diff --git a/docs/configuration.md b/docs/configuration.md
index 780706a255..4991d9c693 100644
--- a/docs/configuration.md
+++ b/docs/configuration.md
@@ -2411,7 +2411,7 @@ How each client is pointed at the proxy (set automatically in the child env):
 | hermes | `HTTPS_PROXY` (plain-http rides absolute-form forward-proxy requests) | `SSL_CERT_FILE` → `combined-ca.pem` (+ legacy `HERMES_CA_BUNDLE` → `root-ca.pem`) |
 | dsh | `HTTPS_PROXY` (+ `HTTP_PROXY` for plain-http) + `DEEPSEEK_BASE_URL`; **loopback-only** isolated `DSH_HOME` | `SSL_CERT_FILE` → `combined-ca.pem` |
 
-`NODE_EXTRA_CA_CERTS` *appends* to the built-in trust store, so it points at the MITM root alone (`root-ca.pem`). `SSL_CERT_FILE` *replaces* the default CA bundle, so for codex/dsh/hermes it points at `combined-ca.pem` — a bundle containing the MITM root **plus** the OS trust store and the Node public roots. The OS-store merge matters because some launched clients treat this file as their *entire* trust pool (codex's rustls HTTP stack replaces rather than appends, #1807): any direct, non-proxied connection of theirs must validate against this file alone, so the file must be a superset of what the OS itself trusts (Windows cert stores via PowerShell, macOS keychains via `security(1)`; Linux already reads the filesystem bundle; rebuilt at most once per 24 h). Keeping pip/git/curl style TLS (blind-tunnelled, real certificates) working inside the child env is the original reason for the bundle (#152; hermes since #1375, because current hermes resolves ambient trust only through `SSL_CERT_FILE`; OS-store merge since #1807).
+`NODE_EXTRA_CA_CERTS` *appends* to the built-in trust store, so it points at the MITM root alone (`root-ca.pem`). `SSL_CERT_FILE` *replaces* the default CA bundle, so for codex/dsh/hermes it points at `combined-ca.pem` — a bundle containing the MITM root **plus** the OS trust store and the Node public roots, narrowed to CA certificates only (#5802: darwin's `security(1)` keychain export includes non-CA leaf identities such as `com.apple.kerberos.kdc`, and strict replace-semantics clients like codex's rustls stack reject the whole file when any entry fails to parse). The OS-store merge matters because some launched clients treat this file as their *entire* trust pool (codex's rustls HTTP stack replaces rather than appends, #1807): any direct, non-proxied connection of theirs must validate against this file alone, so the file must be a superset of what the OS itself trusts (Windows cert stores via PowerShell, macOS keychains via `security(1)`; Linux already reads the filesystem bundle; rebuilt at most once per 24 h). Keeping pip/git/curl style TLS (blind-tunnelled, real certificates) working inside the child env is the original reason for the bundle (#152; hermes since #1375, because current hermes resolves ambient trust only through `SSL_CERT_FILE`; OS-store merge since #1807).
 
 Claude Code is routed through the `/bili/` URL form via its own base-URL variables rather than cert MITM — every upstream, including a pre-configured `ANTHROPIC_BASE_URL` relay and the Vertex endpoint under `CLAUDE_CODE_USE_VERTEX=1`; no CA trust is required. Older builds ignored proxy env vars outright, but newer ones (e.g. 2.1.301) honour `HTTPS_PROXY`, so the launcher merges the loopback hosts into `NO_PROXY`/`no_proxy` (preserving any value already set) to keep the `/bili/` leg direct regardless of which behavior the child has (#3446).
