LithosAnanake/src/starkernel/capsule/capsule_birth.c

/*
  StarForth — Steady-State Virtual Machine Runtime

  Copyright (c) 2023–2025 Robert A. James
  All rights reserved.

  This file is part of the StarForth project.

  Licensed under the StarForth License, Version 1.0 (the "License");
  you may not use this file except in compliance with the License.
*/

/**
 * capsule_birth.c - VM Birth Protocol Implementation (M7.1)
 *
 * Mama init, baby birth, and experiment execution.
 * Freestanding - no libc dependency.
 *
 * Birth sequence for a baby VM:
 *   1. Find capsule by name (capsule_find_by_name)
 *   2. Assert CAPSULE_BIRTH_ELIGIBLE
 *   3. Validate content hash
 *   4. vm_alloc_hook() — fresh VM
 *   5. vm_exec_hook(payload) — IDENTITY (init capsule from Hera's store)
 *   6. vm_exec_hook("1 LOAD") — PERSONALITY (baby's personal init.4th from block 1, if present)
 *   7. Log parity record
 */

#include "starkernel/capsule_birth.h"
#include "starkernel/capsule.h"
#include "starkernel/capsule_run.h"
#include "starkernel/capsule_generated.h" /* capsule_get_signatures() */
#include "starkernel/capsule_sig.h"
#include "starkernel/kmalloc.h"
#include "starkernel/console.h"
#include "starkernel/vm/stadium.h" /* item 4.1a -- stadium_grant_quota() */
#include "starkernel/vm/arena.h" /* FABRIC-3.md §XXVIII Stage 1 -- sk_vm_native_stack_alloc() */
#include "starkernel/session.h" /* session_register()/session_set_pinned() -- FABRIC-2.md §H.12 step 5 */
#include "starkernel/timer.h" /* timer_calibration_record()->vm_mode -- FABRIC-2.md §I.5 CONTRIB trust tier */
#include "starkernel/capsule_vm_switch_signal.h" /* FABRIC-3.md §XXVIII Stage 4 -- capsule_vm_force_reap() */
#include "vm.h"
#include "platform_alloc.h"
/* No LOG_LINE_MAX include-order constraint anymore: vm.h's own
 * LOG_LINE_MAX (persistent block-log, 64) and log.h's in-memory line
 * length (renamed LOG_MSG_LINE_MAX, 256) are distinct names, so include
 * order no longer redefines anything (the -Werror collision found
 * 2026-08-26 wiring capsule signature logging is structurally gone). */
#include "log.h"

/*===========================================================================
 * VM Execution Hooks
 *===========================================================================*/

static CapsuleExecFn     vm_exec_fn      = 0;
static CapsuleDictHashFn vm_dict_hash_fn = 0;
static CapsuleVMAllocFn  vm_alloc_fn     = 0;

void capsule_birth_set_hooks(
    CapsuleExecFn     exec_fn,
    CapsuleDictHashFn dict_hash_fn,
    CapsuleVMAllocFn  vm_alloc_fn_arg)
{
    vm_exec_fn      = exec_fn;
    vm_dict_hash_fn = dict_hash_fn;
    vm_alloc_fn     = vm_alloc_fn_arg;
}

/*===========================================================================
 * VM Registry — dynamic linked list, heap-allocated via kmalloc
 *===========================================================================*/

typedef struct vm_node {
    VMRegistryEntry  entry;
    struct vm_node  *next;
} vm_node_t;

static vm_node_t *vm_registry_head  = (void *)0;
static uint32_t   vm_registry_count = 0;
/* item 3.8: vm_id generation moved to vm_uuid_next()'s deterministic pool;
 * the monotonic next_vm_id counter this replaced is gone. Hera's id is
 * vm_uuid_hera() (fixed, reserved), not drawn from the pool. */

/* Copy at most VM_NAME_MAX-1 chars, always null-terminate */
static void vm_name_copy(char *dst, const char *src) {
    uint32_t i;
    for (i = 0; i < (VM_NAME_MAX - 1u) && src[i]; i++)
        dst[i] = src[i];
    dst[i] = '\0';
}

/* Case-sensitive equality test (no libc) */
static int vm_name_eq(const char *a, const char *b) {
    while (*a && *b) {
        if (*a != *b) return 0;
        a++; b++;
    }
    return *a == *b;
}

/* Internal: return mutable pointer into registry node for vm_id */
static VMRegistryEntry *vm_find_entry_ptr(VMUuid vm_id) {
    vm_node_t *node = vm_registry_head;
    while (node) {
        if (vm_uuid_equal(node->entry.vm_id, vm_id)) return &node->entry;
        node = node->next;
    }
    return (void *)0;
}

