diff --git a/core/package.json b/core/package.json
index e1bc451ca..1d730d9b7 100644
--- a/core/package.json
+++ b/core/package.json
@@ -45,7 +45,7 @@
   ],
   "scripts": {
     "build": "node scripts/build-client.mjs",
-    "test": "node --import ./test/harness-resolve.mjs --test \"test/*.test.js\"",
+    "test": "node --import ./test/harness-resolve.mjs --test --test-concurrency=4 --test-timeout=120000 \"test/*.test.js\"",
     "lint": "node scripts/lint.mjs",
     "arch-docs": "node scripts/check-arch-docs.mjs",
     "harness": "npm install --prefix dev/harness --legacy-peer-deps=false --no-package-lock --no-fund --no-audit",
diff --git a/core/test/test-script-bounds.test.js b/core/test/test-script-bounds.test.js
new file mode 100644
index 000000000..c15926ea2
--- /dev/null
+++ b/core/test/test-script-bounds.test.js
@@ -0,0 +1,84 @@
+import { test } from 'node:test'
+import assert from 'node:assert/strict'
+import { readFileSync, mkdtempSync, writeFileSync, rmSync } from 'node:fs'
+import { execFileSync } from 'node:child_process'
+import { tmpdir } from 'node:os'
+import { join } from 'node:path'
+
+// `node --test` fans out to `availableParallelism() - 1` files at once — 191 on a 192-core box —
+// and a child whose spawn fails (`EAGAIN`) never exits, so the run wedges at the same output for as
+// long as the shell stays open (#2725). The `test` script therefore has to name a small fan-out and
+// a per-file deadline itself rather than inherit the host's core count.
+const root = new URL('../../', import.meta.url)
+const read = path => readFileSync(new URL(path, root), 'utf8')
+const script = JSON.parse(read('core/package.json')).scripts.test
+const flag = name => {
+  const match = script.match(new RegExp(`--${name}=(\\d+)(?:\\s|$)`))
+  return match ? Number(match[1]) : null
+}
+
+test('the test script bounds its fan-out instead of inheriting the core count', () => {
+  const concurrency = flag('test-concurrency')
+  assert.notEqual(concurrency, null, 'npm test passes no --test-concurrency, so it starts one child per core')
+  assert.ok(concurrency >= 1, `--test-concurrency=${concurrency} starts no test file`)
+  assert.ok(concurrency <= 8, `--test-concurrency=${concurrency} is not a small constant; a high-core host spawns that many at once`)
+})
+
+test('the test script gives every test file a deadline', () => {
+  const timeout = flag('test-timeout')
+  assert.notEqual(timeout, null, 'npm test passes no --test-timeout, so one stuck file holds the run open')
+  assert.ok(timeout >= 60000, `--test-timeout=${timeout} is too short for the slower host files`)
+  assert.ok(timeout <= 300000, `--test-timeout=${timeout} is longer than a run of the whole suite`)
+})
+
+test('the test script still runs the harness resolver over the whole suite', () => {
+  assert.ok(script.includes('--import ./test/harness-resolve.mjs'), 'the harness resolver is what makes `@deepseek-ai/*` load in the tests')
+  assert.ok(script.includes('"test/*.test.js"'), 'the glob is the whole suite; a narrower one would hide files')
+})
+
+// The flag has to reach node's own parser, not just sit in package.json: this runs the same deadline
+// over a file that would otherwise never return, and reads the cancellation it produces.
+test('a stuck test file fails inside the deadline instead of hanging', () => {
+  const dir = mkdtempSync(join(tmpdir(), 'flybot-stuck-'))
+  try {
+    writeFileSync(join(dir, 'stuck.test.js'), [
+      "import { test } from 'node:test'",
+      "test('deliberately stuck', () => new Promise(resolve => setTimeout(resolve, 60000)))",
+      '',
+    ].join('\n'))
+    let output = ''
+    try {
+      output = execFileSync(process.execPath, ['--test', '--test-timeout=750', join(dir, 'stuck.test.js')], {
+        encoding: 'utf8',
+        // A node that ignored the flag would hang here instead of failing this test.
