leonard_agent 0.1.3

Web-compatible harness library.

leonard_agent

Web-compatible harness library for Leonard. This package MUST NOT import dart:io (enforced by tool/check_no_dart_io.sh); concrete sinks and frontends live in sibling packages (CLI, DevTools extension).

Trajectory format (JSONL)

The harness writes one trajectory per session as newline-delimited JSON (JSONL). The TrajectoryWriter (in lib/src/trajectory/writer.dart) serializes typed records via a TrajectorySink and flushes after every record, so a crashed session preserves progress through the last fully written record (PRD §14).

Ordering: exactly one header on line 1, zero or more turn and extension_disabled records interleaved in execution order, exactly one footer on the last line. The writer flushes after every record.

Size budget: sessions are expected to stay under 50 MB / 30 minutes (PRD §23). Readers should stream rather than slurp.

Each record is a JSON object with a type discriminator and snake_case keys.

header

Session metadata: goal, AGENTS.md hash, build identifier, model identifier, harness version, and the manifest of active extensions. The package_version on each extension lets readers detect extension schema mismatches between sessions.

{
  "type": "header",
  "goal": "login",
  "agents_md_hash": "sha256:abc...",
  "build_identifier": "debug-1.0.0",
  "model_identifier": "qwen3.6-35b-a3b@8bit",
  "harness_version": "0.1.0",
  "extensions": [
    {
      "namespace": "router",
      "package_version": "1.2.3",
      "contract_version": "1.0.0"
    }
  ],
  "config": {"turn_budget_ms": 30000}
}

turn

One record per perception-action turn. observation.extensions and diff.extensions are namespace-keyed maps so each extension's contribution can be sliced out by readers without parsing the core payload.

{
  "type": "turn",
  "index": 0,
  "observation": {"core": {}, "extensions": {}},
  "stability": {"policy": "action_relative"},
  "proposed_action": {"tool": "core.tap"},
  "validation": {"result": "ok", "retries": 0},
  "executed_action": {"tool": "core.tap"},
  "diff": {"core": {}, "extensions": {}},
  "summary_update": "tapped login button",
  "model_metadata": {"tokens_in": 10, "tokens_out": 5, "duration_ms": 200}
}

extension_disabled

Emitted when an extension is auto-disabled mid-session (e.g. after repeated failures). The turn field is the index of the next turn the extension is absent from — the timeline panel renders this as the auto-disable point.

{
  "type": "extension_disabled",
  "namespace": "dio",
  "reason": "auto_disabled_after_3_failures",
  "turn": 7
}

footer

Always written exactly once on close(), including on harness_error paths. outcome is one of done, budget_exhausted, harness_error. harness_error is present only when outcome == "harness_error".

{
  "type": "footer",
  "outcome": "budget_exhausted",
  "final_summary": "ran out of turns",
  "total_turns": 25,
  "total_duration_ms": 30000
}

On crash:

{
  "type": "footer",
  "outcome": "harness_error",
  "final_summary": "crashed",
  "total_turns": 4,
  "total_duration_ms": 5000,
  "harness_error": "connection_lost"
}