deepseek-harness/docs/user/guide/python-sdk.md

# Get started with the Python SDK

English | [中文](python-sdk.zh.md)

This tutorial installs the Python SDK, runs a checked-in Cordis composition without the Web UI, and uses the same API in your own program. It uses the compact [`minimal.cordis.yml`](../../../examples/jsonrpc-agent/minimal.cordis.yml) configuration as a complete example with a configurable system prompt, a two-tool catalog, persistent-shell behavior, and context compaction disabled.

## Prerequisites

- Python 3.10 or newer
- Linux x64, Linux arm64, or macOS arm64
- A DeepSeek-compatible API endpoint and credential
- An isolated workspace that the agent may modify

## Install the SDK

Choose either the public package or a source build. Both install the `deepseek-harness-sdk` distribution and expose the `deepseek_harness` Python module.

### Install from PyPI

Create a virtual environment and install the SDK with its same-version bundled runtime:

```sh
python -m venv .venv
. .venv/bin/activate
python -m pip install deepseek-harness-sdk
```

### Build from source

A source build additionally requires Git, Node.js ^22.19 or >= 24, Corepack-enabled pnpm 11, and `uv`. The following commands build the runtime for the current supported host platform, build both wheels, and install them into the active virtual environment:

```sh
git clone https://github.com/deepseek-ai/deepseek-harness.git deepseek-harness
cd deepseek-harness
python -m pip install uv==0.11.23
corepack enable
pnpm install

case "$(uname -s):$(uname -m)" in
  Linux:x86_64) runtime_platform=linux-x64 ;;
  Linux:aarch64|Linux:arm64) runtime_platform=linux-arm64 ;;
  Darwin:arm64) runtime_platform=macos-arm64 ;;
  *) echo "unsupported platform" >&2; exit 1 ;;
esac

pnpm exec tsx scripts/build-exe-for-python-sdk.ts --targets="node24-$runtime_platform"
version="$(node -p "require('./package.json').version")"
python scripts/build-python-release.py --package sdk --output-dir dist-python
python scripts/build-python-release.py \
  --package runtime \
  --platform "$runtime_platform" \
  --runtime-exe "dist-exe/dsh-jsonrpc-agent-pkg-$runtime_platform" \
  --output-dir dist-python
python -m pip install --find-links dist-python "deepseek-harness-sdk==$version"
```

The runtime wheel contains the JSON-RPC executable and every plugin used by the complete [`minimal.cordis.yml`](../../../examples/jsonrpc-agent/minimal.cordis.yml), so neither installation path needs Node.js after installation.

## Run the checked-in example

Set the credential in the environment. Set `DEEPSEEK_BASE_URL` as well when the model is served by an OpenAI-compatible proxy rather than the default DeepSeek endpoint.

```sh
export DEEPSEEK_API_KEY=sk-your-key-here
# export DEEPSEEK_BASE_URL=http://127.0.0.1:8000/v1
# export DSH_MODEL=deepseek-v4-flash
# export DSH_SYSTEM_PROMPT='You are a helpful software engineer assistant.'
```

Run one task from the repository checkout:

```sh
python examples/jsonrpc-agent/minimal.py \
  --workspace /absolute/path/to/workspace \
  --session-root /absolute/path/to/sessions \
  --session-id example-001 \
  "Inspect the repository and fix the failing tests."
```

The script prints the final assistant response. The session root receives a JSONL session log containing the assembled model request and every tool call.

## Use the SDK in your own program

The example is a thin wrapper around this SDK call:

```python
from pathlib import Path

from deepseek_harness import DeepSeekHarness

config = Path("examples/jsonrpc-agent/minimal.cordis.yml").resolve()
workspace = Path("/absolute/path/to/workspace").resolve()
sessions = Path("/absolute/path/to/sessions").resolve()

with DeepSeekHarness(
    provider="deepseek-official",
    model="deepseek-v4-flash",
    max_tokens=49_152,
    cwd=str(workspace),
    session_root=str(sessions),
    cordis=str(config),
) as harness:
    result = harness.run(
        "Inspect the repository and fix the failing tests.",
        session_id="example-001",
    )

print(result.final_response)
```

`DeepSeekHarness` starts the bundled JSON-RPC runtime lazily and reuses it until the context manager exits. Reusing the same harness and session id across calls also preserves the session-owned Bash process, including its working directory, exported variables, and shell functions.

## Understand the example configuration

| Property | Value |
|---|---|
| System prompt | `DSH_SYSTEM_PROMPT`, falling back to `You are a helpful software engineer assistant.` |
| Model in `minimal.py` | `--model`, then `DSH_MODEL`, then `deepseek-v4-flash` |
| Model-facing tools | Persistent `bash` and `str_replace_editor` only |
| Bash timeout | 300 seconds |
| Editor output limit | 16,000 characters |
| Context compaction | Disabled |
| Filesystem | Bare local backend; absolute editor paths may address any path visible to the runtime process |
| Session persistence | Uncompressed JSONL under `DSH_SESSION_ROOT` |

The configuration omits harness identity, workspace prompt text, skills, one-shot Bash, task tools, compaction, and every other model-facing plugin. Sandbox-policy facts are logged as runtime user context rather than appended to the system prompt. The editor requires absolute paths as an unconditional current contract, so the obsolete `requireAbsolutePath` option is absent.

## Choose workspace and session IDs

`cwd` selects the workspace available to the agent, while `session_root` stores session logs and state. Use a fresh session id for an independent task; reuse an id only when the next call should continue the same conversation and persistent shell state.

The composition uses `danger-full-access`. Run it only inside a disposable checkout or container: Bash and the editor can modify any path allowed to the runtime process. The persistent PTY backend requires a POSIX terminal substrate, so this composition does not support Windows agents.

For the complete SDK lifecycle and result contract, see the [Python SDK reference](../../../python/sdk/README.md). For Cordis composition syntax, see [Configuration](./config.md).