V2 SDK Migration for Polymarket Bots: What Changed from py-clob-client and What to Update
If your bot still runs a legacy V1 client, it’s running on borrowed time — production endpoints now expect the V2 SDKs, and V1 shapes fail in ways that look like random errors. The migration is mostly mechanical, but it touches authentication, signing, and endpoint paths — the three places where mid-migration mistakes cost real money. Here’s what changed and the upgrade sequence that keeps a live bot alive through it.
Why migrate to the V2 SDK?
Legacy V1 clients no longer work against production — the current documentation recommends the V2 SDKs (the py-clob-client-v2 lineage for Python). Beyond access, V2 aligns with the post-April-2026 exchange upgrade’s contract and collateral changes (see the v2 migration notes and pUSD-era flows). Running V1 against drifting endpoints produces intermittent authentication and signing failures — the worst kind of bug, intermittent and money-adjacent.
What the migration actually touches
1. Authentication shape. Header construction, timestamp/salt handling, and key derivation moved — stale timestamps and reused salts reject harder in V2; sync against the server time endpoint and stop signing requests in the past (the mechanics are in authentication).
2. Endpoint paths and payloads. Market data, order placement, and account endpoints reorganized; field names and nesting changed in places. Inventory every endpoint your bot calls (the API guide maps the current surface).
3. Order signing. The signing scheme for orders aligned with the new contracts — order structs, chain IDs, and verifying contracts changed; a bot mixing V1-signed orders with V2 endpoints fails at placement in ways that read as “invalid order.”
4. Collateral assumptions. pUSD-era balances and allowances — code that assumed legacy USDC.e paths needs the updated collateral handling (see deposit mechanics).
The safe upgrade sequence
- Freeze and inventory. List every endpoint, auth path, and signing assumption in your current bot (the 8-component map is the checklist).
- Parallel run. Stand up the V2-based bot alongside the live V1 bot — same signals, paper or minimal size — and diff behavior: fills, rejections, latency.
- Cut over in a quiet window. Not into an event, not before funding windows (funding mechanics). Cancel resting orders on the old bot before killing it — orphaned rests are how migrations end (see worst-case margin).
- Verify externally. First hour on V2: reconcile fills and positions against the UI/API reads — a successful call is not a successful migration until positions agree.
- Keep the rollback path. Old config intact until the new bot has traded through a full session including a reconnect (see the websocket pattern).
FAQ
Do old py-clob-client bots still work on Polymarket? Legacy V1 clients no longer work against production — migrate to the V2 SDK lineage. Until then, expect intermittent auth/signing failures that read as random; see the migration notes.
What breaks during a V1 to V2 SDK migration? Authentication construction, endpoint paths/payloads, order signing structs, and collateral assumptions (pUSD era). The safe sequence: inventory, parallel run, quiet-window cutover, external verification.
Can I run V1 and V2 bots at the same time? Yes — that’s the parallel-run pattern: same signals, one on each SDK, diff the behavior before cutting over. Just mind the shared account: both bots’ resting orders count toward worst-case margin.
How do I avoid losing positions during SDK migration? Cancel all resting orders on the outgoing bot, cut over in a quiet window, verify positions externally in the first hour, keep rollback intact until a full session (including reconnect) trades clean — see the deployment checklist.
Does the V2 SDK change rate limits? Endpoint budgets are platform-side and independent of SDK version — your request patterns matter more; see rate-limit design.
Educational content, not financial advice. Not affiliated with Polymarket. Last updated October 2026.