diff --git a/errors/concurrency-timing/ct-105.yml b/errors/concurrency-timing/ct-105.yml
new file mode 100644
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+++ b/errors/concurrency-timing/ct-105.yml
@@ -0,0 +1,114 @@
+id: ct-105
+title: 'Environment Protection Approval Gate Holds `cancel-in-progress: false` Concurrency Slot — Intermediate Pushes Silently Dropped'
+category: concurrency-timing
+severity: silent-failure
+tags:
+  - concurrency
+  - cancel-in-progress
+  - environment-protection
+  - approval-gate
+  - human-review
+  - starvation
+  - deployment
+  - silent-failure
+patterns:
+  - regex: 'cancel-in-progress:\s*false'
+    flags: 'i'
+  - regex: 'environment:\s*\n\s+name:\s*\w+'
+    flags: 'im'
+  - regex: 'Canceling since a higher priority waiting request'
+    flags: 'i'
+error_messages:
+  - 'Canceling since a higher priority waiting request for'
+  - 'This run was waiting for a concurrent run to finish'
+  - 'Run was cancelled'
+root_cause: |
+  When a deployment workflow uses `concurrency.cancel-in-progress: false` at the
+  workflow or job level AND the workflow targets an environment with manual approval
+  protection rules (required reviewers), the first pending run occupies the single
+  available "pending" slot in the concurrency queue indefinitely while awaiting
+  human review.
+
+  GitHub Actions concurrency with `cancel-in-progress: false` allows exactly one
+  run to be executing and at most one run to be pending — a maximum of two active
+  runs per group. Any third or subsequent run that arrives while the queue is full
+  (one running, one pending-approval) is immediately cancelled with "Canceling since
+  a higher priority waiting request exists."
+
+  Unlike a wait-timer (which resolves automatically after a configured delay),
+  an approval gate can remain unresolved for hours or days. Every push to the
+  protected branch during that approval window is silently discarded. When the
+  approver finally reviews, they approve the OLDEST queued run, not the most
+  recent code — potentially deploying a version that is now out of date.
+fix: |
+  Choose between two strategies depending on whether you want the latest code or
+  ordered deployments:
+
+  **Option A (deploy latest, cancel stale):** Use `cancel-in-progress: true`.
+  Each new push cancels the previously pending approval, so approvers always
+  review the current code. The trade-off is that the approver must re-approve
+  after every new push.
+
+  **Option B (ordered deployments, no drops):** Split the workflow into two
+  separate jobs. Use `cancel-in-progress: true` on a pre-deployment job (lint,
+  test, artifact build) and a separate concurrency group with `cancel-in-progress:
+  false` only on the final deployment job that targets the environment. The test
+  jobs race and only the winner enters the deployment queue.
+
+  **Option C (awareness only):** Keep `cancel-in-progress: false` but add a
+  notification step that alerts on cancellation so the team knows intermediate
+  commits were skipped.
