Thanks @nideweilaiya for the substantial effort. I have to decline this one, and I want to be direct about why so you don't put more work into a revision that I'd still turn down.

Direction is off for this project. Reasonix's positioning rests on being the cheap option — cache-first, flash-first, single conversation per task. Spawning three independent reasonix run subprocesses for each /parallel invocation is exactly the multi-shot / parallel-sampling shape we've publicly committed not to take. Even at 85% cache hit on later rounds, that's still 3× the rate-limit and API-call cost per prompt against a workflow a single subagent dispatch already covers. The cache benefit you cite is per-worker over multiple rounds, not 3× per round — the three workers don't share a prompt, so they don't share a cache.

Setting direction aside, the PR has concrete blockers that would have to be resolved before any version of this could land:

1. parallel_server.py:40-43 hard-codes D:/Reasonix/dist/cli/index.js — your local checkout path. Reasonix has no D:/Reasonix; this wouldn't work for any user but you. The glob fallback is fine but the hard-coded constant has to go.

2. src/cli/ui/slash/handlers/parallel.ts:18 points the built-in slash command at a personal third-party repo (nideweilaiya/Collusion). Built-in commands must reference project-owned docs only.

3. Blackboard paths are hard-coded /tmp/parallel_*; Windows has no /tmp. Use os.tmpdir() or equivalent.

4. Workers are launched with --no-config, which would also drop the DEEPSEEK_API_KEY for users who put it in ~/.reasonix/config.json via the setup wizard. Those users' workers would fail to authenticate.

5. Five Chinese-only worker system prompts hard-coded in two places; the rest of the project's system prompts are English (see the recent refactor(prompt): compress codeSystemPrompt (-51%, ~3.1k tokens/request) #1323 compression). This locks the orchestrator to a single language.

6. Bundling a separate PyPI package (parallel-mcp/) inside an npm TypeScript repo splits the dist/install/maintenance story across two language ecosystems. If we did want a parallel MCP server, it would live in its own repo, not here.

7. CI hasn't run on this PR (statusCheckRollup: [], mergeStateStatus: UNSTABLE). 672 new lines, zero tests added.

If you want a parallel-execution feature in the agent ecosystem, publishing parallel-mcp as a standalone PyPI package that any MCP-aware client can wire up — Reasonix included via .mcp.json — is the right shape. That keeps Reasonix's own surface lean and gives users who want the trade-off an opt-in path without us committing the project to it. Happy to discuss other smaller contributions.

Closing.