diff --git a/agent-computer/tests/shell.test.ts b/agent-computer/tests/shell.test.ts
index f83c8322..048e4291 100644
--- a/agent-computer/tests/shell.test.ts
+++ b/agent-computer/tests/shell.test.ts
@@ -216,6 +216,7 @@ describe("the command that actually runs", () => {
     );
 
     const result = await createShell(root, source()).run({
+      // biome-ignore lint/suspicious/noTemplateCurlyInString: the literal `${...}` is the fixture — this asserts on unexpanded placeholder text, so a real template would break the test.
       command: 'echo "[${MARKER:-clean}]"',
     });
 
diff --git a/biome.json b/biome.json
index e1c542f3..753a792c 100644
--- a/biome.json
+++ b/biome.json
@@ -21,5 +21,17 @@
     "parser": {
       "tailwindDirectives": true
     }
-  }
+  },
+  "overrides": [
+    {
+      "includes": ["**/tests/**", "**/*.test.ts", "**/*.test.tsx"],
+      "linter": {
+        "rules": {
+          "style": {
+            "noNonNullAssertion": "off"
+          }
+        }
+      }
+    }
+  ]
 }
diff --git a/package.json b/package.json
index d202dbbf..451c99c9 100644
--- a/package.json
+++ b/package.json
@@ -15,7 +15,7 @@
     "generate:app-config": "bun --env-file=.env scripts/generate-app-config.ts",
     "format": "bunx biome format --write .",
     "format:check": "bunx biome format .",
-    "lint": "bunx biome lint .",
+    "lint": "bunx biome lint --error-on-warnings .",
     "test": "bun test",
     "typecheck": "bun run --filter '*' typecheck",
     "test:ci": "bun scripts/test-ci.ts",
diff --git a/server/tests/skill-ownership.integration.test.ts b/server/tests/skill-ownership.integration.test.ts
index cdb44a40..770f7d80 100644
--- a/server/tests/skill-ownership.integration.test.ts
+++ b/server/tests/skill-ownership.integration.test.ts
@@ -1,6 +1,6 @@
 import { afterAll, beforeAll, describe, expect, test } from "bun:test";
 import { randomUUID } from "node:crypto";
-import { eq, inArray } from "drizzle-orm";
+import { inArray } from "drizzle-orm";
 import { createAuditStore } from "../src/audit";
 import type { ActionPolicy } from "../src/computer/policy";
 import { createDatabase } from "../src/db/client";
@@ -24,7 +24,7 @@ const database = createDatabase(
   TEST_POOL,
 );
 
-let policy: ActionPolicy = { mode: "enforce", deny: [], allow: ["true"] };
+const policy: ActionPolicy = { mode: "enforce", deny: [], allow: ["true"] };
 
 const store = createPluginStore({
   database,
diff --git a/server/tests/tenant-package.test.ts b/server/tests/tenant-package.test.ts
index 5e1dc3c8..911e9684 100644
--- a/server/tests/tenant-package.test.ts
+++ b/server/tests/tenant-package.test.ts
@@ -606,6 +606,7 @@ describe("expanding a package file against the environment", () => {
 
   test("takes the value from the environment", () => {
     expect(
+      // biome-ignore lint/suspicious/noTemplateCurlyInString: the literal `${...}` is the fixture — this asserts on unexpanded placeholder text, so a real template would break the test.
       expandEnvironment("endpoint: ${AG_UI_URL}", file, {
         AG_UI_URL: "https://bots.example.test/ag-ui",
       }),
@@ -615,6 +616,7 @@ describe("expanding a package file against the environment", () => {
   test("falls back to the default when the name is not set", () => {
     expect(
       expandEnvironment(
+        // biome-ignore lint/suspicious/noTemplateCurlyInString: the literal `${...}` is the fixture — this asserts on unexpanded placeholder text, so a real template would break the test.
         "endpoint: ${AG_UI_URL:-http://localhost:4200}",
         file,
         {},
@@ -624,6 +626,7 @@ describe("expanding a package file against the environment", () => {
 
   test("prefers the environment over the default", () => {
     expect(
+      // biome-ignore lint/suspicious/noTemplateCurlyInString: the literal `${...}` is the fixture — this asserts on unexpanded placeholder text, so a real template would break the test.
       expandEnvironment("endpoint: ${AG_UI_URL:-http://localhost:4200}", file, {
         AG_UI_URL: "https://bots.example.test",
       }),
@@ -632,6 +635,7 @@ describe("expanding a package file against the environment", () => {
 
   test("treats an empty value as unset", () => {
     expect(
+      // biome-ignore lint/suspicious/noTemplateCurlyInString: the literal `${...}` is the fixture — this asserts on unexpanded placeholder text, so a real template would break the test.
       expandEnvironment("endpoint: ${AG_UI_URL:-http://localhost:4200}", file, {
         AG_UI_URL: "",
       }),
@@ -639,12 +643,14 @@ describe("expanding a package file against the environment", () => {
   });
 
   test("an empty default is allowed and is not an error", () => {
+    // biome-ignore lint/suspicious/noTemplateCurlyInString: the literal `${...}` is the fixture — this asserts on unexpanded placeholder text, so a real template would break the test.
     expect(expandEnvironment("suffix: ${NOTHING:-}", file, {})).toBe(
       "suffix: ",
     );
   });
 
   test("refuses a name with neither a value nor a default", () => {
+    // biome-ignore lint/suspicious/noTemplateCurlyInString: the literal `${...}` is the fixture — this asserts on unexpanded placeholder text, so a real template would break the test.
     expect(() => expandEnvironment("endpoint: ${AG_UI_URL}", file, {})).toThrow(
       /agents\.yaml refers to \$\{AG_UI_URL\}/,
     );
diff --git a/tests/compose.test.ts b/tests/compose.test.ts
index ce020334..c80b6eba 100644
--- a/tests/compose.test.ts
+++ b/tests/compose.test.ts
@@ -10,6 +10,7 @@ test("provides PostgreSQL with pgvector for local development", () => {
 
   expect(compose).toContain("postgres:");
   expect(compose).toContain("pgvector/pgvector:");
+  // biome-ignore lint/suspicious/noTemplateCurlyInString: the literal `${...}` is the fixture — this asserts on unexpanded placeholder text, so a real template would break the test.
   expect(compose).toContain("${POSTGRES_PORT:-5432}:5432");
 });