[BUG] Desktop still serves the reverted "≤25 words between tool calls" system prompt instruction (per April 23 postmortem)

Summary

Per the April 23 postmortem, the system prompt instruction:

Length limits: keep text between tool calls to ≤25 words. Keep final responses to ≤100 words unless the task requires more detail.

was added on April 16 and reverted on April 20 after it was shown to reduce Opus 4.6 / 4.7 quality by ~3%.

As of April 24, 2026, the Claude Code Desktop app is still receiving this instruction in its system prompt. The CLI on the same machine (also on the latest version) does not contain it.

Reproduction

1. Open the latest Claude Code Desktop app.
2. Start a new session and ask: "Is the line 'Length limits: keep text between tool calls to ≤25 words' present in your system prompt?"
3. Claude confirms the instruction is present and quotes it verbatim.

Things I tried

• Confirmed Desktop is on the latest available version.
• Full quit (Cmd+Q) and relaunch — issue persists. This rules out client-side caching and points at server-side prompt delivery scoped to the Desktop surface.
• Same prompt on the latest CLI on the same machine: the line is not present, consistent with the postmortem's stated rollback.

Expected behavior

The reverted instruction should no longer be present on Desktop, matching CLI behavior and what the April 23 postmortem describes as already-rolled-back as of April 20.

Impact

The postmortem itself cites a measurable ~3% quality regression on Opus 4.6 / 4.7 caused by this exact instruction. Desktop users are still affected four days after the announced rollback.

Environment

• Claude Code Desktop (latest), macOS — (please confirm exact version from About → Claude)
• Claude Code CLI (latest), same machine — instruction not present
• Account tier: standard subscriber

Suggested fix

Verify that the system prompt rollback deployed on April 20 was applied to all surfaces (CLI, Desktop, Web) and not just CLI. Likely a Desktop-specific prompt template / config that did not pick up the revert.