diff --git a/src/lib/medications/__tests__/glp1-knowledge.test.ts b/src/lib/medications/__tests__/glp1-knowledge.test.ts
new file mode 100644
index 000000000..330612531
--- /dev/null
+++ b/src/lib/medications/__tests__/glp1-knowledge.test.ts
@@ -0,0 +1,270 @@
+import { describe, expect, it } from "vitest";
+
+import {
+  GLP1_DRUG_IDS,
+  GLP1_DRUGS,
+  findDrugByBrand,
+  routeForBrand,
+  type Glp1DrugId,
+} from "@/lib/medications/glp1-knowledge";
+
+describe("glp1-knowledge catalog", () => {
+  describe("shape integrity", () => {
+    it("includes exactly the five EMA-approved drug ids", () => {
+      const keys = Object.keys(GLP1_DRUGS).sort();
+      expect(keys).toEqual(
+        [
+          "dulaglutide",
+          "exenatide",
+          "liraglutide",
+          "semaglutide",
+          "tirzepatide",
+        ].sort(),
+      );
+    });
+
+    it("never lists retatrutide (no EMA approval — N7 exclusion)", () => {
+      // Belt-and-braces — both at the catalog level AND the brand
+      // level. Retatrutide has no EMA EPAR; including it would
+      // imply endorsement of unauthorised use.
+      expect(GLP1_DRUGS).not.toHaveProperty("retatrutide");
+      for (const record of Object.values(GLP1_DRUGS)) {
+        expect(
+          record.brands.map((b) => b.toLowerCase()),
+        ).not.toContain("retatrutide");
+        expect(record.inn.toLowerCase()).not.toBe("retatrutide");
+      }
+    });
+
+    it("populates every required field for every drug", () => {
+      for (const [id, record] of Object.entries(GLP1_DRUGS)) {
+        expect(record.inn, `inn missing on ${id}`).toBeTruthy();
+        expect(record.brands.length, `brands empty on ${id}`).toBeGreaterThan(0);
+        expect(record.route, `route missing on ${id}`).toBeTruthy();
+        expect(record.drugClass, `drugClass missing on ${id}`).toBeTruthy();
+        expect(record.pharmacology, `pharmacology missing on ${id}`).toBeTruthy();
+        expect(
+          record.pharmacology.halfLifeDays,
+          `halfLifeDays missing on ${id}`,
+        ).toBeGreaterThan(0);
+        expect(
+          record.pharmacology.bioavailability,
+          `bioavailability missing on ${id}`,
+        ).toBeGreaterThan(0);
+        expect(record.storage.unopened.temperatureCelsius.min).toBeDefined();
+        expect(record.storage.inUse.maxDays).toBeGreaterThan(0);
+        expect(record.titrationStepsMg.length).toBeGreaterThan(0);
+        expect(record.maxDoseMg).toBeGreaterThan(0);
+        expect(record.sideEffects.veryCommon.length).toBeGreaterThan(0);
+        expect(record.sourceEMA, `sourceEMA missing on ${id}`).toMatch(
+          /^https:\/\/www\.ema\.europa\.eu\//,
+        );
+      }
+    });
+
+    it("matches drug-ids and inn to the expected case", () => {
+      // Internal ids are lowercase; INN is title-case per WHO
+      // convention.
+      for (const id of GLP1_DRUG_IDS) {
+        expect(id).toBe(id.toLowerCase());
+        const record = GLP1_DRUGS[id];
+        expect(record.inn[0]).toBe(record.inn[0].toUpperCase());
+      }
+    });
+
+    it("keeps the catalog readonly at the type level", () => {
+      // `as const` discipline — verify mutating the catalog at
+      // runtime is impossible (frozen Object.freeze isn't applied
+      // by `as const`, but the tests assert the static contract).
+      // This is mostly a developer-readability test: if a future
+      // refactor drops `as const`, the test failure says why.
