From 1b11690aa1e88f069ffa1d06fbfb04420a7ea1fc Mon Sep 17 00:00:00 2001
From: Christoph Knittel <ck@cca.io>
Date: Tue, 22 Sep 2026 15:51:25 +0200
Subject: [PATCH 1/5] Fix deterministic rewatch scheduling

Signed-off-by: Christoph Knittel <ck@cca.io>
---
 CHANGELOG.md                                  |  2 +
 rewatch/src/build/compile.rs                  | 38 ++++----
 ...chedule-independent-modules-after-error.sh | 92 +++++++++++++++++++
 rewatch/tests/suite.sh                        |  1 +
 4 files changed, 117 insertions(+), 16 deletions(-)
 create mode 100755 rewatch/tests/compile/20-schedule-independent-modules-after-error.sh

diff --git a/CHANGELOG.md b/CHANGELOG.md
index d444142eb85..e1aa7b066cc 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -20,6 +20,8 @@
 
 #### :bug: Bug fix
 
+- Make rewatch compile independent modules after an unrelated failure and recompile blocked dependents when a changed interface survives a failed implementation. https://github.com/rescript-lang/rescript/pull/8667
+
 #### :memo: Documentation
 
 #### :nail_care: Polish
diff --git a/rewatch/src/build/compile.rs b/rewatch/src/build/compile.rs
index 6a0868dd507..9f726e724b1 100644
--- a/rewatch/src/build/compile.rs
+++ b/rewatch/src/build/compile.rs
@@ -440,7 +440,11 @@ pub fn compile(
     rayon::in_place_scope(|scope| {
         let mut in_flight: usize = 0;
         loop {
-            while in_flight < capacity && !has_errors {
+            // Keep dispatching work that was already independent of any
+            // failed module. Otherwise diagnostics vary with worker count:
+            // a warning-producing module may or may not have started before
+            // an unrelated error finishes.
+            while in_flight < capacity {
                 let Some(work) = ready_heap.pop() else { break };
                 let module_name = work.module_name.clone();
                 let is_dirty = dirty_set.contains(&module_name);
@@ -462,10 +466,6 @@ pub fn compile(
             }
 
             if in_flight == 0 {
-                if !ready_heap.is_empty() {
-                    // Errors suppressed new spawns; nothing left to drain.
-                    break;
-                }
                 if completed.len() < compile_universe_count && !has_errors {
                     stalled = true;
                 }
@@ -475,7 +475,8 @@ pub fn compile(
             let Ok(msg) = rx.recv() else { break };
             in_flight -= 1;
 
-            if msg.result.is_err() || msg.interface_result.as_ref().is_some_and(|r| r.is_err()) {
+            let failed = msg.result.is_err() || msg.interface_result.as_ref().is_some_and(|r| r.is_err());
+            if failed {
                 has_errors = true;
             }
 
@@ -493,16 +494,21 @@ pub fn compile(
                 if !compile_universe.contains(dep) {
                     continue;
                 }
+                // A successful interface can replace the CMI even when its
+                // implementation fails. Keep dependents dirty for recovery,
+                // but do not release them until the module succeeds.
                 if !is_clean {
                     dirty_set.insert(dep.clone());
                 }
-                let count = pending_deps.get_mut(dep).unwrap();
-                *count -= 1;
-                if *count == 0 && !completed.contains(dep) {
-                    ready_heap.push(WorkUnit {
-                        priority: priorities[dep],
-                        module_name: dep.clone(),
-                    });
+                if !failed {
+                    let count = pending_deps.get_mut(dep).unwrap();
+                    *count -= 1;
+                    if *count == 0 && !completed.contains(dep) {
+                        ready_heap.push(WorkUnit {
+                            priority: priorities[dep],
+                            module_name: dep.clone(),
+                        });
+                    }
                 }
             }
         }
@@ -523,9 +529,9 @@ pub fn compile(
     let mut num_compiled_modules = 0;
 
     // Persist propagated dirtiness back onto build_state. Modules that were
-    // marked dirty (because a predecessor's cmi changed) but never scheduled
-    // — e.g. the first compile error aborted further dispatch — must keep
-    // compile_dirty = true so the next incremental build recompiles them.
+    // marked dirty (because a predecessor's cmi changed) but blocked by a
+    // failed prerequisite must keep compile_dirty = true so the next
+    // incremental build recompiles them.
     // Successful recompiles in the result loop below override this back to
     // false for the modules that actually ran.
     for name in &dirty_set {
diff --git a/rewatch/tests/compile/20-schedule-independent-modules-after-error.sh b/rewatch/tests/compile/20-schedule-independent-modules-after-error.sh
new file mode 100755
index 00000000000..170b0f764a9
--- /dev/null
+++ b/rewatch/tests/compile/20-schedule-independent-modules-after-error.sh
@@ -0,0 +1,92 @@
+#!/bin/bash
+
+cd $(dirname $0)
+source "../utils.sh"
+
+bold "Test: Independent modules compile after an unrelated error"
+
+fixture=$(mktemp -d 2>/dev/null || mktemp -d -t rewatch-schedule-after-error)
+trap "rm -rf '$fixture'" EXIT
+
+mkdir -p "$fixture/src"
+
+cat > "$fixture/rescript.json" <<'EOF'
+{
+  "name": "rewatch-schedule-after-error",
+  "sources": { "dir": "src" },
+  "warnings": { "number": "+26+27+32", "error": false },
+  "package-specs": { "module": "esmodule", "in-source": true },
+  "suffix": ".mjs"
+}
+EOF
+
+cat > "$fixture/src/Failing.res" <<'EOF'
+let value = 1
+EOF
+
+cat > "$fixture/src/Blocked.res" <<'EOF'
+let mirrored = Failing.value
+EOF
+
+cat > "$fixture/src/IndependentWarning.res" <<'EOF'
+let unusedValue = 42
+
+let hello = () => Console.log("hello")
+EOF
+
+cd "$fixture"
+if ! RAYON_NUM_THREADS=1 RUST_BACKTRACE=1 "$REWATCH_EXECUTABLE" build > /dev/null 2>&1; then
+  error "Initial fixture build failed"
+  exit 1
+fi
+
+# Make the dependent's generated output an observable signal: the failing build
+# must leave it absent, and the recovery build must recreate it.
+rm -f src/Blocked.mjs
+
+cat > src/Failing.res <<'EOF'
+let value: int = "not an int"
+EOF
+
+cat > src/IndependentWarning.res <<'EOF'
+let unusedValue = 42
+
+let hello = () => {
+  let secondUnusedValue = 43
+  Console.log("hello")
+}
+EOF
+
+compiler_output=$(RAYON_NUM_THREADS=1 RUST_BACKTRACE=1 "$REWATCH_EXECUTABLE" build 2>&1)
+build_status=$?
+
+if [ $build_status -eq 0 ]; then
+  error "Build unexpectedly succeeded despite the type error"
+  printf "%s\n" "$compiler_output" >&2
+  exit 1
+fi
+
+if ! printf '%s\n' "$compiler_output" | grep -q "unused variable secondUnusedValue"; then
+  error "Independent warning was not emitted after the unrelated failure"
+  printf "%s\n" "$compiler_output" >&2
+  exit 1
+fi
+
+if [ -f src/Blocked.mjs ]; then
+  error "Blocked dependent was compiled despite its failed dependency"
+  exit 1
+fi
+
+printf 'let value = "recovered"\n' > src/Failing.res
+if ! compiler_output=$(RAYON_NUM_THREADS=1 RUST_BACKTRACE=1 "$REWATCH_EXECUTABLE" build 2>&1); then
+  error "Build did not recover after fixing the failed dependency"
+  printf "%s\n" "$compiler_output" >&2
+  exit 1
+fi
+
+if [ ! -f src/Blocked.mjs ]; then
+  error "Previously blocked dependent was not compiled after recovery"
+  exit 1
+fi
+
+success "Independent diagnostics and blocked dependents are scheduled correctly"
diff --git a/rewatch/tests/suite.sh b/rewatch/tests/suite.sh
index 22cc77935d7..69d888af06a 100755
--- a/rewatch/tests/suite.sh
+++ b/rewatch/tests/suite.sh
@@ -132,6 +132,7 @@ fi
 ./compile/17-prod-flag.sh &&
 ./compile/18-external-dep-uncurried-dot.sh &&
 ./compile/19-utf8-warning.sh &&
+./compile/20-schedule-independent-modules-after-error.sh &&
 ./compile/14-no-testrepo-changes.sh &&
 ./compile/15-no-new-files.sh &&
 ./compile/16-snapshots-unchanged.sh &&

