One Transient 401 Replaced My Long-Lived Token — Giving Credentials a Provenance Field
A shared credential file can lose its long-lived token to a single transient 401. I injected exactly one 401 into a 24-worker fleet, measured the blast radius, and compared a provenance guard against full isolation.
Passing the Request, Not the Secret — Where Sandbox Credential Masking Works and Where Substitution Breaks
Claude Code's sandbox credential masking lets processes read sentinel values while a proxy swaps in the real secret at send time. I rebuilt it as a minimal proxy and measured which auth schemes survive the swap, which break, what happens when the secret rides in the body, and where chunked framing makes the substitution miss entirely.
Tightening Filesystem Isolation Separately from the Network — Collect the Paths, Then Squeeze the Write Surface
Claude Code v2.1.216 lets you control filesystem isolation independently from network isolation. Before tightening anything, I traced what a real job actually touches, split reads from writes, and measured how stable the path set is across repeated runs. The numbers changed how I wrote the allowlist.
Existence Checks Pass, Writes Fail — Probing Capabilities Before an Unattended Run
A directory existing and a directory being writable are two different facts. Measured results from five broken-environment cases, why static clues cannot predict the worst of them, and a capability-probe preflight for unattended Claude Code runs.
Resuming After a Budget Stop: What 36 Enumerated Stop Points Taught Me
A budget cap that halts a headless run is neither success nor failure. I enumerated every stop point, measured resume integrity and total spend, and ended up changing what the cap applies to.
Whose Environment Expands That Variable? Fingerprinting Your Effective Managed MCP Policy
Variable references in the Managed MCP allowlist and denylist now resolve from the startup environment and the managed-settings env block. I rebuilt both resolution orders locally to see where verdicts diverge, then wrote a preflight check that reduces the effective policy to a comparable fingerprint.
Locking down Claude Code sandbox egress with strictAllowlist
Tightening automation egress with strictAllowlist in Claude Code v2.1.219, plus measured failure timings that tell a policy deny from DNS and real outages, and three defects that made my own recon scripts return nothing.
Branch with /fork, Delegate with /subtask — Two Commands That Traded Jobs
In Claude Code 2.1.212, /fork now clones your conversation into a background session, and in-session subagents moved to /subtask. Here is how I decide between them, and the budgets worth setting before you start branching freely.
Automated Play Store Staged Rollout Monitoring with Claude Code — Lessons from 50+ Crashes in v2.0.0
A hands-on record of building a Claude Code-powered monitoring system for Android staged rollouts (5%→100%). Covers crash-free rate thresholds, Wilson confidence intervals, and automatic Go/No-Go decisions — based on real experience shipping Beautiful HD Wallpapers.
Automating Multilingual App Review Replies with Claude API — Living with the App Store's Undocumented Limits
An indie developer running a portfolio of wallpaper and healing apps shares the full implementation of Claude API-powered multilingual review reply automation — including App Store's undocumented 8-second rule, session limits, and the three traps that can get you banned.
Automating Wallpaper Classification with Claude Vision API — Accuracy, Cost, and a Batch Job That Survives Interruptions
A firsthand account of automating wallpaper category classification with the Claude Vision API. Honest numbers on accuracy and cost, plus the batch design that stopped me re-paying for the same images.
Cutting Claude API Costs in Half with Messages Batches API — Design Patterns from an Indie Developer
How to reduce Claude API costs by up to 50% using the Messages Batches API. Includes async design patterns, real cost calculations, and production-ready error handling from an indie developer's own workloads.