this derivation will be built:
  /nix/store/124p7zskg5aygbg6iqqrrplrcckspj2a-treefmt-check.drv
building '/nix/store/124p7zskg5aygbg6iqqrrplrcckspj2a-treefmt-check.drv'
treefmt-check> treefmt v2.5.0traversed 71 files
treefmt-check> emitted 48 files for processing
treefmt-check> formatted 48 files (2 changed) in 215ms
treefmt-check>  M crates/ssync-core/src/session_filesystem.rs
treefmt-check>  M crates/ssync-core/src/session_filesystem/pathmap.rs
treefmt-check> diff --git a/crates/ssync-core/src/session_filesystem.rs b/crates/ssync-core/src/session_filesystem.rs
treefmt-check> index ef6f593..cfe149f 100644
treefmt-check> --- a/crates/ssync-core/src/session_filesystem.rs
treefmt-check> +++ b/crates/ssync-core/src/session_filesystem.rs
treefmt-check> @@ -9,14 +9,13 @@ pub use pathmap::PathMap;
treefmt-check>  use std::collections::{HashMap, HashSet};
treefmt-check>  use std::path::{Path, PathBuf};
treefmt-check>  
treefmt-check> +use crate::reconcile::LocalFile;
treefmt-check>  use anyhow::{Context, Result, anyhow, ensure};
treefmt-check>  use ssync_adapters::{Adapter, SessionIdentity};
treefmt-check> -use crate::reconcile::LocalFile;
treefmt-check>  
treefmt-check>  use crate::exclude;
treefmt-check>  use pathmap::Resolver;
treefmt-check>  
treefmt-check> -
treefmt-check>  /// Session discovery, translation, policy, and mutation for one engine.
treefmt-check>  pub(crate) struct SessionFilesystem {
treefmt-check>      adapters: Vec<Box<dyn Adapter>>,
treefmt-check> @@ -51,7 +50,6 @@ impl SessionFilesystem {
treefmt-check>          self.resolver = Resolver::new(map, canonical_home);
treefmt-check>      }
treefmt-check>  
treefmt-check> -
treefmt-check>      /// Every configured session root (watch targets).
treefmt-check>      pub fn roots(&self) -> impl Iterator<Item = &Path> {
treefmt-check>          self.adapters.iter().map(|a| a.session_root())
treefmt-check> @@ -63,7 +61,6 @@ impl SessionFilesystem {
treefmt-check>              .is_some_and(|a| a.is_session_file(path))
treefmt-check>      }
treefmt-check>  
treefmt-check> -
treefmt-check>      /// Decode an index key back to its session-root-relative path (the
treefmt-check>      /// inverse of the key encoding): strip the `{agent}/` prefix of a
treefmt-check>      /// configured adapter.
treefmt-check> @@ -208,7 +205,6 @@ impl SessionFilesystem {
treefmt-check>              .canonical_plaintext(self.adapters[idx].as_ref(), bytes)
treefmt-check>      }
treefmt-check>  
treefmt-check> -
treefmt-check>      /// Localize and atomically materialize one decrypted wire value.
treefmt-check>      pub async fn write(&mut self, key: &str, plaintext: Vec<u8>) -> Result<Option<(u64, u64)>> {
treefmt-check>          let Some((idx, rel)) = self.key_parts(key) else {
treefmt-check> @@ -279,7 +275,6 @@ fn index_key(id: &SessionIdentity) -> String {
treefmt-check>      format!("{}/{}", id.agent, id.relative_path.display())
treefmt-check>  }
treefmt-check>  
treefmt-check> -
treefmt-check>  /// Recursively collect session files under `root` accepted by `adapter`.