 
diff --git a/docs/configuration.zh-CN.md b/docs/configuration.zh-CN.md
index da99ac3aff..f1d6452666 100644
--- a/docs/configuration.zh-CN.md
+++ b/docs/configuration.zh-CN.md
@@ -2378,7 +2378,7 @@ MITM 只对一份**白名单**中的模型域名生效（`open.bigmodel.cn`、`a
 | hermes | `HTTPS_PROXY`（明文 http 走 absolute-form 正向代理请求） | `SSL_CERT_FILE` → `combined-ca.pem`（另设旧版 `HERMES_CA_BUNDLE` → `root-ca.pem`） |
 | dsh | `HTTPS_PROXY`（明文 http 另加 `HTTP_PROXY`）+ `DEEPSEEK_BASE_URL`；**仅回环**隔离 `DSH_HOME` | `SSL_CERT_FILE` → `combined-ca.pem` |
 
-`NODE_EXTRA_CA_CERTS` 是**追加**到内置信任库，所以只指向 MITM 根证书（`root-ca.pem`）即可。`SSL_CERT_FILE` 会**替换**默认 CA bundle，所以 codex/dsh/hermes 指向 `combined-ca.pem` —— 包含 MITM 根证书**加上**操作系统信任库与 Node 公共根。合并 OS 信任库很关键：部分被启动的客户端把这个文件当作**整个**信任池（codex 的 rustls HTTP 栈是替换而非追加，#1807），它们的直连（不经代理）连接只能靠这个文件校验，因此文件必须是 OS 自身信任集合的超集（Windows 经 PowerShell 读证书库、macOS 经 `security(1)` 读钥匙串；Linux 本就直读文件系统 bundle；最多每 24 小时重建一次）。最初引入该 bundle 是为了让子进程环境里 pip/git/curl 类 TLS（盲转发、真证书）不受影响（#152；hermes 自 #1375 起，因为当前 hermes 只经 `SSL_CERT_FILE` 解析环境信任；OS 信任库合并自 #1807 起）。
+`NODE_EXTRA_CA_CERTS` 是**追加**到内置信任库，所以只指向 MITM 根证书（`root-ca.pem`）即可。`SSL_CERT_FILE` 会**替换**默认 CA bundle，所以 codex/dsh/hermes 指向 `combined-ca.pem` —— 包含 MITM 根证书**加上**操作系统信任库与 Node 公共根，且只保留 CA 证书（#5802：darwin 的 `security(1)` 钥匙串导出会混入非 CA 叶子身份证书（如 `com.apple.kerberos.kdc`），codex 这类替换语义客户端只要有一个条目解析失败就拒绝整份文件）。合并 OS 信任库很关键：部分被启动的客户端把这个文件当作**整个**信任池（codex 的 rustls HTTP 栈是替换而非追加，#1807），它们的直连（不经代理）连接只能靠这个文件校验，因此文件必须是 OS 自身信任集合的超集（Windows 经 PowerShell 读证书库、macOS 经 `security(1)` 读钥匙串；Linux 本就直读文件系统 bundle；最多每 24 小时重建一次）。最初引入该 bundle 是为了让子进程环境里 pip/git/curl 类 TLS（盲转发、真证书）不受影响（#152；hermes 自 #1375 起，因为当前 hermes 只经 `SSL_CERT_FILE` 解析环境信任；OS 信任库合并自 #1807 起）。
 
 Claude Code 的 undici fetch 忽略 `HTTPS_PROXY`，所以证书 MITM 拦不到它。claude 的所有上游 —— 包括预先配置的 `ANTHROPIC_BASE_URL` relay，以及 `CLAUDE_CODE_USE_VERTEX=1` 下的 Vertex 端点 —— 一律改走 `/bili/` URL 形式，通过客户端自己的 base URL 变量下发；无需任何 CA 信任。
 
diff --git a/src/ca.ts b/src/ca.ts
index a84418783c..b7e9ef287c 100644
--- a/src/ca.ts
+++ b/src/ca.ts
@@ -11,6 +11,11 @@ import { log as loggerLog } from "./logger.js";
 const ROOT_CERT_FILE = "root-ca.pem";
 const ROOT_KEY_FILE = "root-ca-key.pem";
 const COMBINED_CA_FILE = "combined-ca.pem";
+// #5802: format marker line at the top of the bundle. A FRESH file lacking it
+// predates the CA-only merge policy and gets rebuilt once after upgrade —
+// without it a pre-fix bundle (carrying keychain leaf certs) would survive
+// until its 24 h age expired and the fix would look inert for a day.
+const BUNDLE_MARKER = "# billion-context combined-ca (ca-only v1, #5802)";
 const ROOT_CN = "billion-context MITM Root CA";
 // #1807: the combined bundle merges the OS trust store, which costs a
 // PowerShell spawn on Windows — bound the rebuild to once per day per machine.