/* FABRIC-2.md §H.12 step 10: creator-ceiling enforcement, birth-time
 * snapshot only, no live sync (§H.3, decided 2026-09-03 -- "if something
 * was developed with a particular set of ACLs, it should remain at
 * that... otherwise parent changes break the child's program"). For
 * every word in child's dictionary also present, by name, in parent's,
 * copy parent's CURRENT acl_allow/acl_mode/acl_pinned/acl_ttl onto
 * child's matching entry -- caps the child at whatever the parent
 * allowed at this exact moment, once, never re-applied afterward. Words
 * the child has that the parent doesn't (baby-specific vocabulary) are
 * left untouched -- there's nothing to cap them against. vm_find_word()
 * is the same C-level lookup FIND itself uses; not modifying FIND, just
 * calling the same lookup it does (CLAUDE.md: "FIND is a proven, tested,
 * registered word. Never modify it" -- this doesn't). */
static void dictionary_snapshot_acl_from_parent(VM *child, VM *parent) {
    DictEntry *ce;
    if (!child || !parent) return;

    for (ce = child->latest; ce != NULL; ce = ce->link) {
        DictEntry *pe = vm_find_word(parent, ce->name, ce->name_len);
        if (!pe) continue;
        ce->acl_allow  = pe->acl_allow;
        ce->acl_mode   = pe->acl_mode;
        ce->acl_pinned = pe->acl_pinned;
        ce->acl_ttl    = pe->acl_ttl;
    }
}

void capsule_vm_registry_init(void *mama_vm_ptr) {
    uint32_t   i;
    vm_node_t *node;
    vm_node_t *next;
    vm_node_t *mama;

    /* Free any nodes from a previous init (defensive) */
    node = vm_registry_head;
    while (node) {
        next = node->next;
        kfree(node);
        node = next;
    }

    vm_registry_head  = (void *)0;
    vm_registry_count = 0;

    /* Mama is always the reserved, fixed vm_uuid_hera() id (item 3.8) */
    mama = (vm_node_t *)kmalloc(sizeof(vm_node_t));
    if (!mama) return;

    mama->entry.vm_id              = vm_uuid_hera();
    mama->entry.state              = VM_STATE_LIVE;
    mama->entry.birth_capsule_id   = 0;
    mama->entry.birth_timestamp_ns = 0;
    mama->entry.birth_dict_hash    = 0;
    mama->entry.flags              = 0;
    mama->entry.parent_vm_id       = vm_uuid_hera();  /* self-referential: Hera is the root */
    mama->entry.vm_ptr             = mama_vm_ptr;
    mama->entry.stadium_patron_cell = STADIUM_CELL_NONE; /* set for real by
                                                           * stadium_birth_hera()
                                                           * separately -- not
                                                           * tracked here */
    for (i = 0; i < VM_NAME_MAX; i++) mama->entry.name[i] = '\0';
    vm_name_copy(mama->entry.name, "Hera");
    mama->next = (void *)0;

    vm_registry_head  = mama;
    vm_registry_count = 1;

    /* From this point on all console output is prefixed [Hera] */
    console_set_vm_name("Hera");
}

static VMRegistryEntry *vm_registry_alloc(void) {
    uint32_t   i;
    vm_node_t *node;
    vm_node_t *tail;

    node = (vm_node_t *)kmalloc(sizeof(vm_node_t));
    if (!node) return (void *)0;

    node->entry.vm_id              = vm_uuid_none();  /* not yet assigned -- NOT
                                                        * vm_uuid_hera(): a
                                                        * newly-allocated embryo
                                                        * is never Hera (item
                                                        * 3.8 caught this exact
                                                        * collision class again) */
    node->entry.state              = VM_STATE_EMBRYO;
    node->entry.birth_capsule_id   = 0;
    node->entry.birth_timestamp_ns = 0;
    node->entry.birth_dict_hash    = 0;
    node->entry.flags              = 0;
    node->entry.parent_vm_id       = vm_uuid_hera();  /* only Hera calls BIRTH
                                          * today; see design doc's "explicitly
                                          * out of scope" for making this dynamic */
    node->entry.vm_ptr             = (void *)0;
    node->entry.stadium_patron_cell = STADIUM_CELL_NONE;
    for (i = 0; i < VM_NAME_MAX; i++) node->entry.name[i] = '\0';
    node->next = (void *)0;

    /* Append to tail */
    if (!vm_registry_head) {
        vm_registry_head = node;
    } else {
        tail = vm_registry_head;
        while (tail->next) tail = tail->next;
        tail->next = node;
    }

    vm_registry_count++;
    return &node->entry;
}

int capsule_vm_registry_get(VMUuid vm_id, VMRegistryEntry *out) {
    VMRegistryEntry *entry;
    if (!out) return -1;
    entry = vm_find_entry_ptr(vm_id);
    if (!entry) return -1;
    *out = *entry;
    return 0;
}

uint32_t capsule_vm_registry_count(void) {
    return vm_registry_count;
}

int capsule_vm_registry_get_by_index(uint32_t index, VMRegistryEntry *out) {
    vm_node_t *node = vm_registry_head;
    uint32_t   i    = 0;
    if (!out) return -1;
    while (node) {
        if (i == index) { *out = node->entry; return 0; }
        node = node->next;
        i++;
    }
    return -1;
}

