[codex] Load AGENTS.md from all bound environments (#27696)

## Why

We already have the machinery to support multiple environments on a
single thread, but we only show the model the contents of `AGENTS.md`
files in the primary environment.

We should show the model all of the relevant project instructions when
we know there's more than one environment.

## Known Gaps

As discussed in the RFC, this implementation:

1. doesn't handle environments being added/removed to/from the thread
after its creation
2. it doesn't enforce an aggregate context budget across environments,
and instead applies the configured project maximum independently to each
environment

## Implementation

- Discover project instructions in environment order with an independent
byte budget per environment and preserve source provenance/order.
- Keep the legacy fragment byte-for-byte when exactly one environment
contributes project instructions; use environment-labeled sections when
two or more environments contribute.
- Freeze the complete rendered fragment in `LoadedAgentsMd`, insert it
directly into requests, and recognize both layouts in contextual and
memory filtering.
- Add exact rendering, independent-budget, source-order,
creation-snapshot, and consumer coverage without changing app-server
schemas.

codex-rs/core/src/agents_md.rs

@@ -16,6 +16,9 @@
 //! 3.  We do **not** walk past the project root.
 
 use crate::config::Config;
+use crate::context::ContextualUserFragment;
+use crate::context::UserInstructions as ContextUserInstructions;
+use crate::environment_selection::ResolvedTurnEnvironments;
 use codex_app_server_protocol::ConfigLayerSource;
 use codex_config::ConfigLayerStackOrdering;
 use codex_config::default_project_root_markers;
@@ -45,15 +48,26 @@ const AGENTS_MD_SEPARATOR: &str = "\n\n--- project-doc ---\n\n";
 pub(crate) async fn load_project_instructions(
     config: &mut Config,
     user_instructions: Option<UserInstructions>,
-    fs: Option<&dyn ExecutorFileSystem>,
+    environments: &ResolvedTurnEnvironments,
 ) -> Option<LoadedAgentsMd> {
     let mut loaded = LoadedAgentsMd::from_user_instructions(user_instructions);
-    if let Some(fs) = fs {
-        match read_agents_md(config, fs).await {
+    for turn_environment in &environments.turn_environments {
+        let filesystem = turn_environment.environment.get_filesystem();
+        match read_agents_md(
+            config,
+            filesystem.as_ref(),
+            &turn_environment.environment_id,
+            &turn_environment.cwd,
+        )
+        .await
+        {
             Ok(Some(docs)) => loaded.entries.extend(docs.entries),
             Ok(None) => {}
             Err(e) => {
-                error!("error trying to find AGENTS.md docs: {e:#}");
+                error!(
+                    environment_id = turn_environment.environment_id,
+                    "error trying to find AGENTS.md docs: {e:#}"
+                );
             }
         }
     }
@@ -77,6 +91,8 @@ pub(crate) async fn load_project_instructions(
 async fn read_agents_md(
     config: &mut Config,
     fs: &dyn ExecutorFileSystem,
+    environment_id: &str,
+    cwd: &AbsolutePathBuf,
 ) -> io::Result<Option<LoadedAgentsMd>> {
     let max_total = config.project_doc_max_bytes;
 
@@ -84,7 +100,7 @@ async fn read_agents_md(
         return Ok(None);
     }
 
-    let paths = agents_md_paths(config, fs).await?;
+    let paths = agents_md_paths(config, cwd, fs).await?;
     if paths.is_empty() {
         return Ok(None);
     }
@@ -129,7 +145,11 @@ async fn read_agents_md(
         if !text.trim().is_empty() {
             loaded.entries.push(InstructionEntry {
                 contents: text,
-                provenance: InstructionProvenance::Project(p),
+                provenance: InstructionProvenance::Project {
+                    source_path: p,
+                    environment_id: environment_id.to_string(),
+                    cwd: cwd.clone(),
+                },
             });
             remaining = remaining.saturating_sub(data.len() as u64);
         }
@@ -146,9 +166,10 @@ async fn read_agents_md(
 /// directory, inclusive. Symlinks are allowed.
 async fn agents_md_paths(
     config: &Config,
+    cwd: &AbsolutePathBuf,
     fs: &dyn ExecutorFileSystem,
 ) -> io::Result<Vec<AbsolutePathBuf>> {
-    let dir = config.cwd.clone();
+    let dir = cwd.clone();
 
     let mut merged = TomlValue::Table(toml::map::Map::new());
     for layer in config.config_layer_stack.get_layers(
@@ -309,6 +330,14 @@ impl LoadedAgentsMd {
 
     /// Returns the concatenated model-visible instruction text.
     pub fn text(&self) -> String {
+        if self.has_multiple_project_environments() {
+            self.environment_labeled_text()
+        } else {
+            self.legacy_text()
+        }
+    }
+
+    fn legacy_text(&self) -> String {
         let mut output = String::new();
         let mut has_previous = false;
         let mut previous_was_project = false;
@@ -317,7 +346,7 @@ impl LoadedAgentsMd {
             has_previous = true;
         }
         for entry in &self.entries {
-            let is_project = matches!(&entry.provenance, InstructionProvenance::Project(_));
+            let is_project = matches!(&entry.provenance, InstructionProvenance::Project { .. });
             if has_previous {
                 // The project-doc marker tells the model where workspace-scoped
                 // instructions begin, so it is only needed on the transition
@@ -336,6 +365,68 @@ impl LoadedAgentsMd {
         output
     }
 