From 3a85c133d50d58e0d80551d235d7d40c687ec590 Mon Sep 17 00:00:00 2001
From: Christoph Knittel <ck@cca.io>
Date: Tue, 22 Sep 2026 15:51:36 +0200
Subject: [PATCH 2/5] Stabilize rewatch integration tests

Signed-off-by: Christoph Knittel <ck@cca.io>
---
 rewatch/AGENTS.md                             |  2 +-
 .../tests/clean/01-clean-single-project.sh    |  2 +-
 .../tests/clean/02-clean-dev-dependencies.sh  |  2 +-
 rewatch/tests/clean/03-clean-node-modules.sh  |  2 +-
 .../04-clean-rebuild-no-compiler-update.sh    | 15 +--
 rewatch/tests/compile/08-remove-file.sh       |  2 +-
 rewatch/tests/compile/09-dependency-cycle.sh  |  2 +-
 .../11-dev-dependency-non-dev-source.sh       |  2 +-
 .../compile/13-no-infinite-loop-with-cycle.sh |  2 +-
 rewatch/tests/compile/17-prod-flag.sh         |  6 +-
 rewatch/tests/format/01-format-all-files.sh   |  2 +-
 rewatch/tests/format/02-format-single-file.sh |  2 +-
 .../tests/format/04-format-current-project.sh |  2 +-
 rewatch/tests/suffix/01-custom-suffix.sh      |  1 -
 rewatch/tests/suite.sh                        |  4 +-
 rewatch/tests/utils.sh                        | 70 ++++++++++++-
 rewatch/tests/watch/01-watch-recompile.sh     | 24 ++++-
 .../02-watch-warnings-persist-atomic-save.sh  | 21 ++--
 .../tests/watch/02-watch-warnings-persist.sh  | 46 ++++-----
 rewatch/tests/watch/03-watch-new-file.sh      | 21 +++-
 rewatch/tests/watch/04-watch-config-change.sh | 71 +++++++++++---
 .../watch/05-watch-ignores-non-source.sh      |  1 -
 .../watch/06-watch-missing-source-folder.sh   |  7 +-
 ...d-interface-after-failed-implementation.sh | 97 +++++++++++++++++++
 24 files changed, 310 insertions(+), 96 deletions(-)
 create mode 100755 rewatch/tests/watch/07-changed-interface-after-failed-implementation.sh

diff --git a/rewatch/AGENTS.md b/rewatch/AGENTS.md
index e0e6846cd19..496d108d5f1 100644
--- a/rewatch/AGENTS.md
+++ b/rewatch/AGENTS.md
@@ -217,5 +217,5 @@ When clippy suggests refactoring that could impact performance, consider the tra
 ## CI Gotchas
 
 - **`sleep` is fragile** — Prefer polling (e.g., `wait_for_file`) over fixed sleeps. CI runners are slower than local machines.
-- **`exit_watcher` is async** — It only signals the watcher to stop (removes the lock file), it doesn't wait for the process to exit. Avoid triggering config-change events before exiting, as the watcher may start a concurrent rebuild.
+- **Wait for watcher shutdown with `exit_watcher`** — It removes the lock file and waits for the recorded watcher process to exit. Check its return status before continuing when later mutations could race with the watcher.
 - **`sed -i` differs across platforms** — macOS requires `sed -i '' ...`, Linux does not. Use the `replace` / `normalize_paths` helpers from `rewatch/tests/utils.sh` instead of raw `sed`.
diff --git a/rewatch/tests/clean/01-clean-single-project.sh b/rewatch/tests/clean/01-clean-single-project.sh
index 7d5aba613da..19971273fc2 100755
--- a/rewatch/tests/clean/01-clean-single-project.sh
+++ b/rewatch/tests/clean/01-clean-single-project.sh
@@ -42,7 +42,7 @@ other_project_compiled_files=$(find packages/new-namespace -type f -name '*.mjs'
 if [ "$other_project_compiled_files" -gt 0 ];
 then
   success "Didn't clean other project files"
-  git restore .
+  git restore --worktree -- .
 else
   error "Expected files from new-namespace not to be cleaned"
   exit 1
diff --git a/rewatch/tests/clean/02-clean-dev-dependencies.sh b/rewatch/tests/clean/02-clean-dev-dependencies.sh
index 2d039a9243d..a2f13f7528c 100755
--- a/rewatch/tests/clean/02-clean-dev-dependencies.sh
+++ b/rewatch/tests/clean/02-clean-dev-dependencies.sh
@@ -31,7 +31,7 @@ project_compiled_files=$(find packages/pure-dev -type f -name '*.mjs' | wc -l |
 if [ "$project_compiled_files" -eq 0 ];
 then
   success "pure-dev cleaned"
-  git restore .
+  git restore --worktree -- .
 else
   error "Expected 0 .mjs files in pure-dev after clean, got $project_compiled_files"
   printf "%s\n" "$error_output"
diff --git a/rewatch/tests/clean/03-clean-node-modules.sh b/rewatch/tests/clean/03-clean-node-modules.sh
index 03630c4d55a..7fe0810062e 100755
--- a/rewatch/tests/clean/03-clean-node-modules.sh
+++ b/rewatch/tests/clean/03-clean-node-modules.sh
@@ -31,7 +31,7 @@ compiler_assets=$(find node_modules/rescript-nodejs/lib/ocaml -type f -name '*.*
 if [ $compiler_assets -eq 0 ];
 then
   success "compiler assets from node_modules cleaned"
-  git restore .
+  git restore --worktree -- .
 else
   error "Expected 0 files in node_modules/rescript-nodejs/lib/ocaml after clean, got $compiler_assets"
   printf "%s\n" "$error_output"
diff --git a/rewatch/tests/clean/04-clean-rebuild-no-compiler-update.sh b/rewatch/tests/clean/04-clean-rebuild-no-compiler-update.sh
index e2b5108221c..d108707fdf3 100755
--- a/rewatch/tests/clean/04-clean-rebuild-no-compiler-update.sh
+++ b/rewatch/tests/clean/04-clean-rebuild-no-compiler-update.sh
@@ -18,24 +18,25 @@ else
   exit 1
 fi
 
-# Rebuild with snapshot output
-snapshot_file=../tests/snapshots/clean-rebuild.txt
-rewatch build &> $snapshot_file
+# Rebuild with captured output. This test checks one lifecycle message; writing
+# into a tracked snapshot made the fixture dirty whenever work counts changed.
+output_file=$(mktemp "${TMPDIR:-/tmp}/rewatch-clean-rebuild.XXXXXX")
+trap 'rm -f "$output_file"' EXIT
+rewatch build &> "$output_file"
 build_status=$?
-normalize_paths $snapshot_file
 if [ $build_status -eq 0 ];
 then
   success "Repo Built"
 else
   error "Error Building Repo"
-  cat $snapshot_file >&2
+  cat "$output_file" >&2
   exit 1
 fi
 