+fix_code:
+  - language: yaml
+    label: 'Option A — cancel-in-progress: true so approvers always see latest code'
+    code: |
+      concurrency:
+        group: deploy-${{ github.ref }}
+        cancel-in-progress: true   # pending approval is cancelled when newer push arrives
+
+      jobs:
+        deploy:
+          environment: production   # has required reviewers
+          runs-on: ubuntu-latest
+          steps:
+            - run: ./deploy.sh
+  - language: yaml
+    label: 'Option B — split jobs: CI races, deployment queues in order'
+    code: |
+      jobs:
+        build:
+          runs-on: ubuntu-latest
+          concurrency:
+            group: build-${{ github.ref }}
+            cancel-in-progress: true   # only the latest build matters
+          steps:
+            - run: ./build.sh
+            - uses: actions/upload-artifact@v4
+              with:
+                name: artifact-${{ github.sha }}
+                path: dist/
+
+        deploy:
+          needs: build
+          runs-on: ubuntu-latest
+          environment: production      # approval gate lives here
+          concurrency:
+            group: deploy-production   # single slot; ordered, no drops
+            cancel-in-progress: false
+          steps:
+            - uses: actions/download-artifact@v4
+              with:
+                name: artifact-${{ github.sha }}
+            - run: ./deploy.sh
+prevention:
+  - 'Never combine `cancel-in-progress: false` with an environment that has human approval rules unless you explicitly want ordered deployment of every commit'
+  - 'Document in the workflow file which combination of concurrency strategy and environment protection is in use and why'
+  - 'Add a Slack/Teams notification on run cancellation so the team knows commits were skipped and can manually trigger a deployment if needed'
+  - 'Consider `cancel-in-progress: true` for non-production environments (staging) where you always want the latest code, and only use `cancel-in-progress: false` for production where you want ordered deploys'
+docs:
+  - url: 'https://docs.github.com/en/actions/writing-workflows/choosing-what-your-workflow-does/using-concurrency'
+    label: 'GitHub Actions — Using concurrency'
+  - url: 'https://docs.github.com/en/actions/managing-workflow-runs-and-deployments/managing-deployments/managing-environments-for-deployment'
+    label: 'GitHub Actions — Managing environments for deployment'
+  - url: 'https://docs.github.com/en/actions/managing-workflow-runs-and-deployments/managing-deployments/reviewing-deployments'
+    label: 'GitHub Actions — Reviewing deployments'
diff --git a/errors/triggers/tr-119.yml b/errors/triggers/tr-119.yml
new file mode 100644
index 0000000..68b8001
--- /dev/null
+++ b/errors/triggers/tr-119.yml
@@ -0,0 +1,106 @@
+id: tr-119
+title: '`repository_dispatch` `client_payload` Property Names Containing Hyphens or Special Characters Are Inaccessible via Expression Syntax'
+category: triggers
+severity: silent-failure
+tags:
+  - repository_dispatch
+  - client_payload
+  - expression
+  - property-access
+  - hyphen
+  - dot-notation
+  - silent-failure
+  - api
+patterns:
+  - regex: 'github\.event\.client_payload\.[a-z0-9_]*-[a-z0-9_]'
+    flags: 'i'
+  - regex: 'client_payload.*[''"][a-z0-9_-]*-[a-z0-9_-]*[''"]'
+    flags: 'i'
+error_messages:
+  - 'Unrecognized named-value'
+  - 'Expected ''}''. Found ''-'''
+  - 'Variable named ''build'' is not defined'
+root_cause: |
+  GitHub Actions expression syntax supports only dot-notation property access
+  (`object.property`) and does not support bracket notation (`object['key']`).
+  When a `repository_dispatch` event is sent with a `client_payload` that contains
+  JSON keys using hyphens, dots, spaces, or other characters that are not valid
+  identifiers, those properties cannot be accessed in a workflow expression.
+
+  For example, dispatching with:
+    client_payload: {"build-type": "release", "target.env": "prod"}
+
+  means that `${{ github.event.client_payload.build-type }}` is a parse error:
+  the `-` is interpreted as a subtraction operator, producing "build" minus "type",
+  and the expression either errors or evaluates to a nonsensical number.
+  `${{ github.event.client_payload.target.env }}` silently evaluates as a nested
+  property access on an undefined sub-object and returns an empty string.
+
+  There is no bracket-notation workaround within a `${{ }}` expression. The
+  `fromJSON()` / `toJSON()` functions do not help because they do not provide
+  bracket-style access within the expression engine.
+
+  The only reliable fix is to restructure `client_payload` to use snake_case or
+  camelCase keys, or to parse the raw payload in a shell step via `jq`.
+fix: |
+  Use only snake_case or camelCase property names in `client_payload` so they
+  are valid identifier tokens accessible via dot notation.
+
+  If you need to parse an existing payload with non-identifier keys, write the
+  payload to a file and parse it with `jq` in a `run:` step — the expression
+  engine is bypassed and all key names work.
