All Articles
The 400 that rejects a thinking block, and finding the edit that caused it
On Claude Fable 5.1, editing the system prompt, tools, or earlier messages before a thinking block makes the request fail with a 400. Here is how to check whether your own agent loop does that in a single request, and how to move a rebuilt system prompt and client-side trimming to patterns that leave the prefix untouched.
Two hooks that record every model switch and stop the ones you never agreed to
Build a PostModelSwitch hook that logs every model change and a PreModelSwitch hook that blocks unapproved switches during unattended runs. Complete scripts, measured timings, and the reason the two jobs must stay separate.
Drop the quotes on a heredoc and the prices in your log quietly change
An unquoted heredoc runs the variables and backticks inside its body. Here are the four ways my log got rewritten, how the three quoting forms compare, a safe placeholder-and-sed pattern, and a small script for auditing what you already have.
Once I passed a dozen MCP servers, I stopped trusting the startup list
Only some of the servers that say connection failed at startup are ones you can actually fix. Here is a probe that separates no-response, launch failure, and protocol rejection, measured across a 14-server fleet where sequential 22.03s became parallel 5.09s, and where trimming the deadline quietly turned healthy servers into failures.
The Same Announcement Reads as '+25%' and as 'a 17% Cut' — Checking the Math on Claude Code's September 14 Weekly Limit Change
From September 14, Claude Code's weekly limit becomes a permanent +25% over the pre-promo baseline. Here is why +25% and a 17% cut are the same change, and how to check your own exposure with /usage and a status line script.
Half of My Scheduled Runs Vanished Without a Single Error
A batch job set to run twice a day was only firing once. No errors, no failure alerts. Here is how to expand your own schedule, count expected runs, and reconcile them against execution records to catch silent misses.
Your Config Asks for effort xhigh With Thinking Off, and It Now Quietly Runs at high
Disabling thinking while asking for effort xhigh or max returns a 400. That failure now degrades silently to high instead, so here is a small preflight that catches the mismatch before you send the request.
Read the Catalog Your CLI Already Ships Before Bulk-Replacing Model IDs
A newer generation makes older model IDs look stale. Here is how to pull the catalog embedded in your installed binary, sort every reference into matched, date-mismatched, and malformed, and stop the replacement that would break working IDs.
The 30-Day Session Cleanup Is Fixed, and It Made Me Rethink Where I Keep Records
Claude Desktop and Cowork sessions were quietly disappearing after 30 days until v2.1.248 fixed it. Here is how to check your own setup, what the new setting actually caps, and a small journal script that keeps one line per run outside the session.
The lock I left in a shared folder shut out every run after the first
A cloud-synced connected folder allows create, append, and rename, but refuses delete. Putting a single-instance lock there quietly disabled every unattended run after the first. Measurements for three lock styles, plus an implementation that picks a safe location.
A small script that catches invisible characters in plugin names before you install
Control characters and zero-width characters hiding in plugin or skill names are invisible in a terminal listing. I built six deliberately confusing names, compared what ls actually shows, and wrote a short check you can run before installing anything — plus an honest note on what that check misses.
Don't let your verification script's full output flow back through a hook
The check was working the whole time. The conversation was what ran out of room. Measured side by side: 58 bytes from one scan of 833 files, 42KB from another. Which paths actually reach the model, and how to enforce a budget on them.