YC-Bench

A long-horizon deterministic benchmark for LLM agents. The agent plays CEO of an AI startup over a simulated 1–3 year run, operating exclusively through a CLI tool against a SQLite-backed discrete-event simulation.

The benchmark tests whether agents can manage compounding decisions: prestige specialisation, employee allocation, cash flow, and deadline risk — sustained over hundreds of turns.

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Simulation Dynamics

┌─────────────────────────────────────────────────────────────────────────┐
│                          AGENT (LLM)                                    │
│                                                                         │
│  Observes: company status · employee skills · market tasks · ledger     │
│  Acts via: run_command("yc-bench <cmd>")  ·  scratchpad (persistent)    │
└───────────────────────┬─────────────────────────────────────────────────┘
                        │ CLI commands (JSON responses)
                        ▼
┌─────────────────────────────────────────────────────────────────────────┐
│                     DISCRETE-EVENT SIMULATION                           │
│                                                                         │
│  ┌─────────────┐    accept    ┌──────────┐   assign+dispatch            │
│  │   MARKET    │ ──────────►  │  PLANNED │ ──────────────────►          │
│  │  100 tasks  │              └──────────┘                              │
│  └─────────────┘                                                        │
│        ▲ replenish                     ┌──────────────────────┐         │
│        │                               │       ACTIVE         │         │
│        │   ┌────────────────────────── │  progress flushes    │         │
│        │   │                           │  every sim-advance   │         │
│        │   │                           └──────────┬───────────┘         │
│        │   │  ┌────────────────────────────────────┘                    │
│        │   │  │  ETA solver fires TASK_COMPLETED event                  │
│        │   │  ▼                                                         │
│        │   │  ┌────────────────────────────────────────────────────┐    │
│        │   │  │            TASK_COMPLETED handler                  │    │
│        │   │  │                                                    │    │
│        │   │  │  on_time?  YES → +reward_funds  +prestige_delta    │    │
│        │   │  │                  +skill_boost   +salary_bump       │    │
│        │   │  │            NO  → -1.4× prestige_delta (penalty)    │    │
│        └───┘  └─────────────────────┬───────────────────────────── ┘    │
│                                     │                                   │
│  ┌──────────────────────────────────┘                                   │
│  │  Monthly payroll (1st biz day)    Bankruptcy check (funds < 0)       │
│  │  Horizon end (1–3 years)          Context truncation (last 20 rounds)│
└──┴──────────────────────────────────────────────────────────────────────┘

Core loop

1. Agent calls yc-bench sim resume to advance time to the next event.
2. The engine flushes task progress, fires due events, applies payroll.
3. Agent reads wake events and decides: accept tasks, assign employees, dispatch, cancel.
4. Repeat until bankruptcy or horizon end.

If the agent doesn't call sim resume for N consecutive turns (default 10), the loop forces one automatically.

---

Economy

Funds

• Start: $250,000 (initial_funds_cents = 25_000_000)
• Payroll deducted on the first business day of each month
• Task reward formula: base × (1 + reward_prestige_scale × (prestige_req − 1))
  • Base: triangular sample in [$5K, $100K], mode $30K
  • reward_prestige_scale = 0.55 (default): a prestige-8 task pays ~4.85× more than prestige-1

Monthly payroll (5 employees, fast_test)

Tier	Share	Salary/month	Skill rate
Junior	50%	$2K–$4K	1.0–6.5 units/hr
Mid	35%	$6K–$8K	3.5–8.5 units/hr
Senior	15%	$10K–$15K	5.5–10.0 units/hr

Monthly payroll ≈ $32K (5 employees). Starting runway ≈ 7.8 months.

Task completion rewards

On success:

• Funds += reward_funds_cents
• Prestige += reward_prestige_delta (beta-distributed, typically 0.1–1.5) per required domain
• Skill rate += skill_boost_pct × current_rate per assigned employee per domain
• Salary += 1% × current_salary per assigned employee (compounding payroll pressure)

On failure (past deadline):

• Prestige −= 1.4 × reward_prestige_delta per domain

On cancel:

• Prestige −= 2.0 × reward_prestige_delta per domain

---

Prestige

7 domains: system · research · data · frontend · backend · training · hardware

• Range: [1.0, 10.0] per domain, starts at 1.0
• Tasks require a minimum prestige level. Agent can only accept tasks where max(company_prestige) >= required_prestige.
• Default distribution: mode=4, so most tasks need prestige 3–5.
• First 10 market tasks are stratified [1,1,1,1,2,2,2,3,3,4] to bootstrap progression.

