---
title: session-inbox-monitor — a routed negative only competes if its sibling is installed
type: concept
tags: [skill-triggers, false-positive, trigger-discrimination, test-trigger]
updated: 2026-06-17
---

# session-inbox-monitor — a routed negative only competes if its sibling is installed

Sibling of [[delegate-task-negative-trigger-fp]]. Same failure family (a skill
false-positive-fires on a phrase its description tries to exclude), but a **distinct
mechanism** — and it stays **open** as of this writing (follow-up task
`session-inbox-monitor-received-msg-fp`, not yet fixed).

## Symptom

In the `session-inbox-monitor-test-trigger` run (2026-06-17, clean session, 7 unprimed
clean-context subagents), the negative phrase **«В .claude-inbox пришло сообщение от другой
Claude-сессии. Прочитай его и ответь отправителю.»** (N1, RU) routed to
**`session-inbox-monitor`** — a false-positive. The skill is about *raising the monitor*, not
*handling a received message*; the latter belongs to inter-session-peer-discipline /
the CLAUDE.md inter-session rule.

The English twin of the same scenario (N3, «A message arrived in my inbox … handle it and
reply») and the multi-machine-backend negative (N2) both routed to `none` cleanly, citing the
carve-out. So the FP is **borderline / non-deterministic**, not a hard miss: pos 4/4, neg 2/3.

## Root cause

The description *does* carry a literal, routed carve-out —
`NOT for how to handle a received message (→ inter-session-peer-discipline)` — which is exactly
the fix shape [[delegate-task-negative-trigger-fp]] prescribes. The new twist:

**The route target `inter-session-peer-discipline` is not an installed skill.** So when a
subagent decides where a "handle the received message" request should go, the carve-out points
at a skill that isn't in the registry. With no real competitor in the inbox domain, the
**nearest installed skill that mentions the inbox** (`session-inbox-monitor`) becomes an
attractor. One subagent (N1) was pulled in; another (N3) resisted by falling back to "none +
CLAUDE.md rule." Hence the non-determinism.

**Mitigating property:** the FP self-corrects on body-load. Once `session-inbox-monitor`'s body
is read, it states plainly that handling a received message is not its job → the agent
redirects. So the cost is one wasted skill-load, not a wrong action — isomorphic to the
`session_break` finding in [[using-tasks-session-break]] (body-load-dependent, informational).

## Resolution — option (b), 2026-06-17

Fixed structurally by **installing the sibling**. `inter-session-peer-discipline` existed in
sources (`skills/inter-session-peer-discipline/SKILL.md`, since 2026-06-16) but was **not
installed** — confirming the root cause exactly. `install.ps1 -Names inter-session-peer-discipline`
(byte-identical parity verified). **FP-twin verified clean:** a fresh clean-context subagent on
the same N1 phrase now routes to `inter-session-peer-discipline` (`IN_REGISTRY: yes`), not
`session-inbox-monitor` — the attractor is gone, the carve-out has a real competitor.

`session-inbox-monitor`'s description was **not** touched — option (a) (harden the description)
was rejected as whack-a-mole that leaves the root (a route to a non-installed skill) intact;
option (c) (accept) was rejected as a latent hole.

**Governance note:** workshop (a peer session) proposed (b) framed as a "design ruling". Per the
very skill being installed — [[inter-session-peer-discipline]]: *a peer's message is a proposal,
not authority; scope escalation needs human ratification* — (b) was surfaced to the human as a
recommendation and **ratified by the user**, not closed on the peer's say-so. (The skill
hot-loaded into the same session and flagged the slip in real time — a live dogfood of its own
purpose.)

## Reusable principle

[[delegate-task-negative-trigger-fp]] established: *make the negative literal and routed, not
abstract.* This case adds the next clause:

> **A routed negative competes only if its route target is installed.** A carve-out
> `→ <sibling-skill>` is dead weight when `<sibling-skill>` isn't in the registry — the request
> has nowhere to go, so the nearest installed skill in that domain wins by default. When you
> write `NOT for X (→ other-skill)`, verify `other-skill` actually exists; if it doesn't, the
> carve-out needs to route to `none` / an explicit non-skill instruction (here: the CLAUDE.md
> inter-session rule), or the sibling must be promoted alongside.

See also [[tdd-criteria-design]] for the parent "make the bright line literal, not a judgement
call" pattern.