CodeOpen Chat — VS Code Extension

A VS Code extension that adds an OpenCode CLI chat panel to the sidebar — no Copilot Chat @ participant required. Built with JavaScript (CommonJS), styled like the built-in Chat view, with a verified-free-models-only picker.

What's New in v1.1.0

• Clearer daily limit errors — separate retry message for temporary rate limits
• Cross-platform installation screen — Windows, macOS, Linux; input hidden until CLI detected
• Persistent tasks — work continues when sidebar is hidden/moved, with live output restored on return
• Smart input sizing — grows up to 220px (or 35% of view height), then scrolls
• Instant thinking indicator — animated "Working/Thinking" shows immediately on Send
• Message editing — edit below a user message to restore it + attachments; Cancel restores draft; Send creates a new conversation branch while preserving the original in History
• Draft recovery, double-send prevention, partial-output retention — plus improved light/dark layouts
• Adaptive timeout — resets whenever CLI output arrives

Test status: All 96 automated tests + browser interaction checks passed. Provider quota responses were mocked; this environment did not run an authenticated provider or native VS Code on Windows/macOS.

Important: VS Code must remain open for background work. A full window reload/restart does not resume a running task.

Official docs: opencode.ai/docs | VS Code WebviewView API

Quick Start

Prerequisites: Node.js >=18 and OpenCode CLI installed.

1. Launch the extension — open this folder in VS Code and press F5 (Extension Development Host)
2. Open the chat panel — click the CodeOpen Chat icon in the activity bar
3. Pick a model — choose any verified free model from the picker in the input footer
4. Start chatting — select code in your editor for context (optional), type a message, press Enter

The extension auto-detects the CLI on activation. If it's not found, set freecli.opencodePath or run CodeOpen: Retry CLI Detection from the Command Palette.

Features

Chat Panel (freecli.main)

Activity-bar view with header toolbar, status strip, welcome suggestions, message list, and bottom input with Send/Stop — mirrors the Copilot Chat layout.

CLI Detection

Probes opencode --version / --help on activation, fixes PATH for macOS GUI apps, honors freecli.opencodePath setting.

Verified Free Models Only

Loads opencode models --verbose and offers only $0/$0 models (see Free-Model Policy).

Streaming Chat

Runs opencode run --format json --thinking with live NDJSON streaming:

• Session resume via --session
• Model selection via --model provider/model
• Workspace context via --dir <workspace>
• Stop sends SIGTERM → SIGKILL
• Reasoning & tool use render in collapsible "Thought & actions" blocks per response
• Debug log (mirrored to CodeOpen output channel) shows detection, catalog, send, and completion diagnostics
• Live elapsed timer while busy
• "Still waiting" notice after firstByteNoticeSec (default 30s)
• Stalled run timeout after requestTimeoutSec (default 300s, 0 disables) — clear message instead of spinning

During OpenCode status incidents, free models can queue for minutes — the extension always reports what's happening.

Editor Context

• Selection chip shows basename:start-end with file icon (full path in tooltip)
• Live selection re-resolves from open editor or disk at send time
• + button attaches whole files (up to 10, 200 KB each)
• Plan/Build picker: propose without editing (plan) or implement with review (build)
• Agent task lists render in a Todos bar above the input

Rich Answers

Headings, lists, tables, quotes, links (open externally), fenced code blocks with language chip + Copy. Sanitized inline SVG fences render as diagrams; all other HTML escaped.

Patch Review

Post-run changes appear as a Changes proposed card with Review / Apply / Reject:

• Review opens each file in VS Code's native diff editor (old=left/red, new=right/green, only changed lines highlighted)
• Old side prefers pre-run snapshot → git HEAD → staged version (so staged-but-uncommitted files diff correctly), including added/deleted files
• Works in git and non-git workspaces
• Reject restores pre-run state
• Each answer shows timestamp + copy action

Requirements

• VS Code ^1.90.0
• Node.js >=18
• OpenCode CLI (verified with 1.18.18) — install per opencode.ai/docs

Installation

Run from Source (Development)

git clone <this-repo-url>
cd extension
npm test   # no npm install needed: zero runtime dependencies
# Open folder in VS Code, press F5 (Run Extension Development Host)

In the dev host: click CodeOpen Chat icon, pick a free model, start chatting. Select code first to target it.