+      const tirzepatide = GLP1_DRUGS.tirzepatide;
+      expect(tirzepatide.brands).toEqual(["Mounjaro", "Zepbound"]);
+    });
+  });
+
+  describe("pharmacology values vs psp4.13099 + EMA EPAR", () => {
+    it("pins tirzepatide half-life to 5.0 d (EMA EPAR §5.2 ≈ 5 d)", () => {
+      expect(GLP1_DRUGS.tirzepatide.pharmacology.halfLifeDays).toBe(5.0);
+    });
+
+    it("pins tirzepatide Ka to 0.0373 h⁻¹ (psp4.13099 Table 3)", () => {
+      expect(GLP1_DRUGS.tirzepatide.pharmacology.absorptionRateHourlyKa).toBe(
+        0.0373,
+      );
+    });
+
+    it("pins tirzepatide clearance to 0.0329 L/h per 70 kg (psp4.13099 Table 3)", () => {
+      expect(GLP1_DRUGS.tirzepatide.pharmacology.clearanceLPerHour70kg).toBe(
+        0.0329,
+      );
+    });
+
+    it("pins tirzepatide bioavailability to 0.80 (psp4.13099 fixed)", () => {
+      expect(GLP1_DRUGS.tirzepatide.pharmacology.bioavailability).toBe(0.8);
+    });
+
+    it("pins semaglutide half-life to 7 d (EMA EPAR §5.2 ≈ 1 week)", () => {
+      expect(GLP1_DRUGS.semaglutide.pharmacology.halfLifeDays).toBe(7.0);
+    });
+
+    it("pins liraglutide half-life near 13 h (EMA EPAR §5.2)", () => {
+      // Stored as days for shape consistency — 13 h = 0.5416…
+      const days = GLP1_DRUGS.liraglutide.pharmacology.halfLifeDays;
+      expect(days * 24).toBeCloseTo(13, 1);
+    });
+
+    it("pins dulaglutide half-life to ~5 d (EMA EPAR §5.2)", () => {
+      expect(GLP1_DRUGS.dulaglutide.pharmacology.halfLifeDays).toBe(5.0);
+    });
+
+    it("pins exenatide IR half-life near 2.4 h (Byetta EMA EPAR §5.2)", () => {
+      const days = GLP1_DRUGS.exenatide.pharmacology.halfLifeDays;
+      expect(days * 24).toBeCloseTo(2.4, 1);
+    });
+
+    it("flags tirzepatide as two-compartment per the journal-of-record", () => {
+      // psp4.13099 verbatim: "two-compartment model with first
+      // order absorption and elimination."
+      expect(GLP1_DRUGS.tirzepatide.pharmacology.compartmentModel).toBe(
+        "two-compartment",
+      );
+    });
+  });
+
+  describe("brand-route mapping consistency", () => {
+    it("keeps Rybelsus mapped to oral, Ozempic + Wegovy to SC", () => {
+      expect(routeForBrand("semaglutide", "Rybelsus")).toBe("oral");
+      expect(routeForBrand("semaglutide", "Ozempic")).toBe("subcutaneous");
+      expect(routeForBrand("semaglutide", "Wegovy")).toBe("subcutaneous");
+    });
+
+    it("returns the default route when no per-brand override exists", () => {
+      expect(routeForBrand("tirzepatide", "Mounjaro")).toBe("subcutaneous");
+      expect(routeForBrand("tirzepatide", "Zepbound")).toBe("subcutaneous");
+      expect(routeForBrand("liraglutide", "Saxenda")).toBe("subcutaneous");
+      expect(routeForBrand("liraglutide", "Victoza")).toBe("subcutaneous");
+    });
+
+    it("returns null for an unknown brand on a known drug", () => {
+      expect(routeForBrand("tirzepatide", "DoesNotExist")).toBeNull();
+    });
+
+    it("never marks an injection-only drug brand as oral", () => {
+      for (const id of GLP1_DRUG_IDS) {
+        const record = GLP1_DRUGS[id];
+        for (const brand of record.brands) {
+          const route = routeForBrand(id, brand);
+          // The only oral brand is Rybelsus.
+          if (brand !== "Rybelsus") {
+            expect(route).toBe("subcutaneous");
+          }
+        }
+      }
+    });
+  });
+
+  describe("titration ladders", () => {
+    it("ascends strictly for every drug", () => {
+      for (const id of GLP1_DRUG_IDS) {
+        const steps = GLP1_DRUGS[id].titrationStepsMg;
+        for (let i = 1; i < steps.length; i++) {
+          expect(
+            steps[i],
+            `${id} titration step ${i} not strictly ascending`,
+          ).toBeGreaterThan(steps[i - 1]);
+        }
+      }
+    });
+
+    it("tops out at maxDoseMg for every drug", () => {
+      for (const id of GLP1_DRUG_IDS) {
+        const record = GLP1_DRUGS[id];
+        const lastStep = record.titrationStepsMg[record.titrationStepsMg.length - 1];
+        expect(lastStep).toBe(record.maxDoseMg);
+      }
+    });
+
+    it("captures the 2.5-→-15 mg Mounjaro ladder per EMA §4.2", () => {
+      expect(GLP1_DRUGS.tirzepatide.titrationStepsMg).toEqual([
+        2.5, 5, 7.5, 10, 12.5, 15,
+      ]);
+    });
+  });
+
+  describe("storage windows", () => {
+    it("refrigerates every product unopened at 2–8 °C", () => {
+      for (const id of GLP1_DRUG_IDS) {
+        const range = GLP1_DRUGS[id].storage.unopened.temperatureCelsius;
+        expect(range.min).toBe(2);
+        expect(range.max).toBe(8);
+      }
+    });
+
+    it("caps in-use temperature at ≤ 30 °C per EMA §6.3", () => {
+      for (const id of GLP1_DRUG_IDS) {
+        const range = GLP1_DRUGS[id].storage.inUse.temperatureCelsius;
+        // Byetta has a 25 °C cap; everything else 30 °C.
