data-harness 0.6.0

Data agent with Python-native tools (no bash)

data-harness

A Python SDK for controlled data-agent workflows.

No bash. Handle-based state. Logs that reconstruct what happened.

Documentation · PyPI · Changelog

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Most agent frameworks hand the model a shell and call it a day. data-harness takes a different approach: the model executes Python only, large data objects live in a session cache and are exposed as named handles, and every turn is logged to JSONL. The result is a data agent that is auditable, reproducible, and safe enough to run in production.

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Install

pip install data-harness          # core
pip install "data-harness[all]"   # + openai, charts, duckdb, sqlalchemy, notebook

Pick individual extras as needed: [openai], [viz], [duckdb], [sql], [notebook]. Requires Python 3.10+.

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Quickstart

Ask a question about a DataFrame in one line. ask() resolves a provider from your environment (ANTHROPIC_API_KEY or OPENAI_API_KEY), loads the data into the session cache, runs the agent, and returns a RunResult:

import pandas as pd
from data_harness import ask

df = pd.read_csv("sales.csv")
result = ask(df, "What was total revenue, and which month was highest?")

print(result.text)      # the written answer
print(result.value)     # the structured result the model computed via answer()
result.charts           # any charts it rendered (notebook-friendly)

Pick a model explicitly (routes to the matching provider):

ask(df, "plot revenue by month", model="gpt-4o-mini")

Or reach many providers through one key with OpenRouter — a provider/model id auto-routes there (great for cross-model testing). Set OPENROUTER_API_KEY:

ask(df, "summarise the data", model="anthropic/claude-3.5-sonnet")  # via OpenRouter
ask(df, "summarise the data", model="google/gemini-2.0-flash-001")
ask(df, "summarise the data", model="deepseek/deepseek-chat")       # cheap

DeepSeek's own (very cheap) API is also supported directly — set DEEPSEEK_API_KEY and use a bare model="deepseek-chat".

In a notebook, the returned RunResult renders prose, the computed value, and charts inline. There's also a %%ask magic (%load_ext data_harness.notebook).

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Multi-turn chat

from data_harness import Chat

chat = Chat(df)
chat.ask("What was total revenue?")
chat.ask("Which month was highest?")   # remembers context

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Charts

matplotlib is available inside the interpreter. The model builds a figure and it is captured automatically as an artefact — the image bytes live on disk and never enter the message history or logs (only a path does):

result = ask(df, "Plot revenue by region as a bar chart.")
result.charts[0]        # a ChartArtifact; renders inline in Jupyter

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SQL over your data

With DuckDB installed, ask exposes a sql_query tool that runs SQL directly against your DataFrames (results become new handles). Point it at a real database with a SQLAlchemy URL:

ask(df, "Use SQL to get total revenue per region.")          # DuckDB, in-process

from data_harness import Agent
agent = Agent.from_dataframe(df).enable_sql(engine_url="postgresql://...")
agent.run("Top 5 customers by spend last quarter?")

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Production controls

from data_harness import Agent, ExecutionCache

agent = (
    Agent.from_dataframe(df, model="gpt-4o-mini")
    .enable_cache(ExecutionCache("cache.json"))   # replay repeat questions, 0 tokens
)

# Run interpreter code in an isolated process (no network, CPU/time limits):
sandboxed = Agent.from_dataframe(df, execution="subprocess")

# Approve or block code before it runs ("show me the code"):
def approve(code: str) -> bool:
    print(code)
    return True

gated = Agent.from_dataframe(df, on_code=approve)
preview = Agent.from_dataframe(df, code_only=True)   # dry-run: never executes

• Code-replay cache — a repeat question over the same data schema replays the recorded code with no model call (zero turns, zero tokens), while staying correct when the data changes.
• Subprocess sandbox — interpreter code runs in a separate process with networking disabled and CPU/wall-clock limits; handles cross by value, results merge back.
• Approval gate — on_code sees every code block before execution and can block it; code_only=True returns the code without running it.

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Evaluation

Measure how well an agent answers real data questions — across models, with programmatic grading that leans on the structured .value:

from data_harness.eval import bespoke_suite, evaluate_matrix

report = evaluate_matrix(
    bespoke_suite(),
    ["openai/gpt-4o-mini", "anthropic/claude-haiku-4.5", "deepseek/deepseek-chat"],
)
print(report.leaderboard())   # accuracy / tokens / turns per model

Built-in graders (numeric, contains, dataframe_equals, chart_produced, refuses, …), a bespoke_suite(), and a public-benchmark loader (load_wikitablequestions, via the [eval] extra). See the Evaluation guide.

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Lower-level Agent and Harness

ask/Chat are conveniences over Agent, which is itself a thin layer over Harness. Drop down when you want full control:

from data_harness import Agent
from data_harness.providers.anthropic import AnthropicAdapter

agent = Agent(adapter=AnthropicAdapter(model="claude-sonnet-4-6"), system="You are a data analyst.")
print(agent.run("Compute the mean of [1, 2, 3, 4, 5]."))

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Data connectors

Connectors group related tools and start hidden — the model loads them on demand. This keeps the tool list short and routing decisions sharp.

market_data = agent.connector("market_data", description="Equity price data.")

@market_data.tool(description="Fetch daily OHLCV data for a ticker.")
def fetch_ohlcv(symbol: str) -> list[dict]:
    ...

agent.run("Load market_data and fetch AAPL prices.")

