For twenty years, the software development lifecycle was like a relay race (I love relays!) It involved a team: one person wrote a ticket, another designed, someone built, and another reviewed. Each handoff had its own tool, artifact, and meeting.

With the rise of AI agents, that process has been unevenly compressed.

Addy Osmani makes this point very well in his write-up of Google's new SDLC paper--worth reading in full, IMO: implementation time drops from weeks to hours, but requirements, architecture, and verification remain slow because they're judgment work.

Generation is pretty much solved and what's left is specification, verification, and the systems that hold them together.

This blog post will go over how those systems keep dropping context.

The 80% problem is a context problem

Addy calls the ceiling the "80% problem": agents get the first 80% of a feature quickly, and the last 20% (ie edge cases and seams between systems) still needs context the models don't usually have.

I'd phrase it slightly differently. That last 20% is hard not just because the code is hard, but because the reasoning that produced the first 80% is already gone. When an agent builds something, the why evaporates when the session ends, leaving developers/builders
with a large diff and a fuzzy memory of what they asked for. Did the agent make the right call on an edge case? Did the plan change halfway through?

We've gotten very good at generating code, but also very bad at remembering how the code got where it did--leaving the hardest 20% getting done by someone debugging code they didn't write, along with none of the context that produced it.

Verification needs the trajectory, not just the output

The most useful distinction in Addy's post is between two kinds of evaluation. Output evaluation asks whether the final result is correct. Trajectory evaluation asks whether the path it took (ie tool calls and reasoning) was sound. You want to have both. An answer that looks correct but skipped its checks is more dangerous
than one that's clearly broken.

This is the difference between a box score and game film. The box score tells us the result, whereas the film tells us whether the result was earned or lucky. Most of our developer tooling only keeps the box score. The PR queue we all still use was built
for human-speed output including a diff, description, and a thumbs-up. Throwing the path away, it displays the output, and at the same time, agents ship volume. This gives developers two not-so-great options: review every diff and become the bottleneck, or ship blindly and hope.

A diff can't answer the question that really matters: did we build the right thing the right way? That answer lives in the path the agent took--and for most teams at the moment, that lives nowhere.

Where this goes next

I don't believe that the SDLC will die. I think it will invert.

Today, code is the artifact and intent is a ticket nobody reopens. That will flip with intent becoming the spine and code turning into just one layer you drill into. The unit of work is no longer the PR— it's the whole arc, including the ask, decisions, path, and evidence it works.

That's the bet we're making at Entire. Capture the reasoning chain, attach it to the code in git, and make that what you review, not a wall of diff. It's also how you close the last 20%: not by waiting for a smarter model, but by never losing the context that makes the hard part hard.

The future of building software isn't "agents write code faster." That's already here (41% of new code is AI-generated, per the numbers in the post)--and it's not enough. The future is teams that can understand, continue, and trust the work an agent did, even after the session ended.

The agents sped up. Now it's our turn to give the work a memory.