/* Live population, distinct from vm_registry_count above: vm_registry_count
 * is monotonic (incremented on every vm_registry_alloc(), never decremented
 * on death), so it counts every VM ever born, not the outer Stadium's
 * current occupancy. FABRIC-0.md item 1.5's bound is on LIVE VMs -- a dead or
 * stillborn slot doesn't hold Stadium capacity, and gating on the monotonic
 * total would mean the fleet could never regrow after any VM's death,
 * which contradicts Hera's own kill-then-rebirth lifecycle (TRIPOD-TEST's
 * "K soak" check, capsule_vm_physics.c). Not exposed in the public header:
 * only capsule_birth_baby's bound check needs it today. */
static uint32_t vm_registry_live_count(void) {
    vm_node_t *node = vm_registry_head;
    uint32_t   live = 0;
    while (node) {
        if (node->entry.state == VM_STATE_LIVE) live++;
        node = node->next;
    }
    return live;
}

int capsule_vm_find_by_name(const char *name, VMRegistryEntry *out) {
    vm_node_t *node;
    if (!name || !out) return -1;
    node = vm_registry_head;
    while (node) {
        if (vm_name_eq(node->entry.name, name)) {
            *out = node->entry;
            return 0;
        }
        node = node->next;
    }
    return -1;
}

/* Fold ASCII letter to lowercase (no libc) */
static char vm_to_lower(char c) {
    return (c >= 'A' && c <= 'Z') ? (char)(c + 32) : c;
}

/* Case-insensitive ASCII equality (no libc) */
static int vm_name_eq_nocase(const char *a, const char *b) {
    while (*a && *b) {
        if (vm_to_lower(*a) != vm_to_lower(*b)) return 0;
        a++; b++;
    }
    return *a == *b;
}

/* Case-insensitive ASCII prefix match up to (and not including) a literal
 * ':' in `str`, or the whole of `str` if it has no ':' -- capsule names use
 * a "namespace:filename" convention (e.g. "hermes:init.4th"), confirmed
 * live via a temporary probe (§H.12 step 6) rather than assumed: bare
 * vm_name_eq_nocase(capsule_name, "Hermes") never matched. `prefix` has no
 * ':' of its own. */
static int vm_name_prefix_eq_nocase(const char *str, const char *prefix) {
    while (*str && *str != ':' && *prefix) {
        if (vm_to_lower(*str) != vm_to_lower(*prefix)) return 0;
        str++; prefix++;
    }
    if (*prefix) return 0; /* prefix longer than str's namespace segment */
    return (*str == '\0' || *str == ':');
}

int capsule_vm_find_by_name_nocase(const char *name, VMRegistryEntry *out) {
    vm_node_t *node;
    if (!name || !out) return -1;
    node = vm_registry_head;
    while (node) {
        if (vm_name_eq_nocase(node->entry.name, name)) {
            *out = node->entry;
            return 0;
        }
        node = node->next;
    }
    return -1;
}

void capsule_vm_set_state(VMUuid vm_id, uint32_t state) {
    VMRegistryEntry *entry = vm_find_entry_ptr(vm_id);
    if (entry) entry->state = state;
}

void capsule_vm_set_pending_reap(VMUuid vm_id, int pending) {
    VMRegistryEntry *entry = vm_find_entry_ptr(vm_id);
    if (entry) entry->pending_reap = pending;
}

void capsule_vm_force_reap(VMUuid vm_id) {
    VMRegistryEntry *entry = vm_find_entry_ptr(vm_id);
    if (!entry) return;

    /* Idempotent, matching capsule_vm_kill()'s own convention -- the
     * Stage 3 checkpoint that calls this cannot itself know whether some
     * other path (a later re-attach's own teardown, say) already reaped
     * this exact VM before the checkpoint got to it. */
    if (entry->state == VM_STATE_DEAD) return;

    /* Hera is never a switch-signal participant subject to pending_reap
     * in the first place, but refuse on principle anyway -- matches
     * capsule_vm_kill()'s own unconditional rule. */
    if (vm_uuid_is_hera(entry->vm_id)) return;

    VM *vm = (VM *)entry->vm_ptr;

    /* Deliberately NOT capsule_vm_kill()'s VM_STATE_SWITCHED_OUT refusal
     * -- that guard exists precisely for the case this function handles:
     * the caller (vm_core.c's Stage 3 checkpoint) has already decided,
     * at a safe cooperative point it alone controls, that this parked
     * native-stack context will never be resumed. Freeing it here is the
     * deferred half of the mark-and-defer design (FABRIC-3.md §XXVIII
     * Stage 4) -- see VMRegistryEntry.pending_reap's own doc comment. */
    if (entry->stadium_patron_cell != STADIUM_CELL_NONE) {
        (void)stadium_evict(entry->stadium_patron_cell);
        entry->stadium_patron_cell = STADIUM_CELL_NONE;
    }

    if (vm) {
        vm_cleanup(vm);
        sf_free(vm);
    }

    /* Generic cleanup, independent of whatever subsystem set
     * pending_reap -- a reaped VM is no longer a switch-signal
     * participant either way. */
    sk_vm_switch_signal_unregister(vm_id);

    capsule_parity_log_kill(vm_id, entry->name);

    console_puts("REAP: ");
    console_puts(entry->name[0] ? entry->name : "(unnamed)");
    console_println(" tombstone reclaimed");

    entry->vm_ptr        = (void *)0;
    entry->state         = VM_STATE_DEAD;
    entry->pending_reap  = 0;
    for (uint32_t i = 0; i < VM_NAME_MAX; i++) entry->name[i] = '\0';
}

void capsule_vm_registry_set_name(VMUuid vm_id, const char *name) {
    VMRegistryEntry *entry;
    if (!name) return;
    entry = vm_find_entry_ptr(vm_id);
    if (!entry) return;
    vm_name_copy(entry->name, name);
}

