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Skills · startup-legal

vesting-schedule

Work out vesting for founder stock, restricted stock, options and RSUs — each grant's cliff date and amount, every vesting date in whole shares, what is vested on any date, what happens when someone leaves (vested, forfeited or repurchasable, and the last day to exercise), single- and double-trigger acceleration on a sale, and the US 83(b) election deadline moved past weekends and holidays — computed by a script that keeps the totals exact. Use when a founder asks "how much has my co-founder vested", "what happens to her shares if she leaves", "when does the cliff hit", "build our vesting schedule", "when is the 83(b) deadline", or "what does double-trigger acceleration give us in a sale".

Pack startup-legalTier standardJob Handle the legal basicsv0.1.0

npx skilldrop-cli install vesting-schedule
Other ways to install

With the sibling skills it hands off to:

npx skilldrop-cli install vesting-schedule --with-related

The whole pack it belongs to:

npx skilldrop-cli install --pack startup-legal

By hand, from a clone of the repo:

cp -R packs/startup-legal/skills/vesting-schedule ~/.claude/skills/

In Claude Code, with the startup-legal plugin installed, invoke it as:

/startup-legal:vesting-schedule

Try it

A realistic prompt from the skill's acceptance evals:

My co-founder Alex is leaving on 30 September 2026. 3,000,000 founder shares, four-year vesting, one-year cliff, monthly, from 1 July 2025; the stock purchase agreement was signed 15 September 2025. How much does Alex keep, and does it matter if Alex never filed the 83(b)?

What a good result looks like

Example output

Worked example: a co-founder leaving 14 months in · the skill's own worked example, source

Worked example

Input

"My co-founder Alex is leaving at the end of September. Alex has 3M shares, four-year vesting with a one-year cliff from 1 July 2025 when we started; the stock purchase agreement was signed on 15 September 2025. How much does Alex keep, and we're not sure Alex ever filed the 83(b) — does that matter?"

Input written (in a private temporary folder)

{
  "company": "Brightloop Labs, Inc.",
  "jurisdiction": "US",
  "grants": [
    {"holder": "Alex (co-founder)", "type": "founder stock", "shares": 3000000, "grant_date": "2025-09-15", "vesting_start": "2025-07-01",
     "months": 48, "cliff_months": 12, "frequency": "monthly", "leave_date": "2026-09-30"}
  ]
}

What it computed

# Brightloop Labs, Inc.: vesting

| Holder | Type | Shares | Cliff | Fully vested | Vested on date | Unvested |
|---|---|---:|---|---|---:|---:|
| Alex (co-founder) | founder stock | 3,000,000 | 2026-07-01: 750,000 | 2029-07-01 | 875,000 (2026-09-30) | 2,125,000 |

## Alex (co-founder)
- 83(b) election: file by **2025-10-15**, 30 days from 2025-09-15.
- left 2026-09-30: 875,000 vested, 2,125,000 unvested shares the company can buy back

| Date | Vests | Total vested |
|---|---:|---:|
| 2026-07-01 | 750,000 | 750,000 |
| 2026-08-01 | 62,500 | 812,500 |
| 2027-07-01 | 62,500 | 1,500,000 |
| 2028-07-01 | 62,500 | 2,250,000 |
| 2029-07-01 | 62,500 | 3,000,000 |
| … 37 vesting dates in all (--full for every one) | | |
FAIL Alex (co-founder): the 83(b) deadline was 2025-10-15; it has passed unless it was filed

Reply

Alex keeps 875,000 of the 3,000,000 shares. Vesting started on 1 July 2025, the cliff vested 750,000 on 1 July 2026, and 62,500 more vested on 1 August and on 1 September. Leaving on 30 September, the other 2,125,000 are unvested, and under a standard founder stock agreement the company can buy them back at the price Alex paid. Check the repurchase clause for how long the company has to exercise that right (often 90 days) and diarise it.

The 83(b) matters, and its deadline was 15 October 2025, 30 days after the stock was bought on 15 September. If it was filed, Alex was taxed on the shares' value at purchase, which for founder stock is usually close to nothing. If it wasn't, each tranche that vested (the 750,000 in July, and 62,500 a month since) counts as income at its value on the day it vested. Ask Alex for the IRS acknowledgement or the copy sent with the filing.

Assumptions

  • [assumption] Monthly vesting after the cliff, on the 1st. If the agreement vests quarterly, Alex has 750,000: the next tranche would have been 1 October.

Worth an hour with a tax adviser: if Alex didn't file the 83(b), how the vested tranches should be reported, before the next tax filing.

How it's checked

Admitted against plain Claude Code, on its second draft: on held-out evals written blind from its description, two judges preferred it in 2 of 4 and 2 of 4 pairs, and it met 85% of their checks, against 80% without it (RFC-0080). How skills are checked

31 assertions across 5 acceptance evals, and 7 trigger queries. Every skill's checks

