René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Frequent websocket_error: Duplicate item found (fc_call_* replay from session-state)","articleBody":"## Summary\nI am repeatedly hitting this failure in Copilot CLI:\n\n```\nExecution failed: CAPIError: 400 {\"error\":{\"code\":\"bad_request\",\"type\":\"websocket_error\",\"message\":\"Duplicate item found with id fc_call_\u003c...\u003e. Remove duplicate items from your input and try again.\"}}\n```\n\nThis appears to be session-state replay/corruption of prior `fc_call_*` items. Once it starts in a session, subsequent prompts in that same session fail quickly with the same duplicate-id error.\n\n## Frequency (from local `~/.copilot/session-state/*/events.jsonl`)\n- Sessions affected: **10**\n- Duplicate-item error events: **29**\n- Time window observed: **2026-05-28 ~18:46Z to ~19:43Z**\n- Worst session: `3604526b-3b17-4790-b5f5-9d4359783706` with **15** events in ~4.5 minutes\n\nAdditional affected sessions:\n- `893105c9-9726-497f-a54c-c384bd5b51b3` (3)\n- `6257b848-6652-450c-b949-b8d0477d3b56` (2)\n- `63d34bda-bddd-4246-aca5-5258e94d88dd` (2)\n- `ce4e9dd9-bca8-4181-ac70-7c398be8e204` (2)\n- plus 5 more sessions with single occurrences\n\n## Repro pattern\n1. Normal interaction with tool calls.\n2. A turn fails with duplicate `fc_call_*` id.\n3. Retrying in the same session keeps failing with duplicate-id style websocket 400s.\n4. Only workaround is deleting the bad session directory or resetting session-state.\n\n## Impact\nThis happens frequently enough to materially disrupt use; repeated manual session resets are not productive.\n\n## Environment\n- Copilot CLI version: 1.0.54\n- OS: macOS (Darwin)\n\nPlease advise on mitigation and whether a client-side de-dup guard can be added before sending websocket payload items.","author":{"url":"https://github.com/drapetomaniac","@type":"Person","name":"drapetomaniac"},"datePublished":"2026-05-28T19:45:47.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":3},"url":"https://github.com/3559/copilot-cli/issues/3559"}