diff --git a/get-shit-done/workflows/settings.md b/get-shit-done/workflows/settings.md
index b540cff61..760056918 100644
--- a/get-shit-done/workflows/settings.md
+++ b/get-shit-done/workflows/settings.md
@@ -160,7 +160,8 @@ Merge new settings into existing config.json:
     "branching_strategy": "none" | "phase" | "milestone"
   },
   "hooks": {
-    "context_warnings": true/false
+    "context_warnings": true/false,
+    "workflow_guard": true/false
   }
 }
 ```
diff --git a/hooks/gsd-workflow-guard.js b/hooks/gsd-workflow-guard.js
new file mode 100644
index 000000000..d8075aaf6
--- /dev/null
+++ b/hooks/gsd-workflow-guard.js
@@ -0,0 +1,93 @@
+#!/usr/bin/env node
+// GSD Workflow Guard — PreToolUse hook
+// Detects when Claude attempts file edits outside a GSD workflow context
+// (no active /gsd: command or Task subagent) and injects an advisory warning.
+//
+// This is a SOFT guard — it advises, not blocks. The edit still proceeds.
+// The warning nudges Claude to use /gsd:quick or /gsd:fast instead of
+// making direct edits that bypass state tracking.
+//
+// Enable via config: hooks.workflow_guard: true (default: false)
+// Only triggers on Write/Edit tool calls to non-.planning/ files.
+
+const fs = require('fs');
+const path = require('path');
+
+let input = '';
+const stdinTimeout = setTimeout(() => process.exit(0), 3000);
+process.stdin.setEncoding('utf8');
+process.stdin.on('data', chunk => input += chunk);
+process.stdin.on('end', () => {
+  clearTimeout(stdinTimeout);
+  try {
+    const data = JSON.parse(input);
+    const toolName = data.tool_name;
+
+    // Only guard Write and Edit tool calls
+    if (toolName !== 'Write' && toolName !== 'Edit') {
+      process.exit(0);
+    }
+
+    // Check if we're inside a GSD workflow (Task subagent or /gsd: command)
+    // Subagents have a session_id that differs from the parent
+    // and typically have a description field set by the orchestrator
+    if (data.tool_input?.is_subagent || data.session_type === 'task') {
+      process.exit(0);
+    }
+
+    // Check the file being edited
+    const filePath = data.tool_input?.file_path || data.tool_input?.path || '';
+
+    // Allow edits to .planning/ files (GSD state management)
+    if (filePath.includes('.planning/') || filePath.includes('.planning\\')) {
+      process.exit(0);
+    }
+
+    // Allow edits to common config/docs files that don't need GSD tracking
+    const allowedPatterns = [
+      /\.gitignore$/,
+      /\.env/,
+      /CLAUDE\.md$/,
+      /AGENTS\.md$/,
+      /GEMINI\.md$/,
+      /settings\.json$/,
+    ];
+    if (allowedPatterns.some(p => p.test(filePath))) {
+      process.exit(0);
+    }
+
+    // Check if workflow guard is enabled
+    const cwd = data.cwd || process.cwd();
+    const configPath = path.join(cwd, '.planning', 'config.json');
+    if (fs.existsSync(configPath)) {
+      try {
+        const config = JSON.parse(fs.readFileSync(configPath, 'utf8'));
+        if (!config.hooks?.workflow_guard) {
+          process.exit(0); // Guard disabled (default)
+        }
+      } catch (e) {
+        process.exit(0);
+      }
+    } else {
+      process.exit(0); // No GSD project — don't guard
+    }
+
+    // If we get here: GSD project, guard enabled, file edit outside .planning/,
+    // not in a subagent context. Inject advisory warning.
+    const output = {
+      hookSpecificOutput: {
+        hookEventName: "PreToolUse",
+        additionalContext: `⚠️ WORKFLOW ADVISORY: You're editing ${path.basename(filePath)} directly without a GSD command. ` +
+          'This edit will not be tracked in STATE.md or produce a SUMMARY.md. ' +
+          'Consider using /gsd:fast for trivial fixes or /gsd:quick for larger changes ' +
+          'to maintain project state tracking. ' +
+          'If this is intentional (e.g., user explicitly asked for a direct edit), proceed normally.'
+      }
+    };
+
+    process.stdout.write(JSON.stringify(output));
+  } catch (e) {
+    // Silent fail — never block tool execution
+    process.exit(0);
+  }
+});
diff --git a/scripts/build-hooks.js b/scripts/build-hooks.js
index dda263e4e..b1b8fa416 100644
--- a/scripts/build-hooks.js
+++ b/scripts/build-hooks.js
@@ -17,7 +17,8 @@ const DIST_DIR = path.join(HOOKS_DIR, 'dist');
 const HOOKS_TO_COPY = [
   'gsd-check-update.js',
   'gsd-context-monitor.js',
-  'gsd-statusline.js'
+  'gsd-statusline.js',
+  'gsd-workflow-guard.js'
 ];
 
 /**