diff --git a/packages/api/src/adapter-aws/AwsLightsailAdapter.test.ts b/packages/api/src/adapter-aws/AwsLightsailAdapter.test.ts
index 86e7ce2..0f6e07c 100644
--- a/packages/api/src/adapter-aws/AwsLightsailAdapter.test.ts
+++ b/packages/api/src/adapter-aws/AwsLightsailAdapter.test.ts
@@ -16,7 +16,9 @@ import {AwsLightsailAdapter} from './AwsLightsailAdapter'
 const originalEndpoint = process.env.FLOCI_ENDPOINT
 
 afterEach(() => {
-    process.env.FLOCI_ENDPOINT = originalEndpoint
+    // Assigning undefined would store the string "undefined" for every later test file.
+    if (originalEndpoint === undefined) delete process.env.FLOCI_ENDPOINT
+    else process.env.FLOCI_ENDPOINT = originalEndpoint
 })
 
 function stubLightsail() {
diff --git a/packages/api/src/auth.test.ts b/packages/api/src/auth.test.ts
index 2f6f566..2798fa6 100644
--- a/packages/api/src/auth.test.ts
+++ b/packages/api/src/auth.test.ts
@@ -13,7 +13,9 @@ const realFetch = globalThis.fetch
 let passwordHash: string
 
 beforeAll(async () => {
-    passwordHash = await Bun.password.hash('correct-horse-battery')
+    // Cheap parameters keep the many sign-in attempts below fast on slow CI runners; verification
+    // reads the parameters from the hash, so the code under test is unchanged.
+    passwordHash = await Bun.password.hash('correct-horse-battery', {algorithm: 'argon2id', memoryCost: 1024, timeCost: 1})
 })
 
 afterEach(() => {
@@ -239,7 +241,8 @@ describe('auth state cleanup', () => {
     test('caps pending OIDC requests and sweeps expired state', async () => {
         const config = authConfig(oidcEnv({FLOCI_UI_OIDC_ALLOW_ALL_USERS: 'true'}))
         const hono = app(config)
-        globalThis.fetch = (async () => Response.json({authorization_endpoint: 'https://idp.test/authorize', token_endpoint: 'https://idp.test/token', jwks_uri: 'https://idp.test/jwks'})) as unknown as typeof fetch
+        // The same document as mockIdp: discovery is cached per issuer for the rest of the run.
+        globalThis.fetch = (async () => Response.json({authorization_endpoint: 'https://idp.test/authorize', token_endpoint: 'https://idp.test/token', jwks_uri: 'https://idp.test/jwks', userinfo_endpoint: 'https://idp.test/userinfo'})) as unknown as typeof fetch
         for (let index = 0; index < 1_050; index++) await request(hono, '/api/auth/oidc/login', `10.1.${Math.floor(index / 250)}.${index % 250}`)
 
         expect(authStateSizes().oidcRequests).toBe(1_000)
diff --git a/packages/api/src/routes/secretsmanager.test.ts b/packages/api/src/routes/secretsmanager.test.ts
index ba00bac..fad710d 100644
--- a/packages/api/src/routes/secretsmanager.test.ts
+++ b/packages/api/src/routes/secretsmanager.test.ts
@@ -1,13 +1,16 @@
 import {beforeEach, describe, expect, mock, test} from 'bun:test'
 
 // The secretsmanager router imports the `secretsManager` singleton directly from
-// `../aws`, so we replace that module with a stub whose `send()` is driven per
-// test. `responder` returns the fake AWS SDK response and `lastCommand` captures
+// `../aws`, so we replace that export with a stub whose `send()` is driven per
+// test. Bun keeps a module mock for the rest of the run, so every other export
+// stays real: test files that load `../aws` after this one still get it whole. `responder` returns the fake AWS SDK response and `lastCommand` captures
 // the command that was dispatched so we can assert on its input shape.
 let lastCommand: {constructor: {name: string}; input: Record<string, unknown>} | null = null
 let responder: (commandName: string, command: {input: Record<string, unknown>}) => unknown
 
+const realAws = await import('../aws')
 mock.module('../aws', () => ({
+    ...realAws,
     secretsManager: {
         async send(command: {constructor: {name: string}; input: Record<string, unknown>}) {
             lastCommand = command
diff --git a/packages/api/src/services/lightsailDeployment.test.ts b/packages/api/src/services/lightsailDeployment.test.ts
index 0795567..1f4a13f 100644
--- a/packages/api/src/services/lightsailDeployment.test.ts
+++ b/packages/api/src/services/lightsailDeployment.test.ts
@@ -5,7 +5,9 @@ const originalEndpoint = process.env.FLOCI_ENDPOINT
 const originalFetch = globalThis.fetch
 
 afterEach(() => {
-    process.env.FLOCI_ENDPOINT = originalEndpoint
+    // Assigning undefined would store the string "undefined" for every later test file.
+    if (originalEndpoint === undefined) delete process.env.FLOCI_ENDPOINT
+    else process.env.FLOCI_ENDPOINT = originalEndpoint
     globalThis.fetch = originalFetch
     mock.restore()
 })