I’m building a “Control Lane” for fixed-price work — early signals before margin disappears

I’ve watched fixed-price projects not break — they drift.
The client is happy. The invoice gets paid.

And only after delivery you realize the margin died quietly through:

• tiny scope additions

•extra review cycles

• “quick” calls

•senior people jumping in “just to help”

• rework you didn’t plan for

Each decision makes sense in isolation. Together, they erase profitability.

So I’m prototyping a lightweight “control lane” for agencies that surfaces early drift signals while you can still intervene.

Idea (very simple):

Track a few inputs that usually spike before margin collapses:

• scope delta (change requests vs baseline)

• unplanned cycles (reviews / fixes / approvals)

• unplanned meetings / support time

• senior time drift

• “blocked waiting” time (client dependencies)

Output = a weekly “risk snapshot” + a clear “what changed” log, so the owner can decide early (renegotiate, de-scope, pause, escalate).

I’m keeping it intentionally lightweight — no heavy PM replacement, just visibility + accountability.

I’d love feedback from agency founders / PMs:

1. What’s your earliest reliable signal that a fixed-price project is drifting?

2. What would you actually track weekly (max 5 metrics) without annoying the team?

3. If you tried tools like this before, what failed and why?

If anyone is open to a quick 10-minute chat, I’m in validation and would love to learn.