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Mahiro Hirakawa profile picture

Mahiro Hirakawa

Independent. Local-first developer tools, and a verification substrate for effects that have to be undoable. Rust. Limits written down before features.

Location Tokyo, Japan Joined Joined on  Personal website https://github.com/TraceFold/tracefold github website twitter website
My safety check was an assert. Five lines made the module refuse to load without it.
mahirhir profile

My safety check was an assert. Five lines made the module refuse to load without it.

#python #security #testing #debugging
6
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3 min read

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git commit with a pathspec ignored my index and committed the file as it sat on disk
mahirhir profile

git commit with a pathspec ignored my index and committed the file as it sat on disk

#git #devops #debugging #testing
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Comments 2
4 min read
A red I expected hid an instrument that was reading an empty directory
mahirhir profile

A red I expected hid an instrument that was reading an empty directory

#testing #rust #debugging #devops
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Comments 1
3 min read
2500 tests in my public repository and nothing was running them
mahirhir profile

2500 tests in my public repository and nothing was running them

#rust #testing #ci #opensource
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Comments
4 min read
A maintainer closed all four of my pull requests in one minute, and the close was correct
mahirhir profile

A maintainer closed all four of my pull requests in one minute, and the close was correct

#opensource #python #career #testing
5
Comments
3 min read
I wrote that their test harness had no denominator. Their own script header said it first.
mahirhir profile

I wrote that their test harness had no denominator. Their own script header said it first.

#testing #opensource #ci #debugging
6
Comments
3 min read
I sent 17 pull requests to one repository and the maintainer locked it for 24 hours
mahirhir profile

I sent 17 pull requests to one repository and the maintainer locked it for 24 hours

#opensource #github #career #writing
6
Comments
4 min read
cast(bool, x) is a promise to the type checker. At runtime it is the identity function.
mahirhir profile

cast(bool, x) is a promise to the type checker. At runtime it is the identity function.

#python #typing #security #ai
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Comments 7
3 min read
Four agent frameworks got the same approval check wrong. Four others got it right.
mahirhir profile

Four agent frameworks got the same approval check wrong. Four others got it right.

#ai #security #opensource #python
5
Comments
3 min read
The scanner read 2581 files and reported zero. The defect was on line 403.
mahirhir profile

The scanner read 2581 files and reported zero. The defect was on line 403.

#python #security #testing #ai
5
Comments
3 min read
47% of my lifetime views are on articles with no link out
mahirhir profile

47% of my lifetime views are on articles with no link out

#writing #career #opensource #meta
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Comments
3 min read
Four filters returned nothing and I read all four as nothing being there
mahirhir profile

Four filters returned nothing and I read all four as nothing being there

#regex #debugging #testing #shell
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Comments
3 min read
I built a tool to catch empty scans read as passes, and shipped it with an empty scan read as a pass
mahirhir profile

I built a tool to catch empty scans read as passes, and shipped it with an empty scan read as a pass

#testing #opensource #javascript #devops
5
Comments
2 min read
My grep filter had no digits in it. The one field with a digit was the one I said was missing
mahirhir profile

My grep filter had no digits in it. The one field with a digit was the one I said was missing

#testing #programming #rust #debugging
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Comments
4 min read
I build a tool that says don't trust self-report. Then I trusted mine seven times in one day

Real examples of silent software failures
mahirhir profile

I build a tool that says don't trust self-report. Then I trusted mine seven times in one day

#testing #devops #programming #debugging
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Comments 8
5 min read
Eight of my nine mutants died, and the survivor wasn't a weak test
mahirhir profile

Eight of my nine mutants died, and the survivor wasn't a weak test

#testing #rust #softwareengineering #debugging
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Comments
3 min read
The rollback in gemini-cli restored an empty directory, and the test for it passed
mahirhir profile

The rollback in gemini-cli restored an empty directory, and the test for it passed

#javascript #typescript #testing #opensource
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Comments
3 min read
Three gotchas installing a plugin into someone else's agent
mahirhir profile

Three gotchas installing a plugin into someone else's agent

#rust #opensource #devops #ai
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Comments
4 min read
The discriminator between a membrane and a logger
mahirhir profile