/*===========================================================================
 * Internal: init.4th dispatch (PERSONALITY layer)
 *
 * After a baby VM runs its identity capsule, attempt to execute block 1.
 * Block 1 is the PERSONALITY layer — the baby's personal init.4th.
 * Failure is silent: the block may not exist, which is normal.
 *===========================================================================*/

static void dispatch_init_forth(void *vm_ctx) {
    /* M9: run baby's personal init.4th from block 1 once per-VM block
     * storage is isolated.  Until then this is a no-op to avoid executing
     * Mama's block 1 content on every child VM. */
    (void)vm_ctx;
}

/*===========================================================================
 * VM Kill
 *===========================================================================*/

int capsule_vm_kill(const char *name) {
    VMRegistryEntry *entry;
    VM              *vm;
    VMUuid           vm_id;
    uint32_t         i;

    if (!name) return -1;

    /* Locate by name (case-insensitive) */
    {
        vm_node_t *node = vm_registry_head;
        entry = (VMRegistryEntry *)0;
        while (node) {
            if (vm_name_eq_nocase(node->entry.name, name)) {
                entry = &node->entry;
                break;
            }
            node = node->next;
        }
    }

    if (!entry) {
        console_puts("KILL: ");
        console_puts(name);
        console_println(" not found");
        return -1;
    }

    /* Hera cannot be killed */
    if (vm_uuid_is_hera(entry->vm_id)) {
        console_println("KILL: cannot kill Hera");
        return -1;
    }

    /* Already dead — idempotent */
    if (entry->state == VM_STATE_DEAD) {
        console_puts("KILL: ");
        console_puts(name);
        console_println(" already dead");
        return 0;
    }

    /* FABRIC-3.md §XXVIII, Stage 2 (2026-09-13): a switched-out VM has a
     * live saved context parked on its own native stack -- freeing vm_ptr
     * here would leave that saved SP pointing into freed memory, a real
     * use-after-free the moment anything ever tried to resume it. Refuse
     * rather than silently corrupt; the caller can retry once the VM has
     * been switched back in and reaches a normal LIVE state. */
    if (entry->state == VM_STATE_SWITCHED_OUT) {
        console_puts("KILL: ");
        console_puts(name);
        console_println(" refused -- switched-out (context parked)");
        return -1;
    }

    vm_id = entry->vm_id;
    vm    = (VM *)entry->vm_ptr;

    /* FABRIC-2.md SS B, VM-COOL: reap this VM's own Stadium patron cell for
     * real, dispatching COOL. Refusal (already naturally reclaimed by
     * unrelated quota pressure, or never admitted) is silently tolerated --
     * KILL tears the VM down unconditionally either way. */
    if (entry->stadium_patron_cell != STADIUM_CELL_NONE) {
        (void)stadium_evict(entry->stadium_patron_cell);
        entry->stadium_patron_cell = STADIUM_CELL_NONE;
    }

    /* Tear down and free */
    if (vm) {
        vm_cleanup(vm);
        sf_free(vm);
    }

    entry->vm_ptr = (void *)0;
    entry->state  = VM_STATE_DEAD;
    for (i = 0; i < VM_NAME_MAX; i++) entry->name[i] = '\0';

    capsule_parity_log_kill(vm_id, name);

    console_puts("KILL: ");
    console_puts(name);
    console_println(" dead");

    return 0;
}

void capsule_vm_kill_all_nonmama(void) {
    vm_node_t *node;
    VM        *vm;
    VMUuid     vm_id;

    node = vm_registry_head;
    while (node) {
        if (vm_uuid_is_hera(node->entry.vm_id) || node->entry.state == VM_STATE_DEAD) {
            node = node->next;
            continue;
        }
        vm_id = node->entry.vm_id;
        vm    = (VM *)node->entry.vm_ptr;
        if (node->entry.stadium_patron_cell != STADIUM_CELL_NONE) {
            (void)stadium_evict(node->entry.stadium_patron_cell);
            node->entry.stadium_patron_cell = STADIUM_CELL_NONE;
        }
        /* FABRIC-3.md §XXVIII, Stage 2 (2026-09-13): a switched-out VM has
         * a live saved context parked on its own native stack -- skip the
         * free (leaked, not corrupted) rather than invalidate memory a
         * parked SP still points into. Harmless here specifically: every
         * caller of this function (BYE/cold-restart) calls
         * arch_cold_reset() immediately afterward, which wipes all memory
         * regardless of what this function left allocated. */
        if (vm && node->entry.state == VM_STATE_SWITCHED_OUT) {
            log_message(LOG_WARN, "capsule_vm_kill_all_nonmama: leaving %s allocated (switched-out)",
                        node->entry.name);
        } else if (vm) {
            vm->halted = 1;
            vm_cleanup(vm);
            sf_free(vm);
        }
        node->entry.vm_ptr = (void *)0;
        node->entry.state  = VM_STATE_DEAD;
        capsule_parity_log_kill(vm_id, node->entry.name);
        node = node->next;
    }
}