 # Verify the undesired message is NOT present
-if grep -q "Cleaned previous build due to compiler update" $snapshot_file; then
+if grep -q "Cleaned previous build due to compiler update" "$output_file"; then
   error "Unexpected compiler-update clean message present in rebuild logs"
-  cat $snapshot_file >&2
+  cat "$output_file" >&2
   exit 1
 else
   success "No compiler-update clean message present after explicit clean"
diff --git a/rewatch/tests/compile/08-remove-file.sh b/rewatch/tests/compile/08-remove-file.sh
index b38d6a8fba7..19610b91ab3 100755
--- a/rewatch/tests/compile/08-remove-file.sh
+++ b/rewatch/tests/compile/08-remove-file.sh
@@ -11,7 +11,7 @@ rewatch build &> /dev/null
 rm packages/dep02/src/Dep02.res
 rewatch build &> ../tests/snapshots/remove-file.txt
 normalize_paths ../tests/snapshots/remove-file.txt
-git checkout -- packages/dep02/src/Dep02.res
+git restore --worktree -- packages/dep02/src/Dep02.res
 
 rewatch build &> /dev/null
 
diff --git a/rewatch/tests/compile/09-dependency-cycle.sh b/rewatch/tests/compile/09-dependency-cycle.sh
index 7c287b81d69..41ae9f8ef25 100755
--- a/rewatch/tests/compile/09-dependency-cycle.sh
+++ b/rewatch/tests/compile/09-dependency-cycle.sh
@@ -11,7 +11,7 @@ rewatch build &> /dev/null
 echo 'Dep01.log()' >> packages/new-namespace/src/NS_alias.res
 rewatch build &> ../tests/snapshots/dependency-cycle.txt
 normalize_paths ../tests/snapshots/dependency-cycle.txt
-git checkout -- packages/new-namespace/src/NS_alias.res
+git restore --worktree -- packages/new-namespace/src/NS_alias.res
 
 rewatch build &> /dev/null
 
diff --git a/rewatch/tests/compile/11-dev-dependency-non-dev-source.sh b/rewatch/tests/compile/11-dev-dependency-non-dev-source.sh
index 5fe5d7b7b8d..3352c08e8c7 100755
--- a/rewatch/tests/compile/11-dev-dependency-non-dev-source.sh
+++ b/rewatch/tests/compile/11-dev-dependency-non-dev-source.sh
@@ -13,7 +13,7 @@ rewatch build &> /dev/null
 echo 'open WebAPI' >> packages/with-dev-deps/src/FileToTest.res
 rewatch build &> ../tests/snapshots/dev-dependency-used-by-non-dev-source.txt
 normalize_paths ../tests/snapshots/dev-dependency-used-by-non-dev-source.txt
-git checkout -- packages/with-dev-deps/src/FileToTest.res
+git restore --worktree -- packages/with-dev-deps/src/FileToTest.res
 
 rewatch build &> /dev/null
 
diff --git a/rewatch/tests/compile/13-no-infinite-loop-with-cycle.sh b/rewatch/tests/compile/13-no-infinite-loop-with-cycle.sh
index cf369ae749c..e4e27a0a23d 100755
--- a/rewatch/tests/compile/13-no-infinite-loop-with-cycle.sh
+++ b/rewatch/tests/compile/13-no-infinite-loop-with-cycle.sh
@@ -7,7 +7,7 @@ bold "Test: It should not loop when clean building with a cycle"
 
 rewatch clean &> /dev/null
 echo 'Dep01.log()' >> packages/new-namespace/src/NS_alias.res
-git checkout -- packages/new-namespace/src/NS_alias.res
+git restore --worktree -- packages/new-namespace/src/NS_alias.res
 rewatch build &> /dev/null
 
 success "No infinite loop detected"
diff --git a/rewatch/tests/compile/17-prod-flag.sh b/rewatch/tests/compile/17-prod-flag.sh
index c3b5572deaa..faecce057fc 100755
--- a/rewatch/tests/compile/17-prod-flag.sh
+++ b/rewatch/tests/compile/17-prod-flag.sh
@@ -17,7 +17,7 @@ then
   success "Build without --prod correctly failed with nonexistent dev-dependency"
 else
   error "Build without --prod should have failed with nonexistent dev-dependency"
-  git checkout -- rescript.json
+  git restore --worktree -- rescript.json
   exit 1
 fi
 
@@ -27,12 +27,12 @@ then
   success "Build with --prod succeeded despite nonexistent dev-dependency"
 else
   error "Build with --prod should have succeeded by skipping dev-dependencies"
-  git checkout -- rescript.json
+  git restore --worktree -- rescript.json
   exit 1
 fi
 
 rewatch clean &> /dev/null
-git checkout -- rescript.json
+git restore --worktree -- rescript.json
 
 # Test 2: --prod should skip dev source files
 rewatch clean &> /dev/null
diff --git a/rewatch/tests/format/01-format-all-files.sh b/rewatch/tests/format/01-format-all-files.sh
index 1b1ece46b6b..7631f9f788a 100755
--- a/rewatch/tests/format/01-format-all-files.sh
+++ b/rewatch/tests/format/01-format-all-files.sh
@@ -11,7 +11,7 @@ git_diff_file_count=$(git diff --name-only ./ | wc -l | xargs)
 if [ $? -eq 0 ] && [ $git_diff_file_count -eq 8 ];
 then
     success "Test package formatted. Got $git_diff_file_count changed files."
-    git restore .
+    git restore --worktree -- .
 else
     error "Error formatting test package"
     echo "Expected 8 files to be changed, got $git_diff_file_count"
diff --git a/rewatch/tests/format/02-format-single-file.sh b/rewatch/tests/format/02-format-single-file.sh
index e5594956f2d..040d7b82b79 100755
--- a/rewatch/tests/format/02-format-single-file.sh
+++ b/rewatch/tests/format/02-format-single-file.sh
@@ -10,7 +10,7 @@ git_diff_file_count=$(git diff --name-only ./ | wc -l | xargs)
 if [ $? -eq 0 ] && [ $git_diff_file_count -eq 1 ];
 then
     success "Single file formatted successfully"
-    git restore .
+    git restore --worktree -- .
 else
     error "Error formatting single file"
     echo $error_output
diff --git a/rewatch/tests/format/04-format-current-project.sh b/rewatch/tests/format/04-format-current-project.sh
index 80fc751553c..c8a2b30ff11 100755
--- a/rewatch/tests/format/04-format-current-project.sh
+++ b/rewatch/tests/format/04-format-current-project.sh
@@ -10,7 +10,7 @@ git_diff_file_count=$(git diff --name-only ./ | wc -l | xargs)
 if [ $? -eq 0 ] && [ $git_diff_file_count -eq 2 ];
 then
     success "file-casing formatted"
-    git restore .
+    git restore --worktree -- .
 else
     error "Error formatting current project file-casing"
     echo "Expected 2 files to be changed, got $git_diff_file_count"
diff --git a/rewatch/tests/suffix/01-custom-suffix.sh b/rewatch/tests/suffix/01-custom-suffix.sh
index 1dd4669aefb..0485d49c2ab 100755
--- a/rewatch/tests/suffix/01-custom-suffix.sh
+++ b/rewatch/tests/suffix/01-custom-suffix.sh
@@ -6,7 +6,6 @@ cd ../../testrepo
 bold "Test: It should support custom suffixes"
 
