8b25daf915
Dogfooded 2026-04-18 on main HEAD a049bd2 from /tmp/cdII.
5 concurrent /compact on same session → 4 succeed, 1 races with
raw ENOENT. Same pattern with concurrent /clear --confirm.
Trace:
session.rs:204-212 save_to_path:
rotate_session_file_if_needed(path)?
write_atomic(path, &snapshot)?
cleanup_rotated_logs(path)?
Three steps. No lock around sequence.
session.rs:1085-1094 rotate_session_file_if_needed:
metadata(path) → rename(path, rot_path)
Classic TOCTOU. Race window between check and rename.
session.rs:1063-1071 write_atomic:
writes .tmp-{ts}-{counter}, renames to path
Atomic per rename, not per multi-step sequence.
cleanup_rotated_logs deletes .rot-{ts} files older than 3 most
recent. Can race against another process reading that rot file.
No flock, no advisory lock file, no fcntl.
grep 'flock|FileLock|advisory' session.rs → zero matches.
SessionError::Io Display forwards os::Error Display:
'No such file or directory (os error 2)'
No domain translation to 'session file vanished during save'
or 'concurrent modification detected, retry safe'.
Fix shape (~90 lines + test):
- advisory lock: .claw/sessions/<bucket>/<session>.jsonl.lock
exclusive flock for duration of save_to_path (fs2 crate)
- domain error variants:
SessionError::ConcurrentModification {path, operation}
SessionError::SessionFileVanished {path}
- error-to-JSON mapping:
{error_kind: 'concurrent_modification', retry_safe: true}
- retry-policy hints on idempotent ops (/compact, /clear)
- regression test: spawn 10 concurrent /compact, assert all
success OR structured ConcurrentModification (no raw os_error)
Affected operations:
- /compact (session save_to_path after compaction)
- /clear --confirm (save_to_path after new session)
- /export (may hit rotation boundary)
- Turn-persist (append_persisted_message can race rotation)
Not inherently a bug if sessions are single-writer, but
workspace-bucket scoping at session_control.rs:31-32 assumes
one claw per workspace. Parallel ulw lanes, CI matrix runners,
orchestration loops all violate that assumption.
Joins truth-audit (error lies by omission about what happened).
New micro-cluster 'session handling' with #93. Adjacent to
#104 on session-file-handling axis.
Natural bundle: #93 + #112 (session semantic correctness +
concurrency error clarity).
Filed in response to Clawhip pinpoint nudge 1494880177099116586
in #clawcode-building-in-public.
Claw Code
ultraworkers/claw-code · Usage · Rust workspace · Parity · Roadmap · UltraWorkers Discord
Claw Code is the public Rust implementation of the claw CLI agent harness.
The canonical implementation lives in rust/, and the current source of truth for this repository is ultraworkers/claw-code.
Important
Start with
USAGE.mdfor build, auth, CLI, session, and parity-harness workflows. Makeclaw doctoryour first health check after building, userust/README.mdfor crate-level details, readPARITY.mdfor the current Rust-port checkpoint, and seedocs/container.mdfor the container-first workflow.ACP / Zed status:
claw-codedoes not ship an ACP/Zed daemon entrypoint yet. Runclaw acp(orclaw --acp) for the current status instead of guessing from source layout;claw acp serveis currently a discoverability alias only, and real ACP support remains tracked separately inROADMAP.md.
Current repository shape
rust/— canonical Rust workspace and theclawCLI binaryUSAGE.md— task-oriented usage guide for the current product surfacePARITY.md— Rust-port parity status and migration notesROADMAP.md— active roadmap and cleanup backlogPHILOSOPHY.md— project intent and system-design framingsrc/+tests/— companion Python/reference workspace and audit helpers; not the primary runtime surface
Quick start
Note
[!WARNING]
cargo install claw-codeinstalls the wrong thing. Theclaw-codecrate on crates.io is a deprecated stub that placesclaw-code-deprecated.exe— notclaw. Running it only prints"claw-code has been renamed to agent-code". Do not usecargo install claw-code. Either build from source (this repo) or install the upstream binary:cargo install agent-code # upstream binary — installs 'agent.exe' (Windows) / 'agent' (Unix), NOT 'agent-code'This repo (
ultraworkers/claw-code) is build-from-source only — follow the steps below.
# 1. Clone and build
git clone https://github.com/ultraworkers/claw-code
cd claw-code/rust
cargo build --workspace
# 2. Set your API key (Anthropic API key — not a Claude subscription)
export ANTHROPIC_API_KEY="sk-ant-..."
# 3. Verify everything is wired correctly
./target/debug/claw doctor
# 4. Run a prompt
./target/debug/claw prompt "say hello"
Note
Windows (PowerShell): the binary is
claw.exe, notclaw. Use.\target\debug\claw.exeor runcargo run -- prompt "say hello"to skip the path lookup.
Windows setup
PowerShell is a supported Windows path. Use whichever shell works for you. The common onboarding issues on Windows are:
- Install Rust first — download from https://rustup.rs/ and run the installer. Close and reopen your terminal when it finishes.
- Verify Rust is on PATH:
If this fails, reopen your terminal or run the PATH setup from the Rust installer output, then retry.cargo --version - Clone and build (works in PowerShell, Git Bash, or WSL):
git clone https://github.com/ultraworkers/claw-code cd claw-code/rust cargo build --workspace - Run (PowerShell — note
.exeand backslash):$env:ANTHROPIC_API_KEY = "sk-ant-..." .\target\debug\claw.exe prompt "say hello"
Git Bash / WSL are optional alternatives, not requirements. If you prefer bash-style paths (/c/Users/you/... instead of C:\Users\you\...), Git Bash (ships with Git for Windows) works well. In Git Bash, the MINGW64 prompt is expected and normal — not a broken install.
Note
Auth: claw requires an API key (
ANTHROPIC_API_KEY,OPENAI_API_KEY, etc.) — Claude subscription login is not a supported auth path.
Run the workspace test suite:
cd rust
cargo test --workspace
Documentation map
USAGE.md— quick commands, auth, sessions, config, parity harnessrust/README.md— crate map, CLI surface, features, workspace layoutPARITY.md— parity status for the Rust portrust/MOCK_PARITY_HARNESS.md— deterministic mock-service harness detailsROADMAP.md— active roadmap and open cleanup workPHILOSOPHY.md— why the project exists and how it is operated
Ecosystem
Claw Code is built in the open alongside the broader UltraWorkers toolchain:
Ownership / affiliation disclaimer
- This repository does not claim ownership of the original Claude Code source material.
- This repository is not affiliated with, endorsed by, or maintained by Anthropic.