opencode run --format json --session writes assistant text to DB but emits empty stdout for an existing session

[maojindao55]

Description

Summary

opencode run --format json --session <sessionID> can complete successfully and persist the assistant response into ~/.local/share/opencode/opencode.db,
but emit no JSON events to stdout.

This only happens for a specific existing session that has prior tool-call / multi-step history. A fresh session and a simple resumed session both stream JSON
correctly.

Environment

• OpenCode version: 1.16.2
• OS: macOS 15.5, arm64
• Model: volcengine-plan/kimi-k2.6
• Command mode: opencode run --format json

Working Case

Fresh session works:

opencode -m volcengine-plan/kimi-k2.6 run --format json "只输出 OK"

stdout includes step_start, text, and step_finish.

Resuming that fresh session also works:

opencode -m volcengine-plan/kimi-k2.6 run --format json \
  --session ses_154ab1ebdfferuLfjWKE1REEOy \
  "只输出 OK111"

stdout includes:

{"type":"text", "...": "...", "part":{"type":"text","text":"OK111"}}

## Failing Case

For an existing session with prior tool calls and multiple assistant steps:

opencode -m volcengine-plan/kimi-k2.6 run --format json \
  --dir /Users/www/dev-task-20260609-1023 \
  --dangerously-skip-permissions \
  --session ses_154eb250dffe9uo50Bn1S51wOu \
  "只输出 OK_BAD"

Actual behavior:

- stdout is empty
- process exits successfully
- OpenCode DB contains the assistant response and step finish

DB evidence:

select id, message_id, json_extract(data,'$.type') as type, json_extract(data,'$.text') as text
from part
where session_id='ses_154eb250dffe9uo50Bn1S51wOu'
order by time_created desc
limit 4;

Result includes:

step-finish
text         OK_BAD
step-start
text         "只输出 OK_BAD"

So the model ran, OpenCode persisted the result, but run --format json did not emit the expected stdout JSON events.

## Expected Behavior

opencode run --format json --session ... should emit the new run's JSON events to stdout, at minimum:

- step_start
- text
- step_finish

This should be consistent with fresh sessions and simple resumed sessions.

## Additional Context

The failing session has prior tool-call history and several assistant steps. Earlier integrations that spawned the same command also saw only step_start or
empty stdout, while the same final assistant text appeared in OpenCode DB.

This looks related to existing opencode run non-interactive / tool-call session issues, but I could not find an exact duplicate where the result is written to
DB while stdout is empty.

### 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 existing issues. Please check:

• opencode run --format json drops text and step-finish events in containerized environments #31435: Similar symptom — opencode run --format json drops text and step-finish events, though that issue attributes it to event ordering in containerized environments
• CLI: JSON stream output truncated when process exits quickly (stdout buffer not flushed) #29866: Similar symptom — JSON stream output truncated/missing events when stdout buffer is not flushed before process exit

If your issue is specifically triggered by sessions with prior tool-call history (rather than container latency or buffering), it may be a distinct root cause — please mention this in your issue if so.