Show the token usage and cost

[DinahK-2SO]

Summary of the Pull Request

Show the token usage and cost of the current session.

References and Relevant Issues

• Token consumption #269

Detailed Description of the Pull Request / Additional comments

Show the <token usage> / <context window size> and cost: <number> <unit> of the current session.

The data displayed are from ACP, not altered.

Validation Steps Performed

• Adds unit tests
• Tested in local build:

PR Checklist

• Closes Token consumption #269
• Tests added/passed
• Documentation updated
  • If checked, please file a pull request on our docs repo and link it here: #xxx
• Schema updated (if necessary)

[Copilot]

Pull request overview

Adds end-to-end support for surfacing ACP session usage (token context window + cumulative cost) in the Terminal UI, wiring ACP UsageUpdate notifications through WTA state/projection into the bottom bar.

Changes:

• Plumb ACP UsageUpdate through WTA (helper/client → app state → WT protocol projection) and render it in the Terminal bottom bar.
• Introduce a provider-usage adapter registry (currently no-op / “standard ACP only”) and normalize standard ACP usage into a stable schema for UI consumption.
• Pin/update agent launch commands (Claude/Codex ACP adapters) and switch Gemini to the official --acp flag across Rust/C++/docs/tests.

Reviewed changes

Copilot reviewed 32 out of 32 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
tools/wta/src/wsl_acp.rs	Updates WSL ACP command expectations (pinned adapter versions).
tools/wta/src/usage/providers/mod.rs	Adds provider usage adapter framework and registry.
tools/wta/src/usage/providers/claude.rs	Claude provider adapter (currently standard ACP only).
tools/wta/src/usage/providers/codex.rs	Codex provider adapter (currently standard ACP only).
tools/wta/src/usage/providers/copilot.rs	Copilot provider adapter (reserved private usage slot).
tools/wta/src/usage/providers/gemini.rs	Gemini provider adapter (currently standard ACP only).
tools/wta/src/usage/providers/opencode.rs	OpenCode provider adapter + normalization test for standard usage.
tools/wta/src/usage.rs	Defines usage snapshot/projection + standard ACP usage normalization + tests.
tools/wta/src/session_registry.rs	Updates serialized metadata tests for pinned Claude adapter command.
tools/wta/src/protocol/acp/client.rs	Handles ACP UsageUpdate, redacts trace logging, and improves Gemini model-set handling.
tools/wta/src/master/tests.rs	Updates agent command expectations; adds coalescing tests for usage updates; extends master state for pending usage.
tools/wta/src/master/mod.rs	Coalesces/delays usage notifications via pending_usage + watch to avoid backpressure and preserve cost across updates.
tools/wta/src/main.rs	Exposes the new usage module.
tools/wta/src/coordinator.rs	Updates adapter command strings and related tests.
tools/wta/src/app.rs	Stores per-tab usage snapshot/staleness and clears it on session-boundary operations.
tools/wta/src/app_tests.rs	Adds unit tests for usage lifecycle, projection, and staleness behavior.
tools/wta/src/app_status_projection.rs	Projects usage into the WT protocol agent_state_changed event payload.
tools/wta/src/app_events.rs	Updates app event handling to merge/clear usage and mark stale on transport loss.
tools/wta/src/app_contracts/event.rs	Adds UsageReported / UsageCleared events.
tools/wta/src/agent_registry.rs	Adds agent ID constants, pins adapter commands, switches Gemini to --acp, and updates identification aliases/tests.
src/cascadia/ut_app/TerminalApp.UnitTests.vcxproj	Registers new TerminalApp unit test compilation unit.
src/cascadia/ut_app/AgentUsageTests.cpp	Adds unit tests for parsing/validation and UI text formatting for usage.
src/cascadia/TerminalSettingsEditor/AIAgentsViewModel.cpp	Updates default launch commands (adapter pins + Gemini --acp).
src/cascadia/TerminalApp/TerminalPage.xaml	Adds UsageGroup container to the bottom bar UI.
src/cascadia/TerminalApp/TerminalPage.cpp	Parses usage from agent_state_changed and renders usage summary in the bottom bar; updates command defaults.
src/cascadia/TerminalApp/TerminalAppLib.vcxproj	Adds AgentUsage implementation to the build.
src/cascadia/TerminalApp/Resources/en-US/Resources.resw	Adds new usage-related localized strings (en-US only in this PR).
src/cascadia/TerminalApp/AgentUsage.h	Declares parsing/formatting helpers for usage payloads.
src/cascadia/TerminalApp/AgentUsage.cpp	Implements usage payload validation + cost formatting for display.
src/cascadia/TerminalApp/AgentPaneContent.h	Adds usage cache storage and accessors on the agent pane content.
src/cascadia/TerminalApp/AgentPaneContent.cpp	Applies incoming usage payload into the cached usage state.
doc/installing-dependencies.md	Updates docs to reflect pinned adapter commands.

Comments suppressed due to low confidence (1)

src/cascadia/TerminalApp/TerminalPage.cpp:5006

• Applying usage can throw (e.g. AgentUsage::Parse rejects an unexpected schema). Right now the exception would propagate out of OnAgentStateChanged and potentially terminate the UI thread. Catch and log instead so a bad usage payload doesn’t crash the session UI.

        if (usage.has_value())
        {
            if (const auto agentContent = targetTab->FindAgentPaneContent())
            {
                winrt::get_self<implementation::AgentPaneContent>(agentContent)->ApplyAgentUsage(*usage);
            }
        }

[github-actions]

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on the user/DinahK-2SO/show-usage-calc branch (ℹ️ how do I use this?):

curl -s -S -L 'https://raw.githubusercontent.com/check-spelling/check-spelling/cfb6f7e75bbfc89c71eaa30366d0c166f1bd9c8c/apply.pl' |
perl - 'https://github.com/microsoft/intelligent-terminal/actions/runs/30603623022/attempts/1' &&
git commit -m 'Update check-spelling metadata'

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Dictionary	Entries	Covers	Uniquely
cspell:csharp/csharp.txt	32	2	2
cspell:aws/aws.txt	232	2	2
cspell:fonts/fonts.txt	536	1	1

Consider adding to the extra_dictionaries array (in the .github/actions/spelling/config.json file):

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