prism

README

Prism

The complete picture for your coding agent — in one call, at a tenth of the tokens.

Give Prism the task. It returns the edit-ready context and the complete, type-resolved change set — every override, implementation, and caller — as ONE deterministic call over your local code graph.

Full benchmark harness, raw results, and every task file are public: provasign/research.

Measured (oracle-scored, 4 languages, blast radii 8–310 sites — see provasign/research):

• Engine completeness: 0.997 recall on change-impact closure vs a compiler-grade oracle; same answer every run.
• Agent-level, current frontier model (Opus, 6 change-impact tasks, 8–310 sites, 2026-08-08): the same answer for ~1/6th the cost. Recall 0.987 with Prism vs 1.000 with grep and file reads — a frontier model gets there either way — but 6.4× fewer turns, 9.3× fewer input tokens, 6.1× cheaper, 6.7× faster (4.2 vs 26.8 turns; 90k vs 836k tokens; $0.27 vs $1.66; 40s vs 271s per task).
• On weaker and cheaper models the gap is capability, not just cost: recall 0.758 → 0.997 at the Haiku tier in the 2026-07 grid, where a text-search agent could not reliably reach a complete change-set at all.
• What the graph actually contributes is precision, not discovery: measured over 127 symbols in 6 repositories, a whole-word grep misses no resolved reference — but ~30% of its hits are not references at all (98% in one typeorm case: 372 hits, 1 real). Against compiler oracles, file-level precision goes 0.51 (grep) → 0.91 (change-impact) at comparable recall.

What Prism is

Prism is an agent-neutral semantic safety layer for code changes. It indexes a repository into a measured semantic graph (symbols, calls, overrides, implements, test edges — via the embedded Grove engine) and exposes that graph at task altitude: one deterministic call answers a whole question an agent would otherwise spend dozens of turns approximating. For bug-fix and implement tasks it delivers the answer as edit-ready, line-numbered source — verbatim windows plus each anchor's callers and covering tests — so the model edits without a second read (prism_query, phase-aware; delivery="symbols" for the compact list).

Prism does not claim uniform compiler completeness across every language or runtime dispatch pattern. Run prism doctor [dir] to inspect the active engine, index readiness, and capability mode. Authoritative operations report their own completeness; stale, unsupported, or heuristic evidence must be treated as degraded rather than silently promoted to certainty.

The need. Agents gather context with text search and file reads. That works for locating things, but it fails exactly where the stakes are highest: enumerating everything a change touches. Overridden methods, interface implementations, overload-specific callers, and indirect call chains are invisible to grep — and an agent that misses one site ships a broken build. How much that costs depends on the model. A 2026-08 frontier model (Opus) does reach a complete change-set from grep alone on 8–310-site tasks — in 26.8 turns and 836k tokens per task, against 4.2 turns and 90k with Prism. Cheaper models do not get there at all: 0.758 recall at the Haiku tier in the 2026-07 grid. See provasign/research for both.

The principles.

1. Correctness and completeness first. A faster or cheaper incomplete answer is a faster broken build. Every design choice is subordinate to returning the complete, type-resolved answer.
2. Task altitude, not primitives. The graph is exposed as whole-task operations (change_impact, rename_plan, missing_implementations, …), not as node/edge primitives the agent must orchestrate. Orchestrating traversals is itself a frontier-model skill; a task-level call works on any model.
3. Determinism. The engine solves the traversal; the agent relays the result. Same query, same index, same answer — testable without an LLM, and never re-filtered through grep/sed (measured to drop real sites).
4. Tier invariance. Because the hard part is done by the engine, the same completeness holds from a free local 30B model to a frontier model — measured at recall 1.00 on both, where orchestration-based approaches collapse on cheap models.
5. Each layer does what it's best at. Shell tools find the first anchor (they win at string location — Prism does not replace grep). Prism answers relationship and whole-task questions. The model reasons and edits.
6. Evidence-backed abstraction. Above the task ops sits a component-level view (prism map / prism cycles): directories as components, dependency edges induced from the real call/import/type edges crossing between them, with weights, dependency cycles, and the evidence tier of every claim. Every abstract edge expands back to its concrete file:line sites — an architecture proof surface, not a narrative repo map. View results claim complete-at-tier, never closed (see docs/DESIGN_LAYERED_INTELLIGENCE.md).
7. Declared architecture, enforced. prism arch validates arch_deny: "<from> -> <to>" rules from prism.yaml against the induced view — every violation cites the exact file:line crossings, and exit 1 makes it a CI gate. Tier-aware by design: violations backed by structural-or-stronger evidence fail the build; heuristic-only evidence (e.g. interface dispatch attributed across a boundary — dependency inversion read backwards) is reported for review, not auto-failed (--strict escalates). Measured at the engine ceiling on injected Go violations: 10/10 detected, 0 false positives (see the injection benchmark in the test suite).
8. Verify the diff — the completeness gate for agent-authored changes. prism verify deterministically checks a diff: it detects contract changes (signature changes, renames, interface-member changes), computes the required change set from the base contract, and reports every dependent site the diff did not touch — line-precise. Measured on 9 real corpora with seeded incomplete edits (27 trials + 9 controls):
   • Verdict is fail-closed — 0 false "complete" across every run; an incomplete change is never waved through. Safe as a CI gate.
   • Site listing catches 88% of forgotten files (django, grafana, jackson-jsonnode, typeorm at 100%; guava 91%; serialize 88%), with zero false accusations — verify never flags a site the diff already handled. It gets there by enumerating dependents of the old contract (base-signature family + callers, generic-aware, member-level for interface blocks), not the post-edit graph the change severs. The one dimension no compiler covers in dynamic languages: a Python or TypeScript signature change with a forgotten caller compiles clean and fails at runtime — verify reports the exact line (see docs/DESIGN_LAYERED_INTELLIGENCE.md, Phase 3).

