[rmahato-code]

JIRA MARSOHS-2171

Summary

• Default doctl harness-runtime exec text output now consumes harness-api SSE (Accept: text/event-stream) so stdout/stderr appear as the guest produces them.
• -o json keeps the existing buffered ExecInSandbox document for scripts.
• Against an older API that does not speak SSE, text mode falls back to the buffered JSON body automatically (same flags / exit codes).

Depends on / pairs with the harness-api work:

• https://github.internal.digitalocean.com/digitalocean/cthulhu/pull/180644 (SSE streaming exec MARSOHS-2167)
• https://github.internal.digitalocean.com/digitalocean/cthulhu/pull/180650 (exec timeout MARSOHS-2168)

Testing

Unit tests

go test ./do/ -count=1 -run 'StreamExec|ReadExec|EmitBuffered'
go test ./commands/ -count=1 -run 'AgentsExec'

Live testing done against local harness (dev/up on :8080)

# Create a session
CREATE_RESP="$(curl -sS -X POST \
  -H 'Authorization: Bearer do_dev_demo@acme.com' \
  -H 'Content-Type: application/x-yaml' \
  --data-binary $'name: doctl-exec-smoke\nagent: codex\ntemplate: coding\n' \
  http://127.0.0.1:8080/v2/agents/sessions)"
SID="$(python3 -c 'import json,sys; print(json.load(sys.stdin)["session"]["session_id"])' <<<"$CREATE_RESP")"

# Wait until READY, then until a trivial exec returns 200
# (guest sandbox-agent must be accepting dials)

DOCTL=(./builds/doctl -u http://127.0.0.1:8080 -t 'do_dev_demo@acme.com' --http-retry-max 0)

# Streaming: expect "one", ~2s pause, then "two"
"${DOCTL[@]}" harness-runtime exec "$SID" -- sh -c 'echo one; sleep 2; echo two'

# Buffered JSON path unchanged
"${DOCTL[@]}" harness-runtime exec "$SID" -o json -- echo hi

# Guest exit code propagation
"${DOCTL[@]}" harness-runtime exec "$SID" -- sh -c 'echo failed; exit 7'; echo "exit=$?"

# Timeout (needs EX15 guest templates for clean 504 near budget;
# without rebuild may still surface ~timeout+30s / 500 on older agents)
"${DOCTL[@]}" harness-runtime exec "$SID" --timeout 3 -- sleep 120; echo "exit=$?"

# Cleanup
curl -sS -X DELETE -H 'Authorization: Bearer do_dev_demo@acme.com' \
  "http://127.0.0.1:8080/v2/agents/sessions/$SID"

Verified locally: unit tests green; streaming showed one then two two seconds apart; -o json returned a buffered document; guest exit 7 propagated. Timeout against the current local guest image still hit the pre-EX15 +30s backstop until templates are rebuilt with SANDBOX_BUILD_TEMPLATES=1 ./dev/up.