The discriminator between a membrane and a logger

#rust #opensource #testing #ai
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Comments 5
3 min read
A red gate and a silent one turned out to mean the same thing
mahirhir profile

A red gate and a silent one turned out to mean the same thing

#testing #ci #debugging #devops
5
Comments
3 min read
Relabeling 22 backlog items moved a progress bar 23 points, and I hadn't shipped anything
mahirhir profile

Relabeling 22 backlog items moved a progress bar 23 points, and I hadn't shipped anything

#productivity #devops #testing
5
Comments
3 min read
My editor's background linter filled the one drive I had left, 341GB at a time
mahirhir profile

My editor's background linter filled the one drive I had left, 341GB at a time

#rust #vscode #windows #devops
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3 min read
Deleting files inside WSL doesn't shrink the disk they lived on
mahirhir profile

Deleting files inside WSL doesn't shrink the disk they lived on

#wsl #windows #devops #cli
5
Comments
3 min read
A double-quoted $HOME sent three of my directories nowhere I could find them
mahirhir profile

A double-quoted $HOME sent three of my directories nowhere I could find them

#powershell #wsl #bash #devops
5
Comments
3 min read
git commit -m with a path argument doesn't commit what you staged
mahirhir profile

git commit -m with a path argument doesn't commit what you staged

#git #github #productivity #devops
5
Comments
3 min read
My CI has been red for 18 days. It never started a single job.
mahirhir profile

My CI has been red for 18 days. It never started a single job.

#ci #devops #testing #github
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4 min read
Undo almost never proves what it undid
mahirhir profile

Undo almost never proves what it undid

#discuss #programming #ai #softwareengineering
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Comments 2
4 min read
The one place in OpenClaw's tool path where a write can still be stopped

Real gateway test proves file writes intercepted
mahirhir profile

The one place in OpenClaw's tool path where a write can still be stopped

#rust #opensource #ai #agents
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Comments 14
5 min read
A real model's write, escrowed before it landed
mahirhir profile

A real model's write, escrowed before it landed

#rust #opensource #ai #agents
5
Comments
4 min read
The bug only showed up once the feature started working
mahirhir profile

The bug only showed up once the feature started working

#rust #testing #softwareengineering #buildinpublic
5
Comments
4 min read
Shipping a binary 4 days late, honestly
mahirhir profile

Shipping a binary 4 days late, honestly

#rust #opensource #devops #buildinpublic
5
Comments
3 min read
The only way our GitHub Action went green was when the verifier was missing

Confesses to shipping a fail-open stub in CI
mahirhir profile

The only way our GitHub Action went green was when the verifier was missing

#github #cicd #opensource #devops
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Comments 8
3 min read
The same wrong number was in six files and I still don't know where it came from
mahirhir profile

The same wrong number was in six files and I still don't know where it came from

#testing #opensource #productivity #devops
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Comments
4 min read
The enum had six reasons and the code needed a seventh
mahirhir profile

The enum had six reasons and the code needed a seventh

#rust #testing #opensource #ai
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Comments
4 min read
Six things reported green and were lying
mahirhir profile

Six things reported green and were lying

#rust #testing #opensource #devops
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Comments 2
4 min read
The limits page is longer than the feature list
mahirhir profile

The limits page is longer than the feature list

#rust #testing #opensource #ai
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4 min read
I ran 10,373 mutations through a reversibility gate. Tamper detection caught 600 of 600.

Honest benchmark caveats and crates link inside
mahirhir profile

I ran 10,373 mutations through a reversibility gate. Tamper detection caught 600 of 600.

#rust #testing #opensource #ai
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Comments 5
14 min read
What "undo" actually means when the target is a real repo, not a fixture
mahirhir profile

What "undo" actually means when the target is a real repo, not a fixture

#rust #git #cli #opensource
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Comments
7 min read
The undo has to exist before the write does

Only 13.8% of tools currently support inverses
mahirhir profile

The undo has to exist before the write does

#showdev #rust #ai #security
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Comments 9
8 min read
ime bugs, display-width bugs, and bidi bugs are the same bug
mahirhir profile

ime bugs, display-width bugs, and bidi bugs are the same bug

#debugging #frontend #javascript #webdev
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Comments
4 min read
Output is cheap now. Keep the receipts.
mahirhir profile

Output is cheap now. Keep the receipts.