Package to VSIX

npm test
npx --yes @vscode/vsce package --no-dependencies
# produces codeopen-1.1.0.vsix (name + version from package.json)
code --install-extension codeopen-1.1.0.vsix   # requires `code` CLI on PATH

Usage

1. Open the sidebar — click the CodeOpen Chat activity-bar icon
2. Pick a model — use the model picker in the input footer (or Command Palette). Gear button → Settings (options, diagnostics, debug log)
3. Chat — type a message, press Enter (Shift+Enter for newline). Select code first to attach as context (file:start-end chip). Conversations auto-save to local VS Code storage — use the history icon in the view title bar to reuse/delete sessions
4. Watch live output — streamed text appears with tool-activity lines; press Stop to cancel. Tool steps include direct Diff and file links.
5. Review changes in the original file — when files change, opening any changed file displays the changes in an up-down block diff directly in the original file:
   • Old code (top): Highlighted with a full-width red background (rgba(248, 81, 73, 0.22)), no left border, and no strikethrough.
   • New code (bottom): Displayed directly below the old code with a full-width green background (rgba(46, 160, 67, 0.18)) and no left border.
   • CodeLens actions: Directly above each changed block, ✓ Keep, ✗ Undo, and ⎘ Review Diff actions allow approving or discarding changes right in the editor.
   • Patch Card: The sidebar also offers Review / Keep / Undo controls and per-file diff comparisons.
6. Diagnostics — run CodeOpen: Show Diagnostics to print versions, catalog cache (retrievedAt, source, expiry, refreshStatus), and install hints to the CodeOpen output channel (secrets redacted)

Commands

Title-bar buttons (when view == freecli.main): New Chat, Retry CLI Detection, Conversation History

Settings (freecli.*)

The free-only policy is not user-configurable (cannot relabel paid models as free).

Free-Model Policy

A model is included only when all conditions hold:

• input == 0 && output == 0 (plus zero cache prices)
• Provider is accessible
• No paid auth/subscription required
• Fresh cache

Excluded (fail closed): paid, input-free-output-paid, unknown, stale, conflicting, quota-then-charge, and locked entries.

Verified 1.18.18: 49 eligible / 397 excluded on test machine. Re-validated before every session.

Supported OpenCode capabilities: detection (--version/--help), catalog (models --verbose + costs), programmatic --model, sessions/resume (--session/--continue), NDJSON streaming, cancellation, patch capture with native diff. serve REST and ACP are intentionally unused in v1 (run --format json one-shot per message).

Troubleshooting

Known Limitations

• WebviewView replica — not the built-in Chat view; cannot reuse Copilot's @ participants, variables, or editor:paste actions. Selection context attaches automatically at send time.
• One-shot per message — cold start each turn (run --format json); no persistent serve connection or ACP session loop.
• Model switching starts a new conversation (history is preserved, not silently dropped).
• "Free" = verified $0/$0 at catalog time — quotas/capacity can change; re-validated before every session, fail closed. Zen -free models are "free for a limited time" per OpenCode docs, not permanent.
• Rollback scope — restores only files the agent touched (git checkout HEAD -- path, git clean for new files); unrelated files untouched; unsafe paths refused. Non-git workspaces restore file contents from pre-run snapshot.

Tests

npm test         # node:test — 96 tests, 30 suites, no network/paid API required
npm run lint     # node --check src/extension.js

Coverage:

• Detection (installed/missing/bad-exit)
• Eligibility (zero-cost in; paid/input-free-output-paid/unknown/stale/subscription/locked/quota out)
• Selection (single/multiline/none/unsaved/languages)
• Patches (valid/traversal/stale/empty/conflict/approval/numstat, staged fallback on unborn HEAD, request-scoped review)
• OpenCode streaming (deltas, split chunks, malformed tolerance, non-zero exit, arg-array safety, workspace gate)
• Sessions (isolation, minimal persistence)
• Chat panel (XSS escaping, layout regions, CSP/offline, provider routing, stable thinking gutter, brand icons)

Security

• No shell execution — spawn(exe, argsArray) only; user text stays a single argv element
• Zero external resources — inline CSS/JS, nonce CSP; all AI text HTML-escaped and rendered by minimal local markdown formatter
• Workspace-contained patches — path.relative containment, .. rejection, absolute-escape block; symlinks resolved via path.resolve
• No secrets stored — globalState keeps only model/session-id/workspace; logs redact *_KEY/SECRET/TOKEN/PASSWORD and Bearer values
• AI output treated as untrusted — never executed; tool activity shown only from real CLI events

File Map

src/
├── extension.js                    # Entry point
├── views/chatPanel.js              # WebviewView panel
├── chat/contextBuilder.js          # Editor context → prompt
├── adapters/
│   ├── cliAdapter.js               # Generic CLI wrapper
│   └── openCodeAdapter.js          # OpenCode-specific logic
├── discovery/
│   ├── cliDetector.js              # CLI detection
│   ├── modelCatalog.js             # Model catalog loading/caching
│   └── freeModelPolicy.js          # Free-model eligibility
├── process/
│   ├── processManager.js           # Process lifecycle
│   └── cancellationManager.js      # SIGTERM/SIGKILL handling
├── sessions/
│   ├── sessionManager.js           # Session state
│   └── chatHistory.js              # Conversation persistence
├── patches/
│   ├── patchManager.js             # Patch orchestration
│   ├── diffProvider.js             # Native diff integration
│   ├── patchValidator.js           # Path safety validation
│   ├── applyPatch.js               # Apply changes
│   └── rollbackManager.js          # Reject/restore
├── security/approvalManager.js     # User confirmations
└── utils/
    ├── logging.js                  # Output channel logging
    └── platform.js                 # OS-specific helpers
test/*.test.js                      # 96 tests, 30 suites