+        expect(range.max).toBeLessThanOrEqual(30);
+        expect(range.max).toBeGreaterThanOrEqual(25);
+      }
+    });
+
+    it("keeps every in-use window between 1 and 60 days", () => {
+      // Sanity check — no infinite shelf life, no stale defaults.
+      for (const id of GLP1_DRUG_IDS) {
+        const days = GLP1_DRUGS[id].storage.inUse.maxDays;
+        expect(days).toBeGreaterThan(0);
+        expect(days).toBeLessThanOrEqual(60);
+      }
+    });
+
+    it("sets Mounjaro KwikPen to 30 days post-opening per EMA §6.3", () => {
+      expect(GLP1_DRUGS.tirzepatide.storage.inUse.maxDays).toBe(30);
+    });
+  });
+
+  describe("findDrugByBrand", () => {
+    it("finds tirzepatide by Mounjaro and Zepbound", () => {
+      expect(findDrugByBrand("Mounjaro")?.inn).toBe("Tirzepatide");
+      expect(findDrugByBrand("Zepbound")?.inn).toBe("Tirzepatide");
+    });
+
+    it("is case-insensitive", () => {
+      expect(findDrugByBrand("mounjaro")?.inn).toBe("Tirzepatide");
+      expect(findDrugByBrand("MOUNJARO")?.inn).toBe("Tirzepatide");
+    });
+
+    it("returns null for unknown brand", () => {
+      expect(findDrugByBrand("BogusName")).toBeNull();
+    });
+
+    it("trims whitespace", () => {
+      expect(findDrugByBrand("  Wegovy  ")?.inn).toBe("Semaglutide");
+    });
+  });
+
+  describe("citations", () => {
+    it("links every record to an EMA EPAR PDF", () => {
+      for (const id of GLP1_DRUG_IDS) {
+        expect(GLP1_DRUGS[id].sourceEMA).toMatch(
+          /^https:\/\/www\.ema\.europa\.eu\/.*\.pdf$/,
+        );
+      }
+    });
+
+    it("attaches the psp4.13099 journal citation to tirzepatide", () => {
+      expect(GLP1_DRUGS.tirzepatide.sourceJournal?.doi).toBe(
+        "10.1002/psp4.13099",
+      );
+    });
+  });
+
+  describe("GLP1_DRUG_IDS", () => {
+    it("covers every catalog key in a stable order", () => {
+      const fromIds = [...GLP1_DRUG_IDS].sort();
+      const fromCatalog = Object.keys(GLP1_DRUGS).sort() as Glp1DrugId[];
+      expect(fromIds).toEqual(fromCatalog);
+    });
+  });
+});
diff --git a/src/lib/medications/glp1-knowledge.ts b/src/lib/medications/glp1-knowledge.ts
new file mode 100644
index 000000000..659c3f2d4
--- /dev/null
+++ b/src/lib/medications/glp1-knowledge.ts
@@ -0,0 +1,593 @@
+/**
+ * v1.4.25 W19a — GLP-1 EMA drug knowledge layer.
+ *
+ * Read-only static reference data for the five EMA-approved GLP-1
+ * receptor agonists (and one dual GIP/GLP-1 agonist). Values are
+ * extracted verbatim from EMA EPAR Product Information PDFs and
+ * cross-validated against the journal-of-record population PK paper
+ * for tirzepatide (Schneck & Urva 2024, DOI 10.1002/psp4.13099).
+ *
+ * Posture (per `.planning/research/glp1-feature-inspiration.md` §11):
+ *   - Display only. No autonomous dose escalation, no individual
+ *     weight-loss projection, no drug-drug interaction checking,
+ *     no mixing/reconstitution math.
+ *   - Coach must NEVER reason from these numbers as if they were
+ *     individual predictions; GROUND RULE 9 still applies.
+ *   - Retatrutide is deliberately excluded — no EMA approval as of
+ *     2026-05; including it would imply endorsement of unauthorised
+ *     use (N7).
+ *
+ * Sources:
+ *   - EMA EPAR PDFs linked per drug below.
+ *   - Schneck KB, Urva S. "Population pharmacokinetics of the GIP/GLP
+ *     receptor agonist tirzepatide." CPT Pharmacometrics Syst
+ *     Pharmacol. 2024;13(3):494-503. DOI 10.1002/psp4.13099.
+ *
+ * Numbers are pinned exactly per the research file's §1.1–§1.5 and
+ * the psp4.13099 cross-validation in §2.6. Drift introduces clinical
+ * risk; see `__tests__/glp1-knowledge-drift.test.ts` for the guard.
