diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index eb50fc15a..7bb07c4b1 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -662,6 +662,11 @@ jobs:
               [ -n "$path" ] && saw_invalid_path=true
               printf '%s' "$flattened" | grep -Eq 'error:[[:space:]]*.*Failed to convert config\.cachix to JSON' && saw_cachix_signature=true || true
               printf '%s' "$flattened" | grep -Eq 'error:[[:space:]]*.*while evaluating the option.*cachix\.package' && saw_cachix_signature=true || true
+              # Nix can surface fetched-source corruption as missing subpaths under
+              # \u00ABgithub:owner/repo/rev\u00BB/... during arbitrary flake evaluation, not only
+              # while resolving the devenv CLI. Retry after clearing fetch/eval caches:
+              # this indicates an incomplete or stale fetched-source view, not project source.
+              printf '%s' "$flattened" | grep -Eq "error:[[:space:]]*path '\u00AB(github|https?)[:/][^\u00BB]+\u00BB/[^']+' does not exist" && saw_fetch_signature=true || true
               printf '%s' "$flattened" | grep -Eq 'error:[[:space:]]*cannot read file from tarball:[[:space:]]*Truncated tar archive detected while reading data' && saw_fetch_signature=true || true
               rm -f "$log"
 
@@ -682,7 +687,7 @@ jobs:
               fi
 
               [ -z "$path" ] || nix-store --realise "$path" 2>/dev/null || true
-              rm -rf ~/.cache/nix/eval-cache-*
+              rm -rf ~/.cache/nix/eval-cache-* ~/.cache/nix/gitv3 ~/.cache/nix/tarball-cache ~/.cache/nix/tarball-cache-v2 ~/.cache/nix/fetcher-cache*.sqlite*
               attempt=$((attempt + 1))
             done
 
@@ -787,6 +792,11 @@ jobs:
               [ -n "$path" ] && saw_invalid_path=true
               printf '%s' "$flattened" | grep -Eq 'error:[[:space:]]*.*Failed to convert config\.cachix to JSON' && saw_cachix_signature=true || true
               printf '%s' "$flattened" | grep -Eq 'error:[[:space:]]*.*while evaluating the option.*cachix\.package' && saw_cachix_signature=true || true
+              # Nix can surface fetched-source corruption as missing subpaths under
+              # \u00ABgithub:owner/repo/rev\u00BB/... during arbitrary flake evaluation, not only
+              # while resolving the devenv CLI. Retry after clearing fetch/eval caches:
+              # this indicates an incomplete or stale fetched-source view, not project source.
+              printf '%s' "$flattened" | grep -Eq "error:[[:space:]]*path '\u00AB(github|https?)[:/][^\u00BB]+\u00BB/[^']+' does not exist" && saw_fetch_signature=true || true
               printf '%s' "$flattened" | grep -Eq 'error:[[:space:]]*cannot read file from tarball:[[:space:]]*Truncated tar archive detected while reading data' && saw_fetch_signature=true || true
               rm -f "$log"
 
@@ -807,7 +817,7 @@ jobs:
               fi
 
               [ -z "$path" ] || nix-store --realise "$path" 2>/dev/null || true
-              rm -rf ~/.cache/nix/eval-cache-*
+              rm -rf ~/.cache/nix/eval-cache-* ~/.cache/nix/gitv3 ~/.cache/nix/tarball-cache ~/.cache/nix/tarball-cache-v2 ~/.cache/nix/fetcher-cache*.sqlite*
               attempt=$((attempt + 1))
             done
 
@@ -1143,6 +1153,11 @@ jobs:
               [ -n "$path" ] && saw_invalid_path=true
               printf '%s' "$flattened" | grep -Eq 'error:[[:space:]]*.*Failed to convert config\.cachix to JSON' && saw_cachix_signature=true || true
               printf '%s' "$flattened" | grep -Eq 'error:[[:space:]]*.*while evaluating the option.*cachix\.package' && saw_cachix_signature=true || true
+              # Nix can surface fetched-source corruption as missing subpaths under
+              # \u00ABgithub:owner/repo/rev\u00BB/... during arbitrary flake evaluation, not only
+              # while resolving the devenv CLI. Retry after clearing fetch/eval caches:
+              # this indicates an incomplete or stale fetched-source view, not project source.
+              printf '%s' "$flattened" | grep -Eq "error:[[:space:]]*path '\u00AB(github|https?)[:/][^\u00BB]+\u00BB/[^']+' does not exist" && saw_fetch_signature=true || true
               printf '%s' "$flattened" | grep -Eq 'error:[[:space:]]*cannot read file from tarball:[[:space:]]*Truncated tar archive detected while reading data' && saw_fetch_signature=true || true
               rm -f "$log"
 
