# Get started with the Python SDK

English | [中文](python-sdk.zh.md)

This tutorial installs the published Python SDK, runs the checked-in minimal profile overlay, and shows how to customize the same `dsh` profile from your own program.

## Prerequisites

- Python 3.10 or newer
- Git
- Linux x64, Linux arm64, or macOS 14 or newer on arm64
- A DeepSeek-compatible API endpoint and credential
- An isolated workspace and an isolated Harness home

## Install the SDK

```sh
git clone https://github.com/deepseek-ai/deepseek-harness.git
cd deepseek-harness
python -m venv .venv
. .venv/bin/activate
python -m pip install deepseek-harness-sdk
```

The installation includes a matching native runtime wheel and the `dsh` command. Normal SDK execution needs no system Node.js. Repository contributors who build the artifacts should use the [Python contributor workflow](../../../python/development.md).

## Run the checked-in example

Export the credential and, when needed, a compatible proxy endpoint:

```sh
export DEEPSEEK_API_KEY=sk-your-key-here
# export DEEPSEEK_BASE_URL=http://127.0.0.1:8000/v1
```

Run one task with explicit workspace and home paths:

```sh
python examples/python-sdk-agent/minimal.py \
  --workspace /absolute/path/to/disposable-workspace \
  --dsh-home /absolute/path/to/example-dsh-home \
  --session-id example-001 \
  "Inspect the repository and fix the failing tests."
```

The script prints the final assistant response. The selected home receives the generated `sdk` profile, settings, credentials if you add them, installed plugins, and Zstandard session logs under `sessions/`. The example and SDK never silently read `~/.dsh`.

## Use the SDK in your program

```python
from pathlib import Path

from deepseek_harness import DeepSeekHarness

workspace = Path("/absolute/path/to/disposable-workspace").resolve()
dsh_home = Path("/absolute/path/to/example-dsh-home").resolve()
patch = Path("examples/python-sdk-agent/minimal.patch.yml").resolve()

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

print(result.final_response)
```

The SDK starts the bundled `dsh --profile sdk` process lazily and reuses it until context-manager exit. The profile, its persistent patch, the home patch, and the ordered `patches` tuple form the application configuration. There is no separate Python runtime bin or complete-config option.

## Install or define plugins

Use `dsh plugin` for dependencies and bundle layers that should persist in this home:

```sh
export DSH_HOME=/absolute/path/to/example-dsh-home
dsh --profile sdk --dump-default-config >/dev/null
dsh plugin --profile sdk add file:/absolute/path/to/my-plugin-bundle
```

The first command initializes the shipped SDK profile. The second forwards package management to `pnpm`, then records any installed package that exports a `dsh.bundle` layer. Install `pnpm` only for this management command; launching the installed SDK does not need it. Edit `$DSH_HOME/profiles/sdk/cordis.patch.yml` for persistent row changes, or pass patch files from Python for per-launch changes.

Another `profile` is valid when it includes `@deepseek-ai/dsh-sdk-app` or another JSON-RPC server row. Missing server rows, unresolved plugins, and invalid patches fail during startup instead of falling back to another composition.

## Understand the minimal overlay

| 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 |
| Session persistence | Zstandard JSONL under `<dsh_home>/sessions` |

The overlay removes runtime-context prompt messages and most default tools while retaining the SDK application's protocol and persistence. Persistent Bash and the editor can modify any path visible to the runtime, so use a disposable checkout or container. The PTY implementation makes this example POSIX-only.

Use a fresh home when profiles, plugins, credentials, settings, and sessions must be isolated. Use a fresh session id for independent work; reuse a harness, home, and id only to continue the same durable conversation and session-owned resources.

The [example reference](../../../examples/python-sdk-agent/README.md) owns the checked-in overlay. The [Python SDK reference](../../../python/sdk/README.md) covers lifecycle, results, notifications, and low-level behavior; the [dsh CLI reference](../../../apps/cli/reference/README.md) covers profile layering.