diff --git a/src/infra/shell-env.test.ts b/src/infra/shell-env.test.ts
index 52d65c9edc8..973f2b14630 100644
--- a/src/infra/shell-env.test.ts
+++ b/src/infra/shell-env.test.ts
@@ -187,6 +187,40 @@ describe("shell env fallback", () => {
     expect(exec2).not.toHaveBeenCalled();
   });
 
+  it("reuses the cached login-shell env probe across repeated fallback reads", () => {
+    resetShellPathCacheForTests();
+    const env: NodeJS.ProcessEnv = {};
+    const exec = vi.fn(() =>
+      Buffer.from("OPENAI_API_KEY=from-shell\0ANTHROPIC_API_KEY=from-shell-anthropic\0"),
+    );
+
+    expect(
+      loadShellEnvFallback({
+        enabled: true,
+        env,
+        expectedKeys: ["OPENAI_API_KEY"],
+        exec: exec as unknown as Parameters<typeof loadShellEnvFallback>[0]["exec"],
+      }),
+    ).toEqual({
+      ok: true,
+      applied: ["OPENAI_API_KEY"],
+    });
+
+    expect(
+      loadShellEnvFallback({
+        enabled: true,
+        env,
+        expectedKeys: ["ANTHROPIC_API_KEY"],
+        exec: exec as unknown as Parameters<typeof loadShellEnvFallback>[0]["exec"],
+      }),
+    ).toEqual({
+      ok: true,
+      applied: ["ANTHROPIC_API_KEY"],
+    });
+
+    expect(exec).toHaveBeenCalledTimes(1);
+  });
+
   it("tracks last applied keys across success, skip, and failure paths", () => {
     const successEnv: NodeJS.ProcessEnv = {};
     const successExec = vi.fn(() =>
diff --git a/src/infra/shell-env.ts b/src/infra/shell-env.ts
index 820c11ea848..db9dbf47948 100644
--- a/src/infra/shell-env.ts
+++ b/src/infra/shell-env.ts
@@ -12,6 +12,9 @@ const DEFAULT_SHELL = "/bin/sh";
 let lastAppliedKeys: string[] = [];
 let cachedShellPath: string | null | undefined;
 let cachedEtcShells: Set<string> | null | undefined;
+let nextExecCacheId = 1;
+const loginShellEnvProbeCache = new Map<string, Array<[string, string]>>();
+const execCacheIds = new WeakMap<object, number>();
 
 function resolveShellExecEnv(env: NodeJS.ProcessEnv): NodeJS.ProcessEnv {
   const execEnv = sanitizeHostExecEnv({ baseEnv: env });
@@ -111,6 +114,52 @@ function parseShellEnv(stdout: Buffer): Map<string, string> {
   return shellEnv;
 }
 
+function resolveExecCacheId(exec: typeof execFileSync | undefined): string {
+  if (!exec) {
+    return "default";
+  }
+  const key = exec as object;
+  let id = execCacheIds.get(key);
+  if (!id) {
+    id = nextExecCacheId;
+    nextExecCacheId += 1;
+    execCacheIds.set(key, id);
+  }
+  return `exec:${id}`;
+}
+
+function createLoginShellEnvCacheKey(params: {
+  shell: string;
+  timeoutMs: number;
+  exec?: typeof execFileSync;
+  execEnv: NodeJS.ProcessEnv;
+}): string {
+  const startupEnvEntries = Object.entries(params.execEnv)
+    .filter(([key]) => {
+      if (
+        key === "HOME" ||
+        key === "PATH" ||
+        key === "TERM" ||
+        key === "LANG" ||
+        key === "LC_ALL" ||
+        key === "LC_CTYPE" ||
+        key === "USER" ||
+        key === "LOGNAME" ||
+        key === "TMPDIR"
+      ) {
+        return true;
+      }
+      return key.startsWith("XDG_") || key.startsWith("OPENCLAW_");
+    })
+    .toSorted(([left], [right]) => left.localeCompare(right));
+  return JSON.stringify([
+    params.shell,
+    params.timeoutMs,
+    resolveExecCacheId(params.exec),
+    startupEnvEntries,
+  ]);
+}
+
 type LoginShellEnvProbeResult =
   | { ok: true; shellEnv: Map<string, string> }
   | { ok: false; error: string };
@@ -124,10 +173,22 @@ function probeLoginShellEnv(params: {
   const timeoutMs = resolveTimeoutMs(params.timeoutMs);
   const shell = resolveShell(params.env);
   const execEnv = resolveShellExecEnv(params.env);
+  const cacheKey = createLoginShellEnvCacheKey({
+    shell,
+    timeoutMs,
+    exec: params.exec,
+    execEnv,
+  });
+  const cached = loginShellEnvProbeCache.get(cacheKey);
+  if (cached) {
+    return { ok: true, shellEnv: new Map(cached) };
+  }
 
   try {
     const stdout = execLoginShellEnvZero({ shell, env: execEnv, exec, timeoutMs });
-    return { ok: true, shellEnv: parseShellEnv(stdout) };
+    const shellEnv = parseShellEnv(stdout);
+    loginShellEnvProbeCache.set(cacheKey, [...shellEnv.entries()]);
+    return { ok: true, shellEnv };
   } catch (err) {
     return { ok: false, error: formatErrorMessage(err) };
   }
@@ -242,6 +303,8 @@ export function getShellPathFromLoginShell(opts: {
 export function resetShellPathCacheForTests(): void {
   cachedShellPath = undefined;
   cachedEtcShells = undefined;
+  loginShellEnvProbeCache.clear();
+  nextExecCacheId = 1;
 }
 
 export function getShellEnvAppliedKeys(): string[] {