# Extension points — AUTOMATIC1111/stable-diffusion-webui

> Canonical page: https://codevetter.com/unpack/stable-diffusion-webui/extension-points

# Extension points — AUTOMATIC1111/stable-diffusion-webui

Scanned commit 82a973c04367123ae98bd9abdf80d9eda9b910e2 (2024-07-27). Generated by codevetter codevetter 1.12.0 on 2026-09-22.

This repo is primarily an extension host. Four plug-in surfaces exist: (1) extensions in extensions/ and extensions-builtin/ — directories with optional preload.py (argparse), install.py (setup), scripts/*.py (Script subclasses), metadata.ini (ordering/deps), and javascript/*.js; (2) the Script base class lifecycle with ~20 hooks from before_process to postprocess; (3) the script_callbacks.py registry with ~20 named callback categories including CFG denoiser per-step hooks; (4) registries for extra networks, samplers, upscalers, optimizers, and UNET patches.
- Extension discovery: extensions.list_extensions() scans extensions-builtin/ then extensions/, building Extension objects gated by --disable-all-extensions/--disable-extra-extensions and opts.disabled_extensions; ExtensionMetadata reads metadata.ini for canonical Name and [Extension] Requires plus per-script Requires/Before/After ordering fields. — [modules/extensions.py#L228-266](https://github.com/AUTOMATIC1111/stable-diffusion-webui/blob/82a973c04367123ae98bd9abdf80d9eda9b910e2/modules/extensions.py#L228-L266) [modules/extensions.py#L37-103](https://github.com/AUTOMATIC1111/stable-diffusion-webui/blob/82a973c04367123ae98bd9abdf80d9eda9b910e2/modules/extensions.py#L37-L103)
- Script loading: scripts.load_scripts() runs list_scripts('scripts','.py') + list_scripts('modules/processing_scripts','.py') over the base dir and every active extension, orders files by topological_sort of metadata dependencies, load_module() exec's each file, and registers every Script or ScriptPostprocessing subclass found into scripts_data/postprocessing_scripts_data. — [modules/scripts.py#L393-531](https://github.com/AUTOMATIC1111/stable-diffusion-webui/blob/82a973c04367123ae98bd9abdf80d9eda9b910e2/modules/scripts.py#L393-L531) [modules/script_loading.py](https://github.com/AUTOMATIC1111/stable-diffusion-webui/blob/82a973c04367123ae98bd9abdf80d9eda9b910e2/modules/script_loading.py)
- Script API: subclass modules.scripts.Script, implement title()/ui(is_img2img)/show()/run(p,*args); AlwaysVisible return from show() makes it always-on; lifecycle hooks include setup, before_process, process, before_process_batch, after_extra_networks_activate, process_batch, postprocess_batch, postprocess_batch_list, on_mask_blend, post_sample, postprocess_image, postprocess_image_after_composite, postprocess, before_hr — each documented in the class. — [modules/scripts.py#L52-348](https://github.com/AUTOMATIC1111/stable-diffusion-webui/blob/82a973c04367123ae98bd9abdf80d9eda9b910e2/modules/scripts.py#L52-L348)
- script_callbacks.py exposes registration functions on_app_started, on_before_reload, on_model_loaded, on_ui_tabs, on_ui_train_tabs, on_ui_settings, on_before_image_saved, on_image_saved, on_extra_noise, on_cfg_denoiser, on_cfg_denoised, on_cfg_after_cfg, on_before_component, on_after_component, on_image_grid, on_infotext_pasted, on_script_unloaded, on_before_ui, on_list_optimizers, on_list_unets, on_before_token_counter — backed by callback_map lists with ordered sorting and per-extension callback naming. — [modules/script_callbacks.py#L219-241](https://github.com/AUTOMATIC1111/stable-diffusion-webui/blob/82a973c04367123ae98bd9abdf80d9eda9b910e2/modules/script_callbacks.py#L219-L241) [modules/script_callbacks.py#L456-613](https://github.com/AUTOMATIC1111/stable-diffusion-webui/blob/82a973c04367123ae98bd9abdf80d9eda9b910e2/modules/script_callbacks.py#L456-L613)
