diff --git a/model-overlays/sonnet-5.md b/model-overlays/sonnet-5.md
new file mode 100644
index 0000000000..39bf42311f
--- /dev/null
+++ b/model-overlays/sonnet-5.md
@@ -0,0 +1,17 @@
+{{INHERIT:claude}}
+
+**Instructions are read literally.** Sonnet 5 does not silently generalize an
+instruction from one item to the next, and it does not infer requests you didn't
+make. When something should apply broadly, say so ("apply this to every section,
+not just the first"). Re-baseline holdover style directives — they now land at
+face value.
+
+**Scope work to the request.** At lower effort especially, Sonnet 5 scopes to
+exactly what was asked rather than going above and beyond. If reasoning looks
+shallow on a genuinely complex task, that is an effort signal: raise effort rather
+than adding prose guardrails.
+
+**Verbosity tracks task complexity.** Responses calibrate length to how complex
+the task looks — shorter on lookups, longer on open-ended analysis. If you need a
+specific length or format, state it; a positive example of the target beats a
+"don't be verbose" instruction.
diff --git a/scripts/models.ts b/scripts/models.ts
index b6d1d368d5..cf144bb187 100644
--- a/scripts/models.ts
+++ b/scripts/models.ts
@@ -14,6 +14,7 @@
 export const ALL_MODEL_NAMES = [
   'claude',
   'opus-4-7',
+  'sonnet-5',
   'gpt',
   'gpt-5.4',
   'gemini',
@@ -53,6 +54,7 @@ export function resolveModel(input: string): Model | null {
   if (/^gpt(-|$)/.test(s)) return 'gpt';
   if (/^o[0-9]+(-|$)/.test(s)) return 'o-series';
   if (/^claude-opus-4-7(-|$)/.test(s)) return 'opus-4-7';
+  if (/^claude-sonnet-5(-|$)/.test(s)) return 'sonnet-5';
   if (/^claude(-|$)/.test(s)) return 'claude';
   if (/^gemini(-|$)/.test(s)) return 'gemini';
 
diff --git a/test/model-overlay-sonnet-5.test.ts b/test/model-overlay-sonnet-5.test.ts
new file mode 100644
index 0000000000..4665efc30a
--- /dev/null
+++ b/test/model-overlay-sonnet-5.test.ts
@@ -0,0 +1,56 @@
+/**
+ * Sonnet 5 model overlay — gate-tier assertions on the family nudges.
+ *
+ * sonnet-5 inherits the claude base and adds Sonnet-5 family nudges: literal
+ * instruction following (state scope explicitly), scope work to the request
+ * (raise effort rather than prompting around shallow reasoning), and
+ * verbosity that tracks task complexity.
+ */
+import { describe, test, expect } from 'bun:test';
+import * as fs from 'fs';
+import * as path from 'path';
+import type { TemplateContext } from '../scripts/resolvers/types';
+import { HOST_PATHS } from '../scripts/resolvers/types';
+import { generateModelOverlay } from '../scripts/resolvers/model-overlay';
+
+function makeCtx(model: string): TemplateContext {
+  return {
+    skillName: 'test-skill',
+    tmplPath: 'test.tmpl',
+    host: 'claude',
+    paths: HOST_PATHS.claude,
+    preambleTier: 2,
+    model,
+  };
+}
+
+const ROOT = path.resolve(__dirname, '..');
+
+describe('Sonnet 5 overlay — family nudges', () => {
+  test('raw sonnet-5.md contains the literal-instructions nudge', () => {
+    const raw = fs.readFileSync(path.join(ROOT, 'model-overlays/sonnet-5.md'), 'utf-8');
+    expect(raw).toContain('Instructions are read literally');
+  });
+
+  test('resolved overlay inherits from claude base (INHERIT:claude)', () => {
+    const out = generateModelOverlay(makeCtx('sonnet-5'));
+    expect(out).toContain('Todo-list discipline');
+    expect(out).toContain('subordinate');
+  });
+
+  test('resolved overlay carries the Sonnet 5 nudges', () => {
+    const out = generateModelOverlay(makeCtx('sonnet-5'));
+    expect(out).toContain('Instructions are read literally');
+    expect(out).toContain('Scope work to the request');
+  });
+
+  test('resolved overlay has no unresolved INHERIT directive', () => {
+    const out = generateModelOverlay(makeCtx('sonnet-5'));
+    expect(out).not.toContain('{{INHERIT:');
+  });
+
+  test('claude overlay (base) does not carry the Sonnet 5 nudge', () => {
+    const out = generateModelOverlay(makeCtx('claude'));
+    expect(out).not.toContain('Instructions are read literally');
+  });
+});