+    fn environment_labeled_text(&self) -> String {
+        let mut output = String::new();
+        let mut has_previous = false;
+        let mut previous_environment: Option<(&str, &AbsolutePathBuf)> = None;
+        if let Some(instructions) = &self.user_instructions {
+            output.push_str(&instructions.text);
+            has_previous = true;
+        }
+        for entry in &self.entries {
+            match &entry.provenance {
+                InstructionProvenance::Project {
+                    environment_id,
+                    cwd,
+                    ..
+                } => {
+                    if has_previous {
+                        output.push_str("\n\n");
+                    }
+                    // One environment can contribute several hierarchical AGENTS.md files from
+                    // its project root through its cwd. Label that environment once for the
+                    // complete group rather than repeating the label before every file.
+                    let environment = (environment_id.as_str(), cwd);
+                    if previous_environment != Some(environment) {
+                        output.push_str(&format!(
+                            "for `{}` with root {}\n\n",
+                            environment_id,
+                            cwd.display()
+                        ));
+                    }
+                    output.push_str(&entry.contents);
+                    previous_environment = Some(environment);
+                }
+                InstructionProvenance::Internal => {
+                    if has_previous {
+                        output.push_str("\n\n");
+                    }
+                    output.push_str(&entry.contents);
+                    previous_environment = None;
+                }
+            }
+            has_previous = true;
+        }
+        output
+    }
+
+    /// Returns the complete model-visible contextual user fragment.
+    pub(crate) fn render(&self) -> String {
+        // One contributing project environment retains the legacy cwd wrapper. With two or more,
+        // the body labels every contributing environment itself, so the outer cwd is omitted.
+        let directory = if self.has_multiple_project_environments() {
+            None
+        } else {
+            self.single_project_cwd()
+                .map(|cwd| cwd.to_string_lossy().into_owned())
+        };
+        ContextUserInstructions {
+            directory,
+            text: self.text(),
+        }
+        .render()
+    }
+
     /// Returns the host-provided user instructions.
     pub(crate) fn user_instructions(&self) -> Option<&UserInstructions> {
         self.user_instructions.as_ref()
@@ -352,6 +443,31 @@ impl LoadedAgentsMd {
                     .filter_map(|entry| entry.provenance.path()),
             )
     }
+
+    fn has_multiple_project_environments(&self) -> bool {
+        let mut first_environment_id = None;
+        self.entries.iter().any(|entry| {
+            let InstructionProvenance::Project { environment_id, .. } = &entry.provenance else {
+                return false;
+            };
+            match first_environment_id {
+                Some(first_environment_id) => first_environment_id != environment_id,
+                None => {
+                    first_environment_id = Some(environment_id);
+                    false
+                }
+            }
+        })
+    }
+
+    fn single_project_cwd(&self) -> Option<&AbsolutePathBuf> {
+        self.entries
+            .iter()
+            .find_map(|entry| match &entry.provenance {
+                InstructionProvenance::Project { cwd, .. } => Some(cwd),
+                InstructionProvenance::Internal => None,
+            })
+    }
 }
 
 /// One model-visible instruction and its provenance.
@@ -367,7 +483,12 @@ struct InstructionEntry {
 #[derive(Clone, Debug, PartialEq, Eq)]
 enum InstructionProvenance {
     /// Workspace instructions discovered from project AGENTS.md files.
-    Project(AbsolutePathBuf),
+    Project {
+        /// Exact AGENTS.md file, distinct from the environment's selected cwd.
+        source_path: AbsolutePathBuf,
+        environment_id: String,
+        cwd: AbsolutePathBuf,
+    },
 
     /// Instructions without a file source, including internally defined guidance.
     Internal,
@@ -376,7 +497,7 @@ enum InstructionProvenance {
 impl InstructionProvenance {
     fn path(&self) -> Option<&AbsolutePathBuf> {
         match self {
-            Self::Project(path) => Some(path),
+            Self::Project { source_path, .. } => Some(source_path),
             Self::Internal => None,
         }
     }

codex-rs/core/src/agents_md_tests.rs

@@ -1,11 +1,14 @@
 use super::*;
 use crate::config::ConfigBuilder;
+use crate::environment_selection::ResolvedTurnEnvironments;
+use crate::session::turn_context::TurnEnvironment;
 use codex_config::ConfigLayerEntry;
 use codex_config::ConfigLayerStack;
 use codex_config::ConfigRequirements;
 use codex_config::ConfigRequirementsToml;
 use codex_exec_server::CopyOptions;
 use codex_exec_server::CreateDirectoryOptions;
+use codex_exec_server::Environment;
 use codex_exec_server::ExecutorFileSystemFuture;
 use codex_exec_server::FileMetadata;
 use codex_exec_server::FileSystemSandboxContext;
@@ -26,6 +29,7 @@ use std::ops::Deref;
 use std::ops::DerefMut;
 use std::path::Path;
 use std::path::PathBuf;
+use std::sync::Arc;
 use tempfile::TempDir;
 
 #[derive(Clone, Copy)]
@@ -228,10 +232,11 @@ async fn get_user_instructions(config: &TestConfig) -> Option<String> {
 async fn load_agents_md(config: &TestConfig, warnings: &mut Vec<String>) -> Option<LoadedAgentsMd> {
     let mut core_config = config.config.clone();
     let existing_warning_count = core_config.startup_warnings.len();
+    let environments = resolved_local_environments([("local", core_config.cwd.clone())]);
     let loaded = load_project_instructions(
         &mut core_config,
         config.user_instructions.clone(),
-        Some(LOCAL_FS.as_ref()),
+        &environments,
     )
     .await;
     warnings.extend(
@@ -244,7 +249,34 @@ async fn load_agents_md(config: &TestConfig, warnings: &mut Vec<String>) -> Opti
 }
 
 async fn agents_md_paths(config: &TestConfig) -> std::io::Result<Vec<AbsolutePathBuf>> {
-    super::agents_md_paths(&config.config, LOCAL_FS.as_ref()).await
+    super::agents_md_paths(&config.config, &config.cwd, LOCAL_FS.as_ref()).await
+}
+
+fn resolved_local_environments<const N: usize>(
+    environments: [(&str, AbsolutePathBuf); N],
+) -> ResolvedTurnEnvironments {
+    ResolvedTurnEnvironments {
+        turn_environments: environments
+            .into_iter()
+            .map(|(environment_id, cwd)| TurnEnvironment {
+                environment_id: environment_id.to_string(),
+                environment: Arc::new(
+                    Environment::create_for_tests(/*exec_server_url*/ None)
+                        .expect("local environment"),
+                ),
+                cwd,
+                shell: None,
+            })
+            .collect(),
+    }
+}
+
+fn project_provenance(path: AbsolutePathBuf, cwd: AbsolutePathBuf) -> InstructionProvenance {
+    InstructionProvenance::Project {
+        source_path: path,
+        environment_id: "local".to_string(),
+        cwd,
+    }
 }
 
 fn assert_invalid_utf8_warning(warnings: &[String], source: &str, path: &Path) {
@@ -466,11 +498,14 @@ async fn total_byte_limit_truncates_later_project_docs() {
         entries: vec![
             InstructionEntry {
                 contents: "root".to_string(),
-                provenance: InstructionProvenance::Project(repo.path().join("AGENTS.md").abs()),
+                provenance: project_provenance(
+                    repo.path().join("AGENTS.md").abs(),
+                    config.cwd.clone(),
+                ),
             },
             InstructionEntry {
                 contents: "abc".to_string(),
-                provenance: InstructionProvenance::Project(config.cwd.join("AGENTS.md")),
+                provenance: project_provenance(config.cwd.join("AGENTS.md"), config.cwd.clone()),
             },
         ],
     };
@@ -490,7 +525,8 @@ async fn read_agents_md_propagates_metadata_errors() {
         failure: InjectedFailure::Metadata(io::ErrorKind::PermissionDenied),
     };
 
