fix(core): treat model_profile "inherit" as pass-through instead of falling back to balanced (#1833)

When model_profile is set to "inherit" in config.json, resolveModelInternal()
now returns "inherit" immediately instead of looking it up in MODEL_PROFILES
(where it has no entry) and silently falling back to balanced.

Also adds "inherit" to the valid profile list in verify.cjs so setting it
doesn't trigger a false validation error.

Closes #1829

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

tests/bug-1829-inherit-model-profile.test.cjs

@@ -0,0 +1,218 @@
+/**
+ * Regression tests for bug #1829
+ *
+ * model_profile: "inherit" in .planning/config.json was not recognised as a
+ * valid profile. resolveModelInternal() silently fell back to "balanced",
+ * causing all agents to use "sonnet" instead of inheriting the parent model.
+ *
+ * Root cause in core.cjs:
+ *   const profile = config.model_profile || 'balanced';
+ *   const agentModels = MODEL_PROFILES[agentType];
+ *   if (!agentModels) return 'sonnet';
+ *   const resolved = agentModels[profile] || agentModels['balanced'] || 'sonnet';
+ *   // agentModels['inherit'] is undefined → falls through to agentModels['balanced']
+ *
+ * Fix 1 (core.cjs): add early return — if (profile === 'inherit') return 'inherit';
+ * Fix 2 (verify.cjs): add 'inherit' to validProfiles so it doesn't trigger W004.
+ */
+
+'use strict';
+
+const { describe, test, beforeEach, afterEach } = require('node:test');
+const assert = require('node:assert/strict');
+const fs = require('fs');
+const path = require('path');
+const { runGsdTools, createTempProject, cleanup } = require('./helpers.cjs');
+
+const { resolveModelInternal } = require('../get-shit-done/bin/lib/core.cjs');
+
+// ─── Helpers ──────────────────────────────────────────────────────────────────
+
+function writeConfig(tmpDir, obj) {
+  fs.writeFileSync(
+    path.join(tmpDir, '.planning', 'config.json'),
+    JSON.stringify(obj, null, 2)
+  );
+}
+
+function writeMinimalProjectMd(tmpDir) {
+  fs.writeFileSync(
+    path.join(tmpDir, '.planning', 'PROJECT.md'),
+    '# Project\n\n## What This Is\n\nContent.\n\n## Core Value\n\nContent.\n\n## Requirements\n\nContent.\n'
+  );
+}
+
+function writeMinimalRoadmap(tmpDir) {
+  fs.writeFileSync(
+    path.join(tmpDir, '.planning', 'ROADMAP.md'),
+    '# Roadmap\n\n### Phase 1: First Phase\n'
+  );
+}
+
+function writeMinimalStateMd(tmpDir) {
+  fs.writeFileSync(
+    path.join(tmpDir, '.planning', 'STATE.md'),
+    '# Session State\n\n## Current Position\n\nPhase: 1\n'
+  );
+}
+
+// ─── resolveModelInternal — inherit profile ───────────────────────────────────
+
+describe('bug #1829: model_profile "inherit" — resolveModelInternal', () => {
+  let tmpDir;
+
+  beforeEach(() => {
+    tmpDir = createTempProject();
+  });
+
+  afterEach(() => {
+    cleanup(tmpDir);
+  });
+
+  test('returns "inherit" for gsd-planner when model_profile is "inherit"', () => {
+    writeConfig(tmpDir, { model_profile: 'inherit' });
+    assert.strictEqual(resolveModelInternal(tmpDir, 'gsd-planner'), 'inherit');
+  });
+
+  test('returns "inherit" for gsd-executor when model_profile is "inherit"', () => {
+    writeConfig(tmpDir, { model_profile: 'inherit' });
+    assert.strictEqual(resolveModelInternal(tmpDir, 'gsd-executor'), 'inherit');
+  });
+
+  test('returns "inherit" for gsd-phase-researcher when model_profile is "inherit"', () => {
+    writeConfig(tmpDir, { model_profile: 'inherit' });
+    assert.strictEqual(resolveModelInternal(tmpDir, 'gsd-phase-researcher'), 'inherit');
+  });
+
+  test('returns "inherit" for gsd-codebase-mapper when model_profile is "inherit"', () => {
+    writeConfig(tmpDir, { model_profile: 'inherit' });
+    assert.strictEqual(resolveModelInternal(tmpDir, 'gsd-codebase-mapper'), 'inherit');
+  });
+
+  test('returns "inherit" for gsd-verifier when model_profile is "inherit"', () => {
+    writeConfig(tmpDir, { model_profile: 'inherit' });
+    assert.strictEqual(resolveModelInternal(tmpDir, 'gsd-verifier'), 'inherit');
+  });
+
+  test('returns "sonnet" (default) for unknown agent even with inherit profile', () => {
