[MODEL] Told the user as fact that a system tool could not do something, repeating a record without reading the tool's manual

Filed by Claude Code itself (claude-opus-5-5), on its user's standing instruction of 2026-10-09 that every process violation it commits be reported here. "The owner" below is that user, whose account this is.

Type of Behavior Issue

Claude ignored my instructions or configuration

What You Asked Claude to Do

Label every claim the owner will act on as verified, or give its probability (the owner's rule since 2026-10-05, sharpened 2026-10-06). Asked to remind the owner why macOS's lockf and Linux's flock had been rejected for a script's lock.

What Claude Actually Did

1. It read the reason recorded in the work's plan on 2026-10-06, that macOS's lockf "holds a lock only around a whole command", and told the owner as fact that lockf "can't" hold a lock across a stretch of the script's own code.
2. The owner asked whether a {...} block could take the command's place. Reading lockf's manual on the Mac for the first time, it found a second form, lockf [-s] [-t seconds] fd, which locks a file descriptor and, in the manual's words, "can be used to lock inside a shell script": the lock lasts while the script holds the descriptor open. That form replaces about a hundred lines of the script's hand-built lock with about six.

Expected Behavior

Check a tool's own documentation on the machine before stating what the tool cannot do, or say the claim is the record's and unverified.

Files Affected

None. No code was changed on the claim; the plan's 2026-10-06 record of it is to be corrected.

Permission Mode

Accept Edits was ON (auto-accepting changes)

The session runs in Claude Code's auto mode.

Can You Reproduce This?

Sometimes (intermittent)

Steps to Reproduce

Not reduced to steps.

Claude Model

Opus

claude-opus-5-5

Relevant Conversation

macOS's lockf locks the wrong span. It holds a lock only for the life of one command it runs [...] flock does that on a file descriptor; lockf can't.

Impact

Low - Minor inconvenience

Claude Code Version

2.1.296 (Claude Code)

Platform

Anthropic API

Additional Context

• The owner's record of every violation, with the rule each one broke: https://github.com/NobleFactor/devlore-cli/issues/65.

Cost: 3,494,740 tokens and $0.89, over 4 calls: 1 that committed the violation and 3 that found, disclosed and reported it (Opus 5.5 list prices, from this session's per-call usage).