diff --git a/packages/net/http-proxy/tests/install.spec.ts b/packages/net/http-proxy/tests/install.spec.ts
index 6b2f1b5e85..431cb3af79 100644
--- a/packages/net/http-proxy/tests/install.spec.ts
+++ b/packages/net/http-proxy/tests/install.spec.ts
@@ -237,9 +237,13 @@ describe('childProxyEnv', () => {
     const dispose = await installGlobalProxy(proxyAll('example.com'))
     try {
       const child = childProxyEnv()
-      // The published policy invented an HTTPS proxy for this process; the child must not see it.
-      expect(child.https_proxy).toBe('socks5://127.0.0.1:1080')
-      expect(child.HTTPS_PROXY).toBeUndefined()
+      // The published policy derived an HTTPS proxy for this process; the child must not see it.
+      // Asserted over both casings rather than one: Windows folds the pair into a single variable,
+      // so which spelling carries the value is the platform's to decide — that it is the user's
+      // value and never the derived one is not.
+      const https = [child.https_proxy, child.HTTPS_PROXY]
+      expect(https).toContain('socks5://127.0.0.1:1080')
+      expect(https).not.toContain(proxyUrl)
       expect(child.HTTP_PROXY).toBe(proxyUrl)
       // The bypass list is the resolved one even though the user set none: it only adds entries,
       // and without it the child sends its own loopback traffic to a proxy that cannot route it.
@@ -312,17 +316,19 @@ describe('childProxyEnv', () => {
       const disposeInner = await installGlobalProxy(nested)
       try {
         const child = childProxyEnv()
-        // Recording the outer install's published environment as the user's would show the
-        // lowercase name it wrote and the outer proxy for a scheme the user never named.
-        expect(child.http_proxy).toBeUndefined()
+        // The user named no HTTPS proxy, so this scheme carries whichever policy is active. Reading
+        // the outer install's published environment as the user's would pin it to the outer proxy
+        // instead — the one discriminator that does not depend on how a platform cases names.
         expect(child.https_proxy).toBe(nestedUrl)
+        expect(child.HTTPS_PROXY).toBe(nestedUrl)
       } finally {
         await disposeInner()
       }
       // Unmounting the inner install must leave the outer one still able to describe that
-      // environment; clearing the record instead sends every later child the normalized values.
+      // environment; clearing the record instead makes this an empty object, so every later child
+      // inherits the normalized values from `process.env` untouched.
       expect(childProxyEnv().HTTP_PROXY).toBe(proxyUrl)
-      expect(childProxyEnv().http_proxy).toBeUndefined()
+      expect(childProxyEnv().https_proxy).toBe(proxyUrl)
     } finally {
       await disposeOuter()
       for (const [name, value] of Object.entries(saved)) {
diff --git a/packages/net/http-proxy/tests/policy.spec.ts b/packages/net/http-proxy/tests/policy.spec.ts
index b76da665fb..6db288e7a1 100644
--- a/packages/net/http-proxy/tests/policy.spec.ts
+++ b/packages/net/http-proxy/tests/policy.spec.ts
@@ -15,6 +15,9 @@ function env(values: Record<string, string>): ReturnType<typeof createLaunchEnvi
   return createLaunchEnvironmentSnapshot([{ source: 'process', values }])
 }
 
+/** Windows folds environment names, so a case distinction cannot be expressed there at all. */
+const FOLDS_ENV_CASE = process.platform === 'win32'
+
 describe('resolveProxyPolicy', () => {
   it('resolves nothing when the environment carries no proxy', () => {
     const { policy, diagnostics } = resolveProxyPolicy(env({}))
@@ -32,7 +35,10 @@ describe('resolveProxyPolicy', () => {
 
   it('prefers the lowercase name, matching undici', () => {
     const { policy } = resolveProxyPolicy(env({ http_proxy: PROXY, HTTP_PROXY: OTHER }))
-    expect(policy.httpProxy).toBe(PROXY)
+    // Windows has no such preference to express: the launch snapshot folds names, so the two
+    // spellings are one variable there and the later entry is simply the value. Asserted rather
+    // than skipped, so a change to that folding fails here instead of passing unnoticed.
+    expect(policy.httpProxy).toBe(FOLDS_ENV_CASE ? OTHER : PROXY)
   })
 
   it('treats a blank lowercase value as unset instead of letting it shadow the uppercase one', () => {
@@ -95,7 +101,9 @@ describe('resolveProxyPolicy', () => {
     const { policy, diagnostics } = resolveProxyPolicy(env({ HTTP_PROXY: 'not a url' }))
     expect(policy).toEqual(DIRECT_POLICY)
     expect(diagnostics[0]?.kind).toBe('invalid')
-    expect(diagnostics[0]?.origin).toBe('HTTP_PROXY')
+    // The origin names the spelling resolution asked for, which on a folded environment is the
+    // lowercase one it tries first — the same variable the user set, reported in the other case.
+    expect(diagnostics[0]?.origin).toBe(FOLDS_ENV_CASE ? 'http_proxy' : 'HTTP_PROXY')
   })
 
   it('reports a proxy URL whose scheme is neither http(s) nor SOCKS', () => {