diff --git a/AGENTS.md b/AGENTS.md
index b366a81..d5c9ce5 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -9,6 +9,10 @@
   - To run tests for a specific file, use `deno task test ./src/server.test.tsx`
   - Prefer running tests more narrowly to reduce token usage. Output is large
     when running all tests.
+  - Use `--reporter=dot` when running all tests, or any run where you don't need
+    a test's console output — it prints detail only for failures, keeping output
+    small. Drop it only when you need debug logs from the specific test you're
+    inspecting.
   - Temporarily change `describe` or `it` to `describe.only` or `it.only` to
     focus specific test groups or cases.
 - Workspace-specific test tasks are available:
diff --git a/docs/getting-started.md b/docs/getting-started.md
index 23d7de8..c992d1d 100644
--- a/docs/getting-started.md
+++ b/docs/getting-started.md
@@ -228,13 +228,11 @@ APP_ENV=production
 NODE_ENV=production
 ```
 
-**`.env.test`** - Test settings (uses a different port so tests can run
-alongside the dev server):
+**`.env.test`** - Test settings:
 
 ```bash
 APP_ENV=test
 OTEL_SERVICE_NAME=my-app-test
-DENO_SERVE_ADDRESS=tcp:0.0.0.0:8100
 ```
 
 > **Note:** These environment files contain only non-sensitive configuration.
@@ -334,13 +332,17 @@ deno task serve:prod
 
 ### Running Tests
 
-Run your test suite on a separate port (8100) so tests don't conflict with the
-dev server:
+Run your test suite:
 
 ```bash
 deno task test
 ```
 
+Tests that spawn the server inject `DENO_SERVE_ADDRESS=tcp:127.0.0.1:0` so it
+binds an OS-assigned free port, then discover the actual URL from the server's
+`Listening on` line. Parallel test runs never collide with each other or with
+the dev server.
+
 ### Code Quality
 
 Check formatting, linting, and type errors:
diff --git a/docs/tutorials/blog.md b/docs/tutorials/blog.md
index 9124f76..3183ab5 100644
--- a/docs/tutorials/blog.md
+++ b/docs/tutorials/blog.md
@@ -915,7 +915,7 @@ Create `main.test.ts` to test the server serves your application:
 
 ```typescript
 // main.test.ts
-import { assertEquals, assertStringIncludes } from "@std/assert";
+import { assert, assertEquals, assertStringIncludes } from "@std/assert";
 import { resolve } from "@std/path/resolve";
 import { mergeReadableStreams, TextLineStream } from "@std/streams";
 import { describe, it } from "@std/testing/bdd";
@@ -948,6 +948,7 @@ describe("serves application when running main.ts", () => {
         `--env-file=${resolve(import.meta.dirname!, "./.env.test")}`,
         resolve(import.meta.dirname!, "./main.ts"),
       ],
+      env: { DENO_SERVE_ADDRESS: "tcp:127.0.0.1:0" },
       stdout: "piped",
       stderr: "piped",
     });
@@ -956,13 +957,16 @@ describe("serves application when running main.ts", () => {
       .pipeThrough(new TextDecoderStream())
       .pipeThrough(new TextLineStream());
 
+    let url = "";
     for await (const line of stdout.values({ preventCancel: true })) {
-      if (line.includes("Listening on")) {
+      if (line.includes("Listening on ")) {
+        url = line.split("Listening on ")[1].split(" ")[0];
         break;
       }
     }
+    assert(url, "server did not report its address");
 
-    const res = await fetch("http://localhost:8100/");
+    const res = await fetch(url);
     assertEquals(res.status, 200);
     assertEquals(res.headers.get("content-type"), "text/html; charset=utf-8");
     const html = await res.text();
@@ -975,7 +979,10 @@ describe("serves application when running main.ts", () => {
 This test:
 
 - Verifies static files are served correctly
-- Spawns the actual server process and makes HTTP requests
+- Spawns the actual server process with `DENO_SERVE_ADDRESS=tcp:127.0.0.1:0` so
+  the OS assigns a free port — parallel test runs never collide
+- Discovers the server's actual URL from its `Listening on` line before making
+  HTTP requests
 - Checks the HTML response contains expected content
 
