diff --git a/docs-site/src/content/docs/guides/providers.md b/docs-site/src/content/docs/guides/providers.md
index d4a0f1c724..d93dbe0af5 100644
--- a/docs-site/src/content/docs/guides/providers.md
+++ b/docs-site/src/content/docs/guides/providers.md
@@ -817,18 +817,23 @@ Select **Zhipu AI — BigModel Coding Plan (Responses)** (`zhipu-bigmodel-respon
 for the `openai-responses` endpoint `https://open.bigmodel.cn/api/v1`. This is separate
 from `zhipu-bigmodel-coding`, which uses Chat Completions at `/api/coding/paas/v4`.
 
-The preset uses a **static roster** (`liveModels: false`) taken from the
-[official BigModel Codex example](https://docs.bigmodel.cn/cn/coding-plan/tool/codex.md):
+The preset uses a **static roster** (`liveModels: false`) taken from the published
+[GLM Coding Plan documentation](https://docs.bigmodel.cn/cn/coding-plan/tool/codex.md):
 
 | Model | Context tokens | Upstream selectable effort | Default effort | Reasoning summaries |
 | --- | ---: | --- | --- | --- |
 | `glm-5.3` | 1,048,576 | `low`, `high`, `max` | `max` | Supported |
+| `glm-5.3-flash` | 1,048,576 | `low`, `high`, `max` | `max` | Supported |
 | `glm-5-turbo` | 204,800 | None (empty list) | `max` | Supported |
 
-Both entries declare upstream text-only input. The Codex catalog advertises text and
-image because opencodex's existing vision sidecar can describe images for text-only
-models. Image handling requires an available, enabled vision sidecar; this does not
-declare native BigModel image support.
+`glm-5.3` and `glm-5-turbo` declare upstream text-only input. The Codex catalog
+advertises text and image for them because opencodex's existing vision sidecar can
+describe images for text-only models; that path requires an available, enabled vision
+sidecar and does not claim native BigModel image support.
+
+`glm-5.3-flash` is the exception: it declares native `text` and `image` input, because
+upstream documents it as a natively multimodal model. It therefore reads pictures
+directly instead of being routed through the describe-it-first sidecar detour.
 
 The default model is `glm-5.3`; Responses reasoning content is preserved on replay.
 The existing Codex export adds its compatibility
@@ -839,9 +844,11 @@ For Turbo, outgoing Responses requests omit `reasoning.effort`, including a call
 selection to the upstream default; opencodex does not inject a selectable or wire `max`.
 
 The example's `models.json` is a local catalog file, not a documented HTTP model-list
-response. This preset does not perform live model discovery. `glm-5.3-flash` is not
-seeded here because its exact Responses metadata is not verified. An existing custom
-provider with the same name keeps its configured destination and metadata.
+response, and not the set of models the endpoint serves — the Coding Plan pages state
+that every plan tier reaches GLM-5.3 and GLM-5.3-Flash, and that GLM-5-Turbo calls are
+auto-switched to Flash, so this endpoint was already serving Flash under the Turbo id.
+This preset still does not perform live model discovery. An existing custom provider
+with the same name keeps its configured destination and metadata.
 CLI key login also skips the undocumented `/models` probe and reports validation as
 unknown; successful key authentication is established by a subsequent inference request.
 
diff --git a/docs-site/src/content/docs/reference/configuration/providers.md b/docs-site/src/content/docs/reference/configuration/providers.md
index d40de409d2..e2769ab807 100644
--- a/docs-site/src/content/docs/reference/configuration/providers.md
+++ b/docs-site/src/content/docs/reference/configuration/providers.md
@@ -836,7 +836,7 @@ container usually has no unlocked keychain session, so requests would fail close
 `${ENV_VAR}` reference in the service environment there instead. Env references are left untouched
 by `store`.
 