@@ -193,14 +198,62 @@ export function collectOsStorePems(platform: NodeJS.Platform = process.platform)
     }
 }
 
-/** Rebuild combined-ca.pem unless a fresh copy (< 24h) already carries the
- *  current MITM root CA — the OS-store merge makes each rebuild expensive on
- *  Windows, so steady-state startups reuse the existing file. */
+// #5802: RFC 5280 KeyUsage extension — OID 2.5.29.15. Per §4.1 the extension
+// body is [BOOLEAN critical] OCTET STRING wrapping a BIT STRING
+// (04 LL | 03 LL <unused-bits> <flags…>); the critical flag is OPTIONAL and
+// skipped when present (RFC-recommended for CA certs, so most real-world
+// anchors carry it). Logical bit 5 (keyCertSign) maps to mask 0x04 of the
+// FIRST flag octet under any valid unused-bits count, so the test is
+// independent of the encoder's padding choice. Scanned on the raw DER because
+// Node's X509Certificate.keyUsage getter is unusable in current runtimes
+// (returns undefined for every cert) and node-forge cannot parse non-RSA
+// subjects — both would misjudge ECDSA CAs.
+const KEY_USAGE_OID = Buffer.from([0x06, 0x03, 0x55, 0x1d, 0x0f]);
+const KEY_CERT_SIGN_BIT = 0x04;
+
+function hasKeyCertSign(raw: Buffer): boolean {
+    let i = raw.indexOf(KEY_USAGE_OID);
+    while (i >= 0) {
+        let b = i + KEY_USAGE_OID.length;
+        if (raw[b] === 0x01 && raw[b + 1] === 0x01) b += 3; // optional critical BOOLEAN
+        if (raw[b] === 0x04 && (raw[b + 1] === 0x04 || raw[b + 1] === 0x05)
+            && raw[b + 2] === 0x03 && (raw[b + 3] === 0x02 || raw[b + 3] === 0x03)) {
+            return (raw[b + 5] & KEY_CERT_SIGN_BIT) !== 0;
+        }
+        i = raw.indexOf(KEY_USAGE_OID, i + 1);
+    }
+    return false;
+}
+
+/** #5802: keep a combined-bundle entry only if it can act as a trust anchor —
+ *  basicConstraints CA:TRUE (X509Certificate.ca), or keyUsage Certificate
+ *  Sign for anchors predating the extension. security(1) find-certificate -a
+ *  exports EVERY keychain entry (Apple system identities, app/content-signing
+ *  and S-MIME leaves alike), not just anchors; replacement-semantics clients
+ *  (codex/rustls) parse every entry of SSL_CERT_FILE strictly, so one
+ *  RFC-violating leaf (com.apple.kerberos.kdc, duplicate EKU) aborts their
+ *  whole HTTP client. Unparseable entries anchor nothing and drop too. */
+export function isCaLike(pem: string): boolean {
+    try {
+        const x = new crypto.X509Certificate(pem);
+        return x.ca || hasKeyCertSign(x.raw);
+    } catch {
+        return false;
+    }
+}
+
+/** Rebuild combined-ca.pem unless a fresh copy (< 24h) already carries both
+ *  the current MITM root CA and the #5802 format marker — the OS-store merge
+ *  makes each rebuild expensive on Windows, so steady-state startups reuse
+ *  the existing file. */
 function writeCombinedBundle(): void {
     const file = path.join(caDir(), COMBINED_CA_FILE);
     try {
         const st = fs.statSync(file);
-        if (Date.now() - st.mtimeMs < COMBINED_MAX_AGE_MS && fs.readFileSync(file, "utf8").includes(rootCertPem!.trim())) return;
+        if (Date.now() - st.mtimeMs < COMBINED_MAX_AGE_MS) {
+            const existing = fs.readFileSync(file, "utf8");
+            if (existing.includes(rootCertPem!.trim()) && existing.includes(BUNDLE_MARKER)) return;
+        }
     } catch { }
     const byFingerprint = new Map<string, string>();
     const add = (pem: string): void => {
@@ -216,7 +269,18 @@ function writeCombinedBundle(): void {
     for (const pem of collectOsStorePems()) add(pem);
     for (const pem of tls.rootCertificates) add(pem);
     add(rootCertPem!);
-    const body = [...byFingerprint.values()].map((pem) => (pem.endsWith("\n") ? pem : pem + "\n")).join("");
+    // #5802: single choke point over ALL sources (keychain/PowerShell exports,
+    // filesystem bundle, Mozilla snapshot, user SSL_CERT_FILE) — the bundle
+    // must hold trust anchors only; see isCaLike.
+    let kept = [...byFingerprint.values()].filter(isCaLike);
+    if (kept.length === 0) {
+        // Availability floor: the MITM root always passes the filter, so an
+        // empty result means certificate parsing itself is broken — degrade
+        // to the pre-#5802 shape (loudly) instead of shipping an empty pool.