treefmt-check>  pub(crate) fn session_files(root: &Path, adapter: &dyn Adapter) -> Vec<PathBuf> {
treefmt-check>      let mut out = Vec::new();
treefmt-check> @@ -287,11 +282,7 @@ pub(crate) fn session_files(root: &Path, adapter: &dyn Adapter) -> Vec<PathBuf>
treefmt-check>      out
treefmt-check>  }
treefmt-check>  
treefmt-check> -fn for_each_session_file(
treefmt-check> -    root: &Path,
treefmt-check> -    adapter: &dyn Adapter,
treefmt-check> -    mut visit: impl FnMut(PathBuf),
treefmt-check> -) {
treefmt-check> +fn for_each_session_file(root: &Path, adapter: &dyn Adapter, mut visit: impl FnMut(PathBuf)) {
treefmt-check>      let mut stack = vec![root.to_path_buf()];
treefmt-check>      while let Some(dir) = stack.pop() {
treefmt-check>          let Ok(entries) = std::fs::read_dir(&dir) else {
treefmt-check> @@ -425,7 +416,6 @@ mod tests {
treefmt-check>          SessionFilesystem::new(vec![Box::new(PiAdapter::new("pi", root))])
treefmt-check>      }
treefmt-check>  
treefmt-check> -
treefmt-check>      #[tokio::test]
treefmt-check>      async fn snapshot_and_write_round_trip_without_map() {
treefmt-check>          let root = scratch("roundtrip");
treefmt-check> @@ -475,9 +465,7 @@ mod tests {
treefmt-check>          );
treefmt-check>          let dir = root.join("--proj--");
treefmt-check>          std::fs::create_dir_all(&dir).unwrap();
treefmt-check> -        let path = dir.join(
treefmt-check> -            "2026-05-23T06-55-21-771Z_019e539d-f6ab-71ac-be20-d3ae2b23ea4a.jsonl",
treefmt-check> -        );
treefmt-check> +        let path = dir.join("2026-05-23T06-55-21-771Z_019e539d-f6ab-71ac-be20-d3ae2b23ea4a.jsonl");
treefmt-check>          std::fs::write(&path, b"{\"type\":\"session\",\"version\":3}\n").unwrap();
treefmt-check>  
treefmt-check>          assert!(filesystem.snapshot().is_empty());
treefmt-check> @@ -492,8 +480,7 @@ mod tests {
treefmt-check>          let root = scratch("mapped-roundtrip");
treefmt-check>          let dir = root.join("--data-Projects-x--");
treefmt-check>          std::fs::create_dir_all(&dir).unwrap();
treefmt-check> -        let name =
treefmt-check> -            "2026-05-23T06-55-21-771Z_019e539d-f6ab-71ac-be20-d3ae2b23ea4a.jsonl";
treefmt-check> +        let name = "2026-05-23T06-55-21-771Z_019e539d-f6ab-71ac-be20-d3ae2b23ea4a.jsonl";
treefmt-check>          let path = dir.join(name);
treefmt-check>          std::fs::write(
treefmt-check>              &path,
treefmt-check> @@ -502,10 +489,7 @@ mod tests {
treefmt-check>          .unwrap();
treefmt-check>          let mut filesystem = pi_map(&root);
treefmt-check>          filesystem.set_path_map(
treefmt-check> -            PathMap::new(vec![
treefmt-check> -                ("/data/Projects".into(), "/canon/Projects".into()),
treefmt-check> -            ])
treefmt-check> -            .unwrap(),
treefmt-check> +            PathMap::new(vec![("/data/Projects".into(), "/canon/Projects".into())]).unwrap(),
treefmt-check>              None,
treefmt-check>          );
treefmt-check>  
treefmt-check> @@ -527,16 +511,13 @@ mod tests {
treefmt-check>          let root = scratch("omp-home");
treefmt-check>          let dir = root.join("-Projects-x");
treefmt-check>          std::fs::create_dir_all(&dir).unwrap();
treefmt-check> -        let name =
treefmt-check> -            "2026-05-23T06-55-21-771Z_019e539d-f6ab-71ac-be20-d3ae2b23ea4a.jsonl";
treefmt-check> +        let name = "2026-05-23T06-55-21-771Z_019e539d-f6ab-71ac-be20-d3ae2b23ea4a.jsonl";
treefmt-check>          std::fs::write(
treefmt-check>              dir.join(name),
treefmt-check>              b"{\"type\":\"session\",\"version\":3,\"cwd\":\"/data/Projects/x\"}\n",
treefmt-check>          )
treefmt-check>          .unwrap();
treefmt-check> -        let mut filesystem = SessionFilesystem::new(vec![Box::new(PiAdapter::new(
treefmt-check> -            "omp", &root,
treefmt-check> -        ))]);
treefmt-check> +        let mut filesystem = SessionFilesystem::new(vec![Box::new(PiAdapter::new("omp", &root))]);
treefmt-check>          filesystem.set_path_map(
