diff --git a/packages/gittensory-engine/src/index.ts b/packages/gittensory-engine/src/index.ts
index 2b8e1a90ae..e4c73f63f1 100644
--- a/packages/gittensory-engine/src/index.ts
+++ b/packages/gittensory-engine/src/index.ts
@@ -406,3 +406,12 @@ export {
   type MaintainerNoiseReport,
   type PullRequestReviewability,
 } from "./reward-risk.js";
+
+// Shared subprocess env-allowlist + secret-redaction helpers (#4284) — one source of truth for every driver that
+// spawns a locally-authenticated CLI subprocess (src/selfhost/ai.ts and the coming gittensory-miner drivers).
+export {
+  SUBPROCESS_CLI_ENV_ALLOWLIST,
+  buildAllowlistedEnv,
+  SECRET_PATTERNS,
+  redactSecrets,
+} from "./subprocess-env.js";
diff --git a/packages/gittensory-engine/src/subprocess-env.ts b/packages/gittensory-engine/src/subprocess-env.ts
new file mode 100644
index 0000000000..455fb7d7ca
--- /dev/null
+++ b/packages/gittensory-engine/src/subprocess-env.ts
@@ -0,0 +1,78 @@
+// Shared subprocess env-allowlist + secret-redaction helpers (#4284). Any driver that spawns a locally-authenticated
+// CLI (the review `claude`/`codex` subprocess in src/selfhost/ai.ts, and the coding-agent drivers coming in
+// gittensory-miner) needs the SAME two safety primitives: hand the child a STRICT allowlisted env (never the full
+// worker/host env, which can carry runtime credentials into a prompt-injectable subprocess), and redact well-known
+// secret shapes out of the child's untrusted stderr before it reaches logs. This module is the single engine-hosted
+// source of truth for both, so those callers depend on one implementation instead of copy-pasting the pattern.
+
+/**
+ * The standard env-var allowlist for a locally-authenticated CLI subprocess: home + proxy + TLS-cert + locale +
+ * XDG config paths, so the CLI keeps its own auth/proxy/cert settings, but nothing else (no runtime secrets) leaks
+ * in. A caller that needs a different/larger set (e.g. a coding-agent driver) passes its own list to
+ * {@link buildAllowlistedEnv} rather than editing this one.
+ */
+export const SUBPROCESS_CLI_ENV_ALLOWLIST = [
+  "HOME",
+  "HTTPS_PROXY",
+  "HTTP_PROXY",
+  "LANG",
+  "LC_ALL",
+  "NODE_EXTRA_CA_CERTS",
+  "NO_PROXY",
+  "PATH",
+  "SSL_CERT_DIR",
+  "SSL_CERT_FILE",
+  "TERM",
+  "XDG_CONFIG_HOME",
+  "XDG_DATA_HOME",
+  "XDG_STATE_HOME",
+  "https_proxy",
+  "http_proxy",
+  "no_proxy",
+] as const;
+
+/**
+ * Build a child-process env by copying ONLY `allowlist` keys from `parent`, then overlaying `extra`. Parameterized
+ * (the allowlist is a caller argument, not hardcoded) so different subprocess kinds can use different allowlists.
+ * `undefined` values are dropped from both sources; `extra` wins over an allowlisted parent value for the same key.
+ * Pure — never reads the ambient process env itself.
+ */
+export function buildAllowlistedEnv(
+  parent: Record<string, string | undefined>,
+  allowlist: readonly string[],
+  extra: Record<string, string | undefined> = {},
+): Record<string, string | undefined> {
+  const child: Record<string, string | undefined> = {};
+  for (const key of allowlist) {
+    const value = parent[key];
+    if (value !== undefined) child[key] = value;
+  }
+  for (const [key, value] of Object.entries(extra)) {
+    if (value !== undefined) child[key] = value;
+  }
+  return child;
+}
+
+/** Well-known secret token shapes to strip from untrusted subprocess output. Ported verbatim from
+ *  src/selfhost/ai.ts (`SECRET_PATTERNS`) — keep the two in sync (or shim ai.ts onto this) rather than weakening. */
+export const SECRET_PATTERNS: readonly RegExp[] = [
+  /\bsk-[A-Za-z0-9_-]{16,}/g, // OpenAI / Anthropic keys (sk-..., sk-ant-..., sk-proj-...)
