diff --git a/docs/CONFIGURATION.md b/docs/CONFIGURATION.md
index 892ce43b68..cccbb07db0 100644
--- a/docs/CONFIGURATION.md
+++ b/docs/CONFIGURATION.md
@@ -453,8 +453,15 @@ The intent is the same as the Claude profile tiers -- use a stronger model for p
 
 ## Global Defaults
 
-Save settings as global defaults for future projects:
+Save settings as global defaults for all GSD commands:
 
 **Location:** `~/.gsd/defaults.json`
 
-When `/gsd-new-project` creates a new `config.json`, it reads global defaults and merges them as the starting configuration. Per-project settings always override globals.
+Global defaults are consulted in two scenarios:
+
+1. **Project initialization:** When `/gsd-new-project` creates a new `config.json`, it reads global defaults and merges them as the starting configuration.
+2. **Pre-project commands:** Commands that run before project initialization (e.g., `map-codebase`) use global defaults as a fallback when no `.planning/config.json` exists.
+
+**Merge order:** `hardcoded defaults ← ~/.gsd/defaults.json ← .planning/config.json`
+
+Per-project settings always override globals.
diff --git a/get-shit-done/bin/lib/core.cjs b/get-shit-done/bin/lib/core.cjs
index 7477741dbf..75f63481cd 100644
--- a/get-shit-done/bin/lib/core.cjs
+++ b/get-shit-done/bin/lib/core.cjs
@@ -365,7 +365,47 @@ function loadConfig(cwd) {
       response_language: get('response_language') || null,
     };
   } catch {
-    return defaults;
+    // No project config — check ~/.gsd/defaults.json as intermediate fallback.
+    // This ensures pre-project commands (e.g., map-codebase) respect user globals.
+    const globalDefaultsPath = path.join(os.homedir(), '.gsd', 'defaults.json');
+    let userDefaults = {};
+    try {
+      if (fs.existsSync(globalDefaultsPath)) {
+        userDefaults = JSON.parse(fs.readFileSync(globalDefaultsPath, 'utf-8'));
+        // Migrate deprecated "depth" key to "granularity"
+        if ('depth' in userDefaults && !('granularity' in userDefaults)) {
+          const depthToGranularity = { quick: 'coarse', standard: 'standard', comprehensive: 'fine' };
+          userDefaults.granularity = depthToGranularity[userDefaults.depth] || userDefaults.depth;
+          delete userDefaults.depth;
+          try { fs.writeFileSync(globalDefaultsPath, JSON.stringify(userDefaults, null, 2), 'utf-8'); } catch { /* intentionally empty */ }
+        }
+      }
+    } catch {
+      // Ignore malformed global defaults
+    }
+
+    // Flatten nested defaults.json keys (git.*, workflow.*) to top-level,
+    // matching how the try block's get() helper resolves both formats.
+    const flat = { ...defaults };
+    for (const [key, val] of Object.entries(userDefaults)) {
+      if (key === 'git' || key === 'workflow') {
+        // Nested section — merge each sub-key, mapping workflow.plan_check → plan_checker
+        if (val && typeof val === 'object') {
+          for (const [subKey, subVal] of Object.entries(val)) {
+            const mapped = (key === 'workflow' && subKey === 'plan_check') ? 'plan_checker' : subKey;
+            if (mapped in flat) flat[mapped] = subVal;
+          }
+        }
+      } else if (key in flat) {
+        flat[key] = val;
+      }
+    }
+    // Include keys that aren't in the hardcoded defaults but loadConfig() returns
+    flat.model_overrides = userDefaults.model_overrides || null;
+    flat.agent_skills = userDefaults.agent_skills || {};
+    flat.manager = userDefaults.manager || {};
+    flat.response_language = userDefaults.response_language || null;
+    return flat;
   }
 }
 
diff --git a/tests/commands.test.cjs b/tests/commands.test.cjs
index a899dcfa57..b86c9dd319 100644
--- a/tests/commands.test.cjs
+++ b/tests/commands.test.cjs
@@ -1048,12 +1048,16 @@ describe('verify-path-exists command', () => {
 
