Session becomes unusable after UnknownError: Failed to parse

At irregular intervals, I encounter the error shown below. When this happens:

opencode still runs, but the affected session becomes unusable.
Any further prompts sent to this session just repeat the same error.
Attempting to reopen the session after starting a new one also fails.

Error Log

failed to send message: POST
"http://127.0.0.1:55413/session/ses_73XXXX2aXffeDTHiXXTUpWNVvX/message": 400 Bad Request
{"name":"UnknownError","data":{"message":"SyntaxError: Failed to parse JSON"}}

Environment

Using: GitHub Copilot with Claude Sonnet 4
opencode version: v0.5.7
OS: Windows with git Bash

Steps to Reproduce

The issue appears sporadically and I haven’t found a deterministic reproduction path, but:

Start a session.
Interact with opencode for some time.
At some point, the session fails with the above error.

Expected Behavior

The session should continue working without requiring a restart.

Actual Behavior

The session becomes permanently stuck, repeating the error until a new session is created. Old sessions cannot be reopened.

Additional Context

The error only occurs intermittently, but once triggered, it breaks the session workflow entirely.

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

TUI failed to send message #1743: TUI failed to send message with similar HTTP 400 Bad Request error pattern and session communication failures
When opencode enters an interactive session, it will be in working... mode indefinitely #1561: Session becomes unusable and gets stuck indefinitely, requiring restart (same core symptom of session becoming permanently unusable)
JSON Parse error: Expected '}' with the write tool after updating to v0.5.5 Description #2002: JSON Parse error with the write tool - reports similar "JSON parsing failed" errors that could be related to the "Failed to parse JSON" error you're experiencing
Multiple message request to the same session get the same response #1895: Multiple message requests to same session causing response issues - demonstrates session-level message handling problems that could be related

Feel free to ignore if none of these address your specific case.

Is there anything special with this session? is it super long or anything

It's not consistent.
Sometimes it only takes one or two prompts, and sometimes it took 10+.

Deleting the cache have some effect on it. But nothing consistent to report.

@maddeye

Are you still encountering this on latest @maddeye

Cannot test ot right now. I will chrck on monday.

The problem seems to be fixed. Thanks a lot!

awesome!

Curious if there is a way to fix this to resume the session? It is happening to us today multiple times leaving a corrupted session that can't continue.

@vanboom

@vanboom whats the error, provider, etc? Can you share the session

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Session becomes unusable after UnknownError: Failed to parse #2135

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Session becomes unusable after UnknownError: Failed to parse #2135

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github-actions commented on Aug 21, 2025

rekram1-node commented on Aug 21, 2025

maddeye commented on Aug 26, 2025

rekram1-node commented on Sep 24, 2025

maddeye commented on Sep 24, 2025

maddeye commented on Sep 29, 2025

rekram1-node commented on Sep 29, 2025

vanboom commented on Dec 4, 2025

rekram1-node commented on Dec 4, 2025

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