[Windows Native] Infinite spinner after Claude response — stdout pipe handle inheritance prevents EOF

[johanbrughmans]

Problem

On Windows, Opcode's spinner never stops and Claude's response never appears after sending a prompt. This affects native Windows users (without WSL).

Relation to existing issues:

• Windows Support for Claudia - Community Fix Available 4.2 FINAL #78 documents a community workaround using WSL as a bridge. That approach works, but requires WSL to be installed. This issue addresses the root cause so that Opcode works natively on Windows without WSL.
• Frontend not displaying Claude Code streaming output despite working backend #71 describes the same symptoms (infinite spinner, no output) on macOS due to missing event listeners. The Windows root cause is different and lies deeper in the process I/O layer.

---

Root cause

When Opcode spawns claude.exe, Claude in turn spawns child processes (Node.js workers, etc.) that inherit the stdout pipe write-handle. When Claude itself exits, those grandchild processes still hold the handle open. The stdout reader in spawn_claude_process never receives EOF — so claude-complete is never emitted and the spinner runs indefinitely.

This is a fundamental behavioral difference between Windows and Unix: on Unix, process groups and signals provide clean separation; on Windows, inherited handles persist until every process holding them exits.

---

Proposed solution — Platform-Abstracted Output Adapter

Rather than a platform-specific workaround, we propose a Ports & Adapters pattern (hexagonal architecture) for session output handling. This separates the what (session lifecycle events) from the how (platform I/O mechanics), making the codebase cleanly extensible to other platforms:

SessionOutputAdapter (trait / port)
├── StdoutAdapter      → Unix: full real-time streaming (existing behavior, unchanged)
└── FileWatchAdapter   → Windows: reads stdout until session init, then defers to child.wait()

FileWatchAdapter (Windows) behaviour:

1. Reads stdout only until the system:init message arrives (captures the session ID)
2. Intentionally drops the reader — breaking the deadlock caused by inherited handles
3. Calls child.wait() to block until Claude actually exits
4. Emits SessionEvent::Complete — frontend reloads the full conversation from the JSONL file Claude already writes to ~/.claude/projects/.../session.jsonl

Platform selection is compile-time via #[cfg(windows)] / #[cfg(not(windows))] — zero impact on Unix builds.

Why this approach:

• The Unix path is completely unchanged — no regression risk for macOS/Linux users
• The adapter boundary makes future platform support straightforward to extend
• Claude already writes the authoritative conversation to disk — reading from JSONL on completion is reliable and complete
• Unlike the WSL bridge in Windows Support for Claudia - Community Fix Available 4.2 FINAL #78, this requires no additional tooling or WSL installation

---

Additional fixes found during investigation

Issue	Fix	Status
tauri dev fails: "cannot determine which binary to run"	Add default-run = "opcode" to Cargo.toml	Fixed
thinking content blocks not visible in new entries	displayableMessages filter was missing content.type === "thinking"	Fixed
Spurious loading spinner cycles at session init	loadSessionHistory silenced during mount; completion guard prevents double-firing	Partially mitigated — minor cosmetic flicker may still occur, low-priority

---

Environment

• Windows 11 Pro, Claude Code 2.1.72
• Opcode 0.2.1, built from source

Related: #78, #71, #314