Fix /history on async saver + 3 config diagnostics (0.6.28: #106, #107, #108, #109)

[dkedar7]

Ships 0.6.28 fixing four cli-local issues in one release. One regression test per issue; full suite green; ruff check + ruff format --check clean.

#106 (bug, regression from #102) — /history throws "Event loop is closed"

In the shipped persist-on default the durable checkpointer is the async-only AsyncSqliteSaver, opened inside each turn's own event loop and closed when the turn ends. cmd_history read state via the sync graph.get_state, which against that async, already-closed saver scheduled aget_tuple as a never-awaited coroutine and surfaced Could not retrieve history: Event loop is closed + a RuntimeWarning — every user hit it (only --no-persist worked). Now reads through the async API (aget_state) on a freshly-opened saver over the same SQLite file, mirroring the run loop; the sync path still serves the in-memory case.

#107 (bug) — --show-config mislabels the source of DEEPAGENT_SPEC

A value set via the oldest legacy alias DEEPAGENT_SPEC was labelled [env:DEEPAGENT_AGENT_SPEC] — the canonical-legacy key the resolver copies it onto, absent from the environment, contradicting the command's own stderr note. The [source] column now reports [env:DEEPAGENT_SPEC] (re-attributed in CodeConfig.resolve, same class of fix as #101/#20).

#108 (enhancement, finishes #102 item 3) — --show-config never surfaced persist/session config

Persistence was visible only in interactive /status. --show-config now shows the resolved persist value with its [source], the (env: LANGSTAGE_PERSIST, toml: session.persist) hint, and the store path when on — in both on and off states, so the off-switch is verifiable. Interactive /config appends the identical block so the two can't diverge.

#109 (bug) — blank, typeless Error: on an empty-message load exception

A bare assert / raise NotImplementedError / RuntimeError() has an empty str(e), so the top-level handlers printed just Error:. They now name the exception class (Error: NotImplementedError) and point at -v, matching the runtime turn-error path.

Tests

• tests/test_history_persist.py (/history is broken in the default (persist-on) config: "Could not retrieve history: Event loop is closed" + unawaited-coroutine warning — cmd_history calls sync get_state on an async AsyncSqliteSaver #106), tests/test_load_error.py (A load/top-level exception whose str(e) is empty prints a blank, typeless Error: — no exception class, no -v hint (inconsistent with the runtime turn-error path) #109), and new tests/test_show_config.py cases (--show-config mislabels the source of DEEPAGENT_SPEC as [env:DEEPAGENT_AGENT_SPEC] — a var the user never set (contradicts its own deprecation note) #107, --show-config never surfaces the persist/session config — only interactive /status does (leaves #102 item 3 half-done) #108). Each verified to fail pre-fix and pass post-fix.
• Tightened two over-broad "stream_mode"/"async_mode" not in output substring checks (they now trip on the sessions_store path, which under pytest embeds the test name) to precise line checks.

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https://claude.ai/code/session_011HWCfJii6gXd3XL3Gq3W8B