[Plugin] dsh-session-integrity: diagnose and safely continue poisoned sessions

[DON738110198]

I built dsh-session-integrity, a zero-dependency Cordis plugin and offline CLI for diagnosing provider-visible Session defects and continuing from a provider-safe boundary without rewriting history.

The original target is the failure family discussed in #3524: an assistant tool request becomes durable, but the model-visible surface has no matching tool result. A closed error turn can then survive tail repair, so later provider requests keep rejecting the same transcript. The bilingual README now explains that full failure chain, why dispatched calls are outcome-unknown, and why blind retries can duplicate external side effects:

• English: https://github.com/DON738110198/dsh-session-integrity#the-problem
• 简体中文: https://github.com/DON738110198/dsh-session-integrity/blob/main/README.zh-CN.md#问题是什么

v0.2.1: safe recovery MVP

• A Continue from here action appears on historical assistant messages in the Web UI.
• It calls the official Session fork operation at that message sequence, opens the child Session, and keeps the source Session unchanged.
• It refuses to fork while the source turn is running.
• The offline recover command finds the latest completed provider-safe prefix and emits a redacted plan.
• Live integrity warnings can include a redacted recovery hint.

This deliberately does not implement in-place rollback, hard delete, automatic archive, tool retry, or rollback of external side effects. Hard deletion needs an explicit core persistence/API policy rather than a browser-only workaround.

Install

dsh plugin --profile web add github:DON738110198/dsh-session-integrity#v0.2.1
dsh --profile web --dump-config
dsh --profile web

Offline diagnosis and recovery planning:

dsh plugin --profile web exec dsh-session-integrity scan ./session.jsonl
dsh plugin --profile web exec dsh-session-integrity recover ./session.jsonl
dsh plugin --profile web exec dsh-session-integrity recover ./session.jsonl --at 120 --json

Verification

• 23 focused tests pass across analysis, recovery, JSONL input, CLI behavior, plugin lifecycle, and browser action behavior.
• JavaScript syntax checks and package checks pass.
• The packed tarball installs into an isolated dsh-v0.1.0-rc.8 Web profile.
• In the full profile smoke, the host plugin is active, the boot manifest contains dsh-session-integrity with its declared dependencies, and the served client bundle registers the recovery action.

Repository and bilingual docs: https://github.com/DON738110198/dsh-session-integrity
Release: https://github.com/DON738110198/dsh-session-integrity/releases/tag/v0.2.1

The separate core patch for the new-session write path remains linked from #3524. Detection/recovery and prevention are intentionally kept as distinct review surfaces; that core proposal has not been merged upstream.