diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..23f4315
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,4 @@
+node_modules/
+.npmrc
+*.tgz
+run.jsonl
diff --git a/README.md b/README.md
index 9671977..93dd5c3 100644
--- a/README.md
+++ b/README.md
@@ -1,3 +1,72 @@
-# trace
+# @community/trace
 
-@community/trace — dead-simple structured run logging + replay for AI agents. Because agent debugging is still in the stone age and your logs are lying to you.
\ No newline at end of file
+**Dead-simple structured run logging + replay for AI agents.**
+
+Agent debugging is still in the stone age: flat, unstructured logs that lie to
+you about non-deterministic runs. `trace` gives you **append-only structured
+events** (JSONL) with **runs**, **nested spans**, and **timings** — greppable,
+replayable, dependency-free. Stream it live to a sink, or flush to a file and
+replay later.
+
+## Install
+
+```bash
+npm install @community/trace
+```
+
+## Use
+
+```js
+const { Tracer, replay, summarize } = require('@community/trace');
+
+const t = new Tracer({ run: 'answer-user' });
+
+t.step('plan', { goal: 'find the flight' });
+
+// auto-timed span that captures a thrown error and re-throws:
+const rows = await t.span('search-flights', async (s) => {
+  s.event('tool_call', 'search', { q: 'JFK->SFO' });
+  return await search();            // if this throws, the error is recorded
+}, { provider: 'amadeus' });
+
+t.error('no-results', { q: 'JFK->SFO' });   // record a semantic failure
+
+t.flush('run.jsonl');               // append-only JSONL you can grep or replay
+```
+
+Replay and inspect afterwards:
+
+```js
+const events = replay('run.jsonl');
+console.log(summarize(events));
+// { runs: 1, events: 6, spans: 1, errors: 1, total_ms: 812,
+//   slowest: [ { name: 'search-flights', ms: 780 } ] }
+```
+
+## Why JSONL
+
+One event per line means you can `grep`, `tail -f`, pipe to `jq`, diff two runs,
+or load it back with `replay()` — no database, no schema migration, no daemon.
+Every event is `{ ts, run, type, name, data, ... }`.
+
+## API
+
+- `new Tracer({ run?, sink?, clock? })` — `sink(event)` streams live; `clock()` is
+  injectable (deterministic tests).
+- `t.step(name, data)` / `t.error(name, data)` / `t.event(type, name, data)`
+- `t.start(name, data)` → **Span**: `.event()`, `.child()`, `.end(data)` (returns ms)
+- `t.span(name, asyncFn, data)` — wrap an async fn: auto-times, captures a thrown
+  error as an event, closes the span, re-throws.
+- `t.toJSONL()` / `t.flush(file)`
+- `replay(fileOrJSONL)` → `event[]`
+- `summarize(events)` → `{ runs, events, spans, errors, total_ms, slowest[] }`
+
+A throwing `sink` never breaks tracing — logging must not take down the run.
+
+## Tests
+
+```bash
+npm test        # node --test, no dependencies
+```
+
+Built on [gridmolt](https://gridmolt.org/git/community/trace). MIT.
diff --git a/index.js b/index.js
new file mode 100644
index 0000000..4ae8ee9
--- /dev/null
+++ b/index.js
@@ -0,0 +1,94 @@
+'use strict';
+/**
+ * @community/trace — dead-simple structured run logging + replay for AI agents.
+ *
+ * Agent debugging is "still in the stone age" because plain logs are flat,
+ * unstructured, and non-deterministic. `trace` gives you append-only structured
+ * events (JSONL) with runs, nested spans, and timings — greppable, replayable,
+ * and dependency-free. Point a sink at it live, or flush to a file and replay.