+fix_code:
+  - language: yaml
+    label: 'Use snake_case keys in client_payload (API caller side)'
+    code: |
+      # When triggering via GitHub REST API, use snake_case keys:
+      # POST /repos/{owner}/{repo}/dispatches
+      # {
+      #   "event_type": "deploy",
+      #   "client_payload": {
+      #     "build_type": "release",        <-- was: "build-type"
+      #     "target_env": "production"      <-- was: "target.env"
+      #   }
+      # }
+
+      # Workflow can now access these safely:
+      jobs:
+        deploy:
+          runs-on: ubuntu-latest
+          steps:
+            - name: Read dispatch inputs
+              run: |
+                echo "Build type: ${{ github.event.client_payload.build_type }}"
+                echo "Target env: ${{ github.event.client_payload.target_env }}"
+  - language: yaml
+    label: 'Parse non-identifier keys with jq in a run step'
+    code: |
+      jobs:
+        deploy:
+          runs-on: ubuntu-latest
+          steps:
+            - name: Parse client_payload with jq
+              id: payload
+              run: |
+                # Write payload to file to use jq (bypasses expression engine)
+                echo '${{ toJSON(github.event.client_payload) }}' > payload.json
+                BUILD_TYPE=$(jq -r '.["build-type"]' payload.json)
+                TARGET_ENV=$(jq -r '.["target.env"]' payload.json)
+                echo "build_type=$BUILD_TYPE" >> $GITHUB_OUTPUT
+                echo "target_env=$TARGET_ENV" >> $GITHUB_OUTPUT
+
+            - name: Use parsed values
+              run: |
+                echo "Building ${{ steps.payload.outputs.build_type }} for ${{ steps.payload.outputs.target_env }}"
+prevention:
+  - 'Always use snake_case or camelCase for all `client_payload` keys in `repository_dispatch` calls — never use hyphens, dots, spaces, or other non-identifier characters'
+  - 'Document your `client_payload` schema in the workflow file using a comment so callers know which key format is expected'
+  - 'Add input validation in the workflow to fail-fast if expected payload keys resolve to empty strings'
+  - 'Use `actionlint` with `--format` checking — it will flag expression syntax errors caused by hyphenated property access'
+docs:
+  - url: 'https://docs.github.com/en/rest/repos/repos#create-a-repository-dispatch-event'
+    label: 'GitHub REST API — Create a repository dispatch event'
+  - url: 'https://docs.github.com/en/actions/writing-workflows/choosing-what-your-workflow-does/evaluate-expressions-in-workflows-and-actions'
+    label: 'GitHub Actions — Evaluate expressions in workflows and actions'
+  - url: 'https://docs.github.com/en/actions/writing-workflows/workflow-syntax-for-github-actions#filter-pattern-cheat-sheet'
+    label: 'GitHub Actions — Workflow syntax: on.repository_dispatch'
diff --git a/errors/yaml-syntax/ys-121.yml b/errors/yaml-syntax/ys-121.yml
new file mode 100644
index 0000000..aadc1d0
--- /dev/null
+++ b/errors/yaml-syntax/ys-121.yml
@@ -0,0 +1,107 @@
+id: ys-121
+title: '`uses:` Field Does Not Evaluate `${{ }}` Expressions — Dynamic Action or Reusable Workflow Versions Are Not Possible'
+category: yaml-syntax
+severity: error
+tags:
+  - uses
+  - expressions
+  - dynamic-version
+  - action-version
+  - reusable-workflow
+  - vars-context
+  - limitation
+  - parse-error
+patterns:
+  - regex: 'uses:\s+[a-zA-Z0-9_./-]+@\$\{\{'
+    flags: 'i'
+  - regex: 'uses:\s+\$\{\{.*\}\}'
+    flags: 'i'
+  - regex: 'uses:\s+[a-zA-Z0-9_./-]*\$\{\{'
+    flags: 'i'
+error_messages:
+  - 'The uses clause must not contain a string template'
+  - 'Expected format''{owner}/{repo}@{ref}'''
+  - 'Unrecognized named-value'
+  - 'Invalid format for ''uses'''
+root_cause: |
+  The `uses:` field in both step definitions (`jobs.<id>.steps[*].uses`) and
+  reusable workflow job calls (`jobs.<id>.uses`) is evaluated at workflow
+  **parse time**, before the expression engine runs. GitHub Actions does not
+  substitute `${{ }}` expressions in `uses:` values — the literal string
+  (including the dollar-brace syntax) is passed to the action/workflow resolver,
+  which fails to find a valid reference.