 # Clean Repo
-sleep 1
 error_output=$(rewatch clean 2>&1)
 if [ $? -eq 0 ];
 then
diff --git a/rewatch/tests/suite.sh b/rewatch/tests/suite.sh
index 69d888af06a..3209eae41d8 100755
--- a/rewatch/tests/suite.sh
+++ b/rewatch/tests/suite.sh
@@ -49,8 +49,7 @@ bold "Rescript version"
 # we need to reset the yarn.lock and package.json to the original state
 # so there is not diff in git. The CI will install new ReScript package
 bold "Reset package.json and yarn.lock"
-git checkout ../testrepo/yarn.lock &> /dev/null
-git checkout ../testrepo/package.json &> /dev/null
+git restore --worktree -- ../testrepo/yarn.lock ../testrepo/package.json &> /dev/null
 success "Reset package.json and yarn.lock"
 
 bold "Make sure the testrepo is clean"
@@ -145,6 +144,7 @@ fi
 ./watch/04-watch-config-change.sh &&
 ./watch/05-watch-ignores-non-source.sh &&
 ./watch/06-watch-missing-source-folder.sh &&
+./watch/07-changed-interface-after-failed-implementation.sh &&
 
 # Lock tests
 ./lock/01-lock-when-watching.sh &&
diff --git a/rewatch/tests/utils.sh b/rewatch/tests/utils.sh
index eee37596b55..72d9d482d5e 100644
--- a/rewatch/tests/utils.sh
+++ b/rewatch/tests/utils.sh
@@ -11,6 +11,25 @@ is_windows() {
   [[ $OSTYPE == 'msys'* || $OSTYPE == 'cygwin'* || $OSTYPE == 'win'* ]];
 }
 
+platform_timeout() {
+  local timeout="$1"
+  if is_windows; then
+    echo $((timeout * 4))
+  else
+    echo "$timeout"
+  fi
+}
+
+process_is_running() {
+  local pid="$1"
+  if is_windows; then
+    WATCH_PID="$pid" powershell.exe -NoProfile -NonInteractive -Command \
+      'if (Get-Process -Id ([int]$env:WATCH_PID) -ErrorAction SilentlyContinue) { exit 0 } else { exit 1 }'
+  else
+    kill -0 "$pid" 2> /dev/null
+  fi
+}
+
 # get pwd with forward slashes
 pwd_prefix() {
   if is_windows; then
@@ -52,12 +71,13 @@ replace() {
 }
 
 wait_for_pid_gone() {
-  local pid="$1"; local timeout="${2:-10}"
-  while kill -0 "$pid" 2> /dev/null && [ "$timeout" -gt 0 ]; do
+  local pid="$1"; local timeout
+  timeout=$(platform_timeout "${2:-10}")
+  while process_is_running "$pid" && [ "$timeout" -gt 0 ]; do
     sleep 1
     timeout=$((timeout - 1))
   done
-  ! kill -0 "$pid" 2> /dev/null
+  ! process_is_running "$pid"
 }
 
 exit_watcher() {
@@ -81,7 +101,8 @@ clear_locks() {
 }
 
 wait_for_file() {
-  local file="$1"; local timeout="${2:-30}"
+  local file="$1"; local timeout
+  timeout=$(platform_timeout "${2:-30}")
   while [ "$timeout" -gt 0 ]; do
     [ -f "$file" ] && return 0
     sleep 1
@@ -90,8 +111,47 @@ wait_for_file() {
   return 1
 }
 
+wait_for_pattern() {
+  local file="$1"; local pattern="$2"; local timeout
+  timeout=$(platform_timeout "${3:-30}")
+  while [ "$timeout" -gt 0 ]; do
+    grep -q "$pattern" "$file" 2>/dev/null && return 0
+    sleep 1
+    timeout=$((timeout - 1))
+  done
+  return 1
+}
+
+wait_for_pattern_count() {
+  local file="$1"; local pattern="$2"; local expected="$3"; local timeout
+  timeout=$(platform_timeout "${4:-30}")
+  while [ "$timeout" -gt 0 ]; do
+    local current_count
+    current_count=$(grep -c "$pattern" "$file" 2>/dev/null || true)
+    current_count=${current_count:-0}
+    [ "$current_count" -ge "$expected" ] && return 0
+    sleep 1
+    timeout=$((timeout - 1))
+  done
+  return 1
+}
+
+wait_for_pattern_gone() {
+  local file="$1"; local pattern="$2"; local timeout
+  timeout=$(platform_timeout "${3:-30}")
+  while [ "$timeout" -gt 0 ]; do
+    if [ -f "$file" ] && ! grep -q "$pattern" "$file" 2>/dev/null; then
+      return 0
+    fi
+    sleep 1
+    timeout=$((timeout - 1))
+  done
+  return 1
+}
+
 wait_for_file_gone() {
-  local file="$1"; local timeout="${2:-30}"
+  local file="$1"; local timeout
+  timeout=$(platform_timeout "${2:-30}")
   while [ "$timeout" -gt 0 ]; do
     [ ! -f "$file" ] && return 0
     sleep 1
diff --git a/rewatch/tests/watch/01-watch-recompile.sh b/rewatch/tests/watch/01-watch-recompile.sh
index 626df386161..2356561df70 100755
--- a/rewatch/tests/watch/01-watch-recompile.sh
+++ b/rewatch/tests/watch/01-watch-recompile.sh
@@ -32,6 +32,16 @@ if ! wait_for_file "$target" 20; then
   exit 1
 fi
 
+# The root output must not become observable before an output it imports.
+# Otherwise consumers can load a superficially completed but unusable build.
+dependency_target=./packages/dep01/src/Dep01.mjs
+if [ ! -f "$dependency_target" ]; then
+  error "Dependency output was not published with the root output: $dependency_target"
+  tail -n 200 rewatch.log || true
+  exit_watcher
+  exit 1
+fi
+
 if node ./packages/main/src/Main.mjs | grep 'added-by-test' &> /dev/null;
 then
   success "Output is correct"
@@ -41,11 +51,21 @@ else
   exit 1
 fi
 
-sleep 1
+if ! wait_for_pattern_count rewatch.log "Finished .*compilation" 1 30; then
+  error "Initial build did not settle"
+  tail -n 200 rewatch.log || true
+  exit_watcher
+  exit 1
+fi
 
 replace '/Console.log("added-by-test")/d' ./packages/main/src/Main.res;
 
-sleep 5
+if ! wait_for_pattern_gone "$target" "added-by-test" 20; then
+  error "Watcher did not rebuild after restoring the source"
+  tail -n 200 rewatch.log || true
+  exit_watcher
+  exit 1
+fi
 
 if git diff --exit-code ./
 then
diff --git a/rewatch/tests/watch/02-watch-warnings-persist-atomic-save.sh b/rewatch/tests/watch/02-watch-warnings-persist-atomic-save.sh
index 63adb0fd2bf..0841dc0a9ca 100755
--- a/rewatch/tests/watch/02-watch-warnings-persist-atomic-save.sh
+++ b/rewatch/tests/watch/02-watch-warnings-persist-atomic-save.sh
@@ -15,18 +15,9 @@ else
   exit 1
 fi
 
