diff --git a/packages/codemode/codemode.md b/packages/codemode/codemode.md
index 2ced2df49a1..155f3cd13b9 100644
--- a/packages/codemode/codemode.md
+++ b/packages/codemode/codemode.md
@@ -121,9 +121,14 @@ closing. Timeout and external interruption cancel immediately instead.
 
 ### Confirmed defects
 
-- [ ] Return rejected promises for invalid `Promise.all`/`allSettled`/`race` inputs instead of throwing during the call.
 - [ ] Align handler callability with the values CodeMode reports as functions, or document the narrower callback
       allowlist. For example, unsupported constructor-like callables are currently treated as absent handlers.
+- [ ] Run synchronous Promise reactions to completion. Reactions currently start in FIFO order but can interleave when
+      Effect auto-yields a long synchronous handler.
+- [ ] Give `Promise.race` settlement the same reaction turn as native promises. Its result currently settles before an
+      independently queued reaction in several Test262 ordering cases.
+- [ ] Drain queued reactions before classifying rejected sources as unhandled. A handler attached by an already-queued
+      reaction can currently lose to execution-boundary rejection reporting.
 
 ### Deliberate deviations and open decisions
 
@@ -152,6 +157,7 @@ closing. Timeout and external interruption cancel immediately instead.
 - Promise reactions and plain, pending, or settled `await` continuations start in deterministic FIFO order. Nested
   reactions preserve enqueue order, while an async reaction can suspend without blocking the next queued reaction.
 - Awaiting the same promise twice settles it once.
+- Sparse combinator inputs consume holes as explicit `undefined` values.
 
 ### Missing coverage
 
@@ -182,7 +188,7 @@ represent accurately rather than guessing semantics.
 | Keep an owned tree-walking interpreter. | The product need is bounded tool orchestration, not arbitrary JavaScript. Owning the language surface keeps authority and behavior explicit. |
 | Treat schemas as the model-facing interface. | Signatures drive correct calls; Effect Schema also provides the runtime validation boundary, while JSON Schema supports adapter interoperability. |
 | Keep authority host-owned. | CodeMode can only confine programs to supplied tools. The host chooses those tools, and each tool enforces its own authorization and side-effect policy. |
-| Use progressive catalog disclosure plus search. | Large tool sets should not consume the prompt, but every namespace must remain discoverable and speculative search calls should remain valid. |
+| Use progressive catalog disclosure plus search. | Large tool sets should not consume the prompt, but every namespace must remain discoverable and speculative search calls must remain valid. |
 | Start tool promises eagerly and supervise them. | This preserves normal call-time parallelism while giving each call run-once settlement and interruption safety. |
 | Keep files outside the sandbox value space. | Models should compose structured data without routing binary payloads through generated code or context. |
 | Treat `execute` as the model-facing invocation boundary. | Nested calls are implementation details of one orchestration program. Reusing the outer context and bounding only the final result preserves complete intermediate data without inventing durable child-call identities. |
diff --git a/packages/codemode/src/interpreter/runtime.ts b/packages/codemode/src/interpreter/runtime.ts
index 429bb4f5eaa..1b98e3d9035 100644
--- a/packages/codemode/src/interpreter/runtime.ts
+++ b/packages/codemode/src/interpreter/runtime.ts
@@ -2270,11 +2270,17 @@ class Interpreter<R> {
       })
     }
 
-    const items = Array.isArray(args[0]) ? args[0] : spreadItems(args[0])
+    // Promise combinators consume arrays through their iterator, which visits holes as
+    // explicit undefined values instead of preserving sparse positions like Array.map.
+    const items = Array.isArray(args[0]) ? [...args[0]] : spreadItems(args[0])
     if (items === undefined) {
-      throw new InterpreterRuntimeError(
-        `Promise.${ref.name} expects an array of promises or plain values (e.g. Promise.${ref.name}(items.map((item) => tools.ns.tool(item)))).`,
-        node,
+      return this.createPromise(
+        Effect.fail(
+          new InterpreterRuntimeError(
+            `Promise.${ref.name} expects an array of promises or plain values (e.g. Promise.${ref.name}(items.map((item) => tools.ns.tool(item)))).`,
+            node,
+          ).as("TypeError"),
+        ),
       )
     }
 