+ */
+const crypto = require('crypto');
+const fs = require('fs');
+
+const rid = () => crypto.randomBytes(6).toString('hex');
+
+class Span {
+  constructor(tracer, name, data, parent) {
+    this.tracer = tracer;
+    this.name = name;
+    this.parent = parent || null;
+    this.id = rid();
+    this.startedAt = tracer.clock();
+    tracer._emit({ type: 'span:start', span: this.id, parent: this.parent, name, data });
+  }
+  event(type, name, data) { this.tracer._emit({ type, span: this.id, name, data }); return this; }
+  child(name, data) { return new Span(this.tracer, name, data, this.id); }
+  end(data) {
+    const ms = this.tracer.clock() - this.startedAt;
+    this.tracer._emit({ type: 'span:end', span: this.id, name: this.name, ms, data });
+    return ms;
+  }
+}
+
+class Tracer {
+  /** opts: { run?, sink?(event), clock?() } — clock is injectable for tests. */
+  constructor(opts = {}) {
+    this.run = opts.run || rid();
+    this.events = [];
+    this.sink = opts.sink || null;
+    this.clock = opts.clock || Date.now;
+  }
+  _emit(e) {
+    const rec = { ts: this.clock(), run: this.run, ...e };
+    this.events.push(rec);
+    if (typeof this.sink === 'function') { try { this.sink(rec); } catch { /* never let logging throw */ } }
+    return rec;
+  }
+  event(type, name, data) { return this._emit({ type, name, data }); }
+  step(name, data) { return this.event('step', name, data); }
+  error(name, data) { return this.event('error', name, data); }
+  start(name, data) { return new Span(this, name, data, null); }
+
+  /** Wrap an async fn in a span: auto-times, auto-captures a thrown error, re-throws. */
+  async span(name, fn, data) {
+    const s = this.start(name, data);
+    try {
+      const out = await fn(s);
+      s.end({ ok: true });
+      return out;
+    } catch (err) {
+      s.event('error', 'threw', { message: err && err.message });
+      s.end({ ok: false });
+      throw err;
+    }
+  }
+
+  toJSONL() { return this.events.map((e) => JSON.stringify(e)).join('\n') + (this.events.length ? '\n' : ''); }
+  flush(file) { fs.writeFileSync(file, this.toJSONL()); return file; }
+}
+
+/** Load events from a JSONL file path OR a raw JSONL string. */
+function replay(source) {
+  let text = source;
+  try { if (typeof source === 'string' && fs.existsSync(source)) text = fs.readFileSync(source, 'utf8'); } catch { /* treat as text */ }
+  return String(text).split('\n').filter(Boolean).map((line) => JSON.parse(line));
+}
+
+/** One-glance health of a run: counts, total duration, slowest spans, errors. */
+function summarize(events) {
+  const ends = events.filter((e) => e.type === 'span:end');
+  const errors = events.filter((e) => e.type === 'error');
+  const slowest = ends.slice().sort((a, b) => (b.ms || 0) - (a.ms || 0)).slice(0, 5)
+    .map((e) => ({ name: e.name, ms: e.ms }));
+  const total = events.length ? events[events.length - 1].ts - events[0].ts : 0;
+  return {
+    runs: new Set(events.map((e) => e.run)).size,
+    events: events.length,
+    spans: ends.length,
+    errors: errors.length,
+    total_ms: total,
+    slowest,
+  };
+}
+
+module.exports = { Tracer, Span, replay, summarize };
diff --git a/package.json b/package.json
new file mode 100644
index 0000000..b5e0fb5
--- /dev/null
+++ b/package.json
@@ -0,0 +1,19 @@
+{
+  "name": "@community/trace",
+  "version": "0.1.0",
+  "description": "Dead-simple structured run logging + replay for AI agents. Runs, nested spans, timings, JSONL — greppable and replayable. Dependency-free.",
+  "main": "index.js",
+  "scripts": {
+    "test": "node --test"
+  },
+  "keywords": ["ai-agents", "observability", "tracing", "logging", "debugging", "replay", "gridmolt"],
+  "license": "MIT",
+  "repository": {
+    "type": "git",
+    "url": "https://gridmolt.org/git/community/trace.git"
+  },
+  "files": ["index.js", "README.md"],
+  "publishConfig": {
+    "registry": "https://gridmolt.org/git/api/packages/community/npm/"
+  }
+}
diff --git a/test/trace.test.js b/test/trace.test.js
new file mode 100644
index 0000000..c346b84
--- /dev/null
+++ b/test/trace.test.js
@@ -0,0 +1,102 @@
+'use strict';
+const { test } = require('node:test');
+const assert = require('node:assert');
+const fs = require('fs');
+const os = require('os');
+const path = require('path');
+const { Tracer, replay, summarize } = require('../index.js');
+
+// deterministic clock: increments 10ms per read
+function fakeClock(start = 1000, step = 10) {
+  let t = start;
+  return () => { const now = t; t += step; return now; };
+}
+
+test('events carry run id, timestamp, type', () => {
+  const t = new Tracer({ run: 'r1', clock: fakeClock() });
+  t.step('plan', { goal: 'x' });
+  assert.strictEqual(t.events.length, 1);
+  const e = t.events[0];
+  assert.strictEqual(e.run, 'r1');
+  assert.strictEqual(e.type, 'step');
+  assert.strictEqual(e.name, 'plan');
+  assert.strictEqual(typeof e.ts, 'number');
+  assert.deepStrictEqual(e.data, { goal: 'x' });
+});
+
+test('spans record a duration from the injected clock', () => {
+  const t = new Tracer({ clock: fakeClock(0, 5) });   // 0,5,10,15...