Specialising in 2–3 domains unlocks progressively higher-reward tasks. Spreading thin keeps you locked at low prestige everywhere.

---

Employee throughput

Each employee has a skill rate (units/hr) per domain.

When an employee is assigned to N active tasks simultaneously:

effective_rate_per_task = base_rate / N

Assigning one senior (rate 8.0) to 4 tasks gives 2.0 units/hr each — often worse than a junior focused on one.

Task completion time = max(remaining[d] / effective_rate[d]) across all required domains.

Deadline = max(7, total_required_qty / deadline_qty_per_day) business days.

deadline_qty_per_day = 200 in both challenge and fast_test. With 10 employees and 5 focused per domain, team throughput ≈ 230 units/domain/day — achievable for up to ~4 simultaneous tasks.

---

Agent interface

All commands return JSON to stdout.

Observe

yc-bench company status              # funds, prestige, runway, payroll
yc-bench employee list               # skills, salary, active tasks
yc-bench market browse               # available tasks (--limit N --offset N)
yc-bench task list [--status X]      # planned|active|completed_*|cancelled
yc-bench task inspect --task-id UUID # progress %, deadline, assignments
yc-bench finance ledger              # full transaction history
yc-bench report monthly              # P&L per month
yc-bench scratchpad read             # persistent notes (survives context truncation)

Act

yc-bench task accept --task-id UUID             # pull from market, set deadline
yc-bench task assign --task-id UUID --employee-id UUID
yc-bench task dispatch --task-id UUID           # start work (≥1 assignment required)
yc-bench task cancel --task-id UUID --reason "" # 2× prestige penalty
yc-bench sim resume                             # advance to next event
yc-bench scratchpad write/append/clear          # persistent memory

---

Context management

• Proactive truncation: keeps the last 20 conversation rounds before each API call. Older rounds are dropped.
• Scratchpad: per-company persistent text in DB. Survives truncation. Use it to store strategy, deadlines, and employee assignments.

---

Repository layout

YC_Bench/
├── src/              # Python package (yc_bench)
├── scripts/          # plot_multi_model.py, run_benchmark.sh
├── logs/             # per-model stdout/stderr logs
├── db/               # SQLite databases (one per model run)
├── results/          # JSON rollout files
├── plots/            # generated PNG charts
├── pyproject.toml
└── README.md

---

Setup

Prerequisites

• Python 3.12+
• uv

Install

git clone <repo-url>
cd YC_Bench
uv sync

No database setup required — the runner auto-creates db/<seed>_<model>.db on first run.

API key

# .env  (any LiteLLM-compatible provider)
OPENROUTER_API_KEY="sk-or-v1-..."
# or
OPENAI_API_KEY="sk-..."
# or set OPENAI_BASE_URL for a custom OpenAI-compatible endpoint

Run a single model

uv run yc-bench run \
  --model openrouter/google/gemini-2.5-flash-preview \
  --seed 1 \
  --config challenge

Outputs:

• db/1_openrouter_google_gemini-2.5-flash-preview.db — SQLite simulation state
• results/yc_bench_result_1_openrouter_google_gemini-2.5-flash-preview.json — full rollout + transcript

Run 5 models in parallel

bash scripts/run_benchmark.sh --seed 1 --config challenge

Generate the comparison plot

uv run python scripts/plot_multi_model.py --seed 1 --config challenge --budget 30
# → plots/funds_curves.png

---

Configuration

Experiment presets live in src/yc_bench/config/presets/ as TOML files. Pass the preset name via --config.

src/yc_bench/config/presets/
├── default.toml      # 3yr, 10 employees, 500 tasks — hardened (deadline_qty=320)
├── challenge.toml    # 3yr, 10 employees, 300 tasks — calibrated for interesting behavior
└── fast_test.toml    # 1yr,  5 employees, 100 tasks — quick iteration (50-turn cap)

The challenge preset is the recommended config for inter-model comparison. It is calibrated so that:

• A focused agent (≤4 simultaneous tasks) consistently beats deadlines and grows prestige.
• A spread agent (5+ tasks in parallel, diluted throughput) misses deadlines, loses prestige, goes bankrupt.
• The best models reach the 3-year horizon; the worst die in month 3.

