cli: session export truncates JSON when stdout is a pipe #57266

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1. opencode-agent commented on Oct 20, 2026

   

   opencode-agentBot

   on Oct 20, 2026 – with OpenCode Agent

   Contributor

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   Thanks for the detailed report! I reproduced this on 2.0.32 (on Linux, so it isn't specific to macOS), and it still happens on the latest dev (16c338372).

   What I did: I imported a session of about 1.2 MB, then exported it three ways.

   • Redirected to a file: 1,206,978 bytes, valid JSON.
   • Piped through cat: 589,824 or 720,896 bytes depending on the run, invalid JSON.
   • Piped to a reader that waits a second before reading: 65,536 bytes every time.

   Every run exited 0, and the truncated sizes are multiples of 4096. The script below reproduces it.

   The likely cause: the export handler writes its JSON to stdout without waiting for the write to finish, and the CLI then exits, which drops whatever is still queued for the pipe. #52925 is the same problem in opencode api get; its open fix (#52955) doesn't cover session export.

   Until this is fixed, redirecting to a file (as you're doing) gives the full export.

   Reproduction script (repro.sh)

   #!/usr/bin/env bash
   # Repro for #57266: `opencode session export` truncates JSON when stdout is a pipe.
   # Usage: ./repro.sh                 (uses `opencode` from PATH)
   #        OC="bun --conditions=browser --preload=.../preload.js .../packages/cli/src/index.ts" ./repro.sh
   set -u
   OC=${OC:-opencode}
   # Server flag: a private server by default, or set SERVER=http://... (+ OPENCODE_SERVER_PASSWORD) to use a running one.
   SRV=${SERVER:+--server $SERVER}; SRV=${SRV:---standalone}
   W=$(mktemp -d /tmp/opencode/repro57266.XXXX)
   export XDG_DATA_HOME=$W/data XDG_CONFIG_HOME=$W/cfg XDG_STATE_HOME=$W/state XDG_CACHE_HOME=$W/cache
   mkdir -p "$W/proj" && cd "$W/proj"
   $OC --version
   
   # Build a ~1.2 MB session transfer file (40 user messages with 30 KB text each) and import it.
   python3 - "$W/big.json" <<'EOF'
   import json, sys, time
   now = int(time.time() * 1000)
   msgs = [{"id": f"msg_{i:026d}", "type": "user", "time": {"created": now + i}, "text": f"msg {i} " + "x" * 30000} for i in range(40)]
   data = {"info": {"id": "ses_repro57266aaaaaaaaaaaaaaa", "projectID": "global", "cost": 0,
                    "tokens": {"input": 0, "output": 0, "reasoning": 0, "cache": {"read": 0, "write": 0}},
                    "time": {"created": now, "updated": now}, "location": {"directory": sys.argv[1].rsplit('/',1)[0] + "/proj"}},
           "messages": msgs}
   json.dump(data, open(sys.argv[1], "w"))
   EOF
   $OC session import $SRV "$W/big.json" || exit 1
   SID=ses_repro57266aaaaaaaaaaaaaaa
   
   $OC session export $SRV $SID > "$W/file.json"; rc=$?; echo "file:  $(wc -c < "$W/file.json") bytes, exit $rc"
   $OC session export $SRV $SID | cat > "$W/pipe.json"; echo "pipe:  $(wc -c < "$W/pipe.json") bytes, exit ${PIPESTATUS[0]}"
   $OC session export $SRV $SID | (sleep 1; cat) > "$W/slow.json"; echo "slow pipe: $(wc -c < "$W/slow.json") bytes, exit ${PIPESTATUS[0]}"
   for f in file pipe slow; do
     python3 -c "import json,sys; json.load(open(sys.argv[1])); print('$f: valid JSON')" "$W/$f.json" 2>/dev/null || echo "$f: INVALID JSON"
   done

   Run it: bash repro.sh
2. opencode-agent

   added

   reproduced

   on Oct 20, 2026
3. Alek2077 commented on Nov 3, 2026

   

   Alek2077

   on Nov 3, 2026

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   Still reproducible on OpenCode 2.2.5 (Linux x86_64, WSL2).

   • opencode session export <id> > full.json → 2,972,714 bytes, valid JSON, exit 0.
   • opencode session export <id> | wc -c → 262,144 bytes, exit 0; jq fails with Unterminated string.
   • A 547,143-byte export also truncates to 262,144 bytes when piped.

   Redirecting to a file is the workaround. This matches the flush-before-exit diagnosis; #57347 looks like the right fix.