+
+  This is a deliberate security constraint: allowing expressions in `uses:` would
+  enable repository variables, secrets, or environment-dependent values to redirect
+  execution to an attacker-controlled action or workflow version, creating a
+  supply-chain attack vector. The parser enforces this by rejecting any `uses:`
+  value containing `${{`.
+
+  Common patterns that fail:
+    uses: actions/checkout@${{ vars.CHECKOUT_VERSION }}
+    uses: ${{ vars.MY_ORG }}/custom-action@v2
+    uses: ./.github/actions/${{ matrix.action_name }}
+
+  All of these produce a parse error or a resolution failure before the workflow run starts.
+fix: |
+  Pin `uses:` values to literal strings. Manage version consistency using tooling
+  rather than runtime expressions:
+
+  - Use **Dependabot** (`dependabot.yml`) to automatically create PRs that bump
+    action versions across all workflow files when a new release is published.
+  - Use **Renovate Bot** for finer-grained version control policies.
+  - For local composite actions, reference them with a literal relative path:
+    `uses: ./.github/actions/my-action`
+  - For SHA pinning (strongest supply-chain guarantee), pin to the full commit SHA:
+    `uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683`
+
+  If you need to conditionally run different actions, use an `if:` condition on
+  separate steps rather than a dynamic `uses:` reference.
+fix_code:
+  - language: yaml
+    label: 'Use literal action version strings — no expressions in uses:'
+    code: |
+      steps:
+        # BAD: expressions are not evaluated in uses: — parse error
+        # - uses: actions/checkout@${{ vars.CHECKOUT_VERSION }}
+        # - uses: ${{ vars.CUSTOM_ORG }}/deploy-action@v3
+        # - uses: ./.github/actions/${{ matrix.action }}
+
+        # GOOD: literal version pins
+        - uses: actions/checkout@v4.2.2
+        - uses: actions/setup-node@v4.1.0
+
+        # GOOD: conditional execution via if: instead of dynamic uses:
+        - uses: my-org/deploy-staging@v2
+          if: ${{ vars.ENVIRONMENT == 'staging' }}
+        - uses: my-org/deploy-production@v2
+          if: ${{ vars.ENVIRONMENT == 'production' }}
+  - language: yaml
+    label: 'Dependabot config to auto-update action versions'
+    code: |
+      # .github/dependabot.yml
+      version: 2
+      updates:
+        - package-ecosystem: "github-actions"
+          directory: "/"
+          schedule:
+            interval: "weekly"
+          groups:
+            github-actions:
+              patterns:
+                - "actions/*"
+                - "github/*"
+prevention:
+  - 'Run `actionlint` in CI — it detects `${{ }}` expressions in `uses:` fields and fails the pipeline before the workflow reaches production'
+  - 'Configure Dependabot or Renovate to automate action version bumps so you never need to parameterize versions at runtime'
+  - 'Use SHA-pinning for critical workflows to freeze the exact action version regardless of tag mutations'
+  - 'For local reusable actions, use relative paths (`uses: ./.github/actions/name`) which are always resolved from the repository root without expressions'
+docs:
+  - url: 'https://docs.github.com/en/actions/writing-workflows/workflow-syntax-for-github-actions#jobsjob_idstepsuses'
+    label: 'GitHub Actions — jobs.<job_id>.steps[*].uses syntax'
+  - url: 'https://docs.github.com/en/actions/writing-workflows/workflow-syntax-for-github-actions#jobsjob_iduses'
+    label: 'GitHub Actions — jobs.<job_id>.uses (reusable workflow)'
+  - url: 'https://docs.github.com/en/code-security/dependabot/working-with-dependabot/keeping-your-actions-up-to-date-with-dependabot'
+    label: 'Keeping your actions up to date with Dependabot'
+  - url: 'https://docs.github.com/en/actions/security-for-github-actions/security-guides/security-hardening-for-github-actions#using-third-party-actions'
+    label: 'Security hardening for GitHub Actions — using third-party actions'