fix(core): strip only the trailing .json from checkpoint names

[he-yufeng]

What

processRestorableToolCalls and getCheckpointInfoList strip the .json suffix from checkpoint names with name.replace('.json', ''), which removes the first .json rather than the trailing extension.

generateCheckpointFileName embeds the edited file's basename: ${timestamp}-${basename}-${toolName}. So editing a .json file yields a checkpoint file like 2025-...-config.json-replace.json, and replace('.json', '') turns it into 2025-...-config-replace.json — the inner .json is dropped and the real extension is left behind, corrupting the name used to map and restore the checkpoint.

Fix

• In processRestorableToolCalls, use the in-scope checkpointFileName directly — it is exactly the name without the .json we just appended.
• In getCheckpointInfoList, use path.basename(file, '.json'), which strips only the trailing extension. This is what the neighbouring getTruncatedCheckpointNames already does for the same kind of name.

Test

Added two cases to checkpointUtils.test.ts: a checkpoint created for an edited config.json keeps config.json-replace in its mapped name, and a 2025-...-config.json-replace.json checkpoint file resolves to 2025-...-config.json-replace. Both fail on main (the name comes back as config-replace) and pass with this change. vitest run on the file is green (17 tests); prettier and eslint are clean.

[gemini-code-assist]

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request addresses a bug in checkpoint filename handling where the use of a global string replacement was causing corruption in filenames containing multiple '.json' segments. By switching to more precise path handling and utilizing existing variables, the fix ensures that only the final file extension is removed, maintaining the correct mapping for restorable tool calls.

Highlights

• Checkpoint Naming Fix: Corrected logic in processRestorableToolCalls and getCheckpointInfoList to ensure only the trailing .json extension is stripped from checkpoint filenames.
• Preventing Name Corruption: Updated the implementation to avoid using .replace('.json', ''), which incorrectly removed internal .json segments from filenames when editing .json files.
• Regression Testing: Added comprehensive test cases to checkpointUtils.test.ts to verify that checkpoints for edited .json files maintain their integrity.

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[github-actions]

📊 PR Size: size/M

• Lines changed: 53
• Additions: +51
• Deletions: -2
• Files changed: 2

[gemini-code-assist]

Code Review

This pull request fixes an issue where checkpoint names were corrupted when editing files that already contained '.json' in their name, by ensuring only the trailing '.json' extension is stripped. The reviewer pointed out that using path.basename to strip the extension might inadvertently remove directory paths and introduce platform-dependent behavior, suggesting a safer regex-based replacement file.replace(/\.json$/, '') instead.

[gemini-code-assist]

Using path.basename(file, '.json') will strip any directory components from the path (e.g., subdir/file.json becomes file). If the checkpoint files contain directory paths, this will corrupt the checkpoint name. Additionally, path.basename is platform-dependent and may behave inconsistently on Windows vs. POSIX environments depending on the path separators used.

Using a regular expression like file.replace(/\.json$/, '') is safer as it only strips the trailing .json extension while preserving any directory structure and avoiding platform-specific path issues.

Suggested change

	// basename(file, '.json') strips only the trailing extension; a
	// plain replace('.json', '') would corrupt names from edited .json
	// files (e.g. "...-config.json-replace.json").
	checkpoint: path.basename(file, '.json'),
	// Strip only the trailing .json extension while preserving any directory structure.
	checkpoint: file.replace(/\.json$/, ''),