diff --git a/.github/workflows/shell-tests.yml b/.github/workflows/shell-tests.yml
index 9a7b8dd1..b70eb98e 100644
--- a/.github/workflows/shell-tests.yml
+++ b/.github/workflows/shell-tests.yml
@@ -60,9 +60,12 @@ jobs:
       # ptrace. Without these the trace file is never produced.
       options: --cap-add=SYS_PTRACE --security-opt seccomp=unconfined
     steps:
-      # base-devel ships neither git (actions/checkout needs it) nor strace.
+      # base-devel ships none of these: git (actions/checkout needs it), strace
+      # (execve counting), or jq (the claude_usage block parses its cache with
+      # it, and without jq that block degrades to "no data" and its assertions
+      # fail).
       - name: Install dependencies
-        run: pacman -Sy --noconfirm --needed git strace
+        run: pacman -Sy --noconfirm --needed git strace jq
 
       - uses: actions/checkout@v4
 
diff --git a/docs/superpowers/evidence/i3blocks-claude-usage-ci-jq-2026-08-10.json b/docs/superpowers/evidence/i3blocks-claude-usage-ci-jq-2026-08-10.json
new file mode 100644
index 00000000..d260b002
--- /dev/null
+++ b/docs/superpowers/evidence/i3blocks-claude-usage-ci-jq-2026-08-10.json
@@ -0,0 +1,37 @@
+{
+  "intent": "Make the claude_usage i3blocks tests pass on CI, where they failed because the Arch container had no jq.",
+  "scope": [
+    ".github/workflows/shell-tests.yml (arch-tests container dependencies)",
+    "linux_configuration/tests/test_i3blocks_efficiency.sh (dependency probe)",
+    "Non-goal: changing claude_usage.sh runtime behaviour — degrading to 'no data' without jq is correct"
+  ],
+  "changes": [
+    "Install jq in the arch-tests container. archlinux:base-devel ships neither git, strace nor jq; the first two were already installed, and claude_usage.sh parses its cache with jq.",
+    "Guard the claude_usage test section on a working jq. The probe runs `printf '{}' | jq -e .` rather than `command -v jq`, because a jq that exists but cannot execute produces exactly the same 'no data' output as an absent one, and `command -v` would pass in that case."
+  ],
+  "verification": [
+    {
+      "command": "bash linux_configuration/tests/test_i3blocks_efficiency.sh",
+      "result": "pass",
+      "evidence": "EXIT=0 with jq present."
+    },
+    {
+      "command": "PATH=<stub-with-failing-jq> bash linux_configuration/tests/test_i3blocks_efficiency.sh",
+      "result": "pass",
+      "evidence": "Reports 'FAIL: a working jq is required for the claude_usage tests (pacman -S jq)' instead of the previous misleading \"expected '🤖 5h 34% · 7d 55%', actual: '🤖 no data'\" — the failure now names its real cause. Confirmed the earlier `command -v jq` form did NOT catch this case."
+    },
+    {
+      "command": "reproduce CI failure locally",
+      "result": "pass",
+      "evidence": "Running claude_usage.sh with a failing jq on PATH reproduced the exact CI output '🤖 no data', confirming the missing dependency rather than a logic defect."
+    }
+  ],
+  "risks": [
+    "Adds one package to the CI container install step, marginally increasing job setup time.",
+    "The guard makes a missing dependency a hard failure rather than a skip; that is intended, since silently skipping would hide the block's assertions entirely."
+  ],
+  "rollback": [
+    "git revert the commit; CI returns to failing on the claude_usage assertions until jq is installed another way.",
+    "Validate with: gh run list --limit 3 after the next push."
+  ]
+}
diff --git a/linux_configuration/tests/test_i3blocks_efficiency.sh b/linux_configuration/tests/test_i3blocks_efficiency.sh
index 760be74b..5303d24d 100755
--- a/linux_configuration/tests/test_i3blocks_efficiency.sh
+++ b/linux_configuration/tests/test_i3blocks_efficiency.sh
@@ -192,6 +192,14 @@ grep -Fq 'iface_path}/device' "$I3BLOCKS_DIR/ethernet.sh" \
   || fail 'ethernet script should require a real device to skip virtual interfaces'
 
 printf 'Checking Claude usage block behavior and fork count...\n'
+# claude_usage.sh parses its cache with jq and degrades to "no data" when jq is
+# missing. That is the right runtime behaviour, but it would make every
+# assertion below fail with a misleading message about percentages, so name the
+# real cause instead of letting a missing tool look like a logic bug.
+# Probe by running jq, not with `command -v`: a jq that exists but cannot
+# execute produces exactly the same "no data" output as one that is absent.
+printf '{}' | jq -e . >/dev/null 2>&1 \
+  || fail 'a working jq is required for the claude_usage tests (pacman -S jq)'
 CLAUDE_STATE_DIR="$TMP_DIR/limit-state"
 mkdir -p "$CLAUDE_STATE_DIR"
 claude_now=1786366861