Complete D&D 5e one-shot adventures, forged from a seed — map, math, and story in one click.
▶ Try it live: carl-prewitt.com/oneshot
OneShotsmith generates a full, runnable adventure module in your browser: a keyed dungeon map in the classic blue style, encounters built on the real DMG XP math, a villain with a plan, boxed read-aloud text, NPCs with voices, a secrets checklist, treasure, pacing — formatted like a proper early-80s adventure module and print-perfect out of the box. The whole app is set at the game table after dark: lamplit paper artifacts in a warm black room, with the blue map glowing at the center of it. No accounts. No server. No AI API. Free forever.
Every adventure is deterministic. The seed lives in the URL, so a module can be shared, bookmarked, or posted like a link to a song — same seed, same adventure, forever.
The tools DMs actually use each solve a quarter of the problem: map generators have no story, story generators have no maps, encounter builders have no plot, and AI tools can't do the math. OneShotsmith does all four at once, coherently — the numbered rooms on the map are the scenes in the text, and the fights in those scenes are budgeted for your exact party.
Every module ships the full anatomy of a professionally written one-shot:
- A synopsis for the GM — what's really going on, twist included
- A strong-start hook with boxed read-aloud text, plus fallbacks for reluctant parties
- A keyed site map — procedurally generated, drawn white-on-blue like the classic modules, with a player-safe version that prints as a separate handout
- 4–6 scenes matched to your session length, each with read-aloud text, DM notes, and a decision or lever — never just description
- Scene transitions — "getting there" connective text between every scene, generated from the map's actual geometry (direction, distance, doors) and aware of what kind of scene just ended and what kind begins
- A floating spare scene to drop in if the table runs fast, alongside the cut list for tables running slow
- A first-time-DM primer — the whole job in eight lines, so someone who has never run a game can pick this up and go
- Encounters with honest math — 2014 DMG XP thresholds and multipliers for your exact party size and level, monster stat lines inline (SRD 5.1), and Sly Flourish's Lazy Encounter Benchmark as a second opinion that flags the edge cases XP math misses
- A villain with a motivation, plan, secret, and mannerism — and a stat block
- Three cast NPCs with appearance, mannerism, voice cue, want, and secret
- Eight secrets & clues to reveal wherever the players look (Lazy DM style)
- A twist, treasure parcels, and a signature magic item with a history
- Scaling advice for weaker/stronger tables, a session clock, a cut list for running behind, and theme-specific random tables
| Six themes | Dungeon Crawl, Heist, Rescue, Haunting, Wilderness, Mystery — each a deep, hand-written content system, not a mad-lib |
| Real knobs | Level 1–20, party size 2–7, four difficulties, 2/3/4-hour session length (the structure actually changes) |
| Surgical re-rolls | New villain, same map. New twist, same everything else. Every section has its own dice, and re-rolls stay in the shareable URL |
| Shareable seeds | The whole adventure derives from the URL — share it, bookmark it, post it |
| Print-perfect | Print/PDF produces a real module: boxed text, keyed entries, stat tables, and the player-map handout on its own page |
| Markdown export | One click copies the entire module as clean Markdown for Obsidian, Notion, or your prep doc |
| Local vault | Save adventures and characters in your browser — rename, reopen, export JSON |
| Character creator | Pick a role and level, get a complete legal 5e character on a goldenrod-style record sheet with tactics that tell you what to do on your turn |
| Pregen library | Ready-made heroes with concepts, voices, and jobs |
git clone https://github.com/rages4calm/oneshotsmith.git
cd oneshotsmith
pnpm install
pnpm dev # web app on http://localhost:3000Build a static export (deploys anywhere — it's just files):
pnpm build # output in apps/web/outRun the test suite (determinism, DMG math, map integrity):
pnpm testEverything derives from a seed string through independent, per-section RNG streams
(hash(seed + section + nonce)), which is what makes surgical re-rolls possible:
bumping the villain's nonce regenerates the villain — and every sentence that
mentions them — without touching the map, the title, or the treasure.
