feat(filter): add openai_responses_compact filter for context window management

Cargo.toml

@@ -49,6 +49,7 @@ serde_yaml = { package = "yaml_serde", version = "0.10.4" }
 sqlx = { version = "0.9.0", default-features = false, features = ["runtime-tokio", "tls-rustls-ring", "sqlite", "postgres"] }
 tempfile = "3.27.0"
 thiserror = "2.0.18"
+tiktoken-rs = "0.12.0"
 tikv-jemallocator = "0.7.0"
 tokio = { version = "1.52.3", features = ["macros", "rt"] }
 tokio-rustls = "0.26.4"

apis/Cargo.toml

@@ -37,6 +37,7 @@ serde_json = { workspace = true }
 serde_yaml = { workspace = true }
 sqlx = { workspace = true, optional = true }
 thiserror = { workspace = true }
+tiktoken-rs = { workspace = true }
 tokio = { workspace = true, features = ["rt", "time", "net"] }
 tracing = { workspace = true }
 zeroize = { workspace = true }

apis/src/openai/mod.rs

@@ -15,7 +15,7 @@ pub(crate) mod translation;
 
 pub use conversations::OpenaiConversationsFilter;
 pub use responses::{
-    DocExtractFilter, FileResolveFilter, McpDispatchFilter, McpToolResolveFilter, ModelRewriteFilter,
+    CompactFilter, DocExtractFilter, FileResolveFilter, McpDispatchFilter, McpToolResolveFilter, ModelRewriteFilter,
     OpenaiResponsesValidateFilter, RehydrateFilter, ResponseStoreFilter, ResponsesFormatFilter, ToolParseFilter,
     WebSearchFilter, openai_responses_proxy::ResponsesProxyFilter, stream_events::OpenaiStreamEventsFilter,
 };

apis/src/openai/responses/compact/config.rs

@@ -0,0 +1,111 @@
+// SPDX-License-Identifier: MIT
+// Copyright (c) 2026 Praxis Contributors
+
+//! Configuration for the `openai_responses_compact` filter.
+
+use praxis_filter::FilterError;
+use serde::Deserialize;
+
+use crate::openai::responses::config_validation::{self, CalloutSettings, FailureMode};
+
+/// Default callout timeout (30 seconds — summarization can be slow).
+const DEFAULT_TIMEOUT_MS: u64 = 30_000;
+
+/// Default HTTP status when the summarization callout fails in closed mode.
+const DEFAULT_STATUS_ON_ERROR: u16 = 502;
+
+// -----------------------------------------------------------------------------
+// CompactFilterConfig (YAML deserialization)
+// -----------------------------------------------------------------------------
+
+/// Raw YAML config, deserialized then validated.
+#[derive(Deserialize)]
+#[serde(deny_unknown_fields)]
+pub(super) struct CompactFilterConfig {
+    /// URL of the inference backend for summarization calls.
+    /// E.g., `"http://localhost:11434/v1/chat/completions"`
+    pub inference_url: String,
+
+    /// Default model for summarization when not overridden
+    /// in the request's `context_management`.
+    #[serde(default = "default_model")]
+    pub default_model: String,
+
+    /// Tiktoken encoding name for local token estimation.
+    /// Used as fallback when `previous_usage` is unavailable.
+    #[serde(default = "default_tiktoken_encoding")]
+    pub tiktoken_encoding: String,
+
+    /// Callout timeout in milliseconds.
+    #[serde(default)]
+    pub timeout_ms: Option<u64>,
+
+    /// Failure mode for the inference callout.
+    #[serde(default)]
+    pub failure_mode: Option<FailureMode>,
+
+    /// HTTP status code to return when rejecting on error.
+    #[serde(default)]
+    pub status_on_error: Option<u16>,
+}
+
+/// Default summarization model when not overridden per-request.
+fn default_model() -> String {
+    "gpt-4o-mini".to_owned()
+}
+
+/// Default tiktoken encoding for local token estimation.
+fn default_tiktoken_encoding() -> String {
+    "cl100k_base".to_owned()
+}
+
+// -----------------------------------------------------------------------------
+// ValidatedConfig (post-validation)
+// -----------------------------------------------------------------------------
+
+/// Validated configuration with defaults applied.
+pub(super) struct ValidatedConfig {
+    /// URL of the inference backend for summarization calls.
+    pub inference_url: String,
+
+    /// Default model for summarization.
+    pub default_model: String,
+
+    /// Tiktoken encoding name.
+    pub tiktoken_encoding: String,
+
+    /// Shared callout settings (timeout, failure mode, status).
+    pub callout: CalloutSettings,
+}
+
+/// Validate raw config and apply defaults.
+///
+/// # Errors
+///
+/// Returns [`FilterError`] if `inference_url` is empty,
+/// `timeout_ms` is zero, or `status_on_error` is out of range.
+pub(super) fn build_config(raw: &CompactFilterConfig) -> Result<ValidatedConfig, FilterError> {
+    if raw.inference_url.is_empty() {
+        return Err(FilterError::from("openai_responses_compact: inference_url is empty"));
+    }
+
+    let timeout_ms =
+        config_validation::validate_timeout_ms("openai_responses_compact", raw.timeout_ms, DEFAULT_TIMEOUT_MS)?;
+
+    let status_on_error = config_validation::validate_status_on_error(
+        "openai_responses_compact",
+        raw.status_on_error,
+        DEFAULT_STATUS_ON_ERROR,
+    )?;
+
+    Ok(ValidatedConfig {
+        inference_url: raw.inference_url.clone(),
+        default_model: raw.default_model.clone(),
+        tiktoken_encoding: raw.tiktoken_encoding.clone(),
+        callout: CalloutSettings {
+            timeout_ms,
+            failure_mode: raw.failure_mode.unwrap_or(FailureMode::Closed),
+            status_on_error,
+        },
+    })
+}