mship journal: add --json / --format jsonl exporter for downstream tooling

[atomikpanda]

Problem

The per-task journal is markdown with a structured key-value schema — machine-parseable by tools that know the format. But the pre-existing ecosystem for agent traces (CodeTracer, AgentStepper, dashboards, eval scripts) expects JSON or JSONL.

Dual-writing a parallel .mothership/events/<slug>.jsonl alongside the markdown journal was proposed and rejected: two serializations of the same data diverge; dual-write discipline is expensive; the markdown is canonical by design.

Proposal

Add a read-time transformer. Markdown stays authoritative; JSON/JSONL is a view.

mship journal --task <slug> --json             # all entries as a JSON array
mship journal --task <slug> --format jsonl     # one entry per line
mship journal --task <slug> --action hypothesis --json
mship journal --task <slug> --since last-phase-change --json
mship journal --task <slug> --since <iso-timestamp> --json

Each entry emits a stable JSON object with known fields from the existing LogEntry schema:

{
  "timestamp": "2026-04-24T14:03:12Z",
  "action": "hypothesis",
  "message": "Token refresh race between middleware and frontend retry logic",
  "id": "a3f4c2e1",
  "evidence": "api/tests/auth_test.py:44-71",
  "repo": null,
  "iteration": null,
  "test_state": null,
  "parent": null,
  "category": null,
  "open_question": null
}

Filters (--action, --since, --repo) narrow the emission without changing the field shape. Unknown fields in the markdown source round-trip faithfully.

Why a read-time transformer, not dual-write

• The markdown schema is already load-bearing for downstream tools per the Workflow: systematic debugging loop — mship-aware diagnose → fix → verify #30 design (CodeTracer/AgentStepper parse the key-value kv directly).
• Dual-write introduces an invariant (the two files must stay in sync) that mship doesn't need and can't cheaply enforce.
• Downstream consumers that want JSONL can run mship journal --format jsonl once per ingestion pass.

Minimum filters for v1

• --action <value> — only entries with that action.
• --since <iso-timestamp> — entries newer than a given time.
• --since last-phase-change — entries since the most recent phase-change entry.
• --repo <name> — entries tagged with that repo.

Additional filters (by id, by parent chain, etc.) are followups if demand surfaces.

Out of scope

• No new on-disk files.
• No cross-task aggregation in v1 (query a single task's journal at a time).
• No format-stability guarantee yet — the JSON output follows the markdown's kv schema; new kv fields appear as new JSON keys.

Related

• Builds on Workflow: systematic debugging loop — mship-aware diagnose → fix → verify #30 (closed — systematic debugging loop established the structured vocabulary).
• Complements mship context: one-shot agent-readable JSON of current workspace state #50 (closed — mship context).
• Downstream CodeTracer / AgentStepper / Agent Trace v0.1.0 are the expected consumers.