-The `zhipu-bigmodel-responses` preset seeds `glm-5.3` and `glm-5-turbo` with
+The `zhipu-bigmodel-responses` preset seeds `glm-5.3`, `glm-5.3-flash` and `glm-5-turbo` with
 `liveModels: false` for `https://open.bigmodel.cn/api/v1`. Its static roster and
 per-model context, effort, and summary metadata come from the
 [BigModel Responses guide](/guides/providers/#bigmodel-coding-plan-over-responses).
diff --git a/src/providers/registry.ts b/src/providers/registry.ts
index d4c6c542d0..c4ea553d2d 100644
--- a/src/providers/registry.ts
+++ b/src/providers/registry.ts
@@ -2640,6 +2640,23 @@ export const PROVIDER_REGISTRY: readonly ProviderRegistryEntry[] = [
   // Narrowed carry of #3641: the official Codex example declares a local static catalog,
   // not an HTTP /models contract. Keep Responses separate from the Chat endpoint above.
   // Source: https://docs.bigmodel.cn/cn/coding-plan/tool/codex.md (checked 2026-09-07).
+  //
+  // #4201 completes the roster. The `models.json` example on that Codex page is a *starter
+  // catalog*, not the set of models the endpoint serves, and reading it as the latter is what
+  // left Flash off a subscription that sells it. Three upstream pages say so directly, all
+  // checked 2026-09-11:
+  //   - coding-plan/latest-model.md pins Codex to THIS baseUrl
+  //     (`Codex：https://open.bigmodel.cn/api/v1`) and opens with GLM Coding Plan supporting
+  //     GLM-5.3 and GLM-5.3-Flash for every tier (Max & Pro & Lite), then treats
+  //     `glm-5.3-flash` as an already-callable id in that same tool.
+  //   - coding-plan/overview.md: every plan supports GLM-5.3 and GLM-5.3-Flash, and calls to
+  //     GLM-5-Turbo are auto-switched to GLM-5.3-Flash. Turbo below is therefore an alias of
+  //     the very model this row omitted, which is the clearest statement that the endpoint
+  //     serves Flash: it was already serving it under another name.
+  //   - guide/models/vlm/glm-5.3-flash.md: native multimodal input, 1M context, and text
+  //     parameters explicitly "consistent with GLM-5.3".
+  // No authenticated /models probe is implied by any of this, so `liveModels` and
+  // `apiKeyValidation` below are deliberately unchanged.
   {
     id: "zhipu-bigmodel-responses",
     label: "Zhipu AI — BigModel Coding Plan (Responses)",
@@ -2648,22 +2665,34 @@ export const PROVIDER_REGISTRY: readonly ProviderRegistryEntry[] = [
     authKind: "key",
     dashboardUrl: "https://bigmodel.cn/console/usercenter/apikeys",
     defaultModel: "glm-5.3",
-    models: ["glm-5.3", "glm-5-turbo"],
+    models: ["glm-5.3", "glm-5.3-flash", "glm-5-turbo"],
     liveModels: false,
     // The local Codex catalog does not establish an authenticated HTTP /models contract.
