vivac 0.16.0

Provenance tree for work: every node knows which node it was born from
vivac-0.16.0 is not a library.

A tree where every node knows which node it was born from.

So that months later something can still answer “why are we here?”

ci crates.io msrv licence

$ vivac why 4

  Why we are here  ->  t4
  ------------------------------------------------------------------

  g1    Ship the 2.0 API
        the first customer is waiting on it
        (4 open / 1 closed below)
        |
        v
  t2    Replace the cache adapter
        the session bug traces back to it
        (3 open / 1 closed below)
        |
        v
  t4    No test for expiry  [closed]
        no way to reproduce the session bug
        ! the corpus run is what settled it
        = reproduced: sessions expire at 300s, not 3600

        ^^^ you are here

  In parallel, still open (3):
      t3     Rate limiting is undecided
      d5     Retry policy: three tries, then fail loudly
      t6     Migrate the callers

  t2 does not close until these close (1):
      t6     Migrate the callers

What you get · See it · Install · First five minutes · Why one map · Bring a project in

Built for one person's own work

I run eight projects in parallel — open source, work and my own — and five of them are large. Every time I came back to one I had to piece together what had been decided in it, and more than once I watched the agent change something we had already settled, because both of us had forgotten we had. What I had against that was manual: ending each stretch of work by asking the model for a safepoint, so we can pick this up later, or keeping a where_are_we.txt at the root of the project.

vivac is what replaced them, and it is still measured on those projects. That is the whole of its pedigree, and it shows in what got built: every mechanism here came out of a defect that had already cost me days, and every number on this page came off a real tree rather than a benchmark written to make a README look good.

The tree this project keeps of itself, 23 days in: 695 nodes, 315 of them closed, 176 standing decisions, 16 levels deep.

Three of those defects, and what each one turned into:

  • A run marked DONE with its findings still open — and 26 days before anybody noticed. Now vivac done refuses, and says what is missing.
  • A reading list of 109 open fronts across 224 lines, with the one touched yesterday at the bottom. Now open answers what is waiting on you, in that order, and stops at ten.
  • Three claims shipped to crates.io that the binary beside them contradicted. Now a test runs every command this page shows and holds its lists against --help.

What I would not give up now is no single feature. It is looking at the tree of what was decided and why; picking a project back up with whichever model is at hand and having it know what the last one settled; and knowing where the work stands at any moment. In my experience that is worth more than anything else here, and I hope it serves you as well.

Issues are open, and I want to hear where it fails you. Pull requests are not open yet; CONTRIBUTING.md says why.

The problem

When you develop with an agentic AI, work spawns more work. Three hops in, you have lost the thread of what you originally set out to do.

It is not a memory problem: usually everything is written down. It is a provenance problem. What is written does not say what it was born from, and without that edge there is no way to reconstruct why you are where you are.

Measured on a real compiler: the path between the goal and the day's work was six levels deep, spread across a chronologically ordered 8,853-line tracker, 52 planning documents and 21 issues. The structure was temporal, which is exactly the opposite of provenance.

Logbooks, decision records, issue trackers and session memory for agents all store the node. None of them stores the edge. Where it sits goes through them category by category, and says where each one is better than this.

What you get

The agent starts oriented, and nobody has to ask it to. A hook runs vivac session start when a session opens, so the first thing in its context is where you are, what has already been decided, and what not to touch:

$ vivac brief

vivac · project: demo · lane: main · 2026-09-21
------------------------------------------------------------

 GOAL g1     Ship the 2.0 API
  |
  |-- t2     Replace the cache adapter
  |     why: the session bug traces back to it
  |
  `-- t6     Migrate the callers   <== HERE
        why: the old adapter had a different signature

 STANDING DECISIONS
  d5     Retry policy: three tries, then fail loudly

 LAST VIVAC
  v5 · push · 2026-09-21 · bcdba21
         you were about to: Migrate the callers

------------------------------------------------------------
 143 tokens · depth 3 · 0 parked

In tokens, that is the whole argument. A project keeping its state in three places was asked to pick up where it left off. A hand-written plan answered in 9,252 tokens. A memory system answered “maybe” in about 12,720, depending on which of two names for the project it resolved. The tree answered in 100. The brief carries a token budget because a context window is the one resource every session spends.

Nothing closes over what is still open. The one operation in the model that rejects, and it earns it: a run marked done over open findings took 26 days to be spotted once.

$ vivac done 2

  t2 CANNOT close: 1 open closure condition(s)

      t6     Migrate the callers

  A run closes with its findings, not with its report.
  Closing it anyway leaves a trace:  vivac done 2 --force

Every decision keeps what it turned down, and what it was judged against. --alternative holds the option rejected, --supersedes links a reversal to what it reverses, and --against records the rule or pillar that decided it — so a decision can be argued with a year later instead of guessed at. This project's own tree carries 176 of them.