The front door — one tool, two moments. Agents don't route well across a tool menu (measured), so the primary surface is a single call:

prism(task="Allow users to revoke an active API token")

Before editing, it returns edit-ready line-numbered source, each anchor's callers and covering tests, and the change obligations — every site that must be handled if those contracts change, completeness-tagged. After editing, the same call with changed_files=[...] runs the verify gate. The specialized tools below remain the advanced surface it orchestrates.

Use cases — the questions Prism answers in one call:

You are about to…	One call
Change or rename a method signature	change-impact — declaration + override family + every resolved caller
Apply a rename, not just find it	rename-plan — every edit line, before/after, review-and-apply
Make an interface method required	missing-implementations — every type that breaks
Delete or extract code	dead-code — unreachable production symbols
Commit / select CI tests	affected — every test covering the changed files
Read code cheaply	read / lookup — session-deduped, ~10-token repeat reads
Expand from a grep hit	query — callers, callees, tests around an anchor

Where Prism is the wrong tool (honesty is a feature): locating a string or file (rg wins), languages outside the supported set below, dispatch wired at runtime through frameworks/reflection/DI (Prism's edges are static and type-resolved — it will show you nothing rather than a guess), and one-line greppable changes where any approach ties.

Prism is not a better grep. Use rg/grep to find the first anchor. Use Prism to answer the follow-up questions that usually cost several file reads:

• What calls this?
• What does this call?
• Which tests define the contract?
• What else is in the blast radius?

The recommended agent mode is both (MCP tools as primary surface, CLI fallback for subagents that don't inherit the MCP session):

prism init .

Agents with an active MCP session call prism_query, prism_read, and prism_lookup directly. For bug-fix and implement tasks prism_query delivers verbatim line-numbered source windows plus each anchor's callers and covering tests (edit-ready, phase-aware; --delivery symbols forces the compact list). Subagents and CI scripts fall back to the CLI:

prism query "fix the coverage-gap builder" --terms buildCoverageGaps --include graph --format text
prism read internal/mcp/tools.go --format text
prism lookup github.com/provasign/prism/internal/mcp.buildCoverageGaps --format text

--format text avoids the large JSON metadata wrappers that made early MCP benchmarks look expensive. Agents see plain source-like context with short headers, and can ask for lean or json only when automation needs it.

Grove is embedded in the Prism binary. There is no separate daemon, token, or grove_url setup in current releases.

---

Why Prism

Shell search gives pointers. Agents still have to chase those pointers by reading files, guessing test names, and manually reconstructing call paths.

Prism precomputes the project graph and lets the agent ask for relationships:

rg buildCoverageGaps internal/
  -> prism query "write tests for buildCoverageGaps" \
       --terms buildCoverageGaps \
       --include graph \
       --format text

On this repository, five real maintenance scenarios were run both ways on 2026-06-07. Shell-only baselines used rg plus targeted sed reads; Prism used one CLI text command per scenario.

