diff --git a/.github/workflows/benchmark.yml b/.github/workflows/benchmark.yml
index 3eb7a29..e44902e 100644
--- a/.github/workflows/benchmark.yml
+++ b/.github/workflows/benchmark.yml
@@ -23,6 +23,11 @@ permissions:
   contents: write
   pull-requests: write
 
+# Cancel previous runs on the same ref (force-push during PR iteration).
+concurrency:
+  group: benchmark-${{ github.ref }}
+  cancel-in-progress: true
+
 jobs:
   benchmark:
     name: Run Benchmarks
diff --git a/.github/workflows/clippy.yml b/.github/workflows/clippy.yml
index 76b7703..3d4cb8f 100644
--- a/.github/workflows/clippy.yml
+++ b/.github/workflows/clippy.yml
@@ -7,6 +7,18 @@ on:
   # lints introduced by Rust toolchain updates.
   pull_request:
     branches: [ "main" ]
+    # Positive filter: clippy only matters when Rust source or build
+    # configuration changes. The .yml itself is included so workflow
+    # tweaks still validate. test.yml's lint job also runs clippy as
+    # part of the broader PR gate; this workflow's SARIF upload is the
+    # value-add over that — keep it firing whenever .rs / Cargo.toml /
+    # build.rs / rust-toolchain changes.
+    paths:
+      - '**/*.rs'
+      - '**/Cargo.toml'
+      - 'build.rs'
+      - 'rust-toolchain.toml'
+      - '.github/workflows/clippy.yml'
   push:
     tags:
       - 'v[0-9]+.[0-9]+.[0-9]+'
@@ -15,6 +27,11 @@ on:
     - cron: '17 20 * * 0'
   workflow_dispatch:
 
+# Cancel previous runs on the same ref (force-push during PR iteration).
+concurrency:
+  group: clippy-${{ github.ref }}
+  cancel-in-progress: true
+
 jobs:
   rust-clippy-analyze:
     name: Run rust-clippy analyzing
diff --git a/.github/workflows/coverage.yml b/.github/workflows/coverage.yml
index 6f8553d..2de1f96 100644
--- a/.github/workflows/coverage.yml
+++ b/.github/workflows/coverage.yml
@@ -7,6 +7,19 @@ on:
   # not running it on every merge saves significant runner time.
   pull_request:
     branches: [ "main" ]
+    # Positive filter: coverage signal only matters when source / tests /
+    # dep manifests change. Doc-only / config-only / examples-only PRs
+    # don't shift the coverage number, and the workflow takes ~10 min
+    # of Linux quota per run. Keeps the PR-time coverage gate but skips
+    # the runs that would have produced an identical number.
+    paths:
+      - 'src/**'
+      - 'crates/**'
+      - 'tests/**'
+      - 'benches/**'
+      - 'build.rs'
+      - 'Cargo.toml'
+      - '.github/workflows/coverage.yml'
   push:
     tags:
       - 'v[0-9]+.[0-9]+.[0-9]+'
@@ -16,6 +29,11 @@ on:
 permissions:
   contents: read
 
+# Cancel previous runs on the same ref (force-push during PR iteration).
+concurrency:
+  group: coverage-${{ github.ref }}
+  cancel-in-progress: true
+
 env:
   CARGO_TERM_COLOR: always
   RUST_BACKTRACE: 1
diff --git a/.github/workflows/e2e-cross-platform.yml b/.github/workflows/e2e-cross-platform.yml
index a2aa24a..732ddfc 100644
--- a/.github/workflows/e2e-cross-platform.yml
+++ b/.github/workflows/e2e-cross-platform.yml
@@ -1,24 +1,29 @@
 # PRD-038: Hybrid Cross-Platform E2E Testing Harness
 #
 # This workflow tests Jarvy tool installations across multiple platforms:
-# - GitHub-hosted runners (FREE): macOS, Ubuntu, Windows
+# - GitHub-hosted runners: Ubuntu (free) + macOS / Windows (paid)
 # - AWS EC2 Spot (future): Fedora, Arch, Alpine, FreeBSD
 #
-# Cost: ~$0/month (GitHub-hosted runners are free for public repos)
+# Correction to a prior comment claim: macOS and Windows runners are NOT
+# free for public repos — only ubuntu-* is. macOS is the priciest at
+# $0.062/min (10x Linux). Nightly cadence × 3 OSes × ~10min/run was
+# burning ~$15-20/month from this workflow alone.
 
 name: E2E Cross-Platform Tests
 
 on:
-  # E2E cross-platform runs are heavy (multi-OS install matrix). The
-  # nightly cron below produces the canonical signal that main is
-  # green; per-push and per-PR runs were redundant and routinely added
-  # ~30 min of runner time without finding bugs the nightly missed.
+  # E2E cross-platform runs are heavy (multi-OS install matrix). Weekly
+  # cadence is sufficient — the registered tools surface changes on the
+  # order of days/weeks, not hours, and the nightly cadence rarely caught
+  # a regression the next weekly run wouldn't have. Tag pushes still get
+  # the full matrix via release.yml + tool-e2e.yml so cuts are validated
+  # at release time regardless of the weekly cron schedule.
   # workflow_dispatch covers ad-hoc validation when a PR touches the
   # tools registry or install scripts and the author wants pre-merge
   # confirmation.
   schedule:
-    # Nightly at 2 AM UTC
-    - cron: '0 2 * * *'
+    # Weekly on Sunday at 2 AM UTC
+    - cron: '0 2 * * 0'
   workflow_dispatch:
     inputs:
       tier:
diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 075d71d..ea76c88 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -1,14 +1,31 @@
 name: Test
 
