diff --git a/packages/deploy/src/modes/cloud.test.ts b/packages/deploy/src/modes/cloud.test.ts
index d1836de5..e12ae4ff 100644
--- a/packages/deploy/src/modes/cloud.test.ts
+++ b/packages/deploy/src/modes/cloud.test.ts
@@ -367,6 +367,9 @@ test('cloud harness plan and BYOK save provider credentials through the cloud co
 });
 
 test('cloud BYOK provider detection avoids substring false positives', async () => {
+  // A bare model name without a provider separator (/) should not match
+  // "openai" via substring — the harness-derived provider wins.
+  // The default test persona has harness: 'codex' → HARNESS_TO_PROVIDER → 'openai'.
   await launch({
     defaultPlanCredential: false,
     persona: persona({ model: 'my-openai-alternative' }),
@@ -374,7 +377,27 @@ test('cloud BYOK provider detection avoids substring false positives', async ()
     input: { harnessSource: 'byok', byokKey: 'sk-test' },
     fetch(url, init) {
       if (url.endsWith('/provider-credentials/byok')) {
-        assert.equal(JSON.parse(String(init?.body)).modelProvider, 'my-openai-alternative');
+        assert.equal(JSON.parse(String(init?.body)).modelProvider, 'openai');
+        return okJson({ providerCredentialId: 'cred-byok' });
+      }
+      if (init?.method === 'GET' && url.endsWith('/deployments')) return okJson({ agents: [] });
+      if (url.endsWith('/deployments')) {
+        return okJson({ agentId: 'agent-byok', deploymentId: 'dep-byok', status: 'active' }, 201);
+      }
+      throw new Error(`unexpected URL ${url}`);
+    }
+  });
+});
+
+test('cloud BYOK opencode harness derives opencode provider', async () => {
+  await launch({
+    defaultPlanCredential: false,
+    persona: persona({ harness: 'opencode', model: 'deepseek-v4-flash-free' }),
+    env: { WORKFORCE_DEPLOY_CLOUD_URL: 'https://cloud.example.test' },
+    input: { harnessSource: 'byok', byokKey: 'sk-or-test' },
+    fetch(url, init) {
+      if (url.endsWith('/provider-credentials/byok')) {
+        assert.equal(JSON.parse(String(init?.body)).modelProvider, 'opencode');
         return okJson({ providerCredentialId: 'cred-byok' });
       }
       if (init?.method === 'GET' && url.endsWith('/deployments')) return okJson({ agents: [] });
diff --git a/packages/deploy/src/modes/cloud/index.ts b/packages/deploy/src/modes/cloud/index.ts
index 03d2e106..d0454831 100644
--- a/packages/deploy/src/modes/cloud/index.ts
+++ b/packages/deploy/src/modes/cloud/index.ts
@@ -953,22 +953,33 @@ async function saveProviderCredential(args: {
   return readCredentialId(body);
 }
 
+const HARNESS_TO_PROVIDER: Record<string, string> = {
+  opencode: 'opencode',
+  claude: 'anthropic',
+  codex: 'openai',
+  grok: 'xai'
+};
+
 function deriveModelProvider(persona: PersonaSpec): string {
-  // Callers gate on `persona.harness` being set before reaching here, so the
-  // harness fallback is always a defined string in practice; default to
-  // 'anthropic' to keep the return type total.
-  const harnessFallback = persona.harness ?? 'anthropic';
+  // When the harness explicitly maps to a known provider, use it directly.
+  // The model string is the model ID within that provider's catalog (e.g.
+  // "deepseek-v4-flash-free" for opencode), not a provider name.
+  const harness = typeof persona.harness === 'string' ? persona.harness.trim().toLowerCase() : '';
+  const harnessProvider = HARNESS_TO_PROVIDER[harness];
+  if (harnessProvider) return harnessProvider;
+
   const model = typeof persona.model === 'string' ? persona.model.trim() : '';
-  if (!model) return harnessFallback;
+  if (!model) return harness || 'anthropic';
   const lower = model.toLowerCase();
   if (matchesProviderToken(lower, ['anthropic', 'claude'])) return 'anthropic';
   if (matchesProviderToken(lower, ['openai', 'codex', 'gpt'])) return 'openai';
   if (matchesProviderToken(lower, ['google', 'gemini'])) return 'google';
-  if (matchesProviderToken(lower, ['openrouter', 'opencode'])) return 'openrouter';
+  if (matchesProviderToken(lower, ['openrouter'])) return 'openrouter';
+  if (matchesProviderToken(lower, ['opencode'])) return 'opencode';
   if (matchesProviderToken(lower, ['grok', 'xai', 'x-ai'])) return 'xai';
   const [provider] = model.split(/[/:]/, 1);
   if (provider?.trim()) return provider.trim().toLowerCase();
-  return harnessFallback;
+  return harness || 'anthropic';
 }
 
