fix(rank,ledger): review-confirmed defect fixes + feat(collide): parallel-session conflict radar

ARCHITECTURE.md

@@ -70,7 +70,7 @@ The four layers, brand-named and emitted cross-tool:
   drift from. Prose rules in CLAUDE.md get acknowledged and then forgotten after
   compaction; a guard does not. Every enforceable invariant belongs here.
 - **mcp** — the protocol layer. Forge ships one stdio server (`src/cortex_mcp.js`)
-  exposing 20 MCP tools: the substrate checks (`substrate_check` / `predict_impact` /
+  exposing 21 MCP tools: the substrate checks (`substrate_check` / `predict_impact` /
   `assumption_gate` / `rank_code` / …), memory reads AND writes (`forge_remember`,
   ledger ratify/retract), and ops/health — the full table is in docs/GUIDE.md.
 
@@ -521,16 +521,16 @@ from the tree it describes.
 ```mermaid
 %%{init: {'theme':'base','themeVariables':{'primaryColor':'#201a15','primaryTextColor':'#f2ede7','primaryBorderColor':'#372c22','lineColor':'#f26430','secondaryColor':'#272019','tertiaryColor':'#171310','edgeLabelBackground':'#201a15','clusterBkg':'#171310','clusterBorder':'#4a3b2e','fontFamily':'ui-sans-serif, system-ui, sans-serif','fontSize':'14px'},'flowchart':{'curve':'basis','padding':10,'nodeSpacing':36,'rankSpacing':44}}}%%
 flowchart LR
-  test["test<br/>98 files"]
-  src["src<br/>93 files"]
+  test["test<br/>100 files"]
+  src["src<br/>94 files"]
   landing["landing<br/>60 files"]
   research["research<br/>35 files"]
   bench["bench<br/>2 files"]
   global["global<br/>2 files"]
   scripts["scripts<br/>2 files"]
   docs["docs<br/>1 file"]
   examples["examples<br/>1 file"]
-  test -- 191 --> src
+  test -- 195 --> src
   bench -- 7 --> src
   examples -- 4 --> src
   test -- 2 --> scripts

CHANGELOG.md

@@ -6,6 +6,45 @@ to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
 
+### Added
+
+- **`forge collide` — the parallel-session conflict radar.** The everyday failure of
+  the agent-fleet era: two sessions silently edit the same or import-coupled files and
+  the conflict surfaces at merge time. Every session already mints a ledger summary of
+  the files it touched, and those claims team-merge over plain git — so "who else was
+  just in here?" is a pure read: no server, no presence protocol, no new storage.
+  `risk = 1 − ∏(1 − recᵢ × strengthᵢ)` over recent foreign sessions (7-day recency
+  half-life — a collision is about now; direct hits count full, 1-hop import
+  neighbors half). Advisory and fail-open, with hook-minted absolute paths
+  relativized like the rank join. Exposed to every MCP-capable agent as
+  `collide_check` (21 MCP tools — counts and tables regenerated by
+  `forge docs render`).
+
+### Fixed
+
+- **The rank hazard join now matches production claims.** Hook-minted lessons and
+  session summaries store raw tool-input paths (absolute), while the atlas speaks
+  repo-relative POSIX — so `forge rank`'s history overlay never matched a real claim
+  and hazard silently degenerated to bare centrality (found by adversarial review,
+  reproduced against the live mint pipeline). `history()` now relativizes claim paths
+  against the repo root; a test pins the production path shape.
+- **`beliefDiff` tombstone edge cases.** A claim minted _and_ retracted inside the
+  diff window was reported as "appeared" with a live confidence — a retracted claim
+  presented as a current belief; it now lands in `retired` (`from:null, to:null`).
+  Claims already tombstoned before the window no longer surface as strengthened or
+  weakened through pure decay — dead beliefs don't move.
+- **`forge rank` determinism and hardening.** All orderings now use locale-independent
+  codepoint comparison (`localeCompare` consults ICU tables that differ across
+  machines, contradicting the module's own cross-machine guarantee); `centrality()`
+  counts a duplicated atlas node id once, as PageRank already did; a corrupt
+  `.forge/atlas.json` degrades to the `built:false` hint instead of crashing the CLI
+  and hanging the `rank_code` MCP call; a negative `--top` clamps instead of slicing
+  in from the end of the list.
+- **Temporal CLI guards.** `forge ledger diff` refuses a `<since>` after `<until>`
+  (previously printed silently inverted classes), and `ledger at`/`diff` reject
+  impossible calendar dates (`2026-02-31`) instead of letting `Date.parse` roll them
+  into a day nobody asked about.
+
 ## [0.29.0] - 2026-08-07
 
 ### Added

README.md

@@ -188,7 +188,7 @@ git pull && forge ledger merge <path-to-their-ledger>
 
 On Claude Code the substrate then runs on **every prompt automatically** via a
 `UserPromptSubmit` hook — advisory only, silent on clean tasks. Every other tool gets a
-native config rule plus **20 MCP tools** it can call itself — pre-action checks
+native config rule plus **21 MCP tools** it can call itself — pre-action checks
 (`substrate_check`, `predict_impact`, `assumption_gate`, `route_task`, `scope_files`),
 memory reads and writes, and ops/health — the full list with schemas is in
 [`docs/GUIDE.md`](docs/GUIDE.md#mcp-tools).
@@ -257,6 +257,7 @@ that never clobbers your existing settings (skip it with `install.sh --no-settin
 |                         | `forge deja`         | anti-repetition — have you done this task before? ranks prior solved/verified sessions                                                                                                                                      |
