diff --git a/README.md b/README.md
index 8566f08e0..52d8d1d7c 100644
--- a/README.md
+++ b/README.md
@@ -545,6 +545,37 @@ At milestone completion, GSD offers squash merge (recommended) or merge with his
 
 ---
 
+## Security
+
+### Protecting Sensitive Files
+
+GSD's codebase mapping and analysis commands read files to understand your project. **Protect files containing secrets** by adding them to Claude Code's deny list:
+
+1. Open Claude Code settings (`.claude/settings.json` or global)
+2. Add sensitive file patterns to the deny list:
+
+```json
+{
+  "permissions": {
+    "deny": [
+      "Read(.env)",
+      "Read(.env.*)",
+      "Read(**/secrets/*)",
+      "Read(**/*credential*)",
+      "Read(**/*.pem)",
+      "Read(**/*.key)"
+    ]
+  }
+}
+```
+
+This prevents Claude from reading these files entirely, regardless of what commands you run.
+
+> [!IMPORTANT]
+> GSD includes built-in protections against committing secrets, but defense-in-depth is best practice. Deny read access to sensitive files as a first line of defense.
+
+---
+
 ## Troubleshooting
 
 **Commands not found after install?**
diff --git a/agents/gsd-codebase-mapper.md b/agents/gsd-codebase-mapper.md
index b351be592..c47ef2a19 100644
--- a/agents/gsd-codebase-mapper.md
+++ b/agents/gsd-codebase-mapper.md
@@ -85,8 +85,9 @@ Explore the codebase thoroughly for your focus area.
 ls package.json requirements.txt Cargo.toml go.mod pyproject.toml 2>/dev/null
 cat package.json 2>/dev/null | head -100
 
-# Config files
-ls -la *.config.* .env* tsconfig.json .nvmrc .python-version 2>/dev/null
+# Config files (list only - DO NOT read .env contents)
+ls -la *.config.* tsconfig.json .nvmrc .python-version 2>/dev/null
+ls .env* 2>/dev/null  # Note existence only, never read contents
 
 # Find SDK/API imports
 grep -r "import.*stripe\|import.*supabase\|import.*aws\|import.*@" src/ --include="*.ts" --include="*.tsx" 2>/dev/null | head -50
@@ -712,6 +713,28 @@ Ready for orchestrator summary.
 
 </templates>
 
+<forbidden_files>
+**NEVER read or quote contents from these files (even if they exist):**
+
+- `.env`, `.env.*`, `*.env` - Environment variables with secrets
+- `credentials.*`, `secrets.*`, `*secret*`, `*credential*` - Credential files
+- `*.pem`, `*.key`, `*.p12`, `*.pfx`, `*.jks` - Certificates and private keys
+- `id_rsa*`, `id_ed25519*`, `id_dsa*` - SSH private keys
+- `.npmrc`, `.pypirc`, `.netrc` - Package manager auth tokens
+- `config/secrets/*`, `.secrets/*`, `secrets/` - Secret directories
+- `*.keystore`, `*.truststore` - Java keystores
+- `serviceAccountKey.json`, `*-credentials.json` - Cloud service credentials
+- `docker-compose*.yml` sections with passwords - May contain inline secrets
+- Any file in `.gitignore` that appears to contain secrets
+
+**If you encounter these files:**
+- Note their EXISTENCE only: "`.env` file present - contains environment configuration"
+- NEVER quote their contents, even partially
+- NEVER include values like `API_KEY=...` or `sk-...` in any output
+
+**Why this matters:** Your output gets committed to git. Leaked secrets = security incident.
+</forbidden_files>
+
 <critical_rules>
 
 **WRITE DOCUMENTS DIRECTLY.** Do not return findings to orchestrator. The whole point is reducing context transfer.
@@ -720,7 +743,7 @@ Ready for orchestrator summary.
 
 **USE THE TEMPLATES.** Fill in the template structure. Don't invent your own format.
 
-**BE THOROUGH.** Explore deeply. Read actual files. Don't guess.
+**BE THOROUGH.** Explore deeply. Read actual files. Don't guess. **But respect <forbidden_files>.**
 
 **RETURN ONLY CONFIRMATION.** Your response should be ~10 lines max. Just confirm what was written.
 
diff --git a/get-shit-done/workflows/map-codebase.md b/get-shit-done/workflows/map-codebase.md
index df59b5993..4de65de21 100644
--- a/get-shit-done/workflows/map-codebase.md
+++ b/get-shit-done/workflows/map-codebase.md
@@ -227,6 +227,41 @@ wc -l .planning/codebase/*.md
 
 If any documents missing or empty, note which agents may have failed.
 
+Continue to scan_for_secrets.
+</step>
+
+<step name="scan_for_secrets">
+**CRITICAL SECURITY CHECK:** Scan output files for accidentally leaked secrets before committing.
+
+Run secret pattern detection:
+
+```bash
+# Check for common API key patterns in generated docs
+grep -E '(sk-[a-zA-Z0-9]{20,}|sk_live_[a-zA-Z0-9]+|sk_test_[a-zA-Z0-9]+|ghp_[a-zA-Z0-9]{36}|gho_[a-zA-Z0-9]{36}|glpat-[a-zA-Z0-9_-]+|AKIA[A-Z0-9]{16}|xox[baprs]-[a-zA-Z0-9-]+|-----BEGIN.*PRIVATE KEY|eyJ[a-zA-Z0-9_-]+\.eyJ[a-zA-Z0-9_-]+\.)' .planning/codebase/*.md 2>/dev/null && SECRETS_FOUND=true || SECRETS_FOUND=false
+```
+
+**If SECRETS_FOUND=true:**
+
+```
+⚠️  SECURITY ALERT: Potential secrets detected in codebase documents!
+
+Found patterns that look like API keys or tokens in:
+[show grep output]
+
+This would expose credentials if committed.
+
+**Action required:**
+1. Review the flagged content above
+2. If these are real secrets, they must be removed before committing
+3. Consider adding sensitive files to Claude Code "Deny" permissions
+
+Pausing before commit. Reply "safe to proceed" if the flagged content is not actually sensitive, or edit the files first.
+```
+
+Wait for user confirmation before continuing to commit_codebase_map.
+
+**If SECRETS_FOUND=false:**
+
 Continue to commit_codebase_map.
 </step>