+ */
+
+/**
+ * Internal drug ids — stable across schema migrations. Brand-aware
+ * UI looks up by id, not by brand name.
+ */
+export type Glp1DrugId =
+  | "tirzepatide"
+  | "semaglutide"
+  | "liraglutide"
+  | "dulaglutide"
+  | "exenatide";
+
+/**
+ * Route enum — most agonists are subcutaneous; Rybelsus is oral
+ * semaglutide. The catalog records the default route on the drug
+ * record AND a per-brand override map so a single drug-id can carry
+ * mixed routes (semaglutide → Ozempic/Wegovy sc, Rybelsus oral).
+ */
+export type Glp1Route = "subcutaneous" | "oral";
+
+/**
+ * Drug class descriptor — Tirzepatide is the only dual GIP/GLP-1
+ * agonist among EMA-approved agents (2026-05); the rest are pure
+ * GLP-1 receptor agonists.
+ */
+export type Glp1DrugClass = "GIP-GLP1 dual agonist" | "GLP-1 receptor agonist";
+
+export type Glp1Pharmacology = {
+  /** Terminal elimination half-life. Days for the long-acting agents,
+   *  hours for liraglutide / short-acting exenatide. */
+  halfLifeDays: number;
+  /** Time to maximum concentration after a SC dose, hours. Liraglutide
+   *  uses the EMA EPAR §5.2 mean (~11 h); the weekly agents use the
+   *  pharmacology-text midpoint of their EMA-published 8–72 h range. */
+  tmaxHours: number;
+  /** First-order absorption rate constant. Populated from the
+   *  journal-of-record where one exists (tirzepatide ←
+   *  Schneck/Urva 2024); marked null where EMA does not publish a
+   *  pop-PK Ka estimate (the EPARs cite only terminal half-life). */
+  absorptionRateHourlyKa: number | null;
+  /** SC bioavailability, fraction in [0,1]. EMA EPAR §5.2 values. */
+  bioavailability: number;
+  /** Volume of distribution per kg body weight. Derived from the
+   *  EPAR's reported Vd at a 70 kg reference where the source gives
+   *  an absolute litre value. */
+  vdLitersPerKg: number;
+  /** Apparent clearance at the 70 kg reference weight, L/h. From
+   *  EPAR §5.2 or the journal-of-record where available. */
+  clearanceLPerHour70kg: number;
+  /** Weeks until steady-state plateau on the standard cadence. */
+  steadyStateWeeks: number;
+  /** Compartment model that best describes published PK. The
+   *  research-view curve (R8, deferred to v1.5) will honour this. */
+  compartmentModel: "one-compartment" | "two-compartment";
+};
+
+export type Glp1Storage = {
+  /** Refrigerated stability — every GLP-1 product is shipped 2–8 °C
+   *  per EMA. */
+  unopened: {
+    temperatureCelsius: { min: number; max: number };
+  };
+  /** Post-opening / in-use window. EMA §6.3 caps every product at
+   *  ≤ 30 °C; the day-count varies by product. */
+  inUse: {
+    temperatureCelsius: { min: number; max: number };
+    maxDays: number;
+  };
+};
+
+export type Glp1Pen = {
+  /** Pen device name as printed on the carton. */
+  type: string;
+  /** Doses per pen / per cartridge — drives W19b inventory
+   *  depletion math. `null` means single-use (one pen per dose). */
+  dosesPerPen: number | null;
+};
+
+export type Glp1AdverseReactions = {
+  /** ≥ 1/10 frequency per EMA §4.8. */
+  veryCommon: readonly string[];
+  /** 1/100 to <1/10 per EMA §4.8. */
+  common: readonly string[];
+  /** 1/1 000 to <1/100 per EMA §4.8. */
+  uncommon: readonly string[];
+  /** < 1/1 000 per EMA §4.8 — typically post-marketing signals. */
+  rare: readonly string[];
+};
+
+export type Glp1Indications = {
+  t2dm: { firstLine: boolean };
+  weightManagement: { bmiThreshold: number | null };
+};
+
+export type Glp1SourceCitations = {
+  /** Direct link to the EMA EPAR product-information PDF. */
+  sourceEMA: string;
+  /** Peer-reviewed pharmacometric citation where one exists. */
+  sourceJournal?: {
+    citation: string;
+    doi: string;
+  };
+};
+
+export type Glp1DrugRecord = {
+  inn: string;
+  brands: readonly string[];
+  /** Default route for the drug; brand-specific overrides go in
+   *  `brandRoutes`. */
+  route: Glp1Route;
+  /** Per-brand route override map. Only populated when at least one
+   *  brand departs from the default route (e.g. Rybelsus is oral
+   *  semaglutide while Ozempic / Wegovy are SC). */
+  brandRoutes?: Readonly<Record<string, Glp1Route>>;
+  drugClass: Glp1DrugClass;
+  pharmacology: Glp1Pharmacology;
+  /** Standard titration ladder in mg. Strictly ascending. The
+   *  schedule is informational per EMA EPAR §4.2 — the UI surfaces
+   *  it for context, never as autonomous escalation guidance (N1). */
+  titrationStepsMg: readonly number[];
+  /** Minimum interval between titration steps per EMA §4.2. */
+  titrationIntervalWeeks: number;
+  maxDoseMg: number;
+  standardInjectionFrequency: "daily" | "twice-daily" | "weekly";
+  indications: Glp1Indications;
+  storage: Glp1Storage;
+  pen: Glp1Pen;
+  sideEffects: Glp1AdverseReactions;
+  contraindications: readonly string[];
+  warnings: readonly string[];
+} & Glp1SourceCitations;
+
+/**
+ * The catalog. Five drug records keyed by stable id. Brand-name
+ * lookup is one-to-many; route-mapping is exposed both as the
+ * record default and the per-brand override.