diff --git a/packages/codemode/test/promise-test262.test.ts b/packages/codemode/test/promise-test262.test.ts
new file mode 100644
index 00000000000..27306a071eb
--- /dev/null
+++ b/packages/codemode/test/promise-test262.test.ts
@@ -0,0 +1,334 @@
+/*
+ * Portions adapted from Test262 at revision 250f204f23a9249ff204be2baec29600faae7b75:
+ * - test/built-ins/Promise/all/S25.4.4.1_A1.1_T1.js
+ * - test/built-ins/Promise/all/S25.4.4.1_A2.1_T1.js
+ * - test/built-ins/Promise/all/S25.4.4.1_A2.3_T1.js
+ * - test/built-ins/Promise/all/S25.4.4.1_A2.3_T2.js
+ * - test/built-ins/Promise/all/S25.4.4.1_A2.3_T3.js
+ * - test/built-ins/Promise/all/S25.4.4.1_A7.1_T1.js
+ * - test/built-ins/Promise/all/S25.4.4.1_A8.2_T1.js
+ * - test/built-ins/Promise/all/S25.4.4.1_A8.2_T2.js
+ * - test/built-ins/Promise/all/iter-arg-is-number-reject.js
+ * - test/built-ins/Promise/all/resolve-non-thenable.js
+ * - test/built-ins/Promise/allSettled/is-function.js
+ * - test/built-ins/Promise/allSettled/returns-promise.js
+ * - test/built-ins/Promise/allSettled/resolves-empty-array.js
+ * - test/built-ins/Promise/allSettled/resolves-to-array.js
+ * - test/built-ins/Promise/allSettled/resolved-all-fulfilled.js
+ * - test/built-ins/Promise/allSettled/resolved-all-mixed.js
+ * - test/built-ins/Promise/allSettled/resolved-all-rejected.js
+ * - test/built-ins/Promise/allSettled/iter-arg-is-number-reject.js
+ * - test/built-ins/Promise/allSettled/resolve-non-thenable.js
+ * - test/built-ins/Promise/race/S25.4.4.3_A1.1_T1.js
+ * - test/built-ins/Promise/race/S25.4.4.3_A7.1_T1.js
+ * - test/built-ins/Promise/race/S25.4.4.3_A7.1_T2.js
+ * - test/built-ins/Promise/race/S25.4.4.3_A7.1_T3.js
+ * - test/built-ins/Promise/race/S25.4.4.3_A7.2_T1.js
+ * - test/built-ins/Promise/race/S25.4.4.3_A7.3_T1.js
+ * - test/built-ins/Promise/race/S25.4.4.3_A7.3_T2.js
+ * - test/built-ins/Promise/race/iter-arg-is-number-reject.js
+ * - test/built-ins/Promise/resolve/S25.4.4.5_A1.1_T1.js
+ * - test/built-ins/Promise/resolve/S25.4.4.5_A2.1_T1.js
+ * - test/built-ins/Promise/resolve/resolve-non-obj.js
+ * - test/built-ins/Promise/resolve/resolve-non-thenable.js
+ * - test/built-ins/Promise/reject/S25.4.4.4_A1.1_T1.js
+ * - test/built-ins/Promise/reject/S25.4.4.4_A2.1_T1.js
+ * - test/built-ins/Array/from/from-array.js
+ * - test/language/statements/async-function/declaration-returns-promise.js
+ * - test/language/statements/async-function/evaluation-body-that-returns.js
+ * - test/language/statements/async-function/evaluation-body-that-returns-after-await.js
+ * - test/language/statements/async-function/evaluation-body-that-throws.js
+ * - test/language/statements/async-function/evaluation-body-that-throws-after-await.js
+ *
+ * Copyright 2014 Cubane Canada, Inc.  All rights reserved.
+ * Copyright (C) 2016 the V8 project authors. All rights reserved.
+ * Copyright (C) 2019 Leo Balter. All rights reserved.
+ * Copyright (C) 2018 Rick Waldron. All rights reserved.
+ * Copyright 2015 Microsoft Corporation. All rights reserved.
+ * Copyright 2016 Microsoft, Inc. All rights reserved.
+ * Test262 portions are governed by the BSD license in LICENSE.test262.
+ */
+import { describe, expect, test } from "bun:test"
+import { Effect } from "effect"
+import { CodeMode } from "../src/index.js"
+
+const value = async (code: string) => {
+  const result = await Effect.runPromise(CodeMode.execute({ code, tools: {} }))
+  if (!result.ok) throw new Error(`expected success, got ${result.error.kind}: ${result.error.message}`)
+  return result.value
+}
+
+describe("Test262 Promise static adaptations", () => {
+  test("Promise statics are callable", async () => {
+    expect(
+      await value(
+        `return [typeof Promise.all, typeof Promise.allSettled, typeof Promise.race, typeof Promise.resolve, typeof Promise.reject]`,
+      ),
+    ).toEqual(["function", "function", "function", "function", "function"])
+  })
+
+  test("invalid combinator inputs return rejected TypeError promises", async () => {
+    expect(
+      await value(`
+        const observe = async (run) => {
+          let returned = false
+          try {
+            const promise = run()
+            returned = promise instanceof Promise
+            await promise
+            return [returned, "fulfilled"]
+          } catch (error) {
+            return [returned, error.name]
+          }
+        }
+        return await Promise.all([
+          observe(() => Promise.all(42)),
+          observe(() => Promise.allSettled(42)),
+          observe(() => Promise.race(42)),
+        ])
