Armin Ronacher's Agentic Coding Practice

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Armin Ronacher's Agentic Coding Practice

Armin Ronacher is an Austrian software engineer born in 1989. He created Flask, Jinja2, Click, and Werkzeug as part of the Pocoo collective. He spent a decade at Sentry as Principal Architect, working on event ingestion, SDKs, and source maps. In 2025, he left Sentry to co-found Earendil and now writes about agentic coding on his blog at lucumr.pocoo.org.

The Workflow

From Agentic Coding Recommendations (June 2025):

“My general workflow involves assigning a job to an agent (which effectively has full permissions) and then waiting for it to complete the task. I rarely interrupt it, unless it’s a small task.”

Key characteristics:

The IDE’s Diminished Role

Ronacher’s approach changes the developer experience fundamentally:

“The role of the IDE — and the role of AI in the IDE — is greatly diminished; I mostly use it for final edits. This approach has even revived my usage of Vim, which lacks AI integration.”

When AI handles the bulk of implementation, the editor becomes a review tool rather than a creation tool.

Token Efficiency

Practical recommendations from his blog. See Token Efficiency Guide for detailed techniques.

PracticeReason
Avoid screenshotsHigh token cost
Skip browser interactionsPrefer API/CLI approaches
Use Sonnet over OpusAdequate quality, lower cost
Batch related changesFewer context switches

Conference Talk: Agentic Coding

Ronacher’s talk at various conferences (July 2025) expanded on his blog posts:

“The agents are now good enough to collaborate. Running independently for hours on tasks, changing how we approach software development.”

Talk chapters included:

Microsoft Azure Interview

The Microsoft Azure Developers YouTube (August 2025) featured Ronacher building a transcription tool live:

Quote on AI’s effect on frameworks:

“AI changes how we think about developer experience and framework consolidation.”

Pragmatic Engineer Podcast

Gergely Orosz interviewed Ronacher for The Pragmatic Engineer (October 2025):

Topics:

Key insight: AI tools are changing the calculus of when unified codebases matter.

Background

Ronacher’s open source footprint:

ProjectImpact
FlaskWeb microframework, millions of users
Jinja2Template engine used by Flask, Ansible, Salt
ClickCLI creation library
WerkzeugWSGI toolkit underlying Flask
RuffInvolved in the Rust-based Python linter

After a decade at Sentry (event ingestion, SDKs, internal developer platform), he founded Earendil.

What Didn’t Work

In Agentic Coding Things That Didn’t Work (July 2025), Ronacher shares failed experiments:

“I only automate things that I do regularly. If I create an automation for something that I do regularly, but then I stop using the automation, I consider it a failed automation and I delete it.”

His approach: delete unused workflow helpers rather than let them clutter your workspace. Most of the time, the simplest solution is talking to the model more, dumping your train of thought into the prompt.

Expectations for Rapid Change

Ronacher ends his recommendations post with a caveat:

“One caveat: I expect this blog post to age very poorly. The pace of innovation here is insane; what was true a month ago barely holds true today.”

In A Year of Vibes (December 2025), he reflected on how 2025 changed his entire programming practice. He published 36 blog posts that year, almost 18% of all posts on his blog since 2007.

Key Insights

PrincipleApplication
Grant full permissionsMinimize intervention
Optimize for tokensAvoid expensive operations
IDE for review, not creationAgent does the work
Vim works fineAI integration in editor optional
Document knowing it’ll ageCapture current best practices

Next: Harper Reed’s LLM Codegen Workflow

Topics: ai-coding workflow open-source claude-code