feat(opencode): extend NativeToolEngine in OpenCodeEngine

[aaight]

Summary

• Migrates OpenCodeEngine to extend NativeToolEngine instead of directly implementing AgentEngine
• Implements abstract methods: getAllowedEnvExact(), getExtraEnvVars(), resolveEngineModel()
• Overrides afterExecute() to call super.afterExecute() for context file cleanup
• Removes standalone filterProcessEnv wrapper from opencode/env.ts

Changes

src/backends/opencode/index.ts

• Changed implements AgentEngine → extends NativeToolEngine
• Added getAllowedEnvExact() returning OPENAI_API_KEY, ANTHROPIC_API_KEY, OPENROUTER_API_KEY, SQUINT_DB_PATH (plus shared set)
• Added getExtraEnvVars() returning { CI: 'true' }
• Added resolveEngineModel() delegating to resolveOpenCodeModel()
• Replaced direct cleanupContextFiles() call in afterExecute() with super.afterExecute() call
• Removed redundant supportsAgentType() and resolveModel() overrides (now handled by base class)
• Removed AgentEngine import (no longer needed)

src/backends/opencode/env.ts

• Removed standalone filterProcessEnv export (deprecated)
• Kept buildEnv() for use by server.ts which calls it directly

Test plan

• All 6764 unit tests pass (npm test)
• TypeScript type check passes (npm run typecheck)
• Linter passes (npm run lint)
• 19 OpenCode-specific tests pass without changes to assertions
• NativeToolEngine contract tests pass for OpenCodeEngine

Trello card

https://trello.com/c/69c1aa83cf1734b4aa1bab3c

🤖 Generated with Claude Code

🕵️ claude-code · claude-sonnet-4-6 · run details

[codecov]

Codecov Report

❌ Patch coverage is 50.00000% with 9 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/backends/opencode/index.ts	47.05%	9 Missing ⚠️

📢 Thoughts on this report? Let us know!

[nhopeatall]

Summary

Clean migration of OpenCodeEngine from implements AgentEngine to extends NativeToolEngine. The abstract method implementations are correct, the removed filterProcessEnv has no remaining consumers, CI is green, and the change follows the same pattern established by the Codex engine migration.

Should Fix (non-blocking)

• Duplicate env allowlist (src/backends/opencode/index.ts:420-436 / src/backends/opencode/env.ts:15-25): getAllowedEnvExact() in the engine class and ALLOWED_ENV_EXACT in env.ts define the same set of env vars (SHARED_ALLOWED_ENV_EXACT + OPENAI_API_KEY, ANTHROPIC_API_KEY, OPENROUTER_API_KEY, SQUINT_DB_PATH). If one is updated without the other, NativeToolEngine.buildEnv() and the standalone buildEnv() from env.ts (used by server.ts) will diverge silently. This is a pre-existing pattern shared with Codex, so not blocking — but worth a follow-up to make server.ts consume the engine instance's buildEnv() instead, establishing a single source of truth.

• Unnecessary afterExecute override (src/backends/opencode/index.ts:458-460): The override is a pure passthrough — it only calls super.afterExecute(plan, result) with no additional logic. The base class method would be inherited automatically if removed. The Claude Code engine has a similar override but adds cleanupPersistedSession() after super, justifying its existence. Here it adds no behavior, just documentation. Consider removing it to reduce noise — the JSDoc on the base class already documents the contract.

🕵️ claude-code · claude-opus-4-6 · run details