treefmt-check>              PathMap::new(vec![("/data".into(), "/canon-home".into())]).unwrap(),
treefmt-check>              None,
treefmt-check> @@ -551,8 +532,7 @@ mod tests {
treefmt-check>          let root = scratch("mapped-exclude");
treefmt-check>          let dir = root.join("--data-Projects-x--");
treefmt-check>          std::fs::create_dir_all(&dir).unwrap();
treefmt-check> -        let name =
treefmt-check> -            "2026-05-23T06-55-21-771Z_019e539d-f6ab-71ac-be20-d3ae2b23ea4a.jsonl";
treefmt-check> +        let name = "2026-05-23T06-55-21-771Z_019e539d-f6ab-71ac-be20-d3ae2b23ea4a.jsonl";
treefmt-check>          std::fs::write(
treefmt-check>              dir.join(name),
treefmt-check>              b"{\"type\":\"session\",\"version\":3,\"cwd\":\"/data/Projects/x\"}\n",
treefmt-check> @@ -560,10 +540,7 @@ mod tests {
treefmt-check>          .unwrap();
treefmt-check>          let mut filesystem = pi_map(&root);
treefmt-check>          filesystem.set_path_map(
treefmt-check> -            PathMap::new(vec![
treefmt-check> -                ("/data/Projects".into(), "/canon/Projects".into()),
treefmt-check> -            ])
treefmt-check> -            .unwrap(),
treefmt-check> +            PathMap::new(vec![("/data/Projects".into(), "/canon/Projects".into())]).unwrap(),
treefmt-check>              None,
treefmt-check>          );
treefmt-check>          filesystem.set_excludes(HashMap::from([(
treefmt-check> @@ -632,10 +609,8 @@ mod tests {
treefmt-check>              PathMap::new(vec![("/data".into(), "/canon".into())]).unwrap(),
treefmt-check>              None,
treefmt-check>          );
treefmt-check> -        let main_key =
treefmt-check> -            "pi/--canon-Projects-x--/2026-05-23T06-55-21-771Z_019e539d-f6ab-71ac-be20-d3ae2b23ea4a.jsonl";
treefmt-check> -        let artifact_key =
treefmt-check> -            "pi/--canon-Projects-x--/2026-05-23T06-55-21-771Z_019e539d-f6ab-71ac-be20-d3ae2b23ea4a/advisor.jsonl";
treefmt-check> +        let main_key = "pi/--canon-Projects-x--/2026-05-23T06-55-21-771Z_019e539d-f6ab-71ac-be20-d3ae2b23ea4a.jsonl";
treefmt-check> +        let artifact_key = "pi/--canon-Projects-x--/2026-05-23T06-55-21-771Z_019e539d-f6ab-71ac-be20-d3ae2b23ea4a/advisor.jsonl";
treefmt-check>  
treefmt-check>          assert!(
treefmt-check>              filesystem
treefmt-check> @@ -647,8 +622,7 @@ mod tests {
treefmt-check>          filesystem
treefmt-check>              .write(
treefmt-check>                  main_key,
treefmt-check> -                b"{\"type\":\"session\",\"version\":3,\"cwd\":\"/canon/Projects/x\"}\n"
treefmt-check> -                    .to_vec(),
treefmt-check> +                b"{\"type\":\"session\",\"version\":3,\"cwd\":\"/canon/Projects/x\"}\n".to_vec(),
treefmt-check>              )
treefmt-check>              .await
treefmt-check>              .unwrap()
treefmt-check> @@ -673,8 +647,7 @@ mod tests {
treefmt-check>          let root = scratch("header-budget");
treefmt-check>          let project = root.join("--project--");
treefmt-check>          std::fs::create_dir_all(&project).unwrap();
treefmt-check> -        let name =
treefmt-check> -            "2026-05-23T06-55-21-771Z_019e539d-f6ab-71ac-be20-d3ae2b23ea4a.jsonl";
treefmt-check> +        let name = "2026-05-23T06-55-21-771Z_019e539d-f6ab-71ac-be20-d3ae2b23ea4a.jsonl";
treefmt-check>          let mut bytes = vec![b'x'; 64 * 1024];
treefmt-check>          bytes.extend_from_slice(b"\n{\"type\":\"session\",\"cwd\":\"/work/project\"}\n");
treefmt-check>          std::fs::write(project.join(name), bytes).unwrap();
treefmt-check> @@ -706,10 +679,7 @@ mod tests {
treefmt-check>          symlink(&outside, root.join("--project--")).unwrap();
treefmt-check>          assert!(
treefmt-check>              filesystem
treefmt-check> -                .write(
treefmt-check> -                    "pi/--project--/session_id.jsonl",
treefmt-check> -                    b"escape".to_vec()
treefmt-check> -                )
treefmt-check> +                .write("pi/--project--/session_id.jsonl", b"escape".to_vec())