+      `),
+    ).toEqual([
+      [true, "TypeError"],
+      [true, "TypeError"],
+      [true, "TypeError"],
+    ])
+  })
+
+  test("Promise.all returns a promise and creates a fresh empty array", async () => {
+    expect(
+      await value(`
+        const input = []
+        const promise = Promise.all(input)
+        const result = await promise
+        return [promise instanceof Promise, result instanceof Array, result.length, result !== input]
+      `),
+    ).toEqual([true, true, 0, true])
+  })
+
+  test("Promise.all preserves values and input order", async () => {
+    expect(
+      await value(`
+        const first = { id: 1 }
+        const second = { id: 2 }
+        const result = await Promise.all([Promise.resolve(3), first, Promise.resolve(second)])
+        return [result.length, result[0], result[1] === first, result[2] === second]
+      `),
+    ).toEqual([3, 3, true, true])
+  })
+
+  test("Promise.all adopts rejection from either input position", async () => {
+    expect(
+      await value(`
+        const observe = async (promise) => {
+          try { await promise; return "fulfilled" } catch (reason) { return reason }
+        }
+        return await Promise.all([
+          observe(Promise.all([Promise.reject(1), Promise.resolve(2)])),
+          observe(Promise.all([Promise.resolve(1), Promise.reject(2)])),
+        ])
+      `),
+    ).toEqual([1, 2])
+  })
+
+  test("Promise.all treats sparse positions as undefined values", async () => {
+    expect(
+      await value(`
+        const input = []
+        input[1] = 1
+        const result = await Promise.all(input)
+        return [result.length, result[0] === undefined, result[1]]
+      `),
+    ).toEqual([2, true, 1])
+  })
+
+  test("Promise.allSettled returns a promise and a fresh array", async () => {
+    expect(
+      await value(`
+        const input = []
+        const promise = Promise.allSettled(input)
+        const result = await promise
+        return [promise instanceof Promise, result instanceof Array, result.length, result !== input]
+      `),
+    ).toEqual([true, true, 0, true])
+  })
+
+  test("Promise.allSettled preserves order and settlement shapes", async () => {
+    expect(
+      await value(`
+        const reason = { id: 4 }
+        const result = await Promise.allSettled([
+          Promise.resolve(1),
+          Promise.reject(2),
+          3,
+          Promise.reject(reason),
+        ])
+        return [result, result.map((item) => Object.keys(item))]
+      `),
+    ).toEqual([
+      [
+        { status: "fulfilled", value: 1 },
+        { status: "rejected", reason: 2 },
+        { status: "fulfilled", value: 3 },
+        { status: "rejected", reason: { id: 4 } },
+      ],
+      [
+        ["status", "value"],
+        ["status", "reason"],
+        ["status", "value"],
+        ["status", "reason"],
+      ],
+    ])
+  })
+
+  test("Promise.allSettled preserves input order across settlement timing", async () => {
+    expect(
+      await value(`
+        const slow = async () => { await Promise.resolve(); return "slow" }
+        return await Promise.allSettled([slow(), Promise.resolve("fast")])
+      `),
+    ).toEqual([
+      { status: "fulfilled", value: "slow" },
+      { status: "fulfilled", value: "fast" },
+    ])
+  })
+
+  test("Promise.allSettled adopts a non-thenable object", async () => {
+    expect(
+      await value(`
+        const object = { id: 1 }
+        const result = await Promise.allSettled([object])
+        return [result, result[0].value === object]
+      `),
+    ).toEqual([[{ status: "fulfilled", value: { id: 1 } }], true])
+  })
+
+  test("Promise.allSettled treats sparse positions as undefined values", async () => {
+    expect(
+      await value(`
+        const input = []
+        input[1] = 1
+        const result = await Promise.allSettled(input)
+        return [result.length, result[0].status, result[0].value === undefined, result[1]]
+      `),
+    ).toEqual([2, "fulfilled", true, { status: "fulfilled", value: 1 }])
+  })
+
+  test("Promise.race returns a promise and settles from its first input", async () => {
+    expect(
+      await value(`
+        const rejected = Promise.reject(2)
+        const fulfilled = Promise.resolve(1)
+        const promise = Promise.race([fulfilled, rejected])
+        return [promise instanceof Promise, await promise]
+      `),
+    ).toEqual([true, 1])
+  })
+
+  test("Promise.race preserves primitive fulfillment and rejection", async () => {
+    expect(
