Task: T-0006 Document heru's public API contract in README and docstrings
Stage: accepting
Stage owner: reviewer
Process profile: Python
Task type: -

Workspace context:
# heru — Litehive Workspace Context

Process profile: Python

You are editing **heru**, a unified headless CLI for coding agents
(codex, claude, copilot, gemini, opencode, goz). Read this whole file
before touching any file in this repository.

## Project

- **Purpose:** a thin adapter layer that wraps each supported agent CLI
  behind a uniform Python interface, with a unified `heru <engine>
  <prompt>` command, one JSONL event schema across engines, and one
  resume mechanism. heru is the engine-I/O layer; it knows nothing
  about task queues, stages, orchestration, or sandboxing — those are
  litehive concerns.
- **Main package:** `heru/` (at the repo root, below `.git/`). Public
  API lives in `heru/__init__.py`, `heru/base.py`, `heru/types.py`,
  and each `heru/adapters/<engine>.py`. Anything prefixed with `_` is
  internal.
- **Commands to know:**
  - `uv sync --extra dev` — install heru's own venv
  - `uv run pytest` — heru's standalone test suite
  - `uv run heru <engine> <prompt>` — the CLI (WIP per task T-0002)
  - `cd ~/git/litehive && uv run pytest -q tests/test_runner_workflow.py tests/test_engine_variants_and_timeline.py tests/test_heru_cli.py tests/test_codex_quota.py` — **litehive contract smoke tests; run before every commit**

## Directory layout

```
heru/
├── heru/                  # the Python package
│   ├── __init__.py        # get_engine, ENGINE_CHOICES — PUBLIC
│   ├── base.py            # ExternalCLIAdapter, CLIInvocation, run_live — PUBLIC
│   ├── types.py           # shared pydantic types — PUBLIC
│   ├── main.py            # `heru <engine> <prompt>` CLI entry — PUBLIC
│   ├── _engine_detection.py   # internal
│   ├── _continuation.py       # internal
│   ├── adapters/
│   │   ├── codex.py, _codex_impl.py         # CodexCLIAdapter PUBLIC, _impl internal
│   │   ├── claude.py, _claude_impl.py
│   │   ├── copilot.py, _copilot_impl.py
│   │   ├── gemini.py, _gemini_impl.py
│   │   ├── opencode.py, _opencode_impl.py
│   │   ├── goz.py, _goz_impl.py
│   │   └── common.py      # shared helpers
│   └── quota/             # per-provider quota check helpers — PUBLIC
├── tests/                 # heru's standalone unit tests (no litehive imports)
├── pyproject.toml
├── README.md
└── .litehive/             # this workspace (tasks, state)
```

## Public API surface — do not break without a semver bump

Anything **not** prefixed with `_` is public. Changing the signature,
return type, or behavior of any of the following is a **semver-major**
breaking change that requires a version bump in `pyproject.toml`, a
CHANGELOG entry, and a migration note for litehive:

- `heru.get_engine(name)`, `heru.ENGINE_CHOICES`
- `heru.base.ExternalCLIAdapter` (subclass, don't modify shape)
- `heru.base.CLIInvocation`, `heru.base.CLIExecutionResult`
- Each adapter class: `CodexCLIAdapter`, `ClaudeCLIAdapter`,
  `CopilotCLIAdapter`, `GeminiCLIAdapter`, `OpencodeCLIAdapter`,
  `GozCLIAdapter`
- Every pydantic model in `heru/types.py`
- `heru.main.main` (the CLI entry)

**Internal** (change freely, no semver implications): every
`_`-prefixed module, every private method on public classes, and the
exact text of rendered transcripts.

## Hard rules — do NOT break these

1. **No imports from `litehive`.** heru is a leaf package. One runtime
   dep: `pydantic`. If your diff adds `from litehive …`, stop — the
   code belongs in litehive, not heru.

2. **Do not break litehive.** litehive depends on heru via an editable
   path install, so every heru change propagates immediately. Before
   you finish any stage that touched code, you MUST run:
   ```
   cd ~/git/litehive && uv run pytest tests/test_runner_workflow.py \
       tests/test_engine_variants_and_timeline.py \
       tests/test_heru_cli.py tests/test_codex_quota.py -q
   ```
   If any fail, your change broke the contract. Either fix heru to
   preserve the contract, or explicitly call out the breakage in your
   stage report with a proposed litehive-side migration.