     apiKeyValidation: "unknown",
     jawcodeBundle: "zai",
     // A pre-existing same-named custom provider must retain its destination and key boundary.
     preserveCustomDestination: true,
-    modelContextWindows: { "glm-5.3": 1_048_576, "glm-5-turbo": 204_800 },
-    modelInputModalities: { "glm-5.3": ["text"], "glm-5-turbo": ["text"] },
+    // Flash tracks its 5.3 sibling on this row rather than the Chat row's 1_000_000. Both
+    // models are documented as "1M", and this preset expresses that family's 1M the way
+    // BigModel's own Codex declaration does. Splitting the two would leave one preset
+    // claiming two different sizes for one documented window.
+    modelContextWindows: { "glm-5.3": 1_048_576, "glm-5.3-flash": 1_048_576, "glm-5-turbo": 204_800 },
+    // Flash is the only row here that can actually see an image. Its siblings are declared
+    // text-only and get `image` back from the vision sidecar at catalog-build time; declaring
+    // Flash text-only would route a native VLM's pictures through a describe-it-first detour
+    // and hand the model prose about an image it could have read (same defect
+    // ZAI_GLM_5X_SIDECAR_VISION_MODELS exists to prevent on the Chat rows).
+    modelInputModalities: { "glm-5.3": ["text"], "glm-5.3-flash": ["text", "image"], "glm-5-turbo": ["text"] },
     modelReasoningEfforts: {
       "glm-5.3": ZAI_GLM_53_REASONING_EFFORTS,
+      // Same three effective tiers: upstream documents Flash's text parameters as identical
+      // to GLM-5.3, and the Codex effort table folds every inbound value into low/high/max.
+      "glm-5.3-flash": ZAI_GLM_53_REASONING_EFFORTS,
       // Explicitly empty: Turbo must not inherit the generic selectable effort ladder.
       "glm-5-turbo": [],
     },
-    modelDefaultReasoningEfforts: { "glm-5.3": "max", "glm-5-turbo": "max" },
-    modelSupportsReasoningSummaries: { "glm-5.3": true, "glm-5-turbo": true },
+    modelDefaultReasoningEfforts: { "glm-5.3": "max", "glm-5.3-flash": "max", "glm-5-turbo": "max" },
+    modelSupportsReasoningSummaries: { "glm-5.3": true, "glm-5.3-flash": true, "glm-5-turbo": true },
     // Responses replay uses this provider-level flag, not the Chat-path model list.
     preserveResponsesReasoningContent: true,
     note: "Domestic BigModel Coding Plan Responses endpoint; static model roster",
diff --git a/tests/providers/provider-registry-parity.test.ts b/tests/providers/provider-registry-parity.test.ts
index ab9a5c64a3..1dcc89ca1f 100644
--- a/tests/providers/provider-registry-parity.test.ts
+++ b/tests/providers/provider-registry-parity.test.ts
@@ -451,9 +451,20 @@ describe("provider registry parity", () => {
     expect(glm53Entry?.default_reasoning_level).toBe("max");
   });
 