 on:
-  # Validation runs on PRs (pre-merge gate) and on release tags
-  # (post-merge integration check). The push-to-main trigger was
-  # removed because every PR is already validated and the merge
-  # commit is identical to the validated PR head — re-running the
-  # same suite on the merge duplicates effort. Tag push covers the
-  # integrated state when a release is cut.
+  # PR gate: Linux only. Public-repo Linux minutes are free; macOS + Windows
+  # are not (macOS is 10x Linux per-minute). Cross-OS validation lives on
+  # the release-tag matrix below + the nightly e2e-cross-platform run.
+  # Doc-only / CI-only / examples-only PRs skipped via paths-ignore so a
+  # README tweak doesn't fire the test suite.
+  #
+  # Tag push: full matrix (Linux + macOS + Windows). Release-cut is the
+  # canonical integration check — full cross-OS validation here catches
+  # regressions before the artifact build runs in release.yml.
   pull_request:
     branches: [ "main" ]
+    # Positive filter: PR test runs only fire when source / tests / dep
+    # manifests / build config change. Excludes doc-only, CI-only,
+    # example-only, lint-config PRs that can't shift the test outcome.
+    # Inverted from paths-ignore for predictability — easier to reason
+    # about "what triggers a run" than "what does NOT trigger".
+    paths:
+      - 'src/**'
+      - 'crates/**'
+      - 'tests/**'
+      - 'benches/**'
+      - 'build.rs'
+      - 'Cargo.toml'
+      - 'rust-toolchain.toml'
+      - '.github/workflows/test.yml'
   push:
     tags:
       - 'v[0-9]+.[0-9]+.[0-9]+'
@@ -18,6 +35,14 @@ on:
 permissions:
   contents: read
 
+# Cancel previous runs on the same ref. Force-pushes during PR iteration
+# previously stacked 2-3 in-flight matrix runs per branch — each one
+# burned its macOS + Windows slot before being cancelled by branch
+# protection.
+concurrency:
+  group: test-${{ github.ref }}
+  cancel-in-progress: true
+
 env:
   CARGO_TERM_COLOR: always
   RUST_BACKTRACE: 1
@@ -49,7 +74,11 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        os: [macos-latest, ubuntu-latest, windows-latest]
+        # PR runs (free Linux minutes) get ubuntu-latest only.
+        # Tag pushes add macos-latest + windows-latest for the
+        # integration check. github.event_name is evaluated at
+        # matrix-expansion time so this composes cleanly.
+        os: ${{ github.event_name == 'pull_request' && fromJSON('["ubuntu-latest"]') || fromJSON('["macos-latest", "ubuntu-latest", "windows-latest"]') }}
     steps:
       - uses: actions/checkout@v4
 
diff --git a/.github/workflows/tool-e2e.yml b/.github/workflows/tool-e2e.yml
index ca47772..068b4b5 100644
--- a/.github/workflows/tool-e2e.yml
+++ b/.github/workflows/tool-e2e.yml
@@ -1,13 +1,23 @@
 name: Tools E2E
 
 on:
-  # Tools E2E exercises the full multi-OS install matrix; running on
-  # every push to every branch was burning ~13 min × N pushes/day.
-  # Restrict to PR validation (pre-merge gate) and release tags
-  # (post-merge integration check). workflow_dispatch covers ad-hoc
-  # validation when working on the tools registry.
+  # Tools E2E exercises the full multi-OS install matrix and was
+  # burning ~13 min × N pushes/day across mac+win+6-distro-linux.
+  # Restrict to PRs that actually touch the tools registry / install
+  # scripts / tools-related tests (everything else can't regress this
+  # surface). Release tags still run the full matrix as the canonical
+  # post-merge integration check. workflow_dispatch covers ad-hoc runs.
   pull_request:
     branches: [main]
+    paths:
+      - 'src/tools/**'
+      - 'crates/jarvy-templates/**'
+      - 'tests/cli_*.rs'
+      - 'tests/e2e_*.rs'
+      - 'tests/tools_*.rs'
+      - 'dist/scripts/install.*'
+      - 'Cargo.toml'
+      - '.github/workflows/tool-e2e.yml'
   push:
     tags:
       - 'v[0-9]+.[0-9]+.[0-9]+'
@@ -54,6 +64,12 @@ jobs:
 
   native-host:
     name: Native host (brew on macOS, winget on Windows)
+    # macOS minutes are $0.062/min (10x Linux) and Windows is $0.01/min.
+    # PR-time native-host runs were the second-largest macOS consumer
+    # behind release.yml. PRs get Linux-only (linux-testcontainers above);
+    # native-host fires on release tags + workflow_dispatch so cross-OS
+    # install verification still gates the canonical artifact builds.
+    if: github.event_name != 'pull_request'
     strategy:
       fail-fast: false
       matrix: