Show HN: A local, extensible session viewer for Pi and Codex

A developer released a local, extensible web viewer for coding-agent session archives that supports Pi and Codex, normalizing both formats into a searchable timeline while preserving raw JSON. The viewer requires Node.js 18 or newer and runs without package installation or build steps, offering features like search, sort, token usage display, and responsive layout.

A local, read-only web viewer for coding-agent session archives. Built-in extensions support Pi https://github.com/badlogic/pi-mono and Codex. The viewer normalizes both formats into one searchable timeline while retaining the original records as expandable raw JSON. - Select between installed session harnesses - Search by prompt, path, session ID, model, or thinking mode - Sort by date, project path, or session ID - Show model, provider, and thinking mode on every event - Display token usage, cache usage, cost when available, timestamps, IDs, and file metadata - Render file writes as code, edits and patches as diffs, and shell calls as commands - Show multi-agent message type, task path, sender, and recipient - Keep tool calls, tool results, skills, reasoning, and raw JSON collapsed until requested - Preserve harness-specific fields in expandable raw JSON - Link directly to a harness and session - Responsive desktop and mobile layout | Harness | Session directory | Default | |---|---|---| | Pi | ~/.pi/agent/sessions | Yes | | Codex | ~/.codex/sessions | No | Only the selected harness is scanned. Results are cached until Refresh is clicked. Codex archives store token usage but not monetary cost, so the viewer reports Not stored instead of inventing an estimate. - Node.js 18 or newer - At least one supported session directory No package installation, template compiler, or build step is required. node server.js Open http://127.0.0.1:4173 http://127.0.0.1:4173 . Harness-aware deep links use this format: http://127.0.0.1:4173/ pi/019f8b7f-f4f4-7441-8291-f18fef3372cf http://127.0.0.1:4173/ codex/SESSION ID Bare SESSION ID links open with whichever installed extension declares default: true . | Environment variable | Default | Purpose | |---|---|---| PORT | 4173 | Local HTTP port | PI SESSIONS DIR | ~/.pi/agent/sessions | Pi session directory | CODEX SESSIONS DIR | ~/.codex/sessions | Codex session directory | Example: PORT=8080 CODEX SESSIONS DIR=~/archives/codex node server.js Every enabled JavaScript file in extensions/ is loaded as trusted local code. An extension implements two operations behind one interface: module.exports = { enabled: true, default: false, id: 'my-harness', label: 'My Harness', defaultRoot: '~/.my-harness/sessions', rootEnv: 'MY HARNESS SESSIONS DIR', async listSessions { root } { return { sessions: , errors: }; }, async loadSession { root, id } { return { summary: {}, events: , parseErrors: }; }, }; Copy extensions/custom-example.js , implement the two methods, and set enabled: true . Extensions may use JSONL, SQLite, or any other local format, but must normalize data into the viewer's shared summary and events shape. The server and browser contain no harness IDs or harness event/tool names. Extensions normalize their records into generic events title , summary , display and message content primitives such as text , context , toolCall , toolResult , command , code , diff , and fileChange . Adding a harness therefore requires only an extension file. Extensions execute with the same filesystem permissions as the server. Install only code you trust. With Node.js: node server.test.js With Bun: bun test server.test.js Use bun test , not bun run : Bun must start its test runner for the node:test API. | File | Purpose | |---|---| server.js | Extension discovery, scan cache, and local HTTP routes | page.html | Static application shell | public/app.js | Harness selector and normalized timeline renderer | public/style.css | Responsive interface styling | extensions/pi.js | Pi adapter | extensions/codex.js | Codex adapter | extensions/custom-example.js | Disabled extension template | extensions/index.js | Trusted extension discovery and validation | lib/jsonl.js | Shared tolerant JSONL reading and recursive discovery | server.test.js | Pi, Codex, extension, page, and stylesheet checks | Session files can contain prompts, source code, command output, paths, and tool results. The viewer: - listens only on localhost; - reads but never modifies session files; - makes no external network requests; - uses only Node.js built-ins at runtime.