diff --git a/get-shit-done/bin/lib/config.cjs b/get-shit-done/bin/lib/config.cjs
index 61d8798b7..a40a0c529 100644
--- a/get-shit-done/bin/lib/config.cjs
+++ b/get-shit-done/bin/lib/config.cjs
@@ -6,6 +6,16 @@ const fs = require('fs');
 const path = require('path');
 const { output, error } = require('./core.cjs');
 
+const VALID_CONFIG_KEYS = new Set([
+  'mode', 'granularity', 'parallelization', 'commit_docs', 'model_profile',
+  'search_gitignored', 'brave_search',
+  'workflow.research', 'workflow.plan_check', 'workflow.verifier',
+  'workflow.nyquist_validation', 'workflow.ui_phase', 'workflow.ui_safety_gate',
+  'workflow._auto_chain_active',
+  'git.branching_strategy', 'git.phase_branch_template', 'git.milestone_branch_template',
+  'planning.commit_docs', 'planning.search_gitignored',
+]);
+
 function cmdConfigEnsureSection(cwd, raw) {
   const configPath = path.join(cwd, '.planning', 'config.json');
   const planningDir = path.join(cwd, '.planning');
@@ -88,6 +98,10 @@ function cmdConfigSet(cwd, keyPath, value, raw) {
     error('Usage: config-set <key.path> <value>');
   }
 
+  if (!VALID_CONFIG_KEYS.has(keyPath)) {
+    error(`Unknown config key: "${keyPath}". Valid keys: ${[...VALID_CONFIG_KEYS].sort().join(', ')}`);
+  }
+
   // Parse value (handle booleans and numbers)
   let parsedValue = value;
   if (value === 'true') parsedValue = true;
diff --git a/get-shit-done/workflows/plan-phase.md b/get-shit-done/workflows/plan-phase.md
index 5290af51f..aa27262dc 100644
--- a/get-shit-done/workflows/plan-phase.md
+++ b/get-shit-done/workflows/plan-phase.md
@@ -238,7 +238,9 @@ Task(
 
 ## 5.5. Create Validation Strategy
 
-MANDATORY unless `nyquist_validation_enabled` is false.
+Skip if `nyquist_validation_enabled` is false OR `research_enabled` is false.
+
+If `research_enabled` is false and `nyquist_validation_enabled` is true: warn "Nyquist validation enabled but research disabled — VALIDATION.md cannot be created without RESEARCH.md. Plans will lack validation requirements (Dimension 8)." Continue to step 6.
 
 ```bash
 grep -l "## Validation Architecture" "${PHASE_DIR}"/*-RESEARCH.md 2>/dev/null
@@ -281,15 +283,15 @@ CONTEXT_PATH=$(printf '%s\n' "$INIT" | jq -r '.context_path // empty')
 
 ## 7.5. Verify Nyquist Artifacts
 
-Skip if `nyquist_validation_enabled` is false.
+Skip if `nyquist_validation_enabled` is false OR `research_enabled` is false.
 
 ```bash
 VALIDATION_EXISTS=$(ls "${PHASE_DIR}"/*-VALIDATION.md 2>/dev/null | head -1)
 ```
 
 If missing and Nyquist enabled — ask user:
-1. Re-run: `/gsd:plan-phase {PHASE} --research`
-2. Disable Nyquist in config
+1. Re-run with research: `/gsd:plan-phase {PHASE} --research`
+2. Disable Nyquist: `node "$HOME/.claude/get-shit-done/bin/gsd-tools.cjs" config-set workflow.nyquist_validation false`
 3. Continue anyway (plans fail Dimension 8)
 
 Proceed to Step 8 only if user selects 2 or 3.
diff --git a/get-shit-done/workflows/settings.md b/get-shit-done/workflows/settings.md
index d89a4d7ac..78650445c 100644
--- a/get-shit-done/workflows/settings.md
+++ b/get-shit-done/workflows/settings.md
@@ -94,6 +94,8 @@ AskUserQuestion([
       { label: "No", description: "Skip validation research. Good for rapid prototyping or no-test phases." }
     ]
   },
+  // Note: Nyquist validation depends on research output. If research is disabled,
+  // plan-phase automatically skips Nyquist steps (no RESEARCH.md to extract from).
   {
     question: "Git branching strategy?",
     header: "Branching",
diff --git a/tests/config.test.cjs b/tests/config.test.cjs
index e76ec0aef..f2ed6d106 100644
--- a/tests/config.test.cjs
+++ b/tests/config.test.cjs
@@ -241,21 +241,21 @@ describe('config-set command', () => {
   });
 
   test('coerces numeric strings to numbers', () => {
-    const result = runGsdTools('config-set some_number 42', tmpDir);
+    const result = runGsdTools('config-set granularity 42', tmpDir);
     assert.ok(result.success, `Command failed: ${result.error}`);
 
     const config = readConfig(tmpDir);
-    assert.strictEqual(config.some_number, 42);
-    assert.strictEqual(typeof config.some_number, 'number');
+    assert.strictEqual(config.granularity, 42);
+    assert.strictEqual(typeof config.granularity, 'number');
   });
 
   test('preserves plain strings', () => {
-    const result = runGsdTools('config-set some_string hello', tmpDir);
+    const result = runGsdTools('config-set model_profile hello', tmpDir);
     assert.ok(result.success, `Command failed: ${result.error}`);
 
     const config = readConfig(tmpDir);
-    assert.strictEqual(config.some_string, 'hello');
-    assert.strictEqual(typeof config.some_string, 'string');
+    assert.strictEqual(config.model_profile, 'hello');
+    assert.strictEqual(typeof config.model_profile, 'string');
   });
 
   test('sets nested values via dot-notation', () => {
@@ -266,17 +266,25 @@ describe('config-set command', () => {
     assert.strictEqual(config.workflow.research, false);
   });
 
-  test('auto-creates nested objects for deep dot-notation', () => {
+  test('auto-creates nested objects for dot-notation', () => {
     // Start with empty config
     writeConfig(tmpDir, {});
 
-    const result = runGsdTools('config-set a.b.c deep_value', tmpDir);
+    const result = runGsdTools('config-set workflow.research false', tmpDir);
     assert.ok(result.success, `Command failed: ${result.error}`);
 
     const config = readConfig(tmpDir);
-    assert.strictEqual(config.a.b.c, 'deep_value');
-    assert.strictEqual(typeof config.a, 'object');
-    assert.strictEqual(typeof config.a.b, 'object');
+    assert.strictEqual(config.workflow.research, false);
+    assert.strictEqual(typeof config.workflow, 'object');
+  });
+
+  test('rejects unknown config keys', () => {
+    const result = runGsdTools('config-set workflow.nyquist_validation_enabled false', tmpDir);
+    assert.strictEqual(result.success, false);
+    assert.ok(
+      result.error.includes('Unknown config key'),
+      `Expected "Unknown config key" in error: ${result.error}`
+    );
   });
 
   test('errors when no key path provided', () => {