>`), read it once during plan extraction. Plans reference requirements rather than restating them — when a task cites a spec section, paste that section's text into the implementer and spec-reviewer prompts along with the task text. Implementer subagents never read the spec file themselves; the spec reviewer may additionally read it at the cited path (its prompt says so).
-
 ## Model Selection
 
 Use the least powerful model that can handle each role to conserve cost and increase speed.
@@ -241,7 +244,7 @@ Done!
 
 **Never:**
 - Start implementation on main/master branch without explicit user consent
-- Skip reviews (spec compliance OR code quality)
+- Skip reviews (spec compliance OR code quality) on a non-trivial task — the Proportionality exception covers only a plan that is one trivial mechanical change
 - Proceed with unfixed issues
 - Dispatch multiple implementation subagents in parallel (conflicts)
 - Make subagent read plan file (provide full text instead)

skills/subagent-driven-development/implementer-prompt.md

@@ -12,8 +12,6 @@ Subagent (general-purpose):
 
     [FULL TEXT of task from plan - paste it here, don't make subagent read file]
 
-    [If the task cites spec sections, paste the cited sections' text here too]
-
     ## Context
 
     [Scene-setting: where this fits, dependencies, architectural context]

skills/subagent-driven-development/spec-reviewer-prompt.md

@@ -12,7 +12,7 @@ Subagent (general-purpose):
 
     ## What Was Requested
 
-    [FULL TEXT of task requirements, including the text of any spec sections the task cites]
+    [FULL TEXT of task requirements]
 
     ## What Implementer Claims They Built
 
@@ -28,7 +28,7 @@ Subagent (general-purpose):
     git diff [BASE_SHA]..[HEAD_SHA]
     ```
 
-    Only read files in this diff. Do not crawl the broader codebase. (One exception: if the requirements cite a spec document, you may read that spec at its cited path.)
+    Only read files in this diff. Do not crawl the broader codebase.
 
     ## Read-Only Review
 

skills/writing-plans/SKILL.md

@@ -11,16 +11,14 @@ Write comprehensive implementation plans assuming the engineer has zero context
 
 Assume they are a skilled developer, but know almost nothing about our toolset or problem domain. Assume they don't know good test design very well.
 
-**Plans reference the spec; they never restate, paraphrase, or summarize it.** The spec owns the WHAT and WHY — requirements, acceptance criteria, design decisions; the plan owns the HOW — tasks, files, code, commands. Cite it by path in the header and by section where a task needs context. Reference discipline never means skipping the spec: if brainstorming produced one, it exists and the plan cites it. No Placeholders still requires repeating code and commands WITHIN the plan; copying FROM the spec is different: a step that needs a requirement's prose is under-specified — turn it into a concrete action. Snapshotting spec text into the plan hides drift, not prevents it. "Zero context" means each step is mechanically executable, not that the plan repeats the spec.
-
-**Two narrow exceptions to reference discipline** — subagents executing the plan see the plan (or a single task of it), never the spec, so two kinds of spec content travel in the plan itself: the `## Global Constraints` section (the spec's project-wide requirements, exact values copied verbatim) and each task's `**Interfaces:**` block (exact signatures). Copy those values exactly; everything else stays referenced, never restated.
+**Plans reference the spec; they never restate it.** The spec owns the WHAT and WHY — requirements, acceptance criteria, design decisions. The plan owns the HOW — tasks, files, code, commands. Cite the spec by path in the header and by section where a task needs context. Re-deriving spec content inline doubles the documents and lets them drift apart. "Zero context" means the engineer can execute each step mechanically; it does not mean the plan repeats what the spec already says — they can read the spec at the cited path.
 
 **Announce at start:** "I'm using the writing-plans skill to create the implementation plan."
 
 **Context:** If working in an isolated worktree, it should have been created via the `superpowers:using-git-worktrees` skill at execution time.
 
 **Save plans to:** `docs/superpowers/plans/YYYY-MM-DD-<feature-name>.md`
-- (An explicit user instruction overrides this default; an existing differently-named docs directory does not)
+- (User preferences for plan location override this default)
 
 ## Scope Check
 
@@ -37,15 +35,6 @@ Before defining tasks, map out which files will be created or modified and what
 
 This structure informs the task decomposition. Each task should produce self-contained changes that make sense independently.
 
-## Task Right-Sizing
-
-A task is the smallest unit that carries its own test cycle and is worth a
-fresh reviewer's gate. When drawing task boundaries: fold setup,
-configuration, scaffolding, and documentation steps into the task whose
-deliverable needs them; split only where a reviewer could meaningfully
-reject one task while approving its neighbor. Each task ends with an
-independently testable deliverable.
-
 ## Bite-Sized Task Granularity
 
 **Each step is one action (2-5 minutes):**
@@ -66,19 +55,12 @@ independently testable deliverable.
 
 **Goal:** [One sentence describing what this builds]
 
-**Spec:** [Path to the spec doc, e.g. `docs/superpowers/specs/YYYY-MM-DD-<topic>-design.md` — requirements and design decisions live there; do not restate them here. Only if no spec doc exists (requirements arrived conversationally; brainstorming never ran): write "none — requirements:" and state them once here, not per task]
+**Spec:** [Path to the spec doc, e.g. `docs/superpowers/specs/YYYY-MM-DD-<topic>-design.md` — requirements and design decisions live there; do not restate them here]
 
 **Architecture:** [2-3 sentences about approach]
 
 **Tech Stack:** [Key technologies/libraries]
 
-## Global Constraints
-
-[The spec's project-wide requirements — version floors, dependency limits,
-naming and copy rules, platform requirements — one line each, with exact
-values copied verbatim from the spec. Every task's requirements implicitly
-include this section.]
-
 ---
 ```
 
@@ -92,12 +74,6 @@ include this section.]
 - Modify: `exact/path/to/existing.py:123-145`
 - Test: `tests/exact/path/to/test.py`
 
-**Interfaces:**
-- Consumes: [what this task uses from earlier tasks — exact signatures]
-- Produces: [what later tasks rely on — exact function names, parameter
-  and return types. A task's implementer sees only their own task; this
-  block is how they learn the names and types neighboring tasks use.]
-
 - [ ] **Step 1: Write the failing test**
 
 ```python