An assumption that falls does not take its children with it. abandon marks the premise refuted and everything under it goes with it, except what you rescue — and what is rescued still hangs where it was born, because being born somewhere is not undone by that place turning out to be wrong.

What it does not promise

It saves tokens, not all of them. Picking a project up took the tree 100 tokens where a hand-written plan took 9,252, and that difference comes back every time a session opens. The agent still reads files, still reasons and still explains itself, and none of that gets cheaper.

It does not make sure nothing is ever forgotten. No memory system can, this one included, because every one of them still runs on the model's judgement: should I save this? is this a finding? do I need to read the tree again before I answer? The best skill in the world, a hundred subagents or a hundred daemons move where that judgement happens, and none of them removes it. vivac hangs capture off the seams of the work rather than off that judgement, and still measures where it slips.

What is left over after that is why the tree is built to be looked at.

See it

vivac web

The agent writes the tree, and you can read it at any moment without asking the agent anything. vivac web opens every project on this machine in a browser: which one moved and which has been sitting still, what changed in one while you were away, a node's whole lineage, and the whole tree. It is where you see the state of each item for yourself, and where you catch what the agent let pass.

Four example projects, written by real vivac commands with tools/web-screenshots.py, which takes these pictures again whenever the pages change.

A server you start and that dies when you close it, bound to 127.0.0.1, reachable through a one-time key it prints. It has no functions of its own: anything a page needs is built on the command line first. → What the web is, and is not

One map

vivac was not built to compete with memory systems. I have used engram, by Alan Buscaglia, and I contribute to it. What I set out to build was a record of decisions, and the road there turned out to need a memory; that is how vivac came to work as one, kept in a file in the project so that whichever harness or model you open it with reads the same thing. It is not a better memory system than engram or any other. It was built for something else.

That is why the advice runs both ways. If you already use a memory system and it serves you, do not add vivac. If you want vivac for the tree, do not keep another one beside it — any one. Each system injects its own context into the model, and two maps collide: each points the agent at what it holds, and sooner or later one settles something the other mapped differently, with nobody noticing which of the two oriented the decision.

That is observed, not assumed:

  • A written rule can create a seat no tool can read. In one project an instruction told the agent to mirror every update into its memory system. That made three seats at the table, and the one that actually governed was the only one nothing could inspect.
  • The harness brings its own map, whether you chose it or not. In the project that builds vivac — with everything else deliberately turned off, precisely to test whether the tree alone could carry the thread — the harness's automatic memory kept injecting a copy of the project's doctrine into every session for five days before anybody noticed. The measurement was not wrong. It was invalid, and nothing said so.

So why not just the harness?

It gives you the session. It does not give you three things, and each absence is a specific failure rather than a missing feature:

  • No edge. It stores what was learned, not which piece of work it came out of, so there is nothing to walk back along.
  • No focus. Everything recalled is equally present, and none of it says you are here — or, more to the point, do not touch that.
  • No open and closed state. Nothing can be reported as still missing.

And the harness's memory belongs to the harness. Change tool and the thread does not come with you. .vivac/ is a file in your project: plain JSON lines, exportable in one command, readable without this binary.

vivac turns nothing off, and neither does setup — another system is not vivac's to touch. What it gives you is a skill that finds every other map the agent receives and offers to retire each one, after you say yes, in a form that can be undone.

What it costs

Budgets, not aspirations: a read is given 50 ms and a write 5 ms, and where that is missed it is named rather than left out.

Measured on 18 September 2026 at ten thousand nodes, 200 calls per cell, on two machines and at two tree shapes, because what brief and open cost is governed by how many fronts are still open rather than by how many nodes exist. p99 in milliseconds:

brief why open find
CLI, cold process, Linux 15.5 18.8 20.4 19.9
MCP, resident server, Linux 0.5 7.1 4.2 8.8

A write over MCP is 0.6 ms at p99 and flat in the size of the tree. And because context is the budget that actually binds, the payloads are measured too: vivac_open over ten thousand nodes went from 1,993,053 bytes to 599,012, and why --json on a deep node from 86,894 to 7,139.

→ The full numbers — both machines, both tree shapes, the write table, and what Windows misses and why.

What it never stores

A provenance tree is a map of where a system is weak and not yet fixed, which forces a few things that are not negotiable:

  • No keys and no secrets. A redaction guard at write time. In doubt it refuses and says why; it never stores in silence.
  • No personal data. No email, no name, no home path. The actor on every event is an opaque identifier.
  • No file contents. Only paths, references and prose about what was decided — so a leak bounds to what was being worked on, never to what the code is.
  • No telemetry. The binary does not phone home. Ever.

These come from the pillars: security vetoes, performance budgets, UX proves a surface is worth reading, DX judges.

Install

Every release carries a precompiled binary — Linux and macOS on x86_64 and aarch64, Windows on x86_64 — listed in SHA256SUMS and carrying signed build provenance. Unpack one and put vivac on your PATH.

With a Rust toolchain, 1.89 or newer:

cargo install vivac

cargo install is not the fallback: it builds from the source published to crates.io, so it stays the auditable path for anyone who cares about the supply chain of a tool that reads their work.

To move to a newer release, run vivac update. It shows how this vivac was installed and what replacing it takes — the cargo install that built it, or the release archive it came from, checked against SHA256SUMS — and does it once you answer yes. On Windows it sets the running copy aside first, so the install does not wait for your sessions to close. With no terminal to answer in, it only says what to type. → Setting it up

The first five minutes

1. In the folder you open your agent in. The first plants the tree, the second gives your agent the hooks, the server and the skill. Both show every file they will touch, and the exact command each hook will run, and then ask:

vivac init
vivac setup claude-code

2. Start the first thread. You were going to say what you are doing anyway; saying it here is what creates the edge, for free:

vivac push "Replace the cache adapter" --why "the session bug traces back to it"
vivac push "No test for expiry" --why "no way to reproduce it" --blocks
vivac pop "reproduced: sessions expire at 300s, not 3600"

3. Ask where you are, and why:

vivac brief        where you are, and what NOT to touch
vivac why 2        the path from the root, narrated
vivac open         what is waiting on you, and what has been sitting
vivac web          the whole tree in a browser, on this machine only

That is the loop. → When each one runs, and what to say when your agent skips one · Every command

Bringing a project in

Nothing moves into vivac on its own.

If your project already keeps what it has learned — in a memory system, in CLAUDE.md, AGENTS.md, MEMORY.md, the harness's own memory, or internal documents — none of that is in the tree after vivac setup. vivac never reads another system and never reads those files, because telling a rule from the prose around it takes judgment, and a tool that guessed would fill your tree with confident nonsense on day one.

So it is a job for the agent, with you deciding what goes in. setup installs the vivac-migrate skill, and you say:

Use the vivac-migrate skill to bring everything this project knows into vivac.

It lists every source it finds, asks which to bring in, shows a plan before writing anything, checks what it wrote — and then offers to retire the other maps, one at a time. That last step is the point, not the tidying up: a full tree with the old records still talking to the agent is two maps, which is the state this gets you out of.

→ Bringing a project in, and what happened on real projects: eight migrations, two measured source by source, and what each failure changed.

Lanes

You work on one product from more than one folder: a checkout on main, a second one for a hotfix, a third for reviewing somebody else's branch. Or one folder and ten branch changes a day.

The record must not fork when the folders do. What was this born from? has one answer for the product, not one per checkout — three trees answering it three ways is three wrong answers.

So the tree belongs to the product, and every folder that works on it is a lane. The branch is a fact recorded on each write, not something the tree is kept in.

What that buys you: the brief tells you when a branch moved under you, and what the other lanes have done since you last wrote here.

Your situation What to run
another folder, under the same tree vivac init there too, then vivac setup claude-code
a folder somewhere else entirely vivac init --join <name>, then vivac setup claude-code
the tree should live elsewhere vivac relocate <destination>
which lanes exist, and what each is on vivac stack --lanes

Read codex for claude-code wherever you use it, including in the same folder as the other: the harness decides which files a folder gets, and never anything about the tree.

→ docs/LANES.md — what a lane is and is not, and the four ways to get it wrong.

Where this is measured
Claude Code vivac setup claude-code writes the hooks, the server and the skill. This is the harness every measurement on this page was taken on.
Codex vivac setup codex leaves a project just as ready, where Codex reads it. A real Codex session was walked end to end on 22 September 2026: the server resolves once the project is trusted, the skill is offered to the model, the opening hook puts the brief into the agent's context, and the closing hook leaves its stop. It merges with what is already there, runs twice without writing anything the second time, and takes itself back — the same way the Claude Code side does, and through the same three flags. The tree is neither side's: vivac init plants it once, and both harnesses read the one it left.
Anything else The hooks call ordinary commands. Any harness that can run one when a session opens and put its output in the agent's context can call the same one, and any MCP client can run vivac mcp.

One step of that walk is not measured and cannot be: approving each hook inside Codex is something a person does, once, and looking at a person is not a measurement.

Not there yet: team mode. The project is in 0.x and breaks on the minor while it is.

Documentation
When each command runs the moments of a session, who acts at each, and what to say if the agent skips one
Using it every command, grouped by who runs it
Setting it up what setup writes, Codex, the MCP server, where things are stored
Bringing a project in the migration, and why it is a migration and not an addition
Lanes one product, several folders, one tree
What it costs the full measurements, and how they were taken
Versioning what breaks when, and what keeps 1.0 away
Where it sits what each category of tool stores, and where each is better than this
Pillars the four arbiters every decision here is judged against

Licence

MIT OR Apache-2.0, at the option of whoever uses it. The text of each is in LICENSE-MIT and LICENSE-APACHE.

The licence covers the code and not the name: a fork is free, and it goes out under a name of its own. TRADEMARKS.md says what the name and the logo can be used for. A security flaw goes privately, as SECURITY.md says.