 describe('resolve-model command', () => {
   let tmpDir;
+  let originalHome;
 
   beforeEach(() => {
     tmpDir = createTempProject();
+    originalHome = process.env.HOME;
+    process.env.HOME = tmpDir;
   });
 
   afterEach(() => {
+    process.env.HOME = originalHome;
     cleanup(tmpDir);
   });
 
diff --git a/tests/config.test.cjs b/tests/config.test.cjs
index 0fbcb3bb65..dd4ba9bd85 100644
--- a/tests/config.test.cjs
+++ b/tests/config.test.cjs
@@ -39,7 +39,8 @@ describe('config-ensure-section command', () => {
   });
 
   test('creates config.json with expected structure and types', () => {
-    const result = runGsdTools('config-ensure-section', tmpDir);
+    // Sandbox HOME to prevent real ~/.gsd/defaults.json from leaking in
+    const result = runGsdTools('config-ensure-section', tmpDir, { HOME: tmpDir });
     assert.ok(result.success, `Command failed: ${result.error}`);
 
     const output = JSON.parse(result.output);
diff --git a/tests/core.test.cjs b/tests/core.test.cjs
index 88428a7db2..db66b2d14f 100644
--- a/tests/core.test.cjs
+++ b/tests/core.test.cjs
@@ -38,14 +38,19 @@ const {
 describe('loadConfig', () => {
   let tmpDir;
   let originalCwd;
+  let originalHome;
 
   beforeEach(() => {
     tmpDir = createTempProject();
     originalCwd = process.cwd();
+    // Sandbox HOME so real ~/.gsd/defaults.json doesn't leak into tests
+    originalHome = process.env.HOME;
+    process.env.HOME = tmpDir;
   });
 
   afterEach(() => {
     process.chdir(originalCwd);
+    process.env.HOME = originalHome;
     cleanup(tmpDir);
   });
 
@@ -121,6 +126,46 @@ describe('loadConfig', () => {
     assert.strictEqual(config.commit_docs, true);
   });
 
+  test('falls back to ~/.gsd/defaults.json when no config.json exists', () => {
+    // Remove .planning/config.json so loadConfig hits the catch path
+    fs.rmSync(path.join(tmpDir, '.planning', 'config.json'), { force: true });
+    // Create ~/.gsd/defaults.json in the sandboxed HOME
+    const gsdDir = path.join(tmpDir, '.gsd');
+    fs.mkdirSync(gsdDir, { recursive: true });
+    fs.writeFileSync(
+      path.join(gsdDir, 'defaults.json'),
+      JSON.stringify({ model_profile: 'quality', resolve_model_ids: true })
+    );
+    const config = loadConfig(tmpDir);
+    assert.strictEqual(config.model_profile, 'quality');
+    assert.strictEqual(config.resolve_model_ids, true);
+    // Keys not in defaults.json should still get hardcoded defaults
+    assert.strictEqual(config.commit_docs, true);
+  });
+
+  test('falls back to hardcoded defaults when no config.json and no defaults.json', () => {
+    fs.rmSync(path.join(tmpDir, '.planning', 'config.json'), { force: true });
+    const config = loadConfig(tmpDir);
+    assert.strictEqual(config.model_profile, 'balanced');
+    assert.strictEqual(config.commit_docs, true);
+  });
+
+  test('defaults.json supports nested keys (git, workflow)', () => {
+    fs.rmSync(path.join(tmpDir, '.planning', 'config.json'), { force: true });
+    const gsdDir = path.join(tmpDir, '.gsd');
+    fs.mkdirSync(gsdDir, { recursive: true });
+    fs.writeFileSync(
+      path.join(gsdDir, 'defaults.json'),
+      JSON.stringify({
+        git: { branching_strategy: 'per-phase' },
+        workflow: { research: false },
+      })
+    );
+    const config = loadConfig(tmpDir);
+    assert.strictEqual(config.branching_strategy, 'per-phase');
+    assert.strictEqual(config.research, false);
+  });
+
   test('handles parallelization as boolean', () => {
     writeConfig({ parallelization: false });
     const config = loadConfig(tmpDir);