DocForge2/docs/COMPATIBILITY.md

# DocForge2 Milestone 0 compatibility contract

Milestone 0 establishes DocForge2 as the successor repository without renaming or replacing the
working DocForge interfaces. Compatibility changes require an explicit decision, a contract-test
update, and migration guidance.

The compatibility gate is:

```bash
make contract
```

The complete repository gate is:

```bash
make gate
```

## Distribution and Python imports

The Python distribution and import package remain `docforge`.

The installed executable names remain:

- `docforge`
- `docforge-mcp`
- `docforge-viewer-manager`

The top-level imports recorded by `docforge.__all__` remain supported. The documented adapter,
model, index, rendering, application, and MCP factory names imported from these submodules also
remain supported:

- `docforge.adapter_contract`
- `docforge.application`
- `docforge.index`
- `docforge.mcp_server`
- `docforge.models`
- `docforge.policy`
- `docforge.render_contract`

Names beginning with an underscore are implementation details. New public names may be added
without breaking this contract.

## CLI and MCP surfaces

Existing `docforge` command names and arguments remain supported. Existing `docforge-mcp` tool
names and arguments remain supported. Additive commands, tools, and response fields are allowed.
Removing or changing an existing name, required argument, stable error code, or safety boundary
requires an explicit compatibility decision.

MCP results retain:

- A structured `status`.
- Project and source identity when available.
- Stable structured domain errors.
- A bounded content warning.
- Staleness information.
- The configured output-size limit.

The result schema describes the common envelope. Operation-specific fields are additive and remain
bounded by the configured tool-output limit.

## Versioned data contracts

Milestone 0 preserves:

- Project descriptor schema version 1.
- Node schema version 1.
- Edge schema version 1.
- Changeset schema version 1.
- Result-envelope schema version 1.
- SQLite index schema version 3. Version 2 indexes remain disposable and automatically rebuild;
  version 3 adds a source-ordered incoming-edge index for bounded impact traversal.
- Index-attestation schema version 1.
- Incremental extraction-cache schema version 1.
- Effective process-policy schema version 1. The project descriptor remains schema version 1;
  machine-specific capability selection is a startup binding, not canonical project content.
- Read-pagination schema version 1. Existing tool names and required arguments are unchanged.
  Context and changeset MCP reads accept optional limits and opaque generation-bound cursors.
  Direct Python changeset methods and the ordinary CLI context command retain full legacy results
  when pagination is not requested.

Indexes, attestations, extraction caches, previews, and rendered artifacts are disposable. A schema
change may rebuild them. Canonical project content and stored proposals may not be silently
rewritten to satisfy a new implementation.

## Adapter compatibility

An adapter implementing only:

```python
load_projection()
```

remains first-class. Incremental manifests, source extraction, deterministic assembly, Logic
projection, and proposal or application support are optional capabilities. Incremental adapters
must retain `load_projection()` as their independent clean-build and equivalence oracle.

Project adapters remain explicitly composed. Generic DocForge does not discover arbitrary adapter
modules or choose a project globally.

## Preserved no-AST binding

`docforge-mcp --project-root /project --no-ast` is a stable shorthand for the
`preserve-no-ast` binding policy.

The binding:

- Keeps one-method complete-projection adapters working.
- Keeps non-AST incremental fingerprinting and caching working.
- Rejects nonempty function-Logic publication.
- Rejects a pre-existing index containing function Logic.
- Blocks `docforge_get_logic`.
- Prevents the live viewer from pinning an index containing Logic.
- Applies the same restriction during hash-bound canonical-application refresh.
- Reports the effective policy through bootstrap and contract results.

The legacy `adapter_policy` payload and error codes remain unchanged. The version-1
`effective_policy` is additive and makes precedence, capability mode, render behavior, blocked
tools, and prohibitions machine-readable.