3. **Stage reports are a litehive concept, not heru's.** `StageReport`,
   `StageResultSubmission`, `StageResultTests`, and `TaskUpdateSubmission`
   currently live in `heru/types.py` as a temporary compromise — they
   are slated to move to litehive. Do not add new stage-report logic
   or fields inside heru. If your task requires you to edit stage
   report semantics, flag it back: it is misfiled and belongs in
   litehive.

4. **Tests must be standalone.** No test under `tests/` may import
   from `litehive`. Every heru test must run in a fresh venv with
   only `heru + pydantic + pytest` installed. For JSONL fixtures,
   hand-craft strings or files under `tests/fixtures/` — do NOT
   shell out to real engine CLIs during tests.

5. **Respect the contract tests** (once `tests/contract/` exists per
   T-0007). Changing an assertion in `tests/contract/` is by
   definition a breaking change and requires the full semver
   checklist.

6. **Every new adapter needs both a public class AND a `_impl` helper
   module.** Shape: `adapters/<engine>.py` for the public class,
   `adapters/_<engine>_impl.py` for parsing/quota internals. Keep the
   symmetry — the base class expects it.

## Before you write code — ask yourself

- **Is this a heru concern or a litehive concern?** If you need task
  queues, retries, worktrees, commit pipelines, sandbox profiles, or
  the `STAGE_RESULT:` agent protocol, this is probably litehive.
  Stop and surface the concern in grooming.
- **Does this change the public API?** If yes, note the intended
  semver bump in your report and explicitly list what litehive needs
  to update.
- **Can I write this as a fixture-driven unit test?** If not, your
  code is probably too coupled to the real CLI subprocess — refactor
  to take parsed inputs.
- **Have I run the litehive contract tests?** If not, the task is not
  done, no matter what your implementation report says.

## Relationship to litehive

heru is maintained **alongside** litehive at `~/git/litehive`. They
share a developer (you) and live on the same laptop. litehive depends
on heru via `uv add --editable ~/git/heru`, so every heru save is
immediately visible to litehive without any reinstall.

**If a heru task requires changes in litehive to stay consistent**
(e.g. adding a new adapter method that litehive needs to call), open
a companion task in the litehive workspace referencing this task,
and land the heru side FIRST. Litehive can then safely bump its own
expectations.

## Process overlay
- Source of truth: tasks and implementation state live under `.litehive/`.
- Task source of truth: issues or task records define scope; prompts and transcripts are supporting evidence.
- Orchestrator model: the local runner is the manager and owns stage routing.
- Routing model: routing stays deterministic and local; subagents execute assigned stages but do not self-route.
- Shared stages: grooming -> implementing -> testing -> accepting -> commit_to_git.
- Role model: `planner` frames the task, `reviewer` performs final PM-style acceptance, `swe` edits code, and `qa` runs focused verification.
- TDD expectations: add or update focused tests near the changed Python module before broad suites.
- Verification discipline: prefer targeted `pytest` evidence close to the changed module before broader smoke coverage.
- Acceptance flow: verify behavior with targeted `pytest` coverage and note any residual risk.
- Commit and recovery: keep checkpoint commits deterministic and easy to recover.

## Project overlay
- Python package or application workflow with pytest-oriented verification.
- Favor incremental, reviewable changes over broad refactors.
- Keep implementation, verification, and acceptance evidence explicit.
- Prefer focused `pytest` coverage for the changed modules.
- Keep dependency and packaging changes explicit and minimal.

## Init scaffold
- Scaffold `.litehive/context.md` from the generic base process template.
- Layer the project profile summary, workspace overlay, and stage overlay onto that base.
- Treat process profiles as overlays on the shared contract rather than separate workflows.
- Keep the task/issue source of truth, verification commands, and recovery policy visible in the scaffold.
- Seed Python workspaces with package layout, test entrypoints, and `uv` or virtualenv expectations.

## Prompt scaffold
- Start from the shared process contract, then add repository context and task data.
- Combine the generic base prompt with the selected project overlay instead of replacing the base.
- Apply stage defaults first, then append any project-specific stage overlay for that step.
- Keep stage prompts explicit about role, verification expectations, and final report format.

## Stage prompt scaffolding

### grooming
Act as the planner: clarify the user problem, inspect the repo if needed, and produce a concrete execution plan.
Focus on scope clarification, acceptance criteria quality, decomposition, follow-up tasks, and PM sizing.
Do not make code changes in this stage.

