chat.message plugin hook: SyncEvent.run: "sessionID" required but not found when pushing to output.parts

OpenCode version: 1.14.18

Plugins that push a text part to output.parts from inside a chat.message hook intermittently crash with:

error: SyncEvent.run: "sessionID" required but not found: {"part":{"type":"text","text":"..."},"time":<epoch>}
    at wl (/$bunfs/root/chunk-ng0j12f1.js:491:37371)
    at ~effect/Effect/evaluate (/$bunfs/root/chunk-3p3b82m7.js:25:4492)
    at runLoop (/$bunfs/root/chunk-3p3b82m7.js:25:2045)

Repro shape (simplified):

"chat.message": async (_input, output) => {
  const ctx = await fetch("https://example/api");  // ~1–3s network call
  output.parts.push({ type: "text", text: await ctx.text() });
}

Synchronous pushes appear fine; pushes after an await (network fetch here) race a closed session scope and SyncEvent.run fails because the emitted part has no sessionID.

Related:

chat.message hook output not visible when plugin injects into output.parts code-yeongyu/oh-my-openagent#885 — same hook + output.parts path silently fails to render on 1.0.150+. Different symptom (silent) vs. this one (hard crash), same fragile contract.
Feature: Include user message text in experimental.chat.system.transform input #17637 — feature request to expose user message in experimental.chat.system.transform, which would let plugins skip chat.message entirely for per-turn injection.
Feature: Add sessionID to experimental.chat.system.transform hook for tracing integration #6142 — related sessionID-propagation ask.

Questions:

Is pushing to output.parts in chat.message a supported API? (It's absent from the official plugin docs.)
If yes, should OC capture sessionID at hook-dispatch and attach it to pushed parts so they survive async resumption?
If no, what's the intended hook for injecting a per-turn text cue based on the user's message? (Feature: Include user message text in experimental.chat.system.transform input #17637 is the only current avenue and it lacks the user text.)

Happy to provide the full failing plugin source if useful.

We encountered exactly this. Beyond the sessionID crash: in some OpenCode builds, chat.message doesn't fire at all — the trigger("chat.message", ...) call site is missing from the session processor entirely. We loaded a plugin with a chat.message hook, the plugin loaded without errors ("loading plugin" in logs), but the hook was never called.

Workaround: use the event hook instead. Listen for message.part.updated bus events:

event: async ({ event }) => {
  if (event.type === "message.part.updated") {
    const text = event.properties.part.text
    // text has the full part content for TextPart/ReasoningPart
  }
}

Also: Bun's fetch() ignores tls: { rejectUnauthorized: false }. Use new https.Agent({ rejectUnauthorized: false }) from node:https for plugins calling HTTPS endpoints with self-signed certs.

Related: #22831 (feature request to expose body to chat.message), #29022 (our findings)

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`chat.message` plugin hook: `SyncEvent.run: "sessionID" required but not found` when pushing to `output.parts` #23440

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chat.message plugin hook: SyncEvent.run: "sessionID" required but not found when pushing to output.parts #23440

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doobidoo commented on May 23, 2026

github-actions commented on Jul 23, 2026

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`chat.message` plugin hook: `SyncEvent.run: "sessionID" required but not found` when pushing to `output.parts` #23440