@@ -1163,7 +1178,7 @@ jobs:
               fi
 
               [ -z "$path" ] || nix-store --realise "$path" 2>/dev/null || true
-              rm -rf ~/.cache/nix/eval-cache-*
+              rm -rf ~/.cache/nix/eval-cache-* ~/.cache/nix/gitv3 ~/.cache/nix/tarball-cache ~/.cache/nix/tarball-cache-v2 ~/.cache/nix/fetcher-cache*.sqlite*
               attempt=$((attempt + 1))
             done
 
@@ -1502,6 +1517,11 @@ jobs:
               [ -n "$path" ] && saw_invalid_path=true
               printf '%s' "$flattened" | grep -Eq 'error:[[:space:]]*.*Failed to convert config\.cachix to JSON' && saw_cachix_signature=true || true
               printf '%s' "$flattened" | grep -Eq 'error:[[:space:]]*.*while evaluating the option.*cachix\.package' && saw_cachix_signature=true || true
+              # Nix can surface fetched-source corruption as missing subpaths under
+              # \u00ABgithub:owner/repo/rev\u00BB/... during arbitrary flake evaluation, not only
+              # while resolving the devenv CLI. Retry after clearing fetch/eval caches:
+              # this indicates an incomplete or stale fetched-source view, not project source.
+              printf '%s' "$flattened" | grep -Eq "error:[[:space:]]*path '\u00AB(github|https?)[:/][^\u00BB]+\u00BB/[^']+' does not exist" && saw_fetch_signature=true || true
               printf '%s' "$flattened" | grep -Eq 'error:[[:space:]]*cannot read file from tarball:[[:space:]]*Truncated tar archive detected while reading data' && saw_fetch_signature=true || true
               rm -f "$log"
 
@@ -1522,7 +1542,7 @@ jobs:
               fi
 
               [ -z "$path" ] || nix-store --realise "$path" 2>/dev/null || true
-              rm -rf ~/.cache/nix/eval-cache-*
+              rm -rf ~/.cache/nix/eval-cache-* ~/.cache/nix/gitv3 ~/.cache/nix/tarball-cache ~/.cache/nix/tarball-cache-v2 ~/.cache/nix/fetcher-cache*.sqlite*
               attempt=$((attempt + 1))
             done
 
@@ -1861,6 +1881,11 @@ jobs:
               [ -n "$path" ] && saw_invalid_path=true
               printf '%s' "$flattened" | grep -Eq 'error:[[:space:]]*.*Failed to convert config\.cachix to JSON' && saw_cachix_signature=true || true
               printf '%s' "$flattened" | grep -Eq 'error:[[:space:]]*.*while evaluating the option.*cachix\.package' && saw_cachix_signature=true || true
+              # Nix can surface fetched-source corruption as missing subpaths under
+              # \u00ABgithub:owner/repo/rev\u00BB/... during arbitrary flake evaluation, not only
+              # while resolving the devenv CLI. Retry after clearing fetch/eval caches:
+              # this indicates an incomplete or stale fetched-source view, not project source.
+              printf '%s' "$flattened" | grep -Eq "error:[[:space:]]*path '\u00AB(github|https?)[:/][^\u00BB]+\u00BB/[^']+' does not exist" && saw_fetch_signature=true || true
               printf '%s' "$flattened" | grep -Eq 'error:[[:space:]]*cannot read file from tarball:[[:space:]]*Truncated tar archive detected while reading data' && saw_fetch_signature=true || true
               rm -f "$log"
 
@@ -1881,7 +1906,7 @@ jobs:
               fi
 
               [ -z "$path" ] || nix-store --realise "$path" 2>/dev/null || true
-              rm -rf ~/.cache/nix/eval-cache-*
+              rm -rf ~/.cache/nix/eval-cache-* ~/.cache/nix/gitv3 ~/.cache/nix/tarball-cache ~/.cache/nix/tarball-cache-v2 ~/.cache/nix/fetcher-cache*.sqlite*
               attempt=$((attempt + 1))
             done
 
