feat(opencode): hardcode agent to 'build' and remove selection

src/backends/catalog.ts

@@ -122,19 +122,8 @@ export const OPENCODE_ENGINE_DEFINITION: AgentEngineDefinition = {
 	logLabel: 'OpenCode Log',
 	settings: {
 		title: 'OpenCode Settings',
-		description: 'Headless OpenCode agent selection and permission policy.',
+		description: 'Headless OpenCode permission policy.',
 		fields: [
-			{
-				key: 'agent',
-				label: 'Agent',
-				type: 'select',
-				description: 'Auto uses `plan` for read-only runs and `build` when file edits are allowed.',
-				options: [
-					{ value: 'auto', label: 'Auto' },
-					{ value: 'build', label: 'Build' },
-					{ value: 'plan', label: 'Plan' },
-				],
-			},
 			{
 				key: 'webSearch',
 				label: 'Web Search',

src/backends/opencode/index.ts

@@ -55,14 +55,6 @@ export function resolveOpenCodeModel(cascadeModel: string): string {
 	return DEFAULT_OPENCODE_MODEL;
 }
 
-export function resolveOpenCodeAgent(
-	setting: 'auto' | 'build' | 'plan',
-	nativeToolCapabilities?: string[],
-): 'build' | 'plan' {
-	if (setting !== 'auto') return setting;
-	return nativeToolCapabilities?.includes('fs:write') ? 'build' : 'plan';
-}
-
 type PermissionDecision = 'allow' | 'deny';
 
 type OpenCodePermissionConfig = NonNullable<Config['permission']>;
@@ -832,7 +824,7 @@ export class OpenCodeEngine implements AgentEngine {
 
 	async execute(input: AgentExecutionPlan): Promise<AgentEngineResult> {
 		const settings = resolveOpenCodeSettings(input.project, input.config);
-		const agent = resolveOpenCodeAgent(settings.agent, input.nativeToolCapabilities);
+		const agent = 'build' as const;
 		const model = resolveOpenCodeModel(input.model);
 		const config = buildConfig(input, model, settings);
 		const { prompt: taskPrompt, hasOffloadedContext } = await buildTaskPrompt(

src/backends/opencode/settings.ts

@@ -6,8 +6,7 @@ import {
 import type { EngineSettings, OpenCodeSettings } from '../../config/engineSettings.js';
 import type { CascadeConfig, ProjectConfig } from '../../types/index.js';
 
-export interface ResolvedOpenCodeSettings
-	extends Required<Pick<OpenCodeSettings, 'agent' | 'webSearch'>> {}
+export interface ResolvedOpenCodeSettings extends Required<Pick<OpenCodeSettings, 'webSearch'>> {}
 
 export function resolveOpenCodeSettings(
 	project: ProjectConfig,
@@ -20,7 +19,6 @@ export function resolveOpenCodeSettings(
 	const opencode = getEngineSettings(merged, 'opencode', OpenCodeSettingsSchema) ?? {};
 
 	return {
-		agent: opencode.agent ?? 'auto',
 		webSearch: opencode.webSearch ?? false,
 	};
 }

src/config/engineSettings.ts

@@ -8,7 +8,6 @@ export const CodexSettingsSchema = z.object({
 });
 
 export const OpenCodeSettingsSchema = z.object({
-	agent: z.enum(['auto', 'build', 'plan']).optional(),
 	webSearch: z.boolean().optional(),
 });
 

tests/unit/backends/opencode.test.ts

@@ -38,7 +38,6 @@ vi.mock('../../../src/utils/logging.js', () => ({
 import {
 	OpenCodeEngine,
 	buildPermissionConfig,
-	resolveOpenCodeAgent,
 	resolveOpenCodeModel,
 } from '../../../src/backends/opencode/index.js';
 import { DEFAULT_OPENCODE_MODEL } from '../../../src/backends/opencode/models.js';
@@ -156,16 +155,6 @@ describe('resolveOpenCodeModel', () => {
 	});
 });
 
-describe('resolveOpenCodeAgent', () => {
-	it('uses build for write-capable runs when auto', () => {
-		expect(resolveOpenCodeAgent('auto', ['fs:read', 'fs:write'])).toBe('build');
-	});
-
-	it('uses plan for read-only runs when auto', () => {
-		expect(resolveOpenCodeAgent('auto', ['fs:read'])).toBe('plan');
-	});
-});
-
 describe('buildPermissionConfig', () => {
 	it('denies write, bash, and web by default', () => {
 		expect(buildPermissionConfig(['fs:read'], false)).toEqual({
@@ -189,10 +178,9 @@ describe('buildPermissionConfig', () => {
 });
 
 describe('resolveOpenCodeSettings', () => {
-	it('defaults to auto agent and webSearch=false', () => {
+	it('defaults to webSearch=false', () => {
 		const input = makeInput();
 		expect(resolveOpenCodeSettings(input.project, input.config)).toEqual({
-			agent: 'auto',
 			webSearch: false,
 		});
 	});
@@ -203,17 +191,16 @@ describe('resolveOpenCodeSettings', () => {
 				...makeInput().config,
 				defaults: {
 					...makeInput().config.defaults,
-					engineSettings: { opencode: { agent: 'plan', webSearch: false } },
+					engineSettings: { opencode: { webSearch: false } },
 				},
 			},
 			project: {
 				...makeInput().project,
-				engineSettings: { opencode: { agent: 'build', webSearch: true } },
+				engineSettings: { opencode: { webSearch: true } },
 			},
 		});
 
 		expect(resolveOpenCodeSettings(input.project, input.config)).toEqual({
-			agent: 'build',
 			webSearch: true,
 		});
 	});

tests/unit/config/schema.test.ts

@@ -123,14 +123,12 @@ describe('ProjectConfigSchema', () => {
 			trello: { boardId: 'b1', lists: {}, labels: {} },
 			engineSettings: {
 				opencode: {
-					agent: 'plan',
 					webSearch: true,
 				},
 			},
 		};
 
 		const result = ProjectConfigSchema.parse(config);
-		expect(result.engineSettings?.opencode?.agent).toBe('plan');
 		expect(result.engineSettings?.opencode?.webSearch).toBe(true);
 	});
 
@@ -334,14 +332,12 @@ describe('validateConfig', () => {
 			defaults: {
 				engineSettings: {
 					opencode: {
-						agent: 'build',
 						webSearch: true,
 					},
 				},
 			},
 		});
 
-		expect(result.defaults.engineSettings.opencode?.agent).toBe('build');
 		expect(result.defaults.engineSettings.opencode?.webSearch).toBe(true);
 	});