Scenario	Shell bytes	Prism CLI bytes	Context reduction
Init agent_mode / CLI steering impact	19,970	12,818	35.8%
coverage_gaps precision	21,226	17,145	19.2%
CLI text/lean/json output formatting	15,820	14,198	10.3%
Session cache / savings ledger	33,134	19,922	39.9%
Release/version/install wiring	21,246	12,157	42.8%

The average reduction was 29.6% with one Prism command instead of 5-6 shell commands. (The coverage_gaps scenario refers to a since-removed feature: heuristic test-coverage edges measured 4–12% recall against real runtime coverage and were removed rather than shipped.)

A controlled A/B re-run (2026-06-12, post Grove-v0.6.2 fixes) on the payflow ground-truth project: total agent-token parity with the shell baseline (the 2026-06-07 run had +27–147% overhead) and 47 vs 84 tool calls. Repeat reads cost 29 tokens (95% saved); a rename under the agent's feet is reported as one breaking renamed entry for ~130 tokens. Full report: docs/AB-Test-Payflow-2026-06-12.md.

More detail, including repeat-read savings: provasign.dev/prism.

---

How It Works

Task + anchor terms
      |
      v
Embedded Grove index
  - symbols
  - call edges
  - dependency edges
  - test edges
      |
      v
Prism ranking
  - graph distance
  - semantic similarity
  - recency
  - test relevance
  - edit frequency / learned weights
      |
      v
Budgeted text context
  - target symbols
  - callers/callees
  - tests
  - docs

Prism supports two distinct saving mechanisms:

1. Context gathering reduction: one graph-aware query replaces multiple shell searches and file reads. This is what CLI text-mode benchmarks measure.
2. Session deduplication: in persistent MCP transports, repeated reads of unchanged files can become a short SHA pointer. This is where the ~99% repeated-read savings come from.

Direct CLI invocations are process-per-command, so they should be evaluated on context gathering and output wrapper size, not same-session re-read dedupe.

---

Installation

# Homebrew (macOS / Linux)
brew install provasign/shale/prism

# macOS / Linux script
curl -fsSL https://raw.githubusercontent.com/provasign/prism/main/install.sh | bash

# Windows PowerShell
irm https://raw.githubusercontent.com/provasign/prism/main/install.ps1 | iex

# Pin a version
VERSION=v0.33.0 curl -fsSL https://raw.githubusercontent.com/provasign/prism/main/install.sh | bash

The installer writes prism to ~/bin by default. Set INSTALL_DIR=/usr/local/bin or another directory to override.

Build from source:

make build
make test
make install

---

Quick Start: Agent CLI Text Mode

Run this once at the project root:

prism init .
prism index .

This writes:

• prism.yaml with agent_mode: "both"
• .mcp.json wiring the MCP server for MCP-capable clients
• steering files such as AGENTS.md, CLAUDE.md, .cursorrules, .windsurfrules, .github/copilot-instructions.md, and others
• compatible tool config files where detected

The generated agent instructions tell agents to use commands like:

prism query "trace the payment refund flow" --terms RefundPayment --include graph,tests --format text
prism query "audit UpdatePayment auth" --terms UpdatePayment,RequireScope --include graph --format text
prism read internal/payment/service.go --format text
prism lookup github.com/example/payflow/internal/payment.(*Service).RefundPayment --format text

Recommended agent workflow:

1. Locate the first anchor with rg, grep, or find.
2. Run prism query with the same anchor terms.
3. Use prism read for whole files only when needed.
4. Use prism lookup for one known function or method.
5. Treat task-op outputs as terminal structured results, not the start of manual cross-referencing.

---

Other Modes

prism init supports three modes:

prism init .              # non-interactive; registers MCP servers and writes
                          # one steering block covering MCP tools and the CLI
                          # (--mode is accepted and ignored since v0.38.0)

MCP

MCP advertises fifteen tools, kept deliberately small (every extra tool is a routing error waiting to happen): the unified task tool (prism), the context surface (prism_query, prism_read, prism_search, prism_lookup, prism_node, prism_references), the task-shaped graph operations (prism_change_impact, prism_missing_implementations, prism_dead_code, prism_rename_plan, prism_map), the gates (prism_verify, prism_arch_check), and prism_index. Search runs a real full-text pass (rg/grep/built-in) alongside symbol search, so agents never need a separate grep tool. prism resolve, prism edges, prism cycles (a field of prism map's result), prism drift, and the telemetry commands (prism savings, prism feedback, prism compact) remain CLI commands without spending schema tokens in every MCP session. Use MCP when the client has first-class MCP support and you want persistent session deduplication.

