diff --git a/docs/CLI.md b/docs/CLI.md
index a43d1bb..4cd0842 100644
--- a/docs/CLI.md
+++ b/docs/CLI.md
@@ -58,7 +58,7 @@ claro package doctor
 claro package lock
 ```
 
-The v1.18.26 package command is a safer local project-file helper. It creates `claro.project`, `claro.lock`, and local folders under `packages/`. It is not yet an online package registry.
+The v1.18.26 package command is a safer local project-file helper. It creates `claro.project`, `claro.lock`, and local folders under `packages/`. Package names may appear only once in `claro.project`; `claro package doctor` reports duplicate entries so the lockfile stays unambiguous. It is not yet an online package registry.
 
 ## IDE metadata
 
diff --git a/docs/CURRENT_STATUS.md b/docs/CURRENT_STATUS.md
index 310f509..314623f 100644
--- a/docs/CURRENT_STATUS.md
+++ b/docs/CURRENT_STATUS.md
@@ -106,6 +106,7 @@ Ready now:
 - `claro package doctor` requires the complete supported `manifest-version: 1` value in `claro.project`, so a prefix such as `manifest-version: 10` is rejected
 - `claro package doctor` requires the complete supported `version: 1` value in each local package manifest, so a prefix such as `version: 10` is rejected
 - `claro package doctor` requires the complete supported `source: local` value in each local package manifest, so a prefix such as `source: local-extra` is rejected
+- package project entries must be unique; `claro package doctor`, `list`, `add`, `init`, and `lock` reject duplicate names instead of generating ambiguous package or lockfile data
 
 Still needed:
 - install from local path
diff --git a/docs/ROADMAP.md b/docs/ROADMAP.md
index 49098d3..aa754dc 100644
--- a/docs/ROADMAP.md
+++ b/docs/ROADMAP.md
@@ -33,7 +33,7 @@ See `CURRENT_STATUS.md` for the detailed feature matrix.
 2. Keep examples aligned with the modern simple syntax (`END`, `DO`, short `SET`, short `ASK`) while documenting older compatibility forms separately.
 3. Expand validation around typecheck diagnostics and package/networking safety. Current Forgejo/Gitea CI runs the documented release gates (`claro validate`, typecheck diagnostics validation, version convention validation, package security validation, and CI workflow coverage validation). Current package safety validation covers safe project creation, rejecting unsafe project names during `claro new`, safe manifest/lockfile creation, rejecting unsafe package names during `package add`, detecting unsafe package names already present in `claro.project` during `package doctor`, refusing to write lockfile data for unsafe package names during `package lock`, making `package list` fail instead of displaying unsafe package entries as normal package names, making `package init` fail instead of reporting the project ready when unsafe package names are already present, making `package add` fail before changing files when unsafe package names are already present, making `package remove` fail instead of reporting success when unsafe package names remain during lockfile refresh, allowing `package remove` to remove an exact unsafe package entry so learners can repair a bad `claro.project`, making `package doctor` reject stale lockfile checksums for listed packages, and making `package doctor` reject lockfile package entries that are not listed in `claro.project`. Current function validation covers correct checked calls, wrong-type arguments, missing checked-argument diagnostics, missing unchecked-argument diagnostics for simple functions in both modern `DO greet` and empty compatibility `CALL greet WITH` forms, extra-argument diagnostics, and beginner-facing unknown-function diagnostics for mistyped modern `DO` and compatibility `CALL ... WITH` calls; current object-method parameter validation covers correct modern `DO object.method ...` and compatibility `CALL object.method WITH ...` checked calls, wrong-type diagnostics for both call forms, checked methods after another method in the same class, missing and extra checked-argument diagnostics including the extra-argument case for a checked method after another method in the same class, missing unchecked-argument diagnostics for simple object methods, missing-object guidance when `DO player.method ...` or compatibility `CALL object.method WITH ...` appears before `NEW` even if the method name is also wrong, and class-specific unknown-method diagnostics for both modern and compatibility calls when a learner calls a method the class does not declare; current object-field validation covers direct NUMBER/TEXT/YESNO field-assignment positives, direct object-field `CHECK TYPE` metadata positives for NUMBER/TEXT/YESNO fields, negative NUMBER/TEXT/YESNO field metadata mismatches, NUMBER/TEXT/YESNO-expectation unknown-field `CHECK TYPE` diagnostics, direct wrong-type field assignment diagnostics, field collection when a `HAS` field appears after a simple method, direct unknown-field diagnostics for NUMBER/TEXT/YESNO values, a beginner-facing fallback for unknown fields assigned from expressions whose type is not inferable yet, and missing-object diagnostics for both `SET object.field value` and `CHECK TYPE object.field IS TYPE` before `NEW`.
