feat(filters): export AI filter registration API

AGENTS.md

@@ -109,8 +109,8 @@ New capabilities require:
 
 1. Create module under `filters/src/` or `apis/src/`
 2. Implement `HttpFilter` from `praxis-filter`
-3. Register in `server/src/lib.rs` via
-   `register_filters!` macro
+3. Register in `praxis_ai_filters::register_ai_filters`
+   (`filters/src/register.rs`) via `register_filters!`
 4. Add unit tests and doctests
 5. Add example config in `examples/configs/`
 

docs/developing/adding-filters.md

@@ -9,8 +9,8 @@ first.
 2. Implement `HttpFilter` (from `praxis-filter`). Add a
    `from_config` factory that deserializes a
    `serde_yaml::Value` into your config struct.
-3. Register it in `server/src/lib.rs` inside the
-   `register_ai_filters` function.
+3. Register it in `praxis_ai_filters::register_ai_filters`
+   (in `filters/src/register.rs`).
 4. Add unit tests and doctests.
 5. Add an example config in the appropriate category
    under `examples/configs/`.

docs/filters/README.md

@@ -36,16 +36,45 @@ in the [Praxis core filter reference][praxis-filters], not duplicated here.
 
 ## Registration
 
-`server/src/lib.rs` builds the registry in three steps:
+In-tree AI filters are registered by
+`praxis_ai_filters::register_ai_filters`. Downstream
+consumers that only need AI filters (for example an
+Envoy ExtProc) can depend on `praxis-ai-filters` without
+the proxy crate:
+
+```rust
+use praxis_filter::FilterRegistry;
+
+let mut registry = FilterRegistry::with_builtins();
+praxis_ai_filters::register_ai_filters(&mut registry);
+// Or: let registry = praxis_ai_filters::build_ai_registry();
+```
+
+`praxis-ai-proxy` builds the full registry in three
+ownership layers:
 
 ```rust
 let mut registry = FilterRegistry::with_builtins();
-register_ai_filters(&mut registry);
-register_external_filters(&mut registry);
+praxis_ai_filters::register_ai_filters(&mut registry);
+register_external_filters(&mut registry); // proxy-only
+```
+
+This keeps core filters, in-tree AI filters, and
+auto-discovered extensions at clear ownership
+boundaries. External filter auto-discovery stays
+proxy-only.
+
+Pipelines that use OpenAI store or rehydrate filters
+must also install the response-store extension:
+
+```rust
+pipeline.add_pipeline_extension(
+    Box::new(praxis_ai_apis::store::ResponseStoreRegistry::new()),
+);
 ```
 
-This keeps core filters, in-tree AI filters, and auto-discovered extensions at
-clear ownership boundaries.
+The AI proxy does this in `server/src/pipelines.rs`.
+Other hosts (such as ExtProc) must do the same.
 
 ## Related documentation
 

filters/src/lib.rs

@@ -12,13 +12,15 @@ pub mod agentic;
 pub mod guardrails;
 pub mod inference;
 pub mod prompt_enrich;
+mod register;
 mod time_to_first_token;
 mod token_usage;
 
 pub use agentic::{a2a::A2aFilter, mcp::McpFilter};
 pub use guardrails::AiGuardrailsFilter;
 pub use inference::ModelToHeaderFilter;
 pub use prompt_enrich::PromptEnrichFilter;
+pub use register::{build_ai_registry, register_ai_filters};
 pub use time_to_first_token::TimeToFirstTokenFilter;
 pub use token_usage::{TokenCountFilter, TokenUsageHeadersFilter};
 