+  /\bgh[oprsu]_[A-Za-z0-9]{20,}/g, // GitHub PAT / OAuth / server / refresh tokens
+  /\bgithub_pat_[A-Za-z0-9_]{20,}/g, // GitHub fine-grained PAT
+  /\beyJ[A-Za-z0-9_-]{6,}\.[A-Za-z0-9_-]{6,}\.[A-Za-z0-9_-]{6,}/g, // JWT (header.payload.signature)
+  /\bAKIA[0-9A-Z]{16}/g, // AWS access key id
+];
+
+/**
+ * Redact secrets from untrusted subprocess output before it flows to logs/Sentry: strip each caller-supplied known
+ * secret value exactly (length-guarded so a short/empty token can't blank unrelated text), then well-known token
+ * shapes ({@link SECRET_PATTERNS}). Ported from src/selfhost/ai.ts's `redactSecrets`. Pure.
+ */
+export function redactSecrets(text: string, knownSecrets: readonly string[] = []): string {
+  let out = text;
+  for (const secret of knownSecrets) {
+    if (secret.length >= 8) out = out.split(secret).join("[redacted]");
+  }
+  for (const pattern of SECRET_PATTERNS) out = out.replace(pattern, "[redacted]");
+  return out;
+}
diff --git a/packages/gittensory-engine/test/subprocess-env.test.ts b/packages/gittensory-engine/test/subprocess-env.test.ts
new file mode 100644
index 0000000000..50f51de0c2
--- /dev/null
+++ b/packages/gittensory-engine/test/subprocess-env.test.ts
@@ -0,0 +1,33 @@
+import { test } from "node:test";
+import assert from "node:assert/strict";
+
+import { SUBPROCESS_CLI_ENV_ALLOWLIST, buildAllowlistedEnv, SECRET_PATTERNS, redactSecrets } from "../dist/index.js";
+
+test("buildAllowlistedEnv: copies only allowlisted keys; a caller-supplied allowlist is honored; extra overlays", () => {
+  const parent = { HOME: "/home/node", SECRET_TOKEN: "sk-should-not-copy", PATH: "/usr/bin", CUSTOM: "keep" };
+  // the standard allowlist copies HOME + PATH, drops SECRET_TOKEN + CUSTOM
+  assert.deepEqual(buildAllowlistedEnv(parent, SUBPROCESS_CLI_ENV_ALLOWLIST), { HOME: "/home/node", PATH: "/usr/bin" });
+  // a DIFFERENT caller-supplied allowlist is honored (CUSTOM now allowed), and `extra` overlays a parent value
+  assert.deepEqual(buildAllowlistedEnv(parent, ["HOME", "CUSTOM"], { EXTRA: "v", HOME: "/override" }), {
+    HOME: "/override",
+    CUSTOM: "keep",
+    EXTRA: "v",
+  });
+  // undefined values are dropped from both the parent and `extra`
+  assert.deepEqual(buildAllowlistedEnv({ A: undefined }, ["A"], { B: undefined }), {});
+});
+
+test("redactSecrets: strips every SECRET_PATTERNS family, plus caller-supplied known secrets", () => {
+  assert.equal(redactSecrets("key sk-abcdefghijklmnop123"), "key [redacted]"); // OpenAI/Anthropic
+  assert.equal(redactSecrets("tok ghp_ABCDEFGHIJKLMNOPQRSTUV"), "tok [redacted]"); // GitHub token
+  assert.equal(redactSecrets("pat github_pat_ABCDEFGHIJKLMNOPQRST"), "pat [redacted]"); // GitHub fine-grained PAT
+  assert.equal(redactSecrets("jwt eyJhbGciOi.eyJzdWIiO.SflKxwRJSM"), "jwt [redacted]"); // JWT
+  assert.equal(redactSecrets("aws AKIAIOSFODNN7EXAMPLE"), "aws [redacted]"); // AWS access key id
+  // a known secret (length >= 8) is stripped exactly; a short one is NOT (guards unrelated diagnostic text)
+  assert.equal(redactSecrets("value=supersecretvalue", ["supersecretvalue"]), "value=[redacted]");
+  assert.equal(redactSecrets("t and t again", ["t"]), "t and t again");
+});
+
+test("SECRET_PATTERNS carries the full ported regex family", () => {
+  assert.equal(SECRET_PATTERNS.length, 5);
+});
diff --git a/src/selfhost/ai.ts b/src/selfhost/ai.ts
index 8e3b6aea76..699ffc8a90 100644
--- a/src/selfhost/ai.ts
+++ b/src/selfhost/ai.ts
@@ -353,6 +353,13 @@ export function createAnthropicAi(opts: { apiKey: string; model?: string | undef
 // SECURITY: subscription CLIs get a strict allowlisted env, not the worker env. This keeps runtime
 // credentials out of prompt-injectable subprocesses while preserving CLI auth/home/proxy/cert settings. The CLI
 // runs read-only / no extra tools, and non-zero exit / empty output / error-envelope THROWS so the caller degrades.