### implementing
Implement the task in this repository.
Keep changes tightly scoped and complete the work needed for the acceptance criteria.
Write tests so each assertion would fail if the feature is broken.
Do not spend test coverage on framework behavior or library guarantees.
Do not add tests that only restate defaults, constants, or static data.
Keep each test focused on one behavior.
Avoid duplicate coverage; extend an existing test only when it is the same behavior.
- Write or update focused tests alongside the code change when feasible.
- Use `pytest` for automated verification.
- Use `tmp_path` or pytest fixtures instead of manual tempfiles in repo code or `/tmp` setup.
- Mock external calls and integration edges, not the internal logic under test.
- Do not use `time.sleep` in tests; use deterministic synchronization or time control.

### testing
Validate the implementation.
Run focused checks or tests where possible and report failures precisely.
Only make minimal fixes if absolutely necessary.
Reject tests whose assertions would still pass if the feature were broken.
Reject tests that duplicate existing coverage instead of covering a new behavior.
Reject tests longer than 50 lines unless a shorter structure is genuinely impossible.
Reject monolithic tests that exercise 5 or more behaviors in one flow.
- Prefer targeted `pytest` invocations before broader test commands.
- Verify new or updated tests use `pytest` idioms and fixtures.
- Reject tests that use manual tempfiles where `tmp_path` would make isolation explicit.
- Reject tests that mock the unit's internal logic instead of external boundaries.
- Reject tests that rely on `time.sleep` instead of deterministic control.

### accepting
Act as the reviewer: validate the end-user outcome against the acceptance criteria and decide whether it should be accepted or sent back.
Be strict about regression detection, evidence quality, and final done versus not-done judgment.

## Python specifics
- Prefer `pytest` for automated verification.
- Keep module boundaries and import hygiene clear.
- Record virtualenv, `uv`, or toolchain expectations when they matter.

## Development rules
- Keep changes scoped to the current task.
- Prefer targeted tests over broad test suites.
- Record assumptions clearly in the final report.

## Tool usage
- Use `uv run pytest -q` for the current smoke test suite.
- Update litehive task artifacts instead of inventing external state stores.
- If you add a new command or workflow, document it here for future runs.

Shared process:
- Orchestrator model: the local runner is the manager and owns stage routing.
- Routing model: routing stays deterministic and local; subagents execute assigned stages but do not self-route.
- Shared stages: grooming -> implementing -> testing -> accepting -> commit_to_git.
- Role model: `planner` frames the task, `reviewer` performs final PM-style acceptance, `swe` edits code, and `qa` runs focused verification.
- Source of truth: tasks and implementation state live under `.litehive/`.
- Task source of truth: issues or task records define scope; prompts and transcripts are supporting evidence.
- TDD expectations: add or update focused tests near the changed Python module before broad suites.
- Verification discipline: prefer targeted `pytest` evidence close to the changed module before broader smoke coverage.
- Acceptance flow: verify behavior with targeted `pytest` coverage and note any residual risk.
- Commit and recovery: keep checkpoint commits deterministic and easy to recover.

Project overlay:
- Python package or application workflow with pytest-oriented verification.
- Favor incremental, reviewable changes over broad refactors.
- Keep implementation, verification, and acceptance evidence explicit.
- Prefer focused `pytest` coverage for the changed modules.
- Keep dependency and packaging changes explicit and minimal.

Prompt scaffold:
- Start from the shared process contract, then add repository context and task data.
- Combine the generic base prompt with the selected project overlay instead of replacing the base.
- Apply stage defaults first, then append any project-specific stage overlay for that step.
- Keep stage prompts explicit about role, verification expectations, and final report format.

Role focus:
- You are the reviewer, a PM-style role representing the user's and product's point of view.
- Validate the strict end-user outcome, look for regressions or missing evidence, and make a final done versus not-done judgment.
- Reject work that is incomplete, weakly verified, or misaligned with the promised outcome.
- If SWE shows the requested work was already implemented before this run and provides concrete verification evidence, accept the task to normal `done` rather than inventing a special closed status.
- Use `wont_do`, `duplicate`, or `deferred` only when the task is genuinely obsolete, superseded, or duplicated.
- You may close a task as duplicate, wont_do, or deferred by including `outcome: <status>` with optional `outcome_reason` in a TASK_UPDATE block. You may park a task with `action: park`.

Stage instructions:
Act as the reviewer: validate the end-user outcome against the acceptance criteria and decide whether it should be accepted or sent back.
Be strict about regression detection, evidence quality, and final done versus not-done judgment.

Goal:
heru is used by litehive and (per the vision) by other callers via 'pip install heru' or 'heru <engine> <prompt>'. Without a clear public API boundary, every identifier looks stable and any change is scary. Explicitly document which classes, methods, functions, and types are part of the stable public contract vs internal (the _prefixed modules, internal helpers, etc). The public contract is what heru commits to preserving across versions. Internal modules can change freely. This makes 'breaking change' vs 'internal refactor' an objective classification.

