stdin: address cubic P2 + P3 on commit 7fceb85

P2 (NPE guard incomplete): a caller that passes `deps.isTTY` bypasses
the outer `process.stdin?.isTTY` guard, and if `process.stdin` is
undefined the default reader crashes on `stdin.on(...)`. Add a defensive
check inside `defaultReadStdin` that returns "" when stdin is absent.
New regression test exercises the path with `deps.isTTY` set + undefined
`process.stdin` + no `readStdin` injection.

P3 (warning text misleading for non-timeout empty results): an empty
result can come from the timer firing, a clean `end` with zero bytes,
or an error event — the previous "no data received within Nms" wording
implied only the first. Reword to cause-neutral "stdin produced no
data" while keeping the env-var tip for slow-producer cases.

Author: Haider

packages/opencode/src/util/stdin.ts

@@ -98,9 +98,13 @@ export async function readStdinIfAvailable(deps: ReadStdinDeps = {}): Promise<st
   const result = await readStdin(timeoutMs)
 
   if (result === "") {
+    // An empty result can come from the timer firing (slow producer), a
+    // clean `end` with zero bytes (intentionally empty pipe), or an error
+    // event. Wording is cause-neutral; the env-var tip is still useful for
+    // the slow-producer case and harmless otherwise.
     warn(
-      `altimate-code: stdin appears piped but no data received within ${timeoutMs}ms; ` +
-        `proceeding without it. Set ${STDIN_TIMEOUT_ENV}=N (ms) to wait longer.`,
+      `altimate-code: stdin produced no data; proceeding without it. ` +
+        `Tip: set ${STDIN_TIMEOUT_ENV}=N (ms) higher if upstream is a slow producer.`,
     )
   }
 
@@ -132,6 +136,11 @@ export function assembleStdinMessage(positional: string, stdinInput: string): st
 function defaultReadStdin(timeoutMs: number): Promise<string> {
   return new Promise<string>((resolve) => {
     const stdin = process.stdin
+    // Defensive: a caller can reach this path with `deps.isTTY` set but
+    // `process.stdin` undefined (embedded/child runtime). The outer
+    // `process.stdin?.isTTY` guard short-circuits the default case but not
+    // this one. Treat absence as "no data" to match the function's contract.
+    if (!stdin) return resolve("")
     const chunks: Buffer[] = []
     let firstByteReceived = false
     let firstByteTimer: ReturnType<typeof setTimeout> | undefined

packages/opencode/test/util/stdin.test.ts

@@ -138,6 +138,28 @@ describe("readStdinIfAvailable", () => {
     }
   })
 
+  // cubic P2 on commit 7fceb85a1: a caller that passes `deps.isTTY` bypasses
+  // the outer `process.stdin?.isTTY` guard. If `process.stdin` is undefined,
+  // the default reader path used to crash on `stdin.on(...)`. The defensive
+  // check inside `defaultReadStdin` covers this.
+  test("default reader returns empty when process.stdin is undefined even when deps.isTTY is passed", async () => {
+    const original = process.stdin
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
+    ;(process as any).stdin = undefined
+    try {
+      const out = await readStdinIfAvailable({
+        isTTY: false,
+        fstat: () => fifo,
+        // no readStdin → exercises defaultReadStdin
+        warn: () => {},
+      })
+      expect(out).toBe("")
+    } finally {
+      // eslint-disable-next-line @typescript-eslint/no-explicit-any
+      ;(process as any).stdin = original
+    }
+  })
+
   // Sury PR #935 review #2: silent drop is bad UX. When fd 0 looked like
   // real input but no first byte arrived, warn so the user knows.
   test("warns when stdin looked like input but readStdin returned empty (silent-drop fix)", async () => {
@@ -150,7 +172,7 @@ describe("readStdinIfAvailable", () => {
     })
     expect(out).toBe("")
     expect(seen).toHaveLength(1)
-    expect(seen[0]).toContain("stdin appears piped")
+    expect(seen[0]).toContain("stdin produced no data")
     expect(seen[0]).toContain("ALTIMATE_STDIN_TIMEOUT_MS")
   })