feat(tooling): replace tox with just

.claude/agents/py-architect.md

@@ -140,7 +140,7 @@ Follow this systematic approach:
 2. **Identify** - Find code smells, duplication, unclear intent, type gaps
 3. **Preserve** - Ensure tests exist before making changes
 4. **Transform** - Make small, incremental improvements
-5. **Verify** - Confirm tests pass, types check (`uvx tox -e typecheck`), lints clean (`uv run ruff check`)
+5. **Verify** - Confirm tests pass, types check (`just typecheck`), lints clean (`just lint`)
 
 ## Quality Bar
 

.claude/rules/workflow.md

@@ -14,11 +14,11 @@ uv run fill --fork=lstar --clean -n auto --scheme=prod  # Generate test vectors
 ## Code Quality
 
 ```bash
-uv run ruff format       # Format code
-uv run ruff check --fix  # Lint and fix
-uvx tox -e typecheck     # Type check
-uvx tox -e all-checks    # All quality checks
-uvx tox                  # Everything (checks + tests + docs)
+just format     # Format code
+just fix        # Auto-fix lint, formatting, and markdown
+just typecheck  # Type check
+just check      # All quality checks (lint, format, typecheck, spell, mdformat, lock)
+just            # List all available recipes
 ```
 
 ## Common Tasks

.claude/skills/checks/SKILL.md

@@ -10,7 +10,7 @@ Run the complete quality check suite.
 ## Command
 
 ```bash
-uvx tox -e all-checks
+just check
 ```
 
 ## What It Runs
@@ -20,6 +20,7 @@ uvx tox -e all-checks
 3. `ty check` - Type checking
 4. `codespell` - Spell checking
 5. `mdformat` - Markdown formatting
+6. `uv lock --check` - Lockfile drift
 
 ## When to Use
 

.claude/skills/fill/SKILL.md

@@ -10,21 +10,22 @@ Run the test filler to generate consensus layer test fixtures.
 ## Default Usage
 
 ```bash
-uvx tox -e fill
+uv run fill --fork=Lstar --clean -n auto
 ```
 
 ## Options
 
 Pass additional arguments after `--`:
 
 - `/fill -- --scheme=prod` - Use production signature scheme (slower)
-- `/fill -- --fork=Electra` - Generate for Electra fork
+- `/fill -- --fork=<other>` - Generate for a different fork
 - `/fill -- path/to/test.py` - Generate fixtures for specific test file
 
 ## What It Does
 
-Runs `fill --fork=Devnet --clean -n auto` via tox, which:
-
 1. Discovers tests in `tests/consensus/`
 2. Executes spec tests to generate fixtures
 3. Outputs JSON fixtures to `fixtures/consensus/`
+
+The `just fill-ci` recipe wraps the same command for CI; contributors should
+invoke `uv run fill` directly so flags like `--fork` and `--clean` stay visible.

.claude/skills/fix/SKILL.md

@@ -10,7 +10,7 @@ Automatically fix linting and formatting issues.
 ## Command
 
 ```bash
-uvx tox -e fix
+just fix
 ```
 
 ## What It Fixes

.claude/skills/review/SKILL.md

@@ -51,6 +51,6 @@ A concise checklist distilled from CLAUDE.md for reviewing leanSpec code.
 ## Before Committing
 
 ```bash
-uvx tox -e fix        # Auto-fix formatting
-uvx tox -e all-checks # Verify all checks pass
+just fix    # Auto-fix lint, formatting, and markdown
+just check  # Verify all checks pass
 ```

.claude/skills/test/SKILL.md

@@ -10,7 +10,7 @@ Run pytest unit tests.
 ## Default
 
 ```bash
-uvx tox -e pytest
+just test
 ```
 