-wait_for_pattern() {
-  local file="$1"; local pattern="$2"; local timeout="${3:-30}"
-  while [ "$timeout" -gt 0 ]; do
-    grep -q "$pattern" "$file" 2>/dev/null && return 0
-    sleep 1
-    timeout=$((timeout - 1))
-  done
-  return 1
-}
-
 wait_for_changed_completed_log() {
-  local file="$1"; local baseline="$2"; local timeout="${3:-30}"
+  local file="$1"; local baseline="$2"; local timeout
+  timeout=$(platform_timeout "${3:-30}")
   while [ "$timeout" -gt 0 ]; do
     if [ -f "$file" ] && ! cmp -s "$file" "$baseline" && grep -q "#Done(" "$file" 2>/dev/null; then
       return 0
@@ -53,7 +44,6 @@ cleanup() {
     cp "$BACKUP_B" "$B_FILE"
   fi
   exit_watcher
-  sleep 1
   rm -rf "$TMP_DIR"
   rm -f "$WATCH_STDOUT" "$WATCH_STDERR"
 }
@@ -113,10 +103,13 @@ else
   exit 1
 fi
 
+cp "$COMPILER_LOG" "$TMP_DIR/before-restore.compiler.log"
 cp "$BACKUP_B" "$B_FILE"
-sleep 1
+if ! wait_for_changed_completed_log "$COMPILER_LOG" "$TMP_DIR/before-restore.compiler.log" 30; then
+  error "Compiler log did not complete a new cycle after restoring B.res"
+  exit 1
+fi
 exit_watcher
-sleep 2
 rm -f "$WATCH_STDOUT" "$WATCH_STDERR"
 
 if git diff --exit-code ./packages/watch-warnings > /dev/null 2>&1;
diff --git a/rewatch/tests/watch/02-watch-warnings-persist.sh b/rewatch/tests/watch/02-watch-warnings-persist.sh
index b67ad0e0aec..214a9bc9268 100755
--- a/rewatch/tests/watch/02-watch-warnings-persist.sh
+++ b/rewatch/tests/watch/02-watch-warnings-persist.sh
@@ -15,29 +15,6 @@ else
   exit 1
 fi
 
-# Wait until a pattern appears in a file (with timeout in seconds, default 30)
-wait_for_pattern() {
-  local file="$1"; local pattern="$2"; local timeout="${3:-30}"
-  while [ "$timeout" -gt 0 ]; do
-    grep -q "$pattern" "$file" 2>/dev/null && return 0
-    sleep 1
-    timeout=$((timeout - 1))
-  done
-  return 1
-}
-
-# Wait until a pattern appears N times in a file (with timeout in seconds, default 30)
-wait_for_pattern_count() {
-  local file="$1"; local pattern="$2"; local count="$3"; local timeout="${4:-30}"
-  while [ "$timeout" -gt 0 ]; do
-    local current_count=$(grep -c "$pattern" "$file" 2>/dev/null || echo "0")
-    [ "$current_count" -ge "$count" ] && return 0
-    sleep 1
-    timeout=$((timeout - 1))
-  done
-  return 1
-}
-
 # Start watcher and capture stderr (where warnings are printed)
 rewatch_bg watch > /dev/null 2> rewatch-stderr.log &
 
@@ -67,13 +44,32 @@ warning_count=$(grep -c "unused value unusedValue" rewatch-stderr.log)
 success "Warning from ModuleA.res persists after recompiling B.res (count: $warning_count)"
 
 # Restore B.res
+warning_count_before_restore=$(grep -c "unused value unusedValue" rewatch-stderr.log 2>/dev/null || true)
+warning_count_before_restore=${warning_count_before_restore:-0}
 printf 'let world = () => Console.log("world")\n' > ./packages/watch-warnings/src/B.res
 
-sleep 1
+if ! wait_for_pattern_count rewatch-stderr.log "unused value unusedValue" \
+  "$((warning_count_before_restore + 1))" 20; then
+  error "Watcher did not finish rebuilding after restoring B.res"
+  cat rewatch-stderr.log
+  exit_watcher
+  exit 1
+fi
 
 exit_watcher
 
-sleep 2
+# A new invocation has no retained in-memory warning state, so the watcher must
+# leave a freshness marker that causes the warning-producing module to run.
+next_output=$(rewatch build 2>&1)
+next_status=$?
+if [ "$next_status" -eq 0 ] \
+  && printf '%s\n' "$next_output" | grep -q "unused value unusedValue"; then
+  success "Warning persists after watcher shutdown"
+else
+  error "Warning was lost after watcher shutdown"
+  printf '%s\n' "$next_output"
+  exit 1
+fi
 
 # Clean up log file
 rm -f rewatch-stderr.log
diff --git a/rewatch/tests/watch/03-watch-new-file.sh b/rewatch/tests/watch/03-watch-new-file.sh
index 1d4cfa19ea5..a087ddf4274 100755
--- a/rewatch/tests/watch/03-watch-new-file.sh
+++ b/rewatch/tests/watch/03-watch-new-file.sh
@@ -28,7 +28,12 @@ if ! wait_for_file "./src/Test.mjs" 20; then
 fi
 success "Initial build completed"
 
-sleep 1
+if ! wait_for_pattern_count rewatch.log "Finished .*compilation" 1 30; then
+  error "Initial build did not settle"
+  cat rewatch.log
+  exit_watcher
+  exit 1
+fi
 
 # Create a new file in the source directory
 cat > ./src/NewWatchTestFile.res << 'EOF'
@@ -55,16 +60,22 @@ else
   exit 1
 fi
 
-# Clean up the new file
+# Clean up the new file. Wait for the resulting rebuild so it cannot race with
+# later tests; stale-output deletion is not part of this new-file watcher test.
+completed_builds=$(grep -c "Finished .*compilation" rewatch.log || true)
 rm -f ./src/NewWatchTestFile.res
 
-# Wait for the compiled output to be removed (full rebuild detects removal)
-sleep 5
+if ! wait_for_pattern_count rewatch.log "Finished .*compilation" "$((completed_builds + 1))" 30; then
+  error "Watcher did not finish rebuilding after deleting the source"
+  cat rewatch.log
+  exit_watcher
+  exit 1
+fi
+
 rm -f ./src/NewWatchTestFile.mjs
 
 exit_watcher
 
-sleep 2
 rm -f rewatch.log
 
 if git diff --exit-code . > /dev/null 2>&1 && [ -z "$(git ls-files --others --exclude-standard .)" ];
diff --git a/rewatch/tests/watch/04-watch-config-change.sh b/rewatch/tests/watch/04-watch-config-change.sh
index 519f77f5e82..ce7d00c6268 100755
--- a/rewatch/tests/watch/04-watch-config-change.sh
+++ b/rewatch/tests/watch/04-watch-config-change.sh
@@ -28,25 +28,56 @@ if ! wait_for_file "./src/Test.mjs" 20; then
 fi
 success "Initial build completed"
 
-sleep 2
+if ! wait_for_pattern_count rewatch.log "Finished .*compilation" 1 30; then
+  error "Initial build did not settle"
+  cat rewatch.log
+  exit_watcher
+  exit 1
+fi
+completed_builds=$(grep -c "Finished .*compilation" rewatch.log 2>/dev/null || true)
+completed_builds=${completed_builds:-0}
+wait_for_next_build() {
+  completed_builds=$((completed_builds + 1))
+  wait_for_pattern_count rewatch.log "Finished .*compilation" \
+    "$completed_builds" 30
+}
+
+wait_for_tracked_outputs() {
+  local timeout
+  timeout=$(platform_timeout 30)
+  while [ "$timeout" -gt 0 ]; do
+    if [ -z "$(git ls-files --deleted -- '*.mjs')" ]; then
+      return 0
+    fi
+    sleep 1
+    timeout=$((timeout - 1))
+  done
+  return 1
+}
 
