[FEATURE]: Allow GUI plugins to replace the left session navigation #61296

Feature hasn’t been suggested before.

• I have searched for existing requests; related issues and the distinction from this request are below.

Describe the enhancement you want to request

Please provide an opt-in GUI plugin extension point for the left session/project navigation, so a plugin can implement a complete alternative to Side tabs or Inbox rather than only adding content to a session’s right-side panel.

The current navigation modes are useful for smaller workloads but flat lists become difficult to manage across many projects and sessions. Different workflows need different navigation models: for example, project and session trees with nested, user-defined groups and labels, different ordering or archive handling, or views dynamically organized with assistance from an agent. A replaceable navigation surface would let people experiment with these patterns without requiring every approach to be built into core.

The experimental GUI plugin API already provides session side panels and several slots, but its documented panel region is the session side region and its slots do not include the left session navigation. A right-side panel is not a substitute for replacing the primary session navigator.

Desired capabilities

• Register a custom left-navigation view that the user can explicitly select in place of a built-in navigation mode, with an easy way to restore the default if the plugin is disabled or fails.
• Access the relevant project and session information and updates, including session status and archive state, and use supported host navigation/actions to open and switch sessions.
• Allow plugins to maintain their own grouping, labels, ordering and expanded/collapsed state, without forcing a particular navigation model on everyone.
• Where appropriate, expose the custom navigation’s state and actions to OpenCode/agents through supported interfaces, so an agent can understand or help organize the navigation—not just render an opaque widget. Agent-driven changes should be under user control.

Desktop is the immediate use case; support in the web client would also be valuable when GUI plugins are supported there.

Related requests

• desktop/web: group sidebar sessions by project like Codex Projects view #55446 requests built-in project grouping of sidebar sessions; feat(app): add project grouping, filtering, and pinned sessions to sidebar inbox #59220 and feat(app): add an independent Side bar mode #60867 explore built-in approaches. These are complementary to a general-purpose plugin extension point.
• [FEATURE]: Add named project groups #39284 requests named project groups.
• [FEATURE]: Plugin UI surface for the web/desktop app, mirroring the TUI plugin API #43132 requests broader GUI plugin support, especially on the web. This request is specifically for replacing the left navigation, not the existing right-side session panels or a general sidebar content slot.