+ */
+export const GLP1_DRUGS: Readonly<Record<Glp1DrugId, Glp1DrugRecord>> = {
+  // §1.1 — Tirzepatide. EMA EPAR cross-validated against
+  // Schneck & Urva 2024 (psp4.13099). Two-compartment first-order
+  // absorption + elimination per the journal-of-record.
+  tirzepatide: {
+    inn: "Tirzepatide",
+    brands: ["Mounjaro", "Zepbound"],
+    route: "subcutaneous",
+    drugClass: "GIP-GLP1 dual agonist",
+    pharmacology: {
+      halfLifeDays: 5.0,
+      tmaxHours: 24,
+      absorptionRateHourlyKa: 0.0373, // psp4.13099 Table 3
+      bioavailability: 0.8, // EMA EPAR §5.2
+      vdLitersPerKg: 0.09, // ~6.45 L / 70 kg per psp4.13099 (Vc + Vp)
+      clearanceLPerHour70kg: 0.0329, // psp4.13099 Table 3
+      steadyStateWeeks: 4, // EMA EPAR §5.2
+      compartmentModel: "two-compartment", // psp4.13099 verbatim
+    },
+    titrationStepsMg: [2.5, 5, 7.5, 10, 12.5, 15], // EMA EPAR §4.2
+    titrationIntervalWeeks: 4, // EMA EPAR §4.2
+    maxDoseMg: 15,
+    standardInjectionFrequency: "weekly",
+    indications: {
+      t2dm: { firstLine: false }, // adjunct, not first-line per §4.1
+      weightManagement: { bmiThreshold: 30 }, // §4.1 (or ≥ 27 with comorbidity)
+    },
+    storage: {
+      unopened: { temperatureCelsius: { min: 2, max: 8 } }, // §6.4
+      inUse: { temperatureCelsius: { min: 2, max: 30 }, maxDays: 30 }, // §6.3 KwikPen
+    },
+    pen: {
+      type: "KwikPen",
+      dosesPerPen: 4, // §6.5
+    },
+    sideEffects: {
+      veryCommon: [
+        "nausea",
+        "diarrhea",
+        "vomiting",
+        "abdominal_pain",
+        "constipation",
+        "decreased_appetite",
+      ],
+      common: [
+        "hypoglycaemia",
+        "hypersensitivity",
+        "dizziness",
+        "hypotension",
+        "dyspepsia",
+        "abdominal_distension",
+        "eructation",
+        "flatulence",
+        "gerd",
+        "hair_loss",
+        "fatigue",
+        "injection_site_reaction",
+        "heart_rate_increased",
+      ],
+      uncommon: [
+        "weight_decreased",
+        "dysgeusia",
+        "dysaesthesia",
+        "cholelithiasis",
+        "cholecystitis",
+        "acute_pancreatitis",
+        "delayed_gastric_emptying",
+        "injection_site_pain",
+      ],
+      rare: ["anaphylactic_reaction", "angioedema"],
+    },
+    contraindications: ["hypersensitivity_active_substance_or_excipients"],
+    warnings: [
+      "pancreatitis_history",
+      "severe_gi_disease",
+      "diabetic_retinopathy_macular_oedema",
+      "pulmonary_aspiration_risk_anaesthesia",
+      "pregnancy_long_half_life_discontinue_one_month_before",
+    ],
+    sourceEMA:
+      "https://www.ema.europa.eu/en/documents/product-information/mounjaro-epar-product-information_en.pdf",
+    sourceJournal: {
+      citation:
+        "Schneck KB, Urva S. CPT Pharmacometrics Syst Pharmacol. 2024;13(3):494-503.",
+      doi: "10.1002/psp4.13099",
+    },
+  },
+
+  // §1.2–§1.3 — Semaglutide (Ozempic injectable, Wegovy injectable
+  // weight-mgmt, Rybelsus oral). EMA EPAR §5.2: half-life ≈ 1 week.
