diff --git a/docs/consumers/pkg-scriptorium.md b/docs/consumers/pkg-scriptorium.md
index b90b2f1..973fcff 100644
--- a/docs/consumers/pkg-scriptorium.md
+++ b/docs/consumers/pkg-scriptorium.md
@@ -20,12 +20,17 @@ fields:
 | `PromptDir` | Prompt-definition directory, required unless a prompt source option is supplied. |
 | `ProfileDir` | Optional custom profile directory over built-ins. |
 | `SchemaDir` | Schema directory; empty uses `.`. |
-| `Timeout` | Default timeout for the built-in OpenAI-compatible client. |
-| `HTTPClient` | Optional HTTP client for that built-in client. |
+| `Timeout` | Base timeout for the built-in OpenAI-compatible client when `HTTPClient` is absent or has a zero timeout. A non-positive value uses the internal default. |
+| `HTTPClient` | Optional HTTP client for that built-in client. It is cloned; a non-zero `Timeout` on it takes precedence over `Config.Timeout` as the base timeout. |
 
 Nil options are ignored. Invalid construction, including
 `WithLLMClient(nil)`, returns an error matching `ErrInvalidConfig`.
 
+An effective positive `timeout_seconds` replaces the base timeout. An explicit
+request override of zero disables the HTTP-client timeout. The timeout is
+otherwise inherited from the supplied client, `Config.Timeout`, or the internal
+default in that order.
+
 Source options replace their matching directory source:
 
 - prompts: `WithPromptFS(fsys, root)`, `WithPromptFile(path)`;
diff --git a/docs/integrations/openai-compatible-chat.md b/docs/integrations/openai-compatible-chat.md
index 18f81bc..a8d8cae 100644
--- a/docs/integrations/openai-compatible-chat.md
+++ b/docs/integrations/openai-compatible-chat.md
@@ -77,9 +77,12 @@ resolves the configured non-empty `api_key_env` at request time and sends the
 same header. If neither mechanism supplies a key, it sends no
 `Authorization` header.
 
-The configured client timeout applies by default. A positive effective
-`timeout_seconds` replaces it. An explicit request override of zero disables
-the HTTP-client timeout; negative values are rejected before a request is sent.
+The client base timeout is chosen at construction: a non-zero timeout on a
+supplied `http.Client` takes precedence over `Config.Timeout`; otherwise a
+positive `Config.Timeout` is used, then the internal default. A positive
+effective `timeout_seconds` replaces that base. An explicit request override
+of zero disables the HTTP-client timeout; negative values are rejected before a
+request is sent.
 
 ## Response Subset And Failures
 
diff --git a/docs/internal/llm.md b/docs/internal/llm.md
index bb97ad4..bbcea3f 100644
--- a/docs/internal/llm.md
+++ b/docs/internal/llm.md
@@ -10,13 +10,14 @@ format and protocol behavior.
 ## Construction
 
 `NewOpenAICompatibleClient` validates a non-empty configured base URL, records
-an optional default model, and establishes the default timeout. A non-positive
-configured timeout uses the internal default.
+an optional default model, and resolves one base timeout. A supplied client with
+a non-zero timeout supplies that base; otherwise a positive configured timeout
+is used, then the internal default.
 
 When callers supply an `http.Client`, construction clones it rather than
 mutating the caller's instance. A supplied client with no timeout receives the
-resolved default in the clone; a supplied non-zero timeout is retained. The
-client stores the trimmed base URL, default model, timeout, and cloned client.
+resolved base timeout in the clone. The client stores the trimmed base URL,
+default model, and cloned client.
 
 ## Generate Flow
 
@@ -28,7 +29,7 @@ client stores the trimmed base URL, default model, timeout, and cloned client.
    request;
 4. prefer a direct API key, otherwise resolve the configured key environment
    variable;
-5. derive a request HTTP client when an explicit timeout changes the configured
+5. derive a request HTTP client only when an explicit timeout changes the base
    client;
 6. execute the request, reject non-success status responses without returning
    provider response bodies; and
diff --git a/internal/llm/openai_compatible_client.go b/internal/llm/openai_compatible_client.go
index 257768d..5fdaa1c 100644
--- a/internal/llm/openai_compatible_client.go
+++ b/internal/llm/openai_compatible_client.go
@@ -36,7 +36,6 @@ type OpenAICompatibleConfig struct {
 type OpenAICompatibleClient struct {
 	baseURL      string
 	defaultModel string
-	timeout      time.Duration
 	httpClient   *http.Client
 }
 
@@ -67,7 +66,6 @@ func NewOpenAICompatibleClient(cfg OpenAICompatibleConfig) (*OpenAICompatibleCli
 	return &OpenAICompatibleClient{
 		baseURL:      strings.TrimRight(baseURL, "/"),
 		defaultModel: cfg.Model,
-		timeout:      timeout,
 		httpClient:   client,
 	}, nil
 }
@@ -116,19 +114,20 @@ func (c *OpenAICompatibleClient) Generate(ctx context.Context, req domain.Genera
 		httpReq.Header.Set("Authorization", "Bearer "+apiKey)
 	}
 