 |                         | `forge reuse`        | proof-carrying code cache — query <spec> / mint <spec> --file <path> / stats                                                                                                                                                |
 |                         | `forge rank`         | load-bearing code — PageRank centrality × past-incident history, circular-dependency clusters, chokepoint files                                                                                                             |
+|                         | `forge collide`      | parallel-session conflict radar — who else recently touched the files (or their import neighbors) you are editing                                                                                                           |
 <!-- forge:render:commands-table:end -->
 
 **→ Every command with a worked example and real output:

ROADMAP.md

@@ -38,7 +38,7 @@ confidence only from independent oracles, and merges across teammates conflict-f
   exposing the complexity tiers as model aliases; point `ANTHROPIC_BASE_URL` at the
   proxy and every model call routes through it.
 - **MCP server** — the cortex MCP server (`src/cortex_mcp.js`) exposes read-path
-  tools for ledger, brain, atlas, recall, cost, substrate, and dashboard (20 MCP tools
+  tools for ledger, brain, atlas, recall, cost, substrate, and dashboard (21 MCP tools
   as of 0.8.x, including the write tools added in 0.8.0).
 - **Cost dashboard** — `forge dash` serves a local HTML dashboard showing model spend,
   event timeline, and ledger health from `.forge/` data.

docs/GUIDE.md

@@ -26,14 +26,14 @@ recipes, and how to extend each piece. If you just want to get going, the
 Every command is real and wired. Grouped by what it does:
 
 <!-- forge:render:command-groups:begin (generated by `forge docs render` — do not edit) -->
-| Group                   | Commands                                                                                                                                                                           |
-| ----------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
-| **Core**                | `forge init` · `forge sync` · `forge doctor` · `forge tools` · `forge catalog` · `forge docs` · `forge update` · `forge config`                                                    |
-| **Substrate**           | `forge substrate` · `forge preflight` · `forge impact` · `forge scope` · `forge context` · `forge route` · `forge verify` · `forge precommit`                                      |
-| **Memory**              | `forge cortex` · `forge recall` · `forge remember` · `forge brain` · `forge ledger` · `forge handoff` · `forge decide` · `forge know`                                              |
-| **Quality**             | `forge scan` · `forge spec` · `forge harden` · `forge radar`                                                                                                                       |
-| **Config**              | `forge brand` · `forge atlas` · `forge stack` · `forge integrations` · `forge cost`                                                                                                |
-| **Labs (experimental)** | `forge taste` · `forge uicheck` · `forge imagine` · `forge lean` · `forge anchor` · `forge diagnose` · `forge dash` · `forge report` · `forge deja` · `forge reuse` · `forge rank` |
+| Group                   | Commands                                                                                                                                                                                             |
+| ----------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
+| **Core**                | `forge init` · `forge sync` · `forge doctor` · `forge tools` · `forge catalog` · `forge docs` · `forge update` · `forge config`                                                                      |
+| **Substrate**           | `forge substrate` · `forge preflight` · `forge impact` · `forge scope` · `forge context` · `forge route` · `forge verify` · `forge precommit`                                                        |
+| **Memory**              | `forge cortex` · `forge recall` · `forge remember` · `forge brain` · `forge ledger` · `forge handoff` · `forge decide` · `forge know`                                                                |
+| **Quality**             | `forge scan` · `forge spec` · `forge harden` · `forge radar`                                                                                                                                         |
+| **Config**              | `forge brand` · `forge atlas` · `forge stack` · `forge integrations` · `forge cost`                                                                                                                  |
+| **Labs (experimental)** | `forge taste` · `forge uicheck` · `forge imagine` · `forge lean` · `forge anchor` · `forge diagnose` · `forge dash` · `forge report` · `forge deja` · `forge reuse` · `forge rank` · `forge collide` |
 <!-- forge:render:command-groups:end -->
 
 Storage in one line: the code graph is `.forge/atlas.json` (plain JSON, not SQLite); the
@@ -283,6 +283,32 @@ Forge impact — blast radius
     - src/session.js
 ```
 