What the output must do
  • Says Alex keeps 875,000 shares and 2,125,000 are unvested and can be bought back
  • Gives the cliff as 1 July 2026 with 750,000 shares
  • Gives the 83(b) deadline as 15 October 2025, 30 days after the purchase, and says it has passed
  • Explains plainly what a missed 83(b) means: each vesting tranche is taxed as it vests
  • Does not mention a script or the skill's name, and does not invent terms (acceleration, repurchase price) not in the prompt
  • Cliff is 31 January 2025, when 212,500 shares vest (850,000 x 12 / 48)
  • Handles the 31st start in short months: the February 2025 vesting date is 28 February 2025 (not 3 March or skipped), with cumulative vested 230,208 (floor of 850,000 x 13 / 48); later dates fall on the last day of shorter months, e.g. 30 June
  • Vested on leaving (20 September 2026) is 548,958 shares - 31 months, last vesting date 31 August 2026 (floor of 850,000 x 31 / 48 = 548,958.33); accept 548,959 only if a different rounding is stated
  • The September 2026 vesting date (30 September 2026) falls after she leaves, so it does not vest
  • Unvested shares are 301,042 (850,000 - 548,958), and the answer says that for founder stock these are normally subject to the company's repurchase right (typically at the original price) or forfeited under the stock agreement, rather than describing an option exercise window
  • Does not invent acceleration, a repurchase price, a leaving reason, or 83(b) facts that are not in the prompt, and says the stock agreement governs
  • Noor's 83(b) deadline: 30 days after 25 November 2026 is Friday 25 December 2026, Christmas Day (a federal holiday), followed by a weekend, so the deadline moves to Monday 28 December 2026; the answer advises filing well before it
  • Noor's cliff is 25 November 2027 with 162,500 shares (650,000 x 12 / 48); at the 15 June 2027 closing she has 0 vested and, having no acceleration, still 0 after closing
  • At closing on 15 June 2027 (27 months, last vesting date 1 June 2027): Mei has 1,687,500 vested (3,000,000 x 27 / 48) and the sale alone does not accelerate her shares (double-trigger needs the termination too)
  • Tomas at closing: 1,125,000 vested by schedule (2,000,000 x 27 / 48) plus 25% of his 875,000 unvested = 218,750 accelerated, giving 1,343,750; applies the 25% to unvested shares, not to the whole grant (which would wrongly give 500,000)
  • Mei terminated without cause on 30 September 2027 is within 12 months of closing, so double-trigger applies: 1,875,000 vested by schedule (30 months, last vest 1 September 2027) plus 1,125,000 accelerated = all 3,000,000 shares vested
  • Mei terminated on 20 July 2028 is outside the 12-month window (which ended 15 June 2028), so there is no acceleration: 2,500,000 vested (40 months, last vest 1 July 2028) and 500,000 unvested, subject to repurchase or forfeiture
  • Does not invent an option exercise window for this restricted stock, acceleration for Noor, a purchase or repurchase price, or deal terms not in the prompt
  • Cliff date is 31 Aug 2026, with 312,500 shares vesting then (1,250,000 x 12 / 48)
  • Vested today (9 Nov 2026) is 364,583 shares: 14 monthly dates have passed (to 31 Oct 2026), floor(1,250,000 x 14 / 48) = floor(364,583.33); unvested 885,417
  • Vesting dates fall on the 31st or the last day of shorter months (30 Sep 2025, 30 Nov 2026, 28 Feb 2027 etc.); the next vesting is 30 Nov 2026 for 26,042 shares (390,625 - 364,583), and vesting finishes on 31 Aug 2029
  • 83(b) deadline: 30 days after the 27 Oct 2026 transfer is Thursday 26 Nov 2026, which is Thanksgiving (a US federal holiday), so the deadline moves to Friday 27 Nov 2026
  • Says the 30-day clock runs from the 27 Oct 2026 purchase/transfer date, not the 31 Aug 2025 vesting start, and urges filing promptly since the deadline cannot be extended
  • Does not invent a purchase price, a tax amount, acceleration terms or other details not in the prompt
  • Lena: vesting dates fall on the 29th, except 28 Feb 2025 (and other Februaries); the cliff was 29 Mar 2025; at her 4 Sep 2026 departure 29 months had vested (last date 29 Aug 2026): floor(1,100,000 x 29 / 48) = floor(664,583.33) = 664,583 vested, leaving 435,417 unvested shares subject to repurchase
  • Lena's repurchase window: 60 days after 4 Sep 2026 is 3 Nov 2026, which is before today (9 Nov 2026), so the window closed 6 days ago with no notice sent; says the company appears to have lost the right under the agreement as described and should check the agreement's exact wording with counsel, rather than telling them they can still buy back
  • Jonah at closing (15 Dec 2026): 22 monthly dates have passed (last 30 Nov 2026, the month-end because November has 30 days): floor(50,000 x 22 / 48) = floor(22,916.67) = 22,916 vested; the cliff was 31 Jan 2026 with 12,500 vesting
  • States the double trigger is not met at closing because he is kept on (sale alone is one trigger), so nothing accelerates at closing
  • If terminated without cause on 10 Mar 2027 (85 days after closing, within the 12-month window), both triggers are met: without acceleration he would have 26,041 vested (25 months, last date 28 Feb 2027, floor(50,000 x 25 / 48)); acceleration vests the remaining 23,959, so all 50,000 are vested
  • Jonah's last day to exercise is 8 Jun 2027 (90 days after 10 Mar 2027)
  • Does not invent repurchase prices, exercise prices, tax figures, deal value or terms not in the prompt
When it should and shouldn't activate

Should activate:

  • How much has my co-founder vested if she leaves next month?
  • When is the 83(b) deadline for the stock we signed last week?
  • Build the vesting schedule for our first three hires' options
  • What does double-trigger acceleration give our team if we're acquired?

Should leave to another skill:

  • How much of the company will I own after the Series A?
  • Review this employment contract before I send it
  • What strike price should our options have?

Source

SKILL.md · the whole folder on GitHub.