diff --git a/README.md b/README.md
index d6d86547..69d7fbf1 100644
--- a/README.md
+++ b/README.md
@@ -167,6 +167,17 @@ recognized child variable (for example `ANTHROPIC_API_KEY`, `OPENAI_API_KEY`, `G
 `ZAI_API_KEY`). Neither the generic file path nor deprecated `PI_PROVIDER_API_KEY` is inherited by
 Pi. Local providers such as Ollama require no model key.
 
+`THT_MODEL_API_KEY_FILE` supports Pi providers whose authentication is exactly one key:
+`ant-ling`, `anthropic`, `cerebras`, `deepseek`, `fireworks`, `github-copilot`, `google`
+(including the `gemini` alias), `google-vertex` when using its API-key mode, `groq`,
+`huggingface`, `kimi-coding`, `minimax`, `minimax-cn`, `mistral`, `moonshotai`,
+`moonshotai-cn`, `nvidia`, `openai`, `opencode`, `opencode-go`, `openrouter`, `together`,
+`vercel-ai-gateway`, `xai`, the four `xiaomi*` providers, `zai`, and `zai-coding-cn`.
+Compound providers are deliberately unsupported: `amazon-bedrock`, `azure-openai-responses`,
+`cloudflare-workers-ai`, and `cloudflare-ai-gateway` require multiple credential/configuration
+values. Selecting one fails before Pi starts; ambient AWS, Azure, and Cloudflare credentials are
+still scrubbed. Supporting them requires a future dedicated provider-specific configuration.
+
 ## Reproducible image verification
 
 Base images use exact tags and immutable multi-platform manifest digests. Dependency update and
diff --git a/backend/src/pi/provider-credentials.ts b/backend/src/pi/provider-credentials.ts
index 66cbde7b..a2791c86 100644
--- a/backend/src/pi/provider-credentials.ts
+++ b/backend/src/pi/provider-credentials.ts
@@ -23,13 +23,9 @@ export const PI_0803_CREDENTIAL_ENV_NAMES = Object.freeze([
 ]);
 
 const PROVIDER_KEY_ENV: Readonly<Record<string, string>> = {
-  "amazon-bedrock": "AWS_BEARER_TOKEN_BEDROCK",
   "ant-ling": "ANT_LING_API_KEY",
   anthropic: "ANTHROPIC_API_KEY",
-  "azure-openai-responses": "AZURE_OPENAI_API_KEY",
   cerebras: "CEREBRAS_API_KEY",
-  "cloudflare-ai-gateway": "CLOUDFLARE_API_KEY",
-  "cloudflare-workers-ai": "CLOUDFLARE_API_KEY",
   deepseek: "DEEPSEEK_API_KEY", fireworks: "FIREWORKS_API_KEY",
   "github-copilot": "COPILOT_GITHUB_TOKEN", google: "GEMINI_API_KEY",
   "google-vertex": "GOOGLE_CLOUD_API_KEY", groq: "GROQ_API_KEY", huggingface: "HF_TOKEN",
@@ -43,6 +39,9 @@ const PROVIDER_KEY_ENV: Readonly<Record<string, string>> = {
   "xiaomi-token-plan-sgp": "XIAOMI_TOKEN_PLAN_SGP_API_KEY", zai: "ZAI_API_KEY",
   "zai-coding-cn": "ZAI_CODING_CN_API_KEY",
 };
+const COMPOUND_PROVIDERS = new Set([
+  "amazon-bedrock", "azure-openai-responses", "cloudflare-ai-gateway", "cloudflare-workers-ai",
+]);
 const LOCAL_PROVIDERS = new Set(["ollama", "lmstudio", "local", "aritmolab", "faux"]);
 