-    let err = read_agents_md(&mut config.config, &fs)
+    let cwd = config.cwd.clone();
+    let err = read_agents_md(&mut config.config, &fs, "local", &cwd)
         .await
         .expect_err("metadata error");
 
@@ -507,7 +543,8 @@ async fn read_agents_md_propagates_read_errors() {
         failure: InjectedFailure::Read(io::ErrorKind::PermissionDenied),
     };
 
-    let err = read_agents_md(&mut config.config, &fs)
+    let cwd = config.cwd.clone();
+    let err = read_agents_md(&mut config.config, &fs, "local", &cwd)
         .await
         .expect_err("read error");
 
@@ -524,7 +561,8 @@ async fn read_agents_md_ignores_files_removed_after_discovery() {
         failure: InjectedFailure::Read(io::ErrorKind::NotFound),
     };
 
-    let loaded = read_agents_md(&mut config.config, &fs)
+    let cwd = config.cwd.clone();
+    let loaded = read_agents_md(&mut config.config, &fs, "local", &cwd)
         .await
         .expect("removed file is recoverable");
 
@@ -591,6 +629,240 @@ async fn merges_existing_instructions_with_agents_md() {
     assert_eq!(res, expected);
 }
 
+#[tokio::test]
+async fn multiple_environment_docs_use_labeled_layout_and_preserve_source_order() {
+    let primary = tempfile::tempdir().expect("primary tempdir");
+    let secondary = tempfile::tempdir().expect("secondary tempdir");
+    fs::create_dir(primary.path().join(".git")).unwrap();
+    fs::write(primary.path().join("AGENTS.md"), "primary root doc").unwrap();
+    let primary_nested = primary.path().join("nested");
+    fs::create_dir(&primary_nested).unwrap();
+    fs::write(primary_nested.join("AGENTS.md"), "primary nested doc").unwrap();
+    fs::write(secondary.path().join("AGENTS.md"), "secondary doc").unwrap();
+    let mut config = make_config(&primary, /*limit*/ 4096, Some("global instructions")).await;
+    config.cwd = primary_nested.abs();
+    let environments = resolved_local_environments([
+        ("primary", config.cwd.clone()),
+        ("secondary", secondary.abs()),
+    ]);
+    let user_instructions = config.user_instructions.clone();
+
+    let loaded = load_project_instructions(&mut config.config, user_instructions, &environments)
+        .await
+        .expect("instructions expected");
+    let inner = format!(
+        r#"global instructions
+
+for `primary` with root {}
+
+primary root doc
+
+primary nested doc
+
+for `secondary` with root {}
+
+secondary doc"#,
+        primary_nested.display(),
+        secondary.path().display(),
+    );
+
+    assert_eq!(loaded.environment_labeled_text(), inner);
+    assert_eq!(loaded.text(), inner);
+    let expected_fragment = format!(
+        r#"# AGENTS.md instructions
+
+<INSTRUCTIONS>
+{inner}
+</INSTRUCTIONS>"#
+    );
+    assert_eq!(loaded.render(), expected_fragment);
+    assert_eq!(
+        loaded.sources().cloned().collect::<Vec<_>>(),
+        vec![
+            config
+                .user_instructions
+                .as_ref()
+                .expect("global instructions")
+                .source
+                .clone(),
+            primary.path().join("AGENTS.md").abs(),
+            primary_nested.join("AGENTS.md").abs(),
+            secondary.path().join("AGENTS.md").abs(),
+        ]
+    );
+}
+
+#[tokio::test]
+async fn secondary_only_project_doc_uses_single_contributor_layout() {
+    let primary = tempfile::tempdir().expect("primary tempdir");
+    let secondary = tempfile::tempdir().expect("secondary tempdir");
+    fs::write(secondary.path().join("AGENTS.md"), "secondary doc").unwrap();
+    let mut config = make_config(&primary, /*limit*/ 4096, Some("global instructions")).await;
+    let environments = resolved_local_environments([
+        ("primary", config.cwd.clone()),
+        ("secondary", secondary.abs()),
+    ]);
+    let user_instructions = config.user_instructions.clone();
+
+    let loaded = load_project_instructions(&mut config.config, user_instructions, &environments)
+        .await
+        .expect("instructions expected");
+    let inner = format!("global instructions{AGENTS_MD_SEPARATOR}secondary doc");
+
+    assert_eq!(loaded.legacy_text(), inner);
+    assert_eq!(loaded.text(), inner);
+    let expected_fragment = format!(
+        "# AGENTS.md instructions for {}\n\n<INSTRUCTIONS>\n{inner}\n</INSTRUCTIONS>",
+        secondary.path().display()
+    );
+    assert_eq!(loaded.render(), expected_fragment);
+}
+
+#[tokio::test]
+async fn primary_only_project_doc_preserves_legacy_layout_with_multiple_bound_environments() {
+    let primary = tempfile::tempdir().expect("primary tempdir");
+    let secondary = tempfile::tempdir().expect("secondary tempdir");
+    fs::write(primary.path().join("AGENTS.md"), "primary doc").unwrap();
+    let mut config = make_config(&primary, /*limit*/ 4096, Some("global instructions")).await;
+    let environments = resolved_local_environments([
+        ("primary", config.cwd.clone()),
+        ("secondary", secondary.abs()),
+    ]);
+    let user_instructions = config.user_instructions.clone();
+
+    let loaded = load_project_instructions(&mut config.config, user_instructions, &environments)
+        .await
+        .expect("instructions expected");
+    let inner = format!("global instructions{AGENTS_MD_SEPARATOR}primary doc");
+
+    assert_eq!(loaded.legacy_text(), inner);
+    assert_eq!(loaded.text(), inner);
+    let expected_fragment = format!(
+        "# AGENTS.md instructions for {}\n\n<INSTRUCTIONS>\n{inner}\n</INSTRUCTIONS>",
+        primary.path().display()
+    );
+    assert_eq!(loaded.render(), expected_fragment);
+}
+
+#[tokio::test]
+async fn project_doc_byte_limit_is_applied_independently_per_environment() {
+    let primary = tempfile::tempdir().expect("primary tempdir");
+    let secondary = tempfile::tempdir().expect("secondary tempdir");
+    fs::write(primary.path().join("AGENTS.md"), "ABCDE").unwrap();
+    fs::write(secondary.path().join("AGENTS.md"), "VWXYZ").unwrap();
+    let mut config = make_config(&primary, /*limit*/ 3, /*instructions*/ None).await;
+    let environments = resolved_local_environments([
+        ("primary", config.cwd.clone()),
+        ("secondary", secondary.abs()),
+    ]);
+    let user_instructions = config.user_instructions.clone();
+
+    let loaded = load_project_instructions(&mut config.config, user_instructions, &environments)
+        .await
+        .expect("instructions expected");
+
+    assert_eq!(
+        loaded.text(),
+        format!(
+            "for `primary` with root {}\n\nABC\n\nfor `secondary` with root {}\n\nVWX",
+            primary.path().display(),
+            secondary.path().display()
+        )
+    );
+}
+
+#[tokio::test]
+async fn multiple_environments_can_exceed_single_environment_project_doc_limit() {
+    // TODO(anp): Add an aggregate cap across environments instead of allowing the combined
+    // project instructions to grow by one full per-environment budget for every binding.
+    const LIMIT: usize = 8;
+    let primary = tempfile::tempdir().expect("primary tempdir");
+    let secondary = tempfile::tempdir().expect("secondary tempdir");
+    let primary_doc = "P".repeat(LIMIT);
+    let secondary_doc = "S".repeat(LIMIT);
+    fs::write(primary.path().join("AGENTS.md"), &primary_doc).unwrap();
+    fs::write(secondary.path().join("AGENTS.md"), &secondary_doc).unwrap();
+    let mut config = make_config(&primary, LIMIT, /*instructions*/ None).await;
+    let environments = resolved_local_environments([
+        ("primary", config.cwd.clone()),
+        ("secondary", secondary.abs()),
+    ]);
+
+    let loaded = load_project_instructions(
+        &mut config.config,
+        /*user_instructions*/ None,
+        &environments,
+    )
+    .await
+    .expect("instructions expected");
+    let project_bytes = loaded
+        .entries
+        .iter()
+        .filter(|entry| matches!(&entry.provenance, InstructionProvenance::Project { .. }))
+        .map(|entry| entry.contents.len())
+        .sum::<usize>();
+
+    assert_eq!(project_bytes, LIMIT * 2);
+    assert!(project_bytes > config.project_doc_max_bytes);
+    assert!(loaded.text().contains(&primary_doc));
+    assert!(loaded.text().contains(&secondary_doc));
+}
+
+#[tokio::test]
+async fn secondary_environment_invalid_utf8_warns_without_suppressing_other_docs() {
+    let primary = tempfile::tempdir().expect("primary tempdir");
+    let secondary = tempfile::tempdir().expect("secondary tempdir");
+    fs::write(primary.path().join("AGENTS.md"), "primary doc").unwrap();
+    fs::write(secondary.path().join("AGENTS.md"), b"secondary\xFFdoc").unwrap();
+    let mut config = make_config(&primary, /*limit*/ 4096, /*instructions*/ None).await;
+    let environments = resolved_local_environments([
+        ("primary", config.cwd.clone()),
+        ("secondary", secondary.abs()),
+    ]);
+
+    let loaded = load_project_instructions(
+        &mut config.config,
+        /*user_instructions*/ None,
+        &environments,
+    )
+    .await
+    .expect("instructions expected");
+
+    assert!(loaded.text().contains("primary doc"));
+    assert!(loaded.text().contains("secondary\u{FFFD}doc"));
+    assert_invalid_utf8_warning(
+        &config.startup_warnings,
+        "Project",
+        secondary.path().join("AGENTS.md").as_path(),
+    );
+}
+
+#[tokio::test]
+async fn child_agents_guidance_is_appended_once_after_environment_groups() {
+    let primary = tempfile::tempdir().expect("primary tempdir");
+    let secondary = tempfile::tempdir().expect("secondary tempdir");
+    fs::write(primary.path().join("AGENTS.md"), "primary doc").unwrap();
+    fs::write(secondary.path().join("AGENTS.md"), "secondary doc").unwrap();
+    let mut config = make_config(&primary, /*limit*/ 4096, /*instructions*/ None).await;
+    config.features.enable(Feature::ChildAgentsMd).unwrap();
+    let environments = resolved_local_environments([
+        ("primary", config.cwd.clone()),
+        ("secondary", secondary.abs()),
+    ]);
+
+    let loaded = load_project_instructions(
+        &mut config.config,
+        /*user_instructions*/ None,
+        &environments,
+    )
+    .await
+    .expect("instructions expected");
+    let text = loaded.text();
+
+    assert_eq!(text.matches(HIERARCHICAL_AGENTS_MESSAGE).count(), 1);
+    assert!(text.ends_with(HIERARCHICAL_AGENTS_MESSAGE));
+}
+
 /// If there are existing system instructions but AGENTS.md docs are
 /// missing we expect the original instructions to be returned unchanged.
 #[tokio::test]
@@ -598,7 +870,6 @@ async fn keeps_existing_instructions_when_doc_missing() {
     let tmp = tempfile::tempdir().expect("tempdir");
 