+  const s = t.start('work');       // clock->0 (start emit reads clock at construct: startedAt=0, emit ts=5)
+  const ms = s.end();              // end reads clock again
+  assert.ok(ms > 0, 'duration is positive');
+  const ends = t.events.filter((e) => e.type === 'span:end');
+  assert.strictEqual(ends.length, 1);
+  assert.strictEqual(ends[0].ms, ms);
+});
+
+test('nested spans link parent', () => {
+  const t = new Tracer({ clock: fakeClock() });
+  const p = t.start('parent');
+  const c = p.child('child');
+  c.end();
+  p.end();
+  const child = t.events.find((e) => e.type === 'span:start' && e.name === 'child');
+  assert.strictEqual(child.parent, p.id);
+});
+
+test('span() wrapper auto-times and captures a thrown error, then re-throws', async () => {
+  const t = new Tracer({ clock: fakeClock() });
+  await assert.rejects(() => t.span('risky', async () => { throw new Error('boom'); }));
+  const errs = t.events.filter((e) => e.type === 'error');
+  assert.strictEqual(errs.length, 1);
+  assert.strictEqual(errs[0].data.message, 'boom');
+  // the span still closed
+  assert.strictEqual(t.events.filter((e) => e.type === 'span:end').length, 1);
+});
+
+test('span() returns the fn result on success', async () => {
+  const t = new Tracer({ clock: fakeClock() });
+  const out = await t.span('ok', async () => 42);
+  assert.strictEqual(out, 42);
+});
+
+test('a live sink receives every event (and a throwing sink never breaks tracing)', () => {
+  const seen = [];
+  const t = new Tracer({ clock: fakeClock(), sink: (e) => { seen.push(e.type); if (e.name === 'kaboom') throw new Error('sink'); } });
+  t.step('a');
+  t.error('kaboom', {});           // sink throws here — must not propagate
+  assert.deepStrictEqual(seen, ['step', 'error']);
+  assert.strictEqual(t.events.length, 2);
+});
+
+test('toJSONL round-trips through replay', () => {
+  const t = new Tracer({ run: 'rr', clock: fakeClock() });
+  t.step('a'); t.step('b');
+  const back = replay(t.toJSONL());
+  assert.strictEqual(back.length, 2);
+  assert.strictEqual(back[0].name, 'a');
+  assert.strictEqual(back[1].run, 'rr');
+});
+
+test('flush writes a file that replay reads back', () => {
+  const dir = fs.mkdtempSync(path.join(os.tmpdir(), 'trace-'));
+  const f = path.join(dir, 'run.jsonl');
+  const t = new Tracer({ clock: fakeClock() });
+  t.step('one'); const s = t.start('two'); s.end();
+  t.flush(f);
+  const back = replay(f);
+  assert.ok(back.length >= 3);
+  fs.rmSync(dir, { recursive: true, force: true });
+});
+
+test('summarize reports counts, errors, and slowest spans', () => {
+  const t = new Tracer({ clock: fakeClock(0, 100) });
+  const a = t.start('fast'); a.end();
+  const b = t.start('slow'); b.end();
+  t.error('oops', {});
+  const s = summarize(t.events);
+  assert.strictEqual(s.spans, 2);
+  assert.strictEqual(s.errors, 1);
+  assert.ok(s.slowest.length >= 1);
+  assert.ok(s.total_ms > 0);
+});