# Field Lessons: Twelve Things That Changed the Next Job

- Link: https://jcody.com/ai-projects/field-lessons/
- Published: 2026-11-10T10:34:40-05:00
- Author: Jeffrey Cody

[AI Projects](https://jcody.com/ai-projects/) › Field lessons

**Twelve lessons, grouped by what they change.** Each one changed how the next job
was built, and each would change how I run a client engagement from day one.

## Identity and proof

### 1. Name and size never prove a copy

A 6.6 TB folder matched another 100% by name and size, and the match was circular.
Only a sha256 proves a copy. On Nov 9 the hash caught truncated files that name 
and size would have passed.

### 2. “Done” migrations were 6% to 24% done

The five-drive rebuild found 12 to 420 times more data on the source drives than
their “verified” migrations showed. The verification had only covered what was copied.

### 3. A success check must prove the result

An exit code of 0 is not proof. A drive export is green only when the pool is really
gone. A copy is verified only when hash, size and date all match.

## Process and time

### 4. Cheapest proof first

Metadata before bytes. A listing of names, sizes and dates showed 1.8 TB changed
out of about 64 TB, which avoided about 97% of a rescan. Every database query is
priced before it runs.

### 5. The slowest box sets the finish line

A single ARM core, not the 28-thread server, decided when the job ended. ETAs from
a 30-second burst were wrong by 2 to 4 times, so use the average rate and re-check
against fixed windows.

### 6. Timestamps are part of the record

Every copy keeps the original modification time and is checked afterward. Missing
dates are inferred into the database and never written back over the file.

## Agents and structure

### 7. Durable messages beat relaying

Prompts went unsubmitted and agents kept stale briefs. Cards, check-backs and nudges
to re-read the current brief fixed a month of stalls.

### 8. One home per fact

When the board and the workers fall out of sync, things unravel quickly. Layered
context, numbered stage folders and short context files keep a multi-week, multi-
agent effort coherent.

### 9. Diagnose before fixing

Three hard resets looked like a dying server. Console photos showed a corrupt pool
panicking at boot. The reformat was cancelled and the unique data salvaged.

## Measurement and evals

### 10. Gates measure what they measure

VMAF proved the picture and missed the 360 flag, flight telemetry tracks and spatial
audio. A compressed child must pass a metadata parity check before it can stand 
in for its original.

### 11. Report both denominators

Once triage removes the worst candidates, “% saved on passes” rises mechanically.
Always report whole-pool savings beside it.

### 12. Recency is not reliability

The newest batch was the corrupted one. Score health and completeness first, and
use the date only as a tiebreaker.

[Read the two nights in detail](https://jcody.com/ai-projects/the-two-nights/)

[Back to AI Projects](https://jcody.com/ai-projects/)

_Sources: decisions log, history log, encode and lineage reports._

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