treefmt-check>                  .await
treefmt-check>                  .is_err()
treefmt-check>          );
treefmt-check> @@ -722,7 +692,10 @@ mod tests {
treefmt-check>                  .await
treefmt-check>                  .is_err()
treefmt-check>          );
treefmt-check> -        assert_eq!(std::fs::read(outside.join("session_id.jsonl")).unwrap(), b"outside");
treefmt-check> +        assert_eq!(
treefmt-check> +            std::fs::read(outside.join("session_id.jsonl")).unwrap(),
treefmt-check> +            b"outside"
treefmt-check> +        );
treefmt-check>      }
treefmt-check>  
treefmt-check>      #[tokio::test]
treefmt-check> @@ -736,7 +709,10 @@ mod tests {
treefmt-check>              .await
treefmt-check>              .unwrap()
treefmt-check>              .expect("write must resolve");
treefmt-check> -        assert_eq!(std::fs::read(root.join("--project--/session_id.jsonl")).unwrap(), b"session");
treefmt-check> +        assert_eq!(
treefmt-check> +            std::fs::read(root.join("--project--/session_id.jsonl")).unwrap(),
treefmt-check> +            b"session"
treefmt-check> +        );
treefmt-check>          assert_eq!(stamp.1, 7);
treefmt-check>          assert!(filesystem.delete(key).await.unwrap());
treefmt-check>          assert!(!root.join("--project--").exists());
treefmt-check> diff --git a/crates/ssync-core/src/session_filesystem/pathmap.rs b/crates/ssync-core/src/session_filesystem/pathmap.rs
treefmt-check> index 429b5e3..2021840 100644
treefmt-check> --- a/crates/ssync-core/src/session_filesystem/pathmap.rs
treefmt-check> +++ b/crates/ssync-core/src/session_filesystem/pathmap.rs
treefmt-check> @@ -196,10 +196,7 @@ impl Resolver {
treefmt-check>          if let Some(path) = oversized
treefmt-check>              && local_cwd.is_none()
treefmt-check>          {
treefmt-check> -            bail!(
treefmt-check> -                "{}: required session header exceeds 64 KiB",
treefmt-check> -                path.display()
treefmt-check> -            );
treefmt-check> +            bail!("{}: required session header exceeds 64 KiB", path.display());
treefmt-check>          }
treefmt-check>          let Some(local_cwd) = local_cwd else {
treefmt-check>              bail!(
treefmt-check> @@ -475,5 +472,4 @@ mod tests {
treefmt-check>          assert_eq!(m.canonical_of("/any").unwrap(), None);
treefmt-check>          assert_eq!(m.local_of("/any").unwrap(), None);
treefmt-check>      }
treefmt-check> -
treefmt-check>  }
error: Cannot build '/nix/store/124p7zskg5aygbg6iqqrrplrcckspj2a-treefmt-check.drv'.
       Reason: builder failed with exit code 1.
       Output paths:
         /nix/store/p8rzhikdmlmmhbp3shxp1c7br2ssq1dh-treefmt-check
       Last 25 log lines:
       >          assert_eq!(stamp.1, 7);
       >          assert!(filesystem.delete(key).await.unwrap());
       >          assert!(!root.join("--project--").exists());
       > diff --git a/crates/ssync-core/src/session_filesystem/pathmap.rs b/crates/ssync-core/src/session_filesystem/pathmap.rs
       > index 429b5e3..2021840 100644
       > --- a/crates/ssync-core/src/session_filesystem/pathmap.rs
       > +++ b/crates/ssync-core/src/session_filesystem/pathmap.rs
       > @@ -196,10 +196,7 @@ impl Resolver {
       >          if let Some(path) = oversized
       >              && local_cwd.is_none()
       >          {
       > -            bail!(
       > -                "{}: required session header exceeds 64 KiB",
       > -                path.display()
       > -            );
       > +            bail!("{}: required session header exceeds 64 KiB", path.display());
       >          }
       >          let Some(local_cwd) = local_cwd else {
       >              bail!(
       > @@ -475,5 +472,4 @@ mod tests {
       >          assert_eq!(m.canonical_of("/any").unwrap(), None);
       >          assert_eq!(m.local_of("/any").unwrap(), None);
       >      }
       > -
       >  }
       For full logs, run:
         nix log /nix/store/124p7zskg5aygbg6iqqrrplrcckspj2a-treefmt-check.drv