/* FABRIC-2.md §I.5, 2026-09-04: contributor-capsule trust tier
 * (QEMU-vs-real-hardware conditional enforcement, decided in
 * conversation). CAPSULE_FLAG_CONTRIB capsules get the same WARN-only
 * treatment as everything else under QEMU (timer_calibration_record()->
 * vm_mode == 1) -- development/test is meant to run contrib capsules
 * freely. On real hardware (vm_mode == 0), a contrib capsule additionally
 * requires CAPSULE_SIG_OK -- MISSING/NO_ROOT_KEY, which stay WARN-only
 * for every other capsule (no offline signing key on most machines,
 * see capsule_birth_mama()'s own comment), are refused here specifically
 * because a contributor's capsule has no other provenance to fall back
 * on the way this project's own capsules do. Never touches the
 * CAPSULE_SIG_INVALID refusal already in place for every capsule --
 * additive, not a replacement. */
static int contrib_capsule_refused(uint32_t flags, CapsuleSigResult sr) {
    if (!(flags & CAPSULE_FLAG_CONTRIB)) return 0;
    if (timer_calibration_record()->vm_mode) return 0; /* QEMU: relaxed */
    return sr != CAPSULE_SIG_OK; /* real hardware: must actually verify */
}

/*===========================================================================
 * Mama Init
 *===========================================================================*/

CapsuleRunResult capsule_birth_mama(
    void                   *mama_vm,
    const CapsuleDirHeader *dir,
    const CapsuleDesc      *descs,
    const CapsuleNameEntry *names,
    const uint8_t          *arena)
{
    if (!mama_vm || !dir || !descs || !names || !arena)
        return CAPSULE_RUN_ERR_INVALID;
    if (!vm_exec_fn || !vm_dict_hash_fn)
        return CAPSULE_RUN_ERR_INVALID;

    const CapsuleDesc *mama_cap = capsule_find_mama_init(dir, descs);
    if (!mama_cap) return CAPSULE_RUN_ERR_INVALID;

    CapsuleValidateResult vr = capsule_validate(mama_cap, arena, dir->arena_size, 1);
    if (vr != CAPSULE_VALID) return CAPSULE_RUN_ERR_INVALID;

    /* Milestone 6 (Phase 8): signature check. Enforced ONLY on INVALID (a
     * signature that IS present but does not verify -- unambiguous
     * tampering/corruption evidence). MISSING and NO_ROOT_KEY stay
     * WARN-only: MISSING is the normal state on every machine without
     * access to the offline signing key (CI, any other checkout) --
     * refusing on it would brick boot everywhere but the one machine
     * that minted this key, not catch anything real. See capsule_sig.h. */
    {
        int idx = (int)(mama_cap - descs);
        CapsuleSigResult sr = capsule_verify_signature(
            descs, names, capsule_get_signatures(), arena, dir->desc_count, idx);
        if (sr != CAPSULE_SIG_OK) {
            log_message(LOG_WARN, "capsule sig: %s: %s",
                        names[idx].name, capsule_sig_result_str(sr));
            if (sr == CAPSULE_SIG_INVALID) return CAPSULE_RUN_ERR_INVALID;
        }
    }

    uint64_t pre_dict_hash = vm_dict_hash_fn(mama_vm);
    (void)pre_dict_hash;

    const uint8_t *payload = capsule_get_payload(mama_cap, arena);
    if (!payload) return CAPSULE_RUN_ERR_INVALID;

    int exec_result = vm_exec_fn(mama_vm, (const char *)payload, mama_cap->length);
    if (exec_result != 0) return CAPSULE_RUN_ERR_EXEC_FAIL;

    uint64_t post_dict_hash = vm_dict_hash_fn(mama_vm);

    capsule_parity_log_mama_init(
        mama_cap->capsule_id,
        mama_cap->content_hash,
        post_dict_hash);

    {
        VMRegistryEntry *mama_entry = vm_find_entry_ptr(vm_uuid_hera());
        if (mama_entry) {
            mama_entry->birth_capsule_id = mama_cap->capsule_id;
            mama_entry->birth_dict_hash  = post_dict_hash;
        }
    }

    /* item 3.8: seed the vm_uuid pool now that the Mama capsule's content
     * hash is known -- before any baby birth (none happens today, item 0.1),
     * so the same capsule booted twice produces the same id sequence. */
    vm_uuid_pool_init(mama_cap->content_hash);

    return CAPSULE_RUN_OK;
}

/*===========================================================================
 * Baby Birth
 *===========================================================================*/

CapsuleRunResult capsule_birth_baby(
    const char             *capsule_name,
    const CapsuleDirHeader *dir,
    const CapsuleDesc      *descs,
    const CapsuleNameEntry *names,
    const uint8_t          *arena,
    VMUuid                  parent,
    int                     skip_pki_sig,
    VMUuid                 *out_vm_id,
    void                  **out_vm_ctx)
{
    if (!capsule_name || !dir || !descs || !names || !arena)
        return CAPSULE_RUN_ERR_INVALID;
    if (!vm_exec_fn || !vm_dict_hash_fn || !vm_alloc_fn)
        return CAPSULE_RUN_ERR_INVALID;