HTTP Server

prism serve is optional. Use it for custom automation that wants HTTP instead of CLI or MCP:

prism serve --port 8888 /path/to/project

It binds to 127.0.0.1.

---

CLI Reference

prism init [--global] [dir]
prism index [dir]
prism status [dir]
prism doctor [dir]

prism map [dir] [--depth N] [--component X] [--expand 'from->to'] [--json]
prism cycles [dir] [--depth N] [--json]
prism arch [dir] [--deny 'from -> to'] [--strict] [--json]   # exit 1 on violation
prism verify [dir] [--base REF] [--strict] [--json]          # exit 1 if incomplete

prism query <task> [dir] \
  --terms a,b,c \
  --include graph,docs \
  --delivery source|symbols \
  --max-files 5 \
  --depth 2 \
  --format text

prism read <file> [dir] --format text
prism lookup <name> [dir] --format text
prism search <keyword> [dir] --format text
prism references <name> [dir] --format text

# Task-shaped graph operations — one deterministic call each
prism change-impact 'Type.method(ParamType, ...)' [dir]   # declaration + override family + all resolved callers
prism rename-plan 'Type.method' NewName [dir]              # every concrete edit line, review-and-apply
prism missing-implementations 'Type.method' [dir]         # types claiming the contract that do not implement it
prism dead-code [dir] [--roots a,b]                       # unreachable production symbols (precision-first)

prism watch [dir]      # background file-watcher: delta-reindex on save, index always warm
prism drift [dir]
prism savings [dir]
prism compact [dir]
prism feedback --tool <name> --rating <0-5> [dir]
prism mcp [dir]
prism serve [--port 8888] [dir]
prism version
prism --version

Output formats:

Format	Use
text	Default and recommended for agents
lean	Compact JSON without most metadata
json	Full metadata for tooling/debugging

---

Configuration

prism.yaml is intentionally small:

version: 1
profile: "default"
agent_mode: "cli"

Optional keys:

model: "claude-sonnet-5"
grove_binary: "grove"
embeddings_backend: "tfidf"

Environment overrides include PRISM_MODEL, PRISM_PROFILE, PRISM_GROVE_BINARY, and PRISM_EMBEDDINGS_BACKEND.

---

Language Support

Prism delegates parsing and graph construction to embedded Grove.

Language	Extensions
Go	.go
TypeScript / TSX	.ts, .tsx
JavaScript / JSX	.js, .jsx, .mjs, .cjs
Python	.py
Java	.java
Rust	.rs
C / C++	.c, .h, .cc, .cpp, .hpp, ...
C#	.cs
PHP	.php, .phtml, ...

Markdown, YAML, JSON, shell scripts, Dockerfiles, Makefiles, SQL, GraphQL, and other non-code files are indexed as document symbols and can be requested with --include docs.

---

Benchmarks

One task, three ways to search — same agent, same frontier model, only the tool changes. A signature change in jackson-databind: find all 8 call sites it breaks, including callers not named after the method (invisible to text search). Oracle-scored.

Tool	Sites found	Turns	Tokens	Cost
Plain grep — the agent's default	5 of 8	19	376K	$0.90
Prism	8 of 8	3	60K	$0.14

Fewer turns, fewer tokens, lower cost — and the only one that found every site. Run the same task through Mason (Prism built in) on a free local 30B model: all 8, at $0 (0.997 mean recall across the 7-task change-impact benchmark). Raw runs: provasign/research.

---

The headline numbers (context reduction per scenario, repeat-read savings by project size, and the SHA-pointer dedup mechanism) are summarized with methodology at provasign.dev/prism. The full benchmark reports were trimmed from this repo to keep it lean; they remain available in git history (git log --diff-filter=D -- docs/ to locate them).

Current practical summary:

• CLI --format text is the recommended default for shell-capable agents.
• Prism is strongest on graph/blast-radius questions.
• Shell tools remain best for locating exact strings or filenames.
• MCP persistent transports add repeated-read deduplication that direct CLI invocations do not fully exercise.

---

Troubleshooting

prism query returns nothing: run prism index . from the project root.

Agent uses wrong steering: re-run prism init . — it rewrites the block between the <!-- prism:start --> markers in CLAUDE.md/AGENTS.md and leaves everything else untouched.

Wrong Prism binary: run command -v prism and prism version. Reinstall if the version is old.

macOS quarantine:

xattr -d com.apple.quarantine "$(which prism)"
codesign -f -s - "$(which prism)"

MCP client does not connect: restart the coding tool after prism init, and approve project MCP configuration if the tool prompts.