PDFToMD/phases/2-marker-adapter/step0.md

Step 0: marker-invocation-adapter

Read First

• /AGENTS.md
• /PLAN.md
• /PROGRESS.md
• /docs/HARNESS.md
• /docs/IMPLEMENTATION_PLAN.md
• /docs/ARCHITECTURE.md
• /docs/TOOLCHAIN.md
• /phases/1-core-runtime-contracts/index.json

Task

Implement the first Marker adapter boundary that invokes Marker through a small internal interface.

Keep this adapter isolated so tests can use fakes without loading large models. Real Marker invocation should be smoke-testable but not required for every unit test.

Sprint Contract

• Done means: Marker invocation is behind a narrow interface and can return structured parse results or clear failures.
• Hard thresholds: Marker remains the primary document parser; Nougat is not used here; unit tests avoid mandatory model downloads; parser errors are structured.
• Files owned: src/pdftomd/marker_adapter.py, related tests, PROGRESS.md, phases/2-marker-adapter/index.json.
• Dependencies: Phase 1 runtime contracts.

Acceptance Criteria

python scripts\validate_workspace.py
.\venv\python.exe -m pytest tests

Verification

1. Run the acceptance commands.
2. Confirm the adapter can be tested without external services.
3. Update PROGRESS.md and this phase index.

Do Not

• Do not parse formulas with Nougat.
• Do not implement Markdown rendering.
• Do not make every test load Marker models.