 For more testing patterns including loader testing, action testing, mocking, and
diff --git a/example/.env.test b/example/.env.test
index 0ae088e..13db43c 100644
--- a/example/.env.test
+++ b/example/.env.test
@@ -1,4 +1,3 @@
 APP_ENV=test
 OTEL_SERVICE_NAME=test
-DENO_SERVE_ADDRESS=tcp:0.0.0.0:8100
 DATABASE_URL=postgresql://test:password@localhost:9401/test
diff --git a/example/README.md b/example/README.md
index b423849..a8f0ea2 100644
--- a/example/README.md
+++ b/example/README.md
@@ -70,7 +70,8 @@ Run your test suite:
 deno task test
 ```
 
-Tests run on port 8100 by default so they don't conflict with the dev server.
+Tests use an OS-assigned port so they don't conflict with the dev server or with
+parallel test runs.
 
 ## Code Quality
 
diff --git a/example/main.test.ts b/example/main.test.ts
index 890e468..f9e9e77 100644
--- a/example/main.test.ts
+++ b/example/main.test.ts
@@ -1,4 +1,4 @@
-import { assertEquals, assertStringIncludes } from "@std/assert";
+import { assert, assertEquals, assertStringIncludes } from "@std/assert";
 import { resolve } from "@std/path/resolve";
 import { mergeReadableStreams, TextLineStream } from "@std/streams";
 import { describe, it } from "@std/testing/bdd";
@@ -31,6 +31,7 @@ describe("serves application when running main.ts", () => {
         `--env-file=${resolve(import.meta.dirname!, "./.env.test")}`,
         resolve(import.meta.dirname!, "./main.ts"),
       ],
+      env: { DENO_SERVE_ADDRESS: "tcp:127.0.0.1:0" },
       stdout: "piped",
       stderr: "piped",
     });
@@ -39,20 +40,16 @@ describe("serves application when running main.ts", () => {
       .pipeThrough(new TextDecoderStream())
       .pipeThrough(new TextLineStream());
 
+    let url = "";
     for await (const line of stdout.values({ preventCancel: true })) {
-      if (line.includes("Listening on")) {
-        const address = Deno.build.os === "windows"
-          ? "http://localhost:8100/"
-          : "http://0.0.0.0:8100/ (http://localhost:8100/)";
-        assertEquals(
-          line,
-          `Listening on ${address}`,
-        );
+      if (line.includes("Listening on ")) {
+        url = line.split("Listening on ")[1].split(" ")[0];
         break;
       }
     }
+    assert(url, "server did not report its address");
 
-    const res = await fetch("http://localhost:8100/");
+    const res = await fetch(url);
     assertEquals(res.status, 200);
     assertEquals(res.headers.get("content-type"), "text/html; charset=utf-8");
     const html = await res.text();
diff --git a/src/utils/global-jsdom.ts b/src/utils/global-jsdom.ts
index c22aab8..9715773 100644
--- a/src/utils/global-jsdom.ts
+++ b/src/utils/global-jsdom.ts
@@ -18,7 +18,7 @@
 import globalJsdom from "global-jsdom";
 import { stubFormData } from "./testing.ts";
 
-// DENO_SERVE_ADDRESS format: "tcp:0.0.0.0:8100".
+// DENO_SERVE_ADDRESS format: "tcp:0.0.0.0:8000".
 const address = Deno.env.get("DENO_SERVE_ADDRESS");
 let port = 8000;
 if (address) {
diff --git a/templates/minimal/.env.test b/templates/minimal/.env.test
index 62dff5a..94e61b3 100644
--- a/templates/minimal/.env.test
+++ b/templates/minimal/.env.test
@@ -1,3 +1,2 @@
 APP_ENV=test
 OTEL_SERVICE_NAME=test
-DENO_SERVE_ADDRESS=tcp:0.0.0.0:8100
diff --git a/templates/minimal/README.md b/templates/minimal/README.md
index 17fab32..8399307 100644
--- a/templates/minimal/README.md
+++ b/templates/minimal/README.md
@@ -67,7 +67,8 @@ Run your test suite:
 deno task test
 ```
 
-Tests run on port 8100 by default so they don't conflict with the dev server.
+Tests use an OS-assigned port so they don't conflict with the dev server or with
+parallel test runs.
 