@@ -2137,6 +2162,11 @@ jobs:
               [ -n "$path" ] && saw_invalid_path=true
               printf '%s' "$flattened" | grep -Eq 'error:[[:space:]]*.*Failed to convert config\.cachix to JSON' && saw_cachix_signature=true || true
               printf '%s' "$flattened" | grep -Eq 'error:[[:space:]]*.*while evaluating the option.*cachix\.package' && saw_cachix_signature=true || true
+              # Nix can surface fetched-source corruption as missing subpaths under
+              # \u00ABgithub:owner/repo/rev\u00BB/... during arbitrary flake evaluation, not only
+              # while resolving the devenv CLI. Retry after clearing fetch/eval caches:
+              # this indicates an incomplete or stale fetched-source view, not project source.
+              printf '%s' "$flattened" | grep -Eq "error:[[:space:]]*path '\u00AB(github|https?)[:/][^\u00BB]+\u00BB/[^']+' does not exist" && saw_fetch_signature=true || true
               printf '%s' "$flattened" | grep -Eq 'error:[[:space:]]*cannot read file from tarball:[[:space:]]*Truncated tar archive detected while reading data' && saw_fetch_signature=true || true
               rm -f "$log"
 
@@ -2157,7 +2187,7 @@ jobs:
               fi
 
               [ -z "$path" ] || nix-store --realise "$path" 2>/dev/null || true
-              rm -rf ~/.cache/nix/eval-cache-*
+              rm -rf ~/.cache/nix/eval-cache-* ~/.cache/nix/gitv3 ~/.cache/nix/tarball-cache ~/.cache/nix/tarball-cache-v2 ~/.cache/nix/fetcher-cache*.sqlite*
               attempt=$((attempt + 1))
             done
 
@@ -7330,6 +7360,11 @@ jobs:
               [ -n "$path" ] && saw_invalid_path=true
               printf '%s' "$flattened" | grep -Eq 'error:[[:space:]]*.*Failed to convert config\.cachix to JSON' && saw_cachix_signature=true || true
               printf '%s' "$flattened" | grep -Eq 'error:[[:space:]]*.*while evaluating the option.*cachix\.package' && saw_cachix_signature=true || true
+              # Nix can surface fetched-source corruption as missing subpaths under
+              # \u00ABgithub:owner/repo/rev\u00BB/... during arbitrary flake evaluation, not only
+              # while resolving the devenv CLI. Retry after clearing fetch/eval caches:
+              # this indicates an incomplete or stale fetched-source view, not project source.
+              printf '%s' "$flattened" | grep -Eq "error:[[:space:]]*path '\u00AB(github|https?)[:/][^\u00BB]+\u00BB/[^']+' does not exist" && saw_fetch_signature=true || true
               printf '%s' "$flattened" | grep -Eq 'error:[[:space:]]*cannot read file from tarball:[[:space:]]*Truncated tar archive detected while reading data' && saw_fetch_signature=true || true
               rm -f "$log"
 
@@ -7350,7 +7385,7 @@ jobs:
               fi
 
               [ -z "$path" ] || nix-store --realise "$path" 2>/dev/null || true
-              rm -rf ~/.cache/nix/eval-cache-*
+              rm -rf ~/.cache/nix/eval-cache-* ~/.cache/nix/gitv3 ~/.cache/nix/tarball-cache ~/.cache/nix/tarball-cache-v2 ~/.cache/nix/fetcher-cache*.sqlite*
               attempt=$((attempt + 1))
             done
 
@@ -7699,6 +7734,11 @@ jobs:
               [ -n "$path" ] && saw_invalid_path=true
               printf '%s' "$flattened" | grep -Eq 'error:[[:space:]]*.*Failed to convert config\.cachix to JSON' && saw_cachix_signature=true || true
               printf '%s' "$flattened" | grep -Eq 'error:[[:space:]]*.*while evaluating the option.*cachix\.package' && saw_cachix_signature=true || true
+              # Nix can surface fetched-source corruption as missing subpaths under
+              # \u00ABgithub:owner/repo/rev\u00BB/... during arbitrary flake evaluation, not only
+              # while resolving the devenv CLI. Retry after clearing fetch/eval caches:
+              # this indicates an incomplete or stale fetched-source view, not project source.
+              printf '%s' "$flattened" | grep -Eq "error:[[:space:]]*path '\u00AB(github|https?)[:/][^\u00BB]+\u00BB/[^']+' does not exist" && saw_fetch_signature=true || true
               printf '%s' "$flattened" | grep -Eq 'error:[[:space:]]*cannot read file from tarball:[[:space:]]*Truncated tar archive detected while reading data' && saw_fetch_signature=true || true
               rm -f "$log"
 
@@ -7719,7 +7759,7 @@ jobs:
               fi
 
               [ -z "$path" ] || nix-store --realise "$path" 2>/dev/null || true
-              rm -rf ~/.cache/nix/eval-cache-*
+              rm -rf ~/.cache/nix/eval-cache-* ~/.cache/nix/gitv3 ~/.cache/nix/tarball-cache ~/.cache/nix/tarball-cache-v2 ~/.cache/nix/fetcher-cache*.sqlite*
               attempt=$((attempt + 1))
             done
 