+      await value(`
+        const fulfilled = await Promise.race([23])
+        let rejected
+        try { await Promise.race([Promise.reject(7)]) } catch (reason) { rejected = reason }
+        return [fulfilled, rejected]
+      `),
+    ).toEqual([23, 7])
+  })
+
+  test("Promise.race observes later fulfillment and rejection", async () => {
+    expect(
+      await value(`
+        const slow = async () => { await Promise.resolve(); await Promise.resolve(); return 1 }
+        const rejectSoon = async () => { await Promise.resolve(); throw 2 }
+        try { await Promise.race([slow(), rejectSoon()]); return "fulfilled" } catch (reason) { return reason }
+      `),
+    ).toBe(2)
+  })
+
+  test("Promise.race selects fulfilled and rejected inputs by settlement order", async () => {
+    expect(
+      await value(`
+        const delayed = async (value) => { await Promise.resolve(); return value }
+        const first = await Promise.race([Promise.resolve(1), Promise.resolve(2)])
+        const second = await Promise.race([Promise.resolve(1), delayed(9)])
+        const third = await Promise.race([delayed(9), Promise.resolve(2)])
+        let fourth
+        try { await Promise.race([Promise.reject(1), Promise.resolve(2)]) } catch (reason) { fourth = reason }
+        return [first, second, third, fourth]
+      `),
+    ).toEqual([1, 1, 2, 1])
+  })
+
+  test("Promise.race treats a sparse first position as undefined", async () => {
+    expect(
+      await value(`
+        const input = []
+        input[1] = 1
+        return (await Promise.race(input)) === undefined
+      `),
+    ).toBe(true)
+  })
+
+  test("Promise.resolve adopts values and nested promises", async () => {
+    expect(
+      await value(`
+        const object = { id: 1 }
+        return [
+          await Promise.resolve(42),
+          await Promise.resolve(Promise.resolve("nested")),
+          (await Promise.resolve(object)) === object,
+        ]
+      `),
+    ).toEqual([42, "nested", true])
+  })
+
+  test("Promise.resolve preserves promise identity", async () => {
+    expect(
+      await value(`
+        const promise = Promise.resolve(1)
+        const identities = new Map([[promise, "same"]])
+        return identities.get(Promise.resolve(promise))
+      `),
+    ).toBe("same")
+  })
+
+  test("Promise.reject preserves primitive and object reasons", async () => {
+    expect(
+      await value(`
+        const object = { reason: true }
+        const reasons = [undefined, null, false, true, 0, "", 42, object]
+        const observe = async (reason) => {
+          try { await Promise.reject(reason); return false } catch (caught) { return caught === reason }
+        }
+        return await Promise.all(reasons.map(observe))
+      `),
+    ).toEqual([true, true, true, true, true, true, true, true])
+  })
+})
+
+describe("Test262 async function adaptations", () => {
+  test("async functions return promises and adopt returned values", async () => {
+    expect(
+      await value(`
+        const plain = async () => 42
+        const afterAwait = async () => { await Promise.resolve(); return 43 }
+        const first = plain()
+        const second = afterAwait()
+        return [first instanceof Promise, second instanceof Promise, await first, await second]
+      `),
+    ).toEqual([true, true, 42, 43])
+  })
+
+  test("async functions reject for throws before and after await", async () => {
+    expect(
+      await value(`
+        const throwsBefore = async () => { throw 1 }
+        const throwsAfter = async () => { await Promise.resolve(); throw 2 }
+        const observe = async (promise) => {
+          try { await promise; return "fulfilled" } catch (reason) { return reason }
+        }
+        return await Promise.all([observe(throwsBefore()), observe(throwsAfter())])
+      `),
+    ).toEqual([1, 2])
+  })
+})
diff --git a/packages/codemode/test/promise.test.ts b/packages/codemode/test/promise.test.ts
index ef96cdeca55..4b45eabe1ee 100644
--- a/packages/codemode/test/promise.test.ts
+++ b/packages/codemode/test/promise.test.ts
@@ -92,33 +92,14 @@ describe("first-class promise values", () => {
         }
         const first = load(1)
         const second = load(2)
-        return [first instanceof Promise, second instanceof Promise, await Promise.all([first, second])]
+        return await Promise.all([first, second])
       `),
     ).toEqual([
-      true,
-      true,
-      [
-        [1, 1],
-        [2, 2],
-      ],
+      [1, 1],
+      [2, 2],
     ])
   })
 