DocForge does not inspect arbitrary adapter source to prove which parser implementation it uses.
The no-AST binding is an owner-selected process policy backed by Logic publication and retrieval
enforcement. It is not a filesystem sandbox and cannot stop an unrelated process with repository
write access from changing adapter code.

## Changesets and application

The following guarantees remain stable:

1. Registration writes one complete proposal atomically.
2. Proposal identity includes its project, root, base revision, canonical source hash, writer, and
   ordered operations.
3. Validation and diff inspection precede application.
4. Append, rebase, abandonment, and application use exact current hashes.
5. Stale, conflicting, unauthorized, unsafe, or invalid proposals fail closed.
6. Canonical application is absent unless one startup-bound applier is configured.
7. Derived refresh failures produce an explicit degraded receipt after canonical application. They
   do not make an applied proposal safe to apply twice.

## Rendering and visualization

The `generic_html` renderer remains the supported version-1 manual projection. It retains confined
paths, raw-HTML suppression, fixed template tokens, deterministic identities, atomic replacement,
and side-effect-free status.

The live graph viewer remains a read-only consumer of a generation-pinned validated index. It does
not become project authority or MCP retrieval authority.

## Task-context compatibility

`docforge_get_task_context` is an additive MCP read tool. The legacy `docforge_get_context`
signature, profile compiler, direct Python results, and custom three-argument context-provider
contract remain unchanged.

The new `ContextCapsuleV1` and `RetrievalPlanV1` types live in the public
`docforge.retrieval` submodule. Version 1 guarantees:

- A closed task-kind vocabulary and core-derived plan. Callers cannot inject arbitrary operations,
  SQL, paths, relations, or Logic requests.
- One immutable index transaction and one exact project, adapter, revision, source, policy,
  request, plan, collection, and capsule identity.
- Deterministic bounded focus, traversal, hydration, token accounting, response packing, and
  continuation, with fixed version-1 ceilings of 1,000 evidence items, 100,000 candidate edges, and
  10,000 task-query characters.
- Raw preservation of project-owned relation names. Only the documented versioned alias map gains
  task semantics; all other relations remain `unclassified`.
- Separate missing, incomplete, blocked, and provenance-limitation evidence.
- No-AST bindings retain task context but never add a Logic retrieval step or weaken the existing
  Logic prohibition.

An integration that replaces the legacy context provider does not silently receive the core task
planner. Version 1 has no custom task-planner protocol. The task-context tool remains registered
for additive name compatibility but returns `task_context_unavailable` without loading or
synchronizing the custom projection.

The exact version-1 relation aliases are frozen by the MCP contract and repository contract tests.
Changing an alias category requires a new planner version; it is not a silent implementation
detail.

`ManualRenderPlan`, `GraphViewPlan`, a portable graph renderer, and independently packaged
renderers are later-milestone direction. Milestone 0 does not claim that those contracts exist.

## Safety boundary

DocForge remains bound to one explicit project root. It rejects absolute paths, root escapes, and
symbolic-link escapes. Documentation text remains untrusted data. Normal MCP operation exposes no
arbitrary filesystem access, renderer execution, shell command, Git mutation, deployment,
publication, or project switching.

## Recorded weaknesses, not compatibility promises

Milestone 0 records rather than redesigns these areas:

- Generic warm reads still repeat whole-project discovery, parsing, and validation.
- Tree-sitter and the JavaScript and C++ grammars remain mandatory installation dependencies even
  when their runtime modules are unused.
- Several version strings and defaults remain duplicated.
- One individually oversized context entry is represented as explicit bounded omission evidence;
  callers use targeted retrieval for that node.
- One individually oversized changeset diff is transported as reconstructable canonical-JSON
  chunks. Cursors are corruption-detecting read tokens, not authenticated authorization tokens.
- Manual planning is not separated from rendering.
- There is no portable graph-planning or graph-rendering contract.
- DocForge2 does not self-host its bootstrap documentation.