diff --git a/src/web/public/app.js b/src/web/public/app.js
index 195a4c43..8e846c18 100644
--- a/src/web/public/app.js
+++ b/src/web/public/app.js
@@ -5440,7 +5440,7 @@ class ClaudemanApp {
           <span class="tab-status ${status}" aria-hidden="true"></span>
           <span class="tab-info">
             <span class="tab-name-row">
-              ${mode === 'shell' ? '<span class="tab-mode shell" aria-hidden="true">sh</span>' : ''}
+              ${mode === 'shell' ? '<span class="tab-mode shell" aria-hidden="true">sh</span>' : mode === 'opencode' ? '<span class="tab-mode opencode" aria-hidden="true">oc</span>' : ''}
               <span class="tab-name" data-session-id="${id}">${this.escapeHtml(name)}</span>
             </span>
             ${showFolder ? `<span class="tab-folder">\u{1F4C1} ${this.escapeHtml(folderName)}</span>` : ''}
@@ -9507,6 +9507,48 @@ class ClaudemanApp {
     }
   }
 
+  async runOpenCode() {
+    const caseName = document.getElementById('quickStartCase').value || 'testcase';
+
+    this.terminal.clear();
+    this.terminal.writeln(`\x1b[1;32m Starting OpenCode session in ${caseName}...\x1b[0m`);
+    this.terminal.writeln('');
+
+    try {
+      // Check if OpenCode is available
+      const statusRes = await fetch('/api/opencode/status');
+      const status = await statusRes.json();
+      if (!status.available) {
+        this.terminal.writeln('\x1b[1;31m OpenCode CLI not found.\x1b[0m');
+        this.terminal.writeln('\x1b[90m Install with: curl -fsSL https://opencode.ai/install | bash\x1b[0m');
+        return;
+      }
+
+      // Quick-start with opencode mode (auto-allow tools by default)
+      const res = await fetch('/api/quick-start', {
+        method: 'POST',
+        headers: { 'Content-Type': 'application/json' },
+        body: JSON.stringify({
+          caseName,
+          mode: 'opencode',
+          openCodeConfig: { autoAllowTools: true },
+        })
+      });
+      const data = await res.json();
+      if (!data.success) throw new Error(data.error || 'Failed to start OpenCode');
+
+      // Switch to the new session
+      if (data.sessionId) {
+        this.activeSessionId = data.sessionId;
+        await this.selectSession(data.sessionId);
+      }
+
+      this.terminal.focus();
+    } catch (err) {
+      this.terminal.writeln(`\x1b[1;31m Error: ${err.message}\x1b[0m`);
+    }
+  }
+
   // ========== Directory Input ==========
 
   toggleDirInput() {
@@ -10263,8 +10305,8 @@ class ClaudemanApp {
 
     this.editingSessionId = sessionId;
 
-    // Reset to Respawn tab
-    this.switchOptionsTab('respawn');
+    // Reset to an appropriate tab — Summary for OpenCode (Respawn/Ralph are Claude-only)
+    this.switchOptionsTab(session.mode === 'opencode' ? 'summary' : 'respawn');
 
     // Update respawn status display and buttons
     const respawnStatus = document.getElementById('sessionRespawnStatus');
@@ -10292,6 +10334,11 @@ class ClaudemanApp {
       respawnSection.style.display = 'none';
     }
 
+    // Hide Claude-specific options for OpenCode sessions
+    const isOpenCode = session.mode === 'opencode';
+    const claudeOnlyEls = document.querySelectorAll('[data-claude-only]');
+    claudeOnlyEls.forEach(el => { el.style.display = isOpenCode ? 'none' : ''; });
+
     // Reset duration presets to default (unlimited)
     this.selectDurationPreset('');
 
