Rebar MCP Server

rebar

A git-native ticket system for coordinating coding agents — and the humans working alongside them.

Point several agents at one repo and they immediately need a shared place to coordinate: to claim work without grabbing the same ticket, record what they discover, and hand off cleanly — while your teammates stay in the loop through Jira. rebar makes the tracker part of the repo itself, so it travels with every clone, needs no database or daemon, and lets many agents and sessions write at once without merge conflicts or lost work.

It's an event-sourced ticket system with a Jira reconciler, exposed three ways:

• CLI — the rebar command
• Python library — import rebar
• MCP server — rebar-mcp (stdio)

Tickets are stored as an append-only event log on a dedicated tickets git orphan branch (worktree at .tickets-tracker/); state is computed by replaying events. A level-triggered reconciler bidirectionally syncs tickets with Jira. Both the branch name and the worktree/symlink dir default to those values but are configurable (tracker.branch / tracker.dir) — see Configuration.

This project was extracted from the digital-service-orchestra Claude Code plugin. It began as a bash + Python engine; that engine has since been fully ported to in-process Python (see docs/bash-migration.md). The reconciler ships under src/rebar/_engine/ as package data, and the three interfaces are thin layers over the in-process core.

Why rebar

If you run coding agents against a repo, you eventually want to run several at once — and the moment you do, they need a shared place to coordinate. Most trackers weren't built for that:

• They're heavy. A daemon to babysit or a local database to keep running, with dependencies thick enough that a routine upgrade can break your work tracking across machines.
• They don't travel with the code. State lives outside the repo, so a fresh clone doesn't come with its tickets.
• They fight your git history. A tracker that writes to your working branch tangles ticket churn into your source-code commits.
• They have no concurrency story. Nothing stops two agents from claiming the same work or clobbering each other's state, and concurrent edits produce merge conflicts you resolve by hand — or lose.
• They buckle at scale. Speed and usability fall off past a few hundred tickets.

rebar's answer is to make the tracker part of the repo. Tickets are an append-only event log on a dedicated tickets orphan branch (linked in through a gitignored worktree); current state is a fast, deterministic replay of that log. That single decision pays off across the board:

• Zero infrastructure, fully portable. No database, no daemon — just git and a lightweight Python install. Clone the repo and the tracker comes with it.
• No commit interference. Ticket events live on their own branch and never touch your source history. Every write auto-commits and auto-pushes, so activity is shared in real time.
• Concurrency by design. Each event gets a globally-unique filename, so parallel writes merge as a clean union, and the rare conflicting fork resolves deterministically — every clone converges with no lost data. claim is an atomic, optimistic-concurrency primitive: agents grab work without stepping on each other.
• Built to scale. The event log plus cached replay stays fast as tickets grow.

On top of that foundation, rebar adds what parallel agent work actually needs:

• Bidirectional Jira sync — agents work in rebar, teammates work in Jira, and a level-triggered reconciler keeps the two in step. To run it automatically in CI, see docs/jira-sync-setup.md (the GitHub Actions reconcile-bridge + heartbeat-canary setup).
• Conflict-aware scheduling — tickets record their file impact, so next-batch hands parallel agents work that won't collide on the same files.
• Scratch space — an invisible per-ticket channel for subagents to pass notes to one another.
• Quality gates — clarity, acceptance-criteria, dispatch-readiness, and repo-wide health checks keep work dispatch-ready.
• Provenance links — discovered_from ties emergent work back to the ticket that surfaced it.
• One store, three interfaces — drive it from the CLI, a Python library, or the MCP server.

Requirements

Runtime (system):

• Python ≥ 3.11
• git — required (the store is a git orphan branch + worktree). The engine is pure in-process Python; bash and jq are not required at runtime.
• flock from util-linux — recommended for robust write serialization, but not strictly required: it is not on PATH by default on macOS (brew install util-linux), and when no util-linux flock is found rebar falls back to a mkdir-based lock automatically. (A non-util-linux flock such as BusyBox's is ignored in favor of the fallback.)
• acli (Atlassian CLI) — only for live Jira reconciliation.

Python dependencies — runtime (prod) vs. rebar development. rebar keeps a deliberately tiny footprint; the distinction is between running rebar (and its optional capabilities) and developing rebar itself:

• Runtime — base. pip install nava-rebar gives the rebar CLI + import rebar library + the lean workflow engine (author/validate/render/run scripted workflows). Its only runtime dependencies are pyyaml (the workflow DSL loader, epic a88f) and jsonschema (the schema-registry + workflow input/output-contract validator) — both lean-runtime paths — so the engine core and reconciler are otherwise stdlib-only.
• Runtime — optional capability extras (install only what you use; each is lazy-imported, so the base stays light and CI enforces that):
  • [mcp] — the rebar-mcp server (mcp>=1.2).
  • [agents] — the LLM agent-operations framework + agentic workflow steps (rebar review, the code_review workflow): the provider-agnostic pydantic-ai runtime (pydantic-ai-slim[anthropic] + json-repair).
  • [eval] — prompt evaluation (rebar prompt eval): Inspect AI. An authoring/CI capability, not needed to serve.
  • [tracing] — the OTLP trace sink (write-only; OpenTelemetry is never read back into a rebar decision).
• Development (working ON rebar). pip install -e '.[dev]' adds the test/lint/type tooling (pytest, ruff, mypy, hatchling) and self-references [agents] so the validation tests run rather than skip. It is required to run the full test suite (the interface-parity tests import the MCP server, so they error — not skip — without mcp).
  • Node/npm are needed only for the workflow visual editor's front-end — rebuilding its vendored bundle (src/rebar/llm/workflow/editor_assets/, the bpmn-js editor) and running the faithful editor E2E tier (tests/e2e/, which drives the real bpmn-io libraries). Both are developer-only: the built bundle is committed/shipped, and the E2E tier self-skips when Node is absent, so neither the base install nor the default test suite needs Node. See docs/workflow-editor.md.

See Install and Tests.

Install

rebar ships from one Python package — PyPI distribution nava-rebar (the import package and commands stay rebar / rebar-mcp). Pick the channel that fits. (System prerequisites in all cases: git and python3 (≥ 3.11); a util-linux flock is used for write serialization when present, with a mkdir fallback otherwise; acli only for live Jira reconciliation.)

Homebrew (CLI)

brew install navapbc/rebar/rebar
# or: brew tap navapbc/rebar && brew install rebar

Installs the rebar CLI (and the rebar library inside the formula's venv). For the MCP server via Homebrew users, install the [mcp] extra with pipx/uvx below.

PyPI — pipx / pip

Runtime (prod) — install what you'll run:

pipx install nava-rebar              # isolated CLI on PATH: rebar (+ lean workflow engine)
pip  install nava-rebar              # library: import rebar  (runtime deps: pyyaml, jsonschema)
pip  install 'nava-rebar[mcp]'       # + MCP server: rebar-mcp
pip  install 'nava-rebar[agents]'    # + LLM agent ops + agentic workflow steps (rebar.llm)
pip  install 'nava-rebar[eval]'      # + prompt evaluation: `rebar prompt eval` (Inspect AI)
pip  install 'nava-rebar[tracing]'   # + OTLP trace sink (write-only)
pip  install 'nava-rebar[agents,eval,tracing]'   # the union, if you want it all

The base install runs scripted workflows (rebar workflow new/validate/show/run) with no extra; agentic workflow steps and rebar review need [agents]. Authoring a workflow visually — rebar workflow edit <file>, a local bpmn-js editor that round-trips the diagram back to the IR — also needs no extra and no Node/npm: the editor front-end ships pre-built in the wheel and is served locally (no CDN). For what the engine is for — when to author a workflow vs a bespoke op, the YAML DSL, the three-pass review pattern, and the prompt-library + eval seam — see docs/workflow-engine.md; for visual editing specifically see docs/workflow-editor.md.

The [agents] extra adds the optional LLM agent-operations framework (rebar.llm) — tool-using agents that review tickets/code and emit structured findings, over library / CLI (rebar review) / MCP. It is multi-provider (Claude and ChatGPT out of the box, plus Gemini and OpenAI-compatible local servers like LMStudio/Ollama via REBAR_LLM_MODEL/REBAR_LLM_MODEL_PROVIDER/ REBAR_LLM_BASE_URL) and is never required by core rebar — none of the LLM stack is installed or imported unless you opt into this extra (CI enforces it); see docs/llm-framework.md.

MCP server — from the MCP Registry

Listed in the MCP Registry as io.github.navapbc/rebar. Registry-aware MCP clients can add it by that name; or register it directly in your client config (zero pre-install via uvx):

{
  "mcpServers": {
    "rebar": {
      "command": "uvx",
      "args": ["--from", "nava-rebar[mcp]", "rebar-mcp"],
      "env": { "REBAR_ROOT": "/path/to/your/repo" }
    }
  }
}

(Already pip/pipx-installed nava-rebar[mcp]? Use "command": "rebar-mcp" instead.) Server flags: REBAR_MCP_READONLY=1 exposes only read tools; reconcile is dry-run unless REBAR_MCP_ALLOW_JIRA_SYNC=1 (deprecated alias REBAR_MCP_ALLOW_RECONCILE_LIVE). Both flags accept any case-insensitive truthy value — 1, true, or yes (surrounding whitespace tolerated); anything else (incl. unset) is off.

Private-repo fetch credentials (code-reading gates)

The LLM code-reading gates (review_plan, verify_completion, review_ticket, review_code, scan_spec) default to attested mode: they git fetch the verified ref from origin and read an immutable snapshot at the pinned SHA — never the server's mutable checkout. So a server pointed (REBAR_ROOT) at a private repository needs read credentials to fetch: a git credential helper, a deploy key, or a token in the server's clone. With no credentials, attested mode fails closed with a descriptive, actionable error (it never hangs on a prompt — GIT_TERMINAL_PROMPT=0); source=local (read the in-place checkout, never signed) is the back-out that needs no fetch. Full semantics, the HMAC trust model, and the snapshot env knobs (REBAR_GATE_TMPDIR, the disk-space watermark, the EFS/NFS flock caveat) are in docs/repo-snapshot-gates.md.

From source

git clone https://github.com/navapbc/rebar && cd rebar
pip install .              # library + CLI (runtime deps: pyyaml, jsonschema)
pip install '.[mcp]'      # + MCP server (FastMCP)
# Developing rebar itself — the full dev environment (test/lint/type tooling +
# the agents stack so the LLM validation tests RUN, not skip):
pip install -e '.[dev]'

Packaging note — why rebar installs unpacked to disk. The library, CLI, MCP server, and the whole read/write core run in-process in Python. The one component that runs as a subprocess is the Jira reconciler, which ships under src/rebar/_engine/ as package data (python -m rebar_reconciler, plus the jira-capability-probe.py script and the alias wordlist): it is launched and read from the filesystem as real on-disk files, so the package must be installed unpacked to a real directory and zipimport / zip-safe bundles (zipapp, shiv, PEX, Lambda zips) are unsupported. Every standard install satisfies this: pip/pipx wheels (hatchling builds unpacked), editable installs, and Homebrew all land real files. engine_dir() asserts the engine dir is present on disk at the first reconciler call and fails loudly otherwise.

CLI

rebar init                                   # create the tickets branch + worktree
rebar create story "Add login page"          # prints the ticket id
rebar list [--status=open] [--has-tag=...]   # JSON array
rebar show <id|alias>                         # compiled ticket state (JSON)
rebar claim <id> --assignee <you>             # atomic open -> in_progress + assignee (the work-start primitive)
rebar transition <id> <current> <target>      # optimistic-concurrency status change
rebar comment <id> "<body>"
rebar link <id1> <id2> <relation>            # relation REQUIRED (see relations below)
rebar unlink <source> <target>               # remove ONE link for the ordered pair (no relation arg)
rebar deps <id>                               # dependency graph
rebar search <query>                          # full-text over titles/descriptions/comments/tags (JSON)
rebar ready                                   # tickets with all blockers closed
rebar next-batch <epic-id>                    # unblocked tickets under an epic's hierarchy
rebar validate                                # repo-wide tracker health (NO ticket id; whole-store score 1-5)
rebar clarity-check <id> / check-ac <id> / quality-check <id>   # per-ticket quality gates
rebar review-plan <id>                        # plan-review gate: DET floor + 3-pass advisory; signs an attestation (exit 0=PASS,1=BLOCK,2=INDETERMINATE)
rebar sign <id> '["ran tests: PASS", "lint clean"]'   # HMAC-sign a manifest of verified steps
rebar verify-signature <id>                   # certify the steps match the signature (exit 0=certified)
rebar export [-o FILE]                        # store -> NDJSON (one ticket/line; for jq/DuckDB/pandas + rebar->rebar migration)
rebar import [FILE]                           # import export NDJSON (fresh local ids; [--dry-run])
rebar reconcile [--mode dry-run|reconcile-check|live]   # Jira sync (default: dry-run)

Run rebar help (or rebar --help / -h) for the subcommand overview, and rebar <subcommand> --help (or rebar help <subcommand>) for a specific subcommand's usage — --help prints usage and never executes the command. Help is only recognized as the first argument after the subcommand, so a --help/-h/help that appears inside a free-text parameter (title, comment body, search query, …) is treated as literal text, not a help request.

Repo root is resolved from REBAR_ROOT, falling back to the git toplevel of the working directory.

Structured output. Every data-returning command emits machine-readable JSON via the canonical --output json flag (short -o json; --output llm gives a token-minified shape for show/list/ready). Each distinct JSON shape is documented by a JSON Schema and validated across the CLI, library, and MCP in CI. See docs/output-schemas.md for the per-command contract and the schema source-of-truth.

validate vs. the per-ticket gates. rebar validate takes no ticket id — it scans the whole store and prints an overall tracker-health score (1-5, exit 0-4) bucketed into critical / major / minor / warning findings (--output json, --terse, --verbose, --fix). Passing it a ticket id errors. The per-ticket quality gates are separate commands that each take an <id>: clarity-check, check-ac, quality-check. They are structural floor checks — they verify a ticket is shaped like dispatchable work, not that the content is good. Every type needs an ## Acceptance Criteria checklist (- [ ] items); check-ac and clarity-check both require it. See the per-type ticket template (Why/What/Scope for stories, Reproduction Steps for bugs, Success Criteria/Context for epics) in CLAUDE.md.

Links. rebar link <id1> <id2> <relation> requires a relation; the six relations are blocks, depends_on, relates_to, duplicates, supersedes, discovered_from. rebar unlink <source> <target> takes no relation argument — it is pair-scoped and removes the most-recently-created link between that ordered pair, one per call, so to remove multiple links between the same pair you call unlink repeatedly. Note that blocking links (blocks/depends_on) may be promoted up the parent hierarchy when created (see below), so unlink must target the promoted (ancestor) endpoint to remove such a link.

Signing a manifest of verified steps

rebar sign <id> <manifest> records a cryptographic attestation on a ticket: a manifest (a JSON array of verified-step strings) plus an HMAC-SHA256 signature computed with a key that is specific to the environment rebar runs in. The key is resolved from REBAR_SIGNING_KEY (injected out-of-band into a shared deployment — e.g. an MCP server) or, failing that, a per-environment .signing-key file generated on first use (gitignored, never committed, never shared). rebar verify-signature <id> recomputes the HMAC with the local key and certifies that the recorded steps still match the signature:

rebar sign abcd-1234 '["unit tests: PASS", "security review: clean", "deployed to staging"]'
rebar verify-signature abcd-1234        # SIGNATURE: certified — verified steps match the signature

The signature binds both the ticket id and the manifest, so it cannot be replayed onto another ticket and any edit to the step list invalidates it. Because the key never leaves the environment, verify-signature reports foreign_key (rather than certified) when a record was signed by a different environment — only the environment that holds the key can certify its own attestations. The signature is stored as a normal append-only SIGNATURE event, so it replays into show output, survives compaction, and flows to other clones like any other write.

The signing key is a shared secret (HMAC), so the attestation proves a signature was produced by a holder of the environment key and that the steps are unaltered since — it is not a public-key identity. Anyone who can read the .signing-key file (written 0600, owner-only) or the injected REBAR_SIGNING_KEY can forge a certified record, so protect read access to the environment accordingly.

Hierarchy promotion of blocking links

For blocking dependencies only (blocks, depends_on), rebar promotes the link endpoints up the parent hierarchy so the dependency sits between tickets at a comparable level (epic↔epic, story↔story, task/bug↔task/bug). When it does so it emits a REDIRECT: A→B promoted to … note. Non-blocking relations (relates_to, duplicates, supersedes, discovered_from) are linked exactly as given, with no promotion.

The store auto-commits and auto-pushes every write

Every rebar write (create, edit, transition, claim, link, …) auto-commits its event to the tickets branch and auto-pushes that branch to origin/tickets whenever an origin remote exists. Local ticket activity is therefore shared with the remote immediately — including test/scratch tickets, so be deliberate when working against a repo with a shared tickets remote. The push is best-effort: with no origin remote nothing is pushed, and a push failure (e.g. non-fast-forward it cannot auto-merge, or no network) never fails the write — it leaves the local commit intact and the branch diverged. rebar fsck reports PUSH_PENDING when the local tickets branch is ahead of origin/tickets, so unpushed activity is observable. See docs/concurrency.md for the push/merge-retry algorithm.

Reads share one freshness policy across CLI, library, and MCP

Every read — show, list, ready, search, deps — first runs a throttled (≤1/min), best-effort git fetch + reconverge of the local tickets branch with origin/tickets, so a read reflects collaborators' pushes within at most a minute. This is one contract shared by all three interfaces: CLI, library (rebar.list_tickets(), …), and the MCP read tools all resolve through a single read implementation. (Previously only CLI reads synced, leaving MCP — the primary agent surface — with the stalest reads; that divergence is gone.)

Opt out for a pure-local replay (offline work, tight loops, or right after a write that already synced): set REBAR_SYNC_PULL=off (honored everywhere; deprecated alias REBAR_NO_SYNC=1) or pass --no-pull to any read subcommand (e.g. rebar list --no-pull; deprecated alias --no-sync). Only the network fetch/merge is skipped; the local reduce/cache path is unchanged. See docs/concurrency.md.

The on-disk store is not human-readable — read it with rebar

The tickets branch is rebar's internal storage format, not a document for people to read. Each ticket is a directory of append-only JSON event files (${hlc}-${uuid}-${TYPE}.json); the current state of a ticket is what you get by replaying those events through the reducer. Two consequences follow:

• It isn't laid out in order. Event files are named by a Hybrid Logical Clock
  • UUID and merge across clones as a union, so the files for one ticket are not a top-to-bottom narrative — they are an unordered set that only becomes meaningful after the reducer sorts and folds them. A single EDIT/STATUS/TAG_DELTA file in isolation tells you a delta, not the ticket.
• The current state is computed, never stored. Nothing on the branch holds the compiled "current" ticket except a local, rebuildable .cache.json (gitignored). Reading the raw files by hand will mislead you — a later event may supersede an earlier one, a SNAPSHOT may fold many away, and concurrent forks resolve by a deterministic rule you'd have to apply yourself.

So don't cat the .tickets-tracker/ worktree to find out where a ticket stands — use the read commands, which run the reducer for you: rebar show <id>, rebar list, rebar deps <id>, rebar search <query> (CLI), the matching library calls (rebar.show_ticket(...)), or the MCP read tools.

For reference, docs/sample-ticket-log.jsonl is a small synthetic event log (one event per line) showing what the underlying data actually looks like — a two-agent epic + child tickets exercising create/claim/comment/link/tag/file-impact/sign/transition. Note that its lines are deliberately not in timestamp order: that is the point. The event body schema is documented in docs/event-schema.md.

Python library

import rebar

rebar.init_repo(repo_root="/path/to/repo")
tid = rebar.create_ticket("story", "Add login page", priority=2)
ticket = rebar.show_ticket(tid)                 # dict
tickets = rebar.list_tickets(status="open")     # list[dict]
try:
    rebar.transition(tid, "open", "in_progress")
except rebar.ConcurrencyError:
    ...                                          # ticket changed since last read

result = rebar.reconcile("dry-run")              # Jira sync (non-mutating)

# Cryptographic attestation (environment-bound HMAC):
rebar.sign_manifest(tid, ["unit tests: PASS", "security review: clean"])
verdict = rebar.verify_signature(tid)            # {"verified": True, "verdict": "certified", ...}

# Native, in-process reads (no subprocess):
from rebar import reduce_all_tickets, reduce_ticket

MCP server

rebar-mcp          # stdio transport

Exposes ticket operations as MCP tools. reconcile defaults to dry-run (live requires REBAR_MCP_ALLOW_JIRA_SYNC=1, deprecated alias REBAR_MCP_ALLOW_RECONCILE_LIVE). Set REBAR_MCP_READONLY=1 to expose only the read tools (no write/mutation tools). To register it in an MCP client (registry name io.github.navapbc/rebar, or a direct uvx config), see Install → MCP server above.

Maintainers: the registry manifest lives in server.json; publish/update it with the mcp-publisher CLI (see docs/releasing.md). The registry verifies PyPI-package ownership via this annotation (kept in this README, which is the PyPI long description):

mcp-name: io.github.navapbc/rebar

License

Apache-2.0 — see LICENSE.

Configuration

rebar reads TOML config from [tool.rebar] in pyproject.toml or a standalone rebar.toml (nearest up-tree, stopping at .git), falling back to a user config at ~/.config/rebar/config.toml (honoring $XDG_CONFIG_HOME). Precedence, highest first: rebar -c SECTION.KEY=VALUE / CLI flag > REBAR_<SECTION>_<KEY> env > project config > user config > built-in default. rebar config prints the resolved values and which layer each came from.

[tool.rebar]
verify.require_signature_for_close = true  # gate story/epic close on a certified
                                           # signature at HEAD (rebar sign); default
                                           # false. Alias: verify.require_verdict_for_close
ticket.display_mode = "auto"               # auto | canonical | alias | short
compact.threshold   = 10
sync.push = "always"                       # always | async | off
sync.pull = "on"                           # on | off
mcp.readonly = false
scratch.base_dir = ""                      # default <repo>/.rebar/scratch
tracker.dir    = ".tickets-tracker"        # store worktree/symlink dir (env REBAR_TRACKER_DIR)
tracker.branch = "tickets"                 # orphan branch the event log lives on (env REBAR_TRACKER_BRANCH)

The full key set, the REBAR_<KEY> env names, and deprecation aliases are in docs/config.md. The legacy flat .rebar/config.conf (key=value) is still read during a deprecation window for back-compat.

When the close gate is enabled, closing a story/epic requires a certified signature made at the current HEAD — sign a manifest of verified steps (rebar sign <id> '[...]') then rebar transition <id> closed; re-sign if HEAD moved, or bypass with --force-close=<reason>. This replaces the older --verdict-hash/compute-verdict-hash.sh gate, which is now deprecated.

rebar keeps its writable state under .rebar/ at the repo root. The scratch store defaults to <repo>/.rebar/scratch/ (override with scratch.base_dir / REBAR_SCRATCH_BASE_DIR; the unprefixed SCRATCH_BASE_DIR is a deprecated alias), and one-shot migration stamps are written under .rebar/ as well.

Tests

Run the suite from an environment with the [dev] extra installed (a venv is recommended); the interface-parity tests import the MCP server, so a bare interpreter without the mcp extra will error rather than skip.

python -m venv .venv && source .venv/bin/activate
pip install -e '.[dev]'                       # editable + pytest, mcp, ruff, mypy
pytest -m "not integration"                   # the single entry point (CI runs this)
pytest tests/interfaces                       # interface-parity tier only
pytest tests/scripts                          # engine/reconciler tier only

pytest is the single entry point. The engine is pure in-process Python (the bash engine and its .sh suites were removed in the bash→Python migration — see docs/bash-migration.md). CI (.github/workflows/test.yml) runs pytest -m "not integration" on Ubuntu and macOS for every push and PR. The integration tier (live Jira / network) is excluded from that default run; run it explicitly with credentials via pytest -m integration.

The Python suite is sub-divided by concern:

• tests/scripts, tests/unit — the in-process engine (reducer, graph, reconciler).
• tests/interfaces — proves the library, CLI, and MCP interfaces behave identically over one git-backed store:
  • test_parity.py runs each operation through all three interfaces (and a cross-interface coherence check: write via one, read via the others);
  • test_surface.py pins the per-interface capability surface (e.g. MCP has no init; there is no classify);
  • test_library.py / test_cli.py / test_mcp.py cover per-interface specifics (typed exceptions, exit-code passthrough, read-only/live gates).