Total Session Cost

A real-time, lightweight plugin for Opencode that tracks and displays the actual cumulative cost of your active session, including all background tasks, sub-agents, and child sessions.

Why this plugin?

By default, Opencode only displays the cost of your active main session. However, any background tasks or specialized sub-agents (like explore, coder, or custom test executors) invoked during your conversation run in their own child sub-sessions, keeping their costs hidden.

Without tracking these sub-sessions, you might see a main session cost of a few cents, while the background agents have spent significantly more.

This plugin solves that. It automatically aggregates the costs of your main session and all its nested child tasks, displaying your real, total spending in real-time directly inside the main session.

Features

• Sidebar-Independent: The cost indicator stays visible even when the Opencode sidebar is closed.
• Recursive Sub-Agent Tracking: Automatically detects and sums up the costs of all child tasks spawned during your session.
• Detailed Cost Breakdown: Offers a /total_cost slash command to show a detailed popup separating your active session cost from child task and sub-agent costs.
• Session List Cost View: Offers a /sessions_cost command that opens a dialog with the sessions of the last 7 days grouped by day, showing the total cost (including sub-agents) of each session and of each day.
• Provider & Model Breakdown: Displays the exact costs accumulated per model across all session hierarchy levels.
• Mouse Click Interaction: Left-clicking on the cost bar in the prompt header right panel triggers the same detailed breakdown popup, while right-clicking opens the session costs list.

Installation

Install it globally with:

opencode plugin opencode-total-session-cost -g

Cost categories

The breakdown separates costs into three buckets:

• Session: the cost of the active/root session.
• Task: child sessions spawned through the Task tool by the explore and general agents.
• Sub-agent: any other child session.

Example /total_cost output:

By session
Session:   $0.12
Task:      $0.34
Sub-agent: $0.08
---------------
Total:     $0.54

By provider/model
anthropic/claude-sonnet-4: $0.40
openai/gpt-5:              $0.14
------------------------------
Total:                     $0.54

Cost that cannot be tied to a model (for example spend recorded in the session total without a matching step or message) is reported as unknown/unknown instead of being guessed onto the currently selected model.

Session list costs

Run /sessions_cost (or /session_costs) to open a centered, read-only dialog with the sessions of the last 7 days grouped by day. Each day header shows the total of its sessions and each session row shows its recursive total (session plus every child sub-session). Use the up/down arrows or mouse click to select a session and enter (or click) to display its detailed cost breakdown popup; esc closes the dialog.

Session Costs                                  last 7 days
Today                                              $0.54
  Refactor the parser                              $0.41
  Add integration tests                            $0.13
Wed Sep 16 2026                                    $0.22
  Fix flaky test                                    $0.22

How it works

The plugin runs inside Opencode's TUI framework, recursively fetching session data:

1. It reads the core cost of your active session.
2. It recursively queries all child sub-sessions spawned by sub-agents.
3. It displays the combined sum dynamically in the TUI.

Development

npm install
npm run typecheck
npm test

License

MIT