feat: VS Code session remaining edge cases (resume delay + duplicate tab fixed in PR #109)

[grimmerk]

Summary

Track VS Code-specific edge cases and resume delay optimization for the session switching feature added in PR #103.

Edge Cases

Edge case	Risk	Current behavior	Suggested fix
code CLI not in PATH	Low	execFile('code') fails silently	Fixed in PR #102 — uses open -b bundleId instead
VS Code Stable + Insiders both installed	Low	vscode:// goes to whichever registered	Detect which has the extension active
Extension version < 2.1.72	Medium	URI handler doesn't exist, silently fails	Check extension version or detect failure + show user message
Extension disabled	Low	Same as above	Same
Remote SSH session	Low	JSONL is on remote, not local	Not easily fixable — document as limitation
First-time URI handler permission dialog	One-time	User must click "Allow"	Document in README / first-use notification

Resume Delay Optimization ✅ Done (PR #109)

Current resume flow for closed VS Code sessions:
1. execFile('code', [projectPath]) — opens/activates VS Code window
2. Hardcoded 2s delay — waits for workspace to load
3. URI handler vscode://anthropic.claude-code/open?session=<UUID>

Replaced with IDE lock file polling (PR #109):

• Reads ~/.claude/ide/*.lock to detect if VS Code has the project open
• If project open → instant URI handler (~0.5s)
• If project not open → open -b + poll lock files (250ms interval) + 1.5s post-ready delay
• Fallback to 2s fixed delay if lock dir doesn't exist

Duplicate Tab (Cold Start) ✅ Fixed (PR #109)

VS Code restore + URI handler race condition caused duplicate Claude Code tabs.

Fixed with two mechanisms:

• Active sessions + project not open → skip URI handler (let VS Code restore handle the tab)
• Closed sessions + project not open → 1.5s post-ready delay (lets restore finish before URI handler)

All 8 test cases now pass (see PR #109 test matrix).

Comparison: VS Code vs Terminal Matching Layers

VS Code uses UUID-based URI handler, which is more precise than terminal title/TTY matching:

Feature	iTerm2	Terminal.app	Ghostty	cmux	VS Code
Same-cwd disambiguation	TTY + title cross-ref	TTY + title	CWD + title	TTY + CWD + title + project name	N/A — UUID precise
Active switch precision	Tab-level	Tab-level	Tab-level	Surface-level	Session-level
Closed resume	claude --resume in new tab	Same	Same	Same	URI handler (opens in VS Code)
Cross-ref refinement	Yes (TTY + tab name)	No	No	Yes (TTY + tree parsing)	N/A — no ambiguity
Fallback layers	3 (title → TTY → activate)	3 (title → TTY → activate)	3 (title → CWD → clipboard)	4+ (title → TTY → CWD → project name)	1 (URI handler)

Related

• PR feat: VS Code session support + real-time preview refresh #103: VS Code session support
• PR feat: adaptive VS Code resume via IDE lock file polling #109: IDE lock file polling + duplicate tab fix
• perf: session tab switching performance regression (PR #103) #106: Session tab performance
• Ghostty: no per-tab TTY/PID — missing cross-reference and TTY switch fallback #63: Ghostty TTY support (waiting on upstream)

🤖 On behalf of @grimmerk — generated with Claude Code

[grimmerk]

Edge case: VS Code cold start + resume = duplicate Claude Code tab

Scenario: VS Code was quit with a Claude Code session tab open → user resumes that session from CodeV (Launch Terminal = VS Code) → VS Code relaunches and restores the old window (including Claude Code tab) → 2s later, CodeV's URI handler opens a second tab for the same session.

Root cause: VS Code's "Restore windows" feature restores the Claude Code tab before our URI handler fires. The URI handler doesn't deduplicate — it opens a new tab even if the session is already open.

Note: cmux has a similar architecture (workspace restore on relaunch), but cmux does NOT auto-restore Claude Code sessions in its workspaces, so opening a new workspace to resume works fine there.

Possible fixes:

1. Extension-side dedup: The Claude Code extension's URI handler could check if a session tab already exists before opening a new one — this would be the cleanest fix but depends on upstream behavior
2. Skip URI handler on cold start: Detect that VS Code was just launched (not already running) and skip the URI handler, letting VS Code's own restore handle it. Risk: if the session tab wasn't in the restored window, user gets no Claude Code tab.
3. Longer delay: Increase from 2s to let restore complete, then URI handler would ideally focus the existing tab. Unreliable — restore time varies.
4. Hybrid: On cold start, wait longer (~5s), then check if VS Code has the session tab open (e.g., via extension API). If yes, focus it; if no, open via URI handler.

🤖 On behalf of @grimmerk — generated with Claude Code

[grimmerk]

Clarification: This only happens on cold start (VS Code was quit and relaunches). When VS Code is already running, the URI handler correctly focuses the existing session tab without opening a duplicate.

🤖 On behalf of @grimmerk — generated with Claude Code

[grimmerk]

Refinement on fix option 2 (skip URI handler on cold start)

The cold-start skip needs two sub-cases:

1. Cold start + Claude Code tab still in restored window → skip URI handler (let VS Code restore handle it)
2. Cold start + Claude Code tab NOT in restored window (user had closed the tab before quitting) → still need URI handler to open the session

Detecting sub-case 1 vs 2 is non-trivial — would need to query VS Code's state after restore completes (e.g., via extension API or by checking if the URI handler would create a duplicate).

This makes option 1 (extension-side dedup) even more appealing — the extension itself knows whether the session tab already exists.

🤖 On behalf of @grimmerk — generated with Claude Code

[grimmerk]

Detection approaches for cold-start duplicate tab

All three detection methods have significant drawbacks:

Approach	Feasibility	Problem
AppleScript	VS Code's AppleScript dictionary is very limited	Cannot see tab content (only window title)
VS Code Extension API	Most precise	Requires Claude Code extension to cooperate — outside our control
Accessibility API	Can walk AX tree to find tab	Needs permission, fragile across versions, MAS incompatible

Conclusion: The cleanest fix is option 1 (extension-side dedup) — the Claude Code extension's URI handler should check if a session tab already exists before opening a new one. This is outside CodeV's control. Consider opening an upstream issue with Anthropic.

🤖 On behalf of @grimmerk — generated with Claude Code