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fix(acp): server crashed on connect — drop export default, read optional service cwd-independently

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Two independent bugs made the ACP server crash the moment an editor (Zed)
connected, despite 178 green unit tests at 100% coverage:

1. `session/new` threw `cannot get property "agents" without inject`. Root
   cause: a stray `export default apply` made the cordis Loader's
   `unwrapExports` (`exports.default ?? exports`) collapse the module to the
   bare `apply` function, discarding the sibling `inject`/`name`/`Config`
   named exports. The plugin fiber was built with empty `inject`, so every
   `ctx.<service>` read in `apply` threw at load. Fix: remove the default
   export so the Loader uses the namespace.

2. `session/load` threw `cannot get property "sessionPersistence" without
   inject`. `AgentLoop.resume` read `this.ctx.sessionPersistence` (a service
   it deliberately does NOT inject); the property proxy's ancestor-only fiber
   walk fails through the bridge's traceable shadow. Fix: read it via
   `this.ctx.get('sessionPersistence', false)`, the topology-independent
   global-store lookup.

Why the suite missed both: every test mounted the plugin by hand
(`ctx.plugin({name,inject,apply})`), bypassing `unwrapExports` entirely, and
the only test driving these RPCs was key-gated (skipped in CI). Added a no-key
`session/new` e2e that boots the real example through the real Loader — it
fails loudly on bug #1 without an API key. Set `TSX_TSCONFIG_PATH` in the e2e
spawn so the subprocess resolves workspace `paths` from a temp cwd (it was
silently falling back to a stale built `lib/`).

Docs: post-mortem 0001; AGENTS.md "line coverage is not behavior coverage" +
with-key/smoke-test philosophy; packages/AGENTS.md plugin-export-shape and
ctx.get rules; dsh-code-review SKILL checks.
This commit is contained in:
Tianyi Cui
2026-06-18 03:12:37 +08:00
parent a9d5a5ba68
commit 6d37b6c33d
10 changed files with 221 additions and 40 deletions
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# Post-mortems
Incident write-ups: a bug reached a place it shouldn't have (a real user, a merged PR, a release), and the interesting part is *why our process let it through*, not just the one-line fix.
A post-mortem is NOT an [ADR](../adr/README.md) (which records a deliberate decision and its rejected alternatives) and NOT an [RFC](../rfc/README.md) (which proposes future work). It is a backward-looking record of a failure: what broke, the mechanism, why every safety net missed it, and the concrete guardrails added so the same class of bug fails loudly next time.
Write one when a bug is **subtle** (the mechanism is non-obvious and a careful engineer would re-derive it the hard way), **systemic** (the reason it escaped is a gap in tests/tooling/conventions, not a one-off typo), and **costly to rediscover** (it cost real debugging time, and would cost it again). Link the guardrails (tests, AGENTS.md rules, ADRs) the post-mortem motivated.
Every post-mortem opens with an **Executive summary**: one short paragraph a busy reader can absorb in thirty seconds — what broke, the root cause in plain terms, why it escaped, and the durable lesson — before the detailed Summary / Timeline / Root cause / Guardrails sections that follow.
| # | Title |
|---|---|
| [0001](0001-acp-default-export-drops-inject.md) | ACP server crashed on connect: `export default` dropped the plugin's `inject` |