+### `forge collide` — who else is in these files right now?
+
+The everyday failure of running agents in parallel: two sessions (yours and a
+teammate's — or two of your own) silently edit the same or import-coupled files and
+the conflict surfaces at merge time. The ledger already knows the answer — every
+session mints a summary claim listing the files it touched, and those claims
+team-merge over plain git — so `forge collide` is a pure read: no server, no presence
+protocol, no new storage. Risk composes by the house noisy-OR,
+`1 − ∏(1 − recᵢ × strengthᵢ)`, over recent foreign sessions: recency uses a
+deliberately short 7-day half-life (a collision is about _now_), and strength counts
+direct file hits full and 1-hop import neighbors half. Advisory, fail-open, and
+exposed to every MCP-capable agent as `collide_check` — an agent can ask "is anyone
+else in here?" before its first edit.
+
+```console
+$ forge collide
+  checking 2 file(s) in play
+  collision risk █████░░░ 0.68
+
+  amina  day 20671  rec 0.91
+    direct  src/ledger.js
+    coupled src/ledger_sync.js
+
+  advisory — coordinate or pull their ledger before editing the shared files
+```
+
 ### `forge rank` — what here is dangerous to touch?
 
 The standing companion to `forge impact`: impact answers "what breaks if I change X",
@@ -1233,7 +1259,7 @@ one extra turn, exactly when that turn was owed.
 > `forge substrate "<task>" --json` (or the MCP tool `substrate_check`). If
 > `okToProceed` is false, ask the questions first; read `impact.impactedFiles` before editing.
 
-…and exposes the substrate as **20 MCP tools** any MCP-capable agent can call directly
+…and exposes the substrate as **21 MCP tools** any MCP-capable agent can call directly
 (the stdio server is launched with `forge cortex-mcp`, wired automatically via the
 emitted `.mcp.json`):
 
@@ -1260,6 +1286,7 @@ emitted `.mcp.json`):
 | `forge_provider_status` | Provider detection — which API provider is active (auto-detected or configured), env vars set, and health checks.                                                                                                                                                 |
 | `forge_remember`        | Store a durable fact in this repo's portable memory (.forge/brain/).                                                                                                                                                                                              |
 | `forge_ledger_ratify`   | Promote a ledger claim's confidence — record an independent oracle ratification (the claim held under test).                                                                                                                                                      |
+| `collide_check`         | Parallel-session conflict radar — which recent teammate/agent sessions touched the files (or their import neighbors) you are about to edit, from the team-merged Forge ledger.                                                                                    |
 | `rank_code`             | Which code is load-bearing and dangerous to touch — PageRank centrality over the Forge atlas graph joined with past-incident history from the evidence ledger, plus circular-dependency clusters and chokepoint files whose removal disconnects the import graph. |
 | `forge_ledger_retract`  | Tombstone a ledger claim with a reason — mark it as no longer valid so it stops influencing routing and memory.                                                                                                                                                   |
 <!-- forge:render:mcp-tools:end -->

