fix(agent-manager): preserve named worktrees on collision

[marius-kilocode]

Calling agent_manager more than once with the same explicit branchName could remove the first live worktree, leave its branch behind, and then create a timestamp-suffixed replacement. This broke the first agent while making the second agent's branch unpredictable. The same collision could occur through the Advanced Worktree modal, where repeated names are valid requests for separate agents.

Resolve branch availability before creating or removing anything. The requested name remains the first branch, subsequent independent requests receive deterministic numeric suffixes such as echo-hello-world-2, and existing worktrees remain untouched. Exact replay of one Agent Manager event is deduplicated by requestID, while distinct tool calls continue to create distinct worktree-backed sessions even when they share a branch-name seed.

Closes #10976

[kilo-code-bot]

Code Review Summary

Status: 1 Issue Found | Recommendation: Merge (advisory only)

Overview

Severity	Count
CRITICAL	0
WARNING	0
SUGGESTION	1

Issue Details (click to expand)

SUGGESTION

File	Line	Issue
packages/kilo-vscode/src/agent-manager/WorktreeManager.ts	309	Unbounded for(;;) loop in availableBranch — safe in practice but has no upper bound

Previously Flagged Issues — Now Resolved

File	Previous Issue	Status
packages/kilo-vscode/src/agent-manager/AgentManagerProvider.ts	WARNING: Off-by-one in LRU eviction — set grew to 101 before pruning	✅ Fixed: >= 100 check now evicts before adding, keeping set at exactly 100
packages/kilo-vscode/src/agent-manager/WorktreeManager.ts	SUGGESTION: Timestamp fallback in availableBranch was redundant	✅ Fixed: Date.now() fallback removed; loop is now unbounded and deterministic

Other Observations (not in diff)

prepareWorktreePath behavior change: When existingBranch is not provided and the directory already exists, the code now throws "Worktree path already exists" rather than silently removing it. In practice resolveBranch + availableBranch always picks a fresh directory upfront (via the fs.existsSync check in available), so this throw is only reachable in extreme edge cases (e.g., a directory appears between resolveBranch and prepareWorktreePath). The stricter behavior is correct.

Retry path double-collision: If two concurrent processes both pass resolveBranch and both hit the already exists catch, the second resolveBranch(params) call in the retry will resolve to a new available name, but there is no catch after the retry runWorktreeAdd — a third concurrent collision would throw. This is an acceptable tradeoff for a rare scenario.

Latest commit (style): The newest commit (6e4fc389) is a pure formatting change — it reformats the resolveBranch parameter object type from a single line to multi-line. No logic changes.

Files Reviewed (6 files)

• .changeset/calm-agents-keep-worktrees.md — no issues
• packages/kilo-vscode/src/agent-manager/AgentManagerProvider.ts — previous WARNING resolved
• packages/kilo-vscode/src/agent-manager/WorktreeManager.ts — previous SUGGESTION remains; latest commit is formatting-only
• packages/kilo-vscode/src/agent-manager/tool-start.ts — no issues
• packages/kilo-vscode/tests/unit/agent-manager-tool-start.test.ts — no issues
• packages/kilo-vscode/tests/unit/worktree-manager.test.ts — no issues

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_{Reviewed by claude-4.6-sonnet-20260217 · 165,776 tokens}

_{Review guidance: REVIEW.md from base branch main}