diff --git a/README.md b/README.md
index a391fc0..7d1490a 100644
--- a/README.md
+++ b/README.md
@@ -130,6 +130,7 @@ All commands are available under the `/5:` namespace:
 | `/5:review-code` | 5 | AI-powered code review (Claude or CodeRabbit) |
 | `/5:address-review-findings` | 5 | Apply annotated findings and address PR comments |
 | `/5:quick-implement` | Fast | Streamlined workflow for small tasks |
+| `/5:eject` | Utility | Permanently remove update infrastructure |
 | `/5:unlock` | Utility | Remove planning guard lock |
 
 ## Configuration
@@ -264,6 +265,7 @@ After installation, your `.claude/` directory will contain:
 │   ├── discuss-feature.md
 │   ├── quick-implement.md
 │   ├── configure.md
+│   ├── eject.md
 │   └── unlock.md
 ├── skills/                   # Atomic operations
 │   ├── build-project/
@@ -364,6 +366,21 @@ npx 5-phase-workflow
 - User-created commands, agents, skills, hooks, and templates are preserved
 - Only workflow-managed files are updated
 
+### Ejecting
+
+If you want to permanently opt out of the update system (e.g., to customize workflow files without future updates overwriting them), run:
+
+```bash
+/5:eject
+```
+
+This permanently removes the update infrastructure:
+- Deletes `check-updates.js` hook, `update.md` and `eject.md` commands
+- Deletes `.5/version.json` and `.5/.update-cache.json`
+- Removes the update check hook entry from `.claude/settings.json`
+
+All other workflow files remain untouched. **This is irreversible.** To restore update functionality, reinstall with `npx 5-phase-workflow`.
+
 ## Development
 
 ### Running Tests
diff --git a/bin/install.js b/bin/install.js
index aa7c88a..8f0744b 100755
--- a/bin/install.js
+++ b/bin/install.js
@@ -626,6 +626,7 @@ function showCommandsHelp(isGlobal) {
   log.info('  /5:address-review-findings   - Apply review findings & PR comments');
   log.info('  /5:configure                 - Interactive project setup');
   log.info('  /5:reconfigure               - Refresh docs/skills (no Q&A)');
+  log.info('  /5:eject                     - Eject from update mechanism');
   log.info('  /5:unlock                    - Remove planning guard lock');
   log.info('');
   log.info(`Config file: ${path.join(getDataPath(isGlobal), 'config.json')}`);
diff --git a/src/commands/5/eject.md b/src/commands/5/eject.md
new file mode 100644
index 0000000..5f39a95
--- /dev/null
+++ b/src/commands/5/eject.md
@@ -0,0 +1,91 @@
+---
+name: 5:eject
+description: Eject from the update mechanism — permanently removes update infrastructure
+allowed-tools: Bash, Read, Edit, AskUserQuestion
+user-invocable: true
+model: haiku
+context: fork
+---
+
+<role>
+You are a Workflow Ejector. You permanently remove the update infrastructure from this installation.
+After ejecting, you are DONE.
+</role>
+
+# Eject from Update Mechanism
+
+Ejecting permanently removes the update system from this installation. After ejecting:
+- The update check hook (`check-updates.js`) is deleted
+- The update command (`/5:update`) is deleted
+- The eject command (`/5:eject`) is deleted
+- Version tracking (`.5/version.json`) is deleted
+- The update cache (`.5/.update-cache.json`) is deleted
+- The `check-updates.js` hook entry is removed from `.claude/settings.json`
+
+All other workflow files (commands, skills, hooks, templates) remain untouched.
+
+**This is irreversible.** To restore update functionality, reinstall with `npx 5-phase-workflow`.
+
+## Step 1: Check Current State
+
+Read `.5/version.json`. If it doesn't exist, tell the user: "No 5-Phase Workflow installation found (or already ejected)." and stop.
+
+Note the `packageVersion` for the confirmation message.
+
+## Step 2: Confirm with User
+
+Tell the user what ejecting means:
+
+> **Eject from 5-Phase Workflow updates?**
+>
+> This will permanently delete:
+> - `.claude/hooks/check-updates.js` (update check hook)
+> - `.claude/commands/5/update.md` (update command)
+> - `.claude/commands/5/eject.md` (this command)
+> - `.5/version.json` (version tracking)
+> - `.5/.update-cache.json` (update cache)
+>
+> The `check-updates.js` hook entry will also be removed from `.claude/settings.json`.
+>
+> All other workflow files remain untouched. To restore updates later, reinstall with `npx 5-phase-workflow`.
+
+Ask: "Proceed with eject?"
+
+If the user declines, stop here.
+
+## Step 3: Delete Update Files
+
+Run this command to delete the update-related files:
+
+```bash
+rm -f .claude/hooks/check-updates.js .claude/commands/5/update.md .claude/commands/5/eject.md .5/version.json .5/.update-cache.json
+```
+
+## Step 4: Clean Up settings.json
+
+Read `.claude/settings.json`. Remove the hook entry from the `hooks.SessionStart` array where the command is `node .claude/hooks/check-updates.js`.
+
+Specifically, find and remove the object in the `SessionStart` array that looks like:
+
+```json
+{
+  "matcher": "startup",
+  "hooks": [
+    {
+      "type": "command",
+      "command": "node .claude/hooks/check-updates.js",
+      "timeout": 10
+    }
+  ]
+}
+```
+
+If the `SessionStart` array becomes empty after removal, remove the `SessionStart` key entirely. Write the updated settings back.
+
+## Step 5: Confirm
+
+Tell the user:
+
+> Ejected successfully. Update infrastructure has been removed from this installation (was v{packageVersion}).
+>
+> To restore update functionality, reinstall with: `npx 5-phase-workflow`