 3a. Keep package validation honest by checking that the project and each listed package manifest declare the exact supported manifest version, package version, local source, and expected package name.
-3b. Keep package security validation in Forgejo/Gitea CI so unsafe names, exact manifest-version/name/checksum mismatches, missing manifests, and lockfile errors remain release blockers.
+3b. Keep package security validation in Forgejo/Gitea CI so unsafe names, exact manifest-version/name/checksum mismatches, missing manifests, duplicate project packages, and lockfile errors remain release blockers.
 4. Add small examples for each foundation feature before adding bigger syntax.
 
 ## Complete-platform milestones
diff --git a/src/claro.c b/src/claro.c
index dfe33ad..da2a15d 100644
--- a/src/claro.c
+++ b/src/claro.c
@@ -630,7 +630,7 @@ static void package_checksum(const char *name,char *out,size_t n){ unsigned long
 static void ensure_project_file(void){ if(!file_exists_simple("claro.project")) write_text_file_simple("claro.project","manifest-version: 1\nname: ClaroProject\nmain: main.claro\nversion: v1.18.26\npackages:\n"); }
 static char *project_value(const char *key){ char *txt=read_file_text("claro.project"); size_t kn=strlen(key); char *p,*out=NULL; if(!txt) return NULL; p=txt; while(*p){ char *line=p; char save; while(*p&&*p!='\n'&&*p!='\r') p++; save=*p; *p=0; { char *t=trim_inplace(line); if(strnicmp2(t,key,kn)==0 && t[kn]==':'){ out=xstrdup(trim_inplace(t+kn+1)); break; } } if(save) p++; while(*p=='\n'||*p=='\r') p++; } free(txt); return out; }
 static int package_has_name(const char *name){ char *txt=read_file_text("claro.project"); char *p; int found=0; if(!txt) return 0; p=txt; while(*p){ char *line=p; char save; while(*p&&*p!='\n'&&*p!='\r') p++; save=*p; *p=0; { char *t=trim_inplace(line); if(strnicmp2(t,"package:",8)==0){ char *pkg=trim_inplace(t+8); if(strcmp(pkg,name)==0){ found=1; break; } } } if(save) p++; while(*p=='\n'||*p=='\r') p++; } free(txt); return found; }
-static int project_package_names_safe(void){ char *txt=read_file_text("claro.project"); char *p; if(!txt) return 1; p=txt; while(*p){ char *line=p; char save; while(*p&&*p!='\n'&&*p!='\r') p++; save=*p; *p=0; { char *t=trim_inplace(line); if(strnicmp2(t,"package:",8)==0){ char *pkg=trim_inplace(t+8); if(*pkg&&!package_name_safe(pkg)){ printf("BAD package name: %s\n",pkg); free(txt); return 0; } } } if(save){ *p=save; p++; } while(*p=='\n'||*p=='\r') p++; } free(txt); return 1; }
+static int project_package_names_safe(void){ char *txt=read_file_text("claro.project"); char *p; char seen[128][65]; int seen_count=0; if(!txt) return 1; p=txt; while(*p){ char *line=p; char save; while(*p&&*p!='\n'&&*p!='\r') p++; save=*p; *p=0; { char *t=trim_inplace(line); if(strnicmp2(t,"package:",8)==0){ char *pkg=trim_inplace(t+8); int i; if(*pkg&&!package_name_safe(pkg)){ printf("BAD package name: %s\n",pkg); free(txt); return 0; } if(*pkg){ for(i=0;i<seen_count;i++){ if(strcmp(seen[i],pkg)==0){ printf("DUPLICATE package: %s\n",pkg); free(txt); return 0; } } if(seen_count<128) snprintf(seen[seen_count++],sizeof(seen[0]),"%s",pkg); } } } if(save){ *p=save; p++; } while(*p=='\n'||*p=='\r') p++; } free(txt); return 1; }
 static int write_package_lock(void){ char *txt=read_file_text("claro.project"); FILE *f; char *p; if(!txt) return 0; if(!project_package_names_safe()){ free(txt); return 0; } f=fopen("claro.lock","wb"); if(!f){ free(txt); return 0; } fputs("# Claro package lock\nlock-version: 1\nversion: v1.18.26\n",f); p=txt; while(*p){ char *line=p; char save; while(*p&&*p!='\n'&&*p!='\r') p++; save=*p; *p=0; { char *t=trim_inplace(line); if(strnicmp2(t,"package:",8)==0){ char *pkg=trim_inplace(t+8); if(*pkg){ char sum[32]; package_checksum(pkg,sum,sizeof(sum)); fprintf(f,"package: %s\nchecksum: %s\n",pkg,sum); } } } if(save) p++; while(*p=='\n'||*p=='\r') p++; } fclose(f); free(txt); return 1; }