Acceptance criteria:
- README has an 'API Contract' section listing every stable public name — ExternalCLIAdapter, CLIInvocation, CLIExecutionResult, get_engine, ENGINE_CHOICES, the six adapter classes, the types in heru.types — with a one-line description of what each guarantees
- The same section explicitly marks which modules are internal (any _prefixed module like _codex_impl, _engine_detection, _continuation) and may change without notice
- Each public class and function gets a module-level docstring that calls out its public status and what callers can rely on
- A stability matrix is added showing heru version → what broke in which public API, to establish a track record of semver discipline going forward
- A brief 'how to submit a breaking change' note: semver bump, CHANGELOG entry, migration note for litehive (and any other known consumer)

Plan:
- No plan defined.

PM sizing:
- Current PM complexity: simple
- Current planned effort: s

Constraints:
- Keep changes scoped to the task.


Discussion thread:

--- [2026-04-10T20:16:44+00:00] planner (grooming) — pass ---
Reviewed current repo state for task T-0006.

What I verified:
- README already documents usage, event schema, layout, and litehive smoke-test expectations, but it does not yet have an `API Contract` section or a semver stability matrix.
- Public modules already have partial top-level docstrings, but the acceptance criteria are not met for per-public-class/function contract callouts.
- The stable surface in code is larger than the task text suggests because `heru/__init__.py` exports additional names; documenting the existing export surface is safe, while shrinking or renaming exports would be a breaking change.
- The opencode adapter class is currently named `OpenCodeAdapter` in code and tests, not `OpencodeCLIAdapter`; the implementation should document the current public name rather than rename it under this task.
- Internal modules are clearly discoverable by path (`heru/_*.py`, `heru/adapters/_*_impl.py`) and can be listed explicitly in README as unstable/internal.

Tests run:
- None. Grooming only; no code changes were made.

Implementation plan for the next stage:
1. Add a new `API Contract` section to `README.md` that separates stable public API from internal modules.
2. Enumerate each stable public name that callers are expected to rely on now: `get_engine`, `ENGINE_CHOICES`, `ExternalCLIAdapter`, `CLIInvocation`, `CLIExecutionResult`, `main`, the six adapter classes actually present in code (`CodexCLIAdapter`, `ClaudeCLIAdapter`, `CopilotCLIAdapter`, `GeminiCLIAdapter`, `GozCLIAdapter`, `OpenCodeAdapter`), and the Pydantic models in `heru.types`.
3. Give each listed public name a one-line guarantee focused on stability boundaries, not implementation detail.
4. Add an internal-module subsection that explicitly marks `_engine_detection`, `_continuation`, and each `_..._impl.py` module as private and changeable without notice.
5. Add a small stability matrix seeded with `v0.1.0` and a “no documented breaking public API changes yet” entry so future releases have a place to record semver history.
6. Add a short breaking-change submission note requiring a semver bump, CHANGELOG entry, and migration note for litehive/other consumers.
7. Update docstrings in `heru/__init__.py`, `heru/base.py`, `heru/main.py`, `heru/types.py`, and each public adapter module/class/function so they explicitly state public status and what callers may rely on.
8. Add focused tests that assert the README contains the API Contract section and that the targeted public modules/classes/functions carry the new public-status docstrings.
9. Run targeted heru pytest coverage for the new documentation/docstring assertions, then run the required litehive smoke suite before handing off.

Scope/acceptance clarification:
- Treat this as documentation and docstring work only. Do not rename exports or reduce `__all__` in this task.
- Where the task text says `OpencodeCLIAdapter`, implement against the actual current public class name `OpenCodeAdapter` unless product explicitly wants a semver-major rename task.

TASK_UPDATE:
  plan:
    - Add a README API Contract section that lists stable public names and internal modules.
    - Document the current exported adapter name `OpenCodeAdapter` instead of renaming it in this task.
    - Add public-status docstrings to the documented modules/classes/functions.
    - Add focused pytest coverage for the new README/docstring contract text.
    - Run heru-targeted tests and the required litehive smoke suite.
  pm_complexity: simple
  planned_effort: s