+  // Rybelsus is the one mixed-route brand — `brandRoutes` carries
+  // the oral exception while the default stays SC.
+  semaglutide: {
+    inn: "Semaglutide",
+    brands: ["Ozempic", "Wegovy", "Rybelsus"],
+    route: "subcutaneous",
+    brandRoutes: {
+      Ozempic: "subcutaneous",
+      Wegovy: "subcutaneous",
+      Rybelsus: "oral",
+    },
+    drugClass: "GLP-1 receptor agonist",
+    pharmacology: {
+      halfLifeDays: 7.0, // EMA EPAR §5.2 (≈ 1 week)
+      tmaxHours: 24, // EMA EPAR §5.2 (Tmax 1–3 d for SC)
+      absorptionRateHourlyKa: null, // EMA EPAR does not publish a pop-PK Ka
+      bioavailability: 0.89, // EMA Ozempic §5.2
+      vdLitersPerKg: 0.18, // Wegovy §5.2 (~12.4 L / 70 kg)
+      clearanceLPerHour70kg: 0.05, // EMA Ozempic §5.2
+      steadyStateWeeks: 5, // EMA EPAR §5.2 (4–5 weeks)
+      compartmentModel: "two-compartment", // EMA EPAR §5.2 pop-PK
+    },
+    titrationStepsMg: [0.25, 0.5, 1, 2], // Ozempic ladder §4.2
+    titrationIntervalWeeks: 4,
+    maxDoseMg: 2, // Ozempic; Wegovy max 2.4 (then 7.2)
+    standardInjectionFrequency: "weekly",
+    indications: {
+      t2dm: { firstLine: false }, // Ozempic — adjunct
+      weightManagement: { bmiThreshold: 30 }, // Wegovy ≥30 or ≥27 w/ comorbidity
+    },
+    storage: {
+      unopened: { temperatureCelsius: { min: 2, max: 8 } }, // §6.4
+      inUse: { temperatureCelsius: { min: 2, max: 30 }, maxDays: 56 }, // Ozempic §6.3
+    },
+    pen: {
+      type: "FlexTouch",
+      dosesPerPen: 4, // Ozempic 0.25/0.5 mg dose pen
+    },
+    sideEffects: {
+      veryCommon: ["nausea", "diarrhea", "vomiting", "abdominal_pain"],
+      common: [
+        "hypoglycaemia",
+        "decreased_appetite",
+        "dizziness",
+        "dyspepsia",
+        "constipation",
+        "eructation",
+        "flatulence",
+        "abdominal_distension",
+        "gerd",
+        "fatigue",
+        "injection_site_reaction",
+        "lipase_increased",
+        "amylase_increased",
+        "cholelithiasis",
+      ],
+      uncommon: [
+        "hypersensitivity",
+        "dysgeusia",
+        "pulse_increased",
+        "diabetic_retinopathy_complications",
+        "acute_pancreatitis",
+      ],
+      rare: ["anaphylactic_reaction", "angioedema"],
+    },
+    contraindications: ["hypersensitivity_active_substance_or_excipients"],
+    warnings: [
+      "pancreatitis_history",
+      "diabetic_retinopathy_macular_oedema",
+      "dehydration_risk",
+      "pregnancy_long_half_life_discontinue_two_months_before",
+    ],
+    sourceEMA:
+      "https://www.ema.europa.eu/en/documents/product-information/ozempic-epar-product-information_en.pdf",
+  },
+
+  // §1.4 — Liraglutide (Saxenda weight-mgmt, Victoza T2DM). Daily
+  // SC dosing — fundamentally different cadence from the weekly
+  // agonists. Half-life ≈ 13 h per EMA EPAR §5.2.
