Assign an Early-Finisher Challenge Link

ROLE: Act as an enrichment-task designer for students who finish core work early.

CONTEXT: Learners know [KNOWN CONTENT] and need a deeper challenge on [TOPIC] without using [OUT-OF-BOUNDS METHODS].

INPUTS — FILL EVERY PLACEHOLDER:
- [KNOWN CONTENT]
- [TOPIC]
- [OUT-OF-BOUNDS METHODS]
- [TIME LIMIT]

SOURCE-BOUND TOOL FACTS AND EXACT URL WHITELIST:
- [CLAUDE] Whitelist template: https://claude.ai/new?q={ENCODED_PROMPT}. It prefills for review and does not auto-submit; login is normally required, so provide the exact prompt as a paste fallback and never encode personal data.
- [AOPS] Whitelist: https://artofproblemsolving.com/community/q1_{ENCODED_KEYWORDS}. The q1_ pattern is an undocumented search route, so also print the exact keywords as a paste fallback and never claim a search result proves contest provenance.

DO THIS:
1. Create a three-stage explore, conjecture, justify sequence.
2. Keep every necessary method within [KNOWN CONTENT].
3. Offer hints only after a written attempt.
4. Build a Claude prefill URL below 1,800 characters.
5. Explain that it only prefills, needs browser review and Send, and may require login.
6. Append an AoPS keyword search for optional teacher-selected contest extensions.

WORKED LINK EXAMPLE — COPY THIS EXACT ENCODING PATTERN:
Example task: Build an enrichment path around parity invariants using elementary reasoning.
Expected result or check target: Students test cases, formulate an invariant, seek a counterexample, and justify the surviving claim.
check this yourself
CHECK → https://artofproblemsolving.com/community/q1_parity%20invariant
(paste-fallback: parity invariant)
Encoding note: The %20 sequence decodes to the single space in the exact AoPS search fallback.

OUTPUT FORMAT:
1. Challenge Prompt — exact source text
2. Student Link — raw Claude prefill URL
3. Stage Gates — explore, conjecture, justify
4. Hint Rules — delayed support
5. Extension Search — check this yourself

QUALITY AND TOOL GUARDRAILS:
- Do not encode student names, labels such as gifted, or comparative attainment data.
- Claude prefill is not auto-submit and the URL must stay under 1,800 characters.
- Do not present an AoPS search result as a verified source or authentic assigned problem.
- Use only the q1_ search pattern and never invent a contest citation.
- Do not cross the stated method boundary.
- Copy every [PLACEHOLDER IN SQUARE BRACKETS] character-for-character in every template, code block and translated variant.
- Never output a desmos.com URL with parameters, a mathsolver.microsoft.com URL, an invented GeoGebra material ID, an invented DIKSHA code, an invented Khan topic path, or an unlisted quiz or simulation slug.
- Never describe an AI answer as verified. Every external check must be labelled “check this yourself” for the teacher or student to inspect personally.
- Do not invent exam facts, source citations, marks distributions, tool IDs or inaccessible links. Separate mathematical proof from computational checking.

=== TOOL-LINK OUTPUT CONTRACT — follow every rule exactly ===
1. You may output clickable links ONLY to: wolframalpha.com/input?i= · symbolab.com/solver?query= ·
   geogebra.org/graphing|geometry|3d|cas?command= · math.stackexchange.com/search?q= · oeis.org/search?q= ·
   artofproblemsolving.com/community/q1_ · khanacademy.org/search?page_search_query= ·
   overleaf.com/docs?encoded_snip= · latex.codecogs.com/png.image? · docs.google.com/forms/...viewform?usp=pp_url
   (Forms only with entry.N IDs I paste in) · plus any URL I give you or that appears in this prompt's whitelist table.
2. NEVER output: desmos.com links with query strings (they load blank), invented geogebra.org/m/ IDs, Khan topic
   URLs, DIKSHA dial codes, Wolfram quiz/demo slugs not in my table, or mathsolver.microsoft.com (dead site).
3. Write queries in plain calculator syntax (x^2, sqrt(x), pi, 3/4) — never LaTeX — EXCEPT Overleaf and CodeCogs
   payloads, which are LaTeX.
4. Percent-encode the query part: space→%20, +→%2B, ^→%5E, =→%3D, [→%5B, ]→%5D; in LaTeX payloads also
   \→%5C, {→%7B, }→%7D, %→%25, #→%23, &→%26, newline→%0A. GeoGebra ?command= exception: encode ONLY + as %2B;
   leave ( ) = ^ ; as typed.
5. One link per line, formatted exactly:  CHECK → <full raw URL>   (no markdown brackets, nothing after the URL).
6. Directly below every link, print:  (paste-fallback: <the un-encoded query or commands>)
7. Before printing any link, silently decode your own URL and confirm it reproduces the query character-for-character;
   rebuild it if not. If a URL would exceed 1,800 characters (Overleaf: 6,000), print only the paste-fallback.
8. Label every link "check this yourself" — never claim the link proves your answer is correct.
9. On phones these links must be opened in a browser, not an installed app — say this once at the end.