-  test("async function errors reject instead of throwing at the call site", async () => {
-    expect(
-      await value(`
-        const fail = async () => { throw new Error("boom") }
-        const promise = fail()
-        try {
-          await promise
-          return "no"
-        } catch (error) {
-          return error.message
-        }
-      `),
-    ).toBe("boom")
-  })
-
   test("an un-awaited tool call starts eagerly, in call order, before any await", async () => {
     const trace = makeTrace()
     const result = await value(
@@ -403,10 +384,6 @@ describe("Promise.all over arbitrary arrays", () => {
     expect(trace.maxActive).toBeLessThanOrEqual(8)
   })
 
-  test("resolves the empty array", async () => {
-    expect(await value(`return await Promise.all([])`)).toEqual([])
-  })
-
   test("rejects with the first failure, catchable in-program", async () => {
     expect(
       await value(`
@@ -564,25 +541,10 @@ describe("Promise.race", () => {
 })
 
 describe("Promise.resolve / Promise.reject", () => {
-  test("resolve wraps plain values and passes promises through", async () => {
-    expect(await value(`return await Promise.resolve(42)`)).toBe(42)
-    expect(await value(`return await Promise.resolve(Promise.resolve("nested"))`)).toBe("nested")
+  test("resolve adopts a tool-call promise", async () => {
     expect(await value(`return await Promise.resolve(tools.host.sleepy({ id: 3 }))`)).toBe(3)
   })
 
