The Powerduck Blog
Product updates, engineering notes, and guides for designing, debugging, testing, mocking, and serving MCP tools from one OpenAPI spec.
Browse the guidesThe agent tracked the last processed event in an environment constant, ran green locally, and reset on the first redeploy; the consumer re-read the whole queue and resent every welcome email to existing users.
Read articleThe agent memoized a slow GET endpoint keyed only on the request path, warmed it locally under one fixed test user, and stayed green. In staging, a second tenant read the first tenant's row because the cache key never included the authenticated subject.
Read articleRenaming a token inside the repo does not rename the secret in CI. The agent updated every code reference, the local run passed, but the deployed read returned undefined under the old registered name. Local dotenv still carried the legacy alias, so nothing reproduced until after deploy.
Read articleThe agent scheduled a nightly report at 02:00, ran it by hand, and committed. The check passed on the developer's local clock, but the container runs UTC, so the expression fired at the wrong hour. A bare schedule has no zone; it inherits the host clock, and a local run cannot catch the offset.
Read articleThe agent moved a file-cache directory into config but wrote its own session scratch path as the default. It passed on the agent's own disk and failed on the next machine and in CI. Portable defaults resolve from the environment, never from the author's home.
Read articleThe agent traced a failing call by logging the whole header map, so the Authorization bearer token landed in plaintext logs on every retry. Local tests use a dummy token and miss it, but aggregation keeps the real credential. Debugging needs the request's shape, not its secrets.
Read articleThe agent wanted a clean reproduction, so it ran a hard reset and threw away uncommitted local work before asking. A clean checkout should never mean destroying unsaved state. Reproduce in an isolated worktree instead, check git status first, and leave the user's scratch edits untouched.
Read articleA one-line bug fix arrived as a PR whose lockfile changed four hundred lines. The agent ran a fresh install instead of adding one pinned package, so unrelated transitive dependencies jumped versions and hid in a diff nobody reviewed. A fix PR should not also be an unplanned supply-chain upgrade.
Read articleThe agent wrote a clear paragraph describing the change and where it belongs, and the reviewer applied it by hand from the thread. No branch was pushed, no PR existed, and the tests never ran against the real artifact. A written explanation of a fix is not the same thing as shipped code.
Read articleThe agent reproduced the bug on main, wrote the fix, watched the suite go green, and reported done. Customers on the supported release branch still hit it, because that branch kept the old code and nobody asked which version lines had to ship the fix.
Read articleThe agent split one change into two stacked PRs, marked the second ready, and merged it while the base PR was still open. CI showed green because it tested a synthetic merge against a base branch that never reached main, and the child broke on landing.
Read articleThe agent needed to raise the request timeout, so it appended a second timeout block to the config instead of editing the existing one. The lenient parser silently kept the last occurrence, and the first tuned value vanished without an error.
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