 export function canonicalPiProvider(provider: string | undefined): string | undefined {
@@ -109,6 +108,12 @@ export function buildPiChildEnv(opts: {
   delete env.THT_MODEL_API_KEY_FILE;
   for (const name of PI_0803_CREDENTIAL_ENV_NAMES) delete env[name];
   const provider = canonicalPiProvider(opts.provider);
+  if (provider && COMPOUND_PROVIDERS.has(provider)) {
+    throw new Error(
+      "compound credential bundles are unsupported by THT_MODEL_API_KEY_FILE; "
+      + "dedicated provider configuration is required",
+    );
+  }
   if (provider && !LOCAL_PROVIDERS.has(provider)) {
     const envName = PROVIDER_KEY_ENV[provider];
     if (!envName || !opts.credentialFile) throw new Error("model provider credential is unavailable");
diff --git a/backend/test/list-models.test.ts b/backend/test/list-models.test.ts
index f8cef6bd..a86efab7 100644
--- a/backend/test/list-models.test.ts
+++ b/backend/test/list-models.test.ts
@@ -141,3 +141,25 @@ test("model-list spawn loads only the selected canonical provider credential", a
     rmSync(path.dirname(script), { recursive: true, force: true });
   }
 });
+
+test.each(["amazon-bedrock", "azure-openai-responses", "cloudflare-workers-ai", "cloudflare-ai-gateway"])(
+  "model listing rejects compound provider %s before spawning Pi", async (provider) => {
+    const script = scriptWith([]);
+    const secret = join(path.dirname(script), "model-key");
+    writeFileSync(secret, "selected-secret", { mode: 0o600 });
+    let spawns = 0;
+    const lister = createPiModelLister(loadConfig({
+      PI_PROVIDER: provider, THT_MODEL_API_KEY_FILE: secret,
+    }), {
+      spawnFn: () => { spawns += 1; throw new Error("must not spawn"); },
+    });
+    try {
+      await expect(lister()).rejects.toThrow(
+        "compound credential bundles are unsupported by THT_MODEL_API_KEY_FILE; dedicated provider configuration is required",
+      );
+      expect(spawns).toBe(0);
+    } finally {
+      rmSync(path.dirname(script), { recursive: true, force: true });
+    }
+  },
+);
diff --git a/backend/test/pi-process-manager.test.ts b/backend/test/pi-process-manager.test.ts
index 6ec5b6c5..43cb38d0 100644
--- a/backend/test/pi-process-manager.test.ts
+++ b/backend/test/pi-process-manager.test.ts
@@ -262,6 +262,25 @@ test("local providers spawn without a model key and scrub ambient generic creden
   }
 });
 