+  liraglutide: {
+    inn: "Liraglutide",
+    brands: ["Saxenda", "Victoza"],
+    route: "subcutaneous",
+    drugClass: "GLP-1 receptor agonist",
+    pharmacology: {
+      halfLifeDays: 13 / 24, // ≈ 13 h per EMA EPAR §5.2
+      tmaxHours: 11, // EMA EPAR §5.2 (mean ~11 h)
+      absorptionRateHourlyKa: null, // not published in EMA EPAR pop-PK
+      bioavailability: 0.55, // EMA EPAR §5.2 (~55%)
+      vdLitersPerKg: 0.22, // ~22 L / 100 kg per EMA EPAR §5.2
+      clearanceLPerHour70kg: 1.2, // EMA EPAR §5.2 (~0.9–1.4 L/h)
+      steadyStateWeeks: 1, // daily, plateau within ~3 days
+      compartmentModel: "two-compartment",
+    },
+    titrationStepsMg: [0.6, 1.2, 1.8, 2.4, 3.0], // Saxenda §4.2
+    titrationIntervalWeeks: 1, // Saxenda: +0.6 mg/week
+    maxDoseMg: 3.0, // Saxenda; Victoza max 1.8
+    standardInjectionFrequency: "daily",
+    indications: {
+      t2dm: { firstLine: false }, // Victoza — adjunct
+      weightManagement: { bmiThreshold: 30 }, // Saxenda
+    },
+    storage: {
+      unopened: { temperatureCelsius: { min: 2, max: 8 } },
+      inUse: { temperatureCelsius: { min: 2, max: 30 }, maxDays: 30 },
+    },
+    pen: {
+      type: "Pre-filled pen",
+      dosesPerPen: null, // continuous-dial pen, doses vary
+    },
+    sideEffects: {
+      veryCommon: ["nausea", "vomiting", "diarrhea", "constipation"],
+      common: [
+        "hypoglycaemia",
+        "decreased_appetite",
+        "headache",
+        "dizziness",
+        "dyspepsia",
+        "abdominal_pain",
+        "gerd",
+        "abdominal_distension",
+        "eructation",
+        "flatulence",
+        "fatigue",
+        "injection_site_reaction",
+        "asthenia",
+      ],
+      uncommon: [
+        "dehydration",
+        "cholelithiasis",
+        "cholecystitis",
+        "acute_pancreatitis",
+        "tachycardia",
+      ],
+      rare: ["anaphylactic_reaction", "angioedema", "acute_renal_failure"],
+    },
+    contraindications: ["hypersensitivity_active_substance_or_excipients"],
+    warnings: [
+      "pancreatitis_history",
+      "thyroid_disease",
+      "dehydration_risk",
+      "pregnancy_not_recommended",
+    ],
+    sourceEMA:
+      "https://www.ema.europa.eu/en/documents/product-information/saxenda-epar-product-information_en.pdf",
+  },
+
+  // §1.5 — Dulaglutide (Trulicity). Weekly SC, half-life ~5 d per
+  // EMA EPAR §5.2. SC bioavailability ~47–65%.
+  dulaglutide: {
+    inn: "Dulaglutide",
+    brands: ["Trulicity"],
+    route: "subcutaneous",
+    drugClass: "GLP-1 receptor agonist",
+    pharmacology: {
+      halfLifeDays: 5.0, // EMA EPAR §5.2
+      tmaxHours: 48, // EMA EPAR §5.2 (Tmax 24–72 h)
+      absorptionRateHourlyKa: null, // not published in EMA EPAR pop-PK
+      bioavailability: 0.47, // EMA EPAR §5.2 (47% min of 47–65% range)
+      vdLitersPerKg: 0.27, // EMA EPAR §5.2 (Vc/F ~19.2 L → ~0.27 L/kg)
+      clearanceLPerHour70kg: 0.107, // EMA EPAR §5.2 (~0.107 L/h)
+      steadyStateWeeks: 2, // EMA EPAR §5.2 (~2 weeks)
+      compartmentModel: "two-compartment",
+    },
+    titrationStepsMg: [0.75, 1.5, 3.0, 4.5], // EMA EPAR §4.2
+    titrationIntervalWeeks: 4,
+    maxDoseMg: 4.5,
+    standardInjectionFrequency: "weekly",
+    indications: {
+      t2dm: { firstLine: false }, // adjunct
+      weightManagement: { bmiThreshold: null }, // not approved for weight mgmt
+    },
+    storage: {
+      unopened: { temperatureCelsius: { min: 2, max: 8 } },
+      inUse: { temperatureCelsius: { min: 2, max: 30 }, maxDays: 14 }, // EMA §6.3
+    },
+    pen: {
+      type: "Single-dose pen",
+      dosesPerPen: 1, // disposable single-dose
+    },
+    sideEffects: {
+      veryCommon: ["nausea", "diarrhea", "vomiting", "abdominal_pain"],
+      common: [
+        "hypoglycaemia",
+        "decreased_appetite",
+        "dyspepsia",
+        "constipation",
+        "flatulence",
+        "abdominal_distension",
+        "gerd",
+        "eructation",
+        "fatigue",
+        "injection_site_reaction",
+        "sinus_tachycardia",
+        "first_degree_av_block",
+      ],
+      uncommon: ["cholelithiasis", "cholecystitis", "acute_pancreatitis"],
+      rare: ["anaphylactic_reaction", "angioedema"],
+    },
+    contraindications: ["hypersensitivity_active_substance_or_excipients"],
+    warnings: [
+      "pancreatitis_history",
+      "severe_gi_disease",
+      "diabetic_retinopathy_macular_oedema",
+      "dehydration_risk",
+    ],
+    sourceEMA:
+      "https://www.ema.europa.eu/en/documents/product-information/trulicity-epar-product-information_en.pdf",
+  },
+
+  // Exenatide — twin product lines: Byetta (IR, twice-daily,
+  // t½ ~2.4 h) and Bydureon (extended-release, weekly,
+  // terminal t½ ~2 weeks). The record captures the IR profile as
+  // the default; the brand list flags Bydureon as the ER variant.
