[BUG] Stream iteration hangs on abort; cleanup failure leaves zombie sessions

[ESRE-dev]

Description

SessionProcessor.process() can deadlock or leave sessions in a permanently running state in two cases:

1. The stream loop uses for await (const value of stream.fullStream). If abort fires while iter.next() is waiting on a stuck tool result, iteration can block indefinitely.
2. Cleanup-time Snapshot.patch() is outside the main error boundary. If it throws, message finalization can be skipped, leaving sessions/tool parts stuck as running.

A related symptom is doom-loop permission prompts blocking cancellation when they are awaited without racing abort.

Plugins

None

OpenCode version

1.3.3 (also observed on dev as of 2026-03-30)

Steps to reproduce

1. Start a session that triggers a long-running or hanging tool call.
2. Cancel while the model stream is waiting for tool output.
3. Observe session remains in cancelling/running state.
4. Separately, force Snapshot.patch() failure during cleanup (for example by invalidating git state) and observe finalization is skipped.

Screenshot and/or share link

N/A

Operating System

macOS 15.4.1 (repro also seen on Linux CI)

Terminal

Ghostty

[github-actions]

This issue might be a duplicate of existing issues. Please check:

• [BUG] Session cancel races cause lost cancels, stale aborts, and dangling waits #20095: Overlapping concern — dangling PermissionNext.ask() / Question.ask() prompts blocking cancellation is also reported there ("Dangling permission/question prompts after cancel" section)
• Tool and task execution can hang indefinitely with no timeout #20096: Overlapping concern — tool execution hanging indefinitely is also covered there ("Tool execution has no timeout protection")

If these are intentionally split reports, it may help to cross-reference them to assist maintainers in triaging.

[ESRE-dev]

Cross-reference for triage: this issue is narrowly scoped to processor stream-loop abort behavior and cleanup-finalization safety. Related but distinct: #20095 (cancel lifecycle + dangling waits), #15080 (task timeout feature), #20099 (runtime watchdog).

[ESRE-dev]

Closing: Resolved by upstream Effect/Stream migration

The stream iteration hang on abort described in this issue is resolved by the upstream migration from raw for await to Effect/Stream.

Upstream commit

860531c275 — refactor(session): effectify session processor (#19485) (Mar 28)

This commit replaces the raw for await loop over the LLM stream with Effect/Stream (Stream.tap → Stream.runDrain). Stream interruption is now native via Fiber.interrupt — when Runner.cancel interrupts the processing fiber, the stream drain is interrupted immediately without waiting for iter.next() to resolve. The cleanup() function handles all dangling state (currentText, reasoningMap, pending tool parts), preventing zombie sessions.

The Runner module introduced in c5442d418d — refactor(session): effectify SessionPrompt service (#19483) (Mar 30) — further solidifies this by providing a clean cancel → Fiber.interrupt pipeline.

See also: #20095 (parent issue, also closed)