 static int append_package_to_project(const char *name){ FILE *f; if(package_name_too_long(name)){ fprintf(stderr,"Package names must be 64 characters or fewer.\n"); return 0; } if(!package_name_safe(name)){ fprintf(stderr,"Package names may use only letters, numbers, dash, and underscore.\n"); return 0; } ensure_project_file(); if(package_has_name(name)){ printf("Package already listed: %s\n",name); return 1; } f=fopen("claro.project","ab"); if(!f) return 0; fprintf(f,"package: %s\n",name); fclose(f); write_package_lock(); return 1; }
 static int remove_package_from_project(const char *name){ char *txt=read_file_text("claro.project"); FILE *f; char *p; int removed=0; if(!txt) return 0; f=fopen("claro.project","wb"); if(!f){ free(txt); return 0; } p=txt; while(*p){ char *line=p; char save; int skip=0; while(*p&&*p!='\n'&&*p!='\r') p++; save=*p; *p=0; { char *copy=xstrdup(line); char *t=trim_inplace(copy); if(strnicmp2(t,"package:",8)==0){ char *pkg=trim_inplace(t+8); if(strcmp(pkg,name)==0){ skip=1; removed=1; } } free(copy); } if(!skip) fprintf(f,"%s\n",line); if(save) p++; while(*p=='\n'||*p=='\r') p++; } fclose(f); free(txt); if(!write_package_lock()) return -1; return removed; }
@@ -643,7 +643,7 @@ static int package_manifest_name_matches(const char *text,const char *name){ con
 static int package_manifest_version_value_matches(const char *text){ const char *p=text; while(p&&*p){ const char *line=p; const char *end; while(*p&&*p!='\n'&&*p!='\r') p++; end=p; if((size_t)(end-line)>=8&&strncmp(line,"version:",8)==0){ const char *value=line+8; while(value<end&&isspace((unsigned char)*value)) value++; while(end>value&&isspace((unsigned char)end[-1])) end--; return (size_t)(end-value)==1&&value[0]=='1'; } while(*p=='\n'||*p=='\r') p++; } return 0; }
 static int package_manifest_source_matches(const char *text){ const char *p=text; while(p&&*p){ const char *line=p; const char *end; while(*p&&*p!='\n'&&*p!='\r') p++; end=p; if((size_t)(end-line)>=7&&strncmp(line,"source:",7)==0){ const char *value=line+7; while(value<end&&isspace((unsigned char)*value)) value++; while(end>value&&isspace((unsigned char)end[-1])) end--; return (size_t)(end-value)==5&&strncmp(value,"local",5)==0; } while(*p=='\n'||*p=='\r') p++; } return 0; }
 static int package_manifest_checksum_matches(const char *text,const char *expected){ const char *p=text; size_t n=strlen(expected); while(p&&*p){ const char *line=p; const char *end; while(*p&&*p!='\n'&&*p!='\r') p++; end=p; if((size_t)(end-line)>=9&&strncmp(line,"checksum:",9)==0){ const char *value=line+9; while(value<end&&isspace((unsigned char)*value)) value++; while(end>value&&isspace((unsigned char)end[-1])) end--; return (size_t)(end-value)==n&&strncmp(value,expected,n)==0; } while(*p=='\n'||*p=='\r') p++; } return 0; }