filters/src/register.rs

@@ -0,0 +1,199 @@
+// SPDX-License-Identifier: MIT
+// Copyright (c) 2026 Praxis Contributors
+
+//! Public AI filter registration for consumers outside `praxis-ai-proxy`.
+
+use praxis_filter::FilterRegistry;
+
+use crate::{
+    A2aFilter, AiGuardrailsFilter, McpFilter, ModelToHeaderFilter, PromptEnrichFilter, TimeToFirstTokenFilter,
+    TokenCountFilter, TokenUsageHeadersFilter,
+};
+
+/// Register all in-tree AI HTTP filters into `registry`.
+///
+/// Does not call [`FilterRegistry::with_builtins`].
+/// Does not register auto-discovered external filters.
+///
+/// Pipelines that use OpenAI store or rehydrate filters must also install:
+///
+/// ```rust,ignore
+/// pipeline.add_pipeline_extension(
+///     Box::new(praxis_ai_apis::store::ResponseStoreRegistry::new()),
+/// );
+/// ```
+pub fn register_ai_filters(registry: &mut FilterRegistry) {
+    register_agentic_filters(registry);
+    register_general_ai_filters(registry);
+    register_anthropic_filters(registry);
+    register_openai_filters(registry);
+}
+
+/// Build a [`FilterRegistry`] with core builtins and in-tree AI filters.
+///
+/// Equivalent to [`FilterRegistry::with_builtins`] followed by
+/// [`register_ai_filters`]. Does not register auto-discovered external
+/// filters.
+///
+/// Pipelines that use OpenAI store or rehydrate filters must also install
+/// [`praxis_ai_apis::store::ResponseStoreRegistry`] as a pipeline extension.
+#[must_use]
+pub fn build_ai_registry() -> FilterRegistry {
+    let mut registry = FilterRegistry::with_builtins();
+    register_ai_filters(&mut registry);
+    registry
+}
+
+/// Register agentic protocol filters (A2A, MCP).
+fn register_agentic_filters(registry: &mut FilterRegistry) {
+    praxis_filter::register_filters!(
+        @register registry,
+        http "a2a" => A2aFilter::from_config
+    );
+    praxis_filter::register_filters!(
+        @register registry,
+        http "mcp" => McpFilter::from_config
+    );
+}
+
+/// Register general-purpose AI filters.
+fn register_general_ai_filters(registry: &mut FilterRegistry) {
+    praxis_filter::register_filters!(
+        @register registry,
+        http "ai_guardrails" => AiGuardrailsFilter::from_config
+    );
+    praxis_filter::register_filters!(
+        @register registry,
+        http "model_to_header" => ModelToHeaderFilter::from_config
+    );
+    praxis_filter::register_filters!(
+        @register registry,
+        http "prompt_enrich" => PromptEnrichFilter::from_config
+    );
+    praxis_filter::register_filters!(
+        @register registry,
+        http "token_count" => TokenCountFilter::from_config
+    );
+    praxis_filter::register_filters!(
+        @register registry,
+        http "token_usage_headers" => TokenUsageHeadersFilter::from_config
+    );
+    praxis_filter::register_filters!(
+        @register registry,
+        http "time_to_first_token" => TimeToFirstTokenFilter::from_config
+    );
+}
+
+/// Register Anthropic-specific filters.
+fn register_anthropic_filters(registry: &mut FilterRegistry) {
+    praxis_filter::register_filters!(
+        @register registry,
+        http "anthropic_messages_format" => praxis_ai_apis::anthropic::AnthropicMessagesFormatFilter::from_config
+    );
+    praxis_filter::register_filters!(
+        @register registry,
+        http "anthropic_messages_protocol" => praxis_ai_apis::anthropic::AnthropicMessagesProtocolFilter::from_config
+    );
+    praxis_filter::register_filters!(
+        @register registry,
+        http "anthropic_stream_events" => praxis_ai_apis::anthropic::AnthropicStreamEventsFilter::from_config
+    );
+    praxis_filter::register_filters!(
+        @register registry,
+        http "anthropic_to_openai" => praxis_ai_apis::anthropic::AnthropicToOpenaiFilter::from_config
+    );
+    praxis_filter::register_filters!(
+        @register registry,
+        http "anthropic_validate" => praxis_ai_apis::anthropic::AnthropicValidateFilter::from_config
+    );
+}
+
+/// Register OpenAI Responses API request-path filters.
+fn register_openai_filters(registry: &mut FilterRegistry) {
+    register_openai_responses_filters(registry);
+    praxis_filter::register_filters!(
+        @register registry,
+        http "openai_conversations" => praxis_ai_apis::openai::OpenaiConversationsFilter::from_config
+    );
+}
+
+/// Register OpenAI Responses API filters.
+fn register_openai_responses_filters(registry: &mut FilterRegistry) {
+    praxis_filter::register_filters!(
+        @register registry,
+        http "openai_doc_extract" => praxis_ai_apis::openai::DocExtractFilter::from_config
+    );
+    praxis_filter::register_filters!(
+        @register registry,
+        http "openai_file_resolve" => praxis_ai_apis::openai::FileResolveFilter::from_config
+    );
+    praxis_filter::register_filters!(
+        @register registry,
+        http "openai_responses_format" => praxis_ai_apis::openai::ResponsesFormatFilter::from_config
+    );
+    praxis_filter::register_filters!(
+        @register registry,
+        http "openai_responses_model_rewrite" => praxis_ai_apis::openai::ModelRewriteFilter::from_config
+    );
+    praxis_filter::register_filters!(
+        @register registry,
+        http "openai_responses_validate" => praxis_ai_apis::openai::OpenaiResponsesValidateFilter::from_config
+    );
+    praxis_filter::register_filters!(
+        @register registry,
+        http "openai_responses_rehydrate" => praxis_ai_apis::openai::RehydrateFilter::from_config
+    );
+    register_openai_response_filters(registry);
+}
+
+/// Register OpenAI Responses API response-path and persistence filters.
+fn register_openai_response_filters(registry: &mut FilterRegistry) {
+    praxis_filter::register_filters!(
+        @register registry,
+        http "openai_response_store" => praxis_ai_apis::openai::ResponseStoreFilter::from_config
+    );
+    praxis_filter::register_filters!(
+        @register registry,
+        http "openai_stream_events" => praxis_ai_apis::openai::OpenaiStreamEventsFilter::from_config
+    );
+    praxis_filter::register_filters!(
+        @register registry,
+        http "openai_responses_proxy" => praxis_ai_apis::openai::ResponsesProxyFilter::from_config
+    );
+    praxis_filter::register_filters!(
+        @register registry,
+        http "openai_mcp_tool_resolve" => praxis_ai_apis::openai::McpToolResolveFilter::from_config
+    );
+    praxis_filter::register_filters!(
+        @register registry,
+        http "openai_tool_parse" => praxis_ai_apis::openai::ToolParseFilter::from_config
+    );
+    praxis_filter::register_filters!(
+        @register registry,
+        http "openai_web_search" => praxis_ai_apis::openai::WebSearchFilter::from_config
+    );
+    praxis_filter::register_filters!(
+        @register registry,
+        http "openai_mcp_dispatch" => praxis_ai_apis::openai::McpDispatchFilter::from_config
+    );
+}
+
+#[cfg(test)]
+mod tests {
+    use super::build_ai_registry;
+
+    #[test]
+    fn build_ai_registry_includes_ai_and_builtin_filters() {
+        let registry = build_ai_registry();
+        let names = registry.available_filters();
+        assert!(names.contains(&"ai_guardrails"), "expected ai_guardrails in registry");
+        assert!(
+            names.contains(&"openai_responses_validate"),
+            "expected openai_responses_validate in registry"
+        );
+        assert!(
+            names.contains(&"request_id"),
+            "expected core builtin request_id in registry"
+        );
+    }
+}