KAN › The method · lesson 4 of 7

Size it with FIB

A FIB number measures how much you don't know yet, and how likely the plan is to fail on a wrong premise. It is not a count of hours or pages.

Teaches from kan/6w-sdmr.md, “Execute through PTE”, and kan/rung-delivery.md, “Estimate and choose a timebox”.

The rule

• 1: one known file, no material unknowns, reversible: a direct small change.
• 2: a known location and one fact to verify: establish that fact first.
• 3: a bounded subsystem whose answer is readable from a few sources: a focused investigation.
• 5: several subsystems in sequence, or one unknown that can change the approach.
• 8: independent cross-boundary concerns whose findings can invalidate the plan; it opens as increments, “typically 5 + 3, riskiest first”.
• 13: a wrong premise is likely and delivery needs waves: SDMR escalation and decomposition.
• 21: oversized: stop, Blocked, until it is decomposed; never execute it as one commitment.

“Size unknowns, not page count: a bounded review over many pages can remain FIB 3.” Any evidence that raises the size calls for a new estimate.

After estimating, set a timebox in wall-clock time with a next checkpoint, verification included. “There is no universal points-to-hours conversion.” And the clock does not decide acceptance: “A ready result does not wait for the clock.”

Try it

In the EchoEdu delivery

Each course lane in the migration epic was sized FIB 8 and opened as 5 + 3: recover and convert the course first, then verify and remediate.

The hand-authored companions show the threshold at work. specs/edu/stories/edu.27.aus.md records its decision: “the total, 174 companions plus a root, is past the decomposition threshold, so it runs as five section waves of FIB 5 each (sum 25), each landing and gated on its own”. This course's own story, edu.29, first planned six waves summing 26, and the gate's answer was short: “FIB 26 is decomposed into gated waves of 5 or less, which is right” (KAN CRS0RWxJg2IS8G). When the course was re-planned on interactive figures, the story as landed (commit 69a84eb1) re-cut it into seven waves summing 29, none above 5.

Check yourself

1. A review touches 200 pages but every answer is in two known documents. What size is it, and why?
2. What must happen before a FIB 13 piece of work starts?
3. The timebox expires with the work nearly done. Does the expiry accept it, extend it, or neither?

Previous: Expose the uncertainty · Next: Deliver through PTE

Teaches ecd/kan at 2d1b5c8e, 25 October 2026.