+test.each(["amazon-bedrock", "azure-openai-responses", "cloudflare-workers-ai", "cloudflare-ai-gateway"])(
+  "session spawn rejects compound provider %s before spawning Pi", async (provider) => {
+    const secret = path.resolve(__dirname, `.compound-key-${process.pid}-${provider}`);
+    writeFileSync(secret, "provider-secret", { mode: 0o600 });
+    let spawns = 0;
+    const mgr = new PiProcessManager(loadConfig({ THT_MODEL_API_KEY_FILE: secret }), {
+      spawnFn: () => { spawns += 1; throw new Error("must not spawn"); },
+    });
+    try {
+      await expect(mgr.spawnFor("compound-provider", { provider })).rejects.toThrow(
+        "compound credential bundles are unsupported by THT_MODEL_API_KEY_FILE; dedicated provider configuration is required",
+      );
+      expect(spawns).toBe(0);
+    } finally {
+      await import("node:fs/promises").then((fs) => fs.unlink(secret));
+    }
+  },
+);
+
 test.each(["missing", "permissive", "unreadable", "directory", "symlink", "unsupported"])(
   "hosted provider credential failure is sanitized: %s", async (kind) => {
     const target = path.resolve(__dirname, `.bad-model-key-${process.pid}-${kind}`);
diff --git a/backend/test/provider-credentials.test.ts b/backend/test/provider-credentials.test.ts
index cd484a49..68f08dc6 100644
--- a/backend/test/provider-credentials.test.ts
+++ b/backend/test/provider-credentials.test.ts
@@ -74,3 +74,44 @@ test("Docker secrets require a secure root-owned /run/secrets parent and 0444 fi
     },
   })).toThrow("model provider credential is unavailable");
 });
+
+test.each(["amazon-bedrock", "azure-openai-responses", "cloudflare-workers-ai", "cloudflare-ai-gateway"])(
+  "compound provider %s fails closed before opening the generic secret", (provider) => {
+    let opens = 0;
+    expect(() => buildPiChildEnv({
+      ambient: {}, provider, credentialFile: "/unused",
+      fsOps: {
+        lstat: () => { throw new Error("must not inspect file"); },
+        open: () => { opens += 1; return 9; },
+        fstat: () => { throw new Error("must not inspect file"); },
+        read: () => "secret", close: () => undefined,
+      },
+    })).toThrow(
+      "compound credential bundles are unsupported by THT_MODEL_API_KEY_FILE; dedicated provider configuration is required",
+    );
+    expect(opens).toBe(0);
+  },
+);
+
+test("single-key providers scrub ambient compound companions before injecting their key", () => {
+  const stat = {
+    dev: 7, ino: 1, uid: process.getuid?.() ?? 0, mode: 0o100600, nlink: 1, size: 6,
+    isFile: () => true, isDirectory: () => false, isSymbolicLink: () => false,
+  };
+  const env = buildPiChildEnv({
+    ambient: {
+      AWS_ACCESS_KEY_ID: "ambient", AWS_SECRET_ACCESS_KEY: "ambient",
+      CLOUDFLARE_ACCOUNT_ID: "ambient", CLOUDFLARE_GATEWAY_ID: "ambient",
+    },
+    provider: "openai", credentialFile: "/safe/key",
+    fsOps: {
+      lstat: () => stat as any, open: () => 9, fstat: () => stat as any,
+      read: () => "secret", close: () => undefined,
+    },
+  });
+  expect(env.OPENAI_API_KEY).toBe("secret");
+  expect(env).not.toHaveProperty("AWS_ACCESS_KEY_ID");
+  expect(env).not.toHaveProperty("AWS_SECRET_ACCESS_KEY");
+  expect(env).not.toHaveProperty("CLOUDFLARE_ACCOUNT_ID");
+  expect(env).not.toHaveProperty("CLOUDFLARE_GATEWAY_ID");
+});
diff --git a/docs/general/pi-configuration.md b/docs/general/pi-configuration.md
index 9c4beeca..ecc2606b 100644
--- a/docs/general/pi-configuration.md
+++ b/docs/general/pi-configuration.md
@@ -12,6 +12,19 @@ le chiavi di provider non selezionati e il vecchio `PI_PROVIDER_API_KEY` vengono
 del child. Provider locali come `ollama`, `lmstudio` e `aritmolab` continuano senza chiave; un provider
 hosted non mappato o un secret mancante/non sicuro fallisce prima dello spawn con errore sanitizzato.
 
+La sorgente generica supporta soltanto provider con una singola chiave: `ant-ling`, `anthropic`,
+`cerebras`, `deepseek`, `fireworks`, `github-copilot`, `google` (anche tramite alias `gemini`),
+`google-vertex` in modalità API key, `groq`, `huggingface`, `kimi-coding`, `minimax`, `minimax-cn`,
+`mistral`, `moonshotai`, `moonshotai-cn`, `nvidia`, `openai`, `opencode`, `opencode-go`,
+`openrouter`, `together`, `vercel-ai-gateway`, `xai`, i quattro provider `xiaomi*`, `zai` e
+`zai-coding-cn`.
+
+I provider composti `amazon-bedrock`, `azure-openai-responses`, `cloudflare-workers-ai` e
+`cloudflare-ai-gateway` non sono rappresentabili da un solo file. La selezione fallisce prima
+dello spawn (anche durante l'elenco modelli); tutte le credenziali ambientali AWS, Azure e
+Cloudflare restano comunque rimosse. Servirà una futura configurazione dedicata per provider per
+supportare questi bundle senza ambiguità.
+
 ## I tre livelli di provenienza di un modello
 
 ### 1. Built-in (compilato dentro Pi)