+        timeout: 20000,
+        stdio: ['ignore', 'pipe', 'pipe'],
+        // Inherited from the runner around this file, it makes the child run as a test child of
+        // this one: it exits 0 at once and never parses `--test-timeout` at all.
+        env: { ...process.env, NODE_TEST_CONTEXT: undefined },
+      })
+    } catch (error) {
+      output = `${error.stdout ?? ''}${error.stderr ?? ''}`
+    }
+    assert.match(output, /(?:not ok|✖)/, 'node has to report the stuck file as failed, not leave it pending')
+    // The wording is a node detail: 22 says "test timed out after 750ms", 24 reports the cancellation
+    // as the test's own duration. Both are the deadline; the fixture asks for 60s.
+    const named = /test timed out after 750ms/.test(output)
+    const reported = output.match(/✖ deliberately stuck \((\d+(?:\.\d+)?)ms\)/)
+    const cancelled = reported ? Number(reported[1]) < 5000 : false
+    assert.ok(named || cancelled, 'the failure has to come from the deadline, not from the fixture finishing on its own')
+  } finally {
+    rmSync(dir, { recursive: true, force: true })
+  }
+})
+
+// The plain CI path is `npm test`, which is where the bounds live; a step that spells out its own
+// `node --test` would go back to starting one child per core (#2723 owns the coverage invocation).
+test('CI runs the plain suite through npm test, so it inherits the bounds', () => {
+  const lines = read('.github/actions/flybot-tests/action.yml').split('\n')
+  const start = lines.findIndex(line => line.trim() === '- name: Unit tests')
+  assert.notEqual(start, -1, 'the plain unit-test step is gone')
+  const step = lines.slice(start, start + 6).map(line => line.trim())
+  assert.ok(step.includes("if: inputs.coverage != 'true'"), 'the plain step no longer guards on coverage')
+  assert.ok(step.includes('run: npm test'), 'the plain CI step must call npm test, not its own node --test invocation')
+})
diff --git a/patches/ds-bot/0007-version-and-tooling.patch b/patches/ds-bot/0007-version-and-tooling.patch
index 23ec8e5c8..13f447b85 100644
--- a/patches/ds-bot/0007-version-and-tooling.patch
+++ b/patches/ds-bot/0007-version-and-tooling.patch
@@ -778,7 +778,8 @@ diff --git a/package.json b/package.json
    ],
    "scripts": {
      "build": "node scripts/build-client.mjs",
-     "test": "node --import ./test/harness-resolve.mjs --test \"test/*.test.js\"",
+-    "test": "node --import ./test/harness-resolve.mjs --test \"test/*.test.js\"",
++    "test": "node --import ./test/harness-resolve.mjs --test --test-concurrency=4 --test-timeout=120000 \"test/*.test.js\"",
      "lint": "node scripts/lint.mjs",
 +    "arch-docs": "node scripts/check-arch-docs.mjs",
      "harness": "npm install --prefix dev/harness --legacy-peer-deps=false --no-package-lock --no-fund --no-audit",
diff --git a/patches/ds-bot/files/test/test-script-bounds.test.js b/patches/ds-bot/files/test/test-script-bounds.test.js
new file mode 100644
index 000000000..c15926ea2
--- /dev/null
+++ b/patches/ds-bot/files/test/test-script-bounds.test.js
@@ -0,0 +1,84 @@
+import { test } from 'node:test'
+import assert from 'node:assert/strict'
+import { readFileSync, mkdtempSync, writeFileSync, rmSync } from 'node:fs'
+import { execFileSync } from 'node:child_process'
+import { tmpdir } from 'node:os'
+import { join } from 'node:path'
+
+// `node --test` fans out to `availableParallelism() - 1` files at once — 191 on a 192-core box —
+// and a child whose spawn fails (`EAGAIN`) never exits, so the run wedges at the same output for as
+// long as the shell stays open (#2725). The `test` script therefore has to name a small fan-out and
+// a per-file deadline itself rather than inherit the host's core count.
+const root = new URL('../../', import.meta.url)
+const read = path => readFileSync(new URL(path, root), 'utf8')
+const script = JSON.parse(read('core/package.json')).scripts.test
+const flag = name => {
+  const match = script.match(new RegExp(`--${name}=(\\d+)(?:\\s|$)`))
+  return match ? Number(match[1]) : null
+}
+
+test('the test script bounds its fan-out instead of inheriting the core count', () => {
+  const concurrency = flag('test-concurrency')
+  assert.notEqual(concurrency, null, 'npm test passes no --test-concurrency, so it starts one child per core')
+  assert.ok(concurrency >= 1, `--test-concurrency=${concurrency} starts no test file`)
+  assert.ok(concurrency <= 8, `--test-concurrency=${concurrency} is not a small constant; a high-core host spawns that many at once`)
+})
+
+test('the test script gives every test file a deadline', () => {
+  const timeout = flag('test-timeout')
+  assert.notEqual(timeout, null, 'npm test passes no --test-timeout, so one stuck file holds the run open')
+  assert.ok(timeout >= 60000, `--test-timeout=${timeout} is too short for the slower host files`)
+  assert.ok(timeout <= 300000, `--test-timeout=${timeout} is longer than a run of the whole suite`)
+})
+
+test('the test script still runs the harness resolver over the whole suite', () => {
+  assert.ok(script.includes('--import ./test/harness-resolve.mjs'), 'the harness resolver is what makes `@deepseek-ai/*` load in the tests')
+  assert.ok(script.includes('"test/*.test.js"'), 'the glob is the whole suite; a narrower one would hide files')
+})
+
+// The flag has to reach node's own parser, not just sit in package.json: this runs the same deadline
+// over a file that would otherwise never return, and reads the cancellation it produces.
+test('a stuck test file fails inside the deadline instead of hanging', () => {
+  const dir = mkdtempSync(join(tmpdir(), 'flybot-stuck-'))
+  try {
+    writeFileSync(join(dir, 'stuck.test.js'), [
+      "import { test } from 'node:test'",
+      "test('deliberately stuck', () => new Promise(resolve => setTimeout(resolve, 60000)))",
+      '',
+    ].join('\n'))
+    let output = ''
+    try {
+      output = execFileSync(process.execPath, ['--test', '--test-timeout=750', join(dir, 'stuck.test.js')], {
+        encoding: 'utf8',
+        // A node that ignored the flag would hang here instead of failing this test.
+        timeout: 20000,
+        stdio: ['ignore', 'pipe', 'pipe'],
+        // Inherited from the runner around this file, it makes the child run as a test child of
+        // this one: it exits 0 at once and never parses `--test-timeout` at all.
+        env: { ...process.env, NODE_TEST_CONTEXT: undefined },
+      })
+    } catch (error) {
+      output = `${error.stdout ?? ''}${error.stderr ?? ''}`
+    }
+    assert.match(output, /(?:not ok|✖)/, 'node has to report the stuck file as failed, not leave it pending')
+    // The wording is a node detail: 22 says "test timed out after 750ms", 24 reports the cancellation
+    // as the test's own duration. Both are the deadline; the fixture asks for 60s.
+    const named = /test timed out after 750ms/.test(output)
+    const reported = output.match(/✖ deliberately stuck \((\d+(?:\.\d+)?)ms\)/)
+    const cancelled = reported ? Number(reported[1]) < 5000 : false
+    assert.ok(named || cancelled, 'the failure has to come from the deadline, not from the fixture finishing on its own')
+  } finally {
+    rmSync(dir, { recursive: true, force: true })
+  }
+})
+
+// The plain CI path is `npm test`, which is where the bounds live; a step that spells out its own
+// `node --test` would go back to starting one child per core (#2723 owns the coverage invocation).
+test('CI runs the plain suite through npm test, so it inherits the bounds', () => {
+  const lines = read('.github/actions/flybot-tests/action.yml').split('\n')
+  const start = lines.findIndex(line => line.trim() === '- name: Unit tests')
+  assert.notEqual(start, -1, 'the plain unit-test step is gone')
+  const step = lines.slice(start, start + 6).map(line => line.trim())
+  assert.ok(step.includes("if: inputs.coverage != 'true'"), 'the plain step no longer guards on coverage')
+  assert.ok(step.includes('run: npm test'), 'the plain CI step must call npm test, not its own node --test invocation')
+})