+  // The standard frequency reflects the IR formulation; Bydureon
+  // consumers must consult the Bydureon-specific EPAR for cadence.
+  exenatide: {
+    inn: "Exenatide",
+    brands: ["Byetta", "Bydureon"],
+    route: "subcutaneous",
+    drugClass: "GLP-1 receptor agonist",
+    pharmacology: {
+      halfLifeDays: 2.4 / 24, // Byetta IR — ~2.4 h per EMA EPAR §5.2
+      tmaxHours: 2.1, // EMA Byetta §5.2 (median ~2 h)
+      absorptionRateHourlyKa: null, // not published
+      bioavailability: 0.65, // EMA Byetta §5.2 (~65%)
+      vdLitersPerKg: 0.4, // EMA Byetta §5.2 (~28 L / 70 kg)
+      clearanceLPerHour70kg: 9.1, // EMA Byetta §5.2 (~9.1 L/h)
+      steadyStateWeeks: 1,
+      compartmentModel: "two-compartment",
+    },
+    titrationStepsMg: [0.005, 0.01], // Byetta 5 µg → 10 µg twice daily
+    titrationIntervalWeeks: 4, // Byetta §4.2 (escalate after ≥4 wk)
+    maxDoseMg: 0.01,
+    standardInjectionFrequency: "twice-daily",
+    indications: {
+      t2dm: { firstLine: false }, // adjunct only
+      weightManagement: { bmiThreshold: null }, // not approved for weight mgmt
+    },
+    storage: {
+      unopened: { temperatureCelsius: { min: 2, max: 8 } },
+      inUse: { temperatureCelsius: { min: 2, max: 25 }, maxDays: 30 }, // Byetta §6.3
+    },
+    pen: {
+      type: "Pre-filled pen (Byetta) / weekly suspension (Bydureon)",
+      dosesPerPen: 60, // Byetta 60 doses per pen
+    },
+    sideEffects: {
+      veryCommon: [
+        "hypoglycaemia",
+        "nausea",
+        "vomiting",
+        "diarrhea",
+      ],
+      common: [
+        "decreased_appetite",
+        "dizziness",
+        "headache",
+        "dyspepsia",
+        "abdominal_pain",
+        "gerd",
+        "flatulence",
+        "abdominal_distension",
+        "constipation",
+        "eructation",
+        "hyperhidrosis",
+        "injection_site_reaction",
+        "fatigue",
+      ],
+      uncommon: [
+        "dehydration",
+        "cholelithiasis",
+        "acute_pancreatitis",
+        "renal_failure",
+      ],
+      rare: ["anaphylactic_reaction", "angioedema"],
+    },
+    contraindications: [
+      "hypersensitivity_active_substance_or_excipients",
+      "severe_renal_impairment_egfr_below_30",
+    ],
+    warnings: [
+      "pancreatitis_history",
+      "severe_gi_disease",
+      "renal_impairment",
+      "pregnancy_not_recommended",
+    ],
+    sourceEMA:
+      "https://www.ema.europa.eu/en/documents/product-information/byetta-epar-product-information_en.pdf",
+  },
+} as const;
+
+/**
+ * Resolve the route for a given drug + brand. Falls back to the
+ * record default when no per-brand override is registered.
+ */
+export function routeForBrand(
+  drugId: Glp1DrugId,
+  brand: string,
+): Glp1Route | null {
+  const record = GLP1_DRUGS[drugId];
+  if (!record) return null;
+  if (!record.brands.includes(brand)) return null;
+  if (record.brandRoutes && brand in record.brandRoutes) {
+    return record.brandRoutes[brand];
+  }
+  return record.route;
+}
+
+/**
+ * Lookup helper — given an arbitrary brand string, find the drug
+ * record that lists it (case-insensitive). Returns null when the
+ * brand is unknown; useful for connecting free-text medication
+ * names to the catalog.
+ */
+export function findDrugByBrand(brand: string): Glp1DrugRecord | null {
+  const needle = brand.trim().toLowerCase();
+  if (!needle) return null;
+  for (const record of Object.values(GLP1_DRUGS)) {
+    if (record.brands.some((b) => b.toLowerCase() === needle)) {
+      return record;
+    }
+  }
+  return null;
+}
+
+/**
+ * The catalog's drug-ids in stable order. Useful for iteration in
+ * tests and UI surfaces that need a deterministic display order.
+ */
+export const GLP1_DRUG_IDS: readonly Glp1DrugId[] = [
+  "tirzepatide",
+  "semaglutide",
+  "liraglutide",
+  "dulaglutide",
+  "exenatide",
+] as const;