 # Change the suffix in rescript.json (same approach as suffix test)
 replace "s/.mjs/.res.mjs/g" rescript.json
+if ! wait_for_next_build; then
+  error "Configuration rebuild did not settle"
+  cat rewatch.log
+  replace "s/.res.mjs/.mjs/g" rescript.json
+  exit_watcher
+  exit 1
+fi
 
 # After a config change, the watcher does a full rebuild. However, a suffix
 # change alone may not recompile files (sources haven't changed). Trigger a
 # source change so the watcher compiles with the new suffix.
-sleep 3
 echo '// config-change-test' >> ./src/Test.res
 
-# Wait for the file with the new suffix to appear
-if wait_for_file "./src/Test.res.mjs" 20; then
+# Wait for the file with the new suffix and the complete source rebuild.
+if wait_for_file "./src/Test.res.mjs" 20 && wait_for_next_build; then
   success "Full rebuild triggered by rescript.json change (new suffix applied)"
 else
   error "No rebuild detected after rescript.json change"
   cat rewatch.log
   replace "s/.res.mjs/.mjs/g" rescript.json
-  git checkout -- ./src/Test.res
+  git restore --worktree -- ./src/Test.res
   exit_watcher
   exit 1
 fi
@@ -58,25 +89,33 @@ else
   error "Watcher crashed after config change"
   cat rewatch.log
   replace "s/.res.mjs/.mjs/g" rescript.json
-  git checkout -- ./src/Test.res
+  git restore --worktree -- ./src/Test.res
   exit 1
 fi
 
-# Restore rescript.json and source file
+# Restore only the configuration while the watcher is running. Mixing the
+# unrelated source cleanup into the same native event batch can make the batch
+# look like an incremental source edit and obscure the configuration transition
+# this test is intended to verify.
 replace "s/.res.mjs/.mjs/g" rescript.json
-git checkout -- ./src/Test.res
-
-# Wait for rebuild with restored suffix (old .res.mjs should go away)
-if wait_for_file_gone "./src/Test.res.mjs" 20; then
-  success "Rebuild after restore removed old suffix files"
+if wait_for_next_build && wait_for_tracked_outputs; then
+  success "Rebuild after configuration restore completed"
 else
-  # Clean up manually if the watcher didn't remove them
-  find . -name "*.res.mjs" -delete 2>/dev/null
+  error "Configuration restore did not settle or restore tracked outputs"
+  git restore --worktree -- ./src/Test.res
+  exit_watcher
+  exit 1
 fi
 
-exit_watcher
+# This test covers watcher reconfiguration, not migration of outputs generated
+# with the previous suffix.
+find . -name "*.res.mjs" -delete 2>/dev/null
+
+if ! exit_watcher; then
+  exit 1
+fi
 
-sleep 2
+git restore --worktree -- ./src/Test.res
 rm -f rewatch.log
 
 if git diff --exit-code . > /dev/null 2>&1 && [ -z "$(git ls-files --others --exclude-standard .)" ];
diff --git a/rewatch/tests/watch/05-watch-ignores-non-source.sh b/rewatch/tests/watch/05-watch-ignores-non-source.sh
index 0bd8f856559..01abb65562b 100755
--- a/rewatch/tests/watch/05-watch-ignores-non-source.sh
+++ b/rewatch/tests/watch/05-watch-ignores-non-source.sh
@@ -77,7 +77,6 @@ rm -rf ./random-dir ./another-dir
 
 exit_watcher
 
-sleep 2
 rm -f rewatch.log
 
 if git diff --exit-code . > /dev/null 2>&1 && [ -z "$(git ls-files --others --exclude-standard .)" ];
diff --git a/rewatch/tests/watch/06-watch-missing-source-folder.sh b/rewatch/tests/watch/06-watch-missing-source-folder.sh
index 08436c4fe19..19d9d948003 100755
--- a/rewatch/tests/watch/06-watch-missing-source-folder.sh
+++ b/rewatch/tests/watch/06-watch-missing-source-folder.sh
@@ -33,7 +33,7 @@ success "Watcher Started"
 if ! wait_for_file "./src/Test.mjs" 20; then
   error "Initial build did not complete"
   cat rewatch.log
-  git checkout "$DEP01_CONFIG"
+  git restore --worktree -- "$DEP01_CONFIG"
   exit_watcher
   exit 1
 fi
@@ -45,7 +45,7 @@ if grep -q 'Could not read folder.*nonexistent-folder' rewatch.log; then
 else
   error "Missing source folder error was NOT reported"
   cat rewatch.log
-  git checkout "$DEP01_CONFIG"
+  git restore --worktree -- "$DEP01_CONFIG"
   exit_watcher
   exit 1
 fi
@@ -54,10 +54,9 @@ fi
 # where the config change triggers a full rebuild that runs concurrently
 # with the subsequent `rewatch build`.
 exit_watcher
-sleep 1
 
 # Restore dep01's rescript.json
-git checkout "$DEP01_CONFIG"
+git restore --worktree -- "$DEP01_CONFIG"
 
 # Rebuild to regenerate any artifacts that were removed by `rewatch clean`
 # but not rebuilt due to the modified config (e.g. Dep01.mjs).
diff --git a/rewatch/tests/watch/07-changed-interface-after-failed-implementation.sh b/rewatch/tests/watch/07-changed-interface-after-failed-implementation.sh
new file mode 100755
index 00000000000..346a6163139
--- /dev/null
+++ b/rewatch/tests/watch/07-changed-interface-after-failed-implementation.sh
@@ -0,0 +1,97 @@
+#!/bin/bash
+
+cd "$(dirname "$0")"
+source "../utils.sh"
+
+bold "Test: A changed interface dirties dependents after its implementation fails"
+
+fixture=$(mktemp -d 2>/dev/null || mktemp -d -t rewatch-failed-implementation)
+cleanup() {
+  cd "$fixture" || return
+  exit_watcher
+  if [ -n "${watch_pid:-}" ]; then
+    if process_is_running "$watch_pid"; then
+      kill "$watch_pid" 2>/dev/null || true
+    fi
+    wait "$watch_pid" 2>/dev/null || true
+  fi
+  rm -rf "$fixture"
+}
+trap cleanup EXIT
+
+mkdir -p "$fixture/src"
+cat > "$fixture/rescript.json" <<'EOF'
+{
+  "name": "rewatch-failed-implementation",
+  "sources": { "dir": "src" },
+  "package-specs": { "module": "esmodule", "in-source": true },
+  "suffix": ".mjs"
+}
+EOF
+
+cat > "$fixture/src/Provider.resi" <<'EOF'
+let value: int
+EOF
+cat > "$fixture/src/Provider.res" <<'EOF'
+let value = 1
+EOF
+cat > "$fixture/src/Consumer.res" <<'EOF'
+let number: int = Provider.value
+EOF
+
+cd "$fixture" || exit 1
+RAYON_NUM_THREADS=1 "$REWATCH_EXECUTABLE" watch > rewatch.log 2>&1 &
+watch_pid=$!
+compiler_log=lib/bs/.compiler.log
+
+wait_for_changed_compiler_log() {
+  local baseline="$1"; local timeout
+  timeout=$(platform_timeout 30)
+  while [ "$timeout" -gt 0 ]; do
+    if [ -f "$compiler_log" ] && ! cmp -s "$compiler_log" "$baseline" &&
+      grep -q '#Done(' "$compiler_log"; then
+      return 0
+    fi
+    sleep 1
+    timeout=$((timeout - 1))
+  done
+  return 1
+}
+
+if ! wait_for_pattern_count rewatch.log "Finished .*compilation" 1 30; then
+  error "Initial watch build did not finish"
+  cat rewatch.log >&2
+  exit 1
+fi
+cp "$compiler_log" initial.compiler.log
+
+# The new interface writes a different CMI, but the old implementation cannot
+# satisfy it. The dependent must remain blocked and dirty across this build.
+printf 'let value: string\n' > src/Provider.resi
+if ! wait_for_changed_compiler_log initial.compiler.log; then
+  error "Watch did not finish the failing interface-change build"
+  cat rewatch.log >&2
+  exit 1
+fi
+if ! grep -q "Provider.res" "$compiler_log"; then
+  error "Changed interface did not expose the implementation error"
+  cat rewatch.log >&2
+  exit 1
+fi
+cp "$compiler_log" failed.compiler.log
+
+# Once the implementation satisfies the interface, Consumer must compile
+# against the new string type and report its now-invalid int annotation.
+printf 'let value = "recovered"\n' > src/Provider.res
+if ! wait_for_changed_compiler_log failed.compiler.log; then
+  error "Watch did not finish the recovery build"
+  cat rewatch.log >&2
+  exit 1
+fi
+if ! grep -q "Consumer.res" "$compiler_log"; then
+  error "Consumer was not recompiled against the changed interface"
+  cat rewatch.log >&2
+  exit 1
+fi
+
+success "Changed CMI reaches blocked dependents after recovery"