 function matchesProviderToken(model: string, tokens: readonly string[]): boolean {
@@ -1069,7 +1080,7 @@ function harnessAliasForModelProvider(modelProvider: string): string {
       return 'codex';
     case 'google':
       return 'gemini';
-    case 'openrouter':
+    case 'opencode':
       return 'opencode';
     case 'xai':
       return 'grok';
diff --git a/packages/runtime/src/cloud-llm.test.ts b/packages/runtime/src/cloud-llm.test.ts
index f64ebe55..dfebf986 100644
--- a/packages/runtime/src/cloud-llm.test.ts
+++ b/packages/runtime/src/cloud-llm.test.ts
@@ -338,3 +338,36 @@ test('empty text content throws instead of returning an empty string', async (t)
   assert.ok(llm);
   await assert.rejects(llm.complete('hi'), /no text content/);
 });
+
+test('OPENCODE_API_KEY routes opencode personas to OpenRouter chat completions', async (t) => {
+  const requests = stubFetch(t, {
+    payload: { choices: [{ message: { content: 'hello from deepseek' } }] }
+  });
+  const llm = createDefaultLlm({
+    persona: { ...basePersona, harness: 'opencode', model: 'deepseek-v4-flash-free' },
+    env: { OPENCODE_API_KEY: 'sk-oc-test' },
+    log: noopLog
+  });
+  assert.ok(llm);
+  const result = await llm.complete('hi', { maxTokens: 512 });
+  assert.equal(result, 'hello from deepseek');
+  const request = requests[0]!;
+  assert.equal(request.url, 'https://openrouter.ai/api/v1/chat/completions');
+  assert.equal(request.headers['authorization'], 'Bearer sk-oc-test');
+  assert.equal(request.body.model, 'deepseek-v4-flash-free');
+  assert.equal(request.body.max_tokens, 512);
+});
+
+test('opencode harness prefers OPENCODE_API_KEY over ANTHROPIC_API_KEY', async (t) => {
+  const requests = stubFetch(t, {
+    payload: { choices: [{ message: { content: 'opencode wins' } }] }
+  });
+  const llm = createDefaultLlm({
+    persona: { ...basePersona, harness: 'opencode', model: 'deepseek-v4-flash-free' },
+    env: { ANTHROPIC_API_KEY: 'sk-ant-test', OPENCODE_API_KEY: 'sk-oc-test' },
+    log: noopLog
+  });
+  assert.ok(llm);
+  await llm.complete('hi');
+  assert.equal(requests[0]!.url, 'https://openrouter.ai/api/v1/chat/completions');
+});
diff --git a/packages/runtime/src/cloud-llm.ts b/packages/runtime/src/cloud-llm.ts
index 4562ab96..03a0d71a 100644
--- a/packages/runtime/src/cloud-llm.ts
+++ b/packages/runtime/src/cloud-llm.ts
@@ -44,6 +44,7 @@ const OPENAI_BASE_URL = 'https://api.openai.com';
 // expect maintenance if chatgpt.com/backend-api/codex changes.
 const CODEX_BACKEND_BASE_URL = 'https://chatgpt.com/backend-api/codex';
 const CODEX_BACKEND_ORIGINATOR = 'codex_cli_rs';
+const OPENROUTER_BASE_URL = 'https://openrouter.ai/api';
 
 export interface CloudLlmOptions {
   persona: PersonaSpec;
@@ -51,8 +52,8 @@ export interface CloudLlmOptions {
   log: WorkforceCtx['log'];
 }
 
-type PersonaModelFamily = 'anthropic' | 'openai' | 'codex';
-type LlmProviderFamily = 'anthropic' | 'openai' | 'codex-backend';
+type PersonaModelFamily = 'anthropic' | 'openai' | 'codex' | 'opencode';
+type LlmProviderFamily = 'anthropic' | 'openai' | 'codex-backend' | 'opencode';
 
 interface LlmCredential {
   family: LlmProviderFamily;
@@ -92,6 +93,9 @@ export function createDefaultLlm(options: CloudLlmOptions): LlmContext | undefin
   if (credential.family === 'codex-backend') {
     return codexBackendLlm(credential, model, options.log);
   }
+  if (credential.family === 'opencode') {
+    return opencodeLlm(credential, model, options.log);
+  }
   return openaiLlm(credential, model, options.log);
 }
 
