diff --git a/src/cmd/init.js b/src/cmd/init.js
index 73bbc47..f058724 100644
--- a/src/cmd/init.js
+++ b/src/cmd/init.js
@@ -27,7 +27,7 @@ export default function register(program) {
             jsonError('agent required', 'run vit init from a coding agent');
             return;
           }
-          console.error(`${name} init should be run by a coding agent (e.g. claude code, gemini cli).`);
+          console.error(`${name} init should be run by a coding agent (e.g. claude code, codex, gemini cli, opencode).`);
           console.error(`open your agent and ask it to run '${name} init' for you.`);
           process.exitCode = 1;
           return;
diff --git a/src/cmd/learn.js b/src/cmd/learn.js
index 30cccbc..a875b74 100644
--- a/src/cmd/learn.js
+++ b/src/cmd/learn.js
@@ -247,7 +247,7 @@ Examples:
             jsonError('agent required', 'run vit learn from a coding agent');
             return;
           }
-          console.error(`${name} learn should be run by a coding agent (e.g. claude code, gemini cli).`);
+          console.error(`${name} learn should be run by a coding agent (e.g. claude code, codex, gemini cli, opencode).`);
           console.error(`open your agent and ask it to run '${name} learn' for you.`);
           process.exitCode = 1;
           return;
diff --git a/src/cmd/remix.js b/src/cmd/remix.js
index 744291c..919bb2f 100644
--- a/src/cmd/remix.js
+++ b/src/cmd/remix.js
@@ -30,7 +30,7 @@ export default function register(program) {
             jsonError('agent required', 'run vit remix from a coding agent');
             return;
           }
-          console.error(`${name} remix should be run by a coding agent (e.g. claude code, gemini cli).`);
+          console.error(`${name} remix should be run by a coding agent (e.g. claude code, codex, gemini cli, opencode).`);
           console.error(`open your agent and ask it to run '${name} remix' for you.`);
           process.exitCode = 1;
           return;
diff --git a/src/cmd/ship.js b/src/cmd/ship.js
index 627d1e3..1941b6b 100644
--- a/src/cmd/ship.js
+++ b/src/cmd/ship.js
@@ -143,7 +143,7 @@ async function shipSkill(opts) {
       jsonError('agent required', 'run vit ship --skill from a coding agent');
       return;
     }
-    console.error(`${name} ship --skill should be run by a coding agent (e.g. claude code, gemini cli).`);
+    console.error(`${name} ship --skill should be run by a coding agent (e.g. claude code, codex, gemini cli, opencode).`);
     console.error(`open your agent and ask it to run '${name} ship --skill' for you.`);
     process.exitCode = 1;
     return;
@@ -352,7 +352,7 @@ async function shipCap(opts) {
       jsonError('agent required', 'run vit ship from a coding agent');
       return;
     }
-    console.error(`${name} ship should be run by a coding agent (e.g. claude code, gemini cli).`);
+    console.error(`${name} ship should be run by a coding agent (e.g. claude code, codex, gemini cli, opencode).`);
     console.error(`open your agent and ask it to run '${name} ship' for you.`);
     console.error(`refer to the using-vit skill (skills/vit/SKILL.md) for a shipping guide.`);
     process.exitCode = 1;
diff --git a/src/cmd/skim.js b/src/cmd/skim.js
index 003317e..715f7c3 100644
--- a/src/cmd/skim.js
+++ b/src/cmd/skim.js
@@ -29,7 +29,7 @@ export default function register(program) {
       try {
         const gate = requireAgent();
         if (!gate.ok) {
-          console.error(`${name} skim should be run by a coding agent (e.g. claude code, gemini cli).`);
+          console.error(`${name} skim should be run by a coding agent (e.g. claude code, codex, gemini cli, opencode).`);
           console.error(`open your agent and ask it to run '${name} skim' for you.`);
           process.exitCode = 1;
           return;
diff --git a/src/lib/agent.js b/src/lib/agent.js
index 52b8235..a71edb4 100644
--- a/src/lib/agent.js
+++ b/src/lib/agent.js
@@ -5,6 +5,7 @@ const CODING_AGENTS = {
   CLAUDECODE: 'claude code',
   GEMINI_CLI: 'gemini cli',
   CODEX_CI: 'codex',
+  OPENCODE: 'opencode',
 };
 