    /* Locate by name */
    const CapsuleDesc *cap = capsule_find_by_name(dir, descs, names, capsule_name);
    if (!cap) return CAPSULE_RUN_ERR_INVALID;

    if (!CAPSULE_BIRTH_ELIGIBLE(cap->flags)) return CAPSULE_RUN_ERR_NOT_ELIGIBLE;

    CapsuleValidateResult vr = capsule_validate(cap, arena, dir->arena_size, 1);
    if (vr != CAPSULE_VALID) return CAPSULE_RUN_ERR_INVALID;

    /* Milestone 6 (Phase 8): enforced only on INVALID -- see the fuller
     * comment in capsule_birth_mama() above for why MISSING/NO_ROOT_KEY
     * stay WARN-only. Skipped entirely when skip_pki_sig is set (RUNCAP,
     * FABRIC-2.md §F.6/F.18): capsule_get_signatures() is the compile-
     * time-baked array, indexed against the build-time capsule_descriptors[]
     * -- meaningless for a heap-built directory sourced from a thumbdrive,
     * where idx 0 would just compare against whatever real capsule happens
     * to occupy that slot. That content's trust already comes from a
     * separate root (CERTVERIFY, run by the caller before this). */
    if (!skip_pki_sig) {
        int idx = (int)(cap - descs);
        CapsuleSigResult sr = capsule_verify_signature(
            descs, names, capsule_get_signatures(), arena, dir->desc_count, idx);
        if (sr != CAPSULE_SIG_OK) {
            log_message(LOG_WARN, "capsule sig: %s: %s",
                        names[idx].name, capsule_sig_result_str(sr));
            if (sr == CAPSULE_SIG_INVALID) return CAPSULE_RUN_ERR_INVALID;
        }
        /* FABRIC-2.md §I.5: contrib trust tier -- see contrib_capsule_
         * refused()'s own doc comment. */
        if (contrib_capsule_refused(cap->flags, sr)) {
            log_message(LOG_WARN, "capsule sig: %s: contrib capsule refused on real hardware (%s)",
                        names[idx].name, capsule_sig_result_str(sr));
            return CAPSULE_RUN_ERR_INVALID;
        }
    }

    if (vm_registry_live_count() >= stadium_max_vm_count()) {
        capsule_parity_log_birth_failed(vm_uuid_none(), cap->capsule_id,
            CAPSULE_RUN_ERR_FLEET_FULL, 0);
        return CAPSULE_RUN_ERR_FLEET_FULL;
    }

    VMRegistryEntry *entry = vm_registry_alloc();
    if (!entry) return CAPSULE_RUN_ERR_INVALID;

    VMUuid vm_id = vm_uuid_next();
    entry->vm_id            = vm_id;
    entry->state            = VM_STATE_EMBRYO;
    entry->birth_capsule_id = cap->capsule_id;

    /* Allocate baby VM */
    void *new_vm = vm_alloc_fn();
    entry->vm_ptr = new_vm;
    if (!new_vm) {
        entry->state = VM_STATE_STILLBORN;
        capsule_parity_log_birth_failed(vm_id, cap->capsule_id,
            CAPSULE_RUN_ERR_STILLBORN, 0);
        return CAPSULE_RUN_ERR_STILLBORN;
    }

    /* item 4.2: set before the IDENTITY exec below, so any word this baby
     * dispatches during her own init capsule already attributes heat to her
     * own reservoir, not vm_uuid_hera()'s (item 4.1's hardcoded default). */
    ((VM *)new_vm)->stadium_vm_id = vm_id;

    /* FABRIC-3.md §XXVIII, Stage 1 (2026-09-13): every VM gets its own
     * native stack from the moment it exists, including WIREBIND-birthed
     * identity VMs -- purely additive here, nothing executes on it yet
     * (that's Stage 2). Allocation failure is not fatal to birth itself:
     * a VM with no native stack yet is exactly as functional today as
     * every VM has always been (nothing currently runs on a dedicated
     * per-VM stack), so this degrades to "not yet switchable," not
     * "stillborn." native_stack_top stays 0, the pre-Stage-2 default. */
    {
        sk_vm_native_stack_t ns;
        if (sk_vm_native_stack_alloc(&ns) == 0) {
            ((VM *)new_vm)->native_stack_paddr       = ns.paddr;
            ((VM *)new_vm)->native_stack_guard_vaddr = ns.guard_vaddr;
            ((VM *)new_vm)->native_stack_top         = ns.stack_top;
        } else {
            log_message(LOG_WARN, "capsule_birth_baby: native stack allocation failed for %s",
                        capsule_name);
        }
    }

