diff --git a/README.md b/README.md
index 6124375..a222e0a 100644
--- a/README.md
+++ b/README.md
@@ -70,8 +70,8 @@ override URLs.
 
 Default output is adaptive:
 
-- coding-agent, CI, non-TTY, and automation signals use compact structured
-  agent output;
+- `AGENT` names/flags, coding-agent, CI, non-TTY, and automation signals use
+  compact structured agent output;
 - interactive TTY sessions use human output;
 - `--json`, `--quiet`, `-q`, `--output <mode>`, `-o <mode>`, and `AKUA_OUTPUT`
   override detection.
diff --git a/docs/architecture.md b/docs/architecture.md
index 2a6ef32..98d71d4 100644
--- a/docs/architecture.md
+++ b/docs/architecture.md
@@ -119,7 +119,8 @@ stored with user-only file permissions.
 The default output mode is adaptive:
 
 - `human`: interactive TTY without automation or coding-agent signals;
-- `agent`: known coding-agent env vars, CI env vars, or non-TTY stdout;
+- `agent`: `AGENT` names/flags, known coding-agent env vars, CI env vars, or
+  non-TTY stdout;
 - `json`: explicit `--json`, `--output json`, `-o json`, or
   `AKUA_OUTPUT=json`;
 - `quiet`: explicit `--quiet`, `-q`, `--output quiet`, `-o quiet`, or
diff --git a/src/runtime/mode.ts b/src/runtime/mode.ts
index 0c55e39..be64809 100644
--- a/src/runtime/mode.ts
+++ b/src/runtime/mode.ts
@@ -9,6 +9,7 @@ export interface OutputModeInput {
 }
 
 const AGENT_ENV_VARS = [
+  "AGENT",
   "CODEX_SANDBOX",
   "CODEX_CLI",
   "OPENAI_CODEX",
diff --git a/test/mode.test.ts b/test/mode.test.ts
index 0315e90..95d0050 100644
--- a/test/mode.test.ts
+++ b/test/mode.test.ts
@@ -11,6 +11,14 @@ describe("detectOutputMode", () => {
     expect(detectOutputMode({ argv: [], env: { CODEX_SANDBOX: "1" }, stdoutIsTTY: true })).toBe("agent");
   });
 
+  test("detects universal agent environment flag", () => {
+    expect(detectOutputMode({ argv: [], env: { AGENT: "true" }, stdoutIsTTY: true })).toBe("agent");
+  });
+
+  test("detects universal agent environment name", () => {
+    expect(detectOutputMode({ argv: [], env: { AGENT: "codex" }, stdoutIsTTY: true })).toBe("agent");
+  });
+
   test("detects CI and non-tty automation", () => {
     expect(detectOutputMode({ argv: [], env: { CI: "true" }, stdoutIsTTY: true })).toBe("agent");
     expect(detectOutputMode({ argv: [], env: {}, stdoutIsTTY: false })).toBe("agent");