 export function detectCodingAgent() {
diff --git a/test/agent.test.js b/test/agent.test.js
index ba6d3f3..3fdc0fc 100644
--- a/test/agent.test.js
+++ b/test/agent.test.js
@@ -8,14 +8,17 @@ describe('agent', () => {
   let originalClaudeCode;
   let originalGeminiCli;
   let originalCodexCi;
+  let originalOpencode;
 
   beforeEach(() => {
     originalClaudeCode = process.env.CLAUDECODE;
     originalGeminiCli = process.env.GEMINI_CLI;
     originalCodexCi = process.env.CODEX_CI;
+    originalOpencode = process.env.OPENCODE;
     delete process.env.CLAUDECODE;
     delete process.env.GEMINI_CLI;
     delete process.env.CODEX_CI;
+    delete process.env.OPENCODE;
   });
 
   afterEach(() => {
@@ -27,6 +30,9 @@ describe('agent', () => {
 
     if (originalCodexCi === undefined) delete process.env.CODEX_CI;
     else process.env.CODEX_CI = originalCodexCi;
+
+    if (originalOpencode === undefined) delete process.env.OPENCODE;
+    else process.env.OPENCODE = originalOpencode;
   });
 
   describe('detectCodingAgent', () => {
@@ -49,6 +55,11 @@ describe('agent', () => {
       expect(detectCodingAgent()).toEqual({ name: 'codex', envVar: 'CODEX_CI' });
     });
 
+    test('returns opencode when OPENCODE=1', () => {
+      process.env.OPENCODE = '1';
+      expect(detectCodingAgent()).toEqual({ name: 'opencode', envVar: 'OPENCODE' });
+    });
+
     test('returns null when env var is 0', () => {
       process.env.CLAUDECODE = '0';
       expect(detectCodingAgent()).toBe(null);
@@ -58,6 +69,11 @@ describe('agent', () => {
       process.env.CLAUDECODE = '';
       expect(detectCodingAgent()).toBe(null);
     });
+
+    test('returns null when OPENCODE is not 1', () => {
+      process.env.OPENCODE = 'true';
+      expect(detectCodingAgent()).toBe(null);
+    });
   });
 
   describe('requireAgent', () => {
diff --git a/test/helpers.js b/test/helpers.js
index 4f0ac9d..1d8b33b 100644
--- a/test/helpers.js
+++ b/test/helpers.js
@@ -5,6 +5,7 @@ import { join } from 'node:path';
 import { execSync } from 'node:child_process';
 
 const vitBin = join(import.meta.dir, '..', 'bin', 'vit.js');
+const nonAgentEnv = { CLAUDECODE: '', GEMINI_CLI: '', CODEX_CI: '', OPENCODE: '' };
 
 export function run(args, cwd, env, input) {
   try {
@@ -14,7 +15,7 @@ export function run(args, cwd, env, input) {
         encoding: 'utf-8',
         timeout: 30000,
         stdio: ['pipe', 'pipe', 'pipe'],
-        env: env ? { ...process.env, ...env } : undefined,
+        env: { ...process.env, ...nonAgentEnv, ...(env || {}) },
         input,
       }).trim(),
       exitCode: 0,
diff --git a/test/json-output.test.js b/test/json-output.test.js
index edcf717..8ed1bdd 100644
--- a/test/json-output.test.js
+++ b/test/json-output.test.js
@@ -29,7 +29,7 @@ function captureJsonError(input, hintArg) {
     };
   } finally {
     console.log = originalLog;
-    process.exitCode = originalExitCode;
+    process.exitCode = originalExitCode ?? 0;
   }
 }