SPDX-License-Identifier: MPL-2.0 Copyright © 2026 Cristian Camargo Filho

Harness Lens

Early preview

This release discovers supported coding-agent harness files and connects to the external harness-lens-lsp reference server. Do not rely on this preview as a policy or compliance gate.

Harness Lens is an early VS Code integration for coding-agent instruction files.

Quick setup on Windows

Install the extension and its matching native language server together from an official GitHub release:

$installer = Join-Path $env:TEMP "install-harness-lens.ps1"
Invoke-WebRequest "https://github.com/harness-lens/harness-lens-vscode/releases/latest/download/install-harness-lens.ps1" -OutFile $installer
powershell -ExecutionPolicy Bypass -File $installer

See Windows install, uninstall, and extra configuration for uninstall instructions, custom server paths, runtime modes, and contributor installation. CodeBurn remains optional and separate.

Evidence at a glance

The Metrics Center follows the active VS Code theme instead of imposing a separate product palette. It uses editor color tokens throughout and preserves contrast in forced-color environments.

Navigate token use turn by turn while keeping the selected action's evidence and metrics visible.

Harness Lens observed-turn token lens

Review coverage, context, findings, quality, runtime status, and deterministic change direction together.

Harness Lens metrics center overview

Compare content-free local snapshots without sending workspace evidence to a remote dashboard.

Harness Lens local history pagination

Available today

Discover supported harness files in the current workspace.
Show the detected file count in the status bar.
Select a discovered file from a quick picker and open it in the editor.
Publish deterministic repetition and heuristic incongruence diagnostics from the Rust language server.
Interoperate with the Problems view and Error Lens through standard LSP diagnostics.
Browse files, findings, cost, and coverage from the Harness Lens Activity Bar.
Open a metrics center with per-file context/cost, score methods, plugin execution, and up to 100 local content-free history snapshots per workspace.
Classify complete-report changes as improving, stable, degrading, or insufficient evidence using an explicit deterministic delta method.
Show consent-controlled aggregate runtime status from newer language servers; provider selection and runtime mode both default to off for each VS Code window.
Validate schema-versioned provider catalog and aggregate envelopes before using Native or optional-provider status.
Render provider-neutral measured adjacent action transitions as an accessible Sankey and equivalent table. Root, hop, window, category, status, minimum-share, and width-metric filters remain server-derived and bounded.

Not available yet

Code actions or automatic fixes.
Attributed per-file effectiveness.
Per-observation tool-call history and attributed effectiveness comparisons.

Runtime evidence defaults to off, and CodeBurn remains separately disabled for the VS Code window. Run Harness Lens: Enable CodeBurn Provider to review and confirm its local execution boundary. Enabling does not install or launch anything. Then choose live to run a separately installed CodeBurn executable through language server, or snapshot to read a canonical safe aggregate snapshot without process launch. Configure mode, executable, period, snapshot path, and report bound under harnessLens.runtime.* and harnessLens.report.maxFiles; disable harnessLens.providers.codeburn.enabled to clear optional selection. CodeBurn is optional, MIT-licensed, and not bundled. Extension never downloads, installs, or updates it. Aggregate runtime evidence never changes deterministic findings or scores.

Observed flow is separate from CodeBurn aggregate selection and defaults to off. To load a local sanitized trace, set harnessLens.observedFlow.mode to snapshot and harnessLens.observedFlow.snapshotPath to its JSON file. The extension passes only these explicit settings to the server, stores no trace, and renders only a validated bounded relationship graph and aligned per-turn token timeline. The token lens distinguishes measured and explicitly estimated totals, keeps absent usage as a gap, and synchronizes its slider with layered Sankey actions. Its wide layout scales centered visualization controls beside the metrics without hiding overflow; narrow layouts place the metrics below the chart and slider. Use Harness Lens: Refresh Observed Flow after the snapshot changes.

Language server

Install harness-lens-lsp from the language-server repository, or set harnessLens.languageServer.path to an existing binary. The extension starts it only for trusted, filesystem-backed workspaces containing harness files. Use Harness Lens: Restart Language Server after changing the binary. The metrics center requires a server supporting harnessLens/providerAggregate, introduced by language-server [PR #23](https://github.com/harness-lens/language-server/pull/23) and accepted in immutable merge 496f288. Observed flow and the per-turn token timeline additionally require harnessLens/observedFlow and harnessLens.refreshObservedFlow support from language-server [PR #35](https://github.com/harness-lens/language-server/pull/35), pinned at immutable revision 2b7d66b. Language server stays external rather than becoming bundled build dependency. Older servers continue to provide standard diagnostics but cannot populate dashboard.

Use the preview

Select the Harness Lens Activity Bar icon or run Harness Lens: Open Metrics Center. Use Harness Lens: Scan Workspace for the quick picker. The status bar shows the current detected file count.

Supported files:

AGENTS.md
AGENTS.override.md
CLAUDE.md and CLAUDE.local.md
GEMINI.md
SKILL.md, including .agents/skills/ and .claude/skills/
GitHub Copilot instructions and .github/agents/*.agent.md
Claude agents and rules under .claude/
Codex config, agents, and rules under .codex/
compatible rules under .agents/rules/ and .cursor/rules/

See the product tour for the Workspace Observer, scores, runtime, plugins, and local history. The repository's manual installation guide covers source builds, WSL, native language-server, VSIX, and CLI setup.

Feedback and bug reports are welcome in the Harness Lens VS Code repository.

License

Early namespace-reservation versions used BSD-3-Clause. The official extension implementation is licensed under MPL-2.0. See LICENSE and the repository's licensing policy.