fix(runtime): truncate assistant summary on UTF-8 char boundary to prevent CJK panic

[donglovejava]

Bug

When assistant_text contains CJK characters (3-byte UTF-8), the byte slice
&assistant_text[..SUMMARY_LIMIT.saturating_sub(3)] (byte 277) can land in
the middle of a multi-byte sequence, causing a panic:

byte index 277 is not a char boundary (it is inside a 3-byte UTF-8 sequence)

Fix

Replace the raw byte-index slice with truncate_with_ellipsis() which already
finds the nearest safe char boundary via char_indices().

Change

-format!("{}...", &assistant_text[..SUMMARY_LIMIT.saturating_sub(3)])
+crate::utils::truncate_with_ellipsis(&assistant_text, SUMMARY_LIMIT, "...")

1 line changed.

Files

• crates/tui/src/runtime_threads.rs:1437

Greptile Summary

This PR fixes a panic that occurred when assistant_text contained CJK (or any multi-byte UTF-8) characters by replacing a raw byte-index slice with the existing truncate_with_ellipsis helper, which already walks char_indices() to guarantee a safe boundary.

• The one-line change in runtime_threads.rs (line 1437) is correct: truncate_with_ellipsis safely handles all UTF-8 sequences by finding the last character start index that fits within the byte budget before appending the ellipsis.
• The outer if assistant_text.len() > SUMMARY_LIMIT guard (lines 1436–1440) is now redundant—truncate_with_ellipsis already has an identical early-return—and is inconsistent with the user_text path on line 1414 that calls the helper directly.

Confidence Score: 4/5

Safe to merge — the fix correctly eliminates the UTF-8 boundary panic and the only remaining note is a minor cleanup opportunity.

The one-line change replaces a demonstrably dangerous raw byte slice with a well-tested helper that walks char_indices(). The surrounding outer guard is now dead weight and inconsistent with the adjacent user_text path, but it does not introduce wrong behavior.

No files require special attention; the change is isolated to a single expression in runtime_threads.rs.

Important Files Changed

Filename	Overview
crates/tui/src/runtime_threads.rs	Single-line fix replaces an unsafe raw byte-index slice with truncate_with_ellipsis; the outer length guard is now redundant but harmless.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A["assistant_text available?"] -->|yes| B["assistant_text.len() > SUMMARY_LIMIT?"]
    B -->|yes, OLD path| C["&assistant_text[..SUMMARY_LIMIT - 3]\n⚠️ panics on CJK char boundary"]
    B -->|yes, NEW path| D["truncate_with_ellipsis()\nwalks char_indices() → safe boundary"]
    B -->|no| E["assistant_text.clone()"]
    D --> F["asst_summary = truncated + '...'"]
    E --> F
    C --> G["💥 panic: byte index not a char boundary"]
    F --> H["save_item(TurnItemRecord { summary: asst_summary })"]

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_{Reviews (1): Last reviewed commit: "fix(runtime): truncate assistant summary..." | Re-trigger Greptile}

Greptile also left 1 inline comment on this PR.

[gemini-code-assist]

Code Review

This pull request refactors the text truncation logic in runtime_threads.rs to use a helper function truncate_with_ellipsis. The reviewer pointed out that the manual length check and conditional cloning are now redundant because the helper function already handles these internally, and suggested simplifying the code by calling the helper directly.

[gemini-code-assist]

The manual length check assistant_text.len() > SUMMARY_LIMIT and the conditional .clone() are redundant because truncate_with_ellipsis already performs this length check internally and returns a new String. We can simplify this block by directly calling truncate_with_ellipsis.

                let asst_summary = crate::utils::truncate_with_ellipsis(&assistant_text, SUMMARY_LIMIT, "...");

[greptile-apps]

The outer if assistant_text.len() > SUMMARY_LIMIT guard is now redundant. truncate_with_ellipsis already contains an identical early-return (if s.len() <= max_len { return s.to_string(); }), so the branch never provides additional protection. The user_text path directly above (line 1414) calls the helper without a guard, making the two paths inconsistent.

Suggested change

	let asst_summary = if assistant_text.len() > SUMMARY_LIMIT {
	format!("{}...", &assistant_text[..SUMMARY_LIMIT.saturating_sub(3)])
	crate::utils::truncate_with_ellipsis(&assistant_text, SUMMARY_LIMIT, "...")
	} else {
	assistant_text.clone()
	};
	let asst_summary = crate::utils::truncate_with_ellipsis(&assistant_text, SUMMARY_LIMIT, "...");