test(plugin): add issue 44788 reproduction

reproductions/44788/.opencode/opencode.json

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+{
+  "autoupdate": false,
+  "model": "test/test-model",
+  "providers": {
+    "test": {
+      "name": "Test",
+      "package": "aisdk:@ai-sdk/openai-compatible",
+      "settings": {
+        "apiKey": "test-key",
+        "baseURL": "http://127.0.0.1:18100/v1"
+      },
+      "models": {
+        "test-model": {
+          "name": "Test Model",
+          "capabilities": {
+            "tools": true,
+            "input": ["text"],
+            "output": ["text"]
+          },
+          "cost": {
+            "input": 0,
+            "output": 0
+          },
+          "limit": {
+            "context": 100000,
+            "output": 10000
+          }
+        }
+      }
+    }
+  }
+}

reproductions/44788/.opencode/plugins/probe.ts

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+import { appendFileSync } from "node:fs"
+
+const EVENTS = "/tmp/opencode-44788-events.log"
+const HOOKS = "/tmp/opencode-44788-hooks.log"
+
+const log = (path: string, value: string) => appendFileSync(path, `${value}\n`)
+
+export default {
+  id: "issue-44788-probe",
+  setup: async (ctx: any) => {
+    void (async () => {
+      for await (const event of ctx.event.subscribe()) log(EVENTS, event.type)
+    })()
+
+    await ctx.session.hook("context", async (event: any) => {
+      const hasSynthetic = JSON.stringify(event.messages).includes("PROBE-TOKEN-C")
+      log(HOOKS, `session=${event.sessionID} messages=${event.messages.length} synthetic=${hasSynthetic}`)
+
+      event.messages.push({
+        role: "user",
+        content: [{ type: "text", text: "PROBE-TOKEN-A" }],
+      })
+      event.system.push({ type: "text", text: "PROBE-TOKEN-B" })
+
+      if (hasSynthetic) return
+      await ctx.session.synthetic({
+        sessionID: event.sessionID,
+        text: "PROBE-TOKEN-C",
+        resume: false,
+      })
+    })
+  },
+}

reproductions/44788/README.md

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+# Issue 44788 reproduction
+
+This fixture checks the three plugin paths reported in #44788 against the
+actual OpenAI-compatible request body:
+
+- `ctx.event.subscribe()` event delivery
+- `ctx.session.hook("context")` message and system mutation
+- `ctx.session.synthetic()` delivery on the following dispatch
+
+The local model server writes every request to
+`/tmp/opencode-44788-requests.jsonl`. The plugin writes observed event names to
+`/tmp/opencode-44788-events.log` and hook invocations to
+`/tmp/opencode-44788-hooks.log`.
+
+## Run
+
+Use `opencode2 v0.0.0-beta-18050` to match the report.
+
+```sh
+cd reproductions/44788
+rm -f /tmp/opencode-44788-{events,hooks,requests}.log \
+  /tmp/opencode-44788-requests.jsonl
+
+# Terminal 1
+bun mock.ts
+```
+
+```sh
+# Terminal 2, still in reproductions/44788
+opencode2 --version
+opencode2 run --standalone --format json first | tee /tmp/opencode-44788-first.jsonl
+
+SESSION_ID=$(head -n 1 /tmp/opencode-44788-first.jsonl | \
+  bun -e 'console.log(JSON.parse(await Bun.stdin.text()).sessionID)')
+
+opencode2 run --standalone --session "$SESSION_ID" --format json second
+bun inspect.ts
+sort /tmp/opencode-44788-events.log | uniq -c | sort -nr
+cat /tmp/opencode-44788-hooks.log
+```
+
+Expected results:
+
+- Main model requests contain `PROBE-TOKEN-A` and `PROBE-TOKEN-B`.
+- `PROBE-TOKEN-C` is absent from the already-materialized first dispatch and
+  present after the synthetic input is delivered on a later dispatch.
+- The event log contains public events such as `session.inbox.enqueued` and
+  `session.step.started`.
+
+`ctx.event.subscribe()` returns an `AsyncIterable`; the plugin deliberately
+consumes it with `for await`. Passing a callback as an extra argument creates
+an iterable but does not consume it.

reproductions/44788/inspect.ts

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+const file = Bun.file("/tmp/opencode-44788-requests.jsonl")
+if (!(await file.exists())) throw new Error("Run the reproduction before inspecting requests")
+
+const requests = (await file.text())
+  .trim()
+  .split("\n")
+  .filter(Boolean)
+  .map((line) => JSON.parse(line))
+
+for (const [index, request] of requests.entries()) {
+  const body = JSON.stringify(request.body)
+  console.log(index + 1, new URL(request.url).pathname, {
+    messageHook: body.includes("PROBE-TOKEN-A"),
+    systemHook: body.includes("PROBE-TOKEN-B"),
+    synthetic: body.includes("PROBE-TOKEN-C"),
+    first: body.includes("first"),
+    second: body.includes("second"),
+  })
+}

reproductions/44788/mock.ts

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+import { appendFileSync } from "node:fs"
+
+const OUTPUT = "/tmp/opencode-44788-requests.jsonl"
+
+const server = Bun.serve({
+  port: 18100,
+  async fetch(request) {
+    const text = await request.text()
+    appendFileSync(
+      OUTPUT,
+      `${JSON.stringify({ url: request.url, body: text === "" ? undefined : JSON.parse(text) })}\n`,
+    )
+
+    const id = crypto.randomUUID()
+    const shared = {
+      id,
+      object: "chat.completion.chunk",
+      created: Math.floor(Date.now() / 1000),
+      model: "test-model",
+    }
+    const textChunk = {
+      ...shared,
+      choices: [{ index: 0, delta: { role: "assistant", content: "ok" }, finish_reason: null }],
+    }
+    const stopChunk = {
+      ...shared,
+      choices: [{ index: 0, delta: {}, finish_reason: "stop" }],
+    }
+
+    return new Response(
+      `data: ${JSON.stringify(textChunk)}\n\ndata: ${JSON.stringify(stopChunk)}\n\ndata: [DONE]\n\n`,
+      { headers: { "content-type": "text/event-stream" } },
+    )
+  },
+})
+
+console.log(`Mock model listening on ${server.url}`)