From b79362b905e84da600d6a4d12f3f03513bbb8369 Mon Sep 17 00:00:00 2001
From: Christoph Knittel <ck@cca.io>
Date: Wed, 23 Sep 2026 12:20:47 +0000
Subject: [PATCH 3/5] Preserve blocked dependents across full rewatch rebuilds

Signed-off-by: Christoph Knittel <ck@cca.io>
---
 CHANGELOG.md                                  |  2 +-
 rewatch/src/watcher.rs                        | 39 +++++++++++++++----
 ...d-interface-after-failed-implementation.sh |  7 ++--
 3 files changed, 37 insertions(+), 11 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index e1aa7b066cc..311d5eee7ff 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -20,7 +20,7 @@
 
 #### :bug: Bug fix
 
-- Make rewatch compile independent modules after an unrelated failure and recompile blocked dependents when a changed interface survives a failed implementation. https://github.com/rescript-lang/rescript/pull/8667
+- Make rewatch compile independent modules after an unrelated failure and recompile blocked dependents when a changed interface survives a failed implementation, including across full watcher rebuilds. https://github.com/rescript-lang/rescript/pull/8667
 
 #### :memo: Documentation
 
diff --git a/rewatch/src/watcher.rs b/rewatch/src/watcher.rs
index e435c757857..afcaaacc7e1 100644
--- a/rewatch/src/watcher.rs
+++ b/rewatch/src/watcher.rs
@@ -172,7 +172,7 @@ fn unregister_watches(watcher: &mut RecommendedWatcher, watch_paths: &[(PathBuf,
     }
 }
 
-fn carry_forward_compile_warnings(previous: &BuildCommandState, next: &mut BuildCommandState) {
+fn carry_forward_compile_state(previous: &BuildCommandState, next: &mut BuildCommandState) {
     for (module_name, next_module) in next.build_state.modules.iter_mut() {
         let Some(previous_module) = previous.build_state.modules.get(module_name) else {
             continue;
@@ -184,6 +184,12 @@ fn carry_forward_compile_warnings(previous: &BuildCommandState, next: &mut Build
         match (&previous_module.source_type, &mut next_module.source_type) {
             (SourceType::SourceFile(previous_source), SourceType::SourceFile(next_source)) => {
                 if previous_source.implementation.path == next_source.implementation.path {
+                    // A changed CMI can leave a dependent blocked behind a failed
+                    // implementation. Asset timestamps alone cannot recover this
+                    // dirtiness when a full watcher rebuild recreates the state.
+                    if previous_module.compile_dirty {
+                        next_module.compile_dirty = true;
+                    }
                     next_source.implementation.compile_warnings =
                         previous_source.implementation.compile_warnings.clone();
 
@@ -501,9 +507,8 @@ async fn async_watch(
                     .expect("Could not initialize build");
 
                     // Full rebuilds can be triggered by editor atomic saves that surface as rename events.
-                    // Preserve warning state for unchanged modules so their warnings are re-emitted after the
-                    // fresh build state replaces the previous one.
-                    carry_forward_compile_warnings(&build_state, &mut next_build_state);
+                    // Preserve warnings and blocked dirty modules when fresh state replaces the previous one.
+                    carry_forward_compile_state(&build_state, &mut next_build_state);
                     build_state = next_build_state;
 
                     // Re-register watches based on the new build state
@@ -804,7 +809,7 @@ mod tests {
         );
         let mut next = test_build_state("ModuleA", test_module("src/ModuleA.res", None, None, None));
 
-        carry_forward_compile_warnings(&previous, &mut next);
+        carry_forward_compile_state(&previous, &mut next);
 
         let module = next.get_module("ModuleA").expect("module should exist");
         let SourceType::SourceFile(source_file) = &module.source_type else {
@@ -826,7 +831,7 @@ mod tests {
         );
         let mut next = test_build_state("ModuleA", test_module("src/ModuleARenamed.res", None, None, None));
 
-        carry_forward_compile_warnings(&previous, &mut next);
+        carry_forward_compile_state(&previous, &mut next);
 
         let module = next.get_module("ModuleA").expect("module should exist");
         let SourceType::SourceFile(source_file) = &module.source_type else {
@@ -853,7 +858,7 @@ mod tests {
             test_module("src/ModuleA.res", None, Some("src/ModuleA.resi"), None),
         );
 
-        carry_forward_compile_warnings(&previous, &mut next);
+        carry_forward_compile_state(&previous, &mut next);
 
         let module = next.get_module("ModuleA").expect("module should exist");
         let SourceType::SourceFile(source_file) = &module.source_type else {
@@ -864,4 +869,24 @@ mod tests {
         assert_eq!(interface.compile_warnings.as_deref(), Some("warning: interface"));
         assert_eq!(interface.compile_state, CompileState::Warning);
     }
+
+    #[test]
+    fn carries_forward_blocked_dirtiness_only_for_matching_sources() {
+        let mut previous = test_build_state("ModuleA", test_module("src/ModuleA.res", None, None, None));
+        previous
+            .build_state
+            .modules
+            .get_mut("ModuleA")
+            .unwrap()
+            .compile_dirty = true;
+
+        let mut same_source = test_build_state("ModuleA", test_module("src/ModuleA.res", None, None, None));
+        carry_forward_compile_state(&previous, &mut same_source);
+        assert!(same_source.get_module("ModuleA").unwrap().compile_dirty);
+
+        let mut different_source =
+            test_build_state("ModuleA", test_module("src/Other.res", None, None, None));
+        carry_forward_compile_state(&previous, &mut different_source);
+        assert!(!different_source.get_module("ModuleA").unwrap().compile_dirty);
+    }
 }
diff --git a/rewatch/tests/watch/07-changed-interface-after-failed-implementation.sh b/rewatch/tests/watch/07-changed-interface-after-failed-implementation.sh
index 346a6163139..40e35e30935 100755
--- a/rewatch/tests/watch/07-changed-interface-after-failed-implementation.sh
+++ b/rewatch/tests/watch/07-changed-interface-after-failed-implementation.sh
@@ -80,9 +80,10 @@ if ! grep -q "Provider.res" "$compiler_log"; then
 fi
 cp "$compiler_log" failed.compiler.log
 
-# Once the implementation satisfies the interface, Consumer must compile
-# against the new string type and report its now-invalid int annotation.
-printf 'let value = "recovered"\n' > src/Provider.res
+# An atomic replacement makes the watcher reinitialize its build state. The
+# blocked dependent must remain dirty through that full rebuild as well.
+printf 'let value = "recovered"\n' > src/Provider.next
+mv src/Provider.next src/Provider.res
 if ! wait_for_changed_compiler_log failed.compiler.log; then
   error "Watch did not finish the recovery build"
   cat rewatch.log >&2

From f4655439e59cc5014547e2b4ed4b4ef90cfbf47f Mon Sep 17 00:00:00 2001
From: Christoph Knittel <ck@cca.io>
Date: Wed, 23 Sep 2026 14:16:42 +0000
Subject: [PATCH 4/5] Abort warning persistence test if watcher stays running

Signed-off-by: Christoph Knittel <ck@cca.io>
---
 rewatch/tests/watch/02-watch-warnings-persist.sh | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/rewatch/tests/watch/02-watch-warnings-persist.sh b/rewatch/tests/watch/02-watch-warnings-persist.sh
index 214a9bc9268..45d3d9f4397 100755
--- a/rewatch/tests/watch/02-watch-warnings-persist.sh
+++ b/rewatch/tests/watch/02-watch-warnings-persist.sh
@@ -56,7 +56,9 @@ if ! wait_for_pattern_count rewatch-stderr.log "unused value unusedValue" \
   exit 1
 fi
 
-exit_watcher
+if ! exit_watcher; then
+  exit 1
+fi
 
 # A new invocation has no retained in-memory warning state, so the watcher must
 # leave a freshness marker that causes the warning-producing module to run.

From 9153fbd7d982c228efc80a15692ae00cbc2153ec Mon Sep 17 00:00:00 2001
From: Christoph Knittel <ck@cca.io>
Date: Wed, 23 Sep 2026 15:54:35 +0000
Subject: [PATCH 5/5] Abort watcher tests when shutdown times out

Signed-off-by: Christoph Knittel <ck@cca.io>
---
 rewatch/tests/lock/01-lock-when-watching.sh          |  8 ++++++--
 rewatch/tests/watch/01-watch-recompile.sh            |  4 +++-
 .../watch/02-watch-warnings-persist-atomic-save.sh   |  4 +++-
 rewatch/tests/watch/03-watch-new-file.sh             |  4 +++-
 rewatch/tests/watch/05-watch-ignores-non-source.sh   |  4 +++-
 .../tests/watch/06-watch-missing-source-folder.sh    | 12 +++++++++---
 6 files changed, 27 insertions(+), 9 deletions(-)

diff --git a/rewatch/tests/lock/01-lock-when-watching.sh b/rewatch/tests/lock/01-lock-when-watching.sh
index a25f4395104..de76c3ae4be 100755
--- a/rewatch/tests/lock/01-lock-when-watching.sh
+++ b/rewatch/tests/lock/01-lock-when-watching.sh
@@ -76,7 +76,9 @@ else
   exit 1
 fi
 
-exit_watcher
+if ! exit_watcher; then
+  exit 1
+fi
 
 if ! wait_for_file_gone "lib/watch.lock" 10; then
   error "watch.lock was not removed"
@@ -93,4 +95,6 @@ else
   exit 1
 fi
 
-exit_watcher
+if ! exit_watcher; then
+  exit 1
+fi
diff --git a/rewatch/tests/watch/01-watch-recompile.sh b/rewatch/tests/watch/01-watch-recompile.sh
index 2356561df70..bfd13eef04a 100755
--- a/rewatch/tests/watch/01-watch-recompile.sh
+++ b/rewatch/tests/watch/01-watch-recompile.sh
@@ -76,4 +76,6 @@ else
   exit 1
 fi
 
-exit_watcher
+if ! exit_watcher; then
+  exit 1
+fi
diff --git a/rewatch/tests/watch/02-watch-warnings-persist-atomic-save.sh b/rewatch/tests/watch/02-watch-warnings-persist-atomic-save.sh
index 0841dc0a9ca..4548fa11385 100755
--- a/rewatch/tests/watch/02-watch-warnings-persist-atomic-save.sh
+++ b/rewatch/tests/watch/02-watch-warnings-persist-atomic-save.sh
@@ -109,7 +109,9 @@ if ! wait_for_changed_completed_log "$COMPILER_LOG" "$TMP_DIR/before-restore.com
   error "Compiler log did not complete a new cycle after restoring B.res"
   exit 1
 fi
-exit_watcher
+if ! exit_watcher; then
+  exit 1
+fi
 rm -f "$WATCH_STDOUT" "$WATCH_STDERR"
 
 if git diff --exit-code ./packages/watch-warnings > /dev/null 2>&1;
diff --git a/rewatch/tests/watch/03-watch-new-file.sh b/rewatch/tests/watch/03-watch-new-file.sh
index a087ddf4274..380e54d0f29 100755
--- a/rewatch/tests/watch/03-watch-new-file.sh
+++ b/rewatch/tests/watch/03-watch-new-file.sh
@@ -74,7 +74,9 @@ fi
 
 rm -f ./src/NewWatchTestFile.mjs
 
-exit_watcher
+if ! exit_watcher; then
+  exit 1
+fi
 
 rm -f rewatch.log
 
diff --git a/rewatch/tests/watch/05-watch-ignores-non-source.sh b/rewatch/tests/watch/05-watch-ignores-non-source.sh
index 01abb65562b..2c1b978e3e3 100755
--- a/rewatch/tests/watch/05-watch-ignores-non-source.sh
+++ b/rewatch/tests/watch/05-watch-ignores-non-source.sh
@@ -75,7 +75,9 @@ success "File in nested non-source subdir was correctly ignored"
 rm -f ./src/WatchProbe.res ./src/WatchProbe.mjs
 rm -rf ./random-dir ./another-dir
 
-exit_watcher
+if ! exit_watcher; then
+  exit 1
+fi
 
 rm -f rewatch.log
 
diff --git a/rewatch/tests/watch/06-watch-missing-source-folder.sh b/rewatch/tests/watch/06-watch-missing-source-folder.sh
index 19d9d948003..3f478b32543 100755
--- a/rewatch/tests/watch/06-watch-missing-source-folder.sh
+++ b/rewatch/tests/watch/06-watch-missing-source-folder.sh
@@ -33,8 +33,10 @@ success "Watcher Started"
 if ! wait_for_file "./src/Test.mjs" 20; then
   error "Initial build did not complete"
   cat rewatch.log
+  if ! exit_watcher; then
+    exit 1
+  fi
   git restore --worktree -- "$DEP01_CONFIG"
-  exit_watcher
   exit 1
 fi
 success "Initial build completed"
@@ -45,15 +47,19 @@ if grep -q 'Could not read folder.*nonexistent-folder' rewatch.log; then
 else
   error "Missing source folder error was NOT reported"
   cat rewatch.log
+  if ! exit_watcher; then
+    exit 1
+  fi
   git restore --worktree -- "$DEP01_CONFIG"
-  exit_watcher
   exit 1
 fi
 
 # Exit the watcher before restoring the config to avoid a race condition
 # where the config change triggers a full rebuild that runs concurrently
 # with the subsequent `rewatch build`.
-exit_watcher
+if ! exit_watcher; then
+  exit 1
+fi
 
 # Restore dep01's rescript.json
 git restore --worktree -- "$DEP01_CONFIG"