#discuss #ai #productivity #career
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4 min read
Teaching a grader the difference between pаypаl and paypal
mahirhir profile

Teaching a grader the difference between pаypаl and paypal

#unicode #i18n #opensource #machinelearning
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Comments
4 min read
a width check said the string was safe to cut. it split a kanji in half.
mahirhir profile

a width check said the string was safe to cut. it split a kanji in half.

#javascript #unicode #i18n #webdev
5
Comments 2
7 min read
The Enter key that submits your form while a Japanese user is still typing
mahirhir profile

The Enter key that submits your form while a Japanese user is still typing

#javascript #i18n #testing #webdev
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Comments 4
5 min read
Three ways CJK text breaks big open-source projects, over and over
mahirhir profile

Three ways CJK text breaks big open-source projects, over and over

#i18n #opensource #javascript #webdev
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Comments 6
6 min read
The Sandwich Test: How I Check If A Dev-Tool Idea Is Actually Winnable Before I Build It
mahirhir profile

The Sandwich Test: How I Check If A Dev-Tool Idea Is Actually Winnable Before I Build It

#devtools #startup #opensource #indiehackers
5
Comments 2
5 min read
How this page breaks Japanese lines
mahirhir profile

How this page breaks Japanese lines

#cjk #typography #javascript #webdev
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Comments
2 min read
The Enter key that fires while you're still typing
mahirhir profile

The Enter key that fires while you're still typing

#cjk #ime #javascript #webdev
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3 min read
I cataloged 93 CJK and Unicode bugs in open source. Most are the same five mistakes.
mahirhir profile

I cataloged 93 CJK and Unicode bugs in open source. Most are the same five mistakes.

#opensource #i18n #javascript #webdev
4
Comments
5 min read
A searchable corpus of CJK and Unicode bugs in open-source libraries
mahirhir profile

A searchable corpus of CJK and Unicode bugs in open-source libraries

#japan #i18n #webdev #unicode
5
Comments
4 min read
Your main input handles IME composition. The rename box next to it doesn't.
mahirhir profile

Your main input handles IME composition. The rename box next to it doesn't.

#javascript #react #i18n #a11y
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Comments 2
4 min read
Japan-readiness is a cliff, not a gradient: what 92 dev tools' front doors actually look like
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Japan-readiness is a cliff, not a gradient: what 92 dev tools' front doors actually look like

#japan #localization #saas #devtools
1
Comments
6 min read
I find Japan-shaped holes in global software
mahirhir profile

I find Japan-shaped holes in global software

#javascript #i18n #react #webdev
1
Comments
4 min read
how to build a CJK/IME regression suite for a terminal or editor app
mahirhir profile

how to build a CJK/IME regression suite for a terminal or editor app

#testing #i18n #ai #japanese
1
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5 min read
I tested whether AI coding agents break on Japanese input
mahirhir profile

I tested whether AI coding agents break on Japanese input

#ai #opensource #i18n #japanese
1
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3 min read
the bugs that only break in Japanese (and how to find them in someone else's repo)
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the bugs that only break in Japanese (and how to find them in someone else's repo)

#opensource #i18n #japanese #webdev
1
Comments
4 min read
the bug a merged fix forgot: how i find first OSS contributions that actually merge
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the bug a merged fix forgot: how i find first OSS contributions that actually merge

#opensource #beginners #github #tutorial
1
Comments
5 min read
I scanned 15 funded developer tools for Japan-readiness. Every one scored F.
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I scanned 15 funded developer tools for Japan-readiness. Every one scored F.

#japan #i18n #webdev
1
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3 min read
The Japan-readiness Standard
mahirhir profile

The Japan-readiness Standard

#japan #i18n #webdev
1
Comments
3 min read
the same few bugs keep hiding in libraries you already trust
mahirhir profile

the same few bugs keep hiding in libraries you already trust

#opensource #debugging #programming #webdev
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6 min read
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