Release v1.0.3: fix header fingerprint (UA, Device-Model, Os-Version)

Plugin was silently 403ing every live request with
'access_terminated_error: only available for Coding Agents'. Discovered by
capturing what kimi-cli actually sends on the wire and diffing.

Three fingerprint bugs, each sufficient on its own to trigger the 403:

* User-Agent was 'KimiCodeCLI/<v>'; upstream sends 'KimiCLI/<v>'.
  (research/kimi-cli/src/kimi_cli/constant.py::get_user_agent)
* X-Msh-Device-Model was 'x86_64'; upstream sends
  '{system} {release} {machine}' e.g. 'Linux 7.0.0 x86_64'.
  (research/kimi-cli/src/kimi_cli/auth/oauth.py::_device_model)
* X-Msh-Os-Version was '{type} {release}' e.g. 'Linux 7.0.0'; upstream
  sends platform.version() i.e. the kernel build string. Node equivalent
  is os.version().

Verified live against api.kimi.com/coding/v1 with a freshly-minted JWT:
200 OK and real K2.6 response after the fix; 403 before.

Locked in with regression tests in test/headers.test.ts and
test/constants.test.ts, and documented in AGENTS.md contract rule 1.

Author: lemon07r

AGENTS.md

@@ -50,7 +50,7 @@ Data flow on a chat request:
 
 These are the invariants that, if broken, silently degrade K2.6 → K2.5 or produce fingerprint-based throttling. Do not "clean them up" without reading the linked upstream.
 
-1. **`X-Msh-Version` and `User-Agent` must track `kimi-cli`.** Bumping involves exactly one line in `src/constants.ts`. See upstream `research/kimi-cli/src/kimi_cli/constant.py`.
+1. **`X-Msh-Version` and `User-Agent` must track `kimi-cli`.** Bumping involves exactly one line in `src/constants.ts`. See upstream `research/kimi-cli/src/kimi_cli/constant.py`. The UA prefix is `KimiCLI/` (not `KimiCodeCLI/`) — Moonshot's `kimi-for-coding` backend 403s with `access_terminated_error: only available for Coding Agents such as Kimi CLI, Claude Code, Roo Code…` on any other prefix. Likewise, `X-Msh-Device-Model` is `"{system} {release} {machine}"` (e.g. `Linux 7.0.0 x86_64`) — NOT just `{arch}` — and `X-Msh-Os-Version` is the kernel build string from `os.version()`, NOT `"{type} {release}"`. Tested live against `api.kimi.com/coding/v1` on 2026-04-17 — any of those three fields off-spec → 403.
 2. **`X-Msh-Device-Id` must be stable across runs.** Never regenerate a fresh UUID at import time. `getDeviceId()` reads/writes `~/.kimi/device_id`; that path is shared with `kimi-cli` on purpose.
 3. **`Authorization` header is owned by `loader.fetch`.** Anything else (opencode core, the SDK, future hooks) must be overridden. Our `loader` deletes both `authorization` and `Authorization` before setting its own.
 4. **Effort ↔ fields mapping** (kimi-cli `llm.py` / `kosong/chat_provider/kimi.py`):

package.json

@@ -1,6 +1,6 @@
 {
   "name": "opencode-kimi-full",
-  "version": "1.0.2",
+  "version": "1.0.3",
   "description": "OpenCode plugin that adds first-class support for Kimi K2.6 (kimi-for-coding) via the official Kimi OAuth device flow, matching the upstream kimi-cli 1:1.",
   "license": "MIT",
   "repository": {

src/constants.ts

@@ -8,7 +8,11 @@
 // secret. scope `kimi-code` is what routes the issued JWT to K2.6.
 
 export const KIMI_CLI_VERSION = "1.35.0"
-export const USER_AGENT = `KimiCodeCLI/${KIMI_CLI_VERSION}`
+// Upstream: research/kimi-cli/src/kimi_cli/constant.py get_user_agent() →
+// f"KimiCLI/{get_version()}". This must match verbatim — Moonshot's
+// `kimi-for-coding` backend 403s on any other UA prefix
+// ("access_terminated_error: only available for Coding Agents").
+export const USER_AGENT = `KimiCLI/${KIMI_CLI_VERSION}`
 
 export const OAUTH_HOST = "https://auth.kimi.com"
 export const OAUTH_DEVICE_AUTH_URL = `${OAUTH_HOST}/api/oauth/device_authorization`

src/headers.ts

@@ -33,15 +33,27 @@ function ascii(value: string): string {
   return value.replace(/[^\x20-\x7e]/g, "?")
 }
 