mintlify/cli/substrate.mdx

@@ -43,6 +43,17 @@ Predict the blast radius for a symbol or file from the atlas graph.
 forge impact <symbol-or-file>
 ```
 
+## `forge collide`
+
+Parallel-session conflict radar: which recent teammate/agent sessions touched the
+files (or their import neighbors) you are editing, read from the team-merged ledger —
+`risk = 1 − ∏(1 − rec × strength)` over recent foreign sessions. Also exposed as the
+`collide_check` MCP tool.
+
+```bash
+forge collide [<file>…] [--json]
+```
+
 ## `forge rank`
 
 Load-bearing code: weighted PageRank centrality over the atlas graph joined with

mintlify/concepts/config-compiler.mdx

@@ -53,7 +53,7 @@ Each layer is brand-named and emitted cross-tool.
     does not. Every enforceable invariant belongs here.
   </Accordion>
   <Accordion title="mcp — the protocol layer" icon="plug">
-    Forge ships one stdio server (`src/cortex_mcp.js`) exposing 20 MCP tools: the
+    Forge ships one stdio server (`src/cortex_mcp.js`) exposing 21 MCP tools: the
     substrate checks (`substrate_check` / `predict_impact` / `assumption_gate` / …),
     memory reads _and_ writes (`forge_remember`, ledger ratify/retract), and ops/health.
   </Accordion>

mintlify/quickstart.mdx

@@ -70,7 +70,7 @@ forge substrate "Change verifyToken in src/auth.js to require length > 20; updat
 <Note>
   On Claude Code the substrate runs on **every prompt automatically** via a
   `UserPromptSubmit` hook — advisory only, silent on clean tasks. Every other tool gets
-  a native config rule plus 20 MCP tools it can call itself.
+  a native config rule plus 21 MCP tools it can call itself.
 </Note>
 
 If `forge substrate` says `ASK FIRST`, ask the returned questions before editing. Read

src/anchor.js

@@ -109,7 +109,9 @@ export function onGoalScore(goalTokens, fileTokens) {
 // advisory coarse check; widen to a managed-file manifest if that ever matters.
 const NOISE = /(^|\/)\.forge\/|(^|\/)\.[^/]+\/|^\.[^/]+$|(^|\/)(AGENTS|CLAUDE)\.md$/i;
 
-function gitFiles(root) {
+/** The working diff (changed vs HEAD + untracked), forge-noise filtered — exported so
+ *  collide.js reads "what am I touching" the exact same way the drift check does. */
+export function gitFiles(root) {
   const run = (args) => {
     try {
       return execFileSync("git", args, {

src/cli.js

@@ -884,7 +884,11 @@ HANDLERS.ledger = async (argv) => {
   const parseDay = (s) => {
     if (/^\d{1,6}$/.test(s ?? "")) return Number(s); // bare epoch-day
     const t = Date.parse(`${s}T00:00:00Z`);
-    return Number.isNaN(t) ? null : Math.floor(t / 86_400_000);
+    if (Number.isNaN(t)) return null;
+    // Round-trip check: Date.parse silently rolls impossible dates over (2026-02-31
+    // → March 3rd), which would answer a temporal query for a day nobody asked about.
+    if (new Date(t).toISOString().slice(0, 10) !== s) return null;
+    return Math.floor(t / 86_400_000);
   };
   if (sub === "at") {
     const day = parseDay(args[2]);
@@ -928,6 +932,13 @@ HANDLERS.ledger = async (argv) => {
       process.exitCode = 1;
       return;
     }
+    if (a > b) {
+      // beliefDiff's contract is dayA ≤ dayB; a reversed window would print silently
+      // inverted appeared/retired classes, so refuse loudly instead.
+      console.error(`  <since> (day ${a}) is after <until> (day ${b}) — swap the arguments`);
+      process.exitCode = 1;
+      return;
+    }
     const lg = await import("./ledger.js");
     const d = lg.beliefDiff(ls.loadState(dir), a, b);
     if (json) return console.log(JSON.stringify({ since: a, until: b, ...d }, null, 2));
@@ -1215,6 +1226,30 @@ HANDLERS.atlas = async (argv) => {
   }
   return;
 };
+HANDLERS.collide = async (argv) => {
+  const { collideReport } = await import("./collide.js");
+  const json = argv.includes("--json");
+  const files = argv.slice(1).filter((a) => !a.startsWith("--"));
+  const r = collideReport(process.cwd(), { files });
+  if (json) return console.log(JSON.stringify(r, null, 2));
+  heading(`${BRAND.brand} collide — parallel-session conflict radar\n`);
+  if (!r.mine.length) return console.log("  working tree clean — nothing to collide with");
+  console.log(paint(`  checking ${r.mine.length} file(s) in play`, "dim"));
+  if (!r.sessions.length)
+    return console.log("  no recent foreign session touched these files or their import neighbors");
+  console.log(`  collision risk ${bar(r.risk, 8)} ${r.risk.toFixed(2)}\n`);
+  for (const s of r.sessions.slice(0, 8)) {
+    console.log(
+      `  ${paint(s.author || "(unknown)", "accent")}  day ${s.day}  ${paint(`rec ${s.rec.toFixed(2)}`, "dim")}`,
+    );
+    for (const f of s.direct) console.log(`    ${paint("direct ", "warn")} ${f}`);
+    for (const f of s.coupled) console.log(`    ${paint("coupled", "dim")} ${f}`);
+  }
+  console.log(
+    paint("\n  advisory — coordinate or pull their ledger before editing the shared files", "dim"),
+  );
+  return;
+};
 HANDLERS.rank = async (argv) => {
   const { rankReport } = await import("./rank.js");
   const json = argv.includes("--json");