Add Thinking key-concepts page

docs.json

@@ -108,6 +108,7 @@
                     ]
                   },
                   "lfm/key-concepts/chat-template",
+                  "lfm/key-concepts/thinking",
                   "lfm/key-concepts/text-generation-and-prompting",
                   "lfm/key-concepts/tool-use",
                   "lfm/key-concepts/vision-capabilities",

lfm/key-concepts/chat-template.mdx

@@ -31,7 +31,7 @@
 The complete chat template definition can be found in the `chat_template.jinja` file in each model's Hugging Face repository.
 
 <Note>
-Using LFM2 or LFM2.5? See [LFM2 and LFM2.5](#lfm2-and-lfm25) for their chat template.
+Using LFM2 or LFM2.5? See [LFM2 and LFM2.5](#lfm2-and-lfm2-5) for their chat template.
 </Note>
 
 ## Text Models
@@ -74,7 +74,12 @@
 
 ### Reasoning
 
-Reasoning is enabled by default, so the template opens every assistant turn with `<think>`. Set `enable_thinking=False` in `apply_chat_template()` for direct answers. Reasoning from turns before the latest user message is removed unless `preserve_thinking=True`.
+Thinking models reason before they answer, so the template opens every assistant turn with `<think>`. Two arguments to `apply_chat_template()` control this:
+
+* **`enable_thinking`** (default `True`) — On models that can switch thinking off, `enable_thinking=False` fills in an empty `<think></think>` block instead, so the model starts on the answer straight away. Models that always think don't support `False`.
+* **`preserve_thinking`** (default `False`) — The template removes the reasoning from assistant turns before the latest user message. Set `preserve_thinking=True` to keep it in the prompt.
+
+See [Thinking](/lfm/key-concepts/thinking) for how to use thinking, separate the reasoning from the answer, and check which models can switch thinking off.
 
 ## Vision Models
 
@@ -116,7 +121,7 @@
 <think>
 ```
 
 ## Audio and Omni Models
 
 LFM3-Omni follows the same chat template. Every input audio clip, image, and video sits inside a `<|vision_start|>` / `<|vision_end|>` span, which `apply_chat_template()` inserts for you. Audio clips render as `<|vision_start|><|audio|><|vision_end|>`.
 
@@ -132,7 +137,7 @@
 
 ## LFM2 and LFM2.5
 
-LFM2 and LFM2.5 use a ChatML-like chat template without the `<think>` prefill:
+LFM2 and LFM2.5 use a ChatML-like chat template. Unlike LFM3, most of their templates don't open the assistant turn with `<think>` (see [LFM2.5 Thinking Models](#lfm2-5-thinking-models)):
 
 <ChatMLExample />
 
@@ -173,6 +178,12 @@
 <|im_start|>assistant
 ```
 
+### LFM2.5 Thinking Models
+
+LFM2.5 thinking models always think, and their templates have no `enable_thinking` argument. Depending on the model, the template opens the assistant turn with `<think>` or the model writes it itself. Either way, the reply contains a closing `</think>` before the answer.
+
+For LFM2.5-8B-A1B and LFM2.5-24B-A2B, reasoning before the latest user message is removed by default, while reasoning from later assistant turns stays. LFM2.5-1.2B-Thinking instead retains only the last assistant message's reasoning by default. Set `preserve_thinking=True` to retain reasoning from all assistant messages; LFM2.5-1.2B-Thinking also accepts the older name `keep_past_thinking`. See [Thinking](/lfm/key-concepts/thinking#multi-turn-conversations) for guidance on agent conversations.
+
 ### LFM2 Vision Models
 
 LFM2-VL models follow the same chat template with additional support for images. When formatted, images are represented with a sentinel token (`<image>`), which is automatically replaced with image tokens by the processor.