+        loggerLog("error", `[ca] CA-only filter dropped all ${byFingerprint.size} certificates including the MITM root — falling back to the unfiltered bundle; certificate parsing appears broken, report this`);
+        kept = [...byFingerprint.values()];
+    }
+    const body = BUNDLE_MARKER + "\n" + kept.map((pem) => (pem.endsWith("\n") ? pem : pem + "\n")).join("");
     try {
         fs.writeFileSync(file, body, { mode: 0o644 });
     } catch (err) {
diff --git a/tests/ca-combined.test.ts b/tests/ca-combined.test.ts
index ade99d898c..3c629f6a57 100644
--- a/tests/ca-combined.test.ts
+++ b/tests/ca-combined.test.ts
@@ -1,10 +1,12 @@
 import assert from "node:assert/strict";
+import crypto from "node:crypto";
 import fs from "node:fs";
 import os from "node:os";
 import path from "node:path";
 import tls from "node:tls";
 import test from "node:test";
-import { combinedCaPath, collectOsStorePems, collectSystemCaPems, decodeOsStoreOutput, ensureRootCA, osStoreExecOptions, osStorePowerShellScript, parseOsStoreNdjson, pemFingerprint, rootCaPath, wrapDerPem } from "../src/ca.js";
+import forge from "node-forge";
+import { combinedCaPath, collectOsStorePems, collectSystemCaPems, decodeOsStoreOutput, ensureRootCA, isCaLike, osStoreExecOptions, osStorePowerShellScript, parseOsStoreNdjson, pemFingerprint, rootCaPath, wrapDerPem } from "../src/ca.js";
 import { resolveCombinedCaPath } from "../src/launcher.js";
 import { setLogCapture } from "../src/logger.ts";
 import { rmrf } from "./tmp-rm.ts";
@@ -223,3 +225,98 @@ test("#5103: write-refused rebuild with NO usable bundle still fails fast", (t)
     // leave the shared tmp home in a healthy state for any later test
     ensureRootCA();
 });
+
+// #5802: security(1) find-certificate -a exports EVERY keychain entry (Apple
+// system identities, app/content-signing and S-MIME leaves), and
+// replacement-semantics clients (codex/rustls) parse every bundle entry
+// strictly — one RFC-violating leaf (com.apple.kerberos.kdc, duplicate EKU)
+// aborted codex's whole HTTP client. The combined bundle must hold anchors only.
+
+function forgedPem(spec: { cn: string; basicConstraints?: boolean; keyCertSign?: boolean; digitalSignature?: boolean; keyEncipherment?: boolean; serverAuth?: boolean; kuCritical?: boolean }): string {
+    const keys = forge.pki.rsa.generateKeyPair({ bits: 512 });
+    const cert = forge.pki.createCertificate();
+    cert.publicKey = keys.publicKey;
+    cert.serialNumber = "01";
+    const now = new Date();
+    cert.validity.notBefore = now;
+    cert.validity.notAfter = now;
+    cert.validity.notAfter.setFullYear(now.getFullYear() + 1);
+    cert.setSubject([{ name: "commonName", value: spec.cn }]);
+    cert.setIssuer(cert.subject.attributes);
+    const exts: Array<Record<string, unknown>> = [];
+    if (spec.basicConstraints !== undefined) exts.push({ name: "basicConstraints", cA: spec.basicConstraints, critical: true });
+    const ku: Record<string, boolean> = {};
+    if (spec.keyCertSign) ku.keyCertSign = true;
+    if (spec.digitalSignature) ku.digitalSignature = true;
+    if (spec.keyEncipherment) ku.keyEncipherment = true;
+    if (Object.keys(ku).length > 0) exts.push({ name: "keyUsage", ...ku, ...(spec.kuCritical ? { critical: true } : {}) });
+    if (spec.serverAuth) exts.push({ name: "extKeyUsage", names: ["serverAuth"] });
+    if (exts.length > 0) cert.setExtensions(exts);
+    cert.sign(keys.privateKey, forge.md.sha256.create());
+    return forge.pki.certificateToPem(cert);
+}
+
+test("#5802: isCaLike keeps anchors, drops serverAuth leaves and unparseable entries (both gate directions)", () => {
+    const realRoot = tls.rootCertificates[0];
+    assert.equal(new crypto.X509Certificate(realRoot).ca, true, "ground truth: public root IS a CA");
+    assert.ok(isCaLike(realRoot), "a real public root must pass");
+
+    const legacyAnchor = forgedPem({ cn: "legacy-anchor", keyCertSign: true });
+    assert.equal(new crypto.X509Certificate(legacyAnchor).ca, false, "ground truth: no basicConstraints extension");
+    assert.ok(isCaLike(legacyAnchor), "keyCertSign without basicConstraints still anchors chains (pre-BC CAs)");
+
+    // RFC 5280 recommends the critical marking for CA certs — the DER scan
+    // must skip the optional critical BOOLEAN between OID and extnValue.