-/** Builds the 7 X-Msh-* / UA headers kimi-cli sends on every request. */
+/**
+ * Builds the 7 X-Msh-* / UA headers kimi-cli sends on every request.
+ *
+ * Values mirror research/kimi-cli/src/kimi_cli/auth/oauth.py → _common_headers
+ * and _device_model. Deviations cause Moonshot's backend to 403 with
+ * "access_terminated_error: Kimi For Coding is currently only available for
+ * Coding Agents". Node equivalents:
+ *   - platform.system()  → os.type()     ("Linux"/"Darwin"/"Windows_NT")
+ *   - platform.release() → os.release()
+ *   - platform.machine() → os.machine?.() (Node 20+ "x86_64"; NOT os.arch() which says "x64")
+ *   - platform.version() → os.version()  (kernel build string on Linux)
+ */
 export function kimiHeaders(): Record<string, string> {
+  const machine = os.machine?.() || os.arch()
   return {
     "User-Agent": USER_AGENT,
     "X-Msh-Platform": "kimi_cli",
     "X-Msh-Version": KIMI_CLI_VERSION,
     "X-Msh-Device-Name": ascii(os.hostname() || "unknown"),
-    "X-Msh-Device-Model": ascii(os.machine?.() || os.arch()),
+    "X-Msh-Device-Model": ascii(`${os.type()} ${os.release()} ${machine}`),
     "X-Msh-Device-Id": getDeviceId(),
-    "X-Msh-Os-Version": ascii(`${os.type()} ${os.release()}`),
+    "X-Msh-Os-Version": ascii(os.version?.() || `${os.type()} ${os.release()}`),
   }
 }

test/constants.test.ts

@@ -10,7 +10,10 @@ test("KIMI_CLI_VERSION is a non-empty semver", () => {
 })
 
 test("USER_AGENT embeds KIMI_CLI_VERSION", () => {
-  expect(C.USER_AGENT).toBe(`KimiCodeCLI/${C.KIMI_CLI_VERSION}`)
+  // Must be `KimiCLI/<version>` verbatim — Moonshot's backend 403s on any
+  // other UA prefix ("access_terminated_error"). See upstream
+  // research/kimi-cli/src/kimi_cli/constant.py → get_user_agent.
+  expect(C.USER_AGENT).toBe(`KimiCLI/${C.KIMI_CLI_VERSION}`)
 })
 
 test("OAuth constants match upstream kimi-cli exactly", () => {

test/headers.test.ts

@@ -58,3 +58,29 @@ test("Device id is also present and matches in the headers map", () => {
   const h = kimiHeaders()
   expect(h["X-Msh-Device-Id"]).toBe(getDeviceId())
 })
+
+// Regression guard: prior to v1.0.3 we were sending `X-Msh-Device-Model =
+// <arch>` and `X-Msh-Os-Version = <type release>`. That didn't match kimi-cli
+// (which uses `platform.system() + release() + machine()` for the model and
+// `platform.version()` — the kernel build string — for the os version) and
+// caused Moonshot to 403 every request from this plugin with
+// "access_terminated_error". Keep these shape-asserts strict so a future
+// "cleanup" of headers.ts can't silently regress the fingerprint.
+test("X-Msh-Device-Model matches kimi-cli _device_model() shape (system release machine)", () => {
+  const h = kimiHeaders()
+  const sys = os.type()
+  const rel = os.release()
+  const mach = os.machine?.() || os.arch()
+  expect(h["X-Msh-Device-Model"]).toBe(`${sys} ${rel} ${mach}`)
+  // Must contain whitespace-separated release and machine — i.e. more than a
+  // bare arch string.
+  expect(h["X-Msh-Device-Model"]).toContain(" ")
+})
+
+test("X-Msh-Os-Version matches os.version() (kernel build string on Linux)", () => {
+  const h = kimiHeaders()
+  // `os.version()` exists in Node 13.13+ — be lenient if missing.
+  if (typeof os.version === "function") {
+    expect(h["X-Msh-Os-Version"]).toBe(os.version())
+  }
+})