 ## Code Quality
 
diff --git a/templates/minimal/main.test.ts b/templates/minimal/main.test.ts
index e81d094..262d1af 100644
--- a/templates/minimal/main.test.ts
+++ b/templates/minimal/main.test.ts
@@ -1,4 +1,4 @@
-import { assertEquals, assertStringIncludes } from "@std/assert";
+import { assert, assertEquals, assertStringIncludes } from "@std/assert";
 import { resolve } from "@std/path/resolve";
 import { mergeReadableStreams, TextLineStream } from "@std/streams";
 import { describe, it } from "@std/testing/bdd";
@@ -31,6 +31,7 @@ describe("serves application when running main.ts", () => {
         `--env-file=${resolve(import.meta.dirname!, "./.env.test")}`,
         resolve(import.meta.dirname!, "./main.ts"),
       ],
+      env: { DENO_SERVE_ADDRESS: "tcp:127.0.0.1:0" },
       stdout: "piped",
       stderr: "piped",
     });
@@ -39,20 +40,16 @@ describe("serves application when running main.ts", () => {
       .pipeThrough(new TextDecoderStream())
       .pipeThrough(new TextLineStream());
 
+    let url = "";
     for await (const line of stdout.values({ preventCancel: true })) {
-      if (line.includes("Listening on")) {
-        const address = Deno.build.os === "windows"
-          ? "http://localhost:8100/"
-          : "http://0.0.0.0:8100/ (http://localhost:8100/)";
-        assertEquals(
-          line,
-          `Listening on ${address}`,
-        );
+      if (line.includes("Listening on ")) {
+        url = line.split("Listening on ")[1].split(" ")[0];
         break;
       }
     }
+    assert(url, "server did not report its address");
 
-    const res = await fetch("http://localhost:8100/");
+    const res = await fetch(url);
     assertEquals(res.status, 200);
     assertEquals(res.headers.get("content-type"), "text/html; charset=utf-8");
     const html = await res.text();
diff --git a/templates/postgres/.env.test b/templates/postgres/.env.test
index 7f83d6c..0988e5b 100644
--- a/templates/postgres/.env.test
+++ b/templates/postgres/.env.test
@@ -1,4 +1,3 @@
 APP_ENV=test
 OTEL_SERVICE_NAME=test
-DENO_SERVE_ADDRESS=tcp:0.0.0.0:8100
 DATABASE_URL=postgresql://postgres:postgres@localhost:5432/app_test
diff --git a/templates/postgres/README.md b/templates/postgres/README.md
index ee8ba1b..566da13 100644
--- a/templates/postgres/README.md
+++ b/templates/postgres/README.md
@@ -83,9 +83,9 @@ point at your managed PostgreSQL instance.
 deno task test
 ```
 
-Tests run on port 8100 and connect to the `app_test` database, so make sure
-PostgreSQL is running and migrated (`deno task docker:start` then
-`deno task db:migrate`) before running them.
+Tests use an OS-assigned port (parallel-safe) and connect to the `app_test`
+database, so make sure PostgreSQL is running and migrated
+(`deno task docker:start` then `deno task db:migrate`) before running them.
 
 Any test that triggers a query should call `await closeDb()` in an `afterAll`
 hook (see [services/message.test.ts](services/message.test.ts)) to release the
diff --git a/templates/postgres/main.test.ts b/templates/postgres/main.test.ts
index 992a5de..9771e25 100644
--- a/templates/postgres/main.test.ts
+++ b/templates/postgres/main.test.ts
@@ -1,4 +1,4 @@
-import { assertEquals, assertStringIncludes } from "@std/assert";
+import { assert, assertEquals, assertStringIncludes } from "@std/assert";
 import { resolve } from "@std/path/resolve";
 import { mergeReadableStreams, TextLineStream } from "@std/streams";
 import { describe, it } from "@std/testing/bdd";
@@ -31,6 +31,7 @@ describe("serves application when running main.ts", () => {
         `--env-file=${resolve(import.meta.dirname!, "./.env.test")}`,
         resolve(import.meta.dirname!, "./main.ts"),
       ],
+      env: { DENO_SERVE_ADDRESS: "tcp:127.0.0.1:0" },
       stdout: "piped",
       stderr: "piped",
     });
@@ -39,20 +40,16 @@ describe("serves application when running main.ts", () => {
       .pipeThrough(new TextDecoderStream())
       .pipeThrough(new TextLineStream());
 
+    let url = "";
     for await (const line of stdout.values({ preventCancel: true })) {
-      if (line.includes("Listening on")) {
-        const address = Deno.build.os === "windows"
-          ? "http://localhost:8100/"
-          : "http://0.0.0.0:8100/ (http://localhost:8100/)";
-        assertEquals(
-          line,
-          `Listening on ${address}`,
-        );
+      if (line.includes("Listening on ")) {
+        url = line.split("Listening on ")[1].split(" ")[0];
         break;
       }
     }
+    assert(url, "server did not report its address");
 
-    const res = await fetch("http://localhost:8100/");
+    const res = await fetch(url);
     assertEquals(res.status, 200);
     assertEquals(res.headers.get("content-type"), "text/html; charset=utf-8");
     const html = await res.text();
diff --git a/templates/tailwindcss/.env.test b/templates/tailwindcss/.env.test
index 62dff5a..94e61b3 100644
--- a/templates/tailwindcss/.env.test
+++ b/templates/tailwindcss/.env.test
@@ -1,3 +1,2 @@
 APP_ENV=test
 OTEL_SERVICE_NAME=test
-DENO_SERVE_ADDRESS=tcp:0.0.0.0:8100
diff --git a/templates/tailwindcss/README.md b/templates/tailwindcss/README.md
index 17fab32..8399307 100644
--- a/templates/tailwindcss/README.md
+++ b/templates/tailwindcss/README.md
@@ -67,7 +67,8 @@ Run your test suite:
 deno task test
 ```
 