Key WorldConfig parameters

Parameter	Default	Controls
initial_funds_cents	25_000_000	Starting cash ($250K)
num_employees	5	Workforce size
num_market_tasks	100	Market pool size
required_prestige_mode	4	Peak of prestige-req distribution
domain_count_mode	2	Most tasks require 2 domains
required_qty_low/mode	500 / 1400	Task work volume (units)
deadline_qty_per_day	200	Units completable per biz day (lower = easier)
deadline_min_biz_days	7	Minimum deadline
penalty_fail_multiplier	1.4	Prestige × this on deadline miss
penalty_cancel_multiplier	2.0	Prestige × this on cancel
reward_prestige_scale	0.55	Extra reward fraction per prestige level above 1
salary_bump_pct	0.01	Salary raise per employee per completed task

AgentConfig

Parameter	Default	Controls
model	openrouter/openai/gpt-4o-mini	LLM model string
temperature	0.0	Sampling temperature
history_keep_rounds	20	Conversation rounds kept in context

LoopConfig

Parameter	Default	Controls
auto_advance_after_turns	5	Force sim resume after N turns without one
max_turns	50	Hard cap on agent turns (null = unlimited)

Environment overrides

YC_BENCH_EXPERIMENT=fast_test     # select preset
DATABASE_URL=sqlite:///custom.db  # SQLite path

---

Terminal conditions

Condition	Trigger
Horizon end	sim_time >= start_date + horizon_years
Bankruptcy	funds_cents < 0 after any payroll
Error	Agent runtime exception (API failure, exhausted retries)
Max turns	turn_count >= max_turns (if set)

---

What makes it hard

The hardened default is designed so that the obvious strategies fail:

• Prestige-1 farming is unprofitable. Most replacement tasks need prestige 3–5 and pay much more. Farming the bottom locks you out.
• Single-specialist dominance is gone. Most tasks need 2 domains. You must allocate across skill combinations.
• Speculative accepting is punished. Cancel penalty (2×) exceeds fail penalty (1.4×) so you can't accept everything and drop the losers.
• Ignoring payroll causes bankruptcy. ~$32K/month burns your $250K in 7.8 months — but task complexity means you must also pace your accepts.
• Parallel dispatch dilutes throughput. Splitting employees across too many tasks extends every deadline — focus beats breadth.
• Salary bumps compound. Every task completion raises assigned employee salaries 1%. Payroll creep accelerates over time.

---

Benchmark results

Run challenge preset (seed=1, 3yr horizon, 10 employees, 500-turn cap) to generate updated results.

---

Simulation rules

• Business time: weekdays only, 09:00–18:00. No leap years.
• Money: stored as integer cents (BIGINT). No floating point.
• Payroll: fired on the first business day of each month.
• Event ordering: deterministic — (scheduled_at, priority, id).
• Determinism: all task generation and employee seeding is reproducible given --seed.
• Prestige: NUMERIC(6,3), hard clamped to [1.0, 10.0].
• DB reuse: if a simulation is terminal (bankrupt or horizon reached), re-running with the same DB wipes and reseeds cleanly.

---

Output format

results/yc_bench_result_<seed>_<model>.json:

{
  "session_id": "run-1-openrouter/openai/gpt-4o-mini",
  "model": "openrouter/openai/gpt-4o-mini",
  "seed": 1,
  "horizon_years": 1,
  "turns_completed": 46,
  "terminal": true,
  "terminal_reason": "bankruptcy",
  "total_cost_usd": 0.100008,
  "started_at": "...",
  "ended_at": "...",
  "transcript": [
    {
      "turn": 1,
      "timestamp": "...",
      "user_input": "## Simulation Start ...",
      "agent_output": "Executed 3 tool call(s): ...",
      "commands_executed": ["yc-bench company status -> {...}", ...]
    }
  ]
}