     const INSTRUCTIONS: &str = "some instructions";
-
     let res =
         get_user_instructions(&make_config(&tmp, /*limit*/ 4096, Some(INSTRUCTIONS)).await).await;
 
@@ -640,11 +911,11 @@ async fn concatenates_root_and_cwd_docs() {
         entries: vec![
             InstructionEntry {
                 contents: "root doc".to_string(),
-                provenance: InstructionProvenance::Project(root_agents.clone()),
+                provenance: project_provenance(root_agents.clone(), cfg.cwd.clone()),
             },
             InstructionEntry {
                 contents: "crate doc".to_string(),
-                provenance: InstructionProvenance::Project(crate_agents.clone()),
+                provenance: project_provenance(crate_agents.clone(), cfg.cwd.clone()),
             },
         ],
     };
@@ -804,7 +1075,7 @@ async fn instruction_sources_include_global_before_agents_md_docs() {
         }),
         entries: vec![InstructionEntry {
             contents: "project doc".to_string(),
-            provenance: InstructionProvenance::Project(project_agents.clone()),
+            provenance: project_provenance(project_agents.clone(), cfg.cwd.clone()),
         }],
     };
     assert_eq!(loaded, expected);
@@ -844,7 +1115,7 @@ async fn child_agents_message_after_project_docs_is_not_an_instruction_source()
         entries: vec![
             InstructionEntry {
                 contents: "project doc".to_string(),
-                provenance: InstructionProvenance::Project(project_agents.clone()),
+                provenance: project_provenance(project_agents.clone(), cfg.cwd.clone()),
             },
             InstructionEntry {
                 contents: HIERARCHICAL_AGENTS_MESSAGE.to_string(),

