chore: move memory prompt builder into extension (#24558)

## Why

The memories extension now owns the read-path developer instructions it
injects at thread start. Keeping that prompt builder and template in
`codex-memories-read` left the extension depending on a helper crate for
extension-specific prompt assembly, and kept async template/truncation
dependencies in the read crate after the remaining read surface no
longer needed them.

## What changed

- Moved `prompts.rs`, its tests, and `templates/memories/read_path.md`
from `memories/read` into `ext/memories`.
- Wired `MemoryExtension` to call the local prompt builder and added the
moved templates to `ext/memories/BUILD.bazel` compile data.
- Removed the now-unused prompt export and prompt-related dependencies
from `codex-memories-read`.

## Testing

- Not run locally.

codex-rs/Cargo.lock

@@ -3182,10 +3182,10 @@ dependencies = [
  "codex-core",
  "codex-extension-api",
  "codex-features",
- "codex-memories-read",
  "codex-tools",
  "codex-utils-absolute-path",
  "codex-utils-output-truncation",
+ "codex-utils-template",
  "pretty_assertions",
  "schemars 0.8.22",
  "serde",
@@ -3202,11 +3202,7 @@ dependencies = [
  "codex-protocol",
  "codex-shell-command",
  "codex-utils-absolute-path",
- "codex-utils-output-truncation",
- "codex-utils-template",
  "pretty_assertions",
- "tempfile",
- "tokio",
 ]
 
 [[package]]

codex-rs/ext/memories/BUILD.bazel

@@ -3,4 +3,7 @@ load("//:defs.bzl", "codex_rust_crate")
 codex_rust_crate(
     name = "memories",
     crate_name = "codex_memories_extension",
+    compile_data = glob([
+        "templates/**",
+    ]),
 )

codex-rs/ext/memories/Cargo.toml

@@ -17,10 +17,10 @@ async-trait = { workspace = true }
 codex-core = { workspace = true }
 codex-extension-api = { workspace = true }
 codex-features = { workspace = true }
-codex-memories-read = { workspace = true }
 codex-tools = { workspace = true }
 codex-utils-absolute-path = { workspace = true }
 codex-utils-output-truncation = { workspace = true }
+codex-utils-template = { workspace = true }
 schemars = { workspace = true }
 serde = { workspace = true, features = ["derive"] }
 serde_json = { workspace = true }

codex-rs/ext/memories/src/extension.rs

@@ -10,10 +10,10 @@ use codex_extension_api::ThreadLifecycleContributor;
 use codex_extension_api::ThreadStartInput;
 use codex_extension_api::ToolContributor;
 use codex_features::Feature;
-use codex_memories_read::build_memory_tool_developer_instructions;
 use codex_utils_absolute_path::AbsolutePathBuf;
 
 use crate::local::LocalMemoriesBackend;
+use crate::prompts::build_memory_tool_developer_instructions;
 use crate::tools;
 
 /// Contributes Codex memory read-path prompt context and memory read tools.

codex-rs/ext/memories/src/lib.rs

@@ -1,6 +1,7 @@
 mod backend;
 mod extension;
 mod local;
+mod prompts;
 mod schema;
 mod tools;
 
@@ -11,6 +12,7 @@ pub(crate) const MAX_LIST_RESULTS: usize = 2_000;
 pub(crate) const DEFAULT_SEARCH_MAX_RESULTS: usize = 200;
 pub(crate) const MAX_SEARCH_RESULTS: usize = 200;
 pub(crate) const DEFAULT_READ_MAX_TOKENS: usize = 20_000;
+pub(crate) const MEMORY_TOOL_DEVELOPER_INSTRUCTIONS_SUMMARY_TOKEN_LIMIT: usize = 2_500;
 
 pub(crate) const MEMORY_TOOLS_NAMESPACE: &str = "memories/";
 pub(crate) const LIST_TOOL_NAME: &str = "list";

codex-rs/ext/memories/src/prompts.rs

@@ -1,5 +1,4 @@
 use crate::MEMORY_TOOL_DEVELOPER_INSTRUCTIONS_SUMMARY_TOKEN_LIMIT;
-use crate::memory_root;
 use codex_utils_absolute_path::AbsolutePathBuf;
 use codex_utils_output_truncation::TruncationPolicy;
 use codex_utils_output_truncation::truncate_text;
@@ -21,14 +20,14 @@ fn parse_embedded_template(source: &'static str, template_name: &str) -> Templat
     }
 }
 
-/// Build the read-path prompt that is added to developer instructions.
+/// Build the memory read-path prompt that is added to developer instructions.
 ///
 /// Large `memory_summary.md` files are truncated at
 /// [MEMORY_TOOL_DEVELOPER_INSTRUCTIONS_SUMMARY_TOKEN_LIMIT].
-pub async fn build_memory_tool_developer_instructions(
+pub(crate) async fn build_memory_tool_developer_instructions(
     codex_home: &AbsolutePathBuf,
 ) -> Option<String> {
-    let base_path = memory_root(codex_home);
+    let base_path = codex_home.join("memories");
     let memory_summary_path = base_path.join("memory_summary.md");
     let memory_summary = fs::read_to_string(&memory_summary_path)
         .await

codex-rs/memories/read/BUILD.bazel

@@ -3,7 +3,4 @@ load("//:defs.bzl", "codex_rust_crate")
 codex_rust_crate(
     name = "read",
     crate_name = "codex_memories_read",
-    compile_data = glob([
-        "templates/**",
-    ]),
 )

codex-rs/memories/read/Cargo.toml

@@ -16,11 +16,6 @@ workspace = true
 codex-protocol = { workspace = true }
 codex-shell-command = { workspace = true }
 codex-utils-absolute-path = { workspace = true }
-codex-utils-output-truncation = { workspace = true }
-codex-utils-template = { workspace = true }
-tokio = { workspace = true, features = ["fs"] }
 
 [dev-dependencies]
 pretty_assertions = { workspace = true }
-tempfile = { workspace = true }
-tokio = { workspace = true, features = ["fs", "macros"] }

codex-rs/memories/read/src/lib.rs

@@ -6,15 +6,10 @@
 
 pub mod citations;
 mod metrics;
-mod prompts;
 pub mod usage;
 
 use codex_utils_absolute_path::AbsolutePathBuf;
 
-pub use prompts::build_memory_tool_developer_instructions;
-
-const MEMORY_TOOL_DEVELOPER_INSTRUCTIONS_SUMMARY_TOKEN_LIMIT: usize = 2_500;
-
 pub fn memory_root(codex_home: &AbsolutePathBuf) -> AbsolutePathBuf {
     codex_home.join("memories")
 }