fix(providers): stop devin-cli spawn error from double-closing SSE controller (#12517) (#13261)

Merged as part of the 39-PR owner batch of 2026-09-11, validated as a unit.

Boarded into one consolidated worktree cut from `release/v3.8.51` with the other 38 — zero conflicts between them.

- ESLint over every changed file: no errors (the only finding was one suppression entry the batch emptied, pruned on #13243)
- `typecheck:core` clean; `check:dashboard-typecheck` OK (206 pre-existing, within baseline); `check:changelog-integrity` OK
- complexity 2821 / baseline 3218 and cognitive-complexity 1272 / baseline 1437 — both under baseline
- 256 assertions green: 246 under node:test and 10 under vitest, which is where `tests/unit/**/*.test.tsx` actually runs
- `check-file-size`: `chatCore.ts` rebaselined 6144 → 6146 for #13278 and #13276, annotated and landed on #13243

⚠️ base-red inherited: #12732 — the provider count (356 in the docs vs the 358 the modules define) and `open-sse/utils/stream.ts` at 3115 > frozen 3098 both reproduce on the pure tip with zero contribution from this batch.

changelog.d/fixes/12517-devin-cli-sse-double-close.md

@@ -0,0 +1 @@
+- fix(providers): stop devin-cli spawn error from double-closing the SSE controller (#12517)

open-sse/executors/devin-cli.ts

@@ -170,11 +170,7 @@ export class DevinCliExecutor extends BaseExecutor {
             err.message.includes("ENOENT") || err.message.includes("not found")
               ? `Devin CLI not found: ${devinBin}. Install via https://cli.devin.ai or set CLI_DEVIN_BIN env var.`
               : `Devin CLI spawn error: ${err.message}`;
-          emit(
-            `data: ${JSON.stringify({ error: { message: msg, type: "devin_cli_error", code: "spawn_failed" } })}\n\n`
-          );
-          emit("data: [DONE]\n\n");
-          controller.close();
+          finish(msg);
         });
 
         if (signal) {

tests/unit/executor-devin-cli-12517-double-close.test.ts

@@ -0,0 +1,55 @@
+import { describe, it, after } from "node:test";
+import assert from "node:assert/strict";
+
+const mod = await import("../../open-sse/executors/devin-cli.ts");
+
+describe("DevinCliExecutor — #12517 spawn error must not double-close SSE controller", () => {
+  it("surfaces a sanitized SSE error and never fires uncaughtException on ENOENT spawn", async () => {
+    const previousBin = process.env.CLI_DEVIN_BIN;
+    process.env.CLI_DEVIN_BIN = "/nonexistent/absolute/path/to/devin-bin-12517";
+
+    let caught: unknown = null;
+    const onUncaught = (err: unknown) => {
+      caught = err;
+    };
+    process.on("uncaughtException", onUncaught);
+
+    try {
+      const executor = new mod.DevinCliExecutor();
+      const { response } = await executor.execute({
+        model: "devin-cli",
+        body: { messages: [{ role: "user", content: "hi" }] },
+        stream: true,
+        credentials: {},
+        signal: undefined,
+        log: undefined,
+      } as never);
+
+      const reader = response.body!.getReader();
+      const decoder = new TextDecoder();
+      let payload = "";
+      for (;;) {
+        const { done, value } = await reader.read();
+        if (done) break;
+        payload += decoder.decode(value);
+      }
+
+      assert.match(payload, /Devin CLI not found/);
+      assert.match(payload, /data: \[DONE\]/);
+
+      // Give the child's async "close" event (which fires after "error" for a
+      // failed spawn) room to run before asserting no uncaughtException fired.
+      await new Promise((resolve) => setTimeout(resolve, 300));
+
+      assert.equal(caught, null, `expected no uncaughtException, got: ${String(caught)}`);
+    } finally {
+      process.removeListener("uncaughtException", onUncaught);
+      if (previousBin === undefined) delete process.env.CLI_DEVIN_BIN;
+      else process.env.CLI_DEVIN_BIN = previousBin;
+    }
+  });
+
+  after(() => {
+    delete process.env.CLI_DEVIN_BIN;
+  });
+});