 ## Options

.claude/skills/workflows/SKILL.md

@@ -11,13 +11,13 @@ Common developer workflows and commands for working in leanSpec.
 
 ```bash
 # Single test file
-uvx tox -e pytest -- tests/lean_spec/subspecs/networking/discovery/test_transport.py -v
+just test tests/lean_spec/subspecs/networking/discovery/test_transport.py -v
 
 # Single test class or method
-uvx tox -e pytest -- -k "TestDiscoveryTransport::test_start" -v
+just test -k "TestDiscoveryTransport::test_start" -v
 
 # With print output visible
-uvx tox -e pytest -- -s -k "test_name"
+just test -s -k "test_name"
 ```
 
 ## Resolving Type Errors
@@ -26,10 +26,10 @@ The project uses two type checkers. Run them separately to isolate issues:
 
 ```bash
 # Full type check (ty — the primary checker used in CI)
-uvx tox -e typecheck
+just typecheck
 
 # Lint check (ruff — catches style and import issues)
-uvx tox -e lint
+just lint
 ```
 
 Common type error patterns:
@@ -43,7 +43,7 @@ After running tests, coverage reports are generated:
 
 ```bash
 # View coverage in terminal
-uvx tox -e pytest
+just test-cov
 
 # Open HTML report
 open htmlcov/index.html
@@ -54,14 +54,14 @@ open htmlcov/index.html
 Interop tests are excluded from the default test run. Run them explicitly:
 
 ```bash
-uv run pytest tests/interop/ -v
+just interop
 ```
 
 ## Spell Check Failures
 
 ```bash
 # Run spell check
-uvx tox -e spellcheck
+just spellcheck
 
 # Add legitimate words to the ignore list
 echo "newword" >> .codespell-ignore-words.txt
@@ -71,11 +71,11 @@ echo "newword" >> .codespell-ignore-words.txt
 
 ```bash
 # Check markdown formatting (docs only)
-uvx tox -e mdformat
+just mdformat
 ```
 
 ## Common Pitfalls
 
 - **Tests pass locally but CI fails**: CI runs checks across Python 3.12, 3.13, and 3.14. Ensure no version-specific syntax is used.
 - **`ruff format` changes after `ruff check --fix`**: Always run format after fix — the fixer doesn't guarantee formatting compliance.
-- **Import ordering issues**: Run `uvx tox -e fix` to auto-sort imports.
+- **Import ordering issues**: Run `just fix` to auto-sort imports.

.github/PULL_REQUEST_TEMPLATE.md

@@ -7,9 +7,9 @@
 ## ✅ Checklist
 <!-- Please check off all required items. For those that don't apply remove them accordingly. -->
 
-- [ ] Ran `tox` checks to avoid unnecessary CI fails:
+- [ ] Ran local quality checks to avoid unnecessary CI fails:
     ```console
-    uvx tox
+    just check
     ```
 - [ ] Considered adding appropriate tests for the changes.
 - [ ] Considered updating the online docs in the [./docs/](/leanEthereum/leanSpec/tree/main/docs/) directory.

.github/workflows/ci.yml

@@ -37,8 +37,13 @@ jobs:
           enable-cache: true
           cache-dependency-glob: "pyproject.toml"
 
-      - name: Run all quality checks via tox
-        run: uvx tox -e all-checks
+      - name: Install just
+        uses: taiki-e/install-action@v2
+        with:
+          tool: just
+
+      - name: Run all quality checks
+        run: just check
 
   test:
     name: Tests - Python ${{ matrix.python-version }} on ${{ matrix.os }}
@@ -63,8 +68,13 @@ jobs:
           enable-cache: true
           cache-dependency-glob: "pyproject.toml"
 
-      - name: Run tests via tox
-        run: uvx tox -e pytest
+      - name: Install just
+        uses: taiki-e/install-action@v2
+        with:
+          tool: just
+
+      - name: Run tests
+        run: just test
 
   coverage-gate:
     name: Coverage gate - Python 3.12
@@ -84,8 +94,13 @@ jobs:
           enable-cache: true
           cache-dependency-glob: "pyproject.toml"
 