- on_ui_tabs is how extensions add top-level Gradio tabs: callback returns [(blocks, label, elem_id)] tuples appended to interfaces in create_ui(); on_before_component/after_component (or Script.on_before_component(elem_id=...)) lets scripts inject/modify any Gradio component by elem_id. — [modules/script_callbacks.py#L278-290](https://github.com/AUTOMATIC1111/stable-diffusion-webui/blob/82a973c04367123ae98bd9abdf80d9eda9b910e2/modules/script_callbacks.py#L278-L290) [modules/ui.py#L1124-1148](https://github.com/AUTOMATIC1111/stable-diffusion-webui/blob/82a973c04367123ae98bd9abdf80d9eda9b910e2/modules/ui.py#L1124-L1148) [modules/scripts.py#L290-328](https://github.com/AUTOMATIC1111/stable-diffusion-webui/blob/82a973c04367123ae98bd9abdf80d9eda9b910e2/modules/scripts.py#L290-L328)
- Extra networks: call extra_networks.register_extra_network(obj) (name matches <name:...> in prompts) and register_extra_network_alias; obj implements activate(p, params_list)/deactivate(p). extensions-builtin/Lora registers ExtraNetworkLora with alias 'lyco' in its scripts/lora_script.py before_ui callback. — [modules/extra_networks.py#L9-29](https://github.com/AUTOMATIC1111/stable-diffusion-webui/blob/82a973c04367123ae98bd9abdf80d9eda9b910e2/modules/extra_networks.py#L9-L29) [modules/extra_networks.py#L48-87](https://github.com/AUTOMATIC1111/stable-diffusion-webui/blob/82a973c04367123ae98bd9abdf80d9eda9b910e2/modules/extra_networks.py#L48-L87) [extensions-builtin/Lora/scripts/lora_script.py](https://github.com/AUTOMATIC1111/stable-diffusion-webui/blob/82a973c04367123ae98bd9abdf80d9eda9b910e2/extensions-builtin/Lora/scripts/lora_script.py)
- preload.py hook: any extension dir containing preload.py gets load_module'd and its preload(parser) called during shared_cmd_options import, letting extensions add CLI args before cmd_opts is parsed (Lora uses it for --lora-dir/--lyco-dir-backcompat). — [modules/script_loading.py#L19-35](https://github.com/AUTOMATIC1111/stable-diffusion-webui/blob/82a973c04367123ae98bd9abdf80d9eda9b910e2/modules/script_loading.py#L19-L35) [modules/shared_cmd_options.py#L9-10](https://github.com/AUTOMATIC1111/stable-diffusion-webui/blob/82a973c04367123ae98bd9abdf80d9eda9b910e2/modules/shared_cmd_options.py#L9-L10) [extensions-builtin/Lora/preload.py](https://github.com/AUTOMATIC1111/stable-diffusion-webui/blob/82a973c04367123ae98bd9abdf80d9eda9b910e2/extensions-builtin/Lora/preload.py)
- Settings extension: update shared.options_templates with shared.options_section(...) dicts of OptionInfo — Lora adds 'sd_lora', 'lora_*' options this way; each OptionInfo can carry an onchange callback and restrict_api flag. — [extensions-builtin/Lora/scripts/lora_script.py](https://github.com/AUTOMATIC1111/stable-diffusion-webui/blob/82a973c04367123ae98bd9abdf80d9eda9b910e2/extensions-builtin/Lora/scripts/lora_script.py) [modules/shared_options.py#L9-34](https://github.com/AUTOMATIC1111/stable-diffusion-webui/blob/82a973c04367123ae98bd9abdf80d9eda9b910e2/modules/shared_options.py#L9-L34) [modules/options.py#L13-58](https://github.com/AUTOMATIC1111/stable-diffusion-webui/blob/82a973c04367123ae98bd9abdf80d9eda9b910e2/modules/options.py#L13-L58)
