ShadowMod

Train new Reddit moderators with structured blind review. Observers record decisions without executing them, Reviewers assess the same posts independently, and a Comparison report lands after the real mod action — with reasoning from both sides.

Built for the Reddit Mod Tools and Migrated Apps Hackathon (May 2026).

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The problem

New moderators learn by doing, which means early mistakes happen on real posts in front of real community members. Reddit's Training Queue is a useful starting point for approve/remove practice, but there is no built-in structured workflow for practising the full range of mod actions, capturing reasoning, or running a blind parallel review by an experienced mod for longitudinal comparison.

The result: new mods get unsupervised access too early, or experienced mods spend disproportionate time hand-holding without a scalable feedback mechanism.

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How it works

1. The Observer opens a post in the mod queue and selects "Record observation". They choose an action (approve, remove, flair, warn, ban, escalate) and write their reasoning. The action is not executed.
2. The Reviewer opens the "Review queue" from the subreddit mod menu, picks a post with pending Observations, navigates to it, and selects "Record review". They record their own independent decision without seeing the Observer's call first (blind review).
3. When the real mod action is taken on the post, ShadowMod detects it via a trigger and schedules a report.
4. The Observer receives a Comparison report via modmail: their Observation vs the Reviewer's Review vs the final Outcome, with reasoning from both sides.
5. Over time, longitudinal stats track Observer accuracy and reveal patterns.

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Key design decisions

• Blind Review: the Reviewer records their call before seeing the Observer's, eliminating anchoring bias in feedback.
• Full action vocabulary: approve, remove, flair, warn, temp ban, perm ban, escalate. Not just approve/remove.
• Review queue: Reviewers discover pending Observations via a subreddit-level queue menu. No push notifications required.
• Async, not immediate: feedback arrives after the real mod action lands, mirroring real moderation flow and preventing Observers from gaming the system for instant validation.
• Passive trigger: ShadowMod listens for real mod actions and correlates them to pending Reviews via post ID. It does not intercept or replace the live mod workflow.

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Tech stack

Layer	Technology
Platform	Devvit (Reddit Developer Platform)
Server	Hono + Node (@devvit/web)
Storage	Devvit Redis (namespaced per subreddit)
Language	TypeScript (strict)

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Development setup

pnpm install
pnpm run build       # compile + type-check
pnpm run dev         # devvit playtest on a registered test subreddit
pnpm run upload      # upload to Reddit developer marketplace (requires approval)

Requires the Devvit CLI and a Reddit account with developer access. The test subreddit is r/shadow_mod_dev.

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Project structure

src/
├── shared/
│   └── types.ts              # Observation, Review, Report types
└── server/
    ├── index.ts              # Hono app entry point
    ├── core/
    │   ├── config.ts         # Reviewer list management (Redis)
    │   ├── decisions.ts      # Redis CRUD for Observations and Reviews
    │   └── reports.ts        # report generation and modmail delivery
    └── routes/
        ├── menu.ts           # menu action handlers
        ├── forms.ts          # form submission handlers
        ├── triggers.ts       # onModAction trigger: detects real action, schedules report
        └── cron.ts           # generate-report scheduled job

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Data model

Observation
  id, postId
  observerId, observerName, action, reason, timestamp
  status: pending_review | pending_report | complete

Review
  postId
  reviewerId, reviewerName, action, reason, timestamp

Report (in-memory, delivered via modmail)
  postId, postTitle, postPermalink
  observer, reviewer, finalAction, agreement, generatedAt

Redis key scheme:

Key pattern	Contents
observer:{postId}:{observerId}	serialised Observation
reviewer:{postId}:{reviewerId}	serialised Review
pending (sorted set)	postIds with open Observations
reviewers_set (sorted set)	postIds with recorded Reviews
config:reviewers	Reviewer usernames
stats:{userId}	Observer accuracy totals

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Configuration

Reviewer assignment is managed through the "ShadowMod settings" subreddit menu action (mod-only). Usernames are stored without the u/ prefix.

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Releases

See CHANGELOG.md for version history.

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Built by @earlgreylabs, u/EarlGrey__ on Reddit