diff --git a/skills/executing-plans/SKILL.md b/skills/executing-plans/SKILL.md
index 78d8854066..f53d5a46ab 100644
--- a/skills/executing-plans/SKILL.md
+++ b/skills/executing-plans/SKILL.md
@@ -15,6 +15,23 @@ Load plan, review critically, execute all tasks, report when complete.
 
 ## The Process
 
+### Step 0: Ensure an Isolated Workspace
+
+**REQUIRED SUB-SKILL — before loading the plan:** Use
+superpowers:using-git-worktrees to create or verify an isolated workspace.
+
+This mirrors the required sub-skill at the *end* of this process
+(finishing-a-development-branch): isolation is a hard gate at the start, not
+an optional footnote. Executing a plan means many edits and commits in the
+current directory — if that is the main checkout, a parallel agent or your
+human partner collides with your branch and uncommitted state. Create the
+worktree *before* the first edit; doing it afterward does not isolate work
+already in progress.
+
+Do not proceed to Step 1 until you have confirmed you are in an isolated
+workspace, or your human partner has explicitly told you to run in the
+current checkout.
+
 ### Step 1: Load and Review Plan
 1. Read plan file
 2. Review critically - identify any questions or concerns about the plan
@@ -61,6 +78,7 @@ After all tasks complete and verified:
 - Reference skills when plan says to
 - Stop when blocked, don't guess
 - Never start implementation on main/master branch without explicit user consent
+- Never start executing before Step 0 — create/verify the worktree first
 
 ## Integration
 
diff --git a/skills/subagent-driven-development/SKILL.md b/skills/subagent-driven-development/SKILL.md
index d8ca081570..0cf0efd08c 100644
--- a/skills/subagent-driven-development/SKILL.md
+++ b/skills/subagent-driven-development/SKILL.md
@@ -60,11 +60,13 @@ digraph process {
         "Mark task complete in todo list and progress ledger" [shape=box];
     }
 
+    "Ensure isolated workspace (superpowers:using-git-worktrees)" [shape=box style=filled fillcolor=lightgreen];
     "Read plan, note context and global constraints, create todos" [shape=box];
     "More tasks remain?" [shape=diamond];
     "Dispatch final code reviewer subagent (../requesting-code-review/code-reviewer.md)" [shape=box];
     "Use superpowers:finishing-a-development-branch" [shape=box style=filled fillcolor=lightgreen];
 
+    "Ensure isolated workspace (superpowers:using-git-worktrees)" -> "Read plan, note context and global constraints, create todos";
     "Read plan, note context and global constraints, create todos" -> "Dispatch implementer subagent (./implementer-prompt.md)";
     "Dispatch implementer subagent (./implementer-prompt.md)" -> "Implementer subagent asks questions?";
     "Implementer subagent asks questions?" -> "Answer questions, provide context" [label="yes"];
@@ -82,6 +84,25 @@ digraph process {
 }
 ```
 
+## Step 0: Isolated Workspace (do this first)
+
+**REQUIRED SUB-SKILL — before reading the plan or creating todos:** Use
+superpowers:using-git-worktrees to ensure an isolated workspace exists
+(create one, or verify you are already in one). This is the first node in
+the flowchart above, not an optional footnote.
+
+Why this is a hard gate, not a suggestion: this skill dispatches many
+subagents that edit and commit in the current working directory. If that
+directory is the main checkout, a second agent (or the human) working in
+parallel collides with your commits, branch state, and uncommitted changes.
+The isolation has to exist *before* the first edit — creating a worktree
+after work has begun does not retroactively isolate it.
+
+Do not proceed to the Pre-Flight review until you have confirmed (e.g. with
+`git rev-parse --git-dir` vs `--git-common-dir`, or your platform's
+worktree tool) that you are working in an isolated workspace, or your human
+partner has explicitly told you to run in the current checkout.
+
 ## Pre-Flight Plan Review
 
 Before dispatching Task 1, scan the plan once for conflicts:
@@ -368,6 +389,9 @@ Done!
 
 **Never:**
 - Start implementation on main/master branch without explicit user consent
+- Begin dispatching subagents before an isolated workspace exists — Step 0
+  (superpowers:using-git-worktrees) runs before the plan is read, not as an
+  afterthought. Working in the main checkout lets parallel agents collide.
 - Skip task review, or accept a report missing either verdict (spec compliance AND task quality are both required)
 - Proceed with unfixed issues
 - Dispatch multiple implementation subagents in parallel (conflicts)