+//
+// NOTE (#4284): the reusable half of this pattern — a parameterized allowlist builder + secret redaction — now also
+// lives in `@jsonbored/gittensory-engine` (`SUBPROCESS_CLI_ENV_ALLOWLIST`, `buildAllowlistedEnv`, `SECRET_PATTERNS`,
+// `redactSecrets`) so the coming gittensory-miner coding-agent drivers can depend on one source of truth. This copy
+// is deliberately kept parallel for now (the review path's `subscriptionCliEnv` also folds in CLI-specific PATH
+// resolution); keep the two in sync, or shim this onto the engine copy (like `src/rules/predicted-gate.ts` does) in
+// a follow-up if it drifts.
 const SUBSCRIPTION_CLI_ENV_ALLOWLIST = [
   "HOME",
   "HTTPS_PROXY",
diff --git a/test/unit/engine-subprocess-env.test.ts b/test/unit/engine-subprocess-env.test.ts
new file mode 100644
index 0000000000..2c19f4a453
--- /dev/null
+++ b/test/unit/engine-subprocess-env.test.ts
@@ -0,0 +1,37 @@
+// App-vitest coverage for the engine subprocess-env helper (#4284). The engine also has its own node:test suite,
+// but codecov/patch is computed from this app vitest run (vitest.config coverage includes
+// packages/gittensory-engine/src/**), so the changed engine lines need a vitest test that imports the SRC directly.
+import { describe, expect, it } from "vitest";
+import {
+  SUBPROCESS_CLI_ENV_ALLOWLIST,
+  buildAllowlistedEnv,
+  SECRET_PATTERNS,
+  redactSecrets,
+} from "../../packages/gittensory-engine/src/subprocess-env";
+
+describe("engine subprocess-env helper (#4284)", () => {
+  it("buildAllowlistedEnv copies only allowlisted keys; a caller allowlist is honored; extra overlays; undefined dropped", () => {
+    const parent = { HOME: "/home/node", SECRET_TOKEN: "sk-should-not-copy", PATH: "/usr/bin", CUSTOM: "keep" };
+    expect(buildAllowlistedEnv(parent, SUBPROCESS_CLI_ENV_ALLOWLIST)).toEqual({ HOME: "/home/node", PATH: "/usr/bin" });
+    expect(buildAllowlistedEnv(parent, ["HOME", "CUSTOM"], { EXTRA: "v", HOME: "/override" })).toEqual({
+      HOME: "/override",
+      CUSTOM: "keep",
+      EXTRA: "v",
+    });
+    expect(buildAllowlistedEnv({ A: undefined }, ["A"], { B: undefined })).toEqual({});
+  });
+
+  it("redactSecrets strips every SECRET_PATTERNS family + caller-supplied known secrets (length-guarded)", () => {
+    expect(redactSecrets("key sk-abcdefghijklmnop123")).toBe("key [redacted]");
+    expect(redactSecrets("tok ghp_ABCDEFGHIJKLMNOPQRSTUV")).toBe("tok [redacted]");
+    expect(redactSecrets("pat github_pat_ABCDEFGHIJKLMNOPQRST")).toBe("pat [redacted]");
+    expect(redactSecrets("jwt eyJhbGciOi.eyJzdWIiO.SflKxwRJSM")).toBe("jwt [redacted]");
+    expect(redactSecrets("aws AKIAIOSFODNN7EXAMPLE")).toBe("aws [redacted]");
+    expect(redactSecrets("value=supersecretvalue", ["supersecretvalue"])).toBe("value=[redacted]");
+    expect(redactSecrets("t and t again", ["t"])).toBe("t and t again"); // short known secret NOT stripped
+  });
+
+  it("SECRET_PATTERNS carries the full ported regex family", () => {
+    expect(SECRET_PATTERNS).toHaveLength(5);
+  });
+});