OpenCode: support plan mode

[swear01]

What feature would you like to see?

Add plan mode support for OpenCode sessions, same as Claude Code. Currently the plan mode option exists in the web UI permission selector for OpenCode sessions, but selecting it has no effect — tools continue to execute normally and no plan mode is applied to the OpenCode process.

Additional information

Claude Code has full plan mode support with tool execution blocking. OpenCode already has 'plan' in its permission mode definitions (shared/src/modes.ts) and the web UI shows it, but the CLI runner (cli/src/opencode/) never applies it to the OpenCode process or restricts tool execution.

[github-actions]

Verified in the current codebase: OpenCode plan mode is not implemented yet. Also, in this checkout plan is not currently part of the OpenCode permission-mode list, so the current web selector should be driven by default/yolo only. If you are seeing Plan Mode for OpenCode in the UI, that looks like a build/version mismatch or stale frontend state rather than what the current shared mode list exposes.

For implementation, the relevant gap is in the CLI OpenCode path: the selected permission mode is stored and passed through, but OpenCode handling only has the generic permission request flow and auto-approval behavior; I did not find a plan-mode branch that blocks tool execution or maps plan into the OpenCode process.

Relevant code:

• shared/src/modes.ts:29 - OpenCode permission modes are currently default and yolo.
• shared/src/modes.ts:100 - flavor-specific permission mode options come from getPermissionModesForFlavor; OpenCode returns OPENCODE_PERMISSION_MODES.
• web/src/components/AssistantChat/HappyComposer.tsx:288 - composer permission selector uses getPermissionModeOptionsForFlavor(agentFlavor).
• web/src/hooks/mutations/useSessionActions.ts:70 - web rejects permission modes not allowed for the session flavor before calling the API.
• hub/src/web/routes/sessions.ts:279 - hub also rejects unsupported permission modes for the flavor.
• cli/src/commands/opencode.ts:14 - hapi opencode parses modes using OPENCODE_PERMISSION_MODES.
• cli/src/opencode/runOpencode.ts:72 - OpenCode runner keeps current permission mode and forwards it into the queue/session config.
• cli/src/opencode/opencodeRemoteLauncher.ts:111 - remote OpenCode creates an OpencodePermissionHandler using the current permission mode.
• cli/src/opencode/utils/permissionHandler.ts:75 - permission handler reads the mode for each request.
• cli/src/modules/common/permission/BasePermissionHandler.ts:56 - auto-approval logic handles yolo, safe-yolo, and read-only; no plan behavior found.

Need more info:

• What HAPI version or commit are you using where the OpenCode UI shows Plan Mode?
• Was the web app freshly rebuilt/reloaded after upgrading?

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HAPI Bot