git.stella-ops.org/docs/reachability/function-level-evidence.md

Function-Level Evidence Readiness (Nov 2025 Advisory)

Last updated: 2025-11-09. Owner: Business Analysis Guild.

This memo captures the outstanding work required to make Stella Ops scanners emit stable, function-level evidence that matches the November 2025 advisory. It does not implement any code; instead it enumerates requirements, links them to sprint tasks, and spells out the schema/API updates that the next agent must land.

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1. Goal & Scope

Goal. Anchor every vulnerability finding to an immutable {artifact_digest, code_id} tuple plus optional symbol hints so replayers can prove reachability against stripped binaries.

Scope. Scanner analyzers, runtime ingestion, Signals scoring, Replay manifests, Policy/VEX emission, CLI/UI explainers, and documentation/runbooks needed to operationalise the advisory.

Out of scope: implementing disassemblers or symbol servers; those will be handled inside the module-specific backlog tasks referenced below.

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2. Advisory Requirements vs. System Gaps

Requirement	Current gap	Task references	Notes
Immutable code identity (code_id = {format, build_id, start, length} + optional code_block_hash)	Callgraph nodes are opaque strings with no address metadata.	Sprint 401 GRAPH-CAS-401-001, GAP-SCAN-001, GAP-SYM-007	code_id should live alongside existing SymbolID helpers so analyzers can emit it without duplicating logic.
Symbol hints (demangled name, source, confidence)	No schema fields for symbol metadata; demangling is ad-hoc per analyzer.	GAP-SYM-007	Require deterministic casing + symbol.source ∈ {DWARF,PDB,SYM,none}.
Runtime facts mapped to code anchors	/signals/runtime-facts is a stub; Zastava streams only Build-IDs.	Sprint 400 ZASTAVA-REACH-201-001, Sprint 401 SIGNALS-RUNTIME-401-002, GAP-ZAS-002, GAP-SIG-003	Need NDJSON schema documenting code_id, symbol.sid, hit_count, loader_base.
Replay/DSSE coverage	Replay manifests don’t enforce hash/CAS registration for graphs/traces.	Sprint 400 REPLAY-REACH-201-005, Sprint 401 REPLAY-401-004, GAP-REP-004	Extend manifest v2 with analyzer versions + BLAKE3 digests; add DSSE predicate types.
Policy/VEX/UI explainability	Policy uses coarse reachability:* tags; UI/CLI cannot show call paths or evidence hashes.	Sprint 401 POLICY-VEX-401-006, UI-CLI-401-007, GAP-POL-005, GAP-VEX-006, EXPERIENCE-GAP-401-012	Evidence blocks must cite code_id, graph hash, runtime CAS URI, analyzer version.
Operator documentation & samples	No guide shows how to replay {build_id,start,len} across CLI/API.	Sprint 401 QA-DOCS-401-008, GAP-DOC-008	Produce samples under samples/reachability/** plus CLI walkthroughs.

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3. Workstreams & Expectations

3.1 Scanner Symbolization (GAP-SCAN-001 / GAP-SYM-007)

• Define SymbolID helpers that glue together {artifact_digest, file, optional section, addr, length, code_block_hash}.
• Update analyzer contracts so every analyzer returns both symbol_id and code_id, with demangled names stored under the new symbol block.
• Persist the data into richgraph-v1 payloads and attach CAS URIs via StellaOps.Scanner.Reachability.
• Deliver fixtures in tests/reachability/StellaOps.ScannerSignals.IntegrationTests that prove determinism (same hash when analyzer flags reorder).

3.2 Runtime + Signals (GAP-ZAS-002 / GAP-SIG-003)

• Extend Zastava Observer NDJSON schema to emit: symbol_id, code_id, hit_count, observed_at, loader_base, process.buildId.
• Implement /signals/runtime-facts ingestion (gzip + NDJSON) with CAS-backed storage under cas://reachability/runtime/{sha256}.
• Update ReachabilityScoringService to lattice states and include runtime evidence references plus CAS URIs in ReachabilityFactDocument.Metadata.

3.3 Replay & Evidence (GAP-REP-004)

• Enforce CAS registration + BLAKE3 hashing before manifest writes (graphs and traces).
• Teach ReachabilityReplayWriter to require analyzer name/version, graph kind, code_id coverage summary.
• Update docs/replay/DETERMINISTIC_REPLAY.md once schema v2 is finalized.

3.4 Policy, VEX, CLI/UI (GAP-POL-005 / GAP-VEX-006)

• Policy Engine: ingest new reachability facts, expose reachability.state, max_path_conf, and evidence.graph_hash via SPL + API.
• CLI/UI: add stella graph explain and explain drawer showing call path (SymbolID list), code anchors, runtime hits, DSSE references.
• Notify templates: include short evidence summary (first hop + truncated code_id).

3.5 Documentation & Samples (GAP-DOC-008)

• Publish schema diffs in docs/data/evidence-schema.md (new file) covering SBOM evidence nodes, runtime NDJSON, and API responses.
• Write CLI/API walkthroughs in docs/09_API_CLI_REFERENCE.md and docs/api/policy.md showing how to request reachability evidence and verify DSSE chains.
• Produce OpenVEX + replay samples under samples/reachability/ showing facts.type = "stella.reachability" with graph_hash and code_id arrays.

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4. Schema & API Touchpoints

The next implementation pass must cover the following documents/files (create them if missing):

1. docs/data/evidence-schema.md – authoritative schema for {code_id, symbol, tool} blocks.
2. docs/runbooks/reachability-runtime.md – operator steps for staging runtime ingestion bundles, retention, and troubleshooting.
3. docs/runbooks/replay_ops.md – add section detailing replay verification using the new graph/runtime CAS entries.

API contracts to amend:

• POST /signals/callgraphs response should include graphHash (BLAKE3) once GRAPH-CAS-401-001 lands.
• POST /signals/runtime-facts request body schema (NDJSON) with symbol_id, code_id, hit_count, loader_base.
• GET /policy/findings payload must surface reachability.evidence[] objects.

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5. Test & Fixture Expectations

• Reachbench fixtures: update golden cases with code_id + symbol metadata. Ensure both reachable/unreachable variants still pass once graphs contain the richer IDs.
• Signals unit tests: add deterministic tests for lattice scoring + runtime evidence linking (tests/reachability/StellaOps.Signals.Reachability.Tests).
• Replay tests: extend tests/reachability/StellaOps.Replay.Core.Tests to assert manifest v2 serialization and hash enforcement.

All fixtures must remain deterministic: sort nodes/edges, normalise casing, and freeze timestamps in test data.

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6. Handoff Checklist for the Next Agent

1. Confirm sprint entries (SPRINT_400 and SPRINT_401) remain in sync when moving GAP-* tasks to DOING/DONE.
2. Start with GAP-SYM-007 (schema/helper implementation) because downstream work depends on the new code_id payload shape.
3. Once schema PR merges, coordinate with Signals + Policy guilds to align on CAS naming and DSSE predicates before wiring APIs.
4. Update the docs listed in §4 as each component lands; keep this file current with statuses and links to PRs/ADRs.
5. Before shipping, run the reachbench fixtures end-to-end and capture hashes for inclusion in replay docs.

Keep this document updated as tasks change state; it is the authoritative hand-off note for the advisory.