-	effectiveTimeout := c.timeout
-	if req.Target.TimeoutSeconds > 0 {
-		effectiveTimeout = time.Duration(req.Target.TimeoutSeconds) * time.Second
-	} else if req.TargetPresence.TimeoutSeconds {
-		effectiveTimeout = 0
-	}
-
 	httpClient := c.httpClient
 	if httpClient == nil {
-		httpClient = &http.Client{Timeout: effectiveTimeout}
-	} else if httpClient.Timeout != effectiveTimeout {
+		httpClient = &http.Client{Timeout: defaults.LLMRequestTimeoutDefault}
+	}
+	if req.Target.TimeoutSeconds > 0 {
+		effectiveTimeout := time.Duration(req.Target.TimeoutSeconds) * time.Second
+		if httpClient.Timeout != effectiveTimeout {
+			cloned := *httpClient
+			cloned.Timeout = effectiveTimeout
+			httpClient = &cloned
+		}
+	} else if req.TargetPresence.TimeoutSeconds && httpClient.Timeout != 0 {
 		cloned := *httpClient
-		cloned.Timeout = effectiveTimeout
+		cloned.Timeout = 0
 		httpClient = &cloned
 	}
 
diff --git a/internal/llm/openai_compatible_client_test.go b/internal/llm/openai_compatible_client_test.go
index a205361..49d6ae3 100644
--- a/internal/llm/openai_compatible_client_test.go
+++ b/internal/llm/openai_compatible_client_test.go
@@ -31,9 +31,6 @@ func TestNewOpenAICompatibleClientDoesNotMutateSuppliedZeroTimeoutClient(t *test
 	if client.httpClient == supplied {
 		t.Fatal("expected constructed client to use a cloned HTTP client")
 	}
-	if client.httpClient.Timeout != client.timeout {
-		t.Fatalf("expected cloned client timeout %v, got %v", client.timeout, client.httpClient.Timeout)
-	}
 	if client.httpClient.Timeout <= 0 {
 		t.Fatalf("expected constructed client to use a positive default timeout, got %v", client.httpClient.Timeout)
 	}
@@ -674,8 +671,9 @@ func TestOpenAICompatibleClientExplicitZeroTimeoutDisablesClientTimeout(t *testi
 	defer ts.Close()
 
 	client, err := NewOpenAICompatibleClient(OpenAICompatibleConfig{
-		BaseURL: ts.URL + "/v1",
-		Timeout: time.Nanosecond,
+		BaseURL:    ts.URL + "/v1",
+		Timeout:    time.Nanosecond,
+		HTTPClient: &http.Client{Timeout: time.Nanosecond},
 	})
 	if err != nil {
 		t.Fatal(err)
@@ -718,6 +716,34 @@ func TestOpenAICompatibleClientOmittedTimeoutUsesClientTimeout(t *testing.T) {
 	}
 }
 
+func TestOpenAICompatibleClientSuppliedHTTPClientTimeoutOverridesConfigTimeout(t *testing.T) {
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		time.Sleep(25 * time.Millisecond)
+		_, _ = w.Write([]byte(`{"choices":[{"message":{"content":"ok"}}]}`))
+	}))
+	defer ts.Close()
+
+	client, err := NewOpenAICompatibleClient(OpenAICompatibleConfig{
+		BaseURL:    ts.URL + "/v1",
+		Model:      "model",
+		Timeout:    5 * time.Millisecond,
+		HTTPClient: &http.Client{Timeout: 100 * time.Millisecond},
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	resp, err := client.Generate(context.Background(), domain.GenerateRequest{
+		Prompt: domain.RenderedPrompt{Messages: []domain.RenderedMessage{{Role: "user", Content: "hi"}}},
+	})
+	if err != nil {
+		t.Fatalf("expected supplied client timeout to allow the request, got %v", err)
+	}
+	if resp.Content != "ok" {
+		t.Fatalf("unexpected response content: %q", resp.Content)
+	}
+}
+
 func TestOpenAICompatibleClientRejectsInvalidExtraParamsBeforeProviderCall(t *testing.T) {
 	tests := []struct {
 		name        string
@@ -1011,9 +1037,10 @@ func TestOpenAICompatibleClientRequestTimeoutOverride(t *testing.T) {
 	defer ts.Close()
 
 	client, err := NewOpenAICompatibleClient(OpenAICompatibleConfig{
-		BaseURL: ts.URL + "/v1",
-		Model:   "m",
-		Timeout: 50 * time.Millisecond,
+		BaseURL:    ts.URL + "/v1",
+		Model:      "m",
+		Timeout:    5 * time.Millisecond,
+		HTTPClient: &http.Client{Timeout: 50 * time.Millisecond},
 	})
 	if err != nil {
 		t.Fatal(err)