fix(cerebro): reject blank memory update fields

[yacosta738]

Related Issues

• None.

---

Summary

This PR closes a small validation gap in Cerebro memory updates.

• add require_optional_non_empty for optional string fields that still must not be blank when provided
• reject whitespace-only topic_key and scope values in mem_update
• add a regression test covering a blank topic_key update request through the MCP tools contract

---

Tested Information

• cargo test --manifest-path modules/cerebro/Cargo.toml mem_update_rejects_blank_topic_key
• cargo test --manifest-path modules/cerebro/Cargo.toml --test mcp_tools_contract

---

Documentation Impact

• Docs updated in:
• No docs update required because this is a small validation fix for existing Cerebro tool behavior and does not change setup, APIs, or user-facing documentation.
• I verified the documentation matches the current behavior.

---

Breaking Changes

• None.

---

Checklist

• I have checked that there isn’t already a PR solving the same problem.
• I have read the Contributing Guidelines.
• I ensured my code follows the project's style guidelines.
• I have added or updated tests that prove my fix is effective or that my feature works.
• I have updated the documentation, or I explained above why no documentation update is needed.
• I verified the documentation matches the current behavior.
• I have documented any breaking changes in the Breaking Changes section.
• I have linked the related issue (if any).

[coderabbitai]

Warning

Rate limit exceeded

@yacosta738 has exceeded the limit for the number of commits that can be reviewed per hour. Please wait 41 minutes and 25 seconds before requesting another review.

Your organization is not enrolled in usage-based pricing. Contact your admin to enable usage-based pricing to continue reviews beyond the rate limit, or try again in 41 minutes and 25 seconds.

⌛ How to resolve this issue?

After the wait time has elapsed, a review can be triggered using the @coderabbitai review command as a PR comment. Alternatively, push new commits to this PR.

We recommend that you space out your commits to avoid hitting the rate limit.

🚦 How do rate limits work?

CodeRabbit enforces hourly rate limits for each developer per organization.

Our paid plans have higher rate limits than the trial, open-source and free plans. In all cases, we re-allow further reviews after a brief timeout.

Please see our FAQ for further information.

ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: ASSERTIVE

Plan: Pro

Run ID: 449c66d0-35a8-49e1-8cf7-f067c8a409f3

📥 Commits

Reviewing files that changed from the base of the PR and between 1adbefa and 9a46505.

📒 Files selected for processing (3)

• modules/cerebro/src/tools.rs
• modules/cerebro/src/validation.rs
• modules/cerebro/tests/mcp_tools_contract.rs

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch bart/fix-cerebro-update-validation

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands and usage tips.}

[github-actions]

✅ Contributor Report

User: @yacosta738
Status: Passed (12/13 metrics passed)

Metric	Description	Value	Threshold	Status
PR Merge Rate	PRs merged vs closed	91%	>= 30%	✅
Repo Quality	Repos with ≥100 stars	0	>= 0	✅
Positive Reactions	Positive reactions received	11	>= 1	✅
Negative Reactions	Negative reactions received	0	<= 5	✅
Account Age	GitHub account age	3097 days	>= 30 days	✅
Activity Consistency	Regular activity over time	108%	>= 0%	✅
Issue Engagement	Issues with community engagement	0	>= 0	✅
Code Reviews	Code reviews given to others	584	>= 0	✅
Merger Diversity	Unique maintainers who merged PRs	2	>= 0	✅
Repo History Merge Rate	Merge rate in this repo	93%	>= 0%	✅
Repo History Min PRs	Previous PRs in this repo	264	>= 0	✅
Profile Completeness	Profile richness (bio, followers)	90	>= 0	✅
Suspicious Patterns	Spam-like activity detection	1	N/A	❌

---

_{Contributor Report evaluates based on public GitHub activity. Analysis period: 2025-04-20 to 2026-04-20}