    /* item 4.6 fix (FABRIC-1.md, 2026-08-18): granted here, before IDENTITY
     * exec, not after a confirmed live birth as item 4.1a originally placed
     * it. item 4.1a's placement assumed no VM's own IDENTITY code would ever
     * need a Stadium quota before birth completes -- true until item 4.6's
     * Artemis capsule started auto-running a block-admission stress campaign
     * as part of her own init.4th load. Without a quota yet, every
     * STADIUM-ADMIT during that campaign refused unconditionally (quota
     * slot < 0), 100% of trials, on all three architectures. Trade-off this
     * introduces: a VM that dies stillborn below (IDENTITY exec fails) has
     * still consumed half of its donor's free list, with no rollback --
     * accepted because stadium_grant_quota() failure was already non-fatal
     * and a stillbirth here is the rare case, not the common one.
     *
     * Donor is whichever live VM currently holds the most free cells
     * (stadium_best_donor(), FABRIC-3.md SXVI) -- NOT unconditionally
     * vm_uuid_hera() as this used to hardcode. Always splitting from Hera
     * specifically converges HER free list toward empty after a bounded
     * number of grants (each halves what remains), silently refusing every
     * later birth once she runs dry even while VMs she granted to earlier
     * still hold nearly all of their own share untouched -- the Stadium as
     * a whole nowhere near full. Falls back to vm_uuid_hera() only if no VM
     * holds a quota yet (stadium_best_donor() returns vm_uuid_none()), which
     * should not happen here since stadium_birth_hera() always runs first. */
    {
        VMUuid donor = stadium_best_donor();
        if (vm_uuid_equal(donor, vm_uuid_none())) donor = vm_uuid_hera();
        (void)stadium_grant_quota(vm_id, donor);
    }

    /* FABRIC-2.md SS B, VM-COOL: admit this VM as a patron of its own
     * quota -- identity 0 (same convention stadium_birth_hera() uses for
     * "patron zero"), heat 0 (no reservoir cost). Admitted unpinned here
     * regardless of which VM this is -- pinning (when it applies) happens
     * through session_set_pinned() below, after admission, same
     * unpinned-then-pin ordering §H.12 step 4 already established for
     * Hera (stadium_admit() has no admission-time-special pin handling,
     * just copies the candidate header, so this ordering is safe).
     *
     * FABRIC-2.md §H.12 step 5: fleet-foundation VMs (Hera/Hermes/Artemis)
     * are pinned -- permanent, exempt from COOL, per §H.1's decision.
     * Ordinary/user VMs stay unpinned, matching the original comment's own
     * reasoning here (unrelated quota pressure can naturally evict this
     * cell before an explicit KILL runs; tolerated, not a bug -- nothing
     * wires COOL's dispatch body to kill anything, so the only visible
     * effect is entry->stadium_patron_cell going stale, which the
     * KILL-time eviction below already tolerates). The original comment's
     * "there is no unpin primitive" concern no longer applies to Hera
     * herself (session_set_pinned() now provides one, §H.12 step 3) but
     * still correctly describes why ordinary VMs -- which DO get killed --
     * must stay unpinned: nothing here ever un-pins a killed ordinary VM,
     * so it must never have been pinned to begin with.
     *
     * Soft failure, same as stadium_grant_quota() above -- a refused
     * admission leaves stadium_patron_cell at STADIUM_CELL_NONE, and
     * nothing downstream depends on it succeeding. session_register()/
     * session_set_pinned() failures are soft-fail the same way (logged,
     * non-fatal) -- same reasoning §H.12 step 4 already established for
     * Hera. */
    {
        StadiumPatronHeader vm_patron;
        uint8_t            *raw = (uint8_t *)&vm_patron;
        size_t               i;
        int                  is_fleet_foundation =
            vm_name_prefix_eq_nocase(capsule_name, "Hera")   ||
            vm_name_prefix_eq_nocase(capsule_name, "Hermes") ||
            vm_name_prefix_eq_nocase(capsule_name, "Artemis");

        for (i = 0; i < sizeof(vm_patron); i++) raw[i] = 0;
        vm_patron.identity  = 0;
        vm_patron.heat      = 0;
        vm_patron.ttl       = 0;
        vm_patron.link      = 0;
        vm_patron.contains  = STADIUM_CONTAINS_NONE;
        vm_patron.mass      = 1;
        vm_patron.flags     = 0;
        vm_patron.behaviour = (uint8_t)STADIUM_BEHAVIOUR_COOL;

        entry->stadium_patron_cell = stadium_admit(vm_id, &vm_patron);

        if (entry->stadium_patron_cell != STADIUM_CELL_NONE) {
            Session *s = session_register(vm_id, parent, capsule_name);
            if (s) {
                s->stadium_cell = entry->stadium_patron_cell;
                if (is_fleet_foundation) session_set_pinned(vm_id, 1);
            }
        }
    }

    const uint8_t *payload = capsule_get_payload(cap, arena);
    if (!payload) {
        entry->state = VM_STATE_STILLBORN;
        capsule_parity_log_birth_failed(vm_id, cap->capsule_id,
            CAPSULE_RUN_ERR_INVALID, 0);
        return CAPSULE_RUN_ERR_INVALID;
    }

    /* IDENTITY: run init capsule */
    int exec_result = vm_exec_fn(new_vm, (const char *)payload, cap->length);
    if (exec_result != 0) {
        uint64_t partial_hash = vm_dict_hash_fn(new_vm);
        entry->state            = VM_STATE_STILLBORN;
        entry->birth_dict_hash  = partial_hash;
        capsule_parity_log_birth_failed(vm_id, cap->capsule_id,
            CAPSULE_RUN_ERR_EXEC_FAIL, partial_hash);
        return CAPSULE_RUN_ERR_EXEC_FAIL;
    }

