Investment Thesis Tracker: Post-Buy Discipline

Track an investment thesis for a holding. First use on a company → build the thesis; later uses → quarterly check.

Supported input: company name (auto-decide build vs track); company build (force rebuild); company quarterly check (against latest earnings).

"Buying is only the beginning. The real work is continuous tracking through the holding period." — Li Lu

"When the facts change, I change my mind. What do you do, sir?" — Keynes

Design Philosophy

Most investors' process is: research → buy → pray. Without systematic post-buy tracking, they: refuse to sell when they should ("wait, it'll come back"); panic-sell when they shouldn't ("down 20%, was I wrong?"); forget why they bought ("why did I buy this again?").

Buffett and Li Lu write down sell conditions before buying, then check the thesis each quarter.

Step 1: Decide the Mode

Check whether a thesis file already exists (use read_file on reports/{company}-thesis.md): not found → Build (Mode A); found → Track (Mode B).

Mode A: Build the Investment Thesis

A0: Data Collection

Use web_search to get the current price, valuation (PE/PB/dividend yield), and latest financials. If a research report exists, read_file it first. Use financial_rigor (command=verify_valuation) to verify valuation, financial_rigor (command=verify_market_cap) to sanity-check market cap.

A1: Core Thesis (must be writable in ≤200 words)

The thesis must answer 5 questions, one sentence each:

I bought {Company} at {price} because:
1. The essence of this business is ___, and I understand how it makes money.
2. Its moat is ___, and it's widening / stable.
3. Management is ___, trustworthy because ___.
4. The current price is a {discount}% to intrinsic value; the margin of safety comes from ___.
5. Even if I'm wrong, downside is contained because ___.

If you can't fill 5 sentences, the thesis itself is flawed — the buy decision isn't clear enough.

A2: Core Assumptions List

Break the thesis into verifiable assumptions (3-7 typically; too few = shallow thinking, too many = unfocused):

A3: Red Lines (triggering any one = must re-evaluate)

The red line on macro trends (demographic clock / consumption / generational) is deliberately explicit: a value-investing thesis that picks a consumer name without weighing population decline and consumption-trend headwinds is incomplete. For non-consumer names (e.g. pure B2B industrial), this red line may be loose; for consumer/retail/education/property names, weight it heavily.

Duan Yongping: "There are only three reasons to sell: 1. you got the buy wrong; 2. the fundamentals changed; 3. you found something better."

A4: Valuation Anchors

A5: Save the Thesis

Use write_file to write reports/{company}-thesis.md, including: build date, buy price and position, core thesis (5 sentences), assumptions list, red lines, valuation anchors, tracking table (empty initially).

Mode B: Tracking Check

B1: Read the Existing Thesis

Use read_file to load core thesis, assumptions, red lines, last check record.

B2: Gather Latest Data

Use web_search / get_stock_news / get_financial_statements: ① latest earnings (if new quarter/year); ② recent material events (management, regulation, competition); ③ current price and valuation; ④ insider transactions (major shareholder changes).

B3: Check Each Assumption

Status definitions:

• 🟢 Holding — latest data supports
• 🟡 Weakening — still acceptable, but trend is unfavorable
• 🔴 Impaired — data clearly does not support
• ⚫ Broken — assumption has been overturned

B4: Red-Line Check

Check each red line; any triggered → flag prominently in the report + clear action recommendation.

B5: Valuation Update

Use financial_rigor (command=verify_valuation) to recompute PE/PB/ROE; compare against buy-time and last check:

B6: Output the Tracking Report

Structure: ① Thesis health score (out of 10); ② Assumption check table; ③ Red-line check table; ④ Key changes this period (≤500 words); ⑤ Valuation update; ⑥ Conclusion and action; ⑦ Focus for next check.

Health formula: 10 - (⚫broken × 3) - (🔴impaired × 2) - (🟡weakening × 1) - (red-lines triggered × 5), min 1, max 10.

The conclusion must clearly answer: ① Is the thesis still intact? (intact / weakening / impaired / broken); ② What to do? (add / hold / trim / exit); ③ Next check timing (next earnings / a specific event).

B7: Update the Thesis File

Use write_file to append this check to the tracking table in reports/{company}-thesis.md:

Key Principles

• Write sell conditions before buying — decisions made calmly beat decisions made in panic.
• Assumptions must be verifiable — "a great company" is not a thesis; "ROE>25% and stable" is.
• Act when a red line triggers — "let's wait and see" is how big losses happen.
• Thesis breaking ≠ stock falling — a 30% price drop doesn't force a sell; a broken thesis does.
• Be honest about mistakes — if the thesis was wrong, admit it; don't defend it to save face.
• Weigh macro headwinds for consumer names — demographic decline and consumption downgrade are slow but can be fatal for consumer/property/education theses; bake them into red lines, not just quarterly checks.