@@ -7812,6 +7852,11 @@ jobs:
               [ -n "$path" ] && saw_invalid_path=true
               printf '%s' "$flattened" | grep -Eq 'error:[[:space:]]*.*Failed to convert config\.cachix to JSON' && saw_cachix_signature=true || true
               printf '%s' "$flattened" | grep -Eq 'error:[[:space:]]*.*while evaluating the option.*cachix\.package' && saw_cachix_signature=true || true
+              # Nix can surface fetched-source corruption as missing subpaths under
+              # \u00ABgithub:owner/repo/rev\u00BB/... during arbitrary flake evaluation, not only
+              # while resolving the devenv CLI. Retry after clearing fetch/eval caches:
+              # this indicates an incomplete or stale fetched-source view, not project source.
+              printf '%s' "$flattened" | grep -Eq "error:[[:space:]]*path '\u00AB(github|https?)[:/][^\u00BB]+\u00BB/[^']+' does not exist" && saw_fetch_signature=true || true
               printf '%s' "$flattened" | grep -Eq 'error:[[:space:]]*cannot read file from tarball:[[:space:]]*Truncated tar archive detected while reading data' && saw_fetch_signature=true || true
               rm -f "$log"
 
@@ -7832,7 +7877,7 @@ jobs:
               fi
 
               [ -z "$path" ] || nix-store --realise "$path" 2>/dev/null || true
-              rm -rf ~/.cache/nix/eval-cache-*
+              rm -rf ~/.cache/nix/eval-cache-* ~/.cache/nix/gitv3 ~/.cache/nix/tarball-cache ~/.cache/nix/tarball-cache-v2 ~/.cache/nix/fetcher-cache*.sqlite*
               attempt=$((attempt + 1))
             done
 
diff --git a/genie/ci-scripts/nix-gc-race-retry.sh b/genie/ci-scripts/nix-gc-race-retry.sh
index e7d3d056f..663d9b93a 100644
--- a/genie/ci-scripts/nix-gc-race-retry.sh
+++ b/genie/ci-scripts/nix-gc-race-retry.sh
@@ -74,6 +74,11 @@ run_nix_gc_race_retry() {
     [ -n "$path" ] && saw_invalid_path=true
     printf '%s' "$flattened" | grep -Eq 'error:[[:space:]]*.*Failed to convert config\.cachix to JSON' && saw_cachix_signature=true || true
     printf '%s' "$flattened" | grep -Eq 'error:[[:space:]]*.*while evaluating the option.*cachix\.package' && saw_cachix_signature=true || true
+    # Nix can surface fetched-source corruption as missing subpaths under
+    # «github:owner/repo/rev»/... during arbitrary flake evaluation, not only
+    # while resolving the devenv CLI. Retry after clearing fetch/eval caches:
+    # this indicates an incomplete or stale fetched-source view, not project source.
+    printf '%s' "$flattened" | grep -Eq "error:[[:space:]]*path '«(github|https?)[:/][^»]+»/[^']+' does not exist" && saw_fetch_signature=true || true
     printf '%s' "$flattened" | grep -Eq 'error:[[:space:]]*cannot read file from tarball:[[:space:]]*Truncated tar archive detected while reading data' && saw_fetch_signature=true || true
     rm -f "$log"
 
@@ -94,7 +99,7 @@ run_nix_gc_race_retry() {
     fi
 
     [ -z "$path" ] || nix-store --realise "$path" 2>/dev/null || true
-    rm -rf ~/.cache/nix/eval-cache-*
+    rm -rf ~/.cache/nix/eval-cache-* ~/.cache/nix/gitv3 ~/.cache/nix/tarball-cache ~/.cache/nix/tarball-cache-v2 ~/.cache/nix/fetcher-cache*.sqlite*
     attempt=$((attempt + 1))
   done
 
diff --git a/genie/ci-scripts/nix-gc-race-retry.test.sh b/genie/ci-scripts/nix-gc-race-retry.test.sh
index 300589dc0..1ec5f2820 100644
--- a/genie/ci-scripts/nix-gc-race-retry.test.sh
+++ b/genie/ci-scripts/nix-gc-race-retry.test.sh
@@ -101,7 +101,28 @@ chmod +x "$fetch_fixture"
 CI_PROGRESS_HEARTBEAT_SECONDS=1 NIX_GC_RACE_MAX_RETRIES=2 run_nix_gc_race_retry "fetch-fixture" "$fetch_fixture" >/dev/null
 assert_eq "2" "$(cat "$test_dir/fetch-attempt")" "truncated tarball retry count"
 
