[Bug] Browser Use (Playwright MCP) rejects every new agent creation once one agent holds the browser — “New Session” silently does nothing (0.1.6-alpha.2)

[SereneSoulful]

Version: dsh 0.1.6-alpha.2 — Windows 11 (10.0.26100), Node v24.19.0, Web (web) profile
Packages: @deepseek-ai/dsh-browser-use 0.1.6-alpha.1 + @deepseek-ai/dsh-experimental-browser-use-playwright-mcp 0.1.6-alpha.1 (bundled @playwright/mcp 0.0.80)

Summary

With the browser-use provider mounted, only the first live agent can be created. Every later agent creation is rejected, so new Sessions are written to disk but never registered, and the Web UI's "New Session" appears to do nothing — no error is shown to the user. Both provider modes fail, with different errors.

Symptoms

• Clicking "New Session" has no visible effect.
• A session directory is created (~/.dsh/sessions/.../session.v3.jsonl.zstd, header only, ~340 bytes), but the session never appears in ~/.dsh/storages/workspace.json, so the client list never shows it.
• Reproduces deterministically by spawning any new agent (a subagent uses the same agent/created path): the call fails with the raw error below and the agent is never created.

Repro A — mode: launch

1. Mount @deepseek-ai/dsh-browser-use + @deepseek-ai/dsh-experimental-browser-use-playwright-mcp with { mode: launch, headless: true, executablePath: '<Chrome>' }.
2. Start DSH and open one Session (its agent acquires the browser tools).
3. Create a second Session (or spawn any new agent).
4. Result:

   mcp-client(playwright-mcp): initial connection or tool synchronization failed
   

Repro B — mode: attach

1. Start an external Chrome with CDP (--remote-debugging-port=9222 --remote-allow-origins=*, dedicated profile).
2. Mount the provider with { mode: attach, endpoint: 'http://127.0.0.1:9222' }.
3. The first agent attaches fine (the exact --cdp-endpoint command navigates successfully when run standalone).
4. Create a second agent. Result:

   tools.restrict() requires a scoped context (agent.ctx): a context-global restriction would mask
   every agent — deny the tool for the intended agent instead
   

Where it fails

A) launch mode — @deepseek-ai/dsh-mcp-client/lib/index.js

• apply() (~line 832) rethrows whenever failOnStartupError is set, wrapping the connection error.
• syncTools() (~lines 152-158) calls ctx.tools.register(definition) and rethrows on registrationFailure: "throw"; the comment at ~lines 112-117 states a conflict there "can only mean a foreign registration squats on this server's mcp__<serverName>__ namespace".
• The browser-use runtime mounts one MCP client per agent with the same serverName (playwright-mcp) — dsh-experimental-browser-use-runtime/lib/types/mcp.js, mountSessionMcp() → resources.open() → scope.ctx.plugin(McpClient, ...) — so the second agent collides with the first agent's tool registrations.

B) attach mode — same file, refreshBlockedMasks() (~lines 53-71)

• For an agent whose state is blocked it calls state.mask.ctx.tools.restrict({ deny: inherited }) on a scope created by createScope(ctx, agent); the tools service rejects that context, and the throw propagates out of agent/created.

Ruled out (with evidence)

• MCP server/transport: running the exact spawned command standalone (node <profile>/node_modules/@playwright/mcp/cli.js --browser chromium --isolated --headless --executable-path <Chrome>) connects in ~263 ms and tools/list returns 24 tools; the attach variant (--cdp-endpoint http://127.0.0.1:9222) navigates successfully.
• JSON-schema validation: assertSupportedJsonSchema rejects 24/24 Playwright tool schemas, but it also rejects 22/57 schemas of the working Cua Driver provider, and it only guards output schemas inside a try/catch (supportedOutputSchema), so it is not the failing path.
• Browser/environment: Chrome 153 launches headless and works with Playwright independently; disabling only the two browser-use rows restores agent creation immediately.

Impact

Browser use cannot coexist with more than one Session/agent per DSH instance. Because the failure rejects agent/created, it also breaks subagent spawning, and the Web UI surfaces no error at all.

Workaround

Keep the provider disabled (disabled: true on the two browser-use rows in cordis.patch.yml). Computer Use (@deepseek-ai/dsh-experimental-computer-use-cua-driver-mcp) is unaffected.

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中文摘要：装上 Browser Use（Playwright MCP 后端）后，同一 DSH 实例里只有第一个代理能建起来，之后每次新建会话或派生代理都会被拒——会话记录写盘了但不进 workspace.json，前端表现就是"点新建会话没反应"且没有任何报错。mode: launch 与 mode: attach 都能稳定复现，两处报错分别指向 dsh-mcp-client 的注册命名空间冲突与 dsh-experimental-browser-use-runtime 的 refreshBlockedMasks()。