fix(ctx_search): label the BM25 fallback when the dense index is missing - #1261
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action=semantic (no mode) and ctx_compose resolve to BM25 ranking, but reported it as "Semantic search (BM25)" — a calling agent reads that as "semantic search ran", not "semantic search was unavailable". mode=dense already fails fast with an actionable build hint; the default path did not. When no mode was requested and embeddings.bin is absent (dense enabled but never built), the header now names the degradation and the fix: Lexical search (BM25 — dense index not built, run: lean-ctx index build-semantic) Explicit mode=bm25 is unchanged — that is not a degradation. The check is a file-existence test, no embedding-engine load on the search path. Fixes yvgude#1259 Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
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Fixes #1259
action=semantic(nomode) andctx_composeresolve to BM25 ranking, but reported it asSemantic search (BM25). A calling agent reads that as "semantic search ran", not "semantic search was unavailable".mode=densealready fails fast with an actionable build hint; the default path did not.Change
When no mode was requested and
embeddings.binis absent (dense enabled in config, never built), the header names the degradation and the one command that fixes it:Compact/TDD header gets
semantic_search(bm25,dense-not-built,K).mode=bm25is unchanged — that is a request, not a degradation.dense_enabled = false(doctor false positives for OpenCode: MCP config checks mcp.servers.lean-ctx but OpenCode uses mcp.lean-ctx; SKILL.md candidates omit OpenCode path #686) reports nothing — there is nothing to build.dense_index_missing()is a file-existence check, so no embedding-engine load lands on the search path.ctx_composepassesmode=None, so it is covered by the same fix.The BM25 fallback itself stays — it beats erroring out. Only the label was wrong.
Test
dense_availability_tests::missing_embeddings_bin_is_reported_as_degraded🤖 Generated with Claude Code