+    const legacyAnchorCritical = forgedPem({ cn: "legacy-anchor-critical", keyCertSign: true, kuCritical: true });
+    assert.equal(new crypto.X509Certificate(legacyAnchorCritical).ca, false, "ground truth: no basicConstraints extension");
+    assert.ok(isCaLike(legacyAnchorCritical), "critical-marked keyCertSign still anchors chains (pre-BC CAs)");
+
+    // The com.apple.kerberos.kdc class: identity leaf with a serverAuth EKU, not an anchor.
+    const kdcLike = forgedPem({ cn: "com.example.kerberos.kdc", basicConstraints: false, digitalSignature: true, keyEncipherment: true, serverAuth: true });
+    assert.equal(new crypto.X509Certificate(kdcLike).ca, false, "ground truth: fixture leaf is NOT a CA");
+    assert.equal(isCaLike(kdcLike), false, "a serverAuth leaf must never enter the bundle");
+
+    // Non-RSA anchors: the predicate must judge ECDSA CAs correctly too
+    // (node-forge cannot parse them; a parser swap would silently drop these).
+    const ecRoots = tls.rootCertificates.filter((pem) => {
+        try { return new crypto.X509Certificate(pem).publicKey.asymmetricKeyType === "ec"; } catch { return false; }
+    });
+    assert.ok(ecRoots.length > 0, "fixture precondition: the Mozilla snapshot contains EC roots");
+    for (const pem of ecRoots.slice(0, 5)) assert.ok(isCaLike(pem), "an ECDSA public root must pass");
+
+    assert.equal(isCaLike("-----BEGIN CERTIFICATE-----\nAAAA\n-----END CERTIFICATE-----\n"), false, "unparseable entries anchor nothing");
+});
+
+test("#5802: the written combined bundle contains ONLY parseable CAs and carries the marker", () => {
+    ensureRootCA();
+    const combined = fs.readFileSync(combinedCaPath(), "utf8");
+    assert.ok(combined.startsWith("# "), "rebuilt bundles carry the format marker line");
+    const blocks = combined.match(/-----BEGIN CERTIFICATE-----[\s\S]*?-----END CERTIFICATE-----\s*/g) ?? [];
+    assert.ok(blocks.length > 10, `bundle should carry the public roots (found ${blocks.length})`);
+    for (const b of blocks) assert.ok(isCaLike(b), `bundle entry is not a CA:\n${b.slice(0, 120)}`);
+    assert.ok(combined.includes(fs.readFileSync(rootCaPath(), "utf8").trim()), "the MITM root survives the filter");
+});
+
+test("#5802: a pre-upgrade bundle (missing marker) is force-rebuilt once even while fresh", () => {
+    ensureRootCA();
+    const file = combinedCaPath();
+    const stripped = fs.readFileSync(file, "utf8").replace(/^# [^\n]*\n/, "");
+    assert.ok(!stripped.startsWith("# "), "fixture: marker line removed");
+    fs.writeFileSync(file, stripped);
+    const future = new Date(Date.now() + 3600e3);
+    fs.utimesSync(file, future, future);
+    ensureRootCA();
+    const after = fs.readFileSync(file, "utf8");
+    assert.ok(after.startsWith("# "), "missing marker forces the one-time convergence rebuild");
+    assert.ok(after.includes(fs.readFileSync(rootCaPath(), "utf8").trim()));
+});
+
+test("#5802: a fresh bundle WITH marker + root is not rewritten (steady state)", () => {
+    ensureRootCA();
+    const file = combinedCaPath();
+    const future = new Date(Date.now() + 3600e3);
+    fs.utimesSync(file, future, future);
+    const mtimeBefore = fs.statSync(file).mtimeMs;
+    ensureRootCA();
+    assert.equal(fs.statSync(file).mtimeMs, mtimeBefore, "marker + root + fresh = reused, not rebuilt");
+});