codex-rs/core/src/context/contextual_user_message_tests.rs

@@ -17,10 +17,38 @@ fn detects_environment_context_fragment() {
 
 #[test]
 fn detects_agents_instructions_fragment() {
-    assert!(is_contextual_user_fragment(&ContentItem::InputText {
-        text: "# AGENTS.md instructions for /tmp\n\n<INSTRUCTIONS>\nbody\n</INSTRUCTIONS>"
-            .to_string(),
-    }));
+    for text in [
+        "# AGENTS.md instructions for /tmp\n\n<INSTRUCTIONS>\nbody\n</INSTRUCTIONS>",
+        "# AGENTS.md instructions\n\n<INSTRUCTIONS>\nbody\n</INSTRUCTIONS>",
+    ] {
+        assert!(is_contextual_user_fragment(&ContentItem::InputText {
+            text: text.to_string(),
+        }));
+    }
+}
+
+#[test]
+fn renders_agents_instructions_with_legacy_directory_header() {
+    assert_eq!(
+        UserInstructions {
+            directory: Some("/tmp".to_string()),
+            text: "body".to_string(),
+        }
+        .render(),
+        "# AGENTS.md instructions for /tmp\n\n<INSTRUCTIONS>\nbody\n</INSTRUCTIONS>"
+    );
+}
+
+#[test]
+fn renders_agents_instructions_without_directory_header() {
+    assert_eq!(
+        UserInstructions {
+            directory: None,
+            text: "body".to_string(),
+        }
+        .render(),
+        "# AGENTS.md instructions\n\n<INSTRUCTIONS>\nbody\n</INSTRUCTIONS>"
+    );
 }
 
 #[test]

codex-rs/core/src/context/user_instructions.rs

@@ -2,7 +2,7 @@ use super::ContextualUserFragment;
 
 #[derive(Debug, Clone, PartialEq)]
 pub(crate) struct UserInstructions {
-    pub(crate) directory: String,
+    pub(crate) directory: Option<String>,
     pub(crate) text: String,
 }
 
@@ -16,10 +16,15 @@ impl ContextualUserFragment for UserInstructions {
     }
 
     fn type_markers() -> (&'static str, &'static str) {
-        ("# AGENTS.md instructions for ", "</INSTRUCTIONS>")
+        ("# AGENTS.md instructions", "</INSTRUCTIONS>")
     }
 
     fn body(&self) -> String {
-        format!("{}\n\n<INSTRUCTIONS>\n{}\n", self.directory, self.text)
+        let directory = self
+            .directory
+            .as_ref()
+            .map(|directory| format!(" for {directory}"))
+            .unwrap_or_default();
+        format!("{directory}\n\n<INSTRUCTIONS>\n{}\n", self.text)
     }
 }

codex-rs/core/src/environment_selection.rs

@@ -42,6 +42,7 @@ impl ResolvedTurnEnvironments {
         self.turn_environments.first()
     }
 
+    #[cfg(test)]
     pub(crate) fn primary_environment(&self) -> Option<Arc<codex_exec_server::Environment>> {
         self.primary()
             .map(|environment| Arc::clone(&environment.environment))

codex-rs/core/src/session/mod.rs

@@ -294,7 +294,6 @@ use crate::SkillLoadOutcome;
 use crate::SkillMetadata;
 use crate::SkillsManager;
 use crate::agents_md::load_project_instructions;
-use crate::context::UserInstructions;
 use crate::exec_policy::ExecPolicyUpdateError;
 use crate::guardian::GuardianReviewSessionManager;
 use crate::mcp::McpManager;
@@ -527,13 +526,9 @@ impl Codex {
         config
             .startup_warnings
             .extend(user_instruction_provider_warnings);
-        // TODO(anp) assemble instructions from multiple environments
-        let primary_environment = environment_selections.primary_environment();
-        let primary_fs = primary_environment
-            .as_ref()
-            .map(|environment| environment.get_filesystem());
         let loaded_agents_md =
-            load_project_instructions(&mut config, user_instructions, primary_fs.as_deref()).await;
+            load_project_instructions(&mut config, user_instructions, &environment_selections)
+                .await;
 
         let exec_policy = if crate::guardian::is_guardian_reviewer_source(&session_source) {
             // Guardian review should rely on the built-in shell safety checks,
@@ -2978,14 +2973,7 @@ impl Session {
             }
         }
         if let Some(user_instructions) = turn_context.user_instructions.as_deref() {
-            contextual_user_sections.push(
-                UserInstructions {
-                    text: user_instructions.to_string(),
-                    #[allow(deprecated)]
-                    directory: turn_context.cwd.to_string_lossy().into_owned(),
-                }
-                .render(),
-            );
+            contextual_user_sections.push(user_instructions.to_string());
         }
         // This is full-context metadata. Steady-state context diffs should not re-emit it.
         if turn_context.features.enabled(Feature::TokenBudget)

codex-rs/core/src/session/turn_context.rs

@@ -553,7 +553,7 @@ impl Session {
             user_instructions: session_configuration
                 .loaded_agents_md
                 .as_ref()
-                .map(LoadedAgentsMd::text),
+                .map(LoadedAgentsMd::render),
             collaboration_mode: session_configuration.collaboration_mode.clone(),
             multi_agent_version,
             personality: session_configuration.personality,

codex-rs/core/src/thread_manager_tests.rs

@@ -491,14 +491,17 @@ async fn resume_and_fork_do_not_restore_thread_environments_from_rollout() {
     );
     let selected_cwd =
         AbsolutePathBuf::try_from(config.cwd.as_path().join("selected")).expect("absolute path");
+    std::fs::create_dir_all(&selected_cwd).expect("create selected cwd");
     let environments = vec![TurnEnvironmentSelection {
         environment_id: "local".to_string(),
         cwd: selected_cwd.clone(),
     }];
     let default_cwd = config.cwd.clone();
+    let mut source_config = config.clone();
+    source_config.cwd = selected_cwd.clone();
     let source = manager
         .start_thread_with_options(StartThreadOptions {
-            config: config.clone(),
+            config: source_config,
             initial_history: InitialHistory::New,
             session_source: None,
             thread_source: None,

codex-rs/core/tests/common/context_snapshot.rs

@@ -99,7 +99,7 @@ pub fn format_response_items_snapshot(items: &[Value], options: &ContextSnapshot
                                         }
                                         if options.strip_agents_md_user_context
                                             && role == "user"
-                                            && text.starts_with("# AGENTS.md instructions for ")
+                                            && text.starts_with("# AGENTS.md instructions")
                                         {
                                             return None;
                                         }
@@ -381,7 +381,7 @@ fn canonicalize_snapshot_text(text: &str) -> String {
     if text.starts_with(PLUGINS_INSTRUCTIONS_OPEN_TAG) {
         return "<PLUGINS_INSTRUCTIONS>".to_string();
     }
-    if text.starts_with("# AGENTS.md instructions for ") {
+    if text.starts_with("# AGENTS.md instructions") {
         return "<AGENTS_MD>".to_string();
     }
     if text.starts_with("<environment_context>") {

