simplify(seams): prune dead methods from the persistence and bash seams

Two capability seams carried abstract methods no production consumer calls.
A method no consumer programs against is not a seam — it is speculative
surface every implementation must still provide and test.

- SessionPersistence: remove has() and delete(), the coordinator's
  has/delete/deleteCore, and the PersistenceBackend.deleteStored hook (with its
  jsonl + sqlite + in-spec memory-stub impls). Surviving service surface:
  create/append/load/list. Production uses only load() (resume) and list()
  (ACP session/list).
- BashExecutor: remove get(id) and list(), the abstract decls and the
  LocalBashExecutor impls. The internal tasks map survives (it backs
  ownerOf/readOutput/kill); get/list were pure public accessors over it with no
  shipping caller and no bash_list tool.
- Migrate tests that reached through ctx.bash.get(id) to the public completion
  seam: a doneFor(id) helper over onTaskDone awaits a task by id, and the
  HMR-reload ownership test now proves task survival through A's own bash_output
  ([status: running]) plus ownerOf + B-rejection — a stronger through-the-tool
  assertion than the removed lookup peek.
- Update seam READMEs (six -> four service methods, drop the deleteStored hook
  and the get/list row) and the two implemented persistence RFCs in place.

Implements docs/rfc/implemented/simplification/2026-06-20-prune-dead-seam-methods.md
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Tianyi Cui
2026-06-21 02:17:27 +08:00
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# RFC: Prune dead methods from the persistence and bash capability seams
Status: implemented (proposed and accepted 2026-06-20)
## Problem
Two capability seams ([interface / implementation / consumer](../../implemented/architecture/2026-06-13-capability-seams.md)) carry abstract methods that no consumer calls. The seam exists to let implementations and consumers evolve independently — but a method no consumer programs against is not a seam, it is speculative surface every implementation must still implement and test.
### `SessionPersistence.has()` and `.delete()`
The abstract service declares four operations beyond create/append: `load`, `list`, `has`, `delete` ([packages/session-persistence/session-persistence/src/index.ts:142-151](../../../../packages/session-persistence/session-persistence/src/index.ts)). Production consumers of `ctx.sessionPersistence` use only two of them: the agent-loop resume path calls `load()` ([packages/core/agent-loop/src/index.ts:176-194](../../../../packages/core/agent-loop/src/index.ts)), and the ACP bridge calls `list()` for `session/list` ([packages/ui/acp/src/index.ts](../../../../packages/ui/acp/src/index.ts)). Grepping every `sessionPersistence.*` / `persistence.*` use across `packages/*/src` and `examples/` finds no `has(` and no `delete(` on the service. The `.has(`/`.delete(` calls in `packages/ui/acp/src/index.ts` are on the in-memory `SessionStore` and a local `Set` of loading ids, not persistence. The only callers of `has`/`delete` are the contract suites and per-backend specs.
`has()` is not just unused — it is the most intricate branch in the shared coordinator: a tracked-vs-untracked dual-probe (`loadLive(id, cwd)` for a live-tracked session vs `loadStored(id)` for an untracked one) with a multi-line rationale ([packages/session-persistence/session-persistence/src/coordinator.ts:298-310](../../../../packages/session-persistence/session-persistence/src/coordinator.ts)). `delete()` drags the `deleteStored` backend hook ([coordinator.ts:99](../../../../packages/session-persistence/session-persistence/src/coordinator.ts), [coordinator.ts:313-319](../../../../packages/session-persistence/session-persistence/src/coordinator.ts)) that every backend must implement. This is the [drop-mutable-session-summary](../../implemented/simplification/2026-06-19-drop-mutable-session-summary.md) pattern: a contract test exercises both, but no shipping code asks "is this session persisted?" or removes one.
### `BashExecutor.get()` and `.list()`
The bash seam declares `get(id)` ("look up a background task by id") and `list()` ("all tracked background tasks") ([packages/bash/bash/src/index.ts:88-107](../../../../packages/bash/bash/src/index.ts)), both implemented by `LocalBashExecutor` ([packages/bash/bash-local/src/index.ts:179-191](../../../../packages/bash/bash-local/src/index.ts)). The sole production consumer — `dsh-tool-bash` — drives tasks via `ownerOf`, `onTaskDone`, `start`, `readOutput`, `kill`, `resolve`, `run`; it never calls `get`/`list` in shipping code, and there is no `bash_list` tool exposing a task roster to the model. So both are dead production seam surface. They are used by tests, more broadly than a single idiom: the bash seam/executor specs assert them directly ([packages/bash/bash/tests/service.spec.ts](../../../../packages/bash/bash/tests/service.spec.ts), [packages/bash/bash-local/tests/executor.spec.ts](../../../../packages/bash/bash-local/tests/executor.spec.ts) both call `get()`/`list()`), and several `dsh-tool-bash` tests reach through `ctx.bash.get(id)` to await a task's `done`, read its `status`, or inspect task fields ([packages/bash/tool-bash/tests/tools.spec.ts](../../../../packages/bash/tool-bash/tests/tools.spec.ts), [packages/bash/tool-bash/tests/integration.spec.ts](../../../../packages/bash/tool-bash/tests/integration.spec.ts)). These are test-harness conveniences, not shipping consumers — but they are real test code an implementing PR must migrate or delete.
## Proposal
Remove the methods nothing consumes, from the abstract seam, the implementation, and the contract/spec suites that exist only to exercise them:
- `SessionPersistence.has()` / `.delete()`: delete the abstract declarations, the coordinator's `has`/`delete`/`deleteCore`, and the `PersistenceBackend.deleteStored` hook. Remove the `has`/`delete` rows from the contract suite and the per-backend specs (jsonl + sqlite each implement `deleteStored` only to satisfy the hook — that implementation goes too). The backends are the [dual-backend](../../implemented/architecture/2026-06-14-session-persistence.md) design and otherwise out of scope, but removing a hook they implement for no consumer is part of removing the hook, not a backend redesign.
- `BashExecutor.get()` / `.list()`: delete the abstract declarations and the `LocalBashExecutor` impls. The seam/executor specs that assert `get()`/`list()` directly (`bash/tests/service.spec.ts`, `bash-local/tests/executor.spec.ts`) lose those assertions (the behavior is being removed). The `dsh-tool-bash` tests that reach through `ctx.bash.get(id)` to await `done`, read `status`, or inspect task fields switch to the public completion/status seam they should use — `onTaskDone` (or the `done` promise and status the `start()` return already exposes) — keeping their coverage without the removed lookup method.
- Update every doc and source-comment reference to the removed methods — not only literal `has(`/`delete(`/`get(`/`list(`/`deleteStored` call spellings, but also `{@link has}`/`{@link delete}` JSDoc links and prose that counts the methods (removing 2 of the persistence service's 6 public methods makes any "six public methods" phrasing wrong). The implementing PR greps `has`/`delete`/`get`/`list`/`deleteStored`/`{@link `/`six ` across `docs/`, `packages/*/README.md`, and source comments, and fixes each. The known doc sites: the seam READMEs ([packages/session-persistence/session-persistence/README.md](../../../../packages/session-persistence/session-persistence/README.md)'s `has(id)`/`delete(id)` API row and its "delegates its six public service methods" prose → four, [packages/bash/bash/README.md](../../../../packages/bash/bash/README.md)'s `get(id)`/`list()` row), the backend READMEs that describe `has`/`list` semantics ([packages/session-persistence/session-persistence-sqlite/README.md](../../../../packages/session-persistence/session-persistence-sqlite/README.md), [packages/session-persistence/session-persistence-jsonl/README.md](../../../../packages/session-persistence/session-persistence-jsonl/README.md) — reword "absent from `has()`/`list()`" to just `list()`), the service-map / seam docs in [docs/architecture.md](../../../architecture.md), and the persistence prose in the [session-persistence RFC](../../implemented/architecture/2026-06-14-session-persistence.md) and [shared write-coordinator RFC](../../implemented/architecture/2026-06-18-shared-persistence-write-coordinator.md). The known source-comment sites: the abstract `create()` JSDoc's `{@link has}/{@link list}` link ([packages/session-persistence/session-persistence/src/index.ts](../../../../packages/session-persistence/session-persistence/src/index.ts) — drop the `has` link), the coordinator's "six public methods"/"six public service methods" module + class JSDoc and its lazy-materialization JSDoc justifying the `materialized` flag by "the signal `has`/`list` rely on" ([packages/session-persistence/session-persistence/src/coordinator.ts](../../../../packages/session-persistence/session-persistence/src/coordinator.ts)), the JSONL backend's `loadStored`/`deleteStored` comment, and the SQLite backend's `schema.ts` and `index.ts` comments that mention "absent from `has`/`list`" — all reworded to the surviving four-method, `list()`-only contract.
## Why not keep them as "the seam should be complete"?
The instinct that a persistence seam "should" offer delete, or a task executor "should" offer enumeration, is real — and it is exactly the speculative-completeness the pre-release stance warns against ([AGENTS.md](../../../../AGENTS.md): optimize for the correct foundation, not for hypothetical callers you do not have). Each of these is one method to re-add the day a consumer needs it:
- A session-management UI that deletes old sessions will want `delete()` — add it then, designed against that UI's real needs (soft-delete? cascade? confirmation?), not guessed now.
- A `bash_list` tool that shows the model its running tasks will want `list()` — add it with the tool.
Re-adding a seam method with a live consumer is cheap and better-designed than the speculative version, because the consumer pins the contract. Carrying it unused means every implementation (and every future backend) must implement and test a method that does nothing.
## Acceptance criteria
- `has`/`delete`/`deleteStored` and `get`/`list` are gone from their seams, impls, and contract suites; `pnpm run knip` reports no new dead exports.
- The remaining seam operations (`create`/`append`/`load`/`list` for persistence; `run`/`start`/`ownerOf`/`onTaskDone`/`readOutput`/`kill`/`resolve` for bash) are untouched; ACP `session/list`, bash tool flows, and crash-recovery behave identically.
- `pnpm run test:coverage` stays 100% per-file (the contract/spec rows for the removed methods are deleted with them).
- Seam READMEs and `docs/architecture.md` no longer list the removed methods.
## Risks
- **`delete()` is the kind of operation a product eventually wants.** True — but "eventually" is the point. Deleting it now and re-adding it against a real consumer is strictly better than shipping a guessed contract. The dual backends each shed a `deleteStored` impl, which is a bounded edit in otherwise-out-of-scope packages.
- **`list()` on the bash seam is the natural seed for a future `bash_list`.** Acknowledged in the [pre-release foundation stance](../../../../AGENTS.md): add the seed when the tool lands. The executor still tracks tasks internally (the `tasks` map backs `ownerOf`/`readOutput`/`kill`); exposing an enumeration is a one-line re-add.
- **Low coupling.** Both removals are confined to their seam + impl + tests; no cross-package consumer references the removed methods, so there is no ripple beyond the docs.
Modest size, but it converts two seams from "what an implementation must provide for nobody" back to "exactly what a consumer uses."