pi-mono-zig

A Zig re-implementation of the core runtime ideas from pi-mono.

Scope (MVP): a small, auditable plan runner with tool execution + run artifacts. Not a 1:1 rewrite of the entire TypeScript monorepo.

MVP features

• plan.json input (schema, workflow, steps[])
• deterministic topo execution (dependsOn)
• built-in tools: echo, sleep_ms
• fail-closed: missing deps / cycles => error
• artifacts:
  • runs/<runId>/plan.json
  • runs/<runId>/run.json
  • runs/<runId>/steps/<stepId>.json

Build

zig build

Run

zig build run -- run --plan examples/hello.plan.json

Verify a run (artifact chain)

zig build run -- verify --run <runId>

Chat loop (TS-style: messages + tools + session log)

This is a minimal AgentLoop clone (uses a deterministic mock model).

JSONL entries are now structured (not just plain messages):

• type: session
• type: message
• type: tool_call
• type: tool_result
• type: leaf (tracks current leaf for branching)

# creates/extends a JSONL session
zig build run -- chat --session /tmp/pi-session.jsonl

# replay the JSONL log
zig build run -- replay --session /tmp/pi-session.jsonl

Try:

• echo: hello
• sh: ls (only if you pass --allow-shell)

Branching + labels (session tree MVP):

# list current leaf path (shows entryIds)
zig build run -- list --session /tmp/pi-session.jsonl

# label a node
zig build run -- label --session /tmp/pi-session.jsonl --to <entryId> --label ROOT

# branch leaf to an earlier node
zig build run -- branch --session /tmp/pi-session.jsonl --to <entryId>

# replay follows current leaf (root -> leaf path)
zig build run -- replay --session /tmp/pi-session.jsonl

# show full details for one entry
zig build run -- show --session /tmp/pi-session.jsonl --id <entryId>

# show full session tree ("*" marks current leaf path)
zig build run -- tree --session /tmp/pi-session.jsonl

# compact current leaf path into a summary + keep last N nodes
zig build run -- compact --session /tmp/pi-session.jsonl --keep-last 8

# preview compaction summary without writing
zig build run -- compact --session /tmp/pi-session.jsonl --keep-last 8 --dry-run

# TS-aligned structured summary (markdown)
zig build run -- compact --session /tmp/pi-session.jsonl --keep-last 8 --dry-run --structured md

# Update an existing structured summary (naive merge):
# - ensures Next Steps / In Progress placeholders are actionable
# - appends new snippets into Critical Context
zig build run -- compact --session /tmp/pi-session.jsonl --keep-last 8 --structured md --update

# Keep last N complete turn-groups (TS-like) instead of last N entries
zig build run -- compact --session /tmp/pi-session.jsonl --keep-last-groups 2 --structured md

# Record thresholds in the summary stats (manual compaction)
zig build run -- compact --session /tmp/pi-session.jsonl --keep-last-groups 2 --structured md --max-chars 8000 --max-tokens-est 2000

# structured summary (json)
zig build run -- compact --session /tmp/pi-session.jsonl --keep-last 8 --dry-run --structured json

# auto-compact while chatting (naive char-count threshold)
# (now calls the same compaction logic: summary + keep-last tail clone)
zig build run -- chat --session /tmp/pi-session.jsonl --auto-compact --max-chars 8000 --keep-last 8

This currently checks:

• runs/<runId>/plan.json exists and is valid
• runs/<runId>/run.json exists
• runs/<runId>/steps/<stepId>.json exists for every step in the plan
• every step artifact has ok: true and matching runId

Example plan

See examples/hello.plan.json.