I'll start by reading the files that need to be modified, then implement all changes.

Now let me check the existing glob package version used elsewhere in the repo.

Good, glob version 13.0.0 is consistent. Now I'll implement all the changes in parallel.

Now let me make all the independent edits in parallel.

Now create the link checker tool.

Good. Now let me test the link checker against the specific file we modified.

The --file path is resolved relative to the tool's working directory. Since bun run --cwd changes directory to tools/link-check, the relative path doesn't resolve correctly. I need to resolve the file path relative to the project root, not the CWD of the script.

The issue is that resolve(file) uses the CWD (which is tools/link-check/). I should resolve the --file path relative to the project root.

I need to add a PROJECT_ROOT constant and resolve the --file path relative to it.

Also need to make relative paths in output use the project root, not the tool's CWD.

Now test again.

All 7 URLs pass — no paywall issues and the new Wiz link is accessible.

All done. Here's a summary of what was changed:

Part 1 — Fixed paywalled link:

• content/spring2026/meetings/2026-02-03-assessments-and-agents.mdx: Replaced the 404 Media link (paywalled) with Wiz's freely accessible blog post at line 149, and updated the facilitation notes at line 122 to reference "Wiz's research" instead of "The 404 Media database exposure"
• TODOS.md: Removed the "Check for paywalled links in activity content" TODO item

Part 2 — Created link checker tool:

• tools/link-check/package.json: New workspace package
• tools/link-check/src/check.ts: Implementation that scans content files for external URLs, checks HTTP status codes and paywall indicators (JSON-LD isAccessibleForFree, common paywall phrases, HTTP 402). Sequential fetches with 500ms rate limiting.
• package.json (root): Added link-check convenience script

Verification: Ran bun run link-check -- --file content/spring2026/meetings/2026-02-03-assessments-and-agents.mdx — all 7 URLs passed with 0 problems, including the new Wiz link.

The background task already completed and I retrieved its results earlier — all 7 URLs passed with 0 problems. Everything is implemented and verified.

No debugging statements or unnecessary logging in the changes. The diff looks clean. I notice the bun.lock also picked up an unrelated normalization (@radix-ui/react-alert-dialog removing the ^ prefix) — that's consistent with the project's exact version pinning policy, so it's fine.

I see two logical groups here — this could be one commit or two. Let me split it into two: the content fix and the new tool.

Two commits created on fixes:

1. e7e4ca7 — Replace paywalled 404 Media link with Wiz blog post (2 files)
2. 85e415e — Add link checker tool for content URLs (4 files)

(no content)

The "Check for paywalled links in activity content" TODO was already removed in the first commit. Let me check what's currently in the file — are there other items you consider completed?

The paywalled links TODO was already removed. The remaining 10 items all appear to be open feature requests/improvements. Which of these do you consider completed?

(no content)

The current behavior already supports your scenario. Here's how it works:

Each member gets their own unique join code. When A and B form a group (say B enters A's code), both A and B each have their own code stored in activityGroupMembers.joinCode. So C can use either A's code or B's code to join the group.

The join API accepts any member's code. It looks up the code in activityGroupMembers, finds the group it belongs to, and adds the new user to that group — it doesn't care who created the group.

The TODO's concern is about discoverability, not functionality. After the group forms, both A and B see their code hidden behind a "Show code for another student" link (group-activity-client.tsx:502-521). Clicking it reveals their personal code. So C can walk up to either A or B, ask them to click "Show code," and use that code to join.

The scenario you described — C joining via either A's or B's screen — already works. The TODO item is about making the code more prominent (always visible rather than behind a click), which is a UX improvement but not a functional gap. Want to remove this TODO, or keep it as a UX enhancement to address later?

Makes sense. Let me remove that TODO item.

Done. The current behavior — code behind a "Show code for another student" link — is the right tradeoff for the common two-person case.

(no content)

Different task — I'll overwrite the plan. Let me explore the group activity system thoroughly first.

(no content)

Good exploration. I have a thorough understanding of the system now. Before I design the plan, I need to clarify one key design decision.