-echo "Test 4: does not retry when literal signature strings appear outside Nix error context"
+echo "Test 4: retries missing pretty flake source subpath failures"
+pretty_source_fixture="$test_dir/pretty-source-fixture.sh"
+cat > "$pretty_source_fixture" <<EOF
+#!/usr/bin/env bash
+set -euo pipefail
+attempt_file="$test_dir/pretty-source-attempt"
+attempt=1
+if [ -f "\$attempt_file" ]; then
+  attempt=\$(cat "\$attempt_file")
+fi
+if [ "\$attempt" -eq 1 ]; then
+  echo 2 > "\$attempt_file"
+  echo "error: path '«github:cachix/devenv/ea3d94a»/xtask' does not exist" >&2
+  exit 1
+fi
+echo "pretty source recovered"
+EOF
+chmod +x "$pretty_source_fixture"
+CI_PROGRESS_HEARTBEAT_SECONDS=1 NIX_GC_RACE_MAX_RETRIES=2 run_nix_gc_race_retry "pretty-source-fixture" "$pretty_source_fixture" >/dev/null
+assert_eq "2" "$(cat "$test_dir/pretty-source-attempt")" "pretty flake source retry count"
+
+echo "Test 5: does not retry when literal signature strings appear outside Nix error context"
 false_positive_fixture="$test_dir/false-positive-fixture.sh"
 cat > "$false_positive_fixture" <<'EOF'
 #!/usr/bin/env bash
@@ -117,7 +138,7 @@ exit_code=$?
 set -e
 assert_exit_code 9 "$exit_code" "non-error-context strings do not trigger retries"
 
-echo "Test 5: preserves the original exit code when no retry signature is present"
+echo "Test 6: preserves the original exit code when no retry signature is present"
 non_retry_fixture="$test_dir/non-retry-fixture.sh"
 cat > "$non_retry_fixture" <<'EOF'
 #!/usr/bin/env bash
diff --git a/genie/ci-workflow.ts b/genie/ci-workflow.ts
index d99db8a92..3757bbc2f 100644
--- a/genie/ci-workflow.ts
+++ b/genie/ci-workflow.ts
@@ -88,6 +88,7 @@ export {
   nixExtraConf,
   runDevenvTasksBefore,
   standardCIEnv,
+  withGcRaceRetry,
   workspaceLocalNixCachePath,
   workspaceLocalNixCacheRoot,
   type NixBinaryCache,
diff --git a/genie/ci-workflow/shared.ts b/genie/ci-workflow/shared.ts
index 79a4f7ae0..33f9e2b3d 100644
--- a/genie/ci-workflow/shared.ts
+++ b/genie/ci-workflow/shared.ts
@@ -402,6 +402,11 @@ run_nix_gc_race_retry() {
     [ -n "$path" ] && saw_invalid_path=true
     printf '%s' "$flattened" | grep -Eq 'error:[[:space:]]*.*Failed to convert config\.cachix to JSON' && saw_cachix_signature=true || true
     printf '%s' "$flattened" | grep -Eq 'error:[[:space:]]*.*while evaluating the option.*cachix\.package' && saw_cachix_signature=true || true
+    # Nix can surface fetched-source corruption as missing subpaths under
+    # «github:owner/repo/rev»/... during arbitrary flake evaluation, not only
+    # while resolving the devenv CLI. Retry after clearing fetch/eval caches:
+    # this indicates an incomplete or stale fetched-source view, not project source.
+    printf '%s' "$flattened" | grep -Eq "error:[[:space:]]*path '«(github|https?)[:/][^»]+»/[^']+' does not exist" && saw_fetch_signature=true || true
     printf '%s' "$flattened" | grep -Eq 'error:[[:space:]]*cannot read file from tarball:[[:space:]]*Truncated tar archive detected while reading data' && saw_fetch_signature=true || true
     rm -f "$log"
 
@@ -422,7 +427,7 @@ run_nix_gc_race_retry() {
     fi
 
     [ -z "$path" ] || nix-store --realise "$path" 2>/dev/null || true
-    rm -rf ~/.cache/nix/eval-cache-*
+    rm -rf ~/.cache/nix/eval-cache-* ~/.cache/nix/gitv3 ~/.cache/nix/tarball-cache ~/.cache/nix/tarball-cache-v2 ~/.cache/nix/fetcher-cache*.sqlite*
     attempt=$((attempt + 1))
   done