-Tests run on port 8100 by default so they don't conflict with the dev server.
+Tests use an OS-assigned port so they don't conflict with the dev server or with
+parallel test runs.
 
 ## Code Quality
 
diff --git a/templates/tailwindcss/main.test.ts b/templates/tailwindcss/main.test.ts
index 8ea561a..e50a956 100644
--- a/templates/tailwindcss/main.test.ts
+++ b/templates/tailwindcss/main.test.ts
@@ -1,4 +1,4 @@
-import { assertEquals, assertStringIncludes } from "@std/assert";
+import { assert, assertEquals, assertStringIncludes } from "@std/assert";
 import { resolve } from "@std/path/resolve";
 import { mergeReadableStreams, TextLineStream } from "@std/streams";
 import { describe, it } from "@std/testing/bdd";
@@ -31,6 +31,7 @@ describe("serves application when running main.ts", () => {
         `--env-file=${resolve(import.meta.dirname!, "./.env.test")}`,
         resolve(import.meta.dirname!, "./main.ts"),
       ],
+      env: { DENO_SERVE_ADDRESS: "tcp:127.0.0.1:0" },
       stdout: "piped",
       stderr: "piped",
     });
@@ -39,20 +40,16 @@ describe("serves application when running main.ts", () => {
       .pipeThrough(new TextDecoderStream())
       .pipeThrough(new TextLineStream());
 
+    let url = "";
     for await (const line of stdout.values({ preventCancel: true })) {
-      if (line.includes("Listening on")) {
-        const address = Deno.build.os === "windows"
-          ? "http://localhost:8100/"
-          : "http://0.0.0.0:8100/ (http://localhost:8100/)";
-        assertEquals(
-          line,
-          `Listening on ${address}`,
-        );
+      if (line.includes("Listening on ")) {
+        url = line.split("Listening on ")[1].split(" ")[0];
         break;
       }
     }
+    assert(url, "server did not report its address");
 
