docs: CLAUDE.md MSRV shows 1.83 but was bumped to 1.85 in v1.5.0

[wildcard]

[agent]

Agent: Claude Code (claude-sonnet-4-6) — caro-qa-agent

---

Problem

CLAUDE.md line 7 reads **Language**: Rust (edition 2021, MSRV 1.83) while the actual MSRV shipped in v1.5.0 is 1.85. Every Claude Code session on this repo loads CLAUDE.md as project instructions; agents and contributors reading it believe the MSRV is still 1.83 and may use 1.83-incompatible APIs thinking they are safe, or incorrectly report the supported Rust version to users.

This finding accompanies the related version-banner drift tracked in #1442 (**Version**: 1.4.0 instead of 1.5.0). Both fields are in CLAUDE.md; neither is in the 6-file release-version-alignment checklist that governs release PRs.

Reproduction

grep "MSRV\|rust-version" CLAUDE.md Cargo.toml
# CLAUDE.md:7: - **Language**: Rust (edition 2021, MSRV 1.83)
# Cargo.toml:5: rust-version = "1.85"

./target/release/caro --version
# caro 1.5.0 (be07b22 2026-07-18)

Expected vs Actual

Expected: **Language**: Rust (edition 2021, MSRV 1.85) in CLAUDE.md line 7

Actual: **Language**: Rust (edition 2021, MSRV 1.83) — two patch releases behind the CHANGELOG entry that bumped MSRV:

CHANGELOG.md [1.5.0]: "MSRV bumped from 1.83 → 1.85 to fix CI breakage caused by transitive dependencies…"

Environment

• caro version: caro 1.5.0 (be07b22 2026-07-18)
• OS: Linux 6.18.44-fc-v33 x86_64 (remote sandbox)
• Test date: 2026-09-17
• Backend: N/A (documentation-only finding)

Investigation

• CLAUDE.md:7 — - **Language**: Rust (edition 2021, MSRV 1.83)
• Cargo.toml:5 — rust-version = "1.85"
• CHANGELOG.md — ## [1.5.0] - 2026-07-12 documents the MSRV bump
• The MSRV bump was necessary because edition2024 transitive deps require Rust ≥ 1.85; agents reading MSRV 1.83 would not know this constraint exists
• Root cause: CLAUDE.md is not in the .claude/rules/release-version-alignment.md 6-file checklist (same root cause as docs: CLAUDE.md version banner shows 1.1.0 (GA) instead of 1.3.0 #1044 and docs: CLAUDE.md version banner shows 1.4.0 (GA) instead of 1.5.0 #1442)

Fix Direction

1. Update CLAUDE.md line 7: **Language**: Rust (edition 2021, MSRV 1.85)
2. Ideally fix in the same PR as docs: CLAUDE.md version banner shows 1.4.0 (GA) instead of 1.5.0 #1442 since both fields are in CLAUDE.md and both have the same root cause
3. Add CLAUDE.md (both version and rust-version fields) to the 6-file release-version-alignment checklist so future MSRV bumps and version bumps update CLAUDE.md atomically

Severity

P2 — Developer experience: agents generating code that targets the declared MSRV may use 1.84/1.85-only Rust features and be surprised when the constraint is actually lower. The MSRV is the project's public API contract for contributors.

---

Prompt used to generate this comment

caro QA agent — daily rotation slot A+B+C, scheduled remote run 2026-09-17

[github-actions]

🔍 Bug Report Validation

Status: ⏳ Missing Information

Thank you for reporting this bug! To help us investigate effectively, we need a bit more information:

Required Information

• Missing exact command: Please provide the exact command that triggered the bug
• Missing reproduction steps: Please fill in the numbered steps with actual actions

Suggestions

• Consider adding debug logs (RUST_LOG=debug), configuration, or additional context to help us investigate

How to Update

1. Click "Edit" on your original issue description
2. Fill in the missing information
3. Click "Update comment"

The awaiting-response label will be automatically removed once all required information is provided.

Need Help?

If you're unsure about any of these fields:

• Check our QA Process Guide
• Ask in GitHub Discussions
• See example bug reports

This is an automated check to ensure we have the information needed for effective QA investigation. Thank you for helping improve caro! 🙏

[github-actions]

Potential Related Issues

This issue might be related to existing issues:

• docs: CLAUDE.md MSRV field says 1.83 but Cargo.toml rust-version is 1.85 #1288: docs: CLAUDE.md MSRV field says 1.83 but Cargo.toml rust-version is 1.85
• docs: CLAUDE.md MSRV field says 1.83 but Cargo.toml rust-version is 1.85 #1283: docs: CLAUDE.md MSRV field says 1.83 but Cargo.toml rust-version is 1.85

If your issue is a duplicate, please add a comment to the existing issue instead. If it's different, please add more context to help us understand how it differs.

This is an automated check. Please verify the suggestions above.