+      - name: Install just
+        uses: taiki-e/install-action@v2
+        with:
+          tool: just
+
       - name: Run tests with coverage gate
-        run: uvx tox -e pytest-cov-gate
+        run: just test-cov-gate
 
   fill-tests:
     name: Fill test fixtures - Python 3.14
@@ -105,11 +120,13 @@ jobs:
           enable-cache: true
           cache-dependency-glob: "pyproject.toml"
 
-      - name: Sync dependencies
-        run: uv sync --no-progress
+      - name: Install just
+        uses: taiki-e/install-action@v2
+        with:
+          tool: just
 
       - name: Fill test fixtures
-        run: uv run fill --fork=Lstar --clean -n auto
+        run: just fill-ci
 
   interop-tests:
     name: Interop tests - Multi-node consensus
@@ -130,14 +147,12 @@ jobs:
           enable-cache: true
           cache-dependency-glob: "pyproject.toml"
 
+      - name: Install just
+        uses: taiki-e/install-action@v2
+        with:
+          tool: just
+
       - name: Run interop tests
-        run: |
-          uv run pytest tests/interop/ \
-            -v \
-            --no-cov \
-            --timeout=120 \
-            -x \
-            --tb=short \
-            --log-cli-level=INFO
+        run: just interop
         env:
           LEAN_ENV: test

.github/workflows/prod-vectors.yml

@@ -65,8 +65,10 @@ jobs:
           enable-cache: true
           cache-dependency-glob: "pyproject.toml"
 
-      - name: Sync dependencies
-        run: uv sync --no-progress
+      - name: Install just
+        uses: taiki-e/install-action@v2
+        with:
+          tool: just
 
       - name: Restore prod key cache
         id: key-cache
@@ -87,7 +89,7 @@ jobs:
           key: prod-keys-${{ hashFiles('src/lean_spec/subspecs/xmss/**', 'src/lean_spec/subspecs/poseidon2/**') }}
 
       - name: Fill production test fixtures
-        run: uv run fill --fork=Lstar --scheme prod --clean -n auto
+        run: just fill-ci --scheme=prod
 
       - name: Bundle keys with fixtures
         run: |

CLAUDE.md

@@ -19,7 +19,7 @@ subspecifications that the Lean Ethereum protocol relies on.
 - Use Pydantic models for validation
 - Keep specs simple, readable, and clear
 - Repository is `leanSpec` not `lean-spec`
-- **Always run linter checks before finishing**: Run `uvx tox -e all-checks` at the end of any code changes to ensure all linting, formatting, type checking, and spell checking passes.
+- **Always run linter checks before finishing**: Run `just check` at the end of any code changes to ensure all linting, formatting, type checking, and spell checking passes.
 - **CRITICAL - NO BACKWARD COMPATIBILITY**: This is a STRICT requirement. NEVER add backward compatibility code under any circumstances. This means:
   - NO legacy constants (like `KEY_TYPE_ED25519 = KeyType.ED25519`)
   - NO wrapper functions that delegate to new classes

CONTRIBUTING.md

@@ -5,9 +5,10 @@
 1. Fork and clone the repository
 2. Install dependencies: `uv sync`
 3. Make your changes
-4. Run checks: `uvx tox -e all-checks`
-5. Run tests: `uvx tox -e pytest`
-6. Submit a pull request
+4. Install `just`: `uv tool install just-bin`
+5. Run checks: `just check`
+6. Run tests: `just test`
+7. Submit a pull request
 
 ## Pull Request Guidelines
 
@@ -22,7 +23,7 @@
 - **Type hints**: Required for all functions and methods
 - **Docstrings**: Use Google style for public APIs
 - **Line length**: 100 characters (enforced by ruff)
-- **Formatting**: Run `uvx tox -e fix` to auto-format
+- **Formatting**: Run `just fix` to auto-format
 
 ## Adding New Subspecifications