- Extra Networks pages: ui_extra_networks.register_page(ExtraNetworksPage subclass) adds browsable card tabs; ui_extra_networks_user_metadata.py shows per-file .json sidecar editing — pages are served to the browser via add_pages_to_demo. — [modules/ui_extra_networks.py](https://github.com/AUTOMATIC1111/stable-diffusion-webui/blob/82a973c04367123ae98bd9abdf80d9eda9b910e2/modules/ui_extra_networks.py) [modules/ui_extra_networks_user_metadata.py](https://github.com/AUTOMATIC1111/stable-diffusion-webui/blob/82a973c04367123ae98bd9abdf80d9eda9b910e2/modules/ui_extra_networks_user_metadata.py) [extensions-builtin/Lora/ui_extra_networks_lora.py](https://github.com/AUTOMATIC1111/stable-diffusion-webui/blob/82a973c04367123ae98bd9abdf80d9eda9b910e2/extensions-builtin/Lora/ui_extra_networks_lora.py)
- Sampler/scheduler/upscaler registration: append SamplerData to sd_samplers_*.py lists consumed by all_samplers; sd_schedulers.schedulers; upscaler.Upscaler subclasses discovered by modelloader.load_upscalers() scanning models dirs; optimizers via on_list_optimizers into sd_hijack_optimizations; UNET patches via on_list_unets into sd_unet. — [modules/sd_samplers.py#L11-16](https://github.com/AUTOMATIC1111/stable-diffusion-webui/blob/82a973c04367123ae98bd9abdf80d9eda9b910e2/modules/sd_samplers.py#L11-L16) [modules/modelloader.py](https://github.com/AUTOMATIC1111/stable-diffusion-webui/blob/82a973c04367123ae98bd9abdf80d9eda9b910e2/modules/modelloader.py) [modules/initialize.py#L118-137](https://github.com/AUTOMATIC1111/stable-diffusion-webui/blob/82a973c04367123ae98bd9abdf80d9eda9b910e2/modules/initialize.py#L118-L137) [modules/sd_unet.py](https://github.com/AUTOMATIC1111/stable-diffusion-webui/blob/82a973c04367123ae98bd9abdf80d9eda9b910e2/modules/sd_unet.py)
- API surface for scripts is automatic: Api.__init__ initializes scripts_txt2img/img2img runners if empty, builds default_script_arg arrays from each script's ui() default component values, and get_script_info exposes Script.api_info — scripts appear in /sdapi/v1/scripts and are addressable by name in requests' script_name/alwayson_scripts. — [modules/api/api.py#L253-333](https://github.com/AUTOMATIC1111/stable-diffusion-webui/blob/82a973c04367123ae98bd9abdf80d9eda9b910e2/modules/api/api.py#L253-L333)
- Built-in extensions in extensions-builtin/ (canvas-zoom-and-pan, extra-options-section, hypertile, LDSR, Lora, mobile, postprocessing-for-training, prompt-bracket-checker, ScuNET, soft-inpainting, SwinIR) are the reference implementations for each extension pattern — is_builtin=True keeps them loaded even under --disable-extra-extensions. — [extensions-builtin](https://github.com/AUTOMATIC1111/stable-diffusion-webui/blob/82a973c04367123ae98bd9abdf80d9eda9b910e2/extensions-builtin) [modules/extensions.py#L20-26](https://github.com/AUTOMATIC1111/stable-diffusion-webui/blob/82a973c04367123ae98bd9abdf80d9eda9b910e2/modules/extensions.py#L20-L26)
- Frontend extension: every .js file under javascript/ (and extension javascript dirs) is bundled into the Gradio page; they hook DOM lifecycle (onUiLoaded/onOptionsChanged/onAfterUiUpdate etc. defined in script.js/ui.js) — e.g. edit-attention.js, extraNetworks.js, contextMenus.js. (inferred) — [javascript/ui.js](https://github.com/AUTOMATIC1111/stable-diffusion-webui/blob/82a973c04367123ae98bd9abdf80d9eda9b910e2/javascript/ui.js) [javascript/edit-attention.js](https://github.com/AUTOMATIC1111/stable-diffusion-webui/blob/82a973c04367123ae98bd9abdf80d9eda9b910e2/javascript/edit-attention.js) [javascript/extraNetworks.js](https://github.com/AUTOMATIC1111/stable-diffusion-webui/blob/82a973c04367123ae98bd9abdf80d9eda9b910e2/javascript/extraNetworks.js) [script.js](https://github.com/AUTOMATIC1111/stable-diffusion-webui/blob/82a973c04367123ae98bd9abdf80d9eda9b910e2/script.js)

Every claim links to its cited files at the pinned commit. Citations identify source evidence; they do not establish runtime correctness. Independent CodeVetter scan — not reviewed by upstream maintainers.

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