diff --git a/src/web/public/index.html b/src/web/public/index.html
index f8cffcb6..50e56dca 100644
--- a/src/web/public/index.html
+++ b/src/web/public/index.html
@@ -238,6 +238,10 @@
               <svg width="20" height="20" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2"><polygon points="5 3 19 12 5 21 5 3"/></svg>
               Run Claude
             </button>
+            <button class="welcome-btn welcome-btn-opencode" onclick="app.runOpenCode()">
+              <svg width="20" height="20" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2"><rect x="3" y="3" width="18" height="18" rx="3"/><path d="M8 12h8M12 8v8"/></svg>
+              Run OpenCode
+            </button>
             <button class="welcome-btn welcome-btn-ralph" onclick="app.showRalphWizard()">
               <svg width="20" height="20" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2"><circle cx="12" cy="12" r="10"/><path d="M12 6v6l4 2"/></svg>
               Start Ralph Loop Wizard
@@ -317,6 +321,9 @@
             <input type="number" id="shellCount" class="tab-count-input" value="1" min="1" max="20" readonly>
             <button class="tab-count-btn" onclick="app.incrementShellCount()">+</button>
           </div>
+          <button class="btn-toolbar btn-opencode" onclick="app.runOpenCode()" title="Run OpenCode (multi-model)">
+            Run OC
+          </button>
           <div class="case-select-group">
             <select id="quickStartCase" class="toolbar-select" title="Select case">
               <option value="testcase">testcase</option>
@@ -496,9 +503,9 @@
         </div>
         <!-- Modal Tabs -->
         <div class="modal-tabs">
-          <button class="modal-tab-btn active" data-tab="respawn" onclick="app.switchOptionsTab('respawn')">Respawn</button>
-          <button class="modal-tab-btn" data-tab="context" onclick="app.switchOptionsTab('context')">Context</button>
-          <button class="modal-tab-btn" data-tab="ralph" onclick="app.switchOptionsTab('ralph')">Ralph / Todo</button>
+          <button class="modal-tab-btn active" data-tab="respawn" data-claude-only onclick="app.switchOptionsTab('respawn')">Respawn</button>
+          <button class="modal-tab-btn" data-tab="context" data-claude-only onclick="app.switchOptionsTab('context')">Context</button>
+          <button class="modal-tab-btn" data-tab="ralph" data-claude-only onclick="app.switchOptionsTab('ralph')">Ralph / Todo</button>
           <button class="modal-tab-btn" data-tab="summary" onclick="app.switchOptionsTab('summary')">Summary</button>
         </div>
         <div class="modal-body">
diff --git a/src/web/public/styles.css b/src/web/public/styles.css
index 61373b3b..908b8b3a 100644
--- a/src/web/public/styles.css
+++ b/src/web/public/styles.css
@@ -616,6 +616,11 @@ body {
   color: var(--yellow);
 }
 
+.session-tab .tab-mode.opencode {
+  background: rgba(16, 185, 129, 0.2);
+  color: #10b981;
+}
+
 /* Timer Banner - Compact */
 .timer-banner {
   display: flex;
@@ -1727,6 +1732,19 @@ body {
   color: #fff;
 }
 
+.welcome-btn-opencode {
+  background: linear-gradient(135deg, #0a2e2a 0%, #0d4a40 100%);
+  border-color: #10b981;
+  color: #6ee7b7;
+}
+
+.welcome-btn-opencode:hover {
+  background: linear-gradient(135deg, #0d4a40 0%, #116a58 100%);
+  border-color: #34d399;
+  box-shadow: 0 0 12px rgba(16, 185, 129, 0.4);
+  color: #a7f3d0;
+}
+
 .welcome-btn-ralph {
   background: linear-gradient(135deg, #3d3415 0%, #4a3f1a 100%);
   border-color: #6b5a1e;
@@ -1876,6 +1894,20 @@ body {
   color: #a8d8a8;
 }
 
+.btn-toolbar.btn-opencode {
+  background: linear-gradient(135deg, #0a2e2a 0%, #0d4a40 100%);
+  border-color: #10b981;
+  color: #6ee7b7;
+  font-weight: 500;
+}
+
+.btn-toolbar.btn-opencode:hover {
+  background: linear-gradient(135deg, #0d4a40 0%, #116a58 100%);
+  border-color: #34d399;
+  box-shadow: 0 0 8px rgba(16, 185, 129, 0.4);
+  color: #a7f3d0;
+}
+
 /* Stop button - hidden on desktop, shown on mobile */
 .btn-toolbar.btn-stop {
   display: none;
diff --git a/src/web/schemas.ts b/src/web/schemas.ts
index a6c10aaf..8ef87ba6 100644
--- a/src/web/schemas.ts
+++ b/src/web/schemas.ts
@@ -34,12 +34,13 @@ const safePathSchema = z.string().max(1000).refine(isValidWorkingDir, {
 // ========== Env Var Allowlist ==========
 
 /** Allowlisted env var key prefixes */
-const ALLOWED_ENV_PREFIXES = ['CLAUDE_CODE_'];
+const ALLOWED_ENV_PREFIXES = ['CLAUDE_CODE_', 'OPENCODE_'];
 
 /** Env var keys that are always blocked (security-sensitive) */
 const BLOCKED_ENV_KEYS = new Set([
   'PATH', 'LD_PRELOAD', 'LD_LIBRARY_PATH', 'NODE_OPTIONS',
   'CLAUDEMAN_MUX_NAME', 'CLAUDEMAN_TMUX',
+  'OPENCODE_SERVER_PASSWORD',  // Security-sensitive: server auth password
 ]);
 
