diff --git a/CHANGELOG.md b/CHANGELOG.md
index 6980c66..e261454 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,12 @@
 
 All notable changes to this project are documented in this file.
 
+## [Unreleased]
+
+### Fixed
+
+- **GitHub Copilot models.dev provider alias** — `resolveProviderAlias()` in `src/models-dev.ts` incorrectly mapped both `gh` and `github` provider prefixes to `google` when looking up models.dev capability/context-window fallback data. GitHub Copilot proxies many upstream providers (Anthropic, OpenAI, xAI, etc.), not just Google, so this misdirected any models.dev fallback lookup for `gh/*`/`github/*` models into the wrong provider's data. Now correctly maps to `github-copilot`, models.dev's actual provider key. 5 new tests in `test/provider-alias.test.mjs`. (resolves #45)
+
 ## [1.2.2] - 2026-05-22
 
 ### Added
diff --git a/src/models-dev.ts b/src/models-dev.ts
index 429f8c7..9089b16 100644
--- a/src/models-dev.ts
+++ b/src/models-dev.ts
@@ -608,8 +608,8 @@ export function resolveProviderAlias(
     glm: 'zai-coding-plan',
     'kimi-coding': 'moonshotai',
     kmc: 'moonshotai',
-    gh: 'google',
-    github: 'google',
+    gh: 'github-copilot',
+    github: 'github-copilot',
     ...config?.modelsDev?.providerAliases,
   };
 
diff --git a/test/provider-alias.test.mjs b/test/provider-alias.test.mjs
new file mode 100644
index 0000000..cfbc30b
--- /dev/null
+++ b/test/provider-alias.test.mjs
@@ -0,0 +1,31 @@
+import test from 'node:test';
+import assert from 'node:assert/strict';
+
+import { resolveProviderAlias } from '../dist/src/models-dev.js';
+
+test('resolveProviderAlias maps gh/github to github-copilot, not google', () => {
+  assert.equal(resolveProviderAlias('gh'), 'github-copilot');
+  assert.equal(resolveProviderAlias('github'), 'github-copilot');
+  assert.equal(resolveProviderAlias('GH'), 'github-copilot');
+  assert.equal(resolveProviderAlias('GitHub'), 'github-copilot');
+});
+
+test('resolveProviderAlias still maps gemini/google to google', () => {
+  assert.equal(resolveProviderAlias('gemini'), 'google');
+  assert.equal(resolveProviderAlias('google'), 'google');
+});
+
+test('resolveProviderAlias allows user config to override defaults', () => {
+  assert.equal(
+    resolveProviderAlias('gh', { modelsDev: { providerAliases: { gh: 'custom-provider' } } }),
+    'custom-provider',
+  );
+});
+
+test('resolveProviderAlias falls back to the lowercased key when unknown', () => {
+  assert.equal(resolveProviderAlias('SomeUnknownProvider'), 'someunknownprovider');
+});
+
+test('resolveProviderAlias returns null for null input', () => {
+  assert.equal(resolveProviderAlias(null), null);
+});