codex-rs/core/tests/suite/agents_md.rs

@@ -3,16 +3,20 @@ use anyhow::anyhow;
 use codex_core::ForkSnapshot;
 use codex_core::StartThreadOptions;
 use codex_exec_server::CreateDirectoryOptions;
+use codex_exec_server::LOCAL_ENVIRONMENT_ID;
+use codex_exec_server::REMOTE_ENVIRONMENT_ID;
 use codex_features::Feature;
 use codex_home::CodexHomeUserInstructionsProvider;
 use codex_protocol::protocol::EventMsg;
 use codex_protocol::protocol::InitialHistory;
 use codex_protocol::protocol::Op;
+use codex_protocol::protocol::TurnEnvironmentSelection;
 use codex_protocol::user_input::UserInput;
 use codex_utils_absolute_path::AbsolutePathBuf;
 use codex_utils_path_uri::PathUri;
 use core_test_support::PathBufExt;
 use core_test_support::create_directory_symlink;
+use core_test_support::get_remote_test_env;
 use core_test_support::load_default_config_for_test;
 use core_test_support::responses;
 use core_test_support::responses::ev_completed;
@@ -61,7 +65,7 @@ async fn agents_instructions(mut builder: TestCodexBuilder) -> Result<String> {
     request
         .message_input_texts("user")
         .into_iter()
-        .find(|text| text.starts_with("# AGENTS.md instructions for "))
+        .find(|text| text.starts_with("# AGENTS.md instructions"))
         .ok_or_else(|| anyhow::anyhow!("instructions message not found"))
 }
 
@@ -79,7 +83,7 @@ fn instruction_fragments(request: &responses::ResponsesRequest) -> Vec<String> {
     request
         .message_input_texts("user")
         .into_iter()
-        .filter(|text| text.starts_with("# AGENTS.md instructions for "))
+        .filter(|text| text.starts_with("# AGENTS.md instructions"))
         .collect()
 }
 
@@ -88,10 +92,31 @@ fn expected_instruction_fragment(cwd: &AbsolutePathBuf, contents: &str) -> Strin
     format!("# AGENTS.md instructions for {cwd}\n\n<INSTRUCTIONS>\n{contents}\n</INSTRUCTIONS>")
 }
 
+fn expected_provider_only_instruction_fragment(contents: &str) -> String {
+    format!("# AGENTS.md instructions\n\n<INSTRUCTIONS>\n{contents}\n</INSTRUCTIONS>")
+}
+
 fn assert_single_instruction_fragment(request: &responses::ResponsesRequest, expected: &str) {
     assert_eq!(instruction_fragments(request), vec![expected.to_string()]);
 }
 
+async fn submit_thread_turn(thread: &Arc<codex_core::CodexThread>, prompt: &str) -> Result<()> {
+    thread
+        .submit(Op::UserInput {
+            items: vec![UserInput::Text {
+                text: prompt.to_string(),
+                text_elements: Vec::new(),
+            }],
+            final_output_json_schema: None,
+            responsesapi_client_metadata: None,
+            additional_context: Default::default(),
+            thread_settings: Default::default(),
+        })
+        .await?;
+    wait_for_event(thread, |event| matches!(event, EventMsg::TurnComplete(_))).await;
+    Ok(())
+}
+
 fn request_body_contains(request: &wiremock::Request, text: &str) -> bool {
     let is_zstd = request
         .headers
@@ -315,7 +340,7 @@ async fn symlinked_cwd_uses_logical_parent_for_agents_discovery() -> Result<()>
         .single_request()
         .message_input_texts("user")
         .into_iter()
-        .find(|text| text.starts_with("# AGENTS.md instructions for "))
+        .find(|text| text.starts_with("# AGENTS.md instructions"))
         .expect("instructions message");
     assert!(instructions.contains("logical parent doc"));
     assert!(instructions.contains("workspace doc"));
@@ -362,7 +387,7 @@ async fn selected_environment_sources_match_model_visible_instructions() -> Resu
         .single_request()
         .message_input_texts("user")
         .into_iter()
-        .find(|text| text.starts_with("# AGENTS.md instructions for "))
+        .find(|text| text.starts_with("# AGENTS.md instructions"))
         .expect("instructions message");
     assert!(instructions.contains("global doc\n\n--- project-doc ---\n\nproject doc"));
 
@@ -561,6 +586,126 @@ async fn fresh_thread_composes_global_before_project_and_reports_sources() -> Re
     Ok(())
 }
 