 /** Validate that an env var key is allowed */
@@ -54,7 +55,7 @@ const safeEnvOverridesSchema = z.record(z.string(), z.string()).optional().refin
     if (!val) return true;
     return Object.keys(val).every(isAllowedEnvKey);
   },
-  { message: 'envOverrides contains blocked or disallowed env var keys. Only CLAUDE_CODE_* keys are allowed.' },
+  { message: 'envOverrides contains blocked or disallowed env var keys. Only CLAUDE_CODE_* and OPENCODE_* keys are allowed.' },
 );
 
 // ========== Session Routes ==========
@@ -63,11 +64,21 @@ const safeEnvOverridesSchema = z.record(z.string(), z.string()).optional().refin
  * Schema for POST /api/sessions
  * Creates a new session with optional working directory, mode, and name.
  */
+/** Schema for OpenCode-specific configuration */
+const OpenCodeConfigSchema = z.object({
+  model: z.string().max(100).regex(/^[a-zA-Z0-9._\-/]+$/).optional(),
+  autoAllowTools: z.boolean().optional(),
+  continueSession: z.string().max(100).regex(/^[a-zA-Z0-9_-]+$/).optional(),
+  forkSession: z.boolean().optional(),
+  configContent: z.string().max(10000).optional(),
+}).optional();
+
 export const CreateSessionSchema = z.object({
   workingDir: safePathSchema.optional(),
-  mode: z.enum(['claude', 'shell']).optional(),
+  mode: z.enum(['claude', 'shell', 'opencode']).optional(),
   name: z.string().max(100).optional(),
   envOverrides: safeEnvOverridesSchema,
+  openCodeConfig: OpenCodeConfigSchema,
 });
 
 /**
@@ -106,7 +117,8 @@ export const CreateCaseSchema = z.object({
  */
 export const QuickStartSchema = z.object({
   caseName: z.string().regex(/^[a-zA-Z0-9_-]+$/, 'Invalid case name format. Use only letters, numbers, hyphens, underscores.').optional(),
-  mode: z.enum(['claude', 'shell']).optional(),
+  mode: z.enum(['claude', 'shell', 'opencode']).optional(),
+  openCodeConfig: OpenCodeConfigSchema,
 });
 
 // ========== Hook Events ==========
diff --git a/src/web/server.ts b/src/web/server.ts
index 73e1eb3f..34108feb 100644
--- a/src/web/server.ts
+++ b/src/web/server.ts
@@ -667,6 +667,15 @@ export class WebServer extends EventEmitter {
     // API Routes
     this.app.get('/api/status', async () => this.getLightState());
 
+    // OpenCode CLI availability check
+    this.app.get('/api/opencode/status', async () => {
+      const { isOpenCodeAvailable, resolveOpenCodeDir } = await import('../utils/opencode-cli-resolver.js');
+      return {
+        available: isOpenCodeAvailable(),
+        path: resolveOpenCodeDir(),
+      };
+    });
+
     // Cleanup stale sessions from state file
     this.app.post('/api/cleanup-state', async () => {
       const cleaned = this.cleanupStaleSessions();
@@ -837,13 +846,24 @@ export class WebServer extends EventEmitter {
         await updateCaseEnvVars(workingDir, body.envOverrides);
       }
 
+      // Check OpenCode availability if requested
+      if (body.mode === 'opencode') {
+        const { isOpenCodeAvailable } = await import('../utils/opencode-cli-resolver.js');
+        if (!isOpenCodeAvailable()) {
+          return createErrorResponse(ApiErrorCode.OPERATION_FAILED, 'OpenCode CLI not found. Install with: curl -fsSL https://opencode.ai/install | bash');
+        }
+      }
+
       const globalNice = await this.getGlobalNiceConfig();
       const modelConfig = await this.getModelConfig();
-      const model = (body.mode !== 'shell') ? modelConfig?.defaultModel : undefined;
+      const mode = body.mode || 'claude';
+      const model = mode === 'opencode'
+        ? body.openCodeConfig?.model
+        : (mode !== 'shell' ? modelConfig?.defaultModel : undefined);
       const claudeModeConfig = await this.getClaudeModeConfig();
       const session = new Session({
         workingDir,
-        mode: body.mode || 'claude',
+        mode,
         name: body.name || '',
         mux: this.mux,
         useMux: true,
@@ -851,6 +871,7 @@ export class WebServer extends EventEmitter {
         model,
         claudeMode: claudeModeConfig.claudeMode,
         allowedTools: claudeModeConfig.allowedTools,
+        openCodeConfig: mode === 'opencode' ? body.openCodeConfig : undefined,
       });
 
