Provider calls are wrapped by a readable Python harness rather than hidden behind a large application shell.
Agent Atlas / Coding agents
alejandro-ao/tau
A Python coding-agent harness whose readable architecture, extension seams, protocol changes, and contributor onboarding make the runtime itself a teaching object.
Coding agent
Full dossier
Reported + sourced
Reviewed July 21, 2026
Intended operator
Developers learning from or extending a compact coding-agent harness.
Primary surfaces
Python CLI / agent harness / extension and protocol seams
Tracked repository
Teaching mechanism
A protocol rewrite preserves yesterday's sessions
Compatibility code and tests keep older serialized message history usable while the wire and extension model changes.
Evidence limitFixture compatibility covers represented histories, not every external client or future migration.
Inspect the source
System Map
Eight inspection boundariesMessages, branch context, and persisted sessions expose what the loop carries forward.
Python extension seams make tool and capability composition visible to contributors.
The teaching surface identifies boundaries but does not by itself prove strong operating-system isolation.
Protocol compatibility and serialized-history tests protect resumable work across rewrites.
The inspected evidence is stronger on extensibility and sessions than on worker hierarchies.
CLI behavior and architecture documentation keep control flow legible.
Small modules, examples, compatibility fixtures, and onboarding documents provide reusable inspection points.
Learn Through This Project
8 lessons
Chapter 1
Before the First Model Request
Chapter 2
The Invisible Prompt
Chapter 3
Tool Calls: Contract, Authorization, Execution
Chapter 4
Loops, Workflows, and Recovery
Chapter 6
Memory Is a Typed Storage Contract
Chapter 8
The Human Control Loop
Chapter 9
Trust Must Make Its Case
Chapter 10
The Future Has Three Branches
Latest Reporting
5 articles
The Hard Part of an Agent Protocol Rewrite Is Yesterday
July 17, 2026 — Tau is replacing its legacy agent protocol with Pi-compatible shapes, but its more consequential promise sits at the JSONL boundary: old sessions are meant to cross without pretending the old runtime still exists. alejandro-ao/tau, earendil-works/pi
API Discovery: Tau's Python Extension SeamJuly 17, 2026 — Tau's public Python extension interface gives a coding agent a place to turn tool completions into a small, inspectable deployment or review ledger. alejandro-ao/tau
Tau's Protocol Rewrite Keeps Yesterday's SessionsJuly 17, 2026 — Tau is choosing Pi-compatible extension and event shapes, but its public migration code makes a more human promise: a user's old session should have a route into the new system. alejandro-ao/tau, earendil-works/pi
Tau Keeps Branch Context For ContributorsJuly 4, 2026 — A July 3 Tau PR from Rian Dolphin turns branch summaries into a contributor-facing safeguard: the next branch should remember why the previous one existed. alejandro-ao/tau
Tau Turns Agent Architecture Into OnboardingJune 29, 2026 — A Tau documentation rewrite moved the coding-agent project from build-log internals toward a public quickstart, reference, package, and license surface. alejandro-ao/tau
Open Questions
- How far can a teaching-oriented harness grow without hiding the boundaries it was built to explain?
Evidence state describes what this Atlas profile can support today. It is not a product score and it is not evidence that uninspected capabilities are absent.