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn multi_environment_thread_loads_every_project_and_keeps_creation_snapshot() -> Result<()> {
+    skip_if_no_network!(Ok(()));
+    let Some(_remote_env) = get_remote_test_env() else {
+        return Ok(());
+    };
+
+    let server = responses::start_mock_server().await;
+    let response_mock = responses::mount_sse_sequence(
+        &server,
+        vec![
+            responses::sse(vec![
+                responses::ev_response_created("multi-env-response-1"),
+                responses::ev_completed("multi-env-response-1"),
+            ]),
+            responses::sse(vec![
+                responses::ev_response_created("multi-env-response-2"),
+                responses::ev_completed("multi-env-response-2"),
+            ]),
+        ],
+    )
+    .await;
+    let home = Arc::new(TempDir::new()?);
+    let global_source =
+        write_global_file(home.as_ref(), GLOBAL_AGENTS_FILENAME, GLOBAL_INSTRUCTIONS)?;
+    let provider = Arc::new(RecordingUserInstructionsProvider::new(Arc::new(
+        CodexHomeUserInstructionsProvider::new(AbsolutePathBuf::try_from(
+            home.path().to_path_buf(),
+        )?),
+    )));
+    let local_root = TempDir::new()?;
+    let local_source = local_root.path().join(GLOBAL_AGENTS_FILENAME);
+    std::fs::write(&local_source, "local project instructions")?;
+    let mut builder = test_codex()
+        .with_home(Arc::clone(&home))
+        .with_user_instructions_provider(provider.clone())
+        .with_workspace_setup(|cwd, fs| async move {
+            fs.write_file(
+                &PathUri::from_path(cwd.join(GLOBAL_AGENTS_FILENAME))?,
+                b"remote project instructions".to_vec(),
+                /*sandbox*/ None,
+            )
+            .await?;
+            Ok(())
+        });
+    let test = builder.build_with_remote_and_local_env(&server).await?;
+    let remote_source = test.config.cwd.join(GLOBAL_AGENTS_FILENAME);
+    let thread = test
+        .thread_manager
+        .start_thread_with_options(StartThreadOptions {
+            config: test.config.clone(),
+            initial_history: InitialHistory::New,
+            session_source: None,
+            thread_source: None,
+            dynamic_tools: Vec::new(),
+            metrics_service_name: None,
+            parent_trace: None,
+            environments: vec![
+                TurnEnvironmentSelection {
+                    environment_id: REMOTE_ENVIRONMENT_ID.to_string(),
+                    cwd: test.config.cwd.clone(),
+                },
+                TurnEnvironmentSelection {
+                    environment_id: LOCAL_ENVIRONMENT_ID.to_string(),
+                    cwd: local_root.path().to_path_buf().try_into()?,
+                },
+            ],
+            thread_extension_init: Default::default(),
+        })
+        .await?;
+    assert_eq!(provider.load_count(), 2);
+    assert_eq!(
+        thread.thread.instruction_sources().await,
+        vec![
+            global_source.clone(),
+            remote_source.clone(),
+            local_source.clone().try_into()?,
+        ]
+    );
+
+    submit_thread_turn(&thread.thread, "first multi-environment turn").await?;
+
+    write_global_file(
+        home.as_ref(),
+        GLOBAL_AGENTS_OVERRIDE_FILENAME,
+        NEW_GLOBAL_INSTRUCTIONS,
+    )?;
+    test.fs()
+        .write_file(
+            &PathUri::from_path(test.config.cwd.join(GLOBAL_AGENTS_OVERRIDE_FILENAME))?,
+            b"new remote project instructions".to_vec(),
+            /*sandbox*/ None,
+        )
+        .await?;
+    std::fs::write(
+        local_root.path().join(GLOBAL_AGENTS_OVERRIDE_FILENAME),
+        "new local project instructions",
+    )?;
+    submit_thread_turn(&thread.thread, "second multi-environment turn").await?;
+
+    let contents = format!(
+        "{GLOBAL_INSTRUCTIONS}\n\nfor `{REMOTE_ENVIRONMENT_ID}` with root {}\n\nremote project instructions\n\nfor `{LOCAL_ENVIRONMENT_ID}` with root {}\n\nlocal project instructions",
+        test.config.cwd.display(),
+        local_root.path().display(),
+    );
+    let expected =
+        format!("# AGENTS.md instructions\n\n<INSTRUCTIONS>\n{contents}\n</INSTRUCTIONS>");
+    let requests = response_mock.requests();
+    assert_eq!(requests.len(), 2);
+    assert_single_instruction_fragment(&requests[0], &expected);
+    assert_single_instruction_fragment(&requests[1], &expected);
+    assert_eq!(provider.load_count(), 2);
+    assert_eq!(
+        thread.thread.instruction_sources().await,
+        vec![global_source, remote_source, local_source.try_into()?]
+    );
+
+    Ok(())
+}
+
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
 async fn global_loading_warning_surfaces_during_thread_creation() -> Result<()> {
     // Set up a malformed global instruction file and one model response.
@@ -604,7 +749,7 @@ async fn global_loading_warning_surfaces_during_thread_creation() -> Result<()>
         "expected warning to contain \"invalid UTF-8\"; observed: {warning}"
     );
     let expected_fragment =
-        expected_instruction_fragment(&test.config.cwd, "global\u{FFFD}instructions");
+        expected_provider_only_instruction_fragment("global\u{FFFD}instructions");
     assert_single_instruction_fragment(&response_mock.single_request(), &expected_fragment);
 
     Ok(())
@@ -690,8 +835,7 @@ async fn cold_resume_replays_rendered_instructions_but_reports_current_config_so
         Some(initial_input.as_slice()),
         "cold resume should replay the original structured input prefix"
     );
-    let expected_fragment =
-        expected_instruction_fragment(&initial.config.cwd, OLD_GLOBAL_INSTRUCTIONS);
+    let expected_fragment = expected_provider_only_instruction_fragment(OLD_GLOBAL_INSTRUCTIONS);
     assert_single_instruction_fragment(&requests[0], &expected_fragment);
     assert_single_instruction_fragment(&requests[1], &expected_fragment);
 
@@ -797,8 +941,7 @@ async fn fork_replays_rendered_instructions_from_shared_history() -> Result<()>
         Some(parent_input.as_slice()),
         "fork should replay the parent's original structured input prefix"
     );
-    let expected_fragment =
-        expected_instruction_fragment(&parent.config.cwd, OLD_GLOBAL_INSTRUCTIONS);
+    let expected_fragment = expected_provider_only_instruction_fragment(OLD_GLOBAL_INSTRUCTIONS);
     assert_single_instruction_fragment(&requests[0], &expected_fragment);
     assert_single_instruction_fragment(&requests[1], &expected_fragment);
 
@@ -933,8 +1076,7 @@ async fn run_subagent_global_instruction_case(fork_context: bool) -> Result<()>
     .map_err(|_| anyhow!("timed out waiting for the subagent request"))?;
 
     // Assert parent and child report and render the parent's creation-time snapshot exactly once.
-    let expected_fragment =
-        expected_instruction_fragment(&test.config.cwd, OLD_GLOBAL_INSTRUCTIONS);
+    let expected_fragment = expected_provider_only_instruction_fragment(OLD_GLOBAL_INSTRUCTIONS);
     assert_single_instruction_fragment(&seed_request, &expected_fragment);
     assert_single_instruction_fragment(&spawn_request, &expected_fragment);
     assert_single_instruction_fragment(&child_request, &expected_fragment);

codex-rs/core/tests/suite/client.rs

@@ -502,7 +502,7 @@ async fn resume_includes_initial_messages_and_sends_prior_items() {
         .position(|(role, text)| {
             role == "user"
                 && text.contains("be nice")
-                && (text.starts_with("# AGENTS.md instructions for "))
+                && text.starts_with("# AGENTS.md instructions")
         })
         .expect("user instructions");
     let pos_environment = messages
@@ -1284,7 +1284,7 @@ async fn includes_user_instructions_message_in_request() {
     assert!(
         user_context_texts
             .iter()
-            .any(|text| text.starts_with("# AGENTS.md instructions for ")),
+            .any(|text| text.starts_with("# AGENTS.md instructions")),
         "expected AGENTS text in contextual user message, got {user_context_texts:?}"
     );
     let ui_text = user_context_texts
@@ -2370,7 +2370,7 @@ async fn includes_developer_instructions_message_in_request() {
     assert!(
         user_context_texts
             .iter()
-            .any(|text| text.starts_with("# AGENTS.md instructions for ")),
+            .any(|text| text.starts_with("# AGENTS.md instructions")),
         "expected AGENTS text in contextual user message, got {user_context_texts:?}"
     );
     let ui_text = user_context_texts

codex-rs/core/tests/suite/compact.rs

@@ -292,7 +292,7 @@ fn instruction_fragments(request: &responses::ResponsesRequest) -> Vec<String> {
     request
         .message_input_texts("user")
         .into_iter()
-        .filter(|text| text.starts_with("# AGENTS.md instructions for "))
+        .filter(|text| text.starts_with("# AGENTS.md instructions"))
         .collect()
 }
 