@@ -103,6 +107,7 @@ function selectCredential(
   const anthropicApiKey = nonEmpty(env.ANTHROPIC_API_KEY);
   const claudeOauth = nonEmpty(env.CLAUDE_CODE_OAUTH_TOKEN);
   const openaiApiKey = nonEmpty(env.OPENAI_API_KEY);
+  const opencodeApiKey = nonEmpty(env.OPENCODE_API_KEY);
   const codexOauth = codexOauthCredential(env);
 
   // Exactly one auth header per request: an OAuth bearer must go on
@@ -142,6 +147,13 @@ function selectCredential(
       source: 'OPENAI_API_KEY'
     });
   }
+  if (opencodeApiKey) {
+    candidates.push({
+      family: 'opencode',
+      headers: { authorization: `Bearer ${opencodeApiKey}` },
+      source: 'OPENCODE_API_KEY'
+    });
+  }
 
   if (candidates.length === 0) return null;
   if (preferred) {
@@ -161,6 +173,9 @@ function preferredCredential(
   if (preferred === 'anthropic') {
     return candidates.find((candidate) => candidate.family === 'anthropic');
   }
+  if (preferred === 'opencode') {
+    return candidates.find((candidate) => candidate.family === 'opencode');
+  }
   if (preferred === 'codex') {
     return (
       candidates.find((candidate) => candidate.family === 'codex-backend') ??
@@ -175,13 +190,16 @@ function preferredCredential(
 
 function personaModelFamily(persona: PersonaSpec): PersonaModelFamily | null {
   const model = nonEmpty(persona.model);
-  if (!model) return null;
-  const normalized = model.toLowerCase();
-  if (normalized.startsWith('anthropic/') || normalized.includes('claude')) return 'anthropic';
-  if (normalized.startsWith('openai-codex/') || normalized.includes('codex')) return 'codex';
-  if (normalized.startsWith('openai/') || normalized.includes('gpt-')) {
-    return 'openai';
+  const harness = nonEmpty(persona.harness);
+  if (!model && !harness) return null;
+  if (model) {
+    const normalized = model.toLowerCase();
+    if (normalized.startsWith('anthropic/') || normalized.includes('claude')) return 'anthropic';
+    if (normalized.startsWith('openai-codex/') || normalized.includes('codex')) return 'codex';
+    if (normalized.startsWith('openai/') || normalized.includes('gpt-')) return 'openai';
+    if (normalized.startsWith('opencode/')) return 'opencode';
   }
+  if (harness === 'opencode') return 'opencode';
   return null;
 }
 
@@ -205,6 +223,7 @@ function resolveModel(persona: PersonaSpec, family: LlmProviderFamily): string {
   }
   if (family === 'anthropic') return DEFAULT_ANTHROPIC_MODEL;
   if (family === 'codex-backend') return DEFAULT_CODEX_BACKEND_MODEL;
+  if (family === 'opencode') return personaModel ?? DEFAULT_OPENAI_MODEL;
   return DEFAULT_OPENAI_MODEL;
 }
 
@@ -214,6 +233,7 @@ function credentialMatchesPersonaFamily(
 ): boolean {
   if (!personaFamily) return false;
   if (credentialFamily === 'anthropic') return personaFamily === 'anthropic';
+  if (credentialFamily === 'opencode') return personaFamily === 'opencode';
   if (credentialFamily === 'codex-backend') {
     return personaFamily === 'codex' || personaFamily === 'openai';
   }
@@ -308,6 +328,41 @@ function openaiLlm(
   };
 }
 
+function opencodeLlm(
+  credential: LlmCredential,
+  model: string,
+  log: WorkforceCtx['log']
+): LlmContext {
+  return {
+    async complete(prompt, opts) {
+      const body = {
+        model,
+        max_tokens: opts?.maxTokens ?? DEFAULT_MAX_TOKENS,
+        messages: [{ role: 'user', content: prompt }]
+      };
+      const payload = await postJson(
+        `${OPENROUTER_BASE_URL}/v1/chat/completions`,
+        {
+          ...credential.headers,
+          'content-type': 'application/json'
+        },
+        body,
+        log
+      );
+      const choices = (payload as { choices?: unknown }).choices;
+      const first = Array.isArray(choices) ? choices[0] : undefined;
+      const text =
+        isRecord(first) && isRecord(first.message) && typeof first.message.content === 'string'
+          ? first.message.content
+          : '';
+      if (!text) {
+        throw new Error('ctx.llm: OpenCode response contained no message content');
+      }
+      return text;
+    }
+  };
+}
+
 function codexBackendLlm(
   credential: LlmCredential,
   model: string,