Re-rolls can't tangle, no matter what order you roll in: every re-roll re-runs
the whole pipeline from scratch as a pure function of (seed, settings, nonce-map) — there is no incremental state to get out of sync, and the test
suite proves order-independence directly. Cross-scene story references resolve
through a story-flag pass (design credit: u/tentkeys): a scene's provides
tags set flags, and any text can write {?confession:clean confident reference|self-contained fallback} — so "per the warden's confession" appears
only in adventures where that scene was actually rolled, a DC-based fallback
renders otherwise, and re-rolls simply re-gather the flags. Tests assert no
adventure can ever mix branches or leak an unresolved span.
packages/core/src/data/themes/— six theme packs: sites, hooks, villains, twists, clue pools, scene templates, complications (~3,000 lines of original, playable content)packages/core/src/data/monsters.ts— 80+ SRD 5.1 monsters with CR, XP, and stat lines, tagged for theme palettespackages/core/src/data/encounter-math.ts— the 2014 DMG thresholds and multipliers, the 2024 revised budgets, adventuring-day XP, and the Lazy Benchmarkpackages/core/src/generators/oneshot.ts— assembles the module: scene structure by session length, encounter building against the party budget, clue distribution, pacingpackages/core/src/generators/dungeon-map.ts— procedural site maps (room placement, corridor MST with loops, doors, features), rendered as SVG in the classic blue style
apps/
web/ Next.js 15 app (static export — no server required)
packages/
core/ The engine: generators, theme packs, SRD data, math
ui/ Shared UI primitives
adapters/, db/ Scaffolding for future VTT export / sync (unused at runtime)
Honest answer, both halves:
- At runtime: no. The generator makes zero AI calls. Every adventure is deterministic, seeded table-assembly — the same math donjon or a stack of printed random tables uses, which is why the same seed produces the same module forever, offline, on any machine.
- In the workshop: yes. The code and the content libraries were built by Carl working with Claude as the tool — directed, curated, tested, and bug-fixed by a human (and by community feedback: several fixes in this repo came straight from Reddit playtest reports). The encounter math comes from the published DMG tables, not from a model's guess.
Every random table is plain TypeScript in
packages/core/src/data/themes/ — readable,
editable, and replaceable. If you'd rather run your own hand-written tables,
fork it and swap the files; the engine won't know the difference.
- Code: MIT License
- Game content: This work includes material from the System Reference Document 5.1 ("SRD 5.1") by Wizards of the Coast LLC, available at https://www.dndbeyond.com/srd. The SRD 5.1 is licensed under the Creative Commons Attribution 4.0 International License. OneShotsmith is an independent product and is not affiliated with Wizards of the Coast.
- All adventure prose, names, and theme content are original.
- Universal VTT export (
.uvttwalls/doors/lighting for Foundry, Roll20, Arkenforge) - A "run mode" initiative tracker preloaded with the module's monsters
- Pregen party pack matched to the generated adventure's hooks
- 2024 rules toggle surfaced in the UI (the math already ships in the engine)
OneShotsmith is free forever — no accounts, no ads, no paywalled themes. If it saved your game night and you'd like to keep the forge lit, sponsoring on GitHub buys the coffee that the next feature runs on. A star helps other DMs find it, too.
- u/tentkeys — playtest hero. Read the actual generated output closely enough to catch the cross-scene reference bug (with reproducing seeds!), pushed for the GM quick-reference summary, and contributed design guidance on re-roll state handling. Several fixes in this repo trace directly to that feedback.
- Sly Flourish's Lazy DM methodology and Lazy Encounter Benchmark, and Johnn Four's Five-Room Dungeon model, inform the adventure structure.
- Dice, lamplight, and table photography generated by Carl on Gemini.
Built by Carl Prewitt Jr.