[Fix] Task history disappears when user reopens a task

[zoomote]

​Created by Roomote. Follow up by mentioning @roomote, in the web UI, or in Discord.

What changed

• Preserve finalized reasoning and other saved messages while a task is rehydrated for resume.
• Distinguish missing, invalid, and unreadable task history from an explicitly empty history instead of converting failures to an empty conversation.
• Stop abandoned history-task hydration before it can persist after eviction.
• Abort delegated-parent reopening when its saved UI history cannot be loaded safely.
• Add deterministic regression coverage for failed hydration, finalized reasoning, and the resume/eviction race.

Why this change was made

Reopening or quickly leaving a saved task could replace valid history with an empty or shortened message list. This resolves #1279 and extends the lifecycle and persistence safety work tracked by #355 and #208.

Impact

Users keep their last saved task content when reopening or resuming tasks. Temporary storage failures no longer become destructive empty writes, and stale task instances cannot write after being evicted.

Related PRs

• Documentation: [Docs] Explain task history recovery safeguards Zoo-Code-Docs#40

[codecov]

Codecov Report

❌ Patch coverage is 74.07407% with 7 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/core/task/Task.ts	70.00%	2 Missing and 1 partial ⚠️
src/core/webview/ClineProvider.ts	0.00%	3 Missing ⚠️
src/core/task-persistence/taskMessages.ts	92.85%	0 Missing and 1 partial ⚠️

📢 Thoughts on this report? Let us know!

[martin-rueegg]

Looks like this might also contribute to fixing some of the things I've experienced in #1231, too

[martin-rueegg]

I think the fix is the right approach but can be strengthened by using the new merge functionality of the safeWriteJson() method and updating the local copy with the merged result.

@roomote

[martin-rueegg]

before throwing the error, I suggest we wait a random number of milliseconds 10-300 and retry. safe writes move the file away and then the new one in place. hence, there is a split-second where no file is accessible.

Throw if the second try fails as well

[martin-rueegg]

I think we should apply the new merge-pattern provided by #1261

the same should be done here:

Zoo-Code/src/core/task-persistence/apiMessages.ts

Lines 109 to 121 in 1ad8f52

	export async function saveApiMessages({
	messages,
	taskId,
	globalStoragePath,
	}: {
	messages: ApiMessage[]
	taskId: string
	globalStoragePath: string
	}) {
	const taskDir = await getTaskDirectoryPath(globalStoragePath, taskId)
	const filePath = path.join(taskDir, GlobalFileNames.apiConversationHistory)
	await safeWriteJson(filePath, messages)
	}

which is called from
https://github.com/Zoo-Code-Org/Zoo-Code/pull/1319/changes#diff-ec3b024cdaad55c3e92c0d0d4293bbc785e69f76bf646132cb0923f44fb3df22R992

[martin-rueegg]

See https://github.com/Zoo-Code-Org/Zoo-Code/pull/1319/changes#r3834600042