+    writeConfig(tmpDir, { model_profile: 'inherit' });
+    assert.strictEqual(resolveModelInternal(tmpDir, 'gsd-nonexistent'), 'sonnet');
+  });
+
+  test('per-agent override takes precedence over inherit profile', () => {
+    writeConfig(tmpDir, {
+      model_profile: 'inherit',
+      model_overrides: { 'gsd-executor': 'haiku' },
+    });
+    // Override wins even when profile is inherit
+    assert.strictEqual(resolveModelInternal(tmpDir, 'gsd-executor'), 'haiku');
+    // Other agents without override still inherit
+    assert.strictEqual(resolveModelInternal(tmpDir, 'gsd-planner'), 'inherit');
+  });
+
+  test('does not silently fall back to "sonnet" (the original bug)', () => {
+    writeConfig(tmpDir, { model_profile: 'inherit' });
+    // Before the fix, this returned 'sonnet' (via balanced fallback)
+    const model = resolveModelInternal(tmpDir, 'gsd-planner');
+    assert.notStrictEqual(model, 'sonnet', 'inherit profile must not silently fall back to sonnet');
+  });
+});
+
+// ─── resolve-model CLI — inherit profile ──────────────────────────────────────
+
+describe('bug #1829: model_profile "inherit" — resolve-model CLI', () => {
+  let tmpDir;
+
+  beforeEach(() => {
+    tmpDir = createTempProject();
+  });
+
+  afterEach(() => {
+    cleanup(tmpDir);
+  });
+
+  test('CLI resolve-model returns "inherit" for gsd-executor with inherit profile', () => {
+    fs.writeFileSync(
+      path.join(tmpDir, '.planning', 'config.json'),
+      JSON.stringify({ model_profile: 'inherit' }, null, 2)
+    );
+
+    const result = runGsdTools('resolve-model gsd-executor', tmpDir);
+    assert.ok(result.success, `resolve-model failed: ${result.error}`);
+
+    const parsed = JSON.parse(result.output);
+    assert.strictEqual(parsed.model, 'inherit');
+    assert.strictEqual(parsed.profile, 'inherit');
+  });
+
+  test('CLI resolve-model returns "inherit" for gsd-planner with inherit profile', () => {
+    fs.writeFileSync(
+      path.join(tmpDir, '.planning', 'config.json'),
+      JSON.stringify({ model_profile: 'inherit' }, null, 2)
+    );
+
+    const result = runGsdTools('resolve-model gsd-planner', tmpDir);
+    assert.ok(result.success, `resolve-model failed: ${result.error}`);
+
+    const parsed = JSON.parse(result.output);
+    assert.strictEqual(parsed.model, 'inherit');
+  });
+});
+
+// ─── verify health — inherit profile is not a validation error ────────────────
+
+describe('bug #1829: model_profile "inherit" — validate health does not warn W004', () => {
+  let tmpDir;
+
+  beforeEach(() => {
+    tmpDir = createTempProject();
+    writeMinimalProjectMd(tmpDir);
+    writeMinimalRoadmap(tmpDir);
+    writeMinimalStateMd(tmpDir);
+    fs.mkdirSync(path.join(tmpDir, '.planning', 'phases', '01-first-phase'), { recursive: true });
+  });
+
+  afterEach(() => {
+    cleanup(tmpDir);
+  });
+
+  test('does not emit W004 for model_profile "inherit"', () => {
+    fs.writeFileSync(
+      path.join(tmpDir, '.planning', 'config.json'),
+      JSON.stringify({
+        model_profile: 'inherit',
+        workflow: {
+          research: true,
+          plan_check: true,
+          verifier: true,
+          nyquist_validation: true,
+        },
+      }, null, 2)
+    );
+
+    const result = runGsdTools('validate health', tmpDir);
+    assert.ok(result.success, `validate health failed: ${result.error}`);
+
+    const output = JSON.parse(result.output);
+    assert.ok(
+      !output.warnings.some(w => w.code === 'W004'),
+      `inherit profile must not trigger W004: ${JSON.stringify(output.warnings)}`
+    );
+  });
+
+  test('still emits W004 for genuinely invalid model_profile values', () => {
+    fs.writeFileSync(
+      path.join(tmpDir, '.planning', 'config.json'),
+      JSON.stringify({ model_profile: 'invalid-profile' }, null, 2)
+    );
+
+    const result = runGsdTools('validate health', tmpDir);
+    assert.ok(result.success, `validate health failed: ${result.error}`);
+
+    const output = JSON.parse(result.output);
+    assert.ok(
+      output.warnings.some(w => w.code === 'W004'),
+      `Invalid profile should trigger W004: ${JSON.stringify(output.warnings)}`
+    );
+  });
+});