# Step 3: parser-foundation

## Sprint Contract

### Objective
Implement the Abaqus input lexical/keyword parser foundation plus Factory + Registry plumbing for Phase 1 objects.

### Required Reading
- /AGENTS.md
- /PROGRESS.md
- /PLAN.md
- /docs/README.md
- /docs/HARNESS_ENGINEERING.md
- /docs/ARCHITECTURE.md
- /docs/ADR.md
- /docs/ABAQUS_INPUT_SUBSET.md
- /phases/1-linear-static-mitc4/step2.md

### Scope
- Tokenize Abaqus keyword lines, parameters, data lines, comments, continuations if documented, and source locations.
- Add a parser result shape that returns Domain data or diagnostics.
- Add keyword Factory + Registry structure without completing every Phase 1 keyword.
- Add smoke parsing for a tiny supported subset such as `*Node` and `*Element, TYPE=S4`.

### Allowed Files
- `include/**`
- `src/**`
- `tests/**`
- `PLAN.md`
- `PROGRESS.md`
- `phases/1-linear-static-mitc4/index.json`

### Explicit Non-Goals
- Do not complete all Phase 1 Abaqus keywords in this step.
- Do not silently accept unsupported keywords or unknown parameters.
- Do not parse `quad_01.inp` as a supported Phase 1 case.

### Tests To Write First
- Lexer tests for keyword names, parameters, comments, blank lines, and source locations.
- Registry tests for supported and unsupported keyword dispatch.
- Parser smoke tests for minimal nodes and S4 elements.

### Reference Artifacts
- None. Existing `references/quad_01.inp` is not a Phase 1 parser acceptance case.

### Acceptance Commands
```bash
python scripts/validate_workspace.py
```

### Evaluator Checklist
- Unsupported input produces diagnostics with line context.
- Factory + Registry is present and parser logic is not hardwired into Domain constructors.
- Parser tests do not expand Phase 1 support beyond `docs/ABAQUS_INPUT_SUBSET.md`.

### Handoff Requirements
- Record progress and validation in `PROGRESS.md`.
- Update `PLAN.md` if parser-scope risks change.
- Update the matching phase index entry: use `completed` with a one-line `summary`, or `blocked` with `blocked_reason`, or `error` with `error_message`.

## Verification
1. Run the acceptance command.
2. Inspect parser tests for line-numbered diagnostic coverage.

## Do Not
- Do not normalize away Abaqus labels that later diagnostics or references need.