Multi-collection search (-c A -c B) returns false empty or incomplete results in v1.0.7

[1kuna]

Summary

In qmd 1.0.7, passing multiple -c/--collection flags can return 0 results (or too few) even when each collection returns results individually.

This appears to be caused by the current multi-collection implementation doing a global top‑K search (no collection constraint) and then post-filtering results to the requested collections. If the requested collections don’t appear in the global top‑K (common when you have a very large collection like chat logs), you get false empty results.

Affected commands in my testing:

• qmd search (FTS/BM25)
• qmd query (hybrid + rerank)
• qmd vsearch (vector)

Environment

• qmd binary: ~/.bun/bin/qmd
• qmd --version: 1.0.7
• Collections: 13 (includes one very large collection)
• (In my setup) OpenClaw sidecar XDG paths were set for all commands:

XDG_CACHE_HOME=~/.openclaw/agents/main/qmd/xdg-cache \
XDG_CONFIG_HOME=~/.openclaw/agents/main/qmd/xdg-config \
~/.bun/bin/qmd …

Repro (FTS: qmd search)

Single collections work:

qmd search openclaw -c core --files -n 5
#6c98dc,0.00,qmd://core/tools.md
#1e1593,0.00,qmd://core/workspace.md
#bfd554,0.00,qmd://core/soul.md

qmd search openclaw -c skills --files -n 5
#cf37a8,0.00,qmd://skills/openclaw-ops/skill.md
#e8f0e8,0.00,qmd://skills/model-routing/skill.md
#184646,0.00,qmd://skills/keep/docs/releasing.md

Multiple -c can produce false empty:

qmd search openclaw -c core -c skills --files -n 5
No results found.

Another example (two other collections):

qmd search openclaw -c memory-dir-main --files -n 5
#e093fd,0.00,qmd://memory-dir-main/entities/openclaw.md
#5955b7,0.00,qmd://memory-dir-main/<redacted>/daily/2026-02-15.md
#9b5958,0.00,qmd://memory-dir-main/bank/world.md

qmd search openclaw -c memory-dir-main -c skills --files -n 5
No results found.

Observation that supports “top‑K then post-filter”: increasing -n (thus increasing candidate fetch) starts to surface results:

qmd search openclaw -c core -c skills --files -n 200 | head
#cf37a8,0.00,qmd://skills/openclaw-ops/skill.md

Repro (hybrid: qmd query)

Single collection works:

qmd query openclaw -c core --files -n 5 | tail -n 4
Reranking 3 chunks...
#… ,…,qmd://core/tools.md
#… ,…,qmd://core/workspace.md
#… ,…,qmd://core/soul.md

Multiple -c can produce false empty:

qmd query openclaw -c core -c skills --files -n 5 | tail -n 1
No results found.

Repro (vector: qmd vsearch)

Single collection works:

qmd vsearch openclaw -c openclaw-docs-main --files -n 5 | tail -n 2
#05a22b,0.76,qmd://openclaw-docs-main/zh-cn/reference/releasing.md
#7f3fc8,0.75,qmd://openclaw-docs-main/cli/setup.md

qmd vsearch openclaw -c chats-main --files -n 5 | tail -n 2
#… ,…,qmd://chats-main/<redacted>.md

Multiple -c returns only a subset (missing the other collection entirely):

qmd vsearch openclaw -c openclaw-docs-main -c chats-main --files -n 5 | tail -n 4
Searching 4 vector queries...
#… ,…,qmd://openclaw-docs-main/…
#… ,…,qmd://openclaw-docs-main/…

Expected vs actual

• Expected: -c A -c B should constrain the search to A ∪ B (OR) before ranking/limiting, and return results from either collection (subject to scoring).
• Actual: results depend on whether matches from the selected collections happen to appear in an unfiltered global top‑K; otherwise results are empty or incomplete.

Likely cause / relevant upstream change

Commit 640ac13 (“fix: support multiple -c collection filters in search commands”) is present in the v1.0.7 range.

That change adds multi‑-c support by:

1. passing a collection filter only when exactly one collection is specified
2. otherwise searching globally, then post‑filtering by qmd://{collection}/ prefix

This approach seems vulnerable to false empty/incomplete results due to candidate limits.

Workarounds

• Run one search per collection and merge client-side (then re-rank if needed).
• If acceptable, omit -c to search globally.

(For OpenClaw specifically: using searchMode: "query" with a single -c works fine; the issue only appears when multiple -c flags are provided.)