-    const res = await fetch("http://localhost:8100/");
+    const res = await fetch(url);
     assertEquals(res.status, 200);
     assertEquals(res.headers.get("content-type"), "text/html; charset=utf-8");
     const html = await res.text();
diff --git a/templates/tanstack/.env.test b/templates/tanstack/.env.test
index 62dff5a..94e61b3 100644
--- a/templates/tanstack/.env.test
+++ b/templates/tanstack/.env.test
@@ -1,3 +1,2 @@
 APP_ENV=test
 OTEL_SERVICE_NAME=test
-DENO_SERVE_ADDRESS=tcp:0.0.0.0:8100
diff --git a/templates/tanstack/README.md b/templates/tanstack/README.md
index 17fab32..8399307 100644
--- a/templates/tanstack/README.md
+++ b/templates/tanstack/README.md
@@ -67,7 +67,8 @@ Run your test suite:
 deno task test
 ```
 
-Tests run on port 8100 by default so they don't conflict with the dev server.
+Tests use an OS-assigned port so they don't conflict with the dev server or with
+parallel test runs.
 
 ## Code Quality
 
diff --git a/templates/tanstack/main.test.ts b/templates/tanstack/main.test.ts
index 262c1e6..7d59b65 100644
--- a/templates/tanstack/main.test.ts
+++ b/templates/tanstack/main.test.ts
@@ -1,4 +1,4 @@
-import { assertEquals, assertStringIncludes } from "@std/assert";
+import { assert, assertEquals, assertStringIncludes } from "@std/assert";
 import { resolve } from "@std/path/resolve";
 import { mergeReadableStreams, TextLineStream } from "@std/streams";
 import { describe, it } from "@std/testing/bdd";
@@ -31,6 +31,7 @@ describe("serves application when running main.ts", () => {
         `--env-file=${resolve(import.meta.dirname!, "./.env.test")}`,
         resolve(import.meta.dirname!, "./main.ts"),
       ],
+      env: { DENO_SERVE_ADDRESS: "tcp:127.0.0.1:0" },
       stdout: "piped",
       stderr: "piped",
     });
@@ -39,20 +40,16 @@ describe("serves application when running main.ts", () => {
       .pipeThrough(new TextDecoderStream())
       .pipeThrough(new TextLineStream());
 
+    let url = "";
     for await (const line of stdout.values({ preventCancel: true })) {
-      if (line.includes("Listening on")) {
-        const address = Deno.build.os === "windows"
-          ? "http://localhost:8100/"
-          : "http://0.0.0.0:8100/ (http://localhost:8100/)";
-        assertEquals(
-          line,
-          `Listening on ${address}`,
-        );
+      if (line.includes("Listening on ")) {
+        url = line.split("Listening on ")[1].split(" ")[0];
         break;
       }
     }
+    assert(url, "server did not report its address");
 
-    const res = await fetch("http://localhost:8100/");
+    const res = await fetch(url);
     assertEquals(res.status, 200);
     assertEquals(res.headers.get("content-type"), "text/html; charset=utf-8");
     const html = await res.text();
diff --git a/tutorials/blog/.env.test b/tutorials/blog/.env.test
index 62dff5a..94e61b3 100644
--- a/tutorials/blog/.env.test
+++ b/tutorials/blog/.env.test
@@ -1,3 +1,2 @@
 APP_ENV=test
 OTEL_SERVICE_NAME=test
-DENO_SERVE_ADDRESS=tcp:0.0.0.0:8100
diff --git a/tutorials/blog/README.md b/tutorials/blog/README.md
index 17fab32..8399307 100644
--- a/tutorials/blog/README.md
+++ b/tutorials/blog/README.md
@@ -67,7 +67,8 @@ Run your test suite:
 deno task test
 ```
 
-Tests run on port 8100 by default so they don't conflict with the dev server.
+Tests use an OS-assigned port so they don't conflict with the dev server or with
+parallel test runs.
 
 ## Code Quality
 
diff --git a/tutorials/blog/main.test.ts b/tutorials/blog/main.test.ts
index 815f8fe..c62526a 100644
--- a/tutorials/blog/main.test.ts
+++ b/tutorials/blog/main.test.ts
@@ -1,4 +1,4 @@
-import { assertEquals, assertStringIncludes } from "@std/assert";
+import { assert, assertEquals, assertStringIncludes } from "@std/assert";
 import { resolve } from "@std/path/resolve";
 import { mergeReadableStreams, TextLineStream } from "@std/streams";
 import { describe, it } from "@std/testing/bdd";
@@ -31,6 +31,7 @@ describe("serves application when running main.ts", () => {
         `--env-file=${resolve(import.meta.dirname!, "./.env.test")}`,
         resolve(import.meta.dirname!, "./main.ts"),
       ],
+      env: { DENO_SERVE_ADDRESS: "tcp:127.0.0.1:0" },
       stdout: "piped",
       stderr: "piped",
     });
@@ -39,20 +40,16 @@ describe("serves application when running main.ts", () => {
       .pipeThrough(new TextDecoderStream())
       .pipeThrough(new TextLineStream());
 
+    let url = "";
     for await (const line of stdout.values({ preventCancel: true })) {
-      if (line.includes("Listening on")) {
-        const address = Deno.build.os === "windows"
-          ? "http://localhost:8100/"
-          : "http://0.0.0.0:8100/ (http://localhost:8100/)";
-        assertEquals(
-          line,
-          `Listening on ${address}`,
-        );
+      if (line.includes("Listening on ")) {
+        url = line.split("Listening on ")[1].split(" ")[0];
         break;
       }
     }
+    assert(url, "server did not report its address");
 
-    const res = await fetch("http://localhost:8100/");
+    const res = await fetch(url);
     assertEquals(res.status, 200);
     assertEquals(res.headers.get("content-type"), "text/html; charset=utf-8");
     const html = await res.text();