-static int package_doctor(void){ int ok=1; char *mainfile; char *txt; printf("%s\n",CLARO_VERSION); printf("Package/project doctor:\n"); printf("  %s claro.project\n",file_exists_simple("claro.project")?"OK":"MISSING"); if(!file_exists_simple("claro.project")) ok=0; mainfile=project_value("main"); if(mainfile&&*mainfile){ printf("  %s main script: %s\n",file_exists_simple(mainfile)?"OK":"MISSING",mainfile); if(!file_exists_simple(mainfile)) ok=0; } else { printf("  MISSING main setting\n"); ok=0; } printf("  %s packages folder\n",path_exists_simple("packages")?"OK":"MISSING"); if(!path_exists_simple("packages")) ok=0; printf("  %s claro.lock\n",file_exists_simple("claro.lock")?"OK":"MISSING"); if(!file_exists_simple("claro.lock")) ok=0; txt=read_file_text("claro.project"); if(txt&& !package_manifest_version_matches(txt)){ printf("  BAD project manifest version: expected 1\n"); ok=0; } if(txt){ char *p=txt; while(*p){ char *line=p; char save; while(*p&&*p!='\n'&&*p!='\r') p++; save=*p; *p=0; { char *t=trim_inplace(line); if(strnicmp2(t,"package:",8)==0){ char *pkg=trim_inplace(t+8); if(*pkg){ char meta[512], *mt, sum[32]; if(!package_name_safe(pkg)){ printf("  BAD package name: %s\n",pkg); ok=0; } else { snprintf(meta,sizeof(meta),"packages/%s/claro.package",pkg); mt=read_file_text(meta); if(mt&&!package_manifest_version_value_matches(mt)){ printf("  BAD package version: %s\n",pkg); ok=0; } else if(mt&&!package_manifest_source_matches(mt)){ printf("  BAD package source: %s\n",pkg); ok=0; } else if(mt&&package_manifest_version_matches(mt)&&strstr(mt,"checksum:")){ if(!package_manifest_name_matches(mt,pkg)){ printf("  BAD package manifest name: %s\n",pkg); ok=0; } else { printf("  OK package manifest: %s\n",pkg); package_checksum(pkg,sum,sizeof(sum)); if(package_manifest_checksum_matches(mt,sum)) printf("  OK package checksum: %s\n",pkg); else { printf("  BAD package checksum: %s\n",pkg); ok=0; } if(package_lock_checksum_ok(pkg)) printf("  OK lock checksum: %s\n",pkg); else { printf("  BAD lock checksum: %s\n",pkg); ok=0; } } } else { printf("  MISSING package manifest: %s\n",pkg); ok=0; } free(mt); } } } } if(save) p++; while(*p=='\n'||*p=='\r') p++; } free(txt); } if(!lock_packages_match_project()) ok=0; free(mainfile); printf("%s\n",ok?"Package/project files look ready.":"Package/project files need attention."); return ok?0:1; }
+static int package_doctor(void){ int ok=1; char *mainfile; char *txt; printf("%s\n",CLARO_VERSION); printf("Package/project doctor:\n"); printf("  %s claro.project\n",file_exists_simple("claro.project")?"OK":"MISSING"); if(!file_exists_simple("claro.project")) ok=0; mainfile=project_value("main"); if(mainfile&&*mainfile){ printf("  %s main script: %s\n",file_exists_simple(mainfile)?"OK":"MISSING",mainfile); if(!file_exists_simple(mainfile)) ok=0; } else { printf("  MISSING main setting\n"); ok=0; } printf("  %s packages folder\n",path_exists_simple("packages")?"OK":"MISSING"); if(!path_exists_simple("packages")) ok=0; printf("  %s claro.lock\n",file_exists_simple("claro.lock")?"OK":"MISSING"); if(!file_exists_simple("claro.lock")) ok=0; txt=read_file_text("claro.project"); if(txt&&!project_package_names_safe()){ ok=0; } if(txt&& !package_manifest_version_matches(txt)){ printf("  BAD project manifest version: expected 1\n"); ok=0; } if(txt){ char *p=txt; while(*p){ char *line=p; char save; while(*p&&*p!='\n'&&*p!='\r') p++; save=*p; *p=0; { char *t=trim_inplace(line); if(strnicmp2(t,"package:",8)==0){ char *pkg=trim_inplace(t+8); if(*pkg){ char meta[512], *mt, sum[32]; if(!package_name_safe(pkg)){ printf("  BAD package name: %s\n",pkg); ok=0; } else { snprintf(meta,sizeof(meta),"packages/%s/claro.package",pkg); mt=read_file_text(meta); if(mt&&!package_manifest_version_value_matches(mt)){ printf("  BAD package version: %s\n",pkg); ok=0; } else if(mt&&!package_manifest_source_matches(mt)){ printf("  BAD package source: %s\n",pkg); ok=0; } else if(mt&&package_manifest_version_matches(mt)&&strstr(mt,"checksum:")){ if(!package_manifest_name_matches(mt,pkg)){ printf("  BAD package manifest name: %s\n",pkg); ok=0; } else { printf("  OK package manifest: %s\n",pkg); package_checksum(pkg,sum,sizeof(sum)); if(package_manifest_checksum_matches(mt,sum)) printf("  OK package checksum: %s\n",pkg); else { printf("  BAD package checksum: %s\n",pkg); ok=0; } if(package_lock_checksum_ok(pkg)) printf("  OK lock checksum: %s\n",pkg); else { printf("  BAD lock checksum: %s\n",pkg); ok=0; } } } else { printf("  MISSING package manifest: %s\n",pkg); ok=0; } free(mt); } } } } if(save) p++; while(*p=='\n'||*p=='\r') p++; } free(txt); } if(!lock_packages_match_project()) ok=0; free(mainfile); printf("%s\n",ok?"Package/project files look ready.":"Package/project files need attention."); return ok?0:1; }
 static int run_package_cmd(int argc,char **argv,int arg){ if(arg>=argc){ printf("Package commands:\n  claro package init\n  claro package add NAME\n  claro package remove NAME\n  claro package list\n  claro package doctor\n  claro package lock\n"); return 0; } if(strcmp(argv[arg],"init")==0){ ensure_project_file(); if(!project_package_names_safe()) return 1; make_folder("packages"); if(!write_package_lock()) return 1; printf("Package project ready: claro.project, claro.lock, packages/\n"); return 0; } if(strcmp(argv[arg],"add")==0&&arg+1<argc){ const char *name=argv[arg+1]; int already; if(package_name_too_long(name)){ fprintf(stderr,"Package names must be 64 characters or fewer.\n"); return 1; } if(!package_name_safe(name)){ fprintf(stderr,"Package names may use only letters, numbers, dash, and underscore.\n"); return 1; } ensure_project_file(); if(!project_package_names_safe()) return 1; make_folder("packages"); already=package_has_name(name); if(!append_package_to_project(name)) return 1; create_package_folder(name); if(!write_package_lock()) return 1; if(!already) printf("Added package: %s\n",name); return 0; } if(strcmp(argv[arg],"remove")==0&&arg+1<argc){ const char *name=argv[arg+1]; int removed; removed=remove_package_from_project(name); if(removed<0) return 1; if(removed) printf("Removed package from project: %s\n",name); else printf("Package was not listed: %s\n",name); return 0; } if(strcmp(argv[arg],"list")==0) return list_project_packages(); if(strcmp(argv[arg],"doctor")==0) return package_doctor(); if(strcmp(argv[arg],"lock")==0||strcmp(argv[arg],"update")==0){ ensure_project_file(); make_folder("packages"); if(write_package_lock()){ printf("Updated claro.lock\n"); return 0; } fprintf(stderr,"Could not write claro.lock\n"); return 1; } printf("Unknown package command. Try: claro package init\n"); return 1; }
 static int print_ide_info(void){
  printf("{\n");
diff --git a/tools/validate_package_security.py b/tools/validate_package_security.py
index f9281fd..dcc0b10 100644
--- a/tools/validate_package_security.py
+++ b/tools/validate_package_security.py
@@ -185,6 +185,17 @@ def main():
             fail(f"package doctor orphan-lock diagnostic was unclear:\n{out}")
         (work / "claro.lock").write_text(lock, encoding="utf-8")
 
+        (work / "claro.project").write_text(
+            project + "package: math-tools\npackage: math-tools\n",
+            encoding="utf-8",
+        )
+        rc, out = run([str(EXE), "package", "doctor"], work)
+        if rc == 0:
+            fail("package doctor must reject duplicate package entries in claro.project")
+        if "DUPLICATE package: math-tools" not in out:
+            fail(f"Package duplicate diagnostic was unclear:\n{out}")
+        (work / "claro.project").write_text(project, encoding="utf-8")
+
         rc, out = run([str(EXE), "package", "add", "../bad"], work)
         if rc == 0:
             fail("Unsafe package names with path separators must be rejected")