Agent Sessions & Tool Trajectories
Session-level data built for agent training. We capture full action sequences, tool calls, and environment-state changes from real dev sessions — including failure, backtracking, and recovery, which is where long-horizon capability comes from.
Coverage
- Real dev sessions
- Tool calls
- Environment state
- Failure recovery
- Long-horizon execution
Deliverables
- Session logs
- Action sequences
- State snapshots
- Result verification
- Failure causes & trajectory summaries
From source to acceptance
We don't hand-label a pile and ship it. Every category moves through a closed, instrumented loop — generated to a brief, checked by machines, adjudicated by experts, and traceable end to end — but the path each data type takes is its own.
- 01
End-to-End Capture
Complete sessions are recorded across real and simulated environments, preserving every tool call, observation, and intermediate decision from first prompt to final outcome.
- 02
State Alignment
Each action is pinned to the environment state it acted on, so the whole trajectory stays faithfully replayable and every step can be re-grounded in its exact context.
- 03
Scripted Verification
A deterministic check settles the outcome of each consequential action, turning a loose transcript into a sequence of verified results with unambiguous success and failure signals.
- 04
Failure & Recovery Labeling
Dead ends, backtracks, and recoveries are labeled explicitly, capturing the corrective behaviour that is precisely where durable long-horizon capability is learned.
- 05
Trajectory Summarization
Each session is distilled into a structured summary of goal, plan, key branches, and recovery paths, making long multi-hundred-turn traces legible and reusable.
- 06
Consistency Review
A review pass reconciles the summary against the verified steps, ensuring the recorded narrative matches what actually happened in the environment.
- 07
Stratified Sampling
A final stratified draw across task types, horizons, and failure modes fixes the distribution and guards quality before the trajectories ship.
Every run emits a learning signal that feeds back into the source set — the pipeline tightens itself, batch over batch.
See the data itself
One real, trimmed sample from this category — the scenarios it serves, why it matters for training, and the shape of the data as delivered.
Where it’s used
- Training long-horizon tool-use and planning behaviour
- Teaching failure recovery and backtracking from real traces
- Distilling frontier coding-agent behaviour into smaller models
Why it matters for training
Critical
Long-horizon tool use is the current frontier, and real multi-hundred-turn recovery traces are the hardest data to collect at quality.
Notable features
The sandbox directory is empty. Write a local command-line todo tool in Python: a package todo/ (store.py for the data model + in-memory store, cli.py using argparse), supporting the three subcommands add / list / done, with pytest tests and a Makefile. First list a plan with TodoWrite, then implement it, and run make test to confirm everything passes.
- Assistant
List the plan first, then start.
TodoWrite{ "todos": [ { "content": "Create the todo/ package and data model", "status": "in_progress" }, { "content": "Implement the add/list/done subcommands", "status": "pending" }, { "content": "Write pytest tests and the Makefile", "status": "pending" } ] } - Result
Todos have been modified successfully. Continue with the plan.
- Assistant
First check the current state of the working directory.
Bash{ "command": "pwd && ls -la" } - Result
/workspace total 0 drwxr-xr-x 2 lx staff 64 Jun 3 12:04 . drwxr-xr-x 18 lx staff 576 Jun 3 12:04 ..
- Assistant
The directory is empty; start writing the in-memory storage layer.
Write{ "file_path": "todo/store.py", "content": "from dataclasses import dataclass\n\n@dataclass\nclass Task:\n id: int\n text: str\n done: bool = False\n..." } - Result
- Assistant
Run acceptance once the implementation and tests are written.
Bash{ "command": "make test" } - Result
===== test session starts ===== collected 6 items tests/test_todo.py ...... [100%] ===== 6 passed in 0.04s ===== DONE: 6 tests passing
Need a sample or a custom build?
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