@@ -306,14 +306,13 @@ fn instruction_fragments_in_items(items: &[Value]) -> Vec<String> {
         .filter_map(|item| item.get("content").and_then(Value::as_array))
         .flatten()
         .filter_map(|span| span.get("text").and_then(Value::as_str))
-        .filter(|text| text.starts_with("# AGENTS.md instructions for "))
+        .filter(|text| text.starts_with("# AGENTS.md instructions"))
         .map(str::to_string)
         .collect()
 }
 
-fn expected_instruction_fragment(cwd: &AbsolutePathBuf, contents: &str) -> String {
-    let cwd = cwd.as_path().display();
-    format!("# AGENTS.md instructions for {cwd}\n\n<INSTRUCTIONS>\n{contents}\n</INSTRUCTIONS>")
+fn expected_instruction_fragment(contents: &str) -> String {
+    format!("# AGENTS.md instructions\n\n<INSTRUCTIONS>\n{contents}\n</INSTRUCTIONS>")
 }
 
 fn assert_single_instruction_fragment(request: &responses::ResponsesRequest, expected: &str) {
@@ -1193,7 +1192,7 @@ async fn multiple_auto_compact_per_task_runs_after_token_limit_hit() {
                 !item
                     .get("text")
                     .and_then(|text| text.as_str())
-                    .is_some_and(|text| text.starts_with("# AGENTS.md instructions for "))
+                    .is_some_and(|text| text.starts_with("# AGENTS.md instructions"))
             })
             .cloned()
             .collect::<Vec<_>>();
@@ -4629,8 +4628,7 @@ async fn manual_compaction_keeps_the_creation_time_global_instructions() -> Resu
     // path now contains new text.
     let requests = response_mock.requests();
     assert_eq!(requests.len(), 3);
-    let expected_fragment =
-        expected_instruction_fragment(&test.config.cwd, OLD_GLOBAL_INSTRUCTIONS);
+    let expected_fragment = expected_instruction_fragment(OLD_GLOBAL_INSTRUCTIONS);
     assert_single_instruction_fragment(&requests[0], &expected_fragment);
     assert_single_instruction_fragment(&requests[1], &expected_fragment);
     assert_single_instruction_fragment(&requests[2], &expected_fragment);
@@ -4702,8 +4700,7 @@ async fn mid_turn_compaction_keeps_the_creation_time_global_instructions() -> Re
     // Assert the initial, compact, and resumed requests all keep the old snapshot and source.
     let requests = response_mock.requests();
     assert_eq!(requests.len(), 3);
-    let expected_fragment =
-        expected_instruction_fragment(&test.config.cwd, OLD_GLOBAL_INSTRUCTIONS);
+    let expected_fragment = expected_instruction_fragment(OLD_GLOBAL_INSTRUCTIONS);
     assert_single_instruction_fragment(&requests[0], &expected_fragment);
     assert_single_instruction_fragment(&requests[1], &expected_fragment);
     assert_single_instruction_fragment(&requests[2], &expected_fragment);
@@ -4776,7 +4773,7 @@ async fn remote_v2_compaction_keeps_creation_time_instructions_after_same_path_m
     // creation-time item despite the file-backed source now containing new text.
     let requests = response_mock.requests();
     assert_eq!(requests.len(), 3);
-    let old_fragment = expected_instruction_fragment(&test.config.cwd, OLD_GLOBAL_INSTRUCTIONS);
+    let old_fragment = expected_instruction_fragment(OLD_GLOBAL_INSTRUCTIONS);
     assert_single_instruction_fragment(&requests[0], &old_fragment);
     assert_single_instruction_fragment(&requests[1], &old_fragment);
     assert_single_instruction_fragment(&requests[2], &old_fragment);

codex-rs/core/tests/suite/hierarchical_agents.rs

@@ -44,7 +44,7 @@ async fn hierarchical_agents_appends_to_project_doc_in_user_instructions() {
     let user_messages = request.message_input_texts("user");
     let instructions = user_messages
         .iter()
-        .find(|text| text.starts_with("# AGENTS.md instructions for "))
+        .find(|text| text.starts_with("# AGENTS.md instructions"))
         .expect("instructions message");
     assert!(
         instructions.contains("be nice"),
@@ -88,7 +88,7 @@ async fn hierarchical_agents_emits_when_no_project_doc() {
     let user_messages = request.message_input_texts("user");
     let instructions = user_messages
         .iter()
-        .find(|text| text.starts_with("# AGENTS.md instructions for "))
+        .find(|text| text.starts_with("# AGENTS.md instructions"))
         .expect("instructions message");
     assert!(
         instructions.contains(HIERARCHICAL_AGENTS_SNIPPET),

codex-rs/core/tests/suite/model_visible_layout.rs

@@ -52,7 +52,7 @@ fn user_instructions_wrapper_count(request: &ResponsesRequest) -> usize {
     request
         .message_input_texts("user")
         .iter()
-        .filter(|text| text.starts_with("# AGENTS.md instructions for "))
+        .filter(|text| text.starts_with("# AGENTS.md instructions"))
         .count()
 }
 

codex-rs/memories/write/src/phase1.rs

@@ -460,7 +460,7 @@ mod job {
             return false;
         };
 
-        matches_marked_fragment(text, "# AGENTS.md instructions for ", "</INSTRUCTIONS>")
+        matches_marked_fragment(text, "# AGENTS.md instructions", "</INSTRUCTIONS>")
             || matches_marked_fragment(text, "<skill>", "</skill>")
     }
 
@@ -487,6 +487,10 @@ mod job {
                     "# AGENTS.md instructions for /tmp\n\n<INSTRUCTIONS>\nbody\n</INSTRUCTIONS>",
                     true,
                 ),
+                (
+                    "# AGENTS.md instructions\n\n<INSTRUCTIONS>\nbody\n</INSTRUCTIONS>",
+                    true,
+                ),
                 (
                     "<skill>\n<name>demo</name>\n<path>skills/demo/SKILL.md</path>\nbody\n</skill>",
                     true,
@@ -665,6 +669,10 @@ mod tests {
                         "# AGENTS.md instructions for /tmp\n\n<INSTRUCTIONS>\nbody\n</INSTRUCTIONS>"
                             .to_string(),
                 },
+                ContentItem::InputText {
+                    text: "# AGENTS.md instructions\n\n<INSTRUCTIONS>\nbody\n</INSTRUCTIONS>"
+                        .to_string(),
+                },
                 ContentItem::InputText {
                     text: "<environment_context>\n<cwd>/tmp</cwd>\n</environment_context>"
                         .to_string(),