-  test("BigModel Responses exports only the officially documented static Codex models", () => {
-    // Independent oracle: https://docs.bigmodel.cn/cn/coding-plan/tool/codex.md,
-    // local models.json example checked 2026-09-07; not an authenticated /models response.
+  test("BigModel Responses exports the documented Coding Plan roster for the Codex endpoint", () => {
+    // Independent oracle, all checked 2026-09-11 and none of them an authenticated /models
+    // response. The earlier version of this test read the models.json sample on
+    // https://docs.bigmodel.cn/cn/coding-plan/tool/codex.md as the endpoint's whole roster and
+    // hard-locked two models. It is a starter catalog, and three other upstream pages contradict
+    // that reading (#4201):
+    //   - coding-plan/latest-model.md binds Codex to https://open.bigmodel.cn/api/v1 and states
+    //     GLM-5.3 and GLM-5.3-Flash are available to every plan tier.
+    //   - coding-plan/overview.md states GLM-5-Turbo calls are auto-switched to GLM-5.3-Flash,
+    //     so this preset was already reaching Flash through the Turbo id it does list.
+    //   - guide/models/vlm/glm-5.3-flash.md gives native multimodal input, a 1M window, and text
+    //     parameters "consistent with GLM-5.3".
+    // What stays locked is the part no document supports: there is still no HTTP /models
+    // contract here, so liveModels and apiKeyValidation must not drift.
     const id = "zhipu-bigmodel-responses";
     const registry = PROVIDER_REGISTRY.find(entry => entry.id === id)!;
     expect(registry).toMatchObject({
@@ -461,17 +472,24 @@ describe("provider registry parity", () => {
       baseUrl: "https://open.bigmodel.cn/api/v1",
       authKind: "key",
       defaultModel: "glm-5.3",
-      models: ["glm-5.3", "glm-5-turbo"],
+      models: ["glm-5.3", "glm-5.3-flash", "glm-5-turbo"],
       liveModels: false,
       preserveCustomDestination: true,
       preserveResponsesReasoningContent: true,
     });
     expect(registry.modelDiscovery).toBeUndefined();
     expect(registry.preserveReasoningContentModels).toBeUndefined();
-    const upstreamModalities = { "glm-5.3": ["text"], "glm-5-turbo": ["text"] };
+    // Flash is the one row upstream documents as natively multimodal; the other two are text.
+    // Pinned separately from the global VLM rule above so that copying glm-5.3's ["text"] onto
+    // Flash fails here, naming this preset, rather than only in a loop over every provider.
+    const upstreamModalities = {
+      "glm-5.3": ["text"], "glm-5.3-flash": ["text", "image"], "glm-5-turbo": ["text"],
+    };
     expect(registry.modelInputModalities).toEqual(upstreamModalities);
+    expect(registry.modelInputModalities?.["glm-5.3-flash"]).toContain("image");
+    expect(registry.noVisionModels ?? []).not.toContain("glm-5.3-flash");
     expect(KEY_LOGIN_PROVIDERS[id]).toMatchObject({
-      models: ["glm-5.3", "glm-5-turbo"], liveModels: false, apiKeyValidation: "unknown",
+      models: ["glm-5.3", "glm-5.3-flash", "glm-5-turbo"], liveModels: false, apiKeyValidation: "unknown",
     });
     const provider = providerConfigSeed(registry);
     enrichProviderFromRegistry(id, provider);
@@ -480,18 +498,23 @@ describe("provider registry parity", () => {
     const models = provider.models!.map(modelId => applyProviderConfigHints(id, provider, {
       provider: id, id: modelId,
     }));
-    // The official upstream declaration stays text-only. Catalog hints add image for the
-    // existing vision sidecar (vision/eligibility.ts), not native BigModel image support.
+    // glm-5.3 and glm-5-turbo stay text-only upstream and get image back from the existing
+    // vision sidecar (vision/eligibility.ts). Flash already declares image, so its catalog
+    // modality is the model's own capability rather than a sidecar detour — the rows look
+    // alike below, and this assertion is what keeps the reason for them different.
     expect(provider.modelInputModalities).toEqual(upstreamModalities);
     expect(models).toMatchObject([
       { id: "glm-5.3", contextWindow: 1_048_576, reasoningEfforts: ["low", "high", "max"],
         defaultReasoningEffort: "max", supportsReasoningSummaries: true, inputModalities: ["text", "image"] },
+      { id: "glm-5.3-flash", contextWindow: 1_048_576, reasoningEfforts: ["low", "high", "max"],
+        defaultReasoningEffort: "max", supportsReasoningSummaries: true, inputModalities: ["text", "image"] },
       { id: "glm-5-turbo", contextWindow: 204_800, reasoningEfforts: [],
         defaultReasoningEffort: "max", supportsReasoningSummaries: true, inputModalities: ["text", "image"] },
     ]);
     const entries = buildCatalogEntries(nativeTemplate(), [], models);
     for (const [modelId, window, efforts] of [
       ["glm-5.3", 1_048_576, ["low", "high", "max", "ultra"]],
+      ["glm-5.3-flash", 1_048_576, ["low", "high", "max", "ultra"]],
       ["glm-5-turbo", 204_800, []],
     ] as const) {
       const entry = entries.find(row => row.slug === `${id}/${modelId}`);
@@ -505,7 +528,9 @@ describe("provider registry parity", () => {
       expect((entry?.supported_reasoning_levels as Array<{ effort: string }>).map(row => row.effort))
         .toEqual([...efforts]);
     }
-    expect(entries.some(entry => String(entry.slug).includes("glm-5.3-flash"))).toBe(false);
+    // The reported gap: Flash reaches the exported catalog for this preset, once, under its
+    // own slug rather than only as the Turbo alias upstream silently redirects.
+    expect(entries.filter(entry => String(entry.slug) === `${id}/glm-5.3-flash`)).toHaveLength(1);
   });
 
   test("BigModel Responses key login does not probe an undocumented models endpoint", async () => {