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Async and streaming

from data_harness import AsyncAgent
from data_harness.providers.anthropic import AnthropicAdapter

agent = AsyncAgent(adapter=AnthropicAdapter(model="claude-sonnet-4-6"), system="...")

# Stream tokens as they arrive
async for event in agent.run_stream("Describe the dataset."):
    if event.type == "content_block_delta":
        from data_harness import TextDelta
        if isinstance(event.delta, TextDelta):
            print(event.delta.text, end="", flush=True)

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Why these constraints?

Design decision	Why it matters
Python only, no bash	No shell side-effects, no destructive commands, reproducible runs
Handle/snapshot pattern	Large objects never bloat message history; the model still operates on them via Python
Prefix-stable system prompt	The provider's KV cache stays warm across turns, reducing latency and cost
Progressive connector disclosure	Fewer visible tools → better model routing decisions
Subagent isolation	Spawned subagents get a fresh cache; state crosses boundaries only through explicit handles
JSONL logging from turn one	Every run is reconstructable without raw data leaking into the log

The design is covered in detail in a three-part series and in the Architecture guide.

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What Agent composes

Agent is a thin layer over lower-level primitives you can wire directly for full control:

Component	Role
Harness	The ReAct loop — messages, tool dispatch, reminders, JSONL logging
SessionCache	Handle-based store; keeps large objects out of message history
ProviderAdapter	Translates provider SDK responses into harness types
python_interpreter	The model's only execution surface
ConnectorRegistry	Hides connector tools until the model loads them
Planner	Opt-in nag reminders when progress stalls
Subagent	Isolated worker with explicit state transfer

See examples/advanced_wiring.py for explicit Harness wiring.

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Running the examples

# Minimal Agent example (requires ANTHROPIC_API_KEY)
uv run python examples/quickstart.py

# Full wiring with connectors, planner, and subagents (requires ANTHROPIC_API_KEY)
uv run python examples/advanced_wiring.py

# Live tour of ask()/charts/SQL on a cheap model (ANTHROPIC or OPENAI key)
uv run python examples/live_demo.py

# Code-replay cache benchmark (no API key, deterministic)
uv run python examples/cache_benchmark.py

# Multi-model evaluation leaderboard (requires OPENROUTER_API_KEY)
uv run python examples/eval_demo.py

See examples/demo.ipynb for an executed notebook covering all the v0.5 features.

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Running the tests

uv run python -m pytest tests/ -v
uv run python -m pytest tests/smoke_tests.py -m live -v  # requires OPENROUTER_API_KEY

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Sandbox disclaimer

The Python interpreter uses AST checks and restricted globals to reduce accidental misuse. It is not a container sandbox and should not be treated as safe for untrusted input.

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Changelog

0.6.0

• Evaluation harness (data_harness.eval): define EvalCases with programmatic graders (numeric, contains, exact, dataframe_equals, chart_produced, refuses, all_of/any_of), run with evaluate / evaluate_matrix, and read an EvalReport (accuracy, leaderboard, per-category, failures)
• Grading leans on the structured RunResult.value; the model matrix runs across providers via OpenRouter
• Built-in bespoke_suite() plus a public-benchmark loader load_wikitablequestions() ([eval] extra)

0.5.0

• Entry points: ask(df, "...") one-liner, Chat/SmartFrame, zero-config provider resolution, Agent.from_dataframe / from_csv, and a %%ask notebook magic
• OpenRouter & DeepSeek: OpenRouterAdapter + OpenAIAdapter(base_url=...); provider/model ids (e.g. anthropic/claude-3.5-sonnet) auto-route to OpenRouter, deepseek-* ids to DeepSeek's direct API, with OPENROUTER_API_KEY / DEEPSEEK_API_KEY picked up automatically — one key for many providers
• Charts: matplotlib in the interpreter; open figures captured as ChartArtifact handles (bytes stay out of messages/logs); RunResult.charts + rich Jupyter display
• Structured results: answer(value) interpreter helper → RunResult.value
• SQL: sql_query tool (DuckDB in-process over cached frames, or a SQLAlchemy URL); Agent.enable_sql
• Semantic layer: per-handle column/units descriptions folded into snapshots (cache.put(..., semantics=...), cache.describe)
• Subprocess sandbox: execution="subprocess" runs interpreter code in an isolated process (no network, CPU/time limits)
• Approval gate: on_code callback and code_only dry-run
• Code-replay cache: Agent.enable_cache(...) replays repeat questions with zero model calls
• New optional extras: [viz], [duckdb], [sql], [notebook], [all]

0.4.0

• python_interpreter: runtime errors now raise PythonInterpreterError so the harness marks ToolResultBlock.is_error=True
• python_interpreter: final-expression capture — bare expressions return their repr automatically (notebook-like behaviour)
• python_interpreter: locals() usage detected at AST level and returns a targeted error with list_variables guidance
• python_interpreter: improved empty-output message directs the model to print(...) or save(name, value)
• python_interpreter: strengthened tool description with explicit guidance on handle usage, stdout capture, fresh locals, and save()

0.3.0

• Streaming protocol: SSE event types, stream_events(), AsyncAgent.run_stream()

0.2.0

• Async support: AsyncAgent, AsyncAgentSession, AsyncHarness
• AgentSession for multi-turn conversations
• RunResult with token usage and cache state

0.1.0

• Initial release: Agent, Harness, SessionCache, ProviderAdapter

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License

MIT