       this.sessions.set(session.id, session);
@@ -1654,7 +1675,7 @@ export class WebServer extends EventEmitter {
         }
 
         await session.startInteractive();
-        getLifecycleLog().log({ event: 'started', sessionId: id, name: session.name, mode: 'claude' });
+        getLifecycleLog().log({ event: 'started', sessionId: id, name: session.name, mode: session.mode });
         this.broadcast('session:interactive', { id });
         this.broadcast('session:updated', { session: this.getSessionStateWithRespawn(session) });
 
@@ -2004,7 +2025,7 @@ export class WebServer extends EventEmitter {
 
         // Start interactive session
         await session.startInteractive();
-        getLifecycleLog().log({ event: 'started', sessionId: id, name: session.name, mode: 'claude', reason: 'interactive_respawn' });
+        getLifecycleLog().log({ event: 'started', sessionId: id, name: session.name, mode: session.mode, reason: 'interactive_respawn' });
         this.broadcast('session:interactive', { id });
         this.broadcast('session:updated', { session: this.getSessionStateWithRespawn(session) });
 
@@ -2598,7 +2619,15 @@ export class WebServer extends EventEmitter {
       if (!result.success) {
         return createErrorResponse(ApiErrorCode.INVALID_INPUT, result.error.issues[0]?.message ?? 'Validation failed');
       }
-      const { caseName = 'testcase', mode = 'claude' } = result.data;
+      const { caseName = 'testcase', mode = 'claude', openCodeConfig } = result.data;
+
+      // Check OpenCode availability if requested
+      if (mode === 'opencode') {
+        const { isOpenCodeAvailable } = await import('../utils/opencode-cli-resolver.js');
+        if (!isOpenCodeAvailable()) {
+          return createErrorResponse(ApiErrorCode.OPERATION_FAILED, 'OpenCode CLI not found. Install with: curl -fsSL https://opencode.ai/install | bash');
+        }
+      }
 
       const casePath = join(casesDir, caseName);
 
@@ -2622,7 +2651,10 @@ export class WebServer extends EventEmitter {
           writeFileSync(join(casePath, 'CLAUDE.md'), claudeMd);
 
           // Write .claude/settings.local.json with hooks for desktop notifications
-          await writeHooksConfig(casePath);
+          // (Claude-specific — OpenCode uses its own plugin system)
+          if (mode !== 'opencode') {
+            await writeHooksConfig(casePath);
+          }
 
           this.broadcast('case:created', { name: caseName, path: casePath });
         } catch (err) {
@@ -2634,7 +2666,9 @@ export class WebServer extends EventEmitter {
       // Apply global Nice priority config and model config from settings
       const niceConfig = await this.getGlobalNiceConfig();
       const qsModelConfig = await this.getModelConfig();
-      const qsModel = (mode !== 'shell') ? qsModelConfig?.defaultModel : undefined;
+      const qsModel = mode === 'opencode'
+        ? openCodeConfig?.model
+        : (mode !== 'shell' ? qsModelConfig?.defaultModel : undefined);
       const qsClaudeModeConfig = await this.getClaudeModeConfig();
       const session = new Session({
         workingDir: casePath,
@@ -2645,6 +2679,7 @@ export class WebServer extends EventEmitter {
         model: qsModel,
         claudeMode: qsClaudeModeConfig.claudeMode,
         allowedTools: qsClaudeModeConfig.allowedTools,
+        openCodeConfig: mode === 'opencode' ? openCodeConfig : undefined,
       });
 
       // Auto-detect completion phrase from CLAUDE.md BEFORE broadcasting
@@ -2671,9 +2706,10 @@ export class WebServer extends EventEmitter {
           getLifecycleLog().log({ event: 'started', sessionId: session.id, name: session.name, mode: 'shell' });
           this.broadcast('session:interactive', { id: session.id, mode: 'shell' });
         } else {
+          // Both 'claude' and 'opencode' modes use startInteractive()
           await session.startInteractive();
-          getLifecycleLog().log({ event: 'started', sessionId: session.id, name: session.name, mode: 'claude' });
-          this.broadcast('session:interactive', { id: session.id });
+          getLifecycleLog().log({ event: 'started', sessionId: session.id, name: session.name, mode });
+          this.broadcast('session:interactive', { id: session.id, mode });
         }
         this.broadcast('session:updated', { session: this.getSessionStateWithRespawn(session) });