Foreword

DeepSeek Harness (DSH) sessions are isolated by default, and subtasks usually exit after completion. Directives, context, or task coordination may be needed across long-running sessions, which can hinder this isolation. The dsh-call-session plugin adds in-process cross-session communication and a shared workspace blackboard to DSH, enabling multi-session collaboration.

Plugin Positioning

  • Name: dsh-call-session
  • Role: Workflow plugin
  • Maintainer: popu2do
  • Core Value: Enables point-to-point communication (unicast) and shared state storage (blackboard) among sessions within the same DSH process, with visual observation of session topology.
  • License: MIT

Core Capabilities

The plugin mainly provides the following capabilities:

  1. Unicast communication between sessions: Send directives or hand off tasks to a specified session via the session_call tool.
  2. Shared blackboard: Publish data via board_post, retrieve data via board_list, and clear data via board_clear, avoiding context window bloat.
  3. Visualization canvas: In the Canvas tab of the DSH Web UI, displays session status, blackboard entries, and invocation traces as a topology graph.
  4. Session creation: Creates a new peer session in the current workspace via the session_create tool.

Installation and Enablement

The plugin runs with built-in configuration by default and can be enabled without complex setup. The command to add it to the target profile is as follows:

dsh plugin --profile web add dsh-call-session

After installation, you can use dsh plugin --profile web list to view installed plugins, or use the remove command to uninstall.

Typical Usage

The plugin implements its features via tool calls. The following are three typical scenarios:

Scenario 1: Task Handoff

A user issues an instruction in the current session, requesting that a task summary be passed to a session named “audit-session”.
* Action: The agent calls session_call.
* Result: If the target session is running, execution is routed; if it is idle, the session is awakened.

Scenario 2: Publishing Results

A user requests that review conclusions be published to the blackboard and that relevant sessions be notified to retrieve them.
* Action: The agent calls board_post to store the detailed report and obtains postId.
* Result: Other sessions can retrieve content on demand via board_list, avoiding stuffing large amounts of historical data into the current conversation context.

Scenario 3: Creating a Session

A user needs to create a new long-running session to handle a specific role.
* Action: The agent calls session_create.
* Result: A new peer session is generated in the current workspace, automatically inheriting the model specifications and presets.

Configuration

The plugin works out of the box, but can also be fine-tuned through a configuration file.

Configuration file location: ~/.dsh/profiles/web/cordis.patch.yml

- id: dsh-call-session
  config:
    debounceMs: 500
    maxCapacity: 500

Main configuration items include:
* debounceMs: Debounce delay for atomic disk writes, default 300.
* maxCapacity: Maximum number of blackboard entries, default 200.
* telemetryCapacity: Maximum number of invocation traces retained in the canvas data buffer, default 200.
* locale: Interaction language preference, supports 'auto', 'zh', 'en', default 'auto'.

Applicable Scenarios and Notes

  • Applicable scenarios: Suitable when multiple independent top-level sessions need direct coordination, directive transfer, or state synchronization; or when sharing large output results (such as reports or codebase state) without increasing context window burden.
  • Comparison with built-in tools: For isolated, one-off tasks (such as code search or script execution), it is recommended to prioritize DSH’s built-in subagent; use this plugin only when long-term multi-session collaboration is required.
  • Notes:
    • The Canvas in the Web UI is observation-only and does not provide control input; all state changes are triggered by agents.
    • The plugin runs with the permissions of the current DSH process. It is recommended to inspect the source code and license before installation.

Ecosystem Context

The design philosophy of DeepSeek Harness is “Everything is a plugin”. Community catalogs (such as SkillHub) provide a plugin index. However, note that this catalog has no affiliation with DeepSeek or High-Flyer’s official body. Plugin developers must independently maintain code quality and security.

  • GitHub repository: https://github.com/popu2do/dsh-call-session
  • Community catalog: https://www.skillhub.cn/plugins/popu2do/dsh-call-session