[BUG] Model ignores session-injected date when making week-relative inferences ("this week" / "next week")

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

Claude Code injects the current date into every session via a system hook (e.g., "Today's date is 2026-04-30"). The model correctly uses this for explicit date lookups, but fails to apply the same grounding when using week-relative language — phrases like "this week," "next week," and "earlier this week." The result is confident, incorrect temporal statements even though the correct date was available.

Example from today's session (Thursday April 30, 2026): asked to summarize upcoming action items, the model described items dated May 5 (the following Tuesday) as "this week" rather than "next week."

What Should Happen?

When the session hook provides today's date, the model should use it for all temporal reasoning — including week-relative language — not just explicit date comparisons. Determining whether a date falls in "this week" or "next week" requires knowing the current day of the week, which is derivable from the injected date. The model should treat week-relative language as a calculation requiring verification, not as plain English it can reason about freehand.

Ideally, a bespoke session hook is not needed at all and there is consistent date/calendar awareness by way of the model or the Code (or Desktop/Cowork) harness.

Error Messages/Logs

Steps to Reproduce

1. Start a Claude Code session on a Thursday (e.g., April 30, 2026 — session hook confirms the date).
2. Ask Claude to summarize upcoming action items. Include items dated the following Tuesday (May 5).
3. Observe that Claude describes the May 5 items as "this week" rather than "next week."
4. Observe that Claude positions May 5 as the "beginning of the week".

Claude Model

Sonnet (default)

Is this a regression?

No, this never worked

Last Working Version

_No response_

Claude Code Version

Claude Code 2.1.116

Platform

AWS Bedrock

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

This is distinct from issue #50499, which describes sessions where no date is injected at all. This issue is specifically about sessions where the date is provided but the model fails to apply it to relative temporal reasoning.

A workaround exists — configuring the model to run date or cal via Bash before making any week-relative statement — but this is a compensating control for a model reasoning failure, not a real fix.