Fix UTF-8 boundary panic in cortex_chat and discord reply truncation

[l33t0]

Fixes #273

cortex_chat.rs:92 panics when truncating tool results containing multi-byte characters (CJK, emoji, etc.) because &result[..200] can slice inside a multi-byte UTF-8 sequence. The same pattern existed in discord.rs for reply content truncation.

Changes

• src/agent/cortex_chat.rs — &result[..200] → &result[..result.floor_char_boundary(200)]
• src/messaging/discord.rs — &reply_content[..200] → &reply_content[..reply_content.floor_char_boundary(200)]

floor_char_boundary rounds down to the nearest char boundary, which is the same approach used throughout the rest of the codebase (worker.rs, telegram.rs, channel.rs, etc.).

Testing

Audited all remaining [..N] slices in src/ — the others operate on ASCII-only data (UUIDs, hex digests, API tokens) and are safe.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 767799e and a611056.

📒 Files selected for processing (1)

• src/agent/cortex_chat.rs

🚧 Files skipped from review as they are similar to previous changes (1)

• src/agent/cortex_chat.rs

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Walkthrough

Two files update truncation to be UTF-8 safe: previews now compute a character-boundary end via floor_char_boundary(200) before slicing, preventing panics when cutting multi-byte UTF-8 text (e.g., CJK) while preserving a 200‑character preview length.

Changes

Cohort / File(s)	Summary
UTF-8 Boundary Safety in String Truncation src/agent/cortex_chat.rs, src/messaging/discord.rs	Replaced direct byte-index slicing with a char-boundary-safe slice using floor_char_boundary(200) when creating 200-character previews/truncated quoted content to avoid slicing inside multi-byte UTF-8 characters.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly describes the main fixes: UTF-8 boundary panic resolution in cortex_chat and discord reply truncation, matching the changeset precisely.
Description check	✅ Passed	The description is directly related to the changeset, explaining the UTF-8 boundary issue and the floor_char_boundary solution applied to both files.
Linked Issues check	✅ Passed	The PR fully implements the fix requested in issue #273: replaces unsafe byte-index slicing with floor_char_boundary in cortex_chat.rs:92 and extends the same fix to discord.rs, directly addressing the panic.
Out of Scope Changes check	✅ Passed	All changes are directly in scope: UTF-8 boundary fixes in cortex_chat.rs and discord.rs to prevent the panic described in issue #273, with no extraneous modifications.

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✨ Finishing Touches

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