Use fnord with Claude Code and Cursor

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What this covers

Running fnord alongside other AI coding tools and knowing which of your existing instruction files it will actually honor — and how reliably. fnord is aware of three tiers of files; this use case is about choosing the right tier for a given instruction so it lands when you expect it to.

When to use it

  • You already have CLAUDE.md, .cursor/rules/, or Agent Skills and want fnord to respect them.
  • An instruction you wrote for Claude or Cursor isn't affecting fnord.
  • You're deciding where shared, cross-tool guidance should live.

The three tiers (most to least reliable)

TierFilesLoadedReliability
1. Always-loadedFNORD.md, FNORD.local.mdEvery session, no toggleGuaranteed
2. Opt-inCursor rules, Cursor/Claude skills, Claude subagentsWhen the external_configs source is enabledGuaranteed if toggled on
3. Research-discoveredREADME.md, CLAUDE.md, AGENTS.md, CONTRIBUTING.mdOn demand, if the task needs contextBest-effort

The rule of thumb: the more guaranteed you need an instruction to be, the lower the tier number it belongs in. FNORD.md is the only thing fnord promises to inject every time.

Steps

  1. Decide what the instruction is for:

    • Must apply on every fnord session → put it in FNORD.md (tier 1). See Project instructions and local overrides.
    • Tool-specific behavior you want fnord to opt into → tier 2.
    • Shared cross-tool orientation you're fine with fnord discovering when relevant → tier 3 (CLAUDE.md / AGENTS.md).

  2. For tier 2, see what fnord found and enable the sources you want:

    fnord config external list
fnord config external enable cursor:rules
fnord config external enable claude:agents

    At fnord ask start, fnord warns (in yellow) about any source that has files on disk but is disabled, with the exact enable command.

  3. For tier 3, just keep your CLAUDE.md / AGENTS.md where the other tools expect them. fnord's research and code phases are prompted to look for these when a task needs project context — but it's on demand, not pre-loaded.

  4. For "both tools must always honor this," use two homes: put the authoritative copy in FNORD.md (guaranteed for fnord) and your other tool's native location (CLAUDE.md for Claude Code, .cursor/rules/ for Cursor). Don't rely on one file to cover both tools.

Expected outcome

  • Tier 1 instructions shape every session.
  • Enabled tier 2 sources show up in the boot listing (Cursor skills:, Claude agents:, etc.) and inject their catalog at session start.
  • Tier 3 files are read mid-session when the task calls for them — visible in the session log as file_contents_tool reads.

Common failure modes

  • Your CLAUDE.md rule didn't fire — it's tier 3, best-effort. If it must always apply, promote it to FNORD.md.
  • A Cursor rule never injected — the source is disabled. Run fnord config external list and enable cursor:rules. Remember alwaysApply rules inject at bootstrap; globs: (auto-attach) rules only fire when a matching file is read or written.
  • A Claude subagent is missing from the catalog — agents whose tools: include Write/Edit are hidden outside edit mode. Re-run with --edit.
  • A skill caused recursion or was filtered — skills whose body shells back into fnord ask are filtered to prevent infinite recursion. Mark intentional shims with fnord_skip: true.
  • fnord ignored .github/copilot-instructions.md or Cursor's UI-stored rules — those are never consumed by any tier. Move the content to a file fnord reads.