--- [2026-04-10T20:22:48+00:00] swe (implementing) — pass ---
Implemented T-0006 as scoped documentation and docstring work only. Added a new README API Contract section that lists the stable public surface: get_engine, ENGINE_CHOICES, heru.main.main, ExternalCLIAdapter, CLIInvocation, CLIExecutionResult, the six current adapter classes (including the current exported OpenCodeAdapter name), and all public pydantic models in heru.types with one-line guarantees. The same section now explicitly marks heru._engine_detection, heru._continuation, and each heru.adapters._*_impl module as internal/changeable without notice, adds a stability matrix seeded with v0.1.0, and documents the required breaking-change process (semver-major bump, CHANGELOG entry, migration note for litehive/other consumers). Updated module/class/function docstrings in heru/__init__.py, heru/base.py, heru/main.py, heru/types.py, and each public adapter module so the public status and caller-reliable contract are called out inline. Added focused regression coverage in tests/test_api_contract_docs.py that asserts the README contract section contains the required public/internal entries and that the targeted public modules/classes/functions have public-contract docstrings. Verification: uv run pytest -q tests/test_api_contract_docs.py -> 2 passed; uv run pytest -q tests/test_heru_cli.py tests/test_base_direct.py -> 48 passed; required litehive smoke suite from ~/git/litehive (tests/test_runner_workflow.py tests/test_engine_variants_and_timeline.py tests/test_heru_cli.py tests/test_codex_quota.py -q) -> 197 passed, 3 unrelated Typer deprecation warnings. This meets the acceptance criteria without changing the exported API shape.
Files: README.md, heru/__init__.py, heru/base.py, heru/main.py, heru/types.py, heru/adapters/codex.py, heru/adapters/claude.py, heru/adapters/copilot.py, heru/adapters/gemini.py, heru/adapters/goz.py, heru/adapters/opencode.py, tests/test_api_contract_docs.py

--- [2026-04-10T20:24:37+00:00] qa (testing) — pass ---
Verified the implementation against the T-0006 acceptance criteria. I inspected the scoped diff in README.md, heru/__init__.py, heru/base.py, heru/main.py, heru/types.py, and the six public adapter modules, and confirmed the change is documentation/docstring-only with no public API shape changes. README now includes an API Contract section that lists the stable public names called out by the task: get_engine, ENGINE_CHOICES, heru.main.main, ExternalCLIAdapter, CLIInvocation, CLIExecutionResult, the six current adapter classes (including the currently exported OpenCodeAdapter name), and the public heru.types models with one-line guarantees. The same section explicitly marks internal modules such as heru._engine_detection, heru._continuation, and heru.adapters._*_impl as unstable, adds a stability matrix seeded with v0.1.0, and documents the breaking-change process requiring a semver-major bump, CHANGELOG entry, and migration note for litehive/other consumers. I also verified the new focused regression test in tests/test_api_contract_docs.py is meaningful rather than trivial: it asserts the README contains the required public/internal entries and parses the source AST to ensure the targeted public classes/functions have explicit public-contract docstrings. Independent verification run: uv run pytest -q tests/test_api_contract_docs.py -> 2 passed; uv run pytest -q tests/test_heru_cli.py tests/test_base_direct.py -> 48 passed; required downstream contract suite from ~/git/litehive, uv run pytest tests/test_runner_workflow.py tests/test_engine_variants_and_timeline.py tests/test_heru_cli.py tests/test_codex_quota.py -q -> 197 passed, with 3 unrelated Typer deprecation warnings. Acceptance criteria are satisfied and I found no regressions.

IMPORTANT: When you are done, you MUST submit your verdict by running:
  litehive report --verdict <pass|reject> --role reviewer --step accepting --message "<your report>"
The environment variable LITEHIVE_TASK_ID is set to T-0006 for this session. Workspace and task resolution should use the injected environment automatically.

Your --message is the PRIMARY way the next agent understands what happened.
Do NOT rely on your raw transcript being read — write the report as if it is the only thing the next agent will see.

Report requirements:
- On PASS/ACCEPT: explain what you verified, what tests you ran, what evidence confirms the acceptance criteria are met.
- On REJECT: you MUST include ALL of the following:
  1. EXPECTED behavior: what should happen according to the acceptance criteria
  2. OBSERVED behavior: what actually happens (exact error messages, test output, wrong values)
  3. Steps to reproduce: the exact command or test that demonstrates the gap
  4. Which acceptance criteria are not met and which ones are already satisfied

A vague rejection like 'tests fail' or 'missing evidence' is useless and causes infinite loops.
A good rejection looks like: 'Expected: `litehive engine gemini` switches the default engine and prints confirmation. Observed: command exits 0 but config.yaml still shows the old engine. Reproduce: run `litehive engine gemini` then `cat .litehive/config.yaml`. Criteria 1-3 are met, criterion 4 (persistence) is not.'
