The loop

The problem

A flight recorder reads the tape after the flight lands. Every other tool in this product does the same thing: it opens a transcript someone already finished writing and tells you what happened. Useful, but it means the answer to "what is my other agent doing right now" is always "let me go check," never "here."

And there's a sharper problem underneath that one. Several agents can share a machine and a checkout. When a file you read five minutes ago is different now, was that you, another one of your own sessions, or something else entirely? A transcript alone can't say — it only knows what its own agent did.

The return path

The fix is a return path from the harness back into Archie, while the agent is still working:

  harness hook ──stdin JSON──▶ archie hook ──socket──▶ archie serve
   (async, exit 0 always)        │  no socket?              │
                                  └──▶ spool/               state + SQLite
                                         ▲                     │
                                   archie scan ingests    agent_status
                                                           session_drift

archie hook reads one event as JSON on stdin, tries to write it to ~/.agentworth/archie.sock with a 50ms budget, and falls back to appending a line to ~/.agentworth/spool/<session_id>.jsonl if nothing is listening. Either way it exits 0. The hook can never slow the agent down and can never make a tool call fail — that's not a nice-to-have, it's the one rule the whole design answers to.

Efference copy, in one paragraph

Biology has a name for this: efference copy. When your brain sends a motor command, it also keeps a copy of that command, so it can tell the difference between "the world moved" and "I moved and the world moved because of it." Archie does the same thing with tool calls. PreToolUse is the copy of the command — which tool, what input, and (for Edit/Write/NotebookEdit) the path it's about to touch. PostToolUse is what came back. At Stop, Archie diffs the checkout against every path this session predicted touching since its last Stop. Anything that changed and nobody in this session predicted is exafference — the world moved on its own, and Archie names the mover when another session's own predictions cover that path.

The support set and drift

Beside the write set, Archie tracks a narrower "support set": the files this session actually read, hashed each time. session_drift re-hashes them and reports which ones changed, when, and — if another session on this machine wrote them — which one. That's the question a harness summary can't answer: did my ground move because of me, or because of someone else.

archie session anchors [id] lists the join keys a session's own tool results carried along the way — a run_id, a file's sha256, a pane id — so this session's work can be tied back to what SpacePilot measured or what MotionVector rendered, without either product needing to know the other exists.

Install

archie hook print claude   # prints the settings.json snippet
# paste it into ~/.claude/settings.json under "hooks"
# restart the session

archie hook print claude only prints. It never writes settings.json for you — you decide what goes into your own hook config.

What stays true

The loop never uploads anything, works offline through the spool, never calls a model, and never blocks or slows the agent down — the hook has a 50ms budget and always exits 0. Raw histories stay the source of truth; the spool is just one more of them. Cursor and Codex hook shapes aren't built yet — Claude Code is the only harness wired up so far.