    /* PERSONALITY: per-VM block storage is M9 scope; no-op until then */
    dispatch_init_forth(new_vm);

    uint64_t dict_hash = vm_dict_hash_fn(new_vm);
    entry->state           = VM_STATE_LIVE;
    entry->birth_dict_hash = dict_hash;

    capsule_parity_log_birth(vm_id, cap->capsule_id, cap->content_hash, dict_hash);

    /* §H.12 step 11: applied AFTER dict_hash/parity logging above, not
     * before -- a runtime ACL snapshot depends on the parent's CURRENT
     * state (which can vary run-to-run once Zuse-granted elevations
     * exist), so applying it before the hash would make birth_dict_hash
     * no longer a pure function of capsule content, breaking the "same
     * capsule booted twice produces the same dict hash" determinism
     * invariant this codebase relies on elsewhere. */
    {
        VMRegistryEntry *parent_entry = vm_find_entry_ptr(parent);
        if (parent_entry && parent_entry->vm_ptr) {
            dictionary_snapshot_acl_from_parent(new_vm, (VM *)parent_entry->vm_ptr);
        }
    }

    if (out_vm_id)  *out_vm_id  = vm_id;
    if (out_vm_ctx) *out_vm_ctx = new_vm;

    return CAPSULE_RUN_OK;
}

/*===========================================================================
 * Experiment Execution
 *===========================================================================*/

CapsuleRunResult capsule_run_experiment(
    void                   *mama_vm,
    const char             *capsule_name,
    const CapsuleDirHeader *dir,
    const CapsuleDesc      *descs,
    const CapsuleNameEntry *names,
    const uint8_t          *arena,
    uint64_t               *out_run_id)
{
    if (!mama_vm || !capsule_name || !dir || !descs || !names || !arena)
        return CAPSULE_RUN_ERR_INVALID;
    if (!vm_exec_fn || !vm_dict_hash_fn)
        return CAPSULE_RUN_ERR_INVALID;

    const CapsuleDesc *cap = capsule_find_by_name(dir, descs, names, capsule_name);
    if (!cap) return CAPSULE_RUN_ERR_INVALID;

    if (!CAPSULE_DOE_ELIGIBLE(cap->flags)) return CAPSULE_RUN_ERR_NOT_ELIGIBLE;

    CapsuleValidateResult vr = capsule_validate(cap, arena, dir->arena_size, 1);
    if (vr != CAPSULE_VALID) return CAPSULE_RUN_ERR_INVALID;

    /* Milestone 6 (Phase 8): enforced only on INVALID -- see the fuller
     * comment in capsule_birth_mama() above for why MISSING/NO_ROOT_KEY
     * stay WARN-only. */
    {
        int idx = (int)(cap - descs);
        CapsuleSigResult sr = capsule_verify_signature(
            descs, names, capsule_get_signatures(), arena, dir->desc_count, idx);
        if (sr != CAPSULE_SIG_OK) {
            log_message(LOG_WARN, "capsule sig: %s: %s",
                        names[idx].name, capsule_sig_result_str(sr));
            if (sr == CAPSULE_SIG_INVALID) return CAPSULE_RUN_ERR_INVALID;
        }
        /* FABRIC-2.md §I.5: contrib trust tier -- see contrib_capsule_
         * refused()'s own doc comment. */
        if (contrib_capsule_refused(cap->flags, sr)) {
            log_message(LOG_WARN, "capsule sig: %s: contrib capsule refused on real hardware (%s)",
                        names[idx].name, capsule_sig_result_str(sr));
            return CAPSULE_RUN_ERR_INVALID;
        }
    }

    uint64_t pre_dict_hash = vm_dict_hash_fn(mama_vm);

    const uint8_t *payload = capsule_get_payload(cap, arena);
    if (!payload) return CAPSULE_RUN_ERR_INVALID;

    int exec_result = vm_exec_fn(mama_vm, (const char *)payload, cap->length);
    uint64_t post_dict_hash = vm_dict_hash_fn(mama_vm);

    CapsuleRunRecord record;
    record.run_id         = 0;
    record.vm_id          = vm_uuid_hera();  /* experiments run on Mama's own VM */
    record.reserved       = 0;
    record.capsule_id     = cap->capsule_id;
    record.capsule_hash   = cap->content_hash;
    record.pre_dict_hash  = pre_dict_hash;
    record.post_dict_hash = post_dict_hash;
    record.started_ns     = 0;
    record.ended_ns       = 0;
    record.result_code    = (exec_result == 0) ? CAPSULE_RUN_OK : CAPSULE_RUN_ERR_EXEC_FAIL;
    record.flags          = cap->flags;

    uint64_t run_id = capsule_run_log_record(&record);

    capsule_parity_log_run(vm_uuid_hera(), run_id, cap->capsule_id, pre_dict_hash, post_dict_hash);

    if (out_run_id) *out_run_id = run_id;

    return (exec_result == 0) ? CAPSULE_RUN_OK : CAPSULE_RUN_ERR_EXEC_FAIL;
}