CLI: JSON stream output truncated when process exits quickly (stdout buffer not flushed)

[zoutaojlq]

Description

When using opencode run <task> --format json and redirecting the output to a file or piping it to another command, the final JSON events (typically text or step_finish) are frequently missing. The output often stops after the initial step_start event.

Steps to Reproduce:

1. Run a simple task with JSON output redirected to a file:

   opencode run "Please reply Hello" --format json > output.jsonl
   cat output.jsonl

2. Observe that the file often contains only the {"type":"step_start", ...} line, missing the subsequent {"type":"text", ...} and {"type":"step_finish", ...} events.
3. Compare with piping to jq:

   opencode run "Please reply Hello" --format json | jq .

   While more stable, this also occasionally fails to show the final events if the process exits too quickly.

Expected Behavior:
All JSON Lines events, including the final text response and step_finish marker, should be consistently written to stdout and successfully captured by redirection or pipes.

Actual Behavior:
The stdout buffer appears to not be fully flushed before the opencode process terminates. This is a classic race condition where the process exits before the OS writes the remaining buffered data to the file or pipe.

Environment:

• OS: macOS 15.7.4
• Node.js Version: [Insert your Node version, e.g., v22.x]
• OpenCode Version: [Insert your opencode version, e.g., run opencode --version]

Suggested Fix:
Ensure that the CLI explicitly waits for process.stdout to drain before exiting. In Node.js, this can be achieved by:

process.stdout.write(lastChunk);
process.stdout.on('drain', () => {
    process.exit(0);
});
// Or ensure all streams are properly ended and drained in the shutdown logic.

Workaround for Users:
Currently, the most reliable way to capture full output in scripts is to implement a retry mechanism with content validation:

#!/bin/bash
for i in {1..3}; do
    opencode run "$TASK" --format json | tee output.jsonl > /dev/null
    if grep -q '"type":"text"' output.jsonl; then
        exit 0
    fi
done
echo "Failed to capture complete output after retries."
exit 1

Plugins

No response

OpenCode version

No response

Steps to reproduce

No response

Screenshot and/or share link

No response

Operating System

No response

Terminal

No response

[github-actions]

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

• Regression in v1.14.50: opencode run --format json drops post-tool-call assistant text for github-copilot/claude-* models #27697: Also reports opencode run --format json output being truncated/dropped — in that case post-tool-call assistant text is silently missing, which overlaps with the stdout not being fully captured before process exit described here.

If your issue is distinct (e.g. reproducible even on simple single-turn prompts with no tool calls), please add a note clarifying how it differs from #27697.

[rekram1-node]

think this was fixed