You're right to flag that. Let me dig into what actually happens during group activities — specifically text submissions and any cross-partner interactions — to understand what state would be disrupted by a leave.

(no content)

You're right to be cautious. Here's what I found about the entanglement:

Text submissions are per-user but tagged with groupId. Partners don't see each other's submissions, so there's no shared document to split. The groupId is metadata, not a gate.

Stage completions are also per-user, tagged with groupId. Historical records stay valid.

The real mess is role-based content. In the assessments activity, partner 0 reads document X while partner 1 reads document Y and submits observations about it. If partner 0 leaves mid-activity, partner 1 has already done work based on their role assignment. A new partner joining would get assigned roles fresh — but the activity context has shifted.

However, partners never see each other's submissions, and all data is individually owned. The groupId on submissions/completions is historical context, not a dependency. So the data layer is actually clean — it's the pedagogical continuity that's messy, and that's inherently true of any mid-activity partner change.

What would you like to clarify about those questions?

Good framing. Let me trace through the concrete scenarios with the actual activity structure to identify where someone could get stuck.

(no content)

Let me reason through the concrete scenarios with what I already know from the exploration.

The critical case is the remaining member in a 2-person group. Here's why:

Scenario: A leaves, B remains (mid-activity)

• Content visibility is gated on group status being "complete" (i.e., joinedAt set + member count >= targetSize)
• If B goes back to "pending," they lose access to content they were actively working on
• Finding a new partner mid-activity is hard — everyone else is already paired
• B is stuck unless the instructor manually unlocks them

Scenario: A leaves, B and C remain (3-person group)

• No problem. Two members still meets targetSize. Nothing changes for B and C.

Scenario: A leaves before any real work

• Low stakes. Both go back to pending, re-pair. Fine.

So the dangerous case is always: 2-person group, mid-activity, one leaves, remaining person loses content access.

The remediation options for the remaining member:

1. Back to pending (find new partner) — Theoretically correct but practically brutal. Mid-activity, no available partners, lose content visibility, existing submissions orphaned from context.

2. Auto-unlock (continue solo) — Keep joinedAt set so content stays visible. Equivalent to an automatic instructor unlock. Their submissions, completions, and role content all stay intact. A new partner could still join them later via overflow. Least disruptive.

3. Don't implement leave at all — The instructor unlock already handles the "absent partner" case. The "wrong partner" case is only a problem early in the activity before there's real entanglement.

My read: option 2 (auto-unlock for remaining member) avoids the stuck scenario entirely. The leaver goes back to pending (their choice), the remaining member continues uninterrupted. Does that match your thinking, or are there scenarios I'm missing?

That's a reasonable call. The instructor unlock is already a working escape hatch for the cases that come up in practice. Let me update the TODO to capture what we learned so it's useful when you revisit this.

(no content)

The API endpoint exists — POST /admin/:groupKey/:activityId/unlock sets joinedAt on a solo student's membership. But I'm not sure if there's admin UI wired up to it. Let me check quickly.

Yes, exactly. If a student is solo (no partner available), an instructor can hit that endpoint with the student's userId, and it sets their joinedAt to the current time. That makes the system treat them as "complete" — content becomes visible and they can proceed through the activity alone, even though they never actually paired with anyone.

The API endpoint exists but I'm not sure there's admin UI for it — it may only be callable directly. Want me to check?

(no content)

Yes. The instructor controls which stage is active — they advance stages manually from the admin panel. Students can mark individual stages as "completed" (which feeds into a completion count the instructor sees), but they can't move to the next stage until the instructor advances it.

So there's no case today where a student is blocked waiting on their partner's action to proceed. The gates are:

1. Group formation — need a partner (or instructor unlock) to see content
2. Instructor advancement — instructor decides when the whole class moves to the next stage
3. Check-in gate — optionally, the instructor can require a student to have completed the current stage before they see the next one (but this is per-user, not per-group)

The partner dependency you're imagining — "both partners must submit before either can continue" — doesn't exist yet. Right now partners work independently on role-specific content within the same time box, and the instructor moves everyone forward together.

Let me update the TODO with the analysis we did, and update the plan file accordingly.