-  test("reject produces a promise whose await throws the reason", async () => {
-    expect(
-      await value(`
-      try {
-        await Promise.reject("nope")
-        return "no"
-      } catch (e) {
-        return e
-      }
-    `),
-    ).toBe("nope")
-  })
-
   test("an abandoned rejected promise surfaces as an unhandled rejection", async () => {
     const diagnostic = await error(`
       Promise.reject(new Error("boom"))
@@ -602,15 +564,12 @@ describe("Promise combinator values", () => {
         const settled = Promise.allSettled([Promise.resolve(3)])
         const race = Promise.race([Promise.resolve(4)])
         return [
-          all instanceof Promise,
-          settled instanceof Promise,
-          race instanceof Promise,
           await all.then((values) => values.join(",")),
           await settled.then((values) => values[0].value),
           await race.then((value) => value + 1),
         ]
       `),
-    ).toEqual([true, true, true, "1,2", 3, 5])
+    ).toEqual(["1,2", 3, 5])
   })
 })
 
diff --git a/packages/codemode/test/test262-promise.md b/packages/codemode/test/test262-promise.md
new file mode 100644
index 00000000000..5c008b94142
--- /dev/null
+++ b/packages/codemode/test/test262-promise.md
@@ -0,0 +1,40 @@
+# Test262 Promise Coverage
+
+The Promise tests adapt Test262 at revision `250f204f23a9249ff204be2baec29600faae7b75`. The upstream Promise tree
+contains 729 files; 459 are under the eight API directories corresponding to CodeMode's five Promise statics and three
+chaining methods. The executable suite currently cites 39 distinct Promise, Array, and async-function sources.
+
+This is coverage of CodeMode's confined Promise surface, not a claim of ECMAScript or Test262 conformance. One upstream
+file may contain both adapted and inapplicable assertions, so a cited source means only that the represented assertions
+were adapted. `LICENSE.test262` contains the upstream BSD terms.
+
+## Covered Surface
+
+- `Promise.all`, `Promise.allSettled`, and `Promise.race` result types, ordering, sparse positions, mixed values, and
+  rejection propagation.
+- `Promise.resolve` value adoption and promise identity.
+- `Promise.reject` reason preservation.
+- Async-function promise creation, returned-value adoption, and throws before and after `await`.
+
+The Promise PR's handwritten tests remain authoritative for tool-call concurrency, execution-scoped lifetime,
+cancellation, output boundaries, model-safe tool failures, unhandled-rejection diagnostics, and chaining behavior.
+
+## Exclusions
+
+- `new Promise`, externally captured resolving functions, and executor semantics.
+- Promise subclasses, constructors, species, realms, proxies, property descriptors, and function metadata.
+- Custom thenables, poisoned `then` accessors, and arbitrary iterable or iterator-closing behavior.
+- `Promise.any`, `Promise.try`, `Promise.withResolvers`, `Promise.allKeyed`, and `Promise.allSettledKeyed`.
+- Exact native microtask behavior for `.then`, `.catch`, and `.finally`; those are exercised separately by the Promise
+  PR's chaining tests and audit.
+- Exact native unhandled-rejection timing. CodeMode drains execution-owned work and reports safe diagnostics at its
+  execution boundary.
+
+## Observed Differences
+
+- Promise combinators accept arrays plus CodeMode's supported spreadable collections. The model guidance currently
+  describes arrays, so this remains a contract decision rather than conformance coverage.
+- `Promise.race([])` returns an actionable error instead of a permanently pending promise, which cannot usefully finish
+  a bounded CodeMode execution.
+- Promise identity is preserved, but CodeMode intentionally rejects general binary operators over Promise references;
+  identity is tested through `Map` keys instead of `===`.